JP2007247862A - Controller of continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set clamping force responding to torque capacity characteristics of a transmission mechanism. <P>SOLUTION: A basic secondary pressure calculation part 67 refers to a characteristic map based on an input torque Ti and a target gear ratio i, and calculates a basic secondary pressure (Psb/Ti) per a unit torque. A correction factor calculation part 68 calculates a correction factor C by referring to a factor map based on an actual primary rotation speed Np' and the target gear ratio i. A basic secondary pressure correction part 69 corrects the basic secondary pressure (Psb/Ti) by the correction factor C, and calculates a target secondary pressure (Ps/Ti) per a unit torque. A target secondary pressure calculation part 70 multiplies the target secondary pressure (Ps/Ti) per a unit torque by an input torque and calculates a target secondary pressure Ps to be supplied to a secondary pulley. Thus, even if the torque capacity characteristics of the transmission mechanism changes according to the input torque Ti and the actual primary rotation speed Np', the target secondary pressure Ps is appropriately set. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for a continuously variable transmission mounted on a vehicle.

  A continuously variable transmission (CVT) mounted on a power transmission system of a vehicle includes a primary pulley provided on an input shaft and a secondary pulley provided on an output shaft. The gear ratio is steplessly controlled by changing the winding diameter. Each of the primary pulley and the secondary pulley includes a fixed sheave and a movable sheave facing the stationary sheave. The pulley groove width can be changed by moving the movable sheave in the axial direction, and the winding diameter of the drive belt can be changed. It is possible to control.

In such a continuously variable transmission, the wrapping diameter of the drive belt is controlled by one pulley (for example, a primary pulley), while slippage of the drive belt is suppressed by the other pulley (for example, a secondary pulley). ing. When the gear ratio is controlled by the primary pulley, the target gear ratio is set with reference to the characteristic map based on the throttle opening and the vehicle speed, and the pulley groove width of the primary pulley is controlled according to the target gear ratio. Then, when the slippage of the drive belt is suppressed by the secondary pulley, the clamp force per unit torque is set by referring to the characteristic map based on the target speed ratio, and then the target clamp is multiplied by the input torque. The force is set, and the pulley groove width of the secondary pulley is controlled in accordance with the target clamping force (see, for example, Patent Document 1). There has also been proposed a continuously variable transmission in which a drive chain composed of a large number of link members is assembled as a power transmission element wound around two pulleys (see, for example, Patent Documents 2 and 3).
JP 2004-124966 A JP 2001-65683 A JP 2001-280467 A

  However, the torque capacity characteristics of the speed change mechanism including power transmission elements such as a pulley and a drive chain not only change according to the speed ratio value depending on the rigidity of the pulley, but also the input torque and input rotation to the speed change mechanism. It was confirmed that it may change depending on the value of the number. That is, the torque capacity of the speed change mechanism has not only a non-linear characteristic with respect to the gear ratio but also a non-linear characteristic with respect to the input torque and the input rotation speed. Therefore, as described in Patent Document 1, when the clamping force per unit torque is set based only on the target gear ratio, it is difficult to appropriately set the target clamping force of the secondary pulley. Depending on the value of the torque and the input rotational speed, the clamping force may be insufficient, and this insufficient clamping force causes a slippage of the transmission mechanism. In addition, setting the target clamping force excessively to suppress slippage of the transmission mechanism increases the load on the oil pump and the power loss in the transmission, which causes a deterioration in engine fuel efficiency. .

  An object of the present invention is to provide a control device for a continuously variable transmission capable of setting a clamping force according to a torque capacity characteristic of a transmission mechanism.

  A control device for a continuously variable transmission according to the present invention includes a speed change mechanism including a speed change pulley on which a power transmission element is wound and a tightening pulley. The speed change pulley controls a winding diameter of the power transmission element, and A control device for a continuously variable transmission that controls the tension of the power transmission element with an attached pulley, the target transmission ratio set based on a vehicle state, the input torque to the transmission mechanism, and the input rotational speed to the transmission mechanism And a clamping force setting means for setting a target clamping force of the tightening pulley.

  In the continuously variable transmission control device according to the present invention, the clamping force setting means sets a basic clamping force based on the target speed ratio and the input torque, and sets a correction coefficient based on the target speed ratio and the input rotational speed. The target clamping force is set based on the basic clamping force and the correction coefficient.

