JP5386228B2 - Control device for continuously variable transmission - Google Patents

Description

  The present invention relates to a control device for a wrapping type continuously variable transmission, and more particularly to a device that reliably downshifts while suppressing oil flow consumption during sudden deceleration.

  In a continuously variable transmission that changes power by changing the effective pulley diameter by changing the effective pulley diameter by transmitting power from the input pulley to the output pulley by means of a winding member such as a chain or belt. Sometimes it is necessary to perform a quick downshift and return the gear ratio to the deceleration side in order to ensure the driving force at the time of restart after stopping.

  Further, such a continuously variable transmission includes a torque converter that is a fluid coupling as a starting device. Such a torque converter has a lockup clutch that directly connects the input / output unit to improve transmission efficiency during traveling, and locks up (fastens) during traveling and prevents engine stall during deceleration stop. Open (release). The lock-up clutch is operated by a duty solenoid and includes a slip control valve that controls the clutch pressure of the lock-up clutch by changing the apply pressure and release pressure, and a switching valve that switches between supplying and shutting off the hydraulic pressure from the slip control valve. ing. Normally, a quick release of the lockup clutch causes a shock. Therefore, the lockup clutch is gently released by gradually increasing the release pressure while the switching valve is on.

Conventionally, as a prior art related to unlocking, for example, in Patent Document 1, when the deceleration force of a vehicle exceeds a predetermined value and the vehicle speed is equal to or less than a specified value, the occupant does not feel a feeling of idling due to unlocking. For this reason, the reduction ratio is temporarily reduced (upshift) to release the lockup clutch.
Further, in Patent Document 2, the lockup release vehicle speed is set to the lower speed side and the operation of the lockup mechanism is performed when it is determined that the amount of depression of the brake pedal detected by the brake sensor is large and the degree of deceleration of the vehicle is large. What is set so that the release time is delayed is described.

JP 2001-99308 A JP 2001-56050 A

When the vehicle suddenly decelerates, it is necessary to perform a quick downshift to secure the driving force when restarting after stopping, and to return the gear ratio to the deceleration side. In order to perform such a fast shift, it is necessary to increase the line pressure of the control oil, so that the required oil flow rate increases compared to the normal time.
However, when the engine is decelerated and stopped, the engine speed is lowered due to the lock-up, so that the oil pump discharge capacity is reduced, and the required oil flow rate is further increased to operate the lock-up release control. become.
On the other hand, when the capacity of the oil pump is increased in order to prevent the oil flow rate from being insufficient, the layout of the entire transmission is affected, and the mass and cost are also increased.
It is also possible to increase the engine speed by downshifting when the accelerator is off and increase the oil pump discharge in preparation for sudden deceleration, but if the engine speed increases when the accelerator is off, the driver will feel uncomfortable. Also, there is a concern that drivability deteriorates as the effectiveness of engine braking increases.
Furthermore, it is conceivable to increase the vehicle speed at which the lockup release control is started. In this case, however, the fuel cut region when the vehicle is coasting becomes narrow, so there is a concern that the fuel consumption may deteriorate.
In view of the above-described problems, an object of the present invention is to provide a control device for a continuously variable transmission that reliably suppresses downshifting while suppressing oil flow consumption during sudden deceleration.

The present invention solves the above-described problems by the following means.
According to the first aspect of the present invention, there is provided a transmission mechanism having an input pulley and an output pulley in which an effective power diameter can be continuously changed while an annular power transmission member is wound thereon, an impeller connected to an engine output shaft, and the input pulley A torque converter having a turbine connected to the torque converter, a lockup clutch that directly connects an input / output unit of the torque converter , a slip control valve that controls a clutch pressure of the lockup clutch by adjusting a control hydraulic pressure of the torque converter , A switching valve that switches between supply and cutoff of the control hydraulic pressure to the torque converter , a shift control valve that adjusts the control hydraulic pressure of the transmission mechanism to perform a shift operation, pressurizing oil, and the slip control valve; A control device for controlling a continuously variable transmission comprising an oil pump for supplying to the shift control valve And a deceleration detecting means for detecting deceleration of the vehicle, wherein the switching is performed after the slip control valve is controlled to decelerate the lockup clutch from the lockup state to the release state when the vehicle is decelerated. A steplessly characterized by shutting off the valve, shutting off the supply of hydraulic pressure to the torque converter, and increasing the transition speed from the lock-up state to the open state as the deceleration increases. This is a transmission control device.

