JP3253033B2 - Traveling hydraulic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling hydraulic circuit for supplying hydraulic pressure discharged from one hydraulic pump to a left and right traveling hydraulic motor in a tracked work vehicle such as a power shovel to travel.

[0002]

2. Description of the Related Art As a power shovel, an upper body is provided on a lower traveling body so as to be able to swing by a swing hydraulic motor. It is known that the lower traveling body is of a track type in which the left and right crawler belts are driven by a left and right traveling hydraulic motor.

[0003] A hydraulic circuit for supplying the discharge pressure oil of one hydraulic pump to each hydraulic actuator of the power shovel is capacity-controlled so that the differential pressure between the load pressure of the hydraulic actuator and the discharge pressure of the pump is constant. Two variable displacement hydraulic pumps, a plurality of directional switching valves connected to the discharge side of the variable displacement hydraulic pump to supply pressure oil to each hydraulic actuator, and directional switching valves provided at the inlet sides of the directional switching valves, respectively. A plurality of pressure compensating valves for controlling the meter-in differential pressure are provided.

For example, as shown in FIG. 1, left and right switching valves 5 and 6 for supplying pressure oil to left and right hydraulic motors 3 and 4 are provided in a discharge path 2 of a variable displacement hydraulic pump 1. , 6 are provided on the inlet side, respectively, and the load pressure detecting ports 5a, 6a of the left and right switching valves 5, 6 are connected to a load pressure introducing passage 9 by a high-pressure priority valve 8. Is connected to the displacement control member 10 to control the displacement of the variable displacement hydraulic pump 1 so that the differential pressure between the load pressure and the pump discharge pressure becomes constant. There is known a hydraulic circuit that controls a differential pressure. Reference numeral 11 denotes a counterbalance valve.

[0005]

In such a hydraulic circuit, the right and left traveling hydraulic motors 3, 4 are varied in the meter-in opening area of the left and right direction switching valves 5, 6 so that the rotational speeds of the left and right traveling hydraulic motors 3, 4 are varied so that the vehicle travels right and left. Speed decreases. That is, when turning left and right, the inner running motor (driven side) is in a braking state because the turning resistance is large, the driving pressure becomes zero (or the counterbalance valve set pressure), and the outer running motor (drive side). Becomes high pressure corresponding to running resistance and turning resistance. As a result, the pressure difference between the inner traveling motor and the outer traveling motor increases, and the flow to the inner traveling motor becomes an energy loss. Normally, horsepower control is activated, the capacity of the variable displacement hydraulic pump 1 is reduced, and the flow to the outer traveling motor is reduced. The flow rate decreases and the traveling speed decreases.

For example, the left traveling hydraulic motor 3 is set by setting the left and right directional switching valves 5 and 6 to the right position A, setting the meter-in opening area of the left and right directional switching valve 5 to be large, and making the meter-in opening area of the right directional switching valve 6 extremely small. Drive side, right traveling hydraulic motor 4
When the vehicle travels in the direction of arrow a with the driven side as the driven side, the right traveling hydraulic motor 4 enters the braking state, the driving pressure PL2 becomes the set pressure of the counter balance valve 11, and the driving pressure PL1 of the left traveling hydraulic motor 3 travels. resistance, because a high pressure corresponding to the turning resistance, the inlet pressure P ₁ in the left direction switching valve 5 becomes higher than the inlet pressure P ₂ in the right direction switching valve 6. Here, the inlet pressure P ₂ is depressurized right direction switching valve 6 meter opening area due to the pressure drop by a driving pressure PL2 + alpha next to the right of the pressure compensating valve 7 the pump discharge pressure P ₀ to the inlet pressure P ₂ (PL2 + alpha) position Therefore, a part of the discharge pressure oil of the variable displacement hydraulic pump 1 flows into the right traveling hydraulic motor 4 and causes a loss.

Accordingly, an object of the present invention is to provide a traveling hydraulic circuit capable of solving the above-mentioned problems.

[0008]

A variable displacement hydraulic pump 1 is provided.
Left and right direction switching valves 5 and 6 for supplying the discharge pressure oil of the variable displacement hydraulic pump 1 to the left and right traveling hydraulic motors 3 and 4; A displacement control member 10 for controlling the pressure difference between the pressure and the pump discharge pressure to be constant, and a displacement control member 10 provided upstream of the left-right switching valves 5 and 6 by the load pressure and the upstream pressure. 6. A traveling hydraulic circuit comprising: a pressure compensating valve 7 for controlling a meter-in differential pressure of 6; and a means for supplying low-pressure oil to the upstream side of the left and right switching valves 5 and 6 via a check valve during a turning traveling operation.

