DE4110910C2 - Hydraulic control system for an automatic transmission - Google Patents

Description

The invention relates to an automatic transmission, according to the preamble of claim 1.

Such a control system is through the publication JP-A-149657/1986 and also the publication DE-A-3827152 are known.

In an automatic transmission of the type specified above takes place switching from one speed range to another speed range in that instead of an oil pressure of at least one of the brakes and used in the automatic transmission Clutches are discharged while at least one oil pressure another of these is fed. There is a possibility and likelihood of such Switching the oil pressures can result in switching surges.  

To remedy this, according to conventional Practice memory with those used in the automatic transmission Brakes as well as clutches connected, and the back pressures on the memories are regulated so that the occurrence of bumps is prevented during a switching operation (see JP-A- 138 553/1981). However, the scheme is under Using a mechanical valve, which is done in a rough pressure control results. It is desirable a smoother, bumpless and functional pressure control to get. For this purpose, the JP-A 149 657/1986 an automatic transmission in which a hydraulic circuit contains an electrically excited pressure control valve, to regulate the back pressure at storage tanks. The working game, with which the pressure control valve is electrically excited, will be in accordance with any of the following or Parameters regulated: opening of a throttle valve, a switching mode or type, an oil temperature of the engine, the cooling water temperature of the engine, the temperature of the intake by the engine Air, an oil temperature of the automatic transmission, a special position of a switch position selector switch, an engine torque, the speed of an engine, a boost pressure the engine, a fuel injection to the engine, an output torque of the automatic transmission and the speed the output shaft of the automatic transmission. To this The back pressure of a reservoir is regulated by regulating the Working cycle of the pressure control valve controlled. That leaves one fine regulation or control of the back pressure at storage tanks too because of the excitation level or the working cycle of the pressure control valve can be electrically controlled, which allows that a more appropriate back pressure at the reservoir is achieved and can be regulated evenly.

However, the tightening or engagement characteristics of frictional links, like brakes and clutches that are in the Automatic transmissions are used, or a game in  mechanical system from vehicle to vehicle and with the Time change, so the switching behavior caused by a time required to prevent switching shocks or to switch between speed ranges is from vehicle to vehicle and also in Agreement with the total travel time of individual Vehicles changes.

Through the publication US-A-870 581 it is at a non-generic control system known, due to of measurements of the input and output speed of the Automatic transmission the time interval required for shifting to determine and the line pressure to the Switching is applied to the clutches depending to control from the measured or determined time interval. The line pressure is controlled in the Way that the time interval in a predetermined range is regulated. So if the determined time interval is in the given range, the line pressure not changed and there is no regulation of the Time interval.

Through the publication EP-A-0 352 803 is a non-generic Control system known in which the line pressure, with which the clutches of an automatic transmission be acted upon depending on one determined time interval required for switching so is controlled by thereby regulating the time interval he follows. This determination of the time interval takes place based on measurements of the speeds of the output shaft of the engine and the output shaft of the automatic transmission. The regulation is carried out in such a way that the difference between the determined time interval and a target value of the time interval becomes zero.

It is therefore the object of the invention, the generic Control system to develop such that a  Change in shift behavior of an automatic transmission diminished to another and a change in switching behavior is suppressed over time.

This object is achieved by the Control systems according to claim 1.  

In the control system according to claim 1 determines the Switching time determination device that Time interval from the triggering to the completion of a Shifting in a mechanical clutch of the automatic transmission during the switching process. The switching time interval is achieved through the mechanical indentation / disengagement in one Switching mechanism occur, determined. The memory pressure Control device reacts to the switching time interval. Updated in particular when the switching time interval is longer than a reference switching time, the accumulator pressure control device an excitation level (a cycle) of the pressure control valve in one direction to the time interval, i.e. H. the Working cycle, reduce or the back pressure at the memory to increase. If, on the other hand, the switching time interval is shorter than the reference switching time, it is updated the accumulator pressure control means the excitation level (the working cycle) of the pressure control valve in a direction to the time interval, i.e. H. the working game, increase or reduce the back pressure at the accumulator.  

When the tightening or engaging characteristics of in the automatic transmission used frictional links, such as brakes and Couplings, or games in the mechanical system of Varying vehicle to vehicle, consequently the back pressure automatically regulated at the memories so that the Switching time interval remains essentially constant. As a result, a shift shock or jerk or an overspeed of the engine resulting from this change result, essentially eliminated, thereby creating a stabilized and shock-free acceleration and deceleration Responsiveness can be guaranteed. That applies in the same way even if the indentation values of Frictional links or the play between parts in the mechanical System vary over time.

However, if the frictional links used in the automatic transmission a greater degree of abrasion to one Point subject that the good switching behavior is not by means of control in accordance with the switching time interval can be maintained or if a payload or payload of the vehicle or by an incline stress is excessive, d. H. with others Words that the switching time interval from a given Range goes out, so the modification ends in the control system according to claim 1 the back pressure on the accumulators in the above described Way, what an application of excessive or excessive avoids low back pressures on the accumulators. That has the effect of any disturbance in the control of the back pressure on the storage tank under exceptional operating conditions, is avoided. It also has an effect that a deviation of a returned back pressure on the memory or a returned switching behavior the gear of a preferred value within a given range can be suppressed if the operating environment  has returned to the predetermined range, such as when the frictional links have been readjusted or replaced or the payload has been removed or reduced is.  

In an advantageous embodiment of the control system according to claim 1 the measures according to claim 2 can be provided. Thereby an abnormality warning is also given, if good switching behavior is not due to the regulation in accordance with the switching time interval as a Result of increased abrasion on frictional links, the maintained in the automatic transmission can be if any irregularity or deviation appears in the switching mechanism or if the payload of the vehicle or due to an incline stress is excessive.

Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. It shows

Figure 1 is a schematic representation of a transmission gear mechanism in an embodiment according to the invention.

FIGS. 2a and 2b are schematic illustrations of respectively one half of a hydraulic circuit, the oil pressures to different brakes and clutches which are disposed within the gear transmission mechanism of FIG. 1 performs, or dissipates from these, FIGS. 2a and 2b along the lines 2A -2A and 2B-2B are to be joined together to form a hydraulic circuit;

FIG. 3 is a table showing the relationship between combinations of excitation and de-excitation of solenoid valves (SL1-SL3) shown in the hydraulic circuit of FIGS . 2a and 2b, around the speed range, and the engagement and disengagement of various brakes and clutches shown in Figure 1;

Fig. 4 is a block diagram of an electrical circuit for energizing the in Fig. Solenoid valves 2a and 2b shown (SL1-SL3), a solenoid valve (SL4) for controlling a lock of a timing solenoid valve (SL5) and a linear solenoid valve (SL6) ;

FIG. 5a, 5b, 5c, 5d and 5e are flow charts, the control operation (main routine) represented by a microcomputer of a control device shown in Figure 4 (130).

