JPH0524374B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a hydraulic control device for an automatic transmission.

(B) Prior Art A conventional hydraulic control device for an automatic transmission is disclosed in, for example, Japanese Patent Laid-Open No. 144338/1983. The automatic transmission shown here has a planetary gear train with three forward speeds, and a gear shift operation is performed by switching the rotational state of the gear train using a plurality of clutches and brakes. During the 2-3 gear shift, the front clutch is engaged and the band brake, which had been engaged up until then, is released. For this purpose 2
Hydraulic pressure is supplied from the -3 shift valve to the front clutch oil chamber and the band brake servo release chamber. A pressure reducing valve is provided between the 2-3 shift valve and the oil chamber of the front clutch, so that reduced pressure is supplied to the oil chamber of the front clutch. The pressure reducing valve is configured to always output a constant hydraulic pressure.

(c) Problems to be Solved by the Invention Due to the pressure reducing valve as described above, oil pressure is applied to the oil chamber of the front clutch and the servo release chamber of the band brake as shown by broken lines and solid lines in FIG. 6, respectively. Supplied. That is, there is a region in which the oil pressure in the servo release chamber is approximately constant during the stroke of the piston, and then, as the piston stroke ends, the oil pressure increases rapidly and the band brake is released. On the other hand, the oil pressure in the front clutch oil chamber initially increases in the same way as the oil pressure in the servo release chamber, but once it reaches a certain value, it no longer increases. At this time, the constant pressure regulating value of the pressure reducing valve is set so that the torque capacity of the front clutch is appropriate.

However, when such a pressure reducing valve is used, there is a problem in that it is difficult to adjust the timing of engagement of the front clutch and release of the band brake. In other words, the oil pressure in the front clutch's oil chamber reaches a predetermined constant value relatively early and the engagement is performed, whereas the oil pressure in the band brake's servo release chamber rises later than this, resulting in a delay in release. Become. This is because the oil pressure in the oil chamber of the front clutch is controlled to a constant value regardless of the oil pressure in the servo release chamber of the band brake. In addition, when such a pressure reducing valve is used, the oil pressure in the front clutch oil chamber is maintained at a constant level even after the gear shift is completed, so for example, in third gear, full throttle is applied and a large torque is applied. In some cases, the front clutch may slip. The present invention aims to solve the above problems.

(d) Means for Solving the Problems The present invention attempts to solve the above problems by using a pressure reducing valve that always outputs a hydraulic pressure that is subtracted by a fixed value from the supplied hydraulic pressure. be. That is, the hydraulic control device for an automatic transmission according to the present invention supplies hydraulic pressure to the servo release chamber S/R of the band brake B through the servo release oil passage 58.
At the same time, by tightening the clutch F/C by supplying hydraulic pressure to the oil chamber 62 of the clutch F/C via the clutch oil passages 58a and 60 branched from the servo release oil passage 58, the specified In a hydraulic control system for an automatic transmission that is configured to achieve a gear position (third speed), a clutch oil passage 58
A pressure regulating valve 50 for regulating the hydraulic pressure to the oil chamber 62 of the clutch F/C is provided in the middle of the clutch F/C, and the same hydraulic pressure as the hydraulic pressure of the servo release chamber S/R is applied to one end of this pressure regulating valve 50. , clutch F/ on the other end
By applying the hydraulic pressure to the oil chamber 62 of the clutch F/C and the pressing force of the pressing means 56, the hydraulic pressure of the oil chamber 62 of the clutch F/C is reduced by the pressing force of the pressing means 56. There is.

Note that the pressing means may be a spring.

(E) Function When the shift valve is switched, hydraulic pressure is supplied to the clutch oil chamber and the band brake servo release chamber. Line pressure is directly supplied to the servo release chamber of the band brake from the shift valve. On the other hand, the hydraulic pressure reduced by the pressure regulating valve is supplied to the oil chamber of the clutch. The pressure regulating valve outputs hydraulic pressure that is the line pressure supplied from the shift valve reduced by a fixed value depending on the force of the pressing means.
This is sent to the servo release room. As a result, hydraulic characteristics as shown in FIG. 3, for example, can be obtained. Since the hydraulic pressure in the band brake servo release chamber and the hydraulic pressure in the clutch oil chamber change at the same timing as shown in Figure 3, it is possible to synchronize the release of the band brake and the engagement of the clutch. . Moreover, since the torque capacity of the clutch can be adjusted by selecting the pressure reducing valve pressing means, the capacity is set to provide the optimum torque capacity during gear shifting. Further, after the shift is completed, the oil pressure increases higher than the oil pressure during the shift, so that sufficient torque capacity can be ensured even in a steady state.

(F) Embodiments Examples of the present invention will be described below with reference to FIGS. 1 to 5 of the accompanying drawings.

(First Embodiment) FIG. 2 shows a schematic diagram of a power transmission mechanism of an automatic transmission with three forward speeds and one reverse speed. This power transmission mechanism includes an input shaft I to which the rotational force from the engine output shaft E is transmitted via a torque converter T/C, an output shaft O to transmit the driving force to the final drive device, a first planetary gear set G1, a second planetary gear set G1, and a second planetary gear set G1. Planetary gear set G2,
Front clutch F/C, rear clutch R/C,
It has band brake B, low and reverse brake L&R/B, and one-way clutch OWC. The first planetary gear set G1 is a sun gear S1
, internal gear R1, and both gears S1 and R
The planetary gear set G2 includes a sun gear S2, an internal gear R2, and a carrier PC1 that supports a pinion gear P2 that meshes with both gears S2 and R2 simultaneously. It consists of PC2. Each component is connected as shown. The above power transmission mechanism includes front clutch F/C, rear clutch R/C, band brake B, and low and reverse brake L&R/
By operating B (one-way clutch OWC) in various combinations, each element (S1, S2, R1, R2, PC1) of planetary gear sets G1 and G2
and PC2), thereby changing the rotational speed of the output shaft O with respect to the rotational speed of the input shaft I.
Three forward speeds and one reverse speed can be obtained by changing the rotation speed.

FIG. 1 shows a hydraulic control device according to the present invention. This hydraulic control device includes an oil pump 2, a pressure regulator valve 4, manual valves 6 and 1.
-2 shift valve 8, 2-3 shift valve 10,
Cutback valve 12, vacuum throttle valve 14, throttle backup valve 1
6. Solenoid downshift valve 18, second lock valve 20, timing valve 22.
It has a governor valve 24 and a pressure reducing valve 50 (pressure regulating valve), and these valves are connected to the torque converter T/C, front clutch F/C, rear clutch R/C, servo apply chamber S/A of band brake B, and It is connected to the servo release chamber S/R and the low and reverse brake L&R/B as shown in the figure, and a predetermined hydraulic pressure is distributed to each friction element by the action of these valves. In the following description, the pressure reducing valve 50 that is directly related to the present invention will be mainly described in detail, and detailed description of other valves will be omitted. The structure and operation of the parts whose explanation is omitted are the same as those disclosed in, for example, Japanese Patent Application Laid-Open No. 132062/1983.

The pressure reducing valve 50 shown in FIG.
-52e, a spool 54 inserted into the valve hole 52, and a spring 56 (pressing means) that presses the spool 54 upward in FIG. The ports 52a and 52d communicate with an oil passage 58a (clutch oil passage) branched from the servo release oil passage 58. Servo release oil path 58
is an oil passage to which line pressure is supplied when the 2-3 shift valve 10 is in the up position, that is, the third gear position, and this servo release oil passage 58 communicates with the servo release chamber S/R. . Similarly, line pressure is supplied to an oil passage 58a branched from the servo release oil passage 58 during the third speed. port 52
b is a drain port. Ports 52c and 5
2e communicates with an oil passage 60 (clutch oil passage). The oil passage 60 is the oil chamber 6 of the front clutch F/C.
2 is connected. Note that ports 52a and 5
Orifices 64 and 66 are installed at the entrance of 2e, respectively.
is provided. The spool 54 has two lands 54a and 54b, and the axial dimension of the groove between them is approximately equal to the dimension between ports 52b and 52d.

Next, the operation of this embodiment will be explained. 2-
3. When the shift valve 10 is switched from the second speed position to the third speed position, the servo release oil passage 58 and the oil passage 5
Line pressure is supplied to 8a. The line pressure of the servo release oil passage 58 acts on the servo release chamber S/R of the band brake B, and the servo release chamber S/R acts on the servo release chamber S/R.
Gradually increase the R oil pressure and release the band brake B. The change in the oil pressure in the servo release chamber S/R at this time is shown by the solid line in FIG. On the other hand, the line pressure of the oil passage 58a is supplied to ports 52a and 52d of the pressure reducing valve 50. As a result, the spool 54 of the pressure reducing valve 50 becomes the pressure regulating position as shown in FIG.
The force of the hydraulic pressure acting upward on the spool 54 and the force of the spring 56 acting upward on the spool 54 are in balance. Therefore, the oil pressure of the port 52e (that is, the oil pressure of the oil passage 60) is the oil pressure of the port 52a (that is, the oil pressure of the oil passage 58a).
The value is lower by a certain value corresponding to the force of the spring 56. The oil pressure in the oil passage 60 acts on the oil chamber 62 of the front clutch F/C to tighten it. Changes in the oil pressure in the oil chamber 62 at this time are shown by broken lines in FIG. In other words, the oil chamber 6
The oil pressure of No. 2 changes at the same timing as the oil pressure of the servo release chamber S/R, and is always lower by a constant value ΔP. Oil pressure value P1 that remains almost constant during gear shifting
is set so that the torque capacity of the front clutch F/C is optimized. Therefore, the release of the band brake B and the engagement of the front clutch F/C are performed at the same timing, and the torque capacity of the front clutch F/C is equal to the servo release chamber S/C.
It can be set to a desired value regardless of the R oil pressure. Therefore, desired 2-3 speed change performance can be obtained.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention. This second
In the embodiment, the pressure reducing valve 50 is
It is designed to stop the depressurizing action of.
This pressure reducing valve 50 is connected to ports 52a to 5 in FIG.
In addition to port 2e, it has ports 52m and 52n. The port 52m communicates with the oil passage 70. The oil passage 70 is an oil passage to which line pressure is supplied when the manual valve 6 is in the R range (reverse range). Port 52n is a drain port. The diameters of the ends 54c and 54d of the spool 54 are the same.

In the case of this second embodiment, when no oil pressure is supplied to the oil passage 70, the same effect as in the first embodiment shown in FIG. 1 can be obtained. However, when the manual valve 6 is selected to the R range, line pressure is supplied to the oil passage 70, and oil pressure acts on the port 52m. Therefore, the downward force acting on the spool 54 in FIG. 4 becomes larger, and the spool 54
is pressed downward against the spring 56,
The pressure regulating function is lost and the port 52d and port 52c are brought into communication. Therefore, the oil passage 58 and the oil passage 60 communicate with each other, and the oil pressure in the oil passage 58a is controlled by the oil passage 60.
0 directly acts on the oil chamber 62 of the front clutch F/C. As described above, in the R range, since the pressure reducing valve 50 does not have a pressure reducing effect, a high oil pressure acts on the oil chamber 62, and the torque capacity of the front clutch F/C becomes large. The reason why the pressure regulating action of the pressure reducing valve 50 is stopped in the R range is that in the R range, there is no need to adjust the shift timing, but rather a large torque capacity of the front clutch F/C is required.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention. This third
The embodiment is based on the oil passage 70 of the second embodiment shown in FIG.
Instead, the oil passage 80 is connected to the port 52m. The oil passage 80 is in a kicked-down state when the manual valve 6 is in the R range or in the D range even when the manual valve 6 is in the D range, that is, when the solenoid downshift valve 18 is in the state shown in the left half of FIG. , is an oil passage to which hydraulic pressure is supplied. Therefore, in this third embodiment, the pressure reducing action of the pressure reducing valve 50 can be stopped not only in the case of the R range but also during kickdown. The reason why the pressure reducing action of the pressure reducing valve 50 is stopped even during kickdown is that during kickdown, the throttle is fully open and the torque is large, and the vehicle speed during gear shifting is also high, so a large torque capacity is required.

(G) Effects of the Invention As explained above, according to the present invention, a pressure regulating valve is provided in the oil chamber of the clutch to supply a hydraulic pressure that is lower than the hydraulic pressure in the servo release chamber of the band brake by a certain value. The hydraulic pressure in the servo release chamber of the band brake and the hydraulic pressure in the clutch oil chamber can be synchronized, and the hydraulic pressure in the clutch oil chamber can be set to a desired value. In this way, it is possible to optimize the shift timing and set the torque capacity of the clutch to an appropriate value, thereby improving shift performance.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a hydraulic circuit according to a first embodiment of the present invention, FIG. 2 is a diagram showing a skeleton diagram of an automatic transmission, and FIG.
The figures are diagrams showing the hydraulic characteristics obtained by the present invention, Fig. 4 is a diagram showing the second embodiment of the invention, and Fig. 5 is a diagram showing the hydraulic characteristics obtained by the present invention.
This figure shows a third embodiment of the present invention, and FIG. 6 is a diagram showing hydraulic characteristics of a conventional hydraulic control device for an automatic transmission. F/C...Front clutch, B...Band brake, S/R...Servo release chamber, 50...
Pressure reducing valve (pressure regulating valve), 56... Spring (pressing means), 58... Servo release oil path, 58
a... Oil passage (clutch oil passage), 60... Oil passage (clutch oil passage), 62... Oil chamber.

Claims (1)

[Claims] 1. The band brake is released by supplying hydraulic pressure to the servo release chamber of the band brake via the servo release oil path, and the clutch is released via the clutch oil path branched from the servo release oil path. In a hydraulic control system for an automatic transmission, which achieves a specific gear by supplying hydraulic pressure to the oil chamber of the clutch and thereby engaging the clutch, there is a hydraulic control device that connects the clutch to the oil chamber in the middle of the clutch oil path. A pressure regulating valve is provided to regulate the hydraulic pressure, and the same hydraulic pressure as the hydraulic pressure in the servo release chamber is applied to one end of the pressure regulating valve, and the hydraulic pressure to the oil chamber of the clutch and the pressing force by the pressing means are applied to the other end. A hydraulic control device for an automatic transmission, characterized in that the hydraulic pressure in the oil chamber of the clutch is reduced by the pressing force of the pressing means. 2. The hydraulic control device for an automatic transmission according to claim 1, wherein the pressing means is a spring.