JPH02279831A - Hydraulic circuit for backhoe - Google Patents

Abstract

PURPOSE:To contrive to improve working efficiency by providing a relief- switching valve for high-low switching of relief pressure in a first and a second oil supply passages, and by additionally providing a check valve, a relief valve and a pilot-operating oil passage to a carry-over oil passage. CONSTITUTION:A travel-operating valve V3 and an arm-operating valve V1 are connected to a first oil-hydraulic pump P1, the travel-operating valve V5, a boom-operating valve V6 and a bucket-operating valve V7 are connected to a second oil-hydraulic pump P2, and a swivel-operating valve V8 is connected to a third oil-hydraulic pump P3. A relief pressure-switching valve 18 is operated by pilot pressure from a third oil supply passage 15, and a check valve 28, a relief valve 29 and a pilot-operating oil passage 30 are provided to a carry- over oil passage 24. When the pressure in the oil passage 24 rises at simultaneous operation of the travel device and the arm, the valve 29 is operated to open and the valve 18 is operated for switching with the pressure to the oil passage 23 relieved, and the oil passages 9 and 12 are maintained thereby under high pressure. Therefore improvement of working efficiency becomes possible.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a first hydraulic pump, a second hydraulic pump, and a third hydraulic pump driven by the same engine, One of the travel operation valves and the arm operation valve are connected to the first hydraulic pump via a first oil supply path, and the other travel operation valve, boom operation valve, and bucket of the left and right travel operation valves are connected to the first hydraulic pump through a first oil supply path. An operation valve is connected to the second hydraulic pump via a second oil supply path, a swing operation valve is connected to the third hydraulic pump via a third oil supply path, and one of the travel operation valve and the arm operation valve The present invention relates to a hydraulic circuit for a backhoe, which is provided with a carryover oil path that connects only the arm operation valve to the swing operation valve so that the arm operation valve is supplied with oil from the swing operation valve when the swing operation valve is in a neutral state.

[Conventional technology]

In the above-mentioned backhoe, conventionally, as shown in Fig. 4,
The relief pressure acting on the oil supply passage (9) from the first hydraulic pump (P1) and the oil supply passage (12) from the second hydraulic pump (P2) was constant.

[Problem to be solved by the invention]

Previously, engine output could not be fully utilized when moving the aircraft or digging.

That is, in the backhoe, 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 driven at the same time. The engine output is set so that the engine top does not occur even if the hydraulic pressure supplied from all of the first to third hydraulic pumps reaches the relief pressure. When the aircraft is traveling or digging, the pressure oil from the first and second hydraulic pumps is used to drive the actuators, so the load placed on the engine to drive 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 is too large (this is due to the fact that the total engine load does not reach the allowable set load). Therefore, when the aircraft is moving or digging, the engine still has an output margin.

An object of the present invention is to make it possible to use the engine output without wasting even when the actuator is driven only by the first and second hydraulic pumps, to achieve compactness, and to connect the traveling device and the arm. The objective is to enable the advantageous driving of

[Means to solve the problem]

In order to achieve the object, in the backhoe hydraulic circuit described at the beginning, the present invention provides a first operating state in which the relief pressure of the first oil supply path and the second oil supply path is reduced to a low pressure;
a relief pressure switching valve that can be freely switched to a second operating state that increases the relief pressure of the oil supply passage and the second oil supply passage;
Providing a spring that biases the relief pressure switching valve to the second operating state, and providing a pilot operating oil passage that switches the relief pressure switching valve to the first operating state using pilot pressure from the third oil supply passage; The carryover oil passage is provided with a check valve that prevents oil flow from the arm operation valve side to the swing operation valve side, and a relief valve is provided at a location upstream of the check valve in the carryover oil passage. At the same time, a pilot operation oil passage for opening the relief valve is connected to a location downstream of the check valve in the carryover oil passage. The functions and effects thereof are as follows.

