JPH02261906A - Hydraulic actuator operational structure of working car - Google Patents

Abstract

PURPOSE:To constitute throttling function to delay the reversion of a direction change-over valve to the neutral stop position in a simple structure by constituting a pilot operating oil for change over operation from the direction change- over valve to discharge oil through a clearance for throttling. CONSTITUTION:Tolerance of a larger diametrical part 16b of a spool 16a of a pilot valve 16 is set at the minus side, and tolerance of the inner surface of a case 22 is set at the plus side and processed. Accordingly, clearance or a clearance 23 for throttling equivalent to the total of the tolerance is formed between the larger diametrical part 16b and the inner surface of the case 22. When the spool 16a of the pilot valve 16 is operated in the neutral position, pilot operating oil is pushed to charging and discharging ports 15a, 15b of one end of a direction change-over valve 11, and it is discharged to oil chambers 21a, 21b for drain through the clearance 23. Then resistance works against the flow of pilot operating oil in the clearance 23 and the valve 11 is reversed to the neutral stop position delaying slightly, while a flow control structure is operated to the flow reduction side and the hydraulic actuator stops with less shock.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydraulic actuator used in a work vehicle such as a construction machine or an agricultural vehicle. A pilot-operated neutral return type directional switching valve for switching operation and a flow rate control mechanism are connected in series, and a pilot valve for supplying and discharging pilot hydraulic oil for switching operation to and from the directional switching valve;
The present invention relates to a hydraulic actuator operating structure for a working vehicle, which includes a human operating tool for switching the pilot valve.

[Conventional technology]

Some backhoes, which are one type of work vehicle, use a hydraulic motor, which is one of the hydraulic actuators, to drive the swivel base, and are equipped with the above-mentioned hydraulic circuit configuration for this hydraulic motor. .

In this way, by providing a flow rate control mechanism separately from the directional control valve, it is possible to relatively accurately adjust the swing speed by controlling the flow rate, and the swing speed can also be adjusted according to the tilting angle of the operating lever, which is a human operating tool. It is easy to make the IJI change so that the rotation speed changes (for example, the turning speed becomes faster as the tilt angle of the operating lever becomes larger). Therefore, in such a configuration, when the control lever begins to return to the neutral stop position, the flow rate is throttled by the flow control mechanism, so that when the control lever is returned to the neutral stop position, the swivel base stops slowly with less shock. It is proposed to be configured to do so.

[Problem to be solved by the invention]

However, if the operating lever is suddenly returned to the neutral position by mistake, the directional control valve is returned to the neutral stop position and the hydraulic motor is operated without the flow rate control mechanism working to throttle the flow rate. The oil supply/drainage is blocked by the directional control valve, resulting in a situation where the swivel base suddenly stops.

Therefore, as shown in FIG. 6, a bypass oil passage (24) is provided to communicate the both supply and discharge boats (15a) and (15b) of the directional control valve (11) at the neutral stop position of the pilot valve (16). There is a structure in which this bypass oil passage (24) is provided with a constriction part (25).

As a result, when the operating lever and pilot valve (16) are operated to return to the neutral stop position, the directional control valve (11) also tries to return to the neutral stop position by the biasing force of the spring, etc., and the directional control valve is switched to one side. The pilot oil chamber (lid)
) or (lie) is pushed out and flows from one supply/discharge boat (15a) or (15b) through the bypass oil passage (24) to the other supply/discharge boat (15b) or (15a). I'm about to try.

In this case, the throttle part (
25), resistance acts on the flow of the pilot hydraulic oil, causing the directional control valve (11) to return to the neutral stop position with a delay. However, with this structure, the hole for the throttle part and the bypass oil Since it was necessary to open a hole in the case of the pilot valve, there was room for improvement in terms of simplifying the structure.

SUMMARY OF THE INVENTION An object of the present invention is to simplify the structure of a throttle function that delays the return of the directional control valve to its neutral stop position.

[Means to solve the problem]

The feature of the present invention is that, in the hydraulic actuator operation structure for a work vehicle as described above, a wandering boat communicating with a pilot oil chamber of a directional control valve and a drain oil chamber are connected to a large diameter portion of a spool of a pilot valve and a case. The directional control valve is connected through a throttle gap provided between the inner surface of the directional control valve and the directional control valve so that the directional control valve returns to the neutral stop position with a time delay from the time when the human operating tool is operated to the neutral stop position. The control means is configured to drain pilot hydraulic oil for switching operation from to through the throttling gap, and includes control means for gradually operating the flow rate control mechanism to decrease the flow rate within the neutral return delay time. , its functions and effects are as follows.

[For production]

When machining the large diameter part of the spool and the inner surface of the case in the pilot valve, the throttle gap as mentioned above should be set to a slightly larger tolerance (with the tolerance of the inner surface of the case on the positive side and the large diameter part of the spool). It can be easily formed by setting the tolerance on the negative side). The aperture gap can also be easily formed by machining the large diameter portion of the spool and the inner surface of the case with normal precision, and then providing a groove for the aperture on the large diameter portion of the spool or the inner surface of the case. It can be done.

With the above configuration, when the spool (16a) of the pilot valve (16) is operated to the neutral stop position as shown in FIGS. 1 and 2, one of the supply and discharge boats (15a) of the directional control valve (11) ), (15b), the pilot hydraulic oil is pushed out, and the throttle gap (23) between the large diameter part (16b) of the spool (16a) and the inner surface of the case (22) in the pilot valve (16) is The oil is then discharged into the drain oil chambers (21a) and (21b).

Then, resistance acts on the flow of pilot hydraulic oil in the throttle gap (23), causing the directional control valve (11) to return to the neutral stop position with a delay, and during that time, the flow rate control mechanism is operated to the flow rate decreasing side. The hydraulic actuator stops with less shock.

〔Effect of the invention〕

Unlike the conventional structure, there is no need to perform special processing such as bypass oil passages on the pilot valve case or incorporate a separate throttle part, but by making some improvements to the processing of the large diameter part of the spool and the inner surface of the case. By simply applying this, a constriction portion that delays the return of the directional control valve to the neutral stop position can be formed, and the structure can be simplified.

〔Example〕

Embodiments of the present invention will be described below using a backhoe, which is one type of work vehicle, based on the drawings.

Figure 3 shows the hydraulic circuit of the backhoe, and shows the pump (
An electromagnetic proportional pressure reducing valve as a flow rate control mechanism (3), a first control valve (4) and a second control valve (5) are connected to the oil path (2) from 1).
are connected in series. This first control valve (4) supplies and discharges hydraulic oil to a hydraulic cylinder (7) that swings the backhoe device (6) shown in Fig. 4 left and right, and the second control valve (5) The hydraulic cylinder (9) which drives the dozer (8) shown in FIG. 4 up and down is supplied with and discharged from the hydraulic cylinder (9).

A pair of oil passages (10) from the electromagnetic proportional pressure reducing valve (3)
) is connected to a directional control valve (11). This directional control valve (11) switches the supply and discharge direction of hydraulic oil to a hydraulic motor serving as a hydraulic actuator (13) for driving the swivel base (12) as shown in FIG. It determines the turning direction, and as shown in Figures 1 and 3, a pair of springs (llc) are used to set the neutral stop position <
1la).

Next, the linkage structure between the operating lever as the human operating tool (14), the directional switching valve (11), and the electromagnetic proportional pressure reducing valve (3) will be described in detail.As shown in FIG. 3, the directional switching valve (
11) is provided with a pilot valve (16) for supplying and discharging pilot hydraulic oil for switching operation. They are mechanically interlocked and connected via. In this case, the maximum stroke position (R) for clockwise rotation and the maximum stroke position (L) for left rotation of the operating lever (14) are made to correspond to both stroke ends of the spool (16a) in the pilot valve (16).

And, for the pilot valve (16), the spool (1
6a) position (corresponding to the tilting angle of the operating lever (14))
A potentiometer (18) is provided to detect the
) is entered. As a result, the operating lever (14)
The control device (
19) issues an operation signal to the electromagnetic proportional pressure reducing valve (3). In other words, the structure is such that the larger the tilt angle of the operating lever (14) is, the faster the turning speed of the swivel table (12) becomes.

In this case, if the operating lever (14) is moved even slightly from the neutral stop position (N) to the (R) side or the stake side, that is, if the spool (16a) of the pilot valve (16) is operated even slightly, As shown in Figure 1, pump port) (
Hydraulic oil from the directional control valve (11) passes through one of the supply/discharge ports (15a) or (15b) and flows into one of the pilot oil chambers (lid) or (lie) of the directional control valve (11). )'s spool (llb) is slid.

Next, a configuration in which when the operating lever (14) is operated to return to the neutral stop position (N), the directional control valve (11) is operated to return to the neutral stop position (lla) with a delay will be described in detail. As shown in FIGS. 1 and 2, the left and right large diameter portions (
16b), there is an annular drain oil chamber (2
1a) and (21b) are provided on the case (22) side of the pilot valve (16). And the spool (1
The tolerance of the large diameter portion (16b) of 6a) is set to the minus side, and the tolerance of the inner surface of the case (22) is set to the plus side. As a result, a slight gap corresponding to the sum of the tolerances is formed between the large diameter portion (16b) of the spool (16a) and the inner surface of the case (22), and this is the aperture gap (23). It is.

With the above configuration, for example, when the operating lever (14) is operated to the right turning side ((R) side), the directional control valve (1) shown in FIG.
Pilot hydraulic oil is supplied to the left pilot oil chamber (lid) of 1), and the spool (ll) of the directional control valve (11)
Suppose that b) is moving to the right on the paper. When the operating lever (14) is returned to the neutral stop position (N) from this state, the spool (16a) of the pilot valve (16) also moves to the third position.
It is operated to return to the neutral stop position (16c) shown in the figure.

In this way, the pilot valve (16)
When the supply of pilot hydraulic oil from (20) is cut off, the spool (llb) of the directional control valve (11), which had been moving to the right in the paper, also moves to the left in the paper due to the biasing force of the right spring (11, c). trying to move towards

In this case, the pilot hydraulic oil in the left pilot oil chamber ciid) is pushed out and drained through the supply/discharge port 1115a) and the throttle gap (23). When passing, resistance acts and the spool (llb) of the directional control valve (11) is delayed and returns to the neutral stop position (11a) in FIG. 3.

Then, the directional control valve (11) is completely at the neutral stop position f(l
Hydraulic oil is supplied from the directional control valve (11) to the hydraulic motor (13) until it is operated to return to position (la). Therefore, after the operation lever (4) is operated to the neutral stop position (N), the directional control valve (11) is completely moved to the neutral stop position (N).
lla) until it is operated, the control device (19
), the electromagnetic proportional pressure reducing valve (3) is gradually operated to the flow rate reduction side. As a result, the swivel base (12) gradually decelerates, and the directional control valve (11) reaches the neutral stop position (l).
It stops when it is operated to return to la).

[Another example]

In the above embodiment, when machining the large diameter part (16b) of the spool (16a) and the inner surface of the case (22) in the pilot valve (16), the throttle gap (23
), but as shown in Figure 5, the spool (16
A notch (16d) may be provided in the large diameter portion (16b) of a), or a longitudinal groove may be provided in the inner surface of the case (22) to serve as the aperture gap (23).

What about the hydraulic actuator (13)? The A Wk control may be performed by duty control in which the on-off valve is opened and closed intermittently. The present invention can be applied not only to hydraulic motors but also to double-acting hydraulic cylinders.

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 the hydraulic actuator operation structure for a work vehicle according to the present invention, in which FIG. 1 is a longitudinal sectional front view of a directional control valve and a pilot valve, and FIG. 2 is an enlarged longitudinal sectional front view of the vicinity of the throttle gap of the pilot valve. , FIG. 3 is a hydraulic circuit diagram of the backhoe, FIG. 4 is an overall side view of the backhoe, FIG. 5 is an enlarged longitudinal sectional front view of the vicinity of the throttling gap in another embodiment, and FIG. 6 is a diagram of the directional control valve and the conventional structure. FIG. 3 is a longitudinal sectional front view of the pilot valve. (3)...Flow rate control mechanism, (11)...
・Directional switching valve, (lla)... Neutral stop position of the directional switching valve, (lid), (lie)...
Directional switching valve pilot oil chamber, (13)...hydraulic actuator, (14)...human operating tool,
(15a), (15b) = = supply and discharge boat, (
16)...Pilot valve, (16a)...
...Pilot valve spool, (16b)...
Large diameter part of pilot valve spool, (19)...
・System'+B means, (21a), (21b)...
...Oil chamber for doshin, (22) ... Case, (
23)...Gap for aperture.

Claims (1)

[Claims] For the hydraulic actuator (13), a pilot-operated, neutral return type directional control valve (11) that switches the supply and discharge direction of hydraulic oil and a flow rate control mechanism (3) are connected in series, and the flow rate control mechanism (3) is connected in series. A work vehicle equipped with a pilot valve (16) for supplying and discharging pilot hydraulic oil for switching operation to and from the switching valve (11), and a human operating tool (14) for switching the pilot valve (16). The hydraulic actuator operation structure includes a wandering port (15a) that communicates with the pilot oil chambers (11d) and (11e) of the directional control valve (11).
), (15b) and oil chamber for drain (21a), (21b
) and the spool (16a) of the pilot valve (16).
) and the inner surface of the case (22) through the throttle gap (23), the human operating tool (14) is operated to the neutral stop position (N). The pilot hydraulic oil for the switching operation from the directional switching valve (11) is supplied to the throttle gap (2) so that the directional switching valve (11) returns to the neutral stop position (11a) with a time delay from the point in time when the directional switching valve (11) returns to the neutral stop position (11a).
A hydraulic actuator operation structure for a working vehicle, which is configured to drain oil through the neutral return delay time and includes a control means (19) for gradually operating the flow rate control mechanism (3) to a side where the flow rate is reduced within the neutral return delay time.