JP2012149660A - Transmission control device for continuously variable transmission - Google Patents

Abstract

A speed change control device for a continuously variable transmission is provided that can prevent a target speed ratio from being unnecessarily limited and unduly narrowing a speed ratio width that can be actually employed.
In a transmission control device for a continuously variable transmission that shifts between a pair of pulleys via an endless torque transmission member 13 wound around the pair of pulleys 11, 12, a target for calculating a target gear ratio of the transmission Limit value calculation units B52 to B54 that calculate a limit value of the target gear ratio based on the gear ratio calculation unit B51, at least one of pulley thrust and pulley rotation speed, and torque input to the transmission, If the target speed ratio calculation value calculated by the target speed ratio calculation unit exceeds the limit value, the limit value is set as the target speed ratio. If the target speed ratio calculation value does not exceed the limit value, the target speed ratio calculation value is set. And a target speed ratio setting unit B55 that sets the target speed ratio.
[Selection] Figure 6

Description

  The present invention relates to an apparatus for controlling a shift of a continuously variable transmission.

  A continuously variable transmission (Continuously Variable Transmission; hereinafter referred to as “CVT” as appropriate) comprising a primary pulley provided on the input shaft, a secondary pulley provided on the output shaft, and an endless torque transmission member stretched over these pulleys Is known. Each of the primary pulley and the secondary pulley includes a fixed sheave and a movable sheave.

  When the speed ratio is controlled, first, the accelerator pedal operation amount and the vehicle speed are applied to the speed change characteristic map to set the target rotational speed of the primary pulley. Next, a target gear ratio for realizing this target rotation speed is set. Then, the movable sheave of the primary pulley moves in the axial direction so as to realize this target gear ratio. In accordance with this, the secondary pulley tightens the endless torque transmission member with a predetermined thrust so that the endless torque transmission member does not slip. By doing in this way, the winding diameter of an endless torque transmission member changes and the gear ratio is controlled steplessly.

  The endless torque transmission member includes a steel belt and a chain belt.

  In the steel belt, a large number of elements are held in an annular shape by bands. The steel belt transmits power by applying a pressing force to the secondary pulley.

  On the other hand, in the chain belt, a large number of blocks are annularly connected via links and pins. The chain belt transmits power by applying a pulling force to the secondary pulley. At this time, the chain belt may be stretched due to elastic deformation. If this elongation is not taken into account, a response delay occurs in the shift control.

  For example, when the target gear ratio is set to the minimum value, i.e., when the vehicle travels in an overdrive state, if the input torque increases and the chain belt (endless torque transmission member) extends, the secondary speed depends on the amount of extension. Pulley winding diameter increases. Then, the actual gear ratio changes to the low side from the target gear ratio. At this time, since the target speed ratio ascertained by the control unit is different from the actual speed ratio of the continuously variable transmission, the control unit performs feedback control toward the target speed ratio. That is, the control unit executes feedback control so as to bring the actual speed ratio closer to the target speed ratio. However, when the chain belt (endless torque transmission member) is extended, the actual gear ratio cannot be made to match the target gear ratio. Nevertheless, the control unit continues to perform feedback control. Then, the feedback value is accumulated on the upshift side.

  If a downshift command is issued in a state where the feedback value is accumulated, the downshift operation of the continuously variable transmission is substantially stopped until the feedback value accumulated on the upshift side is eliminated. That is, the responsiveness of the shift control is lowered. When there is such a response delay, the driver feels uncomfortable.

  Thus, if the chain belt (endless torque transmission member) is not extended, even if the target gear ratio can be realized, it may not be realized when the chain belt (endless torque transmission member) is extended.

  Therefore, in Patent Document 1, accumulation of feedback values is prevented by limiting the target gear ratio to a realizable range according to the input torque.

JP 2006-189079 A

  However, the inventors of the present invention have made extensive researches, and in Patent Document 1, the target gear ratio is unnecessarily limited depending on the driving state of the vehicle, and the gear ratio width that can be actually used is unduly narrowed. I found out that there is a possibility that the transmission of the continuously variable transmission is controlled more precisely.

  The present invention has been made paying attention to such conventional problems, and the object of the present invention is to limit the target gear ratio unnecessarily and unduly narrow the gear ratio width that can be actually employed. It is an object of the present invention to provide a transmission control device for a continuously variable transmission that can prevent this.

  The present invention solves the above problems by the following means.

  The present invention relates to a shift control device for a continuously variable transmission that shifts between a pair of pulleys via an endless torque transmission member that is wound around the pair of pulleys. Then, a target speed ratio limit value is calculated based on a target speed ratio calculation unit that calculates the target speed ratio of the transmission, at least one of pulley thrust and pulley rotation speed, and torque input to the transmission. If the limit value calculation unit to calculate and the target gear ratio calculation value calculated by the target gear ratio calculation unit exceed the limit value, the limit value is set as the target gear ratio, and the target gear ratio calculation value is A target speed ratio setting unit that sets a target speed ratio calculation value as a target speed ratio if the value does not exceed the value;

  According to the present invention, since the limit value of the target speed ratio is calculated based on not only the torque input to the transmission but also at least one of the pulley thrust and the pulley rotational speed, the target speed ratio is unnecessary. Therefore, it is possible to prevent the speed ratio width that can be actually used from being unduly narrowed.

