JP2008106896A - Controller of vehicle with belt-type continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To fully return a transmission ratio to a low side by preventing insufficient hydraulic pressure immediately before a vehicle stops. <P>SOLUTION: In a vehicle with a belt-type continuously variable transmission, pressure supplied to a secondary pulley is increased immediately before the vehicle stops so as to shift the transmission ratio of the belt-type continuously variable transmission to the lowest side, and when the pressure supplied to the secondary pulley is increased by a low returning means, the clutch capacity of a forward clutch is reduced to release the forward clutch (S21). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for a vehicle equipped with a belt type continuously variable transmission.

  In the belt-type continuously variable transmission, a technique is known that improves the running performance at the time of most start by shifting the gear ratio to the lowest side immediately before the vehicle stops. However, when the vehicle is suddenly braked, the gear ratio may not be fully returned to the lowest side.

Therefore, by engaging the lock-up clutch and temporarily increasing the engine torque, the reduction of the input shaft rotation speed of the continuously variable transmission is suppressed, and the gear ratio is sufficiently low even during sudden braking. A technique to return is disclosed in Patent Document 1.
JP 2005-170233 A

  In the above prior art, since the lockup clutch is engaged and the engine and the continuously variable transmission are connected, the engine rotational speed decreases as the vehicle speed decreases, and the oil is driven to rotate by the driving force of the engine. The pump discharge pressure decreases. As a result, the hydraulic pressure supplied to each pulley of the continuously variable transmission decreases, and the hydraulic pressure necessary for shifting may become insufficient, and the gear ratio may not be sufficiently returned to the low side.

  It is an object of the present invention to sufficiently return the gear ratio to the low side by preventing insufficient hydraulic pressure immediately before the vehicle stops.

  The present invention includes a primary pulley connected to the engine side, a secondary pulley connected to the drive shaft side, and a belt wound around both pulleys, and adjusts supply pressure to the primary pulley and the secondary pulley. In a control device for a vehicle equipped with a belt-type continuously variable transmission, comprising: a belt-type continuously variable transmission mechanism capable of changing the transmission ratio steplessly; and a clutch provided so as to be able to connect and disconnect between the engine and the primary pulley. Immediately before the vehicle stops, the supply pressure to the secondary pulley is increased by the low return means for increasing the supply pressure to the secondary pulley to shift the gear ratio of the belt-type continuously variable transmission mechanism to the lowest side, and the low return means. And a clutch release means for releasing the clutch by reducing the clutch capacity of the clutch.

  According to the present invention, the clutch is released during the low return immediately before the vehicle stops, so that the engine and the like on the upstream side of the clutch are separated from the portion where the rotational speed changes due to the shift, and the shift is accordingly performed. The required inertia is reduced. As a result, the pulley thrust required for gear shifting is reduced, and gear shifting can be performed at a lower oil pressure, so that the oil pressure can be ensured more reliably. In addition, since the hydraulic pressure required for the shift is low, the shift is started earlier, so that the difference between the hydraulic pressure at the start of the shift and the upper limit value of the hydraulic pressure is increased, and the shift speed can be increased.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a configuration of a control device for a vehicle equipped with a belt type continuously variable transmission according to the present embodiment. The driving force of the engine 1 is transmitted to the drive wheels 5 through the torque converter 2, the forward / reverse switching mechanism 3, and the belt type continuously variable transmission mechanism 4.

  The forward / reverse switching mechanism 3 has a planetary gear mechanism 6 inside, can switch between the input side and the output side according to the shift position, and can switch the rotation direction of the input shaft. When the vehicle moves forward, the forward clutch 7 that transmits the driving force of the engine 1 to the belt-type continuously variable transmission mechanism 4 is engaged. The clutch capacity, which is the torque that can be transmitted by the forward clutch 7, depends on the fastening force of the forward clutch 7. When the fastening force is reduced, the clutch capacity is also reduced. The fastening force of the forward clutch 7 is controlled by adjusting the clutch pressure by the hydraulic control unit 9 in accordance with a command from the controller 8.

  The belt-type continuously variable transmission mechanism 4 includes a primary pulley 10, a secondary pulley 11, and a belt 12 that is wound around both pulleys 10, 11, and changes the groove width of each pulley 10, 11 to change the belt 12. The gear ratio can be adjusted steplessly by changing the contact diameter between the pulleys 10 and 11. The groove width of each pulley 10, 11 can be changed by controlling a primary pressure that is a hydraulic pressure supplied to the primary pulley 10 and a secondary pressure that is a hydraulic pressure supplied to the secondary pulley 11. The hydraulic pressure supplied to the pulleys 10 and 11 increases the secondary pressure as the gear ratio is higher, that is, the lower side, and increases the primary pressure as the gear ratio is lower, that is, the higher side.

  The primary pressure and the secondary pressure are controlled by the hydraulic control unit 9 in accordance with a command from the controller 8. The primary pressure and the secondary pressure generated in the hydraulic control unit 9 are based on the line pressure, and the upper limit values of the primary pressure and the secondary pressure increase as the line pressure increases. The line pressure is generated based on the discharge pressure of the oil pump that is rotationally driven by the driving force of the engine 1, and the discharge pressure of the oil pump increases as the rotational speed of the engine 1 increases. That is, the upper limit values of the primary pressure and the secondary pressure increase as the rotational speed of the engine 1 increases.

  The driving force shifted by the belt type continuously variable transmission mechanism 4 is transmitted to the drive wheels 5 through the differential 13. The driving wheel 5 and the driven wheel 14 are provided with a brake 15, and the braking force of the brake 15 is controlled by the controller 8.

  The vehicle speed sensor 16, the acceleration sensor 17, and the accelerator opening sensor 18 detect the vehicle speed, vehicle deceleration, and accelerator opening, respectively, and transmit them to the controller 8.

  The controller 8 determines the primary pressure, the secondary pressure, the clutch capacity of the forward clutch 7, the engine speed based on the vehicle speed, deceleration, accelerator opening, engine speed, line pressure, and thrust difference between the primary pulley 10 and the secondary pulley 11. And the braking force of the brake 15 is controlled.

  Next, control performed by the controller will be described with reference to FIGS. 2 to 5 are flowcharts showing the control performed by the controller 8, FIG. 2 shows the control of the hydraulic pressure supplied to the pulley, FIG. 3 shows the control of the clutch capacity, and FIG. 4 shows the control of the engine speed. FIG. 5 shows the control of the brake braking force. Note that the control shown in FIGS. 2 to 5 is executed in parallel at the same time, and is repeatedly performed every minute time.

  First, the control of the hydraulic pressure supplied to the pulley will be described with reference to FIG.

  In step S10, it is determined whether there is a Low return request. If it is determined that there is a low return request, the process proceeds to step S11. If it is determined that there is no low return request, the process proceeds to step S15. When there is a Low return request, it is when it is necessary to perform a so-called Low return in which the speed ratio is shifted to the lowest side in order to improve the traveling performance at the time of the start immediately before the vehicle stops. The Low return request is determined to be requested when the vehicle deceleration is equal to or greater than a predetermined deceleration and the accelerator opening is zero or the driving force target value is equal to or less than zero.

  In step S11, a gear ratio target value is calculated based on the deceleration and the vehicle speed of the vehicle. The speed ratio target value is calculated by referring to the map of FIG. 6, and is set to the lower side as the vehicle speed is lower and the deceleration is higher.

  In step S12, it is determined whether the clutch capacity target value is smaller than the braking force correction value. If the clutch capacity target value is smaller than the braking force correction value, the process proceeds to step S13, and if it is greater than the braking force correction value, the process proceeds to step S14. The clutch capacity target value is a target value of the transmittable torque of the forward clutch 7, and is set in the capacity control of the forward clutch 7 in FIG. The braking force correction value is calculated based on the following equation (1).

Here, F _brake is the braking force, ip is the gear ratio, R _d is the tire moving radius, T _in is the transmission input torque, I _in is the inertia on the transmission input side, and ω _out is the rotational speed of the wheel.

  In step S13 (low return means), hydraulic control is performed. In the hydraulic control, the primary pressure is decreased to a limit at which no belt slip occurs so that the thrust difference between the primary pulley 10 and the secondary pulley 11 is increased, and the secondary pressure is increased. Further, the line pressure is increased so that the secondary pressure is not insufficient.

  In step S14 (low return means), hydraulic control different from that in step S13 is performed. In the hydraulic control in this step, the primary pressure is set as a set value in the normal control, and the secondary pressure is increased. Further, the line pressure is increased so that the secondary pressure is not insufficient.

