JPH0546468B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic control circuit for an automatic transmission in which a switching valve for selecting forward/reverse movement and a speed stage is switched and controlled by a solenoid valve.

For example, Japanese Patent Application No. 149942/1984 is known as a conventional automatic transmission in which the switching valve is switched on/off by a solenoid valve. However, in the conventional circuit described above, if a foreign object gets caught in the solenoid valve, it becomes difficult to switch the switching valve.
No. 32839 has been proposed. In this application, the switching valve is made to be manually switched by a screw rod, so that it can be evacuated in an emergency or moved to a repair shop in the event of a breakdown. The priority circuit prevents these from becoming double clutches. For this reason, for example, if the electromagnetic valve of the switching valve that controls the reverse clutch fails, the reverse clutch will no longer be able to be controlled, leading to problems such as difficulty in emergency evacuation, especially when stuck on the edge of a cliff.

This invention was made with the aim of improving this problem. For example, an emergency switching valve that can switch the switching valve that controls the reverse clutch even if the electromagnetic valve provided in the switching valve that controls the reverse clutch breaks down is connected in series to the pilot circuit. At the same time, the forward/reverse switching valve is connected in parallel to the hydraulic power source, and the 1st to 3rd speed switching valves are connected in series to form a priority circuit.
The present invention aims to provide a hydraulic control circuit for an automatic transmission that improves the start-up of operation by constantly supplying hydraulic pressure below the engagement pressure to the speed clutch.

An embodiment of the present invention will be described in detail below with reference to the drawings. The figure shows a hydraulic control circuit for an automatic transmission with three forward speeds and three reverse speeds. 4 to a switching valve group 7 connected to a main circuit 6. The switching valve group 7 is a first speed switching valve ₇₁ that controls a first speed clutch ₈₁ of a clutch 8 provided at the first speed of an automatic transmission (not shown).
and a second speed switching valve ₇₂ that controls the second speed clutch ₈₂ .
and a third-speed switching valve ₇₃ that controls the third-speed clutch ₈₃ .
and a forward switching valve ₇₄ that controls the forward clutch ₈₄ .
and a reverse selector valve ₈₅ that controls the reverse clutch _85.
Therefore, the first speed clutch ₈₁ , which is a rotary clutch, is operated by the reusing valve 5 provided in the middle of the circuit 6a branched from the main circuit 6.
The hydraulic pressure reduced to a pressure lower than the engagement pressure of the first speed clutch ₈₁ is applied to the position ₇ of the first speed changeover valve 71.
This hydraulic pressure is constantly supplied through the circuit 20 and the position 7b of the second or third speed switching valves ₇₂ , ₇₃ when the second or third speed switching valves ₇₂ , ₇₃ are operated. It is becoming more and more common.

Further, each of the switching valves 7 ₁ to 7 ₅ is constituted by a pilot switching valve, and a part of the discharge pressure of the hydraulic pump 1 is transferred to both ends of each switching valve 7 1 to 7 ₅ via a pilot valve 10 and a pilot circuit ₁₁ . A solenoid valve 1 is connected to the pilot circuit 11 via an emergency switching valve 12.
3 is connected. The emergency switching valve 12 and the solenoid valve 13 are provided for each of the switching valves _{71 to 75} , and when one or more of these solenoid valves 13 is turned on, the switching valve 13 to which the solenoid valve 13 is connected The pilot circuits 11 of ₁ to ₇₅ are drained via the neutral position 12a of the emergency switching valve 12, thereby switching one or more of the switching valves ₇₁ to ₇₅ from position 7a to position 7b. This switching valve 7 ₁
Clutches 8 ₁ to 8 controlled by 7 to _5
5 is now turned on.

On the other hand, the first to third speed switching valves 7 ₁ to 7 ₃ are connected in series to the main circuit 6, while the forward switching valve 7 ₄ and the reverse switching valve 7 ₅ are connected in parallel to the main circuit 6. 1st to 3rd speed switching valve ₇ For priority circuits 1 to ₇₃ , forward/reverse switching valve 7
₄ , 7, _{and 5} cannot be switched at the same time. That is, the circuit 15 leading to the reverse clutch ₈₅ is the circuit 1.
6 to the forward switching valve ₇₄ ,
When forward switching valve ₇₄ is switched, reverse clutch ₈₅
The circuit 15 is drained through the circuit 16, which causes the forward and backward clutches 8 ₄ ,
This prevents the so-called double clutch in which 8 _{and 5} are engaged at the same time.

Further, the emergency switching valve 12 provided in the pilot circuit 11 between each switching valve 7 ₁ to 7 ₅ and each solenoid valve 13 is a manual switching valve, and is a manual switching valve.
If the electrical system fails and the solenoid valve cannot operate due to manual switching from 2a to drain position 12b or from 12a to cut position 12c of the hydraulic circuit 11, switch from 12a to 12b.
If the circuit 11 is constantly drained due to a failure of the solenoid valve, the circuit 11 is drained and the switching valve is operated.If the circuit 11 is constantly drained due to a failure of the electromagnetic valve, the circuit 11 can be cut off by switching to the 12c position rather than 12a, and the switching valve can be stopped from operating.

Next, to explain the operation, when the solenoid valve 13 is off, the compression spring 7 installed in each switching valve 7 ₁ to 7 ₅
The switching valves ₇₁ to ₇₅ are held in position 7a by the action of c, and the oil in each of the clutches ₈₂ to ₈₅ except the first gear clutch ₈₁ is drained, and the first gear clutch consisting of a rotary clutch is drained. clutch 8 ₁
When in neutral, a hydraulic pressure lower than the engagement pressure of the first speed clutch ₈₁ is supplied from the circuit 6a to improve the start-up of the first speed clutch ₈₁ . In order to move the vehicle forward or backward from this state, the switching valve 7 ₄
or one of the solenoid valves 13 connected to 7 ₅ and 1
When the solenoid valve 13 connected to the speed changeover valve ₇₁ is turned on, the pilot circuits 11 of these changeover valves ₇₄ or ₇₅ and ₇₁ are drained, and these changeover valves ₇₄ or ₇₅ and ₇₁ are set to the position. 7b, each clutch ₈₄ or 85 from the main circuits 6 and _6a.
Hydraulic pressure is supplied to and 8 ₁ , turning them on,
The vehicle starts moving forward or backward in first gear, and
For forward movement, circuit 1 leads to reverse clutch 8 ₅
5 is connected to the drain via the circuit 16 and position 7b of the forward switching valve ₇₄ , so-called double clutches in which the forward and reverse clutches ₈₄ and ₈₅ are engaged simultaneously can be prevented. Thereafter, the solenoid valve 1 is connected to the 2nd speed switching valve 7 ₂ and the 3rd speed switching valve 7 ₃ .
2 is sequentially turned on, and accordingly, the 2nd and 3rd speed switching valves 7 ₂ and 7 ₃ are also sequentially switched to position 7b, and the speed gears of the automatic transmission are automatically changed from 1st gear to 2nd gear and from 2nd gear to 3rd gear. can be switched.

The above is the speed change operation, but next, the solenoid valve 13
To explain the effect in the event that one or _more of valve 7 ₅
and a pilot circuit 11 connecting between the solenoid valve 13 and the solenoid valve 13.
Put the emergency switching valve 12 provided at a into the drain position 12b. As a result, the reverse switching valve 7
₅ is in position 7b, and the reverse clutch ₈₅ is turned on. Therefore, in this state, the first speed switching valve ₇₁ turns on the first speed clutch ₈₁ to move the vehicle backward, thereby making it possible to make an emergency evacuation.

Also, even if other solenoid valves 13 fail,
Since an emergency switching valve 12 is provided for each electromagnetic valve 13, there is no problem in forward/reverse movement and switching between speed stages.

As described in detail above, this invention provides an emergency switching valve between the switching valve that selects forward/reverse movement and speed stage and the solenoid valve that controls these switching valves, so that the solenoid valve can be prevented from getting caught in foreign objects. Even in the event of a breakdown, it becomes possible to select forward/reverse movement and speed by operating the emergency switching valve, thereby facilitating emergency evacuation. In addition, the forward/reverse switching valve is connected in parallel to the hydraulic power source, and when moving forward, the reverse clutch is drained via the forward switching valve, so it is possible to prevent the so-called double clutch in which the forward/reverse clutch engages at the same time. The gear switching valves are connected in series to form a priority circuit, and at the same time, hydraulic pressure below the engagement pressure is always supplied to the 1st gear clutch, so even if a rotating clutch with a lot of leakage is used for the 1st gear clutch, it will not start up. is good, and responsiveness is also improved.

[Brief explanation of drawings]

The drawing is a circuit diagram showing an embodiment of the present invention. ₇₁ to ₇₅ are switching valves, 81 to ₈₅ are clutches, _11a is a pilot circuit, 12 is an emergency switching valve, and 13 is a solenoid valve.

Claims (1)

[Claims] 1. A plurality of switching valves ₇₁ to 75 for selecting forward and backward movement of the automatic transmission and each speed stage, and each switching valve ₇₁ by draining _{the pilot pressure supplied to these switching valves 71 to 75} . In those equipped with a solenoid valve 13 for switching control between 7 and ₅ ,
An emergency switching valve 12 for manually draining or cutting off the pilot circuit 11a is provided in the middle of the pilot circuit 11a connecting each of the switching valves ₇₁ to ₇₅ and the solenoid valve 13, and the forward/reverse switching valves ₇₄ , 7 ₅ is a forward/reverse clutch 8 which is connected in parallel to the hydraulic power source and which is controlled by the other switching valves 7 ₅ , 7 ₄ when one switching valve 7 ₄ , 7 ₅ is switched.
₄ and ₈₅ are drained through one of the switching valves ₇₄ and ₇₅ , and the switching valves ₇₁ to ₇₃ of each speed stage are connected in series and connected to the first speed clutch _81. is a hydraulic control circuit for an automatic transmission that constantly supplies hydraulic pressure below the engagement pressure.