JPH0751797B2 - Backhoe hydraulic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a first hydraulic pump, a second hydraulic pump, and a third hydraulic pump in a state of being driven by the same engine. One of the traveling operation valves and the arm operation valve are connected to the first hydraulic pump via a first oil supply passage, and the other traveling operation valve, the boom operation valve and the bucket of the left and right traveling operation valves are connected. An operation valve is connected to the second hydraulic pump via a second oil supply passage, a swing operation valve is connected to the third hydraulic pump via a third oil supply passage, and the traveling operation valve and the arm operation valve are connected. The hydraulic circuit of the backhoe provided with a carry-over oil passage connecting to the swivel operation valve in a state where oil is supplied from the swivel operation valve in the neutral state of the swivel operation valve only.

(Prior Art) In the above backhoe, conventionally, as shown in FIG.
The relief pressure acting on the oil supply passage (9) from the first hydraulic pump (P ₁ ) and the oil supply passage (12) from the second hydraulic pump (P ₂ ) was constant.

[Problems to be Solved by the Invention]

Conventionally, the engine output could not be fully utilized when traveling or excavating the airframe.

That is, in the above backhoe, in consideration of the case where the actuator connected to the first hydraulic pump, the actuator connected to the second hydraulic pump, and the actuator connected to the third hydraulic pump are simultaneously driven, The engine output is set so that the engine top does not occur even when the hydraulic pressure supplied from all of the first to third hydraulic pumps reaches the relief pressure. When the vehicle travels or excavates, the pressure oil from the first and second hydraulic pumps is used to drive the actuator, so that the load on the engine for driving the first and second hydraulic pumps is large. However, since the pressure oil from the third hydraulic pump is not used to drive the actuator, the engine load for driving the third hydraulic pump does not become too large. Therefore, the total load of the engine is lower than the allowable set load. Becomes smaller. Therefore, an output margin remains in the engine when the vehicle is traveling or excavating.

An object of the present invention is to enable the engine output to be utilized without waste even when the actuator is driven by only the first and second hydraulic pumps, and to achieve compactness, and at the same time, the traveling device and the arm. It is to be possible while enabling the advantageous driving of the.

[Means for Solving the Problems]

In the hydraulic circuit of the backhoe described at the beginning for attaining the object, the present invention provides a first operating state in which the relief pressure of the first oil supply passage and the second oil supply passage is reduced, and the first operation state.
A relief pressure switching valve capable of switching to a second operating state for increasing the relief pressure of the oil supply passage and the second oil supply passage to a high pressure;
A spring for urging the relief pressure switching valve to the second operating state is provided, and a pilot operation oil passage for switching the relief pressure switching valve to the first operating state by the pilot pressure from the third oil supply passage is provided. A check valve for blocking oil flow from the arm operation valve side to the swivel operation valve side is provided in the carryover oil passage, and a relief valve is provided at a location upstream of the check valve in the carryover oil passage. In addition to the connection, a pilot operation oil passage for opening the relief valve is connected to a portion of the carryover oil passage downstream of the check valve. The action and effect are as follows.

[Action]

When the swing operation valve is operated to the drive position, the internal pressure of the third oil supply passage increases due to the actuator drive load, and the pilot pressure is supplied to the pilot operation oil passage. The relief pressures of the first and second oil supply passages become low by switching to the operating state, and all of the first to third hydraulic pumps are driven without an engine stop in a state where an actuator drive load is applied. It will be possible. When the swivel operation valve and the arm operation valve are operated to be neutral, the oil supplied from the third hydraulic pump to the third oil supply passage returns to the tank through the swivel operation valve, the carryover oil passage and the arm operation valve, and is pilot operated. The pilot pressure supply to the oil passage is released, the relief pressure switching valve is brought into the second operating state due to the spring, and the relief pressure in the first and second oil passages becomes high.
That is, when the actuators are driven only by the first and second hydraulic pumps, the first and second hydraulic pumps are driven by the engine output that is provided so that all the hydraulic pumps can be exposed when all the pumps are driven. Even if it is driven more strongly than when all pumps are driven and the first and second hydraulic pumps supply a higher pressure than when all pumps are driven simultaneously, the pressure oil can be used for actuator drive without relief.

