JPS5815681Y2 - Load sensing hydraulic system - Google Patents

Description

[Detailed explanation of the idea] The present invention uses a load sensing hydraulic system.

Conventionally, as this type of load sensing hydraulic system, one shown in FIG. 1 is known.

That is, the discharge passage 2 of the variable displacement pump 1 is connected to the actuator 4 via the switching valve 3, and the chamber 5a of the hydraulic actuator 5 for changing the discharge amount of the variable displacement pump 1 is connected to the hydraulic pressure source 6. , load sensing control valve 7
, the first W path 12 , the cut-off control valve 8 and the second pipe 14 . A first pressure receiving chamber 9a is provided in the second pressure receiving chamber 9a, and a second pressure receiving chamber 9b is provided in the second pressure receiving chamber 9b. If the spool 9 is in this state, the hydraulic pressure source 6 and the first pipe line 12 are connected, and if the spool 9 is biased toward the second pressure receiving chamber 9b against the spring 11, the first pipe line 12 is connected to the hydraulic pressure source 6. The structure is such that the line 12 and the hydraulic pressure source 6 are cut off, and the line 12 is communicated with a drain 13.

The cut-off control valve 8a has a built-in slidable spool 15, and has a pressure receiving chamber 15a on one side of the spool 15, and a spring 11 stronger than the spring 11 in the load sensing control valve 7 on the other side. A spring 17 (with a large set load) is provided to constantly bias the spool 15 toward the pressure receiving chamber 158 and press the button, and when the spool 15 is in this state, the first
When the pipe line 12 is communicated with the second pipe line 14 and the spool 15 is biased against the spring 17, the first pipe line 12 and the second pipe line 14 are cut off, and the pipe line 14 is connected to the drain 16. It has a continuous sliding structure.

A first pressure receiving chamber 9a of the load sensing control valve 7 and a pressure receiving chamber 15a of the cutoff control valve 8
The discharge pressure (hereinafter referred to as pump discharge pressure) PI of the variable displacement pump 1 is supplied to each of the above, and the pressure Pi of the actuator 4 is supplied to the second pressure receiving chamber 9b of the load sensing control valve 7 via the shuttle valve 10. It is configured to supply

The switching valve 3 also has an inlet port 18 communicating with the discharge path 2 of the variable displacement pump 1, a pair of outlet ports 19 and 19 communicating with the actuator 4, and a pair of drain ports 20, 20. and the inlet port 18
to one of the pair of outlet ports 19, 19, and the other outlet port 19 is connected to one of the drain ports 20 of the pair of drain ports 20, 20; Inlet port 1
The inlet port 1
8 and the outlet port 19 can be increased or decreased to appropriately set the flow rate of the flowing liquid.

Therefore, in the conventional load sensing hydraulic system configured as described above, when the discharge amount of the variable displacement pump 1 is larger than the set flow rate of the switching valve 3, the pressure P1 of the actuator 4 The pump discharge pressure P1 increases, and this acts on the first pressure receiving chamber 9a of the load sensing control valve 7, causing the second pressure receiving chamber 9a of the load sensing control valve γ to increase.
Overcoming the pressure P2 of the pressure receiving chamber 9b and the biasing force of the spring 11 (
(more than the set differential pressure), move the spool 9 and open the first pipe line 12.
and the drain 13, so that the hydraulic pressure in the chamber 5a of the hydraulic actuator 5 for changing the discharge amount of the variable displacement pump 1 is controlled by the second pipe line 14, the cut-off control valve 8, and the first pipe line 12.
and the drain 13 via the load sensing control valve T.
The piston 22 of the hydraulic actuator 5 for changing the discharge amount is moved by the urging force of the spring 23, and the swash plate 24
The button shown in the figure is pressed to the right to decrease the pump discharge amount Q.

