JPH0777203A - Pressure oil supply device - Google Patents

Abstract

PURPOSE:To reduce a speed drop at the time of turning in the case where an engine for driving a hydraulic pump for supplying pressure oil to right and left travelling hydraulic motors drives an auxiliary hydraulic pump to operate a blade. CONSTITUTION:Discharged pressure oil from a hydraulic pump 20 is supplied from check valve parts 23 and pressure reducing valve parts 24 to right and left travelling hydraulic motors 88-1, 88-2 by pressure-compensated valves 25 and directional control valves 22. An auxiliary hydraulic pump 1 is driven by an engine for driving the hydraulic pump 20, and the discharged pressurized oil of the auxiliary hydraulic pump expands and contracts a blade cylinder 3 to operate a blade 4. The discharge path 5 of the auxiliary hydraulic pump 1 is communicated respectively with the ports 44 of the right and left directional control valves 22 through pipe-lines 8 having check valves 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure oil supply device for supplying discharge hydraulic oil from one hydraulic pump to left and right traveling hydraulic motors and supplying discharge hydraulic oil from an auxiliary hydraulic pump to a blade cylinder.

[0002]

2. Description of the Related Art As a pressure oil supply device for supplying pressure oil discharged from one hydraulic pump to a plurality of actuators, for example, one shown in FIG. 1 is known. As shown in FIG. 1, such a pressure oil supply device is provided with a plurality of directional control valves 22 in a discharge passage 21 of a hydraulic pump 20, and a check valve portion 23 and a pressure reducing valve portion 24 are provided on the inlet side of each directional control valve 22. Each of which is provided with a pressure compensating valve 25.
The pressure compensating valve 25 is constructed as shown in FIG.

That is, as shown in FIG. 2, the valve block 30 has a substantially rectangular parallelepiped shape, and a spool hole 31 is formed in the left and right side surfaces 32 and 33 near the upper portion of the valve block 30, and the spool 31 is opened. The first and second actuator ports 34 and 35 are formed so as to open in the upper surface 36, and a check valve hole 37 opened in the left side surface 32 and a pressure reducing opening in the right side surface 33 are formed near the lower part of the valve block 30. The valve hole 38 is formed concentrically, the first port 39 opening to the check valve hole 37 is formed to open on the front and rear surfaces, and the second and third ports 42 opening to the pressure reducing valve hole 38. , 43 are formed with openings in the front and rear surfaces, and when the front and rear surfaces of the plurality of valve blocks 30 are butted and connected to each other,
The second and third ports 39, 42, 43 communicate with each other.

The valve block 30 has a pump port 44 opened in the spool hole 31, first and second load pressure detection ports 45 and 46, and first and second actuator ports 3
4, 35, first and second tank ports 47 and 48 are formed, and first and second small diameter portions 50 and 51 and a communication groove 52 are formed in the main spool 49 fitted in the spool hole 31. Yes, the main spool 49 has a first oil passage 53 that constantly connects the first and second load pressure detection ports 45 and 46, and a second oil that connects and disconnects the second load pressure detection port 46 and the second tank port 48. The passage 54 is formed, the spool 49 blocks each port with a spring, and is held in the neutral position where the second load pressure detection port 46 and the second tank port 48 communicate with each other by the second oil passage 54. Sliding on the second small diameter portion 51 communicates the second actuator port 35 with the second tank port 48, the communication groove 52 allows the pump port 44 to communicate with the second load pressure detection port 46, and the first small diameter portion 50. With the first actuator Over door 34 is the first load pressure detection port 4
When the spool 49 slides leftward, the first small diameter portion 50 causes the first actuator port 34 to communicate with the first actuator port 34. To the first tank port 47, the communication groove 52 connects the pump port 44 to the first load pressure detection port 45, and the second small diameter portion 51 connects the second actuator port 35 to the second load pressure detection port 46. Communication,
And the second load pressure detection port 46 and the second tank port 48
The directional control valve 22 is configured to be the second pressure oil supply position where it is shut off.

The check valve hole 37 is opened to the pump port 44 by the oil passage 56, and the check valve hole 37 is fitted with a valve 60 for shutting off the communication between the first port 39 and the pump port 44. The valve 60 is restricted by a stopper rod 62 provided on the plug 61 so as not to slide to the left from the illustrated position, and is held at the cutoff position to form the check valve portion 23. The pressure reducing valve hole 38 is provided with the fourth port 57 and the oil passage 5.
8 communicates with the second load pressure detection port 46, and the pressure reducing valve hole 38 is fitted with the spool 64 to form a first pressure chamber 65 and a second pressure chamber 66. The second pressure chamber 66 communicates with the third port 43, and the spring 69 is provided between the free piston 68 inserted into the blind hole 67 of the spool 64 and the bottom portion of the blind hole 67. The piston 68 abuts on the plug 70, and the pushing rod 71 integrally provided on the spool 64 projects from the through hole 72 to abut the valve 60 on the stopper rod 62. The spool 64 has a second port 42. The pressure reducing valve portion 24 and the check valve portion 23 form a pressure compensating valve 25 by forming a fine hole 73 communicating with the blind hole 67.

As shown in FIG. 1, the hydraulic pump 20
The discharge passage 21 of the first port 39 and the second port 42, and the load pressure detection passage 82 is connected to the third port 43.
-The actuator 88 is connected to the second actuator ports 34 and 35. In FIG. 2, 83 is a swash plate that controls the discharge flow rate of the hydraulic pump 80, 84 is a servo cylinder, and 85 is a directional control valve for pump adjustment.

Next, the operation will be described with reference to FIG. When the directional control valve 22 is in the neutral position A. The oil sucked up from the tank 86 by the hydraulic pump 20 is guided through the discharge passage 21 to the pressure chamber a in the opening direction of the check valve portion 23. At this time, since the pressure chambers 65 and 66 of the pressure reducing valve portion 24 are both communicated with the tank 86, the pressures of the pressure chambers 65 and 66 are both zero, so the pressure reducing valve portion 24 is pushed by the weak spring 69. The rod 71 is only in contact with the check valve portion 23. On the other hand, the pump discharge pressure is kept constant by the spring 87 of the pump adjustment directional control valve 85, which has a differential pressure from the pressure of the load pressure detection path 82. Now, assuming that this differential pressure is 20 kg / cm ² , the pressure in the load pressure detection path 82 is zero, so the pump discharge pressure is 2
The stroke is increased to 0 kg / cm ² and at the same time, the pump discharge pressure flows into the pressure chamber a of the check valve unit 23 and the inlet pressure of the directional control valve 22 (the outlet pressure of the check valve unit 63) becomes equal to the pump discharge pressure. And if equal, weak spring 6
Receipt by 9. The pressure reducing valve portion 24 connects the pump discharge passage 81 and the pressure chamber 66 only at the stroke end, while the check valve portion 23 connects the pump discharge passage 81 and the outlet side before reaching the stroke end. When the control valve 22 is in the neutral position A, the pump discharge passage 21 and the pressure chamber 66 do not communicate with each other, and the pressure chamber 65
The pressure remains at zero.

Only one of the directional control valves 22 has a first
When making a stroke to the pressure oil supply position B. Now, the left direction control valve 22 is stroked to the first pressure oil supply position B, and the right direction control valve 22 is set to the neutral position A. Stroke the direction control valve 22 to pump port 4
4 and the first actuator port 34 are connected, and at the same time, the second actuator 35 and the second tank port 48 are connected. At this time, when the pressure (load pressure) in the conduit 89 connecting the first actuator port 34 and the actuator 88 is higher than the pump discharge pressure (20 kg / cm ² ), the check valve portion 23 receives the pressure in the pressure chamber b. It is possible to prevent the actuator 88 from naturally descending. The pressure of the conduit 89 of the actuator 88, that is, the load pressure, is introduced into the pressure chamber 65 of the pressure reducing valve portion 24 from the first oil passage 53 and the passage 58. Since the pressure in the other pressure chamber 66 is zero, the pressure reducing valve unit 24 is
Strokes in the direction of disengagement from the stroke end to the stroke end, and the pump discharge passage 21 and the load pressure detection passage 82 communicate with each other via the throttle of the pressure reducing valve portion 24. When the pressure (load pressure) in the conduit 89 is higher than the pump discharge pressure (= 20 kg / cm ² ), the pressure is closed by the pressure in the pressure chamber b of the check valve portion 23, and the pressure is one of the pressure reducing valve portions 24. Since it is guided to the pressure chamber 65, even if the other pressure chamber 66 and the pump discharge passage 21 communicate with each other, the pressure reducing valve portion 24 remains stroked.
On the other hand, the pressure (load pressure) in the conduit 41 is equal to the pump discharge pressure (=
When the pressure is less than 20 kg / cm ² ), the load pressure is guided to one pressure chamber 65 of the pressure reducing valve section 24, and
Strokes with the pressure of one pressure chamber 65, but when the pressure of the other pressure chamber 66 rises to the pressure of one pressure chamber 65 (that is, the load pressure), the weak spring 69 closes the check valve portion 23. In any case, the pressure reducing valve section 24 is configured to change the pressure in the pressure chamber 65 on one side and the pressure chamber 6 on the other side.
The pump discharge passage 21 and the pressure chamber 66 are made to communicate with each other until the pressures in 6 become equal, and when the pressures in both pressure chambers 65, 66 become equal, they are closed by the weak spring 69 and contact the check valve portion 23. As a result, the pressure in the load pressure detection path 82 becomes equal to the load pressure, and the pump discharge pressure is adjusted to a certain differential pressure (here, 20 kg / c by the pump adjustment directional control valve 85).
The pressure is controlled to be higher than the pressure in the load pressure detection path 82 by m ² ). This pump discharge pressure is determined by the check valve 23
Since it is guided to the pump port 44 via the, that is, the differential pressure (= 20 kg / cm ² ) is maintained between the inlet pressure and the outlet pressure (= load pressure) of the directional control valve 22. become. Therefore, the flow rate supplied to the actuator 88 is controlled only by the change in the opening area of the throttle between the inlet side and the outlet side due to the stroke of the directional control valve 22. When the directional control valve 22 is stroked, the conduit 89 or 90 of the actuator 88 and a second load pressure introducing second
The oil passage 53 is connected, while the second oil passage 53 is connected to one pressure chamber 65 of the pressure reducing valve portion 24. However, in the pressure reducing valve portion 24, the load pressure is the pilot pressure (setting of the pressure reducing valve portion). Since the pressure is not used, the pressure is not lost, that is, when the directional control valve 22 is stroked, the load pressure is removed and the actuator 88
There is no natural descent.

