JPH0744771Y2 - Variable displacement hydraulic / mechanical power converter constant flow rate horsepower controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a constant flow rate horsepower control device for a variable displacement hydraulic / mechanical power converter such as a variable displacement hydraulic pump or a variable displacement hydraulic motor. .

[Prior Art] A variable displacement hydraulic / mechanical power converter has a swash plate, and by changing the tilt angle of the swash plate, the capacity of the converter, for example, the discharge flow rate of a hydraulic pump. Can be changed.

As a flow rate control device for a variable displacement hydraulic pump, a swash plate is driven by a differential cylinder, and pressure oil is supplied to the differential cylinder by three.
Some of the three-way guide valves are operated by using the discharge pressure of the hydraulic pump as a pilot pressure, and some of these three-way guide valves are provided with a constant horsepower function.

This conventional constant flow rate horsepower control device is shown in FIG.

Reference numeral 25 denotes a differential cylinder. The differential cylinder 25 is a variable displacement hydraulic pump 1 (variable displacement hydraulic / mechanical power converter) when the piston 25A moves in a direction in which the volume of the small pressure receiving chamber 26 increases. ) So as to increase the tilt angle θ of the swash plate 2 and to decrease the tilt angle θ of the swash plate 2 when the piston 25A moves in the direction in which the volume of the large pressure receiving chamber 27 increases.
The piston rod 25B is connected to the swash plate 2.

Inside the small pressure receiving chamber 26 of this differential cylinder 25, the piston
A spring 25C for urging 25A toward the large pressure receiving chamber 27 is installed.

28 is a flow rate control valve (three-way guide valve for flow rate control), and the flow rate control valve 28 moves one of the two secondary side ports 28B and 28C to one primary side port 28A by the movement of the spool 28D. Are configured to communicate with each other.

29 is a servo pressure line, and the servo pressure line 29
Is configured to apply fluid pressure from the variable displacement hydraulic pump 1 to the primary side port 28A of the flow rate control valve 28.

Reference numeral 30 is a small pressure-receiving chamber servo pressure line, and the small pressure-receiving chamber servo pressure line 30 applies fluid pressure from the servo pressure line 29 to the small pressure-receiving chamber 26 of the differential cylinder 25.

Reference numeral 31 is a large pressure-receiving chamber servo pressure line, and the large pressure-receiving chamber servo pressure line 31 applies fluid pressure from the servo pressure line 29 to the large pressure-receiving chamber 27 of the differential cylinder 25.

Reference numeral 32 is an adjustment servo pressure line, and the adjustment servo pressure line 32 communicates one secondary side port 28B of the flow control valve 28 with the small pressure receiving chamber 26 of the differential cylinder 25.

33 is a tank line, and the tank line 33 connects the other secondary side port 28C of the flow control valve 28 to the tank 6.

34 is a bar (or link) for flow rate control, 35 is a spring, and these bar 34 and spring 35 are small pressure receiving chambers.
When the piston 25A moves in the direction in which the volume of 26 increases, the spool 28D of the flow control valve 28 is moved to a position where one secondary side port 28B communicates with the primary side port 28A and a large amount. When the piston 25A moves in a direction in which the volume of the pressure receiving chamber 27 increases, the spool 28D is differentially moved to a position where the other secondary port 28C communicates with the primary port 28A. It is connected to the piston rod 25B of the cylinder 25.

36 is a flow rate control pilot line, and the flow rate control pilot line 36 is urged toward a position where the spool 28D of the flow rate control valve 28 communicates with the primary port 28A and one secondary port 28D. In addition, fluid pressure from an external hydraulic source is applied to the spool 28D.

In the constant flow horsepower control device shown in FIG. 3, the tilt angle θ of the swash plate 2 of the variable displacement hydraulic pump 1 is increased or decreased by the cooperation of the flow control valve 28 and the differential cylinder 25 described above. The flow rate of the variable displacement hydraulic pump 1 is adjusted.

Discharge flow rate Q and flow control valve of this variable displacement hydraulic pump 1
The relationship of the pilot pressure P _{P applied} to the spool 28D of 28 is a proportional relationship as shown in FIG.

Further, 37 is a relief valve, and the relief valve 37 is connected to the flow rate control pilot line 36.

The relief valve 37 operates based on both the pilot pressure of the flow rate control pilot line 36 and the discharge pressure of the variable displacement hydraulic pump 1, and the relief valve 37 provides a pilot to the flow rate control valve 28. The upper limit of the pressure changes, and as a result, the maximum displacement of the variable displacement hydraulic pump 1 is limited.

The problem to be solved by the invention is that, in the constant flow horsepower control device shown in FIG. 3, the control means of the flow control valve 28 is pilot pressure, so that the range to which the constant flow horsepower control device can be applied is limited. There is a problem that it is limited.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a constant flow rate horsepower control device for a variable displacement hydraulic / mechanical power converter capable of performing flow rate control by means other than pilot pressure. I am trying.

[Means for Solving the Problems] In order to achieve the above object, the constant flow rate horsepower control device of the variable displacement hydraulic / mechanical power converter of the present invention has a piston 3A in a direction in which the volume of the small pressure receiving chamber 7 increases. When the piston 3A moves so as to increase the tilt angle θ of the swash plate 2 of the variable displacement hydraulic / mechanical power converter 1 and to increase the volume of the large pressure receiving chamber 9, The swash plate 2
To reduce the tilt angle θ of the piston rod 3B to the swash plate 2 and the spool 4D moves either one of the two primary ports 4A and 4B into one secondary port. Closed center type three-way guide valve for flow control that communicates with 4C, and closed center type that either one of the two primary ports 5A and 5B communicates with one secondary port 5C due to movement of the spool 5D. Constant horsepower control three-way guide valve 5, a servo pressure line 8 to which fluid pressure is applied from an external hydraulic source or a variable displacement hydraulic / mechanical power converter 1, and a small differential cylinder 3 from the servo pressure line 8. A small pressure receiving chamber servo pressure line 19 for applying fluid pressure to the pressure receiving chamber 7, and a large pressure receiving chamber servo pressure line for connecting the secondary side port 4C of the flow control three-way guide valve 4 to the large pressure receiving chamber 9 of the differential cylinder 3. 20 and the sir The flow control three-way guide valve servo pressure line 21 for applying fluid pressure from the pressure line 8 to one of the primary side ports 4A of the flow control three-way guide valve 4, and the servo pressure line 8 constant horsepower control three-way guide valve 5 A constant pressure control three-way guide valve servo pressure line 22 for applying fluid pressure to one primary side port 5A, and a secondary side port 5C of the constant horsepower control three-way guide valve 5 to the other of the flow rate control three-way guide valve 4. Connecting servo pressure line 23 communicating with the primary side port 4B, a tank line 24 communicating the other primary side port 5B of the constant horsepower control three-way guide valve 5 with the tank 6, an orifice 18, and a connecting servo pressure Bypass line 17 that connects line 23 to large pressure chamber servo pressure line 20
When the piston 3A moves in the direction in which the volume of the small pressure receiving chamber 7 increases, the spool 4D of the flow control three-way guide valve 4 is moved to a position where the secondary side port 4C communicates with one primary side port 4A. When the piston 3A is moved in the direction in which the volume of the large pressure receiving chamber 9 is increased so as to move the spool 4D
So as to move the secondary side port 4C to the other primary side port 4B toward a position communicating with the secondary side port 4B, the bar 11 or link for flow rate control connected to the piston rod 3B of the differential cylinder 3, and the spring 12 When the piston 3A moves in the direction in which the volume of the small pressure receiving chamber 7 increases, the spool 5D of the constant horsepower control three-way guide valve 5 is located at a position where the secondary port 5C communicates with one primary port 5A. When the piston 3A moves in the direction in which the volume of the large pressure receiving chamber 9 increases so as to move toward the spool, the spool
A bar 14 or link for constant horsepower control connected to the piston rod 3B of the differential cylinder 3 so as to move the 5D toward the position where the secondary port 5C communicates with the other primary port 5B, and With a spool consisting of a spring 15 and a pilot pressure applying mechanism or an electromagnetic drive mechanism that urges the spool 4D of the flow control three-way guide valve 4 toward a position where the secondary side port 4C communicates with the other primary side port 4B. A variable displacement hydraulic / mechanical power is provided so that the urging means 13 and the spool 5D of the constant horsepower control three-way guide valve 5 are urged toward a position where one primary side port 5A communicates with the secondary side port 5C. A constant horsepower control pilot line 16 for applying the fluid pressure from the converter 1 to the spool 5D.

[Operation] The fluid pressure applied from the flow rate control pilot line 13 to the spool 4D of the three-way guide valve 4 for flow rate control is increased so that the spool 4D is in the neutral position or the secondary side port 4C is connected to the other primary side port 4B. When in communication, the constant horsepower control pilot line 16 controls the constant horsepower by reducing the discharge pressure of the variable displacement hydraulic / mechanical power converter 1 or the inflow pressure to the variable displacement hydraulic / mechanical power converter 1. When the fluid pressure applied to the spool 5D of the three-way guide valve 5 for operation decreases, the spool 5D of the three-way guide valve 5 for constant horsepower control moves to the secondary side port 5C with respect to the other primary side port 5B by the repulsive force of the spring 15. Move to a position where they communicate with each other, and the large pressure receiving chamber 9 of the differential cylinder 3 passes through the flow control three-way guide valve 4 and the constant horsepower control three-way guide valve 5, or the orifice 18 of the bypass line 17 and the constant horsepower. Control Through the use three-way guide valve 5 in communication with the tank 6.

At this time, since the fluid pressure from the servo pressure line 8 is applied to the small pressure receiving chamber 7 of the differential cylinder 3, the fluid pressure applied to the large pressure receiving chamber 9 is changed to the three-way guide valve 4 for flow control. Alternatively, the piston rod 3B of the differential cylinder 3 is opened by being opened to the tank 6 via the bypass line 17.
The swash plate 2 moves in a direction to increase the tilt angle θ, and the discharge flow rate of the variable displacement hydraulic / mechanical power converter 1 or the variable displacement hydraulic / machine is changed according to the decrease of the discharge pressure or the inflow pressure. The amount of inflow to the power converter 1 increases, and constant horsepower control is performed.

The discharge pressure of the variable displacement hydraulic / mechanical power converter 1 or the variable displacement hydraulic / mechanical power converter with the secondary side port 4C communicating with the other primary side port 4B of the flow control three-way guide valve 4. When the inflow pressure to 1 increases, the fluid pressure applied from the constant horsepower control pilot line 16 to the spool 5D of the constant horsepower control three-way guide valve 5 increases, and one of the primary side ports
The spool 5D moves to a position where the secondary port 5C communicates with 5A, and the large pressure receiving chamber 9 of the differential cylinder 3 communicates with the servo pressure line 8 via the constant horsepower control three-way guide valve 5.

Thereby, the fluid pressure from the servo pressure line 8 is applied to the small pressure receiving chamber 7 of the differential cylinder 3 via the small pressure receiving chamber servo pressure line 19, and the flow control three-way guide valve servo pressure line 21 and the flow rate control are provided. Is applied to the large pressure receiving chamber 9 via the three-way guide valve 4 and the large pressure receiving chamber servo pressure line 20, and the piston rod 3B of the differential cylinder 3 is
The swash plate 2 moves in a direction of decreasing the tilt angle θ, and the discharge flow rate of the variable displacement hydraulic / mechanical power converter 1 or the variable displacement hydraulic / mechanical power converter is increased according to the increase of the discharge pressure or the inflow pressure. The inflow amount for 1 is reduced, and constant horsepower control is performed.

When the fluid pressure applied from the flow control pilot line 13 to the spool 4D of the flow control three-way guide valve 4 is reduced, and the spool 4D is in a state where the secondary port 4C communicates with one primary side port 4A. The spool of the three-way guide valve 5 for constant horsepower control from the constant horsepower control pilot line 16 due to an increase in the discharge pressure of the variable displacement hydraulic / mechanical power converter 1 or the inflow pressure to the variable capacity hydraulic / mechanical power converter 1. When the fluid pressure applied to 5D rises, the spool 5D of the constant horsepower control three-way guide valve 5 resists the repulsive force of the spring 15, and the secondary side port 5C communicates with one primary side port 5A. The large pressure receiving chamber 9 of the differential cylinder 3 communicates with the servo pressure line 8 via the flow control three-way guide valve 4.

As a result, the piston rod 3B of the differential cylinder 3 moves in a direction to decrease the tilt angle θ of the swash plate 2, and the variable displacement hydraulic / mechanical power converter 1 responds to the increase in the discharge pressure or the inflow pressure. The discharge flow rate or the inflow amount to the variable displacement hydraulic / mechanical power converter 1 decreases, and constant horsepower control is performed.

The discharge pressure of the variable displacement hydraulic / mechanical power converter 1 or the variable displacement hydraulic / mechanical power converter with the secondary side port 4C communicating with the primary side port 4A on one side of the flow control three-way guide valve 4. When the inflow pressure to 1 decreases, the fluid pressure applied from the constant horsepower control pilot line 16 to the spool 5D of the constant horsepower control three-way guide valve 5 decreases, and the repulsive force of the spring 15 causes the other primary side port 5B to flow. Secondary port 5C
The spool 5D moves to the position where
The large pressure receiving chamber 9 communicates with the tank 6 via the bypass line 17 and the constant horsepower control three-way guide valve 5.

As a result, the fluid pressure applied to the large pressure receiving chamber 9 from the servo pressure line 8 via the flow rate adjusting three-way guide valve 4 escapes to the tank 6 via the bypass line 17 and the constant horsepower control three-way guide valve 5. The piston rod 3B of the differential cylinder 3 moves in a direction to increase the tilt angle θ of the swash plate 2, and the discharge flow rate of the variable displacement hydraulic / mechanical power converter 1 according to the decrease of the discharge pressure or the inflow pressure. Alternatively, the amount of inflow to the variable displacement hydraulic / mechanical power converter 1 is increased and constant horsepower control is performed.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a constant flow rate horsepower control device for a variable displacement hydraulic / mechanical power converter according to the present invention. In the figure, the same reference numerals as those in FIG. 3 represent the same parts. ing.

Reference numeral 3 denotes a differential cylinder, which is a variable displacement hydraulic pump (variable displacement hydraulic / mechanical power converter) when the piston 3A moves in a direction in which the volume of the small pressure receiving chamber 7 increases. 1 so as to increase the tilt angle θ of the swash plate 2 and to decrease the tilt angle θ of the swash plate 2 when the piston 3A moves in the direction in which the volume of the large pressure receiving chamber 9 increases. Thus, the piston rod 3B is connected to the swash plate 2.

Reference numeral 4 is a closed center type flow control valve (three-way guide valve for flow control), and the flow control valve 4 has one of the two primary side ports 4A and 4B depending on the movement of the spool 4D. It is configured to communicate with 4C.

5 is a closed center type constant horsepower control valve (three-way guide valve for constant horsepower control), and the constant horsepower control valve 5 is a spool.
One of the two primary ports 5A and 5B communicates with one secondary port 5C by the movement of 5D.

Reference numeral 8 denotes a servo pressure line, and the servo pressure line 8 has an external hydraulic source (may be the variable displacement hydraulic pump 1).
More fluid pressure is applied.

Reference numeral 19 is a small pressure receiving chamber servo pressure line, and the small pressure receiving chamber servo pressure line 19 is adapted to apply a fluid pressure from the servo pressure line 8 to the small pressure receiving chamber 7 of the differential cylinder 3.

Reference numeral 20 denotes a large pressure receiving chamber servo pressure line, and the large pressure receiving chamber servo pressure line 20 connects the secondary side port 4C of the flow rate control valve 4 to the large pressure receiving chamber 9 of the differential cylinder 3.

21 is a flow control valve servo pressure line (three-way guide valve servo pressure line for flow control), and the flow control valve servo pressure line 21 is a fluid from the servo pressure line 8 to one primary side port 4A of the flow control valve 4. It is designed to apply pressure.

22 is a constant horsepower control valve servo pressure line (three-way guide valve servo pressure line for constant horsepower control), and the constant horsepower control valve servo pressure line 22 is from the servo pressure line 8 to one primary side of the constant horsepower control valve 5. A fluid pressure is applied to the port 5A.

Reference numeral 23 is a communication servo pressure line, and the communication servo pressure line 23 connects the secondary side port 5C of the constant horsepower control valve 5 to the other primary side port 4B of the flow rate control valve 4.

24 is a tank line, and the tank line 24 connects the other primary side port 5B of the constant horsepower control valve 5 to the tank 6.

A bypass line 17 has an orifice 18 and connects the communication servo pressure line 23 with the large pressure receiving chamber servo pressure line 20.

11 is a bar (or link), and 12 is a spring.

The bar 11 is attached to the piston rod 3B of the differential cylinder 3, and the spring 12 is connected to both the tip of the bar 11 and the spool 4D of the flow control valve 4.

The bar 11 is located at a position where the secondary port 4C communicates with the primary port 4A of the spool 4D of the flow control valve 4 when the piston 3A moves in the direction in which the volume of the small pressure receiving chamber 7 increases. When the piston 3A moves in the direction in which the volume of the large pressure receiving chamber 9 increases, the spool 4D is moved toward the secondary side port 4B with respect to the other primary side port 4B.
It is designed to move to a position where 4C communicates.

14 is a bar (or link), and 15 is a spring.

The bar 14 is attached to the piston rod 3B of the differential cylinder 3, and the spring 15 is connected to both the tip of the bar and the spool 5D of the constant horsepower control valve 5.

The bar 14 has a spool 5D of the constant horsepower control valve 5 when the piston 3A moves in a direction in which the volume of the small pressure receiving chamber 7 increases.
Is moved toward a position where the secondary side port 5C communicates with one primary side port 5A, and when the piston 3A moves in the direction in which the volume of the large pressure receiving chamber 9 increases. 5D is moved toward the position where the secondary port 5C communicates with the other primary port 5B.

Reference numeral 13 is a flow rate control pilot line (spool energizing means), and the flow rate control pilot line 13 has a proportional pressure reducing valve (not shown), and by operating the proportional pressure reducing valve, Spool 4D is the other primary port
Fluid pressure from an external hydraulic source is applied to the spool 4D so that the secondary port 4C is urged to communicate with 4B.

In this embodiment, as the spool energizing means, the flow control pilot line 13 which is a pilot pressure applying mechanism is applied, but means other than the pilot pressure applying mechanism, that is,
The spool 4D may be biased by an electromagnetic drive mechanism such as a solenoid.

Reference numeral 16 is a constant horsepower control pilot line, and the constant horsepower control pilot line 16 is urged toward a position where the spool 5D of the constant horsepower control valve 5 communicates with the primary side port 5A and the secondary side port 5C. As described above, the fluid pressure from the variable displacement hydraulic pump 1 is applied to the spool 5D.

The operation will be described below.

As is well known, the output horsepower of the hydraulic pump 1 is discharge pressure P × discharge flow rate Q. Therefore, in principle, the discharge pressure × the discharge flow rate may be controlled to be constant. Here, the output characteristics of the hydraulic pump are shown in FIG. In FIG. 2, the discharge flow rate Q and the discharge pressure P are limited because of the structural limitation of the hydraulic pump 1. Therefore,
The constant flow rate horsepower control described below corresponds to the curved portion in FIG.

Assuming that the hydraulic pump 1 is driven at a constant rotation speed,
The discharge flow rate is determined by the tilt angle θ of the swash plate 2, that is, the position of the differential cylinder 3. Also, the discharge pressure is the pilot line
It is fed back to the spool 5D of the constant horsepower control valve 5 by 16, and the force of the spring 15 opposes the discharge pressure. Therefore, it is the repulsive force of the spring 15 that determines the discharge pressure. Therefore, the specifications of the spring 15 may be determined so that the discharge pressure P × the discharge flow rate Q becomes constant according to the position of the differential cylinder 3.

From the state where the constant horsepower control valve 5 is in balance, or the state where the discharge flow rate is smaller than the discharge pressure, that is, the spool 5D of the constant horsepower control valve 5 is in the n or b position, When the pressure reducing valve is operated to reduce the pressure in the pilot line 13, the force of the spring 12 causes the flow control valve 4
The spool 4D is moved to the right and the servo pressure line 8 and the large pressure receiving chamber 9 communicate with each other, and the hydraulic pressure of the servo pressure line 8 acts on the sides of the small pressure receiving chamber 7 and the large pressure receiving chamber 9, so that the differential pressure receiving area causes The piston rod 3B of the cylinder 3 moves the swash plate 2 in the direction in which the tilt angle θ decreases. The movement of the differential cylinder 3 is fed back to the spool 4D of the flow control valve 4 via the bar 11 and the spring 12, and when the required discharge amount decreases, the spool 4D of the flow control valve 4 returns to the b position. The differential cylinder 3 is balanced by the balance between the pressure flowing from the flow rate control valve 4 into the large pressure receiving chamber 9 and the pressure escaping from the large pressure receiving chamber 9 to the tank 6 via the orifice 18 and the constant horsepower control valve 5.
Stops moving. The movement of the differential cylinder 3 is also fed back to the spool 5D of the constant horsepower control valve 5 by increasing the repulsive force of the spring 15, and the increase of the repulsive force of the spring 15 causes the spool 5D of the constant horsepower control valve 5 to move. n
Move from position to position b or maintain position b.

When the fluid pressure in the flow control pilot line 13 is increased by operating the proportional pressure reducing valve described above, the spool 4D of the flow control valve 4 is moved to the left against the force of the spring 12, and the large pressure receiving chamber 9 and constant horsepower are exerted. Spool of constant horsepower control valve 5 in communication with control valve 5
When 5D is in the n position, the differential cylinder 3 remains stopped and the discharge flow rate does not change, but in the b position, the large pressure receiving chamber 9 communicates with the tank 6 via the flow rate control valve 4 and the constant horsepower control valve 5. Therefore, the oil in the large pressure receiving chamber 9 is discharged to the tank 6, and the differential cylinder 3 moves in the direction in which the tilt angle θ of the swash plate 2 increases. The movement of the differential cylinder 3 depends on the bar 11 and the spring.
It is fed back to the spool 4D of the flow rate control valve 4 via 12 and when the required discharge amount increases, the spool 4D of the flow rate control valve 4 is pushed back to the a position side, and as described above, from the flow rate control valve 4 to the large pressure receiving chamber 9. The movement of the differential cylinder 3 is stopped by the balance between the pressure that flows in and the pressure that escapes from the large pressure receiving chamber 9 to the tank 6 through the orifice 18 and the constant horsepower control 5. The movement of the differential cylinder 3 is also fed back to the spool 5D of the constant horsepower control valve 5 by reducing the repulsive force of the spring 15, and before the movement of the differential cylinder 3 stops. When the spool 5D of the constant horsepower control valve 5 is moved to the n position due to the reduction of the repulsive force, the movement of the working cylinder 3 is stopped there, the increase of the discharge flow rate is suppressed, and the output of the hydraulic pump 1 is maintained in the curve of FIG. It That is, even if the pilot pressure in the pilot line 13 is manipulated so that the discharge amount of the hydraulic pump 1 exceeds the characteristics shown in FIG. 2, the operation of the constant horsepower control valve 5 takes precedence and the hydraulic pump 1 is operated as described above.
Is controlled. Of course, when the discharge amount of the hydraulic pump 1 does not exceed the characteristics shown in FIG. 2, the discharge flow rate of the hydraulic pump 1 is controlled by the pilot pressure of the pilot line.

Even when the pilot pressure of the pilot line 13 is not changed, if the discharge force increases and the spool 5D of the constant horsepower control valve 5 is in the a position, the servo pressure line 8 passes through the bypass line 17 and the large pressure receiving chamber. As described above, the differential cylinder 3 moves the swash plate 2 in the direction to decrease the tilt angle θ. The movement of the differential cylinder 3 is fed back to the spool 5D of the constant horsepower control valve 5 via the bar 14 and the spring 15, and when the required amount of discharge decreases, the spool 5D of the constant horsepower control valve 5 becomes the n position and becomes differential. The movement of the piston rod 3B of the cylinder 3 stops. In this case, the movement of the differential cylinder 3 is also fed back to the spool 4D of the flow control valve 4 by reducing the repulsive force of the spring 12, so that the position of the spool 4D of the flow control valve 4 is the n position or the b position. However, the bypass line 17 does not hinder the communication between the servo pressure line 8 and the large pressure receiving chamber 9, and the differential cylinder 3 can operate as described above without any trouble.

It should be noted that the above-mentioned embodiment is for explaining the basic essence of the constant flow rate horsepower control device of the variable displacement hydraulic / mechanical power converter of the present invention, and when embodying the present invention,
It goes without saying that various changes can be made.

That is, by appropriately changing the arrangement of the differential cylinder 3 and both control valves 4 and 5, a bar 11 is provided to a mechanism for feeding back the movement of the piston rod 3B of the differential cylinder 3 to the spools 4D and 5D of both control valves 4 and 5. It is not deviated from the gist of the present invention to apply a link in place of 14 and 14, and to appropriately select the connecting structure of the piston rod 3B of the differential cylinder 3 and the swash plate 2. The displacement hydraulic pump 1 may be replaced by a variable displacement hydraulic motor.

[Advantage of the Invention] As described above, according to the present invention, it is possible to reliably control the constant horsepower of the flow rate by increasing the degree of freedom of the flow rate control with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining the essence of the present invention, FIG. 2 is a graph showing the relationship between discharge flow rate and discharge pressure when constant horsepower control is performed, and FIG. 3 is an explanatory view of a conventional example, FIG. FIG. 4 is a graph showing the relationship between the discharge flow rate and the pilot pressure in the conventional example. 1 is a variable displacement hydraulic pump (variable displacement hydraulic / mechanical power converter), 2 is a swash plate, 3 is a differential cylinder, 3A is a piston, 3B is a piston rod, 4 is a flow control valve (three-way guide for flow control) Valve), 5 is a constant horsepower control valve (three-way guide valve for constant horsepower control), 4A, 4B, 5A, 5B are primary ports, 4C, 5C are secondary ports, 4D, 5D are spools, 6 is a tank, 7 is a small pressure chamber,
8 is a servo pressure line, 9 is a large pressure receiving chamber, 11 and 14 are bars, 1
2, 15 are springs, 13 are flow rate control pilot lines (spool biasing means), 16 are constant horsepower control pilot lines,
17 is a bypass line, 18 is an orifice, 19 is a small pressure chamber servo pressure line, 20 is a large pressure chamber servo pressure line, 21 is a three-way guide valve servo pressure line for flow control (flow control valve servo pressure line), and 22 is constant. Three-way guide valve servo pressure line for horsepower control (constant horsepower control valve servo pressure line), 23 is a connecting servo line, 24 is a tank line, and θ is a tilt angle.

Claims (1)

[Scope of utility model registration request] 1. A tilt angle of a swash plate (2) of a variable displacement hydraulic / mechanical power converter (1) when a piston (3A) moves in a direction in which the volume of a small pressure receiving chamber (7) increases. (Θ) is increased and the tilt angle (θ) of the swash plate (2) is decreased when the piston (3A) moves in the direction in which the volume of the large pressure receiving chamber (9) increases. In addition, the differential cylinder (3) in which the piston rod (3B) is connected to the swash plate (2) and the movement of the spool (4D) cause two primary ports (4
Closed center type flow control three-way guide valve (4) in which either (A) or (4B) communicates with one secondary port (4C), and two primary ports due to movement of spool (5D) (Five
A closed center type three-way guide valve (5) for constant horsepower control, in which either A) or (5B) communicates with one secondary side port (5C), and an external hydraulic source or variable displacement hydraulic / machine Servo pressure line (8) to which fluid pressure is applied from the power converter (1)
A small pressure-receiving chamber servo pressure line (19) that applies fluid pressure from the servo pressure line (8) to the small pressure-receiving chamber (7) of the differential cylinder (3), and a three-way guide valve (4) for flow control. Large pressure chamber servo pressure line (20) that connects the secondary port (4C) to the large pressure chamber (9) of the differential cylinder (3), and the three-way guide valve (4) for flow control from the servo pressure line (8) Flow control three-way guide valve servo pressure line (21) that applies fluid pressure to one of the primary side ports (4A), and one primary of the constant horsepower control three-way guide valve (5) from the servo pressure line (8) 3-way guide valve for constant horsepower control that applies fluid pressure to the side port (5A) Servo pressure line (22) and secondary port (5C) of the 3-way guide valve for constant horsepower control (5C) 3-way guide for flow control The other primary side port of the valve (4) (4
The communication servo pressure line (23) communicating with B) and the tank line (24) communicating the other primary side port (5B) of the constant horsepower control three-way guide valve (5) with the tank (6).
And an orifice (18) and a connecting servo pressure line (2
Piston (3A) in the direction in which the volume of the bypass line (17) that connects 3) to the large pressure chamber servo pressure line (20) and the small pressure chamber (7) increases
So that the spool (4D) of the flow control three-way guide valve (4) moves toward a position where the secondary side port (4C) communicates with one primary side port (4A). Piston (3A) in the direction to increase the volume of large pressure receiving chamber (9)
Of the differential cylinder (3) so that the spool (4D) moves toward a position where the secondary side port (4C) communicates with the other primary side port (4B) when moving. Flow control bar (11) connected to rod (3B)
Alternatively, the piston (3A) moves in the direction in which the volume of the link, the spring (12) and the small pressure receiving chamber (7) increases.
When the vehicle moves, the spool (5D) of the constant horsepower control three-way guide valve (5) is moved toward a position where the secondary port (5C) communicates with one primary port (5A). In addition, in the direction in which the volume of the large pressure receiving chamber (9) increases, the piston (3
The differential cylinder (3) is arranged to move the spool (5D) toward a position where the secondary port (5C) communicates with the other primary port (5B) when A) moves. The constant horsepower control bar (14) or link connected to the piston rod (3B) and the spring (15), and the spool (4D) of the flow control three-way guide valve (4) are connected to the other primary side port ( 4B) spool biasing means (13) consisting of a pilot pressure applying mechanism or an electromagnetic drive mechanism for biasing the secondary side port (4C) to communicate with it, and a three-way guide valve for constant horsepower control (5) From the variable displacement hydraulic / mechanical power converter (1) so that the spool (5D) is biased toward the position where the primary port (5A) communicates with the secondary port (5C). Constant horsepower control pilot line (16) that applies fluid pressure to the spool (5D) The variable displacement hydraulic / mechanical power converter of the flow constant horsepower control apparatus characterized in that it comprises a.