JPH0444871Y2 - - 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. In other words, if the pump discharge pressure increases, the pump displacement control device moves the swash plate or oblique shaft of the pump to reduce the pump displacement, thereby reducing the pump discharge volume and maintaining the pump horsepower constant. .

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 that 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 control cylinder b stops moving and the discharge amount of the pump a decreases, the pump horsepower 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 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 a must be set within the range of the rated output of the prime mover j. It is convenient because it can prevent the prime mover j from being overloaded just by leaving it in place.

(Problem to be solved by the invention) When a plurality of pumps a equipped with pump capacity control devices 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 high altitude areas 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.

The object of the present invention is to provide a horsepower setting device that can easily change the settings of each pump capacity control device for a plurality of pumps driven by a single prime mover according to the power state of the prime mover. .

(Means for solving the problem) 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 pressure fluid are provided, and these hydraulic pumps are combined into one prime mover. In the hydraulic pump, the pressure fluid passages acting on each pump displacement control device are connected to each other, and the highest discharge pressure of each hydraulic pump selected by a shuttle valve is introduced into the passage. The pressure introduction path is connected to the pressure introduction path, and the pressure introduction path is provided with an opening/closing control member that slides to open and close the pressure introduction path and connect the passage to the tank. A plurality of pressure receiving surfaces of the same area are formed so that the discharge pressure of each hydraulic pump acts in the same direction so as to be pressed in the opening direction, and the pressure introduction passage is closed and pressed in the direction to connect the passage to the tank. has the total area of each of the pressure receiving surfaces and forms an opposing pressure receiving surface on which the pressure introduced into the pump displacement control device acts, and further in the same direction as the force generated on the opposing pressure receiving surface by the action of the pilot pressure from the outside. An auxiliary pressure-receiving surface is formed to generate a force, and the horsepower is controlled to a setting proportional to the pilot pressure.

(Function) Conventionally, for example, two variable displacement hydraulic pumps are connected to one prime mover, and each pump is provided with a pump displacement control device that uses pressure fluid to control pump horsepower to a constant level. However, in the present invention, the discharge pressure of each pump acts in one direction on the pressure receiving surface of the on-off control valve, and the pressure introduced into the pump displacement control device acts on the opposing pressure receiving surface. Furthermore, since the pilot pressure acts on the auxiliary pressure receiving surface, the fluid pressure acting on the servo valve of the pump displacement control device via the opening/closing control member is adjusted to a pressure corresponding to the discharge pressure and pilot pressure of each pump. Moreover, since the fluid pressure acting on the servo valve is selected by the shuttle valve and used by the highest fluid pressure among the pumps, a special hydraulic power source for operating the servo valve is not required.

The force generated on the auxiliary pressure receiving surface is calculated by multiplying the pilot pressure PP, which is pressure-controlled by the control valve, by its area B. For example, there are two pumps, their discharge pressures are P ₁ and P ₂ respectively, the area of each pressure receiving surface is A,
If the area of the opposing pressure-receiving surface is 2A and the pressure acting on the pump displacement control device is P _c , the balance of the opening/closing control member is expressed as (P ₁ +P ₂ )A=2AP _c +B·PP. According to this, P _c is (P ₁ + P ₂ )/2−(B×
PP)/2A. Therefore, pressure can be applied to the pump displacement control device in accordance with each discharge pressure and pilot pressure of the pump, and the servo valve of each pump displacement control device is automatically operated according to the pressure, thereby increasing the horsepower of each pump. can be controlled at a constant level. The opening/closing control member operates intermittently to connect the pressure introduction path to the tank, and does not constantly flow pressure fluid into the tank, so there is little loss of fluid energy.

(Embodiment) An embodiment of the present invention will be explained with reference to FIG. 2, which shows two hydraulic pumps.
Reference numeral 1 indicates a variable displacement hydraulic pump driven by one prime mover 21, and 2 and 2 indicate pump capacity control devices provided in each hydraulic pump 1 to variably control the pump capacity. 2 is the same as the conventional one, and the rod 4 of the control cylinder 3 is connected to the swash plate of the pump 1, and the pump discharge pressure of the own pump 1 is applied to the chamber 5 on the rod side of the control cylinder 3. Pilot circuit 6
Further, the chamber 7 on the head side of the control cylinder 3 is provided with a force due to pressure fluid and a set of two springs 8, long and short.
A servo valve 9 that is reciprocated by the force of the rod 4 through the tank 10 or the chamber 5 on the rod side
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 displacement control device 2 are connected to each other, and the passage 12 receives the highest discharge pressure of each hydraulic pump 1 selected by a shuttle valve 13. A spool-shaped opening/closing control member 15 is connected to the pressure introduction path 14 to be introduced, and is provided with a spool-shaped opening/closing control member 15 that slides to open and close the pressure introduction path 14 and connect the passage 12 to the tank 10. . The opening/closing control member 15
, two pressure receiving surfaces 16 and 17 of the same area are formed on which the discharge pressures of the two hydraulic pumps 1 and 1 act respectively and in the same direction, and the direction in which the member 15 opens the pressure introduction path 14 is formed. At the same time, the pressure introduction passage 14 is closed and the passage 12 is connected to the tank 1.
An opposing pressure receiving surface 18 having the total area of the respective pressure receiving surfaces 16 and 17 and on which the pressure introduced into the servo valve 9 acts is formed so as to press the member 15 in the direction of connecting to the pilot circuit. At 19, an auxiliary pressure receiving surface 20 is formed which generates a force in the same direction as the force generated on the opposing pressure receiving surface 18 by the action of a pilot pressure introduced from the outside as required.

The opening/closing control member 15 controls the discharge pressure of the pumps 1, 1 acting on the pressure receiving surfaces 16, 17 and the auxiliary pressure receiving surface 20.
In response to changes in pilot pressure, the pressure introduction passage 14 is opened and closed, and the passage 12 is slid to connect it to the tank 10, and the sliding action changes the pressure in the passage 12, that is, the pressure acting on the pump displacement control devices 2, 2. Stops when satisfies the above formula. The pressure controlled by the opening/closing control member 15 acts on the servo valve 9 of the pump displacement control device 2, 2 through the passage 12, and the pump displacement is controlled by the same operation as that shown in the first figure. 1 horsepower is controlled to be constant.

The control form changes as shown by curves A and B in Figure 3. When no pilot pressure is applied, the discharge flow rate changes along curve A, and when pilot pressure is applied, it remains unchanged in proportion to the pilot pressure. The horsepower of the pumps 1, 1 can be controlled to be constant along the upwardly slid curve B, and in this case, the set horsepower increases. If the prime mover 21 is an internal combustion engine, the output will be different depending on whether it is operated at high altitudes or at low altitudes, but when operating on level ground, a certain value of pilot pressure is applied and the engine is operated at the high horsepower setting of curve B. At high altitudes, by setting the pilot pressure to 0 kgf/cm ² and using the low horsepower setting (curve A), the engine's output horsepower can always be used effectively without the need for special adjustment. In the illustrated example, the opening/closing control member 15 is composed of a plunger 15a on which pressure receiving surfaces 16 and 17 are formed, a spool 15b on which an opposing pressure receiving surface 18 is formed, and a plunger 15c on which an auxiliary pressure receiving surface 20 is formed. etc., can also be constructed from a single member.

(Effects of the invention) As described above, in this invention, the fluid pressure acting on the servo valve of each pump displacement control device of a plurality of variable displacement hydraulic pumps driven by one prime mover is combined with the pilot pressure and each hydraulic pressure. Since it is controlled by an opening/closing control member operated by the discharge pressure of the pump, the horsepower setting of each pump can be changed steplessly by changing the pilot pressure in response to changes in the output of the prime mover from the outside. Since the opening/closing control member only communicates the pressure introduction path with the tank intermittently for control purposes, only a small amount of flow is consumed and fluid energy loss is small. Further, since the pressure source for operating the servo valve of each pump capacity control device uses the discharge pressure of each pump, special equipment is not required and the structure of the device is simplified.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the conventional example, FIG. 2 is a diagram of the embodiment of the present invention, and FIG. 3 is a constant horsepower control curve diagram of the embodiment of the present invention. 1, 1... Variable displacement hydraulic pump, 2, 2...
Pump capacity control device, 9... Servo valve, 10...
Tank, 12... Passage, 13... Shuttle valve, 1
4...Pressure introduction path, 15...Opening/closing control member, 1
6, 17...Pressure receiving surface, 18...Opposing pressure receiving surface, 20
... Auxiliary pressure receiving surface, 21 ... 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 that act on the servo valves of each pump capacity control device are connected to each other, and the passages are connected to a pressure introduction passage that introduces the highest discharge pressure of each hydraulic pump selected by the shuttle valve. The pressure introduction passage is provided with an opening/closing control member that slides to open and close the pressure introduction passage and connect the passage to the tank, and the opening/closing control member is pressed in a direction to open the pressure introduction passage. A plurality of pressure-receiving surfaces having the same area are formed so that the discharge pressure of each hydraulic pump acts in the same direction, and each of the pressure-receiving surfaces is formed so as to close the pressure introduction passage and press the passage in the direction of connecting it to the tank. An auxiliary pressure receiving surface that has a total area and forms an opposing pressure receiving surface on which the pressure introduced into the servo valve acts, and further produces a force in the same direction as the force generated on the opposing pressure receiving surface due to the action of external pilot pressure. A horsepower setting device for multiple hydraulic pumps, characterized in that: