JP2002022054A - Directional control valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a directional control valve capable of ensuring the more satisfactory operability of a hydraulic actuator controlled by the directional control valve. SOLUTION: This directional control valve comprises a spool 11 slidable according to pilot pressure oil; pilot caps 12 and 13 provided opposite to the end of the spool 11 and having pilot chambers 12a and 13a for guiding the pilot pressure oil thereto; and a restrictor 31 formed into a hole shape allowing the inflow of the pilot pressure oil and provided within the pilot cap 13 while having a shock absorbing function for gently operating the spool 11 in the switching of the spool 11 from a neutral position. A rod 30 comprising a conical part insertable into the restorictor 31 is provided at the end of the spool 11, so that the opening area of the restorictor 31 is variable according to the sliding operation of the spool 11. Accordingly, the sliding speed of the spool 11 can be variably controlled, so that the flow rate supplied to a boom cylinder 7 in driving can be most suitably controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to a direction in which pilot pressure oil is supplied to a spool end through a throttle having a buffer function, which is mounted on various machines including construction machines such as a hydraulic excavator. It relates to a control valve.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram showing a hydraulic circuit including a conventional directional control valve, and FIG. 6 is an enlarged sectional view of a pilot cap portion of the conventional directional control valve shown in FIG.

The conventional directional control valve 1 is provided, for example, in a hydraulic shovel. The conventional directional control valve 1 is provided so as to face a spool 11 slidable in accordance with pilot pressure oil and to both ends of the spool 11. , A first pilot cap 12 and a second pilot cap 13 having pilot chambers 12a and 13a into which pilot pressure is introduced, respectively. A spring 14 for urging the spool 11 is disposed in the first pilot cap 12. As shown in FIG. 6, the second pilot cap 13 is formed in a hole shape into which pilot pressure oil can flow.
A throttle 31 having a buffer function of operating the spool 11 at a slow speed when switching from the neutral position is provided.

In the hydraulic circuit shown in FIG. 5, 5 is a main hydraulic pump, 20 is a tank, 6 is a main relief valve for regulating the maximum discharge pressure of the main hydraulic pump 5, and 7 is drive-controlled by a direction control valve 1. Hydraulic actuator, for example, a boom cylinder. Reference numeral 2 denotes an operation device for switching the direction control valve 1, and includes an operation lever 2a,
Pilot valves 2b and 2c are provided. 3 is a pilot pump for supplying pilot pressure to the operating device 2, 4 is a pilot relief valve for regulating the maximum discharge pressure of the pilot pump 3, and 17 is a pilot valve 2b of the operating device 2.
And a pilot line 18 for connecting the pilot chamber 12a of the first pilot cap 12 of the directional control valve 1 to the pilot chamber 18a of the pilot valve 2c of the operating device 2 and the pilot chamber 13a of the second pilot cap 13 of the directional control valve 1. Pilot pipeline. The damper chamber 13b has a diaphragm 31
Is a space separated from the pilot room 13a.

In the directional control valve 1 constructed as described above, for example, when the operating lever 2a of the operating device 2 is tilted rightward in FIG. 5 from a neutral state, and the pilot valve 2c is operated, the pilot valve 2c The pilot pressure oil reduced in pressure is guided to the pilot pipeline 18, supplied to the pilot chamber 13 a of the second pilot cap 13, and supplied to the right end of the spool 11 through the throttle 31 in FIG. As a result, the spool 11 moves to the left in FIG. 5 against the force of the spring 14, and for example, the center bypass formed at the center of the directional control valve 1 is closed,
The main hydraulic pump 5 communicates with the bottom chamber of the boom cylinder 7 via the directional control valve 1, and the rod-side chamber of the directional control valve 1 communicates with the tank 20 via the directional control valve 1. Therefore, the pressure oil of the main hydraulic pump 5 is supplied to the boom cylinder 7
And the boom cylinder 7 operates to extend.