  On the other hand, if it is determined in step S10 that there is no low return request, the process proceeds to step S15 to perform normal control. Note that normal control is hydraulic control in an operating state in which there is no need to perform Low return, and the control in this case is the same as that conventionally performed, and thus description thereof is omitted.

  Next, the capacity control of the forward clutch 7 will be described with reference to FIG.

  In step S20, it is determined whether there is a Low return request. If it is determined that there is a low return request, the process proceeds to step S21. If it is determined that there is no low return request, the process proceeds to step S22.

  In step S21, the clutch capacity target value is gradually reduced to zero.

  In step S22, it is determined whether or not the clutch capacity target value is smaller than the clutch capacity target value in the normal control. If the clutch capacity target value is smaller than the clutch capacity target value in normal control, the process proceeds to step S23. If the clutch capacity target value is equal to or greater than the clutch capacity target value in normal control, the process proceeds to step S24. The clutch capacity target value in the normal control is a clutch capacity target value in an operating state where there is no need to perform Low return, and is the clutch capacity target value set in step S24.

  In step S23, a clutch capacity target value is calculated based on the driving force target value, the engine torque, and the operating speed of the forward clutch 7. The relationship among the clutch capacity, the driving force target value, the engine torque, and the operating speed of the forward clutch 7 is obtained in advance through experiments or the like. This step is a control performed when there is a re-acceleration request when the clutch capacity target value is decreased in step S21 and it is necessary to re-engage the clutch.

  In step S24, the clutch capacity target value is set to a value in normal control.

  Next, engine speed control will be described with reference to FIG.

  In step S30, it is determined whether there is a Low return request. If it is determined that there is a low return request, the process proceeds to step S31. If it is determined that there is no low return request, the process proceeds to step S33.

  In step S31, it is determined whether the clutch capacity target value is smaller than a predetermined value. If the clutch capacity target value is smaller than the predetermined value, the process proceeds to step S32, and if it is greater than the predetermined value, the process proceeds to step S33. When the rotational speed of the engine 1 is increased, a shock is generated due to an increase in torque transmitted through the forward clutch 7. This shock becomes smaller as the clutch capacity of the forward clutch 7 becomes lower, and no shock occurs when the clutch capacity becomes zero. Therefore, the predetermined value is set to a limit clutch capacity that allows a shock caused by an increase in the engine speed.

  In step S32 (engine rotation increasing means), the engine rotation speed is increased. The engine speed is controlled based on a target value of the engine speed. The target value of the engine rotation speed is calculated so as to realize a desired oil amount balance based on the engine rotation speed, the line pressure, and the thrust difference between the primary pulley 10 and the secondary pulley 11. The relationship between the engine speed, the line pressure, and the thrust difference between the primary pulley 10 and the secondary pulley 11 is obtained in advance through experiments or the like.

  On the other hand, when it is determined in step S30 that there is no low return request, or when it is determined in step S31 that the clutch capacity target value is greater than or equal to a predetermined value, the operation state where it is not necessary to proceed to step S33 and perform low return. Perform normal control at.

  Next, the control of the brake braking force will be described with reference to FIG.

  In step S40, it is determined whether there is a Low return request. If it is determined that there is a low return request, the process proceeds to step S41. If it is determined that there is no low return request, the process proceeds to step S44. The braking force correction value is calculated according to the above equation (1).

  In step S41, it is determined whether the clutch capacity target value is smaller than the braking force correction value. If the clutch capacity target value is smaller than the braking force correction value, the process proceeds to step S42, and if it is greater than the braking force correction value, the process proceeds to step S44.

  In step S42, the braking force correction value is gradually decreased until it becomes zero.

  In step S43 (brake braking force increasing means), the brake braking force is increased. The brake braking force is controlled based on the target value of the brake braking force. The target value of the brake braking force is obtained by adding a value obtained by subtracting the clutch capacity from the braking force correction value to the brake braking force during normal control. When this step is executed, since it is determined in step S41 that the clutch capacity target value is smaller than the braking force correction value, the value obtained by subtracting the clutch capacity from the braking force correction value is a positive value. The target value of the braking force is larger than the brake braking force during normal control.

  On the other hand, when it is determined in step S40 that there is no low return request, or when it is determined in step S41 that the clutch capacity target value is greater than or equal to the braking force correction value, it is not necessary to proceed to step S44 and perform low return. Performs normal brake control during operation.

