JPH08326708A - Pressure peducing pilot valve - Google Patents

Abstract

PURPOSE: To relieve an impact when an actuator is driven and stopped with a simple structure by providing a spool which is displaced in response to each output port via a spring having a specified spring force and providing the each spool with a restrictor which always makes a tank port communicate with the output port. CONSTITUTION: When an operating lever 23 is operated in a direction shown in a drawing, a spool 40a is moved via a rod 27a and a spring 35a to supply pressurized oil to a pilot room 16a of directional control valve 16, thereby discharging the pressurized oil of a pilot room 16b to a tank 17 through a restrictor 44b. The spool is moved by an amount which balances the pressure in the spool against a spring force and the output port 30b communicates with a spring room 35b at an opening area corresponding to the amount of movement. The pressurized oil in the pilot room 16b is slowly drained and the directional control valve 16 is slowly displaced, thereby relieving an impact when hydraulic actuator is driven and also relieving an impact by the same action when it is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure reducing valve type pilot valve for driving a directional control valve for driving and controlling a hydraulic actuator of a hydraulic machine such as a hydraulic excavator with pilot pressure, particularly when the load is an inertial body. The present invention relates to a pressure reducing valve type pilot valve suitable for.

[0002]

2. Description of the Related Art Various hydraulic machines are provided with required hydraulic actuators, and by appropriately driving these hydraulic actuators, desired operations of the hydraulic machines are performed. By the way, the driving of the hydraulic actuators is controlled by the direction switching valves of the respective hydraulic actuators, and these direction switching valves are driven by the operation of the operating lever. 2. Description of the Related Art In recent years, a pilot-type operating device that drives a directional control valve using pilot pressure generated by a pressure reducing pilot valve operated by an operating lever is generally used. An example in which such a pressure reducing valve type pilot pressure is used in a hydraulic excavator will be described.

4 and 5 are a side view and a plan view of the schematic construction of the hydraulic excavator. In each figure, 1 is an upper revolving structure, 2 is a lower traveling structure, 3 is a revolving motor for revolving the upper revolving structure 1, 4 and 6 are left and right crawler tracks of the lower traveling structure 2, 5 and 7 are lower traveling structures, respectively. The left and right traveling motors for traveling 2. Reference numeral 8 is a boom rotatably supported by the upper swing body 1, 9 is an arm rotatably supported by the boom 8, and 10 is a bucket rotatably supported by the arm 9. Reference numeral 11 is a boom cylinder, 12 is an arm cylinder, and 13 is a bucket cylinder, which drive the boom 8, the arm 9, and the bucket 10, respectively.

FIG. 6 is a sectional view of a conventional pressure reducing valve type pilot valve. In the figure, 15 is a hydraulic pump mounted on a hydraulic excavator, 16 is a direction switching valve that controls the supply of pressure oil from the hydraulic pump 15 to the traveling motor 5, and 16a and 16b are provided on both left and right sides of the direction switching valve 16. Pilot room, 17
Is a hydraulic oil tank, 18a and 18b are left and right main pipes connecting the direction switching valve 16 and the traveling motor 5, and 19 is a main pipe 18.
It is a crossover relief valve connected to a and 18b.

Reference numeral 21 is a pilot pump, 22 is a relief valve that regulates the maximum discharge pressure of the pilot pump 21, and 2 is a relief valve.
Reference numeral 3 indicates an operation lever for operating the drive of the traveling motor 5, and reference numeral 24 indicates a pressure reducing valve type pilot valve which is switched by the operation lever 23. 25a and 25b are two spring chambers of the pilot valve 24 which accommodate the springs 35a and 35b, and 26a and 26b.
Is a spool inserted in the spring chambers 25a, 25b, 27
Reference numerals a and 27b are rods connected to the spools 26a and 26b. 28 is the pilot pump 21 and each spring chamber 2
Pump ports 30a, 30 for connecting 5a, 25b
Reference numeral b is an output port that connects the pilot chambers 16a and 16b of the direction switching valve 16 and the spring chambers 25a and 25b. 31a and 31b are output ports 30a and 30 respectively.
This is a pilot conduit that connects b with the pilot chambers 16a and 16b of the direction switching valve 16.

