JPS5980504A - fluid equipment - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

The present invention relates to an energy-saving fluid device in which the discharge volume of a variable discharge volume pump is controlled by a pressure control valve, and the differential pressure across a variable flow rate adjustment orifice provided in a main circuit is controlled to be substantially constant. Conventionally, this type of fluid device has a main flow circuit 1 between an actuator 102 and a variable discharge rate pump 1.0 which always attempts to discharge the maximum flow rate, as shown in Figure 1, for example.
03 is provided with a variable flow rate adjustment orifice 104,
The cylinder 105 and the main circuit 10 that control the swash plate as a discharge rate variable element of the variable discharge rate pump 101] 01a
A two-boat pressure control valve 131 having a primary port 106 and a secondary port 107 is connected between the line 1 and the secondary port 107, and the line 1 between the secondary port 07 and the swash plate control cylinder 105. 5) A throttle 116 is interposed to branch a line 117 leading to the tank 18, while a closed center switching valve 20 provided downstream of the variable flow rate adjustment orifice 04 is in the switching position. When controlling the flow rate, the pressures before and after the variable flow rate adjustment orifice 104 are transmitted to both ends of the pressure control valve 111 (7 pools) 12, respectively, and the pressure control valve 1'll is controlled by the pressure difference before and after the variable flow rate adjustment orifice 104. The discharge amount and discharge pressure of the variable discharge pump 101 are adjusted according to the opening degree of the variable orifice 104 and the load of the actuator 102 so that the differential pressure before and after the variable flow rate adjustable orifice 104 becomes constant. is controlled accordingly to prevent unnecessary flow and pressure (U.S. Patent 2,
892.81'; l i). Further, the fluid device throttles the back pressure chamber 124 of the pressure control valve 114 when the switching valve 120 is in the neutral position.
The discharge pressure of the variable discharge pump 101 is controlled by the back pressure chamber 1.
The pressure is controlled to an extremely low level corresponding to the spring pressure of the spring ring 113 of No. 24, and a so-called vent unload operation is performed to minimize power loss. However, since the above-mentioned conventional fluid device is equipped with the tank fin [26] with the throttle 125 interposed therebetween, when controlling the flow rate with the switching valve 320 located at the switching position, the flow rate is completely wasted from the tank line 126. There is a disadvantage that a loss occurs and, eventually, a power loss occurs. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to control the discharge amount and discharge pressure of a variable discharge 1 pump according to demand, thereby maintaining the energy saving effect of reducing power loss, while also reducing the amount of leakage that occurs in the conventional pump. The purpose is to obtain the advantages of eliminating the flow rate and further reducing power loss. It is also an object of the present invention to provide a flowchart with which the downstream load pressure is the highest among the plurality of variable flow rate adjustment orifices when a plurality of actuators are driven by one variable discharge pump through each variable flow rate adjustment orifice. The purpose of this invention is to obtain the advantage that the differential pressure before and after the adjustable orifice can be controlled to be substantially constant, so that priority can be given to speed control of the actuator with the largest load pressure. Sarani, the purpose of this invention is to accurately control the speed of multiple actuators at the same time by controlling the differential pressure before and after each variable flow rate adjustment orifice for each actuator to be approximately constant when driving multiple actuators at the same time. The purpose is to make it possible. For this reason, the fluid device according to 7J) of the present invention has a variable discharge rate pump and an actuator that are designed to maintain the discharge rate at the maximum value by biasing the variable discharge rate control element in one direction at the most. A decompression expansion pressure control valve and a variable flow rate adjustment orifice are sequentially provided from the upstream side in the mainstream circuit between the decompression and expansion pressure control valves, and another mainstream circuit that communicates with other actuators is branched from the mainstream circuit upstream of the decompression expansion pressure control valve. The mainstream circuit is also provided with a pressure reducing pressure control valve and a variable flow rate adjustment orifice sequentially from the upstream side, and has a primary s7-port and a secondary port, which can be freely opened and closed between these ports. The secondary port of the two-boat type pressure control valve that closes the secondary boat on the outer peripheral surface of the cylinder is connected via a line to the cylinder that drives the variable discharge amount control element in the neutral direction, and Along with branching the tank line with a throttle,
The primary port is connected to the mainstream circuit, and the pressure on the upstream side of the decompression expansion pressure control valve is transmitted to one end of the spool of the two-port pressure control valve, and the spring at the other end of the spool is compressed. Connect the control line of the shuttle valve to the equipped back pressure chamber, and connect the pilot line of the shuttle valve to the
In conjunction with the opening and closing of each of the above variable flow rate adjustment orifices, the rear of each of the variable flow rate adjustment orifices is switched and communicated with the vent passage which forms a low pressure. The maximum load pressure among the respective load pressures downstream of the orifice is selected by a shuttle valve and transmitted to the back pressure chamber of the pressure control valve, and the two-port pressure control valve is transmitted to both ends of the spool. The device is characterized in that the discharge amount of the variable discharge amount tip is controlled by freely opening and closing the gap between the primary port and the secondary boat in response to the differential pressure of the measured pressure applied thereto. Something,
In the main circuit in front of each variable flow rate adjustment orifice,
By providing a pressure reducing type pressure control valve and controlling the differential pressure before and after each variable flow rate adjustment orifice to be approximately constant using each pressure reducing type pressure control valve, it is possible to accurately control the speed of multiple actuators at the same time. It is characterized by the fact that DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to illustrated embodiments. As shown in FIG. 2, this device includes one variable discharge pump 1, a plurality of actuators 50, 50a, 50b, one pressure control valve 30, a plurality of flow direction control valves 1o,
ioa and tob, each of these flow rate directional control valves 1
0. 10a and 10b have the same structure. Therefore, based on FIGS. 3 and 4, such a specific example is shown in FIG.
Next, a fluid system consisting of one pressure control valve 30 and one flow direction control valve 10 will be explained. The variable discharge amount pump 1 includes a cylinder 4 for displacing the variable discharge amount control element 2 about a trunnion shaft 8 as a fulcrum, and a spring 5 is installed within the cylinder 4. The spring 5 is installed at a position that urges the variable discharge amount control element 2 in the direction of maximum inclination, and therefore the pump 1 has a characteristic of always maintaining the discharge amount at the maximum value. ing. Further, the suction side of the pump 1 communicates with a tank 7a via a circuit 6, and the main circuit 8 connected to the discharge side communicates with an actuator 50 via the flow direction control valve 0. On the other hand, the flow rate directional control valve O is a P boat P that connects the main circuit 8 to the block 11, two A boats A-B ports B that connect the actuator 50, and a tank 7b.
A tank boat T connects the tank boat T, and a bow 14 connects the pilot line 13, and a three-land 15 * 1611,7 type tD movable valve 18 is provided inside to form a center oar boat block shape. . Further, the flow rate directional control valve 0 is a variable orifice 7 for adjusting the flow rate between the corners on both sides of the central land 15 and the block by displacing the movable valve 18 as shown in FIG.
19, and communicates with the filled pack passage 20T--the boat 4, which has one end open at the rear, i.e., downstream side, of the variable flow rate adjustment orifice 19. The land 17 of the movable valve 18 is formed with a bend switching portion 21 consisting of its outer peripheral surface and an annular groove.
A vent passage 22 formed so as to communicate with the feedback passage 20 and the tank port T is connected to the vent switching section 21.
It opens and closes by moving 0J. That is, the vent switching section 21 opens the vent passage 22 when the movable valve [8] is in neutral, and closes the vent passage 22 when the movable valve 18i is displaced. Further, the pressure control valve 3o is of a two-boat type with a housing 2
In addition, a pilot port 27 and a drain boat 28 are formed.
- Connect the secondary boat 24 to the main circuit 8, the secondary port 25 to the branch line 29, the drain port 28 to the tank line 40, and the pilot boat 27 to the pilot line 13, and plug the pressure relief port 26. 26
I'm doing aV. Furthermore, Nupoo 71/81 is installed in the housing 23, and the pilot boat 2
7 pulling 3 in the back pressure chamber 32 formed so as to communicate with 7.
3 force is applied to the spool 3], -next boat 24
and the secondary boat 25 are kept normally closed. Further, the pilot valve 8° C. has a valve body 35 pressed against a valve seat 34 formed between the back pressure chamber 32 and the drain boat 28 by means of a spring 36. Further, the branch line 29' connected to the secondary boat 25 is connected to the side opposite to the spring ring of the cylinder 4, and the line 39 connected to the spring side of the cylinder 4 is opened to the tank 7a. Furthermore, a throttle 37 is interposed from the line 29 to branch a tank line 160 leading to the tank 7al, and a safety valve 38
is interposed to branch the line 161 leading to the tank 7a. In the above embodiment, as shown in FIG. 3, even when the movable valve 18 is set to neutral and no fluid is supplied to the actuator 50,
It has a control function that prevents the fluid pump 1 from discharging excess fluid and from generating excess pressure, and the operation thereof will be explained below. That is, since the fluid pump 1 has the characteristic of always trying to maintain the discharge amount at the maximum value, the variable pump 1 simultaneously drives the prime mover for the variable pump 1 and discharges fluid at the maximum flow rate through the mainstream circuit 8. However, when the movable valve 18 is in the neutral position as shown in FIG. 3, the entire amount of the discharged fluid is supplied toward the primary port 24 of the pressure control valve 300. On the other hand, when the movable valve [8] is neutral, the back pressure chamber 32 is opened to the tank 7b via the vent switching section 2I and the vent passage 22. Therefore, in the pressure control valve 30, the primary
Only the force of spring 3.3 resists the pressure of 24. Therefore, the fluid discharged from the variable discharge pump 1 forces 1 to displace the nup ring 33 to the right as shown in FIG. is opened to flow into the branch line 29'ji:'. This fluid has a constant pressure due to the action of the throttle 37, and a portion of the fluid flows into the opposite side of the cylinder 4 to the opposite side of the cylinder 4, positioning the variable discharge amount control element 2 on the neutral side and controlling the variable pump. Reduces the amount of discharge. A certain amount of time is required to displace the variable discharge amount control element 2 to the neutral position, and the pressure in the main circuit 8 tends to rise excessively, but the safety valve 38 prevents the discharge fluid from the variable pump from increasing. IJ IJ- can be turned off to ensure circuit safety. If the fluid pump 1 completely stops its discharge amount, the pressure in the main circuit 8 will disappear and the spool 31 will return to the state shown in FIG. By opening the tank 7a and tilting the discharge amount variable control element 2 again in the direction of the maximum angle of inclination by the spring 5 in the cylinder 4 to increase the discharge amount, the pressure in the main circuit 8 and In other words, the pressure in the main circuit 8 is calculated by dividing the spring pressure of the spring 33 by the cross-sectional area of the end surface of the spool 31 so that the pressure difference between the pressure of the pilot line and the pilot line leading to the tank 7b corresponds to the spring pressure In of the spring 33. The discharge amount of the pump ( ) is automatically controlled so that the pressure is maintained. For this reason, the spool 310
By making the land diameter, that is, the pressure-receiving area of the end surface and the pinuton pressure-receiving area of the cylinder 4 large, the discharge amount and discharge pressure from the pump 1 when the flow rate directional control valve 10 is in the neutral state can be very small. When fluid is not supplied to the pump 50, the discharge amount of the fluid pump l is suppressed to an extremely small amount to prevent excessive discharge, and at the same time, it is possible to prevent the generation of excess pressure, resulting in extremely low power loss. This can be reduced by Next, in the above embodiment, when fluid is supplied to the actuator 50 by displacing the movable valve 8 as shown in FIG. It has a control function that prevents the generation of unnecessary extra pressure, and its operation will be explained below. That is, when the movable valve 18 is displaced to open the variable flow rate adjustment orifice 19 to a predetermined opening degree as shown in FIG. 4, the fluid being discharged from the variable pump l begins to be supplied to the actuator 50. In this case, the vent path 22 is connected to the vent switching section 2.
], the actuator 50 is connected to the back pressure chamber 32 via the feedback passage 207il.
A pressure corresponding to the load W is applied, and as a result, the space between the primary boat 24 and the secondary boat 25 of the pressure control valve 30 is temporarily closed, and the diversion action to the diversion line 29 is stopped. Therefore, the fluid in the chamber on the opposite side of the cylinder 40 to the spring is pushed out from the throttle 37 to the tank 7a by the force of the spring 5, and as a result, the variable discharge amount control element 2 begins to tilt in the direction of the maximum oblique angle due to the spring force of the spring 5. Start increasing the discharge amount. Then, the pressure control j'fao enters the pressure compensation mode as described below. That is, pump discharge pressure acts on the primary port 24 side of the spool 31, and fluid pressure due to the negative pressure W and the spring 33 act on the back pressure chamber 32 at the other end.
The spring pressure is acting on the pool 7, and the pool 31 moves forward and backward in the axial direction. Therefore, when the pressure difference between the fluid pressure on the primary port 24 side of the pressure control valve 30 and the fluid pressure on the back pressure chamber 32 side is equal to or less than the spring pressure of the spring 33,
The pressure control valve 3o is connected to the secondary boat 25,! :1st bow) 24
The fluid on the opposite side of the cylinder 4 is discharged from the throttle 37 to the tank 7a, and the variable discharge amount control element 2 is tilted toward the maximum flow rate discharge side, that is, the maximum inclination side.
Increase the discharge amount. On the other hand, when the pressure difference between the fluid pressure on the primary port 24 side and the fluid pressure on the back pressure chamber 32 side of the pressure control valve 3o is equal to or higher than the spring pressure of the Nupling 330J, the pressure control valve 30 By communicating with the boat 25, the fluid in the main circuit 8 is transferred to the branch line 29)? through the cylinder 40 to the anti-spring side, and position the variable discharge amount control element 2 on the neutral side, that is, on the minimum slope side,
Decrease the discharge amount of the variable pump 1. Oh, at this time,
Due to the action of the throttle 37, the pressure in the branch line 29 is maintained at a constant pressure. In this way, the pressure control valve 30 controls the fluid pressure difference between the primary port 24 side and the back pressure chamber 32, that is, the flow rate adjustment variable. Before and after. Differential pressure 1 - ML, ? , secondary boat 25
and the primary boat 24 to control the discharge amount and discharge pressure of the variable pump 1 according to the opening degree and load of the variable orifice 19 to prevent wasteful discharge of fluid and adjust the flow rate. The differential pressure before and after the variable orifice 19 is controlled to a constant value corresponding to the spring pressure of the 7-pull 33. Therefore, power loss is reduced. Furthermore, during flow rate control when the flow rate directional control valve 10 is in the switching position, the vent passage 22 is closed by the vent switching section 21, so that the back pressure chamber 32 of the pressure control valve 30 is not in contact with the pressure in the back pressure chamber 32 of the pressure control valve 30. Unlike the conventional example shown in FIG. 1, wasteful leakage flow 9 does not occur, and therefore power loss is further reduced. It is assumed that during the operation of the pressure control valve 30, the pilot valve 80 is closed because the pressure in the back pressure chamber 32 is below its set pressure. On the other hand, when the movement of the hydraulic cylinder serving as the actuator 50 is restricted, for example at the lock end, and the pressure in the back pressure chamber 32 of the pressure control valve 30 increases, the pilot valve 80 adjusts the set pressure in the back pressure chamber 32. Control pressure. Therefore, the pressure control valve 80 opposes the fluid pressure of the primary boat 24 acting on one end of the spool 31 and the set pressure of the pilot valve 80 (/j) acting on the other end of the spool 31. The spool 81 is moved forward and backward in the axial direction to open and close the gap between the secondary boat 25 and the primary boat, and the discharge amount of the variable pump 1 is controlled as described above.
The fluid pressure is controlled to be higher than the set pressure by a constant value corresponding to the spring car C of the spring 83. At this time, the fluid discharged from the variable pump 1 is transferred to the mainstream circuit 8. Variable flow rate adjustment orifice 19, feedback passage 20, throttle 8
Pilot line with 8] 3, back pressure chamber 32. Pilot valve 80° drain port 28 and tank line 40
The pressure in the back pressure chamber 32 is controlled by the operation of the throttle 88, which has a small opening, regardless of the opening of the variable flow rate adjustment orifice 9.
The set pressure is 0. Further, due to the action of the throttle 88, the discharge amount of the variable pump 1 is very small, close to zero. Therefore, this fluid device can control the pressure in the main stream circuit 8 to a constant pressure with very little power. The first embodiment shown in FIG. 5 is the second embodiment. 3. The main structure shown in FIG. 4 is the main structure, and the main circuit 8 is formed into a closed circuit. In the case of this figure, the fluid controlled by the low pressure valve 44 is replenished into the suction 1H1 of the fluid pump 1 by the charge pump 45, but the replenishment flow rate is in a closed circuit. Since the amount of leakage is only equivalent to the amount of leakage in

[This is advantageous in that it allows the volume of the tank to be made smaller. The pressure control valve 80a in the embodiment shown in FIG.
The pressure control valve 80a, which corresponds to the pilot valve 80 in FIG. By communicating the cylinders 4 in this manner, it is possible to easily carry out safety control in the event of overload by using the existing pressure control valve 80a. Further, the fluid device shown in FIG. In addition to the structure of the fluid device shown in FIG. 4, each actuator 5oa+
Mainstream circuit 3a communicates with 50b. 8b is branched, and variable flow rate adjustment orifices 19a and 19b are provided in each of the main flow circuits 8a and 8b, respectively, and the shuttle valve 42a, 42b and transmits it to the back pressure chamber 32 of the pressure control valve 30. Therefore, this fluid control device prevents wasteful leakage flow from occurring during flow rate control, and maintains the effect of reducing power loss, while also controlling the plurality of actuators 50, 50a, 5013 to each variable flow rate adjustment orifice. 1
9+ 19a, ' 19b when simultaneously driven, the largest load pressure is transmitted to the back pressure chamber 32 of the pressure control valve 30. Variable flow rate adjustment orifice with the highest rear load pressure (
For example, by controlling the differential pressure before and after 19a) to be constant, priority can be given to speed control of actuator 5Qa with the largest load pressure. Further, the fluid device in the embodiment shown in FIG.
