JP6179359B2 - Hydraulic piston pump / motor - Google Patents

Description

  The present invention relates to a hydraulic piston pump / motor.

  2. Description of the Related Art Conventionally, there are known hydraulic piston pumps and motors that are used as a hydraulic source or a hydraulic actuator and rotate by supplying and discharging hydraulic oil.

  In such a hydraulic piston pump and motor, if an oil film cannot be maintained on the sliding contact surface between the cylinder block and the valve plate, wear or seizure occurs. For this reason, a seal land surface for sealing the flow of hydraulic oil supplied to and discharged from the cylinder block and a pad surface for properly maintaining the surface pressure between the cylinder block and the valve plate are formed on the sliding contact surface. Is done.

  For example, in Patent Document 1 below, an oil reservoir is provided on the sliding contact surface together with the seal land surface and the pad surface, thereby maintaining the oil film on the pad surface and improving the lubricity of the pad surface.

JP 2010-116813 A

  In the above-described conventional hydraulic piston pump / motor, since the hydraulic oil in the oil reservoir portion passes through the escape groove, the pressure drops to a pressure close to the tank pressure, which is almost atmospheric pressure. Even when the oil film thickness changes, the oil film pressure distribution in the radial direction of the sliding contact surface does not change, and the load resistance (hereinafter referred to as bearing load) of the oil film that supports the cylinder block does not change.

  Therefore, in conventional hydraulic piston pumps and motors, when a large load is applied to the hydraulic piston pumps and motors and the pump discharge pressure increases, the load load exceeds the bearing load of the oil film and the oil film cannot be maintained. Can occur. At this time, due to the pressure in the piston bore, the cylinder block slides in a state of being strongly pressed against the valve plate, and there is a possibility that wear, seizure, or the like may occur.

  It is an object of the present invention to provide a hydraulic piston pump / motor in which lubricity is improved on a sliding contact surface between a cylinder block and a valve plate.

  A hydraulic piston pump / motor according to an embodiment of the present invention is in sliding contact with a rotating cylinder block, a plurality of pistons reciprocating with respect to the cylinder block, a cylinder bore in a cylinder block expanded or contracted by the piston, and the cylinder block. A hydraulic piston pump / motor having a valve plate that switches between supply and discharge of hydraulic oil to and from a cylinder bore in the cylinder block, wherein the cylinder block and the valve plate are in sliding contact with each other. On the other hand, there is a first seal land surface adjacent to the opening through which the hydraulic oil flows, and a second seal land surface located outside the first seal land surface with respect to the opening, The separation distance from the valve plate is the separation distance on the first seal land surface. There longer than the distance at the second sealing land surface.

  In the hydraulic piston pump / motor, when the load load fluctuates, the gap between the cylinder block and the valve plate is adjusted so that the bearing load of the oil film and the load load are balanced. That is, when a large load is applied and the gap between the cylinder block and the valve plate becomes small, the bearing load of the oil film becomes large. Even in such a case, the sliding contact surface between the cylinder block and the valve plate High lubricity can be achieved.

  Further, the sliding contact surface further has a recess portion located between the first seal land surface and the second seal land surface on at least one of them, and a separation distance in the recess portion is a separation distance in the first seal land surface. It may be an aspect longer than the distance.

  Further, the sliding contact surface has a high pressure region through which high pressure hydraulic oil passes, and a low pressure region through which hydraulic oil having a pressure lower than the pressure in the high pressure region passes, and the sliding contact surface is at least in the high pressure region, The aspect which has a 1st seal land surface and a 2nd seal land surface may be sufficient.

  ADVANTAGE OF THE INVENTION According to this invention, the hydraulic piston pump motor which improved the lubricity in the slidable contact surface of a cylinder block and a valve plate is provided.

FIG. 1 is a schematic sectional view showing a variable displacement piston pump according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part of the variable displacement piston pump of FIG. 1, showing a sliding contact surface between the cylinder block and the valve plate. FIG. 3 is a view showing a sliding contact surface on the valve plate side. 4 is a cross-sectional view further enlarging the portion surrounded by the broken line in FIG. FIG. 5 is a view showing a sliding contact surface on the valve plate side. FIG. 6 is a cross-sectional view further enlarging a portion surrounded by a broken line in FIG. FIG. 7 is a graph showing the relationship between the oil film thickness and the load on the sliding contact surface of FIG. FIG. 8 is a view showing a sliding contact surface on the valve plate side in a different mode. FIG. 9 is a view showing a sliding contact surface on the cylinder block side in a different mode.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected about the same or equivalent element, and the description is abbreviate | omitted when description overlaps.
(Hydraulic piston pump / motor)

  First, a variable displacement piston pump (hereinafter simply referred to as a pump) 1 as a hydraulic piston pump / motor according to the present embodiment will be described with reference to FIG.

  The pump 1 includes a pump housing 10 and a rotating shaft 20 protruding from the pump housing 10.

  The pump housing 10 has a crank chamber 12 therein. The pump housing 10 is formed by joining a front housing 10a, a center housing 10b, and a rear housing 10c.

  The rotating shaft 20 is supported in the crank chamber 12. The rotating shaft 20 has a projecting end portion from the pump housing 10 connected to a power take-off device (not shown) and is directly rotated by the engine.

  The crank chamber 12 of the pump housing 10 accommodates a cylinder block 14 that is spline-fitted to the rotary shaft 20 so as to be integrally rotatable. The cylinder block 14 has a plurality of cylinder bores 14a around the rotation shaft 20 in the cylinder block 14 (nine in this embodiment), and a piston 16 is accommodated in each cylinder bore 14a.

  The crank chamber 12 of the pump housing 10 accommodates a swash plate 30 that is supported by the pump housing 10 via a support shaft 30 a and that can swing in the axial direction of the rotary shaft 20. Each piston 16 accommodated in the cylinder block 14 is pressed by a swash plate 30 through a shoe whose one end (left end in FIG. 1) is connected by a spherical joint. It is pressed against the valve plate 40 fixed to the inner end wall surface of 10c.

  Then, when the cylinder block 14 is rotated integrally with the rotary shaft 20, each piston 16 is reciprocated along a stroke defined by the inclination angle of the swash plate 30, and the cylinder bore 14 a is provided through the valve plate 40. Further, the suction port 40a and the discharge port 40b having an arc shape are alternately communicated. As a result, the hydraulic oil is sucked into the cylinder bore 14a from the suction port 40a, and the hydraulic oil in the cylinder bore 14a is discharged from the discharge port 40b by a pump action. The suction passage 10d and the discharge passage 10e are formed in the rear housing 10c, and communicate with the suction port 40a and the discharge port 40b, respectively.

  The pump 1 further includes a control piston 50. The control piston 50 is provided on the side of the center housing 10 b of the pump housing 10 and has a housing 52 that communicates with the crank chamber 12.

  The housing 52 of the control piston 50 extends in a direction inclined with respect to the rotation shaft 20 and has a substantially cylindrical shape extending toward the edge of the swash plate 30.

  Of the openings in the housing 52, the opening far from the swash plate 30 is closed by a screw 54. As a result, a piston accommodation chamber 56 is defined in the housing 52, and a piston portion 58 is accommodated in the piston accommodation chamber 56. In the piston accommodating chamber 56, the space between the piston portion 58 and the screw 54 functions as a control chamber 56a into which hydraulic oil flows.

  The piston portion 58 has a cylindrical outer shape, and the diameter thereof is such that there is no gap between the piston portion 58 and the inner wall surface of the piston accommodating chamber 56, and the piston portion 58 can slide in the piston accommodating chamber 56. Designed as such.

According to the control piston 50, the piston portion 58 can be reciprocated in the direction of the swash plate 30 by controlling the hydraulic oil to the control chamber 56a. When the piston portion 58 presses the sphere 32 provided on the edge portion 30b of the swash plate 30, the inclination angle of the swash plate 30 is changed, and as a result, the discharge capacity of the pump 1 is changed.
(Sliding contact surface between cylinder block and valve plate)

  Next, the sliding contact surface between the cylinder block 14 and the valve plate 40 described above will be described with reference to FIGS.

  As shown in FIGS. 2 to 4, the surface on the cylinder block 14 side of the valve plate 40 described above is a slidable contact surface 41 that is in sliding contact with the surface 15 of the opposing cylinder block 14. The surface 15 of the cylinder block 14 is also a sliding contact surface that is in sliding contact with the surface 41 of the valve plate 40.

  The discharge area of the sliding contact surface 41 of the valve plate 40 (that is, the high pressure area that discharges the hydraulic oil from the cylinder block 14 with a relatively high pressure; the right area in FIG. 3) and the suction area (that is, the hydraulic oil is relatively discharged. The first seal land surface 42 and the second seal land surfaces 43A and 43B are provided in both of the low pressure region (the left region in FIG. 3) supplied to the cylinder block 14 at a low pressure (pressure lower than the discharge region pressure). ing.

  Here, the formation regions of the first seal land surface 42 and the second seal land surfaces 43A and 43B are as shown in FIG.

  That is, on the sliding contact surface 41 of the valve plate 40, the openings of the arc-shaped suction port 40a and the discharge port 40b whose center of curvature is the center O of the valve plate 40 are exposed, and the first seal land surface 42 is It is provided in a semi-annular region that surrounds the discharge port 40b in the discharge region so as to be adjacent to the discharge port 40b and that makes a half turn around the center O of the valve plate 40.

  On the other hand, the second seal land surfaces 43A and 43B are located outside the first seal land surface 42 with respect to the opening of the discharge port 40b in the discharge region. The second seal land surface 43A provided in the semi-annular region outside the region, and the second seal land surface 43B provided in the semi-annular region inside the semi-annular region of the first seal land surface 42. It consists of and. Note that, in the suction region of the sliding contact surface 41 of the valve plate 40, the region other than the suction port 40 a is the second seal land surface 43.

  Further, the distance between the first seal land surface 42 and the second seal land surfaces 43A and 43B from the sliding contact surface 15 of the cylinder block 14 is as shown in FIG.

That is, the first seal land surface 42 is separated from the sliding contact surface 15 of the cylinder block 14 by a height h ₁ . Second sealing land surface 43A, both 43B are spaced apart by the height _{h 2} with respect to the sliding surface 15 of the cylinder block 14. As shown in FIG. 4, the separation distance h _{1 on} the first seal land surface 42 is designed to be longer than the separation distance h ₂ on the second seal land surfaces 43A and 43B (that is, h ₁ > h ₂ ). Thereby, the boundary between the first seal land surface 42 and the second seal land surfaces 43A and 43B becomes a stepped portion as shown in FIG.

  As a result of intensive research, the inventors have provided the first seal land surface 42 and the second seal land surfaces 43A and 43B as described above on the sliding contact surface 41 of the valve plate 40. It was newly found that the characteristics are expressed.

That is, in the pump 1, the bearing load of the oil film on the second seal land surfaces 43 </ b> A and 43 </ b> B is increased as the piston bore pressure P ₀ determined from the discharge pressure increases and the gap between the cylinder block 14 and the valve plate 40 becomes narrower. The characteristic that becomes large is developed.

  The above characteristics are obtained when the first seal land surface 42 and the second seal land surfaces 43A and 43B are provided not on the sliding contact surface 41 side of the valve plate 40 but on the sliding contact surface 15 side of the cylinder block 14. Also expressed.

  Further, as shown in FIG. 4, it is not necessary to provide the first seal land surface 42 and the second seal land surfaces 43A and 43B symmetrically on both sides of the discharge port 40b, and the first seal is provided only on one side. The land surface 42 and the second seal land surfaces 43A and 43B may be provided.

  Furthermore, as shown in FIGS. 5 and 6, annular grooves 44 </ b> A and 44 </ b> B may be provided as depressions between the first seal land surface 42 and the second seal land surfaces 43 </ b> A and 43 </ b> B.

  As shown in FIG. 5, the annular grooves 44A and 44B are both provided around the center O of the valve plate 40, and the annular groove is provided between the first seal land surface 42 and the second seal land surface 43A. 44A is provided, and an annular groove 44B is provided between the first seal land surface 42 and the second seal land surface 43B.

As shown in FIG. 6, the annular grooves 44 </ b> A and 44 </ b> B are all separated from the sliding contact surface 15 of the cylinder block 14 by a height h <b> ₃ . The separation distance h ₃ in the annular grooves 44A and 44B is designed to be longer than the separation distance h ₁ in the first seal land surface 42 (ie, h ₃ > h ₁ > h ₂ ). Accordingly, the boundaries between the annular grooves 44A and 44B and the first seal land surface 42 and the second seal land surfaces 43A and 43B are stepped portions as shown in FIG.

The values of the pressures P _1A and P _1B inside the annular grooves 44A and 44B are values between the piston bore internal pressure P ₀ and the tank pressures P _2A and P _2B outside the valve plate 40, and the annular grooves 44A and 44B. It can be said that the region provided with is an intermediate pressure region.

In order to verify the characteristics of the pump 1 described above, the inventors set the radial lengths (r ₁ to r ₈ ) of the feature points of the valve plate 40 as shown in FIG. It was. r ₁ is up to the inner edge of the valve plate 40 in length, _{r 2} is the length from the center O to the inner edge of the annular groove 44B, _{r 3} is the length from the center O to the outer edge of the annular groove 44B, _{r 4} is the center O from to the inner edge of the discharge port 40b length, r ₅ is the length from the center O to the outer edge of the discharge port 40b, r ₆ is from the center O to the inner edge of the annular groove 44A in length, r ₇ is annular from the center O length to the outer edge of the groove 44A, r ₈ is a length of up to the outer edge of the valve plate 40.

At this time, the bearing load F of the oil film on the second seal land surfaces 43A and 43B can be expressed by the following equation.

From this equation, it can be seen that the bearing load F becomes maximum when the gap h ₂ = 0 and becomes minimum when h ₂ = ∞. That is, the second sealing land surface 43A, spaced at 43B distance (i.e., the oil film thickness) as _{h 2} is decreased, the bearing load of the oil film increases.

When the bearing load F of the above formula is schematically graphed, a graph as shown in FIG. 7 is obtained. That is, as the second sealing land surface 43A, the oil film thickness h ₂ at 43B decreases (moves to the left of the graph), bearing load F of the oil film is increasing. Therefore, when a certain load F ₁ is applied to the pump 1, the oil film thickness h ₂ is automatically adjusted to the thickness of the point P where the bearing load F balances the load load F ₁ .

Incidentally, bearing load F ₀ of the pump according to the prior art having no above characteristics is expressed by the following equation. In the following equation, r ₁ is the length from the center to the inner edge of the seal land surface, r ₂ is the length from the center to the inner edge of the port, r ₃ is the length from the center to the outer edge of the port, and r ₄ is This is the length from the center to the outer edge of the seal land surface.

In this equation, the bearing load F ₀ does not include the separation distance between the cylinder block 14 and the valve plate 40. That is, the bearing load F ₀ is a constant value determined by the piston bore internal pressure P ₀ determined from the discharge pressure. That is, even if the gap between the cylinder block 14 and the valve plate 40 becomes narrow, the bearing load F ₀ does not increase, and the difference between the load load F ₁ and the bearing load F _{0 is} the difference between the cylinder block 14 and the valve plate 40. It is supported by the metal contact, and wear or seizure occurs.

  The present invention is not limited to the above embodiment, and various modifications are possible.

  For example, the first seal land surface 42, the second seal land surfaces 43A and 43B, and the annular grooves 44A and 44B described above are either or both of the sliding contact surface 41 of the valve plate 40 and the sliding contact surface 15 of the cylinder block 14. Can be provided.

  Further, as shown in FIG. 8, the annular grooves 44A and 44B may be provided only on the ejection region side. In this case, since it is not necessary to provide an annular groove on the suction area side, the area where the suction port 40a is formed can be enlarged accordingly.

  Furthermore, as shown in FIG. 9, only the annular grooves 17A and 17B corresponding to the annular grooves 44A and 44B described above may be provided on the sliding contact surface 15 on the cylinder block 14 side. In this case, the suction pressure loss can be reduced, so that the occurrence of cavitation can be prevented.

  Further, the recess is not limited to the annular groove, and may be a hole disposed between the first seal land surface and the second seal land surface or a groove having a predetermined length.

  When the hydraulic piston pump / motor is a pump such as the variable displacement piston pump 1 described above, the hydraulic oil pressure in the discharge region is higher than the hydraulic oil pressure in the suction region, and at least the sliding contact It is preferable to provide a first seal land surface and a second seal land surface (and further a recess) on the side of the discharge region which is the high pressure side. On the other hand, when the hydraulic piston pump / motor is a motor, the hydraulic oil pressure in the suction area is higher than the hydraulic oil pressure in the discharge area, and at least on the high pressure side of the sliding contact surface. It is preferable to provide a first seal land surface and a second seal land surface (further, a recess).

  DESCRIPTION OF SYMBOLS 1 ... Hydraulic piston pump motor (variable capacity type piston pump), 14 ... Cylinder block, 14a ... Cylinder bore, 15 ... Sliding contact surface, 40 ... Valve plate, 15, 41 ... Sliding contact surface, 42 ... 1st seal land surface , 43, 43A, 43B ... second seal land surface, 17A, 17B, 44A, 44B ... annular groove.

Claims (2)

A rotating cylinder block;
A plurality of pistons reciprocating relative to the cylinder block;
A cylinder bore in the cylinder block that is expanded and contracted by the piston;
A hydraulic piston pump / motor that is disposed in sliding contact with the cylinder block and includes a valve plate that switches supply and discharge of hydraulic oil to and from the cylinder bore in the cylinder block;
At least one of the sliding contact surfaces where the cylinder block and the valve plate are in sliding contact with each other,
A first seal land surface adjacent to an opening through which hydraulic fluid flows;
A second seal land located outside the first seal land surface with respect to the opening and provided in both an outer diameter side region and an inner diameter side region relative to the formation region of the first seal land surface . And having a surface,
The distance between the cylinder block and the valve plate in sliding contact surfaces, the distance of the first seal land surface rather long than the distance in the second sealing land surface,
The sliding contact surface further has at least one indented portion located between the first seal land surface and the second seal land surface of both the regions,
The distance has a length than the hydraulic piston pump-motor distance in the recess portion of the first seal land surface. The sliding contact surface has a high pressure region through which the hydraulic oil at a high pressure passes, and a low pressure region through which the hydraulic oil at a pressure lower than the pressure in the high pressure region passes,
2. The hydraulic piston pump / motor according to claim 1, wherein the sliding contact surface has the first seal land surface and the second seal land surface at least in the high pressure region.

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