Heavy four-station automatic tool holder for crankshaft machining

Abstract

This invention discloses a heavy-duty four-station automatic tool holder for crankshaft machining, belonging to the technical field of metal cutting machine tool accessories. It includes a base, a tool holder body, a hydraulic locking mechanism, an indexing drive mechanism, and a position detection unit. The base has a convex structure with a hollow center. The tool holder body has a cross structure, forming four indexing stations. Tool clamping stations are provided at the four ends of the tool holder body, and tool holders are fixed to these stations with bolts. A convex through-hole is provided at the center of the tool holder body. A flange is fixed to the top of the through-hole with bolts. Crankshaft machining tools are clamped and fixed on the tool holders. The hydraulic locking mechanism is installed inside the through-hole. This invention's heavy-duty four-station automatic tool holder for crankshaft machining not only enables rapid tool changing but also features high rigidity and high precision, allowing for heavy-duty cutting of crankshafts with large depths of cut, further improving crankshaft machining efficiency.

Description

Technical Field

[0001] This invention specifically relates to a heavy-duty four-station automatic tool holder for crankshaft machining, belonging to the technical field of metal cutting machine tool accessories. Background Technology

[0002] The crankshaft is a core transmission component in internal combustion engines, compressors, heavy machine tools, and other equipment. Its machining quality directly affects the operating accuracy and service life of the entire machine. To ensure the mechanical strength, fatigue performance, and wear resistance of the crankshaft, the industry typically selects high-strength alloy steels such as 38CrMoAl and 40CrNiMoA as blanks. These materials have high toughness, high cutting resistance, and are difficult to process. At the same time, crankshaft blanks are mostly irregular forgings with uneven machining allowances and large blank errors. During the cutting process, the tool overhang length is relatively long, and the crank section is offset cutting, which will generate a large overturning moment and impact load. This places extremely high demands on the overall rigidity, locking accuracy, and operational reliability of the tool holder. Currently, the commonly used tool holder structures in crankshaft machining processes are mainly divided into two categories: one is a single-station fixed tool holder, which can only clamp one tool at a time. When switching processes, manual disassembly and tool replacement are required, resulting in long tool change auxiliary time, high labor intensity for operators, low production efficiency, and difficulty in meeting the production needs of batch crankshaft machining; the other is a general four-station tool holder, which adopts a separate clamping method with a tool holder body and an extended tool shank. The extended tool shank extends the tool position to adapt to the machining space of the irregular crankshaft structure. However, there is a connection gap between the tool shank and the tool holder, resulting in high overall rigidity loss, insufficient vibration resistance, and inability to withstand heavy cutting with large depth of cut. Only a small allowance and multiple passes can be used for machining, which not only has low machining efficiency but also easily generates cutting vibration marks, affecting the surface quality and dimensional accuracy of the crankshaft. In addition, existing tool holders are prone to circumferential or axial movement under working reaction forces. Summary of the Invention

[0003] To address the aforementioned issues, this invention proposes a heavy-duty four-station automatic tool holder for crankshaft machining. The tool holder body not only enables rapid tool changing but also features high rigidity and high precision, allowing for heavy-duty cutting of crankshafts with large depths of cut, thereby further improving crankshaft machining efficiency.

[0004] The heavy-duty four-station automatic tool post for crankshaft machining of the present invention includes: The base has a convex structure and a hollow center. The tool holder body has a cross-shaped structure, forming four indexing stations. Tool clamping stations are located at each of the four ends of the tool holder body, and tool holders are bolted to these stations. Each station directly clamps the crankshaft machining tool, eliminating the need for extended tool shanks and reducing rigidity losses associated with separate structures. A convex through-hole is located at the center of the tool holder body. A flange is bolted to the top of the through-hole. The crankshaft machining tool is clamped and fixed on the tool holder. The tool holder body is a single, integrally cast cross-shaped structure. The entire tool holder body is a single, integral part, with the four tool arms completely integrated with the central base. When the cutting force is transmitted from the tool tip through the tool arms to the center, the force is continuous and uninterrupted throughout the entire process, eliminating the rigidity losses associated with separate structures. The rigidity loss is reduced due to contact deformation at the joint surface and movement of the fitting clearance. In addition, the tool holder body adopts a large cross section and thick wall, which has a strong load-bearing capacity: the cross arm adopts a thick-walled box section, and the moment of inertia and section modulus of the section are much greater than those of the slender tool bar. Under the same cutting force, the bending deformation and torsional deformation of the tool arm itself are greatly reduced. It can withstand the large torque and bending moment generated by the large depth of cut of the crankshaft. Moreover, the four ends of the tool holder are directly integrated with the tool holder, and the crankshaft machining tool is directly clamped in the tool holder without the need for an extended tool bar. During the cutting process, the cutting force on the tool tip will generate a bending moment on the tool holder. Under the same cutting force, the bending moment at the tool tip is greatly reduced, and the actual machining rigidity of the tool tip is significantly improved. This allows for a larger depth of cut and avoids the generation of chatter marks. A hydraulic locking mechanism is installed inside a through hole. The hydraulic locking mechanism includes a movable cylinder body, inside which a piston rod is movably fitted. The bottom of the piston rod is fitted to a base via multiple O-ring seals. A bottom cover is fitted to the bottom of the base and fixed with bolts. The bottom cover is fixed to the bottom of the piston rod with bolts. A wiring hole is provided at the center of the bottom cover and the piston rod. A cylinder pressure cover is fitted to the top of the movable cylinder body. The top of the piston rod movably protrudes from the cylinder pressure cover via a YX sealing ring. The upper part of the piston rod is integrally formed with a sealing section; multiple sets of YX sealing rings are sleeved between the sealing section and the movable cylinder; a meshing gear plate is fixed at the bottom of the movable cylinder; an external gear plate meshes with the bottom of the meshing gear plate; the external gear plate is fixed to the bottom of the inner side of the tool holder body, and after the meshing gear plate and the external gear plate mesh, the position of the tool holder body is rigidly limited; two oil passages are provided inside the piston rod, and the output ends of the two oil passages are respectively connected to the top and bottom surfaces of the sealing section; the input ends of the two oil passages are connected to the hydraulic system through the base. The piston rod is vertically fixed to the center of the base bottom, serving as the central reference axis of the entire tool holder. The tool holder body can smoothly rotate around the central axis of the piston rod. Two independent axial oil passages are machined inside the piston rod, connecting the upper and lower working chambers of the oil cylinder respectively. The movable cylinder body is coaxially sleeved on the outside of the piston rod. The mating surfaces of the piston rod and the movable cylinder body only have axial reciprocating relative movement, without circumferential relative torsion. The outer gear plate is fixedly installed on the inner bottom of the tool holder body and rotates synchronously with the tool holder body. The meshing gear plate is fixed to the lower end face of the movable cylinder body, moves axially with the cylinder body, and remains stationary circumferentially. When the movable cylinder body moves downward, the meshing gear plate engages with the end face teeth of the outer gear plate, achieving rigid locking of the tool holder. When the movable cylinder body moves upward, the gear plate disengages and releases the locking. The indexing drive mechanism is located between the top of the piston rod and the tool holder body. It is used to output rotational torque and drive the tool holder body to rotate at a fixed angle relative to the base to achieve workstation switching.

