JPH0447481Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a hydraulic control device for an automatic transmission for an automobile.

BACKGROUND ART Automatic transmissions that achieve low gears by engaging a hydraulic friction engagement device are provided with an accumulator to reduce the impact caused by downshifting when the throttle valve is fully closed (for example, as disclosed in a patent application). Showa 59-91072
In this case, the accumulator operates even during kickdown, so there is a problem that the accuracy of underlap control during kickdown cannot be improved. That is, during kickdown, an underlap period is formed in which the low speed friction engagement device is held in the released state for an appropriate period of time after the high speed friction engagement device is released, and during this underlap period, the engine rotational speed is reduced to a low speed. It is necessary to increase the rotational speed to the speed corresponding to the reduction ratio of the gear, but if an accumulator is installed in the oil passage for supplying hydraulic medium to the friction engagement device for the low gear, the rate of increase in the servo oil pressure of the friction engagement device for the low gear will increase. decreases, the time required for the low-speed friction engagement device to engage becomes longer.
This is disadvantageous in terms of control accuracy.

Problems to be Solved by the Invention The purpose of the invention is to provide a hydraulic control system for an automatic transmission that can reduce the shock during downshifts at low throttle openings and improve the control system during downshifts. It is to provide.

Means for Solving the Problems In order to achieve this objective, the hydraulic control device according to the present invention selects the oil passage for operating hydraulic pressure as the oil passage for a high-speed gear friction engagement device or the oil passage for a low-speed gear friction engagement device. The first shift valve that connects the shift valve, and the oil passage for the friction engagement device for low gears, corresponds to the low throttle opening.
a switching valve selectively connected to the oil passage portion or the second oil passage portion corresponding to a high throttle opening; an accumulator connected to the first oil passage portion; A shuttle valve that selectively switches and connects the higher pressure oil passage to the low-speed friction engagement device, and a discharge oil passage that branches from the low-speed friction engagement device oil passage. The solenoid valve is provided with a solenoid valve that immediately closes when the shift valve is switched from a high gear to a low gear at a low throttle opening and closes after a predetermined time when the shift valve changes from a high gear to a low gear at a high throttle opening.

Effects of the Invention Thus, according to the present invention, when switching the shift valve from a high gear to a low gear at a low throttle opening, ie, a so-called downshift, the solenoid valve closes at the same time as the switching, so that the friction engagement device for the low gear The operating oil pressure is immediately established in the oil passage, but the accumulator in the first oil passage allows the servo oil pressure in the low-speed friction engagement device to rise slowly, allowing for shock-free gear changes. . On the other hand, when switching from high speed to low speed at a high throttle opening, so-called downshift during kickdown, the solenoid valve does not close at the same time as switching, but closes after a predetermined time, thereby delaying the supply of hydraulic pressure. Moreover, since the servo oil pressure in the low-speed friction engagement device is quickly increased through the second oil passage portion, the underlap period is shortened and fluctuations in the output shaft torque of the automatic transmission are reduced. I can do it.

Example The present invention will be explained with reference to the embodiments shown in the drawings.

In FIG. 1, the 2-3 shift valve 10 includes a drain 12, ports 16 and 18 connected to a line pressure oil passage 14, a port 24 connected to a drain oil passage 22 having an orifice 20, and a port 24 for third speed. It has a port 30 connected to the clutch 26 via an oil line 28 and a port 36 connected to a second speed brake 32 via an oil line 34. The oil passage 34 is provided with oil passage portions 38 and 40 parallel to each other in the middle thereof, and the oil passage portion 3
A switching valve 42 and a shuttle valve 44 are provided at both ends of the valves 8 and 40, respectively. An orifice 46 and a check valve 48 are provided in parallel with each other in the middle of the oil passage section 40, and the accumulator 50 is connected to the shuttle valve 44 by the orifice 46 and the check valve 48.
It communicates with the oil passage section 40 on the side.

The switching valve 42 controls the throttle opening corresponding to the throttle opening via a port 56 connected to the oil passage 34, ports 58 and 60 connected to the oil passage parts 38 and 40, a drain 62, and an oil passage part 64, respectively. Control port 66, port 5 supplied with pressure Pth
6 to port 58 or 60, and a spring 70 biasing spool 68 toward control port 66.

The drain oil passage 72 branches from the oil passage 34 and reaches the drain oil passage 22, and is opened and closed by a solenoid valve 74.
The CPU 76 controls on/off of the solenoid valve 74.

The position of the 2-3 shift valve 10 is controlled by a shift valve electromagnetic valve, and the port 30 is connected to the port 16 and the port 36 is connected to the port 24 in the high speed position. Therefore, the third speed clutch 26 is supplied with line pressure Pl and held in an engaged state, and the second speed brake 32 is drained of oil and held in a released state. In the low gear position, port 30 is connected to drain 12 and port 36 is connected to port 18. As a result, the third speed clutch 26 is held in the released state.

Note that the oil passage portions 38 and 40 are hydraulically separated by a switching valve 42 and a shuttle valve 44.
That is, the mutual influence of the oil pressures in the oil passage portions 38 and 40 during downshifting is eliminated.

The operation during downshifting will be explained with reference to FIGS. 2 and 3. Note that Pc and Pb are the third speed clutch 26 and the second speed brake 3, respectively.
2 servo oil pressure.

FIG. 2 shows changes in each parameter during a downshift when the throttle valve is almost fully closed. In this case, since the throttle pressure Pth is low, the spool 68 in the switching valve 42 is pressed toward the control port 66 by the spring 70, and the port 56 is connected to the port 60.

Until time t1, the 2-3 shift valve 10 is held at the high speed position, the servo oil pressure Pc is held at a large value, and the servo oil pressure Pb is held at zero.

At time t1, a downshift is performed from the D (drive) range to the 2 (second) range, and the 2
-3 The shift valve 10 is switched from a high speed position to a low speed position. Switching between the 2-3 shift valves is performed, for example, by a shift valve solenoid valve (not shown). Further, in the case of downshifting from the D range to the 2nd range, the solenoid valve 74 is turned off from time t1 and closes the drain oil passage 72.

As a result, the servo oil pressure Pc quickly decreases from time t1. Further, the oil in the port 36 is supplied to the accumulator 50 and the second speed brake 32 through the port 60 and the orifice 46. As a result of the action of the accumulator 50, the rise in the servo oil pressure Pb from time t2 to t3 becomes gradual, the second speed brake 32 is gently engaged, and the shift impact is alleviated.

FIG. 3 shows changes in each parameter during kickdown from third speed to second speed. In this case, the throttle pressure Pth is high, so the spool 68 in the switching valve 42 adjusts the throttle pressure at the control port 66.
Pth moves against the spring 70, and the port 56
is connected to port 58.

Before time t1, the 2-3 shift valve 10 is in the high speed position, the servo oil pressure Pc is held at a large value, and the servo oil pressure Pb is held at zero.

2-3 at time t11 due to kickdown
The shift valve 10 switches from a high speed position to a low speed position. As a result, the port 30 is connected to the drain 12, the servo oil pressure Pc rapidly decreases, and the third
The speed clutch 26 is quickly released. Also, the port 36 is connected to the port 18 and oil is guided to the port 36, but the solenoid valve 74 is
Since the discharge oil path 72 is kept open even after time t11, the servo oil pressure Pb is still maintained at zero even after time t11, and the engagement of the second speed brake is delayed.

At time t12, the solenoid valve 74 closes the discharge oil passage 72, and as a result, oil is supplied to the port 56 of the switching valve 42. Port 56 in switching valve 42
is connected to the port 58, oil is supplied to the second speed brake 32 via the oil passage portion 38, and the servo oil pressure Pb rapidly increases.

When the servo oil pressure Pb reaches the predetermined value Pb1 at time t13, the second speed brake 32 becomes engaged, and the underlap period ends.

In the conventional device, as shown by the broken line, during kickdown, oil passes through the orifice 46 and the accumulator 50 operates in the same way as during downshift when the throttle valve is almost fully closed. Since the time from when the servo oil pressure Pb is closed until the servo oil pressure Pb reaches the predetermined value Pb1 increases, it is necessary to close the discharge oil passage 72 to time t12' earlier than time t12 in the case of the present invention.
In the conventional device, the time from time t12' to time t13 is due to variations in the diameter of the orifice 46, and due to variations in the piston stroke of the second speed brake 32 due to the small supply speed due to the supply of oil through the orifice 46. However, in the present invention, during kickdown, oil is supplied through the oil passage section 38 and the servo oil pressure Pb quickly rises, so the influence of these variations on the time from time t12 to time t13 is can be eliminated.
Furthermore, since the time from time t12 to t13 is short, there is little variation, and control accuracy can be improved. In the conventional device, due to the dispersion, the underlap period becomes long, the engine revs up excessively, and fluctuations in the output shaft torque of the automatic transmission increase.

In the embodiment, the throttle pressure Pth is guided to the control port 66 of the switching valve 42, but the throttle pressure Pth
Instead, it is also possible to introduce a control pressure to the control port 66 that is zero when the intake throttle opening is less than a predetermined intake throttle opening and becomes a large value when the intake throttle opening is above a predetermined intake throttle opening.

It will be obvious to those skilled in the art that the present invention can be implemented with various modifications and variations without departing from the spirit set forth in the claims for utility model registration.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an embodiment of the present invention, and Fig. 2 is a diagram showing changes in various parameters during downshift depending on the shift range from D range to 2 range when the throttle valve is almost fully closed. , FIG. 3 is a diagram showing changes in various parameters during kickdown. 10... Shift valve, 14... Oil passage for operating hydraulic pressure (line pressure oil passage), 26... Friction engagement device for high speed gear (clutch for third gear), 32... Friction engagement device for low gear gear ( 2nd speed brake), 34... oil path,
38, 40...Oil passage portion, 42...Switching valve, 4
4... Shuttle valve, 50... Accumulator, 7
2...Discharge oil path, 74...Solenoid valve.

Claims (1)

[Scope of utility model registration request] The operating oil pressure oil passage 14 is connected to the high-speed friction engagement device 2.
The shift valve 10 selectively connects to the oil passage 28 for 6 or the oil passage 34 for the friction engagement device 32 for low gear, and the oil passage 34 for the friction engagement device 32 for low gear is connected to the oil passage 34 for the friction engagement device 32 for low gear. A switching valve 42 selectively connects to the first oil passage portion 40 or the second oil passage portion 38 corresponding to a high throttle opening degree, and an accumulator 5 connected to the first oil passage portion 40.
0, the first oil passage portion 40 and the second oil passage portion 3
A shuttle valve 44 selectively connects the oil passage 40 or 38 with the higher pressure among the oil passages 40 or 38 to the low-speed friction engagement device 32, and a discharge branching from the oil passage 34 for the low-speed friction engagement device 32. It is located in the oil passage 72 and closes immediately when the shift valve 10 is changed from a high speed to a low speed at a low throttle opening, and for a predetermined time when the shift valve 10 is changed from a high speed to a low speed at a high throttle opening. A hydraulic control device for an automatic transmission, characterized by having a solenoid valve 74 that later closes.