[For production]

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 pilot pressure is supplied to the pilot operation oil passage, and this pilot pressure causes the relief pressure switching valve to switch to the first Switching to the operating state, the relief pressures of the first and second oil supply passages become low pressures, and all of the first to third hydraulic pumps are driven without engine stop while the actuator drive load is applied. becomes possible. When the swing operation valve and the arm operation valve are operated neutrally, the oil supplied from the third hydraulic pump to the third oil supply passage passes through the swing operation valve, the carryover oil passage, and the arm operation valve and returns to the tank for pilot operation. Pilot pressure supply to the oil line is released,
Due to the spring, the relief pressure switching valve enters the second operating state, and the relief pressures in the first and second oil supply passages become high. That is, when the actuator is 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 it can be generated when all the hydraulic pumps are driven by the actuators. Even if the first and second hydraulic pumps are driven more powerfully 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 does not relieve and can be used to drive the actuator.

The relief pressure is changed by the pilot pressure from the third oil supply path, and the pilot operation oil path is formed by a drilled oil path in the valve block or by piping, and a mechanism for automatic relief pressure switching is established. Even if it can be made compact, if the relief valve of the carryover oil passage is configured as shown in Fig. 3, if the traveling device and the arm are driven simultaneously, the internal pressure of the carryover oil passage will increase due to the arm drive load. The relief pressure switching valve enters the first operating state. That is, the traveling device and the arm cannot be driven simultaneously while the relief pressures of the first and second oil supply passages are on the high pressure side. In contrast, in the configuration of the present invention, a check valve, a relief valve, and a pilot operation oil path for the relief valve are attached to the carryover oil path in the above arrangement, so that the traveling device and the arm can be driven simultaneously. Even if the internal pressure of the carryover oil passage increases due to the arm drive load, when the internal pressure reaches the set value, the relief valve is activated 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, and the load acting on the engine for driving the third hydraulic pump is lower than before the relief, and for the third pump relief, the changeover valve is The application of pilot pressure to the pilot operation oil passage is canceled, the relief pressure switching valve enters the second operating state, and the relief pressures of the first and second oil supply passages are maintained on the high pressure side.

〔Effect of the invention〕

By switching the relief pressure, the first
Even when the actuator is driven only by the second hydraulic pump, the engine output is used efficiently to make the machine movement and excavation faster and more powerful, making it possible to work more efficiently.

Furthermore, by operating the relief pressure switching valve using pilot pressure, it has become possible to construct a mechanism for switching the relief pressure compactly and to facilitate its assembly.

Moreover, because of the relief structure of the carryover oil passage, the arm and traveling device can be powerfully driven under high relief pressure to ensure escape from the wetland, which is advantageous.

〔Example〕

Next, examples will be shown.

As shown in Fig. 2, a swivel base (2) is attached to a crawler type traveling machine base having an earth removal plate (1), and a driving unit (3) and a driving unit (4) are attached to this swivel base (2). In addition, a backhoe device (6) is attached via a swing bracket (5) so that the direction can be changed, thereby forming a backhoe with a dozer.

The first to third hydraulic pumps (P, I), (Pg), (P3) are used to enable the operation of the earth removal plate (1), the swivel table (2), the traveling device, and the backhoe device (6). The driving part (
3), and the hydraulic circuit is constructed as shown in FIG.

That is, the service port operation valve (S), the arm operation valve (V1) for the arm cylinder (7), the merging spacer (8), the boom merging valve (V2), the left and right travel motors (M1), (M The traveling operation valve (V3) and the merging valve (V3) for one of the two are formed as a center bypass type multi-delivery valve, and pressure oil is supplied through the first oil supply path (9), and The operating valves (S), (V1) and (V2) are connected in parallel to the first hydraulic pump (P1).Left and right travel motor (M1).

Travel control valve (V3) for the other of (M2), boom control valve (V3) for the boom cylinder (10), and bucket control valve (V7) for the bucket cylinder (11)
is formed into a center bypass type multiple valve, and is connected to a second hydraulic pump (P2) so as to be supplied with pressure oil via a second oil supply path (12). A swing operation valve (V3) for the swing motor (M3) and a swing operation valve (V, 3) for the swing cylinder (14) are formed into a center bypass type multiple valve, and a third oil supply path (15) It is connected to a third hydraulic pump (P3) so that pressure oil is supplied through the pump.

A piping oil passage (24) extending between the multiple valves formed by the operating valve (V3) to the operating valve (Vlo) and the merging spacer (8).
5), and only the arm operation valve (V1) of the traveling operation valve (V2) and the arm operation valve (V1) is rotated by the spacer oil passage (245) bored in the merging spacer (8). Carryover oil line (2) connected to operation valve (V3)
4) so that the pressure oil supplied by the third hydraulic pump (P3) can be used to drive the arm. That is, the piping oil passage (245) is the operating valve (V3) or V.

