JPH0754680Y2 - Hydraulic transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to improvement of a hydraulic transmission device.

(Prior Art) A hydraulic transmission device is commonly called a hydraulic transmission,
The pump and the motor are closed circuit, and the high pressure generated from the pump is pushed into the motor, and the return flow from the motor is directly pushed into the suction port of the pump.

For example, in FIG. 3, 1 is a variable displacement main pump driven by an engine 2 and the like, 3 is a main pump 1
The main pump 1 is a motor that is driven by the discharge pressure from the main pump 1, and a charge pump 4 that integrally drives the main pump 1 is attached to the main pump 1. This allows external drain (leakage) from the closed circuit 5.
The amount is supplied via the check valves 8A and 8B. Reference numeral 6 is a relief valve that regulates the maximum discharge pressure of the charge pump 4, and 7A and 7B are relief valves with check valves 9A and 9B that regulate the maximum pressure on the high-pressure side of the closed circuit 5.

(Problems to be solved by the invention) By the way, when the rotation of the motor is stopped, the swash plate angle of the variable displacement pump 1 is held at the zero point position (the pump discharge amount is zero), and the high pressure side and the low pressure side of the closed circuit 5 are connected. Block and do. In that case, when an external force acts on the motor 3, a holding pressure commensurate with the external force is generated by the pumping action of the motor 3. Since the motor 3 does not have a no-leak structure, a leak occurs due to the holding pressure, and slip rotation is performed according to the leak amount. At this time, if the engine 2 or the like is operating, the amount of leakage (case drain amount) from the motor 3 is compensated by the discharge oil from the charge pump 4 attached to the pump 1, so that the negative pressure in the closed circuit 5 is reduced. Does not occur, the motor 3 always holds a pressure commensurate with the external force, and maintains a minute rotation (slip rotation) state.

However, when the engine 2 or the like is stopped, that is, when the charge pump 4 is stopped, the drain amount from the motor 3 when the motor 3 is rotated by an external force and acts as a pump is not replenished at all, so that the negative pressure in the closed circuit 5 is reduced. Since the generated holding pressure cannot be obtained, the motor 3 runs away.

(Means for Solving Problems) In order to solve such problems, the present invention makes the main pump and the hydraulic motor into a closed circuit, and closes them by a charge pump that is integrally driven with the main pump by an engine or the like. In a hydraulic power transmission device that replenishes the amount of external drain from the circuit, drain oil from the case of the hydraulic motor and the drain oil of the oil tank when the engine is stopped etc. to the low pressure side of the closed circuit via the drain passage. A suction check valve to be replenished is provided in the short-circuit passage that connects the suction port and the discharge port in the port block to the port communicating with the motor case drain.

(Operation) When the hydraulic motor is rotated by an external force and pumps while the engine or the like is stopped, hydraulic oil from the motor case and the tank is replenished into the closed circuit through the suction check valve. Therefore, the holding pressure commensurate with the external force is secured for a long period of time, and the motor is surely prevented from running away.

Further, by providing the suction check valve in the short-circuit passage that connects the suction port and the discharge port in the port block to the port communicating with the motor case drain, the suction line length becomes the shortest and the pressure loss is reduced. Furthermore, it is possible to connect to the tank using a motor case drain.

(Embodiment) In FIG. 1, a hydraulic motor 11 in a closed circuit 10 is a variable displacement pump driven by an engine (not shown) or the like (a charge pump for replenishing the amount of external drain from the closed circuit 10 as before). The discharge pressure (pressure energy of oil) from (provided) is converted into a rotational force.

The drain passage 13 that returns the amount of drainage into the case of the motor 11 to the oil tank 12 is provided on the low-pressure side of the closed circuit 10 (motor
Since 11 can rotate forward and backward by controlling both sides of the swash plate of the pump, short-circuit passages 14A and 14B connected to both the motor suction side and the discharge side of the closed circuit 10) are provided.
Suction check valves 15A and 15B for supplying the drain amount from the motor 11 to the low pressure side of the closed circuit 10 are provided in 4B. The suction check valves 15A and 15B are, as shown in FIG. 2, specifically, internal (short-circuit) passages 14A, which connect the suction port 17 and the discharge port 18 to the drain port 19 in the port block 16 of the motor 11.
Mounted on 14B.

With such a configuration, when the engine is stopped, that is, when the charge pump is stopped, the case drain in the motor 11 when the motor 11 is rotated by an external force and acts as a pump is entirely supplied through the suction check valve 15A or 15B. As a result, the negative pressure is not generated in the closed circuit 10 because it is sucked back to the low pressure side of the closed circuit 10. Therefore, the holding pressure commensurate with the external force is secured, and the escape of the motor 11 can be prevented. Also,
At this time, replenishment of hydraulic oil to the closed circuit 10 is also performed from the tank 12, so even if the closed circuit is stopped for a long time, the closed circuit is closed.
It is possible to reliably prevent the hydraulic motor 11 from running away while the hydraulic motor 11 is stopped without running out of the amount of oil in 10.

On the other hand, by providing a suction check valve in the short-circuit passage that connects the suction port and discharge port in the port block to the port that communicates with the motor case drain, the suction line length can be minimized, resulting in less pressure loss and higher suction. Since the connection with the tank can be performed by using the motor case drain, a new line for self-priming is not required, which is compact and inexpensive.

(Effect of the Invention) In summary, according to the present invention, the drain oil from the hydraulic motor and the tank while the engine is stopped is supplied to the low pressure side of the closed circuit through the suction check valve.
Even when the engine is stopped, the hydraulic motor can be reliably prevented from running away for a long period of time.

Further, since the suction check valve is provided in the short-circuit passage that connects the suction port and the discharge port in the port block to the port communicating with the motor case drain, pressure loss is reduced and high suction performance is obtained. There is also an effect that the suction line is omitted and the apparatus can be made compact and inexpensive.

[Brief description of drawings]

FIG. 1 is a main part hydraulic circuit diagram showing an embodiment of the present invention, and FIG.
The figure also shows a partially cutaway front view of the motor port block.
FIG. 3 is a hydraulic circuit diagram showing a conventional technique. 10 ... Closed circuit, 11 ... Motor, 13 ... Drain passage, 14A, 14B ...
Short circuit passage, 15A, 15B ... Suction check valve, 16 ... Port block, 17 ... Suction port, 18 ... Discharge port, 19 ... Drain port.

Claims (1)

[Scope of utility model registration request] 1. A hydraulic transmission device comprising a main pump and a hydraulic motor in a closed circuit, and a charge pump driven integrally with the main pump by an engine or the like to supplement the external drain amount from the closed circuit. The suction check valve that replenishes the drain oil from the hydraulic motor case and the drain oil in the oil tank to the low-pressure side of the closed circuit via the drain passage when the motor is stopped. A hydraulic power transmission device, characterized in that the hydraulic power transmission device is provided in a short-circuit passage that connects a port communicating with a case drain.