Static pressure knife rest of gear shaping machine

Abstract

The static pressure knife rest of the gear shaping machine comprises an eccentric disc, a swing rod is hinged to the eccentric disc, and the other end of the swing rod is hinged to the top end of a knife shaft through a ball pull rod and a ball head. The cutter shaft penetrates through the cutter rest body; a cutter is mounted at the lower end of the cutter shaft; a worm gear and a worm are installed at the upper end of the tool rest body, and the worm gear is pressed through a large flange plate to be axially fixed. The cutter shaft penetrates through the worm gear and an inner hole of the cutter shaft sleeve at the same time. Due to the fact that the outer circle profile face of the four-tooth tooth-shaped tooth crest of the formed hydrostatic guide rail is wide, enough space can be provided for designing a radial four-cavity centripetal hydrostatic bearing, and therefore the upper end of a cutter shaft not only has centripetal clamping static pressure formed by static pressure cavities of involute tooth faces of the hydrostatic spline guide rail but also has static pressure clamping force of the tooth crest. The rigidity of the upper end of the cutter shaft is enhanced through superposition of the two clamping forces.

Description

Technical Field

[0001] The utility model relates to the technical field of gear shaping machine tool holders, in particular to a gear shaping machine static pressure tool holder. Background Art

[0002] Gear shaping machines are commonly used for machining cylindrical gears, typically deep-hole internal gears. Cutting is achieved through the rotation of the worktable and cutter shaft according to the hobbing ratio, while the cutter shaft moves up and down. The toolholder encases the cutter shaft, primarily supporting its rotation and up and down motion. To achieve the high precision and efficiency required for gear shaping, the cutter shaft's movement within the toolholder must exhibit both high rigidity and low wear. Currently, hydrostatic toolholder technology is the primary approach used to address this problem, both domestically and internationally.

[0003] Existing toolholders using hydrostatic technology typically feature a four-cavity centripetal hydrostatic bearing at the bottom of the toolholder. These four oil chambers are evenly distributed around the cutter shaft sleeve. Hydraulic oil at a constant pressure is fed to these four chambers via a throttle, creating a hydraulic centripetal thrust that imparts high radial rigidity to the cutter shaft. The top of the toolholder is designed as a hydrostatic guideway with a structure similar to a hydrostatic spline. Four involute tooth profiles are evenly distributed around the guideway, flanked by hydrostatic oil chambers. Hydraulic oil at a constant pressure is also fed to each chamber via a throttle. This generated hydrostatic thrust is directed inward along the normal direction of the tooth surface. The combined force of these hydrostatic thrusts on both sides of the tooth profile is a centripetal thrust and a clamping force that inhibits rotational motion. The static pressure resultant is characterized by the following: the static pressure resultant on both sides of the four involute tooth profiles can be decomposed into two components: one is the centripetal force directed toward the center of the cutter shaft. The centripetal force generated by the four tooth profiles is evenly distributed around the cutter shaft and all points toward the axis. These four centripetal thrusts provide radial rigidity to maintain the upper end of the cutter shaft at the center of the circle. The other component can be understood as a pair of thrusts in opposite directions at the pitch circle of the tooth profile center plane, along the tangent direction of the pitch circle. The two thrusts are of equal magnitude and serve to clamp the tooth profile and prevent the cutter shaft from rotating. A hydrostatic bearing is installed at the lower end of the cutter shaft, and a hydrostatic guide rail is installed at the upper end. A worm gear is installed on the outside of the hydrostatic guide rail, allowing the cutter shaft to move up and down while rotating with the worm gear.