When the above operation is performed, the pilot pressure oil supplied to the pilot chamber 13 a of the second pilot cap 13 through the pilot line 18 and further supplied to the end of the spool 11 is throttled by the throttle 31. Therefore, actually, it is gradually applied to the end side of the spool 11 for a short time, for example, about one second to several seconds. Therefore, the sudden movement of the spool 11 when switching the direction control valve 1 from the neutral position is suppressed, and the spool 11 is switched gently.

When the operating lever 2a is returned to the neutral state from such a driving state, the pilot chamber 13a of the second pilot cap 13 communicates with the tank 20. Therefore, the spool 11 moves to the right in FIG.
Return to neutral position. As a result, the center bypass communicates with the tank 20, and the main hydraulic pump 5 and the tank 20 are disconnected from the bottom chamber and the rod chamber of the boom cylinder 7, and the operation of the boom cylinder 7 is stopped.

When stopping from such a driving state, since the vicinity of the right end of the spool 11 shown in FIG. 5 communicates with the tank 20 through the throttle 31, the pressure of the damper chamber 13b acting on the end of the spool 11 is reduced. Since it gradually decreases, the spool 11 is gradually switched.

In this prior art, in particular, the boom cylinder 7
When the directional control valve 1 is switched from the neutral position to extend the spool 11, the spool 11 can be switched gently because the oil flows through the throttle 31 as described above, and the boom driven by the boom cylinder 7 In addition, the entire hydraulic excavator can be prevented from generating an impact when the boom cylinder 7 is driven.

[0010]

By the way, in the above-mentioned prior art, since the throttle 31 is a fixed throttle, the amount of oil flowing in and out through the throttle 31 is constant. Of the spool 11 at a constant slow speed until the end of the stroke. Accordingly, a relatively gentle flow of pressure oil is supplied to the boom cylinder 7 via the spool 11, and it is possible to prevent the boom cylinder 7 from generating a large impact when the boom cylinder 7 starts up. However, due to the constant speed sliding of the spool 11 of the directional control valve 1 depending on the constant opening area of the throttle 31, the boom is moved in a stroke region of, for example, 70% to 90% with respect to the entire spool stroke region where the impact is likely to be affected. The degree of the increase in the flow rate of the pressure oil supplied to the cylinder 7 cannot be reduced, so that a slight shock occurs when the boom cylinder 7 is started, and the operability of the boom cylinder 7 is slightly increased due to the slight shock. May be deteriorated.

In the above description, the hydraulic actuator including the boom cylinder 7 has been described. However, the same applies to other hydraulic actuators such as an arm cylinder, in which the spool 11 of the direction control valve 1 slides at a constant speed. Accordingly, there is a concern that a slight shock may occur during driving.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described prior art, and has as its object to provide a directional control valve capable of ensuring better operability of a hydraulic actuator controlled by the directional control valve. is there.

[0013]

In order to achieve the above object, the invention according to claim 1 of the present application provides a spool slidable in response to pilot pressure oil, and a spool provided opposite to an end of the spool. A directional control including a pilot cap having a pilot chamber into which the pilot pressure oil is guided, and a throttle formed in a hole shape and having a buffer function for gently operating the spool when the spool is switched from a neutral position. In the valve, the throttle is provided in the pilot cap, and an opening area control means for changing an opening area of the throttle according to a stroke of the spool is provided.

According to the present invention, the relationship between the stroke of the spool and the opening area of the throttle in consideration of the desired movement of the hydraulic actuator controlled by the directional control valve is considered. What is necessary is just to produce an opening area control means.

