JP2629064B2 - Work vehicle hydraulic circuit structure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic circuit structure of a working vehicle.

[Background Art] In a backhoe which is one of working vehicles, for example,
Some have a structure as shown in the figure. That is,
Control valve (37) for multiple sets of hydraulic actuators (36)
Are connected in parallel to one pump (38). The control valve (37) shown in the figure is of a center bypass type and is connected in parallel by oil passages (39a), (39b) and (39c).

In this case, even when the control valve (37) is in the neutral position and the hydraulic actuator (36) is not used, if hydraulic oil flows from the pump (38), problems such as a pressure loss and an increase in oil temperature occur.

Therefore, in the structure shown in FIG. 4, the pump (38) is of a variable displacement type, and an actuator (40) (corresponding to a change means) for changing the discharge amount of the pump (38) is provided, and the control valve (37) is provided. Is detected as a pilot pressure, and when this flow rate becomes large (when the number of hydraulic actuators used is small), the flow rate is reduced so that the discharge amount of the pump is decreased. When the number of hydraulic actuators used is large), the pump is controlled to increase the discharge amount of the pump.

As described above, by changing the discharge amount of the pump based on the flow rate on the lower side, each hydraulic actuator can be operated without hindrance while suppressing pressure loss and oil temperature rise.

[Problems to be solved by the invention]

When a large number of hydraulic actuators are used, such as a backhoe, a plurality of sets of pumps are provided, and a plurality of sets of hydraulic actuators are connected to each pump in parallel, for example, as shown in FIG. In this case, it is conceivable to provide each pump with a variable displacement type and to provide each pump with an actuator and a control function as shown in FIG. 4. However, independently controlling each pump in this way significantly increases costs. Accompanied by

Therefore, it has been considered that a plurality of sets of pumps are of a variable displacement type and the discharge amount of each pump is increased or decreased by the same amount in the same direction by one changing means. SUMMARY OF THE INVENTION It is an object of the present invention to provide a configuration in which, when changing the discharge amounts of a plurality of sets of pumps with one change unit, the discharge amounts can be changed without any trouble in each unit.

[Means for solving the problem]

The feature of the present invention resides in that the hydraulic circuit structure of the working vehicle as described above is configured as follows. That is, a plurality of hydraulic actuators are connected in parallel to each of the plurality of sets of variable displacement pumps, and the discharge amount of the plurality of sets of pumps is increased or decreased by the same amount in the same direction. Means for detecting the average value of the flow rate on the lower side of each of the plurality of sets of hydraulic actuators; and when the average value shifts to the low flow rate side, the pump discharge rate increases, and the average value indicates the flow rate. A control means for operating the changing means is provided on the discharge amount decreasing side of the pump when shifting to the large side.

A plurality of sets of variable displacement pumps, respectively, a plurality of sets of hydraulic actuators connected in parallel, and a change means capable of increasing or decreasing the discharge amount of the plurality of sets of pumps by the same amount in the same direction; Detecting means for detecting the minimum flow rate of the lower flow rate of each of the plurality of sets of hydraulic actuators; and, when the minimum flow rate shifts to the lower flow rate side, the pump discharge amount increase side, and When the minimum flow rate is shifted to the larger flow rate side, a control means for operating the changing means is provided on the discharge rate decreasing side of the pump.

(Operation)

If the discharge rate is changed based on the pump system with the largest flow rate (the system that uses the least number of hydraulic actuators), the change means generally operates on the discharge rate decreasing side.
Hydraulic oil runs short in the pump system with the smallest flow rate (the system that uses the largest number of hydraulic actuators).

However, if the discharge rate is changed based on the average value of the flow rate on each lower side as described in the preceding paragraph, or based on the pump system with the minimum flow rate as described in the preceding paragraph, the pump system with the maximum flow rate will be changed. Although the flow rate is slightly increased, in the pump system with the minimum flow rate, the situation where the hydraulic oil is insufficient and the hydraulic actuator does not operate properly does not occur.

〔The invention's effect〕

As described above, when changing and controlling the discharge amounts of a plurality of sets of pumps by one changing unit, the change control is performed based on the average value of the respective flow rates or the minimum flow rate so that each hydraulic actuator can be operated without any trouble. , A control for suppressing a pressure loss, an increase in hydraulic pressure, and the like.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows the entire side surface of the backhoe, in which a swivel (2) is supported on the upper part of the crawler device (1), and a backhoe device (3) is provided in front of the swivel (2).

The backhoe device (3) includes a boom (4), which is vertically driven by a first hydraulic cylinder (7) (corresponding to a hydraulic actuator), and a back and forth by a second hydraulic cylinder (8) (corresponding to a hydraulic actuator). It is composed of an arm (5) that is driven to swing, and a bucket (6) that is driven to be swung and driven by a third hydraulic cylinder (9) (corresponding to a hydraulic actuator).

Next, the first, second, and third hydraulic cylinders (7), (8),
The hydraulic circuit structure for (9) will be described. As shown in FIG. 1, the oil passage (11) from the first pump (10)
An oil passage (13) branched from an oil passage (11) is connected to a control valve (12) for a hydraulic motor (24) (corresponding to a hydraulic actuator) of the right crawler traveling device (1). ) For the second hydraulic cylinder (8).

An oil passage (16) from the second pump (15) is connected to a control valve (18) for a hydraulic motor (17) (corresponding to a hydraulic actuator) of the left crawler traveling device (1). An oil passage (19) branched from the oil passage (16) is provided with an oil passage (21) for the control valve (20) of the first hydraulic cylinder (7) for the boom (4) and an oil passage (21) for the bucket (9). The third hydraulic cylinder (9) branches in parallel with an oil passage (23) for the control valve (22).

