Machine tool power head

Abstract

The invention discloses a machine tool power head, belongs to the machine tool technology, and aims at solving the problem that an existing lead screw thread grinding machine cannot meet the high-precision machining requirement. One axial end of an outer rotor is arranged on a clamp used for clamping a workpiece and driving the workpiece to rotate, and an inner stator is fixed to a base at the other axial end of the outer rotor; the sensor is arranged between the outer rotor and the inner stator, the positioning device is directly or indirectly fixed to the base or the inner stator, and the positioning center line of the positioning device coincides with the rotating center line of the outer rotor. The theoretical error of radial run-out of the positioning device is zero, and run-out errors caused by radial run-out of the positioning device during workpiece machining are avoided, and machining errors of machined workpieces are prevented from being reflected. And through the high rotation precision of the outer rotor, the arc-second-level precise control is realized. The positioning device positions a machined workpiece, the outer rotor drives the workpiece to rotate through the clamp, the positioning device and the outer rotor are divided in function, and the machine tool power head is endowed with the capacity of being very small in positioning error and very high in rotating precision.

Description

Technical Field

[0001] The invention belongs to machine tool technology, and in particular relates to a machine tool power head, which is used for accurately positioning a workpiece and driving the workpiece to rotate so as to perform precision machining on the workpiece. Background Art

[0002] As the requirements for precision screw grinding become increasingly higher, the existing technology is difficult to meet the grinding requirements.

[0003] The existing screw grinding basically supports the center holes at both ends of the screw for positioning, and the screw is driven by the power head to rotate. Since the top rotates with the power head spindle, the runout error of the top cone surface is reflected in the processing error of the workpiece being processed. Another existing thread grinder can keep the top still, but when the power of the thread grinder drives the workpiece to rotate through a transmission mechanism such as belt drive or gear drive, the rotation accuracy of the transmission mechanism is far from enough and cannot reach the "arc second" level of accuracy. Therefore, there is no machine tool power head with very small positioning error and very high rotation accuracy in the existing technology. Summary of the invention

[0004] The task and purpose of the present invention is to overcome the defect that the existing screw thread grinder is difficult to meet the high-precision processing requirements, and to provide a machine tool power head with very small positioning error and very high rotation accuracy.

[0005] To achieve the above-mentioned purpose, the machine tool power head of the present invention includes a base, an outer rotor, an inner stator, a sensor and a positioning device. The outer rotor is mounted on the radial outer side of the inner stator to rotate around the inner stator by virtue of the rotating magnetic field of the inner stator. The invention is characterized in that: a clamp for clamping a workpiece and driving the workpiece to rotate is arranged at one axial end of the outer rotor, the inner stator is fixed to the base at the other axial end of the outer rotor, the sensor is arranged between the outer rotor and the inner stator, the positioning device is directly or indirectly fixed to the base or the inner stator, and the positioning center line of the positioning device coincides with the rotation center line of the outer rotor.

[0006] The inner stator may be fixed to the base in the axial direction, in the radial direction, or in both the axial direction and the radial direction.

[0007] The power head of the machine tool fixes the positioning device so that the positioning center line of the positioning device coincides with the rotation center line of the outer rotor, so that the theoretical radial runout error of the positioning device is 0, thereby avoiding the radial runout error of the positioning device during the processing of the workpiece and the reflection of the processing error of the processed workpiece. The high circumferential rotation accuracy of the outer rotor realizes precise control at the "arc second" level. The positioning device positions the workpiece to be processed, and the outer rotor rotates the workpiece through the fixture. The functional division of the positioning device's zero error positioning and the outer rotor's "arc second" level circumferential precise rotation gives the power head of the machine tool a very small positioning error and very high rotation accuracy.

[0008] Preferably, in order to configure the structure of the machine tool power head as required, the inner stator is directly or indirectly fixedly assembled on the base. The inner stator can be configured on the base as required to suit the structure and processing requirements of the entire machine tool.

[0009] In one embodiment, the center of the inner stator has a stator tapered hole, and the positioning device is assembled in the stator tapered hole via a tapered handle. Accordingly, the power head has a simple structure, and the concentricity of the positioning device and the outer rotor can be ensured, thereby reducing the assembly error of the machine tool power head and ensuring the processing accuracy.

[0010] In another embodiment, the base has a barrel, the center of which has a base conical hole, the positioning device is assembled in the base conical hole through a tapered handle, and the inner stator is sleeved on the radial outer side of the barrel. In this structure, there is a gap between the inner stator and the barrel of the base, which is convenient for the inner stator to dissipate heat; at the same time, the barrel and the base body are designed as an integrated whole, which increases the rigidity of the cantilevered barrel and avoids the micro-vibration error that may be generated after the positioning device is installed on the barrel.

