JPH0216221A - Hydraulic structure of work vehicle - Google Patents

Abstract

PURPOSE:To reduce load during operation by a method in which in an oil- pressure structure having three oil pressure systems, a switching action-type distribution valve is provided by which working oil passing through one center bypass oil path among three control valves is distributed to the other oil pathes. CONSTITUTION:An oil-pressure structure for working vehicle consists of three oil-pressure pumps P1, P2, and P3 to be operated by single engine E, three oil pressure systems B1, B2, and B3 to supply working oil from the pumps P1, P2, and P3 to actuators, and three center bypass-type control valves A1, A2, and A3. A distribution valve mechanism 12 by which working oil passing through one center bypass oil path 9 of the valves A1, A2, and A3 is distributed to the two other oil paths is also provided. The valve 12 is switched to neutral and non-neutral positions according to loading and non-loading conditions of the oil paths.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention simultaneously drives three hydraulic pumps with a single engine, and supplies hydraulic fluid from these hydraulic pumps to independent hydraulic actuators. Therefore, the hydraulic structure of the work vehicle, which is composed of three oil passage systems and three center bypass type control valve groups, is monitored.
This invention relates to a technology for merging hydraulic fluid from a center bypass oil path into other hydraulic systems.

[Conventional technology]

Conventionally, there is a hydraulic structure for a work vehicle configured as described above, for example, as shown in Japanese Unexamined Patent Publication No. 61-282522. The merging oil passage leads to a hydraulic cylinder that drives the arm, thereby improving the operating speed of the arm.

[Problem to be solved by the invention]

Here, considering the oil system that is equipped with an oil passage system for merging as in the above-mentioned example, in a system that merges hydraulic oil from the center bypass oil passage, even when not in operation, the center bypass Since all the strains of the hydraulic oil from the oil passages merge, the pressure loss associated with the increase in hydraulic oil is promoted in the oil passage system on the merging side, leading to an increase in the load on the engine.

In other words, if the flow rate of hydraulic oil increases by n times, the pressure drop will reach n2 times, so when the working oil from the center bypass oil passage is merged into another oil passage system, While this has the advantage of increasing the drive speed of the hydraulic actuator, it has the disadvantage of significantly increasing the load during non-operation, so there is room for improvement.

The purpose of the present invention is to reduce the load during non-work while maintaining an increase in the drive speed of the hydraulic actuator on the merging side during work, through rational modification.

[Means to solve the problem]

The feature of the present invention is that in a hydraulic structure having both configurations, a distribution valve mechanism distributes the hydraulic oil that has passed through the center bypass oil passage of one of the three control valve groups to the other two oil passage systems. is provided, and when the other two oil passage systems are under no load, the distribution valve is switched to the neutral position to distribute approximately the same amount of hydraulic oil to the other two oil passage systems, and the other two oil passage systems are When a larger load is applied to one side of the two oil passage systems than the other, the distribution valve switches to the non-neutral position, causing the oil passage system on the side on which the large load is applied to In order to distribute a larger amount of hydraulic oil, the distribution valve mechanism is configured to be a switching type, and its functions and effects are as follows.

[For production]

If the above characteristics are configured as shown in FIG. 1, for example, two oil passage systems (B+) on the merging side are used during work.

(B2), the distribution valve mechanism (12) is switched to allow the hydraulic oil to join only on the side with the higher load, and the distribution valve mechanism (12) is switched to the neutral position when not in operation. Two oil/road systems (Bl) on the merged side, (
82), the hydraulic oil in the center bypass oil passage (9) is divided into approximately equal amounts and merges therein.

In other words, when not working, the center bypass oil passage (
The entire amount of oil in 9) does not flow into only one oil path system, but is divided and flows into each of the two oil path systems, so pressure loss can be reduced.

In addition, when comparing the conventional combined system and the combined system of the present invention,
If the discharge oil amount of each hydraulic pump is set to ``0'' and the pipe resistance of each oil line is set to ``R,'' in a conventional combined system, the total pressure loss is as shown in Figure 2 (a). 5Q2.R, whereas it can be easily seen that in the combined system of the present invention, the total pressure loss is suppressed to 4.50".R, as shown in FIG. 2 (b).

〔Effect of the invention〕

Therefore, by modifying the oil passages to send hydraulic oil to the two oil passage systems and installing a distribution valve mechanism, the advantage of increasing the driving speed of the hydraulic actuator on the merging side during work can be avoided ( The aim was to reduce the load when not working.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

As shown in Fig. 3, a swivel table (2) and a dozer device (3) are attached to a crawler traveling device (1), and a backhoe device (
4), the boarding operation section (5) and the driving section (6) are mounted on the swivel platform (2).
), it constitutes a small backhoe work vehicle that can also be used for earth removal work.

The fluid pressure circuit for driving the traveling device (1), the swivel table (2), the dozer device (3), the backhoe device (4), etc. is configured as a hydraulic type and will be described in detail below.