[0009]

[Operation] When the left and right direction switching valves 5 and 6 are operated so as to have different meter-in opening areas, low pressure oil is supplied to the upstream circuit in the driven side direction switching valve, and the pressure compensating valve 7 is closed to change the variable displacement hydraulic pressure. Since the discharge pressure oil of the pump 1 is no longer supplied to the traveling hydraulic motor on the driven side, it is assumed that the entire amount of discharge pressure oil of the variable displacement hydraulic pump 1 is supplied to the traveling hydraulic motor on the drive side, and the traveling speed decreases. Can be prevented.

[0010]

[Embodiment] A first embodiment of the present invention will be described with reference to FIG. The same members as those in the related art have the same reference numerals. The return circuits 21 and 22 of the left and right switching valves 5 and 6 are connected to the switching valve 23.
To control the connection of the auxiliary relief valve 24 and the tank 25 with the circuit 26 and the check valve 2
7, the upstream and downstream circuits 28, 29 of the left and right switching 5, 6
Connect to The switching valve 23 is moved to the drain position B by a spring force.
And is switched to the left position C and the right position D by the pressure oil supplied to the left and right pressure receiving units 30 and 31, and the left and right pressure receiving units 30 and 31 are connected by the left and right circuits 32 and 33 to the upstream circuit 29 and 28, and is switched to the right position D or the left position C by the pressure difference between the upstream circuits 29 and 28. The switching valve 23 may be switched using a pilot pressure for switching the left and right switching valves 5 and 6.

Next, the operation will be described. Left / right directional switching valve 5,
6, the left traveling hydraulic motor 3 is driven on the right side, and the right traveling hydraulic motor 4 is driven on the right side by setting the meter-in opening area of the left direction switching valve 5 to be large and the meter-in opening area of the right direction switching valve 6 to be small. When the vehicle travels turning in the direction of arrow a, the right traveling hydraulic motor 4 enters the braking state and the driving pressure PL2
Is the set pressure of the counterbalance valve, and the driving pressure PL1 of the left traveling hydraulic motor 3 is a high pressure corresponding to the traveling resistance and the turning resistance. Therefore, the inlet pressure P1 of the leftward switching valve 5 is It becomes higher than the inlet pressure P2. This allows
The switching valve 23 is brought to the right position D by the inlet pressure P1, the return circuit 21 of the leftward switching valve 5 is connected to the inlet side of the auxiliary relief valve 24, and the return circuit 22 of the rightward switching valve 6 is connected to the tank 2
Runs directly to 5.

The inlet side of the auxiliary relief valve 24 has a set pressure P
The pressure oil rises to _3, and flows from the circuit 26 and the check valve 27 into the inlet-side circuit 29 of the rightward switching valve 6. At this time, the pressure of the downstream circuit 34 of the rightward switching valve 6 becomes the set pressure PL2 of the counterbalance valve 11, and the upstream circuit 2
Since the pressure P ₂ of 9 it is thus that determined by the pressure compensating valve 7 in the right direction switching valve 6, the downstream pressure + difference on pressure of the set pressure P ₃ of the auxiliary relief valve 24 is the right direction switching valve 6, that is right When the upstream pressure determined by the meter-in opening area of the direction switching valve 6 and the downstream pressure becomes equal to or less than the set pressure P ₃ of the auxiliary relief valve 24, the pressure oil on the inlet side of the auxiliary relief valve 24 is controlled rightward by the check valve 27. It enters an inlet-side circuit 29 of the valve 6, the pressure compensating valves 7 by the upstream pressure P ₂
Is closed, and the pressure oil discharged from the variable hydraulic pump 1 is no longer supplied from the pressure compensating valve 7 to the right traveling hydraulic motor 4. When the meter-in opening area of the right direction switching valve 6 is extremely small and the downstream pressure rises only up to the counterbalance valve set pressure, the entire discharge pressure oil of the variable displacement hydraulic pump 1 is supplied to the left traveling hydraulic motor 3 and the drive side flow rate is increased. It is possible to prevent the traveling speed from decreasing without causing a decrease.

When the meter-in opening area of the right direction switching valve 6 is increased, the driving pressure PL2 of the right traveling hydraulic motor 4 increases, and the pressure on the inlet side exceeds the set pressure of the auxiliary relief valve 24. Operate.

FIG. 3 shows a second embodiment, in which a discharge passage 41 of an auxiliary hydraulic pump 40 is connected to upstream circuits 28, 29 of left and right direction switching valves 5, 6 via a check valve 42. An auxiliary relief valve 43 is provided on the pressure receiving section 44, and the auxiliary relief valve 43 is set to a set state with pilot pressure oil supplied to the pressure receiving section 44. When the pilot pressure oil is not supplied, the auxiliary relief valve 43 is set to a drain state. ,
The pilot pressure oil is supplied when the meter-in opening area of No. 6 is different, that is, during the turning operation.

Also in this case, the pressure oil of a predetermined pressure is supplied to the upstream circuits 28 and 29 of the left and right switching valves 5 and 6 during the turning operation, so that the pressure compensating valve 7 on the driven side is closed as described above. be able to.

[0016]

When the left and right direction switching valves 5 and 6 are operated so as to have different meter-in opening areas, low pressure oil is supplied to the upstream circuit in the driven side direction switching valve and the pressure compensating valve 7 is supplied.
Is closed and the discharge hydraulic oil of the variable displacement hydraulic pump 1 is no longer supplied to the driven hydraulic motor on the driven side, so that the entire discharge hydraulic oil of the variable displacement hydraulic pump 1 is fully supplied to the drive hydraulic motor on the drive side and travels. A reduction in speed can be prevented.

[Brief description of the drawings]

FIG. 1 is a conventional hydraulic circuit diagram.

FIG. 2 is a hydraulic circuit diagram showing a first embodiment of the present invention.

FIG. 3 is a hydraulic circuit diagram showing a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Variable displacement hydraulic pump, 2 ... Discharge path, 3 ... Left traveling hydraulic motor, 4 ... Right traveling hydraulic motor, 5 ... Left direction switching valve, 6
... right direction switching valve, 7 ... pressure compensation valve, 21 ... return circuit, 2
2: return circuit, 23: switching valve, 24: auxiliary relief valve,
25 tank, 27 check valve, 28 upstream circuit
29 ... upstream circuit.

Continued on the front page (72) Inventor Kazuyoshi Ishihama 3-20-1 Nakase, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Komatsu Manufacturing Co., Ltd. Kawasaki Plant (72) Inventor Kazunori Ikei 3-20-1 Nakase, Kawasaki-ku, Kawasaki-shi, Kanagawa Shares (56) References JP-A-4-203504 (JP, A) JP-A-4-285304 (JP, A) JP-A-4-203505 (JP, A) JP-A-4-203503 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F15B 11/02 E02F 9/22

Claims (3)

(57) [Claims] 1. A variable displacement hydraulic pump 1; left and right direction switching valves 5 and 6 for supplying discharge hydraulic oil of the variable displacement hydraulic pump 1 to left and right traveling hydraulic motors 3 and 4; And a displacement control member 10 for controlling the differential pressure between the load pressure of the left and right traveling hydraulic motors 3 and 4 and the pump discharge pressure to be constant, and the load pressure provided upstream of the left and right direction switching valves 5 and 6. Left / right directional control valve 5, due to upstream pressure
6, a pressure compensating valve 7 for controlling the meter-in differential pressure, and means for supplying low-pressure oil to the upstream side of the left and right switching valves 5 and 6 via a check valve during turning operation. Hydraulic circuit for traveling. 2. A return circuit 21 for the left and right switching valves 5 and 6,
A switching valve 23 for controlling the connection of the auxiliary relief valve 22 to the auxiliary relief valve 24 and the tank 25 is provided, and the inlet side of the auxiliary relief valve 24 is connected to the upstream circuits 28, 29 of the left and right switching valves 5, 6 via the check valve 27. When the switching valve 23 is operated with the left and right switching valves 5 and 6 having different meter-in opening areas, the return circuits 21 and 22 on the high pressure side are connected to the auxiliary relief valve 24.
The traveling hydraulic circuit according to claim 1, wherein the hydraulic circuit is located at a position connected to the traveling hydraulic circuit. 3. The discharge path 41 of the auxiliary hydraulic pump 40 is connected to the upstream circuit 28 of the left and right direction switching valves 5 and 6 by a check valve 42.
The hydraulic circuit for traveling according to claim 1, further comprising an auxiliary relief valve (43) connected to the exhaust passage (41) and set in the discharge path (41) during a turning operation.