JPH03172662A - Hydraulic control device for continuously variable transmission - Google Patents

Abstract

PURPOSE:To reduce capacity of a clutch by a method wherein the control pressure of a solenoid valve is applied on a shuttle valve, and a shuttle pressure generated by means of lubricating oil serving as an original pressure is exerted on a relief valve, and a working pressure is controlled according to transmission torque. CONSTITUTION:A working pressure by using a lubricating pressure is selectively introduced through a select valve 46 to a forward clutch 17 and a reverse brake 18 of a hydraulic forward reverse shifting device on the input side of a continuously variable transmission 5. The clutch is engaged for forward or reverse. When transmission torque is high, a control unit 73 controls the control pressure of a solenoid valve 70 to increase and control the line pressure of a line pressure control valve 50. The control pressure is also inputted to a shuttle valve 80 to switch a shuttle pressure. A working pressure is increased by a relief valve 60 to increase the engaging force of the clutch 17 and the brake 18 regardless of a line pressure responding to a change gear ratio. This constitution performs reliable transmission of a power and reduces capacity of the clutch and the like.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a hydraulic control device for a belt-type continuously variable transmission of a vehicle, which is equipped with a hydraulic forward/reverse switching device on its input side. The present invention relates to a device that variably controls the operating pressure of a forward/reverse switching device in accordance with transmitted torque.

[Conventional technology]

As a drive system of this type of continuously variable transmission, there is one in which a torque converter and a mechanical or electromagnetic clutch are configured to transmit power to the continuously variable transmission via a forward/reverse switching device. In this case, the forward/reverse switching device is composed of a planetary gear, a clutch, and a brake for forward/reverse movement, and the hydraulic control system of the continuously variable transmission generates operating pressure, which is then applied to the clutch when moving forward or backward.

A method for introducing this into brakes has been proposed.

Here, in the hydraulic control system of the continuously variable transmission, line pressure is controlled to ensure belt tension that does not cause belt slip in response to changes in transmitted torque. On the other hand, even with the above-mentioned hydraulic forward/reverse switching device, it is necessary to ensure that the clutch torque does not slip in response to changes in the transmitted torque.In particular, in the case of a device equipped with a torque converter with lockup, it is necessary to ensure that the clutch torque does not slip due to changes in the transmitted torque. Since the transmission torque changes greatly each time the converter operates, it is necessary to take measures to deal with this.

Therefore, conventionally, regarding the operating pressure control of the hydraulic forward/reverse switching device attached to the above-mentioned continuously variable transmission, for example,
There is a prior art of Publication No. 3-203437. Here, a forward/reverse switching device is provided on the output side of the continuously variable transmission to switch the shifting power to two high and low gears or reverse the gear. In addition, the hydraulic control system has a sub-primary valve, which regulates the first line pressure according to the pressure of the throttle opening and gear ratio to generate a second line pressure, and this second line pressure is used to switch forward and reverse. It is indicated for use in the operating pressure of the device.

[Problem to be solved by the invention]

By the way, in the prior art described above, the shifting power is applied manually to the forward/reverse switching device, which has a large influence on the gear ratio, etc., and therefore control using the second line pressure is required. Therefore, compared to the case where the forward/reverse switching device is disposed on the input side as in the present case, the operating pressure control is fundamentally different. Further, since the second line pressure of the operating pressure is regulated based on the throttle opening degree and the gear ratio, lockup or the operating state of the torque converter is not controlled.

The present invention has been made in view of the above points, and its purpose is to control the line pressure control system in the operating pressure control of a hydraulic forward/reverse switching device disposed on the input side of a continuously variable transmission. It is an object of the present invention to provide a hydraulic control device for a continuously variable transmission that can appropriately perform variable control according to the transmitted torque.