Incidentally, (A) and (B) show the detailed structure of a portion surrounded by a dot-and-dash line circle in the figure, and 32a and 32b are passages communicating with the output ports 30a and 30b, 33a and 3b.
3b, 34a, 34b indicate notches formed in the spools 26a, 26b.

The operation of the pilot valve 24 will now be described. When the pilot valve 24 is in the neutral position, the pilot chambers 16a and 16b of the directional control valve 16, as shown in FIG.
Pilot lines 31a, 31b, output ports 30a, 3
0b, the passages 32a and 32b, the notches 33a and 33b, and the spring chambers 25a and 25b to communicate with the hydraulic oil tank 17, and the directional control valve 16 is in a neutral state. When the operating lever 23 is operated to the left as shown in this state, the rod 27a moves downward and the spool 26a is displaced downward via the spring 35a. Spool 26
When "a" is displaced downward, as shown in FIG. 3B, the passage 32a and the spring chamber 25a which were connected by the notch 33a are connected.
Of the pump port 28 connected to the pilot pump 21 and the passage 32a by the notch 34a.
To communicate with each other, and pressure is generated in the passage 32a. Passage 32a
When the pressure becomes higher than the preset load of the spring 35a, the pressure reducing action starts, and finally, a pressure commensurate with the movement amount of the rod 27a in which the pressure of the passage 32a and the pressure of the spring 35a are balanced can be generated in the passage 30a. . The pressure generated in the output port 30a is transmitted to the pilot chamber 16a of the directional control valve 16 via the pilot conduit 31a,
The direction switching valve 16 is moved to the left position. By this movement, the hydraulic oil in the pilot chamber 16b of the direction switching valve 16 is removed and a flow is generated in the pilot pipe line 31b, but the spool 26b notches the passage 32b and the spring chamber 25b as shown in FIG. Since it is connected via 33b,
The pilot chamber 16b communicates with the hydraulic oil tank 17 with almost no pressure loss.

Next, the operation of each section shown in FIG. 6 will be described with reference to the time charts shown in FIGS. Now, when the operator of the hydraulic excavator tilts the operation lever 23 to the left as shown at time t ₁ , the spool 26a is displaced downward as described above, and the pressure oil from the pilot pump 21 passes from the pump port 28 to the passage 32.
It is supplied to the pilot chamber 16a of the directional control valve 16 via a, the output port 30a, and the pilot conduit 31a. As a result, the directional control valve 16 starts operating at time t ₃ and reaches the maximum displacement amount at time t ₄ , as shown in FIG. 7B. The response delay from the operation of the operation lever 23 to the start of the driving of the direction switching valve 16 depends on the pilot conduit 3
1a or the like is generated by the compressibility of the hydraulic oil, and the time (t
_3- t ₁ ) is a pressure loss when the oil discharged from the pilot pump 21 is supplied to the pilot chamber 16a of the direction switching valve 16,
Determined by the compressibility of the hydraulic oil hose. When the direction switching valve 16 is driven from the neutral position to the left position as shown in FIG.
6, is supplied to the traveling motor 5 through the main pipe 18b, effective pressure is generated between the main pipes on both sides of the traveling motor 5 as shown in FIG. Continue to rotate and run the hydraulic excavator.

At time t _5, when the operator returns the operating lever 23 to the neutral position in order to stop the hydraulic excavator, the spring chamber 25a of the pilot valve 24 is disconnected from the pump port 28, and the pilot chamber 16a is in the pilot line. Three
It is electrically connected to the hydraulic oil tank 17 via 1a, the output port 30b, the passage 32b, and the notch 33b. Therefore, as shown in FIG. 7B, the directional control valve 16 starts the return operation at time t ₆ which is slightly delayed from time t ₅ and becomes the neutral position at time t ₇ . The return speed of the directional control valve 16 in this case is determined by the spring force of springs provided at both ends of the directional control valve 16 and the return pressure loss occurring in the pilot conduit 31a and the pressure reducing valve type pilot valve 24.

