JP4248036B2 - Intake valve control device and control method for turbocharged internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine with a turbocharger used as an engine for automobiles, and more particularly to a gasoline engine, and more specifically, an intake valve control device and control method for an internal combustion engine with a turbocharger having a variable valve mechanism. About.
[0002]
[Prior art]
A turbocharger that drives a compressor on the same axis by an exhaust turbine has been widely used in an automobile gasoline engine or the like. The turbocharger is characterized by its A / R (as shown in FIG. 1). A is a cross-sectional area of the narrowest part of the scroll, and R is a distance from the shaft center). FIG. 2 shows the difference in torque characteristics depending on the A / R setting. As shown in the figure, when the A / R is large, the turbocharger is more efficient at a high speed with a large exhaust flow rate. Therefore, the maximum output performance is good, but on the other hand, the turbocharger speed does not increase at a low speed when the exhaust flow rate is low, so the rise of the supercharging pressure is delayed, and the low-speed torque under steady conditions is low. Of course, the responsiveness of the turbocharger at the time of transition such as starting is low, and the drivability is deteriorated. Therefore, in an internal combustion engine with a turbocharger of a general automobile, the A / R setting of the turbocharger is set to be relatively small with an emphasis on responsiveness.
[0003]
Many of the turbocharged internal combustion engines in practical use are combined with a valve operating mechanism having a fixed characteristic, and the opening / closing timing of the intake valve is always constant. Normally, the intake valve closing timing is set around 50 ° after bottom dead center (ABDC).
[0004]
On the other hand, various types of variable valve mechanisms that variably control the opening / closing timing of the intake valve of the internal combustion engine have been proposed, and some of them have already been put into practical use. For example, it is possible to change the intake valve opening / closing timing in the same direction by relatively shifting the phase relationship between the camshaft and the crankshaft that drives the camshaft, or to two cams having different cam profiles. A device or the like in which two lifter arms to be driven are provided and the valve lift characteristics are switched between two types by selectively switching the rocker arm with which the intake valve is actually interlocked is put into practical use. Further, in Japanese Patent Laid-Open No. 6-185321, the valve lift characteristics can be continuously variably controlled by rotating the cylindrical camshaft at an inconstant speed by applying the principle of the inconstant speed shaft coupling. A variable valve mechanism is disclosed.
[0005]
[Problems to be solved by the invention]
As described above, in many turbocharged internal combustion engines, the A / R of the turbine is set to be relatively small. When the A / R is thus small, the inlet of the turbine is throttled. Therefore, the exhaust pressure upstream of the turbine is at a high level. In FIG. 2, after the supercharging pressure reaches the target level, the wastegate valve for bypassing the exhaust opens and the increase in the exhaust pressure is suppressed. However, the exhaust pressure level at this point is already at a considerably high level. (See FIG. 4). Thus, when the exhaust pressure level is high, (1) output decrease due to increase in exhaust work in the exhaust stroke, (2) intake amount (filling rate) decrease due to increase in residual gas amount, (3) high temperature residual There arises a problem that the intake air temperature rises due to the gas and the knock resistance deteriorates.
[0006]
The decrease in output (1) and the decrease in filling rate (2) can be compensated for to some extent by increasing the supercharging pressure. However, regarding the deterioration of knock resistance (3), even if an intercooler is installed, the residual gas temperature in the combustion chamber cannot be lowered, so there is no effect and the compression ratio is set low to prevent knocking. I have to. This reduction in the compression ratio causes a deterioration in fuel consumption.
[0007]
An object of the present invention, in an internal combustion engine turbocharged, the variable valve mechanism you variably controls the closing timing of the intake valve in accordance with the opening timing of the waste gate valve was set large turbine A / R By combining with a turbocharger, it is possible to set a high compression ratio of the engine while preventing occurrence of knocking . In addition, it aims to make up for both power performance improvement and fuel efficiency improvement by compensating for lowering of torque at low speed and worsening of responsiveness caused by setting A / R large by optimizing the intake valve closing timing. To do .
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an intake valve control device according to claim 1 of the present invention includes a variable valve mechanism that can control the closing timing of the intake valve by variably controlling the operating angle of the intake valve. In addition, in an internal combustion engine with a turbocharger comprising a turbocharger,
The turbocharger is the narrowest part of the scroll of the turbine so that the exhaust pressure at the turbine inlet is approximately the same level or lower than the supercharging pressure at the compressor outlet in the full load region before the wastegate valve opens. The supercharging pressure characteristic is set by a value (A / R) obtained by dividing the cross-sectional area A by the distance R from the center of the turbine shaft .