  Embodiments of the present invention and advantages of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing a first embodiment of a transmission control device for a continuously variable transmission according to the present invention. FIG. 2 is a diagram illustrating an example of a thrust ratio map. FIG. 3 is a diagram illustrating a breakdown of the indicated thrust in a region where the thrust ratio is 1 or more. FIG. 4 is a block diagram showing the control contents of the speed change controller. FIG. 5 is a diagram illustrating an example of a gear ratio map. FIG. 6 is a block diagram showing the control contents of the speed change controller. FIG. 7 is a diagram illustrating an example of a gear ratio map. FIG. 8 is a diagram illustrating an example of a three-dimensional map for obtaining the chain elongation amount ΔL based on the primary input torque Tp and the secondary thrust Fs. FIG. 9 is a diagram showing an example of a map for obtaining the speed ratio upper limit and the speed ratio lower limit from the chain extension amount. FIG. 10 is a diagram for explaining the operational effects of the present embodiment. It is a figure explaining the case where primary rotation speed Ns differs even if primary input torque Tp is constant. FIG. 12 is a block diagram showing the control contents of the speed change controller in the second embodiment. FIG. 13 is a diagram illustrating an example of a three-dimensional map for obtaining the chain elongation amount ΔL based on the primary input torque Tp and the primary rotation speed Ns. FIG. 14 is a diagram for explaining the operational effects according to the second embodiment.

(First embodiment)
FIG. 1 is a schematic configuration diagram showing a first embodiment of a transmission control device for a continuously variable transmission according to the present invention.

  Referring to FIG. 1, the vehicle drive system includes an internal combustion engine 1 as a driving power source. The output rotation of the internal combustion engine 1 is transmitted to the drive wheels 7 via the torque converter 2, the first gear train 3, the CVT 4, the second gear train 5, and the terminal reduction device 6.

  CVT4 is a chain type continuously variable transmission mechanism. The CVT 4 includes a primary pulley 11, a secondary pulley 12, and a V chain 13.

  The primary pulley 11 is provided on the input shaft, and the rotational torque of the internal combustion engine 1 is input via the torque converter 2 and the first gear train 3. The primary pulley 11 includes a fixed sheave and a movable sheave that forms a V-groove with the sheave surface facing the fixed sheave. A hydraulic cylinder 15 that displaces the movable sheave in the axial direction is provided on the back surface of the movable sheave of the primary pulley 11.

  The basic structure of the secondary pulley 12 is the same as that of the primary pulley 11. That is, the secondary pulley 12 is provided on the output shaft, and is output to the drive wheel 7 via the second gear train 5 and the terminal reduction device 6. The secondary pulley 12 includes a fixed sheave and a movable sheave that forms a V-groove with the sheave surface facing the fixed sheave. A hydraulic cylinder 16 that displaces the movable sheave in the axial direction is provided on the back surface of the movable sheave of the secondary pulley 12.

  The V chain 13 is an endless torque transmission member that is stretched between the primary pulley 11 and the secondary pulley 12. The V chain 13 transmits the rotational torque of the primary pulley 11 to the secondary pulley 12. The cross section of the V chain 13 has a V shape that gradually decreases in width toward the center of the V chain 13. The V chain 13 has a large number of blocks connected in a ring via links and pins. The V chain 13 transmits power by applying a pulling force to the secondary pulley. Therefore, the V chain 13 tends to be stretched due to elastic deformation.

  The hydraulic cylinders 15 and 16 apply a thrust according to the supplied hydraulic pressure to the movable sheave to change the width of the V groove. As a result, the winding radii around the pulleys 11 and 12 of the V chain 13 change, and the CVT 4 changes the gear ratio steplessly. The “speed ratio” is a value obtained by dividing the rotational speed of the primary pulley 11 by the rotational speed of the secondary pulley 12.

  The shift control of the CVT 4 includes an oil pump 10 that is driven using a part of the power of the internal combustion engine 1, a hydraulic control circuit 21 that regulates the hydraulic pressure from the oil pump 10 and supplies the hydraulic cylinders 15 and 16 with the hydraulic pressure. This is performed by a shift controller 22 that controls the hydraulic control circuit 21.

  The transmission controller 22 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller may be composed of a plurality of microcomputers.

  The speed change controller 22 determines a target speed ratio by a known method based on the load of the internal combustion engine 1 and the speed of the vehicle, and feedback-controls the speed ratio of the CVT 4 to the target speed ratio.

  The shift controller 22 includes an accelerator pedal operation amount sensor 41 that detects an accelerator pedal operation amount APO provided in the vehicle as a load of the internal combustion engine 1, an inhibitor switch 45 that detects a select position of a selector lever provided in the vehicle, and a primary pulley. The detection data is input from a rotation speed sensor 42 that detects a rotation speed Np of 11 and a rotation speed sensor 43 that detects a rotation speed Ns of the secondary pulley 12. Since the rotational speed Ns of the secondary pulley 12 and the vehicle speed VSP are in a fixed proportional relationship, the vehicle speed VSP can be obtained from the rotational speed Ns detected by the rotational speed sensor 43.

  Then, the setting method of the thrust of the primary pulley of CVT4 and a secondary pulley is demonstrated. In the following description, the thrust applied by the hydraulic cylinder 15 to the primary pulley 11 is referred to as primary thrust, and the thrust applied by the hydraulic cylinder 16 to the secondary pulley 12 is referred to as secondary thrust.

  First, the slip limit thrust will be described. When at least one of the primary thrust and the secondary thrust falls below the reference thrust, substantial slip occurs, and the surface state deteriorates due to wear of the friction surface, which may impair the durability of the endless torque transmission member. Therefore, a reference thrust necessary for preventing substantial slip when transmitting torque between the endless torque transmitting member and the pulley is referred to as a slip limit thrust. The reason that the substantial slip is described is that in the case of the V chain 13, even when normal torque is transmitted, the primary pulley 11 and the secondary pulley 12 are each caused by extremely small slip. In the following description, substantial slip means slip of the V chain 13 that hinders torque transmission.

  In order not to cause slippage between the primary pulley and the endless torque transmission member and between the secondary pulley and the endless torque transmission member, both the primary thrust and the secondary thrust must be larger than the slip limit thrust. .

  Next, the balance thrust will be described. The balance thrust is a thrust that satisfies the thrust ratio when the target gear ratio is realized. The thrust ratio is a ratio (Fp / Fs) between the primary thrust Fp and the secondary thrust Fs.

  When the input torque acting on the primary pulley is zero, that is, in the no-load state, the gear ratio is 1 when the primary thrust and the secondary thrust are equal. If the primary thrust is made smaller than the secondary thrust, a low gear ratio is obtained. If the primary thrust is made larger than the secondary thrust, a high gear ratio is obtained.

  When the input torque acting on the primary pulley is positive, that is, a load is applied to the belt, the primary winding radius tends to be reduced because the tension at the belt inlet on the primary pulley side is greater than the tension at the outlet. Therefore, a larger primary thrust is required than in the no-load state. Therefore, in order to realize the target gear ratio, the primary thrust and the secondary thrust need to be balanced thrusts that realize the thrust ratio determined by the target gear ratio and the load state applied to the endless torque transmission member, respectively.

  The secondary thrust and the primary thrust do not cause the endless torque transmitting member to slip, and in order to achieve the target gear ratio, each must be set to be larger than the slip limit thrust and become a balance thrust.

  Here, the slip limit thrust (slip limit secondary thrust and slip limit primary thrust) is generally expressed by the following equation (1).

  The slip limit secondary thrust is also expressed by the following equation (2).

  Usually, assuming that the gear ratio is ip, the primary pulley input torque Tp and the secondary pulley input torque Ts have the relationship of the following equation (3).

  Further, the winding radius Rp of the V chain 13 around the primary pulley 11 and the winding radius Rs of the V chain 13 around the secondary pulley 12 are in the relationship of the following equation (4).

  From the above relationship, the equations (1) and (2) are equivalent, that is, the secondary slip limit thrust Fs_min and the primary slip limit thrust Fp_min can be made the same. In order to reliably avoid the belt slip even if there is a manufacturing error of parts, it is desirable to set the slip limit thrust to a value slightly larger than the value obtained by the equation (1).

  The balance secondary thrust Fs and the balance primary thrust Fp are generally obtained from the thrust ratio map shown in FIG. In FIG. 2, the horizontal axis represents an input torque ratio (Tp / Tin_max) which is a ratio of the input torque Tp to the primary pulley with respect to the transmission torque capacity (Tin_max) of the endless torque transmission member. Here, the transmission torque capacity is the maximum torque that can be transmitted from the primary pulley to the secondary pulley without slipping the endless torque transmission member. In other words, the transmission torque capacity is actually calculated back from Equation (1). The torque input to the primary pulley when the lower of the secondary thrust and the primary thrust is the slip limit thrust (the maximum primary pulley that does not cause the endless torque transmission member to slide against the actual secondary thrust / primary thrust) Input torque). In FIG. 2, the vertical axis represents the ratio of the balance primary thrust to the balance secondary thrust for each target gear ratio, that is, the thrust ratio (Fp / Fs).

  From the above, in order to achieve the target gear ratio while preventing the endless torque transmission member from slipping, in the region where the thrust ratio is 1 or more, the secondary thrust is set to at least the slip limit thrust and the balance thrust with this secondary thrust Set the primary thrust so that On the other hand, in the region where the thrust ratio is less than 1, the primary thrust is set to at least the slip limit thrust, and the secondary thrust is set so as to be a balance thrust with the primary thrust.

  FIG. 3 is a diagram illustrating a breakdown of the indicated thrust in a region where the thrust ratio is 1 or more.

  First, both the secondary thrust Fs and the primary thrust Fp are made larger than the slip limit thrust. Then, the shortage of the primary thrust is increased so that the ratio of the secondary thrust Fs and the primary thrust Fp satisfies the thrust ratio. By doing in this way, it can be set as a balance thrust, without both the secondary thrust Fs and the primary thrust Fp falling below a slip limit thrust. In this way, the secondary thrust Fs and the primary thrust Fp are set.

  FIG. 4 is a block diagram showing the control contents of the speed change controller.

  Note that the blocks B1-B15 shown in FIG. 4 show the control function of the speed change controller 22 as a virtual unit, and do not mean physical existence.

  The shift controller 22 calculates a primary input torque calculation unit B1, a slip limit thrust calculation unit B2, and a V chain transmission torque in order to calculate the slip limit thrust Fmin, the target speed ratio Dip, the secondary balance thrust Fs, and the primary balance thrust Fp. A capacity calculator B3, a target primary rotational speed calculator B4, a target gear ratio setting unit B5, a thrust ratio calculator B6, a secondary balance thrust calculator B7, and a primary balance thrust calculator B8 are provided.

  The primary input torque calculation unit B1 receives the engine torque Teng received from the engine control unit (ECU), the clutch engagement state, the torque converter lockup state (that is, the speed ratio and the fluid performance), the engine to the primary pulley. Based on the inertia torque in the portion, the primary input torque Tp is calculated.

  The slip limit thrust calculation unit B2 calculates the slip limit thrust Fmin from the primary input torque Tp, the primary winding radius Rp, the V chain-pulley friction coefficient μ, and the sheave angle α based on the formula (1). To do. The primary winding radius Rp is calculated based on the normal gear ratio. The slip limit thrust Fmin is calculated from the sheave angle α. In order to reliably prevent the V chain from slipping, a slightly larger value may be obtained by adding a margin to the calculation result obtained by Expression (1).

  The V chain transmission torque capacity calculation unit B3 calculates the V chain transmission torque capacity Tin_mix (Tp in Expression (1)) from the primary input torque Tp and the slip limit thrust Fmin based on Expression (1).

  The target primary rotation speed calculation unit B4 calculates the target primary rotation speed DNp from the accelerator pedal operation amount APO and the secondary rotation speed Ns based on the shift line (an example is shown in FIG. 5). Specific contents will be described later.

  The target speed ratio setting unit B5 calculates the target speed ratio Dip from the target primary rotational speed DNp and the secondary rotational speed Ns.

  The thrust ratio calculation unit B6 calculates the thrust ratio Fp / Fs from the target speed ratio Dip, the primary input torque Tp, and the input torque ratio Tp / Tin_max based on the V chain transmission torque capacity Tin_max.

  The secondary balance thrust calculation unit B7 outputs Fmin as the secondary balance thrust Fs when the thrust ratio Fp / Fs is 1 or more, and Fmin / (Fp / Fs) when the thrust ratio Fp / Fs is less than 1. Output as secondary balance thrust Fs.

  The primary balance thrust calculation unit B8 sets Fmin × Fp / Fs as the primary balance thrust Fp when the thrust ratio Fp / Fs is 1 or more, and sets Fmin as the primary balance thrust Fp when the thrust ratio Fp / Fs is less than 1. And

  Further, the transmission controller 22 performs feedback control of the actual transmission ratio ip with respect to the target transmission ratio Dip, an actual transmission ratio calculation unit B9, a transmission ratio feedback secondary thrust calculation unit B10, a transmission ratio feedback primary thrust calculation unit B11, A transmission ratio feedback secondary thrust addition unit B12 and a transmission ratio feedback primary thrust addition unit B13 are provided.

  The actual gear ratio calculation unit B9 calculates the actual gear ratio ip from the primary rotation speed Np and the secondary rotation speed Ns.

  The transmission ratio feedback secondary thrust calculation unit B10 calculates the transmission ratio feedback secondary thrust Fs_fb based on the actual transmission ratio ip and the target transmission ratio Dip. Note that the transmission ratio feedback secondary thrust Fs_fb is calculated within a range in which the instruction secondary thrust after addition of the transmission ratio feedback secondary thrust does not fall below the slip limit thrust.

  The transmission ratio feedback primary thrust calculation unit B11 calculates a transmission ratio feedback primary thrust Fp_fb based on the actual transmission ratio ip and the target transmission ratio Dip. Note that the transmission ratio feedback primary thrust Fp_fb is calculated within a range in which the command primary thrust after addition of the transmission ratio feedback primary thrust does not fall below the slip limit thrust.

  The transmission ratio feedback secondary thrust adding unit B12 adds the transmission ratio feedback secondary thrust Fs_fb to the secondary balance thrust Fs. As a result, gear ratio feedback is applied to the secondary thrust.

  The gear ratio feedback primary thrust adding unit B13 adds the gear ratio feedback primary thrust Fp_fb to the primary balance thrust Fp. As a result, the gear ratio feedback is also applied to the primary thrust.

  Furthermore, the transmission controller 22 includes a secondary hydraulic pressure conversion unit B14 and a primary hydraulic pressure conversion unit B15 in order to calculate the target secondary pressure Ps and the target primary pressure Pp.

  The secondary hydraulic pressure conversion unit B14 calculates the target secondary pressure Ps by subtracting the centrifugal thrust and the spring thrust from the secondary thrust after the gear ratio feedback and dividing by the secondary pressure receiving area. The centrifugal thrust is calculated from the rotational speed Ns of the secondary pulley 12 and a predetermined secondary pulley centrifugal thrust coefficient. The spring thrust is calculated from the stroke distance of the hydraulic cylinder 16.

  The primary hydraulic pressure conversion unit B15 calculates the target primary pressure Pp by subtracting the centrifugal thrust and the spring thrust from the primary thrust after the gear ratio feedback and then dividing by the primary pressure receiving area. The centrifugal thrust is calculated from the rotational speed Np of the primary pulley 11 and a predetermined secondary pulley centrifugal thrust coefficient. The spring thrust is calculated from the stroke distance of the hydraulic cylinder 15.

  And while the secondary pressure solenoid is adjusted based on the target secondary thrust and the primary pressure solenoid is adjusted based on the target primary thrust, while securing the V chain transmission torque capacity in each of the secondary pulley and the primary pulley, A target gear ratio can be realized.

  FIG. 5 is a diagram illustrating an example of a gear ratio map.

  The target primary rotation speed calculation unit B4 calculates the target primary rotation speed DNp by applying the secondary rotation speed Ns (output rotation, ≈ vehicle speed VSP) and the accelerator pedal operation amount APO to the gear ratio map.

  As shown in FIG. 5, a plurality of shift lines corresponding to accelerator pedal operation amounts are set in the gear ratio map between the lowest gear ratio and the highest gear ratio. In FIG. 5, only one transmission line is shown by a broken line in addition to the lowest transmission ratio line and the highest transmission ratio line in order to prevent the drawing from being complicated.

  From these shift lines, it can be seen that even if the secondary rotational speed is constant, the target primary rotational speed is small if the accelerator pedal operation amount is small, and the target primary rotational speed is large if the accelerator pedal operation amount is large.

  When the secondary rotation speed is Ns0 and the accelerator pedal operation amount is APO0, the target primary rotation speed is DNp0 from the shift line.

  In this case, the target gear ratio is Dip from the secondary rotational speed Ns0 and the target primary rotational speed DNp.

  For this reason, when the secondary rotational speed is low (that is, when the vehicle speed is low), if the accelerator pedal operation amount is large, the target gear ratio becomes the lowest gear ratio. When the secondary rotation speed is high (that is, when the vehicle speed is high), if the accelerator pedal operation amount is small, the target gear ratio becomes the highest gear ratio.

  As described above, the CVT 4 used in the present embodiment is a chain type continuously variable transmission mechanism that uses the V chain 13 as an endless torque transmission member. That is, the CVT 4 transmits the rotational torque of the primary pulley 11 to the secondary pulley 12 through the V chain 13. The V chain 13 transmits power by a pulling force with respect to the secondary pulley. Therefore, the V chain 13 tends to be stretched due to elastic deformation. If this elongation is not taken into account, a response delay occurs in the shift control.

  For example, when the target gear ratio is set to the minimum value, that is, when the vehicle travels in an overdrive state, if the input torque increases and the V chain (endless torque transmission member) extends, the secondary speed depends on the amount of extension. Pulley winding diameter increases. Then, the actual gear ratio changes to the low side from the target gear ratio. At this time, since the target speed ratio ascertained by the control unit is different from the actual speed ratio of the continuously variable transmission, the control unit performs feedback control toward the target speed ratio. That is, the control unit executes feedback control so as to bring the actual speed ratio closer to the target speed ratio. However, when the V chain (endless torque transmission member) is extended, the actual gear ratio cannot be made to match the target gear ratio. Nevertheless, the control unit continues to perform feedback control. Then, the feedback value is accumulated on the upshift side.

  If a downshift command is issued in a state where the feedback value is accumulated, the downshift operation of the continuously variable transmission is substantially stopped until the feedback value accumulated on the upshift side is eliminated. That is, the responsiveness of the shift control is lowered. When there is such a response delay, the driver feels uncomfortable.

  Thus, if the V chain (endless torque transmission member) is not extended, even if the target gear ratio can be realized, it may not be realized when the V chain (endless torque transmission member) is extended.

  Therefore, as described above, in Patent Document 1, accumulation of feedback values is prevented by limiting the target gear ratio to a realizable range according to the input torque, but it has been found that this is still insufficient. It was.

  That is, for example, when the accelerator pedal is depressed while the vehicle is stopped, a large input torque is expected immediately after that, so that the endless torque transmission member (V chain) is prevented from slipping in advance by increasing the pulley thrust in advance. The torque transmission member (V chain) is tightened. In such a state, the input torque remains unchanged, but since the pulley thrust is increased, the amount of elongation of the endless torque transmission member (V chain) may increase.

  Therefore, even in such a case, a method for controlling the shift of the continuously variable transmission more precisely by accurately estimating the extension amount of the endless torque transmission member (V chain) is proposed. Specific contents will be described below.

  FIG. 6 is a block diagram showing the control contents of the speed change controller.

  As described above, the speed change controller 22 includes the target primary rotation speed calculation unit B4 and the target speed ratio setting unit B5. The details will be described below.

  The target primary rotation speed calculation unit B4 calculates a target primary rotation speed DNp based on the accelerator pedal operation amount APO and the rotation speed Ns of the secondary pulley 12. Although this description overlaps with the previous description, it will be described in order to understand the invention accurately. Specifically, the target primary pulley rotation speed DNp is obtained by applying the accelerator pedal operation amount APO and the rotation speed Ns of the secondary pulley 12 to the gear ratio map as shown in FIG. In FIG. 7, the secondary rotation speed is Ns1, and the accelerator pedal operation amount is APO1. In this case, the target primary rotational speed is DNp1 from the shift line.

  The target gear ratio calculation unit B51 calculates the target gear ratio calculation value Dip1 by dividing the target primary rotation speed DNp by the rotation speed Ns of the secondary pulley 12.

  The chain elongation calculation unit B52 obtains the chain elongation amount ΔL based on the primary input torque Tp and the secondary thrust Fs. Specifically, the chain elongation amount ΔL is obtained by applying the primary input torque Tp and the secondary thrust Fs to the three-dimensional map in which the xz coordinate is shown in FIG. 8A and the yz coordinate is shown in FIG. 8B. Ask. The elongation amount ΔL of the V chain 13 depends on the tension of the V chain 13. As can be seen from FIG. 8 (A), the extension amount ΔL of the V chain 13 is such that the transmission ratio between the primary pulley 11 and the secondary pulley 12, the movable sheave thrust Fs of the secondary pulley 12, and the rotational speed Np of the primary pulley 11 are constant. Then, it gradually increases as the input torque Tp of the primary pulley 11 increases. Further, as can be seen from FIG. 8B, the amount of extension ΔL of the V-chain 13 is equal to the secondary pulley 12 when the input torque Tp and the rotational speed Np of the primary pulley 11 and the gear ratio between the primary pulley 11 and the secondary pulley 12 are constant. The larger the movable sheave thrust Fs, the larger.

  As described above, the primary input torque Tp includes the engine torque Teng received from the engine control unit (ECU), the clutch engagement state, the torque converter lockup state (that is, the speed ratio and the fluid performance), the engine And the inertia torque in the portion from the primary pulley to the primary pulley. The primary rotation speed Np is detected by the primary rotation speed sensor 42. As the secondary thrust Fs, a value estimated from the input torque, a previously calculated value, or the like may be used.

  The gear ratio upper limit calculation unit B53 calculates the gear ratio upper limit Dip_MAX based on the chain elongation amount ΔL. Specifically, the gear ratio upper limit Dip_MAX is obtained by applying the chain elongation amount ΔL to the gear ratio map as shown in FIG. For example, the gear ratio upper limit Dip_MAX is the lowest gear ratio indicated by a broken line if the chain elongation amount ΔL is zero, and the lowest gear ratio indicated by a solid line if the chain elongation amount ΔL is the maximum value. During this time, the lowest gear ratio is set in proportion to the chain elongation. Similarly, the transmission gear ratio lower limit calculation unit B54 calculates the transmission gear ratio lower limit Dip_MIN based on the chain elongation amount ΔL.

  The target speed ratio setting unit B55 sets the speed ratio upper limit Dip_MAX as the target speed ratio Dip when the target speed ratio calculated value Dip1 is larger than the speed ratio upper limit Dip_MAX. When the target speed ratio calculated value Dip1 is smaller than the speed ratio lower limit Dip_MIN, the speed ratio lower limit Dip_MIN is set as the target speed ratio Dip. If the target gear ratio calculated value Dip1 is less than or equal to the gear ratio upper limit Dip_MAX and greater than or equal to the gear ratio lower limit Dip_MIN, the target gear ratio calculated value Dip1 is set as the target gear ratio Dip.

  In FIG. 7, since the target speed ratio calculated value Dip1 is smaller than the speed ratio lower limit Dip_MIN, the speed ratio lower limit Dip_MIN is set as the target speed ratio Dip.

  The gear ratio upper limit Dip_MAX and the gear ratio lower limit Dip_MIN are determined by hardware specifications such as the chain length L and the position of the pulley stopper. Since the chain length L is determined by the tension acting on the chain, it is determined by the input torque Tp, the primary thrust Fp, the secondary thrust Fs, and the centrifugal term (which can be calculated based on the primary rotational speed Np and the secondary rotational speed Ns). Since the gear ratio upper limit Dip_MAX and the gear ratio lower limit Dip_MIN are determined by the chain length L and the position of the stopper, the gear ratio upper limit calculation unit B53 and the gear ratio lower limit calculation unit B54 set these calculation results in a map, The gear ratio upper limit Dip_MAX and the gear ratio lower limit Dip_MIN corresponding to each input may be calculated. For example, when a stopper corresponding to the highest gear ratio is provided on the primary pulley side, the lowest gear ratio is shifted low when the chain is extended. When only the input torque Tp of each input is increased, the tension applied to the chain is increased and the chain is extended, so that the highest gear ratio is shifted low. When only the primary rotational speed Np and the secondary rotational speed Ns increase among the inputs, the tension applied to the chain is increased and the chain is extended, so that the highest gear ratio is shifted low. Further, when only the secondary thrust Fs and the primary thrust Fp of each input are increased, the tension applied to the chain is increased and the chain is extended, so that the highest gear ratio is shifted low.

  FIG. 10 is a diagram for explaining the operational effects of the present embodiment.

  When the accelerator pedal is depressed at time t11 (FIG. 10A), a large input torque is expected immediately after that, so that the pulley thrust increases to prevent the endless torque transmission member (V chain) from slipping (FIG. 10). 10 (C)). As a result, the tension of the V chain is increased and the V chain is extended (FIG. 10D).

  At this time, in this embodiment, the chain length L is calculated based on the torque Tp input to the primary pulley and the thrust Fs acting on the secondary pulley. At this time, the larger the thrust Fs acting on the secondary pulley, the longer the chain length L is calculated. Since the target speed ratio limit value is set in accordance with this, the target speed ratio limit value is changed at time t11 (FIG. 10E).

  On the other hand, when the limit value of the target speed ratio is set based only on the torque Tp input to the primary pulley as in the comparative embodiment, the target speed ratio limit value also changes as the torque Tp increases (see FIG. 10 (E)). Therefore, in this way, the target speed ratio is unnecessarily limited, and there is a possibility that the speed ratio width that can actually be adopted is unduly narrowed.

  On the other hand, according to the present embodiment, since the limit value of the target speed ratio is changed at time t11 (FIG. 10E), the target speed ratio is not limited unnecessarily and is actually used. The maximum gear ratio range can be secured within the possible range.

  In addition, when calculating the lower limit value of the target gear ratio, it is possible to respond to a thrust increase independent of the input torque at the time of wheel spin correspondence or fail safe, and the target gear ratio and the actual gear ratio are prevented from deviating and feedback. Accumulation of control feedback values can be avoided.

  Furthermore, in the present embodiment, not only the input torque but also the chain elongation amount corresponding to the thrust is estimated and the gear ratio upper limit Dip_MAX and the gear ratio lower limit Dip_MIN are calculated, so that a more appropriate gear ratio width can be ensured. Therefore, it is possible to avoid the accumulation of feedback values of feedback control due to the difference between the target speed ratio and the actual speed ratio more precisely.

  Furthermore, in the present embodiment, the gear ratio upper limit Dip_MAX can be raised at the time of start where a high gear ratio is required by largely estimating the chain elongation amount in accordance with the thrust increase correction at the time of start.

  When the target gear ratio is set to the minimum value, that is, when the vehicle travels in an overdrive state, if the input torque increases and the V chain (endless torque transmission member) extends, the secondary pulley will The winding diameter increases. Then, the actual gear ratio changes to the low side from the target gear ratio. If the target speed ratio ascertained by the control unit is different from the actual speed ratio of the continuously variable transmission, the control unit executes feedback control toward the target speed ratio. That is, the control unit executes feedback control so as to bring the actual speed ratio closer to the target speed ratio. If this embodiment is not applied, when the V chain (endless torque transmission member) is extended, the actual gear ratio may not be matched with the target gear ratio. Nevertheless, the control unit continues to perform feedback control. Then, the feedback value is accumulated on the upshift side. If a downshift command is issued in a state where the feedback value is accumulated, the downshift operation of the continuously variable transmission is substantially stopped until the feedback value accumulated on the upshift side is eliminated. That is, the responsiveness of the shift control is lowered. When there is such a response delay, the driver feels uncomfortable.

