JPS624708Y2 - - Google Patents

Description

[Detailed description of the invention] This invention consists of an even number of variable displacement pumps driven by one prime mover, a regulator that increases or decreases the discharge flow rate of each pump, and a control system that supplies operating hydraulic pressure to each regulator. and a pump, the regulator operates to reduce the pump discharge flow rate by the discharge pressure of the variable displacement pump to which the regulator itself belongs, and the variable displacement pump to which the other regulator belongs. The present invention relates to a control device for an even number of variable displacement pumps that operates to reduce the pump discharge flow rate depending on the discharge pressure of the pump, and is particularly suitable for controlling an even number of variable displacement pumps that are suitable for operating actuators of different capacities. Regarding a control device.

FIG. 1 shows the pressure-flow characteristics of a variable displacement pump controlled by a conventional control device of this type. Each variable displacement pump is limited by the equal horsepower curve A-A' that can be effectively utilized from the prime mover.
Normally, the characteristics are as shown by the solid line a-b-c. Here, two variable displacement pumps B 1 with a maximum discharge flow rate Q ₀ and a maximum discharge pressure P ₀ are used with a prime mover having an effective horsepower twice that of _the equal horsepower curve A-A'.
(hereinafter simply referred to as pump B ₁ ) and variable displacement pump B ₂ (hereinafter simply referred to as pump B ₂ ), the above-mentioned pumps B ₁ and B ₂ usually have the same a-b-c characteristics. It is set to . In controlling pump B ₂ in such a case, if pump B ₁ has characteristics between a and b, that is, pump
When the discharge pressure of B ₁ is small, the full horsepower of the prime mover is not used, so the horsepower used by pump B ₂ can be controlled to be increased so that the full horsepower can be used effectively. That is, the characteristics of the pump _B2 can be temporarily changed to a-b-de by an amount equivalent to the horsepower that is not being used by the pump _B1 . In the characteristic range of d-e, when the discharge pressure of pump B ₂ is high, pump B ₂ reduces the discharge flow rate, and conversely, when the discharge pressure is low, the discharge flow rate is increased and approximately the same horsepower is used. Perform such control. Further, when the discharge pressure of pump _B1 increases, the characteristics of pump _B2 decrease from de to bc.

The control described above is exactly the same for pump _B1 .

As described above, in the conventional control device, the pressure-flow characteristics of each pump can be changed in order to use the full horsepower of the prime mover. However, this control is based on the same capacity and characteristics, and changes the characteristics only when there is surplus power in the prime mover to increase the discharge flow rate for the same discharge pressure. More precisely, it is a control that changes the characteristics within the range from de to bc. For this reason, even in circuits equipped with actuators of different capacities, the effective horsepower of the prime mover has to be divided into two equal parts.

Figure 2 shows a specific example of a conventional control device, in which pumps B ₁ and B ₂ are driven simultaneously by one prime mover (not shown), and each pump discharges It is equipped with regulators R ₁ and R ₂ that increase and decrease the flow rate.

Further, the pump B ₂ side is provided with a control pump 1 that supplies operating oil pressure to the regulators R ₁ and R ₂ . Since the regulators R ₁ and R ₂ have exactly the same configuration, one regulator R ₂ will be described in detail, and the corresponding parts of the other regulator R ₁ will be appended with ''. The servo cylinder 2 has a head side oil chamber 2a with a large pressure receiving area, and a rod side oil chamber 2b.
The piston 2c has a small pressure receiving area, and a piston rod 2d. Said piston rod 2
d is connected to the swash plate 4 of the pump B ₂ via a fork 3 and to the sleeve 7 of the servo spool 6 via a link 5. Further, pressure oil from the control pump 1 is guided to the rod side oil chamber 2b via a conduit 8. Further, a conduit 11 is connected to the head side oil chamber 2a by a servo spool 6 and is switched and connected to a tank T or a conduit 10 branching from the conduit 8. The servo spool 6 has a position A for connecting the conduit 11 to the tank T, a position R for connecting the conduit 11 to the conduit 10, and a neutral position for blocking both. Also, the servo spool 6 is
A conduit 12 for guiding part of the pressure oil from the pump _B2 as pilot pressure is connected to one side thereof, and a single acting cylinder 13 is disposed on the other side. The single acting cylinder 1
3, a spring 14 is interposed between the piston 13c and the cylinder head wall in the head side oil chamber 13a, and the piston rod 13d is locked to the servo spool 6 via the spring 15. Further, a conduit 16 is connected to the rod-side oil chamber 13b of the single-acting cylinder 13 for guiding a portion of the pressure oil of _the pump _B1 to which another regulator R1 belongs. A conduit 16' for guiding part of the pressure oil of the variable displacement pump _B2 is connected to the rod side oil chamber 13b' of the single acting cylinder 13' in the other regulator _R1 .
In addition, 17 in the figure shows a relief valve provided in the discharge conduit 18 of the control pump 1.