[Means to solve the problem]

In order to achieve the above object, the hydraulic control device of the present invention generates a control pressure by a solenoid valve in response to a duty signal corresponding to a transmitted torque, and applies the control pressure to a line pressure control valve to control a line pressure level. In the control system, a circuit is configured so that the drain of the line pressure control valve is guided to the relief valve to generate operating pressure, and the operating pressure is guided to the clutch and brake of the forward/reverse switching device, and the control pressure of the solenoid valve is transferred to the shuttle. The shuttle pressure generated by acting on the valve and using the lubricating pressure as the source pressure acts on the relief valve, and the operating pressure is controlled according to the transmitted torque.

[For production]

Based on the above configuration, operating pressure using lubricating pressure is introduced into the clutch and brake of the hydraulic forward/reverse switching device on the input side of the continuously variable transmission for engagement, thereby driving the vehicle forward or backward. When the transmitted torque is large, the control pressure of the solenoid valve that increases the line pressure with the line pressure control valve is also manually applied to the shuttle valve to switch the shuttle pressure, and the relief valve increases the operating pressure to control the clutch and brake. The engagement force is strengthened independently of line pressure control according to the gear ratio, and power is transmitted reliably.

〔Example〕

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

Referring to FIG. 2, an outline of the drive system of a continuously variable transmission with a lock-up converter will be described. Reference numeral 1 indicates an engine, and the crankshaft 2 is connected to a torque converter device 81, 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 IO. 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. A lock-up clutch 15 integral with the turbine shaft 13 is installed between the converter cover 11 and transmits engine power to the forward/reverse switching device 4 via the torque converter 12 or the lock-up clutch 15.

The forward/reverse switching device 4 has a double pinion planetary gear 1B, the turbine 13 is input to the sun gear 16a,
The primary shaft 20 outputs from the carrier 16b. A forward clutch 17 is provided between the sun gear lea and the carrier tab, and a reverse brake 18 is provided between the ring gear lee and the case.
The planetary gear 16 is integrated by the engagement of the turbine shaft 1.
3 and the primary shaft 20 are directly connected. Also, when the reverse brake 18 is engaged, reversed power is output to the primary shaft 20, and the forward clutch 17 and reverse brake 1
8 releases the planetary gear 16.

The continuously variable transmission 5 has a hydraulic cylinder 21 on a primary shaft 20.
The variable-boot interval primary pulley 22 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 2B is wound between the drive belt 2 and the secondary pulley 25. Here, the primary cylinder 21 is set to have a larger pressure receiving area, and its primary pressure 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 B, 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 high hydraulic pressure source for controlling the continuously variable transmission 5 and the like, the continuously variable transmission 5 is provided with an oil pump 34, and this oil pump 34 is directly connected to the crankshaft 2 via a pump drive shaft 35. .

In FIG. 1, the hydraulic control system will be described.

First, the line pressure oil passage 41 from the oil pump 34 that communicates with the oil pan 40 communicates with the line pressure control valve 50 to control the line pressure, and the line pressure of the line pressure oil passage 41 is always supplied to the secondary cylinder 24. Ru.

The line pressure in the line pressure oil passage 41 is supplied to and discharged from the primary cylinder 21 via the shift control valve 42 and the oil passage 43, and a predetermined primary pressure is generated to control the gear shift.

Further, the drain oil passage 44 of the line pressure control valve 50 communicates with the relief valve 60 to generate operating pressure, and this operating pressure is transferred to the oil passage 45.
It is guided to the select valve 4B by the forward clutch 17 or the oil passage 4B by the oil passage 47 when moving forward or backward.
8 to the reverse brake 18. On the other hand, it has a solenoid valve 70 for introducing line pressure to generate control pressure for controlling the line pressure control valve 50,
The control pressure of this solenoid valve 70 is guided to the line pressure control valve 50 through an oil passage 71 6 Furthermore, the line pressure of the oil passage 41 and the operating pressure of the oil passage 44 9 The control pressure of the passage 710 is introduced for controlling the relief valve 60 . The shuttle valve 80 generates a shuttle pressure corresponding to the transmitted torque, and the shuttle pressure is guided to the relief valve 60 through the oil passage 72.