When the return operation of the directional control valve 16 is started, the difference in pressure between both ends of the traveling motor 5 is rapidly reduced as shown in FIG. 7 (c). Since the traveling motor 5 has a large inertia, the traveling motor 5 continues to rotate without stopping even if the pressure difference between the both ends becomes 0, sucks the oil in the main pipeline 18b and discharges it to the main pipeline 18a. At this time, since the directional control valve 16 is almost in the shut-off state, the hydraulic pressure in the main conduit 18a (negative hydraulic pressure when viewed from the main conduit 18b side) rapidly rises as shown in FIG. Then, the traveling motor 5 is stopped. The crossover relief valve 19 operates due to the increase in the pressure of the main pipe 18a,
The oil is returned to the main line 18b, both ends the pressure of the traveling motor 5 at time t ₈ becomes substantially zero.

[0011]

By the way, in the above-mentioned conventional hydraulic circuit, when the operating lever 23 is operated from the neutral position to the operating position, the directional control valve 16 moves rapidly, and therefore, in FIG. As is clear from c), the traveling motor 5 is suddenly driven, which causes an impact on the vehicle body. Further, when the operating lever 23 is returned from the operating position to the neutral position, the speed at which the directional control valve 16 returns to the neutral position is extremely high. Therefore, the rising of the brake pressure generated in the main pipe line 18a is also shown in FIG. As shown in (3), it becomes extremely steep, and the shock applied to the entire vehicle body of the hydraulic excavator when stopped is also extremely large. As described above, due to the impact generated at the time of starting and stopping, the operability of the hydraulic excavator is deteriorated, the operator's feeling of fatigue is increased, and the durability of the machine is impaired. Such a defect occurs not only in the traveling motor of the hydraulic excavator but also in the hydraulic actuators of other working machines, and the defects become more remarkable as the load inertia of the hydraulic actuators increases.

In order to mitigate such an impact, a means for interposing a flow control valve with pressure compensation in the pilot conduits 31a, 31b is disclosed in Japanese Utility Model Publication No. 3722/1990, which is used for each pilot conduit. Since independent flow control valves with pressure compensation must be used for the passages 31a and 31b, there is a problem that the structure becomes complicated and large, and the cost also increases.

An object of the present invention is to solve the above-mentioned problems in the prior art, to reduce the impact at the time of starting and stopping the actuator with a simple structure, and to achieve improvement in operability and durability. It is to provide a pressure reducing valve type pilot valve that can be used.

[0014]

In order to achieve the above object, the present invention provides a pump port, each output port communicating with pilot chambers at both ends of a directional control valve for controlling the drive of a hydraulic actuator having a large inertia. In the pressure reducing valve type pilot valve having a tank port, there is provided a spool corresponding to each of the output ports, the spool being displaced via a spring having a predetermined spring force. It is characterized in that a diaphragm for communicating with the output port is provided.

[0015]

[Operation] When the pressure reducing valve type pilot valve is operated to drive the hydraulic actuator having a large inertia, pressure oil is supplied from the pump port to one pilot chamber of the directional control valve, and the pressure oil of the other pilot chamber to the tank port. Will be eliminated.
At this time, since the pressure oil to be removed is removed from the spool through the throttle, pressure is generated in the spool, and the spool is moved by an amount that balances the pressure and the spring force. Connect the output port and the tank port with. As a result, the pressure oil in the other pilot chamber is gently removed to the tank port, and accordingly, the displacement of the directional control valve is also moderated, and the impact when the hydraulic actuator is activated is moderated. Also, when the pressure reducing valve type pilot valve is operated to the neutral position to stop the hydraulic actuator that is being driven, the pressure oil in the pilot chamber where the pressure oil was supplied from the pump port is discharged from the spool to the tank port through the throttle. Will be done. In this case as well, the pressure oil is gently discharged to the tank port by the same operation as described above, so that the return of the directional control valve to the neutral position is also moderate, and the impact when the hydraulic actuator is stopped is moderated.

