JPH0326350Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The invention is applicable to automatic transmissions, especially for forward/reverse switching and one-way transmission.
This invention relates to a shift pilot circuit for an automatic transmission in which pressure oil is supplied to each clutch of a transmission having a plurality of gears, such as 4-speed to 4-speed, through switching valves that are switched by pilot pressure controlled by electromagnetic valves. It is something.

Prior Art Power transmission in this type of automatic transmission is achieved by connecting two clutches, one clutch for forward and backward movement and one clutch for each speed gear. If three clutches are connected, the transmission will be damaged.

Problems that the invention aims to solve In conventional automatic transmissions, a priority circuit is provided in the shift pilot circuit to prevent more than two clutches from engaging. There was a problem that the circuit became complicated.

Means and Effects for Solving the Problems The present invention has been developed in view of the above-mentioned problems. Automatic transmission gear shift system that allows easy configuration of a gear shift pilot circuit that prevents three or more clutches from engaging due to incorrect operation by installing a protection valve that detects and shuts off the circuit. It is intended to provide a pilot circuit.

Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings.

In the figure, 1 is a hydraulic pump, 2 is a pressure gradually increasing valve consisting of a gradually increasing valve 3, a load piston 4, and a quick return valve 5, and 6 is a transmission.

The transmission device 6 includes a forward clutch 7, a reverse clutch 8, a first gear clutch 9, and a second gear clutch 1.
It has a clutch 11 for 0 and 3 speeds and a clutch 12 for 4 speed, and each clutch has a switching valve 13a to 13.
It is connected in parallel to the pressure increasing valve 2 via f.

Each of the above switching valves 13a to 13f is controlled by pilot pressure.
It is turned ON and is biased toward the OFF side by a spring. The ON side acting part of each switching valve is connected to the main pilot circuit 14, and the OFF side acting part is connected to manual switching valves 15a to 15f and electromagnetic switching valves 16a to 16a.
It is connected to the drain side via 6f. Further, the operating portions on both sides of each switching valve are connected via a throttle 17.

The main pilot circuit 14 is connected to the hydraulic pump 1. A main aperture 18 is interposed in this main pilot circuit 14,
A protection valve 19 is provided on the upstream side of this throttle 18.
A drain circuit 20 is connected thereto. The protection valve 19 has a relief valve structure,
It is biased in the blocking direction by a spring 21, and pilot circuits connected to the upstream and downstream sides of the throttle 18 are communicated on both sides thereof.

The biasing force of the spring 21 of the protective valve 19 in the blocking direction is caused by the differential pressure across the main throttle 18 when a flow rate sufficient to switch the three switching valves flows through the main pilot circuit 14. It acts as a biasing force against the spring 21 to move to the communicating position.

In the above configuration, for example, when the forward solenoid switching valve 16a and the 1st speed solenoid switching valve 16c are turned on and communicated with each other, the pilot connected to the forward switching valve 13a and the 1st speed switching valve 13c A flow occurs in the circuit, and each switching valve 13a, 13c
is turned on due to the differential pressure of the throttle 17, pressure oil flows into the forward and first speed clutches 7 and 9, and these are turned on, causing the vehicle to run at the first forward speed.

If you accidentally turn on the third solenoid valve other than the one for forward or first gear during the above gear shifting operation, that solenoid valve will also cause the switching valve to which the pilot circuit is connected.
It turns ON and the clutch is in a state of overlapping engagement.

However, at this time, the pilot flow rate flowing through the main pilot circuit 14 increases accordingly, and the flow rate is sufficient to switch the three switching valves. In this way, the main pilot circuit 14 at that time
The protective valve 19 is brought into communication due to the differential pressure of the main throttle 18, and the main pilot circuit 14
The pilot is drained, all switching valves 13a to 13f of the transmission are closed, and the vehicle is stopped.

Effects of the invention Since the invention is as described above, if the three clutches are turned on by accidentally operating the three electromagnetic switching valves, the pilot switching operation of each clutch will become impossible and the vehicle will stop. This prevents damage to the transmission due to three or more clutches being connected due to erroneous operation. Further, according to the present invention, the above-mentioned protection structure is achieved by interposing a main throttle 18 in the main pilot circuit 14 and interposing a protective valve 19 to the main throttle 18 which is operated by the differential pressure caused by the throttle 18. By simply connecting the equipped drain circuit 20, the construction of the variable speed pilot circuit can be simplified.

[Brief explanation of drawings]

The drawing is a circuit diagram showing an embodiment of the present invention. 7 to 12 are clutches, 13a to 13f are switching valves, 17 is a throttle, 18 is a main throttle, 19 is a protection valve, 20 is a drain circuit, and 21 is a spring.

Claims (1)

[Scope of utility model registration request] It has clutches 7 to 12 for front, reverse, and a plurality of speed stages that are operated by hydraulic pressure, and the hydraulic chambers of each clutch 7 to 12 are connected to a hydraulic power source via pilot pressure operated switching valves 13a to 13f. One of the pilot pressure acting parts provided at both ends of the switching valves 13a to 13f is connected to the main pilot circuit 14, and the other is connected to the drain side via the electromagnetic switching valves 16a to 16f. In an automatic transmission in which both pilot pressure acting parts are connected by a pilot circuit through a throttle 17, a throttle 18 is interposed in the main pilot circuit 14, and a drain circuit 20 is connected to the main pilot circuit 14. A protective valve 19 is interposed in a communicating position against the spring 21, and a pilot pressure-based switching section of the protective valve 19 is connected to the upstream side of the main throttle 18 of the main pilot circuit 14.
The biasing force in the closing direction of the spring 21 of the protective valve 19 is applied to the main pilot circuit 14 to three or more of the switching valves 13a to 13f.
A speed change pilot circuit for an automatic transmission, characterized in that the biasing force is switched by a pressure difference caused by a main throttle 18 when a flow occurs in the pilot circuits 3a to 13f.