When the hydraulic actuator is driven, the pilot pressure oil is supplied to the pilot chamber of the pilot cap of the direction control valve and further supplied to the end of the spool via the throttle. The sliding speed is a sliding speed corresponding to a preset relationship between the spool stroke and the opening area of the throttle. That is, the sliding speed of the spool can be variably controlled. Accordingly, the flow rate of the pressure oil supplied to the hydraulic actuator via the spool also becomes a flow rate that depends on the sliding speed of the spool, that is, the opening area where the throttle changes, and for example, the degree of increase in the flow rate is selectively supplied to the hydraulic actuator. The operating speed of this hydraulic actuator is set to a relatively low operating speed by supplying a small amount of pressure oil, and otherwise, for example, the operating speed of the hydraulic actuator is increased by supplying a large amount of pressure oil having an increased flow rate to the hydraulic actuator. Can be done.
This makes it possible to realize the operation of the hydraulic actuator, which further reduces the shock when the hydraulic actuator is driven from the stopped state.

In the above-mentioned configuration, the opening area control means may be provided at an end of the spool, and may be constituted by a rod which can be inserted through the inside of the throttle.

In this case, the rod may include a conical portion.

In the above configuration, the length of the rod may be set to a length such that the rod is not detached from the throttle during the movement of the spool to the stroke end. Good.

It is convenient to provide such a directional control valve in a construction machine such as a hydraulic shovel.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a directional control valve according to the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a hydraulic circuit including an embodiment of the directional control valve of the present invention. FIG. 2 is an enlarged sectional view showing a pilot cap portion of the embodiment shown in FIG.
FIG. 3 is a diagram showing spool operation characteristics of the embodiment shown in FIG.

FIG. 1 is drawn corresponding to FIG. 5 described above, and FIG. 2 is drawn corresponding to FIG. 6 described above. The components shown in FIGS. 1 and 2 which are the same as those in FIGS. 5 and 6 are denoted by the same reference numerals.

The directional control valve 1 of the present embodiment shown in FIGS. 1 and 2 is also mounted on, for example, a hydraulic shovel.
A spool 11 slidable in accordance with the pilot pressure oil, and pilot chambers 12a, 1 provided opposite to both ends of the spool 11 to guide the pilot pressure oil.
A first pilot cap 12 and a second pilot cap 13 each having 3a are provided. A spring 1 for urging the spool 11 is provided in the first pilot cap 12.
4 is arranged. The second pilot cap 13 is formed in a hole shape as shown in FIG.
Is provided with a throttle 31 having a buffering function for gently operating the spool 11 when switching from the neutral position.
These configurations are, for example, equivalent to those shown in FIGS.

In particular, in the present embodiment, there is provided an opening area control means for making the opening area of the diaphragm 31 variable according to the stroke of the spool 11. This opening area control means is provided, for example, as shown in FIG. 2 at one end of the spool 11, and is constituted by a rod 30 which can be inserted through the inside of the diaphragm 31. As shown in FIG. 2, the rod 30 cuts the heads of the two conical bodies and attaches the cut portions to each other to form a symmetrical shape with respect to the central portion, that is, two conical portions. It is formed in a shape that includes. Therefore, the central portion of the rod 30 forms a small-diameter portion 30a, and the diameter gradually increases as the distance from the central portion to the left and right increases.
30c. That is, the aperture area of the diaphragm 31 is
When the spool 11 is in the neutral position, the diameter becomes the largest when the small diameter portion 30a which is the central portion of the rod 30 is located at the throttle 31 portion. When the spool 11 is operated to the left or right and slides toward the stroke end, a portion having a larger diameter of the rod 30 is gradually positioned in the throttle 31, and accordingly, the throttle 31 is moved.
The opening area changes gradually.

The length of the rod 30 is such that, for example, when the spool 11 is slid to the left or right, the rod 30 is kept from separating from the throttle 31 while sliding to the stroke end. Is set to

The rod 30 constituting the above-described opening area control means is connected to the boom cylinder 7 controlled by the directional control valve 1.
The stroke of the spool 11 and the throttle 31 are taken into consideration so that the desired movement can be performed for the reduction of the shock at the time of driving.
In order to maintain the relationship with the opening area of the above-mentioned structure, it is manufactured in advance to have two conical portions as described above.