This decrease in the pump discharge amount Q is due to the pressure P in the first pressure receiving chamber 9a.
In other words, until the combined force of the pressure P2 of the second pressure receiving chamber 9b and the biasing force of the spring 11 overcomes the pressure P2 of the second pressure receiving chamber 9b and the spool 9 is biased toward the first pressure receiving chamber 9a, the pump discharge pressure P1 and the actuator This is continued until the differential pressure between the pressure P2 and the pressure P2 of 4 becomes a predetermined value.

However, contrary to the above case, if the discharge amount Q of the variable displacement pump 1 is smaller than the set flow rate of the switching valve 3, the pump discharge pressure P1 becomes lower than the actuator pressure P2, The spool 9 is biased toward the first pressure receiving chamber 9a by the biasing force of the spring 11 and the pressure P2 of the actuator 4, and communicates the hydraulic pressure source 6 with the first pipe line 12. is supplied to the chamber 5a of the hydraulic actuator 5 for changing the discharge amount through the cut-off control pulp 8 and the second pipe line 14, and the piston 22 is pushed against the spring 23, and the swash plate 2
4 to the left as shown in the figure to increase the pump discharge amount Q.

This increase in the pump discharge amount Q is caused by the increase in the first pressure receiving chamber 9a with respect to the resultant force of the urging force of the spring 11 and the pressure P2 of the actuator 4.
This continues until the pressure P1 overcomes and the spool 9 is biased toward the second pressure receiving chamber 9b, in other words, until the differential pressure between the pump discharge pressure P1 and the actuator P2 reaches a predetermined value.

Similarly, when the discharge amount Q of the variable displacement pump 1 increases, the pump discharge pressure P1 increases, which acts on the pressure receiving chamber 15a of the cut-off control rib 8 and causes the spool 15 to 17 is biased against the set load of the spring 11) and the second pipe line 14 is communicated with the drain 16, the hydraulic pressure in the chamber 5a of the discharge amount changing hydraulic actuator 5 is applied to the tray 716. It flows out, moves the swash plate 24 to the right as shown in the figure, and reduces the pump discharge amount Q.

If the pump discharge amount Q decreases and the pump discharge pressure P1 decreases,
The spool 15 is deflected toward the pressure receiving chamber 15a by the biasing force of the spring 17, and the second pipe line 14 and the drain 16 are cut off, and the first pipe line 12 and the second pipe line 14 are brought into a steady state in communication. Therefore, the pump discharge pressure P1 never exceeds the set load of the spring 17.

As described above, according to the conventional load sensing hydraulic system, the load sensing control valve γ is operated depending on whether the discharge amount Q of the variable displacement pump 1 is excessive or insufficient with respect to the set flow rate of the switching valve 3. to control the hydraulic actuator 5 for changing the discharge amount of the variable displacement pump 1.
The discharge amount Q of the variable displacement pump 1 can be decreased or increased, and the pump discharge pressure P1 can be increased based on the increase in the discharge amount Q of the variable displacement pump 1.
If the pressure is higher than the set pressure, the cut-off control valve 8 is activated to control the hydraulic actuator 5 for changing the discharge amount of the variable displacement pump 1, thereby reducing the discharge amount Q of the variable displacement pump 1. However, these are all based on the pump discharge pressure P1 based on the change in the discharge amount Q of the variable displacement pump 1.
The load sensing control valve 7 or the cut-off control valve 8 is braked by detecting only the
For example, even if the pump discharge pressure P1 slightly increases from the set value, the hydraulic actuator 5 for changing the discharge amount is a variable displacement type. The discharge amount Q of the pump 1 gradually progresses in the direction of decrease, and this movement is caused by the discharge amount Q of the variable displacement pump 1 being reduced by controlling the discharge amount changing hydraulic actuator 50 in the direction of decrease. The pump discharge pressure P1 continues until the control valve 7.8 is actuated.

