JPH0663252B2 - Hydraulic circuit of backhoe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention links a variable displacement first hydraulic pump and a second hydraulic pump, and a constant displacement third hydraulic pump to one engine. A part of a hydraulic cylinder for driving a backhoe mounted on the swivel base is connected to the first hydraulic pump and the rest is connected to the second hydraulic pump, and a hydraulic motor for rotating the swivel base is connected to the third hydraulic pump. Connect to the first
To a hydraulic circuit of the backhoe provided with an engine stop prevention means for automatically program-controlling the discharge amounts of the first and second hydraulic pumps in accordance with the change in the sum of the discharge side pressures of the third hydraulic pumps.

[Conventional technology]

Conventionally, as shown in FIG. 6, the discharge side pressure p _{1 of} the first hydraulic pump (P ₁ ) is formed to form an engine stop prevention means.
Discharge pressure _{p 2} of the second hydraulic pump _{(P 2),} by applying the pilot circuit the discharge pressure _{p 3} of the third hydraulic pump _{(P 3)} to the regulator (9), by the action of the regulator (9), First to third hydraulic pumps (P ₁ ), (P ₂ ),
(P ₃₎ with the variation of the sum of the discharge pressure of the first and second hydraulic pumps _{(P 1), (P 2} ) of the discharge amount adjusting hydraulic cylinder (10a), an operation to be applied to (10b) Change the pressure,
It is configured to automatically adjust the discharge amounts of the first and second hydraulic pumps (P ₁ ) and (P ₂ ) in inverse proportion to the sum of the discharge side pressures, and prevent the engine (E) from stopping due to overload. However, the hydraulic motor (M ₃ ) of the swivel base can be driven at a constant speed, and the hydraulic cylinder (C ₂ ) of the backhoe device,
(C ₃ ) and (C ₄ ) can be driven at the highest speed possible (see, for example, JP-A-53-111601).

[Problems to be solved by the invention]

However, when the swivel base is started, the discharge side pressure of the third hydraulic pump (P ₃ ) suddenly and largely fluctuates in about 1 second, and the pressure fluctuation is directly applied to the regulator (9), and the first and second hydraulic pressures are applied. The discharge amounts of the pumps (P ₁ ) and (P ₂ ) are drastically and drastically reduced, and the speed of the backhoe device is drastically reduced, which is a drawback in terms of operation.

An object of the present invention is to prevent a sudden decrease in the speed of the backhoe when the swivel base is started up without stopping the engine.

[Means for solving problems]

The characteristic configuration of the present invention is that the first and second hydraulic pumps for driving the backhoe device and the discharge side pressure of the third hydraulic pump for driving the swivel base change with the variation of the sum of the first and second hydraulic pumps. (2) A pressure buffer that suppresses a pressure increase due to the start of the swivel base in a pilot circuit that applies the discharge side pressure of the third hydraulic pump to an engine stop prevention unit that automatically controls the discharge amount of the hydraulic pump. The function and effect are as follows.

[Action]

In other words, paying attention to the fact that the high pressure state of the discharge side pressure of the third hydraulic pump was about 1 second when the swivel base was started, and when the operating characteristics of the engine were examined, it was found that the third hydraulic pump was operated for 1 second. In a high pressure state due to the start of the swivel base, even if the discharge amounts of the first and second hydraulic pumps are hardly changed, the engine speed does not drop significantly due to the inertia of the engine, and the engine is stopped due to overload. I was able to confirm the fact that I could certainly prevent.

Based on this new finding, by providing a pressure buffer in the pilot circuit, as shown in FIG. 4, a temporary large fluctuation of the discharge side pressure p ₃ of the third hydraulic pump due to the start of the swivel base is generated. , Is configured to convert the pilot pressure ₃ with gentle and small pressure fluctuations and to apply the pilot pressure ₃ to the engine stop prevention means,
The sudden decrease in speed of the backhoe caused by the start of the swivel,
This can be prevented by suppressing fluctuations in the discharge amounts of the first and second hydraulic pumps.

〔The invention's effect〕

As a result, there is no engine stop due to overload, the swivel base can be driven at a constant speed, the backhoe device can be driven as fast as possible, and there is no sudden decrease in speed of the backhoe device due to activation of the swivel base. It has become possible to provide a backhoe that is extremely excellent in operability.

〔Example〕

 Next, examples will be shown.