[0011] Preferably, the outer rotor and the inner stator constitute a direct drive motor, which is conventionally referred to as a DD motor (Direct Drive Motor), and the controller controls the direct drive motor based on the feedback signal of the sensor. Accordingly, a direct drive motor of appropriate technical specifications can be selected as needed to achieve the precision requirements of the rotational drive. Specifically, the sensor is used to sense information such as the speed, position and load of the motor. The controller is responsible for controlling and regulating the motor. That is, through the feedback of the sensor, the controller supplies appropriate current to the motor according to the feedback signal of the sensor, according to the set parameters and algorithms, and accurately controls the motor. Common sensors include Hall sensors, photoelectric sensors, and magnetic encoders.

[0012] Preferably, the positioning device is a tip, and the head of the tip is an outward convex structure or an inward concave structure, so as to be suitable for supporting the ends of the workpiece to be processed in different structural forms.

[0013] Preferably, the positioning device is provided with a handle, which has a taper; the handle is positioned by being installed in the base taper hole of the base or the stator taper hole of the inner stator through static fit. The taper of the handle is preferably a Morse taper. Since the taper is very small, a certain torque can be transmitted by utilizing the principle of friction, and since it is a taper fit, it can be easily disassembled. Within a certain range of the same taper, the workpiece can be freely disassembled and assembled, and at the same time, the use effect will not be affected during operation. When the positioning device needs to be disassembled during use, reassembly after disassembly will not affect the center position of the positioning device.

[0014] Preferably, the central axis of the base cone hole of the base or the central axis of the stator cone hole of the inner stator coincides with the rotation centerline of the outer rotor. This ensures the concentricity of the positioning device, the outer rotor and the fixture, and reduces the assembly error of the machine tool power head; and the fixture is cleverly designed to reduce the possible error in the concentricity of the outer rotor and the fixture, which may cause the part processing reflection error to zero, thereby maximizing the processing accuracy.

[0015] Preferably, the positioning center of the positioning device is the geometric axis of the top, thereby ensuring that the positioning device has a regular shape and can reliably and accurately support the workpiece being processed.

[0016] Preferably, the sensor includes a reading head and an encoder or circular grating for the reading head to read dynamic signals, the reading head is directly or indirectly fixed to the inner stator and / or the base, and the encoder or circular grating is directly or indirectly fixed to the outer rotor. Accordingly, when the outer rotor rotates, the encoder or circular grating rotates accordingly and reflects the rotation dynamics of the outer rotor, the reading head reads the dynamic signal from the rotation of the encoder or circular grating, obtains the rotation data of the outer rotor, and is used to provide the rotation data of the outer rotor to the controller, and the controller controls the rotating magnetic field of the inner stator to control the rotation of the outer rotor.

[0017] The present invention provides a fixture for clamping a workpiece and driving the workpiece to rotate at one axial end of the outer rotor, the inner stator is fixed to the base at the other axial end of the outer rotor, the sensor is arranged between the outer rotor and the inner stator, the positioning device is directly or indirectly fixed to the base or the inner stator, and the positioning center line of the positioning device coincides with the rotation center line of the outer rotor. The theoretical radial runout error of the positioning device is set to 0, so as to avoid the radial runout of the positioning device during the processing of the workpiece and the runout error generated and reflected on the processing error of the processed workpiece. The high rotation accuracy of the outer rotor can achieve precise control at the "arc second" level. The positioning device positions the processed workpiece, and the outer rotor rotates with the workpiece through the fixture. The zero error positioning of the positioning device and the "arc second" level circumferential precise rotation of the outer rotor are divided into two functions, which endows the machine tool power head with very small positioning error and very high rotation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic cross-sectional structure diagram of a machine tool power head according to Embodiment 1 of the present invention;

[0019] Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of the base in FIG.

[0020] Figure 3 for Figure 1 A schematic diagram of the cross-sectional structure of the inner stator in FIG.

[0021] Figure 4 It is a schematic cross-sectional structure diagram of a machine tool power head according to Embodiment 2 of the present invention;

[0022] Figure 5 for Figure 4 A schematic diagram of the cross-sectional structure of the base in FIG.

[0023] Figure 6 A schematic diagram of the structure of the positioning device of the present invention;

[0024] Figure 7 Another structural schematic diagram of the positioning device of the present invention;

[0025] Figure 8 for Figure 1 A magnified view of part A in FIG.

[0026] Description of the numbers in the figure:

[0027] 1 outer rotor, 11 rotation center line;

[0028] 2 base, 21 base cone hole, 22 center axis, 23 cylinder, 24 vertical surface;

[0029] 3 inner stator, 31 stator cone hole, 32 center axis, 33 end surface, 34 skirt, 35 gap;

[0030] 4 sensors, 41 circular gratings, 42 reading heads;

[0031] 5 positioning device, 51 head, 52 handle, 53 positioning center line;

[0032] 6 clamps;

[0033] 7 artifacts. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention are intended to cover non-exclusive inclusions. For example, a method or product comprising a series of technical features is not necessarily limited to those technical features clearly listed, but may also include other technical features that are not clearly listed and can be included in the method or product.

[0036] The present invention is described in detail below in conjunction with specific embodiments and accompanying drawings.