However, in the case of practical use, the reduction in the discharge pressure P1 lags behind the decrease in the discharge quantity Q due to the pressure accumulating function of the pipeline, etc., so the discharge quantity Q of the variable displacement pump 1 tends to decrease too much. This phenomenon is caused by the pump discharge pressure PI
A similar problem occurs when the pump discharge amount Q falls below the set value, and a phenomenon occurs in which the pump discharge amount Q changes too much in response to fluctuations in the pump discharge pressure P1, causing the load sensing hydraulic system to become unstable. This has the disadvantage of being unstable.

The present invention was devised in view of the above-mentioned circumstances, and is designed to stabilize the pump discharge amount by reducing fluctuations in the pump discharge amount and making it operate more agilely than conventional pump discharge pressure fluctuations. The purpose of this invention is to provide a load-sensing hydraulic system with a

An embodiment of the present invention will be described below based on FIG. 2.

3 in Figure 2, 1 is a variable displacement pump, 3 is a switching valve,
4 is an actuator, 5 is a hydraulic actuator for changing the discharge amount, and 10 is a shuttle valve, and the same reference numerals indicate the same members, and since they are all the same as the conventional one shown in FIG. 1, a description will be given. will be omitted, and the load sensing control valve 71 and cutoff control valve 81, which are different from the conventional one shown in FIG. 1, will be described below.

The load sensing control valve 71, like the conventional one shown in FIG. , a first pressure receiving chamber 9a is provided, and a small-diameter tenth piston 30 is provided on one end surface of the spool 9 exposed in the first pressure receiving chamber 9a, the one end surface of which comes into contact with the first pressure receiving chamber 9a.
A second pressure receiving chamber 30a is provided on the other end surface of the zero-dead piston 30.

The other end of the spool 9 (upper O1!D in the figure) is provided with a 20th dowel piston 31 whose one end face abuts the other end face r of the spool 9, and a third A pressure receiving chamber 31a is provided, and a spring 11 is provided to constantly urge the spool 9 toward the first pressure receiving chamber 9a.

However, the 20th-dead piston 31 is not necessarily required, and if it is not provided, the end of the spool 9 is directly exposed to the third pressure receiving chamber 31a, as in the conventional one shown in FIG. The spring 11 is in direct contact with the end of the spool 9.

If the spool 9 is biased toward the first pressure receiving chamber 9a, the fluid pressure source 6 and the first pipe line 12 are communicated, and the spool 9 is biased toward the third pressure receiving chamber 31a. For example, the first pipe line 12 and the liquid pressure source 6 are cut off, the first pipe line 12 is communicated with the drain 13, and the pressure Pc of the first pipe line 12 is controlled to be connected to the first pressure receiving chamber 9a. In this configuration, the first pipe line 12 and the first pressure receiving chamber 9a are communicated with each other via a passage 32 so as to be introduced into the first pressure receiving chamber 9a.

In addition, the cut-off control leg 81, like the conventional one shown in FIG.
A first pressure receiving chamber 15a'& is provided in the lower side in the figure, and a load belt 33 is provided with one end surface abutting one end surface 15' of the spool 15 exposed in the first pressure receiving chamber 15a. A second pressure receiving chamber 3 is provided on the other end surface of the piston 33.
3a is provided.

Similar to the conventional one shown in FIG. 1, a groove 17 is provided on the other side (the upper side in the figure) of the spool 15 to constantly urge the spool 15 toward the first pressure receiving chamber 15a. , if the spool 15 is in this state, the first conduit 12 is communicated with the second conduit 14, and when the spool 15 is biased against the spring 17, the second conduit 14 is communicated with the drain 16. and the pressure Pc of the second pipe line 14 is
In this configuration, the second pipe line 14 and the first pressure receiving chamber 15a are communicated through a passage 34 so as to be introduced into the pressure receiving chamber 1' 5a.