  According to the present invention, the target clamping force of the tightening pulley is set based on the target gear ratio, the input torque, and the input rotational speed, so the target clamping force is appropriately set according to the torque capacity characteristics of the transmission mechanism. Thus, it is possible to suppress the slip of the power transmission element and reduce the power loss of the continuously variable transmission.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a skeleton diagram showing a continuously variable transmission 10, and this continuously variable transmission 10 is controlled by a control device according to an embodiment of the present invention. As shown in FIG. 1, the continuously variable transmission 10 is a chain drive type continuously variable transmission, and includes a primary shaft 12 driven by an engine 11 and a secondary shaft 13 parallel to the primary shaft 12. . A transmission mechanism 14 is provided between the primary shaft 12 and the secondary shaft 13. The rotation of the primary shaft 12 is transmitted to the secondary shaft 13 via the transmission mechanism 14, and the rotation of the secondary shaft 13 is transmitted to the speed reduction mechanism 15 and the secondary shaft 13. It is transmitted to the left and right drive wheels 17 and 18 through the differential mechanism 16.

  The primary shaft 12 is provided with a primary pulley 20 as a speed change pulley. The primary pulley 20 is slidable in the axial direction on the primary shaft 12 opposite to the fixed sheave 20a integrated with the primary shaft 12. And a movable sheave 20b. The secondary shaft 13 is provided with a secondary pulley 21 as a tightening pulley. The secondary pulley 21 has a fixed sheave 21a integrated with the secondary shaft 13 and an axially opposite to the secondary shaft 13 in the axial direction. The movable sheave 21b is slidable. A drive chain 22 as a power transmission element in which a large number of link members are connected by pin members is wound around the primary pulley 20 and the secondary pulley 21, and the pulley groove width between the primary pulley 20 and the secondary pulley 21 is changed. Thus, the winding diameter of the drive chain 22 can be changed steplessly. If the winding diameter of the drive chain 22 around the primary pulley 20 is Rp and the winding diameter of the secondary pulley 21 is Rs, the transmission ratio of the continuously variable transmission 10 is Rs / Rp.

  In order to change the pulley groove width of the primary pulley 20, the plunger 23 is fixed to the primary shaft 12, and the movable sheave 20 b is fixed to the cylinder 24 slidably contacting the outer peripheral surface of the plunger 23, A hydraulic oil chamber 25 is defined by the plunger 23 and the cylinder 24. Similarly, in order to change the pulley groove width of the secondary pulley 21, a plunger 26 is fixed to the secondary shaft 13, and a cylinder 27 that slidably contacts the outer peripheral surface of the plunger 26 is fixed to the movable sheave 21b. The hydraulic oil chamber 28 is partitioned by the plunger 26 and the cylinder 27. Each pulley groove width is controlled by adjusting the primary pressure Pp supplied to the primary hydraulic fluid chamber 25 and the secondary pressure Ps supplied to the secondary hydraulic fluid chamber 28.

  A torque converter 30 and a forward / reverse switching mechanism 31 are provided between the crankshaft 11 a and the primary shaft 12 to transmit engine power to the primary pulley 20. The torque converter 30 includes a pump shell 30a connected to the crankshaft 11a and a turbine runner 30b facing the pump shell 30a. A turbine shaft 32 is connected to the turbine runner 30b. Furthermore, a lock-up clutch 33 for fastening the crankshaft 11a and the turbine shaft 32 is incorporated in the torque converter 30 according to the running state.

  The forward / reverse switching mechanism 31 includes a double pinion planetary gear train 34, a forward clutch 35, and a reverse brake 36. By operating the forward clutch 35 and the reverse brake 36, the transmission path of engine power is changed. It can be switched. When both the forward clutch 35 and the reverse brake 36 are released, the turbine shaft 32 and the primary shaft 12 are disconnected, and the forward / reverse switching mechanism 31 is switched to a neutral state in which power is not transmitted to the primary shaft 12. When the reverse brake 36 is released and the forward clutch 35 is engaged, the rotation of the turbine shaft 32 is transmitted to the primary pulley 20 as it is, and when the forward clutch 35 is released and the reverse brake 36 is engaged, The rotated rotation of the turbine shaft 32 is transmitted to the primary pulley 20.

