JPH02484Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a hydraulic circuit for driving a work vehicle such as a hydraulic power shovel, in which surplus fluid generated from a first pump on one side is merged with fluid discharged from a second pump on the other side. It is characterized by being used effectively.

This type of vehicle is mainly equipped with two hydraulic pumps, and these pumps drive the traveling vehicles on both sides individually.When the vehicle is stopped, the same pump drives the work actuator, and the surplus flow is transferred to each vehicle. A relief valve is used to return the water to the tank. For this reason, there was a problem of large power loss due to flow loss (Japanese Utility Model Publication No. 50-26866). The present invention was devised in view of the above points, and its purpose is to use two independent hydraulic circuits to drive the actuators of both circuits without impairing the flow control function.
The purpose of this invention is to reduce power loss due to flow rate loss by effectively utilizing the surplus fluid by merging the surplus fluid from the pump on one side with the discharge fluid from the pump on the other side.
Therefore, in the hydraulic pressure circuit for a work vehicle of the present invention, a normally open first pressure control section 13 is provided between the primary port 11 and the secondary port 12, and a normally closed first pressure control section 13 is provided between the primary port 11 and the branch port 14. A first flow rate directional control valve 7a is connected to the secondary port 12 of the three-port pressure compensating valve 5, each of which has a second pressure control unit 15 formed therein. When opened and closed, a feedback line 23 that guides the pressure downstream of the opening/closing part 24 and a line 12a that guides the pressure of the secondary port 12 are connected to both end chambers of the pressure compensating valve 5. On the other hand, the primary port 11 of the pressure compensation valve 5 is connected to the first main stream line 25 of the first pump 1, and the branch line 34 of the branch port 14 of the pressure compensation valve 5 is connected to the second main stream line of the second pump 2. 33, and this second main flow line 33 is provided with a two-port pressure compensating valve 6 and a second flow rate directional control valve 8a, which are opened and closed by the opening/closing part 24 of this flow rate directional control valve 8a. a line 32 that guides the pressure behind the opening/closing part 24 when
A line 33 that guides the pressure of the second main stream line 33
a is connected to both end chambers of the two-port pressure compensating valve 6, and the third valve is connected to the load pressure of the actuator connected to the first flow direction control valve 7a.
Back pressure chamber 17 and tank 18 of port type pressure compensation valve 5
A pilot relief valve 19 is interposed in between, and when the pilot relief valve 19 is activated, the first pressure control section 13 is closed and the second pressure control section 15 is opened. Said 3
By controlling the pressure with either the first pressure control section or the second pressure control section in the port type pressure compensation valve, the pressure of the secondary port is compensated, and this pressure compensation allows the flow rate to be preferentially directed to the secondary port. and bypassing excess fluid to the second main line of the second pump.

When the load pressure of the actuator in the first flow rate directional control valve reaches the set pressure of the pilot relief valve, the pilot relief valve opens and releases the fluid to the tank via the back pressure chamber. As a result, the pressure in the back pressure chamber decreases and the differential pressure between both ends of the pressure compensation valve increases, so the first pressure control section closes and the second pressure control section fully opens to reduce the total flow rate of the first main flow line. It is merged into the second main line.

Therefore, while maintaining the pressure of the actuator of the first flow direction control valve, the fluid in the first main flow line is transferred to the second flow direction control valve.
Can be effectively used in mainstream lines.

On the other hand, in the second pump, the discharge fluid of this pump and the surplus fluid of the first pump drive an actuator, and this actuator is operated by a second pump whose differential pressure is kept constant by a two-port pressure compensation valve. Even with a two-flow directional control valve, the actuator is driven at a speed corresponding to the opening degree of the control valve, and even if the surplus fluid increases rapidly, the speed of the actuator is maintained constant.

Embodiments of the present invention will be described below based on the drawings.

The hydraulic circuit shown in FIG. 1 is composed of two constant discharge pumps 1 and 2 and two multiple valves 3 and 4.

The multiple valves 3 and 4 each include one pressure compensating valve 5 and 6, and a plurality of flow direction control valves 7a, 7b, 8a, 8b, 8c, 8d, 8e.
These multiple valves 3 and 4 differ only in the structure of the pressure compensating valves 5 and 6, and the other structures are the same as described below.

Specifically, as shown in FIG. 2, specific examples of the first multiple valve 3 on one side include a 3-port pressure compensating valve 5 with a pilot valve, and a 4-port flow rate directional control valve 7a, 7b with a neutral port block. are connected in a stacked manner. The pressure compensating valve 5 has a plunger 9 fitted into the valve body so as to freely reciprocate.
A normally open first pressure control section 13 is formed between the primary port 11 and the secondary port 12, and a normally closed second pressure control section 15 is formed between the primary port 11 and the branch port 14. A pilot chamber 17a formed at one end of 9
is connected to the secondary port 12 via a line 12a bored in the plunger 9, and a spring 16 is installed in a back pressure chamber 17 formed at the other end of the plunger 9, and the back pressure chamber 17 and tank 18
A pilot valve 19 is provided in a line 35 connecting the two. Note that the line 12a bored through the plunger 9 may be provided on the valve body side.
On the other hand, when each of the flow rate directional control valves 7a and 7b holds the spool 20 at the neutral position,
The ports P, T, A, and B are sealed off from each other, and the spool 20 is connected to a vent passage 21.
The opening/closing part 22 of the feedback line 23 and the opening/closing part 24 of the feedback line 23 are alternately opened and closed, and when the opening/closing part 24 is opened, the opening/closing part 22 is closed and the pressure behind the opening/closing part 24 is The opening/closing section 24 also has the function of adjusting the degree of opening between the port P and the port A or B. Then, via the first pressure control section 13 of the pressure compensation valve 5, the two flow rate directional control valves 7a,
7b are connected in parallel, and both flow rate directional control valves 7
A connecting line 26 between the vent passage 21 and the feedback line 23 in a and 7b and a line 27 connected to the back pressure chamber 17 of the pressure compensating valve 5 are connected via a shuttle valve 28.

On the other hand, the pressure compensation valve 6 in the second multiple valve 4 on the other side in FIG. The difference in structure from that of a relief valve is that a line 33a is connected to one end chamber of the pressure compensation valve 6.
The pressure of the second mainstream line 33 is applied via the flow direction control valves 8a, 8b, 8c, 8.
Among the load pressures generated by the actuators connected to the actuators d and 8e, the largest load pressure is applied to the other end chamber of the pressure compensation valve 6 via the shuttle valves 31... and the line 32. .
The flow rate direction control valves 8a, 8b, 8c, 8d, and 8e in the second multiple valve 4 have the same structure as the flow rate direction control valves 7a and 7b in FIG. Flow direction control valve 8
a, 8b, 8c, 8d, and 8e are connected in parallel to the second pump 2, while the branch port 1 in the first multiple valve 3 is connected as shown in FIG.
4 and the second main flow line 33 of the second pump 2 are connected via a branch line 34.

The operation of the embodiment configured as described above will be explained below.

As shown in FIG. 2, each flow rate directional control valve 7a, 7b
When the spools 20, 20 of 1 When the pump 1 is driven, the plunger 9 is displaced to the right by the fluid discharged from the pump 1, and the second pressure control section 15 is opened. Therefore, the entire amount of fluid discharged from the first pump 1 is diverted to the diversion line 34.

On the other hand, even in the case of the second multiple valve 4 in FIG.
Since it is opened to the tank 18 through the line 32 and each shuttle valve 31 sequentially, the fluid discharged from the second pump 2 to the second main stream line 33,
The fluid discharged from the first pump 1 to the branch line 34 as described above is unloaded from the pressure compensating valve 6 to the tank 18 after merging.

