KR100296773B1 - Piston for bent axis type piston pump - Google Patents

Abstract

The present invention relates to a piston of a bent axis axial piston pump, and in particular, to improve the strength by modifying the shape of the piston for driving the cylinder block, and to provide a piston suitable for increasing and minimizing the suction and supply of hydraulic fluid,

A curved land portion in contact with the inner diameter of the cylinder block is formed in the piston head, and a piston ring is coupled to the upper side of the land portion, and the diameter of the rod 35 is smaller than the diameter of the head 34. Angle( ), The head 34, the rod 35 and the sphere 31 are formed integrally.

The tapered piston is also designed The taper angle between ∠1 ° and ∠10 ° can be freely rotated with respect to the center of the cylinder block and the hydraulic lateral component can be minimized. It is characterized by having).

Since the tapered piston is integral, the present invention has high strength, and has a land portion and a piston ring, so that airtightness can be maintained during operation to increase volume efficiency, and is designed to be equivalent to the piston performance and efficiency of a conventional pump. This is very useful to miniaturize the whole pump.

Description

Piston of bent axis axial piston pump {PISTON FOR BENT AXIS TYPE PISTON PUMP}

The present invention relates to a piston of a bent axis axial piston pump, and in particular, increases the strength by integrating the rod and the piston, increases the volumetric efficiency by preventing leakage between the cylinder and the piston, and rotation of the cylinder block with respect to the drive shaft midline. It relates to a piston of a bent axis axial piston pump which is easy to miniaturize the pump by increasing the suction amount of the working oil by increasing the inclination angle of the center to the maximum.

In general, the bent axis axial piston pump has a rod-piston coupling type in which a piston is coupled to a rod mouth, and a reciprocating motion is carried out in the cylinder. Refers to suction and discharge of the working oil by the reciprocating piston.

The conventional piston used in the bent axis type is a combination of the piston 130 and the rod 131 as shown in Figure 7, and is currently used most in the bent axis axial piston pump. The piston 130 and the rod 131 is characterized in that the spherical portion is connected to be freely inclined and rotated by rolling, and had a much stronger durability than the combination using a ring or pin, but with such a piston In the coupled type of rod, rotational movement occurs between the drive shaft and the cylinder block by simultaneously performing the operation of sucking and discharging the hydraulic oil and the operation of rotating the cylinder block. Therefore, if the rotational fluctuations generated in the piston, rod, drive shaft, and cylinder block become extremely large at high speed rotation, large stresses are generated in the piston and / or rod and are easily broken. Therefore, in order to prevent breakage of the piston and the rod, the structure must be enlarged to have a large strength, and thus there is a limit in miniaturizing the pump.

In addition, the bent axis is inclined to the center of the drive shaft and the center of rotation of the cylinder block has a constant angle, the larger the inclination angle, the longer the stroke length of the piston, so that the suction amount of the hydraulic fluid is increased so that the piston can be made smaller In the case of the combination of the 130 and the rod 131, as the stroke length of the piston increases, a greater rotational variation occurs, and the current inclination angle is limited to a range of up to ∠25 ° to ∠28 °.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to intervene when reciprocating in the cylinder block, as well as integrating a coupling type of a rod and a piston for driving the cylinder block. Designed with a minimum taper angle to increase the strength, the piston ring is coupled to the upper part of the land portion of the piston tip to prevent leakage between the cylinder and the piston to increase the volumetric efficiency, and the center of rotation of the cylinder block about the center of the drive shaft. It is to provide a piston of a bent axis axial piston pump that is easy to miniaturize the pump by increasing the intake amount of the working oil by increasing the inclination angle to the maximum.

1 is a longitudinal sectional view showing a bent axis axial piston pump having a tapered piston according to the present invention;

2 is a partial cross-sectional view of the tapered piston according to the present invention;

3 is a conceptual diagram showing a rotational trajectory of a tapered piston operating in a cylinder block according to the present invention;

4a, 4b is a conceptual diagram showing the positional relationship of the drive shaft disk, piston, cylinder block in a bent axis piston pump having a tapered piston according to the present invention,

Figure 5a is a cross-sectional view showing the position and inclination relationship that the tapered piston in accordance with the present invention is smoothly operated in the cylinder block,

5b is a conceptual diagram showing the hydraulic lateral force generated when the tapered piston operates in the cylinder block according to the present invention;

6 is a partial cross-sectional view of a conventional piston.

* Description of the symbols for the main parts of the drawings *

2: pump 21: drive shaft

22: drive shaft disk 23: hemispherical groove

30: taper piston 31: piston bend

32: piston ring 33: land portion

40: cylinder block 41: cylinder

43: cylinder port 45: valve plate

53: suction port 53 ': discharge port

The present invention for achieving the above object is coupled to the drive shaft center fixed to the drive shaft in the state in which the center of rotation of the drive shaft and the center of rotation of the cylinder block is inclined at a predetermined angle, having a suction port and a discharge port In the piston reciprocating in the cylinder of the cylinder block rotated in contact with the valve plate, the piston has a curved land portion is formed in the head in contact with the cylinder inner diameter, the piston ring is coupled to the upper side of the land portion, the head The taper angle is formed so that the diameter of the rod is smaller than the diameter of the, and the head, the rod, and the spherical portion are integrally formed.

In addition, the present invention provides a taper angle that allows the piston to rotate freely about the center of the cylinder block and at the same time minimize hydraulic lateral force. Formulation for the design of) and taper angles between (1 ° and ∠10 ° to minimize hydraulic lateral forces It is characterized by having).

In addition, the present invention is characterized in that the inclination angle (α) is arranged to be inclined up to a maximum ∠40 ° to increase the stroke distance of the piston 30 to increase the suction amount of the working oil to be smaller than the conventional piston pump.

Hereinafter, a piston of a bent axis axial piston pump of the present invention will be described in detail with reference to the accompanying drawings.

1 is a longitudinal sectional view showing a bent axis piston pump having a piston according to the present invention, wherein the bent axis piston pump has an inclination angle α at which the center of rotation of the drive shaft 21 and the center of rotation of the cylinder block 40 are inclined at a constant angle. In the state of forming a valve plate 45 having a suction port 53 and a discharge port 53 'are coupled to the drive shaft disc 22 fixed to the drive shaft 21 and the rod 31 of the rod 35. And a tapered piston 30 reciprocating in the cylinder 41 of the cylinder block 40 rotated in contact with

In the above configuration, when the inclination angle, which is an angle formed between the center of the drive shaft 21 and the center of rotation of the cylinder block 40, has an arbitrary angle other than 0, the rotation of the rod section 31 from the center of the cylinder block 40 is achieved. The trajectory appears as an ellipse when the movement path of the center is drawn in the coordinate system of the cylinder block 40 as shown in FIG. 3.

Meanwhile, an angle formed by a line connecting the center of the cylinder at the center of the cylinder block 40 and a line connecting the center of the taper piston 30 at the center of the cylinder according to the rotation of the drive shaft disk 22 (the azimuth angle of the taper piston) ) Rotates in a direction opposite to the rotational direction of the drive shaft disk 22. At this time, the bottom dead center of the tapered piston 30 is located toward the center of the cylinder block 40, and at the neutral point, it faces toward the outside of the cylinder, and when rotated to the top dead center, it is located toward the center of the cylinder block 40 again. Done.

Therefore, when the drive shaft disk 22 is rotated 180 ° from the bottom dead center, the azimuth angle of the tapered piston 30 changes 360 ° in the reverse direction of the rotation direction of the drive shaft disk 22. That is, the taper piston 30 rotates twice in the cylinder during one rotation of the drive shaft disk 22.

2 is a cross-sectional view showing a tapered piston according to the present invention, wherein the piston 30 has a curved land portion 33 in contact with the inner diameter of the cylinder 41 in the head 34. The piston ring 32 is coupled to the upper side of the land part 33, and the taper angle (so that the diameter of the rod 35 is smaller than the diameter of the head 34) ), The head 34, the rod 35 and the sphere 31 are integrally formed, and the center of rotation of the drive shaft 21 and the center of rotation of the cylinder block 40 form an inclined shape at a predetermined angle. The inclination angle α is produced up to a maximum of 40 °.

Therefore, the piston 30 of the present invention, in which the piston and the rod are combined with the conventional piston 130 and the rod 131, obtains about 2,5 times the strength improvement compared to the conventional combined type. The land 33 portion of the head 34 and the piston ring 32 maintain an optimum clearance when the piston 30 reciprocates to suck and discharge hydraulic fluid in the cylinder 41 of the cylinder block 40. In particular, the piston ring 32 is expanded by the discharge pressure is induced on the back surface of the ring during discharge to prevent the leakage of the working oil to obtain an increase in the volumetric efficiency. In addition, if the inclination angle of the center of rotation of the cylinder block 40 with respect to the center of the drive shaft 21 is inclined to a maximum of 40 °, the stroke of the piston 30 becomes long and the same size. The capacity of the piston is increased by 1.5 times compared to the conventional pump having a tilt angle of ° 25 °. Therefore, the increase in the inclination angle according to the increase in the strength of the piston 30 is designed and configured to be equivalent to the piston performance and efficiency of the existing pump it is possible to miniaturize the entire pump (2).

On the other hand, the most important thing in manufacturing the piston 30 as described above depends on how to design the taper angle, and if the design is incorrect, the cylinder block 40 is not driven at all, or extremely the cylinder block 40 and And / or a phenomenon in which the piston 30 is destroyed.

Therefore, the design of the taper angle of the piston 30 which integrally forms the head 34 and the rod 35 includes the length of the tapered piston, the pitch circle radius of the cylinder block, the pitch circle radius of the drive shaft disc 22, and the drive shaft ( 21) is determined by the inclination angle α of the center of the cylinder block 40 with respect to the center, and the taper angle of the piston 30 ( ) And the influence of the hydraulic lateral component on the angle of the piston 30 will be described.

First, Figure 4 is a conceptual diagram showing the positional relationship between the drive shaft disk, the piston, the cylinder block in the bent axis piston pump having a tapered piston, wherein the rotational movement of the drive shaft disk 22 is an ellipse when viewed from the side of the cylinder block 40 Piston part 31 of piston 30 located in hemispherical groove 23 of drive shaft disk 22 because of movement. In terms of appearance, the delay / leading angle with respect to the cylinder block 40 ).

Therefore, when the drive shaft disk 22 is rotated by an arbitrary rotation angle θ from the bottom dead center at an arbitrary inclination angle α, the delay / leading angle ( ), The azimuth angle of the piston ( ) And the taper angle (the angle between the center of the cylinder and the center of the piston 30) For geometric considerations,

therefore,

Also,

As can be seen from the equations (3) and (4), the tapered piston 30 rotates in the cylinder 41, and since the rotational movement region changes according to the inclination angle, the piston 30 The taper angle should be given to the piston 30 so that the piston 30 can rotate freely with respect to the center of the cylinder so that the and cylinder do not interfere with each other.

In addition, among the forces acting on the piston 30 when the cylinder block 40 rotates, the hydraulic lateral force most affects the piston 30 and the taper angle of each piston 30 passing through the discharge side. And azimuth Can be calculated as the rotational torque acting on the piston.

FIG. 5A is a cross-sectional view showing the positional relationship between the cylinder block and the piston in the piston pump, and FIG. 5B is a conceptual diagram showing the hydraulic lateral force from the center of the cylinder block in the piston pump, wherein the piston 30 is with respect to the center of the cylinder. Lateral component, if Is as follows.

here, Is the cross section of the tapered piston 3, Is the discharge pressure, and the distance between the lateral component action point and the center of the cylinder block 40 is is φ.

Therefore, the torque by the lateral component force with respect to one piston 30 becomes (6).

here,Is the pitch circle radius of the cylinder block 40,AndFrom the relationship with the rotation angle θ, to be.

Therefore, the torque sum of all the tapered pistons 3 on the discharge side Is given by the following equation (7).

Average torque from this Is expressed by equation (8).

As a result, the hydraulic lateral force increases in proportion to the taper angle of the piston, as can be clearly seen in Equation (6), so that this angle should be made as small as possible.

Therefore, the taper angle to which the piston 30 is given should be freely rotated with respect to the center of the cylinder and the center of the taper piston 30 should be made at the same time to minimize the hydraulic lateral force. It is a value between ~ 10 °.

Next, operation of the present invention having the configuration as described above will be described.

When the drive shaft 21 and the drive shaft disk 22 of the pump 2 are rotated, the tapered pistons 30 having the spherical portions 31 coupled to the plurality of hemispherical grooves 23 formed on the drive shaft disk 22 rotate. At the same time, the tapered piston 30 rotates the cylinder block 40. At this time, the piston 30 moves upwardly in the cylinder 41 and the hydraulic oil sucked from the suction port 53 of the valve plate 45 into the cylinder 41 through the cylinder port 43 of the cylinder block 40. The piston 30 moves downward while the cylinder 30 moves downward after the cylinder block 40 is rotated. The discharge port 53 ′ of the cylinder port 43 and the valve plate 45 of the cylinder block 40 is introduced. It will be discharged efficiently.

On the other hand, when the taper piston 30 of the present invention is used in the swash plate piston pump to form the head, the rod and the sphere integrally as described above and maintains a fine taper angle of ∠1 ° to ∠10 °, the piston is in the cylinder. As the rotational area becomes large while rotating, the shoe (part connected to the piston's bend) swings greatly during high-speed rotation, resulting in lubrication problems between the swash plate and the shoe or slipping of the shoe. Is generated. In addition, when the piston reciprocates, the end of the cylinder and the piston are in local contact with friction, and if the friction is severe, the cylinder and / or the piston may be destroyed. Therefore, the tapered piston 30 of the present invention cannot be used as a swash plate piston, and the piston used in the swash plate type is cylindrical or has a rod 1 / diameter than the diameter of the head as disclosed in Japanese Laid-Open Patent Publication No. 60-135678. Smaller than 2, the piston is used only as a function to suck and discharge hydraulic oil while reciprocating in the cylinder, and the cylinder block must be driven by a universal joint connected to the drive shaft. Therefore, it should be noted that the piston 30 of the present invention can be used only in a bent axis type.

According to the present invention, the piston and the rod driving the cylinder block as described above are integrally formed with the piston and the rod, thereby obtaining about 2,5 times the strength improvement compared to the conventional coupling type, and the land portion of the piston head. The piston ring and the piston ring have a structure that can maintain an optimum gap when the piston reciprocates to suck and discharge the hydraulic fluid in the cylinder of the cylinder block.In particular, the piston ring is expanded by inducing a discharge pressure on the back surface of the ring during discharge. By preventing leakage of hydraulic oil, the volumetric efficiency can be increased, and the piston of which the strength is increased can be configured to incline the inclination angle of the center of rotation of the cylinder block with respect to the center of the drive shaft to a maximum of 40 °. This increases the suction volume of the hydraulic fluid, resulting in increased capacity compared to conventional pumps with an incline angle of ∠25 ° using a piston of the same size. Since 1.5 times the increase can be obtained, it is useful to design and configure the same as the piston performance and efficiency of the existing pump to miniaturize the whole pump.

Claims (3)

The center of the drive shaft 21 and the center of rotation of the cylinder block 40 are inclined to form a predetermined inclination angle α, and the bend of the rod 35 is fixed to the drive shaft disk 22 fixed to the drive shaft 21. In the piston (30) is coupled and reciprocates in the cylinder (41) of the cylinder block (40) rotated in contact with the valve plate (45) having the suction port (53) and the discharge port (53 '). , The head 34 of the piston 30 is formed with a curved land portion 33 in contact with the inner diameter of the cylinder 41, the piston ring 32 is coupled to the upper side of the land portion 33 The rod 35 of the piston 30 has a taper angle (the diameter of which becomes smaller from the head 34 upward) Piston of the four-axis axial piston pump, characterized in that the head 34, the rod 35 and the sphere 31 is formed integrally. The method of claim 1, The taper angle ( ) Piston of a four-axis axial piston pump, which satisfies the formula, and at the same time is in the range of 1 ° ~ 10 °. The method according to claim 1 or 2, Said inclination angle (alpha) is the range of # 10 degrees-# 40 degrees piston of a four-axis axial piston pump.