JPS5813111Y2 - Piston device in hydraulic pump/motor - Google Patents

Description

[Detailed description of the invention] This invention is a piston device for a hydraulic pump/motor in which a piston equipped with a piston shoe that slides on a guide surface is slidably fitted into a cylinder hole formed in a cylinder block. It is related to.

The pistons of hydraulic pumps and motors can be roughly divided into two types based on their structure: integral types and assembled types.

The former is easy to manufacture, but those with a structure in which the piston shoe makes surface contact with the guide surface are directly susceptible to manufacturing errors, and those with a structure in which the piston shoe makes surface contact with the guide surface have an extremely high surface pressure. Also, stable sliding contact cannot be obtained.

The latter has relatively stable sliding contact compared to the integral type, but on the other hand, the number of parts increases, the structure becomes complicated, and workability deteriorates.

Next, an example of a conventional radial type hydraulic pump/motor will be explained with reference to FIGS. 1 to 5.

The cylinder block 11 is rotatably housed in a casing 12, and has a plurality of cylinder holes 11.
A is provided.

A piston 13 is housed in each cylinder hole 11a so as to be able to freely slide in the axial direction.

At the end of the piston 13 on the casing 12 side, a spherical concave dust 13a having a dot as its center is formed. The portion 15a is fitted, and the piston shoe 15 is supported so as to be rotatable about the center.

A cam surface (guide surface) 12a eccentric to the rotational axis of the cylinder block 11 is formed on the inner periphery of the casing 12, and the piston shoe 15 slides on the cam surface 12a.

When the piston shoe 15 slides on the cam surface 12a as the cylinder block 11 rotates, the piston shoe 1
5 is tilted in the direction of rotation about the center of the spherical concave dust 13H.

At this time, as shown in FIG. 3, the piston shoe 15 is
Frictional force f generated on the sliding surface between it and the cam surface 12a,
Moment) M is received by the distance l from the center of rotation of the piston shoe 15 to the cam surface 12a.

Therefore, the pressure distribution on the sliding surface between the piston shoe 15 and the cam surface 12a changes.

That is, as shown in FIGS. 4 and 5, the hydraulic balance force F moves to F' with respect to the piston pressing force Fp, resulting in an imbalance.

Therefore, the stability of the sliding contact of the piston shoe 15 is poor.

In FIG. 5, a solid line N represents a normal pressure distribution, and a chain line U represents a pressure distribution when a moment M is applied.

The purpose of this invention is to provide an assembled piston with good sliding contact stability between piston shoes and a simple structure.

An embodiment of this invention will be described below with reference to FIG.

The cylinder block 1 is supported so as to rotate concentrically with the axis of a fixed shaft (not shown).

A plurality of cylinder holes 1a are provided radially on a surface of the cylinder block 1 that is perpendicular to the axis of the fixed shaft.

However, in order to simplify the figure, only one cylinder hole 1a is shown.

A piston 2 is housed in the cylinder hole 1a so as to be able to freely slide in the axial direction.

An eccentric ring 3 is provided on the outer circumferential side of the cylinder block 1 and eccentrically disposed via an eccentric device (not shown).

An interspherical guide surface 3a is formed inside the eccentric ring 3.

At the end of the piston 2 on the eccentric ring 3 side, a spherical concave seat 2a is formed whose center is approximately at the intersection 4 between the extension of the axis of the piston 2 and the spherical inter-spherical guide surface 3a.

A spherical convex surface portion 6a of a piston shoe 6 attached to the piston 2 by a stepped rivet 5 is fitted into the spherical concave seat 2a.

The outer end surface of the piston shoe 6 is formed into a spherical convex surface having the same radius as the interspherical guide surface 3a.

The spherical concave seat 2a is much shallower than that provided on the shoe of an ordinary swash plate type hydraulic pump, and is therefore extremely easy to process.

A small hole 5a is provided in the axial portion of the stepped rivet 5, and this small hole 5a passes through an oil chamber 1b of the cylinder hole 1a and an oil well 2b provided in the piston 2.

A gap S is formed between the step at the lower end of the stepped rivet 5 and the hole of the piston shoe 6.

The piston shoe 6 can swing relative to the piston 2 by an amount corresponding to the gap S.

The end of the stepped rivet 5 on the oil reservoir 2b side is caulked.

The operation when this hydraulic pump/motor is used as a hydraulic pump will be described.

The eccentric device is operated to move the axis of the eccentric link 3 to a point P with respect to the axis O of the cylinder block 1, thereby making it eccentric by e.

If the cylinder block 1 is rotated in this state, the screw 1
The cylinder 2 rotates together with the cylinder block 1 and reciprocates within the cylinder hole a in a stroke 2e, pressurizes the oil that has flowed into the oil chamber 1b, and drains it through an oil drain path (not shown). Exhale.

At this time, the piston shoe 6 is aligned with the axis of the piston 2.
It tilts in accordance with the eccentricity e between the cylinder block 1 and the eccentric ring 3, and swings as the cylinder block 1 rotates.

The piston 2 is pushed by discharge pressure when discharging pressure oil from the oil chamber 1b side, and by boost pressure when sucking oil into the oil chamber 1b, and the load is balanced by the spherical concave seat 2a. do.

The sliding surfaces for the guide surfaces 3a of the screws 1 to 6 are as follows:
Pressure oil from the oil chamber 1b is supplied through the small hole 5a, providing static pressure balance and preventing excessive force from being applied to the sliding surfaces.

In addition, since the center of the spherical surface of the spherical concave seat 2a is located near the intersection 4, the point of application of the hydraulic pressure that presses the piston 2 from the oil chamber 1b side and the corresponding point of action of the balance pressure of the sliding surface of the piston shoe 6. coincides near the intersection 4 regardless of the inclination of the piston shoe 6, and the piston shoe 6 and the guide surface 3
Since the frictional force with a acts only as a load, no unbalance moment 1 of the balance pressure occurs, so a stable hydraulic balance is always obtained.

Although a radial type hydraulic pump/motor has been described as an embodiment of this invention, this invention can also be applied to an axial type hydraulic pump/motor.

According to the invention described above, it is possible to provide at a low cost a hydraulic pump/motor in which the sliding contact of the piston shoe is stable and a stable hydraulic balance is always obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional side view showing a conventional radial hydraulic pump/motor, Fig. 2 is a sectional view taken along line II-II in Fig. 1, and Fig. 3 is an explanatory diagram showing the operating state of the screw 1 in Fig. 2. , FIGS. 4 and 5 are explanatory diagrams showing the pressure distribution on the sliding surface between the piston shoe and the cam surface in FIGS. 1 and 2, and the resulting hydraulic balance force. FIG. It is a sectional view showing an example. 1... Cylinder block, 1a... Cylinder hole, 11]... Oil filled, 2... Screw 1-hen, 2a... Spherical Concave seat, 3...
・Eccentric ring, 3a... Spherical concave guide surface, 4...
...Intersection of the extension of the piston axis and the spherical concave guide surface, 5...Stepped rivet, 5a...Small hole, 6...Piston shoe, 6a・・・・・・
Spherical convex part.

Claims (1)

[Scope of utility model registration request] In a hydraulic pump/motor in which a piston equipped with a piston shoe that slides on a guide surface is slidably fitted into a cylinder hole formed in a cylinder block, an extension of the axis of the piston and a guide surface are formed on the outer end surface of the piston. A piston shoe is formed with a spherical concave surface whose center is approximately at the point of intersection with the spherical concave surface, and a spherical convex surface is slidably fitted onto the spherical concave surface, and a gap is provided between the piston shoe and the center hole of the piston shoe. A piston device that is swingably mounted using a stepped rivet, and characterized in that the stepped rivet is provided with a small hole for guiding pressure oil to the sliding surface of the piston shoe.