In the above control device, when the discharge pressure of pump B ₁ is 0, and the characteristics of pump B ₂ at this time are shown as a-b-de in FIG. Then, the servo spool 6 and the servo sleeve 7, which control the position of the swash plate 4 that determines the discharge flow rate of the variable displacement pump _B2 , are balanced at the position shown in FIG. Assume that the flow rate has reached a certain level. When the discharge pressure of pump B ₂ increases from this state, the pilot pressure taken out from conduit 12 causes servo spool 6 to spring 14 and 1.
The head side oil chamber 2a of the servo cylinder 2 communicates with the tank T and the piston 2c moves to the right due to the pressure oil of the control pump 1 acting on the rod side oil chamber 2b. As a result, the servo sleeve 7 moves by the same amount as the movement of the servo spool 6 via the link 5, and is blocked and stops moving as shown in the figure. At this time, the fork 3 is attached to the piston rod 2d of the servo cylinder 2.
The amount of tilting of the swash plate 4 of the pump B ₂ connected via the pump B ₂ decreases, thereby reducing the discharge flow rate of the pump B 2 . Further, when the discharge pressure of the pump _B2 decreases, the servo spool 6 is moved to the right by the springs 14 and 15 and switched to the position R. As a result, the head side oil chamber 2a and the rod side oil chamber 2b of the servo cylinder 2
The pressure oil from the control pump 1 acts on the pump _B2 , but due to the difference in the pressure-receiving area of the piston 2c, the piston 2c moves to the left, and the opposite operation to that described above is performed. Increase the discharge flow rate.

As mentioned above, in the range of characteristics d-e in Fig. 1, when the discharge pressure of pump _B2 increases, the pump
_B2 reduces the discharge flow rate, and conversely increases the discharge flow rate when the discharge pressure decreases, thereby controlling to use approximately the same horsepower. This also applies to pump _B1 .

Further, when the discharge pressure of pump B ₁ rises from a zero state, it operates to reduce the discharge flow rate of pump B ₂ . That is, when the discharge pressure of the pump _B1 increases, the pressure in the rod side oil chamber 13b of the single acting cylinder 13 increases due to the pressure oil taken out from the conduit 16, and the piston 13c moves to the left against the springs 14 and 15. go With this, the piston rod 13d
The servo spool 6, which is engaged with the pump B2, switches to the positive position, and the discharge flow rate of the pump _B2 decreases. In this way, the discharge pressure of pump B ₁ causes pump B ₂
The characteristics of are controlled to decrease from d-e to b-c in FIG. This control is exactly the same for pump _B1 .

However, in the control device, as described above, even when pump B ₁ and pump B ₂ operate actuators of different capacities, the effective horsepower of the prime mover must be divided into two and used.

The purpose of the present invention is to change the pump characteristics in accordance with the capacity when operating actuators of different capacities, such as reducing the discharge flow rate for the same discharge pressure of a variable displacement pump on the small capacity actuator side. , and the pump characteristics are changed to increase the discharge flow rate for the same discharge pressure of the variable displacement pump on the actuator side, which has a larger capacity, so that the total horsepower remains constant. Besides the usual characteristics of b-c,
An object of the present invention is to provide a control device for an even number of variable displacement pumps that can be used in a variety of ways as pumps having different pump characteristics such as a-de or a-f-g.

