An adaptive cylinder preload structure

Abstract

The present invention discloses an adaptive cylinder preload structure, comprising a drive shaft rotatably mounted in a pump housing, a rocker, a swash plate, and a cylinder. The bottom surface of the cylinder is fitted with an oil distribution plate, and a sliding shoe on the plunger in the cylinder is press-fitted onto the rocker via the swash plate. A casing arc surface is formed on the inner wall of the pump housing, with the center of the casing arc surface 5 mm eccentric to the axis of the drive shaft. An adaptive preload mechanism is provided in the cylinder, comprising a ball joint, a preload spring, and an ejector pin. The ball joint is slidably mounted on the drive shaft and positioned between the swash plate and the cylinder housing, with the ball joint arc surface articulated with a reamed hole in the swash plate. The preload spring is press-fitted into the central axis hole of the cylinder, and the ejector pin presses between the ball joint and the preload spring. The cylinder preload of the present invention can be automatically adjusted according to the operating conditions of the pump, reducing the preload under low-pressure conditions and increasing the preload under high-pressure conditions, thereby improving the service life and performance of the pump.

Description

Technical Field

[0001] The present invention relates to the technical field of swash plate type variable displacement plunger pumps, in particular to a cylinder pre-tightening mechanism of the variable displacement plunger pump, specifically an adaptive cylinder pre-tightening force structure. Background Art

[0002] Cylinder preload is a crucial parameter in plunger pump design. Inside the plunger pump, the cylinder body is held in contact with the oil distribution plate by a spring-loaded preload. During operation, the cylinder body is subjected to high pressure and relative sliding speeds, and the preload must be neither too small nor too large. If the preload is too small, the cylinder body will be pushed apart under high-pressure conditions, increasing oil leakage. If the preload is too large, the contact surface will wear more severely under low-pressure conditions.

[0003] Many variable displacement pumps currently utilize control methods such as constant power control and pressure cutoff control. Their primary operating principle is that when output pressure increases, the control valve and variable piston reduce the swash plate angle, reducing or even eliminating output flow. During this process, the cylinder's preload remains constant, and the magnitude of this preload depends entirely on the stiffness of the preload spring and component dimensions. However, in this configuration, the preload remains constant under high and low pressure conditions, which can easily lead to wear between the distribution plate and the cylinder. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an adaptive cylinder preload structure in response to the current status of the above-mentioned existing technology. This preload structure can cooperate with constant power control or pressure cut-off control to achieve: under low-pressure conditions, the swash plate angle is large and the preload is reduced; under high-pressure conditions, the swash plate angle is small and the preload is increased.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] An adaptive cylinder preload structure comprises a transmission shaft rotatably mounted in a pump housing, and a rocker, a swash plate, and a cylinder body sequentially mounted on the transmission shaft. The bottom surface of the cylinder body is affixed to an oil distribution plate. The sliding shoe on the plunger in the cylinder body is press-fitted onto the rocker via the swash plate. The inner wall of the pump housing is formed with a housing arc surface for fitting with the arc surface of the rocker. The center of the housing arc surface has an eccentricity of 5 mm relative to the axis of the transmission shaft. The cylinder body is provided with an adaptive preload mechanism that is in contact with the swash plate and is used to force the cylinder body to elastically press against the oil distribution plate. The adaptive preload mechanism is composed of a ball joint. , a preload spring and an ejector pin; the ball joint is slidably mounted on the drive shaft and is located between the swash plate and the cylinder body, and the arc surface of the ball joint is hingedly matched with the hinge hole of the swash plate; the preload spring is pressed into the central axis hole of the cylinder body, and the ejector pin is pressed between the ball joint and the preload spring; when the pump is in a low-pressure working condition and the inclination angle of the swash plate increases, the preload spring pushes the ball joint forward to increase the gap between the ball joint and the cylinder body and reduce the preload pressure; when the pump is in a high-pressure working condition and the inclination angle of the swash plate decreases, the swing pushes the ball joint through the swash plate to compress the preload spring, so that the gap between the ball joint and the cylinder body is reduced and the preload pressure is increased.

