JP2991378B2 - Lockup control device for automatic transmission - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lock-up control device for an automatic transmission (AT) for an automobile, and more particularly, to an automatic transmission (AT) for an automobile even when an abnormality occurs in a lock-up clutch control system. The present invention relates to a lock-up control device for an automatic transmission that does not become unable to run.

[Prior art and problems] Conventionally, as an automatic transmission for an automobile, a torque converter and a planetary gear train are mainly combined to form a planetary gear train and a friction element such as a band brake or a clutch for connecting and fixing each element of the planetary gear train. And a control circuit for controlling the operation of the friction element according to the operation load state, and a shift control mechanism such as a solenoid, a shift valve, and an oil pump are often used.

In particular, from the viewpoint of quietness during high-speed operation and improvement of fuel efficiency, recently, a four-speed automatic transmission with a lock-up mechanism has become mainstream. This lock-up mechanism normally operates at the high speed stage of the third and fourth speeds to achieve the above-mentioned purpose, but since it can transmit power without passing through the torque converter, it naturally contributes to improvement of power transmission efficiency.

An automatic transmission in which the lock-up mechanism operates in three stages of 2, 3, and 4 speeds as well as in 3 and 4 speeds is also in practical use.

The shift control mechanism will be described below.

The conventional automatic transmission has no control electronic circuit,
A shift valve controlled by a hydraulic source of a gear pump or a vane type pump, a governor hydraulic pressure based on vehicle speed detection, and a throttle hydraulic pressure according to a throttle (accelerator) opening degree.
It was controlled by switching the oil path to the friction element.

However, recent automatic transmissions have become more complicated due to the fact that they have been shifted to 4-speed (and some 5-speed gears have been introduced) and the addition of a direct-connection clutch for lock-up. Has become indispensable. For this purpose, an electronically controlled automatic transmission having a microcomputer (ECAT: Electronica)
lly Controlled Automatic Transmission) has begun to be commonly used.

Compared to the conventional AT, this ECAT has the advantages that the followability (time constant) to changes in vehicle speed and accelerator opening can be freely changed, and that the AT control itself can be performed more precisely.

However, on the other hand, it is undeniable that the number of solenoid valves and the like increase and the control system becomes complicated, so that the chance of failure tends to increase.

One of the problems is that when the lock-up clutch control valve sticks (sticks) or the solenoid for that purpose short-circuits, the lock-up clutch is not disengaged even in the first-speed start stage, and the lever is released in the engine idle operation state. When the vehicle is moved from the P and N ranges to the D range, an engine stall occurs and the car cannot start.

 Let me elaborate a little on this background now.

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

In FIG. 3, for example, from the D range switch 2, the stop lamp switch 3, and the engine coolant temperature switch, the information that the stop lamp is not lit and the water temperature is 72 ° C. or higher, which are in the D range, respectively, is obtained. When the control circuit 200 receives the command that the accelerator opening is equal to or less than the set value, the control circuit 200 issues a command to turn on the lock-up solenoid 204, and the lock-up control valve 201
Is pressed to the left, and a line pressure is drained. Then, the lock-up control valve 201 moves rightward by the spring force and the line pressure. Thus, the oil in the F chamber 16 is drained through the A groove 7, the oil flows into the R chamber 14 through the B groove 8, and the F chamber in the torque converter 20 is
The damper piston 17 is pressed against the converter cover 16 by a differential pressure between the R chamber 15 and the R chamber 14 to bring it into a lock-up state. At this time, the pump 22 and the turbine 23 of the torque converter 20 rotate synchronously and do not function as a liquid joint. Reference numeral 25 denotes a stator, 6 denotes a relief valve, and 9 denotes a torque converter pressure holding valve.

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

First, when the control circuit 200 determines unlocking, a 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 into the F chamber 15 from the A groove 7 and the F chamber 15
The oil pressure of 15 becomes higher than the oil pressure of R chamber 14, and the damper piston
17 is slid to the left to release the lock-up, and the torque converter 20 can function as a fluid coupling.

The aforementioned failure is caused by the solenoid 204 of the solenoid valve 204.
Short or lock-up control valve 20
Lock-up cannot be released due to the occurrence of stick 1.