  Next, the operation of this embodiment will be described with reference to FIG. FIG. 7 is a time chart showing the operation of the control device for a vehicle equipped with a belt-type continuously variable transmission according to this embodiment, where (a) is a control operation state, (b) is an engine speed, (c) is a line pressure, (D) shows the gear ratio, and (e) shows the forward clutch pressure.

  If it is determined that there is a low return request at time t1 while the vehicle is decelerating, the forward clutch pressure decreases and the clutch capacity decreases. In addition, the actual engine speed increases according to the target value of the engine speed, and further, the thrust difference between the primary pulley 10 and the secondary pulley 11 is increased by increasing the line pressure, decreasing the primary pressure, and increasing the secondary pressure. Increases and the gear ratio is reliably shifted to the Low side.

  As described above, in the present embodiment, when the Low return request is satisfied, the clutch capacity is gradually reduced to release the forward clutch 7, so that the upstream side of the forward clutch 7 in the portion where the rotational speed changes due to the speed change. As a result, the engine 1 and the like located at is separated from each other, and the inertia required for shifting is reduced accordingly. As a result, the pulley thrust required for gear shifting is reduced, and gear shifting can be performed at a lower oil pressure, so that the oil pressure can be ensured more reliably. In addition, since the hydraulic pressure required for the shift is low, the shift is started earlier, so that the difference between the hydraulic pressure at the start of the shift and the upper limit value of the hydraulic pressure is increased, and the shift speed can be increased.

  In addition, the clutch capacity is gradually reduced to release the forward clutch 7 and the engine rotational speed is increased, so that the discharge pressure of the oil pump is increased, the line pressure can be increased, and the secondary pressure is increased accordingly. Can be made. As a result, the hydraulic pressure required to shift the gear ratio to the Low side can be ensured, and the speed difference can be increased by increasing the thrust difference between the primary pulley 10 and the secondary pulley 11.

  Further, the clutch capacity is gradually reduced to release the forward clutch 7 and the brake braking force is increased, so that the reduction in the braking force of the entire vehicle due to the engine braking force being reduced as the forward clutch 7 is released is compensated. It is possible to prevent the driver from feeling uncomfortable by maintaining the deceleration before releasing the forward clutch.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea.

It is a schematic block diagram which shows the structure of the control apparatus of the vehicle with a belt-type continuously variable transmission in this embodiment. It is a flowchart which shows control of the hydraulic pressure supplied to a pulley. 3 is a flowchart showing control of the capacity of a forward clutch 7. It is a flowchart which shows control of an engine speed. It is a flowchart which shows control of brake braking force. It is a map which shows the relationship between a vehicle speed, deceleration, and a gear ratio. It is a time chart which shows the effect | action of the control apparatus of the vehicle with a belt-type continuously variable transmission in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 4 Belt type continuously variable transmission mechanism 5 Drive wheel 7 Forward clutch 8 Controller 10 Primary pulley 11 Secondary pulley 12 Belt 14 Driven wheel 15 Brake

Claims (3)

It is composed of a primary pulley connected to the engine side, a secondary pulley connected to the drive shaft side, and a belt wound around both pulleys, and by adjusting the supply pressure to the primary pulley and the secondary pulley In a control device for a vehicle equipped with a belt-type continuously variable transmission, comprising: a belt-type continuously variable transmission mechanism capable of continuously changing a gear ratio; and a clutch provided so as to be capable of connecting / disconnecting between the engine and the primary pulley.
Immediately before the vehicle stops, a low return means for increasing the supply pressure to the secondary pulley to shift the speed ratio of the belt type continuously variable transmission mechanism to the lowest side;
Clutch release means for reducing the clutch capacity of the clutch and releasing the clutch when increasing the supply pressure to the secondary pulley by the low return means;
A control device for a vehicle equipped with a belt-type continuously variable transmission.   The control device for a vehicle with a belt-type continuously variable transmission according to claim 1, further comprising engine rotation increasing means for increasing the rotation speed of the engine when the clutch capacity is reduced.   The belt-type continuously variable transmission according to claim 1 or 2, further comprising brake braking force increasing means for increasing a braking force of a brake provided on a wheel of the vehicle when the clutch capacity is reduced. A control device for a machine-mounted vehicle.