The load pressure detecting path 82 is provided in the other directional control valve 22 and the pressure reducing valve portion 2 of the pressure compensating valve 25 is arranged.
4 is also connected to the other pressure chamber 66, but one pressure chamber 65 of the pressure reducing valve portion 24 is connected to the tank 86 by the neutral position A of the directional control valve 22, and therefore is used for introducing load pressure. The pressure in the first oil passage 53 is zero, so the pressure chamber 66
The pressure reducing valve portion 24 urges the pressure reducing valve portion 24 in a direction to close the check valve portion 23. On the other hand, since the pump discharge pressure is guided from the pump discharge passage 81 to the pressure chamber a in the direction of opening the check valve portion 24, the difference between the pump discharge pressure and the pressure in the load pressure detection passage 82 (= 20 kg / cm ² ), the check valve portion 23 and the pressure reducing valve portion 24 are stroked in the opening direction of the check valve portion 23, but they are slightly stroked so that the pressure at the pump port 44 is equal to the differential pressure (= 20 k).
g / cm ² ), the weak spring 69 causes a receipt, and as a result, the pressure reducing valve section 24 does not stroke to the stroke end, and there is no influence on the hydraulic control of the directional control valve 22 side. .

When any of the directional control valves 22 is stroked to the first pressure oil supply position B. -When the total flow rate required for each actuator 88 is at the maximum discharge flow rate position of the hydraulic pump 20. Now, it is assumed that the directional control valve 22 is both stroked to the first pressure oil supply position B, and the pump ports 44, the conduits 89, and the first oil passages 53 for guiding the load pressure are connected to each other.
One of the pressure reducing valve portions 24 has the pressure in the pressure chamber 66 equal to the pressure in one of the pressure chambers 65, and the other pressure reducing valve portion 24 has the pressure in the pressure chamber 66 of the one pressure chamber 65. Each stroke remains to the stroke end until it becomes equal to the internal pressure. Now, assume that the load pressure of the left actuator 88 is larger than the load pressure of the two actuators 88, 88. It is assumed that the load pressure of the left actuator 26 is 100 (kg / cm ² ) and the load pressure of the right actuator 27 is 10 (kg / cm ² ). The load pressure detection path 82 is connected to the tank 8 via the throttle 91.
6, the pressure in the load pressure detection path 82 is zero before the stroke of the directional control valve. Therefore, each pressure reducing valve section 24 also strokes by the pressure in the first oil passage 53 for detecting the load pressure, and the pump discharge pressure communicates with the pressure in the pressure detecting conduit 34. When the pressure in the load pressure detection path 82 rises to the pressure (10 kg / cm ² ) in the conduit 90 of the actuator 88 on the right side which is the low pressure side, first, the pressure reducing valve portion 24 of the pressure compensating valve 25 on the right side is closed. The pressure reducing valve portion 24 of the pressure compensating valve 25 on the left side remains stroked, and the pressure in the load pressure detection path 82 is the pump discharge pressure (20 kg / c).
m ² ). At this time, the pressure of the pump port 44 of the direction control valve 55 of the left side actuator 88 on the high pressure side is 100 (kg / cm ² ), the check valve portion 23 of the pressure compensation valve 25 is closed, and the pressure reducing valve portion 24 is closed. Is dissociated from. On the other hand, the pressure reducing valve portion 24 of the pressure compensating valve 25 is provided with a pressure difference (20) between the two pressure chambers 65 and 66.
The check valve portion 23 is urged in the closing direction at −10 = 10 kg / cm ² ). On the other hand, the pressure in the pressure chamber a in the opening direction of the check valve portion 23 (pump discharge pressure) is 20 (kg / c
m ² ), the check valve portion 23 is opened until the pressure of the pump port 44 of the directional control valve 22 becomes 10 (kg / cm ² ), and then a receipt is made by the weak spring 69. By a pump adjusting direction control valve 85, there differential pressure (20kg / cm ²⁾ amount corresponding, pump discharge pressure from the high pressure pressure (20kg / cm ²⁾ of the load pressure Detchi 82 is controlled (40 kg / cm ² ). At this time as well, the check valve portion 23 of the high-pressure side pressure compensating valve 25 remains closed and the pressure reducing valve portion 24 remains in the stroke, and the load pressure detection path 82
The internal pressure is 40 (kg / cm ² ), while the pressure reducing valve portion 24 of the pressure compensating valve 25 on the low pressure side has the load pressure detecting path 82.
And the pressure difference in the first oil passage 53 for introducing the load pressure (= 30 kg
/ Cm ² ) urges the check valve portion 23 in the closing direction,
As a result, the pressure at the pump port 44 of the directional control valve 22 remains at 10 kg / cm ² . In this way, the pressure in the load pressure detection path 82 and the pump discharge pressure continue to rise, and when the pump discharge pressure eventually becomes equal to the load pressure (100 kg / cm ² ) of the high-pressure side actuator 88, the high-pressure side pressure compensation is performed. Two pressure chambers 65 and 66 of the pressure reducing valve portion 23 of the valve 25
The internal pressures are both 100 kg / cm ² , and the weak spring 69 makes contact with the closing check valve portion 23. At this time, the pressure reducing valve portion 24 of the pressure compensating valve 25 on the low pressure side has a pressure difference (1) between the load pressure detecting passage 82 and the first oil passage 53 for introducing the load pressure.
00-10 = 90 kg / cm ² ) to urge the check valve portion 23 in the closing direction, and as a result, the directional control valve 2 on the low pressure side
The pressure at the second pump port 44 remains at 10 kg / cm ² . Again, by the directional control valve 85 for pump adjustment,
The pump discharge pressure is controlled to 120 (kg / cm ² ).
At this time, the pressure reducing valve portion 23 of the pressure compensating valve 25 on the high pressure side is only in contact with the check valve portion 23 by the weak spring 69, and due to the pressure difference between the two pressure chambers a and b of the check valve portion 23, For the first time, the check valve section 23 opens,
The pump discharge pressure (120 kg / cm ² ) depends on the direction control valve 22.
Of the pump port 44. On the other hand, the pressure reducing valve portion 24 of the pressure compensating valve 25 on the low pressure side has a pressure difference (= 90 kg / cm ² ) between the load pressure detecting passage 82 and the first oil passage 53 for introducing the load pressure.
Continue to urge the check valve unit 23 in the direction to close in minutes,
The pressure in the pressure chamber a in the opening direction of the check valve portion 23 is 12
Since it has become 0 (kg / cm ² ), the pressure of the inlet port 44 of the directional control valve 22 is 30 (kg / cm ² ) (120-9
0), the check valve portion 23 and the pressure reducing valve portion 24
Balances pressure. That is, the check valve portion 23 and the pressure reducing valve portion 24 make a slight stroke, and the check valve portion 2
3 to 120 kg / cm ² to 30 kg / cm ²
It will be in a state where it is squeezed so that it becomes. For the first time, the hydraulic control system is balanced so that the pressure of the pump port 44 of the directional control valve 22 on the high pressure side is 120 kg / cm ² and the pressure of the pump port 44 of the directional control valve 22 on the low pressure side is 30 kg / cm ² .
cm ² , that is, the two directional control valves 22, 22
The difference between the inlet pressure and the outlet pressure (load pressure) of both is 20 kg /
By being kept at cm ² , the two directional control valves 22,
22 is only for the stroke and actuator 8
It becomes possible to control the flow rate supplied to 8,88.