[0005] A position detection unit, fixed to the top of the piston rod, is used to detect the indexing position signal of the tool holder body and transmit the signal to the control system to realize the automated control of the tool changing action.

[0006] Furthermore, the lower part of the base is provided with an oil distribution ring, and the base is machined with two independent oil holes, which are respectively connected to the oil distribution ring and two oil passages. External hydraulic oil enters the inside of the movable cylinder through the oil distribution ring, the independent oil holes and the oil passages in the piston rod.

[0007] Furthermore, the indexing drive mechanism includes a drive motor, an external gear, and an internal gear ring; the drive motor is fixedly mounted on the top of the piston rod via a motor mounting plate, the external gear is coaxially fixed to the output shaft end of the drive motor, and the internal gear ring is fixedly disposed on the inner wall of the flange and coaxially disposed with the through hole; the external gear meshes with the internal gear ring; when the drive motor starts, it drives the internal gear ring to rotate synchronously through the external gear transmission, and the internal gear ring synchronously drives the tool holder body to rotate around the central axis of the piston rod, thus completing the workstation switching.

[0008] Furthermore, it also includes a signal detection unit, which is a proximity detection switch positioned directly opposite the indexing position of the tool holder body. A positioning rod is fixed to the inside of the flange directly opposite the proximity detection switch. The proximity detection switch is fixed to the top surface of the motor mounting plate and is connected to the tool holder's control system. Through the cooperation of the proximity detection switch and the positioning rod, it is possible to accurately monitor whether the indexing position of the tool holder body has been switched into place.

[0009] Furthermore, the meshing gear disc is fixed to the bottom of the movable cylinder body via a mounting plate seat. The mounting plate seat and the piston rod are integrally formed with mutually sliding splines. Through the splines, circumferential locking between the mounting plate seat and the piston rod can be achieved, thereby synchronously locking the piston rod and the movable cylinder body circumferentially. The upper part of the tool holder body is locked circumferentially by an external gear and an internal gear ring, the middle and lower parts of the tool holder body are locked circumferentially by splines, and the lower part of the tool holder body is locked circumferentially by the meshing gear disc and the external gear disc. This ensures that after the tool holder body completes tool changing, circumferential movement of the tool can be prevented during the machining process. At the same time, high-pressure oil can be used to prevent axial movement of the tool holder body during the machining process.

[0010] Furthermore, a limit bearing is provided between the bottom of the through hole and the base of the tool holder body. The limit bearing can limit the axial movement of the tool holder body and guide its circumferential rotation.

[0011] Furthermore, an O-ring is pressed between the movable cylinder body and the cylinder cover. The O-ring prevents the pressure oil from leaking out and losing pressure when pressurizing and injecting oil between the top of the sealing section and the cylinder cover.