The line pressure control valve 50 has a spool 52 in the valve body 51, and controls the line pressure by controlling the flow rate of oil in the oil path 41 supplied to the boat 51a and draining it to the boat 51b. On one side of the spool 52,
The sensor shoe 53 is connected to the adjustment screw 54. It is mechanically connected via a bush 55 and a spring 56, and a spring force is applied by a sensor shoe 58 according to the gear ratio. On the other side of the spool 52, the line pressure acts on the boat 51C, and the control pressure of the oil passage 71 acts on the boat 51d, and the pressure is adjusted by these elements.

That is, the spring force F, line pressure PL, and
Assuming that the control pressure Pc is the effective pressure receiving area A14°Ac of each hydraulic pressure, the following balance equation is established.

PL -AL +Pc-Ac KasumiF On the other hand, since the control pressure Pc is controlled by the solenoid valve 70 using the line pressure PL as the source pressure and by the duty ratio of the electric signal, it is Pc-DΦPL. Therefore, the above formula becomes as follows.

PL -F/ (AL +DψAc) From this, the line pressure PL becomes high due to the large spring F in the low speed gear where the gear ratio is large as well as the transmitted torque as shown in Fig. 3 (a), and the spring increases depending on the gear ratio. It is controlled to become lower by reducing the force F. In addition, the maximum line pressure (F/AL) with a duty ratio of 0%
and 100% minimum line pressure (F/ (AL +Ac)
) is also controlled.

Then, assuming a constant value DO that is equal to the duty ratio, the line pressure is the minimum and maximum line pressure as (1-Do)/(A L
+ A c ): A value that is internally divided into D □ / A L.

Therefore, it can be seen that the value of the duty ratio corresponds approximately 1:1 to the transmitted torque, and in the electronic control system described later, when the transmitted torque is large, it is necessary to output a duty signal that reduces the value of the duty ratio. good. On the other hand, the state of the transmitted torque can be determined by the control pressure Pc corresponding to the duty ratio.

The shuttle valve 80 generates shuttle pressure by using the control pressure indicating the transmission torque, and the valve body 81 has a first
Second spool 84 inside spool 82 and sleeve 83
are coaxially connected, and the first spool 82 is biased by an extremely weak spring 85. By moving the first spool 82 from side to side, the operating pressure of the boat 81b is communicated and a high shuttle pressure equal to the operating pressure is output, or the boat 81a is communicated with the drain boat 81c and the shuttle pressure is made zero.

Here, the control pressure of the oil passage 71 acts on one boat 81d of the first spool 82, and the line pressure of the oil passage 41 acts on the boats 81e and 81r on the second spool 84 side.
A working pressure of 4 is applied.

Therefore, control pressure P c (= DφPL), line pressure PL
.

Lubricating pressure Pa, each hydraulic pressure receiving area Ac, AL.

Assuming Aa, the first. Pc-Ac>PL-AL+Pa-Aa-(1) when the second spool 82.84 moves to the left,
Conversely, when moving to the right, Pc 11Ac <PL φAL +Pa −Aa
-(2) holds true. And in the case of (1), boat 81
A shuttle pressure Ps equal to the lubricating pressure Pa is generated by the communication between a and 81b, and in the case of (2), the shuttle pressure Ps is made zero.

Therefore, when the duty ratio is small and the control pressure Pc is low as shown in Figure 3(b), the shuttle pressure Ps is lowered based on the relationship (2) above, and the duty ratio becomes higher than the set value. When the relationship (1) increases, the shuttle pressure Ps is switched to a higher value, and the switching point in this case is shifted and has a hysteresis characteristic, which promotes stabilization of the switching operation.

The relief valve BO is provided with a spool 62 biased on one side by a spring 63 on the valve body B1, and controls the operating pressure of the boat 61b to the boat 61c according to the shuttle pressure of the oil passage 72 of the spool 62 (one bow) 81a. Drain and adjust the operating pressure. Therefore, when the shuttle pressure Ps is high, a portion of the working pressure Pa is drained to generate a low working pressure Pa, and when the shuttle pressure Ps becomes zero, switching is performed so that a high working pressure Pa is generated.