When the waste gate valve is closed, the target value of the closing timing is searched from the throttle opening and the engine speed using the first control map, and when the waste gate valve is opened. Using the second control map, the target value for the closing time is searched from the boost pressure and the engine speed,
The first control map has a characteristic that the target value changes mainly depending on the engine speed, and the intake valve closing timing is set so as to approach the bottom dead center in the low speed range.
The second control map has a characteristic that the target value changes mainly due to the supercharging pressure, and in the high speed range, the intake valve closing timing is more retarded so that the actual compression ratio becomes smaller than the actual expansion ratio. It is characterized by being set to.
[0009]
Further, the intake valve control method according to claim 7 includes a variable valve mechanism capable of controlling the closing timing of the intake valve by variably controlling the operating angle of the intake valve, and further includes a turbocharger. In an internal combustion engine with a turbocharger,
The supercharging pressure characteristics of the turbocharger are calculated by dividing the cross-sectional area A of the scroll scroll of the turbine by the distance R from the turbine shaft center (A / R). In the load region, set the exhaust pressure at the turbine inlet to be approximately the same level or lower than the supercharging pressure at the compressor outlet,
When the waste gate valve is closed, the target value of the closing timing is searched from the throttle opening and the engine speed using the first control map, and when the waste gate valve is opened. The second control map is used to search for the target value for the closing timing from the boost pressure and the engine speed,
The first control map has a characteristic that the target value changes mainly depending on the engine speed, and the intake valve closing timing is set so as to approach the bottom dead center in the low speed range.
The second control map has a characteristic that the target value changes mainly due to the supercharging pressure, and in the high speed range, the intake valve closing timing is more retarded so that the actual compression ratio becomes smaller than the actual expansion ratio. It is characterized by being set to.
[0010]
The supercharging pressure characteristic as described above is set by adjusting the A / R of the turbine of the turbocharger, for example, as in claim 2.
[0011]
In the third aspect of the present invention, the supercharging pressure characteristic is set to be satisfied in the entire load region of the engine steady condition.
[0012]
That is, when the intake valve closing timing is fixedly set at, for example, about 50 ° after bottom dead center, it may be in the middle speed range, but in the low speed range, the inertia effect of the intake is small, so the cylinder is in the initial stage of the compression stroke. The intake air flows backward from. In contrast, in the present invention, the intake valve closing timing, in the institutional low speed range, for example, early in the 20 ° after bottom dead center, the medium-speed range-high speed range, for example 40 ° to 60 ° about after bottom dead center Delay. By doing so, the intake backflow at the beginning of the compression stroke can be prevented at low speeds, so that the low speed torque can be improved. In addition, since the rising characteristic of the rotational speed of the turbocharger is also improved by increasing the intake air amount and thus the exhaust amount, the operability is not deteriorated even with a turbocharger having a large A / R of the turbine.
[0013]
By the way, in order to reduce the amount of residual gas, it is better that the exhaust pressure is lower, and it is necessary to increase A / R. On the other hand, if A / R is excessively large, it does not function as a supercharger. It is important to select an A / R in the vicinity of the limit that does not deteriorate knockability. In the present invention, the supercharging pressure characteristic of the turbocharger is set so that the exhaust pressure at the turbine inlet becomes substantially the same level as the supercharging pressure at the compressor outlet in the full load region before the wastegate valve opens. As a result, the optimum A / R is obtained.
