JPH03213770A - Control device for continuously variable - Google Patents

Abstract

PURPOSE:To improve the durability of a pulley and a belt by fixing a primary control valve so that the primary pressure becomes maximum at the time of failure such as disconnection or the like, and preventing the abnormal pressure rise with a relief valve device provided in a circuit between a primary cylinder and the primary control valve. CONSTITUTION:A non-stage transmission 5 is controlled for speed change on the basis of the primary pressure of a primary control valve 60 to be controlled by a primary control unit 72. In the case that the electrical signal is not input because of disconnection or the like, the primary pressure is made maximum to forcedly fix the non-stage transmission 5 to a high-speed stage of the minimum speed change ratio for fail-safe so that the quick deceleration and a slip of a belt 26 is not generated. At this stage, when the primary pressure rises more than a required value with the secondary pressure, the oil pressure of a primary cylinder 21 is restricted by a relief valve device 81 to avoid an overload of the belt 26 and pulleys 22, 25. Durability of the belt is thereby improved to eliminate unrequired increase of rigidity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device that performs speed change control using secondary pressure control and primary pressure in a held-type continuously variable transmission for a vehicle. Concerning fail-safe measures in the event of a breakdown such as wire breakage.

[Conventional technology]

Generally, in this type of continuously variable transmission, the various control valves of the actuator of the hydraulic control system are improved to, for example, current control type ones, and the control system optimally calculates the secondary pressure and the primary pressure based on various information.

The aim is to operate the control valve using the electrically operated amount to optimally control the secondary pressure corresponding to the transmitted torque and the primary pressure corresponding to each driving and driving condition. In addition, it is thought that such computerization will enable effective measures to be taken against various troubles, such as fail-safe measures, effective use of continuously variable transmission, and optimization of devices such as anti-lock braking systems (ABS) and lock-up clutches. ing.

Here, we will specifically discuss the fail-safe situation when the electrical signal of the primary control valve is no longer input due to a failure such as a disconnection. In this case, you can set the primary control valve to the oil drain position by not inputting an electrical signal and set the primary pressure to zero and fix it at the maximum gear ratio, or conversely, set the primary control valve to the oil supply position and set the primary pressure to zero. Either the gear ratio is set to the maximum and the gear ratio is fixed to the minimum. For example, if we consider the possibility of a failure during high-speed driving, the method of fixing the gear ratio to the maximum gear ratio lacks safety due to sudden downshifting and braking, and a sudden drop in primary pressure may cause belt slipping, etc. There are concerns. Therefore, in the event of a failure, it is preferable to maximize the primary pressure and fix the gear ratio to the minimum gear ratio.

By the way, in the secondary pressure control system, the actual gear ratio is calculated from the rotation speed ratio of the primary pulley rotation speed to the secondary pulley rotation speed, and the target secondary pressure is calculated from the corresponding required secondary pressure and engine torque, etc. It controls the pressure. Therefore, even in the event of the above-mentioned failure on the primary side, the secondary pressure is controlled regardless of the failure, and when the vehicle is stopped, the maximum gear ratio is detected and a high secondary pressure is set accordingly. Therefore, when the vehicle stops due to such a primary side failure, high secondary pressure is guided to the primary cylinder via the primary control valve at the refueling position, and the primary pressure increases to several times its normal maximum value. In this way, excessive hydraulic pressure is applied to the primary pulley and belt, which deforms the cylinder and stretches the belt.

Unnecessary loads such as deformation may be applied.

For this reason, as a fail-safe measure against the failure on the primary side described above, it is necessary to further add a mechanical means to prevent an abnormal increase in the primary pressure.

Conventionally, there is a prior art, for example, Japanese Unexamined Patent Publication No. 60-249761, regarding a fail-safe method for the electric signal input fail-safe of the control valve of the continuously variable transmission. Here, in a device equipped with a shift direction switching valve and a shift speed control valve as primary control valves, it has been shown that if one of the solenoid is disconnected, the other one is also de-energized as a failsafe. .

[Invention or problem to be solved]

By the way, the above-mentioned prior art restricts mutual operation of the valves when the primary control valve has two valves, and cannot be applied to a case where there is only one valve as in the present application. Furthermore, it is not possible to prevent abnormal increases in primary pressure, which is a problem of the present application.

The present invention has been made in view of the above points, and its purpose is to prevent an abnormal increase in primary pressure in the case of fail-safe to increase the primary pressure in the event of a failure such as disconnection of the electrical signal on the primary side. Prevents the durability of pulleys and belts.

It is an object of the present invention to provide a control device for a continuously variable transmission that can improve running performance and the like.

[Means to solve the problem]

In order to achieve the above object, the control device for a continuously variable transmission of the present invention sets the primary control valve that controls the primary pressure by an electric signal so as to fix the primary pressure to the maximum in the event of a failure such as a wire breakage. A relief valve device is provided in the circuit between the primary control valve and the primary cylinder to prevent an abnormal increase in cylinder oil pressure.

[For production]

Based on the above configuration, the continuously variable transmission is controlled to change speed based on the primary pressure of the primary control valve, and if the electric signal is not input due to a disconnection etc., the primary pressure is maximized and the gear is forcibly fixed at the high speed gear with the minimum gear ratio. This is a failsafe to prevent sudden deceleration, belt slip, etc. At this time, if the primary pressure as well as the secondary pressure becomes higher than necessary, the oil pressure of the primary cylinder is regulated by the relief valve device to avoid overloading the belt and the boob.

〔Example〕 Embodiments of the present invention will be described below based on the drawings.

Referring to FIG. 1, an outline of the drive system of a continuously variable transmission with a lock-up converter will be described. Reference numeral 1 is an engine, and a crankshaft 2 is connected to a torque converter device 31, a forward/reverse switching device 4. Continuously variable transmission 5 and differential device 6
The transmission is configured sequentially.

In the torque converter device 3, the crankshaft 2 is connected to a converter cover 11 and a pump impeller 12a of a torque converter 12 via a drive plate 10. A turbine runner 12b of the torque converter 12 is connected to a turbine shaft 13, and a stator 12c is guided by a one-way clutch 14. The lock-up clutch 15, which is integral with the turbine runner 12b, is installed so as to be engageable or disengageable with the drive plate IO, and transfers the engine power to the torque converter I2 or the lock-up clutch 15.
communicate through.

The forward/reverse switching device 4 has a double pinion planetary gear 16, the turbine shaft 13 is input to the sun gear 16a, and output is output from the carrier 16b to the primary shaft 20. A forward clutch 17 is provided between the sun gear 16a and the ring gear 16c, and a reverse brake 18 is provided between the ring gear 16c and the case, and when the forward clutch 17 is engaged, the planetary gear 16 is integrated to connect the turbine shaft 13 and the primary shaft. 20 is directly connected. Furthermore, the reverse brake 18 is engaged to output reversed power to the primary shaft 20, and the forward clutch 17 and reverse brake 18 are released to free the planetary gear 16.

The continuously variable transmission 5 has a hydraulic cylinder 21 on a primary shaft 20.
The primary pulley 22 with variable pulley spacing has
A secondary pulley 25 having a hydraulic cylinder 24 is similarly provided on the secondary shaft 23, and the primary pulley 2
A drive belt 26 is wound between the pulley 2 and the secondary pulley 25. Here, the pressure-receiving area of the primary cylinder 21 is set to be larger than that of the primary cylinder 21, and the primary pressure of the primary cylinder 21 causes the primary pulley 22. The winding around the secondary pulley 25 is configured to change the diameter ratio so as to be continuously variable.

In the differential device 6, an output shaft 28 is connected to a secondary shaft 23 via a pair of compression gears 27.
The drive gear 29 of this output shaft 28 is the final gear 3.
meshes with 0. And the differential device 31 of the final gear 30
is connected to left and right wheels 33 via an axle 32.

On the other hand, in order to obtain a hydraulic power source for controlling the continuously variable transmission, a main oil pump 34 is disposed adjacent to the torque converter 12, and this main oil pump 34 is connected to the converter cover 11 by a pump drive shaft 35, so that the main oil pump 34 is always connected to the converter cover 11 by a pump drive shaft 35. The pump is driven by engine power to generate hydraulic pressure. Here, in the continuously variable transmission 4, since the oil pressure is controlled over a wide range of high and low levels, the oil pump 34 is, for example, a roller vane type, and has a plurality of sets of suction and discharge ports, and is configured as a variable displacement type.

Next, a continuously variable transmission control system will be described as a hydraulic control system.

