JPH0441269Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) This invention is a horsepower application applied when driving multiple hydraulic pumps with one prime mover in industrial machinery such as construction machinery and cargo handling equipment. Concerning a setting device.

(Prior art) Conventionally, a single prime mover has been used to drive multiple hydraulic pumps, and in this case, the hydraulic pump has a pump capacity that controls the pump horsepower to a constant level by variable control of the pump capacity. A variable displacement hydraulic pump with a control device is usually used.

This type of pump can automatically control the pump horsepower, which is the product of the pump's discharge pressure and discharge amount, to a constant level by applying the pressure fluid discharged by the pump itself to the pump displacement control device. I can do it. For example, if the pump discharge pressure increases, the pump displacement control device moves the pump's swash plate or diagonal shaft to reduce the pump displacement, reducing the pump's displacement and maintaining the pump horsepower constant. do.

An example of the pump displacement control device is schematically shown in Figure 1, in which a rod c of a control cylinder b is connected to a swash plate or the like of a variable displacement hydraulic pump a, and a rod c of a control cylinder b is connected to the swash plate of a variable displacement hydraulic pump a. A pilot circuit e is provided to apply the discharge pressure of the pump a to the chamber d. Furthermore, the chamber f on the head side of the control cylinder b
is connected to the tank i or the chamber d on the rod side by a servo valve h which is reciprocated by the force of the discharge pressure of the pump a and the force of the rod c via the spring g. . When the discharge pressure of hydraulic pump a increases, servo valve h moves against spring g and communicates chambers d and f of control cylinder b, so that rod c of control cylinder b reduces the capacity of pump a. Move the swash plate, etc. The rod c
servo valve h moves chamber f on the head side to tank i.
When the pump is connected to the pump, the movement of the control cylinder b stops and the discharge amount of the pump a decreases, so that the pump horsepower, which is expressed as the product of the discharge pressure and the discharge amount, can be automatically maintained constant. Furthermore, when the discharge pressure of pump a becomes low, servo valve h is pushed by the elasticity of spring g and moves to connect chamber f on the head side to tank i. According to this, the rod of control cylinder b Since c moves to increase the pump capacity and at the same time moves to weaken the elasticity of spring g, servo valve h gradually narrows the passage between chamber f on the head side and tank i, causing control cylinder b and rod c to move. Stop. Therefore, even when the discharge pressure of pump a is low, the pump horsepower can be kept constant by increasing the discharge amount.

When a plurality of such pumps a, which can be controlled to maintain constant horsepower by themselves, are driven by one prime mover j, the total horsepower of each pump is set within the range of the rated output of the prime mover i. This is convenient because it can prevent the prime mover j from being overloaded just by doing so.

(Problem to be solved by the invention) When a plurality of pumps a equipped with a pump capacity control device capable of controlling horsepower at a constant level as described above are driven by one prime mover j, each pump a can easily be
There is an inconvenience that you cannot change the horsepower setting. For example, when prime mover j is an internal combustion engine, the output of prime mover j will be lower in areas with high altitudes than when it is on level ground, so unless the total horsepower of each pump a is also reduced, prime mover j will be overloaded. In this case, it is necessary to operate the pump capacity control device of each pump a to reduce the horsepower setting.

An object of the present invention is to provide a horsepower setting device that can change the setting of each pump capacity control device for a plurality of pumps driven by one prime mover into two stages depending on the power state of the prime mover. It is.

(Means for Solving the Problems) In the present invention, a plurality of variable displacement hydraulic pumps each equipped with a pump displacement control device that controls the pump horsepower to a constant level using a servo valve to which pressure fluid acts are provided, and these hydraulic pumps are are driven by a single prime mover, the oil passages for the pressure fluid acting on the servo valves of each pump displacement control device are connected to each other, and the passages are connected to each hydraulic pump selected by a shuttle valve. connected to a pressure introduction passage that introduces the highest discharge pressure among the pressure introduction passages, an opening/closing control member that slides to open and close the pressure introduction passage and connect the passage to the tank; A plurality of pressure receiving surfaces of the same area are formed on the opening/closing control member so that the discharge pressure of each hydraulic pump acts in the same direction so that the opening/closing control member is pressed in the direction of opening the pressure introduction passage, and the pressure introduction passage is closed to open the passage. forming an opposing pressure receiving surface having a total area of the respective pressure receiving surfaces so as to press in the direction of connection to the tank and on which the pressure introduced to the servo valve acts;
Furthermore, by switching the switching valve, the pressure introduced into the servo valve instead of the opposing pressure receiving surface substantially acts on the opposing pressure receiving surface to generate a force in the same direction as the force that was being generated on the opposing pressure receiving surface. Auxiliary pressure receiving surfaces having different areas are formed, and by switching the switching valve, either the opposing pressure receiving surface or the auxiliary pressure receiving surface applies a force in the direction of closing the pressure introduction passage to the opening/closing control member and connecting the passage to the tank. Now generates the power and changes the horsepower setting.

(Function) When two hydraulic pumps are driven by one prime mover, the discharge pressures of each hydraulic pump are P ₁ and P ₂ , the area of each pressure receiving surface of the opening/closing control member is A, and the area of the opposing pressure receiving surface is is 2A, the pressure acting on the servo valve of the pump displacement control device is Pc, and the area of the auxiliary pressure receiving surface is 3A.

When the switching valve is in a normal position where no switching operation is performed, the pressure introduced into the servo valve acting on the auxiliary pressure receiving surface does not substantially generate a force to press the opening/closing control member, and the opposing pressure receiving surface is introduced into the servo valve. When a force is generated to press the opening/closing control member with the same pressure, the balance of forces of the opening/closing control member is (P ₁ +P ₂ )×A=2APc.

In other words, Pc = (P ₁ + P ₂ ) ÷ 2, and since the flow rate is controlled by the total pressure of the two hydraulic pumps, the set horsepower L is L = (P ₁ + P ₂ ) / 2 x Q (Q is the flow rate), so the horsepower is Constant control is performed.

When the switching valve is switched, the force pressing the opening/closing control member that had been generated on the opposing pressure receiving surface disappears, and instead, the force applied to the opening/closing control member due to the pressure introduced to the servo valve is applied to the auxiliary pressure receiving surface. Since a pressing force is generated, the force balance of the opening/closing control member is (P ₁ +P ₂ )A=3APc.

In other words, Pc=(P ₁ +P ₂ )÷3.

For example, when P ₁ = P ₂ = P, Pc = 2/3P, which is 2/3 compared to when the switching valve is in the normal position.
, which acts on the servo valve of the pump displacement control device.

In other words, the discharge flow rate is greater than in the case of the same pressure at the normal position of the switching valve, and the set horsepower is increased. Therefore, the setting horsepower of each hydraulic pump can be changed by switching the switching valve, and the total of these setting horsepower can be easily adjusted to match the horsepower of the prime mover.

(Embodiment) An embodiment of the present invention will be explained with reference to the one shown in FIG. 2, which is equipped with two hydraulic pumps. 2, 2 indicates a pump capacity control device provided in each hydraulic pump 1 to variably control the pump capacity, and the constituent members of each pump capacity control device 2 are the same as those of conventional ones. A pilot circuit 6 is provided to connect the rod 4 of the control cylinder 3 to the swash plate, etc. of the control cylinder 3, and apply the pump discharge pressure of the own pump 1 to the chamber 5 on the rod side of the control cylinder 3. The chamber 7 on the head side of 3 is connected to the tank 10 or the chamber 5 on the rod side by a servo valve 9 which is reciprocated by the force of the pressure fluid and the force of the rod 4 via a pair of long and short springs 8 configured to be connected to. In the illustrated example, pressure fluid acts on the servo valve 9 via a piston 11.

The features of the present invention are as follows. That is, the pressure fluid passages 12 acting on each servo valve 9 of each pump capacity control device 2 are connected to each other, and the passage 12 is connected to the highest discharge pressure of each hydraulic pump 1 selected by the shuttle valve 13. A spool-shaped opening/closing control member 15 is provided on the pressure introduction passage 14 to open and close the pressure introduction passage 14 and connect the passage 12 to the tank 10 by sliding. It will be done.

The opening/closing control member 15 is formed with two pressure receiving surfaces 16, 17 having the same area, on which the discharge pressures of the two hydraulic pumps 1, 1 act, respectively, and in the same direction. The total area of each pressure-receiving surface 16, 17 is set so that the member 15 is pressed in the direction of opening the introduction passage 14 and the member 15 is pressed in the direction of closing the pressure introduction passage 14 and connecting the passage 12 to the tank 10. and on which the pressure introduced into the servo valve 9 acts through the passage 12, and furthermore, the switching valve 21 forms an opposing pressure receiving surface 18.
Instead, the pressure introduced into the servo valve 9 substantially acts to generate a force in the same direction as the force that was being generated on the opposing pressure receiving surface 18, and an auxiliary pressure receiving surface 20 having a different area from that of the opposing pressure receiving surface 18. is formed. In the illustrated case, the auxiliary pressure receiving surface 20 is formed on the pressure receiving surface of the auxiliary piston that contacts the opposing pressure receiving surface 18, and the area of the auxiliary pressure receiving surface 20 is formed to be larger than the opposing pressure receiving surface 18. However, even if the area of the auxiliary pressure receiving surface 20 is smaller than the area of the opposing pressure receiving surface 18, the essence of the present invention does not change.

When the switching valve 21 is switched, the pressure introduced into the servo valve 9 that is constantly acting on the auxiliary pressure receiving surface 20 substantially generates a force that presses the opening/closing control member 15, and the switching valve 21 When the switching operation is not performed, a force is generated on the opposing pressure receiving surface 18 that presses the opening/closing control member 15 due to the pressure introduced into the servo valve 9. To explain this further, when the switching valve 21 is switched to the switching position 21a shown in FIG. The introduced pressure acts, and only the pressure of the tank 10 acts on the surface opposite to the auxiliary pressure receiving surface 20. Therefore, a force pushing the opening/closing control member 15 to the right in the drawing is generated on the auxiliary pressure receiving surface 20. Further, when the switching valve 21 is in the normal position 21b shown in the second figure, the pressure introduced into the servo valve 9 acts on both the opposing pressure receiving surface 18 and the auxiliary pressure receiving surface 20, but the auxiliary piston itself Since the same pressure acts on the pressure-receiving surface 20 and the surface on the opposite side thereof, substantially no force is generated in the auxiliary piston that presses the opening/closing control member 15, and the force acts on the opposing pressure-receiving surface 18. The opening/closing control valve 15 is pushed to the right in the drawing by the force caused by the pressure.

Therefore, the opening/closing control member 15 has pressure receiving surfaces 16,1
The discharge pressure of the hydraulic pumps 1 and 2 acting on the pressure receiving surface 18 or the pressure acting on the auxiliary pressure receiving surface 20 opens and closes the pressure introduction path 14 and slides the passage 12 to connect it to the tank 10. The movement is passage 1
2, that is, the pressure acting on the pump displacement control devices 2, 2, stops when the above equation is satisfied. The pressure controlled by the opening/closing control member 15 is transmitted through the passage 12 to the pump capacity control devices 2, 2.
act on the servo valves 9, 9, and the devices 2, 2 act on the servo valves 9, 9 of
By performing operations similar to those shown in the figure, the pump capacity is controlled and the horsepower of the pumps 1, 1 is controlled to be constant.

The control form changes as shown by curves A and B in FIG. , the discharge flow rate changes along curve B.

If the prime mover 23 is an internal combustion engine, the output will be different depending on whether it is used at high altitudes or at flatlands.
If the pump displacement control devices 2, 2 are controlled along the curve B as the position 21b on flat ground, and the pump capacity control devices 2 and 2 are controlled along the curve A as the position 21b, then the motor 23
output can always be used effectively. Also, the prime mover 2
If 3 is an electric motor, the pumps 1, 1 can be driven according to the output of the prime mover 23 by switching the switching valve 21 in each region of 60 Hz and 50 Hz.

(Effects of the invention) As described above, according to the invention, an opening/closing control member is provided in the pressure introduction path that leads the highest pump discharge pressure to the servo valve of each pump displacement control device, and the opening/closing control member is provided with the opening/closing control member.
The pressure receiving surface on which the discharge pressure of each pump acts, the opposing pressure receiving surface on which pressure acts on the servo valve facing it, and the switching valve, the pressure on the servo valve acts on the opposing pressure receiving surface instead of the opposing pressure receiving surface, and the pressure on the servo valve acts on the opposing pressure receiving surface. Since an auxiliary pressure receiving surface is formed that has a different area from the opposing pressure receiving surface that generates a force in the same direction as the surface, the pressure acting on the servo valve can be controlled by switching the switching valve, making it easy to use as a pump displacement control device. The horsepower setting of the motor can be changed, and the output of the prime mover can be used effectively.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a conventional example, FIG. 2 is a diagram of an embodiment of the present invention, and FIG. 3 is a diagram of control characteristics. 1, 1... Variable displacement hydraulic pump, 2, 2...
Pump capacity control device, 9, 9... Servo valve, 12
... Passage, 14 ... Pressure introduction path, 15 ... Opening/closing control member, 16, 17 ... Pressure receiving surface, 18 ... Opposite pressure receiving surface, 20 ... Auxiliary pressure receiving surface, 21 ... Switching valve, 2
3... Prime mover.

Claims (1)

[Scope of utility model registration request] A plurality of variable displacement hydraulic pumps each equipped with a pump displacement control device that controls the pump horsepower to a constant level using a servo valve applied with pressure fluid are installed, and these hydraulic pumps are driven by a single prime mover. The pressure fluid passages acting on the servo valves of each pump displacement control device are connected to each other, and the passages are connected to each other.
The shuttle valve is connected to the pressure introduction path that introduces the highest discharge pressure of each hydraulic pump selected, and the pressure introduction path is opened and closed by sliding, and the passage is connected to the tank. A plurality of pressure receiving surfaces having the same area are formed on the opening/closing control member to which the discharge pressure of each hydraulic pump acts in the same direction so that the opening/closing control member is pressed in the direction of opening the pressure introduction path. An opposing pressure receiving surface having a total area of the respective pressure receiving surfaces and on which the pressure introduced into the servo valve acts is formed so as to close the pressure introduction passage and press the passage in a direction to connect the passage to the tank, and further includes a switching valve. By switching, the pressure introduced into the servo valve instead of the opposing pressure-receiving surface substantially acts on the opposing pressure-receiving surface to generate a force in the same direction as the force generated on the opposing pressure-receiving surface. A horsepower setting device for multiple hydraulic pumps, characterized by forming a pressure receiving surface.