Figures 6a and 6b are flow charts showing the detail of "TSO, TSE Discovery" (step 64 in Figure 5d);

Fig. 7a and 7b are flow charts showing the detail of "controlling a linear solenoid valve" (step 65 in Figure 5d.) Play;

Figures 8a, 8b and 8c are flowcharts showing the detail of "timing solenoid valve control" (step 66 in Figure 5d);

Figure 9a is a timing chart representing the timing of determination of a switching operation, a switching output and the completion of a switching process performed by the microcomputer in the control unit 130 of FIG. 4,.;

9b graphically an oil pressure outputted from the linear solenoid valve SL6, compared to the current level used to energize the coil.

9C graphically illustrates the current level used to energize the linear solenoid valve SL6 and is determined by the microcomputer in the control unit 130 on the basis of a throttle opening R and the rotational speed Nt of a disc in a clutch C1.

Is used 10a graphically a correction factor K11, which depends on an oil temperature and in determining the working cycle shown in Figure 7 (steps 117-128)..;

FIG. 10B graphically a further correction factor K12, the (steps 117-128 in FIG 7 s..) Is used as a function of the opening angle R of the throttle valve when determining the working cycle;

Fig. 10c graphically a correction factor K2 which (steps 117-128 in FIG 7 s..) Is used as a function of the switching type and the opening R of the throttle valve when determining the working cycle;

Fig. 10d is used graphically a relationship between a time reference value TS for a mechanical circuit in accordance with the opening R of the throttle valve and in accordance with areas in which this reference value;

Figure 11 graphically illustrates a change in oil pressure of a brake B0 and a clutch C2 of Figure 1 during a circuit 2 → 3, wherein the solid line represents a switching operation under power..;

Fig. 12a graphically illustrates a set of reference vehicle speeds used to determine the need to perform a shift if a economy mode is not specified during the "decision to shift" (step 14 in Fig. 5a);

FIG. 12b graphically illustrates a set of reference vehicle speeds used to determine the need to perform a shift when a economy mode is specifically determined during the "decision for any shift" (step 14 in FIG. 5a).

Fig. 1 shows the general structure of an automatic transmission in an embodiment according to the invention, the torque converter 1 with a directly coupled clutch 50 , a secondary gear 2 formed by an overdrive or overdrive gear and a main gear 3 formed by a change gear transmission with three forward speed ranges and a reverse speed range, which are switched in the order given.

The torque converter 1 has a pump 5 , a turbine 6 and a stator 7 , which are assembled in a manner known per se. The pump 5 is connected to the crankshaft 8 of an engine, while the turbine 6 is connected to a turbine shaft 9 , which is an output shaft of the torque converter 1 and also forms the input shaft of the auxiliary transmission 2 , in which it is connected to the carrier 10 of a planetary gear . The directly coupled clutch 50 is arranged between the crankshaft 8 of the engine and the turbine shaft 9 . When the clutch 50 is actuated, it connects the crankshaft 8 to the turbine shaft 9 , ie, locking takes place.

A planet pinion 14 is rotatably mounted on the carrier 10 and meshes with a sun gear 11 and a ring gear 15 . An overdrive multi-plate clutch C0 and an overdrive one-way clutch F0 are arranged between the sun gear 11 and the carrier 10 , while an overdrive multi-plate brake B0 is inserted between the sun gear 11 and a housing accommodating the overdrive gear.

The ring gear 15 of the secondary gear 2 is connected to an input shaft 23 of the main gear 3 . A forward multi-plate clutch C1 lies between the input shaft 23 and an intermediate or countershaft 29 , and a reverse multi-plate clutch C2 is arranged between the input shaft 23 and a sun gear shaft 30 . A multi-disc brake B1 is located between the sun gear shaft 30 and the housing of the transmission, while a sun gear 32 arranged on the sun gear shaft 30 has two power transmission paths of a planetary gear set together with a carrier 33 , a planet pinion 34 carried by it , a ring gear 35 meshing with this pinion, one forming further carrier 36, a support 36 carried by the planet pinion 37 and a pinion 37 meshing with the ring gear 38th A one-way clutch F1 and a brake B2 are connected between the carrier 36 and the gear housing. The ring gear 35 , which is arranged in one of the two power transmission paths of the planetary gear, is connected to the intermediate shaft 29 . The carrier 33 of this planetary gear is connected to the ring gear 38 of the other planetary gear, and the carrier and the ring gear are connected to the output shaft (load drive shaft) 39 .

In response to an output from an engine and in accordance with the driving speed becomes an automatic transmission with an overdrive unit as described above by a hydraulic control system to be explained later controlled to various clutches and brakes indent or solve, so that a shift to four Forward ranges (first, second, third, fourth Speed range: O / D) including overdrive (O / D) a forward range by a manual shift (1.5 speed range = LS) and a reverse range becomes.

A hydraulic circuit, which selectively actuates the clutches C0, C1, C2 as well as the brakes B0, B1, B2 and the directly coupled clutch 50 of the torque converter in the automatic transmission in order to achieve an automatic shifting process, is shown in FIGS. 2a and 2b .

The hydraulic circuits shown in FIGS. 2a and 2b include an oil tank 100 , an oil pump 101 , a pressure control valve 102 , an auxiliary pressure control valve 103 , a linear solenoid valve SL6, a manual switching valve 200 , a 1-2 switching valve 220 , a second -3 switching valve 230 , a 3-4 switching valve 240 , a ½ switching control valve SL1, a ² / ₃ switching control valve SL2, a 2 switching control valve SL3, memory 260 , 270 , 280 and 290 , a Accumulator pressure control valve 110 , a modulator valve 90 , a throttle control valve 80 , a timing solenoid valve SL5, an idling modulator valve 250 , a delivery pressure valve 70 , a lock or engagement control valve 360 , an engagement control signal valve 370 , an engagement or Locking control solenoid valve SL4 and other hydraulic components as well as oil lines that establish connections between these valves and form a servo circuit connection for the oil pressures of the clutches and brakes.

Working oil that is pumped out of the oil tank 100 by the pump 101 is brought to a predetermined oil pressure (line pressure) by means of the pressure control valve 102 and then supplied to oil circuits or lines 104 and 105 . The oil pressure supplied to the auxiliary pressure regulator valve 103 via line 105 is then regulated by the linear solenoid valve SL6 to generate a torque converter pressure, a lubrication pressure and a cooling pressure which are determined in accordance with the throttle valve opening and the vehicle speed. The manual shift valve 200 connected to the oil line 104 is mechanically coupled to a shift lever located near the driver's seat, and it can be manually operated to a P-, R-, N-, D-, S- and L- Position can be set according to the range of the shift lever.

In the hydraulic circuit shown in FIG. 2, a combination in the excitation or de-excitation of the shift control valves SL1-SL3 determines a special speed or speed range of the automatic transmission shown in FIG. 1. The table in FIG. 3 shows the corresponding speed ranges, where o denotes the excitation and × the de-excitation of the respective solenoid valves. It should be noted that O / D, which is included in the speed range column in FIG. 3, indicates the fourth speed range (overdrive), while LS indicates a speed range that is between the first speed range (with a gear ratio of 2.905) and a second speed range (with a gear ratio of 1.530) and can be referred to as a 1.5 speed range, which has a gear ratio of 2.257.

Taking into account the features of the automatic transmission described, which are shown in Fig. 1, 2a and 2b, it should be noted that LS (1.5 speed range) lies between the first and the second speed range. The purpose of LS (1.5 speed range) is to achieve a smooth, bumpless driving behavior, which ensures a relatively high speed with sufficient performance when driving on an uphill road, and to achieve a quiet, bumpless driving behavior, which ensure adequate engine braking during a downhill descent, even when the vehicle is driving on a slope with a high load, the choice of the first speed range will result in decelerated speed and the choice of a second speed range will result in insufficient performance to cause an unstable driving condition (there will be a relatively frequent shift between the first and second speed ranges and this shifting easily leads to bumps) and even if the choice of the first speed range results in excessive engine braking and the choice of the second speed range will result in moderate engine braking when the vehicle is driving down a downhill road (there will be a relatively frequent shift between the first and second speed ranges and such a shift will also easily cause bumps).

When an order is made around the 1.5 speed range (LS) automatically between the first and second area of the D range, the speed zones, the in the first and second speed range of the D range exist in three segments instead of divided two segments, which in a reduced width of the resulting speed zones results in an increase in the frequency of switching as well as a unusual feeling on the part of the driver be what's on the resulting bumps and switching between speed ranges.

For this reason, according to the invention, the 1.5 speed range (LS) in response to a command for this 1.5 speed range set, this command by a shift is given by the driver when the shift lever assumes a position within the L range.

In the automatic transmission of Fig. 1, when the sub-transmission 2 assumes an overdrive state (O / D; C0 disengaged, B0 released) and the main transmission 3 assumes a first speed range (C1 engaged, C2 disengaged, B1 released and B2 tightened), the result is Get gear ratio a value (2.257), which lies between the gear ratios (2.950 and 1.530) of the first and second speed range. As a result, this value is determined as the 1.5 speed range. If this 1.5 speed range is commanded, the auxiliary transmission 2 is in its O / D state, while the first speed range is selected for the main transmission 3 ( FIG. 3).

Another feature of the automatic transmission of FIGS. 1, 2a and 2b relates to the provision of memories 260 , 270 , 280 and 290 , which serve to prevent the occurrence of shocks as a result of the shifting process. Each accumulator contains a piston inside, which is pushed up by a helical compression spring. The back pressure on this piston is controlled by the linear solenoid valve SL6 via the accumulator pressure control valve 110 , while the timing solenoid valve SL5 is effective to produce a quiet switching of the pressures when the associated clutches and brakes are actuated or switched off, by supplying an oil pressure to the brake B1 through the two throttles 81 and 82 (delayed increase) or by bypassing the throttle 82 (rapid increase).

In the present embodiment, an output pressure from the linear solenoid valve SL6 (a proportional thereto pressure is determined by the memory pressure control valve 110 each of the memories 260 - supplied 290) substantially to the operating cycle of the current flow, which the valve SL6 energized inversely proportional. In detail, the back pressure when the working cycle of the linear solenoid valve SL6 causing current flow increases, the piston of each of the memory 260 - decreased 290, thereby causing the oil pressure of the engagement or tightening of the associated clutch or brake is reduced . In a particular shift mode or style that tends to produce shocks as a result of a shift, such shocks are prevented by determining a high cycle value for the SL6 linear solenoid valve.

When the timing solenoid valve SL5 operates to accomplish the 100% duty cycle, it connects a pilot pressure chamber of the throttle control valve 80 to a drain, whereby this valve 80 connects to the brake to a line connecting the throttles 81 , 82 B1 (memory 280 ) bypasses. As a result, when brake B1 is released, the pressure is reduced at a rapid rate, which releases the brake quickly (or, conversely, if the brake is applied, this process will occur quickly). However, when the timing solenoid valve SL5 is turned off to effect the 0% duty cycle, the oil pressure in the pilot pressure chamber of the throttle control valve 80 increases , causing this valve 80 to connect the connecting line between the throttles 81 and 82 from the brake B1 ( Memory 280 ) separates. As a result, the brake B1 is connected to the oil pressure line through the restrictors 81 and 82 , so that the pressure when the brake B1 is released is decreased at a delayed rate (the brake is released slowly), while when the brake B1 is applied, the Pressure rises at a slow rate (the brake is slowly applied).

Fig. 4 schematically illustrates an electrical control system that the energization of the shift solenoid valves SL1-SL3, the on-coming control solenoid valve SL4, the timing solenoid valve SL5 and the linear solenoid valve SL6 controls the hydraulic circuit illustrated in FIGS. 2a and 2b.

The heart of the electrical control system is constituted by a control device (control panel) 130 which comprises a microcomputer and an input / output interface, hereinafter referred to as ZE, which are arranged together on a printed circuit board. Connected to the input interface of the control device 130 are: a pulse generator 140 which generates electrical pulses at a frequency which is proportional to a rotational speed Ne of the input shaft 8 of the torque converter 1 (= output shaft of the motor); a pulse generator 141 which generates electrical pulses at a frequency proportional to a rotational speed Nt of the input shaft 23 (disk of C1) of the sub gear 2 ; a pulse generator 142 that generates electric pulses at a frequency proportional to a speed No of the output shaft (load drive shaft) 39 of the main transmission 3 ; a first speed range (LS) command switch 131 ; a fuel economy command switch 132 ; a fourth speed range (O / D) lock switch 133 ; a shift lever position detection switch 134 ; a sensor 135 that detects the temperature of the engine cooling water; a sensor 136 which detects the temperature of the oil in the oil reservoir 100 of the hydraulic circuit (see FIGS. 2a and 2b); a brake switch 137 ; a throttle valve opening sensor 138 ; an idle switch 139 ; an IGS switch; onboard batteries 163 and 164 .

Various input switches mentioned above are associated with associated indicator lights. When the first speed range command switch 131 is closed, thereby commanding the selection of the first speed range, a lamp 152 is lit. When the fuel economy command switch 132 is closed, thereby giving a command to drive the vehicle in a fuel economy mode, a lamp 153 is lit. When the fourth speed range lock switch 133 is closed, which commands the (O / D) to be locked accordingly, the lamp 154 is illuminated.

When the shift lever is in its neutral position N, the switch 134 will be in its N position and the lamp 155 will light. In the reverse position R of the shift lever, the lamp 156 is illuminated. The lamp 157 lights up in the parking position P of the shift lever. In the L position of the shift lever, the switch 134 is in its L position, in which the lamps 158 and 161 light up. In the S position of the shift lever, lamps 159 and 161 are lit, and in the D position of the shift lever, lamps 160 and 161 are lit. The lighting of the lamp 161 indicates that the shift lever is in a forward position. When the brake switch 137 is closed, which indicates that the brake pedal has been depressed, a lamp 162 lights.

Electrical pulses caused by the pulse generators 140 , 141 and 142 are converted into square waves of a predetermined level by the input interface before they are connected to an external interrupt input connection of the CPU in the control unit 130 . A binary signal that goes high H for a commanded condition when the associated switch is open and goes low L. which is equal to a commanded state in which the switch is closed, e.g. B. from the first speed range command switch 131 , the shift lever position detection switch 134 or the like. The input interface is supplied, in which a fluctuation or jump occurring between a change in the level of the signal is eliminated by a single To deliver rising or falling pulse, which is applied to the input terminal of the ZE in the control unit 130 . Analog signals from the cooling water temperature sensor 135 , from the oil temperature sensor 136 and from the throttle valve opening sensor 138 are subjected to a smoothing and level conversion gain in the input interface before they are fed to an analog signal input connection (A / D conversion input connection) of the ZE in the control unit 130 .

In response to the falling edge of a pulse generated by one of the pulse generators 140 , 141 and 142 , the CPU executes in the control unit 130 : an interrupt process to determine the engine speed Ne, the engine speed Nt of the output shaft 23 of the auxiliary transmission 2 and the engine speed No To determine load drive shaft 39 ; reading the open or closed state of the various input and detection switches, indicating the presence or absence of various commands; reading the cooling water temperature signal, the oil temperature signal and the throttle valve opening signal after their analog / digital conversion; Determining a speed range as indicated in FIG. 3; Performing a shift to the specific speed range; Detect any abnormality that occurs in the transmission; Detecting an irregularity in the water or oil temperature; Illuminate the abnormality indicator lamp 151 in a flickering manner, which corresponds to the specific abnormality whenever such is detected.

If a speed range is determined or a shift to a different speed range is effected (see FIG. 3) and if the locking is activated and deactivated, the CPU in control unit 130 performs such a process by changing and regulating the pressures supplied to the various clutches and brakes via an output interface from this ZE, that is, the solenoid valves SL1-SL3 are either switched on or off, the solenoid valves SL4 and SL5 are either switched on or off or their working cycle is regulated, and it becomes the working cycle for the current flow regulated by the linear solenoid valve SL6 in accordance with the opening angle R of the throttle valve and the driving speed No.

Controller 130 includes a memory backup circuit that maintains a memory activating voltage applied to the CPU even when the IGS switch is open, so that data written to the CPU's internal memory is retained. The input switches, lamps and various sensors are connected to a signal processing circuit which is fed by a single circuit which in turn is supplied by the batteries 163 and 164 via the ignition switch IGS. On the other hand, the solenoid valves SL1-SL6 are connected to the output connections of solenoid drivers, which are fed by a high-energy circuit, which in turn is supplied by the same batteries 163 and 164 via the ignition switch IGS. A predetermined voltage is supplied to a control signal input circuit of each of the solenoid drivers from the signal circuit. Consequently, in the time when the ignition switch IGS remains open, the energy consumption on the battery side by the memory fuse circuit and the CPU is minimal.

FIGS. 5A-5E are flow charts of a main routine of the CPU contained in the control unit 130 to execute their control operations. When power is supplied to controller 130 in a step (1) in Fig. 5a (hereinafter, a particular step or subroutine is designated with an assigned number in parentheses alone, without using the term "step" or "subroutine") , then the battery 163 is connected to the control device 130 . Internal registers, timers, and counters within the ZE are reset to their initial standby positions, while standby signal levels are applied to the output terminals (2). In this way, the valves SL1-SL6 are all switched off or de-energized. The battery 164 is connected in the manner shown in FIG. 4, and thus when the ignition switch IGS is closed and as long as it remains closed, the ZE performs a control operation of one cycle through steps (3) - (79) in is shown Fig. 5a-5e, and repeats this with a TP-period.

At the beginning of the control process of one cycle, a timer TP is started (3). Then input switch, the throttle valve opening sensor u. Like. Read (4). During data processing 1 (5), inputs read in this manner are written into registers referred to during the execution of a control program, and various parts are checked for any indication of an abnormality based on what this input data takes place. Whenever an abnormality is detected, the lamp 151 is made to light.

Then, during data processing 2 (6), the CPU in the controller 130 determines a current speed range based on the shift lever position, which is currently set by the automatic transmission shown in FIG. 1, and depending on whether the fuel economy command switch 132 is on - or is switched off, a possible shift type or a next speed range, on which an up / down shift from the current range, which is indicated by the content of the register PS for the current speed range, is to be carried out. In the embodiment in question, a reference vehicle speed (actually a group of reference vehicle speed values) which has a throttle valve opening as a parameter and which determines the need to perform a shift from a certain speed range (first, second or fourth gear) is used, is provided in two sentences, ie one that is used when the fuel economy mode is determined (economy mode data group: FIG. 12b) and another that is used when such driving is not determined (full throttle - or power mode data group: Fig. 12a). Accordingly, during data processing 2 (6), data indicating a possible shifting mode from the current speed range is determined as well as data indicating whether or not the economy mode is used to specify a specific reference vehicle speed group.

