JPH04284179A - Variable capacity piston pump - Google Patents

Abstract

PURPOSE:To economize power consumption and simplify a pump driving unit by reducing the starting-up torque of a pump by electromagnetically controlling an opening/closing valve and a restraining piece. CONSTITUTION:A variable capacity piston pump is equipped with an opening/ closing valve 40 interposed in a pressurized fluid introducing passage 28 to a control cylinder 26, lever 51 which is externally installed so as to cooperate with the inclined pivotal shaft 24a of a swash plate 24, restraining piece 52 for restaining the lever 51 in free engagement/disengagement state at the nearly zero phase of the inclination angle of the swash plate, and a control means for controlling the opening/closing valve 40 and the restraining piece 52 electromagnetically. At the completion of loading, the swash plate 24 energized by a control cylinder 26 is restrained at the nearly zero capacity phase, and the pump work is disabled substantially. At the start of loading, the smooth starting-up from the nearly zero capacity is enabled by the release of the swash plate 24 and the urging force of a control spring 25, and power is economized, and the constitution can be simplified by omitting an input cut-off mechanism.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement piston pump used in hydraulic operating systems of various machines.

0002

[Prior Art] Axial piston pumps (hereinafter simply referred to as pumps) are widely used in various industrial machines and industrial vehicles, and FIG. 4 specifically illustrates a variable displacement pump equipped with a swash plate inclination adjustment mechanism. This is what I did. In this pump, a sealed operating space 3 is formed by a casing 1 and an end cover 2 that closes the open end of the casing 1, and a drive shaft 4 inserted into this operating space 3 is connected to both members 1,
2 via a bearing 5. A cylinder block 6 that is connected to the drive shaft 4 and rotates integrally with the drive shaft 4 within the operating space 3 has a plurality of bores 7 formed around its axis that are approximately parallel to the axis. Shoe 8
A piston 10, which is moored to the swash plate 9 via the swash plate 9, is fitted so as to be reciprocally movable.

The valve plate 11, which is fixed to the end cover 2 and seals the opening end surface of each bore 7, has a suction port 12a formed in an opposing arc shape in line with the rotation locus of the bore opening 7a.
and a discharge port 12b are drilled, and the same ports 12a, 1
2b is configured to align with the edges of the suction and discharge ports 13a and 13b of the end cover 2, which are formed in the same shape as this. Therefore, when the piston 10 that is moored to the swash plate 9 and moves directly with the rotation of the cylinder block 6 that moves together with the drive shaft 4 tends to expand the sealed space volume of the bore 7, the bore 7 is closed to the suction port. - When the piston 10 tends to reduce the volume of the sealed space of the bore 7, the bore 7 sucks hydraulic oil corresponding to the discharge port 12b.
Hydraulic oil is discharged in response to this. The swash plate 9, which is pivotally supported on a support shaft (not shown), is always biased in a direction to increase the inclination angle by a control spring 14, and by moving the opposing control cylinder 15 forward and backward using fluid pressure, the swash plate 9 can be tilted. The plate inclination angle, that is, the theoretical discharge amount per revolution of the pump, is configured to be changeable and adjustable.

0004

However, in the pump configured as described above, the control spring 14 is arranged to bias the swash plate inclination angle in the direction of increasing the angle of inclination of the swash plate. Since the pressure in the discharge system decreases due to leakage of pressure oil through the dynamic gap and the derivation of pressure oil from the oil return orifice provided in the control cylinder 15 or its control circuit, the counterforce exerted by the control cylinder 15 disappears. The swash plate 9 remains stationary while maintaining the maximum inclination angle due to the biasing force of the control spring 14. Therefore, during the next operation, the pump is started at the maximum swash plate inclination angle, that is, the maximum capacity, resulting in an unavoidable problem that the start-up torque becomes extremely large. Moreover, since the same pump cannot continue to operate with the swash plate tilt angle maintained near zero degrees (the operating pressure for the control cylinder 15 cannot be obtained), a clutch mechanism is installed to cut off the input to the pump when there is no load. There is a need to.

[0005] The technical problem to be solved by the present invention is to contribute to power saving by reducing the start-up torque of the pump, and to simplify the pump drive unit by omitting an input cutoff mechanism such as a clutch. It is.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a control spring that always biases the inclination angle of the swash plate in a direction to increase, and a control spring that biases the swash plate in a direction that reduces the inclination angle of the swash plate. A control cylinder to be energized, an on-off valve interposed in a pressure fluid introduction path to the control cylinder, a lever externally mounted to cooperate with the tilting axis of the swash plate, and a swash plate whose inclination angle is approximately zero degrees. a restraining piece that releasably restrains the lever in the phase;
A novel configuration is adopted that includes control means for electromagnetically controlling both the on-off valve and the restraining piece.

[0007]

[Operation] When starting the pump, pressure fluid (
Although the on-off valve provided in the discharge oil introduction passage is in an open state, no hydraulic pressure is generated in the introduction passage, and the pressure including the bore of the control cylinder is maintained at drain pressure. On the other hand, the lever that moves together with the tilting axis of the swash plate is restrained by the restraining piece, so that the swash plate maintains a phase of almost zero capacity, and the clutch (off)
It replaces the function. When the control means is electromagnetically activated by a signal (switch) that essentially commands the pump to start operating, the on-off valve is switched to the closed state, and at the same time the lever is released from being restrained by the restraining piece. , the control spring biases the swashplate inclination to increase while promoting retraction of the control piston. That is, the pump smoothly starts up from a minimum capacity equal to zero, and when the swash plate reaches its maximum inclination angle, it shifts to steady operation at the maximum capacity.

[0008] When the work such as cargo handling is completed and a signal is issued which instructs the pump to stop operating, the on-off valve is switched to the open state through the electromagnetic operation of the control means, and at the same time, the restraining piece is switched to the above-mentioned state. Return the lever to a position where it can be detained. As a result, discharge oil is supplied to the control cylinder via the on-off valve and the pressure fluid introduction path, which urges the control piston to move forward and bias it toward reducing the swash plate inclination angle. When the swash plate inclination angle is reduced to a phase close to zero capacity, the lever that moves together with the tilting axis interferes and displaces the locking piece, and when the swash plate reaches almost zero capacity, the lever moves the locking piece. Detained for reversal. In other words, the pump continues to operate with the swash plate restrained and shifts to a minimum displacement equal to zero.

[0009]

[Embodiments] Hereinafter, embodiments of the present invention will be explained in detail based on the drawings. FIG. 1 is a cross-sectional view of a variable displacement piston pump taken across the center of the tilting axis of the swash plate, and FIG. 2 is a partial sectional view schematically showing only the variable displacement mechanism (the tilt angle displacement mechanism of the swash plate).

In the figure, 21 is a casing, and 22 is an end cover that closes the open end of the casing to form a sealed operating space 23 within the casing 21. A swash plate 24 that controls the discharge capacity of the pump in the operating space 23 has a trunnion-type tilting pivot 24a rotatably supported on the casing 21, and the swash plate 24 is supported by a control spring 25.
is always biased in a direction that increases its inclination angle. Reference numeral 26 denotes a control cylinder that biases the swash plate 24 in a direction that reduces the inclination angle against the control spring 25. The control cylinder 26 extends from the end cover 22 in parallel to the drive axis, and is shown in FIG. represents a state in which the control piston 27 moves and holds the swash plate 24 at the minimum inclination angle of approximately zero degrees.

At the rear end of the bore of the control cylinder 26, there is an introduction path 2 for pressure fluid (discharge oil) via an end cover 22.
8 is connected, and the introduction path 28 and a discharge oil outlet path 30 opened to the discharge port 29 can communicate with each other via an on-off valve 40. The on-off valve 40 and its control means keep the spool 41 open (communicated) with a spool 41 installed internally to selectively communicate the inlet path 28 and the outlet path 30.
a coil spring 42 that biases and holds the spool in position, and a solenoid 44 that directly moves the spool to a closed (non-communicating) position against the biasing force of the coil spring 42 when a signal (for example, a cargo handling switch) 43 is turned on. It consists of In addition, 45
4 is a restraining piece that restricts the maximum inclination angle of the swash plate 24;
Reference numeral 6 denotes an oil return orifice that connects the introduction path 28 and the operating space 23.

On the other hand, a lever 51 that moves together with the tilting shaft 24a is fixed to the outer end of the tilting shaft 24a supported by the casing 21, as shown in FIGS. 1 and 3. -51 is restrained by the restraining piece 52 when the tilt angle of the swash plate 24 is approximately 0 degrees. In more detail,
The locking piece 52 is pivotally connected to the casing 21 and is supported by a spring 53.
When the swash plate inclination angle is reduced to a phase close to zero capacity, the tip of the rotated lever 51 resists the spring 53. When the locking piece 52 is displaced by interference, and the locking piece 52 is reversely biased when the capacity reaches almost zero, the lever 51 is moved by the claw 5.
2a is configured to be detained. Then, the lever 51 is released by the control means (excitation of the electromagnet 54) which is activated synchronously based on the ON operation of the signal 43, and the accompanying rotation of the retaining piece 52 by attraction.

Therefore, when the pump is started, the on-off valve 40 provided in the introduction passage 28 that supplies pressure fluid (discharge oil) to the control cylinder 26 is kept open; is not occurring, and everything including the bore of the control cylinder 26 is maintained at drain pressure. On the other hand, there is a lever mounted on the exterior so as to move together with the tilting axis 24a of the swash plate 24.
51 is restrained by the claw 52a of the spring-biased restraining piece 52, and the swash plate 24 maintains a nearly zero-capacity phase and replaces the clutch (off) function. When the control means (solenoid 44 and electromagnet 54) is activated by turning on the cargo handling switch 43, which essentially commands the start of operation of the pump, the on-off valve 40 is switched to the closed state, and at the same time, the locking piece 52 closes the lever. -51's detention is lifted. At this time, the inside of the bore of the control cylinder 26, which has been cut off from communication with the introduction passage 28, continues to be maintained at drain pressure, and the control spring 25 is biased to increase the swash plate inclination angle while promoting the retraction of the control piston 27. do. That is, the pump smoothly starts up from a minimum capacity equal to zero capacity, and when the swash plate 24 reaches the maximum inclination angle regulated by the stopper piece 45, the pump shifts to steady operation at the maximum capacity.

When the cargo handling switch 43 is turned off, which essentially commands the pump to stop operating, after the cargo handling work is finished, the control means (solenoid 44 and electromagnet 54) are de-energized and the on-off valve is turned off. 40 is switched to the open state by the biasing force of the coil spring 42, and at the same time, the retaining piece 52 is switched to the open state by the biasing force of the coil spring 42.
The lever 51 is returned to the position where it can be restrained by the urging force No. 3. As a result, discharged oil is supplied to the control cylinder 26 via the outlet passage 30, the on-off valve 40, and the introduction passage 28, and the control piston 27 moves against the biasing force of the control spring 25, changing the inclination angle of the swash plate 24. It is energized in the direction of shrinking. When the swash plate inclination angle is reduced to a phase close to zero capacity, the tip of the lever 51 that moves together with the tilting shaft 24 interferes with and displaces the locking piece 52 against the spring 53, and almost zero capacity is reached. Due to the reversal bias of the locking piece 52 at the time when the lever 51 is
Detained again by 2a. In other words, the pump continues to operate and shifts to the minimum capacity equal to zero, and the pressure oil is drawn out from the oil return orifice 46 etc. to control the control cylinder 26.
The pressure inside the bore will soon drop to the drain pressure.

[0015] If such a pump is directly connected to the power take-off device of a specially equipped vehicle and used in an always-on state, the pump's clutch substitution function not only simplifies the structural unit, but also allows the cargo handling switch to be turned on and off. The operation of the pump can be easily controlled just by movement.

[0016]

[Effects of the Invention] As detailed above, according to the present invention,
Since the actual operation (discharge) of the pump always starts from the minimum capacity, which is equal to zero, the start-up torque is small, which not only saves power but also suppresses drastic load fluctuations. Since the capacity of the motor can be maintained at a minimum capacity equal to zero, an input cutoff mechanism such as a clutch can be omitted, contributing to the simplification of the structural unit.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a variable displacement piston pump according to an embodiment of the present invention, taken across a tilting axis of a swash plate.

[Figure 2] Partial cross-sectional view schematically showing only the variable capacity mechanism of the pump

[Figure 3] Front view showing the swash plate detention mechanism of the pump

[Figure 4]
Cross-sectional view showing the entire structure of a conventional variable displacement piston pump

[Explanation of symbols]

21 is a casing, 22 is an end cover, 24 is a swash plate,
24a is a tilting axis, 25 is a control spring, 26 is a control cylinder, 27 is a control piston, 28 is a pressure fluid introduction path, 40
is an on-off valve, 43 is a signal (switch), 51 is a lever, 5
2 is a restraining piece

Claims (1)

[Claims] [Claim 1] A cylinder block that rotates together with a drive shaft has a plurality of bores approximately parallel to the axis around the axis, and a piston that is moored to the swash plate is inserted into each bore through a shoe. At the same time, the valve plate that slides and seals the opening end surfaces of these bores is provided with suction and discharge ports that are arc-shaped and opposite to each other, coinciding with the rotation locus of the bore openings. In a piston pump configured to align with suction and discharge ports formed in an end cover, a control spring biases the swash plate in a direction that constantly increases the inclination angle of the swash plate; A control cylinder that is biased in the direction of contraction, an on-off valve that is interposed in a pressure fluid introduction path to the control cylinder, a lever that is externally mounted to move in conjunction with the tilt axis of the swash plate, and a swash plate inclination angle. 1. A variable displacement piston pump comprising: a locking piece for releasably locking the lever when the lever is in a phase of approximately zero; and control means for electromagnetically controlling both the opening/closing valve and the locking piece.