JPH041202B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic circuit that combines pressure oil discharged from two pumps and supplies the mixture to an actuator.

[Conventional technology]

A first control valve is provided on the discharge side of the first pump, a second control valve is provided on the discharge side of the second pump, and when the second control valve is in a neutral state, the pressure oil discharged from the second pump is transferred to the first pump. A hydraulic circuit is known in which the discharge pressure oil of the first and second pumps can be combined and supplied to the actuator by merging the discharge side and switching the first control valve.

[Problem to be solved by the invention]

With such a hydraulic circuit, in order to supply the discharge pressure oil of the first and second pumps to other actuators when pressure oil is not supplied to the actuator, it is necessary to
It is necessary to isolate the discharge side of the pump from the tank side, but if you do this, the pressure on the discharge side of the first and second pumps will increase when other actuators are not used, and the driving horsepower of the first and second pumps will be wasted. It will be consumed by.

Therefore, an object of the present invention is to provide a hydraulic circuit that can solve the above-mentioned problems.

[Means and actions to solve the problem]

An unload valve 6 is provided on the discharge side of the first pump 1, and the unload valve 6 is brought into an unload state by the discharge side pressure of the first pump acting on one port, and on-loaded by the pressure acting on the other port. When the second control valve 5 provided on the discharge side of the second pump 2 is activated, the discharge side is connected to the pilot pipe, and the first chamber is connected to the spool hole 110 of the valve body 7. 9
A spool 12 that connects and disconnects the second chamber 60 and the third chamber 59 is inserted, and the spool 12 is connected to the first chamber 9 and the second chamber 60 by the pressure of the spring 58 and the first chamber 9. communication, and the second chamber 60 and the third chamber 5
9 is set to the first position where it is shut off, and the spool 12 is connected to the third chamber 59 and the second chamber 60 by the pressure of the third chamber 59 acting on the small diameter piston 56 inserted into the spool 12. , and the second chamber 60 and the first
A shuttle valve 55 is provided with a structure in which the first chamber 9 is connected to the output side of the first control valve 3, and the second chamber 60 is connected to the output side of the first control valve 3.
is connected to the other port of the unload valve 6, and a third chamber 59 is connected to the pilot conduit 54.

As a result, when the first and second control valves are in the neutral state, the unload valve can be brought into the unload state, and when one of the control valves is in the operating state, the unload valve can be brought into the on-load state. spool 1
2 is the second position unless the difference between the pressure in the third chamber 59 and the pressure in the first chamber 9 is equal to or greater than the difference between the pressure receiving area of the spool 12 and the pressure receiving area of the piston 56 and the spring force of the spring 58. Therefore, when the first and second control valves are operated simultaneously, the output side pressure of the first control valve is supplied to the other port of the unload valve 6, and the unload valve 6 is connected to the first control valve 3. The function of the proportional control valve with pressure compensation is not hindered.

〔Example〕

Hereinafter, the present invention will be explained with reference to FIGS. 1 to 3.

In Fig. 1, 1 and 2 are the first and second pumps, and 3
1 is a first control valve for the blade, 4 is a second control valve for tilting, 5 is a third control valve, 6 is an unload valve, 17 is a main valve, and 55 is a shuttle valve. The first control valve 3 and the unload valve 6 constitute a proportional control valve A with pressure compensation.

The third control valve 5 includes a valve body 91, and the valve body 91 has a spool hole 92.
is provided in the valve body 91, and a spool hole 9 is provided in the valve body 91.
Room 23, 30, 75, 77, 53, 2 leading to 2
2, 24, and 28 are provided. A spool 19 is fitted into the spool hole 92, and spring seats 94 and 95 are provided at the ends of the spool 19 in contact with their respective shoulders.
6 is provided. The chambers 22, 24 communicate with the chamber 28 via a passage 97, in which the check valve 27 is provided.

The passage 97, the check valve 27, the chamber 77, and the chamber 30 form an operating pressure circuit section E, and the passage 97, the chamber 23, the passage 97, the chamber 24, and the chamber 53 form a pilot pressure circuit section F.

The main valve 17 includes a valve body 98, and the valve body 98 has spool holes 99, 10.
0,101 are provided.

The valve body 98 has a chamber 4 communicating with the spool hole 99.
Further, the valve body 98 is provided with chambers 32, 35 communicating with the spool hole 100, and the valve body 98 is provided with chambers 50, 73 communicating with the spool hole 101.

A spool 18 is fitted into the spool hole 99, and the spool 18 is held neutrally by springs 48 and 48' at both ends thereof. 4
7, and these form the first valve part I.