On the basis of the input data, which are read when the input (4) is read and written into the registers in the data processing 1 (5), the CPU in the control unit 130 then checks (7, 11) whether a 1.5- Speed range (LS) in view of the interrelation between the shift lever position (output from switch 134 ) and the presence or absence of a command for the 1.5 speed range (open or closed state of switch 131 ). In the embodiment in question, the 1.5 speed range is only achieved in the L position of the shift lever and with switch 131 closed. In this case, 1, which indicates the need for establishing the 1.5 speed range, is written into the register LSF (12). Otherwise the register LSF is deleted (13).

During a shift decision (14), the current speed range (contents of the current speed range register PS), the contents of the LSF register, and the input data from the fourth speed range lock switch 133 are referred to, and the 1.5 speed range becomes reproduced Data is written into a target or target speed range register DS when the content of the register LSF is 1, indicating the need to set the 1.5 speed range.

If the content of register LSF is 0, which indicates that there is no command, reference is made to data that specify a special reference travel speed group. Such data include those that are possible Specify switching type from the current speed range, and those that indicate whether the economy mode is used will or not.

Initially, a certain reference running speed group (one of the curves shown in solid lines in Figs. 12a and 12b) is specified from a highest (SRi speed range) of the speed ranges to which an upshifting from the current speed range (contents of the register PS) can be performed, and from which the first speed range is excluded when the lock switch 133 is closed. From this group, the value of a specific speed corresponding to the current throttle opening and representing a single point on the specific solid curve is selected and compared with a current vehicle speed No. When the vehicle speed No is equal to or greater than the reference vehicle speed value, which indicates the need for an upshift, data indicative of the SRi speed range is written in the target speed range register. In the other case, such a registration is not carried out, but a similar decision is repeated for a next lower speed range.

If the need for an upshift to any speed range higher than the current range is not determined, a particular reference vehicle speed group (one of the dotted curves in Figures 12a and 12b) is determined from a lowest (SRj) of the speed ranges to which a downshift from the current speed range can be made. From this group, a value of a particular reference speed, which represents a single point on the specified dashed curve, which corresponds to the current throttle valve opening, is selected and compared with the current driving speed No. If this vehicle speed No is equal to or lower than the reference vehicle speed, which indicates the need for a downshift, data characterizing the SRj speed range is written into the target speed range register DS. If the reference driving speed is exceeded, such a registration does not take place, but a similar decision is repeated for a next higher speed range.

Note that when the switch 133 is closed, indicating a lock of the fourth speed range, and when the content of the register PS for the current speed range indicates the fourth speed range, the third speed range is written in the target speed range register DS to perform a downshift from the fourth to the third speed range.

The ZE in the control device 130 then compares the current speed range (content of the register PS) with the content of the target speed range register DS (speed range to be achieved) and in the event that these do not correspond to one another, which indicates the need for a switching operation, the special, Speed range stored in the target speed range register DS is written into a next speed range register SS and into a next following speed range register SSN ( 15-16-17-18 ), if a switching operation is not currently being carried out. However, if a shift is in progress , the speed range in register DS is only written into the next speed range register SSN ( 15-16-17-36 ).

If a shift is not currently in progress, a timer TB is started ( 19 ) and 1, which indicates that the timer TB is active, is written to a register TBF ( 20 ). When the timer TB expires, the solenoid valves SL1-SL3 and the timing solenoid valve SL5 are energized to accomplish a special speed range which is written in the next speed range register SS. A timing timer is started to achieve a smooth, smooth transition of oil pressures to the clutches and brakes during a shift and data is entered into the various registers ( 44-54 ).

The determination of a switching time (TSO, TSE) in ( 64 ), the control of the linear solenoid valve SL6 (in 65 ), the control of the time control solenoid valve SL5 (in 66 ), the locking control (in 67 ) and the output control (in 68 ) are carried out one after the other in the order given. When the timer TP expires ( 69 ), the timer TP is restarted ( 3 ) so that the control process is triggered for the next one cycle. By repeating the control operation from one cycle with the TP period, the decision for a shift and the control over the up / down shift when the need for a shift is determined can be achieved smoothly in a time sequence.

The determination ( 64 ) of the switching time (TSO, TSE), which is shown in FIG. 5d, is explained in detail with reference to FIGS. 6a and 6b. The regulation ( 65 ) of the linear solenoid valve SL6 (see FIG. 5d) is shown in detail in FIGS. 7a and 7b. The regulation ( 67 ) of the timing control solenoid valve SL5 (see FIG. 5d) is shown in detail in FIGS. 8a, 8b and 8c. Nomenclatures that appear in these figures are explained below.
LSF: a register for storing information indicating the presence or absence of a command for the 1.5 speed range. If its content is "1", then there is a command for the 1.5 speed range, which means that "0" indicates the absence of such a command.
PS: a register for the current speed range, which has a content which indicates a current speed range of the automatic transmission of FIG. 1, including a park state P, a reverse state R, a neutral state N, a first, a 1.5- , a second, a third or a fourth speed range.
DS: a register for temporary storage of a speed range (a first, 1.5, a second, a third or a fourth speed range), which is determined by the shift decision to be accomplished.
SS: a next speed range register for storing a speed range (a first, 1.5, a second, a third or a fourth speed range) to be formed. A type of switching is determined by the content of the registers PS and SS.
SSN: a subsequent speed range register for storing a speed range, which is to be established following a shift from PS to SS.
TBF: a flag register that indicates whether the timer TB is in operation or not. Its content "1" indicates that the timer is working, and "0" indicates that the timer TB is not in operation or has not been started.
TEF: a flag register that indicates whether the timer TE is in operation or not. Its content "1" indicates that the timer is working, and "0" indicates that the timer TE is not in operation or has not been started.
PUF: a flag register for an upshift under power (gas supply). Its content "1" indicates that there is an upshift or shift to a higher speed range under the condition that a driving load is applied to the engine, while "0" a downshift or a shift to a lower speed range or an upshift under no load condition on the engine (gas supply switched off, which means that the vehicle is idling or coasting or there is an engine braking process).
TEIF: a flag register that indicates the start of a switching time. The content "1" indicates that there is a state immediately after the timer is started.
TEFF: a flag register that indicates that a state exists immediately after the switching period has ended. The content "1" indicates that it is in a time interval that follows the expiration of the timer TE, but is before the expiration of a timer T2D.
i, j: a number register in which the number of times is entered with which a power or full throttle state (a drive load is imparted to the engine) or a powerless state (gas supply switched off) has been determined.
k: a number register for storing a number of times that the inequality is Nt1 <Nt2, where Nt2 represents a current Nt, while Nt1 denotes the value of Nt that previously prevailed on a TP, which is used to determine the start of a shift becomes.
TTF: a flag register which marks the end of the determination of the switching time. Its content "1" indicates that the determination of the switching time TT has ended, while "0" indicates that the determination of the switching time has not yet been completed.
TCR: a flag register that indicates an abnormality in the switching time TT when it has a value of "1".
CR: a register into which data are entered that indicate the suitability or adequacy of the switching time TT.
POI: a flag register that indicates the need to determine an output value for the duty of the linear solenoid valve SL6, indicating the completion of the determination of the output value when the content is "1".
ADMEM: a register for storing a learned value for the working cycle of the linear solenoid valve SL6.
ADIN: a register for storing a calculated value of the working cycle for the linear solenoid valve SL6.
ATIN: a register for storing a calculated value of the working cycle for the time control solenoid valve SL5.