[0014]
FIG. 3 shows the change in residual gas amount (calculated by calculation) when the exhaust pressure is increased (assuming that A / R is gradually reduced) when the intake pressure (supercharging pressure) is constant. Stuff). This figure summarizes the characteristics when the valve overlap is 10 °, 20 °, and 30 °. When the intake pressure (supercharging pressure Pc) is constant, the exhaust pressure Pe and the intake pressure ( Under the condition where the supercharging pressure Pc) is equal, there is no difference in the residual gas amount due to the size of the valve overlap, and the change in the residual gas amount is greatly affected by the valve overlap in the region before and after that. The reason is that the change in the amount of residual gas due to the backflow of the exhaust gas due to the differential pressure between the exhaust pressure Pe and the intake pressure is affected by the valve overlap. Even with a normal valve overlap of about 20 °, In the region where the exhaust pressure Pe is larger than the intake pressure (the region on the right side of the Pe = Pc line), the residual gas amount increases rapidly. On the other hand, a condition where the exhaust pressure Pe is lower than the intake pressure (region on the left side of the line Pe = Pc) is conceivable. In this case, new air blows from the intake system to the exhaust system. However, when a turbocharger is provided, it is unlikely in principle that the intake pressure (supercharge pressure Pc) greatly exceeds the exhaust pressure Pe, and in the normal case, the A / R of the turbine is set large. However, as shown in FIG. 5, the supercharging pressure Pc is only slightly higher than the exhaust pressure Pe. In addition, when A / R is small, as shown in FIG. 4, the exhaust pressure Pe greatly exceeds the supercharging pressure Pc. For this reason, when the exhaust pressure Pe is decreased by increasing A / R, the influence of the exhaust pressure Pe is limited only to the density change in the region of the exhaust pressure Pe <the intake pressure (supercharging pressure Pc) in FIG. The change in the residual gas amount has a characteristic as indicated by a solid line a regardless of the size of the valve overlap.
[0015]
Therefore, if the exhaust pressure level is set so as not to exceed the supercharging pressure before the wastegate valve is opened, that is, under the condition that the total amount of exhaust gas passes through the turbine, the residual gas amount level can be kept low. This is possible and the knock resistance is improved, so that the compression ratio can be set high even in an internal combustion engine with a turbocharger.
[0016]
Note that, in the region on the high speed side after the wastegate valve is opened, the supercharging pressure is limited to a predetermined value, so the exhaust pressure is inevitably higher, but the larger the A / R is set. Since the opening operation of the wastegate valve is performed on the high speed side and knocking is less likely to occur at high speed, the characteristics in the region until the wastegate valve is opened are very important.
[0017]
An important point in the present invention is that a variable valve mechanism that changes the intake valve closing timing by variably controlling the operating angle is used. In particular, as in claim 4, it is desirable that the intake valve opening timing be kept substantially constant, and that the intake valve closing timing change relatively greatly with variable control of the operating angle. As a result, it is possible to control to the optimal intake valve closing timing without greatly changing the valve overlap.
[0018]
By the way, the relationship of FIG. 5 and the like described above is in the full load region of the steady condition where the engine load, the rotational speed, the temperature, etc. are substantially constant. Even if the exhaust pressure level rises higher than normal and the A / R is set to the characteristics described above, the exhaust pressure significantly increases the boost pressure when the wastegate valve does not open. A phenomenon exceeding that occurs. Even in the actual usage mode, the frequency of the start acceleration is high as a characteristic of the turbocharged internal combustion engine. However, the impact of compression ratio on knocking is most severe in steady full load conditions. The reason is that by continuing full load operation for a certain period of time, the temperature of each part has been raised to the maximum, which is the most severe condition thermally. The knock resistance is most affected by this thermal condition. Therefore, if the compression ratio is optimally given in the entire load region under a steady condition where the engine load, rotation speed, temperature, or the like is substantially constant, there is no problem at the time of transient such as a short start acceleration.
[0019]
Further, in the present invention, in the full load region of the high-speed side than the wastegate valve open condition of the upper Symbol turbocharger, the actual compression ratio to control the intake valve closing timing so as to be smaller than the actual expansion ratio. That is, the actual compression ratio is lowered by delaying the closing timing of the intake valve from the normal time in the high speed region where the supercharging pressure has reached a predetermined value. Thereby, it becomes what is called a mirror cycle, and knock resistance improves.
[0020]
Further, as in claim 5 , there may be provided means for detecting the boost pressure upstream of the intake valve, and the intake valve closing timing may be controlled in accordance with the engine operating conditions including this boost pressure.
[0021]
In order to realize the variable control of the intake valve closing timing as described above, an intake valve control device according to a sixth aspect includes a drive shaft that rotates in synchronization with the rotation of the engine as the variable valve mechanism, A camshaft disposed coaxially with the drive shaft and having a cam on the outer periphery for driving the intake valve; and one of the camshafts provided at an end of the camshaft and having an engagement groove formed in a radial direction Swing between the flange portion and the other flange portion provided on the drive shaft side so as to face the one flange portion and having an engagement groove formed along the radial direction. An annular disk arranged freely, pins projecting in opposite directions on both sides of the annular disk, and engaging with the engaging grooves of the flanges, respectively, and the annular disk in an engine operating state Drive mechanism that swings according to Eteiru.
