JPH0546469B2 - - 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, there is a problem in which it becomes difficult to switch the switching valve due to foreign matter getting stuck in the solenoid valve or failure of the electrical system. is also 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 solenoid valve of the switching valve that controls the reverse clutch malfunctions, the reverse clutch cannot be controlled, which may lead to problems such as difficulty in emergency evacuation, especially if you are stuck on the edge of a cliff. Ta.

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. It provides a hydraulic control circuit for the connected automatic transmission, making emergency evacuation possible from cliff edges and the like.

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 clutch 8 provided at the first gear of an automatic transmission (not shown).
1st speed switching valve 7 ₁ that controls 1st speed clutch 8 ₁
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 switching valve ₇₅ 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 like this.

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 to which the solenoid valve 13 is connected The pilot circuits 11 of 7 ₁ to 7 ₅ are drained via the neutral position 12a of the emergency switching valve 12, thereby shifting one or more of the switching valves 7 ₁ to 7 ₅ from position 7a to position 7b. This switching valve 7
The clutches 8 ₁ to 8 ₅ controlled by the clutches ₁ to 7 ₅ are 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 the forward switching valve ₇₄ is switched, the reverse clutch ₈₅
circuit 15 is adapted to be drained through circuit 16, thereby causing 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.
2a to drain position 12b, and 12a
If the electrical system breaks down and the solenoid valve cannot operate due to manual switching to the cut position 12c of the hydraulic circuit 11, the position 12c is changed from 12a to 1.
2b position, drain the circuit 11 and operate the switching valve, so that the circuit 11 is constantly closed due to a failure of the solenoid valve.
When the switching valve is being drained, it is possible to change the position from 12a to 12c, cut off the circuit 11, and stop operating the switching valve.

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 when the oil in each clutch ₈₂ to ₈₅ except the first gear clutch ₈₁ is drained, the first gear consisting of a rotating clutch is The clutch ₈₁ is constantly supplied with hydraulic pressure lower than the engagement pressure of the first speed clutch ₈₁ from the circuit 6a, thereby improving the start-up of the first speed clutch ₈₁ . From this state, when one of the solenoid valves 13 connected to the switching valve 7 ₄ or 7 ₅ and the solenoid valve 13 connected to the 1st speed switching valve 7 ₁ are turned on in order to move the vehicle forward or march, these switching valves 7 ₄ or 7 ₅ and 7 ₁ pilot circuit 1
1 is drained and these switching valves 7 ₄ or 7 ₅
and 7 ₁ becomes position 8 ₆ , main circuit 6, 6a
Hydraulic pressure is then supplied to each clutch 8 ₄ or 8 ₅ and 8 ₁ and these are turned on, and the vehicle starts moving forward or backward in first gear. Then 2nd speed switching valve 7 ₂
The solenoid valves 13 connected to the speed changeover valve ₇₃ and the speed changeover valve 73 are sequentially turned on, and accordingly, the second speed and third speed changeover valves 7 are turned on.
₂ and ₇₃ are also sequentially switched to position 7b, and the gear stage of the instruction transmission is also automatically switched from 1st gear to 2nd gear and from 2nd gear to 3rd gear.

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 path 11 connecting between the solenoid valve 13 and the solenoid valve 13.
Put the emergency switching valve 12 provided in 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, the present invention provides a pilot circuit that connects the switching valves for selecting forward/reverse and speed stages of an automatic transmission and the solenoid valves for switching and controlling these switching valves. An emergency switching valve that connects the circuit to the drain is installed, so even if the solenoid valve breaks down due to foreign matter, the emergency switching valve allows forward/reverse movement and speed selection. It will be possible to safely evacuate stranded vehicles.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing an embodiment of the present invention. ₇₁ to ₇₅ are switching valves, 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 a device equipped with a solenoid valve 13 for switching and controlling the switching valves ₇₁ to ₇₅ , the pilot circuit 11a is manually drained or cut in the middle of the pilot circuit 11a connecting each of the switching valves 71 to ₇₅ and the solenoid valve 13. A hydraulic control circuit for an automatic transmission including an emergency switching valve 12.