In the following, the control operation of the invention Embodiment explained in detail.  

(1) Determination of Ne, Nt, No

Immediately after the ignition lock switch IGS is closed, the CPU starts in the control unit 130 of a program timer with three time limits (timers 1-3), which enables an interrupt process in response to a pulse supplied by one of the pulse generators 140 , 141 and 142 . For example, in response to the falling edge of a pulse caused by the pulse generator 140 , the CPU enters an interrupt process in which a count register 1 is incremented, followed by a check as to whether the timer 1 has expired or not. If the timer has not expired, the CPU returns to a special control process that is accepted before the interrupt process begins. If the timer 1 has expired, the content of the counting register is written into a register Nef, which is used to calculate a rotational speed Ne, while the timer 1 is started again and the CPU returns to the previous control. In response to the falling edge of a pulse caused by the pulse generator 141 , the CPU enters an interrupt process in which a counter register 2 is incremented by one, followed by a check as to whether the timer 2 has expired or not. If the timer has not expired, the CPU returns to its control that existed before the interrupt operation started. If the timer 1 has expired, the content of the counting register 2 is written into a register Ntf for calculating a speed Nt. The timer 2 is started again and the ZE returns to its previous control. In response to the falling edge of a pulse generated by the pulse generator 142 , the CPU enters an interrupt process in which a count register 3 is incremented by one, followed by a check as to whether the timer 3 has expired or not. In the negative case, the CPU returns to its previous control, which existed before the interrupt process started. If, on the other hand, the timer 3 has expired, the content of the counting register 3 is written into a register Nof for calculating a rotational speed No, the timer 3 is started again and the CPU returns to its previous control.

As a result of the execution of these interrupt processes, the number of pulses generated by the respective pulse generators 140 , 141 and 142 during a last given time limit is written into the registers Nef, Ntf and Nof. During data processing 2 from FIG. 5a ( 6 ), the CPU in the control unit 130 calculates speeds Ne, Nt and No on the basis of data stored in the registers Nef, Ntf and Nof, which represent the number of pulses generated in a specific time limit, and writes them into the speed registers Ne, Nt and No, respectively. In this way, the last or updated speed information is maintained in these speed registers.

(2) Summary of timing from the determination the need for a shift to completion of the switching process

For an upshift, timer TB is started ( 19 ) when the need for a shift is decided as indicated by the white triangle in Fig. 9a. When the timer runs out, the energization of the solenoid valves SL1-SL3 is switched so that a next speed range is established ( 43-48 ). This time is indicated by a black triangle in FIG. 9a and is referred to as "switching output". For example, for a circuit from 2 → 3, the excitation / de-excitation of the solenoid valves SL1-SL3 is regulated in accordance with the D-3 line shown in FIG. 3. Then the timer TE is started ( 46 ).

In this embodiment, TB = 0.2 s. TE is chosen equal to 0.8 s for a downshift from 4 → 3 and 1.5 s for other upshifts and downshifts. This TE value is set to be greater than a sum TSE of a time TSO which elapses from the output of the switching output ( 48 ) until the actual mechanical switching process is initiated, and a time TT from the initiation of the mechanical switching until its completion. It should be noted that a mechanical switching time represents the real switching time.

(3) Determination of a mechanical switching time TT

A mechanical switching time TT changes with wear on friction elements of the automatic transmission and with one associated with driving the vehicle Burden. If such a time is too short, it will be greatest Probability of a shift shock or jerk to occur. On the other hand, if this time is too long, an overspeed may occur of the engine or poor acceleration the result his. In view of these disadvantages, the mechanical one Shift time a measure of the value or preference of the automatic transmission.

For the present invention, for an upshift from 1 → 2 or 2 → 3, the mechanical switching time TT is determined after the timer TE has started. This determination is shown in detail in Fig. 6a. In particular, the initiation of a mechanical circuit is determined in such a way that it must take place after a reduction in the speed Nt following two or more TP periods, and the determination of the mechanical switching time TT is initiated at ( 81-87 ). A mechanical circuit is determined to terminate in units of a TP period in response to a decrease in a new Nt value that is 2.5 RPM or more less than a previous Nt value. The value TT thus set is written in the register TT ( 88-90 ), and 1 is written in the flag register TTF ( 91 ) to indicate the completion of the determination of the time TT.

(4) Determine an error in the transmission using the mechanical switching time TT

When a load associated with driving the vehicle is abnormally high, when frictional members such as clutches or brakes are subjected to a greater degree of wear in the automatic transmission of Fig. 1, when some kind of abnormality develops within the transmission mechanism or the vehicle drives irregularly, or if a fault or an abnormality appears within the transmission mechanism, the mechanical shift time TT will become excessively long or extremely short, which creates the possibility of a shift shock or an overspeed of the engine. In order to counteract this, eight areas or zones are determined according to the invention - around a basic switching time (fixed value) TS using the throttle valve opening R as a parameter, as shown in FIG. 10d. A switching time TT which is determined is checked to see which zone it is in ( 92 in Fig. 6b), and if it is in a zone or, 1 is written to the abnormality register TCR ( 103 ), which is a Anomaly is indicated by the lamp 151 lighting up ( 104 ). If the switching time TT is determined to be in a zone or lying, the number of times An with which this is determined is counted. If this number An is less than 4, 2 is written into the degree of adequacy register CR ( 99-102 ). If the number of times is equal to or greater than 4, an operation is carried out in the same way as if the switching time is in a zone or. If the switching time falls in a zone or, the abnormality is deleted ( 96 , 97 ) and 1 is written into the degree of adequacy register CR ( 98 ). If the switching time is in a zone or, the abnormality register is cleared ( 93 , 94 ) and 0 is written into the register CR while clearing this register ( 95 ). As a result, the data in the registers CR and TCR reflect the degree of appropriateness or suitability of a switching time.