FIG. 4 is a diagram showing the opening area characteristic of the spool 11 with respect to the spool stroke of the directional control valve 1, that is, the opening area characteristic of the spool 11 depending on the change in the opening area of the throttle 31, and 42 is the center bypass opening area. The characteristic 43 indicates the meter-in opening area characteristic when the pressurized oil is supplied to the boom cylinder 7, and the reference numeral 44 indicates the meter-out opening area characteristic when the pressurized oil from the boom cylinder 7 is returned to the tank 20. In the present embodiment, the opening area of the center bypass is set to be zero in a region where the stroke of the spool 11 is slightly before the stroke end, for example, in a stroke that is 80% of the entire stroke region. Generally, it is known that at the moment when the opening area of the center bypass becomes zero, the flow rate of the pressure oil supplied to the hydraulic actuator greatly increases.

In the hydraulic circuit shown in FIG. 1, similarly to the hydraulic circuit shown in FIG. 5, the main hydraulic pump 5, the tank 20, the main relief valve 6, which defines the maximum discharge pressure of the main hydraulic pump 5, A hydraulic actuator driven and controlled by the direction control valve 1, for example, a boom cylinder 7 is provided. An operating device 2 having an operating lever 2a and pilot valves 2b and 2c, and a pilot pump 3 for supplying pilot pressure oil to the operating device 2
A pilot relief valve 4 for regulating the maximum discharge pressure of the pilot pump 3, a pilot line 17 for communicating the pilot valve 2b of the operating device 2 and the pilot chamber 12a of the first pilot cap 12 of the directional control valve 1.
And the pilot valve 2c and the direction control valve 1 of the operating device 2.
And a pilot pipeline 18 for communicating with the pilot chamber 13a of the second pilot cap 13.

The operation of the directional control valve 1 of this embodiment having the above-described structure is as follows.

For example, when the operating lever 2a of the operating device 2 is tilted rightward in FIG. 1 from the neutral state, and when the pilot valve 2c is operated, the pilot pressure discharged from the pilot pump 3 and reduced by the pilot valve 2c. The oil is guided to the pilot line 18 and supplied to the pilot chamber 13 a of the second pilot cap 13,
The air is supplied to the damper chamber 13b through a gap between the rod 1 and the rod 30. As a result, the spool 11 moves to the left in FIG. 1 against the force of the spring 14, the center bypass formed at the center of the directional control valve 1 is closed, and the main hydraulic pump 5 Through the bottom-side chamber of the boom cylinder 7 so that the rod-side chamber of the directional control valve 1
Through the tank 20. Therefore, the pressure oil of the main hydraulic pump 5 is supplied to the bottom chamber of the boom cylinder 7, and the boom cylinder 7 operates to extend.

When the above operation is performed, the pilot pressure oil output from the pilot valve 2, that is, the second pilot cap 13
And the spool 11
The pilot pressure oil supplied to the end of the spool 11 is throttled between the throttle 31 and the rod 30 and is gradually given to the end of the spool 11. In this case, as the stroke of the spool 11 increases, the area of the gap between the throttle 31 and the rod 30, that is, the opening area of the throttle 31 changes so as to gradually decrease, and the meter-in opening area of the spool 11 responds to this change. The characteristic 43 gradually opens the output port leading to the bottom chamber of the boom cylinder 7 as shown in FIG. Then, 70% to 90% of the entire spool stroke area.
% Up to the stroke region of FIG.
As shown by 1, since the spool stroke per unit time is reduced, the opening area of the center bypass 42 in FIG. 4 is gradually reduced to zero, and the rapid movement of the spool 11 is suppressed, and the spool 11 is switched slowly. Can be

Incidentally, reference numeral 40 shown in FIG. 3 denotes a characteristic in the prior art shown in FIGS. Compared with the characteristic 41 of the present embodiment, the prior art has a large spool stroke per unit time especially in a 70% to 90% stroke region near the stroke end of the spool 11 of the directional control valve 1, and It can be seen that the movement is relatively fast.