First, an oil passage 4I from the oil pump 34 that communicates with the oil pump 0 communicates with the secondary control valve 50 to generate a predetermined secondary pressure Ps, and this secondary pressure Ps is constantly supplied to the secondary cylinder 24 through the oil passage 42. Supplied. The secondary pressure Ps is guided to the primary control valve 60 via the oil passage 43, and is supplied to and discharged from the secondary cylinder 2I through the oil passage 44, thereby generating the primary pressure Pp.

The secondary control valve 50 is a direct-acting proportional electromagnetic relief valve, and a stepped spool 52 is inserted into the valve body 51.
A spring 53 is biased on one side of the spool 52, and a rod 55 of a proportional solenoid 54 is connected to the other side. The spool 52 is formed with a large diameter land 52a and a small diameter land 52b, and a hydraulic chamber 51a of the oil passage 41 applies a secondary pressure Ps to both lands 52a and 52b, and a chamfer 52c drains oil to the drain port 51b. It is supposed to be done. As a result, spring 5
In response to the spring force Fs of 3, the hydraulic reaction force Ps ・ΔS of the secondary pressure Ps (ΔS is the difference in pressure receiving area) and the electromagnetic pressing force -Is due to the solenoid current Is oppose, and the pressure is adjusted so that both are balanced. . Therefore, the balance equation in this case is as follows.

K-Is +Ps-·Δ5-Fs Therefore, as shown in FIG. 2(a), the secondary pressure Ps has a characteristic of changing in a one-to-one proportional relationship with respect to the solenoid current Is. When the solenoid current Is is zero, the secondary pressure Ps becomes the maximum value (F s / ΔS), and the secondary pressure Ps decreases as the solenoid current Is increases, resulting in the decrease of the solenoid current Is. It has a fail-safe function that prevents belt slip in case of signal failure.

The primary control valve 60 is a direct-acting proportional solenoid valve,
A spool 62 is inserted into the valve body 61, and a spring 63 is biased on one side of the spool 62. Further, a rod 65 that protrudes by the electromagnetic force of the proportional solenoid 64 is connected to the other side of the spool 62, so that the spool opening area can be varied along with the spring load. Spool 6
2 is a port 61b of the oil passage 43 on the proportional solenoid 64 side.
It has a land 62a that opens and closes the drain port 61c on the spring 63 side, and a land 62b that opens and closes the drain port 61c.
Both lands 62a and 62b are connected to the hydraulic chamber 61a which communicates with the hydraulic chamber 61a.
Primary pressure Pp acts on. and Rand [i2a
By introducing the secondary pressure Ps and reducing the primary pressure Pp by draining it through the land 1li2b, control is performed so that a predetermined primary pressure Pp is generated.

As a result, the spring force Fp of the spring 63 is opposed by the electromagnetic pressing force 1p due to the solenoid current II) of the proportional solenoid 64, and the pressure is reduced so that both are released. Therefore, the balance equation in this case is as follows.

K-1p -Fp Therefore, in this case, as shown in FIG. 2(b), the primary opening area changes in a 1:1 proportional relationship with respect to the solenoid current 1p. And solenoid current! In the case of p or zero, the primary pressure Pp becomes the maximum value (Ps), and the primary pressure Pp has a decreasing function characteristic with respect to the solenoid current 1p, and the primary pressure pp is maximized when the signal of the solenoid current 1p fails. It has a fail-safe function.

The control unit 70 uses a secondary pressure control section 71 to calculate a target secondary pressure according to the transmission torque of the pulley and the belt, and accordingly determines the flow IS in a proportional relationship and outputs it to the proportional solenoid 54. .

The primary pressure control unit 72 also controls the primary pressure necessary to maintain a predetermined gear ratio with a predetermined transmission torque.
The target primary flow rate is calculated based on the primary pressure necessary to achieve the deviation of the gear ratio, and the solenoid current 1p is determined in a proportional relationship according to the calculated primary pressure, and is output to the proportional solenoid 64.

Note that a relatively high lubricating pressure is always generated in the oil passage 45 on the drain side of the secondary control valve 50. Therefore, this lubricating pressure
Torque converter 12. Forward/forward switching device 4, belt 24
The circuit is configured so that the lubricant is supplied to the lubricating parts, etc.

