JPH0988810A - Multi-flow pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always ensure balanced pressure and prevent the occurrence of unbalance moment causing vibration by arranging a plurality of discharge ports nearly symmetrically with respect to a line which are made on a valve plate for multi-distribution even if there happens pressure difference between a plurality of independent discharge ports. SOLUTION: One suction port 1a and a plurality of discharge ports 1b to 1f on a valve plate 1 are arranged like an arc on a circumference. The suction port 1a is arranged like a kidney. In the discharge port range of the valve plate 1, the range from a top dead center position A to a bottom dead center position B is devided into five ranges θ1 to θ5 and the discharge ports 1b to 1f are arranged at each range. The range θ3 and the discharge port 1d are introduced to one discharge port of the pump and the discharge ports 1b, 1f and the discharge ports 1c, 1e are respectively merged and introduced into the other discharge ports, to produce three discharge flows in total, whereby discharge ports are arranged symmetrically with respect to a symmetrical axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial piston type multi-flow variable displacement pump for distributing and discharging pressure oil from a single pump to a plurality of pump discharge passages independent of each other.

[0002]

2. Description of the Related Art As one of hydraulic pumps for small construction machines such as mini power shovels and mini wheel loaders, an axial piston type variable pump that converts rotational movement of a shaft into stroke movement of a piston to suck and discharge pressure oil. A capacity pump is mentioned.

This axial piston type variable displacement pump has a cylinder barrel in which a plurality of cylinder chambers into which pistons are fitted are arranged at equal angular intervals from the axis of rotation at equal eccentric distances, and during rotation of the cylinder barrel. The swash plate that is supported by the housing at an angle inclined to the rotation axis of the cylinder barrel to give each piston a suction and discharge stroke motion, and the suction and discharge holes on the bottom surface of the cylinder barrel that slide into contact with the bottom surface of the rotating cylinder barrel The housing is provided with a valve plate (port plate) provided with an intake port and a discharge port so as to sequentially circulate.

It is known in the prior art to construct a multi-distributor pump, that is, a multi-flow pump, which produces a plurality of independent discharge flows by such an axial piston pump, and the first type thereof is, for example, Jpn.
In No. 7977, as shown in FIG. 3, the discharge port P of the valve plate is divided into a plurality of parts in the rotation direction of the cylinder barrel, and the discharge ports P _{31 to} P ₃₃ are not joined to each other and independent pump discharges are performed. It is described that it takes a plurality of independent discharge streams by leading them to an outlet. In this case, parts of the normal single-discharge port axial piston pump can be shared except for the valve plate, and the pressure oil discharged in one stroke of the piston is divided into strokes by the valve plate and distributed to different flow paths in order. And can be taken out as, for example, three mutually independent discharge streams.

A second type of multi-flow pump having another structure is disclosed in Japanese Patent Laid-Open Nos. 52-35304 and 1-1998.
The ones disclosed in JP-A-267367 and JP-A-1-267368 are also known.

In all of these second types, as shown in FIG. 4, the cylinder chambers h _{1 to} h _{6 are formed on the} bottom surface of the cylinder barrel.
The intake and exhaust holes Q _{41 to} Q ₄₆ communicating with each other are alternately bored at positions with different eccentric distances, and the discharge flow of the valve plate is radial in the discharge section so that discharge flows are independent on two concentric circles at each eccentric distance. It has a structure in which two separate discharge ports P ₄₁ and P ₄₂ arranged side by side are formed.

In this case, the total discharge amount for one stroke of each piston is discharged from one of the discharge ports, and the discharge flow is alternately supplied to the two discharge ports from every other cylinder chamber. Therefore, for example, a pump having six pistons is a multi-flow pump equivalent to two pumps each having a discharge amount of three pistons.

[0008]

However, in the conventional multi-flow pump according to the first type configuration,
By simply dividing the discharge port of the valve plate in the axial piston type variable displacement pump of a general configuration in the rotational direction, the discharge amount for one stroke of each piston is divided at a constant ratio to obtain a multiple discharge flow. However, there is no countermeasure against the difference in pressure oil pressure between the discharge ports separated and arranged in the rotation direction, and if the discharge port of the valve plate is simply divided into a plurality of rotation directions, the closing pressure of the cylinder chamber will be reduced. The pump noise increases due to the occurrence of the noise, and an unbalance moment around the tilt axis is generated in the swash plate due to the difference in pressure oil pressure between each discharge port. In horsepower control, the swash plate becomes vibrating due to the unbalance moment, and in the worst case, this may cause an unexpected deviation in the discharge amount of each discharge port.

Further, in the case of the conventional multi-flow pump of the second type, a plurality of independent discharge flows are obtained by expanding and expanding the arrangement of the suction and discharge holes of each cylinder chamber on the bottom surface of the cylinder barrel in the radial direction. Therefore, in order to obtain three or more independent discharge flows, from the viewpoint of preventing leakage between each discharge port, the radial dimension of the suction / exhaust holes at the bottom of each cylinder chamber is limited to set the radial separation distance. It is necessary to take enough, and the discharge ports provided on the valve plate must also be increased in parallel in the radial direction, which results in
This is not preferable because it causes an increase in size of the device. Of course, it is extremely difficult to design in consideration of the pressure balance of each intake / exhaust hole and the discharge port in the vicinity of the valve plate in order to obtain three or more independent discharge flows without greatly changing the size of the device. However, in reality, a multi-flow pump with three or more split flows has not been commercialized.

The object of the present invention is to maintain the advantages of the first type in that the parts of an axial piston pump having a normal single discharge port can be shared as the main parts,
With a relatively simple structure, an unbalanced moment does not act on the swash plate, and therefore an instability factor is not given to the tilt angle control of the swash plate, and a plurality of independent discharge flows can be stably obtained. The present invention provides a multi-flow pump capable of maintaining the independence of each discharge port and preventing generation of a closing pressure in each cylinder chamber to reduce noise. Especially.

[0011]

SUMMARY OF THE INVENTION According to the present invention, the above object is achieved by providing a multi-flow pump of the first type, that is, a piston and a swash plate respectively in a plurality of cylinder chambers of a cylinder barrel rotated by a shaft. A non-rotating valve plate having a plurality of independent discharge ports arranged at equal eccentric distances with respect to the axis of rotation of the cylinder barrel, while reciprocating with a stroke according to the tilt angle.
By making sliding contact with the bottom surface of the cylinder barrel in which a plurality of suction and discharge holes that individually communicate with each cylinder chamber are opened, the discharge flow for one stroke of the piston in each cylinder chamber is divided and taken out through the plurality of discharge ports. In an axial piston type multi-flow pump, which is led to a plurality of pump discharge ports independent of each other and produces discharge flows independent from each other, the same pump discharge port among the plurality of pump discharge ports is communicated. It is achieved by arranging the discharge port on the valve plate so as to be substantially line-symmetrical with a line segment obtained by projecting the tilt axis of the swash plate on the valve plate in the rotation axis direction of the cylinder barrel as a symmetry axis. It

That is, in the first type multi-flow pump, the discharge flow from each cylinder chamber is divided from one stroke of the piston and is guided to a plurality of pump discharge ports independent of each other. Since the port is divided into multiple parts in the direction of rotation of the cylinder barrel, the reaction force generated at the valve plate part on the bottom surface of the cylinder barrel due to the difference in pressure oil pressure at each of the divided discharge ports is about the tilt axis of the swash plate. In contrast to trying to give an unbalance moment, in the present invention, among the plurality of pump discharge ports provided in the valve plate, the discharge port leading to the same pump discharge port is
Since the tilt axis of the swash plate is arranged on the valve plate so as to be substantially line-symmetrical with the line segment projected on the valve plate in the direction of the rotation axis of the cylinder barrel as the axis of symmetry, each pump discharge Even if the pressures at the outlets differ from each other, the pressures at the discharge ports leading to the same pump discharge port act symmetrically on the valve plate with the line segment as the axis of symmetry, and the reaction force also balances around the axis of symmetry. Therefore, the unbalance moment around the tilt axis of the swash plate does not always occur.

There may be a single or even number of discharge ports on the valve plate leading to the same pump discharge port. In the case of a single number, the line segment serving as the axis of symmetry corresponds to a radial line segment that bisects the discharge port. However, in the case of an even number, each discharge port provided at a position that is substantially line-symmetrical with the line segment as the axis of symmetry provides a discharge flow merged into one pump discharge port.

In the multi-flow pump of the first type, when the cylinder barrel is rotating, there is a section in which the suction and discharge holes on the bottom surface thereof are not opened to any of the discharge ports. In order to avoid this in the multi-flow pump of the present invention, the distance between the plurality of discharge ports on the valve plate in the direction of rotation of the cylinder barrel may be made smaller than the diameter of the suction / exhaust hole.