The first and second pumps (10) and (15) are of a variable displacement type, and a single hydraulic cylinder (25) (corresponding to a change means) can increase or decrease the discharge amount by the same amount in the same direction. I have.

Next, the operation of the hydraulic cylinder (25) for changing the discharge amount will be described. Hydraulic cylinder (25) as shown in FIG.
And an operation cylinder (27) for switching the operation valve (26). On the other hand, the lowermost oil passage (28) on the first pump (10) side
The oil passage (29) on the lowermost side of the second pump (15) joins and is returned to the tank (30). And the oilway (28),
A throttle (31) is provided on the lower side from the junction with (29), and a pilot oil passage (32) branched from between the junction and the throttle (31) is connected to the operating cylinder (27). It is connected.

With the structure shown in FIG. 1, for example, oil passages (28), (29)
When the combined flow rate of the fluid passages becomes small (that is, when the average value of the flow rates of the oil passages (28) and (29) shifts to the small flow rate side), many hydraulic cylinders and hydraulic motors are operating. In this case, the operating valve (26) is
Operating to the first position (26a), the pilot hydraulic oil in the pilot oil passage (33) from the oil passages (11) and (16) is supplied to the first oil chamber (25a) of the hydraulic cylinder (25). You. As a result, the hydraulic cylinder (25) contracts, and the first and second pumps (10) and (15) are operated to increase the discharge amount.

Next, when the combined flow rate of the oil passages (28) and (29) increases (that is, when the average value of the flow rates of the oil passages (28) and (29) shifts to the larger flow side), the operating hydraulic pressure is increased. There will be less cylinders and hydraulic motors. Accordingly, the operating cylinder (27) operates the operating valve (26) to the second position (26b) by the pilot hydraulic oil from the pilot oil passage (32).

In this case, the pilot hydraulic oil from the pilot oil passage (33) is supplied in parallel to the first oil chamber (25a) and the second oil chamber (25b) of the hydraulic cylinder (25).
The hydraulic cylinder (25) expands due to the difference between the pressure receiving areas of the pistons of the first and second oil chambers (25a) and (25b). As a result, the first and second pumps (10) and (15) are operated toward the discharge amount decreasing side.

(Another embodiment)

As shown in FIG. 3, the lowermost oil passages (28) and (29) on the first pump (10) side and the second pump (15) side, respectively.
Are returned to the tank (30) without merging, and a throttle section (31) is provided for each. In addition to providing a pilot-operated switching valve (41) for the operating cylinder (27),
Pilot oil passage (3) from each of oil passages (28) and (29)
4) and (35) are connected to the switching valve (41) as shown in FIG.

With the structure shown in FIG. 3, for example, it is assumed that the flow rate of the oil passage (28) on the first pump (10) side is larger than the flow rate of the oil passage (29) on the second pump (15) side. (That is, when many hydraulic cylinders etc. on the second pump (15) side are operating). In this case, the switching valve (41) is switched to the first position (41a) by the pilot hydraulic oil from the pilot oil passage (34) on the first pump (10) side, and the second pump (15)
The pilot hydraulic oil from the pilot oil passage (35) is supplied to the operation cylinder (27).

Therefore, the second pump (15) having a small flow rate in the oil passage (29)
With reference to the side, the hydraulic cylinder (25) expands and contracts as in FIG. 1, and the discharge amounts of the first and second pumps (10) and (15) are changed.

The structures of FIGS. 1 and 3 may be suitable for a hydraulic circuit having three or more sets of variable displacement pumps.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

The drawings show an embodiment of a hydraulic circuit structure of a working vehicle according to the present invention, FIG. 1 is a hydraulic circuit diagram, FIG. 2 is an overall side view of a backhoe, FIG. 3 is a hydraulic circuit diagram in another embodiment, FIG. The figure is a hydraulic circuit diagram of a conventional structure. (7), (8), (9), (17), (24) ... hydraulic actuator, (10), (15) ... pump, (25) ... changing means.

Claims (2)

(57) [Claims] A plurality of sets of variable displacement pumps (10), (1)
For each of 5), a plurality of sets of hydraulic actuators (7), (8), (9), (17), (24) are connected in parallel, and the plurality of sets of pumps (10), ( 15) a changing means (25) capable of increasing and decreasing the discharge amount by the same amount in the same direction, and the plurality of sets of hydraulic actuators (7),
(8), (9), (17) and (24) detecting means for detecting the average value of the flow rate on the lower side, and the discharge of the pumps (10) and (15) when the average value shifts to the low flow rate side. To increase the amount and
When the average value shifts to the larger flow rate side, pumps (10), (1
5) A hydraulic circuit structure of a working vehicle including a control means for operating the change means (25) on the discharge amount decreasing side. 2. A plurality of sets of variable displacement pumps (10), (1).
For each of 5), a plurality of sets of hydraulic actuators (7), (8), (9), (17), (24) are connected in parallel, and the plurality of sets of pumps (10), ( 15) a changing means (25) capable of increasing and decreasing the discharge amount by the same amount in the same direction, and the plurality of sets of hydraulic actuators (7),
(8), (9), (17), and (24) detecting means for detecting the smallest flow rate among the lower flow rates, and a pump (10) when the smallest flow rate shifts to the lower flow rate side. , (15) and control means for operating the changing means (25) on the discharge amount decreasing side of the pumps (10) and (15) when the minimum flow rate shifts to the large flow rate side. Hydraulic circuit structure of the working vehicle equipped with.