[0012] Furthermore, the top surface of the cylinder cover is integrally formed with an annular reference surface. The motor mounting plate has a ranging hole facing the reference surface, and a ranging unit is fixed inside the ranging hole. The ranging unit is connected to the control system, which is also connected to an electric switch connected in series with the starting circuit of the drive motor. A pressure-reducing and pressure-holding valve is provided on the output side of the hydraulic system, and the control circuit of the pressure-reducing and pressure-holding valve is connected to the control system. The ranging unit is a laser displacement sensor. The reference surface is the hardened surface of the cylinder head, which is flat and perpendicular to the detection axis of the ranging unit, ensuring ranging accuracy and long-term stability. The pressure-reducing and pressure-holding valve is connected in series on the oil supply branch between the distribution ring and the independent oil hole. The control system obtains the real-time position of the movable cylinder through the ranging unit and uses the real-time position as the switching node, with two working states: full-pressure direct connection and low-pressure holding. The low-pressure holding pressure value can be calibrated according to the total weight of the floating assembly consisting of the cylinder head, movable cylinder, and meshing gear, balancing the self-weight of the floating assembly and retaining a small amount of clamping margin. The control system presets three sets of position parameters: disengagement threshold, engagement start threshold, and rated engagement threshold, and realizes the pressure in each threshold range through the pressure-reducing and pressure-holding valve. Force control; when the distance value collected by the ranging unit reaches the disengagement threshold, it is determined that the meshing gear disc and the outer gear disc are completely disengaged. The control system sends a closing signal to the electric switch to release the start lock of the drive motor, and at the same time controls the pressure reducing and holding valve to open, switching the upper chamber of the cylinder to low-pressure floating pressure holding mode; when the meshing gear disc and the outer gear disc reset to the meshing critical value, the pressure reducing and holding valve is automatically opened, switching to low-pressure alignment mode, and the gear disc is pushed into the groove at a constant low speed with constant low pressure; after reaching the rated meshing depth, the pressure reducing and holding valve is closed, switching to the system full-pressure holding mode, that is, when the ranging value falls back to the rated meshing threshold, it is determined that the meshing gear disc and the outer gear disc have reached the rated meshing depth, and the control system controls the pressure reducing and holding valve to close, restoring the system full-pressure lock; the specific process is as follows: Disengagement and Floating Pressure Holding: When the distance value collected by the ranging unit reaches the disengagement threshold, it is determined that the three-tooth disc is completely disengaged. The control system simultaneously executes two actions: first, it releases the start lock of the drive motor, allowing indexing; second, it opens the pressure reducing and holding valve, switching the upper chamber of the cylinder from the unloading state to the low-pressure floating pressure holding mode. The low-pressure holding pressure is just enough to balance the weight of the moving cylinder and the meshing tooth disc, which can prevent the cylinder from slightly falling and rubbing against the teeth due to oil pressure fluctuations and machine tool vibration. At the same time, it greatly reduces the pressure ratio of the sealing surface and extends the service life of the seals. Low-pressure alignment and meshing: During the locking process, the moving cylinder adopts low-pressure alignment mode throughout the entire process, or adopts full-pressure rapid advance in the early stage of descent to improve tool changing efficiency; when the distance measurement value drops to the meshing start threshold (meshing critical value) and the tooth surface is about to contact, the control system automatically opens the pressure reducing and holding valve, switches to low-pressure alignment mode, and pushes the tooth plate into the groove at a constant low pressure; the low-pressure thrust is gentle, which can avoid tooth surface impact and springback under high pressure, guide the tooth tip to slide naturally into the tooth groove along the triangular tooth inclined surface, greatly reduce the probability of tooth tip jamming, and ensure smooth meshing; Full-pressure final locking: When the ranging value falls back to the rated engagement threshold, it is determined that the meshing gear plate and the outer gear plate have reached the rated engagement depth. The control system closes the pressure reducing and holding valve, restores the full-pressure locking and holding of the system, and provides the maximum locking force; it can prevent circumferential deviation caused by machining in the semi-engaged state.

[0013] The control system has pre-stored standard meshing displacement and time curves to achieve full-stroke meshing state identification: During locking, the ranging unit continuously collects the downward displacement data of the movable cylinder at high frequency sampling, generating real-time displacement and time curves, and performs multi-dimensional feature comparison with the pre-stored standard curves; under normal and full meshing, the downward curve of the movable cylinder is smooth and continuous, and the termination position is stable within the threshold range; if false meshing of tooth tips occurs, the cylinder will stop abruptly after tooth surface contact, and the termination position is significantly higher than the rated meshing threshold, with the curve showing a steep drop followed by a sudden stop; the system Upon detecting false engagement, the control system immediately controls the hydraulic cylinder to further reduce the hydraulic pressure, and drives the motor to rotate at low speed with the load in both forward and reverse directions by the set value. Within the set value range, when the downward displacement data of the movable cylinder reaches the engagement threshold, the drive motor is immediately locked. When the drive motor is in the rotational positioning state, and the downward displacement data of the movable cylinder does not change within the set unit time, the machine is immediately stopped and rotates in the reverse direction. When neither rotation enters the rated engagement threshold range, the hydraulic cylinder reverses direction, and the movable cylinder reverses direction and retracts to retry. If the retry fails continuously, a fault alarm is triggered. After locking is completed and cutting begins, the ranging unit maintains low-power continuous sampling to achieve in-situ monitoring of the cutting process: the periodic strong impact of intermittent crankshaft cutting will cause slight springback of the tooth surface, resulting in dynamic decay of the engagement depth; the ranging unit continuously monitors the axial position of the moving cylinder at a set sampling frequency. When the axial upward floating (or axial movement) of the moving cylinder is detected to exceed the set safety margin threshold, it is determined that the engagement depth has decayed to below the safe range; the control system immediately triggers a cutting speed reduction or pause command, and at the same time controls the upper chamber of the hydraulic cylinder to replenish pressure, pushing the moving cylinder to return to the rated engagement depth. After confirming that the locking is reliable, normal processing is resumed, ensuring the effective engagement of the gear plate throughout the process and avoiding circumferential axial movement caused by impact accumulation; After the tool post is debugged, the distance value corresponding to the rated meshing position in the initial state is recorded as the reference value. Each time the tool is locked in place, the system records the current distance value and compares it with the reference value to calculate the cumulative wear of the tooth surface. When the tooth surface wears down over a long period of time, causing the meshing position to gradually move down, the control system automatically updates the meshing judgment threshold and the hydraulic cylinder pressure holding stroke to compensate for the loss of meshing depth caused by wear. This ensures that the gear plate always maintains the rated meshing height and effective contact area throughout its entire life cycle, avoids the decrease in locking stiffness due to natural thinning caused by wear, and prevents circumferential displacement under cutting reaction force.

[0014] Compared with the prior art, the heavy-duty four-station automatic tool holder for crankshaft machining of the present invention has the following advantages: 1. High overall clamping rigidity, suitable for heavy cutting: The tool holder body adopts an integrated cross-casting structure, and the tool is directly clamped on the tool holder at the end of the workstation, eliminating the rigidity loss and fit clearance of the split connection structure. The overall vibration resistance and load-bearing capacity are greatly improved, which can withstand heavy cutting loads with large depth of cut, reduce the number of tool passes, and improve the machining efficiency of crankshaft roughing process.

[0015] 2. High locking accuracy and good positioning stability: The hydraulically driven end face gear plate meshing locking structure provides high locking force and high indexing repeatability. During cutting, the upper part of the tool holder body is locked circumferentially by the external gear and the internal gear ring, the middle and lower parts of the tool holder body are locked circumferentially by the spline, and the lower part of the tool holder body is locked circumferentially by the meshing gear plate and the external gear plate. This ensures that after the tool holder body completes the tool change, it can prevent the tool from circumferentially moving back during the machining process. At the same time, high-pressure oil can prevent the tool holder body from axially moving during the machining process, which can effectively ensure the dimensional accuracy and surface quality of crankshaft machining and meet the requirements of high-precision finishing processes.

[0016] 3. High efficiency of automatic tool changing and strong structural integration: The indexing position is achieved by driving the gear transmission through the drive motor. With the position detection unit's arrival signal and the hydraulic system's automatic locking control, automatic and rapid tool changing in four positions can be realized. All components are integrated inside the tool holder body, without changing the external installation dimensions and main structure of the tool holder, and can be directly adapted to the installation interface of heavy-duty crankshaft machining tools.

[0017] 4. Coordinated ranging and pressure switching ensures safe floating and precise locking: The position signal of the ranging unit is used as the sole switching node, and the pressure reducing and holding valve is controlled to achieve automatic pressure switching between disengagement floating, low pressure alignment, and full pressure locking. This balances tool changing efficiency, meshing stability, and seal life. In the disengagement state, low pressure suspends and supports the moving cylinder, avoiding non-working wear on the tooth surface caused by its own weight falling and reducing long-term high-pressure load on the sealing surface, thus improving the service life of the seals and tooth surface. During the meshing alignment stage, low pressure and slow advance are used, resulting in gentle tooth surface contact and guiding the triangular teeth to slide naturally into the tooth groove, reducing tooth tip jamming and meshing rebound, and avoiding false meshing failures. In addition, by binding the rated meshing depth threshold with full pressure locking, full pressure hydraulic locking is only performed after the ranging confirms that the target meshing depth has been reached. The effective contact area of ​​the tooth surface is sufficient, and the resistance to circumferential shearing is strong, completely avoiding tool holder displacement and tooth breakage accidents caused by the cutting reaction force breaking through the constraint in the semi-meshing or false meshing state. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the heavy-duty four-station automatic tool holder for crankshaft machining according to the present invention.

[0019] Figure 2This is a top view schematic diagram of the heavy-duty four-station automatic tool holder for crankshaft machining according to the present invention.

[0020] Figure 3 For the present invention along Figure 2 A schematic diagram of the BB line cross-section structure.

[0021] Figure 4 For the present invention Figure 3 A magnified schematic diagram of the structure at point A in the middle.

[0022] Figure 5 For the present invention along Figure 2 A schematic diagram of the CC-line cross-section structure.

[0023] Figure 6 This is a schematic diagram of the meshing gear plate and the external gear plate of the heavy-duty four-position automatic tool holder for crankshaft machining of the present invention in the meshing and locking state.

[0024] Figure 7 This is a schematic diagram of the disengaged gear plate and the external gear plate of the heavy-duty four-station automatic tool holder for crankshaft machining according to the present invention.

[0025] Figure 8 This is a schematic diagram of the installation structure of the heavy-duty four-station automatic tool holder and distance measuring unit for crankshaft machining according to the present invention.

[0026] Figure 9 This is a schematic diagram of the connection structure of the ranging unit, pressure reducing and holding valve and control system of the present invention.

[0027] Reference numerals in the attached diagram: 1. Base, 2. Tool holder body, 3. Tool holder, 4. Flange, 5. Movable cylinder, 6. Piston rod, 7. O-ring seal, 8. Bottom cover, 9. Wiring hole, 10. Cylinder cover, 11. YX sealing ring, 12. Separator section, 13. Meshing gear disc, 14. External gear disc, 15. Oil passage, 16. Independent oil hole, 17. Drive motor, 18. External gear, 19. Internal gear ring, 20. Motor mounting plate, 21. Proximity detection switch, 22. Positioning rod, 23. Mounting plate base, 24. Distance measuring unit. Detailed Implementation