) is connected to a point on the downstream side of the operating valve (Vlo) of one center bypass oil passage (25) that passes through the control valve (Vlo) so that oil is supplied from here, and the spacer oil passage (24b) is connected to the operating valve (S). , (V1) or V4), and is connected to one center bypass oil passage (26) passing through the oil supply passage (V1) or V4), and is located between the traveling operation valve (V2) and the arm operation valve (V3) of the first oil supply passage (9). In addition, the first oil supply path (9
) Install a check valve (
27), the swing operation valve (V8),
Swing operation valve (V3) and dozer operation valve (V, 3)
When both of them are in a neutral state, the carryover oil path (2
4) discharges the pressure oil supplied from the third hydraulic pump (P3) from the operating valves (V5), (Vs) and (V, 3) to the center bypass oil path (26) so as to return to the tank; Alternatively, it is configured to join the pressure oil supplied from the first hydraulic pump (P3) to the arm operating valve (V1) and supply the arm operating valve (V3) so as to increase the speed of the arm.

High pressure relief valve (16), low pressure relief valve (17), switching valve (18), pair of check valves (20), <21
), one check valve (20) prevents backflow to the first oil supply passage (9), and the other check valve (21) prevents the relief oil passage (19) from flowing back into the first oil supply passage (9). 12) so as to prevent backflow to the first oil supply path (
9) and the second oil supply path (12). and,
When the switching valve (18) is switched to the open state, the low pressure relief valve (17) acts preferentially to the high pressure relief valve (16) connected to the check valves (20) and (21), so that the relief oil is released. When the relief pressure of the passage (19) reaches the low pressure developed by the low pressure relief valve (17) and the switching valve (18) is switched to the closed state, the low pressure relief valve (17) closes the check valve (20) and ( 21) and the high pressure relief valve (16) is always connected to the check valves (20) and (21), the relief pressure in the relief oil passage (19) is reduced to the high pressure relief valve (21). 16). That is, when the switching valve (18) is in the open state, the relief pressure of the first and second oil supply passages (9), <15) is made low pressure, and when the switching valve (18) is in the closed state, the relief pressure of the first and second oil supply passages (9), <15) is made low pressure.
And the relief pressure of the second oil supply passages (9) and (15) is set to high pressure. Then, the switching valve (18) is closed and biased by the spring (22), and the third oil supply path (15) is operated by the pilot operated oil path (23).
Further, the carryover oil passage (24) is provided with a check valve (24) that prevents oil from flowing from the side of the arm operation valve (V1) to the side of the swing operation valve (V8). 28) is provided, and a relief valve (29) is connected to the upstream side of the check valve (28) in the carryover oil passage (24), and the pilot operation oil passage (30) of this relief valve (29) is connected to the carryover oil passage (24). Check valve (2) for passage (24)
8) Connected so that pilot pressure is supplied from here to a point on the downstream side to open the relief valve (29), thereby increasing the relief pressure of the first and second oil supply passages (9) and (12). The pressure is automatically switched between low pressure and high pressure in accordance with the operation of the operating valve, so that the actuator can be driven while making efficient use of engine output.

That is, the swing motor (M3), the swing cylinder (
13) and the dozer cylinder (14), the third oil supply path (15) is used for the driving load.
The internal pressure of the pilot-operated oil passage (
23) is supplied with pilot pressure, and the switching valve (18)
is switched to the open state, and all hydraulic pumps (P1)
, (P1), and (P3) are driven without engine stop even when the actuator drive load is applied, the relief pressure of the first and second oil supply passages (9) and (12) is set to the low pressure side. It will become. When the swing motor (M3), the swing cylinder (13), the dozer cylinder (14), and the arm cylinder (7) are not driven, the inside of the third oil supply path (15) is used to release the actuator drive load. When the pressure drops below the set value, the pilot pressure supply to the pilot operating oil line (23) is released and the switching valve (22) is closed due to the spring (22).
18) is switched to the closed state, and the first and second oil supply passages (p1) are switched to the closed state, compared to when all pumps are driven.

The relief pressures of the first and second oil supply passages (9) and (12) are on the high pressure side so that (P1) can be strongly driven and high-pressure oil pressure can be supplied to the actuator. In addition, when escaping from a wetland, etc., the traveling motor (M3) and (
M2) and the arm cylinder (7) at the same time, until the internal pressure of the carryover oil passage (24) rises to the set value determined by the relief pressure (29) regardless of the drive of the arm cylinder (7). is the relief pressure (2
9) is closed, pilot pressure is supplied to the pilot operation oil path (23), the switching valve (18) is in the open state, and all hydraulic pumps (PI), (P1), (P3) are in the open state.
) to drive the actuator.

The relief pressure (12) is on the low pressure side. When the internal pressure of the carryover oil passage (24) rises to the set value due to the arm cylinder drive load, pilot pressure is supplied to the pilot operation oil passage (30) and the check valve (28
), the relief pressure (29) is operated and maintained open, oil from the third hydraulic pump (P3) is relieved, and the pilot pressure supply to the pilot operation oil path (30) is released. The switching valve (18) is switched to the closed state, and the first and second hydraulic pumps (PI), (P1)
The first and second oil supply passages (
9).

The relief pressure (12) is on the high pressure side.

[Another example]

As shown in the above embodiment, two types of high and low pressure relief valves and switching valves are used, and these are connected to both oil supply lines (9) and (12).
), a variable relief valve may be used, or means may be adopted in which separate relief oil passages are attached to both oil supply passages so that the pressure can be switched between IJ and IJ.

Therefore, these are collectively referred to as relief pressure switching valves (18).

Swing cylinder (13) and dozer cylinder (14)
) The present invention can also be applied in cases where the steps are omitted.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of drawings]

The drawings show an embodiment of a hydraulic circuit for a backhoe according to the present invention, and 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 path, (12)...
Second oil supply path, (15)...Third oil supply path, (18
)... Relief pressure switching valve, (22)...
... Spring, (23) ... Pilot operation oil path, (24) ... Carryover oil path, (28
)...Check valve, (29)...Relief valve, (30)...Pilot operated oil path, (P1
)...First hydraulic pump, (P1)...
Second hydraulic pump, (P3)...Third hydraulic pump, (E)...Engine, (V1)...
Arm operation valve, (V3), (V5)...Travel operation valve, (V6)...Boom operation valve, (V7)
...Bucket operation valve, (V3) ...Swivel operation valve.

Claims (1)

[Claims] First hydraulic pump (P_1), second hydraulic pump (P_2)
and the third hydraulic pump (P_3) with the same engine (E)
The left and right traveling operation valve (V
One of the traveling operation valves (V_3) and (V_5)
), and the arm operation valve (V_1) is connected to the first oil supply path (9).
The other travel operation valve (V_5) of the left and right travel operation valves (V_3) and (V_5), the boom operation valve (V_6), and the bucket operation valve are connected to the first hydraulic pump (P_1) via (V_7) is connected to the second hydraulic pump (P_2) via the second oil supply path (12), and the swing operation valve (V_8) is connected to the third hydraulic pump (P_3) via the third oil supply path (15). ), and the traveling operation valve (V_3)
and the arm operating valve (V_1) of the arm operating valve (V_1).
Hydraulic pressure of a backhoe provided with a carryover oil passage (24) that connects only V_1) to the swing operation valve (V_8) in a state where only the swing operation valve (V_8) is supplied with oil from the swing operation valve (V_8) in its neutral state. A circuit comprising: a first operating state in which the relief pressure of the first oil supply passage (9) and the second oil supply passage (12) is reduced to a low pressure; a relief pressure switching valve (18) that can be freely switched to a second operating state in which the relief pressure of 12) is made high; and a spring (22) that biases the relief pressure switching valve (18) to the second operating state. At the same time, a pilot operation oil passage (23) is provided for switching the relief pressure switching valve (18) to the first operating state by pilot pressure from the third oil supply passage (15), and a pilot operation oil passage (23) is provided in the carryover oil passage (24). The arm operation valve (V_
1) is provided with a check valve (28) that prevents oil from flowing from the swing operation valve (V_8) side, and the carryover oil path (24) is provided with a check valve (28) that prevents oil from flowing from the side of A relief valve (29) is connected to the point, and a pilot operation oil passage (23) is connected to the relief valve (29) to open the relief valve (29).
) of the check valve (28) of the carryover oil passage (24).
) The backhoe's hydraulic circuit is connected downstream.