[0022]
In this configuration, when the rotational center of the annular disk is concentric with the center of the drive shaft and the camshaft, the drive shaft and the camshaft rotate at the same speed, and when the annular disk is in the eccentric position. Both rotate at unequal speed. Accordingly, the valve lift characteristic of the intake valve continuously changes in accordance with the position of the annular disk, and the opening / closing timing and operating angle of the intake valve change. In addition, if the same phase point where the phases of the drive shaft and the camshaft always coincide is made coincident with the valve lift start timing, the intake valve opening timing is always constant as in the fourth aspect.
[0023]
【The invention's effect】
As described above, according to the present invention, in an internal combustion engine with a turbocharger, it is possible to use a turbocharger in which the A / R of the turbine is set large, and the compression ratio of the engine is improved by improving the knock resistance. Can be set high. And it is possible to optimize the torque drop at low speed and the deterioration of responsiveness caused by setting the A / R of the turbine large by controlling the intake valve closing timing in accordance with the opening timing of the wastegate valve. In addition, it is possible to reliably prevent the occurrence of knocking by effectively discharging the residual gas in a relatively low speed region before the opening of the waste gate valve .
[0024]
Further, in the present invention, knock resistance can be further enhanced as a so-called mirror cycle in a relatively high speed region after the waste gate valve is opened .
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0026]
FIG. 6 shows an embodiment of an internal combustion engine with a turbocharger according to the present invention. A plurality of cylinders 2 are arranged in series on a cylinder block 1 and a piston 3 slides in each cylinder 2. It is movably fitted. The cylinder head 4 covering the top of the cylinder 2 is formed with an intake port 6 that is opened and closed by an intake valve 5 and an exhaust port 8 that is opened and closed by an exhaust valve 7. A turbocharger 9, specifically a compressor 9a, is interposed upstream of the intake passage connected to the intake port 6. An exhaust turbine 9 b that drives the compressor 9 a is interposed in an exhaust passage downstream of the exhaust port 8. Further, an exhaust bypass passage 10 is provided between the outlet side and the inlet side of the exhaust turbine 9b, and an electronically controlled waste gate valve 11 is interposed therein. Further, a supercharging pressure sensor 12 for detecting a supercharging pressure is disposed on the outlet side of the compressor 9a, that is, on the upstream side of the intake port 6.
[0027]
The wastegate valve 11 is opened on the engine high speed side so as to keep the supercharging pressure at a predetermined characteristic, and is specifically controlled by the control unit 13. The control unit 13 receives detection signals such as the engine speed, load, cooling water temperature, lubricating oil temperature, and supercharging pressure by the supercharging pressure sensor 12, and the supercharging pressure is a characteristic according to engine operating conditions. Is controlling.
[0028]
In the turbocharger 9, the A / R of the turbine 9b is set to a relatively large value. As a result, the compression ratio of the engine can be set high. Specifically, the supercharging pressure characteristics, specifically A, are set so that the exhaust pressure at the turbine inlet is substantially the same as the supercharging pressure at the compressor outlet in the full load region before the waste gate valve 11 is opened. / R is set. The exhaust pressure at the turbine inlet may be set to be slightly lower than the supercharging pressure at the compressor outlet.
[0029]
The exhaust valve 7 is opened and closed at a fixed valve timing by an exhaust camshaft (not shown). On the other hand, the intake valve 5 is configured to be able to variably control the closing timing together with the operating angle by a variable valve mechanism described later.
[0030]
The variable valve mechanism described above is disclosed in Japanese Patent Laid-Open No. 6-185321, US Pat. No. 5,365,896, etc. The valve lift characteristics can be continuously variably controlled by rotating the camshaft 22 at an unequal speed.
[0031]
Since this mechanism itself is known, a brief description will be given with reference to FIGS. 7 and 8. In the figure, reference numeral 21 denotes a drive shaft to which rotational force is transmitted from an engine crankshaft not shown through the timing chain 14, Reference numeral 22 denotes a hollow cylindrical camshaft that is rotatably fitted to the outer periphery of the drive shaft 21. The camshaft 22 is divided for each cylinder.