A spool 33 is fitted into the spool hole 100, and is held neutrally by a spring 38. Perforated holes 37 and 42 are formed in the spool 33, and these form a first valve portion G.

A spool 71 is inserted into the spool hole 101, and this spool 71 is held neutrally by a spring 38'.The spool 71 is also formed with drilled holes 79 and 91, which allow the second
A valve portion H is formed.

The valve body 98 is provided with shuttle valves 40 and 45.

The chamber 35 has a suction valve 140 in the chamber 51.
communicated through.

Port 40a of shuttle valve 40 communicates with chamber 102 via passage 39, port 40b of shuttle valve 40 communicates with chamber 80 via passage 90, and port 40c communicates with chamber 102 via passage 90'.
It leads to 1.

Port 45a of shuttle valve 45 communicates with chamber 103 via passage 92, another port 45b communicates with chamber 43 via passage 44, and yet another port 45c communicates with chamber 47 via passage 46. I understand. A check valve 66 is provided in the passage 104 from the chamber 65 to the chamber 49.

The shuttle valve 55 includes a valve body 7,
A spool hole 110 is provided in the valve body 7, and a plug 57 is fitted into the end of the spool hole 110. A spool 12 is provided in the spool hole 110, and a piston 56 is fitted into the end of the spool 12. The spool 12 is urged toward the plug 57 by a spring 58. The valve body 7 is provided with chambers 9, 59, 60 communicating with the spool hole 12.

The discharge side of the first pump 1 is connected to the chamber 65 of the main valve 17 via a pipe 64, and the first
The discharge side of the pump 1 is connected to the port 6a of the unload valve 6 via a branch point 63. The chamber 51 of the main valve 17 is connected to the tank 1 via piping 70.
It leads to 11. chamber 35 of main valve 17;
50 is connected to the ripper cylinder 16, which is the work machine actuator B, via pipes 36 and 68. Further, the chambers 32 and 73 of the main valve 17 are connected to the third control valve 5 through pipes 31 and 74.
It is connected to the chambers 30 and 75.

The discharge side of the second pump 2 is connected to the third pump via piping 20.
It is connected to the passage 97 of the control valve 5, and the other work machine actuator C is connected to this piping 20.
A second control valve 4 of the tilt cylinder 112 is provided. The chamber 23 of the third control valve 5 is connected to the port 6b of the unload valve 6 via the pipe 21, and the chamber 23
is connected to port 3a of first control valve 3 via piping 15.

The first control valve 3 operates the blade cylinder 113, which is another working machine actuator D. The chamber 77 of the third control valve 5 is connected to the tank 111 via a pipe 78.

The chamber 53 of the third control valve 5 is connected to the chamber 59 of the shuttle valve 55 via a pilot line 54, and the chamber 60 of the shuttle valve 55 is connected to the pilot port 6d of the unload valve 6 via a pilot line 62. It is connected to.

A throttle 11 is provided in this pilot conduit 62. A pilot line 115 branches off from the pipe 15, and this pilot line 115 is connected to a pilot port 6e of the unload valve 6.

The chamber 9 of the shuttle valve 55 is connected to the shuttle valve 10 via a pilot line 13.

Operation of the device of the embodiment When the engine is rotating and the first, second, and third control valves 3, 4, and 5 are in the neutral state as shown in FIG. Since it is in the closed state, the pilot pressure at the left end of the unload valve 6 increases, and the spring side pressure at the right end of the unload valve 6 decreases to the throttle 1.
1. It is connected to the chamber 9 through the groove 8 cut out in the spool 12 of the shuttle valve 55, and the pilot pipe 1
3 from the shuttle valve 10 to the tank 11 from the first control valve 3 through the drain passage 14.
1, the unload valve 6 is in the state shown in FIG. 2, and the first pump 1 is in the unload state at low pressure. On the other hand, the second pump 2
The discharge side is the second and third control valves 4 and 5.
The unload valve 6 is connected to the unload valve 6 through the pipe 15, but the unload valve 6 is in the communication position on the port side as shown in Fig. 2, and the second pump 2 is also in the unload state at low pressure. It is in.

Note that when the first control valve 3 and the third control valve 5 are operated simultaneously, the first control valve 3 is given priority. Therefore, the spool 12 of the shuttle valve 55 is pressed against the plug 57, and the unload valve 6 assumes a position where it can supply oil from the first and second pumps 1 and 2 to the first control valve 3. But in this case,
Since the relationship between the first control valve 3 and the main valve 17 is a parallel circuit, the pump oil flows to the side with the lighter load. In the circuit shown in FIG. 1, it is practically rare to operate the first and third control valves 3 and 5 simultaneously, and no particular consideration is given to the flow distribution in that case.