As shown in Figure 1, the first to third pumps (P1), (P2), (P, l) are arranged in the driving part (6) in conjunction with the same engine (E), and one of the left and right crawlers The first traveling operation valve (vl) of the hydraulic motor (Ml), the operation valve (v2) of the boom hydraulic cylinder (-), and the operation valve (V3) of the packet hydraulic cylinder (C2) are arranged in that order. It is a multiple valve type with a center bypass and is connected in parallel to the first pump (Pl). Second traveling operation valve (v4) for the hydraulic motor (M2) for the left and right crawlers
, a multiple valve type with center bypass, in which the boom expansion valve (V3), the arm hydraulic cylinder (C3) operation valve (v6), and the service port (7) strain valve (v7) are arranged in that order. The operation valve (v
8), operating valve (V3) for the hydraulic motor (M3) for the swivel table;
The operating valve (Vl.) of the dozer hydraulic cylinder (C5),
It is a multiple valve type with center bypass arranged in that order and connected in parallel to the third pump (P3).

The hydraulic motors (M3) and (M2) for the left and right crawlers are the first
and a low speed state in which the second pumps (P1) and (P2) are connected separately, and pressure oil from both pumps (P1) and (P2) is combined to drive both hydraulic motors (M3) and (M□). A speed change valve (8) is provided for switching to a high speed state where the power is supplied in series.

Further, the three operating valves (of the system of the first pump (Pl)
Vl), (V2), (V3), second pump (P2)
The four operating valves (V4), (Vs), (V
s), (v3), and the three operating valves (V8) and (V9) of the third pump (P3) system.

(Vlo) are respectively called the first control well group (A1), the second control well group (A2), and the third control well group (A3), and in this hydraulic system, the oil line system (B3) of the third pump (P3) ) from the center bypass oil passage (9) of the first. Second pump (P
Two oil passages (10), (11) and a distribution valve mechanism (12) are provided to merge with the oil passage systems (Bl) and (82) of 1) and (P2), respectively.

In other words, there is a distribution valve mechanism (12) on the downstream side of the center bypass oil passage (9) of the oil passage system (B3) of the third pump (P3).
is provided, and this distribution valve mechanism (12), in the neutral position, merges the hydraulic oil in the center bypass oil passage (9) in approximately equal amounts, and flows through the two oil passages (10) and (11). Through 1st. It is configured to merge with the discharge oil passages (13), (14) of the second pumps (P1), (P2), and the oil passage system (Bl) of the first and second pumps (P1), (P2). , (B2) reaches a larger load than the other, the hydraulic oil from the center bypass oil passage (9) flows only into the larger load side as a result of switching operation by pilot pressure. is configured to do so.

Note that the oil passages (10) and (11) are provided with check valves (15) and (15), respectively, and a relief valve (16).

(16) is provided in a branched state.

[Another example]

In addition to the embodiments described above, the present invention also includes, for example, the distribution valve mechanism (1).
As shown in Fig. 4, when 2) is switched to a non-neutral position, it is possible to configure a structure in which more hydraulic oil flows to the side with a large load, and this distribution valve mechanism (12) may be of an electromagnetically operated type.

Furthermore, the present invention can also be applied to work vehicles other than backhoes.

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 the drawing]

The drawings show an embodiment of the hydraulic structure of a working vehicle according to the present invention,
Figure 1 is a hydraulic circuit diagram, Figures 2 (a) and (0) are schematic diagrams showing the total pressure loss in the conventional hydraulic circuit and the hydraulic circuit of the present invention, and Figure 3 is an overall side view of the backhoe. FIG. 4 shows another embodiment of the hydraulic circuit. (9)... Center bypass oil passage, (12)...
...Distribution valve mechanism, (^1), (A2), (A
3)...Control valve group, (Bl), (B2),
(83)...Oil system, (p1), (P2),
(P3)...Hydraulic pump, (F3)...
··engine.

Claims (1)

[Claims] Three hydraulic pumps (P_) by a single engine (E)
1), (P_2), and (P_3) are simultaneously driven, and the hydraulic oil from these hydraulic pumps (P_1), (P_2), and (P_3) is supplied to independent hydraulic actuators, so three oil systems are used. Road system (B_1), (B_2), (B_
3), and a three-system center bypass type control valve group (
A_1), (A_2), and (A_3) are formed in the hydraulic structure of a working vehicle, wherein the three control valve groups (A_1)
), (A_2), and (A_3) are provided with a distribution valve mechanism (12) that distributes and supplies the hydraulic oil that has passed through one of the center bypass oil passages (9) to the other two oil passage systems. , when the other two oil passage systems are under no load, the distribution valve (1
By switching to the neutral position in 2), approximately the same amount of hydraulic oil is distributed to the other two oil passage systems, and a larger load is applied to one side of the other two oil passage systems than the other. When the distribution valve (12) is switched to the non-neutral position,
A hydraulic structure for a working vehicle in which a distribution valve mechanism (12) is configured to be of a switching type so as to distribute a larger amount of hydraulic oil to the oil passage system on the side on which a large load is applied than on the other side.