In addition to the structure of the fluidic device shown in the figure, each flow rate adjustment variable orifice 19+19a is further provided. Mainstream circuits 8.8a, 8b in front of the main circuit 19.19b are provided with pressure reducing type pressure control valves 43, 48a, 4Bb, respectively, and each flow rate adjustment variable orifice 19. The pressure difference before and after L9a and 19b is controlled to be constant. Therefore, this fluid device maintains the effect that no cross-flow portion occurs and power loss is small, and when simultaneously driving a plurality of actuators 50, 50a, 50b, each variable flow rate adjustment orifice for each actuator is adjusted. By controlling the differential pressure before and after IL]9a+19b at a substantially constant level using the pressure reducing type pressure control valves 43, 4831431), it is possible to accurately control the speeds of the multiple flOJ actuators 50, 50a, and 5Qb at the same time. Furthermore, the fluid device shown in FIG. 8 has approximately the same configuration as the fluid device shown in FIG. 7, and differs from the one shown in FIG. . As is clear from the above description, the fluid device according to the present invention has a variable discharge rate pump ( Main circuit C8 between 1) and the actuator (50)]! The pressure-reducing expansion pressure control valve (43) is sequentially operated from the upstream side.
and a variable flow rate adjustment orifice (] 9), and another mainstream circuit (3a) connected to another actuator (5Qa) from the mainstream circuit (8) on the upstream side of the decompression and expansion pressure control valve (43). ) is branched, and the main stream circuit (8a) is also provided with a pressure-reducing expansion pressure control valve +48a) and a variable flow rate adjustment orifice (19a) sequentially from the upstream side, while the primary boat (
24) and a secondary port (25), which can be opened and closed between these ports (31).
the secondary bow (25) of the two-boat pressure control valve (30) that closes the secondary bow (25) on the outer peripheral surface of the cylinder; and the cylinder that drives the variable discharge amount control element (2) in the neutral direction. (4) via a line (29), and from the line (29) a tank line (16) having a throttle (37).
0), the primary boat (24) is connected to the mainstream FIJ path (8), and the upper d11 is connected to one end of the spool (31) of the two-boat type pressure control valve (30).
A back pressure chamber (32) (this A/ Connect the control line of the torque valve (42a) and
) Pilot line (L3) of the valve (42a). t13a) above, each diversion adjustment variable orifice (19
11 (19x), the rear of each variable flow rate adjustment orifice (391, +19xl) and the vent passage (22) which provides low pressure are connected to the opening and closing of the variable flow rate adjustment orifice (391, +19xl). At the moment, the famous flow rate i1/IA seikawa orifice dog (19), (1
The maximum load pressure among the rear load pressures of 9xl is selected with the shuttle valve (42al), and the pressure control valve (
30) to convey the message to the back pressure chamber (32),
The above two-boat pressure control valve (30) is attached to the spool (31).
In response to the surface pressure difference 5 transmitted to both ends of The discharge amount of the variable discharge pump is controlled according to the demand, so power loss is reduced, and the vent unload MWi is controlled in the vent path. Moreover, it is possible to prevent leakage flow from the rear chamber of the pressure control valve during flow rate control, further reducing power loss.In addition, the load of the main circuit that supplies fluid to the actuator can be reduced. l: By directly sensing the force with the pressure control valve, the discharge volume and discharge 1E force of the variable discharge volume pump are controlled without being affected by the operation of the actuator, using only the differential pressure before and after the flow adjustment IIR variable orifice valve. Because of this, it has the advantage of excellent control responsiveness and stability.Furthermore, the fluid device of the present invention has a separate mainstream circuit that communicates with other actuators from the mainstream circuit in front of the variable flow adjustment orifice. The main circuit is also provided with a variable flow rate adjustment orifice, while the other end of the spool of the pressure control valve is connected to a back pressure chamber compressed by a spring. Since the structure is such that the maximum load pressure among them is transmitted through the shuttle valve selector 1j, in addition to the effects of the present invention, the discharge amount of the variable pump can be controlled,
Of the multiple flow meter adjustment 0I change orifices, the rear detective 1
1: It is said that the differential pressure before and after the variable flow rate adjustment orifice, where the force is the maximum load capacity, is controlled to be constant, and the speed control of the large-input 1-hand yuator with the highest load of 1 mo is given priority. effect can be obtained. Moreover, the fluid device of this invention has each flow rate adjustment variable first
)In the main circuit at the front of the line, a pressure control valve 11 of the reduced pressure type is provided, and the difference "1" before and after the variable orifice for adjusting each flow is kept approximately constant by each pressure control valve of the reduced pressure type. Therefore, it is possible to simultaneously control the speed of a plurality of single unit units to the market price, thereby obtaining an advantageous effect.

[Brief explanation of the drawing]

FIG. 1 is a circuit M of a conventional fluid device, 21% is a circuit diagram of an uninvented embodiment, FIG. 3 is a partial sectional view of FIG. 1, and 4th
1 (description of operation of the embodiment shown in FIG. 3)
l'Il, FIG. 6 is a circuit 1 of another embodiment of the invention, respectively.
TS1 and j; (<Cross-sectional view 1, FIG. 7 is a circuit diagram of another uninvented embodiment, and FIG. 8 is a circuit diagram showing a modification of FIG. 7. 1... Discharge variable amount pump, 2... discharge amount EiJ variable control element, 4... cylinder, 7a, 71),
7C...tank, 8.8a, 8b-...mainstream circuit,
19.19a. 19b...Takigawa adjustment riJ odd orifice, 2]...
・Vent switching part, 22...Vent path, 24・
...Primary port, 25...Secondary port, 26
...Tuck port, 30 ・3 port pressure control valve,
43, 43a. 43b...Reduction type pressure control valve, 50, 50a. 50b...1 Rimi Yueta. Patent Applicant: Daikin Industries, Ltd. Agent: Attorney: Aoyama Aoyama and 2 others Procedural amendment (voluntary) May 1981 TI 411 2. Title of the invention; Relationship with person '1'1 Patent n'1 Applicant Ic Place Osaka Yo Osaka Municipalization Ward tf'1lnl-1'r]1
No. 2-39 New 1 and the name of the emergency pill (2B!'3) Dakin Kogyo (:1; Shiki company representative Yama 1) Minoru 4, agent 〒541 11:, Address 2 Honmachi, Higashi-ku, Osaka-shi, Osaka -10 Name in Honmachi Building Patent Attorney (6214) Aoyama Hajime
(Two idiots) 5. ti(;l) in the notice of reasons for refusal 6. Full text of the specification to be amended. Drawing. 4.5.6, °7 figure deleted, figure 2 and 3
Replace the diagram as shown in the attached sheet, and replace Figure 8 with Figure 4. Description 1, Title of the invention Fluid device 2, Claims (1) Discharge with a characteristic that the discharge rate variable control element (2) is biased toward the maximum side body direction to maintain the discharge rate at the maximum value. The main circuit (8) between the variable volume pump (1) and the actuator (50) is sequentially provided with a pressure reduction and expansion pressure control valve (43) from the upstream side.
and a variable flow rate adjustment orifice (19) are provided, and another mainstream circuit (8a) that communicates with another actuator (5Q al) is branched from the mainstream circuit (8) on the upstream side of the decompression and expansion pressure control valve (43). The mainstream circuit (8a) is also provided with a pressure reducing pressure control valve (43a) and a variable flow rate adjustment orifice (19a') sequentially from the upstream side, while a primary port)
(241) and a secondary port (25), and a spool [31
) (25) of the two-boat pressure control valve (30) which closes the secondary port (251) on the outer peripheral surface of the cylinder (25) which drives the variable discharge amount control element (2) in the neutral direction. 41 through a line (29), and from the line (29) a tank line ('1) having a throttle (37).