  According to the present invention, by rapidly increasing the transition speed of the lockup clutch from the lockup state to the release state at the time of sudden deceleration, the lockup release is terminated early, the switching valve is shut off, and the lockup release control is performed. Oil consumption can be terminated. Then, by performing a downshift of the continuously variable transmission mechanism after the switching valve is shut off, the lockup release control and the downshift control are performed at the same time, so that the oil flow rate does not run short. Even if it exists, it can prevent that the oil flow rate required for a downshift is insufficient, and can perform a downshift reliably.

It is a schematic diagram showing a configuration of a continuously variable transmission for a vehicle including an embodiment of a control device for a continuously variable transmission to which the present invention is applied. It is a figure which shows the structure of the hydraulic control mechanism in the continuously variable transmission of FIG. Changes in the lock-up signal, switching valve signal, engine speed, turbine speed, lock-up duty instruction (target clutch pressure), and oil consumption image of the lock-up release during sudden deceleration stop in the continuously variable transmission of FIG. It is a timing chart which shows an example.

  The present invention aims to provide a control device for a continuously variable transmission that suppresses oil flow consumption during sudden deceleration and reliably downshifts, and provides a rate of change per hour of the target clutch pressure of a lockup clutch during sudden deceleration. The problem was solved by increasing the speed and opening it quickly, then shutting off the switching valve and downshifting the transmission mechanism.

Embodiments of a control device for a continuously variable transmission to which the present invention is applied will be described below.
FIG. 1 is a schematic diagram illustrating a configuration of a continuously variable transmission for a vehicle including a control device of an embodiment.
FIG. 2 is a diagram showing a configuration of a hydraulic control mechanism in the continuously variable transmission of FIG.
This continuously variable transmission (CVT) is of a chain type that changes the engine output of an automobile such as a passenger car.
The continuously variable transmission 1 includes a transmission mechanism unit 10, a torque converter 20, an oil pan 30, an oil pump 40, a control valve assembly 100, a transmission control unit (TCU) 200, and the like.

The transmission mechanism unit 10 includes an input pulley 11, an output pulley 12, a chain 13, and the like, and constitutes a transmission unit of a chain type continuously variable transmission (CVT).
The input pulley 11 and the output pulley 12 are provided adjacent to each other so as to be rotatable around axes arranged in parallel.
The input pulley 11 is a drive pulley connected to the output part of the torque converter 20.
The output pulley 12 is a driven pulley connected to the front and rear axle differentials via an AWD transfer (not shown) or the like.
The chain 13 is formed in an annular shape by connecting a large number of metal link plates so as to be swingable by a pin serving as a rotation shaft. The chain 13 is wound around the input pulley 11 and the output pulley 12, and transmits power between them.
Each of the input pulley 11 and the output pulley 12 has a pair of tapered surfaces that sandwich both end surfaces of the pins of the chain 13, and the effective diameter is changed by changing the interval between these tapered surfaces by hydraulic pressure, thereby changing the transmission ratio. It can be changed.

The torque converter 20 is a fluid coupling that is provided at the input portion of the continuously variable transmission 1 and is used as a starting device. The torque converter 20 includes an impeller connected to an output shaft of an engine (not shown), a turbine connected to the input pulley 11, a stator that is a fixed blade, and the like.
The torque converter 20 includes a lock-up clutch that mechanically connects the input / output unit directly. The lock-up clutch is configured to eliminate slippage of the torque converter 20 (rotational difference between the impeller and the turbine) and improve transmission efficiency during traveling by fastening a lock-up piston that is operated by hydraulic pressure.

The oil pan 30 is provided at the bottom of a transmission case (not shown), which is a casing in which the transmission mechanism 10 and the torque converter 20 are accommodated, and is an automatic transmission fluid (hereinafter simply referred to as oil and hydraulic fluid) that is hydraulic oil for the continuously variable transmission 1. Is stored).
The oil pump 40 is connected to the output shaft of the engine via the impeller side of the torque converter 20, is driven by the output of the engine, and pressurizes and discharges oil.

The control valve assembly 100 is a unitized valve used for various hydraulic controls such as shift control, lock-up control, AWD transfer control, etc. in the continuously variable transmission 1.
As shown in FIG. 1, the control valve assembly 100 includes a line pressure valve 101, a speed change valve 102, a slip control valve 103, a duty solenoid 104, a switching valve 105, and the like.

