JPH0456150B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diagonal shaft type axial piston machine, and more particularly to a fully hydrostatic bearing supported diagonal shaft type axial piston machine used at high pressures.

[Conventional technology]

The conventional device supports the thrust load by providing a static pressure shoe corresponding to each piston, as described in, for example, Japanese Patent Laid-Open No. 59-131776. On the other hand, in this type of piston machine, the number of pistons that contribute to the discharge pressure varies depending on the total number of pistons. For example, when the total number of pistons is nine, there are two cases: five pistons and four pistons. Therefore, the point of application of the resultant force of the piston reaction load is linked to the number of pistons located in the discharge pressure area, and is proportional to the rotation speed of the drive shaft, generally at the number "8".
Draw a trajectory like this. Due to the dynamic behavior of this piston reaction force, not only a thrust load but also a moment load acts on the drive disk portion of the drive shaft that supports the plurality of piston rod members. This moment load is ultimately supported by the static pressure shoe, but in this case, the moment load naturally acts on the static pressure shoe located on the suction pressure side. However, since the static pressure shoe on the suction pressure side does not have the ability to support the moment load, it must be supported by metal contact. For this reason, the sliding surface built into the drive disk and constituted by a plurality of static pressure shoes is no longer perpendicular to the drive axis.
This causes uneven wear on the static pressure shoe, which shortens the life of the static pressure shoe and increases the amount of leakage from the shoe surface. This results in increased power losses in the piston machine due to leakage flow.

[Problem to be solved by the invention]

When the axes that pass through the axis of the drive shaft and are orthogonal to each other in the axial direction are respectively the x-axis and the y-axis,
In the above conventional technology, even though alternating moment loads around the x-axis and y-axis act on the drive disk based on the discharge pressure, the drive disk is evenly supported by a hydrostatic bearing having a constant pocket pressure. It is located mainly on the suction side, with no consideration given to
In order to simultaneously support both a static pressure shoe without static pressure load capacity and a hydrostatic bearing shoe located on the discharge pressure side that has static pressure load capacity, the suction side static pressure shoe is mounted on the body (or the operating shaft). Metallic contact with the pressure plate) cannot be avoided.
This tends to cause uneven wear or seizure due to the one-sided rotational sliding motion of the plurality of static pressure shoes. In addition, since the sliding surfaces between the drive disk portion of the operating shaft and the plurality of static pressure shoes form an inclined surface with a certain slope, the leakage flow rate from both sliding surfaces also increases, resulting in an increase in power loss. There were other problems.

An object of the present invention is to provide a diagonal shaft type axial piston machine that has low leakage even under high pressure and has high durability.

[Means to solve the problem]

The above object includes a cylinder block having a housing cover and a plurality of cylinder holes, and a piston that is movable back and forth within the cylinder hole and is fixed to a piston rod, and the piston is tilted with respect to a drive shaft and rotates freely. In the axial piston machine, the axial piston machine is fitted to the housing cover and rotatably supports the drive shaft via a bearing, and is configured such that the supply direction of high-pressure oil can be selected by a shuttle valve. This is achieved by providing a bearing sleeve in which a plurality of static pressure pads are arranged axially symmetrically with respect to an axis with a cross section perpendicular to the drive shaft.

[Effect]

The static pressure pad provided on the bearing sleeve completely covers the range of variation of the piston reaction force load, and
Because they are independently arranged in positions where the bending moment about the point of application of the resultant force of the average piston reaction force is always balanced, even if a variable load synchronized with the rotation speed of the drive shaft acts eccentrically on the drive disk, the load will not change. Able to perform adapted and smooth movements.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2 for a case of an oblique shaft type axial piston motor among axial piston machines.