  FIG. 2 is a schematic diagram showing a hydraulic control system and an electronic control system of the continuously variable transmission 10. As shown in FIG. 2, in order to supply hydraulic oil to the primary pulley 20 and the secondary pulley 21, the continuously variable transmission 10 is provided with an oil pump 40 that is driven by engine power. A line pressure control valve 42 is connected to the line pressure path 41 connected to the discharge port of the oil pump 40, and the line pressure control valve 42 regulates the line pressure PL that is the basic hydraulic pressure of the hydraulic control circuit. . Further, the line pressure path 41 is branched, and the primary pressure control valve 43 is connected to one line pressure path 41 a extending toward the primary pulley 20, and the other line pressure extending toward the secondary pulley 21. A secondary pressure control valve 44 is connected to the path 41b.

  Then, by supplying the primary pressure Pp regulated by the primary pressure control valve 43 from the primary pressure path 45 to the primary pulley 20, the pulley groove width of the primary pulley 20 can be adjusted to control the gear ratio. It becomes possible. Further, by supplying the secondary pressure Ps regulated by the secondary pressure control valve 44 from the secondary pressure path 46 to the secondary pulley 21, a predetermined clamping force is generated in the secondary pulley 21 to suppress the slip of the drive chain 22. It becomes possible.

  Such a line pressure control valve 42, a primary pressure control valve 43, and a secondary pressure control valve 44 are electromagnetic pressure control valves each having a solenoid part 42a, 43a, 44a, and each solenoid part 42a, 43a, 44a is supplied with a drive current from the CVT control unit 50 that functions as a clamping force setting means. The CVT control unit 50 includes a microprocessor (CPU) (not shown), and a ROM, a RAM, and an I / O port are connected to the CPU via a bus line. The ROM stores control programs, various map data, and the like, and the RAM temporarily stores data processed by the CPU. Further, detection signals indicating the running state of the vehicle are input from various sensors to the CPU via the I / O port.

  Various sensors for inputting a detection signal to the CVT control unit 50 include a primary rotational speed sensor 51 for detecting the primary rotational speed of the primary pulley 20, a secondary rotational speed sensor 52 for detecting the secondary rotational speed of the secondary pulley 21, and an accelerator pedal. There are an accelerator pedal sensor 53 for detecting the depression amount, a vehicle speed sensor 54 for detecting the vehicle speed, and the like. An engine control unit 55 is connected to the CVT control unit 50, and engine control information such as throttle opening and engine speed is input from the engine control unit 55.

  Hereinafter, the calculation procedure of the target primary pressure Pp and the target secondary pressure Ps by the CVT control unit 50 will be described. FIG. 3 is a block diagram showing a shift control system of the CVT control unit 50.

  As shown in FIG. 3, in order to set the target primary pressure Pp, the target primary rotation speed calculation unit 60 calculates a target primary rotation speed Np by referring to a predetermined shift map based on the vehicle speed V and the throttle opening degree To. The target gear ratio calculation unit 61 calculates the target gear ratio i based on the target primary rotation speed Np and the actual secondary rotation speed Ns ′. Next, the hydraulic ratio calculation unit 62 calculates the hydraulic ratio (Pp / Ps) between the target primary pressure Pp and the target secondary pressure Ps corresponding to the target speed ratio i, and the target primary pressure calculation unit 63 calculates the hydraulic ratio. A target primary pressure Pp is calculated by multiplying a target secondary pressure Ps described later. Further, the actual speed ratio calculating unit 64 calculates the actual speed ratio i ′ based on the actual primary speed Np ′ and the actual secondary speed Ns ′, and the feedback value calculating unit 65 determines the actual speed ratio i ′ and the target speed change. A feedback value f is calculated based on the ratio i. The CVT control unit 50 sets the drive current based on the target primary pressure Pp subjected to feedback control, and then outputs this drive current to the primary pressure control valve 43 to set the pulley groove width of the primary pulley 20 to the target speed change. Control is performed toward the ratio i.

  Next, in order to calculate the target secondary pressure Ps, the input torque calculation unit 66 calculates the engine torque based on the engine speed Ne and the throttle opening degree To, and then the engine torque is amplified by the torque converter 30. An input torque Ti input to the primary pulley 20 is calculated by multiplying the torque ratio. The basic secondary pressure calculating unit 67 calculates a basic secondary pressure (Psb / Ti) per unit torque by referring to a predetermined characteristic map based on the input torque Ti and the target speed ratio i. Here, FIG. 4 is a schematic diagram illustrating an example of a characteristic map referred to by the basic secondary pressure calculation unit 67. As shown in FIG. 4, for example, when the input torque calculated by the input torque calculation unit 66 is T3 and the target speed ratio calculated by the target speed ratio calculation unit 61 is ia, the basic secondary pressure is calculated. Pa is set as the basic secondary pressure by the portion 67. As shown in the figure, the basic secondary pressure (Psb / Ti) per unit torque is set so as to change according to the value of the input torque Ti as well as the target speed ratio i.

  Subsequently, as shown in FIG. 3, the correction coefficient calculation unit 68 refers to the predetermined coefficient map shown in FIG. 5 based on the actual primary rotational speed (input rotational speed) Np ′ and the target speed ratio i, and A correction coefficient C corresponding to the rotation speed Np ′ and the target speed ratio i is calculated. Then, the basic secondary pressure correcting unit 69 calculates the target secondary pressure (Ps / Ti) per unit torque by correcting the basic secondary pressure (Psb / Ti) by the correction coefficient C. In this way, by correcting the basic secondary pressure (Psb / Ti), the basic secondary pressure per unit torque (Psb / Ti) is increased or decreased according to the value of the actual primary rotational speed Np ′, and the target per unit torque is increased. The secondary pressure (Ps / Ti) can be set.

  Such basic secondary pressure (Psb / Ti) correction processing will be described with reference to FIG. As shown in FIG. 4, the characteristic lines T1 to T4 of the basic secondary pressure (Psb / Ti) set for each numerical value of the input torque Ti are clamped appropriately when the primary pulley 20 is rotated at a predetermined reference value. It is set to gain power. That is, when the actual primary rotational speed Np ′ deviates from a predetermined reference value, the torque capacity characteristic of the speed change mechanism 14 changes. Therefore, the basic secondary pressure (Psb) set based on the characteristic lines T1 to T4 is changed. / Ti) may be excessive or insufficient. Therefore, by setting the correction coefficient C based on the actual primary rotation speed Np ′ and correcting the basic secondary pressure (Psb / Ti) by this correction coefficient C, the target secondary from the low rotation range to the high rotation range of the primary pulley 20 is obtained. The pressure (Ps / Ti) is set appropriately.

  For example, when the input torque is T3, the target gear ratio is ia, and the actual primary rotational speed Np ′ is a reference value, the clamping force is determined by the basic secondary pressure Pa set along the characteristic line of FIG. However, when the actual primary rotational speed Np ′ deviates from the reference value, the clamping force is insufficient and the drive chain 22 slips or the clamping force becomes excessive. Power loss may increase. Therefore, by executing the correction process by the basic secondary pressure correction unit 69, the basic secondary pressure can be corrected to Pa ′ or Pa ′ ′ according to the increase / decrease amount with respect to the reference value of the actual primary rotation speed Np ′. It is possible to generate a strong clamping force. In addition, since the correction coefficient C is set so as to change according to the target speed ratio i, the correction increase amounts a ′ and b ′ and the correction decrease amounts a ′ ′ and b ′ according to the value of the target speed ratio i. 'Can be changed, and the target secondary pressure (Ps / Ti) can be appropriately set from the low gear ratio to the overdrive state.

  As shown in FIG. 3, the target secondary pressure calculation unit 70 multiplies the target secondary pressure per unit torque (Ps / Ti) by the input torque Ti, and calculates the target secondary pressure Ps to be supplied to the secondary pulley 21. . Subsequently, the CVT control unit 50 sets the drive current based on the target secondary pressure Ps, and then outputs the drive current to the secondary pressure control valve 44, thereby tightening the secondary pulley 21 with an appropriate clamping force. Therefore, it is possible to suppress the slip of the drive chain 22.

  Next, the procedure for calculating the target secondary pressure Ps will be described with reference to a flowchart. FIG. 6 is a flowchart showing a procedure for calculating the target secondary pressure Ps. As shown in FIG. 6, in step S1, the input torque Ti, the target gear ratio i, and the actual primary rotational speed Np 'are read. In step S2, a basic secondary pressure (Psb / Ti) per unit torque is calculated based on the input torque Ti and the target speed ratio i, and in step S3, the target speed ratio i and the actual primary rotation speed Np ′ are calculated. Based on the above, a correction coefficient C is calculated. Subsequently, the process proceeds to step S4, where the basic secondary pressure (Psb / Ti) is corrected by the correction coefficient C, and the target secondary pressure (Ps / Ti) per unit torque is calculated. In step S5, the target secondary pressure (Ps / Ti) per unit torque is multiplied by the input torque Ti, and the target secondary pressure Ps supplied to the secondary pulley 21 is calculated.

  Thus, since the target secondary pressure Ps is calculated based on the input torque Ti, the target speed ratio i, and the actual primary rotational speed Np ′, the torque capacity characteristic of the speed change mechanism 14 depends on the target speed ratio i. In addition to changing, even if the input torque Ti changes in accordance with the actual primary rotational speed Np ′, the target secondary pressure Ps can be appropriately set without causing excess or deficiency. Thereby, since the target clamping force of the secondary pulley 21 can be set appropriately, it is possible to protect the continuously variable transmission 10 by suppressing the slip of the drive chain 22. In addition, since the target secondary pressure Ps is not excessively supplied, the load on the oil pump 40 can be reduced, the power loss in the continuously variable transmission 10 can be reduced, and the fuel consumption of the engine 11 can be reduced. It becomes possible to improve.

  It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the above description, the drive chain 22 is used as a power transmission element. However, the present invention is not limited to this, and the control device of the present invention is applied to a continuously variable transmission including a drive belt as a power transmission element. May be applied.

  In the above description, the primary pressure Pp is adjusted to control the winding diameter of the drive chain 22, and the secondary pressure Ps is adjusted to control the tension of the drive chain 22. However, the present invention is not limited to this. The primary pressure Pp may be adjusted to control the tension of the drive chain 22, and the secondary pressure Ps may be adjusted to control the winding diameter of the drive chain 22. That is, the primary pulley 20 may function as a tightening pulley, and the secondary pulley 21 may function as a transmission pulley.

  Further, in the above description, by setting the basic secondary pressure (Psb / Ti), the basic clamping force generated in the secondary pulley 21 is set, and by setting the target secondary pressure (Ps / Ti), the secondary pulley However, the present invention is not limited to this, and the basic clamping force and the target clamping force are set directly, and the target secondary pressure is calculated from the target clamping force. It goes without saying that it is also good.

It is a skeleton figure which shows the continuously variable transmission controlled by the control apparatus which is one embodiment of this invention. It is the schematic which shows the hydraulic control system and electronic control system of a continuously variable transmission. It is a block diagram which shows the transmission control system of a CVT control unit. It is the schematic which shows an example of the characteristic map referred by the basic | foundation secondary pressure calculation part. It is the schematic which shows an example of the coefficient map referred by the correction coefficient calculation part. It is a flowchart which shows the calculation procedure of a target secondary pressure.

Explanation of symbols

10 continuously variable transmission 14 transmission mechanism 20 primary pulley (transmission pulley)
21 Secondary pulley (clamping pulley)
22 Drive chain (power transmission element)
50 CVT control unit (clamping force setting means)
i Target speed ratio Ti Input torque Np 'Actual primary speed (input speed)

Claims (2)

A transmission mechanism having a transmission pulley and a tightening pulley around which the power transmission element is wound, wherein a winding diameter of the power transmission element is controlled by the transmission pulley, and a tension of the power transmission element is controlled by the tightening pulley; A control device for a continuously variable transmission,
Clamping force setting means for setting a target clamping force of the tightening pulley based on a target transmission ratio set based on a vehicle state, an input torque to the transmission mechanism, and an input rotational speed to the transmission mechanism. A control device for a continuously variable transmission.   2. The continuously variable transmission control device according to claim 1, wherein the clamping force setting means sets a basic clamping force based on a target speed ratio and an input torque, and sets a correction coefficient based on the target speed ratio and an input rotational speed. A control device for a continuously variable transmission, characterized in that the target clamping force is set based on a basic clamping force and a correction coefficient.

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