[0004] Since the gear shaping machine's primary motion is to convert the main motor's rotational motion into the up-and-down motion of the tool holder and cutter shaft via a slider-crank mechanism, the longer the cutter shaft's up-and-down stroke, the greater the eccentricity of the swing arm's mounting position on the eccentric disk. This increases the maximum angle formed by the swing arm with the cutter shaft during swing, subjecting the upper end of the cutter shaft to a greater radial force component. To ensure the cutter shaft remains vertical despite radial thrust, the hydrostatic rigidity of the hydrostatic guideway at the upper end of the cutter shaft must be increased. Consequently, in practice, maintaining cutter shaft verticality is difficult, particularly when machining gears with very large tooth widths, resulting in poor tooth profile accuracy. Utility Model Content

[0005] The purpose of the present utility model is to overcome the above-mentioned shortcomings and provide a hydrostatic tool holder for a gear shaping machine. The outer cylindrical profile of the four-tooth tooth top of the hydrostatic guide rail is wide, so that there is enough space to design a radial four-cavity centripetal hydrostatic bearing. In this way, the upper end of the cutter shaft is not only subject to the centripetal clamping static pressure formed by the hydrostatic cavity of the involute tooth surface of the hydrostatic spline guide rail, but also to the hydrostatic clamping force of the tooth top. The superposition of the two clamping forces enhances the rigidity of the upper end of the cutter shaft.

[0006] In order to achieve the above technical features, the purpose of the utility model is achieved as follows: a static pressure tool holder for a gear shaping machine includes an eccentric disk, a rocker arm is hinged on the eccentric disk, and the other end of the rocker arm is hingedly connected to the top end of the tool shaft through a ball head via a ball pull rod; the tool shaft passes through the tool holder body, and a tool is installed at the lower end of the tool shaft; a worm gear and a worm are installed at the upper end of the tool holder body, and the worm gear is pressed by a large flange to fix it axially; a tool shaft sleeve and a sealing ring are installed at the lower end of the tool holder body, and the tool shaft passes through the inner holes of the worm gear and the tool shaft sleeve at the same time.

[0007] The eccentric disk is connected to a driving motor and is driven to rotate by the motor.

[0008] The top end of the rocker arm is hinged on the outer wall of the eccentric disk through rotation.

[0009] The bottom end of the swing rod is connected to the ball pull rod through a thread, and the ball head of the ball pull rod is hingedly connected to the top end of the knife shaft.

[0010] There are four static pressure oil chambers evenly distributed in the inner hole of the cutter shaft sleeve, and the pressure oil is passed through to form a centripetal static pressure bearing. The cutter shaft sleeve wraps the cutter shaft in an annular shape, and the gap between the two is 0.02~0.04mm; the lower end of the cutter shaft is sealed by a sealing ring.

[0011] The inner hole of the worm gear cooperates with the cutter shaft to form a toothed guide rail structure with an involute spline. A tooth side static pressure oil chamber is distributed on the tooth side of each toothed guide rail structure, and a tooth top static pressure oil chamber is distributed on the tooth top of each toothed guide rail structure, and a static pressure guide rail is formed by pressure oil.

[0012] The toothed guide rail structure adopts a positive displacement involute cylindrical gear tooth profile with twelve teeth, two adjacent teeth are merged, and redundant teeth are removed at the tooth groove, thereby forming four groups of toothed guide rail structures.

[0013] The outer arc surface of the hydrostatic guide rail is used to form a 4-cavity centripetal hydrostatic bearing to improve the overall hydrostatic stiffness of the cutter shaft.

[0014] The tooth top profile of the toothed guide rail structure is a standard outer arc surface, and then a cylindrical grinder is used for high-precision processing to ensure that the circumference of the outer cylindrical surface of the guide rail is within 0.005mm and the oil film gap is controlled at 0.02~0.04mm.

[0015] The utility model has the following beneficial effects:

[0016] 1. The hydrostatic guide rail of the present invention has a four-tooth involute tooth profile, which is the tooth profile of a twelve-tooth positive displacement involute cylindrical gear, formed by merging two adjacent teeth and removing redundant teeth at the tooth groove. This characteristic is that the outer cylindrical profile of the tooth tops of the four-tooth tooth profile is relatively wide, allowing sufficient space for the design of a radial four-cavity centripetal hydrostatic bearing. This way, the upper end of the cutter shaft not only receives the centripetal clamping static pressure formed by the hydrostatic cavity of the involute tooth flank of the hydrostatic spline guide rail, but also receives the hydrostatic clamping force of the tooth tops. The combined clamping force enhances the rigidity of the upper end of the cutter shaft.