[0007] To optimize the above technical solutions, specific measures taken also include:

[0008] The above-mentioned pump housing consists of a front pump housing and a rear cover that covers the front pump housing; a first bearing for cooperating with the front rotation support of the drive shaft is positioned and installed in the front pump housing, and a second bearing for cooperating with the rear end rotation support of the drive shaft is positioned and installed on the rear cover; the oil distribution plate is fixed to the rear cover in a rotation-proof manner, and the rocking plate, swash plate and cylinder body are all located in the front pump housing of the pump housing.

[0009] A variable piston cavity is formed in the above-mentioned front pump housing, in which a variable piston is slidably installed to change the inclination angle of the swash plate by driving the swaying motion; a piston ball head is formed on the top of the variable piston, and a ball socket is formed in the swinging motion to be hinged to the piston ball head.

[0010] The above-mentioned casing arc surface is formed on the inner wall of the front pump shell, and a wear-resistant bearing bush is clamped on the casing arc surface.

[0011] The center of the arc surface of the shell is offset by 5 mm toward the direction of the variable piston cavity.

[0012] The central axis hole of the above-mentioned cylinder body is composed of a front end hole with a relatively smaller front end diameter and a rear end hole with a relatively larger rear end diameter; the preload spring is arranged in the rear end hole of the cylinder body, and a hole retaining ring is installed in the rear end hole. The tail end of the preload spring is pressed against the hole retaining ring, and the front end of the preload spring is connected to the tail end of the ejector pin, and the front end of the ejector pin slides through the front end hole of the cylinder body and is connected to the bottom surface of the ball joint.

[0013] A limit screw for limiting the minimum inclination angle of the swash plate is spirally mounted on the front pump housing, and the limit screw cooperates with the swing limit top joint; the maximum inclination angle of the swash plate is 16 degrees, and the minimum inclination angle of the swash plate is 0 degrees.

[0014] The front end hole of the cylinder body is connected to the transmission shaft. The front end hole of the cylinder body is processed with multiple ejector slots in a medium arc, and the ejector pins are slidably arranged in the ejector slots.

[0015] Compared to the prior art, the present invention provides a casing arc surface in the pump housing, the center of which is 5 mm eccentric to the axis of the drive shaft. An adaptive preload mechanism consisting of a ball joint, a preload spring, and a thimble is provided in the cylinder body. The ball joint is mounted on the drive shaft. During swinging and rotation, the center of the ball joint remains unchanged relative to the swinging motion. However, due to the 5 mm eccentricity of the casing arc surface, the center of the ball joint is offset relative to the cylinder body, causing the gap between the ball joint and the cylinder body to change. This increases the gap between the ball joint and the cylinder body under low-pressure conditions, reducing the preload pressure of the cylinder body on the oil distribution plate and reducing wear between the oil distribution plate and the cylinder body. Under high-pressure conditions, the gap between the ball joint and the cylinder body decreases, further compressing the preload spring, increasing the preload pressure between the cylinder body and the oil distribution plate, thereby preventing leakage between the contact surface of the oil distribution plate and the cylinder body. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the present invention under low-pressure working conditions, large displacement, and a swing angle of 16 degrees;

[0017] Figure 2 This is a schematic diagram of the state of the present invention under high pressure working conditions, small displacement, and a swing angle of 0 degrees;

[0018] Figure 3 It is a cross-sectional structural diagram of the swing of the present invention;

[0019] Figure 4 is a cross-sectional structural diagram of the swash plate of the present invention;

[0020] Figure 5 It is a sectional structural diagram of the cylinder body of the present invention. DETAILED DESCRIPTION

[0021] The embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

[0022] Figures 1 to 5 It is a structural schematic diagram of the present invention.

[0023] The figures are marked as follows: hole retaining ring D, axis L, limit screw M, eccentricity S, bearing shell W, clearance X, first bearing Z1, second bearing Z2, pump housing 1, front pump housing 11, housing arc surface 11a, rear cover 12, transmission shaft 2, swing 3, ball socket 3a, swash plate 4, reaming hole 4a, sliding shoe hole 4b, cylinder body 5, front end hole 5a, rear end hole 5b, ejector slot 5c, oil distribution plate 6, ball joint 71, preload spring 72, ejector 73, variable piston 8, piston ball head 81, plunger 9, sliding shoe 91.

[0024] In existing technology, the cylinder of a variable displacement plunger pump utilizes a spring-applied preload to tightly fit the oil distribution plate, ensuring unobstructed oil flow and preventing leakage at the contact surface. In actual operation, the cylinder rotates at high speed relative to the distribution plate. Traditional plunger pumps maintain a constant preload regardless of whether the pump is operating at low or high pressure. This can lead to accelerated wear of the cylinder, shortening the pump's service life.

[0025] The present invention discloses an adaptive cylinder preload structure used in a variable displacement piston pump, the cylinder preload structure comprising a transmission shaft 2 rotatably mounted in a pump housing 1, and a rocker 3, a swash plate 4 and a cylinder 5 sequentially mounted on the transmission shaft 2. Figure 5 As shown, the cylinder body 5 is axially and transparently machined with a central axis hole and multiple plunger holes arranged around the central axis hole. The central axis hole consists of a front hole 5a with a relatively small diameter at the front end and a rear hole 5b with a relatively large diameter at the rear end. Spline teeth are machined into the front hole 5a of the cylinder body 5, and a spline groove is machined on the transmission shaft 2 at the front hole 5a. The transmission shaft 2 can drive the cylinder body 5 to rotate together through the engagement of the spline groove and the spline teeth. A plunger 9 is slidably mounted in the plunger hole of the cylinder body 5, and a sliding shoe 91 is rotatably hinged on the ball head of the plunger 9. The bottom surface of the cylinder body 5 is liquid-tightly attached to an oil distribution plate 6, which is formed with an oil inlet groove and an oil outlet groove for connecting to the plunger hole. During the rotation of the cylinder body 5, the plunger 9 can complete the action of sucking and discharging oil through the oil inlet groove and the oil outlet groove. It is best to maintain a certain pre-tightening pressure between the cylinder body 5 and the oil distribution plate 6. This pre-tightening pressure can not only make the cylinder body 5 rotate freely relative to the oil distribution plate 6, but also ensure that the contact surface between the two is liquid-tight and will not leak oil. Figure 1 and Figure 2As can be seen, the shoe 91 is press-fitted onto the bottom surface of the rocker 3 via the swash plate 4. The swash plate 4 is provided with a shoe hole 4b, through which the shoe 91 slides and abuts against the bottom surface of the rocker 3. The shoe 91 is formed with an annular boss with a diameter larger than that of the shoe hole 4b to prevent it from falling out. The inner wall of the pump housing 1 is formed with a casing curved surface 11a, which mates with the curved surface of the rocker 3. This curved surface 11a supports and guides the rocker 3, allowing it to swing about the center of the casing curved surface 11a. A key feature of the present invention is that the center of the casing curved surface 11a is eccentric with respect to the axis L of the drive shaft 2, with an eccentricity S of 5 mm. The cylinder body 5 is equipped with an adaptive preload mechanism that, through abutment with the swash plate 4, forces the cylinder body 5 toward the oil distribution plate 6. The adaptive preload mechanism of the present invention consists of a ball joint 71, a preload spring 72, and a pin 73. The ball joint 71 is slidably mounted on the transmission shaft 2 and is located between the swash plate 4 and the cylinder body 5. The preload spring 72 is press-fitted into the rear end hole 5b of the cylinder body 5. The pin 73 is pressed between the ball joint 71 and the preload spring 72. Figure 2 As can be seen, a retaining ring D is installed in the rear end hole 5b. The tail end of the preload spring 72 presses against the retaining ring D. The front end of the preload spring 72 abuts against the tail end of the ejector pin 73. The front end of the ejector pin 73 slides through the front end hole 5a of the cylinder body 5 and abuts against the bottom surface of the ball joint 71. Because the ball joint 71 abuts against the swash plate 4, the spring force of the preload spring 72 allows the cylinder body 5 to maintain a constant preload pressure on the oil distribution plate 6. During the swinging motion of the swing 3, the center of the ball joint 71 remains unchanged relative to the swing 3. However, due to the 5mm eccentricity of the housing curved surface 11a relative to the axis L of the drive shaft 2, the center of the ball joint 71 is offset relative to the cylinder body 5. Figure 1 The figure is a schematic diagram of the state under low-pressure working conditions, large displacement, and a swing angle of 16 degrees. As shown in the figure, when the pump is in low-pressure working conditions and the inclination angle of the swash plate 4 increases, the center of the ball joint 71 will be offset forward relative to the cylinder body 5, so that the preload spring 72 can push the ball joint 71 forward to increase the gap X between the ball joint 71 and the cylinder body 5 (when the swing angle is 16 degrees, the gap X is a maximum of 2 mm). As the distance increases, the spring force of the preload spring 72 decreases, thereby reducing the preload pressure of the cylinder body 5 on the oil distribution plate 6 and reducing the wear between the cylinder body 5 and the oil distribution plate 6. Figure 2 As shown, when the pump is operating under high-pressure conditions and the inclination angle of the swash plate 4 decreases, the center of the ball joint 71 will be offset backward relative to the cylinder body 5. At this time, the swing 3 pushes the ball joint 71 through the swash plate 4, compressing the preload spring 72, thereby reducing the gap X between the ball joint 71 and the cylinder body 5 (when the swing angle is 0 degrees, the gap X is a minimum of 0.6 mm). As the distance decreases, the spring force of the preload spring 72 increases, thereby increasing the preload pressure of the cylinder body 5 on the oil distribution plate 6, ensuring that there is no oil leakage between the contact surfaces of the cylinder body 5 and the oil distribution plate 6 under high-pressure conditions.

[0026] In the embodiment, the pump housing 1 of the present invention is composed of a front pump housing 11 and a rear cover 12 covering the front pump housing 11. A first bearing Z1 for cooperating with the front rotation support of the drive shaft 2 is positioned and installed in the front pump housing 11, and a second bearing Z2 for cooperating with the rear end rotation support of the drive shaft 2 is positioned and installed on the rear cover 12. The oil distribution plate 6 is fixed to the rear cover 12 in a rotation-proof manner, and the rocker 3, the swash plate 4 and the cylinder body 5 are all located in the front pump housing 11 of the pump housing 1. In order to allow the drive shaft 2 to move axially, a positioning boss is formed on the front part of the drive shaft 2 for positioning and cooperating with the first bearing Z1, and a shaft retaining ring for positioning and cooperating with the second bearing Z2 is installed on the rear part of the drive shaft 2.

[0027] In the embodiment of the present invention, a variable displacement piston chamber is formed in the front pump housing 11, in which a variable displacement piston 8 is slidably mounted. The swing angle of the rocker 3 is driven by the variable displacement piston 8. A piston ball head 81 is formed at the top of the variable displacement piston 8, and the rocker 3 is formed with a ball socket 3a hingedly connected to the piston ball head 81.

[0028] In the embodiment, the casing arc surface 11a of the present invention is formed on the inner wall of the front pump casing 11. In order to improve the wear resistance of the casing arc surface 11a and ensure the service life of the front pump casing 11, a wear-resistant bearing W is clamped on the casing arc surface 11a.

[0029] In the embodiment, the center of the arc surface 11a of the shell is offset by 5 mm toward the direction of the variable piston cavity.

[0030] The tilt angles of the rocker 3 and swash plate 4 are consistent. In this embodiment, the maximum tilt angle of the rocker 3 is 16 degrees, and the minimum tilt angle is 0 degrees. A limit screw M is screwed onto the front pump housing 11 to define the minimum tilt angle of the rocker 3. The limit screw M engages the rocker 3's limit contact when the rocker 3's tilt angle is 0 degrees.

[0031] In the embodiment, in order to enable the ejector pin 73 to slide through the front end hole 5a of the cylinder body 5, the front end hole 5a of the cylinder body 5 is processed with multiple ejector pin grooves 5c with a medium arc, and the ejector pin 73 is slidably arranged in the ejector pin grooves 5c.

[0032] The best embodiment of the present invention has been described, and various changes or modifications can be made by those skilled in the art without departing from the scope of the present invention.