[0028] Example: like Figures 1 to 9 The heavy-duty four-position automatic tool post for crankshaft machining shown includes: Base 1, which has a convex structure and is hollow at the center; Base 1 is integrally cast from high-strength gray cast iron and is fixedly installed on the machine tool slide by a ring of fastening bolts at the bottom. The tool holder body 2 has a cross-shaped structure, forming four indexing stations. Tool clamping stations are located at each of the four ends of the tool holder body 2. Tool holders 3 are bolted to these stations for clamping crankshaft machining tools such as external turning tools, grooving tools, and fillet tools, enabling automatic tool changing. Each station directly clamps crankshaft machining tools, eliminating the need for extended tool holders and reducing rigidity losses in a split structure. A convex through-hole is located at the center of the tool holder body 2. A flange 4 is bolted to the top of the through-hole. The tool holder body 2 is a single, integrally cast cross-shaped structure. The four tool arms are completely integrally formed with the central base. When the cutting force is transmitted from the tool tip through the tool arms to the center, the force is continuous and uninterrupted throughout the entire process, preventing the contact deformation and clearance shifting that occur in split structures. In addition to rigidity loss, the tool holder body 2 adopts a large cross-section and thick wall, which has a strong load-bearing capacity: the cross arm adopts a thick-walled box-shaped cross section, and the moment of inertia and section modulus of the cross section are much greater than those of the slender tool bar. Under the same cutting force, the bending deformation and torsional deformation of the tool arm itself are greatly reduced, which can withstand the large torque and bending moment generated by the large depth of cut of the crankshaft. Moreover, the four ends of the tool holder directly integrate the tool holder 3, and the crankshaft machining tool is directly clamped in the tool holder 3 without the need for an extended tool bar. During the cutting process, the cutting force on the tool tip will form a bending moment on the tool holder. Bending moment = cutting force × tool overhang length. Bending moment is the core reason for tool deflection and chatter. The tool overhang length is compressed to the shortest, and the bending moment at the tool tip is greatly reduced under the same cutting force. The actual machining rigidity of the tool tip is significantly improved, which allows for a larger depth of cut and avoids the generation of chatter marks. A hydraulic locking mechanism is installed inside a through hole. The hydraulic locking mechanism includes a movable cylinder 5, inside which a piston rod 6 is movably fitted. The bottom of the piston rod 6 is fitted to a base 1 via multiple O-ring seals 7. A bottom cover 8 is bolted to the bottom of the base 1, and the bottom cover 8 is bolted to the bottom of the piston rod 6. A wiring hole 9 is provided at the center of the bottom cover 8 and the piston rod 6 for introducing power and control lines. A cylinder cover 10 is fitted and fixed to the top of the movable cylinder 5. The top of the piston rod 6 extends through the cylinder cover 10 via a YX seal 11. The upper part of the piston rod 6 is integrally formed with a sealing section 12; multiple sets of YX sealing rings 11 are sleeved between the sealing section 12 and the movable cylinder 5; a meshing gear plate 13 is fixed at the bottom of the movable cylinder 5; an external gear plate 14 meshes with the bottom of the meshing gear plate 13; the external gear plate 14 is fixed to the bottom of the inner side of the tool holder body 2, and after the meshing gear plate 13 and the external gear plate 14 mesh, the position of the tool holder body 2 is rigidly limited; two oil passages 15 are provided inside the piston rod 6, and the output ends of the two oil passages 15 are respectively connected to the top and bottom surfaces of the sealing section 12 to form an upper working chamber and a lower working chamber; the input ends of the two oil passages 15 are connected to the hydraulic system through the base 1. The piston rod 6 is vertically fixed to the center of the bottom of the base 1, serving as the central reference axis of the entire tool holder. The tool holder body 2 can rotate smoothly around the central axis of the piston rod 6. Two independent oil passages 15 are machined axially inside the piston rod 6, which connect the upper working chamber and the lower working chamber of the oil cylinder respectively. The movable cylinder 5 is coaxially sleeved on the outside of the piston rod 6. The mating surfaces of the piston rod 6 and the movable cylinder 5 only have axial reciprocating relative movement, without circumferential relative torsion. The outer gear plate 14 is fixedly installed on the bottom inner side of the tool holder body 2 and rotates synchronously with the tool holder body 2. The meshing gear plate 13 is fixed to the lower end face of the movable cylinder 5, moves axially with the movable cylinder 5 and remains stationary circumferentially. When the movable cylinder 5 moves downward, the meshing gear plate 13 meshes with the end face teeth of the outer gear plate 14, realizing the rigid locking of the tool holder. When the movable cylinder 5 moves upward, the meshing gear plate 13 and the outer gear plate 14 disengage and release the locking. The indexing drive mechanism is located between the top of the piston rod 6 and the tool holder body 2. It is used to output rotational torque and drive the tool holder body 2 to rotate at a fixed angle relative to the base 1 to realize the switching of work positions.

[0029] The position detection unit is fixed to the top of the piston rod 6 and is used to detect the indexing position signal of the tool holder body 2 and transmit the signal to the control system to realize the automated control of the tool changing action.

[0030] The lower part of the base 1 is provided with an oil distribution ring. The base 1 has two independent oil holes 16 machined inside, which are respectively connected to the oil distribution ring and two oil passages 15. External hydraulic oil enters the inner side of the movable cylinder 5 through the oil distribution ring, the independent oil holes 16 and the oil passages 15 in the piston rod 6. That is, the two oil passage interfaces of the hydraulic system are connected to the oil distribution ring. After the pressure oil is distributed by the oil distribution ring, it enters the two independent oil holes 16 inside the base 1.

[0031] The indexing drive mechanism includes a drive motor 17, an external gear 18, and an internal gear ring 19. The drive motor 17 is fixedly mounted on the top of the piston rod 6 via a motor mounting plate 20. The external gear 18 is coaxially fixed to the output shaft end of the drive motor 17. The internal gear ring 19 is fixedly disposed on the inner wall of the flange 4 and coaxially disposed with the through hole. The external gear 18 and the internal gear ring 19 mesh. When the drive motor 17 starts, it drives the internal gear ring 19 to rotate synchronously through the external gear 18. The internal gear ring 19 synchronously drives the tool holder body 2 to rotate around the central axis of the piston rod 6, thus completing the workstation switching.

[0032] It also includes a signal detection unit, which is a proximity detection switch 21 positioned opposite the indexing position of the tool holder body 2. A positioning rod 22 is fixed to the inside of the flange 4 opposite the proximity detection switch 21. The proximity detection switch 21 is fixed to the top surface of the motor mounting plate 20. The proximity detection switch 21 is connected to the control system of the tool holder. When the proximity detection switch 21 and the positioning rod 22 are aligned, the proximity detection switch 21 is triggered, which can accurately monitor whether the indexing position of the tool holder body 2 has been switched to the correct position.

[0033] The meshing gear plate 13 is fixed to the bottom of the movable cylinder 5 via the mounting plate seat 23. The mounting plate seat 23 and the piston rod 6 are integrally formed with mutually sliding splines. The splines can achieve circumferential locking between the mounting plate seat 23 and the piston rod 6, thereby synchronously locking the piston rod 6 and the movable cylinder 5 circumferentially. The upper part of the tool holder body 2 is circumferentially locked by the external gear 18 and the internal gear ring 19. The middle and lower parts of the tool holder body 2 are circumferentially locked by the splines. The lower part of the tool holder body 2 is circumferentially locked by the meshing gear plate 13 and the external gear plate 14. This can ensure that after the tool holder body 2 completes the tool change, the tool can be prevented from circumferentially moving during the machining process. At the same time, high-pressure oil can be used to prevent the tool holder body 2 from axially moving during the machining process.

[0034] The tool holder body 2 is provided with a limit bearing between the bottom of the through hole and the base 1. The limit bearing can limit the axial movement of the tool holder body 2 and guide its circumferential rotation.

[0035] An O-ring 23 is pressed between the movable cylinder 5 and the cylinder cover 10. The O-ring 23 prevents the pressure oil from leaking out and losing pressure when pressurizing and injecting oil between the top of the sealing section 12 and the cylinder cover 10.

[0036] The top surface of the cylinder cover 10 is integrally formed with an annular reference surface. The motor fixing plate 20 has a distance measuring hole facing the reference surface. A distance measuring unit 24 is fixed in the distance measuring hole. The distance measuring unit 24 is connected to the control system. The control system is also connected to an electric switch. The electric switch is connected in series to the starting circuit of the drive motor 17. A pressure reducing and holding valve is provided on the output side of the hydraulic system. The control circuit of the pressure reducing and holding valve is connected to the control system. The distance measuring unit 24 is a laser displacement sensor. A pressure reducing and holding valve is connected in series on the oil supply branch between the oil distribution ring and the oil passage 15. The pressure reducing and holding valve is an electromagnetically controlled pressure reducing valve with two working states: full pressure direct flow and low pressure holding. The pressure value of low pressure holding can be calibrated by a knob. The reference surface is the hardened surface of the top surface of the cylinder cover 10, which is flat and perpendicular to the detection axis of the ranging unit 24 to ensure ranging accuracy and long-term stability. The pressure reducing and holding valve is connected in series on the oil supply branch between the oil distribution ring and the independent oil hole 16. The control system obtains the real-time position of the movable cylinder 5 through the ranging unit 24 and uses the real-time position as the switching node, with two working states: full pressure direct connection and low pressure holding. The low pressure holding pressure value can be calibrated according to the total weight of the floating assembly composed of the cylinder cover 10, the movable cylinder 5, and the meshing gear 13, balancing the self-weight of the floating assembly and retaining a small amount of clamping margin. The control system presets three sets of thresholds: disengagement threshold, engagement initiation threshold, and rated engagement threshold. Position parameters are set, and pressure control is achieved for each threshold range via a pressure-reducing and pressure-holding valve. When the distance value collected by the ranging unit 24 reaches the disengagement threshold, it is determined that the meshing gear disk 13 and the outer gear disk 14 are completely disengaged. The control system sends a closing signal to the electric switch to release the start lock of the drive motor 17, and simultaneously controls the pressure-reducing and pressure-holding valve to open, switching the upper chamber of the cylinder to a low-pressure floating pressure-holding mode. When the meshing gear disk 13 and the outer gear disk 14 reset to the meshing critical value, the pressure-reducing and pressure-holding valve is automatically opened, switching to a low-pressure alignment mode. When the ranging value falls back to the rated meshing threshold, it is determined that the meshing gear disk 13 and the outer gear disk 14 have reached the rated meshing depth. The control system controls the pressure-reducing and pressure-holding valve to close, restoring the system to full-pressure lock. The specific process is as follows: Disengagement and Floating Pressure Holding: When the distance value collected by the ranging unit 24 reaches the disengagement threshold, it is determined that the meshing gear disk 13 and the outer gear disk 14 are completely disengaged. The control system simultaneously executes two actions: first, it releases the start lock of the drive motor 17, allowing indexing; second, it opens the pressure reducing and holding valve, switching the upper chamber of the oil cylinder from the unloading state to the low-pressure floating pressure holding mode. The low-pressure holding pressure just balances the weight of the movable cylinder 5 and the meshing gear disk 13, which can prevent the movable cylinder 5 from slightly falling and rubbing against the teeth due to oil pressure fluctuations and machine tool vibration. At the same time, it greatly reduces the pressure ratio of the sealing surface and extends the service life of the seals. Low-pressure alignment and meshing: During the locking process, the moving cylinder 5 adopts low-pressure alignment mode throughout the entire process, or adopts full-pressure rapid advance in the early stage of descent to improve tool changing efficiency; when the distance measurement value drops to the meshing start threshold and the tooth surface is about to contact, the control system automatically opens the pressure reducing and holding valve and switches to low-pressure alignment mode, using constant low pressure to push the tooth plate into the groove at low speed; the low-pressure thrust is gentle, which can avoid tooth surface impact and springback under high pressure, and guide the tooth tip to slide naturally into the tooth groove along the triangular tooth inclined surface, greatly reducing the probability of tooth tip jamming and ensuring smooth meshing; Full-pressure final locking: When the distance measurement value falls back to the rated engagement threshold, it is determined that the meshing toothed disc 13 and the outer toothed disc 14 have reached the rated engagement depth. The control system closes the pressure reducing and holding valve, restores the full-pressure locking and holding of the system, and provides the maximum locking force; it can prevent circumferential deviation caused by machining in the semi-engaged state.