In the shuttle valve 55, the spool 12 and the piston 56 are provided with a difference in area in order to give priority to the circuit of the first control valve 3 as described above.

In other words, the pressure receiving area of the spool 12 is the piston 5
When pressure oil with the same pressure acts on chamber 9 and chamber 59, the spool 12 is in the position shown in the figure, and the pressure in chamber 59 is greater than the pressure in chamber 9, and corresponds to the area difference and spring force. , the spool 12 slides to the left to form chambers 59 and 60.
This is a position where chamber 60 and chamber 9 are communicated with each other, and chamber 60 and chamber 9 are isolated.

Therefore, even if the operator operates the third control valve 5 while finely operating the first control valve 3 and pressure oil flows from the third control valve 5 into the chamber 59 through the pilot pipe 54, the pressure receiving area difference will not be the same. The spool 12 is held at the position shown in the figure due to the biasing force of the spring force and the spring force of the spring 58, and the output side pressure of the first control valve 3 is supplied to the port 6d of the unload valve 6. The function of the first control valve 3 as a proportional control valve with pressure compensation is not inhibited, and the required flow rate can be supplied from the first control valve 3 to the blade cylinder 113.

When the spool 19 of the third control valve 5 is operated to the pulled state, the flow of the second pump 2 that has been flowing from the piping 20 from the chambers 22, 24 of the third control valve 5 through the constrictions 25, 26 of the spool 19 is reduced. At the same time, the flow pushes open the check valve 27 and flows from the chamber 28 to the spool 1.
It passes around the constriction 29 of 9 and communicates with the chamber 30. It flows from the chamber 30 through the conduit 31, from the chamber 32 of the main control valve 17, through the notch 34 of the spool 33, into the chamber 35, and at the same time flows into the bottom side of the ripper cylinder 16 through the conduit 36. The pressure on the high speed side before passing through the spool 33 is guided from a drilled hole 37 in the spool 33 through a chamber 102 of the spool 33 to a chamber 41 which is a pressure chamber at one end of the spool 18 of the main valve 17 through a passage 39 and a shuttle valve 40. It will be destroyed. On the other hand, the pressure on the low pressure side after passing through the notch 34 of the spool 33 is guided from a drilled hole 42 in the spool 33 through a chamber 43 at one end of the spool 33 to a chamber 47 which is a pressure chamber at the other end of the spool 18. . As a result, the spool 18 moves until the differential pressure between the pressure chambers 41 and 47 and the spring 48 in the chamber 47 are balanced.
Communication between chamber 49 and chamber 35 of main valve 17 is changed from closed to open. Also, the ripper cylinder 16
The chamber 50 connected to the rod side of the main valve 17 also changes its relationship with the chamber 51, which is the tank port of the main valve 17, from a closed state to an open state.

On the other hand, in response to a pull signal from the third control valve 5, the gap between the chambers 24 and 53 is changed from the closed state to the open state by the notched groove 52 cut out in the spool 19, and the pump pressure is controlled by the pilot pipe 54 to the shuttle valve. 55
acts on the piston 56 provided in the spool 12, which is held down by a plug 57,
The spool 12 is moved to the left by the spring 58,
The notch 8 that opened the chambers 60 and 9 is closed, and the chambers 59 and 60 are opened through the constriction 61 of the spool 12, leading to the spring chamber side of the unload valve 6 through the pilot pipe 62 and the throttle 11. It will be destroyed.
As a result, the pressure of the second pump 2 forces the unload valve 6, which was in the unload state shown in FIG. 2, into the on-load state shown in FIG. The chamber 6, which is the pump port of the main valve 17, passes through the pipe 64.
5, press the check valve 66 to open the chamber 49, pass through the constriction 67 of the open spool 18, merge with the flow rate of the second pump 2 in the chamber 35, and flow to the cylinder bottom side, extending the ripper cylinder 16 from the cylinder rod side. The return flow rate is returned from the pipe 68 to the chamber 50, through the constriction 69 of the spool 18 in the open state, and from the chamber 51, which is a tank port, to the tank 111 through the pipe 70.

Similarly, spool 1 of third control valve 5
The ripper cylinder 16 can also be driven to the contraction side when the lever 9 is in the push position.

