JPH07103133A - Variable displacement swash plate type hydraulic power unit - Google Patents

Abstract

PURPOSE:To prevent any possible liquid leak from occurring in a simple and accurate manner by fitting the projection of a bearing in a long groove of a swash plate shaft, dividing the long groove into plural volumetric parts, while setting an opening area of the long groove so as to make such a force as floating a swash plate by dint of hydraulic pressure to be taken into the volumetric part, become the specified value. CONSTITUTION:A swash plate shaft 2 with a convex curved surface of a swash plate 1 is supported free of sliding motion by a concave curved surface 3a of a bearing 3. In addition, a cylinder block 4 fitted with a piston 5 is connected to a main shaft 6 piercing through the swash plate 1. Further the piston 5 is connected to the swash plate 1 via a shoe 7. In this case, a long groove 15 extending in a sliding direction is formed on the convex curved surface 2a, while a projection 16 adhering to the long groove 15 is formed on a concave curved surface 3a, and then the long groove 15 is divided into plural parts in the longitudinal direction. By the way, discharge pressure is made to act on a volumetric part 15a-1 on one side, where the long groove 15 is divided, and the swash plate 1 is turned round in an A direction, while another discharge pressure is made to act on another volumetric part 15a-2 on the other, thereby turning the swash plate 1 round in a B direction as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement swash plate type hydraulic device used for power transmission of industrial machines such as vehicles and machine tools, and more particularly to a variable capacity mechanism thereof.

[0002]

2. Description of the Related Art Conventionally, as a variable displacement type swash plate type hydraulic device of this type, there is one shown in FIG. In the figure, reference numeral 1 denotes a swash plate, and swash plate shafts 2 each having a semi-cylindrical convex curved surface 2a are provided at both ends thereof, and each swash plate shaft 2 is a semi-cylindrical cylinder of a bearing 3 provided in a casing 10. Concave curved surface 3
It is slidably supported by a. That is, the swash plate 1 is slidably supported by the semi-cylindrical swash plate shaft 2 and the bearing 3 so as to rotate about the swash plate axis 11. Reference numeral 4 is a cylinder block in which a plurality of pistons 5 are fitted, and is connected to a main shaft 6 that penetrates the swash plate 1. Each piston 5 is connected to the swash plate 1 via a piston shoe 7 that is a universal joint. . Further, the swash plate 1 is in contact with a bias piston 12 to which the discharge pressure is guided and a control piston 13 to which the control pressure of a control valve (not shown) is guided, at a position separated in the radial direction. Reference numeral 14 denotes a valve plate that sucks and discharges liquid by the reciprocating motion of the piston 5 caused by the rotation of the main shaft 7 and the cylinder block 4, and is fixed to the casing 10.

The conventional variable displacement swash plate type hydraulic device is constructed as described above, and its capacity is determined by the inclination angle of the swash plate 1 with respect to the main shaft 6. Since the swash plate 1 is slidably supported by a semi-cylindrical swash plate shaft 2 and a bearing 3 so as to be rotatable about a swash plate shaft core 11, the capacity control of this hydraulic device is performed. , The bias piston 12 and the control piston 13, which are pressed against the swash plate 1 from the direction opposite to the bearing 3, generate the operating moment.

However, such a conventional device has the following problems. Bias piston 12 and control piston 13
Due to this, the outer diameter of the casing becomes very large, and the entire device becomes large. Since a portion of the swash plate 1 that receives an operation moment from the bias piston 12 and the control piston 13 is brought into contact with and slid, a problem such as abrasion may occur in durability. Generally, the number of parts is large, and the ease of assembly is not so high.
High cost. The swash plate 1 receives a force in the main axis direction by the discharge pressure acting on the piston 5 of the cylinder block 4. This force is a radial load on the swash plate shaft 2 and bearing 3, and as a result,
It is necessary to increase their strength, and very large sliding friction is generated on the swash plate shaft and the bearing portion.

On the other hand, in Japanese Utility Model Laid-Open No. 57-204476, the tilt angle of the swash plate with respect to the main shaft is adjusted by supplying the pressure liquid to the space provided between the swash plate shaft and the semi-cylindrical sliding surface of the bearing. A swash plate oscillating device adapted to be changed is disclosed. The structure is that a semi-cylindrical convex curved surface of the swash plate shaft is provided with a long groove extending in the sliding direction, and a partition plate fixed to the bearing is fitted into the long groove to divide the long groove into two parts. The bearing is provided with a port communicating with each part, and a plurality of oil holes are opened on the semi-cylindrical concave curved surface of the bearing.

According to this swash plate oscillating device, in order to change the inclination angle of the swash plate, if the pressure liquid is introduced from one of the ports, the volume of the long groove on the introduction side increases, so The plate shaft rotates, whereby the inclination angle of the swash plate can be changed. At this time, the hydraulic fluid is also supplied to the multiple oil holes, and the lubricating oil is supplied between the sliding surfaces of the swash plate shaft and the bearing through the throttle provided at the tip of the oil holes, and the static pressure is applied between these sliding surfaces. It is said to constitute a bearing.

[0007]

However, in the conventional swash plate swinging device as described above, in order to prevent the swash plate from being lifted up by hydraulic pressure, pins for preventing the lift up are provided on the shafts of both sides of the swash plate. Therefore, the size of the casing cannot be reduced, and since the semi-cylindrical swash plate shaft rotates, the shape and structure of the pin becomes extremely complicated, and a reliable liquid There was a problem that it was difficult to prevent leakage. Further, since there is only one long groove provided on each swash plate shaft, the capacity can be controlled only by the four-way valve, and there is a problem that the capacity control cannot be performed by the generally widely used three-way valve.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to prevent the lifting without providing the lifting prevention pin of the swash plate as in the conventional case, and to control the capacity easily. An object is to provide a swash plate type hydraulic device.

[0009]

In order to achieve the above object, a variable displacement type swash plate type hydraulic device according to the present invention comprises a swash plate having semi-cylindrical shafts at both ends and a shaft of the swash plate. A bearing having a semi-cylindrical concave curved surface that slidably supports, a long groove provided in the convex curved surface of the shaft of the swash plate in the sliding direction, and provided in the bearing, and fitted into the long groove, A variable capacitor having a protrusion that divides the long groove into two volume portions in the longitudinal direction, and by changing the inclination angle of the swash plate with respect to the main axis by supplying liquid to the volume portion of the long groove, the volume control is possible. In the swash plate type hydraulic device, a plurality of long grooves are provided in parallel to the sliding direction on the convex curved surface of the shaft of the swash plate, fitted in the respective long grooves, and each long groove is divided into two volume portions in the longitudinal direction. The bearing is provided with a plurality of projections that A force that lifts the swash plate by the hydraulic pressure introduced into the volume of the long groove presses the swash plate against the bearing by the piston of the cylinder block while forming the fitting shape similar to the shape. The opening area of the long groove is determined so as to be substantially equal to or slightly smaller than the pressing force.

Further, the discharge pressure is introduced into one volume portion divided by the plurality of long grooves and the projection, and all the volume portions located on the opposite side of the long groove and the long groove adjacent to the long groove from the discharge pressure introducing side. The control pressure of the control valve is introduced into and the other volume part has a circuit configuration that communicates with the drain.

The long groove has a circular arc bottom shape, the projection has a cylindrical shape, and the tip has an arc shape similar to the groove bottom shape of the long groove.

The protrusion is slidably provided on the bearing so that it can be pressed against the groove bottom of the long groove by hydraulic pressure.

[0013]

The plurality of long grooves formed on the convex curved surface of the semi-cylindrical swash plate shaft are divided into two volume portions in the longitudinal direction by fitting the protrusions provided on the concave curved surface of the bearing. The discharge pressure, the drain pressure, and the control pressure of the control valve that controls the volume are introduced into each of the divided volume portions of the long groove. At this time, the protrusion on the bearing receives an operating force due to the difference in pressure acting on each volume portion of the divided long groove. This operating force is a moment around the swash plate axis, and the bias piston in the conventional structure is used. And the one by the control piston. Therefore, even if the bias piston and the control piston are not provided, the inclination angle of the swash plate can be changed by the plurality of long grooves provided on the convex curved surface of the swash plate shaft and the protrusions of the bearings fitted into the respective long grooves. You can
The capacity can be easily controlled.

Further, the swash plate receives a force that is pressed against the bearing from the piston fitted in the cylinder block and a force that floats from the bearing due to the hydraulic pressure introduced into the long groove, but both forces are roughly balanced or float. By determining the opening area in contact with the bearing of the long groove so that the force to be applied is slightly smaller than the force to be pressed, the above-mentioned variable volume function is satisfied without causing liquid leakage.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of the essential part showing an embodiment of the present invention. 2 is a view of the swash plate of FIG. 1 viewed from the bearing side, FIG. 3 is a sectional side view of the swash plate and the bearing in a state of being supported by the bearing, and FIG. 4 is a top view of the bearing on one side. FIG. 7 is a diagram showing a control circuit connected to each long groove in the case of performing capacity control by self-discharge pressure. A similar control circuit is connected to the swash plate shaft on the other side. The same parts as those in FIG. 7 are designated by the same reference numerals.

In this embodiment, a plurality of long grooves 15 extending in the sliding direction are provided in parallel with each other on the semi-cylindrical convex curved surface 2a of each swash plate shaft 2 provided on both sides of the swash plate 1. The semi-cylindrical concave curved surface 3a of the bearing 3 is provided with projections 16 which are closely fitted to the respective long grooves 15, and these projections 16 divide each long groove 15 into two parts in the longitudinal direction. It will be.

In the embodiment, each of the three protrusions 16a, 16a
b, 16c and three long grooves 15 each corresponding to them
a, 15b, 15c are provided. In addition, the long groove volume portion divided by each protrusion is 15a-1 and 15b- in the direction of increasing capacity (direction of arrow A in FIG. 1), respectively.
1, 15c-1 and 15a-2, 15b-2, and 15c, respectively, in the direction of decreasing capacity (direction of arrow B in FIG. 1).
-2.

Then, each long groove is connected to a control circuit as shown in FIG. 4, for example, so that the pressurized liquid is guided. Here, an example is shown in which a three-way control valve is used as the capacity control valve 18 and capacity control is performed by self-discharge pressure. In the figure, 19 is a solenoid and 20 is a pump constituted by the apparatus of this embodiment. Further, the bearing 3 has a supply hole 21 for guiding the discharge pressure to one volume portion 15a-1.
And a supply hole 22 for guiding the discharge pressure of the control pressure from the capacity control valve 18 to all the volume parts 15a-2, 15b-2, 15c-2 on the opposite side, and the other volume parts 15b-1, 15c. -1
And a communication hole 23 for communicating with the drain.

That is, the discharge pressure is guided to one volume portion 15a-1 of the central long groove 15a among the volume portions divided as described above, and the other volume portion 15a-2 is positioned on the same side as the volume portion 15a-2. The control ports 18a of the capacity control valve 18 are communicated with the volume portions 15b-2, 15c-2 of the left and right long grooves 15b, 15c, and the other volume portions 15b-1, 15c.
-1 communicates with the drain.

The operation of the present embodiment configured as described above will be described. The control port 18a of the capacity control valve 18 is communicated with either the drain or the discharge pressure. First, when the control port 18a is communicated with the drain, one volume portion 1 of the central long groove 15a is formed.
Discharge pressure acts on 5a-1 and all other volume 1
Since 5a-2, 15b-2, 15c-2, 15b-1 and 15c-1 are communicated with the drain, the discharge pressure introduced into the volume 15a-1 causes the swash plate 1 to move in the direction of arrow A in FIG. It rotates, and as a result, an operating moment acts in the direction of increasing the capacity. On the other hand, when the control port 18a communicates with the discharge pressure, the discharge pressure also acts on the volume portions 15a-2, 15b-2, 15c-2,
The operation moment generated by the discharge pressure acting on the volume portion 15a-1 is overcome, and the swash plate 1 is rotated in the direction of arrow B in FIG. 1 as a total, and as a result, the operation moment acts in the direction of volume reduction.

As described above, the operation pressure generated by the discharge pressure of the volume portion 15a-1 acting on the pressure receiving area of the projection 16a and the distance between the swash plate shaft cores 11 of the pressure is the conventional bias piston in FIG. 12 corresponds to the operation moment, and the volume parts 15a-2, 15b-2,
The control pressure of the capacity control valve 18 of 15c-2 is set to the projections 16a, 16
The operating moment generated by the pressure acting on the pressure receiving area of b and 16c and the distance between the swash plate shaft cores 11 of the pressure is
This corresponds to the operation moment by the conventional control piston 13 in FIG. Therefore, since it is not necessary to provide the bias piston 12 and the control piston 13 as in the conventional case, the entire apparatus can be downsized.

Further, in the case of the above construction, it is necessary that the protrusions 16a, 16b and 16c accurately divide the volumes of the long grooves 15a, 15b and 15c at any inclination angle of the swash plate 1. As a shape that satisfies this and can be easily processed, it is desirable that the tip of each protrusion is a hemispherical cylindrical shape. However, it is clear that even if each projection is plate-shaped or has any cross-sectional shape, as long as it can accurately divide the volume of the long groove, it can sufficiently perform its function. is there.

Further, as shown in FIG.
It is possible to more accurately divide the above-mentioned long groove volume by slidably providing to the rear side and guiding the pressure liquid to the rear side so that it can be pressed against the bottom of the long groove.

On the other hand, the discharge pressure and the control pressure act on the opening area of each of the long grooves 15a, 15b, 15c in contact with the bearing 3, so that the swash plate shaft 2 receives the force (opening force) to float from the bearing 3. However, this separating force opposes the force in the main axis direction that the swash plate 1 receives from the piston 5 fitted into the cylinder block 4, and the friction that the semi-cylindrical sliding curved surfaces of the swash plate shaft 2 and the bearing 3 receive. Power can be greatly reduced. However, when this opening force becomes larger than the force in the main axis direction received from the piston 5 of the cylinder block 4, the swash plate shaft 2 is further levitated from the bearing 3 and liquid leakage occurs and the function is satisfied. Disappear. Therefore, the opening area of each long groove in contact with the bearing is required to be designed so that the opening force does not become larger than the force in the main axis direction received from the piston 5 of the cylinder block 4.

When pressure is applied to the plurality of protrusions, a moment is generated in each of the protrusions in a plane substantially orthogonal to the main axis 6. In order to reduce this value, the protrusions 16b and 16c are arranged symmetrically with respect to the protrusion 16a as shown in FIG. The point of application of the pressing force of the piston 5 of the cylinder block 4 to the swash plate 1 is eccentric from the center of the swash plate 1. However, if the pressing force is greater than the force for floating the swash plate 1, each protrusion is attached to the swash plate. The symmetrical arrangement with respect to the center of 1 has little effect.

FIG. 6 shows a case where two protrusions 16a, 16b and long grooves 15a, 15b are arranged. In FIG. 6 (a), the discharge pressure is guided to the volume portion 15a-1 of the inner long groove 15a, and the other volume is introduced. Volume part 1 of part 15a-2 and outer long groove 15b
5b-2 guides the control pressure of the capacity control valve 18, and the other volume portion 15b-1 communicates with the drain. In the same figure (b), the discharge pressure is delivered to the volume portion 15b-1 of the outer long groove 15b. The control pressure of the capacity control valve 18 is introduced to the other volume part 15b-2 and the volume part 15a-2 of the inner long groove 15a, and the other volume part 15a-1 communicates with the drain. These embodiments also have the same effects as the above embodiments.

In the embodiment, the displacement control valve 18 is a three-way control valve, and the discharge pressure, the drain pressure, and the control pressure of the control valve are introduced into the long groove, but the displacement control valve is a four-way control valve. It can also be controlled as a control valve.

[0028]

As described above, according to the present invention, a plurality of long grooves are provided in parallel to the semi-cylindrical convex curved surface of the swash plate shaft in the sliding direction, and are fitted into the respective long grooves to make each long groove long. The bearing is provided with a plurality of projections that divide the volume into two volume portions, and the force of floating the swash plate by the hydraulic pressure introduced into the volume portion of each long groove pushes the swash plate against the bearing by the piston of the cylinder block. Since the opening area of the long groove is determined so as to be almost equal to or slightly smaller than the pressing force, liquid leakage can be surely prevented even without the conventional lifting prevention pin, The structure is simplified, which contributes to downsizing, weight reduction, and cost reduction of the device.

Further, the discharge pressure is introduced into one of the volume portions of each long groove, and the control valve is provided in all of the volume portions located on the opposite side of the long groove and the long groove adjacent to the long groove from the discharge pressure introducing side. Since the control pressure is introduced and the other volume portion communicates with the drain, the inclination angle of the swash plate can be accurately controlled, and the capacity can be easily controlled.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of the present invention.

FIG. 2 is a view of the swash plate of FIG. 1 viewed from a bearing side.

FIG. 3 is a sectional side view showing a state in which a swash plate shaft is supported by a bearing.

FIG. 4 is a circuit diagram showing an example of capacity control.

FIG. 5 is a diagram showing another method of attaching the protrusions.

FIG. 6 is a diagram showing another example of arrangement of protrusions and long grooves.

FIG. 7 is a sectional side view of a conventional variable displacement swash plate type hydraulic device.

[Explanation of symbols]

 1 Swash plate 2 Swash plate shaft 3 Bearing 4 Cylinder block 5 Piston 6 Main shaft 15 Long groove 16 Protrusion

Claims (4)

[Claims] 1. A swash plate having semi-cylindrical shafts at both ends, a bearing having a semi-cylindrical concave curved surface slidably supporting the shaft of the swash plate, and a convex shape of the shaft of the swash plate. A long groove provided on a curved surface in a sliding direction and a projection provided on the bearing and fitted into the long groove to divide the long groove into two volume portions in the longitudinal direction are provided. In a variable displacement type swash plate type hydraulic device capable of changing the inclination angle of the swash plate with respect to the main axis by supplying the swash plate, the swash plate is provided in parallel with the convex curved surface of the shaft in the sliding direction. A plurality of long grooves, and a plurality of protrusions provided on the bearing, which are fitted into the plurality of long grooves and divide each long groove into two volume portions in the longitudinal direction, wherein the protrusions have a groove bottom shape It is formed so that it has the same fitting shape as the above, and is introduced into the volume of the long groove. The opening area of the long groove is determined so that the force for floating the swash plate by the hydraulic pressure is almost equal to the force for pressing the swash plate to the bearing by the piston of the cylinder block or slightly smaller than the force. A variable displacement type swash plate type hydraulic device characterized in that 2. A discharge pressure is introduced into one volume portion divided by the plurality of long grooves and protrusions, and all the volume portions located on the opposite side of the discharge groove introducing side of the long groove and the long groove adjacent to the long groove. 2. The variable displacement swash plate type hydraulic device according to claim 1, wherein the control pressure of the control valve is introduced into and the other volume portion is connected to the drain. 3. The variable capacitor according to claim 1, wherein the groove bottom shape of the long groove is arcuate, the projection is cylindrical and the tip thereof is arcuate like the groove bottom shape of the long groove. Swash plate type hydraulic device. 4. The protrusion is slidably provided on the bearing,
2. The variable capacity type swash plate type hydraulic device according to claim 1, wherein the groove bottom of the long groove can be pressed by hydraulic pressure.