At the same time, the primary port (241) is connected to the mainstream circuit (8), and one end of the spool (31) of the two-port pressure control valve (30) is connected to the vacuum expansion pressure control valve (241). 43),, (A shuttle valve [4
Connect the control line of 2a) to the shuttle valve (42a+
The pilot line [131+ (13a) is linked to the opening and closing of each of the variable flow rate adjustment orifices (19) and (19x), and the pilot line [131+ (13a) is
+ (19
Only when the pressure control valve (19x) is opened, the shuttle valve (42a) selects the maximum load pressure among the load pressures downstream of the variable flow rate adjustment orifices (191, (19x)), and the pressure control valve (19x) is opened. 30) to the back pressure chamber (32), and connect the 12-port pressure control valve (30) to the spool (30).
31) in response to the differential pressure between the two river forces transmitted to both ends of the
The primary port (24) and the secondary port [25] are freely opened and closed to control the discharge amount of the -1id:p,l variable pump (1). fluid equipment. 3. Detailed Description of the Invention This invention controls the discharge volume of a variable discharge volume pump using a pressure control valve to control the differential pressure before and after a variable flow resistance adjustment orifice provided in the main circuit to be approximately constant. This invention relates to an energy-saving fluid device. Conventionally, this type of fluid device has a main flow circuit 103 between an actuator 102 and a variable discharge pump 101 that always tries to discharge the maximum ore, as shown in FIG. 1, for example.
A variable flow adjustment orifice 104 is provided in the pump, and a primary port 106 and a secondary port 107 are provided between the main circuit 103 and the cylinder 105 that controls the swash plate 101a as a variable discharge element of the variable discharge pump 101. A two-port pressure control valve 111 having a
A throttle 116 is interposed to branch a line 117 leading to a tank 118 from a line 115 between the next port 107 and the swash plate control cylinder 105. During flow rate control when the center type switching valve 120 is in the switching position,
The pressures before and after the variable flow rate adjustment orifice 104 are transmitted to both ends of the spool 112 of the pressure control valve 111, respectively, so that the pressure control valve 111 is connected to the variable flow rate adjustment orifice 104.
The discharge amount and discharge pressure of the variable discharge amount pump 101 are opened and closed according to the differential pressure before and after the flow rate adjusting variable orifice 104 so that the differential pressure before and after the variable flow rate adjusting orifice 104 becomes constant. and actuator 10
2 to prevent wasteful flow and pressure from occurring (U.S. Pat. No. 2,892,31).
No. 2). Furthermore, the fluid device throttles the back pressure chamber 124 of the pressure control valve 114 when the switching valve 120 is in the neutral position.
The discharge pressure of the variable discharge pump 101 is controlled by the back pressure chamber 1.
The pressure is controlled to an extremely low level corresponding to the spring pressure of the spring 113 of No. 24, and a so-called pent unload operation is performed to minimize power loss. However, since the above-mentioned conventional fluid system is equipped with a tank line 126 with a throttle 125 interposed therebetween, during flow control with the switching valve 120 located at the switching position, there is a completely wasteful flow loss compared to the tank line 126. This has the drawback of causing power loss. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to control the discharge volume and discharge pressure of a variable discharge volume pump according to demand, while maintaining the energy-saving effect of reducing power loss, while also reducing the leakage of conventional pumps. The purpose is to eliminate the flow rate and further obtain the advantage of reducing power loss. Another object of the present invention is to control the differential pressure before and after each variable flow rate adjustment orifice for each actuator to be substantially constant when driving a plurality of actuators at the same time, thereby accurately controlling the speed of the plurality of actuators at the same time. The purpose is to make it possible. For this reason, the structure and operation of the present invention are directed to a mainstream circuit between a variable discharge rate pump and an actuator, which has a characteristic of biasing the variable discharge rate control element in the direction of maximum inclination to maintain the discharge rate at the maximum value. A decompression expansion pressure control valve and a variable flow rate adjustment orifice are sequentially provided from the upstream side, and another mainstream circuit communicating with another actuator is branched from the mainstream circuit upstream of the decompression expansion pressure control valve, and the main circuit is connected to the main circuit. A pressure reducing pressure control valve and a variable flow rate adjustment orifice are sequentially provided from the upstream side, and the secondary port is provided on the outer peripheral surface of the spool, which has a primary boat and a secondary port, and can be freely opened and closed between these boats. The secondary port of the two-boat type pressure control valve that closes the valve and the cylinder that drives the variable discharge control element in the neutral direction are connected via a line, and a tank line having a restriction is branched from the line. , the primary boat is connected to the mainstream circuit, and the pressure on the upstream side of the decompression and expansion pressure control valve is transmitted to one end of the spool of the two-boat pressure control valve, and the spring at the other end of the spool is connected to the main boat. The control line of the shuttle valve is connected to the compressed back pressure chamber, and the pilot line of the shuttle valve is linked to the opening and closing of each of the variable flow rate adjustment orifices to create a low pressure downstream of each of the variable flow rate adjustment orifices. Only when the variable flow rate adjustment orifice is opened, the shuttle valve selects the maximum load pressure among the load pressures downstream of each variable flow rate adjustment orifice, and the pressure control valve At the same time, the two-boat type pressure control valve is made to respond to the differential pressure between the two pressures transmitted to both ends of the spool, so that the connection between the primary boat and the secondary port can be opened and closed. By controlling the discharge volume of the variable discharge volume pump, the discharge volume and discharge pressure of the variable discharge volume pump can be controlled according to demand, and power loss can be reduced, which is an energy-saving effect. Eliminate unnecessary leakage flow while retaining the flow rate. Furthermore, the present invention is characterized in that power loss is reduced, and even if the load pressures of a plurality of actuators are different, the speeds of the actuators can be accurately controlled (at the time of i8i1). As shown in Fig. 2.3, this device consists of one variable discharge pump 1 and several actuators 50°5 Q a,
50b, one pressure control valve 30, and a plurality of flow direction control valves 10.10a, 10b, each of which has the same structure. 1qfl Discharge amount n "The variable pump 1 includes a cylinder 4 that displaces the discharge amount variable control element 2 supported by a trunnion shaft 3, and a spring 5 is installed in the cylinder 4. The spring 5 The variable discharge amount control element 2 is arranged in such a manner that the variable discharge amount control element 2 is energized to the maximum inclined blade height, and therefore, the pump 1 has an e-characteristic that always tries to maintain the discharge amount at the maximum value. Further, the suction side of the pump 1 is connected to a tank 7a via a circuit 6.