Relief pressure switching is configured to use pilot pressure from the third oil supply passage, and the pilot operation oil passage is formed by a drilling oil passage in the valve block or by piping to provide a mechanism for automatic relief pressure switching. Even if it can be obtained compactly, if the relief valve of the carryover oil passage is configured as shown in FIG. 3, when the traveling device and the arm are simultaneously driven, the internal pressure of the carryover oil passage increases due to the arm driving load. Then, the relief pressure switching valve enters the first operating state. That is, simultaneous driving of the traveling device and the arm cannot be performed while the relief pressures of the first and second oil supply passages are set to the high pressure side.
On the other hand, in the configuration of the present invention, the check valve, the relief valve, and the pilot operation oil passage of the relief valve are additionally provided in the carryover oil passage in the above-described arrangement, so that the traveling device and the arm can be simultaneously driven. Then, even if the internal pressure in the carryover oil passage increases due to the arm drive load, when the internal pressure reaches the set value, the relief valve is applied due to the pilot pressure applied from the carryover oil passage to the pilot operation oil passage. Is opened, the oil from the third hydraulic pump is relieved, the load acting on the engine for driving the third hydraulic pump is lower than before the relief, and the switching valve is used for the third pump relief. The relief pressure changeover valve is the second because the pilot pressure application to the pilot operation oil passage is released.
The working state is achieved, and the relief pressures of the first and second oil supply passages are maintained on the high pressure side.

〔The invention's effect〕

By switching the relief pressure, not only when the actuators are driven by all the hydraulic pumps,
Also, even when the actuator is driven only by the second hydraulic pump, the engine output can be utilized without waste to speed up and strengthen the machine body movement and excavation, and work can be performed efficiently.

In addition, by using the pilot pressure for the relief pressure switching valve, the mechanism for switching the relief valve can be made compact and easy to assemble.
Moreover, because of the relief structure of the carryover oil passage, the arm and the traveling device can be strongly driven under a high relief pressure to ensure the escape of the wetland, which is advantageous.

〔Example〕

 Next, examples will be shown.

As shown in FIG. 2, the swivel base (2) is attached to the crawler type traveling machine base having the soil discharging plate (1), and the driving part (3) and the operating part (4) are attached to the swivel base (2). A backhoe with a dozer is configured by being equipped with a backhoe device (6) which is changeable in orientation via a swing bracket (5).

The first to third hydraulic pumps (P ₁ ), (P ₂ ), (P ₃ ) are provided to enable operation of the soil discharge plate (1), the swivel base (2), the traveling device and the backhoe device (6). The same engine (E)
The hydraulic circuit is constructed as shown in FIG. 1 while being provided in the driving part (3) so as to be driven by.

That is, the service port operation valve (S), the arm operation valve (V ₁ ) for the arm cylinder (7), the merging spacer (8), the boom merging valve (V ₂ ), the left and right traveling motors (M ₁ ), The traveling operation valve (V ₃ ) and the merging valve (V ₄ ) for one of (M ₂ ) are formed as a center bypass type multiple valve, and pressure oil is supplied through the first oil passage (9). In addition, the operating valves (S), (V ₁ ) and (V ₂ ) are connected to the first hydraulic pump (P ₁ ) in parallel connection. For the left and right travel motors (M ₁ ), (M ₂ ) travel operation valve (V ₃ ) for the other, boom cylinder (10) for boom operation valve (V ₆ ), and bucket cylinder (11) The bucket operation valve (V ₇ ) is formed as a center bypass type multiple valve and is connected to the second hydraulic pump (P ₂ ) so that pressure oil is supplied through the second oil supply passage (12). Swing motor (M ₃ )
Turning operation valve for (V _8), a swing cylinder (14)
The swing operation valve (V ₁₀ ) for the valve is formed as a center bypass type multiple valve and is connected to the third hydraulic pump (P ₃ ) so that pressure oil is supplied through the third oil supply passage (15). There is.

A pipe oil passage (24a) extending from the operation valve (V ₈ ) or the multiple valve formed by the operation valve (V ₁₀ ) and the confluence spacer (8),
Also, only the arm operation valve (V ₁ ) of the travel operation valve (V ₂ ) and the arm operation valve (V ₁ ) is swung by each of the spacer oil passages (24a) formed in the merging spacer (8). By forming a carryover oil passage (24) connected to the operating valve (V ₈ ),
Third hydraulic pump (P ₃₎ is are to be able to use the pressure oil supplied to the arm drive. That is, the piping oil passage (24a)
Is connected to one center bypass oil passage (25) passing through the operation valves (V ₈ ) to (V ₁₀ ) at a location downstream of the operation valve (V ₁₀ ) so as to be refueled from here, and The spacer oil passage (24b) is connected to one center bypass oil passage (26) that passes through the operation valves (S), (V ₁ ) or (V ₄ ) and also the travel operation valve of the first oil passage (9). (V ₂ ) and the arm operation valve (V ₁ ) connected to the location,
Since the check valve (27) is provided at the upstream side of the spacer oil passage connection portion of the oil supply passage (9), the swing operation valve (V ₈ ), the swing operation valve (V ₉ ) and the dozer operation valve ( V
_When all ₁₀ ) are in the neutral state, the carryover oil passage (24) supplies the pressure oil supplied from the third hydraulic pump (P ₃ ) to the operation valves (V ₈ ), (V ₉ ) and (V ₁₀ ). From the first bypass pump (P ₁ ) to the arm bypass valve (V ₁ ) to return to the tank from the center bypass oil passage (26), or to join the pressure oil supplied to the arm operation valve (V ₁ ) to accelerate the arm. It is configured to supply to the arm operation valve (V ₁ ) so as to operate.

A high pressure relief valve (16), a low pressure relief valve (17), a switching valve (18), a relief oil passage (19) equipped with a pair of check valves (20), (21), and one check valve (20). To prevent the reverse flow to the first oil supply passage (9) and to prevent the reverse flow to the second oil supply passage (12) by the other check valve (21). 2 It is connected to the oil supply passage (12). Then, when the switching valve (18) is switched to the open state, the low pressure relief valve (17) is connected to the check valves (20) and (21) and the high pressure relief valve (16).
When the relief valve (18) is switched to the closed state by reducing the relief pressure of the relief oil passage (19) to the low pressure developed by the low pressure relief valve (17), the low pressure relief valve (17) is a check valve (20) and (2
1) disconnected from the high pressure relief valve (1
6) is always connected to the check valves (20) and (21) so that the relief pressure in the relief oil passage (19) becomes the high pressure developed by the high pressure relief valve (16). There is. That is, when the switching valve (18) is opened, the relief pressures of the first and second oil supply passages (9) and (15) are reduced, and when the switching valve (18) is opened, the first and second oil supply passages (9) are opened. ) And (15) are set to high pressure. The switching valve (18) is closed by the spring (22), and the pilot operation oil passage (23) applies the pilot pressure from the third oil passage (15). A check valve (28) is provided in the carryover oil passage (24) to prevent oil flow from the arm operation valve (V ₁ ) side to the swing operation valve (V ₈ ) side.
Connect a relief valve (29) to the upstream side of the check valve (28) of the carryover oil passage (24), and connect the pilot operation oil passage (30) of this relief valve (29) to the carryover oil passage (24). Pilot pressure is supplied from a location downstream of the check valve (28) to the relief valve (29) so that the relief valve (29) is opened, and the first and second oil supply passages (9), (1) are connected.
The relief pressure of 2) is automatically switched between low pressure and high pressure according to the operation of the operating valve, so that the actuator can be driven while using the engine output without waste.

That is, the turning motor (M _3), swing cylinder (1
3) and at least one of the dozer cylinders (14), the internal pressure of the third oil supply passage (15) rises above the set value due to the driving load, and the pilot pressure is applied to the pilot operation oil passage (23). After the supply, the switching valve (18) is switched to the open state and all the hydraulic pumps (P ₁ ), (P ₂ ),
Even if (P ₃ ) is under the actuator drive load, it can be driven without engine stop.
And, the relief pressures of the second oil supply passages (9) and (12) are on the low pressure side. Then, when none of the swing motor (M ₃ ), the swing cylinder (13), the dozer cylinder (14), and the arm cylinder (7) are driven, the third oil supply passage (15) is opened to release the actuator drive load. The internal pressure drops below the set value, the pilot pressure supply to the pilot operating oil passage (23) is released, and the spring (22)
Therefore, the switching valve (18) is switched to the closed state, and the first and second oil supply passages (P ₁ ) are
The relief pressure of the first and second oil supply passages (9), (12) is on the high pressure side so that (P ₂ ) can be strongly driven to supply a high hydraulic pressure to the actuator.
Further, when the traveling motors (M ₁ ) and (M ₂ ) and the arm cylinder (7) are driven simultaneously, such as when the vehicle escapes from a wetland, the internal pressure of the carryover oil passage (24) is irrespective of the driving of the arm cylinder (7). Is raised to the set value determined by the relief pressure (29), the relief pressure (29) is closed, the pilot pressure is supplied to the pilot operation oil passage (23), and the switching valve (18) is open. The relief pressure of the first and second oil supply passages (9), (12) is on the low pressure side so that all hydraulic pumps (P ₁ ), (P ₂ ), (P ₃ ) drive the actuators. . When the internal pressure of the carryover oil passage (24) rises to the set value due to the arm cylinder drive load, the pilot pressure is supplied to the pilot operation oil passage (30) and the position of the check valve (28) The relief pressure (29) is operated open and maintained for the third
The oil from the hydraulic pump (P ₃ ) relieves, the pilot pressure supply to the pilot operating oil passage (23) is released, the switching valve (18) is switched to the closed state, and the first and second hydraulic pumps (P ₁₎ ), (P ₂ ), the relief pressure of the first and second oil supply passages (9), (12) is on the high pressure side so that a high hydraulic pressure can be supplied.