On the other hand, the control unit 73 outputs a duty signal to the solenoid valve 70 to generate control pressure, but the control unit 73 estimates the transmitted torque by determining engine output, lockup, or torque converter operation. Then, as shown in FIG. 3(C), a signal with the duty ratio reduced in inverse proportion to the increase in the transmitted torque is output.

Next, the operation of the hydraulic control system for the continuously variable transmission constructed as described above will be described using the time chart shown in FIG.

First, when the engine is running, the oil pressure from the oil pump 34 is guided to the line pressure control valve 50. In this case, when the gear ratio has returned to the maximum, the spring force from the sensor shoe 53 is large, but when the engine is idling, the control unit 73 controls the duty ratio. In this case, a 100% signal is input to the solenoid valve 70, and the highest control pressure is generated. Therefore, the line pressure control valve 50 controls the line pressure to the highest value of the minimum line pressure shown in FIG. 3(a), and this line pressure is introduced into the secondary cylinder 24 through the oil passage 41.

At this time, the highest control pressure is introduced into the shuttle valve 80 and the first. Moving the second spool 82, 84 to the left switches to create a higher shuttle pressure equal to the operating pressure. Therefore, the relief valve 60 regulates the pressure of the drain of the line pressure control valve 50 to a low operating pressure, which is led to the select valve 4B by the oil passage 45.

Therefore, in the parking (P) and neutral (N) ranges, the forward clutch 17 and reverse brake 1B of the forward/reverse switching device 4 are both drained by the select valve 4B, but when shifting to the drive (D) range, the select valve 4B 4B, the operating pressure of the oil passage 45 is introduced into the forward clutch 17 via the oil passage 47 and coupled thereto. Therefore, the planetary gear 1B is integrated to directly connect the turbine shaft 13 and the primary shaft 20, and engine power is input to the continuously variable transmission 5 via the torque converter 12 or the lock-up clutch 15. and primary pulley 22
．． The power of the maximum gear ratio generated by the secondary pulley 25 and the belt 2B is transmitted from the secondary shaft 23 to the differential device 6 and thereafter, and forward travel is started. On the other hand, after this start, the primary cylinder 21 is activated by the speed change control valve 42.
By supplying oil to the primary pressure and increasing the primary pressure, the gear shift is controlled to the high gear side.

The transmission torque is estimated by the control unit 73 at the time of starting driving, and when the torque converter 3 is activated at the time of starting, if the engine output is large and the transmission torque increases even if the gear is locked up after the shift starts, the duty ratio of the duty signal is The value of R becomes smaller, reducing the control pressure by the solenoid valve 70. Therefore, the line pressure control valve 50 is controlled to a sequentially higher line pressure level based on the characteristics shown in FIG. 3(a) to prevent belt slip. In this case, when the control pressure and the duty ratio decrease below the set value Pc1, the shuttle valve 80 operates as shown in FIG. Second spool 82, 8
4 moves to the right side, drains the shuttle pressure in the oil passage 72, and switches it to zero. For this reason, the relief valve 60 is controlled to increase so that a high operating pressure is generated, and thus the engagement force of the forward clutch 17 is strengthened in accordance with the transmitted torque, and a large torque is reliably transmitted via the planetary gear IB. It becomes possible to do so. On the other hand, even when this large torque is transmitted, the line pressure is controlled to decrease in response to an upshift to a high speed gear, but the clutch operating pressure is maintained at a high state regardless of this.

Then, when the transmitted torque decreases again and the value of the duty ratio becomes less than the set value, the clutch operating pressure is controlled to decrease, and at this time, the hysteresis characteristic of the shuttle valve 80 prevents hunting near the set value.

Note that the same control is performed when the operating pressure is introduced to the reverse brake 18 during backward movement.

Referring to FIG. 5, another embodiment of the invention will be described.

In this embodiment, line pressure is used as the clutch operating pressure and shuttle pressure, and the line pressure of the oil passage 4I is applied to the pressure reducing valve 90.
The operating pressure of the pressure reducing valve 90 is guided to the select valve 4B and the shuttle valve 80 through the oil passage 45.