The total flow rate required for each actuator 88, 88 is greater than the maximum discharge flow rate of the hydraulic pump 80. Now, the load pressure and the required flow rate of the actuators 88, 88 are 100 kg / cm ² for the left actuator 88,
501 / min, the right actuator 88 is 10 kg
/ Cm ² , 501 / min. When the maximum discharge flow rate of the hydraulic pump 80 is 1001 / min or more, as described above, the difference between the inlet pressure and the outlet pressure of the directional control valves 22, 22 is kept constant (= 20 kg / cm ² ), so that the stroke The flow rate can be controlled by, and the flow rate can be distributed by 501 / min. Next, assume that the stay discharge amount of the hydraulic pump 80 becomes 701 / min. Two directional control valves 2
The inlet pressure of 2, 22 is 120 kg / cm ² , 3 as described above.
Since it is 0 kg / cm ² , the flow rate to the directional control valve 22 on the high pressure side is reduced from 501 / min to 201 / min. The flow rate to the low-pressure side directional control valve 22 remains at 501 / min. If the strokes (opening areas) of the two directional control valves 22 and 22 are not changed, the pressure difference between the inlet pressure and the outlet pressure of the directional control valve 22 on the high-pressure side is reduced by 20 k
Down from g / cm ² . Now the differential pressure is 14kg / c
m ² , that is, the inlet pressure is 120 kg / cm ² to 1
Suppose it has fallen to 14 (100 + 14) kg / cm ² .
At this time, the two pressure chambers 6 of the pressure reducing valve portion 24 of the pressure compensating valve 25
Since the pressures of 5 and 66 are still 100 kg / cm ² , the pressure reducing valve portion 24 is only in contact with the check valve portion 23 by the weak spring 69, and the check valve portion 2
The pressure in the pressure chamber b in the closing direction of 3 is 120 kg / cm
If the pressure is reduced from ² to 114 kg / cm ² , the pressure in the pressure chamber a in the opening direction of the check valve portion 23, that is, the pump discharge pressure is 120 kg / cm ² while the check valve portion 23 remains open (stroke end). To 114 kg / cm ²
Decrease to. At this time (when the pump discharge flow rate is insufficient), the pump discharge pressure is not controlled by the pump adjustment directional control valve 85. On the other hand, the pressure reducing valve portion 24 of the pressure compensating valve 25 on the low pressure side
The two pressure chambers 65 and 66 are 100 kg / cm ² , 1
While maintaining 0 kg / cm ² , the pressure difference of 90 kg / cm ² continues to urge the check valve portion 63 in the closing direction. on the other hand,
Since the pressure in the pressure chamber a in the opening direction of the check valve portion 23, that is, the pump discharge pressure is reduced to 114 kg / cm ² , the pressure in the pressure chamber b in the closing direction of the check valve portion 23 is 30 kg / cm ² to 24 kg. The pressure is balanced by the check valve portion 23 and the pressure reducing valve portion 24 in the state where the pressure is reduced to / cm ² . Therefore, the differential pressure between the inlet pressure and the outlet pressure of the directional control valve 22 on the low pressure side is 20 kg / cm ² to 14 kg / cm ² (2
4-10). Due to the decrease in the differential pressure of the directional control valve 22, the supply flow rate to the low-pressure side actuator 88 is 5
The flow rate decreases from 01 / min, and the supply flow rate to the high-pressure side actuator 88 increases from 201 / min. That is, in a state in which the differential pressure between the inlet pressure and the outlet pressure of the directional control valves 22 and 22 is equal, and the supply amounts to the two actuators 88, 88 are both divided into 351 / min,
This hydraulic control system is in balance.

When the number of actuators loaded by one hydraulic pump 80 is three or more. Even when there are three or more actuators, the same check valve section 23 and pressure reducing valve section 24 are provided between the directional control valve and the hydraulic pump.
Even if there are three or more actuators, the operation according to the above-described operation principle can be achieved simply by disposing the pressure compensating valve 25 provided with, and communicating all the pressure differences in the closing direction of each pressure reducing valve section by the load pressure detecting path 82. Will be realized.

[0013]

With such a pressure oil supply device, as shown in FIG.
The discharge pressure oil of the hydraulic pump 20 is supplied to 88-2, the auxiliary hydraulic pump 1 is driven by the engine E that drives the hydraulic pump 20, and the discharge pressure oil is supplied to the blade cylinder 3 by the blade direction control valve 2. Then, when the blade 4 is operated, the following problems occur.

When the left and right direction control valve 22 is operated with the same stroke to drive the left and right traveling hydraulic motors 88-1 and 88-2 at the same number of revolutions to travel straight, the traveling resistance is small and the load pressure is low, so the hydraulic pump. Since the discharge pressure of 20 is low and the absorption horsepower has a margin, the vehicle can travel at a predetermined traveling speed even if the absorption horsepower of the hydraulic pump 20 is reduced by the driving horsepower of the auxiliary hydraulic pump 1.

However, the left and right traveling hydraulic motors 88-1 and 88-1 are operated by operating the left and right direction control valve 22 with different strokes.
Since the load pressure of the traveling hydraulic motor 88-1 on the inner side of the swing is high and the swing traveling resistance is large during the swing traveling in which the 88-2 is driven to rotate at different speeds, the discharge pressure of the hydraulic pump 20 is high and the discharge amount is large. It decreases and the turning traveling speed becomes lower than the straight traveling speed.

That is, the hydraulic pump 20 is controlled so that the discharge amount × the discharge pressure (absorption horsepower) becomes constant, and the discharge amount of the hydraulic pump 20 during the above-described turning traveling is the left and right traveling hydraulic motors 88-1, 88-. The flow rate corresponds to the higher load pressure in 2, and the vehicle travels at a turning speed corresponding to the flow rate.

However, when the auxiliary hydraulic pump 1 is driven by the engine E which drives the hydraulic pump 20, a part of the horsepower of the engine E is consumed by the auxiliary hydraulic pump 1 and the absorbed horsepower of the hydraulic pump 20 is equal to that horsepower. Therefore, even if the higher load pressures of the left and right traveling hydraulic motors 88-1 and 88-2 are the same, that is, even if the turning traveling resistance is the same, the discharge amount of the hydraulic pump is reduced and the turning traveling speed is reduced. Will become bigger.

Therefore, an object of the present invention is to provide a pressure oil supply device capable of solving the above problems.

[0019]

[Means for Solving the Problems] A pump port 44 opened in a spool hole 31 in a valve block 30, first and second load pressure detection ports 45 and 46, first and second actuator ports 34 and 35, and first and second actuator ports 34 and 35, respectively. The second tank ports 47 and 48 are formed, and the main spool 49 that connects and disconnects the respective ports is fitted into the spool hole 31 to form the directional control valve 22, and the valve block 30 is opened to the check valve hole 37. 1 port 39 and check valve hole 37 to pump port 4
4, an oil passage 56 communicating with the check valve hole 3 is formed.
7, a spool 60 that connects and disconnects the first port 39 and the oil passage 56 and that is stopped at the cut-off position is inserted into the check valve portion 23, and the valve block 30 includes the pressure reducing valve hole 3
8, second and third ports 42 and 43 are formed, and a spool 64 is inserted into the pressure reducing valve hole 38 to form a first pressure chamber 65 and a second pressure chamber 66. 65 communicates with the second load pressure detection port 64, communicates the second pressure chamber 66 with the third port 43, and connects the spool 64 with the spring 69.
Is urged in one direction by the spool 6 of the check valve portion 23.
0 is pressed to the shut-off position and held to form the pressure reducing valve section 24. The pressure reducing valve section 24 and the check valve section 23 make the pressure compensating valve 2
5, the pair of pressure compensating valves 25 and the pair of directional control valves 22 are provided in the discharge passage 21 of the hydraulic pump 20 so that the discharge pressure oil of the hydraulic pump 20 is moved to the left and right traveling hydraulic motors 88-1 and 88.
-2, and the auxiliary hydraulic pump 1 is driven by the engine E that drives the hydraulic pump 20, and the discharge passage 5 is connected to the blade cylinder 3 by the blade direction control valve 2, and the discharge passage of the auxiliary hydraulic pump 1 is connected. A pressure oil supply device in which 5 is connected to a pump port 44 of the pair of directional control valves 22 via a check valve 9.

[0020]

[Operation] Since a part of the pressure oil discharged from the auxiliary hydraulic pump 1 can be supported by the left and right traveling hydraulic motors 88-1 and 88-2 from the pump port 44 of the left and right direction control valve 22 during turning traveling, The decrease in speed can be reduced.

[0021]

[Example] As shown in FIG. 4, the upstream side of the check valve 7 connected to the pump port 6 of the blade directional control valve 2 in the discharge passage 5 of the auxiliary hydraulic pump 1 is pressure-compensated to the left and right via the pipe line 8. The oil passage 65 of the valve 25, that is, the pump ports 44 of the left and right direction control valves 22 are respectively connected, and the check valves 9 are provided in the pipe lines 8.

Next, the operation will be described. Left and right directional control valve 2
At the same time, the two strokes are simultaneously switched to the same stroke to supply the hydraulic oil discharged from the hydraulic pump 20 to the left and right traveling hydraulic motors 88-1 and 88-2 to travel straight. The discharge amount of the hydraulic pump 20 becomes a flow rate commensurate with the load pressure detected by the load pressure detection path 82, and since the load pressure is low, the discharge amount is large,
The supply amount to the left and right traveling hydraulic motors 88-1 and 88-2 is determined by the opening amount of the cutout 52 of the spool 49 of the left and right direction control valve 22, that is, the meter-in opening area of the direction control valve 22. For this reason, even if the discharge pressure of the hydraulic pump 20 due to the running resistance is lower than the discharge pressure of the auxiliary hydraulic pump 1 due to the resistance of the drain circuit of the auxiliary hydraulic pump 1, the hydraulic pump 20 is equal to or more than the oil amount determined by the meter-in opening area. Is not discharged, the traveling speed is the same as when there is no auxiliary hydraulic pump 1.

At the time of turning traveling in which the left and right direction control valve 22 is simultaneously switched to different strokes to supply the pressure oil discharged from the hydraulic pump 20 to the left and right traveling hydraulic motors 88-1 and 88-2. The discharge amount of the hydraulic pump 20 decreases as the turning traveling resistance increases and the load pressure increases. Assuming that the discharge amount during straight running is (Q-1) and the discharge amount during turning is (Q-2), it decreases by (Q-1)-(Q-2) / (Q-1) x 100%. To do.

Moreover, since the engine horsepower absorbed by the hydraulic pump 20 for driving the auxiliary hydraulic pump 1 is reduced by the amount of the driving horsepower of the auxiliary hydraulic pump 1, the discharge amount of the hydraulic pump 20 at the time of turning traveling is the engine. Compared with the case where only the hydraulic pump 20 is driven by E, the amount is reduced more.

However, the discharge pressure of the auxiliary hydraulic pump 1 rises by the amount of the circuit resistance, and the discharge amount of the auxiliary hydraulic pump 1 is increased from the pipe 8 to the pump port 44 of the left / right direction control valve 22.
Flows in as a support flow rate (Q-3).

For this reason, the left and right traveling hydraulic motor 88-
1, 88-2 has a flow rate of (Q-2) + (Q-3) in the meter-in opening area A ₁ of the directional control valve 22 on the inside of the turn and the meter-in opening area A ₂ of the directional control valve 22 on the outside of the turn, respectively. It is supplied after being distributed comparatively. Therefore, the reduction amount of the turning traveling degree is (Q-1)-(Q-2) + (Q-3) / (Q-1) * 1.
It becomes 00%, and the reduction amount of the turning traveling degree is improved by (Q-3) / (Q-1).

FIG. 5 shows a second embodiment, in which a back pressure compensating valve 11 is provided in the drain circuit 10 of the blade direction control valve 2, and the upstream side of the back pressure compensating valve 11 is connected to the right and left direction control valve 2 by a pipe line 8.
It is connected to two pump ports 44. In this way, the pressure in the conduit 8 is increased, so that the support flow rate to the left and right traveling hydraulic motors 88-1 and 88-2 can be increased.

FIG. 6 shows a third embodiment, in which a discharge passage 5 of the auxiliary hydraulic pump 1 is provided with a throttle 12, and the upstream side of the throttle 12 is connected to a pump port 44 of the left / right direction control valve 22 by a pipe line 8. There is. In this way, the pressure in the conduit 8 is increased, so that the support flow rate to the left and right traveling hydraulic motors 88-1 and 88-2 can be increased.

The pressure compensating valve 25 shown in the above first, second and third embodiments is constructed as shown in FIG. That is,
The spool 64 blocks the third port 43 and the second pressure chamber 66 of the pressure reducing valve portion 24, and the spool 64 has a slit-shaped opening 100 for communicating and blocking the third port 43 and the second port 42.
Formed on the outer peripheral surface of the load pressure detecting path 82 on the third port 43.
Connect. The blind hole 67 of the spool 64 has a stepped shape,
The seat 68 has a shape having a blind hole 68a and an annular recess 68b, the seat 68 is fixed by abutting against the outward step 67a of the blind hole 67, and a spring 69 is provided between the seat 68 and the plug 70. The check valve 101 is pressed against the opening peripheral edge of the blind hole 68a of the seat 68 with the spring 102, and the blind hole 68a is opened.
a pressure chamber 103 is formed between a and the check valve 101,
The pressure chamber 103 is communicated with the second pressure chamber 66 by the first throttle 104, and is communicated with the annular recess 68b by the second throttle 105, and the annular recess 68b is opened by the throttle 106 of the spool 64 to the third port 43. , Check valve 101 spring chamber 1
07 is opened to the second port 42 by the diaphragm 108. In the first pressure chamber 65, the notch 109 of the spool 64 and the fine hole 11 are formed.
At 0, communication is established between the seat 68 and the check valve 101.

With such a pressure compensating valve 25, when the main spool of the left / right direction control valve 22 is operated in the same stroke, the main spool 49 of the right direction control valve 22 is slid rightward toward the neutral position. Since the opening areas of the second load pressure detection port 46 and the second actuator port 35 are small, the flow rate flowing to one of the right traveling hydraulic motors 88-2 is reduced. As a result, the right traveling hydraulic motor 88
-2 decreases and the pressure in the first pressure chamber 65 of the pressure reducing valve section 24 on the right side decreases, and the spool 64 of the spool 64 on the left side is supplied to the second pressure chamber 66 by the load pressure detection path 82. Since the second port 42 and the first pressure chamber 65 are not communicated with each other by the cutout groove 109 because they are pushed leftward by the load pressure (that is, control pressure) in the second pressure chamber 66, if the load pressures on the left and right sides are the same pressure. Instead, the load pressure of the traveling hydraulic motor 88-2 is low, and the load pressure of the left traveling hydraulic motor 88-1 is high, so that the vehicle turns right. At this time, the check valve 1 of the pressure reducing valve section 24 on the right side
In the spring chamber 102 of 01, the passage 115, the second port 42,
The load pressure of the left traveling hydraulic motor, which is the actuator 88 on the left side of the throttle 108, is introduced and acts on the left side surface of the check valve 101. On the other hand, the control pressure acts on the right side surface of the check valve 101 from the load pressure detection path 82, the third port 43, the throttle 106 of the spool 64, and the second throttle 105.
Since this control pressure is substantially equal to the load pressure of the left traveling hydraulic motor that is the left actuator 88, the check valve 101
Is pressed against the sheet 68.