In the above-described control system, a measure to prevent an abnormal increase in primary pressure in the event of an electrical failure on the primary side will be described. A relief valve device 80 is provided in the oil passage 44 between the primary cylinder 21 and the primary control valve 60. In this relief valve device 80, a relief valve 81 has a spool 83 on a valve body 82, and a splinter 84 on one side of the spool 83.
is energized, and a hydraulic pressure chamber 85 is provided on the other side. It also has two outlet ports 82b, 82c and a drain port 82d for the human port 82a,
The oil passage 44 from the primary control valve 60 is connected to the inlet port 82
a, and one outlet port 82b communicates with the primary cylinder 21 via an oil passage 44'. Furthermore, the oil passage 44' communicates with the hydraulic chamber 85 via the oil passage 46, and the outlet port 82c is connected via the oil passage 48 having an orifice 47.
communicate with. Here, the spring force of the spring 84 is set to a value slightly larger than the maximum value of the normal hydraulic pressure acting on the spool 83 in the hydraulic chamber 85.

Next, the operation of the continuously variable transmission control device having such a configuration will be described.

First, when the engine 1 is operated, the converter cover 11 of the torque converter 12 is opened. The oil pump 34 is driven by the pump drive shaft 35 to generate oil pressure, and this oil pressure is guided to the secondary control valve 50. Therefore, when the vehicle is stopped, the target gear ratio is, etc. of the primary pressure control system is set to a value larger than, for example, 2.5 as the mechanical maximum gear ratio of the continuously variable transmission 5. Therefore, the target primary pressure becomes the lowest, and the solenoid current Ip corresponding to this is input to the proportional solenoid 64 of the primary control valve 60 and operates to the drain side, so that the primary pressure Pp is not generated. Therefore, all of the secondary pressure Ps from the secondary control valve 50 is supplied only to the secondary cylinder 24, and the continuously variable transmission 5 is in the low speed stage with the maximum gear ratio in which the belt 26 is shifted most toward the secondary pulley 25.

At this time, the lock-up clutch 15 is released by a hydraulic control system (not shown), and the torque converter 12 is supplied with oil. Therefore, for example, when shifting to the drive range, the forward clutch 17 of the forward/reverse switching device 4 is engaged by refueling and becomes the forward position.

Therefore, the power of the engine l is transferred to the torque converter 12,
It is input to the primary shaft 20 of the continuously variable transmission 5 via the forward/reverse switching device 4, and the primary pulley 22. The power of the maximum gear ratio is output to the secondary shaft 23 by the secondary pulley 25 and the heald 26, which is transmitted to the differential device 6.
The signal is transmitted to the wheels 33 via , and the vehicle can be started.

Therefore, when the vehicle starts by pressing the accelerator, the secondary pressure control section 71 of the control unit 70 estimates the transmitted torque, and a solenoid current Is corresponding to this is input to the proportional solenoid 54 of the secondary control valve 50. Here, when the transmitted torque is large at the time of starting, the pressing force is small due to the solenoid current Is, so the secondary pressure Ps is set high.

On the other hand, when the gear ratio decreases after the start of gear shifting, the lock-up clutch 15 engages, and the accelerator pedal depression is further reduced to reduce the target secondary pressure, the solenoid current Is
By increasing the pressing force, the amount of drain increases in the control valve 50, and the secondary pressure Ps is controlled to decrease.

In this way, optimal control is performed to always ensure the minimum pulley pressing force that does not cause belt slip in relation to the transmitted torque.

This secondary pressure Ps is guided to the primary control valve 60 and is reduced to generate a primary pressure Pp, thereby controlling the speed change. That is, at the maximum gear ratio when starting, the solenoid current i
p is large, the primary control valve 60 and the proportional solenoid 6
The primary pressure Pp becomes the lowest level due to the large pressing force caused by the large diameter land 62b moving toward the drain side to open the drain port file. Then, when the gear shift starts, the solenoid current 1p is gradually controlled to be smaller, and the pressing force is accordingly reduced and the land E12a is moved to the oil supply side, that is, the land E12a is operated to open 61b, and the primary pressure Pp is gradually increased. Therefore, belt 2B
In this case, the winding of the primary pulley 22 is shifted to a larger diameter, and the gear ratio is upshifted to a high speed gear with a small gear ratio. On the other hand, during deceleration or acceleration, the solenoid current 1p is controlled to increase, and the land 62b of the primary control valve 60 again operates to the drain side to open the drain port 61c, reducing the primary pressure Pp. The winding of the primary pulley 22 shifts to a smaller diameter to downshift to a lower speed, and thus the primary pressure Pp controls the speed change in the maximum and minimum speed range according to each driving and driving condition.

In controlling the above secondary pressure and primary pressure,
A case where the solenoid current Ip for primary pressure control is no longer input due to a broken wire shade will be described. In the event of such a failure, the primary control valve 60 reduces the solenoid current to 1.
Since p becomes approximately zero, the spool 62 is stroked by the force of the spring 63, closing the drain port 61c and opening the oil supply port 61b to the oil supply position. Therefore, the primary pressure Pp is controlled to a maximum value equal to the secondary pressure Ps, and therefore, if a gear shift is in progress, it is immediately upshifted to the minimum gear ratio and is forcibly held fixed at the minimum gear ratio. In this way, various inconveniences caused by sudden downshifts,
Fail-safe is provided to avoid belt slip etc. due to decrease in primary pressure Pp.

At this time, in the control unit 70, the primary pulley 22
The actual gear ratio is calculated from the ratio of the rotation speed of the secondary pulley 25 to the rotation speed of the secondary pulley 25. When the actual gear ratio is on the high speed side while driving, the secondary pressure Ps is relatively low, and therefore the primary pressure P is also be at a lower level. Therefore, the relief valve 8
1, the spool 83 moves into the hydraulic chamber 85 due to the spring force.
side, the ports 82c and 82d are closed and the ports 82a and 82b are switched to communicate with each other, and the primary pressure Pp is directly transferred to the primary cylinder 21.
It acts on

On the other hand, when the secondary pressure Ps is controlled to increase according to the maximum gear ratio etc. when the vehicle is stopped, an equally high primary pressure Pp acts on the hydraulic chamber 85 of the relief valve 8I together with the primary cylinder 21.

Therefore, in the relief valve 81, the spool 83 strokes toward the spring side, closing the port 82b and opening the port 82c.
, 82d is switched to open, and the primary pressure Pp
is led to the primary cylinder 21 via an oil passage 48. Also, due to the orifice 47, the oil pressure on the primary cylinder 21 side is always lower than the primary pressure Pp, so that the spring force and the oil pressure in the oil pressure chamber 85 are balanced. In this way, using the primary pressure Pp as the source pressure, the oil pressure of the primary cylinder 21 is controlled to a predetermined value equal to the pressure set by the spring 84, and the primary cylinder 21
This prevents an abnormal rise in oil pressure.

Although the embodiments of the present invention have been described above, the present invention can be similarly applied even when the configurations of the secondary control valve and the primary control valve are different.

〔Effect of the invention〕

As described above, according to the present invention, in the electronic control of a continuously variable transmission, when the primary pressure is increased in the event of a failure such as a disconnection on the primary side for fail-safe, the hydraulic pressure of the primary cylinder is controlled by the relief valve device. Since it is controlled to prevent abnormal rise, the durability of the pulley and belt is improved and there is no need to increase the rigidity.

Furthermore, it becomes possible to perform speed change control based on the secondary pressure and the set pressure of the relief valve device, which improves driving performance in a faulty state.

Further, since the relief valve device is configured to control the lubrication of the primary cylinder at a constant level using the primary pressure as the source pressure, the cylinder oil pressure can be controlled without impairing the fail-safe function.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a control device for a continuously variable transmission according to the present invention, and FIGS. 2(a) and 2(b) are characteristic diagrams of solenoid current, primary pressure, and secondary pressure. 5...Continuously variable transmission, 2I...Primary cylinder,
24...Secondary cylinder, 44.44'...Primary pressure oil passage, 50...Secondary control valve, 51.
131... Proportional solenoid, 60... Primary control valve, 70... Control unit, 80... Relief valve device, 81... Relief valve 21fJ (1)) p (Q) s

Claims (2)

[Claims] (1) The primary control valve, which controls the primary pressure using an electric signal, is set so that the primary pressure is fixed at the maximum in the event of a failure such as a wire breakage. A control device for a continuously variable transmission, characterized in that it is provided with a relief valve device that prevents an abnormal rise in . (2) The relief valve device consists of an oil passage equipped with a relief valve and an orifice, and is configured to control the hydraulic pressure of the primary cylinder to the set pressure using the primary pressure as the source pressure when the primary pressure is higher than the set pressure. The control device for a continuously variable transmission according to claim 1, characterized in that: