JPS6145153A - Hydraulic controller of automatic speed changing gear - Google Patents

Abstract

PURPOSE:To prevent a shock from being created when a speed is changed by sending different clamping pressures in accordance with different two speed changing gear positions to a frictionally clamping member which is clamped when the speed changing gears come into two different positions. CONSTITUTION:The band brake 1 of a forward-drive four-speed automatic transmission is clamped when gear is in the second and the fourth position. A line pressure passage 5 and a shift valve 6 are connected to the clamping side port 3a of a servo piston 3. A second reducing valve 7 and a second control valve 15 are mounted as a pressure regulating means and a compensating means, respectively. When the gear is in either of the second and the fourth position, the brake is therefore clamped by an oil pressure P2 which is lower than line pressure P0, on account of which a speed change shock which is caused by sudden braking operation when speed is changed from the first to the second position and from the third to the second position can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a hydraulic control device for an automatic transmission installed in an automobile, and is intended to improve the engine braking effect.

(Prior art) In general, automatic transmissions selectively engage a plurality of friction engagement members using hydraulic supply/discharge control to obtain a plurality of gears by switching the power transmission path of a gear transmission mechanism. However, in this type of automatic transmission, one frictional engagement member may be engaged at different gear positions. In this case, if the torque to be transmitted by this frictional fastening member is equal or approximately equal in each gear, the same fastening pressure may be supplied; however, if the torque to be transmitted differs depending on the gear, this At gears where the transmission torque is large, the engagement pressure is increased to ensure the required engagement force, and at gears where the transmission torque is small, the engagement pressure is lowered to prevent shift shock due to the pressure being too high. must be done. Furthermore, in the case of a band brake in which a frictional fastening member is wound around a rotating member, such a problem also occurs when the direction of torque acting on the rotating member differs depending on the gear position. That is, as shown in FIG. 3, a band brake E is wound around a rotating member A, one end of which is supported by a fixed pin B, and the narrow end of which is engaged with a piston rod D of a servo piston C. In this case, when torque in the leap-in direction (direction a) acts on the rotating member A, this torque acts to wrap the band brake E around the rotating member so that a large braking force is obtained for a constant fastening pressure. In contrast, the trailing direction (b direction) toward the rotating member
When this torque acts, the band brake E tends to expand, so the braking force for the same fastening pressure becomes smaller. Therefore, if the fastening pressure is set so that the required braking force is obtained when the braking force becomes small, the fastening force will become excessive when torque in the opposite direction is applied, and a shock will occur during fastening.

To solve the above-mentioned problems in automatic transmissions, for example, as disclosed in U.S. Pat. A relatively high fastening pressure is supplied so as to obtain a fastening force of Also, efforts are being made to ensure that appropriate fastening force is obtained. However, in this case, when the frictional engagement member is engaged in a range used when engine braking is required, such as the "2°" range, the gear position at that time is a gear position that reduces the engagement pressure. At some point, the fastening force may be insufficient during engine braking during high-speed driving, which requires especially large braking torque, and a problem arises in that a sufficient engine braking effect cannot be obtained.

(Object of the Invention) The present invention deals with the above-mentioned problems in automatic transmissions. By supplying fastening pressure, appropriate fastening force can be obtained in any gear to prevent shock during gear shifting, and gears to which fastening pressure is supplied after being reduced are especially used during engine braking. If the gear position is
The purpose is to obtain the required engine braking effect.

(Structure of the Invention) In order to achieve the above object, the hydraulic control system for an automatic transmission according to the present invention is constructed as follows.

That is, the FJyAvrJ coupling member is engaged at two different gears to transmit power, and the coupling pressure supplied to the friction coupling member is reduced from the line pressure to the line pressure depending on the two gears. a pressure adjusting means for adjusting the pressure to a predetermined opening; a throttle opening detecting means for detecting the opening of a throttle valve of the engine; and a correction means for maintaining the pressure adjusted by the pressure adjustment means at the line pressure.With such a structure, the fastening force by the FJta fastening member can be adjusted to an appropriate level at each gear. Being discovered.

Shift shock caused by excessive tightening force is prevented, and the tightening pressure is maintained at line pressure without being reduced during engine braking, providing sufficient engine braking effect even when driving at high speeds. It will be done.

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

This embodiment relates to an automatic transmission with four forward speeds, and concerns a band brake 1 that is engaged in 2nd and 4th speeds.
However, in the rotating member 2 braked by the band brake 1, in the leading direction (direction a) where the braking torque is amplified for a constant fastening pressure in the second gear, there are four
At high speeds, the braking torque is applied in the trailing direction (direction b), where the braking torque is weakened.

A tightening oil pressure introduction passage 4 is connected to the engagement side boat 3a of the servo piston 3 that engages the band brake 1, and a line led from the introduction passage 4 and a pump (not shown) via a regulator valve. A shift valve 6 and a second reducing valve 7 are interposed between the pressure passage 5 and the pressure passage 5.

The shift valve 6 has an input port a into which line pressure Po is constantly introduced from the line pressure passage 5, and an input port a which is selectively communicated with the input port a by movement of a spool 6b.
The spool 6b has a spring 6e at one end, and a control boat 6f connected to a control hydraulic passage 8 at the other end. When the control oil pressure P1 is introduced into the control boat 6t, the spool 6b is positioned to the left as shown in the figure against the spring 6e, and the input port a is connected to the output porto C for second gear. When the control oil pressure P1 is drained, the spool 6b is moved to the right in the drawing by the spring 6e, so that the input port a is connected to the fourth-speed output port d. . Further, a fourth speed passage 9 is connected to this fourth speed output port d, and the above-mentioned 1tl
The second speed output capotro C is connected to the coupling oil pressure introduction passage 4, and the second speed upstream passage 11 is connected to the second speed upstream passage 11, which is led to the second reducing valve 7.

This second reducing valve 7 has an input port door a to which the second speed upstream passage 11 is connected, an output port door b to which the second speed downstream passage 12 is connected, and a drain boat 7C. A spring 7e is provided at one end of the spool 7d for adjusting the opening degree of the input port door a and the drain boat 7c, and a branch passage 13 is provided at the other end.
A feedback boat 7f is provided which communicates with the second-speed downstream passage 12 via the feedback boat 7f. When the hydraulic pressure in the feedback boat 7f, that is, the downstream hydraulic pressure P2 of the second reducing valve 7 overcomes the biasing force of the spring 7e, the spool 7d moves to the right in the drawing, and the input port door a is closed and the drain boat 7C is opened, thereby lowering the downstream hydraulic pressure P2, and when the spool 7d moves to the left in the drawing due to the decrease in hydraulic pressure P2, the input port door a opens and the second speed upstream hydraulic pressure P2 decreases. The hydraulic pressure (line pressure Po) in the passage 11 is introduced, and the drain boat 7C is closed to reduce the downstream hydraulic pressure P2.
rises. In this way, the downstream oil pressure P2 is reduced with respect to the upstream line pressure Po due to the balance relationship with the spring 7e. Here, the line pressure Po is regulated by the action of a regulator valve (not shown) so that it increases as the throttle opening increases, but in order to impart this characteristic to the downstream hydraulic pressure P2, A branch passage 14 branched from the upstream passage 11 is connected to the correction boat 7g, and the line pressure PO is transferred to the spool 7.
d is made to act in the same direction as the spring 7e. The second speed downstream passage 12 into which the hydraulic pressure P2 reduced in the above manner is introduced into the two-way check valve 1.
0 to the fastening oil pressure introduction passage 4.

Furthermore, in addition to the above configuration, this hydraulic circuit is provided with a second control lever rib 15. This control valve 15 has an input boat 15a to which the line pressure passage 5 is connected, and an output port 15c that is communicated with or shut off from the input boat 15a by movement of the spool 15b. And at one end there is a spool 15
b to the right in the drawing, and the above person and output boat 15a
, 15C are provided, and a throttle pressure boat 15e is provided at the other end, so that when the throttle pressure P3 introduced from the throttle pressure passage 16 is equal to or higher than a predetermined value P30, as shown in the figure, The spool 15b is positioned to the left against the spring 15d to block people and the output boats 15a and 15C. Here, the throttle pressure P3 is regulated so as to increase as the opening degree of a throttle valve (not shown) in the engine increases, and is regulated to be close to fully closed throttle valve (for example, the opening degree is 1/8 or less). Then, it becomes below the predetermined value P30. Therefore, when the throttle valve is fully closed, the spool 15b is moved to the right in the drawing by the spring 15d, and the input boat 15a communicates with the output port 15C. A decompression release line 17 connected to this output port 150 is connected to a decompression release boat 7h provided at the end of the second reducing valve 7 on the spring 7e side.

Next, the operation of the above embodiment will be explained.

First, when braking to the 4th gear in which the rotating member 2 is braked by the band brake 1, in this case, in the shift valve 6, the control hydraulic pressure P1 in the control boat 6f is
is drained and the spool 6b is moved to the right, so that the line pressure Po in the line pressure passage 5 is transferred from the input port loa of the shift valve 6 to the 4th gear output port d to the 4th gear passage 9. The oil is further introduced into the engagement side boat 3a of the servo piston 3 via the two-way check valve 10 and the engagement oil pressure introduction passage 4. As a result, the band brake 1
As a result, the rotating member 2 is braked, and the gear position becomes 4th speed. In this case, a torque in the trailing direction (direction b) that weakens the braking force acts on the rotating member 2.
As shown in FIG. 2, the relatively high line pressure Po acts on the servo piston 3 as the fastening hydraulic pressure without being reduced, so the required control is achieved regardless of the above-mentioned effect of weakening the braking force. Power or fastening force will be obtained.

On the other hand, in the second gear when the rotating member 2 is braked by the band brake 1 and a torque in the leading direction (direction a) that amplifies the braking force acts on the rotating member 2, the spool 6b of the shift valve 6 is By being held at the position shown in the figure by the control pressure P1, line pressure Po is introduced from the input port low a of the shift valve 6 to the second speed upstream passage 11 via the second speed output port low C.

The oil is guided through the passage 11 to the input port door a of the second reducing valve 7, and is reduced in pressure by the action of the valve 7 to a hydraulic pressure P2 corresponding to the biasing force of the spring 7e, as shown in FIG. It is then introduced into the second speed upstream passage 12, and further introduced into the engagement side boat 3a of the servo piston 3 via the two-way check valve 10 and the engagement oil pressure introduction passage 4. In other words, in the case of 2nd speed, the band brake 1 is engaged by a hydraulic pressure P2 that is lower than the engagement hydraulic pressure (line pressure) Pa in the case of 4th speed, but in this case, the braking force amplification effect is reduced as described above. As a result, the required braking force can be obtained in the same way as in the case of 4th gear, and since the engagement oil pressure P2 is reduced, it is not possible to shift by sudden braking when shifting from 1 to 2 or from 3 to 2. Shock will be prevented.

However, in this 2nd speed state, especially when the shift lever is
When the throttle valve of the engine is fully opened to apply the engine brake while the gear is shifted to the I+ range, if the engagement hydraulic pressure P2 supplied to the servo piston 3 remains reduced as described above,
A sufficient engine braking effect will not be obtained.

However, in this case, the throttle pressure P3 corresponding to the opening of the throttle valve becomes lower than the predetermined value P30 due to the first operation of the throttle valve.
In the second control valve 15 in which the valve 3 is introduced, the spool 15b is moved to the right in the drawing by the spring 15d, and as a result, the valve 15 and the output boats 15a and 15c are communicated with each other, and the line pressure Po is introduced into the decompression release passage 17. This pressure reduction release passage 17 is connected to a pressure reduction release boat 7h that applies hydraulic pressure in the same direction as the spring 7e in the second reducing valve 7, so that the line pressure Po is introduced into the boat 7h and the spool 7d is It is fixed at the left position in the drawing. Therefore, in the second reducing valve 7, the drain boat 7C is completely closed and the input port door a is completely opened, so that the pressure reducing effect of the valve 7 is eliminated. As a result, even in the 2nd speed state where the reduced pressure P2 is supplied to the servo piston 3, during engine braking when the throttle valve is closed, the oil pressure (line pressure Po) that is not reduced is maintained as shown by the arrow X in Fig. 2. This is supplied as the engagement hydraulic pressure for the band brake 1, and a sufficient brake effect can be obtained even during engine braking during high-speed driving.

(Effects of the Invention) As described above, according to the present invention, different engagement pressures are supplied to the friction engagement members engaged at two different gears depending on the respective gears, so that either The required fastening force is ensured even in the gear position, and shift shock due to excessive fastening force is prevented, and even in the gear position where reduced fastening pressure is normally supplied, the required fastening force is ensured during engine braking. The fastening pressure is supplied without being reduced, and as a result, the required engine braking effect can be obtained even when driving at high speed.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, FIG. 2 is a hydraulic characteristic diagram showing the operation of the embodiment, and FIG. 3 is a schematic diagram of a band brake shown as an example of a friction fastening member. 1... Friction fastening member (band brake), 7... Pressure adjustment means (second reducing valve), 15.
...Correction means (second control valve). Figure 2 P2O slot number 5-

Claims (1)

[Claims] (1) A frictional fastening member that is fastened at two different gears to transmit power, and the fastening pressure supplied to the frictional fastening member is reduced from the line pressure to the line pressure depending on the two gears. a pressure adjusting means for adjusting the pressure; a throttle opening detecting means for detecting the opening of the throttle valve;
An automatic transmission characterized by comprising: a correction means for maintaining the pressure adjusted by the pressure adjustment means at line pressure when the opening of the throttle valve detected by the throttle opening detection means is less than a predetermined opening. Machine hydraulic control device.