The line pressure valve 101 adjusts the oil pressure by discharging excess oil from the oil line pressure circuit discharged by the oil pump 40 in accordance with control by the TCU 200, and generates a predetermined line pressure suitable for the operating state. It is. This line pressure is supplied to each hardware H through other control valves V in addition to the shift valve 102, the slip control valve 103, and the like.
The speed change valve 102 adjusts the hydraulic pressure supplied from the line pressure valve 101 in accordance with control by the TCU 200 and supplies it to the speed change mechanism unit 10 to perform a speed change operation.
The slip control valve 103 adjusts the hydraulic pressure supplied from the line pressure valve 101 and supplies it to the torque converter 20 to change the clutch pressure (engagement force) of the lockup clutch. The slip control valve 103 controls an apply pressure that presses the lock-up piston to the fastening side and a release pressure that presses the lock-up piston to the opening side. The pressure-bonding force of the lock-up clutch is the difference between the apply-side thrust acting on the lock-up piston by the apply pressure and the release-side thrust acting by the release pressure.
The duty solenoid 104 controls the slip control valve 103 by generating a signal pressure of the slip control valve 103 according to control by the TCU 200.
The switching valve 105 is provided in the middle of a pipe through which the slip control valve 103 supplies the apply pressure and the release pressure to the torque converter 20, and switches between supplying and shutting off the hydraulic pressure from the slip control valve 103 to the torque converter 20.

Further, as shown in FIG. 2, the control valve assembly 100 includes a switching valve control solenoid 106, a drain back prevention valve 107, a torque converter pressure regulator 108, a pilot regulator 109, a lubrication valve 110, and the like.
The switching valve control solenoid 106 controls the switching valve 105 by generating a signal pressure of the switching valve 105 according to control by the TCU 200.
The drain back prevention valve 107 is provided in the middle of the line for supplying the apply pressure from the switching valve 105 to the torque converter 20.
The torque converter pressure regulator 108 and the pilot regulator 109 adjust the line pressure and maintain the hydraulic pressure supplied to the slip control valve 103 and the switching valve 105 within a predetermined range.
The lubrication valve 110 switches the lubricating oil passage when the torque converter 20 is locked up.

The TCU 200 includes an information processing device such as a CPU, a storage device such as a RAM and a ROM, an input / output interface, and the like. For example, various information such as an accelerator pedal opening, an engine speed, an engine torque, a vehicle speed, and a turbine speed The control device for the continuously variable transmission 1 that controls the gear ratio of the speed change mechanism unit 10, the clutch pressure of the lockup clutch, and the like.
The speed ratio control is executed based on a speed map in which a speed ratio set in advance according to the driving state of the vehicle, such as the vehicle speed and engine torque, is read. In addition, when the vehicle is decelerated to a stop, a downshift to the large reduction ratio side is performed in preparation for a restart immediately before the vehicle stops.

The TCU 200 is preprogrammed with the lockup clutch engagement and disengagement conditions. The establishment of such engagement and release conditions is determined based on, for example, the accelerator pedal opening, the vehicle speed, and the like.
When the lockup is released, the duty solenoid 104 causes the pilot pressure to act on the release side end of the slip control valve 103 in the valve body while the switching valve 105 is turned on. As a result, the slip control valve 103 increases the release pressure of the torque converter 20. Further, the slip control valve 103 reduces the apply pressure by discharging oil from the apply pressure line of the torque converter 20. Then, the lockup piston is driven by the differential pressure between the apply pressure and the release pressure, and the lockup clutch is released. Since the TCU 200 gradually changes the lock-up duty instruction to the duty solenoid 104, the slip control valve 103 moves gradually, and the clutch pressure of the lock-up clutch decreases smoothly.

  After the lockup clutch is released, the TCU 200 turns off (cuts off) the switching valve 105. The lock-up release control consumes oil during its execution, but when the switching valve 105 is turned off after completion, the oil consumption in the torque converter is substantially eliminated, and the oil discharged from the oil pump 40 is used for lubrication. Most of them can be used by the shift valve 102 or the like except for a small amount.

A front / rear G sensor 201 for detecting longitudinal acceleration acting on the vehicle body is connected to the TCU 200.
The TCU 200 changes the target clutch pressure change rate when the lockup clutch is released according to the increase in the deceleration detected by the front-rear G sensor 201 when the lockup clutch release condition is established at the time of deceleration stop (FIG. 3). (Gradient) in order to increase the transition speed from the lock-up state to the open state.
Here, the change rate of the target clutch pressure may be changed steplessly according to the magnitude of the deceleration, or may be changed stepwise by providing one or a plurality of threshold values for the deceleration. You may do it.