[Another embodiment]

As shown in the above embodiment, two kinds of high and low pressure relief valves and a switching valve are used, and these are also used for both oil supply passages (9) and (12). In addition, a variable relief valve is used or both oil supply oils are used. A means for attaching relief oil passages to each passage so that the relief pressure can be switched may be adopted. Therefore, these are collectively referred to as the relief pressure switching valve (18).

The present invention can be applied to a case where the swing cylinder (13) and the dozer cylinder (14) are omitted.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the structures of the accompanying drawings by the entry.

[Brief description of drawings]

The drawings show an embodiment of a hydraulic circuit for a backhoe according to the present invention. Fig. 1 is a hydraulic circuit diagram and Fig. 2 is a side view of the entire backhoe with a dozer. FIG. 3 is a comparison circuit diagram. FIG. 4 is a conventional circuit diagram. (9) …… First oil supply passage, (12) …… Second oil supply passage, (15)
...... 3rd oil supply passage, (18) ...... Relief pressure switching valve, (2
2) …… Spring, (23) …… Pilot operating oil passage,
(24) …… Carryover oil passage, (28) …… Check valve, (2
9) …… Relief valve, (30) …… Pilot operating oil passage,
(P ₁ ) …… first hydraulic pump, (P ₂ ) …… second hydraulic pump, (P ₃ ) …… third hydraulic pump, (E) …… engine,
(V ₁ ) ... Arm operation valve, (V ₃ ), (V ₅ ) ... Travel operation valve, (V ₆ ) ... Boom operation valve, (V ₇ ) ... Bucket operation valve, (V ₈ ) ... … Turning control valve.

Claims (1)

[Claims] 1. A first hydraulic pump (P ₁ ), a second hydraulic pump (P ₂ ) and a third hydraulic pump (P ₃ ) are provided in a state where they are driven by the same engine (E), and a left and right traveling operation is performed. the valve (V _3), one of the travel operation valves of the (V ₅₎ (V _3), and said arm operating valve (V ₁₎ through the first oil supply passage (9) the first hydraulic pump (P ₁ ) and connect the other of the left and right travel operation valves (V ₃ ) and (V ₅ ) to the other travel operation valve (V ₅ ), boom operation valve (V ₆ ) and bucket operation valve (V ₇ ). Connected to the second hydraulic pump (P ₂ ) via a second oil supply passage (12),
The turning operation valve (V ₈ ) is connected to the third oil supply passage (15) via the third oil supply passage (15).
Connected to the hydraulic pump (P _3), the neutral state of the travel operation valve (V ₃₎ and the arm operating valve (V ₁₎ arm operating valve of the (V ₁₎ only the turning operation valve (V ₈₎ In the state in which oil is supplied from this turning operation valve (V ₈ ), the turning operation valve (V ₈ )
A hydraulic circuit of a backhoe provided with a carryover oil passage (24) connected to the first operation state for reducing the relief pressure of the first oil passage (9) and the second oil passage (12) to a low pressure; A relief pressure switching valve (18) capable of switching to a second operating state in which the relief pressure of the first oil supply passage (9) and the second oil supply passage (12) is increased, and the relief pressure switching valve (18). A pilot operating oil for switching the relief pressure switching valve (18) to the first operating state by providing a spring (22) for urging the relief pressure switching valve (18) to the second operating state and pilot pressure from the third oil supply passage (15). A passage (23) is provided, and a check valve (2) for blocking oil flow from the arm operation valve (V ₁ ) side to the swivel operation valve (V ₈ ) side is provided in the carryover oil passage (24).
8), a relief valve (29) is connected to a portion of the carryover oil passage (24) upstream of the check valve (28), and a pilot for opening the relief valve (29). The operation oil passage (23) is replaced with the carry-over oil passage (24).
The hydraulic circuit of the backhoe connected to a location downstream of the check valve (28).