Further, as shown in FIG. 7, the spool 60 of the check valve portion 23 of the pressure compensating valve 25 in the above-mentioned first, second and third embodiments has a first port 39 and a pump port 44, as shown in FIG.
Forming a small diameter part 150 for communicating and blocking the spool 60
To the right to partition the pressure chamber 151 and the first port 39,
Damper diaphragm 152 formed on the spool 60 and the communication hole 1
53 communicates with the first port 39. As a result, when the spool 60 slides to the right and left, pressure oil flows between the first port 39 and the pressure chamber 151 through the damper throttle 152, so that the spool 60 suddenly moves to the left and right. It is possible to prevent sliding.

The pressure compensating valve 25 shown in the first, second and third embodiments may be the one shown in FIG. Further, the pressure compensating valve 25 and the direction control valve 22 may be provided in different valve blocks and each port may be connected by piping.

[0033]

[Effects of the Invention] Since a part of the hydraulic fluid discharged from the auxiliary hydraulic pump 1 can be supported by the left and right traveling hydraulic motors 88-1 and 88-2 from the pump port 44 of the left and right direction control valve 22 during the turning traveling, The decrease in speed can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a conventional pressure oil supply device.

FIG. 2 is a sectional view showing a specific example of a pressure compensation valve and a direction control valve.

FIG. 3 is a diagram illustrating a conventional defect.

FIG. 4 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a third embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a specific example of a pressure compensation valve according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Auxiliary hydraulic pump, 2 ... Blade direction control valve, 3 ... Blade cylinder, 4 ... Blade, 5 ... Discharge passage, 8 ... Pipe line, 9 ... Check valve, 20 ... Hydraulic pump, 21 ... Discharge passage, 22 ... Direction Control valve, 23 ... Check valve section, 24 ... Pressure reducing valve section, 25 ... Pressure compensation valve, 30 ... Valve block, 31 ...
Spool hole, 34 ... First actuator port, 35 ...
2nd actuator port, 37 ... Check valve hole, 3
8 ... Pressure reducing valve hole, 39 ... First port, 42 ... Second port, 43 ... Third port, 44 ... Pump port, 45 ... First load pressure detection port, 46 ... Second load pressure detection port, 4
7 ... 1st tank port, 48 ... 2nd tank port, 49
... Main spool, 53 ... First oil passage, 54 ... Second oil passage, 56
... Oil hole, 58 ... Oil hole, 60 ... Spool, 64 ... Spool, 65 ... First pressure chamber, 66 ... Second pressure chamber, 69 ... Spring, 82 ... Load pressure detection path, 88-1 ... Left traveling hydraulic pressure Motor, 88-2 ... right running hydraulic motor, E ... engine.

Claims (1)

[Claims] 1. A pump port 44 opened to a spool hole 31 in a valve block 30, a first and second load pressure detection port 4
5, 46, first and second actuator ports 34, 3
5, the first and second tank ports 47 and 48 are formed respectively, and the main spool 49 for communicating and blocking each port is fitted into the spool hole 31 to form the directional control valve 22. The valve block 30 has a check valve hole. An oil passage 56 that communicates the first port 39 and the check valve hole 37 opened in 37 with the pump port 44 is formed, and the first port 39 and the oil passage 56 are communicated with and cut off from the check valve hole 37, and The spool 60, which is stopped at the shutoff position, is inserted to form the check valve portion 23, and the valve block 30 has a second opening that opens into the pressure reducing valve hole 38.
-The third port 42, 43 is formed, and the pressure reducing valve hole 38 is formed.
The first pressure chamber 65 and the second pressure chamber 66 are formed by inserting the spool 64 into the first pressure chamber 65, the first pressure chamber 65 is communicated with the second load pressure detection port 46, and the second pressure chamber 66 is connected to the third port 43. And the spool 64 of the check valve portion 23 is pressed and held in the shut-off position to form a pressure reducing valve portion 24. The pressure reducing valve portion 24 and the check valve portion 24 are connected to each other. 23 as a pressure compensating valve 25, and the pair of pressure compensating valves 2 in the discharge passage 21 of the hydraulic pump 20.
5 and a pair of directional control valves 22 are provided to supply the discharge pressure oil of the hydraulic pump 20 to the left and right traveling hydraulic motors 88-1 and 88-2, and the auxiliary hydraulic pump 1 is driven by the engine E that drives the hydraulic pump 20. Driven, the discharge passage 5 is connected to the blade cylinder 3 by the blade directional control valve 2, and the discharge passage 5 of the auxiliary hydraulic pump 1 is connected to the pump port 44 of the pair of directional control valves 22 via the check valve 9. A pressure oil supply device characterized in that