As shown in FIG. 1, a dozer device (2) and a swivel base (3) are attached to a crawler type traveling device (1), and a backhoe device (4), a driving part (5) and a boarding operation part (6) are swiveled. A backhoe that is provided on the table (3) and is also capable of soil removal work is formed.

In order to form the backhoe device (4), the boom (4b) is secondly attached to the swing bracket (4a) attached to the swivel base (3) so as to be freely changeable in the left-right direction by the first hydraulic cylinder (C ₁ ).
A hydraulic cylinder (C ₂ ) is attached so that it can swing up and down, an arm (4c) is swingably attached to a boom (4b) by a third hydraulic cylinder (C ₃ ), and a bucket (4d) is attached to a fourth hydraulic cylinder (C It is attached to the arm (4c) rotatably by ₄ ).

A hydraulic circuit for the traveling device (1), the swivel base (3), the backhoe device (4) and the dozer device (2) will be described below with reference to FIG.

The variable displacement first hydraulic pump (P
₁ ), the second hydraulic pump (P ₂ ) and the constant displacement type third hydraulic pump (P ₃ ) are linked to one engine (E). Operation valve (V ₁ ) of the first traveling hydraulic motor (M ₁ ) that drives the left crawler, operation valve (V ₂ ) of the third hydraulic cylinder (C ₃ ) for driving the arm, and operation for the service port The valve (V ₉ ) is connected in parallel to the first hydraulic pump (P ₁ ) and the operation valve (V ₃ ) of the second traveling hydraulic motor (M ₂ ) for driving the crawler on the right side, the second for driving the boom the hydraulic cylinder _{(C 2)} of the operating valve _(V 4), connected in parallel to the fourth hydraulic cylinder for bucket driving _{(C 4)} of the operating valve _{(V 5)} of the second hydraulic pump _{(P 2),} swivel base (3) a hydraulic motor for driving the _{(M 3)} of the operating valve _(V 6), swing the first hydraulic cylinder _{(C 1)} of the operating valve for the bracket drive _(V 7), up and down the dozer device (2) fifth hydraulic cylinder _{(C 5)} of the operating valve _{(V 8)} the third hydraulic Pont that It is connected in parallel to the _{(P 3).}

During the operating valve _{(V 3)} and the operating valve _{(V 4),} iris (11) and a check valve (12a), the spacer (13) provided with (12b), the third hydraulic pump _{(P 3)} Connected to the spacer (13), the second and third hydraulic pumps (P ₂ ) and (P ₃ ) are connected to the boom operation valve (V ₄ ) and the bucket operation valve (V ₅ ).
It is configured so that the pressure oil from can be supplied together.

First to third hydraulic pumps (P ₁ ), (P ₂ ),
The discharge side respectively of the _{(P 3)} s, the relief valve _(R 1),
The return oil passages (7), (8) and (14) for preventing overload having (R ₂ ) and (R ₃ ) are connected and the first and second hydraulic pumps (P ₁ ) and (P ₂ ) are connected. A regulator (9) is connected to change the discharge amounts of the inks in the same amount. Regulator (9), discharge pressure _{p 3} of the discharge-side pressure _{p 2} at the discharge side pressure _{p 1} and the second hydraulic pump of the first hydraulic pump _{(P 1) (P 2)} third hydraulic pump _{(P 3)} Sum of k ₁ (p ₁ + p ₁ + k ₂ p ₃ ) [where k ₁ and k ₂
Is a constant], the first and second hydraulic pumps (P
₁ ), which controls the discharge amount Q of (P ₂ ) by a program, and the discharge amount adjusting hydraulic cylinders (10a), (10b) for the first and second hydraulic pumps (P ₁ ), (P ₂ ) The applied operation pressure is adjusted so that the discharge amount Q changes, for example, as shown in FIG.

An accumulator (16) is provided in the pilot circuit (15) that applies pressure from the third hydraulic pump (P ₃ ) to the regulator (9), and when the swivel base (3) is started, as shown in FIG. Even if the discharge side pressure p ₃ of the hydraulic pump (P ₃ ) fluctuates greatly in about 1 second, the pilot circuit (1
Pilot pressure applied to regulator (9) in 5)
_{3 is made} to be a gentle and small change, and the decrease in the discharge amount of the first and second hydraulic pumps (P ₁ ) and (P ₂ ) can be made small.

