JPS61228172A - Insensitive zone time shortening device in directional control valve - Google Patents

Abstract

PURPOSE:To shorten only an insensitive zone time and to improve rsponse, by a method wherein a spring, which works with a low spring contact at an insensitive zone and with a high spring constant at an actual actuating area, is mounted to the end part of a spool. CONSTITUTION:Since, during the initial stage of the slide of a spool 1, only a cylinder compression coil spring 4 on the inner side having a low spring constant works on the spool 1, the spool 1 is increased in a slide speed. When the spool 1 slides by an overlap amount DELTAL, a cylinder compression coil spring 5 on the outer side having a high spring constant also works on the spool 1, and thereby the slide speed of the spool 1 is decreased. Thus, since, even if an input signal is specified, the slide speed of the spool 1 is high at an insensitive zone, response of the spool 1, and in its turn, response of a hydraulic cylinder is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a spool valve among various directional control valves, and relates to a device for shortening the dead zone time thereof.

(Prior Art and Problems to be Solved by the Invention) Conventionally, as this type of valve, for example, a closed center 4 boat 3 position spring center pilot type directional control valve is well known, as shown in FIGS. 11 to 13. The facing valve is normally provided with an overlap amount ΔL to prevent leakage. During this overlap amount ΔL, there is a dead zone in which the direction of fluid flow does not change even if the spool 1 slides, and after that, it becomes an actual operating region where the direction of flow is changed. In this case, the relationship between the spool displacement L (film) and the response time t (sec) is as shown in FIG. The response time required to slide up to 2 is the sum of these values, ie, t2. If this response time t2 is long, there is an inevitable drawback that the responsiveness until the flow direction of the backward valve that gives the switching signal to the directional switching valve is completely switched and fluid is supplied to the cylinder etc. will be poor. . In order to eliminate this drawback, it is necessary to shorten the dead band time t1 as much as possible to improve responsiveness. However, if the overlap amount Δ is reduced in order to shorten the dead band time t1, There was a problem that the amount of leakage increased.

Therefore, by installing a special spring at the end of the spool, we can reduce the amount of overlap without reducing the amount of overlap.
The present invention shortens only the dead band time.

Structure of the Invention (Means for Solving the Problem Lts4γ Circle) That is, the present invention has a spool formed with a circumferential groove that is slidably fitted in the axial direction of the valve hole and communicates with the valve hole. In this directional control valve, the circumferential groove of the spool can be opened and closed as the spool slides, and an overlap part is provided between them when the spool is blocking the #lJ of the boat. A spring is attached to the end of the spool that works at a spring constant and has a large spring constant in the actual operating range when the boat opens, and changes in the spring constant change the vibration speed of the spool in the dead zone. The sliding speed will be faster than the actual operating range.

(First Embodiment) First, a first embodiment in which the present invention is embodied in a spool valve type directional control valve will be described with reference to FIGS. 1 to 8.

The directional control valve shown in Figs. 1 and 2 is a closed center 4 boat 3 position spring center pilot type, in which a spool 1 with a circumferential groove 18 vibrates against the valve hole 2 in the direction of its axis. Boats P and T are able to be fitted together and communicated with this valve hole 2.

A, 8, the circumferential groove 1a of the spool 1 can be opened and closed as it slides. When the boats P, T, A, and B are closed by the spool 1, an overlap portion (for example, an overlap amount ΔL in FIG. 1) is provided between them to prevent leakage.

In particular, in this embodiment, both controls corresponding to both ends of the spool 1 as shown in FIG. 3a.

A pair of cylindrical compression coil springs 4 and 5 having different free lengths are mounted concentrically in parallel to the spring 3b. That is, as shown in FIG.
, 3b, and is always held between the opposing inner surfaces of spool 1.
are pressed together.

Further, the outer cylindrical compression coil spring 5 has a washer 7 fitted to the outer periphery of the end of the spool 1 and a control seedling 38.

3b and the opposing inner surface of the washer 7, so that a gap S that is approximately equal to the overlap amount Δ is always created between the washer 7 and the washer 7. Furthermore, the inner cylindrical compression coil spring 4 has a smaller spring constant than the outer cylindrical compression coil spring 5. For example, in this embodiment, the inner cylindrical compression coil spring 4 has a spring characteristic diagram (force Fka, spring length amra, spring constant = 1k) shown in FIG.
a/mm), when set σ1=12mm, σ
max = 2Qmm, cy2 = 25mm when in close contact, free length 73 = 30mm, and the outer cylindrical compression coil spring 5 has the spring characteristic diagram (force Fk (1, spring length σn) shown in Figure 5).
+m, spring constant K = 10 kmMmm), crmax = 6m1m, σ2 = 8111O11 when in close contact
The free length cy3=2Qmm. The spring characteristic diagram of the parallel combination spring of these springs 4 and 5 is as shown in FIG. When it becomes equal to the overlap amount ΔL, the spring constant changes with the conversion point C as a boundary.

This directional control valve is applied, for example, to a hydraulic control circuit for a forklift or the like, as shown in FIG.

In this circuit, a hydraulic main pump 8 is connected to a hydraulic cylinder 10 via a main relief valve 9 and a directional valve, and both control chambers 3a, 3b of the directional valve
A pilot pressure hydraulic pump 11 is connected to the hydraulic pump 11 via a pilot relief valve 12 and a throttle 13. Also, both control rooms 3a.

3b is connected to the tank 15 via poppet valves 14a, 14b. Both poppet valves 14a.

14b transmits the signal from the operation box 16 to the controller 1.
7, and is opened and closed by this signal.

When the directional switching valve in the same circuit is in the neutral position, the oil discharged from the hydraulic main pump 8 stops at the boat P of the switching valve and is not supplied to the hydraulic cylinder 10, but from the main relief valve 9 to the tank 15. run away to On the other hand, oil discharged from the pilot pressure hydraulic pump 11 is supplied to both control chambers 3a of the same switching valve.

3b and stops at the closed poppet valves 14a and 14b, and when the pressure exceeds a predetermined pressure, it escapes from the pilot relief valve 12 to the tank 15, and the pilot pressure in both control chambers 3a and 3b is maintained constant.

In this state, the spool 1 of the switching valve is controlled to open by W3.
The pressure is balanced by the inner cylindrical compression coil springs 4 and the pilot pressure at a and 3b and held at the neutral position.

When only one poppet valve 14b is opened by the duty signal from the operation box 16, the oil in one control chamber 3b escapes to the tank 15, the pressure balance of the spool 1 is disrupted, and the spool 1 slides and undergoes a constant displacement. Boats P and B and boats A and T communicate with each other. Therefore, oil discharged from the hydraulic main pump 8 is guided to the hydraulic cylinder 10, and its piston rod 10a moves forward. Moreover, when only the other poppet valve 14a is opened, the spool 1 similarly slides and the boats P and A and the boat B and the king are connected.
The piston rod 10a retreats.

At the beginning of the sliding of the spool 1 mentioned above, only the inner cylindrical compression coil spring 4 with a small spring constant acts on the spool 1 (up to the conversion point C in Fig. 6), so the sliding speed of the spool 1 becomes faster. . Next, when the spool 1 slides by the overlap amount ΔL (the gap S), the outer cylindrical compression coil spring 5 having a large spring constant also acts on the spool 1 (after the conversion point C in FIG. 6). The sliding speed of the spool 1 becomes slower. That is, the spool displacement L(Ill
) and the response time t (sec) is shown in Figure 8, and there is a dead zone (range of overlap amount ΔL) in which the direction of fluid flow does not change even if the spool 1 slides.
In this case, a passing time t1' is required, and a passing time t2= is required in the actual operating range until the spool 1 slides by a constant displacement L2 after the flow direction is switched. Therefore, when comparing the transit time t between the prior art described above and the embodiment, the transit time t in the actual operating range is the same for both (t
2-tl=t2--tl-), the passing time t in the dead band is shorter in this embodiment <(ti>low), and in the end it is difficult to obtain 2 with the same spool displacement. The embodiment requires a shorter time (t2>t2=). When this is applied to the hydraulic control circuit, the response time t2' required for the flow direction of the directional control valve to be completely switched in response to a command from the operation box 16 can be shortened. Therefore, even if the input signal is constant, the sliding speed of the spool 1 in the dead zone is fast, so the responsiveness of the spool 1 and, by extension, the responsiveness of the hydraulic cylinder 10 are improved.