In the unload control state as described above, the second
By displacing the spools 20, 20 in the figure to the right, one opening/closing part 22, 22 is closed, and the other opening/closing part 24,
24 is opened, and a predetermined flow rate adjustment opening is established between the first main flow line 25 and the two A ports A, A, while the B ports B, B are communicated with the tank line 35 to connect the two actuators. When the first pump 1 starts operating at the same time, the discharge pressure of the first pump 1 starts to increase due to the load. Immediately before that, the plunger 9 temporarily returns to its home position due to the displacement of the spools 20, 20 and closes off the second pressure control section 15, but it is displaced again and opens the second pressure control section 15, causing the surplus The fluid is passed through the second pressure control section 15 to the branch line 34.
Begin to divert water to On the other hand, load pressure acts on both ends of the shuttle valve 28 via the feedback lines 23, 23, and the larger load pressure is guided preferentially to the back pressure chamber 17 by the shuttle valve 28. For this reason, the pressure compensating valve 5 adjusts the opening degree of the second pressure control section 15 so as to always control the flow rate to the actuator on which the larger load acts to be constant, and discharges surplus fluid corresponding to the adjusted opening degree. The flow is diverted to a diversion line 34. In this case, if the load on the branch line 34 is greater than the load on the first main stream line 25, the second pressure control section 15 is fully opened;
The opening degree of the first pressure control section 13 becomes smaller, and the pressure compensation function is switched from the second pressure control section 15 to the first pressure control section 13.

On the other hand, when each of the flow direction control valves 8a to 8e in the second multiple valve 4 shown in FIG. It is also supplied to each actuator connected to each of the flow direction control valves 8a to 8e. Also in the second multiple valve 4, each shuttle valve 31... selectively applies the maximum load pressure to the back pressure chamber of the pressure compensation valve 6, so the operating speed of the actuator to which the largest load acts is preferentially kept constant. Under this control, excess fluid is allowed to flow out of the pressure compensating valve 6 into the tank 18.

Therefore, the load pressure of the actuator in the first multiple valve 3 is reduced to the pilot relief valve 1.
When the set pressure of 9 is reached, the pilot relief valve 1
9 opens, restricting the fluid in line 27 and releasing it through back pressure chamber 17 to tank 18 . As a result, the pressure in the back pressure chamber 17 decreases and the pressure difference between both ends of the plunger 9 increases, so the plunger 9 moves to the right, closes the first pressure control section 13, and closes the second pressure control section 15. Fully open and open the first main line 2
5 is merged into the second main flow line 33.

Therefore, the fluid in the first mainstream line 25 can be effectively used in the second mainstream line 33 while maintaining the pressure of the actuator of the first multiple valve 3.

The above explanation is for each flow rate directional control valve 7a, 7b, 8a.
I have described the case where 8e is switched at the same time,
It is possible to individually switch each of these flow direction control valves to operate each actuator individually. In this case, the actuation speed of the actuators is controlled individually by pressure compensation valves 5, 6.

Each actuator of the hydraulic pressure circuit that performs the above-mentioned control action is, for example, each actuator 40a, 40b, 41a, 4 provided in the vehicle shown in FIG.
This corresponds to 1b, 41c, and 41d. Of these actuators, actuators 40a and 41c connected to the traveling vehicles 42 and 42 on both sides are connected to flow direction control valves 7a and 8c. Moreover, the actuator 41a for turning is connected to the flow direction control valve 8a. Furthermore, the actuator 40b that operates the boom 43 includes two flow direction control valves 7b,
Connected to 8d. Further, the actuator 41b that drives the arm 44 is connected to the flow direction control valve 8b. Further, an actuator 41d that operates the bucket 45 is connected to the flow direction control valve 8e.

Therefore, the running speed of the vehicle is guaranteed to be constant by both pressure compensation valves 5 and 6, and in performing constant speed control of the vehicle 42 on one side, the surplus fluid of the first pump 1 operates the vehicle 42 on the other side. It is used as part of the power to

Also, during bucket work while the vehicle is stopped,
The ascending and descending speed of the boom 43 is controlled by the pressure compensating valve 5 on one side, and the surplus fluid of the first pump 1 during the operation is merged with the fluid discharged from the second pump 2, so that each of the rotation, bucket swing, and arm elevation is controlled. Of these operations, the maximum load operation is controlled at a constant speed by the pressure compensating valve 6 on the other side.