[0017] 2. A tool shaft sleeve is fixed to the lower end of the tool shaft hole of the tool holder body of the utility model. Four static pressure oil chambers are evenly distributed on the inner side of the tool shaft sleeve. The tool shaft sleeve wraps the tool shaft in a ring shape, and the gap between the two is only 0.02~0.04mm. A worm gear is installed on the upper end of the tool holder body. The center of the worm gear is coaxial with the tool shaft, and the upper and lower end faces are fixed by the tool holder body and the large flange. The tool shaft passes through the center of the worm gear to form a four-tooth static pressure guide structure.

[0018] 3. The tooth profile of the traditional hydrostatic spline guide is an eight-tooth positive displacement involute cylindrical gear tooth profile, and the redundant teeth in the tooth groove are removed. The tooth profile of the present invention is a twelve-tooth positive displacement involute cylindrical gear tooth profile, which is formed by merging two adjacent teeth, and the redundant teeth in the tooth groove are removed. Its advantage is that the tooth top profile of the merged teeth is wider, and there is enough space to design a four-cavity centripetal hydrostatic bearing. The bottom profile of the tooth groove of the traditional hydrostatic spline guide is also wider, but since it is impossible to fine-tune the grinding control accuracy and clearance, it is impossible to design a hydrostatic bearing. The tooth top profile of the guide rail of the present invention is a standard outer arc surface, which can be processed with high precision using an external cylindrical grinder to ensure that the circumference of the outer cylindrical surface of the guide rail is within 0.005mm, and the oil film gap is controlled at 0.02~0.04mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Figure 1 (a) (b) (c) are the overall structural diagrams of the utility model.

[0021] Figure 2 for Figure 1 The AA cross-section diagram reflects the tooth profile shape of the hydrostatic guide rail in the traditional hydrostatic tool holder.

[0022] Figure 3 (a) (b) are the comparison and differences between the cross-section of a traditional hydrostatic spline guide and the cross-section of the hydrostatic spline guide of the present invention.

[0023] Figure 4 for Figure 1 The AA cross-sectional view reflects the tooth profile shape of the hydrostatic guide rail in the hydrostatic tool holder of the present invention.

[0024] Figure: eccentric disc 1, swing bar 2, ball pull rod 3, cutter shaft 4, large flange plate 5, worm 6, worm 7, tool holder 8, cutter shaft sleeve 9, sealing ring 10, tool 11, first oil return cavity 12, first static pressure oil cavity 13, first tooth removal 14, tooth groove 15, second tooth removal 16, tooth top static pressure oil cavity 17, tooth top oil return cavity 18, tooth side static pressure oil cavity 19, tooth heel oil return cavity 20, tooth profile guide rail structure 21. DETAILED DESCRIPTION

[0025] The embodiments of the utility model will be further described below with reference to the drawings.

[0026] Example 1:

[0027] Referring to Figure 1 A gear shaping machine static pressure tool holder, including eccentric disc 1, swing bar 2 is hinged on eccentric disc 1, the other end of swing bar 2 is connected through ball pull rod 3 with the top end of cutter shaft 4 through ball head hinged connection;Cutter shaft 4 passes through tool holder 8, and cutter shaft 4 lower end is installed with tool 11;Tool holder 8 upper end is installed with worm 6 and worm 7, and is compressed tightly worm 6 through large flange plate 5, makes its axial fixed;Tool holder 8 lower end is installed with cutter shaft sleeve 9 and sealing ring 10, and cutter shaft 4 passes through the inner hole of worm 6 and cutter shaft sleeve 9 simultaneously.

[0028] Further, the eccentric disc 1 is connected to drive motor, and rotates by motor drive.

[0029] Further, the top end of the swing bar 2 is hinged on the outer wall of the eccentric disc 1 by rotating.

[0030] Further, the bottom end of the swing bar 2 is connected to the ball pull rod 3 by screwing, and the ball head of the ball pull rod 3 is hinged to the top end of the cutter shaft 4.

[0031] Further, the inner hole of the cutter shaft sleeve 9 is uniformly distributed with four static pressure oil cavities, and the through pressure oil forms a centripetal static pressure bearing, the cutter shaft sleeve 9 annularly wraps the cutter shaft 4, and the gap between the cutter shaft sleeve 9 and the cutter shaft 4 is 0.02-0.04mm; the lower end of the cutter shaft 4 is sealed by the sealing ring 10.