The axial piston motor consists of a housing cover 1, a cylinder block 3 having a plurality of cylinder holes 2, and a piston 5 which is movable back and forth within the cylinder holes 2 and is fixed to a piston rod 4. The piston rod 4 is pivotally mounted within a drive disk 6B of a drive shaft body 6 consisting of a shaft 6A and a drive disk 6B connected to an operation input shaft (not shown) of an axial piston motor. In addition, when no input is applied to the shaft 6A of the axial piston motor,
The shaft 6A and the drive disk 6B are fitted to each other at a spline shaft coupling portion 7 with a specific gap maintained in the radial direction. Further, a bearing 9 is disposed between the outer periphery of the shaft 6A and the bearing sleeve 8 to rotatably support the shaft 6A. Further, the cylinder block 3 is rotatably provided via a spherical universal joint or a center rod (both not shown), and is connected to the center shaft 1.
0 is supported on a head cover 12 via a valve plate 11 having a working medium suction port 11A and a discharge port 11B. The head cover 12 is provided with a suction port 12A and a discharge port 12B, and these ports are connected to the suction port 1 on the valve plate 11.
1A and discharge port 11B, respectively. The spherical universal joint also includes a spherical bearing (both not shown) and is pivotally mounted within the drive disk 6B.

The adjustment for changing the angle of inclination of the cylinder block 3 (not shown) is carried out by means of a yoke or a regulator (not shown). By changing the inclination angle, the piston 5 in the cylinder hole 2
Change the process. The drive disk 6B and the shaft 6A are connected, for example, by a spline shaft 7, and the shaft 6A acts as an input shaft in accordance with the operating method of the axial piston motor.

The bearing sleeve 8 also includes a chamber 13 , and the bearing sleeve 8 includes a chamber 13 .
A rod portion 17 of a hydrostatic bearing pad 16 consisting of a constriction portion 14 and a pressure chamber 15 is inserted therein, and a flange portion 18 of the hydrostatic axial pressure pad 16 is inserted.
has both end surfaces 2 between the end surface 20 of the bearing sleeve 8 perpendicular to the axial direction and the end surface 21 of the drive disk 6B.
It is interposed so as to be in contact with 0 and 21.

As mentioned above, the hydrostatic bearing pad 16 has the constricted portion 14 and the pressure chamber 15, and is disposed at a specific position with respect to the bearing sleeve 8, as shown in FIG. Further, a working medium having a discharge pressure Pd is directly introduced to the end surface 19 of the rod portion 17 of the hydrostatic bearing pad 16, and communicates with the pressure chamber 15 via the constriction portion 14.

On the other hand, the drive disk 6B is supported on its outer peripheral surface as a radial slide bearing on a bearing sleeve 22 disposed within the housing 1.

At least four or more pressure chambers 23 corresponding to the number of pistons 5 at the maximum are provided on the inner circumferential surface of the bearing sleeve 22 around the drive shaft 6B at a pitch of at least 90 degrees. Discharge pressure is applied to the outer peripheral surface of the bearing sleeve 22.
A Pd supply port 24 is provided corresponding to the pressure chamber 23, and the supply port 24 and the pressure chamber 23 are connected via a constriction part 25 for controlling the static pressure of the pressure chamber 23 in accordance with the load. It's communicating.

Normally, the operating shaft is used in forward rotation (clockwise rotation when viewed from the counter-operation axis) or reverse rotation (counterclockwise rotation when viewed from the counter-operation axis). A shuttle valve 26 is provided in the middle of the line that communicates with the backflow port 11A and the discharge port.

Next, the operation of the fully static pressure bearing supported oblique shaft type axial piston motor constructed as described above will be explained.

In axial piston motor, discharge pressure
Number of pressurizing pistons to generate Pd and discharge pressure (for example, if the total number of pistons is 7, the maximum number of pressurizing pistons is 4, the minimum number of pressurizing pistons is 3, and the average number of pressurizing pistons is 3.5 The piston reaction force load and moment load are synchronized with the rotation speed of the drive shaft 6 and act on the drive disk 6B while changing in proportion to the rotation speed of the drive shaft 6. The load acting on the drive disk 6B is diffused into an axial component force and a radial component force on the drive disk 6B on the support surface of the piston rod 4. Further, if the axes that pass through the drive shaft center and are orthogonal to each other are defined as the x-axis and the y-axis, moment loads around the x- and y-axes are induced by the piston reaction force. The load consisting of the load and moment spread in two directions in this way is caused by the hydrostatic pressure and It is supported by a hydrodynamically acting sliding bearing. In particular, the axial component and moment component of the drive disk of the load are supported by three independently arranged static pressure pads, as shown in FIG. . Thereby, the loaded drive disk 6B is supported axially and radially within the machine housing 1 in hydrostatic and hydrodynamic slide bearings by means of the hydrostatic pad 16 and the bearing sleeve 22.

Here, let us consider in detail how the load acting on the drive disk 6B is supported in the axial direction. Now, when the total number of pistons is Za,
As shown in Fig. 4, as the number of pistons located on the discharge pressure side changes to (Za+1/2) or (Za-1/2), the resultant force of the piston reaction load increases accordingly. The point of application of force also changes as shown in FIG. Therefore, the drive disk 6B is subjected to not only a simple thrust load but also an x-axis and a y-axis load.
Moment loads around the axis also act. However, in the present invention, the three static pressure parts 16a to 16c are set in consideration of the balance of the force of the axial component of the drive disk with respect to the load and the moment balance with respect to the force application point P of the resultant force of the average piston reaction force. They are placed at appropriate positions as shown in Figure 2. Therefore, thrust loads and moment loads are supported hydrostatically and hydrodynamically by the static and dynamic pressures created by the static pressure pads 16a-16c, adapting to the loads. .

To explain in more detail, as shown in Figs. 3 and 4, in an axial piston machine, the piston reaction force Fp against the drive disk of the axial piston machine is As shown in Figure 4, the effect is variable.
That is, when the rotation axis of the cylinder block (not shown) is inclined at an angle α° with respect to the drive shaft 6,
The piston reaction force load and moment load acting on the drive disk 6B are expressed by the following equation.

Ft＝Fpcosα …(1) Fr＝FpSinα …(2) Here, Ft: Axial component of piston reaction force load Fr: Radial component of piston reaction force load Moreover, Fp is given by the following formula.

Fp=Zp・Pd・Ap…(3) Here, Zp: Number of pistons contributing to the discharge pressure Pd: Discharge pressure Ap: Piston cross-sectional area (=π/4dp ² ) On the other hand, the axial component of the piston reaction force load Ft The moment components around the x-axis and y-axis induced by
・sinθ My=Ft・(Za〓1/2)・cosα・e(Za〓1/2)・cosθ…(5)

Here, 〓: Displays the number of pistons located on the high pressure side when Za is an odd number.

In this way, the piston reaction load and the moment load will act simultaneously on the drive disc.

However, in the present invention, the variation range of the piston reaction force load is completely covered, and the x-axis and y-axis are
Three static pressure pads are independently arranged at positions where the bending moments around the axis are always balanced. This results in a moment load based on the piston reaction force.
A total of 3 pads, consisting of one static pressure pad with a static pressure loading capacity installed on the side opposite to the force point with respect to Mx and My, and two static pressure pads installed on the side of the force point of the resultant force of the piston reaction force. However, the sliding surface of the drive disk is always kept parallel to the sliding surface of the static pressure pad in accordance with the magnitude of the load. This not only supports the axial component of the piston reaction force load, but also allows direct metal contact with the sliding surfaces of both the drive disk and the static pressure pad even when the moment load component consisting of Mx and My acts. does not occur. Furthermore, since the drive disk and the static pressure pad form parallel sliding surfaces having a uniform oil film thickness, leakage flow from both sliding surfaces can be suppressed to a minimum. This makes it possible to minimize power loss due to leakage flow and realize smooth operation.

As a result, according to this embodiment, the load can be followed,
Since the contact surfaces between the drive disk and the static pressure pads are formed so as to always maintain a parallel plane without exhibiting an excessively inclined surface, the three static pressure pads 16a to 16c
On the sliding surface between the drive disk and the drive disk, problems such as uneven wear and seizure due to metal contact between the two can be prevented. Further, according to the present invention, the sliding surface formed by the drive disk and the pad acts so as to always maintain straightness in the axial direction of the drive disk. As a result, the thickness of the oil film on the sliding surfaces of the three static pressure pads and the drive disk is formed to be substantially uniform in accordance with the load, so that the leakage flow rate from the sliding surfaces can be suppressed to a minimum.

In addition to this, according to the present invention, compared to the conventional method,
Since the thrust component of the piston reaction force can be supported by a small number of pads, that is, the minimum number of pads (three pads), it is possible to reduce the cost of a high-pressure, low-leakage axial piston machine. Furthermore, since the slack load and moment load acting on the drive shaft of an axial piston machine are all hydrostatically and hydrodynamically supported by the static pressure pad, the stress generated in the shaft portion of the drive shaft is The main stress is torsional stress. As a result, the diameter of the shaft portion can be made smaller than in the conventional case of bending stress + torsional stress. Furthermore, since the point of support for the thrust component of the piston reaction force can be shifted to the end face of the disk portion of the drive shaft, that is, to the side where the piston reaction force is applied, the length of the shaft portion of the drive shaft can be shortened compared to the conventional system.
This allows the axial piston machine to be made smaller and lighter.

Although an embodiment relating to a piston pump has been described in detail above, as shown in FIG. 2, the present invention can achieve the same effect even in the case of a piston motor by the same operation as in the case of a pump. That is, in the case of a motor specification, this can be realized by arranging a set of three static pressure pads at symmetrical positions along the y-axis. For example, if the motor is used in reverse, static pressure pads would be placed at positions 16a', 16b' and 16c'.

On the other hand, the present invention is not limited to fully static pressure supported axial piston machines, and may be used in combination with, for example, roller bearings conventionally used to support piston reaction forces. As a result, the durability of the roller bearing in the axial piston machine can be increased, and power loss due to leakage from the pads can be minimized.

〔Effect of the invention〕

According to the present invention, even if a variable load synchronized with the rotational speed of the drive shaft acts eccentrically on the drive disk, it is possible to prevent metal-to-metal contact on the sliding surface of the drive disk, and moreover, it is possible to prevent metals from contacting each other on the sliding surface of the drive disk. Since the movement can be realized, high pressure and high durability can be achieved for long-term use of a small, fully static pressure bearing supported oblique axis type axial piston machine. Furthermore, leakage flow rate from the sliding surface of the drive disk can be suppressed to a minimum. As a result, it is possible to reduce power loss due to leakage flow, and it is possible to realize higher performance of the axial piston machine.

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view of a fully hydrostatic bearing supported oblique axis type axial piston machine representing an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along the line - - of Fig. 1, and Fig. 3 is a piston of the axial piston machine. FIG. 4 is a diagram illustrating the action of the reaction force on the drive disk, and is a diagram illustrating the locus of the point of application of the piston reaction force in an axial piston machine. DESCRIPTION OF SYMBOLS 1... Housing cover, 3... Cylinder block, 4... Piston rod, 5... Piston, 6... Drive shaft, 6A... Shaft, 6B... Driving piston, 7
...Spline shaft joint, 8...Bearing sleeve, 11
... Valve plate, 12... Head cover, 14, 25... Throttle section, 15, 23... Pressure chamber, 16... Static pressure pad, 2
2...Bearing sleeve, 26...Shuttle valve.

Claims (1)

[Claims] 1 A drive shaft consisting of a housing cover, a shaft supported within the housing cover, and a drive disk provided on the shaft, and a plurality of cylinder holes, and rotates at an angle with respect to the drive shaft within the housing cover. An axial piston machine comprising a removably supported cylinder block and a piston which is inserted into said cylinder bore on the one hand so as to be movable back and forth and on the other hand is connected to a drive disk, the end plate of the bearing sleeve being connected to the end face of said drive disk. A cylindrical portion of a bearing sleeve is fitted into the housing cover so as to face the housing cover, and a shaft of a drive shaft is rotatably supported via a bearing on the inner surface of the cylindrical portion of the bearing sleeve. A plurality of static pressure pads are provided on the end face facing the drive disk, each axially symmetrical with respect to at least two orthogonal axes in a plane perpendicular to the axis of the shaft, and the housing cover is provided with a plurality of static pressure pads facing the outer periphery of the drive disk. An axial piston machine characterized by being equipped with a static pressure pad.