In addition, in the main valve 17, if the ripper cylinder 16 is extended even when the flow rate of the chamber 35 and the first pump 1 merges with the flow rate of the second pump 2, the ripper cylinder 16 will be on the downstream side with respect to the chamber 32. ing.
Therefore, the flow rate of the first pump 1 merges with the flow rate of the second pump 2 in the chamber 35, and the pressure in the chamber 35 increases.
Increase the pressure in step 2. Because of this, the pressure difference is maintained.

Furthermore, since the differential pressure caused by the flow of oil is utilized, it is not affected by the load pressure of the ripper cylinder 15 or the direction of the load.

That is, if the extension side of the ripper cylinder 16 is the natural fall side in FIG. The cylinder 16 moves to the extension side due to the weight of the ripper, and the volume on the bottom side increases faster than the supply flow rate, and the supply flow rate to the bottom side becomes insufficient and a vacuum is generated, and the ripper cylinder 16
operates on the extension side, the flow rate from the rod side of the ripper cylinder 16 to the chamber 50 may be greater than the flow rate from the chamber 35 to the bottom side of the ripper cylinder 16.

In this case, the differential pressure is determined by the pressure before and after the notch 72 of the spool 71, that is, the pressure in the chamber 50 (upstream side) and the chamber 73 (downstream side). Shuttle valve 40 via 90
is led to the chamber 41 from the port 4c of the spool 18.
is moved downward in Figure 3, therefore,
The oil of the first pump 1 flows into the chamber 35 and enters the bottom side of the ripper cylinder 16.

At this time, when the opening area from the chamber 50 to the chamber 51 determined by the stroke of the spool 18 increases, most of the return flow from the ripper cylinder 16 passes from the chamber 50 to the chamber 51 through the constriction 69 of the spool 18. As a result, the flow rate from the chamber 50 to the chamber 73 through the notch 72 decreases, making it impossible to ensure a differential pressure across the notch 72, and the spool 18 is pushed back by the spring 47, reducing the opening area of the constricted portion 69 of the spool 18. As a result, the flow rate from the chamber 50 to the chamber 73 through the notch 72 increases, and the differential pressure across the notch 72 increases, pushing the spool 18 again, and this operation is repeated until the spool 18 is pushed. This will cause the ripper cylinder 16 to vibrate and cause hunting. However, since the lowest differential pressure between the oil chamber 41 and the oil chamber 47 of the spool 18 is secured by the differential pressure generated by the flow rate from the chamber 32 to the chamber 35 through the pipe line 31 from the second pump 2, There is no vibration of the spool 18 mentioned above and no hunting of the ripper cylinder 16.

In this way, by providing the throttles that communicate with the chambers 35 and 50 connected to the ripper cylinder 16, a stable differential pressure can be obtained over the entire stroke of the spool 18, and smooth operation of the ripper cylinder is achieved. It becomes possible.

Also, the engine stopped and the first and second pumps 1 and 2
Although it is necessary to lower the work equipment to the ground even when there is no flow rate, for example, the ripper cylinder 1
Considering the case where 6 acts on the side being pushed, the third
When the spool 19 of the control valve 5 is placed in the pulled position, the return flow rate on the rod side of the ripper cylinder 16 flows from the pipe 68 through the chamber 50 to the spool 71.
It passes through the notch 72 of the chamber 73, passes through the pipe 74 to the chamber 75 of the third control valve 5, and returns to the tank 111 through the constriction 76 of the spool 19, which is in the open state, from the chamber 77, which is the tank port, through the pipe 78. , due to the flow, the spool 71
A differential pressure is generated before and after the notch 72 of.

If the operation stroke of the spool 19 to the pulled position is small and the opening areas of the chambers 75 and 77 are small, the differential pressure across the notch 72 will be small and the spool 18 will not switch, but the spool 18 will not switch. Since the oil in the chamber 51 is sucked through the injection valve 140, the ripper cylinder 16 slowly descends.

