JP2748554B2 - Servo hydraulic control unit for hydraulically operated friction engagement device of automatic transmission - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo hydraulic control device that controls a servo hydraulic pressure applied to a hydraulic servo chamber of a hydraulic servo friction engagement device of an automatic transmission.

2. Description of the Related Art In an automatic transmission used for a vehicle such as an automobile, a hydraulic pressure applied to a hydraulic servo chamber of a hydraulically operated friction engagement device such as a clutch or a brake for switching gears, that is, The servo oil pressure is a line oil pressure set according to the load of the prime mover, such as the throttle opening. When shifting gears,
From the viewpoint of reducing shift shock, an accumulator is provided in the middle of the oil passage that guides the hydraulic pressure to the hydraulic servo chamber so that the line hydraulic pressure is not suddenly supplied to the hydraulic servo chamber. Has been conventionally performed so that the engagement of the friction engagement device is gradually performed by gradually ascending at a predetermined rising speed. A back pressure chamber is provided in the accumulator,
It has already been considered that the accumulator characteristics of the accumulator are variably set by controlling the hydraulic pressure supplied to the back pressure chamber, and thereby the engagement characteristics of the friction engagement device are appropriately set according to various operating conditions. This is disclosed in, for example, JP-A-58-151291 and JP-A-61-149657.

[Problem to be Solved by the Invention] The engagement control of the friction engagement device by the back pressure control of the accumulator as described above can be satisfactorily satisfied, but in this case, a plurality of friction engagement devices are required. It is necessary to provide an accumulator, and since the accumulator has a larger volume than a general pressure regulating valve or the like, there is a disadvantage that the hydraulic control device of the transmission is increased in size,
There is also a disadvantage that the weight of the hydraulic control device is greatly increased.

Also, the gradual change time of the hydraulic pressure by the accumulator is limited by the volume of the accumulator, and the gradual change time of the hydraulic pressure cannot be freely set.

As a technique for gradually increasing the hydraulic pressure supplied to the hydraulic servo chamber during shifting to reduce shift shock, a pressure regulating valve is provided in the middle of an oil path that guides the hydraulic pressure to the hydraulic servo chamber, and the hydraulic pressure is controlled by this pressure regulating valve. It is conceivable to control the hydraulic pressure applied to the servo chamber, that is, the servo hydraulic pressure itself.

In this case, however, it must be ensured that the hydraulic servo chamber is always supplied with the line oil pressure or a correspondingly high oil pressure so that the frictional engagement device is completely engaged. There is a possibility that normal gear shifting control is not performed due to lack of reliability.

In particular, in the case where the pressure adjusting valve for servo oil pressure control changes the pressure adjustment value in accordance with the control oil pressure by duty ratio control or current control, the final oil pressure at the time of gear shifting is changed to the line oil pressure. I have to rely on control. Moreover, if the operation is ensured, it is necessary to make the land area of the spool valve to which the control oil pressure is applied considerably larger than the land area of the spool valve to which the feedback oil pressure is applied. This makes the pressure adjustment characteristics sensitive to the control oil pressure, and deteriorates the accuracy of servo oil pressure adjustment.

The present invention can increase the servo hydraulic pressure supplied to the hydraulic servo chamber of the friction engagement device at the time of shifting without using an accumulator with high accuracy with an appropriate rate of increase to reduce shift shocks. It is an object of the present invention to provide a servo hydraulic control device capable of surely supplying a line hydraulic pressure or a high hydraulic pressure corresponding to the line hydraulic pressure to a hydraulic servo chamber and performing appropriate shift control with high reliability.

Means for Solving the Problems According to the present invention, as described above, an object of the present invention is to apply a hydraulic pressure to a boost port provided in the middle of an oil passage for guiding a hydraulic pressure to a hydraulic servo chamber of a hydraulically operated friction engagement device. When the boost pressure is not supplied, the pressure is adjusted according to the equilibrium relationship between the hydraulic pressure applied to the control port and the feedback hydraulic pressure applied to the feedback port. A servo hydraulic pressure control valve for outputting hydraulic pressure and controlling a servo hydraulic pressure to be supplied to the hydraulic servo chamber; and a boost control valve for responding to the hydraulic pressure of the hydraulic servo chamber and applying hydraulic pressure to the boost port when the hydraulic pressure is equal to or higher than a predetermined value. This is achieved by a servo hydraulic control device of a hydraulically operated friction engagement device of an automatic transmission having:

According to the configuration described above, the servo hydraulic pressure supplied to the hydraulic servo chamber is directly controlled by the servo hydraulic control valve, and when the hydraulic pressure in the hydraulic servo chamber reaches a predetermined value, the boost control valve is activated. Since the hydraulic pressure is applied to the boost port of the servo hydraulic control valve, the hydraulic pressure output by the servo hydraulic control valve always becomes a high hydraulic pressure, for example, a line hydraulic pressure. This ensures that the hydraulic pressure applied to the hydraulic servo chamber of the friction engagement device eventually becomes a high hydraulic pressure, for example, a line hydraulic pressure.
Accordingly, engagement of the friction engagement device is guaranteed, and highly reliable shift control is performed.

In addition to the above effects, it is possible to increase the land area to which the feedback hydraulic pressure is applied in the servo hydraulic control valve as compared with the land area to which the hydraulic pressure applied to the control port is applied. As a result, the pressure regulation characteristic with respect to the hydraulic pressure applied to the control port becomes insensitive, the variation of the servo hydraulic pressure with respect to the variation of the hydraulic pressure applied to the control port is reduced, and the pressure regulation accuracy of the servo hydraulic pressure is kept high. Will be able to

In this case, the accumulator can be omitted, and the time for gradually changing the hydraulic pressure can be made free.

[Example] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a hydraulic control device for an automatic transmission equipped with a servo hydraulic control device according to the present invention, with respect to the essential parts thereof.

In the figure, reference numeral 10 denotes a servo hydraulic control valve, and the servo hydraulic control valve 10 is provided in the middle of oil passages 31 and 34 for guiding oil pressure to a hydraulic servo chamber 30 of an input clutch which is one of frictional engagement devices. Is provided.

The servo hydraulic control valve 10 has a spool valve 12, and the spool valve 12 has a compression coil spring 24, an upward pressing force and an oil passage in a diagram by a hydraulic pressure applied to a control port 20 and a control hydraulic pressure applied to a boost port 26. The degree to which the output port 14 is connected to the input port 16 and the drain port 18 according to the equilibrium relationship with the downward pressing force in the figure by the hydraulic pressure given to the feedback port 22 by 34, and the output port 14 is connected to the input port 16 and the drain port 18 By controlling the pressure, the hydraulic pressure from the input port 16 is regulated to generate a regulated hydraulic pressure at the output port 14, that is, a servo hydraulic pressure.

The spool valve 12 has a first land portion 12a to which the feedback oil pressure of the feedback port 22 is applied, a second land portion 12b to which the oil pressure of the boot port 2 is applied, and a third land portion 12c to which the oil pressure of the control port 20 is applied. The cross-sectional area of the first land portion 12a is Aa, and the second land portion 1
Assuming that the cross-sectional area of 2b is Ab and the cross-sectional area of the third land portion 12c is Ac, these cross-sectional areas are determined so as to maintain the following relationship.

Ab> Ac ... (1) Ab-Ac> Ac ... (2) Aa> Ac ... (3) The output port 14 is connected to the hydraulic servo chamber 30 by an oil passage 34, and the input port 16 is connected to the hydraulic servo chamber 30 by an oil passage 32. It is connected to the port 44 of the four-shift valve 40.

The 3-4 shift valve 40 has a spool valve 42,
Reference numeral 42 denotes the lower position shown in the right half of the figure only at the fourth speed, and the port 44 is connected to the drain port 48 at other times, that is, at the first speed and the second speed. In the third speed and the third speed, the spool valve 42 is located at the ascending position shown in the left half of FIG. Is supplied to the input port 16 of the servo hydraulic control valve 10.

A control oil pressure regulated by duty ratio control by a duty ratio solenoid valve 60 is supplied to a control port 20 of the servo oil pressure control valve 10 through an oil passage 62. The duty ratio solenoid valve 60 has a general structure, and opens and closes repeatedly with a time ratio corresponding to the duty ratio of the pulse signal given to the electromagnetic coil 61, and applies a hydraulic pressure according to the duty ratio to the oil passage 62. Is to occur.

Note that the base pressure of the control oil pressure regulated by the duty ratio solenoid valve 60 is a modulated oil pressure that is a constant oil pressure provided from the modulator valve 70 by the oil passage 66. An accumulator 64 for reducing the pulsation of the control oil pressure is provided in the middle of the oil passage 64.

The boost port 26 of the servo hydraulic control valve 10 is connected to a port 84 of the boost control valve 80 through an oil passage 68 so that hydraulic pressure can be selectively applied thereto.

The boost control valve 80 has a spool valve 82,
Reference numeral 82 denotes a port located at the ascending position shown in the left half of the drawing by the spring force of the compression coil spring 92 when the oil pressure equal to or higher than the predetermined value Pset is not applied to the port 90, and the port 84 is connected to the drain port.
When a hydraulic pressure equal to or more than a predetermined value Pset is applied to the port 90, the pressure is applied to the port 90, and the pressing force by the hydraulic pressure is shown in the right half of the drawing against the spring force of the compression coil spring 92. In such a position, the port 84 is separated from the drain port 88 so as to be connected to the hydraulic pressure supply port 86. The port 86 is provided with a line hydraulic pressure. Port 90 is connected to oil passage 34 by oil passage 94.
And a hydraulic pressure in the oil passage 34, that is, a servo hydraulic pressure.

If the input clutch is engaged when a manual shift change is made from the N range to the D range, at the beginning of the manual shift change, the hydraulic servo chamber 30 of the input clutch is substantially installed. Since there is no substantial oil pressure and no substantial oil pressure exists in the oil passage 34, the spool valve 82 of the boost oil pressure control valve 80 is located at a raised position as shown in the left half of the drawing, 84 is connected to drain port 88. Accordingly, at this time, no hydraulic pressure is applied to the boost port 26 of the servo hydraulic control valve 10, and the servo hydraulic control valve 10 operates according to the balance between the control hydraulic pressure applied to the control port 20 and the feedback hydraulic pressure applied to the feedback port 22. It operates to perform the pressure regulating action. The pressure adjustment type of the servo hydraulic control valve 10 at this time is
If the servo oil pressure (feedback oil pressure) at 34 is Ps, the control oil pressure applied to the control port 20 is Pd, and the spring force of the compression coil spring 24 is F, the following expression is obtained.

PsAa = F + PdAc Therefore, the servo hydraulic pressure Ps at this time is represented by the following equation.

Ps = (Ac / Aa) Pd + F / Aa The servo oil pressure Ps can be set freely by controlling the control oil pressure Pd.

Since the cross-sectional area Aa of the first land portion 12a is larger than the cross-sectional area Ac of the third land portion 12b, the servo hydraulic pressure Ps is insensitive to the variation of the control hydraulic pressure Pd due to the duty ratio control. Thus, the variation of the servo oil pressure Ps with respect to the variation of the control oil pressure Pd is reduced, and the pressure adjustment accuracy of the servo oil pressure is maintained at a high level.

The control oil pressure applied to the control port 20 of the servo oil pressure control valve 10 may be increased at a predetermined rate when the input clutch is engaged, whereby the servo oil pressure Ps increases and the oil pressure in the hydraulic servo chamber 30 increases by a predetermined amount. As the speed increases, the engagement of the input clutch proceeds.

When the servo oil pressure Ps reaches the predetermined value Pset, the spool valve 82 of the boost control valve 80 is switched to the lowered position as shown in the right half in the drawing by this oil pressure, and the port 84 is replaced with the drain port 88 by the oil pressure. It will be connected to the supply port 86. As a result, the line oil pressure of the oil pressure supply port 86 is changed to an oil passage.
Through 68, the hydraulic pressure is supplied to the boost hydraulic port 26 of the servo hydraulic control valve 10. Spool valve 12 boost boat
26 is an area difference Ab-Ac between the cross-sectional area Ab of the second land portion 12b and the cross-sectional area Ac of the third land portion 12c. Since the cross-sectional area (effective pressure receiving area) Aa of the first land portion 12a to which the hydraulic pressure Ps) is applied, the boost port
When the line oil pressure is applied to 26, the spool 12 is fixed at the raised position as shown in the left half of the figure regardless of the feedback oil pressure of the feedback port 22. As a result, the servo hydraulic control valve 10 loses the above-mentioned pressure regulation function of the pressure regulation type. At this time, the servo hydraulic control valve 10
The output port 14 and the input port 16 are in direct communication with each other, and the hydraulic pressure of the input port 16, that is, the line hydraulic pressure, is supplied to the output port 14, in other words, the oil passage 34, without being reduced in pressure. . This mechanically guarantees that the servo hydraulic pressure Ps eventually becomes the line hydraulic pressure.

The change characteristic of the servo hydraulic pressure Ps due to the above-described action is the second characteristic.
It will be as shown in the figure. In addition, in FIG.
T ₀ is a hydraulic rise time, the pressure regulating starting point of T _1, T ₂ indicates respectively the end pressure regulation.

Next, a conventional example of a servo hydraulic control device will be described with reference to FIG. 3 for reference. In FIG. 3, portions corresponding to FIG. 1 are indicated by the same reference numerals as those given in FIG. In the conventional servo hydraulic control device, the boost port 26 and the boost control valve 80 of the servo hydraulic control valve 10 are not provided.

In this case, it is necessary to rely entirely on the electronic control by the duty ratio solenoid valve 60 to make the final oil pressure at the time of shifting into the line oil pressure, and if the operation is surely obtained, the control by the solenoid valve 60 is performed. It becomes necessary to make the spool valve land area B to which the hydraulic pressure is applied considerably larger than the spool valve land area A to which the feedback hydraulic pressure is applied. This makes the pressure adjustment characteristic of the control oil pressure by the solenoid valve sensitive, and the pressure adjustment speed of the servo oil pressure is deteriorated.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing one embodiment of a hydraulic control device for an automatic transmission having a servo hydraulic control device according to the present invention, and FIG. 2 is a servo hydraulic characteristic controlled by the servo hydraulic control device according to the present invention. FIG. 3 is a hydraulic circuit diagram showing a conventional example of a servo hydraulic control device. 10 servo hydraulic control valve, 20 control port, 22 feedback port, 26 boost port, 30 hydraulic servo chamber, 40
... 3-4 shift valve, 60 ... duty ratio solenoid valve, 70 ...
Modulating valve, 80 ... boost control valve

Claims (1)

(57) [Claims] The hydraulic pressure is applied to a control port and the feedback is applied to a feedback port when hydraulic pressure is not applied to a boost port. A servo that performs a pressure adjusting operation according to an equilibrium relationship with an oil pressure and outputs a higher oil pressure than the pressure adjusting operation when the oil pressure is applied to the boost port and controls a servo oil pressure supplied to the hydraulic servo chamber. Servo hydraulic pressure of a hydraulically operated friction engagement device of an automatic transmission having a hydraulic control valve and a boost control valve responsive to the hydraulic pressure of the hydraulic servo chamber and applying hydraulic pressure to the boost port when the hydraulic pressure is equal to or higher than a predetermined value. Control device.