JP2915559B2 - Variable displacement pump or motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a variable displacement pump used in general industrial machines and capable of changing a pump displacement by changing a tilt angle of a swash plate.

(Prior Art) Such a conventional variable displacement pump is disclosed in, for example,
US Patent No. 59-79078, in which a piston as a driving member for tilting a swash plate is arranged on the inner surface of the housing on the back side of the swash plate to change the tilt angle and change the pump capacity in two stages, United States Japanese Patent No. 3,070,031 discloses a device in which a piston, which is a driving member for tilting a swash plate, is arranged on the outer periphery of a cylinder barrel and presses the swash plate from the cylinder barrel side. 2-4625
In the structure shown in Fig. 1 described in No. 7, the ball is made of bearing steel (SUJ
Some were formed in 2).

(Problems to be Solved by the Invention) However, the inclination angle of the swash plate is changed by tilting around two balls or cylindrical bodies forming an axis perpendicular to the rotation axis of the shaft. Each of the variable displacement pumps has the advantages that the structure is extremely simple, the number of parts is small, it is easy to manufacture and inexpensive, and it requires only a small space. Since a concentrated load was repeatedly applied, the ball or the cylindrical body was worn out in about 3 to 5 hours, and could not be used for practical use, resulting in paper intervention. That is, the ball or cylindrical body of such a pump is made of bearing steel (SUJ2, etc.), heat-treated to increase the hardness, and the receiving surface of the ball or cylindrical body is different from another to prevent seizure of the ball surface. A member, for example, a copper alloy or a brass-based soft material was used. For this reason, damage to the ball or cylindrical body due to foreign matter in the oil and abnormal wear due to abnormal vibration of the swash plate have led to short-term pump breakdown. In addition, the processing of the receiving surface of the ball or the cylindrical body requires precision processing for the surface roughness and the roundness, resulting in an increase in cost.

On the other hand, in Japanese Unexamined Utility Model Publication No. Hei 2-137575, in order to prevent the piston forming the head of the piston and the piston shoe from being caulked, it is necessary to provide a technique disclosed in Japanese Utility Model Laid-Open No. 61-125683.
In Japanese Patent Application Laid-Open Publication No. H11-157, the use of ceramic for the material of each piston shoe is disclosed in order to prevent wear between the piston and the piston shoe. Japanese Utility Model Application Laid-Open No. 64-13280 discloses a technique in which a ceramic coating such as Al ₂ O ₃ is deposited on the surface of a piston cylindrical portion or a ball tip portion by physical vapor deposition to prevent baking wear. However, the surface pressure generated between the piston and the piston shoe or the cylinder barrel is small. For example, if the pump pressure is Pkgf / cm ² , the surface pressure is 0.5 to 1
× Pkgf / cm ² , and does not particularly require ceramic strength.

On the other hand, in the above-described variable displacement pump in which the inclination angle of the swash plate is changed by tilting around two balls or a cylindrical body forming an axis perpendicular to the rotation axis of the shaft described above. , The swash plate receives thrust of about half of the total number of pistons, and sometimes the spring force is added,
Since it is received by two balls or cylindrical bodies having a diameter approximately equal to the diameter of the shaft, the surface pressure is several times as large as the surface pressure between the piston and the shoe. In addition, since the conventional ceramics described above have lower tensile strength and compressive strength than the bearing steel SUJ2, etc., the ball is considered to be unsuitable for the above-mentioned severe operating conditions of the pump, which is susceptible to cracking, and is subjected to such surface pressure. No ceramic material was used for such parts.

Further, when ceramic is used on the concave side of the shoe or the like, it is difficult to secure accuracy and the strength is low. Further, there is a problem that the physical vapor deposition method is costly.

An object of the present invention is to provide a variable displacement pump in which the inclination angle of a swash plate is changed by tilting around two balls or a cylindrical body forming an axis perpendicular to the rotation axis of the shaft. Another object of the present invention is to provide a variable displacement pump that can be practically used without wear of a cylindrical body.

(Means for Solving the Problems) Therefore, the present invention provides a cylinder barrel rotatably supported in a housing together with a shaft, and a plurality of piston heads inserted into the cylinder barrel so as to be slidable in the axial direction. And a swash plate supported in a housing so as to be slidable and not to rotate relative to the rotation of the shaft, wherein the swash plate is pressed by a driving device provided in the housing to rotate the shaft. Form an axis perpendicular to the rotation axis 2
A variable displacement pump adapted to incline around two balls or cylinders to change the angle of inclination of the swash plate, wherein the two balls or cylinders are formed of a ceramic material; The material is composed of 92-99.5% by weight of aluminum oxide (Al ₂ O ₃ ) and SiO ₂ , CaO ₂ , MgO, and trace amounts of Na ₂ O, K ₂ O, and Fe as inevitable impurities. The above-described object of the present invention has been solved by providing a variable displacement pump or a motor characterized by including the following.

The reason that the weight percentage of aluminum oxide (Al ₂ O ₃ ) is set to 92% or more is that if it is less than 92%, the bonding force between the ceramic particles is weak, and the ceramic particles are slippery and easily worn. Also,
If the content is 99.5% or more, the purity is high and the cost is high.
In addition, the ceramic of this component has a compressive strength of 30,000 kgf / c
This is because a strength of about m ² can be obtained, and in particular, abrasion and peeling in a fine rotation state under a high surface pressure are prevented.

(Embodiment) Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3 showing a variable displacement pump. A variable displacement pump shown in an overall view in FIG. 1 includes a cylinder barrel 4 rotatably supported within a housing 1, 2 together with a shaft 3, and a plurality of pistons inserted into the cylinder barrel 4 so as to be slidable in the axial direction. The swash plate 8 is supported by the shoe holder 21 so that the swash plate 5 is supported by the shoe holder 21 and slidable relative to the rotation of the shaft 3.
The swash plate 8 is tiltable about two balls 9 (or may be cylindrical bodies) forming an axis 26 (FIG. 2A) adjacent to the shaft 3 and orthogonal to the rotation axis of the shaft. The inclination angle of the swash plate 8 is changed. The shoe holder 21 applies the pressing force of the spring 25 to the ring 27 and the pin 24.
Then, the shoe 6 is pressed in the axial direction via the barrel holder 22. In the pump of FIG. 1, an axis connecting the centers of the balls 9
26 (FIG. 2 (a)) is shifted upward from the rotation axis 28 of the shaft 3, so that the spring 25
The swash plate 8 receives a rotational force in the clockwise direction because the swash plate 8 is pressed with a non-biased force parallel to the axial direction of the shaft 3 by the pressing force pressing the 22 and the pressing force of the pressure oil introduced into the piston 5. The swash plate 8 is blocked by a spring 11 that pushes an arm 14 extending from one end 13 of the swash plate 8, is at the position shown in FIG. 1, the inclination angle α of the swash plate 8 is maximized, and the hydraulic pump is at the maximum displacement position.

When the pressing force of the pressure oil introduced into the piston 5 increases,
The clockwise rotation force increases, and the moment for tilting the swash plate 8 becomes larger than the pressing force of the spring 11, so that the swash plate 8 has an axis 26 perpendicular to the rotation axis 28 of the shaft 3.
Of the two balls 9 forming the center of the swash plate 8 and the spring 11
The swash plate 8 stops at the position where the pressing force is balanced, and the hydraulic pump is set to the small capacity position. That is, in the embodiment, the pressing force of the piston 5 due to the shift of the axis 26 connecting the center of the ball 9 from the rotation axis 28 of the shaft 3 is reduced by the swash plate 8.
Is formed.

In the present invention, the two balls 9 or the cylindrical body are formed of a ceramic material, and the ceramic material of the ball 9 or the cylindrical body is 92-99.5% by weight of aluminum oxide (Al ₂ O _3). ) And the remainder as inevitable impurities, silica (SiO ₂ ), calcium oxide (CaO ₂ ), magnesium oxide (MgO), and a trace amount of sodium oxide (Na
₂ O), potassium oxide (K ₂ O), and iron (Fe) (hereinafter referred to as the ball of the present invention).

The two balls 9 are inserted into complementary holes 18 and 30 formed in the back surface of the swash plate 8 and the inner surface 29 of the shaft-side housing. As shown in FIG. 3, the holes 18 (a) in close contact with the hemispherical surface of the ball 9
It may be a hole 19 (b) contacting a part of the ball 9 or a drill hole 20 (c) contacting the ball 9 with the bottom.

Table 1 shows a comparison between the ball 9 of the present invention (Al ₂ O ₃ : 99.5% by weight) and a conventional (SUJ2) ball.

(I): Tensile strength kgf / cm ² ; Compressive strength kgf / cm ² As described above, conventional ceramics have lower tensile strength and compressive strength than bearing steel SUJ2 etc. It was considered unsuitable for the harsh conditions of use of a pump that was intended to be received at a factory. In the present invention, in particular, 92-99.5% of aluminum oxide (Al) in a weight% at which a compressive strength of about 30,000 kgf / cm ² can be obtained.
_The use of ceramics containing ₂ O ₃ ) prevents wear and peeling in the state of fine rotation under high surface pressure, thus breaking the conventional stereotype and pump specifications; pump pressure: 250 kgf / cm ² pump Discharge rate: 54.61 / min Pump rotation speed: 2600 rpm Swash plate angular displacement / tilting time: 0-5 ゜ /0.05sec As a result of continuous operation, the first using conventional bearing steel SUJ2 balls
The pump shown in the figure has a continuous operation of 3 to 5 hours / 5000 to 800
The ball of the present invention, that is, 99.5% by weight of aluminum oxide (Al ₂ O ₃ ) and the remaining part were unavoidable impurities such as SiO ₂ and CaO
_{2. The} pump shown in FIG. 1 using a ceramic material ball 9 containing MgO, and trace amounts of Na ₂ O, K ₂ , and Fe has no abnormality even after continuous operation for 900 hours / 1,500,000 times. As a result, the ball had a life that was about 300 times or more longer than that of the ball, and it was confirmed that the ball could be put to practical use.

(Effects of the Invention) As described above, in the present invention, two balls or cylindrical bodies that are pressed by the drive device provided in the housing and form an axis perpendicular to the rotation axis of the shaft are tilted. A variable displacement pump adapted to change the angle of inclination of the swash plate, wherein said two balls or cylinders are formed of a ceramic material, said ceramic material being 92-9% by weight.
A 9.5% aluminum oxide (Al ₂ O ₃ ) and a variable displacement pump with the remainder being unavoidable impurities, so that the swash plate and ball or cylindrical body have much higher surface pressure than the piston and piston shoe. Even when used for a short period of time, there is no wear or peeling in the state of fine movement rotation, continuous operation 900 hours / 1,500,000 times switching, no abnormality at all, about 300 times longer life than the conventional variable displacement pump with balls Thus, the present invention provides a variable displacement pump that can be put to practical use sufficiently, has a very simple structure, has a small number of parts, is easy to manufacture and is inexpensive, and requires only a small space. Was.

In addition, since the ball side is made of ceramic, accuracy can be easily obtained. Further, since wear occurs on the swash plate side, the performance is stable without deterioration in accuracy even when used for a long time. Furthermore, the cost was lower than that of physical vapor deposition.

In the embodiment, the variable displacement pump has been described, but it is needless to say that the present invention can be applied to a variable speed motor.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a variable displacement pump according to an embodiment of the present invention;
FIG. 2 (a) is a front view of the pump of FIG. 1 and (b) is a side view thereof. 3 (a), 3 (b) and 3 (c) are partial sectional views showing different embodiments of the holes of the complementary shape on the back surface of the swash plate in FIG. 1.2 ... housing, 3 ... shaft, 4 ... cylinder barrel, 5 ... piston, 8 ... swash plate, 9 ... ball,
26… axis

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A 2-137575 (JP, U) JP-A 61-125683 (JP, U) JP-A 64-13280 (JP, U) 500459 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F04B 1/20

Claims (1)

(57) [Claims] A cylinder barrel rotatably supported in a housing together with a shaft, and a plurality of piston heads axially slidably inserted into the cylinder barrel so as to be slidable in contact with the head and to rotate the shaft. A swash plate supported in the housing such that the swash plate cannot rotate relative to the swash plate, and the swash plate is pressed by a driving device provided in the housing to form two balls forming an axis perpendicular to the rotation axis of the shaft or In a variable displacement pump adapted to change the inclination angle of a swash plate by tilting around a cylindrical body, the two balls or the cylindrical body are formed of a ceramic material, and the ceramic material has a weight % 92-99.5% aluminum oxide (Al ₂ O ₃ )
And the rest as unavoidable impurities, SiO ₂ , CaO ₂ , MgO,
And a trace amount of Na ₂ O, K ₂ O, and Fe.