[0032] Further, the inner hole of the worm 6 cooperates with the cutter shaft 4 and forms the tooth profile guide rail structure 21 of involute spline, and the tooth side of each tooth profile guide rail structure 21 is distributed with the tooth side static pressure oil cavity 19, and the tooth top of each tooth profile guide rail structure 21 is distributed with the tooth top static pressure oil cavity 17, and forms a static pressure guide rail by pressure oil.

[0033] Further, the tooth profile guide rail structure 21 is a positive displacement involute cylindrical gear tooth profile with twelve teeth, and the adjacent two teeth are combined, and the excess teeth are removed at the tooth groove, thereby forming four groups of tooth profile guide rail structures 21.

[0034] Furthermore, the outer arc surface of the hydrostatic guide rail is used to form a 4-cavity centripetal hydrostatic bearing to improve the overall hydrostatic stiffness of the cutter shaft.

[0035] Furthermore, the tooth top profile of the toothed guide rail structure 21 is a standard outer arc surface, and is then processed with high precision using an outer cylindrical grinder to ensure that the circumference of the outer cylindrical surface of the guide rail is within 0.005 mm and the oil film gap is controlled within 0.02~0.04 mm.

[0036] like Figure 2 As shown, Figure 1 The AA cross-sectional view in the middle reflects the tooth profile shape of the hydrostatic guide rail in the traditional hydrostatic tool holder. Its first hydrostatic oil chamber 13 is only distributed on both sides of the tooth profile, and the first return oil chamber 12 is distributed at the tooth top and tooth heel. The inside of the worm gear 6 is a hydrostatic guide sleeve, and oil circuits are distributed around it to provide hydraulic oil with constant pressure to each first hydrostatic oil chamber 13.

[0037] like Figure 3 The figure shows the difference between the cross section of the traditional hydrostatic spline guide rail and the cross section of the hydrostatic spline guide rail of the utility model. Figure 3 (a) is a traditional structure with an eight-tooth positive displacement involute tooth profile. The first tooth portion 14 is removed to enlarge the tooth groove, forming a large tooth groove static pressure spline guide rail; right Figure 3 (b) is the structure of the present invention, which is a twelve-tooth positive displacement involute tooth profile, with the four second removed tooth portions 16 removed, the tooth grooves enlarged, the retained tooth groove portions 15 included, and the adjacent tooth profiles merged to form a large tooth top static pressure spline guide.

[0038] like Figure 4 As shown, Figure 1 The middle AA cross-sectional view reflects the tooth profile shape of the hydrostatic guide rail in the hydrostatic tool holder of the present invention. Its hydrostatic oil chambers are not only distributed on both sides of the tooth profile to form tooth side hydrostatic oil chambers 19, but also on the top surface of the large tooth to form a tooth top hydrostatic oil chamber 17. The inside of the worm gear 6 is a hydrostatic guide sleeve, and oil circuits are distributed around it to provide hydraulic oil at a constant pressure to each hydrostatic oil chamber.

[0039] The working principle of the present invention is as follows: The four-tooth involute tooth profile of the hydrostatic spline guide is a twelve-tooth positive displacement involute cylindrical gear tooth profile, formed by merging two adjacent teeth and removing redundant teeth at the tooth groove. Its characteristic is that the outer cylindrical profile of the tooth top formed by the four-tooth tooth profile is relatively wide, which provides sufficient space for the design of a radial four-cavity centripetal hydrostatic bearing. In this way, the upper end of the cutter shaft is not only subjected to the centripetal clamping static pressure formed by the hydrostatic cavity of the involute tooth surface of the hydrostatic spline guide, but also to the hydrostatic clamping force of the tooth top. The superposition of these two clamping forces enhances the rigidity of the upper end of the cutter shaft.

[0040] A method for operating a static pressure tool holder of a gear shaping machine comprises the following steps:

[0041] During operation, the eccentric disk 1 drives the swing rod 2, which drives the cutter shaft 4, and the cutter shaft 4 drives the cutter 11 to achieve reciprocating motion;

[0042] During the matching process between the cutter shaft 4 and the inner hole of the worm wheel 6, based on the tooth profile shape of the hydrostatic guide rail, its hydrostatic oil chambers are not only distributed on both sides of the tooth profile, but also on the large tooth top surface. The inside of the worm wheel 6 is a hydrostatic guide sleeve, and oil circuits are distributed around it to provide hydraulic oil of constant pressure to each hydrostatic oil chamber, thereby forming a radial four-cavity centripetal hydrostatic bearing. In this way, the upper end of the cutter shaft not only has the centripetal clamping static pressure formed by the hydrostatic chamber of the involute tooth surface of the hydrostatic guide rail, but also has the hydrostatic clamping force of the tooth top. The superposition of the two clamping forces enhances the rigidity of the upper end of the cutter shaft.

Claims

1. A static pressure tool holder for a gear shaping machine, characterized in that: The utility model comprises an eccentric disk (1), a swing rod (2) is hinged on the eccentric disk (1), and the other end of the swing rod (2) is hingedly connected to the top end of the tool shaft (4) through a ball pull rod (3) through a ball head; the tool shaft (4) passes through a tool holder body (8), and a tool (11) is installed at the lower end of the tool shaft (4); a worm gear (6) and a worm (7) are installed at the upper end of the tool holder body (8), and the worm gear (6) is pressed by a large flange (5) to be axially fixed; a tool shaft sleeve (9) and a sealing ring (10) are installed at the lower end of the tool holder body (8), and the tool shaft (4) passes through the inner holes of the worm gear (6) and the tool shaft sleeve (9) at the same time.

2. The hydrostatic tool holder for a gear shaping machine according to claim 1, characterized in that: The eccentric disk (1) is connected to a driving motor and is driven to rotate by the motor.

3. The hydrostatic tool holder for a gear shaping machine according to claim 1, characterized in that: The top end of the rocker arm (2) is hinged to the outer wall of the eccentric disc (1) through rotation.

4. The hydrostatic tool holder for a gear shaping machine according to claim 1, characterized in that: The bottom end of the swing rod (2) is connected to the ball pull rod (3) via a thread, and the ball head of the ball pull rod (3) is hingedly connected to the top end of the knife shaft (4).

5. The hydrostatic tool holder for a gear shaping machine according to claim 1, characterized in that: The inner hole of the knife shaft sleeve (9) is evenly distributed with four static pressure oil chambers, through which pressure oil is passed to form a centripetal static pressure bearing. The knife shaft sleeve (9) wraps the knife shaft (4) in an annular shape, and the gap between the two is 0.02-0.04 mm; the lower end of the knife shaft (4) is sealed by a sealing ring (10).

6. The hydrostatic tool holder for a gear shaping machine according to claim 5, characterized in that: The inner hole of the worm wheel (6) cooperates with the cutter shaft (4) to form an involute spline toothed guide rail structure (21), a tooth side static pressure oil cavity (19) is distributed on the tooth side of each toothed guide rail structure (21), and a tooth top static pressure oil cavity (17) is distributed on the tooth top of each toothed guide rail structure (21), and a static pressure guide rail is formed by pressure oil.

7. The hydrostatic tool holder for a gear shaping machine according to claim 6, characterized in that: The toothed guide rail structure (21) adopts a positive displacement involute cylindrical gear tooth profile with twelve teeth, two adjacent teeth are merged, and redundant teeth are removed at the tooth groove, thereby forming four groups of toothed guide rail structures (21).

8. The hydrostatic tool holder for a gear shaping machine according to claim 7, characterized in that: The outer arc surface of the hydrostatic guide rail is used to form a 4-cavity centripetal hydrostatic bearing to improve the overall hydrostatic stiffness of the cutter shaft.

9. The hydrostatic tool holder for a gear shaping machine according to claim 7, characterized in that: The tooth top profile of the toothed guide rail structure (21) is a standard outer arc surface, and is then processed with high precision using an outer cylindrical grinder to ensure that the circumference of the outer cylindrical surface of the guide rail is within 0.005 mm and the oil film gap is controlled within 0.02-0.04 mm.

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