JPH0459470B2 - - 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 in particular to a piston suitable for a fully static pressure bearing supported diagonal shaft type axial piston pump/motor used at high pressure. The present invention relates to an axial piston machine that supports a thrust component of a reaction load and a moment load due to the thrust component.

[Conventional technology]

A conventional device is described, for example, in Japanese Patent Application Laid-open No. 131776/1983. It only states that the shoe floats freely in the thrust direction, but there is no mention of the force relationship between the piston reaction force and the pad thrust, which is the issue in this application.

On the other hand, if the shoe follows the piston reaction force and floats, the positioning accuracy of the drive shaft in the thrust direction decreases, and this decrease in holding accuracy causes an apparent thickening of the oil film formed on the static pressure guide surface of the shoe. It is equivalent to summer. This increases power loss due to increased leakage flow from the shoe surface, resulting in a loss of effective fluid power output from the axial piston machine. Also, when Shu repeats the dynamic floating phenomenon,
Since a pure step-like dynamic load synchronized with the rotation speed of the drive shaft acts on the static pressure guide surface of the shoe, wear occurs on the sliding surface of the shoe due to collisions, reducing the durability of the shoe. It is expected that.

[Problem to be solved by the invention]

The thrust static pressure bearing support device for axial piston machines, which supports the thrust component of the piston reaction force of axial piston machines with shoes or pads, is of the so-called full static pressure bearing support type, and is designed to provide stable operation with low leakage and low vibration. To make this possible, the positioning of the drive shaft that directly supports the piston reaction force in the thrust direction must be made comparable to that of conventional roller bearings.

On the other hand, in one known example disclosed in JP-A-59-131776, the shoe that directly supports the thrust component of the piston reaction force is of a type that floats following fluctuations in the piston reaction force. Since the drive shaft also moves in the above-mentioned direction, it is expected that the positioning accuracy of the drive shaft in the thrust direction will decrease. If the holding accuracy of the drive shaft in the thrust direction is reduced in this way, the thickness of the oil film formed on the sliding surface of the shoe or pad may become thicker. In this case, there is a concern that the power loss of the axial piston machine will increase due to an increase in the amount of leakage from the sliding surface.

An object of the present invention is to provide a structure in which the shoe or pad supports the piston reaction force while being in close contact with the fixed part at all times, thereby achieving low leakage and high durability even under high pressure. An object of the present invention is to provide an oblique shaft type axial piston machine (pump motor) having the following features.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a housing cover, a shaft supported within the housing cover, a drive shaft comprising a drive disk provided on the shaft, and a plurality of cylinder holes. a cylinder block rotatably supported at an angle with respect to the drive shaft; and a piston, one of which is inserted into the cylinder hole so as to be movable back and forth, and the other of which is connected to the drive disk. In an axial piston machine in which the outer peripheral surface of the drive disk is supported by a first bearing and the end surface on the drive shaft side is supported by a second bearing, the second bearing is supported on the housing cover side opposite to the end surface on the drive shaft side of the drive disk. It consists of a static pressure pad that can be moved to
The load capacity on the static pressure guide surface of the static pressure pad is W,
When the rod thrust of the static pressure pad is Fs, the load capacity of the static pressure pad is configured to satisfy Fp>W>Fs.

[Effect]

The piston reaction force acts directly on the drive shaft. on the other hand,
The load capacity on the static pressure guide surface of the pad and the thrust force on the rod portion of the pad are always smaller than the thrust component of the piston reaction force generated in the axial piston machine. As a result, when a piston reaction load is applied, the pad always acts to hydrostatically and hydrodynamically support the drive shaft in a state where it is pressed against the fixed part. As a result, an oil film thickness determined by the thrust balance between the piston reaction force and the pad load capacity is formed on the pad sliding surface. As a result, the leakage flow rate from both sliding surfaces can be suppressed to a minimum. Thereby, power loss due to leakage flow rate can be minimized and smooth operation can be realized.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2 in the case of an oblique shaft type axial piston pump among axial piston machines. The axial piston pump consists of a housing cover 1, a cylinder block 3 having a plurality of cylinder holes 2, and a piston 5 which is freely movable within the cylinder holes 2 and is fixed to a piston rod 4.
The piston rod 4 is connected to a shaft 6A that connects to an operation input shaft (not shown) of an axial piston pump.
Of the drive shaft main body 6 consisting of the drive disk 6B and the drive disk 6B, the drive shaft body 6 is pivotally mounted within the drive disk 6B. In addition, when no input is applied to the shaft 6A of the axial piston pump, the shaft 6A and the drive disk 6B are fitted to each other at the spline shaft coupling portion 7 with a specific gap maintained in the radial direction. There is. Furthermore, shaft 6
The shaft 6 is located between the outer periphery of A and the bearing sleeve 8.
A bearing 9 is provided to rotatably support A. Further, the cylinder block 3 is rotatably provided via a spherical universal joint or a center rod (both not shown), and is connected by a center shaft 10 to a valve plate 11 having a suction port 11A and a discharge port 11B for the working medium. and is supported on the head cover 12. The head cover 12 is provided with a suction port 12A and a discharge port 12B, and these ports communicate with the suction port 11A and the discharge port 11B on the valve plate 11, respectively. Spherical universal joints and spherical bearings (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 according to the operating method of the axial piston pump.

The bearing sleeve 8 also includes a chamber 13 , and the bearing sleeve 8 includes a chamber 13 .
The rod portion 17 of the hydrostatic bearing pad 16 consisting of the constriction portion 14 and the pressure chamber 15 is inserted into the rod portion 17 of the hydrostatic bearing pad 16 , and the flange portion 18 of the hydrostatic bearing pad 16 is inserted into the rod portion 17 of the hydrostatic bearing pad 16 .
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 constriction part 14 and the pressure chamber 15, and is arranged at a specific position with respect to the bearing sleeve 8, as shown in FIG. Further, the rod portion 1 of the hydrostatic bearing pad 16
A working medium having a discharge pressure Pd is directly introduced into the end face 19 of the pressure chamber 15 through the constriction part 14.
It communicates with

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 a maximum are provided on the inner peripheral surface of the bearing sleeve 22 around the drive disk 6B at a pitch of at least 90 degrees. A supply port 24 for the discharge pressure Pd is provided on the outer circumferential surface of the bearing sleeve 22 in correspondence with the pressure chamber 23, and the supply port 24 and the pressure chamber 2
3 is in communication with the pressure chamber 23 through a throttle section 25 for controlling the static pressure in the pressure chamber 23 in accordance with the load.

On the other hand, in the case of an axial piston motor,
Normally, the operating shaft is used in forward rotation (clockwise when viewed from the counter-operating axis) or reverse (counterclockwise when viewed from the counter-operating axis), so the discharge pressure from the axial piston motor is applied to the pad in accordance with this direction of rotation. A shuttle valve 26 is provided in the middle of a line that communicates with the suction port 11A and the discharge port (in the case of a piston pump specification).

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

In axial piston pumps, the 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 drive disk 6B on which the load acts is moved in the axial direction in the machine housing 1 with a hydrostatic and hydrodynamic sliding bearing by means of a hydrostatic bearing pad 16 and a bearing sleeve 22. and radially supported.

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 the number of pistons changes to (Za + 1/2) or (Za - 1/2), the point of application of the resultant force of the piston reaction force also changes to the second point around P.
It fluctuates as shown in the figure. Therefore, the drive disk 6B is subjected to not only a simple thrust load but also
Moment loads about the x and y axes also act.
However, in the present invention, the load capacity of the pad and the rod thrust are always smaller than the resultant force of the piston reaction forces when the number of pistons located on the discharge side of the pump is (Za-1/2). That is, in Figures 2 and 3, the resultant force of the piston reaction force is
Fp, the load capacity on the pad static pressure guide surface corresponding to the static pressure pads 16a to 16c is W ₁ to
W ₃ and the rod thrust corresponding to the pad from Fs ₁ to
When Fs ₃ , the power relationship between the three parties is Fp> ₃ 〓 ⁱ⁼¹
A static pressure pad was formed so that Wi> ₃ 〓 ⁱ⁼¹ Fsi.
As a result, the pad hydrostatically and hydrodynamically supports the drive shaft in a state where it is always pressed against the fixed part when the piston reaction force load is applied, and it always supports the drive shaft hydrostatically and hydrodynamically, regardless of the magnitude of the resultant force of the piston reaction force. The drive shaft of an axial piston machine can be reliably positioned in the thrust direction. Therefore, the leakage flow rate from both sliding surfaces can be suppressed to a minimum.
As a result, power loss due to leakage flow rate can be minimized and smooth operation can be realized.

In the embodiment of the present invention described above, a case where the piston pump is supported at three points has been described, but the present invention is not limited to this, and the present invention is not limited to this. The present invention can also be applied to a corresponding axial piston machine in the same manner as the three-point support case, and the same effects as in the above-mentioned embodiment can be achieved.

〔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, the static pressure pad remains in close contact with the fixed part at all times and absorbs the piston reaction force hydrostatically and dynamically. Since the structure is hydrodynamically supported, it is possible to provide a fully hydrostatic bearing supported axial piston machine (pump motor) that has low leakage even at high pressures and has high durability.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a thrust hydrostatic bearing support device for a fully hydrostatic bearing supported oblique shaft type axial piston machine according to an embodiment of the present invention, FIG. The figure is a diagram illustrating the force relationship in the thrust direction of an axial piston machine according to an embodiment of the present invention. 1... Housing cover, 3... Cylinder block, 4... Piston rod, 5... Piston,
6... Drive shaft, 6A... Shaft, 6B... Drive disk, 7... Spline shaft joint, 8... Bearing sleeve, 11... Valve plate, 12... Head cover, 16... Static pressure pad, 22 ... Bearing sleeve, 15, 23 ... Pressure chamber, 14, 25 ... Throttle section, 26 ... Shuttle valve.

Claims (1)

[Claims] 1 A drive shaft consisting of a housing cover, a shaft supported within the housing cover, a drive disk provided on the shaft, and a plurality of cylinder holes, the drive shaft being inclined with respect to the drive shaft within the housing cover. It comprises a rotatably supported cylinder block, and a piston, one of which is inserted into the cylinder hole so as to be movable back and forth, and the other is connected to a drive disk, and the outer peripheral surface of the drive disk is supported by a first bearing. In an axial piston machine in which the end face on the drive shaft side is supported by a second bearing, the second bearing is constituted by a static pressure pad movably provided on the housing cover side facing the end face on the drive shaft side of the drive disk. Then, when the resultant force of the piston reaction force is Fp, the load capacity on the static pressure guide surface of the static pressure pad is W, and the rod thrust of the static pressure pad is Fs, the load capacity of the static pressure pad is Fp＞W＞
An axial piston machine characterized by being configured to be Fs.