JPS61266801A - Vehicle with turntable driven by hydraulic motor - Google Patents

Abstract

PURPOSE:To enable accurate flow rate control in transient period of a direction control valve spool switching by communicating a pressure port and a tank port with a load port through throttles so that leakage is made to zero after switching. CONSTITUTION:A direction control valve 20 has a pressure port P, a tank port T and a load port A. With a spool at the neutral position, the first throttle 53 is closed and the second throttle 51 is opened. It is so constituted that with the spool in the switching position the first throttle is opened and the second throttle is closed. On the other hand when the spool is under transient condition, both of the throttles are opened. Due to this, in the transient period of switching the spool 23 of the direction control valve 20, the load port A is communicated with the tank port T through the second throttle 51 so that any shock in the load can be relieved, preventing circuit vibration or surge pressure from being generated without causing leakage after switching, leading to accurate flow rate control.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a vehicle having a swivel platform driven by a hydraulic motor, such as a hydraulic excavator or a crane.

<Prior art> Conventionally, in this type of vehicle, when switching the directional control valve that controls the hydraulic motor that drives the swivel base, the compression of oil in the circuit due to the inertial load of the swivel base and the response of the pressure compensation means are In order to eliminate circuit vibration caused by entanglement with delays,
The structure was as shown in Figures 7 and 8.

For example, in the vehicle shown in FIG. A pressure compensating means consisting of a bypass type pressure compensating valve 5 is installed on the side to control the flow rate by keeping the differential pressure before and after the throttle valve 3 constant. The spring chamber of the compensation valve 5 is connected to the tank 8a via a vent line 7 with a throttle 6 installed in the middle to dampen the compression of oil in the circuit by the swivel table 400, which is an inertial load, thereby reducing circuit vibration. It was designed to resolve this issue.

In addition, in the vehicle shown in FIG. 8, the secondary side of the throttle valve 3 is
It is connected to the tank 8b via a vent line 7 with a constrictor 6 installed in the middle, thereby eliminating circuit vibration by relaxing the compression of oil in the circuit.

<Problems to be Solved by the Invention> However, in the vehicle having the swivel base 400 shown in FIGS. 7 and 8, there is always a leakage flow from the vent line 7, which causes power loss and heat generation. In addition, the maximum discharge flow rate of the pump l cannot be used for the hydraulic motor 4, and even if the flow rate of the throttle valve 3 is controlled by the bypass type pressure compensation valve 5, it is not possible to supply all of it to the hydraulic motor 4. , there was a problem that the speed control became inaccurate.

That is, in this vehicle, there was a problem in that the maximum flow rate of the pump could not be used for the turning hydraulic motor 4 of the turning base 400 due to the above-mentioned leakage flow rate that always occurs.

Therefore, the purpose of this invention is to generate leakage flow from the load side to the tank at the initial start-up of the swivel base of a vehicle such as a hydraulic excavator to alleviate the shock, and to ensure a large flow rate by eliminating the leakage flow during normal operation. The object of the present invention is to quickly and accurately control the speed of a swivel table, which is a large load, by obtaining accurate flow rate control.

<Means for Solving the Problems> A vehicle having a swivel base driven by a hydraulic motor of the present invention has a hydraulic motor that drives the swivel base; and at least 63 ports (P), (T), and (A). Insert the spool into the provided body, and connect the pressure port (P) between the spool and the body.
A first throttle is formed between the load port (A) and the load port (A), and a second throttle is formed between the load port (A) and the tank port (T), and the first throttle is closed when the spool is in a neutral position. The second throttle is opened, and at the switching position of the spool, the first throttle is opened and the second throttle is closed, while the first throttle is opened during the transition period from the neutral position to the switching position. a directional control valve that opens the second throttle; and pressure compensating means that maintains the differential pressure across the first throttle constant using a spool that responds to the pressure of a differential pressure passage branching from before and after the first throttle. , the driving direction of the hydraulic motor is controlled by the direction control valve.

<Function> During the switching transition of the spool of the above-mentioned directional control valve, the load port (A) and the tank (T) communicate with each other through the second restrictor and a leakage flow occurs, so even if there is a large inertial load of the swivel base, there is no shock. is alleviated, the generation of circuit vibration and surge pressure is prevented, and after the switching of the directional control valve is completed, the first vi
The leakage flow is eliminated, and accurate flow control is performed without causing power loss or heat generation, and accurate speed control of the swivel table, which is a large load, is achieved.