[0032]
The camshaft 22 is rotatably supported by a cam bearing at the upper end of the cylinder head 4 and a pair of cams 26 for opening the pair of intake valves 5 for each cylinder is formed on the outer periphery. The camshaft 22 is divided into a plurality of parts as described above, and the first flange part 27 is provided at one of the divided ends. A sleeve 28 and an annular disk 29 are disposed between the ends of the camshaft 22 divided into a plurality of parts. The first flange portion 27 is formed with an elongated engagement groove along the radial direction.
[0033]
The sleeve 28 is fixed to the drive shaft 21, and a second flange portion 32 that faces the first flange portion 27 is formed on the sleeve 28. The second flange portion 32 is formed with a long and narrow engagement groove along the radial direction.
[0034]
The annular disk 29 located between the flange portions 27 and 32 has a substantially donut plate shape, has an annular gap with the outer peripheral surface of the drive shaft 21, and rotates on the inner peripheral surface of the disk housing 34. It is held freely. Moreover, it has a pair of pin 36,37 which protrudes on the opposite side in the opposing position on a diameter line which mutually differs 180 degrees, and each pin 36,37 is engaging with each engagement groove | channel.
[0035]
The disk housing 34 has a substantially triangular shape, the annular disk 29 is held in the circular opening thereof, and the first cam fitting hole 38 and the second cam fitting hole are respectively provided at two places which are the tops of the triangle. 39 is formed through.
[0036]
The circular cam portions 41a and 43a of the first eccentric cam 41 and the second eccentric cam 43 are rotatably fitted in the first cam fitting hole 38 and the second cam fitting hole 39, respectively. Yes.
[0037]
As shown in FIG. 5, the second eccentric cam 43 includes a cylindrical shaft portion 43b and a circular cam portion 43a which are eccentric by a predetermined amount, and both are rotatably fitted and integrated. . The circular cam portion 43a is prevented from being detached by the snap ring 30. The shaft portion 43b is press-fitted and fixed to the partition wall portion of the frame 33 as shown in FIG.
[0038]
The first eccentric cam 41 includes a control cam shaft 42 that is continuous over a plurality of cylinders along the longitudinal direction of the engine, and a plurality of circular cam portions fixed to the cam shaft 42 corresponding to each cylinder. 41a, both of which are eccentric by a predetermined amount. The circular cam portion 41a of each cylinder is eccentric at a predetermined angular position of the cam shaft 42. The control cam shaft 42 is rotatably held by the frame 33 via a cam bracket 35. At one end of the control cam shaft 42 located at one end of the engine, a rotary hydraulic actuator 46 is attached as a drive mechanism. A rotary potentiometer 47 for detecting the rotational position of the control cam shaft 42, that is, the phase of the circular cam portion 41a, is attached to the other end of the control cam shaft 42 located at the front portion of the internal combustion engine.
[0039]
In the variable valve mechanism described above, the eccentric position of the annular disk 29 is variably controlled via the first eccentric cam 41, so that the camshaft 22 rotates at an unequal speed and the eccentricity with the drive shaft 21. A phase difference corresponding to the amount occurs. For example, as shown in FIG. 8A, when the center Y of the annular disk 29 and the center X of the drive shaft 21 coincide with each other, the camshaft 22 rotates synchronously with the drive shaft 21 at a constant speed. The valve lift characteristic along the cam profile as shown by the solid line (A) in FIG. 9 is obtained. On the other hand, as shown in FIG. 9B, when the center Y of the annular disk 29 is eccentric to one side, a phase difference corresponding to the amount of eccentricity is generated. The valve lift characteristics as indicated by
[0040]
Note that a positive phase difference and a negative phase difference occur during one rotation of the drive shaft 21, and the same phase point exists in the middle. In this embodiment, the start point of the cam lift substantially coincides with the same phase point. Therefore, even if the center of the annular disk 29 is decentered and the valve operating angle is increased or decreased, as shown in FIG. 9, the opening timing hardly changes and only the closing timing changes.
[0041]
The hydraulic pressure supplied to the hydraulic actuator 46 is controlled via a hydraulic control valve (not shown) based on the control signal from the control unit 13 described above. As described above, various signals indicating engine operating conditions are input to the control unit 13, and the closing timing of the intake valve 5 is variably controlled based on these signals.