Then, the discharge pressure P1 of the town displacement pump 1 is applied to the second pressure receiving chamber 30a of the load sensing control valve 11 and the second pressure receiving chamber 33a of the cutoff control pulp 81.
respectively, and the load sensing control valve 7
The pressure P2 of the actuator 4 is supplied to the third pressure receiving chamber 31a of the third pressure receiving chamber 31a through the shuttle valve 10.

Therefore, in the load sensing hydraulic system according to the embodiment of the present invention configured as described above, if the discharge amount of the town displacement pump 1 is larger than the set flow rate of the switching valve 3, the actuator 4 The pump discharge pressure P1 becomes higher than the pressure P2, and this acts on the second pressure receiving chamber 30a of the load sensing control valve 71, and the first pipe line communicating with the chamber 5a of the hydraulic actuator 5 for changing the discharge amount. 12 pressure Pc passes through the passage 32 to the first pressure receiving chamber 9a'.
The resultant force moves the spool 9 by overcoming the pressure P2 of the third pressure receiving chamber 31a of the load sensing control valve 71 and the biasing force of the spring 11, and causes the spool 9 to move.
and the drain 13, so that the hydraulic pressure in the chamber 5a of the hydraulic actuator 5 for changing the discharge amount of the variable displacement pump 1 is connected to the first pipe line 14 and the cut-off control knob 81, as in the conventional pump. , the piston 22 of the hydraulic actuator 5 for changing the discharge amount is moved by the biasing force of the spring P3, and the swash plate 24 is rotated as shown in the figure. This movement in the decreasing direction of the pump discharge amount Q is due to a decrease in the pressure Pc in the first pipe line 12 due to the communication between the first pipe line 12 and the drain 13. It is immediately reflected in the first pressure receiving chamber 9a via the passage 32, and the movement of the spool 9 is immediately regulated, so that the pump discharge pressure P based on the reduced pump discharge amount Q is reduced as in the conventional one.
Compared to a system in which the movement in the decreasing direction continues until the spool 9 is operated due to a decrease of 1, the control is more rapid and prevents excessive movement in the decreasing direction.

However, contrary to the above case, the discharge pressure Pl of the variable displacement pump 1 becomes lower than the set flow rate of the switching valve 3, and the spring 1
1 and the pressure P2 of the actuator 4 is the second pressure receiving chamber 30 of the load sensing control knob 71.
a and the spool pressing force of the first pressure receiving chamber 9a,
The spool 9 is biased toward the first pressure receiving chamber 9a, the hydraulic pressure source 6 and the first pipe line 12 are connected, and the discharge liquid pressure of the hydraulic pressure source 6 is controlled by the cut-off control valve 8 and the first pipe line 14. to the chamber 5a of the hydraulic actuator 5 for changing the discharge amount, the piston 22 is pushed against the spring 23, and the swash plate 24 is pushed to the left by pressing the button shown in the figure to change the pump discharge amount Q. increase.

This movement in the direction of increase in the pump discharge amount Q is caused by the movement in the first pipe line 1
2 and the hydraulic pressure source 6 is immediately reflected in the first pressure receiving chamber 9a via the passage 32, and the movement of the spool 9 is immediately regulated.
Compared to the conventional one, which continues to move in the increasing direction until the spool 9 is operated by increasing the pump discharge pressure P1 based on the increased pump discharge amount Q, the control is faster and the pump discharge pressure P1 continues to move in the increasing direction. This is to prevent overexertion.

Similarly, when the discharge amount Q of the town displacement pump 1 becomes extremely large, the pump discharge pressure P1 becomes extremely high;
This acts on the second pressure receiving chamber 33a of the cut-off control pulp 81, and together with the pressure Pc of the second pipe line 14 acting on the first pressure receiving chamber 15a via the passage 34, the spool 15 is Since the second pipe line 14 is biased against the set load (more than the spring 11) and communicated with the drain 16, the hydraulic pressure in the chamber 5a of the hydraulic acticoator 5 for changing the discharge amount is applied to the drain 16. The pump discharge amount Q is decreased by pressing the button shown in the figure and moving the swash plate 24 to the right.