<Example> Hereinafter, a vehicle having a swivel table driven by a hydraulic motor according to the present invention will be described in detail with reference to the illustrated example.

FIG. 1 shows the upper stage directional control valve 20 and the lower stage pressure compensation means 60.

The directional control valve 20 is a four-point/one-three-position switching valve, and a spool 23 is slidably fitted into a spool chamber 22 provided in a main body 21.

The spool chamber 22 has five annular grooves 2 in order from the left.
4, 25, 26, 27, and 28 are provided, and each of the annular grooves is communicated with tank port T1 load port B1 pressure port P1 load port A and tank port T, respectively. The load port A is connected to an actuator having an inertial load (not shown). Further, a small annular groove 31 provided between the annular grooves 25 and 26 and a small annular groove 32 provided between the annular grooves 26 and 27 are communicated with the annular groove 26 through passages not shown, respectively. . That is, the above-mentioned small ring 1
31, 32 always communicate with pressure port P.

On the other hand, the spool 23 has four lands 35°36.3
7.38. The above land 35°36.37.
38 and the sliding surface of the spool chamber 22 switches the pressure port P to the load port A or B, and the load port A or B to the tank port T. A first throttle 53 is formed between the pressure port P and the load port A by the interaction between the land 35 and the sliding surface of the spool chamber 22. Similarly, a first aperture is formed between port P and load port B. That is, in the illustrated neutral position of the spool 23, the pressure port P is closed;
Load ports A and B communicate with tank port T, and when spool 23 is positioned on the left: Pressure port P and load port A; Tank port T and load port B communicate, and spool 23 is positioned on the right. When the pressure port P
and load port B; tank port T and load port A communicate.

A cover 41 is fixed to the left end of the main body 21 to form a spring chamber 42, and a spring 43 provided in the spring chamber 42 always urges the upper B4 spool 23 to a neutral position.

Further, a cover 58 is fixed to the upper part of the main body 21, and a passage 59 provided in the cover 58 is connected to the annular 1R2 at both ends.
4 and 28 are connected.

On the other hand, each inner end of the sliding surface of the lands 35 and 38 at both ends of the spool 23 is provided with respective notch grooves 46 and 45 in the axial direction. 445.46 and each sliding surface 22a, 22 of the spool chamber 22
b respectively form second apertures 51 and 52. That is, in the second throttle 51, when the spool 23 moves to the left, the central land 37 touches the sliding surface 22 of the spool chamber 22.
When the load port A communicates with the pressure port P at a distance from c, the outer land 38 comes into contact with the sliding surface 22a and tries to cut off the communication between the load port A and the tank port T. and the sliding surface 22a. Therefore, the second diaphragm 51 is connected to the spool 23.
When the flow rate from the pressure port P to the load port A is small immediately after switching, the tank port T is communicated with the load port A so that a leakage flow rate occurs.

Further, the second throttle 51 is arranged so that when the spool 23 is further moved to the left to achieve maximum displacement, the notch groove 45 is completely covered by the sliding surface 22a of the spool chamber 22 and closed. ing.

As a result, when the flow rate from pressure port P to load port A is large enough to prevent circuit vibration, load port A
There is no leakage flow from the tank port T to the tank port T.

The specific dimensional structure of the opening and closing of the second throttle 51 and the opening and closing between ports A and T in response to the stroke displacement of the spool 23 is shown in FIG. That is, the entire stroke of the spool 23 from its neutral position. =8.5
mm, and the pressure port P and load port A are 2.mm in diameter when the spool 23 is moved leftward from the neutral position. = 2.5 mm, while the load port A and tank port T communicate with each other when the spool 23 moves leftward from the neutral position i, 2.
Communication is maintained through the second throttle 51 until the spool 23 is displaced by 7.5 mm, and when the spool 23 is displaced by 7.5 mm or more, the second throttle 5I is closed and the communication is cut off.

On the other hand, the main body 2I is provided with a pilot passage 54 and openings 54a and 54b of the pilot passage 54.
are provided on each sliding surface 22c, 22d of the spool chamber 22, and by displacing the land according to the spool 23, the opening 54a or 54b is made to communicate with the load port A or B. That is, the opening 54a is provided between the annular groove 27 and the small annular groove 32, while the opening 54b is provided between the annular groove 25 and the small annular groove 31. When the land 37 is displaced in the direction shown in FIG. When the land 37 is displaced to the right, the sliding surface of the land 37 closes the opening 54a, while the sliding surface of the land 36 separates from the opening 54b and communicates the opening 54b with the load port B. Therefore, the pilot passage 54 communicates with the load port A or B that communicates with the pressure port P when the spool 23 is switched from the neutral position.