The main flow circuit 8 connected to the discharge side and the main flow circuit branched from it (#t'r 8 a . 8 b are connected to the actuators 50 , 5 ( la , 50b. On the other hand, as shown in FIG. B port B, a tank port T that connects the tank 7b, and a port 14 that connects the pilot line 13 are formed, and a 3-land 15, 16, 17 type movable valve 18 is formed inside.
is provided to form a center all port block shape. Further, the flow rate directional control valve 10 has variable flow rate adjustment orifices 1,9.
19 is formed, and a feedback passage 20 having one end opened downstream of the variable flow adjustment orifice 19.19 is communicated with the port 14. The land 17 of the movable valve 18 is formed with a bend switching portion 21 consisting of its outer periphery and an annular groove. A vent passage 22 formed so as to communicate the feedback passage 20 and the tank port T is connected to the vent switching section 21.
It opens and closes by moving. That is, the vent switching section 21 opens the vent passage 22 when the movable valve 18 is in neutral, and closes the vent passage 22 when the movable valve 18 is displaced. Further, the pressure control valve 30 is of a two-port type and has two main ports 24 and 25 formed in the housing 23, a pilot port 27 and a drain port 28, and connects the secondary port 24 to the mainstream circuit. 8, the secondary port 25 to the branch line 29, and the drain port 28 to the tank line 40.
- The pilot boat 27 is connected to the pilot line 13.
are connected to each. Note that 26 is a plug. Further, a spool 31 is installed in the housing 23, and the force of a spring 33 in a back pressure chamber 32 formed so as to communicate with the pilot port 27 is transferred to the spool 31.
1 to keep the space between the negative port 24 and the secondary port 25 normally closed. The pilot valve 80 also has a valve body 35 attached to a spring 36 formed between the back pressure chamber 32 and the drain port 28.
It is crimped with the spring force. Further, a branch line 29 connected to the secondary port 25 is connected to the opposite spring side of the cylinder 4, and a line 39 further connected to the spring side of the cylinder 4 is connected.
is opened to the tank 7a. Furthermore, the above line 29
From there, a throttle 37 is interposed to branch a tank line 160 leading to the tank 7a, and a safety valve 38 is interposed to branch a line 161 leading to the tank 7a. Also, the mainstream circuit 8a in front of the variable flow m adjustment orifice 19 of the flow direction control valve 10 is connected to the actuators 50a and 5011 as described in i11.
, 8b, each main stream, circuit 3a. Variable flow rate adjustment orifices 19a and 19 are provided at 8b, respectively.
b, and - each flow directional control valve 10.103°1
Variable flow rate adjustment orifice 19, 19a of 0b. The shuttle valves 42 a and 42 b select the maximum load pressure among the load pressures downstream of the pressure control valve 19 b and transmit it to the back pressure chamber 32 of the pressure control valve 30 . Moreover, each flow rate adjustment variable orifice 19,19a. Reduction type pressure control valves 43, 43al and 43b are provided in the main circuits 8, 8a and '8b in front of 19b, respectively, and each flow rate adjustment variable orifice 19, The differential pressure before and after 19a and 19b is controlled to be constant. In the above-mentioned embodiment, all the flow direction control valves 10. as shown in FIGS. 10. Even when fluid is not supplied to the actuator 50 with a and 10b set to neutral, the fluid pump 1 has a control function that prevents excess fluid from being discharged and no excess pressure from being generated. The effect of this will be explained below. That is, since the variable discharge amount pump 1 has the characteristic of always trying to maintain the discharge amount at the maximum value, the variable pump 1 simultaneously drives the prime mover for the variable pump 1 and simultaneously pumps fluid at the maximum flow rate through the mainstream circuit 8. However, when all the movable valves 18 are in the neutral position as shown in FIGS. 2 and 3, the entire amount of the discharged fluid is supplied toward the primary port 24 of the pressure control valve 30. On the other hand, when all the movable valves 18 are neutral, the back pressure chamber 32 is opened to the tank 7b via the vent switching section 21 and the vent path 22. Therefore, in the pressure control valve 30, only the force of the spring 33 resists the pressure of the primary boat 24. Therefore, the fluid discharged from the variable discharge pump 1 displaces the sprue 31 to the right in FIG. 3 against the ring 33, opening the gap between the primary boat 24 and the secondary boat 25. and flows into the branch line 29. A portion of the fluid flows into the opposite side of the cylinder 4 to the side opposite to the spring, positioning the variable discharge amount control element 2 on the neutral side. The discharge amount of the variable pump 1 is reduced. A certain amount of time is required to displace the variable discharge amount control element 2 to the neutral position, and the pressure in the main circuit 8 tends to rise excessively, but the safety valve 38 prevents the discharge fluid from the variable pump 1 from increasing. The safety of one circuit can be ensured by shutting down the IJ IJ-. If the fluid pump 1 completely stops its discharge amount, the pressure in the main circuit 8 will disappear and the spool 31 will return to the state shown in FIG. Since the discharge amount variable control element 2 is opened to the tank 7a and the spring 5 in the cylinder 4 is tilted again in the direction of the maximum angle of inclination to increase the discharge amount, the pressure in the main circuit 8 and the tank 7b are increased. The pressure difference between the pressure in the pilot line 13 leading to the spring 33
The discharge amount of the pump 1 is automatically controlled so that the pressure in the main circuit 8 is equal to the spring pressure of the spring 33 divided by the cross-sectional area of the end surface of the spool 31. Ru. For this reason, by making the land diameter of the spool 31, that is, the pressure receiving area of the end face large, and the piston pressure receiving area of the cylinder 4 large, the flow direction control valve 10
The discharge amount and discharge pressure from the pump 1 during the neutral state may be very small. Therefore, when fluid is not supplied to the actuator 50, the discharge amount of the fluid pump 1 is kept to an extremely small amount to avoid excess discharge. At the same time, it is possible to prevent the generation of excess pressure, and as a result, the loss of power can be extremely reduced. Next, for example, when the movable valve 18 of the flow direction control valve 10 is displaced to supply fluid to the actuator 50,
It has a control function that prevents the variable pump 1 from discharging excess fluid that is not required by the actuator, and also does not generate excess pressure that is not required by the load, and the operation will be explained below. That is, when the movable valve 18 is displaced to open the flow section adjustment variable orifice 19 to a predetermined opening degree, the fluid being discharged from the variable pump 1 begins to be supplied to the actuator 50. In this case, the vent path 22 is closed by the movement of the vent switching section 21. A pressure corresponding to the load W of the actuator 50 acts on the back pressure chamber 32 via the feedback passage 20, and as a result, the primary port 24 and the secondary port 25 of the pressure control valve 30
The space between them is temporarily closed, and the diversion action to the diversion line 29 is stopped. Therefore, the fluid in the chamber on the opposite side of the cylinder 4 is transferred from the throttle 37 to the tank 7 by the force of the spring 5.
As a result, the discharge rate control element 2 begins to tilt in the direction of the maximum inclination angle due to the spring force of the spring 5, and begins to increase the discharge rate. The pressure control valve 30 then enters the pressure compensation mode as described below. Namely. The pump discharge pressure acts on the primary port 24 side of the spool 31, and the fluid pressure due to the load W and the spring pressure of the spring 33 act on the back pressure chamber 32 at the other end.
1 moves forward and backward in the axial direction. Therefore, the fluid pressure on the primary port 24 side of the pressure control valve 30 and the back pressure chamber 3
When the pressure difference with the fluid pressure on the second side is less than the spring pressure of the spring 33, the pressure control valve 30 closes the space between the secondary bow [25] and the primary boat 24 and drains the fluid on the opposite spring side of the cylinder 4. The fluid is discharged from the throttle 37 into the tank 7a, and the discharge amount variable control element 2 is inclined toward the maximum flow rate discharge side to increase the discharge amount. On the other hand, the primary port 2 of the pressure control valve 30
When the pressure difference between the fluid pressure on the 4 side and the fluid pressure on the back pressure chamber 32 side is greater than the spring pressure of the spring 33, the pressure control valve 3
0 connects the primary boat 24 and the secondary port 25,
The fluid in the main stream circuit 8 is supplied to the opposite spring side of the cylinder 4 through the branch line 29 to control the discharge amount variable control element 2.
Position the variable pump 1 on the neutral side, that is, on the minimum slope side.
Reduce the discharge amount. Note that at this time, pressure fluctuations in the branch line 29 are reduced due to the action of the throttle 37. In this way, the pressure control valve 30 responds to the fluid pressure difference between the primary port 24 side and the back pressure chamber 32, that is, the pressure difference before and after the variable flow rate adjustment orifice 19, and adjusts the pressure between the secondary port 25 and the primary boat. 24 to control the discharge amount and discharge pressure of the variable pump 1 according to the opening degree and load of the variable flow rate adjustment orifice 19 to prevent unnecessary fluid from being discharged. The differential pressure between the front and rear is controlled to a constant value corresponding to the spring pressure of the spring 33. Therefore, power loss is reduced. Furthermore, during flow control when the flow rate directional control valve 10 is in the switching position, the vent path 22 is closed by the vent switching section 21, so that the back pressure chamber 32 of the pressure control valve 30 is Unlike the conventional example, wasteful leakage flow does not occur, and therefore power loss is further reduced. In addition, this fluid control device does not cause wasteful leakage flow during flow rate control and maintains the effect that power loss is small, and furthermore, the plurality of actuators 50,
50a, 5Qb as each flow direction control valve 101 10at
10b flow rate adjustment variable orifice 19.19a, 19
When simultaneously driven via the shuttle valve 42b,
Since the largest load pressure is transmitted to the back pressure chamber 32 of the pressure control valve 30 via 42a, the pressure control valve 3o can control the discharge pressure and discharge amount according to the maximum load pressure, and the individual actuators 50, 50a , 50b, each flow rate adjusting variable orifice 19.19a. Pressure control valve 43° 43a that reduces the pressure difference before and after 19b
, 43b are controlled at substantially constant speeds, and the speeds of the plurality of actuators 50, 50a, 50b can be controlled simultaneously and accurately. Note that while the pressure control valve 30 is in operation. It is assumed that the pilot valve 80 is closed because the pressure in the back pressure chamber 32 is below its set pressure. Furthermore, when the movement of the hydraulic cylinders as all the actuators 5ot-soa+50b is restricted, for example at the end of the stroke, and the pressure in the back pressure chamber 32 of the pressure control valve 3° increases, the pilot valve 80 adjusts the back pressure to the set pressure. The pressure in chamber 32 is controlled. For this reason, the pressure control valve 3o opposes the fluid pressure of the primary boat 24 acting on one end of the spool 31 with the set pressure of the pilot valve 8° acting on the other end of the spool 31, and rotates the spool 31 into the axis. The discharge amount of the variable pump 1 is controlled as described above by opening and closing the space between the secondary port 25 and the primary boat 24, so that the fluid pressure in the primary boat 24 is lower than the set pressure. The pressure is also controlled to be high by a certain value corresponding to the spring force of the spring 33. At this time, the fluid discharged from the variable pump 1 is supplied to a pilot line 13, which has a main flow circuit 8, a variable flow rate adjustment orifice 19°, a feedback passage 20, and a throttle 88, as shown in FIG. The tank 7 passes through the back pressure chamber 32, the pilot valve 8L drain boat 28 and the tank line 4o.
However, due to the action of the throttle 88 with a small opening degree, the pressure in the back pressure chamber 32 is the set pressure of the pilot valve 80 regardless of the opening degree of the variable flow rate adjustment orifice 19. Further, due to the operation J'T:4 of the throttle 88, the discharge amount of the variable pump 1 is extremely small, close to zero. therefore,. This fluid device can control the pressure in the main circuit 8 to a constant pressure with very little power. The embodiment shown in FIG. 4 has the second and third main structures and the main circuit 8 is formed into a closed circuit. In the case of 1, there is a low pressure IJ valve 4 on the suction side of the fluid pump 1.
The fluid controlled in step 4 is replenished by the charge pump 45, but since this replenishment flow rate only corresponds to the amount of leakage in a closed circuit, the volume of the tank can be made smaller than in an open circuit. It is advantageous. As is clear from the above description, the fluid device according to the present invention has a variable discharge rate pump and an actuator that maintain the discharge rate at the maximum value by biasing the variable discharge rate control element in the direction of maximum inclination. An 11-failure pressure reducing type pressure control valve and a variable flow rate adjustment orifice are provided in the mainstream circuit between the valves from the upstream side, and another mainstream circuit is connected from the mainstream circuit upstream of the pressure reducing pressure control valve to other actuators. branch out,
The mainstream circuit is also provided with a pressure reducing pressure control valve and a variable flow rate adjustment orifice sequentially from the upstream side, and has a primary port and a secondary port, and the outer peripheral surface of the spool that can be freely opened and closed between these ports. A secondary port of a two-boat pressure control valve that closes the secondary port and a cylinder that drives the variable discharge amount control element in a neutral direction are connected via a line,
A tank line with a restriction is branched from the line, and one of the above primary ports is connected to the mainstream circuit, and the above is further connected to one end of the spool of the two-boat type pressure control valve. In addition to transmitting the pressure upstream from the decompression expansion pressure control valve,
The control line of the shuttle valve is connected to the back pressure chamber compressed with a spring at the other end of the spool, and the pilot line of the shuttle valve is linked to the opening and closing of each variable flow rate adjustment orifice to adjust each flow rate. Only the opening 11i''1 of the flow rate adjusting hood 1 variable orifice is switched to communicate with the rear of the variable orifice and the vent path which has a low pressure, and the maximum load among the respective load pressures at the rear of the variable flow rate adjusting orifice is The pressure is selected by the shuttle valve and transmitted to the back pressure chamber of the pressure control valve, and the two-port pressure control valve is made to respond to the differential pressure between the two pressures transmitted to both ends of the spool. The discharge volume of the variable discharge volume pump is controlled by freely opening and closing between the next port and the secondary port, so the discharge volume and discharge pressure of the variable volume pump can be controlled as required. While maintaining the energy saving effect of reducing power loss, unnecessary leakage flow rate can be eliminated and power loss can be further reduced, and
Even if the load pressures of the plurality of actuators are different, it is possible to obtain the effect that the speeds of the plurality of actuators can be accurately controlled at the same time. 4. Brief description of the drawings Fig. 1 is a circuit diagram of a conventional fluid device, Fig. 2 is a circuit diagram of an embodiment of the present invention, Fig. 3 is a partial sectional view of Fig. 1, and Fig. 4 is a circuit diagram of an embodiment of the present invention. FIG. 3 is a circuit diagram of another embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Variable discharge amount pump, 2... Variable discharge amount control element, 4... Cylinder, 7a, 7b, 7
c...tank, 8. 8a, 8b, - Mainstream circuit, 1゛9゜19a, 19b... Variable flow rate adjustment orifice, 21... Pen switching section, 22.
・・Vent path, 24・・Primary port, 25・
...Secondary port, 26...Tank port, 3
0...2 port pressure control valve, 43°43a,...
43b...pressure reducing type pressure control valve, 50°50a,
50b...actuator. Patent applicant Daikin Industries Co., Ltd. Agent Patent attorney Aoyama Aoyama and two others Procedural amendment November 29, 1981 Patent application No. 61644 1988 Name of invention Fluid device 3 Case of person making amendment Relationship with Patent applicant (1 location: Osaka Prefectural University 1, City 11. Do [11]) 1-cho-ro 12
New Hankyu Building name on the 39th (2H::,)! , Ire 1. :1, Shikisha I ('z2 -, I+,,
II+ 111
I will submit 4 representatives including Hei.

Claims (1)

[Claims] (1) Mainstream circuit between the variable discharge amount pump (1) and the actuator (50) (8) Sequentially from the upstream side, the pressure-reducing expansion pressure control valve (4)
3) and a variable flow rate adjustment orifice [19].
) to another actuator +5Qa, ) is branched off to another mainstream circuit (8a), and this mainstream circuit [8a] is also sequentially equipped with a decompression expansion pressure control valve (48a) and a variable flow rate adjustment orifice (19a) from the upstream side. On the other hand, it has a primary port (24") and a 22nd port (25), and a nupool (3") which can be opened and closed between these ports (24") and (25).
1) Close the above secondary bow) (251 on the outer peripheral surface of 2)
The secondary port (25,) of the port type pressure control valve (30) and the cylinder (4) that drives the variable discharge amount control element (2) in the neutral direction are connected via a line (29), and the A tank line (159) having a throttle (37) is branched from the line (29), and the primary boat (24)
) is connected to the mainstream circuit [8], and furthermore, the pressure on the upstream side of the decompression and expansion pressure control valves (48) and (48a) is connected to one end of the Nupur (81) of the two-hode type pressure control valve (80). At the same time, the control line of the shuttle valve c42a) is connected to the back pressure chamber (32) in which the nupling (33) at the other end of the nupling (31) is compressed.
2a) pilot line (13).
). (19X), each flow rate adjustment variable O IJ
The flow rate adjustment variable orifices '19) + C1, 9x) are switched to communicate with the rear of the pipes 7 [19) and (19x) and the low pressure vent passage (22) to adjust the respective flow rates. Variable orifice (19L
x) The shuttle valve (42a) selects the maximum load pressure among the load pressures after the tv, and the pressure control valve (80)
The back pressure chamber (32)j is transmitted, and the above 2.
The boat-type pressure control valve (80) is made to respond to the differential pressure between both positive forces transmitted to both ends of the Nupur (31), so that the gap between the primary boat (24) and the secondary boat (251) can be opened and closed. A fluid device characterized in that the discharge amount of the variable discharge amount pump (1) is controlled.