[0037] The control system has pre-stored standard meshing displacement and time curves to achieve full-stroke meshing state identification: During the locking process, the ranging unit 24 continuously collects the downward displacement data of the movable cylinder 5 at high frequency, generates real-time displacement and time curves, and performs multi-dimensional feature comparison with the pre-stored standard curves; under normal and full meshing, the downward curve of the movable cylinder 5 is smooth and continuous, and the termination position is stable within the threshold range; if false meshing occurs, the movable cylinder 5 will stop abruptly after the tooth surfaces contact, and the termination position will be significantly higher than the rated meshing threshold, with the curve showing a steep drop followed by a sudden stop; the system identifies... Upon detecting a false engagement characteristic, the control system immediately controls the hydraulic cylinder to further reduce the hydraulic pressure, and drives the motor 17 to rotate at low speed with the load in both forward and reverse directions according to the set value. Within the set value range, when the downward displacement data of the movable cylinder 5 reaches the engagement threshold, the drive motor 17 is immediately locked. When the drive motor 17 is in the rotational positioning state, and the downward displacement data of the movable cylinder 5 does not change within the set unit time, the machine is immediately stopped and rotates in the reverse direction. When neither rotation enters the rated engagement threshold range, the hydraulic cylinder reverses direction, and the movable cylinder 5 reverses direction and retracts to retry. If the retry fails continuously, a fault alarm is triggered. After locking is completed and cutting begins, the ranging unit 24 maintains low-power continuous sampling to achieve in-situ monitoring of the cutting process: the periodic strong impact of intermittent crankshaft cutting will cause a slight springback of the tooth surface, resulting in a dynamic decay of the meshing depth; the ranging unit 24 continuously monitors the axial position of the movable cylinder 5 at a set sampling frequency. When the axial upward floating (or axial movement) of the movable cylinder 5 is detected to exceed the set safety margin threshold, it is determined that the meshing depth has decayed to below the safe range; the control system immediately triggers a cutting speed reduction or pause command, and at the same time controls the upper chamber of the hydraulic cylinder to replenish pressure, pushing the movable cylinder 5 to return to the rated meshing depth. After confirming that the locking is reliable, normal processing is resumed, ensuring the effective meshing amount of the gear plate throughout the process and avoiding circumferential axial movement caused by impact accumulation; After the tool post is debugged, the distance value corresponding to the rated meshing position in the initial state is recorded as the reference value. Each time the tool is locked in place, the system records the current distance value and compares it with the reference value to calculate the cumulative wear of the tooth surface. When the tooth surface wears down over a long period of time, causing the meshing position to gradually move down, the control system automatically updates the meshing judgment threshold and the hydraulic cylinder pressure holding stroke to compensate for the loss of meshing depth caused by wear. This ensures that the gear plate always maintains the rated meshing height and effective contact area throughout its entire life cycle, avoids the decrease in locking stiffness due to natural thinning caused by wear, and prevents circumferential displacement under cutting reaction force.

[0038] The heavy-duty four-station automatic tool changer process for crankshaft machining of the present invention is as follows: Disengagement and floating stage: After receiving the tool change command, the control system controls the hydraulic system to reverse. The pressurized oil enters the lower working chamber of the cylinder through the lower chamber oil passage 15, pushing the movable cylinder 5 to move upward along the fixed piston rod 6, which in turn drives the meshing gear plate 13 to move upward synchronously. The distance measuring unit 24 monitors the position of the cylinder in real time. When the distance value reaches the disengagement threshold L1, it is determined that the three gear plates are completely disengaged. The system simultaneously releases the start lock of the drive motor 17 and opens the pressure reducing and holding valve. The upper chamber of the cylinder switches to a low-pressure floating and holding state to support the movable cylinder 5 and prevent it from falling and rubbing against the gears. Indexing and indexing stage: Drive motor 17 starts and drives tool holder body 2 to rotate at high speed around the central axis through the meshing transmission of external gear 18 and internal gear ring 19; when the tool holder rotates to the target position, the position detection unit triggers the position signal, and the control system controls the motor to slow down and stop. Low-pressure alignment stage: The hydraulic system reverses direction again, pressurized oil enters the upper working chamber, the pressure reducing and holding valve closes, and the cylinder advances rapidly under full pressure; when the distance measurement value drops to the engagement start threshold, the system opens the pressure reducing and holding valve, switches to low-pressure alignment mode, and gently pushes the gear plate into the groove at low speed. Full-pressure final locking stage: When the distance measurement value drops to the rated engagement threshold, the system closes the pressure reducing and holding valve and restores the full-pressure final locking pressure holding of the system; at the same time, the displacement curve is compared to confirm that the engagement is normal, and a locking completion signal is sent to the CNC system to unlock the cutting permission; if false engagement is identified, the external gear plate 14 and the meshing gear plate 13 are automatically re-aligned. Cutting monitoring stage: After entering the machining state, the measuring head continuously samples with low power to monitor the engagement depth; if the impact causes the upward floating to exceed the tolerance, it automatically compensates for pressure and resets to ensure reliable engagement throughout the process and avoid circumferential deviation; Wear compensation stage: After each locking, the system automatically records the engagement position and calculates the wear amount. When the compensation threshold is reached, the parameters are automatically updated to maintain accuracy throughout the entire cycle.