The main body 21 also includes a vent passage 5 whose one end communicates with the pilot passage 54 and whose other end communicates with the passage 59 of the cover 58.
5 are installed vertically. When the spool 23 is in the neutral position, the vent passage 55 is opened by the annular narrow groove 37a provided in the land 37, and when the spool 23 is displaced from the neutral position, the land 37 is opened.
It is designed to be closed by the sliding surface of. Therefore, the pilot passage 54 communicates with the tank port T via the vent passage 55 and the passage 59 when the spool 23 is in the neutral position.

On the other hand, the pressure compensating means 60 is comprised of a bypass type pressure compensating valve. However, a pressure reduction type pressure compensation valve or a preferential expansion pressure compensation valve may be used instead of the bypass type pressure compensation valve.

The bypass type pressure compensating valve 60 is fitted into a spool chamber 62 provided in a main body 61 so as to be slidable on a spool 63. The spool chamber 62 includes an annular groove 6 in order from the left.
5, 66, 67, the bipedal annular 71y65 is connected to the pump 90 and via the passage 69 to the pressure port P of the directional control valve 20, while the annular groove 67 is connected to the pressure port P of the directional control valve 20.
is connected to the tank 91 and to the tank port T of the directional control valve 20 via the passage 70.

On the other hand, the spool 63 is provided with lands 7I, 72°73, and each land 71. , 72 and 73 are sliding surfaces 62a and 62b of the spool chamber 62, respectively.

62c is slidably fitted. Then, as the spool 63 moves left and right, the sliding surface 62b and the sliding surface of the land 72 come into contact with and separate from each other, opening and closing the passage between the annular grooves 65 and 67, and draining the oil from the pump 90 into the tank. I am trying to bypass it to 9I.

A spring chamber 76 provided at the other end of the main body 61 is connected to the pilot passage 54 of the directional control valve 20 via a pilot passage 81 which is a differential pressure passage, while a pilot chamber 78 provided at the right end of the main body 61 The annular groove 6
Connected to 5. Therefore, in the spring chamber 76,
While the hydraulic pressure of the load port A or B of the directional control valve 20 is applied, the hydraulic pressure of the pressure port P of the directional control valve 20 is applied to the pilot chamber 78, so that the spool 63 of the bypass type pressure compensation valve 60 is is the above directional control valve 20
The differential pressure before and after the spring 79 provided in the spring chamber 76
is actuated to a value corresponding to the spring force of . Note that FIG. 6 is a diagram showing the structure of FIG. 1 using circuit symbols. 53 indicates a first aperture. The load ports (A) and (B) of this directional control valve 20 are connected to a hydraulic motor that drives the same swivel base as the hydraulic motor 4 that drives the swivel base 400 shown in FIGS. (not shown).

The vehicle configured as described above operates as follows.

When the spool 23 of the directional control valve 20 is in the neutral position shown in FIG. 1.6, the pressure port P is connected to the land 36.3.
7 and is closed by load port A.

B is connected to the tank port T, and the spring chamber 76 of the bypass type pressure compensation valve 60 is connected to the tank 91 via the pilot passage 81, the pilot passage 54, and the vent passage 55, so that the pump 90 performs unload operation. Let's do it.

Now, when the spool 23 of the directional control valve 20 is displaced to the left from the illustrated position, the sliding surface of the land 37
The pressure port P is connected to the load port A apart from the sliding surface 22c of No. 2. At this time, the sliding surface of the land 38 comes into close contact with the sliding surface 22a of the spool chamber 22 and tries to cut off the communication between the load port A and the tank port T, but the notch groove 45 provided on the sliding surface of the land 38 The load port A and the tank port T remain in communication with each other due to the second throttle 51 formed by the sliding surface 22a and the sliding surface 22a. Therefore, oil leaks from the load port A to the tank port T through the second throttle 51, and this action causes a delay in the response of the bypass type pressure compensation valve 60 and compression of oil due to the large inertial load of the swivel base. Prevents circuit vibration and surge pressure caused by entanglement.

Furthermore, move the spool 23 7.5 to the left from the neutral position.
When the displacement is more than mm, the sliding surface 22a of the spool chamber 27 completely covers the notched groove 45 provided on the sliding surface of the land 38, and the second throttle 51 is sealed.