When the operating lever 2a is returned to the neutral state from such a driving state, the pilot chamber 13a of the second pilot cap 13 communicates with the tank 20. Therefore, the spool 11 moves rightward in FIG. 1 by the force of the spring 14, and returns to the neutral position. As a result, the center bypass communicates with the tank 20, and the main hydraulic pump 5 and the tank 20 are disconnected from the bottom chamber and the rod chamber of the boom cylinder 7, and the operation of the boom cylinder 7 is stopped.

When stopping from such a driving state, the oil near the right end of the spool 11 shown in FIG.
Is returned to the tank 20 through a gap between the boom cylinder 7 and the rod 30. Since the opening area gradually increases, the tank 20 is switched at a relatively high speed, and the boom cylinder 7 stops relatively quickly.

Further, for example, from the neutral state, the operation lever 2a
When the pilot valve 2b is operated by operating the pilot valve 2b, the pilot pressure oil depressurized by the pilot valve 2b is guided to the pilot pipe line 17 and supplied to the pilot chamber 12a of the first pilot cap 12, It is supplied to the left end of the spool 11 in FIG. This allows
The spool 11 moves rightward in FIG. 1 against the force of the spring 14, the center bypass is closed, and the main hydraulic pump 5 communicates with the rod-side chamber of the boom cylinder 7 via the directional control valve 1. The bottom chamber of the control valve 1 is the directional control valve 1
Through the tank 20. Therefore, the pressure oil of the main hydraulic pump 5 is supplied to the rod-side chamber of the boom cylinder 7, and the boom cylinder 7 operates to contract.

When the above-described operation is performed, the area of the gap between the throttle 31 and the rod 30, that is, the opening area of the throttle 31 changes gradually by the rod 30 that moves integrally with the spool 11, and this gradually increases. The oil is returned to the tank 20 through the gap having the smaller opening area, and the meter-in opening area characteristic 43 of the spool 11 is correspondingly changed.
, The output port communicating with the rod side chamber of the boom cylinder 7 is gradually opened as shown in FIG. Also in this case, as described above, 70% to 9% of the entire area of the spool stroke.
Since the spool stroke per unit time becomes small as shown by the characteristic 41 of this embodiment in FIG. 3 up to the region of 0%, as shown by the center bypass opening area characteristic 42 in FIG. Of the opening area of the boom cylinder 7 is relatively small, whereby the increase in the flow rate of the pressure oil supplied to the boom cylinder 7 is suppressed to a small degree, and the boom cylinder 7 operates at a slow speed.

When the operating lever 2a is returned to the neutral state from such a driving state, the pilot chamber 12a of the first pilot cap 12 communicates with the tank 20. Therefore, the spool 11 moves to the left in FIG. 1 by the force of the spring 14, and returns to the neutral position. As a result, the center bypass communicates with the tank 20, and the main hydraulic pump 5 and the tank 20 are disconnected from the bottom chamber and the rod chamber of the boom cylinder 7, and the operation of the boom cylinder 7 is stopped.

In the stopping operation in this case, the spool 11 is switched at a relatively high speed, and the boom cylinder 7 stops relatively quickly.

In this embodiment constructed as described above, when the directional control valve 1 is switched from the neutral position to either the extending direction or the contracting direction of the boom cylinder 7,
Since the oil flows through the gap between the throttle 31 and the rod 30, the spool 11 can be switched gently, and the entire hydraulic excavator including the boom driven by the boom cylinder 7 receives the impact of the impact when the boom cylinder 7 is driven. Occurrence can be prevented.

Particularly, in the present embodiment, when the boom cylinder 7 is driven, as shown in FIG.
Spool 11 is 70% to 90% of the entire stroke area
The extent of the decrease in the opening area of the center bypass of the directional control valve 1 during the stroke area of the directional control valve 1, that is, the extent of the increase in the pressure oil supplied to the boom cylinder 7, can be made relatively small. The occurrence of a slight shock at the time of starting the motor 7 can also be suppressed, and excellent operability of the boom cylinder 7 can be ensured.

In the above-described embodiment, the boom cylinder 7 is described as an example of the hydraulic actuator controlled by the direction control valve 1. However, the present invention is not limited to this, and can be applied to various actuators. Further, the present invention is applicable to various machines such as construction machines different from hydraulic excavators.

[0042]

According to the invention of each claim of the present invention,
Along with being able to variably control the sliding speed of the spool of the direction control valve by the opening area control means, when driving the hydraulic actuator, the degree of increase in the flow rate of the pressure oil supplied to the hydraulic actuator is determined by the amount of the hydraulic actuator. The control can be performed so as to correspond to a desired driving mode, whereby the occurrence of a slight shock at the time of driving the hydraulic actuator can be suppressed, and the operability of the hydraulic actuator more excellent than that of the related art can be secured.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a hydraulic circuit including one embodiment of a directional control valve of the present invention.

FIG. 2 is an enlarged sectional view showing a pilot cap portion of the embodiment shown in FIG. 1;

FIG. 3 is a diagram showing operating characteristics of a spool provided in the embodiment shown in FIG. 1;

FIG. 4 is a view showing an opening area characteristic of a spool provided in the embodiment shown in FIG. 1;

FIG. 5 is a circuit diagram showing a hydraulic circuit including a conventional directional control valve.

FIG. 6 is an enlarged sectional view showing a pilot cap portion of the conventional directional control valve shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Direction control valve 2 Operating device 2a Operating lever 2b Pilot valve 2c Pilot valve 3 Pilot pump 4 Pilot relief valve 5 Main hydraulic pump 6 Main relief valve 7 Boom cylinder 10 Main body 11 Spool 12 First pilot cap 12a Pilot chamber 13 Second pilot Cap 13a Pilot chamber 14 Spring 17 Pilot line 18 Pilot line 20 Tank 30 Rod (opening area control means) 30a Small diameter portion 30b Large diameter portion 30c Large diameter portion 31 Restrictor 41 Characteristics of the present embodiment 42 Center bypass opening area characteristics 43 Meter-in opening area characteristics 44 Meter-out opening area characteristics

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H051 AA10 BB10 CC11 FF07 3H053 AA35 BC03 BD10 DA11 3H056 AA09 BB04 CA02 CB02 CC05 CD02 GG12 3H089 AA60 BB05 CC01 DA02 DB13 DB46 DB49 DB55 DB76 EE17 EE22 GG02

Claims (6)

[Claims] 1. A spool slidable in accordance with pilot pressure oil, a pilot cap provided opposite to an end of the spool, and having a pilot chamber into which the pilot pressure oil is guided, and wherein the pilot pressure oil is A directional control valve provided with a restrictor formed in a hole shape capable of inflow and having a buffer function of gently operating the spool when switching from the neutral position of the spool, wherein the restrictor is provided in the pilot cap, A directional control valve, comprising an opening area control means for changing an opening area of the throttle according to a stroke of the spool. 2. The directional control valve according to claim 1, wherein the opening area control means is a rod provided at an end of the spool and capable of passing through the inside of the throttle. 3. The directional control valve according to claim 2, wherein said rod includes a conical portion. 4. The length dimension of the rod is set to a length dimension such that the rod is kept from separating from the throttle during the movement of the spool to the stroke end. The directional control valve according to 2 or 3. 5. A spring for urging the spool is provided in a pilot cap provided at one end of the spool, and the throttle and the throttle are provided in a pilot cap provided at the other end of the spool. 2. The directional control valve according to claim 1, further comprising an opening area control means. 6. The directional control valve according to claim 1, wherein the directional control valve is provided in a construction machine.