This movement in the decreasing direction of the pump discharge amount Q is caused by the movement in the second pipe line 1
The pressure P in the first pipe line 12 due to the communication between the drain 16 and the
The decrease in c is immediately reflected in the first pressure receiving chamber 15a via the passage 34, and the movement of the spool 15 is immediately regulated. Compared to the one that continues to move in the decreasing direction until the spool 9 is operated due to a decrease in Pl,
This allows quick control and prevents overshooting in the direction of decrease.

Incidentally, this cut-off control valve 8I has a structure including a load piston 33, a passage 34, a second pressure receiving chamber 33a, etc., but the spring 1 in the load sensing control valve 7
It has a spring 17 that is stronger (larger set load) than 1.
In other words, it operates only when the pump discharge pressure P1 becomes extremely high, and it plays the role of a so-called safety valve, so it is not necessarily limited to the configuration shown in FIG. A conventional cut-off control valve 8 as shown in the figure may be used instead.

As described above, the present invention connects the discharge passage 2 of the variable displacement pump 1 to the actuator 4 via the switching valve 3, and also connects the discharge passage changing hydraulic actuator 5 of the variable displacement pump 1 to the actuator 4. The hydraulic pressure source 6 is connected to a load sensing control valve I connected to the hydraulic pressure source 6, a first pipe line 12 connected to the load sensing control valve 7, and a cutoff connected to the first pipe line 12. A spool 9 is built into the valve body 7a by pressing a button on the control valve 8 and a load sensing hydraulic system connected via a second pipe line 14 connecting the cut-off control valve 8 and the hydraulic actuator for changing the discharge amount. , a first pressure receiving chamber 9a on one side of the spool 9.
At the same time, a small-diameter 10th piston 30 is provided on one end surface 9' of the spool 9 exposed to the first pressure receiving chamber 9a, and the 10th piston 30 has a small diameter and is brought into contact with the one end surface of the spool 9.
A second pressure receiving chamber 30a is provided on the other end surface of the spool 9, and a third pressure receiving chamber 31a is provided on the other end of the spool 9.
is provided to always urge the spool 9 toward the first pressure receiving chamber 9a, and if the spool 9 is biased toward the first pressure receiving chamber 9a, the hydraulic pressure source 6 and the first pipe line 12 If the spool 9 is biased toward the third pressure receiving chamber 3Ia, the first pipe line 12 and the hydraulic pressure source 6 are disconnected, and the first pipe line 12 is connected to the drain 13. configuring the load sensing control valve 71 so as to communicate with each other,
The second pressure receiving chamber 30a of the load sensing control valve 71
The discharge pressure P1 of the town displacement pump 1 is supplied to the pump 1, and the pressure P2 of the actuator 4 is supplied to the third pressure receiving chamber 31a, and the first pipe line 12 and the first pressure receiving chamber 9a are in communication with each other via a passage 32, and further,
A spool 15 is built into the valve body 8a, and one side of the spool 15 is provided with a pressure receiving chamber 15a, and the other side is provided with a spring 17 stronger than the spring 11 in the load sensing control valve 71, so that the spool 15 is always connected to the pressure receiving chamber 15a. If the spool 15 is biased toward the pressure receiving chamber 15a side, the first conduit 12 and the second conduit 14 are communicated, and the spool 15 is biased toward the spring 17 side. If the drain is biased to Since the discharge pressure P1 of the town displacement pump 1 is configured to act on the end face of the spool 15 located in the pressure receiving chamber 15a of the cut-off control valve 81, The discharge amount Q of the variable displacement pump 1 is
The spool 9 can be operated to reduce or increase the discharge amount Q of the variable displacement pump 1 by operating the spool 9 depending on whether the pump discharge pressure P1 is high or low based on the amount of the pump discharge pressure P1. The pressure Pc of the first pipe line 12 connecting the hydraulic actuator 5 and the load sensing control valve 71 acts on the first pressure receiving chamber 9a of the load sensing control valve 71 via the passage 32, and the movement of the spool 9 is controlled. corresponding first
Pressure P in conduit 12.