  When the movable sheave of the secondary pulley expands and abuts against the stopper, that is, when the winding radius of the V chain (endless torque transmission member) around the secondary pulley is fixed, the V chain (endless torque transmission member) extends. The winding diameter of the primary pulley increases according to the amount of elongation. Then, the actual gear ratio changes to a higher side than the target gear ratio. At this time, since the target speed ratio ascertained by the control unit is different from the actual speed ratio of the continuously variable transmission, the control unit performs feedback control toward the target speed ratio. That is, the control unit executes feedback control so as to bring the actual speed ratio closer to the target speed ratio. If this embodiment is not applied, when the V chain (endless torque transmission member) is extended, the actual gear ratio may not be matched with the target gear ratio. Nevertheless, the control unit continues to perform feedback control. Then, the feedback value is accumulated on the downshift side. When an upshift command is issued in a state where the feedback value is accumulated, the upshift operation of the continuously variable transmission is substantially stopped until the feedback value accumulated on the downshift side is eliminated. That is, the responsiveness of the shift control is lowered. When there is such a response delay, the driver feels uncomfortable.

  In contrast, in this embodiment, the chain length L is calculated based on the torque Tp input to the primary pulley and the thrust Fs acting on the secondary pulley, and the target speed ratio limit value is set accordingly. The limit value of the target gear ratio is changed appropriately. Therefore, since a target speed ratio that cannot be realized is not set, a feedback value is not accumulated, a reduction in response of the speed change control can be prevented, and the driver does not feel uncomfortable.

(Second Embodiment)
In the first embodiment, in view of technical knowledge that the tension acting on the chain is influenced not only by the input torque Tp but also by the pulley thrust, the chain elongation amount ΔL is obtained based on the primary input torque Tp and the secondary thrust Fs. It was.

  However, the tension acting on the chain is also affected by the rotational speed of the pulley. That is, the greater the rotational speed of the pulley, the greater the centrifugal force acts and the greater the tension acting on the chain. Therefore, in this embodiment, the chain elongation amount ΔL is obtained based on the primary input torque Tp and the primary rotational speed Ns.

  Here, the case where the primary rotational speed Ns is different even when the primary input torque Tp is constant will be described with reference to FIG.

  When the lock-up clutch of the torque converter is on (engaged state), the engine torque becomes the input torque to the CVT. The engine torque Te has a predetermined value for each accelerator pedal operation amount (intake throttle opening) APO and engine rotational speed Ne, and is expressed as shown in FIG. Even when the engine torque is Te0 at a predetermined accelerator pedal operation amount APO, there are cases where the engine rotation speed is Ne2 and Ne3. If the accelerator pedal operation amount APO changes (becomes larger), the engine speed may be Ne1 even if the engine torque is Te0.

  Furthermore, even when the lock-up clutch of the torque converter is off (disengaged), depending on the situation of the torque ratio and capacity coefficient determined from the engine speed Ne and speed ratio (turbine speed divided by engine speed) Even if the input torque is the same, the input rotation speed may change.

  For this reason, even when the primary input torque Tp is constant, the primary rotational speed Ns may be different.

  FIG. 12 is a block diagram showing the control contents of the speed change controller in the second embodiment.

  In the following description, parts having the same functions as those described above are denoted by the same reference numerals, and redundant description is omitted as appropriate.

  In view of the above technical knowledge, in this embodiment, the chain elongation calculation unit B521 calculates the chain elongation amount ΔL based on the primary input torque Tp and the primary rotational speed Ns. Specifically, the chain extension amount ΔL is obtained by applying the primary input torque Tp and the primary rotation speed Ns to the three-dimensional map in which the xz coordinate is shown in FIG. 13A and the yz coordinate is shown in FIG. 13B. Ask for. FIG. 13A is the same as FIG. As can be seen from FIG. 13 (B), the extension amount ΔL of the V chain 13 is the rotational speed of the primary pulley 11 when the input torque to the primary pulley 11, the movable sheave thrust of the secondary pulley 12, and the primary pulley 11 are constant. The larger Np, the larger.

  FIG. 14 is a diagram for explaining the operational effects according to the second embodiment.

  When the accelerator pedal is depressed at time t21 (FIG. 14 (A)), the torque Tp input to the primary pulley increases accordingly and becomes constant after time t22 (FIG. 14 (B)). The rotational speed Np may increase after time t22 (FIG. 14C). Considering a specific driving scene, for example, when the road surface gradient changes, the vehicle speed increases even if the input torque Tp does not change.

  In such a case, in this embodiment, the chain elongation amount ΔL is calculated based on the torque Tp input to the primary pulley and the rotation speed Np of the primary pulley 11. At this time, the larger the rotation speed Np of the primary pulley 11, the longer the chain elongation amount ΔL is calculated. Since the target speed ratio limit value is set accordingly, the target speed ratio limit value is also changed after time t22 (FIG. 14E).

  On the other hand, when the target speed ratio limit value is set based only on the torque Tp input to the primary pulley as in the comparative embodiment, the target speed ratio limit value is not changed after time t22 (FIG. 14E). ). Therefore, in this way, the target speed ratio is unnecessarily limited, and there is a possibility that the speed ratio width that can actually be adopted is unduly narrowed.

  On the other hand, according to the present embodiment, the target speed ratio limit value is changed after time t22, so that the target speed ratio is not unnecessarily limited, and the maximum speed change within the range that can be actually employed. A specific width can be secured.

  Further, since the rotational speed of the primary pulley 11 varies depending on the vehicle speed even if the coast torque is the same near the highest gear ratio, the gear ratio lower limit Dip_MIN is set on the premise that the maximum rotational speed at which the chain extends most is always input in the comparative form. It was necessary to set. On the other hand, in this embodiment, since the speed ratio lower limit Dip_MIN can be changed according to the rotational speed, the target speed ratio can be lowered in a region where the rotational speed is small. From the above, according to the present embodiment, a more appropriate speed ratio upper limit Dip_MAX can be instructed, and the maximum speed ratio width can be secured within a range that can be actually employed.