In the embodiment shown in FIG. 1, all the surplus fluid generated from both pumps 1 and 2 is returned to the tank 18 from the pressure compensating valve 6 of the second multiple valve 4, so that the surplus fluid is There is only a loss. In this regard, in the embodiment shown in FIG. 6a, each flow rate directional control valve 8 is connected to the second main stream line 33 on the secondary side.
a to 8e are connected in parallel, while both pumps 1 and 2
are variable type, and the discharge lines of these pumps and the cylinders 36a, 36 for controlling the discharge amount of these pumps.
b are connected through lines 37a and 37b, respectively, to prevent surplus fluid from being generated as described below.

That is, first, in the case of FIG. 4, both variable pumps 1 and 2
swash plate variable setting pressure [cylinders 36a, 36
(minimum pressure for reducing the discharge amount by acting on b) are set to the same value (for example, 100 kg/cm ² for both). Therefore, when both pumps 1 and 2 are driven to operate their respective actuators, suppose that the discharge pressure of the first pump 1 changes to 50 kg/kg depending on the load.
cm ² is generated, and the discharge pressure of the second pump 2 is only 40Kg/cm ² , which is lower than that, the pressure compensation valve 5
is a throttle resistance [second
[control by the second pressure control unit 15 in the figure] is added to compensate the pressure of the supply amount to the first main stream line 25, and only the surplus fluid is diverted to the branch line 34 and merged with the discharge fluid of the second pump 2. second
It is supplied to the main stream line 33. Then, the actuator connected to the second mainstream line 33 is actuated.
However, in order to create the above pressure relationship,
Since the required flow rate of the actuator in the second mainstream line 33 is naturally larger than the amount supplied to the second mainstream line 33 as described below, the fluid supplied to the second mainstream line 33 is not pressure compensated, but only in the first mainstream line 25. is pressure compensated. That is, if the second
If the amount supplied to the second main line 33 is larger than the required flow rate of the actuator of the main line 33, the surplus fluid will be used due to the resistance of the flow rate adjustment part in the flow direction control valve 8a or 8b to 8e. As a result, the discharge pressure of the second mainstream line 33 tends to increase without limit. Therefore, the second pressure compensation valve 6a compensates the pressure on the secondary side of the valve 6a by its throttling action.
The surplus fluid generated on the primary side of the valve 6a flows backward through the branch line 34 and attempts to flow into the first main stream line 25. Here, the first pressure compensating valve 5 throttles the flow rate supplied to the first main stream line 25 to compensate the pressure of the main stream line 25. When the pressure in the branch line 34 reaches the swash plate variable set pressure (100Kg/cm ² ), the cylinder 36a,
Both pumps 1, 2 are operated by the fluid supplied to 36b.
By reducing the discharge amount of the fluid, the generation of surplus fluid for pressure compensating both the main flow lines 25 and 33 is suppressed.
In short, no surplus fluid is generated.

As described above, the present invention includes a normally open first pressure control section 13 between the primary port 11 and the secondary port 12, and a normally closed second pressure control section 13 between the primary port 11 and the branch port 14. A first flow rate directional control valve 7a is connected to the secondary port 12 of the three-port pressure compensation valve 5 each forming a pressure control unit 15, and is opened and closed by the opening/closing unit 24 of the flow rate directional control valve 7a, and a feedback line 2 that guides the pressure behind the opening/closing part 24 when opened.
3, and a line 1 leading to the pressure of the secondary port 12.
2a to both end chambers of the pressure compensation valve 5, while connecting the primary port 11 of the pressure compensation valve 5 to the first main stream line 25 of the first pump 1,
The branch line 34 of the branch port 14 in the pressure compensating valve 5 is connected to the second main stream line 33 of the second pump 2.
A two-port pressure compensating valve 6 and a second flow rate directional control valve 8a are provided in the second main stream line 33, and are opened and closed by the opening/closing portion 24 of the flow rate directional control valve 8a. At this time, the line 32 leading to the pressure downstream of the opening/closing part 24 and the line 33a leading to the pressure of the second main flow line 33 are connected to both end chambers of the two-port pressure compensating valve 6, while the first flow rate is The three-port pressure compensating valve 5 is actuated by the load pressure of the actuator connected to the directional control valve 7a.
A pilot relief valve 19 is interposed between the back pressure chamber 17 and the tank 18, and the pilot relief valve 19
When the system is activated, the first pressure control section 13 is closed and the second pressure control section 15 is opened, so that the surplus flow can be effectively utilized while maintaining the characteristics of two independent hydraulic pressure circuits. Available. That is, in the first main flow line, the first flow direction control valve and the third
Port type pressure compensation valve, in the second main line, the second
Since each actuator is individually controlled at a constant speed using a flow direction control valve and a two-port pressure compensation valve, each actuator can be controlled independently without mutual interference, and the surplus flow rate in the first main flow line can be controlled independently. It can be effectively used in the second mainstream line. Moreover, even if the surplus flow rate suddenly increases, for example, the two-port pressure compensating valve in the second main line maintains the differential pressure across the opening and closing part of the second flow control valve constant, so the actuator speed will not fluctuate. do not have.