[0016]

The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a sectional view of a pressure reducing valve type pilot valve according to an embodiment of the present invention. In this figure, the same parts as those shown in FIG. 40a, 40
Reference numeral b is a spool corresponding to the spools 26a and 26b shown in FIG. The spools 40a and 40b of this embodiment and FIG.
The spools 26a and 26b shown in FIG.
It differs from the latter in that it has a and 44b. FIG. 2 shows the details of the structure of the portion indicated by the circular dashed lines (C) and (D) in FIG.
Shown in

FIG. 2 is a sectional view of portions (C) and (D) shown in FIG. The structures of these (C) and (D) parts are the same, but (C) of FIG. 2 is a cross-sectional view showing a neutral state, and (D) of FIG. In FIG. 2, the same parts as those shown in FIG. 1 are designated by the same reference numerals. Similar to the case shown in FIG. 6, the portion on the left side of the pressure reducing valve type pilot valve 24 is denoted by the reference numeral “a”, and the portion on the right side is denoted by the reference numeral “b”. 41a and 41b are passages that communicate with the output ports 30a and 30b, respectively.
Reference numerals a and 42b are upper notches formed on the spools 40a and 40b, and 43a and 43b are lower notches formed on the spools 40a and 40b. As shown in FIG. 2D, the notches 42a and 42b are formed on the spools 40a and 40a.
When b is moved upward by the distance L ₁ , the passages 41a and 41b (output ports 30a and 30b) and the spring chambers 25a and 25b (tank port) are formed at a position where they communicate with each other, and the notches 43a and 43b are formed in the spools 40a and 40b. passages 41a, 41b (output port 30 when but a distance L ₂ moves downward
a, 30b) and the pump port 28 communicate with each other. 44a and 44b are spools 40a and 40
It is a diaphragm formed in b and is always provided with the passages 41a, 41
b, that is, the output ports 30a and 30b and the spring chamber 25a,
25b, that is, the tank port. Aperture 4
The diameter of 4a and 44b is selected to be 1 mm or less, for example.

The operation of the pressure reducing valve type pilot valve of this embodiment will now be described with reference to the time chart shown in FIG. In FIG. 3, (a), (b), and (c) show the lever displacement, the directional control valve displacement, and the motor effective pressure on the vertical axis and the time on the horizontal axis, as in FIG. 7. , Fig. 7
The same time as the time indicated by is indicated by the same symbol.

When the pilot valve 24 is in the neutral position, as shown in FIG. 2 (C), the passage 41b (41a) and the spring chamber 25b (25a) are cut off from each other at the notch 42b (42a) portion, and the notch 43b. In the portion (43a), the passage 41b (41a) and the pump port 28 are blocked. Therefore, the pilot chamber 16b of the direction switching valve 16
(16a) communicates with the hydraulic oil tank 17 via the pilot conduit 31b (31a), the output port 30b (30a), the passage 41b (41a), the throttle 44b (44a), and the spring chamber 25b (25a). The directional control valve 16 is in the neutral state.

[0020] From this state, to drive the hydraulic excavator operator a hydraulic motor 5, the operating lever 23 is operated to the left as shown in Figure 1 at time t _1, the rod 27a moves downward, the spring 35a Through spool 4
0a is displaced downward. When the displacement reaches the distance L _{2 as} shown in FIG. 2D, the notch 43a causes
The pump port 28 and the passage 41a communicate with each other, and the passage 41a
The pressure will increase. When this pressure becomes higher than the preset load of the spring 35a, the pressure reducing action starts, and eventually the passage 4
The pressure of 1a is a pressure balanced with the force of the spring 35a, that is,
The pressure corresponding to the operation amount of the rod 27 is maintained. This pressure is transmitted to the pilot chamber 16a of the directional control valve 16 via the output port 30a and the pilot conduit 31a,
At time t ₃ , the directional control valve 16 starts moving to the right.

By this movement, the hydraulic oil in the pilot chamber 16b of the directional control valve 16 is discharged to the passage 41b via the pilot conduit 31b and the output port 30b. In this case, since the spool 40b is in the neutral state as shown in FIG. 2C, the pilot chamber 1 discharged into the passage 41b.
The hydraulic oil from 6b passes through the throttle 44b, and the spring chamber 25b.
Will be discharged to the tank 17. Since this discharge of the hydraulic oil passes through the throttle 44b, pressure is generated in the output port 30b and the passage 41b. When the flow rate through the throttle 44b increases, the generated pressure also increases, and the pressure is the preset load of the spring 35a. When it becomes higher than the above, the spool 40b is pushed upward. When the spool 40b is pushed up by the distance L ₁ , the notch 4
2b, the output port 30b (passage 41b) and the spring chamber 25b (tank port) communicate with each other, and the pilot chamber 16
The opening area for discharging the hydraulic oil from b is
The opening area of the notch 24b increases from the diameter of b. As a result, the pressure of the output port 30b decreases, and the spool 4
0b is displaced downward by the force of the spring 35b, and the notch 44
The opening area of b decreases again, and the pressure of the output port 30b increases. And finally, the output port 30b
The pressure is determined by the spring force of the spring 35b, and a flow rate corresponding to the pressure is discharged from the pilot chamber 16b to the tank port.

Since the pressure of the output port 30b is controlled as described above, the pressure of the pilot chamber 16b communicating with the output port 30b is also controlled to be higher by the pressure loss of the pilot pipe 31b. That is, even if the operation lever 23 is operated and the pressure corresponding to the operation amount of the operation lever 23 is supplied to the pilot chamber 16a of the direction change valve 16, the direction change valve 16
Will switch and move according to the pressure in the pilot chamber 16b, and as a result, rapid switching will be avoided.
As shown in FIG. 3B, the directional control valve 16 starts operating at time t ₃ and reaches the maximum movement amount only at time t ₄₀ . The time t ₄₀ is a time later than the time t ₄ shown in FIG. 7 to some extent, and this delay alleviates the impact.

In this way, when the direction switching valve 16 is switched from the neutral position to the left position, the pressure oil of the hydraulic pump 15 is supplied to the traveling motor 5 via the direction switching valve 16 and the main pipe line 18b, and the traveling motor 5 is moved. Effective pressure is (c) in Fig. 3
As shown by, the traveling motor 5 starts to rotate, and after time t _{40, the} normal rotation continues and the hydraulic excavator travels. As described above, since the switching of the direction switching valve 16 is gradual, the effective pressure of the traveling motor 5 rises as shown in FIG.
Compared with the conventional rise of the effective pressure shown in (c) of FIG. 3, it becomes much more gradual as shown in (c) of FIG.

Next, in the above running state, time t ₅
When the operator returns the operation lever 23 to the neutral position, the spool 40a is displaced upward by the force of the spring 35a and becomes in the state shown in FIG. 2C, and the output port 30a and the passage 41a are not connected to the pump port 28. The connection is cut off, and the spring chamber 25a (tank port) is connected via the throttle 44a. Therefore, the pilot chamber 16a of the direction switching valve 16
The pressure oil that accumulates in the pilot pipe 31a is
It will be discharged to the tank 17 via a. Due to the discharge of the pressure oil, pressure is generated in the passage 41a as in the case of starting the hydraulic motor 5 described above, and when the pressure becomes higher than the preset load of the spring 35a, the spool 40a moves upward. The output port 30a and the spring chamber 25a (tank port) communicate with each other when pushed up by the distance L ₁ and the opening area for discharging the pressure oil increases by the opening area of the notch 24a. Finally,
The pressure of the output port 30a is determined by the spring force of the spring 35b, and a flow rate corresponding to the pressure is discharged from the pilot chamber 16a and the pilot pipe 31a to the tank port. By discharging such pressure oil, the output port 30
When the pressure in the passage 41a decreases, the directional control valve 16 moves toward the neutral position accordingly, and finally becomes the neutral state as shown in FIG. 2C.