[0042]
FIG. 10 is a flowchart showing a control flow of the closing timing of the intake valve 5 executed by the control unit 13. First, in step 1, a control map of the intake valve closing timing (IVC) is read. As the control map, a map for normal operation whose characteristic is shown in FIG. 11, a map for high supercharging / low compression ratio whose characteristic is shown in FIG. 12, and a map for cold time (not shown) are shown. Are set in advance. Next, in step 2, the cooling water temperature tw is compared with a predetermined reference temperature (a temperature at which warm-up is completed) t0. If it is equal to or lower than t0, the process proceeds to step 3. In step 3, a target value for the intake valve closing timing corresponding to the load, engine speed, etc. at that time is determined using a cold control map (not shown). Further, when the warm-up is completed and the cooling water temperature tw is higher than the reference temperature t0, the process proceeds to Step 4. In step 4, it is determined based on a signal from a hydraulic sensor (not shown) whether the hydraulic pressure in the lubrication system of the engine is equal to or higher than the reference hydraulic pressure p0. The reference oil pressure p0 is set to a level at which the above-described variable valve mechanism can be normally controlled. When the oil pressure is equal to or lower than the reference oil pressure p0 immediately after starting, the oil pressure is sufficiently increased. Wait until. If the hydraulic pressure is larger than the reference hydraulic pressure p0, the process proceeds to step 5 to determine whether or not the supercharging pressure Pc is higher than a predetermined reference level Pc0. This reference level Pc0 substantially corresponds to the supercharging pressure when the wastegate valve 11 in the turbocharger 9 starts to open. That is, it is determined whether or not the entire amount of exhaust gas is introduced into the turbine 9b. Instead of determining the supercharging pressure, the open / closed state of the waste gate valve 11 may be determined.
[0043]
If the supercharging pressure Pc is lower than the reference level Pc0 in step 5, the process proceeds to step 6, and the normal operation control map shown in FIG. The target value for the intake valve closing timing is determined. Similarly, if the supercharging pressure Pc is higher than the reference level Pc0 in step 5, the process proceeds to step 7, and the engine operating condition at that time is determined using the control map for high supercharging / low compression ratio shown in FIG. In particular, the target value of the intake valve closing timing corresponding to the supercharging pressure is determined.
[0044]
In step 8, the hydraulic actuator 46 is driven in accordance with the closing timing target value. In step 9, the actual rotational position of the control cam shaft 42 is detected by the potentiometer 47, and the hydraulic actuator 46 is closed-loop controlled.
[0045]
In this embodiment, as shown in FIG. 11, the intake valve closing timing is advanced to about 20 ° after the bottom dead center in the engine low speed range, so that the intake backflow at the initial stage of the compression stroke can be prevented, and the low speed torque is reduced. improves. In addition, since the rising characteristic of the rotational speed of the turbocharger 9 is also improved by increasing the intake air amount and hence the exhaust gas amount, the responsiveness is improved. That is, even if the turbocharger 9 has a large A / R of the turbine 9a, the drivability does not deteriorate.
[0046]
At the time of high supercharging when the wastegate valve 11 is open, as shown in FIG. 12, the intake valve closing timing is greatly delayed from the bottom dead center so that the actual compression ratio becomes smaller than the actual expansion ratio. Thereby, a so-called mirror cycle is realized.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of A / R of a turbocharger.
FIG. 2 is a fully open torque characteristic diagram of an engine showing a difference in torque characteristics depending on the setting of A / R.
FIG. 3 is a characteristic diagram showing a change in residual gas due to exhaust pressure.
FIG. 4 is a characteristic diagram showing the relationship between supercharging pressure Pc and exhaust pressure Pe when A / R is small.
FIG. 5 is a characteristic diagram showing a relationship between a supercharging pressure Pc and an exhaust pressure Pe when A / R is large.
FIG. 6 is a structural explanatory view showing an embodiment of an internal combustion engine with a turbocharger according to the present invention.
FIG. 7 is a perspective view of the main part showing the configuration of the variable valve mechanism.
8A and 8B are explanatory views showing the operation of this variable valve mechanism, where FIG. 8A is a concentric state and FIG. 8B is an explanatory view showing an eccentric state.
FIG. 9 is a characteristic diagram showing a valve lift characteristic obtained by this variable valve mechanism.
FIG. 10 is a flowchart showing a flow of control of intake valve closing timing.