(5) Multiple switching

If there is a change in the throttle valve opening or the driving speed No during a time interval (TB + TE) from deciding the need a switching operation until the actual termination of this Switching process is present, it may be necessary to switch to a speed range that during that of the interval (TB + TE) updated speed range is different.

When the necessity for a switching operation during an interval TB, which means the time interval from the start of the timer TB until its expiration, is determined, a speed range for which the necessity for the completion has been determined is written into the next speed range register SS ( 23 in Fig. 5b). As a result, the speed range that was written to this register SS immediately before the TB interval occurs is now cleared as a result of this writing, and therefore that for the speed range when the timer TB expires ( 48 in Fig. 5c ) available switching output is effective to establish a speed range that is determined during the TB interval.

If the necessity of a switching operation during the switching time or during the time when the timer TE is running is decided after the TB interval ( 15-16-17 ), it should be noted that the immediately preceding switching operation has ended. Accordingly, the next speed range to be accomplished is written into the next speed range register SSN ( 36 ), and when the timer TE expires, a switching output is output to output the speed range for which the need for a switching operation has been recognized ( 41-42 -55-56-57-58-44 to 48 ). In other words, this means that the switching to the speed range takes place immediately after the previous TE without adding another TB interval.

(6) Determine an upshift under power

A shift shock is likely to occur during a power shift (TE), while an engine overspeed is likely to occur during a powerless upshift. Accordingly, during an upshift (TE), the rate at which the oil pressure is changed is determined in a manner that corresponds to the condition with or without power (full throttle or idle gas), thereby avoiding the occurrence of a shift shock or an overspeed of the engine. For this purpose, the determination of the condition with or without performance is necessary. This is preferably done immediately before shifting (TE), since the throttle valve opening R, the driving speed No, the speed of the engine Ne and the speed Nt of the output shaft of the auxiliary transmission 2 change from time to time. Accordingly, according to the invention, the determination of the state under or without power is carried out during the TB interval ( 16-23 to 35 ). It should be noted that the decision to use empty gas is also made during the TE interval ( 17-36-30 to 35 ).

Specifically, when Ne ≧ Nt applies during the TB interval (TBF = 1) during an up shift as a switching mode, the content of the register number i is incremented by one (16 - 23-24-27-28-29). If the content of register i is equal to or greater than 2, 1, which represents the power upshift, is written into the flag register PUF ( 31 ). If this happens in the TB or TE interval, the content of the number register j is decremented by one if Ne <Nt ( 32, 33 ), and if the content of the register j is equal to or greater than 2, it will Flag register PUF deleted ( 35 ). If the register is deleted, this means that the no-power operating mode prevails. In this way, if the shift type is an upshift, the state with or without power is determined in succession until the timer TB expires, whereupon the powerless state (empty gas) is recognized. If the power state is decided, the content of the register PUF is set equal to 1, while it is equal to 0 when the powerless state is recognized. Accordingly, when the switching output is given ( 48 ), information is stored in the register PUF which indicates whether the condition under power is present or not.

(7) steady state control of the working cycle for the linear solenoid valve SL6 ( Fig. 7a and 7b)

The linear solenoid valve SL6 develops an oil pressure that is substantially proportional to the magnitude of the current flowing through its electrical coil, and an oil pressure proportional to this pressure is applied to the accumulators 260-290 by the accumulator pressure control valve 110 as the piston back pressure. The relationship between the magnitude of the current flow through the coil of the solenoid valve SL6 and the back pressure on the piston of the accumulators 260-290 is shown graphically in FIG. 9b. According to the invention, the size of a current flow through the solenoid valve SL6 is determined by the working cycle. The relationship between the cycle and the mean current flow is also shown in Fig. 9b.

The linear solenoid valve SL6 is used as a replacement for a conventional throttle valve, which is used in the conventional hydraulic circuit, which is mechanically connected to the rotary shaft of a throttle valve and responds to the control pressure, which in turn depends on the speed of the engine, so that a line pressure can be adjusted, which corresponds to the throttle valve opening and the control pressure. At a predetermined point in time, principally during the TE interval in a special manual transmission, the CPU in the control unit 130 regulates the work cycle in order to control the back pressure, as explained in the following paragraph ( 8 ), so that the back pressure of the accumulators 260 -290 is regulated so as to prevent the occurrence of a shift shock . At other times, however, the ZE causes excitation with a current level (or with a corresponding work cycle), as shown in FIG. 9c, ie in a manner corresponding to the throttle valve opening R and the speed Nt of the output shaft of the auxiliary transmission 2 . In particular, a pressure which corresponds to the throttle valve opening R and the rotational speed Nt is applied to the accumulators 260-290 and to the 2 → 3 changeover valve 60 ( 115 , 116 in FIG. 7a).

(8) The back pressure control on the accumulators during a switching operation ( Fig. 7)

For an upshift 1 → 2, from 2 → 3 or from 3 → 4 under power (PUF = 1), in order to prevent the occurrence of a shift shock, during the shift interval (TE: see FIG. 9a), if it currently prevails , the working cycle of the linear solenoid valve SL6 or the back pressure on the piston of the accumulators 260-290 essentially determined as follows:

K1 × K2 × [K3 (1-TT / TS) + ADMEM]

Here are:

K1 is a milieu or environment change correction factor which is given by K1 = K11 + K12, K11 representing an oil temperature correction factor and K12 a correction factor corresponding to the throttle valve opening,
K2 is a correction factor corresponding to the type of shift and the throttle valve opening, and
K3 is a correction factor that corresponds to the switching type. The values of these correction factors are shown in FIGS. 10a, 10b, 10c and 10d.

The correction factor K11 is calculated in a manner that corresponds to the temperature determined by the oil temperature sensor 136 ( 118 in FIG. 7b). The correction factor K12 is calculated in a manner corresponding to the throttle valve opening R ( 118 ). The correction factor K2 is calculated in a manner corresponding to the throttle valve opening R and the type of shifting ( 120 ). The correction factor K3 corresponds to a 1: 1 relationship to the switching type, and consequently a value corresponding to the switching type or the content of the registers PS and SS is selected.

TT represents the last mechanical switching time TT or an indication which is determined by the flow diagram shown in FIG. 6a and is stored in the register TT, while TS denotes a basic switching time (fixed value). ADMEM represents the work cycle that is determined by the correction that occurs as a result of a learning effect.