Next, the effect of the above-described embodiment will be described in comparison with a comparative example of the present invention described below.
The control device for the continuously variable transmission of the comparative example has substantially the same configuration as that of the embodiment except that the target clutch pressure is changed at a predetermined change rate regardless of the deceleration of the vehicle during the lockup release control. Yes.
FIG. 3 is a diagram of lockup signal, switching valve signal, engine speed, turbine speed, lockup duty instruction (target clutch pressure), and oil consumption image of unlocking release in sudden deceleration stop in the embodiment and the comparative example. It is a timing chart which shows an example of transition.
In FIG. 3, an example is shown by a broken line and a comparative example is shown by a solid line.

  As shown in FIG. 3, in the comparative example, the rate of change of the target clutch pressure at the time of sudden deceleration is smaller than that in the example, and the lockup release is completed and the switching valve 105 is changed in order to gently change the target clutch pressure. It takes a long time to turn off (shut off), and during this time, the amount of oil consumed by the lock-up opening control increases. In addition, because the lock-up release is delayed, the engine speed decreases with the turbine speed for a long time. During this time, the discharge amount of the oil pump 40 decreases, and the amount of oil necessary for the shift control is insufficient. There is a concern to do. Furthermore, when the lockup release is completed, the engine speed is low, so the discharge amount of the oil pump 40 is further reduced.

  On the other hand, in the embodiment, the target clutch pressure is quickly reduced at the time of sudden deceleration as compared with the comparative example, so that the lockup release is completed at an early stage, the switching valve 105 is shut off, and the oil by the lockup release control is Consumption can be completed in a short time. After that, most of the oil discharged from the oil pump 40, excluding the lubrication flow rate, can be used for the shift control. Further, after the lockup is released, the engine speed becomes higher than the turbine speed, and the discharge amount of the oil pump 40 directly connected to the engine also increases. Furthermore, since the lock-up release ends while the engine speed is high, it is possible to generate an oil flow rate that can be used for speed change control from a region where the engine speed is higher than before. This increases the oil flow rate that can be used for gear shifting control, and it is possible to increase the line pressure and perform a quick downshift. Even if there is, it can be done reliably.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
(1) The configuration of the continuously variable transmission and its control device is not limited to the above-described embodiments, and can be changed as appropriate. For example, the continuously variable transmission of the embodiment is of a chain type, but the present invention can also be applied to a belt type continuously variable transmission. Further, the configuration of the hydraulic circuit can be changed as appropriate.
(2) Although the deceleration of the vehicle is detected using the acceleration sensor in the embodiment, the deceleration may be detected by other methods. For example, the deceleration may be calculated based on the transition of the detection value of the vehicle speed sensor. Further, the deceleration may be detected based on the depression amount of the brake pedal, the depression force, and the brake fluid pressure.

DESCRIPTION OF SYMBOLS 1 Continuously variable transmission 10 Transmission mechanism part 11 Input pulley 12 Output pulley 13 Chain 20 Torque converter 30 Oil pan 40 Oil pump 100 Control valve assembly 101 Line pressure valve 102 Shift valve 103 Slip control valve 104 Duty solenoid 105 Switching valve 106 Switching valve Control solenoid 107 Drain back prevention valve 108 Torcon pressure regulator 109 Pilot regulator 110 Lubrication valve 200 Transmission control unit (TCU)
201 Front and rear G sensor

Claims (1)

A transmission mechanism having an input pulley and an output pulley on which an annular power transmission member is wound and an effective diameter can be continuously changed;
A torque converter having an impeller connected to an engine output shaft and a turbine connected to the input pulley;
A lock-up clutch directly connecting the input / output part of the torque converter;
A slip control valve for adjusting the control hydraulic pressure of the torque converter to control the clutch pressure of the lockup clutch ;
A switching valve for switching between supply and cutoff of the control hydraulic pressure to the torque converter ;
A shift control valve for adjusting a control hydraulic pressure of the transmission mechanism unit to perform a shift operation;
A control device for controlling a continuously variable transmission comprising: an oil pump that pressurizes oil and supplies the slip control valve and the shift control valve;
A deceleration detecting means for detecting the deceleration of the vehicle;
Controlling the slip control valve during deceleration of the vehicle to gradually change the lockup clutch from a lockup state to an open state, and then shutting off the switching valve and shutting off the supply of hydraulic pressure to the torque converter , A control device for a continuously variable transmission, wherein the speed of transition from the lock-up state to the open state is increased as the deceleration increases.

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