The present invention includes an even number of variable displacement pumps driven by a single prime mover, and a control hydraulic pump that supplies operating hydraulic pressure to each regulator that increases or decreases the discharge flow rate of the variable displacement pump. is a servo cylinder that operates the variable tilting angle mechanism of a variable displacement pump, and the pressure oil direction with respect to the servo cylinder is determined by the discharge pressure P ₁ from one of the pair of variable displacement pumps. A servo spool that switches the servo spool to the side that increases the pump discharge flow rate, and a single unit that switches the servo spool in the same direction as the switching caused by the discharge pressure P ₁ by the discharge pressure P ₂ from the other variable displacement pump. In a control system for an even number of variable displacement pumps, each regulator's single-acting cylinder is replaced with a double-rod type double-acting cylinder with equal pressure receiving area, and half of the double-acting cylinders are The first chambers of the double-acting cylinders and the second chambers of the remaining half of the double-acting cylinders are connected to each other via conduits, and the second chambers of half of the double-acting cylinders and the first chambers of the remaining half of the double-acting cylinders are connected to each other via conduits. and each of the conduits is connected to the control pump and oil tank via a directional valve, and the first half of the double-acting cylinders is connected to the
and the second chambers of half of the double-acting cylinders and the second chambers of the remaining half of the double-acting cylinders so that the servo spool performs the switching when pressure oil acts on the second chambers of half of the double-acting cylinders and the second chambers of the other half of the double-acting cylinders. The present invention is characterized in that the piston rod of each double-acting cylinder is locked to the servo spool so that when pressure oil acts on one chamber, the servo spool is switched to reduce the pump discharge flow rate.

Hereinafter, one embodiment of the control device for the variable displacement pump of the present invention will be described with reference to FIG. In the figure, variable displacement pump B ₃ (hereinafter simply referred to as pump B ₃ ) and variable displacement pump B ₄ (hereinafter simply referred to as pump B ₄ ) are driven simultaneously by one prime mover. In addition, regulators R ₃ and R ₄ are provided for increasing and decreasing the pump discharge flow rate, respectively. Further, the pump B ₄ side is provided with a control pump 21 that supplies operating oil pressure to the regulators R ₃ and R ₄ . Said regulator R ₃
and R ₄ have exactly the same configuration, so one regulator R ₄ will be described in detail, and
For the other regulator _R3 , '' is added to the reference numeral of the corresponding part. Servo cylinder 2
2 includes a piston 22c whose head side oil chamber 22a has a large pressure receiving area and whose rod side oil chamber 22b has a small pressure receiving area, and a piston rod 22d. The piston rod 22d is connected to the swash plate 24 of the variable displacement pump _B4 via a fork 23 and to the sleeve 27 of the servo spool 26 via a link 25. Further, pressure oil from the control pump 21 is guided to the rod side oil chamber 22b via a conduit 28. Furthermore, a servo spool 26 is provided in the head side oil chamber 22a.
A conduit 31 is connected to the tank T or to a conduit 30 branching off from the conduit 28 by means of a switch. The servo spool 26 is connected to the conduit 31
position A to connect the tank T to the tank T, and the conduit 3
1 to the conduit 30, and a neutral position that blocks both. The servo spool 26 also has a pump _B4 on one side.
A conduit 32 that guides a part of the pressure oil as pilot pressure.
is connected, and a double-acting cylinder 33 is disposed on the other side. The double-acting cylinder 33 includes a piston 33c having piston rods 33d and 33e on both sides with equal pressure receiving area, and connects one piston rod 33d to the servo spool 26 via a spring 34.
and the other piston rod 33e is locked to a fixed wall via a spring 35. The first oil chamber (oil chamber on the left side in the figure) 33a of the double-acting cylinder 33 and the second oil chamber (oil chamber on the right side in the figure) 3 of the double-acting cylinder 33' in the other regulator _R3 .
3b' are connected to each other via a conduit 50, and the second oil chamber (right side oil chamber in the figure) 3 of the double-acting cylinder 33
3b and the first oil chamber (the left oil chamber in the figure) 33a' of the double-acting cylinder 33' are communicated with each other via a conduit 51. Conduits 36 and 37 are connected to the conduits 50 and 51, respectively, and the conduits 36 and 37 are connected to the control pump 21 and the oil tank T via a directional control valve 38. Said directional control valve 3
8 connects the conduit 36 to the control pump 21 and the conduit 3
7 to the oil tank T, and
It has a position for connecting the conduit 36 to the oil tank T and a conduit 37 to the control pump 21, and a position for connecting both the conduits 36 and 37 to the oil tank T. Each spring 34, 35 and 34', 3 of the plurality of cylinders 33 and 33' described above
5' is set such that the spring force thereof is such that when the directional control valve 38 is in the position, the characteristics of the pumps B ₃ and B ₄ become b-c in FIG.

In the control device having the above configuration, when the discharge pressure of pump _B3 is 0, and the pump at this time
The characteristics of _B4 are shown as abde in FIG. The servo spool 26 and the servo sleeve 27, which control the position of the swash plate 24 that determines the discharge flow rate of the pump B ₄ , are balanced in the illustrated positions and the discharge flow rate corresponds to the inclination of the swash plate 24. do. It is also assumed that the directional control valve 38 is placed in the position. When the discharge pressure of pump B ₄ increases from this state, the conduit 32
The servo spool 26 is switched to position 1 against the springs 34 and 35 by the pilot pressure taken out from the servo cylinder 22, and the head side oil chamber 22a of the servo cylinder 22 communicates with the oil tank T, and the pressure decreases, so that the rod side oil The piston 22c moves to the right due to the pressure oil of the control pump 21 acting on the chamber 22b. As a result, the servo sleeve 27 is connected via the link 25.
moves by the same amount as the moving amount of the servo spool 26 and is blocked as shown in the figure and stops moving. At this time, the pump is connected to the piston rod 22d of the servo cylinder 22 via the fork 23.
The amount of tilting of the swash plate 24 of _B4 is reduced, reducing the pump discharge flow rate. Also, when the discharge pressure of the pump B ₄ decreases, the servo spool 26 is activated by the spring 34,
35 to move to the right and switch to position R. As a result, the head side oil chamber 22 of the servo cylinder 22
Pressure oil from the control pump 21 acts on the rod side oil chamber 22b and the piston 22c due to the difference in the pressure receiving area of the piston 22c.
c moves to the left, and the operation opposite to the above is performed to increase the pump discharge flow rate. In this way, in the range of characteristics d-e in Fig. 1, when the discharge pressure of pump _B4 increases, the pump discharge flow rate is decreased, and when the discharge pressure decreases, the pump discharge flow rate is increased, and the horsepower is approximately equal. Perform control such as using . This also applies to pump _B3 .

The control described above is completely the same as that of the prior art.
Next, the directional control valve 38 is switched to position H to connect the conduit 37 to the control pump 21 and the conduit 36 to the oil tank T, respectively. As a result, the second oil chamber 33b of the double-acting cylinder 33 and the double-acting cylinder 3
The pressure oil of the control pump 21 acts on the first oil chamber 33a' of the double-acting cylinder 33, and the piston 33c of the double-acting cylinder 33
moves to the left, switches the servo spool 26 to position E, and also moves the piston 33 of the double-acting cylinder 33'.
C' moves to the right and switches the servo spool 26' to position R'. That is, the discharge flow rate of pump B ₄ decreases, and its pump characteristics change as shown in f-g in Figure 1, and the discharge flow rate of pump B ₃ increases, and its pump characteristics change as shown in d-e. change like that.

Furthermore, the directional control valve 38 is switched to position 2, and the conduit 36 is connected to the control pump 21, and the conduit 36 is changed to the control pump 21.
7 to the oil tank T, the first oil chamber 33a of the double-acting cylinder 33 and the double-acting cylinder 3
The pressure oil of the control pump 21 acts on the second oil chamber 33b' of the double-acting cylinder 33, and the piston 33c of the double-acting cylinder 33
moves to the right, switches the servo spool 26 to position RO, and also moves the piston 33 of the double-acting cylinder 33'.
C moves to the left and switches the servo spool 26' to position A'. In other words, the discharge flow rate of pump _B4 increases, and its pump characteristics change as shown by de,
Furthermore, the discharge flow rate of pump _B3 decreases, and its pump characteristics change as shown by f-g.

Therefore, in the control device of the present invention, the pump characteristics of the pumps B ₃ and B ₄ having the same capacity are controlled so that they have completely different characteristics. More precisely, for the same discharge pressure, the discharge flow rate of one pump is decreased to change its pump characteristics, and the discharge flow rate of the other pump is increased so that the total horsepower remains constant. Since the pump characteristics are controlled to change, even if the capacities of the actuators operated by each pump differ, they can be operated optimally.

In addition, in the above embodiment, the control pump 21
By varying the set pressure of the relief valve 170 in the discharge conduit 180 of each pump B ₃ , B _{4 .}
The amount of movement of the pump characteristics can be changed arbitrarily. Further, instead of the relief valve 170, a pressure reducing valve may be installed between the control pump 21 and the directional switching valve 38 to change the pressure of the pressure oil to the double acting cylinders 33 and 33'.

FIG. 4 shows another embodiment of the control device of the present invention.
Directional switching valves 39, 3 for actuators (hydraulic cylinders are shown in the figure) C, C' operated by the directional switching valve 38 and each pump B ₃ , B ₄
This figure shows a circuit in which the switch 9' can be switched depending on the pilot pressure. In the figure, the same reference numerals as in FIG. 3 indicate the same or equivalent parts. Pilot conduits 40 and 41 are led to both ends of the directional control valve 39 for actuator C, respectively, and pilot conduits 40' and 41' are led to both ends of the directional control valve 39' for actuator C', respectively. . The pilot conduits 40, 41 are provided with switching valves 42, 43 which can selectively connect the conduits to the control pump 21 or the oil tank T. Further, the pilot conduits 40', 41' are provided with switching valves 42', 43' which can selectively connect the conduits to the control pump 21 or the oil tank T. Both the switching valves 42 and 43 are operated by a control lever 44.
The operating lever 4
4 is moved in the direction of the arrow, the switching valve 42 switches to connect the pilot conduit 40 to the control pump 21, and the pilot pressure generated in the pilot conduit 40 causes the directional switching valve 39 to connect to the actuator C.
The position is changed to shorten the piston rod. When the operating lever 44 is moved in the opposite direction to the arrow, the switching valve 43 connects the pilot conduit 41 to the control pump 21, and the directional switching valve 39 switches to a position in which the piston rod of the actuator C is extended. Similarly, the switching valves 42' and 43' are operated by an operating lever 44'.
When C is moved in the direction of the arrow, the switching valve 42' switches to connect the pilot conduit 40' to the control pump 21, and the pilot pressure generated in the pilot conduit 40' causes the directional switching valve 39' to connect the actuator C'. The position is changed to extend the piston. When the operating lever 44' is moved in the opposite direction to the arrow, the switching valve 43' switches to connect the pilot conduit 41' to the control pump 21, and the directional switching valve 39' shortens the piston rod of the hydraulic cylinder C'. switch to the position where the In this control circuit, a conduit 46 is provided which communicates the pilot conduits 40 and 41 via a shuttle valve 45, and also connects the pilot conduits 40' and 41' via a shuttle valve 45'. A conduit 46' is provided. A pilot conduit 47 taken out from the shuttle valve 45 is led to one end of the directional control valve 38, and a pilot conduit 47' taken out from the shuttle valve 45' is led to the other end.

In the control circuit configured as described above, when one operating lever 44 is moved in the direction of the arrow, the pilot pressure generated by switching the switching valve 42 causes the directional switching valve 39 to switch to a position where the piston rod of the actuator C is shortened. A portion of the pilot pressure acts on one end of the directional control valve 38 via the shuttle valve 45 and the pilot conduit 47, so that the directional control valve 38 is switched to position 2. Therefore, similarly to the first embodiment, the discharge flow rate of pump B ₄ increases and the discharge flow rate of pump B ₃ decreases, changing the characteristics of each pump. When the other operating lever 44' is moved in the direction of the arrow, the pilot pressure generated by switching the switching valve 42' causes the directional switching valve 39' to switch to a position that extends the piston rod of the actuator C'. A portion of the pilot pressure acts on the other end of the directional valve 38 via the shuttle valve 45' and the pilot conduit 47', causing the directional valve 38 to switch to position H. Therefore, the discharge flow rate of pump B ₄ decreases, and the discharge flow rate of pump B ₃ increases, changing the characteristics of each pump. Furthermore, if both operating levers 44, 44' are operated simultaneously,
The same pilot pressure acts on both ends of the directional control valve 38, so that the directional control valve 38 maintains the neutral position, and the pump characteristics of both pumps B ₃ and B ₄ become equal.

In this embodiment as well, the horsepower of the prime mover can be used effectively by increasing the discharge flow rate of the pump that operates the actuator. That is, for the same pressure, the discharge flow rate of one variable displacement pump is decreased to change its pump characteristics, and the discharge flow rate of the other variable displacement pump is increased so that the total horsepower remains constant. Since the pump characteristics are controlled to change, even if the capacities of actuators C and C' are different, they can be operated optimally.

In the first and second embodiments described above, the control of two variable displacement pumps has been described, but the above-mentioned also applies to systems using an even number of pumps, such as 4 or 6 pumps. Of course, it is possible to achieve effects and effects.

As described above, according to the control device of the present invention, the discharge flow rate of one variable displacement pump is reduced for the same discharge pressure to change its pump characteristics, and the total horsepower remains constant. By increasing the discharge flow rate of the other variable displacement pump and changing its pump characteristics, it is possible to control the same pump to have different pump characteristics, so the horsepower of the prime mover can be effectively used to control actuators of different capacities. can be operated optimally.

[Brief explanation of the drawing]

Fig. 1 is a graph that compares and explains the discharge pressure-discharge flow rate characteristics of a variable displacement pump according to the present invention and a conventional one, and Fig. 2 is a circuit diagram showing a control device for a conventional variable displacement pump. , FIG. 3 is a circuit diagram showing one embodiment of the control device of the present invention, and FIG. 4 is a circuit diagram showing another embodiment of the present invention. B ₃ , B ₄ ... Variable displacement pump, R ₁ , R ₂ ... Regulator, 21 ... Control pump, 22, 2
2'... Servo cylinder, 26, 26'... Servo spool, 27, 27'... Servo sleeve, 3
3, 33'...Double acting cylinder, 33a, 33a'...
...First oil chamber, 33b, 33b'...Second oil chamber, 33
c, 33c'...Piston, 33d, 33e, 33
d', 33e...Piston rod, 34, 35, 3
4', 35'... Spring, 38... Directional switching valve, 5
0,51... Conduit.

Claims (1)

[Scope of utility model registration request] It is equipped with an even number of variable displacement pumps driven by one prime mover, and a control hydraulic pump that supplies operating hydraulic pressure to each regulator that increases or decreases the discharge flow rate of the variable displacement pump, and each regulator has a variable displacement pump. The servo cylinder that operates the variable displacement mechanism of the displacement pump and the discharge pressure from one of the pair of variable displacement pumps.
_P1 causes the servo spool to switch the direction of the pressure oil to the servo cylinder to the side that increases the pump discharge flow rate, and the discharge pressure _P2 from the other variable displacement pump changes the servo spool to the discharge pressure. In a control system for an even number of variable displacement pumps, which have single-acting cylinders that switch in the same direction as the switching by P ₁ , the single-acting cylinder of each regulator is replaced by a double-acting double-acting cylinder with equal pressure receiving area. of the double-acting cylinders, the first chamber of half of the double-acting cylinders and the second chamber of the other half of the double-acting cylinders, and the second chamber of half of the double-acting cylinders and the second chamber of the remaining half of the double-acting cylinders. The first chambers of half of the double-acting cylinders and the other half of the double-acting cylinders are connected to each other via conduits, and each conduit is connected to the control pump and oil tank via a directional control valve, and the first chambers of half of the double-acting cylinders and the other half of the double-acting cylinders are Pressure is applied to the second chambers of half of the double-acting cylinders and the first chambers of the remaining half of the double-acting cylinders so that when pressure oil acts on the second chambers of the double-acting cylinders, the servo spool performs the switching. An even number of variable displacement pumps, characterized in that the piston rod of each double-acting cylinder is locked to a servo spool so that the servo spool is switched to the side that reduces the pump discharge flow rate when oil acts on the servo spool. control device.