The change is immediately reflected in the first pressure receiving chamber 9a, and the movement of the spool 9 is immediately regulated. Increase until spool 9 is operated only by high
Its movements are more agile than those that continue to move downwards,
Excessive control can be prevented, resulting in a stable load sensing hydraulic system.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional example, and FIG. 2 is an explanatory diagram showing an embodiment of the present invention. 1 is a variable displacement pump, 2 is a discharge path, 3 is a switching valve, 4 is an actuator, 5 is a hydraulic actuator for changing the discharge amount, 6 is a hydraulic pressure source, 7 is a load sensing control valve, 81
is a cut-off control valve, 9 is a spool, 9a is a first pressure receiving chamber, 11 is a spring, 12 is a connecting pipe, 13 is a drain,
30 is the 10th Toviston, 30a is the second pressure receiving chamber, 31
a is the third pressure receiving chamber, and 32 is a passage.

Claims (1)

[Scope of utility model registration request] The discharge passage 2 of the variable displacement pump 1 is connected to the actuator 4 via the switching valve 3, and the hydraulic actuator 5 for changing the discharge amount of the variable displacement pump 1 and the hydraulic pressure source 6 are connected to the hydraulic pressure source 6. a load sensing control valve 7 connected to the source 6; a first conduit 12 connected to the load sensing control valve 7; a cutoff control valve 8 connected to the first conduit 12; and a cutoff control valve 8 connected to the first conduit 12. and the hydraulic actuator for changing the discharge amount are connected via a second pipe line 14, a spool 9 is built into the valve body 7a, and one of the spools 9 includes: A first pressure receiving chamber 9a is provided, and the first pressure receiving chamber 9a is provided.
A small-diameter 10th-hole piston 30 is provided on one end surface of the spool 9 exposed to the pressure receiving chamber 9a, and one end surface of the spool 9 abuts, and a second pressure receiving chamber 30a is provided on the other end surface of the 10th-hole piston 30. A third pressure receiving chamber 3 is provided on the other side of the spool 9.
1a is provided, and a spring 11 is provided to always urge the spool 9 toward the first pressure receiving chamber 9a.
If the spool 9 is biased toward the first pressure receiving chamber 9a side, the hydraulic pressure source 6 and the first pipe line 12 are communicated, and if the spool 9 is biased toward the third pressure receiving chamber 31a side, Said first
The pipe line 12 and the hydraulic pressure source 6 are cut off, and the first pipe line 1
2 is configured to communicate with the drain 13, and the discharge pressure P1 of the variable displacement pump 1 is supplied to the second pressure receiving chamber 30a of the load sensing control valve 71, and the third Pressure receiving chamber 31a
KmJ is configured to supply the pressure P2 of the actuator 4, the first pipe line 12 and the first pressure receiving chamber 9a are communicated via the passage 32, and the valve body 8a has a built-in spool 15. , a pressure receiving chamber 15 is provided on one side of the spool 15.
A is provided with a spring 1T stronger than the spring 11 in the load sensing control valve γ1 on the other side to constantly urge the spool 15 toward the pressure receiving chamber 15a, so that the spool 15 is biased toward the pressure receiving chamber 15a. If the spool 15 connecting the first conduit 12 and the second conduit 14 is biased toward the spring 17, the first
The cut-off control valve 81 is configured to cut off the pipe line 12 and the second pipe line 14 and communicate the second pipe line 14 with the drain 16, and the cut-off control valve 81 is configured to A load sensing hydraulic system configured such that the discharge pressure P1 of the variable displacement pump 1 acts on the end face of the spool 15 located at 15a.