FIG. 11 is a characteristic diagram showing characteristics of an intake valve closing timing control map for normal operation.
FIG. 12 is a characteristic diagram showing characteristics of an intake valve closing timing control map for a high supercharging / low compression ratio.
[Explanation of symbols]
5 ... Intake valve 9 ... Turbocharger 11 ... Wastegate valve 12 ... Supercharging pressure sensor

Claims (7)

In an internal combustion engine with a turbocharger comprising a variable valve mechanism that can control the closing timing of the intake valve by variably controlling the operating angle of the intake valve, and a turbocharger,
The turbocharger is the narrowest part of the scroll of the turbine so that the exhaust pressure at the turbine inlet is approximately the same level or lower than the supercharging pressure at the compressor outlet in the full load region before the wastegate valve opens. The supercharging pressure characteristic is set by a value (A / R) obtained by dividing the cross-sectional area A by the distance R from the center of the turbine shaft .
When the waste gate valve is closed, the target value of the closing timing is searched from the throttle opening and the engine speed using the first control map, and when the waste gate valve is opened. Using the second control map, the target value for the closing time is searched from the boost pressure and the engine speed,
The first control map has a characteristic that the target value changes mainly depending on the engine speed, and the intake valve closing timing is set so as to approach the bottom dead center in the low speed range.
The second control map has a characteristic that the target value changes mainly due to the supercharging pressure, and in the high speed range, the intake valve closing timing is more retarded so that the actual compression ratio becomes smaller than the actual expansion ratio. An intake valve control device for an internal combustion engine with a turbocharger, wherein   2. An intake valve for an internal combustion engine with a turbocharger according to claim 1, wherein the supercharging pressure characteristic is set as described above by adjusting the A / R of the turbine of the turbocharger. Control device.   The intake valve control device for an internal combustion engine with a turbocharger according to claim 1 or 2, wherein the supercharging pressure characteristic is set to be satisfied in a full load region of engine steady conditions.   The turbocharger according to any one of claims 1 to 3, wherein the intake valve opening timing is kept substantially constant, and the intake valve closing timing changes relatively greatly with variable control of the operating angle. Intake valve control device for internal combustion engine.   The turbocharger according to claim 4, further comprising means for detecting a supercharging pressure upstream of the intake valve, and controlling the intake valve closing timing in accordance with an engine operating condition including the supercharging pressure. Intake valve control device for an internal combustion engine with a motor.   The variable valve mechanism includes a drive shaft that rotates in synchronization with the rotation of the engine, a camshaft that is disposed coaxially with the drive shaft and that has a cam that drives an intake valve on the outer periphery, One flange portion provided at the end and having an engagement groove formed along the radial direction, and provided on the drive shaft side so as to face the one flange portion, and engaged along the radial direction. The other flange portion formed with a joint groove, an annular disk disposed so as to be swingable between the two flange portions, and projecting in opposite directions on both side portions of the annular disc. Provided with a pin that engages in each engagement groove of each part and a drive mechanism that swings the annular disk according to engine operating conditions, and the operating angle of the intake valve changes according to the position of the annular disk The claim of claim 5 an intake valve control apparatus for an internal combustion engine with turbocharger according to any one of. In an internal combustion engine with a turbocharger comprising a variable valve mechanism that can control the closing timing of the intake valve by variably controlling the operating angle of the intake valve, and a turbocharger,
The supercharging pressure characteristics of the turbocharger are calculated by dividing the cross-sectional area A of the scroll scroll of the turbine by the distance R from the turbine shaft center (A / R). In the load region, set the exhaust pressure at the turbine inlet to be approximately the same level or lower than the supercharging pressure at the compressor outlet,
When the waste gate valve is closed, the target value of the closing timing is searched from the throttle opening and the engine speed using the first control map, and when the waste gate valve is opened. The second control map is used to search for the target value for the closing timing from the boost pressure and the engine speed,
The first control map has a characteristic that the target value changes mainly depending on the engine speed, and the intake valve closing timing is set so as to approach the bottom dead center in the low speed range.
The second control map has a characteristic that the target value changes mainly due to the supercharging pressure, and in the high speed range, the intake valve closing timing is more retarded so that the actual compression ratio becomes smaller than the actual expansion ratio. An intake valve control method for an internal combustion engine with a turbocharger, characterized in that:

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