JPH0450181Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a hydraulic motor circuit suitable for driving drive wheels of vehicles such as loaders and bulldozers.

(Prior Art) An example of a conventional hydraulic motor circuit of this type is shown in FIG. 3, where 1 is a hydraulic pump, 2 is a hydraulic motor, and 3 is a hydraulic motor circuit.
a and 3b are main passages connecting the hydraulic pump 1 and the hydraulic motor 2; 4a and 4b are main passages 3a and 3;
6 is an engine for driving the hydraulic pump 1 and the charge pump 7, and 8 is a main relief valve that connects the liquid discharged from the charge pump 7 to the main flow path. A relief valve is interposed in the replenishment channel 9 for introducing the fuel into the fuel tank 3a, 10 is a differential gear, 11 is a drive wheel, and 12 is a tank.

When the hydraulic pump 1 is driven by the engine 6,
The liquid discharged from this will be in the main flow path 3a or 3.
enters the hydraulic motor 2 through either one of b.
This is driven to rotate. This rotational force is applied to the differential gear 10
The signal is transmitted to the drive wheels 11 through the , and causes the vehicle to move forward or backward. The liquid flowing out from the hydraulic motor 2 returns to the hydraulic pump 1 through either the main channel 3b or 3a, and this process is repeated thereafter.

By changing the discharge amount of the hydraulic pump 1, the rotational speed of the hydraulic motor 2 can be changed. When excessive pressure occurs in the main flow path 3a or either one, the main relief valve 4a or 4b opens and the liquid in the high pressure main flow path 3a or 3b is transferred to the other main flow path 5a or 5b. It is made to flow through the flow path 3b or 3a. When the amount of liquid in the closed circuit becomes low due to liquid leakage or other reasons, liquid is replenished from the charge pump 7 through the replenishment channel 9 into the closed circuit.

(Problems to be solved by the invention) In the above-mentioned conventional hydraulic motor circuit, the input shaft of the hydraulic pump 1 and the output shaft of the hydraulic motor 2 are always completely connected via liquid, so the engine Unlike direct drive cars, where rotational force is mechanically transmitted to the drive wheels via a transmission and clutch, the clutch cannot connect or disconnect the rotational force transmitted from the engine to the drive wheels, and therefore it is not possible to connect or disconnect the rotational force transmitted from the engine to the drive wheels by a half-clutch. It was not possible to obtain the necessary power or to prevent the engine from stalling by cutting off power transmission in the event of overload. Moreover, the hydraulic pump 1 occupies a neutral position,
Even if the discharge amount was zero, there was a problem in that the vehicle would move due to liquid leakage from the closed circuit.

(Means for Solving the Problems) The present invention has been proposed to solve the above problems, and its gist is to provide a hydraulic pump, a hydraulic motor, and a pair of mains that connect them. In a hydraulic motor circuit that includes a flow path and a charge pump in a closed circuit, a pilot pressure control valve that adjusts the differential pressure between the liquid in the pair of main flow paths is installed in one of the pair of main flow paths. A pipe is installed in series on one side to introduce pilot pressure discharged from the charge pump into one pilot pressure chamber of the control valve, the other pilot pressure chamber of the control valve, and a liquid reservoir of the hydraulic pump. A variable throttle valve is interposed in the bypass pipe that communicates with the communicating pipe, and the opening degree of the control valve is adjusted by changing the throttle amount of the variable throttle valve in accordance with the amount of depression of the clutch pedal. The hydraulic motor circuit is characterized by:

(Function) Since the present invention has the above configuration, when the throttle amount of the variable throttle valve is changed by depressing the clutch pedal, the opening degree of the control valve is adjusted and The differential pressure between the liquids can be adjusted freely, and thus the power transmission between the hydraulic pump and the hydraulic motor can be switched off or on at will.

(Embodiment) An embodiment of the present invention is shown in FIG. 1
is a hydraulic pump, 2 is a hydraulic motor, 3a, 3b are main flow paths, 4a, 4b are main relief valves, 5
a, 5b are bypass channels, 7 is a charge pump,
13 is a spring offset pilot pressure type pressure control valve for freely adjusting the differential pressure between the liquids in the main flow paths 3a and 3b;
It is inserted in series with a.

The pilot pressure discharged from the charge pump 7 is supplied to the pilot pressure chamber on one side of the pressure control valve 13 via piping 17, and the pilot pressure chamber on the other side is supplied to the liquid reservoir of the hydraulic pump 1 via piping 18. It is communicated. A variable throttle valve 20 is interposed in a bypass pipe 19 that connects the pipe 17 and the pipe 18. The variable throttle valve 20 is configured such that its throttle amount is increased by depressing the clutch pedal 14.

The other configurations are the same as the conventional one shown in FIG.

Thus, when the clutch pedal 14 is depressed, the throttle amount of the variable throttle valve 20 increases, the differential pressure between the pipes 17 and 18 decreases, and the opening degree of the pressure control valve 13 correspondingly increases. As a result, the pressure difference between the liquids in the main channels 3a and 3b is reduced.

Therefore, the amount of power transmitted is the main flow paths 3a and 3b.
Since it is determined by the differential pressure between the liquids in the liquid, by freely adjusting this differential pressure, it is possible to cut off the transmission of power or to arbitrarily reduce the amount of transmitted power. When the hydraulic pump 1 is set to neutral, it becomes possible to completely stop the vehicle by opening the pressure control valve 13, and
Pressure control valve 13 when engine stalls
By opening the engine, stalling of the engine can be prevented.

FIG. 2 shows another embodiment of the present invention, in which another bypass pipe 2 is provided before the bypass pipe 19.
1, and a fixed throttle 22 is provided in this bypass piping 21.
The second embodiment differs from the first embodiment shown in FIG. 1 in that it is interposed, but the other configurations are the same.

Piping 1 until the engine speed increases and the discharge amount from charge pump 7 exceeds a certain flow rate.
Since no liquid flows into the control valve 13
The spool is moved by the elastic force of the spring, and the main channels 3a and 3b are in communication with each other. When the engine speed exceeds the specified idle speed, the pressure in the pipe 17 increases, the spool of the control valve 13 moves in the opposite direction, and the liquid discharged from the hydraulic pump 1 flows into the hydraulic motor 2. and start transmitting power. Thereafter, the amount of power transmitted can be adjusted depending on the amount of depression of the clutch pedal 14.

(Effect of the invention) In the present invention, power is transmitted between the hydraulic pump and the hydraulic motor by freely adjusting the differential pressure between the liquids in the pair of main flow paths by depressing the clutch pedal. can be cut or spliced arbitrarily. By fully opening the control valve, the hydraulic motor can be completely stopped, and it is also possible to prevent the engine that drives the hydraulic pump from stalling.

Furthermore, in the present invention, since the pressure control valve is interposed in series in either one of the pair of main flow paths, piping becomes easy, pressure loss is reduced, and costs are also reduced.

In addition, in the present invention, piping that introduces the pilot pressure discharged from the charge pump into one pilot pressure chamber of the control valve, and piping that connects the other pilot pressure chamber of the control valve to the liquid reservoir of the hydraulic pump are provided. A variable throttle valve is installed in the communicating bypass pipe, and the opening degree of the control valve is adjusted by changing the throttle amount of this variable throttle valve according to the amount of depression of the clutch pedal. By changing the characteristics of the engine, various controls such as changing the opening characteristics of the control valve relative to the amount of depression of the clutch pedal and changing the setting of the engine idle speed become possible.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing the first embodiment of the present invention;
FIG. 2 is a partial system diagram showing a second embodiment of the present invention, and FIG. 3 is a system diagram of a conventional hydraulic motor circuit. Hydraulic pump...1, Hydraulic motor...2, Charge pump...7, Main flow path...3a, 3b, Control valve...13, Piping...17, 18, Bypass piping...19, Variable throttle valve ...20, clutch pedal ...14.

Claims (1)

[Scope of utility model registration request] In a hydraulic motor circuit that includes a hydraulic pump, a hydraulic motor, a pair of main flow paths connecting these, and a charge pump in a closed circuit, the differential pressure between the liquid in the pair of main flow paths is adjusted. A pilot pressure type control valve is installed in series in either one of the pair of main flow passages, and a piping for introducing the pilot pressure discharged from the charge pump into the pilot pressure chamber of one of the control valves is connected to the control valve. A variable throttle valve is installed in the bypass pipe that communicates the other pilot pressure chamber with the pipe that communicates with the liquid reservoir of the hydraulic pump, and the throttle amount of this variable throttle valve is changed according to the amount of depression of the clutch pedal. A hydraulic motor circuit characterized in that the degree of opening of the control valve is adjusted by adjusting the opening degree of the control valve.