After all, even if the operating lever 23 is rapidly returned to the neutral position, the pressure oil that has accumulated in the pilot chamber 16a of the directional control valve 16 and the pilot pipe 31a is not immediately discharged, but the throttle 44a of the spool 40a and the notch 42a. Since the gas is slowly discharged from the opening of the directional control valve 16, the return speed of the directional control valve 16 becomes slow, and the neutral position is reached at time t _{80 as} shown in FIG. 3B. This time t ₈₀ is much later than the conventional time t ₈ shown in FIG. 7B.

In this way, the return speed to the neutral position of the direction switching valve 16 is limited, so that the shut-off speed of the main pipe line 18a of the hydraulic motor 5 is also suppressed. As a result, the main pipe line 18
The effective motor pressure (brake force) generated in a does not rise sharply as shown in FIG. 7C, but rather rises gently as shown in FIG. 3C. As a result, the impact applied to the entire vehicle body when the hydraulic excavator is stopped is significantly reduced.

Thus, in this embodiment, the spool is
Since the throttle that always connects the tank port and the output port is provided, the shock at the time of starting and stopping the hydraulic motor can be mitigated with a simple configuration, and by extension, the shock applied to the entire body of the hydraulic excavator is reduced. Operability and durability can be improved and operator fatigue can be reduced.

In the above description of the embodiment, the hydraulic motor of the hydraulic excavator was illustrated as the hydraulic actuator, but the present invention is not limited to this, and the present invention can be applied to other machines and other hydraulic actuators. Obviously it can be applied.

[0029]

As described above, in the present invention, the spool of the pressure-reducing valve type pilot valve is provided with the throttle for constantly connecting the tank port and the output port, so that the structure is simple.
It is possible to mitigate the shocks at the time of starting and stopping the hydraulic actuator having a large inertia, and eventually to reduce the shock applied to the mechanism including the hydraulic actuator to improve its operability and durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a pressure reducing valve type pilot valve according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of points (C) and (D) shown in FIG.

FIG. 3 is a time chart illustrating a lever displacement, a direction switching valve displacement, and a motor pressure change when the pressure reducing valve type pilot valve shown in FIG. 1 is used.

FIG. 4 is a schematic side view of a hydraulic excavator.

FIG. 5 is a schematic plan view of a hydraulic excavator.

FIG. 6 is a cross-sectional view of a conventional pressure reducing valve type pilot valve.

FIG. 7 is a time chart explaining a lever displacement, a direction switching valve displacement, and a motor pressure change when a conventional pressure reducing valve type pilot valve is used.

[Explanation of symbols]

 5 hydraulic motor 16 directional switching valve 24 pressure reducing pilot valve 25a, 25b spring chamber 28 pump port 30a, 30b output port 35a, 35b spring 40a, 40b spool 44a, 44b throttle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kinya Takahashi 650 Jinrachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura factory (72) Inventor Yusaku Nozawa 650 Kintate-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Ceremony Company Tsuchiura Factory

Claims (1)

[Claims] 1. A pressure reducing valve type pilot valve having output ports communicating with pilot chambers at both ends of a directional control valve for controlling the drive of a hydraulic actuator having a large inertia, a pump port, and a tank port. It is characterized in that it comprises spools that can be displaced corresponding to the output ports via springs having a predetermined spring force, and that each of these spools is provided with a throttle that constantly communicates the tank port with the output port. Pressure reducing valve type pilot valve.