When the operation stroke of the third control valve 5 to the pulled position of the spool 19 is large, the notch 7 of the spool 71 is
The differential pressure generated before and after increases, passing through the through hole 79 of the spool 71 on the high pressure side, passing through the chamber 80, and passing through the passage 9.
0, the low pressure side is led to the pressure chamber 41 of the spool 18 through the shuttle valve 40, and the low pressure side is connected to the drilled hole 9 of the spool 71.
1 is led to a chamber 47 which is a pressure chamber of the spool 18 via a passage 92 and a shuttle valve 45. As a result, the spool 18 is pushed downward and the chamber 50
The relationship between the cylinder head and the chamber 51 changes from closed to open, and a large amount of the return flow from the cylinder head passes through the constriction 69 of the spool 18, passes through the pipe 70 to the tank 111, returns to the tank 111, and flows between the chambers 51 and 35. are in communication via the suction valve 140, so when the ripper cylinder 16 expands due to its own weight, the chamber 51 communicating with the tank 111 supplies oil to the chamber 35 via the suction valve 140. . This allows the ripper cylinder 16 to be lowered rapidly. As described above, even when the engine is stopped, the ripper cylinder 16 can be lowered slowly by operating the spool 19 of the third control valve 5, or the ripper cylinder 16 can be lowered by switching the spool 18 of the main valve 17. It is possible to rapidly lower the machine, which is necessary for construction machinery, and it is possible to perform sudden falls of the work equipment (emergency brake when the engine stops).

〔Effect of the invention〕

When the first control valve 3 and the second control valve 5 are brought into a neutral state, pressure oil does not act on the other port of the unload valve 6, and the unload valve 6 becomes an unload state.
The pressure on the discharge side of the pumps 1 and 2 does not increase much.

Therefore, it is possible to prevent the drive horsepower of the first and second pumps 1 and 2 from being wasted when other actuators are not used.

When one of the first control valve 3 and the second control valve 5 is activated, pressure oil is supplied to the other port of the unload valve 6 via the shuttle valve 55, and the unload valve 6 becomes on-load. 1. The pressure oil discharged from the second pumps 1 and 2 can be supplied to other actuators.

When the first control valve 3 is activated, the first control valve 3 is connected to the other port of the unload valve 6.
The output side pressure of the control valve 3 is supplied, and one port of the unload valve 6 is supplied with the output side pressure of the control valve 3.
Since the discharge side pressure of the pump 1 is supplied, the unload valve 6 functions as a proportional control valve with pressure compensation, and the first control valve 3 can supply pressure oil to the actuator with pressure compensation.

The spool 12 of the shuttle valve 55 is located in the third chamber 59
The second position cannot be reached unless the pressure in the first chamber 9 becomes higher than the pressure in the first chamber 9 by a value corresponding to the pressure receiving area difference and the spring force of the spring 58. Therefore, the first and second control valves 3 and 5 must be operated simultaneously. When this happens, the output side pressure of the first control valve 3 is supplied to the other port of the unload valve 6, and the function of the proportional control valve with pressure compensation described above is not inhibited.
By finely operating the control valve 3, pressure can be compensated for the actuator and a flow rate proportional to the operation stroke can be supplied.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, with FIG. 1 being an explanatory diagram of the configuration, and FIGS. 2 and 3 being explanatory diagrams of the operation of the unload valve. 1 is a first pump, 2 is a second pump, 5 is a control valve, 5 is a second control valve,
6 is an unload valve, and 54 is a pilot pipe.

Claims (1)

[Scope of Claims] 1. A first control valve 3 is provided on the discharge side of the first pump 1, and has a neutral state in which the discharge side and the tank side are cut off, and an operating state in which the discharge side is connected to an actuator, A neutral state in which the discharge side of the second pump 2 is connected to the discharge side of the first pump 1, and an operating state in which the discharge side is connected to the pressure oil supply side chambers 30, 75 and the pilot pipe 54. A second control valve 5 is provided on the discharge side of the first pump 1, and an unloading state is provided on the discharge side of the first pump 1, in which the pressure acting on one port causes an unloading state, and the pressure acting on the other port causes an onloading state. A valve 6 is provided, one port of the unload valve 6 is connected to the discharge side of the first pump 1, and the other port is connected to the outlet side of the first control valve 3 and the pilot via a shuttle valve 55. The shuttle valve 55 is connected to the pipe line 54, and the shuttle valve 55 is connected to the spool hole 1 of the valve body 7.
10, a first chamber 9, a second chamber 60 and a third chamber 59
A spool 12 is inserted into the spool 12 that connects and blocks communication between the first chamber 9 and the second chamber 60 using the spring 58 and the pressure of the first chamber 9. a first position for blocking the chamber 59;
The pressure of the third chamber 59 acting on the small diameter piston 56 inserted into the spool 12 causes the spool 12 to
is a second position that communicates the third chamber 59 and the second chamber 60 and blocks the second chamber 60 and the first chamber 9, and the first chamber 9 is connected to the first chamber 9. A hydraulic circuit connected to the output side of the control valve 3, a second chamber 60 connected to the other port of the unload valve 6, and a third chamber 59 connected to the pilot conduit 54. .