[0039] The above embodiments are merely preferred embodiments of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of the present invention are included within the scope of the present invention.

Claims

1. A heavy-duty four-position automatic tool post for crankshaft machining, characterized in that: include: The base has a convex structure and a hollow center. The tool holder body has a cross structure, forming four indexing stations. Tool clamping stations are provided at the four ends of the tool holder body, and tool holders are fixed to the tool clamping stations by bolts. An inverted convex through hole is provided at the center of the tool holder body. A flange is fixed to the top of the through hole by bolts. A crankshaft machining tool is clamped and fixed on the tool holder. A hydraulic locking mechanism is installed inside a through hole. The hydraulic locking mechanism includes a movable cylinder body, inside which a piston rod is movably fitted. The bottom of the piston rod is fitted to a base via multiple O-ring seals. A bottom cover is fitted to the bottom of the base and fixed with bolts. The bottom cover is fixed to the bottom of the piston rod with bolts. A wiring hole is provided at the center of the bottom cover and the piston rod. A cylinder pressure cover is fitted to the top of the movable cylinder body. The top of the piston rod movably protrudes from the cylinder pressure cover via a YX sealing ring. The upper part of the piston rod is integrally formed with a sealing section; multiple sets of YX sealing rings are sleeved between the sealing section and the movable cylinder; a meshing gear plate is fixed at the bottom of the movable cylinder; an external gear plate meshes with the bottom of the meshing gear plate; the external gear plate is fixed to the bottom of the inner side of the tool holder body, and after the meshing gear plate and the external gear plate mesh, the position of the tool holder body is rigidly limited; two oil passages are provided inside the piston rod, and the output ends of the two oil passages are respectively connected to the top and bottom surfaces of the sealing section; the input ends of the two oil passages are connected to the hydraulic system through the base. A rotation drive mechanism is disposed between the top of the piston rod and the tool holder body; A position detection unit is fixed to the top of the piston rod.

2. The heavy-duty four-station automatic tool post for crankshaft machining according to claim 1, characterized in that: The base is provided with an oil distribution ring at the bottom and two independent oil holes are machined inside the base, which are respectively connected to the oil distribution ring and two oil passages. External hydraulic oil enters the inside of the movable cylinder through the oil distribution ring, the independent oil holes and the oil passages in the piston rod.

3. The heavy-duty four-station automatic tool holder for crankshaft machining according to claim 1, characterized in that: The indexing drive mechanism includes a drive motor, an external gear, and an internal gear ring; the drive motor is fixedly mounted on the top of the piston rod via a motor mounting plate, the external gear is coaxially fixed to the output shaft end of the drive motor, and the internal gear ring is fixedly disposed on the inner wall of the flange and coaxially disposed with the through hole; the external gear meshes with the internal gear ring.

4. The heavy-duty four-station automatic tool holder for crankshaft machining according to claim 3, characterized in that: It also includes a signal detection unit, which is a proximity detection switch installed at the indexing position facing the tool holder body. A positioning rod is fixed to the inside of the flange facing the proximity detection switch. The proximity detection switch is fixed to the top surface of the motor mounting plate. The proximity detection switch is connected to the tool holder control system.

5. The heavy-duty four-station automatic tool post for crankshaft machining according to claim 1, characterized in that: The meshing gear plate is fixed to the bottom of the movable cylinder by a mounting plate seat, and the mounting plate seat and the piston rod are integrally formed with splines that slide against each other.

6. The heavy-duty four-position automatic tool holder for crankshaft machining according to claim 1, characterized in that: The tool holder body has a limit bearing installed between the bottom of the through hole and the base.

7. The heavy-duty four-station automatic tool post for crankshaft machining according to claim 1, characterized in that: An O-ring is pressed between the movable cylinder body and the cylinder cover.

8. The heavy-duty four-station automatic tool post for crankshaft machining according to claim 3, characterized in that: The top surface of the cylinder cover is integrally formed with an annular reference surface. The motor fixing plate has a distance measuring hole facing the reference surface. A distance measuring unit is fixed in the distance measuring hole. The distance measuring unit is connected to the control system. The control system is also connected to an electric switch. The electric switch is connected in series to the starting circuit of the drive motor. A pressure reducing and holding valve is provided on the output side of the hydraulic system. The control circuit of the pressure reducing and holding valve is connected to the control system.

9. The heavy-duty four-station automatic tool post for crankshaft machining according to claim 8, characterized in that: The ranging unit is a laser displacement sensor.

10. The heavy-duty four-station automatic tool post for crankshaft machining according to claim 8, characterized in that: The control system obtains the real-time position of the moving cylinder through the ranging unit, and uses the real-time position as the switching node. When the meshing gear plate and the outer gear plate disengage and unlock, the pressure reducing and holding valve is automatically opened, switching to the low-pressure floating pressure holding mode. When the meshing gear plate and the outer gear plate reset to the meshing critical value, the pressure reducing and holding valve is opened again, switching to the low-pressure alignment mode, and the gear plate is pushed into the groove at a low speed with constant low pressure. After reaching the rated meshing depth, the pressure reducing and holding valve is closed, and the system switches to the full-pressure holding mode.

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