At this time, the land 37 is far away from the sliding surface 22c, and the controlled flow rate from the pressure port P to the load port A is larger, so the second throttle 51 is fully closed as described above to cause leakage oil. Even if you do not do so, circuit vibration will not occur. On the other hand, as mentioned above, since leakage oil is not generated, a large flow rate can be ensured. In other words, the entire flow rate controlled by the bypass type pressure compensation means 60 can be supplied to the hydraulic motor that drives the swivel base.

FIG. 3 shows the directional control valve 2 relative to the load pressure using the stroke displacement of the spool 23 of the directional control valve 20 as an auxiliary variable.
This shows a control flow rate of 0.

Each curve Sl, S2, S*, S4. Ss, Ss is
Stroke displacement: 3.5mm, 4.5mm, respectively 5.
5mm, 6. 5mm, 7. 5mm. Flmm
Indicates the status of As is clear from this, when the stroke displacement is 7.5n+m or more, no leakage flow occurs regardless of the load pressure.

The first diaphragm 51a shown in FIG. 4 is a modification of the second diaphragm 5I shown in FIG.
, the aperture amount is changed.

The groove width of the groove 49 provided in the land 38 to form the second aperture 51a is enlarged in a V-shape toward the end surface of the land 38. Therefore, when circuit vibration is likely to occur immediately after switching, the second diaphragm 51a is
The cross-sectional area of the second throttle 51a is increased to increase the leakage flow rate and circuit vibration is prevented, while the cross-sectional area of the second throttle 51a is decreased as the stroke displacement increases to reduce the leakage flow rate. Further, the second aperture 51b shown in FIG.
This is the second modification of No. 1, which has a shape in which the amount of restriction changes little with the stroke displacement of the spool 23, and is shown in Fig. 4 or 5.
The aperture shape shown in the figure can be selected depending on the load situation.

In each of the above embodiments, each first aperture 51.51a, 5
1b is formed by providing each notch groove 45, 46 on the sliding surface of the land 38, 35 of the spool 23, but the above-mentioned notch grooves are provided on the sliding surface 22a of the spool chamber 22 to form a diaphragm. Good too.

<Effects of the Invention> As is clear from the above, the vehicle having the swivel table driven by the hydraulic motor of the present invention generates a leakage flow only during the switching transition of the directional control valve, and after the switching is completed, the leakage flow is reduced. This eliminates circuit vibration and shock (surge pressure) during the initial start-up of the hydraulic motor that drives the swivel table, which is a large inertial load, and eliminates leakage flow after the directional control valve has been switched. , power loss and heat generation are eliminated, and accurate flow control is possible, allowing accurate speed control of the swivel table.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of essential parts of one embodiment of the present invention, and FIG.
A diagram showing the opening/closing relationship between each port with respect to the stroke displacement of the directional control valve shown in the figure, Figure 3 is a load pressure-control flow characteristic diagram with the spool displaced, Figures 4 and 5 are the throttle FIG. 6 is a diagram showing a modification of FIG. 1 using circuit symbols, and FIG. 7-8 is a hydraulic circuit diagram of a conventional hydraulic excavator. 20... Directional control valve, 2 ■... Main body, 23... Spool, 5 [... First throttle, 53... Second throttle, 6
0...Pressure compensation means, 63...Spool, 81.8
3...Differential pressure passage.

Claims (1)

[Claims] (1) A spool (23) is inserted into a main body (21) equipped with a hydraulic motor that drives a swivel table and at least three ports (P), (T), and (A), and the spool (23) and the main body are connected to each other. (21) and the above pressure port (P)
A first throttle (53) is formed between the load port (A) and the tank port (T), and a second throttle (51, 51a, 51b) is formed between the load port (A) and the tank port (T). At the neutral position of (23), the first aperture (53)
At the switching position of the spool (23), the first throttle (53) is opened and the second throttle (51, 51b) is opened.
1a, 51b), while the first and second apertures (53) (51) are closed during the transition period from the neutral position to the switching position.
, 51a, 51b), and a differential pressure passage (8) branching from before and after the first throttle (53).
1) pressure compensating means (60) that maintains a constant differential pressure across the first throttle (53) with a spool (63) that responds to the pressure of (83); A vehicle having a turning base driven by a hydraulic motor, characterized in that the drive direction of the hydraulic motor is controlled.