However, in order to shorten the dead band time with conventional devices, for example, the spool position is detected and fed back to the input signal of the poppet valve, and the input signal is changed only in the dead band to speed up the spool (sliding speed). This requires a means for adjusting the spring constant, which makes the system complicated.In this respect, this embodiment uses a change in the spring constant, so it is structurally simple.

Note that this first embodiment uses two types of cylindrical compression coil springs 4.
, 5 has been exemplified, but three or more types of cylindrical compression coil springs may also be used.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. 9.10.

This second embodiment is different from the first embodiment in that the open control room 3a is
This is a modification of the cylindrical compression coil springs 4 and 5 of , 3b, and utilizes a compression coil spring whose spring constant changes according to displacement.

For example, in this second embodiment, the conical compression coil spring 18
are mounted between the end of the spool 1 and the opposing inner surfaces of the control chambers 3a, 3b. Note that the spring 18 may be oriented in any direction. The spring characteristic diagram of the spring 18 is similar to the case shown in FIG. 6 in the first embodiment, since the spring constant increases with the conversion point C as the border, so in the dead zone, the conversion point C
By setting the spring constant so that it works with a small spring constant up to the point C and a large spring constant after the conversion point C in the actual operating range, the same function as in the first embodiment can be achieved with just one spring.

In addition, there are other compression coil springs that perform a similar function, such as a chain-shaped compression coil spring.

Effects of the Invention In short, according to the present invention, only the dead band time can be shortened without reducing the amount of overlap, so that not only can leakage be reliably prevented, but also responsiveness can be improved.

[Brief explanation of drawings]

1 to 8 show a first embodiment of the present invention, FIG. 1 is a sectional view showing a directional control valve, FIG. 2 is a symbol diagram thereof, and FIG. 3 is a sectional view of the main part of FIG. Figures 4 and 5 are spring characteristic diagrams of each cylindrical compression coil spring, Figure 6 is a spring characteristic diagram of a parallel combination spring made by combining the same springs, and Figure 7 is a directional control valve of this embodiment. Fig. 8 is a diagram showing the relationship between spool displacement and response time in the same circuit, Fig. 9 is a sectional view of the main part of a directional control valve according to the second embodiment, Fig. 10 is a spring characteristic diagram of the conical compression coil spring used in the same embodiment, Figs. 11 to 13 show the conventional example, Fig. 11 is a sectional view showing the directional control valve, and Fig.
FIG. 2 is a symbol diagram thereof, and FIG. 13 is a diagram showing spool displacement and response time. 1 is a spool, 3a and 3b are control chambers, 4 and 5 are cylindrical compression coil springs, 18 is a conical compression coil spring, ΔL is an overlap amount, and S is a gap. Patent Applicant Toyota Industries Corporation Representative
Person Patent Attorney On 1) Hironobu Figure 4 Figure 5 Figure 6 Figure 9'M10 Figure

Claims (1)

[Claims] 1. A spool with a circumferential groove formed therein is fitted into a valve hole so as to be slidable in the axial direction thereof, and the circumferential groove of the spool is slidably fitted into a port communicating with the valve hole. In a directional control valve that can be opened and closed when the port is closed by the spool, and has an overlapping part between them when the port is closed by the spool, the sliding speed of the spool in the dead zone due to the overlap part is determined by the actual opening of the port. A directional control valve characterized in that a spring is attached to the end of the spool, which operates with a small spring constant in the dead zone and with a large spring constant in the actual operating region, so as to make the sliding speed faster than the sliding speed in the operating region. Dead band time reduction device. 2. The spring is a parallel combination compression coil spring that combines two or more types of cylindrical compression coil springs with different free lengths. In the dead zone, only one cylindrical compression coil spring is pressed against the end of the spool, while the other A gap approximately equal to the amount of overlap is provided between the cylindrical compression coil spring and the end of the spool, and the other cylindrical compression coil spring is also pressed against the end of the spool in the actual operating range. A dead band time reduction device in a directional control valve according to item 1. 3. The dead band time reduction device in a directional control valve according to claim 1, wherein the spring is a compression coil spring such as a conical compression coil spring whose spring constant changes according to displacement.