Also, the secondary port 12 of the 3-port pressure compensation valve 5
For example, when the pressure in the branch line 34 becomes higher than the pressure in the second pump 2 due to pressure fluctuations in the second pump 2, the first pressure control section 13 reduces the pressure in the secondary port 12 to control the first flow direction. Since the pressure corresponds to the load pressure of the actuator connected to the valve 7a, constant speed control of the actuator that is not affected by pressure fluctuations of the second pump 2 is possible.

Furthermore, the entire flow rate of the first main flow line 25 can be made to join the second main flow line 33 while maintaining the load pressure of the actuator in the first flow direction control valve 7a at the set pressure of the pilot relief valve 19.

Therefore, when the actuator in the first flow rate directional control valve 7a is operated, regardless of whether the pressure is maintained, the first
Not only can the liquid in the mainstream line 25 be effectively used in the second mainstream line 33 without discharging it into the tank, but also power loss due to flow loss can be reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a partial three-dimensional view of the previous figure, FIG. 3 is an explanation of a shovel car, and FIG. 4 is an explanatory diagram of another embodiment. 1...first pump, 2...second pump, 3...
First multiple valve, 4...Second multiple valve, 5
...Pressure compensation valve, 6...Pressure compensation valve, 7a, 7b
...Flow rate directional control valve, 8a to 8e...Flow rate directional control valve, 13...First pressure control section, 15...Second pressure control section, 23...Feedback line, 25
...first mainstream line, 33...second mainstream line,
34...Diversion line.

Claims (1)

[Scope of utility model registration request] A normally open first pressure control section 13 is formed between the primary port 11 and the secondary port 12, and a normally closed second pressure control section 15 is formed between the primary port 11 and the branch port 14. A first flow rate directional control valve 7a is connected to the secondary port 12 of the three-port pressure compensation valve 5, and is opened and closed by the opening/closing part 24 of this flow rate directional control valve 7a, and when opened, the opening/closing part A feedback line 23 that leads to the pressure downstream of 24 and a line 12a that leads to the pressure of the secondary port 12 are connected to both end chambers of the pressure compensating valve 5, while the primary port 11 of the pressure compensating valve 5 is It is connected to the first main stream line 25 of the first pump 1, and the branch line 34 of the branch port 14 in the pressure compensating valve 5 is connected to the second main stream line 33 of the second pump 2.
A two-port pressure compensating valve 6 and a second flow rate directional control valve 8a are provided in the main flow line 33, and are opened and closed by the opening/closing part 24 of the flow rate directional control valve 8a, and when opened, the second flow rate directional control valve 8a opens and closes after the opening/closing part 24. Line 3 leading to the pressure of
2 and a line 33a leading the pressure of the second main flow line 33 to both end chambers of the two-port pressure compensation valve 6, while the first flow direction control valve 7a
A pilot relief valve 19 is interposed between the tank 18 and the back pressure chamber 17 of the three-port pressure compensating valve 5 to which the load pressure of the actuator connected to acts, and when the pilot relief valve 19 is operated, the first pressure A hydraulic pressure circuit for a work vehicle, characterized in that the control section 13 is closed and the second pressure control section 15 is opened.