Claims

1. An adaptive cylinder preload structure, comprising a drive shaft (2) rotatably mounted in a pump housing (1), and a rocker (3), a swash plate (4), and a cylinder (5) sequentially mounted on the drive shaft (2), wherein an oil distribution plate (6) is attached to the bottom surface of the cylinder (5), and a sliding shoe (91) on a plunger (9) in the cylinder (5) is press-fitted onto the rocker (3) via the swash plate (4), wherein: The inner wall of the pump housing (1) is formed with a housing arc surface (11a) for fitting with the arc surface of the swing (3), and the center of the housing arc surface (11a) has an eccentricity (S) of 5 mm relative to the axis (L) of the transmission shaft (2); the cylinder body (5) is provided with an adaptive pre-tightening mechanism for forcing the cylinder body (5) to be elastically pressed against the oil distribution plate (6) by being in contact with the inclined plate (4), and the adaptive pre-tightening mechanism is composed of a ball joint (71), a pre-tightening spring (72) and a push pin (73); the ball joint (71) is slidably mounted on the transmission shaft (2) and is located between the inclined plate (4) and the cylinder body (5), and the spherical arc surface of the ball joint (71) is in contact with the inclined plate (4). The reaming hole (4a) of the disc (4) is hinged and matched; the preload spring (72) is pressed into the central axis hole of the cylinder body (5), and the ejector pin (73) is pressed between the ball joint (71) and the preload spring (72); when the pump is in a low-pressure working condition and the inclination angle of the swash plate (4) increases, the preload spring (72) pushes the ball joint (71) to move forward, thereby increasing the gap (X) between the ball joint (71) and the cylinder body (5) and reducing the preload pressure; when the pump is in a high-pressure working condition and the inclination angle of the swash plate (4) decreases, the swing (3) pushes the ball joint (71) through the swash plate (4) to compress the preload spring (72), thereby reducing the gap (X) between the ball joint (71) and the cylinder body (5) and increasing the preload pressure; The central axis hole of the cylinder body (5) is composed of a front end hole (5a) with a relatively small front end diameter and a rear end hole (5b) with a relatively large rear end diameter; the preload spring (72) is arranged in the rear end hole (5b) of the cylinder body (5), and a hole retaining ring (D) is installed in the rear end hole (5b), and the tail end of the preload spring (72) is pressed against the hole retaining ring (D), and the front end of the preload spring (72) is connected to the tail end of the ejector pin (73), and the front end of the ejector pin (73) slides through the front end hole (5a) of the cylinder body (5) and is connected to the bottom surface of the ball joint (71).

2. The adaptive cylinder preload structure according to claim 1, characterized in that: The pump housing (1) is composed of a front pump housing (11) and a rear cover (12) covering the front pump housing (11); a first bearing (Z1) for cooperating with the front rotation support of the transmission shaft (2) is positioned and installed in the front pump housing (11), and a second bearing (Z2) for cooperating with the rear end rotation support of the transmission shaft (2) is positioned and installed on the rear cover (12); the oil distribution plate (6) is fixed to the rear cover (12) in a rotation-proof manner, and the rocker (3), swash plate (4) and cylinder body (5) are all located in the front pump housing (11) of the pump housing (1).

3. The adaptive cylinder preload structure according to claim 2, characterized in that: A variable piston cavity is formed in the front pump housing (11), in which a variable piston (8) is slidably installed, which drives the swing (3) to swing and change the inclination angle of the swash plate (4); a piston ball head (81) is formed on the top end of the variable piston (8), and the swing (3) is formed with a ball socket (3a) hinged to the piston ball head (81).

4. The adaptive cylinder preload structure according to claim 3, characterized in that: The center of the shell arc surface (11a) is offset by 5 mm in the direction of the variable-shaped piston cavity.

5. The adaptive cylinder preload structure according to claim 4, characterized in that: A limit screw (M) for limiting the minimum inclination angle of the swash plate (4) is spirally mounted on the front pump housing (11), and the limit screw (M) cooperates with the swing (3) limit top connection; the maximum inclination angle of the swash plate (4) is 16 degrees, and the minimum inclination angle of the swash plate (4) is 0 degree.

6. The adaptive cylinder preload structure according to claim 5, characterized in that: The front end hole (5a) of the cylinder body (5) is connected to the transmission shaft (2) in a transmission manner. The front end hole (5a) of the cylinder body (5) is processed with a plurality of ejector slots (5c) in a medium arc, and the ejector pin (73) is slidably arranged in the ejector slots (5c).

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