As described above, each intake / discharge hole on the bottom surface of the cylinder barrel and each discharge port of the valve plate have a so-called underlap structure, so that each intake / discharge hole is surely communicated with one of the discharge ports during rotation. The pressure oil that is pushed out by the piston in each cylinder chamber is always discharged to some discharge port during the piston stroke, and the pressure is not closed inside the cylinder chamber, so the pressure inside the cylinder chamber does not become unnecessarily high. Further, inconveniences such as pulsation of discharge pressure and increase of pump noise do not occur.

Further, in the first type multi-flow pump, when the pressure difference between the discharge ports communicating with the pump discharge ports independent from each other becomes large, the discharge ports of the valve plate come around while the cylinder barrel rotates. Although there is a concern that pressure shock may occur in the cylinder chamber, in order to mitigate this in the multi-flow pump of the present invention, at least one of the two discharge ports adjacent to each other on the valve plate at the sliding contact surface with the cylinder barrel. The pressure-conducting groove extending in a part of the distance from the other discharge port may be communicated.

That is, by providing such a pressure guiding groove,
When the pressure oil in the cylinder chamber is discharged from the suction / discharge hole to the discharge port, a part of the pressure of the discharge port is distributed to the adjacent discharge port by the pressure guide groove on the sliding contact surface between the valve plate and the cylinder barrel. Therefore, it is possible to reduce the occurrence of pressure shock in the cylinder chamber due to the pressure difference between the ports.

Of course, even if the space between the discharge ports is the widest, it is made narrower than the diameter of the suction and discharge holes, and a groove for pressure guiding is provided between the adjacent discharge ports, so that the closing pressure in the cylinder chamber is generated. It is possible to more effectively suppress the occurrence of pressure shock in the cylinder chamber, but this should be designed so that the amount of leakage between the discharge ports is within a practically acceptable range.

According to the present invention, even if a pressure difference occurs between a plurality of pump discharge ports independent from each other, the plurality of discharge ports for multi-distribution formed in the valve plate are always pressure balanced by the line-symmetric arrangement. Therefore, the swash plate does not generate an unbalance moment due to the pressure difference, and therefore the tilt angle of the swash plate is controlled by the pump discharge pressure for various purposes such as cut-off control and approximate constant horsepower control. As the regulator mechanism, an ordinary method can be adopted. As such a regulator mechanism, for example, a hydraulic operation piston mechanism that drives a swash plate so as to change the tilt angle, and a plurality of independent pump discharge ports Of the highest pressure so that the deviation between the sum of the respective pressures and the position feedback amount of the hydraulically operated piston mechanism is balanced with a predetermined spring load. Pressurized oil up the discharge port to the hydraulic operating piston mechanism is configurable by the control valve device to direct the operation pressure oil.

[0020]

1 (a) is a schematic cross-sectional view showing an example of an embodiment of a multi-flow pump according to the present invention, and FIG. 1 (b) is an explanatory view showing a port arrangement of a valve plate thereof.
In this example, a regulator with a hydraulically operated piston mechanism of a load pressure counter type using a spring with the simplest structure is provided.
The split-flow axial piston type multi-flow pump is illustrated.

In FIG. 1A, the cylinder barrel 2
Rotates with a shaft 3 that is rotated by a driving prime mover such as an internal combustion engine or an electric motor, and a piston 4 inserted into each cylinder chamber of the cylinder barrel 2 has its head portion slidably contactable with a swash plate 5 for rotation. Since it is held, when the cylinder barrel 2 rotates with the rotation of the shaft 3, the head portion of the piston 4 slides around the swash plate 5 around the rotation axis of the shaft 3 to make a circular contact movement.

Since the position of each piston 4 in the cylinder chamber at this time is determined by the tilt angle between the cylinder barrel 2 and the swash plate 5, the piston 4 is moved while the head portion makes a revolving motion on the swash plate 5. Will reciprocate in the cylinder chamber.

The head portion of the piston 4 is the cylinder barrel 2
When the piston 4 reaches the position closest to the position (called the bottom dead center position), the piston 4 minimizes the volume of the cylinder chamber, and the head of the piston 4 moves farthest from the cylinder barrel 2 (called the top dead center position). The piston 4 maximizes the volume of the cylinder chamber.

Therefore, when the piston 4 moves in the direction to increase the volume of the cylinder chamber, the pressure oil is sucked into the cylinder chamber, and conversely, when the piston 4 moves in the direction to decrease the volume of the cylinder chamber, the pressure oil in the cylinder chamber is increased. Will be discharged to the outside.

The displacement of the cylinder chamber due to the stroke motion of the piston 4 is determined by the tilt angle of the swash plate 5, which is tilted by the hydraulic operating piston 7 of the regulator mechanism which opposes the return spring 6. Since the turning angle is controlled, the discharge amount of the pump can be adjusted by the position of the hydraulic operation piston 7.

A non-rotating valve plate 1 fixed to the pump housing is slidably arranged on the bottom surface of the cylinder barrel 2, and the valve plate 1 is shown in FIG. 1 (b). To the top dead center position A and the bottom dead center position B of the piston 4.
With a line segment AB (perpendicular to the shaft axis and the swash plate tilt axis) passing through as a boundary, the discharge port region and the suction port region on one side and the other side are based on the rotation direction of the cylinder barrel. It is divided.

One suction port 1a provided in the suction port region of the valve plate 1 and a plurality of independent discharge ports 1b-1f provided in the discharge port region are all circles on one circumference. The suction ports 1a are arranged in an arc shape and are provided in a kidney shape over almost the entire suction port region, and continuously in each cylinder chamber in a section from the bottom dead center position B to the top dead center position A. Pressure oil is inhaled.

On the other hand, in the discharge port region of the valve plate 1, there are five regions θ1 from the top dead center position A to the bottom dead center position B.
.About..theta.5, and a total of five separate discharge ports 1b to 1f, one for each of the divided areas, are arranged at intervals. Of these discharge ports, the divided area θ
The discharge port 1d provided in 3 is guided to one independent pump discharge port, and each discharge port 1 in the divided regions θ1 and θ5
b and 1f are merged and guided to another independent pump discharge port, and the discharge ports 1c and 1 in the divided regions θ2 and θ4, respectively.
The e is merged and guided to another independent pump discharge port so that a total of three mutually independent discharge flows are generated.

The divided areas θ1 and θ5 are in the same angular range, and the divided areas θ2 and θ4 are also in the same angular range. Assuming that the line segment XX, which is the tilt axis of the swash plate 5 projected on the valve plate 1 in the direction of the rotation axis of the cylinder barrel 2, is the pressure balance boundary symmetry axis, the discharge ports 1b and 1f are line segments. XX is provided in a line symmetric position with respect to the axis of symmetry, and discharge ports 1c and 1e are also provided in a line symmetric position with respect to the line segment XX as a symmetry axis. Further, the discharge port 1d is also provided along the line segment XX in the symmetry axis. It is provided at a position that has a line-symmetrical shape.

In this case, the discharge flows from the discharge ports 1b and 1f provided in the divided areas θ1 and θ5 are joined and guided to one independent discharge port, and one independent discharge of the pressure P ₁ and the flow rate Q _1. Since it is taken out as a flow, the pressures in the cylinder chambers acting on the divided regions θ1 and θ5 are always balanced on both sides with respect to the axis of symmetry XX, and against the swash plate that receives the reaction force of the pressures in the cylinder chambers in the rotational axis direction. Divided area θ1 and θ
The reaction force due to the pressure of 5 is always kept in equilibrium.

Similarly, the discharge flows from the discharge ports 1c and 1e provided in the divided regions θ2 and θ4 are joined and guided to another independent discharge port, and one of the pressure P ₂ and the flow rate Q ₂ is independent. Since it is taken out as the discharged flow,
And the pressure in the cylinder chamber acting on θ4 are always balanced on both sides with respect to the axis of symmetry XX, and the reaction due to the pressure in the divided regions θ2 and θ4 against the swash plate that receives the reaction force of the pressure in the cylinder chamber in the direction of the rotation axis. Forces are always kept in equilibrium.

Further, the discharge flow from the single discharge port 1d provided in the divided area θ3 is guided to another independent pump discharge port and further independent discharge of the pressure P ₃ and the flow rate Q _3. Since the discharge port 1d is arranged so as to have an opening shape that is line-symmetric with respect to the axis of symmetry XX, the pressure in the cylinder chamber that acts on the divided region θ3 is on both sides with respect to the axis of symmetry XX. The reaction force due to the pressure in the divided area θ3 is also kept in equilibrium with respect to the swash plate that is always balanced and receives the reaction force of the pressure in the cylinder chamber in the direction of the rotation axis.

In this way, the plurality of discharge ports are arranged so as to be pressure-symmetrical with respect to the axis of symmetry, and the discharge flows from the respective discharge ports are independently arranged so as to maintain this pressure balance. Since it is distributed to the pump discharge port, the pressure balance on the symmetry axis is always maintained as the whole valve plate, and an unbalance moment around the swash plate tilt axis due to the pressure difference between these multiple discharge ports may be generated. There is also no vibration of the swash plate due to it.

FIG. 2 is an explanatory view of the distance between the plurality of discharge ports on the valve plate, and here, for simplification, only the distance between the two discharge ports is shown.

In FIG. 2, the portion shown by the solid line is the discharge port (pressures P ₁ and P ₂ respectively), and the portion Q shown by the dotted line is the intake and exhaust holes at the bottom of the cylinder chamber. In FIG. 2, the moving direction of the suction / exhaust hole Q is shown by a straight line for convenience of description, but it goes without saying that this straight line is actually a circle.

FIG. 2A shows the case where the distance L1 between the discharge ports is larger than the diameter L2 of the cylinder hole Q. In order to avoid the phenomenon of pressure confinement in the cylinder chamber, the discharge ports may be brought close to each other to shorten the distance L1 between the discharge ports to form a so-called underlap structure.
Furthermore, if it is necessary to maintain a high degree of independence of each port, rather than underlap structure between the discharge ports,
As shown in FIG. 2 (b) or (c), one discharge port is provided with a wedge-shaped or semi-circular pressure guiding groove extending toward the other discharge port, and the discharge ports as pressure acting areas are provided between the discharge ports. It is preferable to make the interval substantially shorter than the diameter L2 of the cylinder hole Q to minimize leakage between the discharge ports.

In the above-mentioned embodiment, the case of a multi-flow pump of 3 split flow is shown as an example.
The present invention is not limited to this, and is similarly applicable to a case where individual discharge flows obtained by dividing the piston stroke are taken out from a desired number of independent pump discharge ports by the discharge port arrangement of the valve plate. is there.

[0038]

As described above, according to the present invention,
Even if a pressure difference occurs between a plurality of pump discharge ports independent of each other, the plurality of discharge ports for multiple distribution formed on the valve plate are
Since the pressure is always balanced by the substantially line-symmetrical arrangement, the swash plate does not generate an unbalanced moment due to the pressure difference that causes vibration. Therefore, it is not necessary to adopt a special method for the regulator mechanism that controls the tilt angle of the swash plate for various purposes such as cutoff control and approximate constant horsepower control by the pump discharge pressure, and it is relatively simple. It is possible to provide a multi-flow pump that can obtain a plurality of discharge flows independent of each other with relatively low noise.

[Brief description of drawings]

1A is a schematic cross-sectional view showing an example of an embodiment of a multi-flow pump according to the present invention, and FIG. 1B is an explanatory view showing a port arrangement of a valve plate thereof.

2 (a), (b) and (c) are schematic views for explaining a gap between discharge ports of a valve plate according to some embodiments of the present invention.

FIG. 3 is an explanatory diagram showing an example of a valve plate of a conventional multi-flow pump.

FIG. 4 is an explanatory diagram showing an example of an arrangement of intake and exhaust holes and a port arrangement of a valve plate on a bottom surface of a cylinder barrel of a conventional multiflow pump.

[Explanation of symbols]

 1: Valve plate 1a: Suction port 1b-1f: Discharge port 2: Cylinder barrel 3: Shaft 4: Piston 5: Swash plate 6: Return spring 7: Hydraulic operation piston Q: Intake / exhaust hole

Claims (3)

[Claims] 1. A piston is reciprocated in a plurality of cylinder chambers of a cylinder barrel rotated by a shaft with a stroke corresponding to a tilt angle of a swash plate, and an eccentric distance is equal to a rotation axis of the cylinder barrel. A non-rotating valve plate having a plurality of arranged independent discharge ports is slidably contacted with the bottom surface of the cylinder barrel having a plurality of suction and discharge holes communicating with each cylinder chamber, so that the piston in each cylinder chamber Axial piston type multi-flow in which the discharge flow for the stroke is divided and taken out through the plurality of discharge ports and guided to a plurality of pump discharge ports that are independent of each other, and discharge flows that are independent of each pump are generated. In the pump, among the plurality of pump discharge ports, a discharge port leading to the same pump discharge port is The tilt axis of the plate is arranged on the valve plate so as to be substantially line-symmetrical with a line segment projecting on the valve plate in the direction of the rotation axis of the cylinder barrel as a symmetry axis. Multi-flow pump. 2. The multi-flow pump according to claim 1, wherein an interval between the plurality of discharge ports is narrower than a radial dimension of an intake / exhaust hole on a bottom surface of the cylinder barrel with respect to a rotation direction of the cylinder barrel. 3. A pressure guiding groove extending at least in one of the two discharge ports adjacent to each other on the valve plate on the sliding contact surface with the cylinder barrel and extending in a part of the distance from the other discharge port. The multi-flow pump according to claim 1 or 2, characterized in that: