JPH03265758A - Lockup control device of automatic transmission - Google Patents

Abstract

PURPOSE:To accomplish the release of lockup at the starting stage securely by connecting a fail-safe passage to which the oil pressure is fed when the starting stage is accomplished and the oil pressure is cut off when a speed change stage is accomplished, to a passage at the lockup releasing side. CONSTITUTION:When the speed is shifted to the first speed of the starting stage by the 1-2 speed shift valve 71, the oil pressure fed from a main oil pressure circuit 100 through a regulator valve 61 flows from an input side oil pressure circuit 300A to an output side oil pressure circuit 300B, bypassing a lockup control valve 201 which is not operated by an disorder and feeding to a lockup clutch 26, and it releases the lockup clutch 26 from a lockup condition. And in a speed change stage in which the lockup clutch 26 is connected at the second speed or higher, the oil pressure is cut off to the fail-safe passage 300B by the 1-2 speed shaft valve 71. As a result, even though the gear is shifted from P or N range to D range in an idling condition, no engine stop is generated, and the fluid coupling effect of a torque converter 20 can be realized.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a lock-up control device for an automatic transmission (AT) for an automobile, and more specifically, the present invention relates to a lock-up control device for an automatic transmission (AT) for an automobile, and more specifically, the invention relates to a lock-up control device for an automatic transmission (AT) for an automobile. This invention relates to a lock-up control device for an automatic transmission that does not cause the vehicle to become inoperable.

[Prior Art and Problems] Conventionally, automatic transmissions for automobiles mainly combine a torque converter and a planetary gear train, and a friction element such as a band brake or clutch that connects and fixes the planetary gear train and each element of the planetary gear train. A control circuit that controls the operation of the friction element according to the operating load condition, and a speed change control mechanism such as a solenoid, a shift valve, and an oil pump are often used.

In recent years, four-speed automatic transmissions with a lock-up mechanism have become mainstream, especially from the standpoint of quietness during high-speed operation and improved fuel efficiency. This lock-up mechanism normally operates at a high speed of 3.4 to achieve the above purpose, but since it is possible to transmit power without going through a torque converter, it naturally contributes to improving power transmission efficiency.

In addition, the lock-up mechanism can be used not only for 3rd and 4th speeds but also for 2nd and 3rd speeds.
．． Automatic transmissions that operate in three four-speed stages are also in practical use.

By the way, the transmission control mechanism will be explained as follows.

Conventional automatic transmissions do not have a specific control electronic circuit, and the shift valve is controlled by a gear pump or vane pump oil pressure source, governor oil pressure based on vehicle speed detection, and throttle oil pressure depending on throttle (accelerator) opening. It was controlled by switching the oil path to the friction element.

However, recent automatic transmissions have become more complex due to the shift to 4 speeds (5 speeds have also appeared in some cases) and the addition of direct coupling clutches for lock-up, so more precise control is required. It has become essential.

For this purpose, an electronically controlled automatic transmission (ECAT) equipped with a microcomputer is used.
y Controlled Automatic Tr
enmission) is beginning to be commonly used.

Compared to conventional AT, this ECAT allows you to freely change the ability to follow changes in vehicle speed and accelerator opening (time constant).
This has the advantage that the T control itself can be precisely performed.

However, it cannot be denied that as the number of solenoid valves and the like increases and the control system becomes more complex, the chances of failure tend to increase.

One of the problems is that when the lock-up clutch control valve sticks (stuck) or the solenoid for it is short-circuited, the lock-up clutch will not be released even in 1st gear starting gear, and the lever will not be released when the engine is running at idle. There was a problem that the engine would stall at the same time as changing from the P or N range to the D range, making it impossible to start the car.

Let me explain this background in a little more detail.

FIG. 3 is a diagram showing the structure and hydraulic circuit of the torque converter (equipped with a lock-up mechanism).

In Fig. 3, for example, information is obtained from the D range switch 2, stop lamp switch 3, and engine coolant water temperature switch 4 that the vehicle is in the D range, the stop lamp is not lit, and the water temperature is 72°C or higher, and the vehicle speed is set. When the control circuit 200 receives input that the speed is higher than the set value and the accelerator opening is lower than the set value, the lock-up solenoid 204
A command is issued to turn on the lock-up control valve 201, and the line pressure that pushes the lock-up control valve 201 to the left is drained. The lockup control valve 201 is then moved to the right by the spring force and line pressure. Thus, the oil in the F chamber 16 is drained through the A groove 7,
Oil flows into the R chamber 14 through the B groove 8, and the differential pressure between the F chamber 15 and the R chamber 14 in the torque converter 20 presses the damper piston 17 against the converter cover 16, resulting in a lock-up state. At this time, torque converter 20
The pump 22 and turbine 23 rotate synchronously and do not function as a liquid coupling. Note that 25 is a stator, 6 is a relief valve, and 9 is a torque converter pressure holding valve.

Next, when the lock-up clutch 26 is normally unlocked (released), the following procedure is performed.

First, when the control circuit 200 decides to unlock, line pressure is applied to the lock-up control valve 201 to push the valve to the left, and the valve moves to the left. In the unlocked state, oil flows from the A groove 7 into the F chamber 15.
, the oil pressure in the F chamber 15 becomes higher than the oil pressure in the R chamber 14, the damper piston 17 slides to the left, the lockup is released, and the torque converter 20 can function as a fluid coupling.

The above-mentioned failure is due to solenoid 2 of solenoid valve 204.
04 or the lock-up control pulp 201 sticks and the lock-up cannot be released.

Therefore, the present inventor came up with the idea that the problem could be solved by connecting a fail-safe passage to the lock-up release side passage of the lock-up clutch 26 and forcibly releasing the lock-up using a separate hydraulic system, and conducted various experimental studies. As a result, we have arrived at the present invention.

[Object of the Invention] An object of the present invention is to reliably perform lock-up release in the starting gear without changing the basic layout of a conventional automatic transmission.

Another object of the present invention is to provide a lock-up control device for an automatic transmission that prevents the vehicle from becoming unable to run even when the lock-up clutch control valve sticks or the solenoid shorts.

[Structure of the Invention] According to the present invention, in a lock-up control device for an automatic transmission equipped with a lock-up clutch, hydraulic pressure is supplied to the lock-up release side passage downstream of the lock-up clutch control valve at least when a starting gear is achieved, and the lock-up clutch A lock-up control device for an automatic transmission is provided, which is characterized in that a fail-safe passage is connected to which hydraulic pressure is cut off when a gear position is reached.

The present invention will be described in detail below using Examples.

[Embodiment] FIGS. 1 and 2 are a conceptual diagram and a hydraulic circuit diagram, respectively, of an embodiment of the present invention.

In FIGS. 1 and 2, 300A and 300B are the inlet and outlet hydraulic circuits of the 1st-2nd speed shift valve 7E, which are the main parts of the embodiment of the present invention.

13 is an oil pump which is a hydraulic pressure source; 100 is a main hydraulic circuit (line pressure); 61 is a regulator valve; 62 is a throttle valve that generates throttle pressure according to the accelerator opening of the engine; 71 is a 1st-2nd speed shift valve; 7
6 is a solenoid valve that controls the 1st-2nd speed shift valve, 201 is a lock-up control valve, 204 is a solenoid valve that controls the lock-up control valve 201, 20 is a torque converter, 22 is a pump, 23 is a turbine, and 25 is a stator. , 26 are lock-up clutches.

In this way, the 1st-2nd speed shift valve 71 selects the 1st gear which is the starting gear.
When the gear is shifted to high speed, the hydraulic pressure supplied from the main hydraulic circuit 100 through the regulator valve 61 flows from the inlet hydraulic circuit 300A to the outlet hydraulic circuit 300B, bypassing the lock-up control valve 201 that is malfunctioning and does not operate. It is supplied to the lock-up clutch and can release the lock-up clutch from the locked state. In addition, at a gear position where the lock-up clutch of 2nd gear or higher is engaged, hydraulic pressure is cut off to the fail-safe passage 300B by the 1st-2nd gear shift valve. Therefore, even if the engine is shifted from the P or N range to the D range while idling, the engine will not stall, and the fluid coupling effect of the torque converter can be utilized. Furthermore, even if the lock-up condition continues in 2nd gear or higher, it is still possible to drive the vehicle on its own until repair work is required. Although the above embodiments have been described using an example of an automatic transmission in which the speed change control is electronically controlled, the present invention is not limited to this, and can also be applied to a system in which the speed change control is hydraulically controlled.

Furthermore, the control of the lock-up mechanism can also be applied to one that is hydraulically controlled, and in this case, it becomes a countermeasure when the control valve sticks.

[Effects of the Invention] By implementing the present invention, all of the above objects can be achieved.

That is, it is possible to reliably release the lock-up at least in the starting gear.

In other words, even when the lock-up clutch control valve sticks or the solenoid shorts out and becomes inoperable, the 1st-2nd gear shift valve will stick in 2nd gear.
This has the effect that, except when the lock-up control valves simultaneously stick to the lock-up side (which rarely occurs), the car will not stall and become unable to drive.

[Brief explanation of drawings]

1 and 2 are a conceptual diagram and a hydraulic circuit diagram of an embodiment of the present invention, respectively, and FIG. 3 is a conceptual diagram of a conventional lock-up control mechanism. 20 Torque comparator, 26'
Lock-up clutch, 71. 1-2 speed shift valve, 200 control circuit, 201 lock-up control valve.

Claims (1)

[Claims] (1) In a lockup control device for an automatic transmission equipped with a lockup clutch, hydraulic pressure is supplied to the lockup release side passage downstream of the lockup clutch control valve, at least when the starting gear is achieved, and the lockup clutch is engaged. A lock-up control device for an automatic transmission characterized by connecting a fail-safe passage in which hydraulic pressure is cut off when a gear is achieved.