In short, the first to third hydraulic pumps (P ₁ ),
When the load on (P ₂ ) and (P ₃ ) changes, the discharge amount Q of the first and second hydraulic pumps (P ₁ ) and (P ₂ ) is automatically adjusted to overload the engine (E). The backhoe device (4) can be driven as fast as possible while being prevented from being stopped. Further, when the swivel base (3) is started, the discharge amount reduction of the first and second hydraulic pumps (P ₁ ) and (P ₂ ) can be reduced by the action of the accumulator (16), and the boom (4b) and the bucket can be reduced. Drive (4d) third
The pressure oil is supplied from the hydraulic pump (P ₃ ), so that the speed can be increased and the operability and working capacity of the backhoe device (4) are improved.

[Another embodiment]

 Next, another embodiment will be described.

Hydraulic cylinder (C ₂ ) for driving the backhoe device (4)
Or (C ₄ ) and the connection relationship between the first hydraulic pump (P ₁ ) and the second hydraulic pump (P ₂ ) can be appropriately changed.

The dozer device (2), swing bracket (4a) and service port may be omitted.

First to third hydraulic pumps (P ₁ ), (P ₂ ),
As the sum of the discharge side pressures of (P ₃ ) changes, the first and second
The means for automatically program-controlling the discharge amounts of the hydraulic pumps (P ₁ ) and (P ₂ ) can be changed to an appropriate means such as an electric type, and these can be changed to engine stop prevention means (9), (10).
Collectively referred to as a) and (10b).

The means for suppressing the rise of the pilot pressure applied from the third hydraulic pump (P ₃ ) to the engine stop prevention means (9), (10a), (10b) due to the start of the swivel base is, for example, the following (a) and (b). ), They can be changed appropriately, and they are collectively referred to as pressure buffers (16) and (17).

(A) Part or all of the pilot circuit (15) is formed of a hose capable of suppressing the pressure increase due to elastic expansion.

(B) As shown in FIG. 5, the pilot circuit (15)
A hydraulic pilot type shockless valve (17) is provided which operates so that the throttle (17a) acts only when the pressure rises.

The third hydraulic pump (P ₃ ) may be connected only to the boom operation valve (V ₄ ), and may not be used to drive the backhoe device.

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]

1 to 4 show an embodiment of the present invention, FIG. 1 is a side view of a backhoe, FIG. 2 is a hydraulic circuit diagram, and FIG. 3 is a description of the discharge amount adjustment of the first and second hydraulic pumps. The graph to
FIG. 4 is a graph explaining the operation of the main part. FIG. 5 is a partial view of a hydraulic circuit showing another embodiment of the present invention. FIG. 6 is a hydraulic circuit diagram of a conventional example. (3) …… Swivel base, (4) …… Backhoe device,
(9), (10a), (10b) ... Engine stop prevention means,
(15) …… Pilot circuit, (16), (17) …… Pressure buffer, (C ₂ ) to (C ₄ ) …… Hydraulic cylinder,
(E) …… Engine, (M ₃ ) …… Hydraulic motor,
(P ₁ ) ... first hydraulic pump, (P ₂ ) ... second hydraulic pump, (P ₃ ) ... third hydraulic pump.

Claims (1)

[Claims] 1. A variable displacement type first hydraulic pump (P ₁ ), a second hydraulic pump (P ₂ ), and a constant displacement type third hydraulic pump (P ₃ ) in one engine (E). A part of the hydraulic cylinders (C ₂ ) to (C ₄ ) which are interlocked and drive the backhoe device (4) attached to the swivel base (3) is provided to the first hydraulic pump (P ₁ ) and the rest is provided to the second hydraulic pump (P ₁ ). A hydraulic motor (M ₃ ) that is connected to a hydraulic pump (P ₂ ) and rotates the swivel base (3) is connected to the third hydraulic pump (P ₃ ), and the first to third hydraulic pumps (P ₃ ). ₁ ),
Engine stop prevention that automatically program-controls the discharge amounts of the first and second hydraulic pumps (P ₁ ) and (P ₂ ) in accordance with the change in the sum of discharge side pressures of (P ₂ ) and (P ₃ ). means (9), to (10a), a hydraulic circuit of the backhoe provided with (10b), said third from said hydraulic pump _{(P 3)} engine stop prevention means (9), (10a), (10b) The hydraulic circuit of the backhoe, wherein the pilot circuit (15) is provided with pressure buffers (16) and (17) for suppressing a pressure increase due to the activation of the swivel base (3).