The CPU in the control unit 130 calculates

K1 × K2 × [K3 (1-TT / TS) + ADMEM]

in the manner described below. Initially, the learned value ADMEM or the content of the register ADMEM is converted into an appropriate value [K3 (1-TT / TS) + ADMEM] in a way that corresponds to the last mechanical switching time TT and the prevailing switching mode, after which this value is converted into the ADMEM register is written to update ( 126 ). The current environmental factor K1 (= K11 + K12) and the correction factor K2 are multiplied by the data stored in the register ADMEM, and the product is output as an output working cycle which is written into an output register ADIN which is intended for the linear solenoid valve SL6 ( 128 ). During the output control ( 68 in FIG. 5d), the ZE in the control unit 130 outputs an on / off signal with the working cycle, which is reproduced by the data stored in the output data register ADIN, to the solenoid driver, which is assigned to the excitation of the solenoid valve SL6 is.

When the batteries 163 and 164 are connected to the control device 130 , energy is supplied to it, and when the ignition lock switch IGS is subsequently closed, control for the automatic transmission shown in FIG. 1 is enabled or triggered for the first time. If this triggering occurs, a learned value is not available for the working cycle of the SL6 solenoid valve. As a result, the value 0 is contained in the POI register. Accordingly, if the content of the POI register is 0, an initial value (fixed value) is written in the ADMEM register to write 1 in the POI register, indicating that the initial value has been established ( 122 , 123 ). Since the learned value does not have to be updated at this time ( 126 ), such an update does not take place and ADMEM multiplied by the environmental factor is used to determine the working cycle ( 124 ).

As mentioned in paragraph (4) above, in the event of an error occurring within the transmission, the shift time TT is shifted from the reference value TS. As a result, it is inappropriate to modify the learned value for the working cycle ( 126 ). In this respect, reference is made to the adequacy of the switching time TT (contents of the registers TCR and CR), and if the switching time TT is in one of the zones,, or ( FIG. 10d), the learned value ( 126 ) is not modified, however the prevailing working cycle (ADMEM) is corrected by a value which corresponds to a change in the milieu or the environment in order to determine the working cycle for the linear solenoid valve SL6 ( 125-128 ). Thus, the learned value of the working cycle is only modified if the switching time TT is in one of the zones. This ensures a uniform automatic pressure control (or correction of the working cycle) as a time sequence only within a suitable range of the shift behavior (TT) of the automatic transmission, in order to bring the shift time TT closer to the suitable value TS.

FIG. 11 shows a change in a time sequence in the oil pressure of the brake B1 and in the oil pressure of the clutch C2 during a 2 → 3 shift. In this figure, the oil pressure of the brake B1 is indicated with a solid line for a power condition and with dashed lines for a powerless condition. The oil pressure for the clutch C2 is shown for the performance state with a thick, solid line and dashed single and colon lines, while the oil pressure for the inoperative state is not shown.

Depending on the working cycle of the linear solenoid valve, which is caused by the back pressure control of the accumulator is obtained, which is only during of the performance state, the oil pressure in the clutch increases C2 rapid on and the switching time TT is short when the work cycle is low, as shown by the dashed colon line is. In contrast, the increase occurs for a high work cycle of the oil pressure of clutch C2 slowly, as by the single point Line is indicated, which causes an increase in the switching time TT becomes. During the powerless state is in the time of the switching process the working cycle made 0, which is why the oil pressure clutch C2 increases as quickly as possible and the neutral range shown shorter than shown in the drawing.

In this respect it can be seen that the mechanical switching time TT depends on the work cycle and assumes a longer value for a higher work cycle and a shorter value for a lower work cycle. During the back pressure control of the accumulator, a correction + K3 (TS-TT) / TS or a correction corresponding to a deviation of the current switching time TT from the reference value TS is added to the previous working cycle in order to generate the next working cycle ( 126 in FIG. 7), with which a modification of the learned value is carried out. In this way, the mechanical switching time TT converges to the reference value TS. In this respect, the work cycle is automatically adjusted in accordance with a change in the engagement or tightening behavior of the frictional engagement members such as the clutch C2 and the brake B1 in response to their abrasion to actually keep the shift time at the reference value TS so that the occurrence of a Switching shock is prevented.

Claims (2)

1. Hydraulic control system for an automatic transmission, which is arranged between an output shaft ( 8 ) of an engine and a load drive shaft ( 39 ), with a hydraulic circuit for the selective supply of an oil pressure to or for the selective discharge of an oil pressure from brakes (B0, B1, B2) and clutches (C0, C1, C2) of the automatic transmission ( 1, 2, 3 ), with accumulators ( 260, 270, 280, 290 ) in the hydraulic circuit, which are connected to the brakes (B0, B1, B2) and clutches (C0, C1, C2) are connected to an electrically excited pressure regulating valve (SL6) for regulating the back pressure at the accumulators and with a accumulator pressure control device which controls an excitation level of the pressure regulating valve (SL6) to regulate the counter pressure at the accumulators during a switching operation of the automatic transmission ( 1, 2, 3 ) to regulate, characterized in
that a shift time determining device ( 130 ) determines a time interval (TT) from the triggering until the end of a shift in one of the mechanical clutches (C0, C1, C2) of the automatic transmission ( 1, 2, 3 ) during a shifting process,
that the accumulator pressure control device ( 130 ) responds to the time interval (TT) determined by the switching time determination device,
that the accumulator pressure control device ( 130 ), when the determined time interval (TT) lies in a given range (zones 3 to 6 Fig. 6b or 10d), approximately in the middle of which a reference switching time (TS) lies, the excitation level of the Pressure control valve (SL6) updated in dependence on the determined time interval (TT) such that the excitation level is updated in a direction shortening the time interval if the determined time interval (TT) is longer than the reference switching time (TS), and that the excitation level in a direction extending the time interval is updated if the determined time interval (TT) is shorter than the reference switching time (TS), and
that the accumulator pressure control device ( 130 ), when the determined time interval (TT) lies outside the given range (zones 3 to 6 and 10d), leaves the excitation level of the pressure control valve (SL6) unaffected by the determined time interval (TT). 2. Hydraulic control system according to claim 1, characterized in that the accumulator pressure control device ( 130 ) when the determined time interval (TT) outside the given area (zones 3 to 6 in Fig. 6b and 10d) in a second area (zones 2 and 7 in FIGS. 6b and 10d), the number of these events counts and, if this number is equal to or greater than a predetermined value, a warning device ( 151 ) is energized, and that the accumulator pressure control device ( 130 ) then, if the determined time interval (TT) lies in a third area (zones 1 and 8 in FIGS. 6b and 10d) which is farther from the reference switching time (TS) than the second area (zones 2 and 7 in FIGS. 6b and 10d), the warning device ( 151 ) is energized.