  Furthermore, in the present embodiment, not only the input torque but also the chain elongation amount corresponding to the rotational speed is estimated to calculate the transmission ratio upper limit Dip_MAX and the transmission ratio lower limit Dip_MIN, so that a more appropriate transmission ratio width can be ensured. Therefore, it is possible to avoid the accumulation of feedback values of feedback control due to the difference between the target speed ratio and the actual speed ratio more precisely.

  Furthermore, in the present embodiment, by estimating the chain elongation amount according to the input rotational speed, the engine is driven at a low rotational speed by lowering the speed ratio lower limit Dip_MIN when traveling at the highest speed gear ratio at a low rotational speed. It is possible to obtain the effect of improving fuel efficiency.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  For example, the chain elongation calculation unit may determine the chain elongation amount ΔL based on the primary input torque Tp, the secondary thrust Fs, and the primary rotation speed Ns by combining the first embodiment and the second embodiment. In this case, the chain elongation is applied by applying the primary input torque Tp, the secondary thrust Fs, and the primary rotational speed Ns to the four-dimensional map having the chain elongation amount ΔL, the primary input torque Tp, the secondary thrust Fs, and the primary rotational speed Ns as axes. What is necessary is just to obtain | require quantity (DELTA) L.

  For example, in the above description, the V chain is exemplified as the endless torque transmission member, but the present invention is not limited to this. For example, rubber or other resin belts may be used. The present invention can be applied to a structure in which elongation due to elastic deformation occurs when power is transmitted by acting on a secondary pulley.

  In the above description, the chain elongation amount is calculated based on the secondary thrust as the pulley thrust, but may be calculated based on the primary thrust.

  Further, in the above description, the chain elongation amount is calculated based on the primary rotation speed as the pulley rotation speed, but may be calculated based on the secondary rotation speed.

  Furthermore, in the above embodiment, the chain extension amount ΔL is once calculated based on the primary input torque Tp and the secondary thrust Fs, or based on the primary input torque Tp and the primary rotational speed Ns, and the speed ratio upper limit Dip_MAX and the speed change Although the ratio lower limit Dip_MIN is obtained, a map or the like may be prepared in advance, and the gear ratio upper limit Dip_MAX and the gear ratio lower limit Dip_MIN may be directly obtained from the primary input torque Tp, the secondary thrust Fs, and the primary rotation speed Ns.

4 Continuously variable transmission (CVT)
11 Primary pulley 12 Secondary pulley 13 V chain (endless torque transmission member)
22 transmission controller B51 target gear ratio calculation unit B52 chain elongation calculation unit (limit value calculation unit)
B53 Gear ratio upper limit calculation unit (limit value calculation unit)
B54 Gear ratio lower limit calculation unit (limit value calculation unit)
B55 Target gear ratio setting unit

Claims (7)

In a transmission control device for a continuously variable transmission that shifts between the pair of pulleys via an endless torque transmission member wound around the pair of pulleys,
A target gear ratio calculation unit for calculating a target gear ratio of the transmission;
A limit value calculation unit that calculates a limit value of the target gear ratio based on at least one of the pulley thrust and the pulley rotation speed and the torque input to the transmission;
If the target gear ratio calculation value calculated by the target gear ratio calculation unit exceeds the limit value, the limit value is set as the target gear ratio, and if the target gear ratio calculation value does not exceed the limit value, the target gear ratio is calculated. A target gear ratio setting unit for setting the ratio calculation value as a target gear ratio;
A transmission control device for a continuously variable transmission. The transmission control device for a continuously variable transmission according to claim 1,
The limit value calculating unit calculates an extension amount of the endless torque transmission member based on at least one of a pulley thrust and a pulley rotation speed and an input torque, and calculates a limit value of the target speed ratio based on the extension amount. calculate,
A transmission control device for a continuously variable transmission. The transmission control device for a continuously variable transmission according to claim 2,
The limit value calculation unit calculates an upper limit value and a lower limit value of the target speed ratio based on the extension amount of the endless torque transmission member,
The target speed ratio setting unit sets the upper limit value as the target speed ratio when the target speed ratio calculated value is larger than the upper limit value, and sets the lower limit value when the target speed ratio calculated value is smaller than the lower limit value. A value is set as the target speed ratio, and when the target speed ratio calculation value is not more than the upper limit value and not less than the lower limit value, the target speed ratio calculation value is set as the target speed ratio.
A transmission control device for a continuously variable transmission. The transmission control device for a continuously variable transmission according to claim 2 or claim 3,
The limit value calculation unit calculates the elongation amount of the endless torque transmission member to be larger as the pulley thrust is larger.
A transmission control device for a continuously variable transmission. The transmission control device for a continuously variable transmission according to any one of claims 2 to 4,
The limit value calculation unit calculates a large amount of elongation of the endless torque transmission member at the time of starting, as compared to a time other than starting.
A transmission control device for a continuously variable transmission. The transmission control apparatus for a continuously variable transmission according to any one of claims 2 to 5,
The limit value calculation unit calculates the elongation amount of the endless torque transmission member to be larger as the pulley rotation speed is larger.
A transmission control device for a continuously variable transmission. The transmission control device for a continuously variable transmission according to any one of claims 2 to 6,
The limit value calculating unit calculates a large amount of elongation of the endless torque transmitting member when traveling on a downhill as compared to when traveling on a road other than a downhill,
A transmission control device for a continuously variable transmission.

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