The pressure reducing valve 90 has a spool 92 of a valve body 91 connected to a boat 91.
A predetermined operating pressure is generated by draining the line pressure of a to the boat 91b, and the reduced pressure state is changed by the spring 93 of the spool 92 and the shuttle pressure of the boat 91c on the opposite side. Therefore, in this embodiment, when the transmitted torque is small and the shuttle pressure is high, the pressure is reduced by the pressure reducing valve 90 to a large extent and the operating pressure decreases, and when the shuttle pressure decreases due to the increase in the transmitted torque, the line pressure of the pressure reducing valve 90 Switch so that the inflow amount increases and the operating pressure becomes higher.

Although the embodiments of the present invention have been described above, the control pressure based on the duty ratio, line pressure control, switching of the shuttle valve 80, etc. may be reversed.

If the shuttle valve 80 continuously variably controls the shuttle pressure in accordance with the control pressure, the clutch operating pressure can be further finely controlled in accordance with the transmitted torque.

〔Effect of the invention〕

As described above, according to the present invention, in a system in which a hydraulic forward/reverse switching device is provided on the input side of a continuously variable transmission, the operating pressure of the clutch and brake of the forward/reverse switching device is controlled according to the transmitted torque. Since the clutch is controlled, the capacity of the clutch etc. can be reduced and the size can be reduced.

Furthermore, line pressure is controlled by the control pressure of the duty signal according to the transmitted torque, and the shuttle valve and relief valve control the operating pressure to increase when the transmitted torque is large, eliminating the need for electronic components. It also has good responsiveness.

Also, while line pressure is controlled according to the gear ratio,
The clutch operating pressure can be controlled regardless of that,
It can also be directly applied to lock-up torque converters.

Furthermore, in an embodiment where the clutch operating pressure is generated by the drain of the line pressure control valve, as in the embodiment shown in Fig. 2, the line pressure is regulated upstream of the operating pressure, so the amount of oil in the operating pressure circuit is There is no influence on the line pressure such as a decrease in line pressure due to consumption, and an embodiment using line pressure like the embodiment shown in FIG. 3 has the advantage of expanding the operating pressure control range.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a hydraulic control device, FIG. 2 is a skeleton diagram showing an example of a continuously variable transmission to which the present invention is applied, FIG. 3(a) is a line pressure characteristic diagram, and FIG. ) is a shuttle pressure characteristic diagram, (C) is a characteristic diagram of transmission torque and duty ratio, FIG. 4 is a time chart diagram showing the operation, and FIG. 5 is a circuit diagram showing another embodiment of the present invention. 4... Forward/forward switching device, 5... Continuously variable transmission, 17.
... Forward clutch, 18... Reverse brake, 41... Line pressure oil path, 44... Drain oil path, 4
5... Operating pressure oil path, 50... Line pressure control valve, 60
...Relief valve, 70...Solenoid valve, 71...
- Control pressure oil path, 72...Shuttle pressure oil path, 80...
shuttle valve

Claims (2)

[Claims] (1) In a hydraulic control system in which control pressure is generated by a solenoid valve in response to a duty signal corresponding to the transmitted torque, and the control pressure is applied to a line pressure control valve to control the line pressure level, the drain of the line pressure control valve is The circuit is configured so that the operating pressure is guided to the relief valve, the operating pressure is guided to the clutch and brake of the forward/reverse switching device, and the control pressure of the solenoid valve is applied to the shuttle valve to generate the lubricating pressure as the source pressure. A hydraulic control device for a continuously variable transmission, characterized in that the shuttle pressure applied to the relief valve is controlled to control the operating pressure according to the transmitted torque. (2) For the clutch and brake of the forward/reverse switching device,
The circuit is configured to introduce the operating pressure generated by guiding the line pressure of the line pressure control valve to the pressure reducing valve, and the shuttle pressure generated by applying the control pressure of the solenoid valve to the shuttle valve and using the operating pressure as the source pressure. 2. The hydraulic control device for a continuously variable transmission according to claim 1, wherein the hydraulic control device acts on a pressure reducing valve to control the operating pressure in accordance with the transmitted torque.