A Plunger Spherical Surface Self-Centering Grinding Fixture for Swash Plate Axial Piston Pump

Abstract

The present invention provides an inclined - disk axial piston pump piston spherical surface self - centering grinding fixture, which is composed of a locator, a spring seat, a locating sleeve, a spring and a set screw. During use, first install the supporting part (composed of the locator, the spring, the spring seat and the set screw) onto the machine tool chuck. During machining, first place the piston to be machined into the locating sleeve. The spherical surface of the piston to be machined is in close contact with the conical surface of the locating sleeve. Then hold the locating sleeve firmly and insert the piston into the machine tool chuck. At this time, the end face of the locating sleeve is in close contact with the end face of the machine tool jaw. The spring inside the locator is compressed by a certain distance, and the piston to be machined is lifted by the spring force to ensure the close contact between the spherical surface of the piston to be machined and the conical surface of the locating sleeve. After installation, the distance from the center of the spherical surface of each piston to be machined to the end face of the chuck is only related to its own ball - head diameter and profile, which can preferably ensure the position of the center of the spherical surface of the piston to be machined in the machine tool coordinate system. This solution can also be used for the spherical surface grinding of similar pistons.

Description

Technical Field

[0001] The present invention belongs to the technical field of machining fixtures, and is mainly applied to the spherical surface machining of the plunger of an inclined-plate axial piston pump, and can also be applied to the spherical grinding of plungers with similar structures. Background Art

[0002] At present, in the construction machinery industry, the application of closed hydraulic systems is becoming more and more widespread. As an important part of the closed hydraulic system, piston pumps are widely used in various construction machinery. The plunger is one of the key components of the piston pump, and its quality has an important impact on the performance of the piston pump. In the design and use of the plunger, a very crucial point is the machining accuracy of the spherical surface, especially the requirements for the profile, size, and roughness of the spherical surface, which are the key elements to meet the plunger movement performance. With the improvement of the pump performance, the requirements are also gradually increasing. To meet the design requirements, grinding has become a common means for spherical surface machining.

[0003] When grinding the spherical surface of the plunger of a construction machinery piston pump, the commonly used clamping and positioning method is to clamp with a precision three-jaw chuck and position at the tail of the plunger. The disadvantages of this clamping method are as follows: 1. The axial positioning uses a manual pressing method, with poor positioning accuracy, resulting in poor consistency of the position of the ball center in the axial direction, uneven grinding amount of the spherical surface. To prevent machine collision, a large idle stroke usually needs to be left, ultimately resulting in a long processing time for the product; 2. The processing tolerance is poor. Once the length dimension from the ball center of the plunger to the positioning surface exceeds 0.05 mm, the spherical surface cannot be completely ground, resulting in the scrapping of the plunger; 3. It is difficult to improve. To improve the uniformity of the grinding amount, it must be achieved by improving the consistency of the dimension from the ball center of the plunger processed in the previous process to the positioning end face. Through verification of multiple batches of processing, the difficulty of this solution is too high, and it is very difficult for the previous process to meet the requirements. Summary of the Invention

[0004] The present invention mainly provides a self-centering grinding fixture for the spherical surface of the plunger of an inclined-plate axial piston pump for plungers with the above characteristics, which can complete the spherical surface grinding of the plunger while improving the processing efficiency and qualification rate and reducing the clamping difficulty.

[0005] The technical solution of the present invention is as follows:

[0006] The present invention provides a self-centering grinding fixture for the spherical surface of the plunger of an inclined-plate axial piston pump, including: a locator, a machine tool chuck, a machine tool jaw, a positioning sleeve, a spring seat, and a spring;

[0007] The locator is fixed on the machine tool chuck, and the locator is provided with a slot on the side facing the side of the plunger to be machined without a ball head;

[0008] The spring seat is movably assembled in the slot, and the spring seat is provided with a spring installation groove on the side facing the bottom of the slot;

[0009] The spring is assembled in the spring installation groove. One end of the spring is in contact with the locator, and the other end is connected to the spring seat.

[0010] The positioning sleeve is provided with an assembly groove for the ball head of the plunger to be machined to insert. The assembly groove has a conical surface that forms a fit with the ball head surface of the plunger to be machined.

[0011] Place the plunger to be machined assembled in the positioning sleeve horizontally on the machine tool jaws, and rely on external force to closely fit the end face of the positioning sleeve with the end face of the machine tool jaws, so as to realize the extrusion of the spring seat by the plunger to be machined, and then compress the spring. Rely on the rebound force of the spring to make the ball head surface of the plunger to be machined form a fit with the conical surface of the positioning sleeve, so as to realize the axial positioning of the plunger.

[0012] Preferably, a set screw hole communicating with the outer wall of the locator is provided on the grooved wall of the locator. An installation groove opposite to the set screw hole is provided on the spring seat. The set screw passes through the set screw hole and extends into the installation groove to limit the displacement of the spring seat in the axial direction of the plunger to be machined.

[0013] Preferably, the outer circle of the positioning sleeve is knurled, and the surface roughness of the conical surface of the assembly groove of the positioning sleeve is greater than Ra0.8.

[0014] Preferably, the clearance between the groove of the locator and the outer circle of the spring seat is between 0.005 - 0.015 mm.

[0015] The present invention has the following advantages:

[0016] (1) High positioning accuracy. Grinding the spherical surface with self-positioning of the spherical surface, the positioning accuracy is only related to the spherical size and profile, without involving other references, reducing the tolerance accumulation caused by the conversion of the positioning reference.

[0017] (2) Greatly reduces the clamping difficulty of a single plunger. The original scheme's clamping relied more on the operator's skills, and the axial positioning was very unstable. The clamping position difference of the same plunger by different operators could be more than 0.1 mm, which was intolerable for precision machining. After adopting the new scheme, even new employees can quickly and stably clamp.

[0018] (3) Greatly reduces the machining time of a single plunger. The original scheme had unstable positioning, and in order to prevent crashing the machine, a large idle stroke was usually left. After adopting the new scheme, the clamping accuracy is high, and the idle stroke distance is greatly reduced. The statistical single-piece grinding time is only half of the original. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the plunger in this embodiment during assembly on the fixture. Detailed Embodiment

[0020] Combined with the attached Figure 1 , the specific implementation manner of the present invention is as follows:

[0021] An embodiment of the present invention provides a self-centering grinding fixture for the spherical surface of a plunger of an inclined-plate axial piston pump, including a locator 1, a spring seat 2, a locating sleeve 4, a spring 3, and a set screw 5. Among them, the locator 1 is fixed on the machine tool chuck 8, and a slot 11 is provided on the side of the locator 1 facing the side of the plunger 6 to be processed without the ball head 61; the spring seat 3 is movably assembled in the slot 11, and a spring installation groove is provided on the side of the spring seat 2 facing the bottom of the slot; the spring 2 is assembled in the spring installation groove, one end of the spring 2 is in contact with the locator 1, and the other end is connected to the spring seat 2; the locating sleeve 4 is provided with an assembly groove for the ball head 31 of the plunger 6 to be processed to insert, and the assembly groove has a conical surface 41 that forms a fit with the spherical surface of the plunger 6 to be processed; the plunger 6 to be processed assembled in the locating sleeve 4 is horizontally placed on the machine tool jaw 7, and by relying on an external force, the end surface of the locating sleeve 6 is closely attached to the end surface of the machine tool jaw 7, so as to realize the extrusion of the spring seat 2 by the plunger 6 to be processed, and further compress the spring 3; relying on the rebound force of the spring to realize the fit between the spherical surface of the plunger to be processed and the conical surface of the locating sleeve, realize the axial positioning of the plunger, and then clamp the jaw and remove the locating sleeve, then the clamping of the plunger can be completed. When the self-centering grinding fixture for the spherical surface of the plunger of the inclined-plate axial piston pump is in use, the locator 1 needs to be installed on the machine tool chuck 8. During processing, first load the plunger 6 to be processed into the locating sleeve 4, the ball head 61 of the plunger 6 to be processed is closely attached to the assembly groove of the locating sleeve 4, then hold the locating sleeve 4 tightly, place the end of the plunger 6 to be processed without the ball head 61 flat on the machine tool jaw 7, and tightly push the end of the plunger 6 to be processed without the ball head 61, so that the end of the plunger 6 to be processed without the ball head 61 forms a tight fit with the spring seat 2. At this time, the end surface of the locating sleeve 4 is in close contact with the end surface of the machine tool jaw 7, and the spring 3 in the spring installation groove is compressed by a certain distance; after the external force disappears, the plunger 6 to be processed is lifted by the rebound force of the spring 3 to ensure the tight fit between the spherical surface of the plunger 6 to be processed and the conical surface 41 of the locating sleeve 4. Ensure that the distance from the ball center of each plunger to the end surface of the machine tool chuck after clamping is only related to its own ball head diameter and runout, and ensure the position of the ball center of the plunger in the machine tool coordinate system.

[0022] In this embodiment, the external shape structure of the locator of the self-centering grinding fixture for the spherical surface of the plunger of the inclined-plate axial piston pump is determined by the structure of the machine tool chuck. It is necessary to ensure that it fits well with the end surface of the machine tool chuck, so its mating shoulder surface and outer circle with the machine tool chuck need to be ground.

[0023] In addition, the spring seat of the spherical surface self-centering grinding fixture for the plunger of the swash plate axial piston pump needs to move flexibly within the locator 1 but cannot come out or skew. This is achieved by controlling the fit clearance, surface roughness, and cylindricity between the slot 11 of the locator 1 and the outer circle of the spring seat 3. Both the slot 11 of the locator 1 and the outer circle of the spring seat 3 need to be ground. The roughness should be above Ra0.8, and the clearance should be between 0.02 - 0.05 mm. Then, the displacement stroke of the spring seat 2 is controlled by the cooperation between the set screw 5 and the mounting groove 21 on the spring seat 2.

[0024] Assembly and use of the spherical surface self-centering grinding fixture for the plunger of the swash plate axial piston pump:

[0025] 1. Measure the dimensions of the machine tool chuck 8 and the machine tool jaws 7, as well as the length of the plunger 6 to be machined, and design and manufacture the corresponding locating sleeve 4, locator 1, and other accessories.

[0026] 2. Install the spring 3 and the spring seat 2 into the locator 1. Align the position of the mounting groove 21 of the spring seat 3 with the set screw hole on the locator 1, and install the set screw 5. The set screw 5 can limit the displacement of the spring seat 2.

[0027] 3. Install the assembled locator 1 onto the machine tool chuck 8. Place the plunger 6 to be machined into the locating sleeve 1, then hold the locating sleeve 1 firmly and insert the plunger 6 to be machined into the machine tool chuck 8, making the end face of the locating sleeve 4 abut against the end face of the machine tool jaw 7. The spring 3 assembled in the locator 1 is compressed by a certain distance, and the plunger 6 to be machined is lifted by the elastic force to ensure the fitting of the spherical head surface of the plunger 6 to be machined with the tapered surface 41 of the assembly groove in the locating sleeve 4.

[0028] 4. Operate the machine tool to clamp the machine tool jaw 7, and remove the locating sleeve 4 to machine the plunger 6 to be machined.

[0029] Through the above device, it is possible to achieve the self-centering of the plunger on the machine tool by using the spherical head surface of the plunger, ensuring that the distance from the spherical center of each plunger to the end face of the machine tool chuck after clamping is only related to its own spherical head diameter and runout, and guaranteeing the position of the spherical center of the plunger in the machine tool coordinate system.

[0030] This fixture uses the self-positioning of the spherical surface of the plunger to be ground. When using this fixture to clamp the workpiece, the distance between the spherical center of the plunger and the end face of the chuck is only related to the size and profile of the ball itself. By controlling the size of the ball head, the grinding allowance can be controlled. Under the condition of meeting the product requirements, the processing difficulty of the previous process is greatly reduced.

Claims

1. A grinding fixture for self - centering the spherical surface of a plunger of an inclined - plate axial piston pump, characterized in that, Including: A locator, a machine tool chuck, machine tool jaws, a positioning sleeve, a spring seat and a spring; The locator is fixed on the machine tool chuck, and a slot is provided on the side of the locator facing the side of the plunger to be machined without a ball head; The spring seat is movably assembled in the slot, and a spring mounting groove is provided on the side of the spring seat facing the bottom of the slot; The spring is assembled in the spring mounting groove, one end of the spring is in contact with the locator, and the other end is connected to the spring seat; The positioning sleeve is provided with an assembly groove for the ball head of the plunger to be machined to insert, and the assembly groove has a conical surface that forms a fit with the ball head surface of the plunger to be machined; Place the plunger to be machined assembled in the positioning sleeve horizontally on the machine tool jaws, and rely on an external force to closely fit the end face of the positioning sleeve with the end face of the machine tool jaws, so as to realize the extrusion of the spring seat by the plunger to be machined, and then compress the spring. Rely on the rebound force of the spring to realize the fit between the ball head surface of the plunger to be machined and the conical surface of the positioning sleeve, and realize the axial positioning of the plunger; Then clamp the jaws and remove the positioning sleeve to complete the clamping of the plunger.

2. The spherical surface self-centering grinding fixture for the plunger of the swash plate type axial piston pump according to claim 1, wherein, A set screw hole communicating with the outer wall of the locator is provided on the slot wall of the locator, and an installation groove opposite to the set screw hole is provided on the spring seat. The set screw passes through the set screw hole and extends into the installation groove to limit the displacement of the spring seat in the axial direction of the plunger to be machined.

3. The spherical surface self-centering grinding fixture for the plunger of the swash plate type axial piston pump according to claim 1, characterized in that, The outer circle of the positioning sleeve is knurled, and the surface roughness of the conical surface of the assembly groove of the positioning sleeve is greater than Ra0.

8.

4. The spherical surface self-centering grinding fixture for the plunger of the swash plate type axial piston pump according to claim 1, characterized in that, The clearance between the slot of the locator and the outer circle of the spring seat is between 0.005 - 0.015 mm.

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