Therefore, the present inventor has conceived that the problem can be solved by connecting the fail-safe passage to the lock-up releasing side passage of the lock-up clutch 26 and forcibly releasing the lock-up by hydraulic pressure of another system to solve the problem. As a result of experimental consideration, the present invention has been reached.

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

It is another object of the present invention to provide a lock-up control device for an automatic transmission in which the vehicle cannot run even when the stick of the lock-up clutch control valve or the solenoid is short-circuited.

According to the present invention, in a lock-up control device for an automatic transmission including a lock-up clutch, the engine is in an idling state in a lock-up releasing side passage downstream of the lock-up clutch control valve when the starting stage is achieved. A lock for an automatic transmission characterized in that a hydraulic pressure is supplied so that the lock-up clutch is released, and a fail-safe passage is connected so that the hydraulic pressure is cut off when a gear position in which the lock-up clutch is engaged is achieved. Up control device.

The lockup control device for an automatic transmission according to claim 1, wherein the fail-safe passage is a 1-2 speed shift valve.

 Hereinafter, the present invention will be described in detail with reference to Examples.

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

1 and 2, reference numerals 300A and 300B denote the hydraulic circuits on the inlet and outlet sides of the 1-2 speed shift valve 71, which are essential parts of the embodiment of the present invention.

13 is an oil pump as a hydraulic pressure source, 100 is a main hydraulic circuit (line pressure), 61 is a regulator valve, 62 is a throttle valve that generates a throttle pressure according to the accelerator opening of the engine, 71 is a 1-2 speed shift valve, 76 is 1-2
Solenoid valve that controls the speed shift valve, 201 is a lock-up control valve, 204 is a solenoid valve that controls the lock-up control valve 201, 20
Denotes a torque converter, 22 denotes a pump, 23 denotes a turbine, 25 denotes a stator, and 26 denotes a lock-up clutch.

As described above, the first stage, which is the start stage by the 1-2 speed shift valve 71,
When shifting to high speed, the hydraulic pressure supplied from the main hydraulic circuit 100 through the regulator valve 61 changes to the incoming hydraulic circuit 300A.
, And is supplied to the lock-up clutch by bypassing the lock-up control valve 201 which does not operate due to a failure, thereby releasing the lock-up clutch from the locked state. Note that, at the speed where the lock-up clutch of the second speed or higher is engaged, the hydraulic pressure is shut off to the fail-safe passage 300B by the 1-2 speed shift valve. Therefore, even when the engine is in the idling state and the engine is switched from the P and N ranges to the D range, the engine does not stall, and the fluid coupling effect of the torque converter can be utilized. Even if the lock-up state continues at the second speed or higher, it is possible to run to the repair shop by itself. In the above embodiment, the automatic transmission for electronically controlling the shift control has been described as an example. However, the present invention is not limited to this, and can be applied to a case where the shift control is hydraulically controlled.
Further, the control of the lock-up mechanism can also be applied to a hydraulically controlled one. In this case, it is a measure against sticking of the control valve.

[Effects of the Invention] All of the above objects can be achieved by implementing the present invention.

That is, the lock-up release at least in the starting stage can be reliably performed.

In other words, when the lock-up clutch control valve sticks or the solenoid becomes short-circuited and inoperable, the 1-2 speed shift valve sticks on the 2nd speed side, and the lock-up control valve simultaneously moves to the lock-up side. Except when sticking (this happens very rarely), there is an effect that the car will not stop and stop running due to engine stoppage.

[Brief description of the drawings]

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

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-60-260762 (JP, A) JP-A-58-24651 (JP, A) JP-A-57-208350 (JP, A) JP-A-56-260 JP-A-61-84474 (JP, A) JP-A-52-98863 (JP, A) JP-A-60-260761 (JP, A) JP-A-2-150567 (JP, A) JP-A-56-138560 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F16H 61/14

Claims (2)

(57) [Claims] In a lock-up control device for an automatic transmission having a lock-up clutch, a lock-up clutch is provided in a lock-up releasing side passage downstream of a lock-up clutch control valve when the engine is in an idling state and a start gear is achieved. A lock-up control device for an automatic transmission, characterized in that a fail-safe passage is connected so that the hydraulic pressure is supplied so as to be released and the hydraulic pressure is cut off when a gear position in which a lock-up clutch is engaged is achieved. 2. A lock-up control device for an automatic transmission according to claim 1, wherein the fail-safe passage is a 1-2 speed shift valve.