[0037] Example 1

[0038] like Figure 1 As shown, the machine tool power head includes a base 2, an outer rotor 1, an inner stator 3, a sensor 4 and a positioning device 5. The outer rotor 1 is mounted on the radially outer side of the inner stator 2 to rotate around the inner stator 2 by the action of the rotating magnetic field of the inner stator 2. One axial end of the outer rotor 1 is assembled with a fixture 6 for clamping a workpiece and driving the workpiece 7 to rotate, and the inner stator 3 is fixed to the base 2 at the other axial end of the outer rotor 1. The sensor 4 is arranged between the outer rotor 1 and the inner stator 3, and the positioning device 5 is directly fixed to the inner stator 3 by a fastener, and the positioning center line 53 of the positioning device 5 coincides with the rotation center line 11 of the outer rotor 1.

[0039] The power head of the machine tool fixes the positioning device so that the positioning center line of the positioning device coincides with the rotation center line of the outer rotor, so that the theoretical radial runout error of the positioning device is 0, thereby avoiding the runout error caused by the radial runout of the positioning device during machining of the workpiece and the machining error of the workpiece being reflected. Through the high-precision rotation of the outer rotor, precise control at the "arc second" level is achieved.

[0040] The positioning device of the machine tool power head positions the workpiece to be processed, and the outer rotor rotates the workpiece through the fixture. The positioning device and the outer rotor have functional divisions, which endow the machine tool power head with very small positioning error and very high rotation accuracy.

[0041] In this embodiment, the end face 33 of the inner stator 3 is abutted against the vertical face 24 of the base and fixed by a fastener, that is, the inner stator is axially fixed to the base. In other embodiments, a third member can be provided between the end face 33 of the inner stator 3 and the vertical face 24 of the base, so that the inner stator is indirectly fastened and assembled to the base. The center of the inner stator 3 has a stator tapered hole 31, and the positioning device 5 is assembled to the stator tapered hole 31 through a tapered handle 52. Accordingly, the concentricity of the positioning device 5, the outer rotor 1, and the fixture 6 can be ensured, the assembly error of the machine tool power head can be reduced, and the processing accuracy can be ensured.

[0042] Figure 1 , Figure 4 The clamp 6 is only a schematic diagram, which only expresses that the outer rotor drives the workpiece 7 to rotate circumferentially through the "clamp", and does not represent a specific clamp structure.

[0043] In this embodiment, the outer rotor 1 and the inner stator 3 form a direct drive motor, which is usually referred to as a DD motor (Direct Drive Motor). The controller controls the direct drive motor according to the feedback signal of the sensor 4. Accordingly, a direct drive motor with appropriate technical specifications can be selected as needed to achieve the precision requirement of the rotation drive.

[0044] Sensor 4 is used to sense information such as the motor's speed, position, and load. The controller is responsible for controlling and adjusting the motor. That is, the sensor obtains and feeds back the motor's working information. The controller supplies appropriate current to the motor based on the feedback signal of the sensor, the set parameters, and the algorithm, and controls the motor accurately. Common sensors include Hall sensors, photoelectric sensors, and magnetic encoders.

[0045] In this embodiment, the positioning device 5 is provided with a handle 52, and the handle 52 has a taper. The handle 52 is fixedly mounted on the stator tapered hole 31 of the inner stator 3 by static fit to be positioned. The taper of the handle 52 and the stator tapered hole 31 is preferably a Morse taper. Since the Morse taper is very small, a certain torque can be transmitted by utilizing the principle of friction. And because it is a taper fit, it can be easily disassembled. Within a certain range of the same taper, the positioning device can be freely disassembled and assembled, and at the same time, it will not affect the use effect during operation. During use, the positioning device that has been disassembled as needed can be reinstalled without affecting the center position of the positioning device.

[0046] The central axis 32 of the stator tapered hole 31 of the inner stator 3 coincides with the rotational centerline 11 of the outer rotor 1. This ensures the concentricity of the positioning device, the outer rotor and the fixture, reduces the assembly error of the machine tool power head, and ensures the processing accuracy.

[0047] In this embodiment, the positioning device 5 is a tip, and the head 51 of the tip is as shown in FIG. Figure 6 The convex structure is shown. It is used to support the end of the concave structure of the workpiece being processed. According to the end structure of the workpiece being processed, if the end of the workpiece being processed is a convex structure, the positioning device 5 is selected Figure 7 The head 51 shown is a positioning device with a concave structure.

[0048] In this embodiment, the positioning center line 53 of the positioning device 5 is the geometric axis center line of the top, thereby ensuring that the positioning device has a regular shape and can reliably and accurately support the workpiece being processed.

[0049] In this embodiment, the sensor 4 is as follows Figure 8 As shown, it includes a reading head 42 and an encoder or circular grating 41 for the reading head to read dynamic signals. The reading head 42 is directly or indirectly fixed to the inner stator and / or the base, and the encoder or circular grating 41 is directly or indirectly fixed to the outer rotor 1. Accordingly, when the outer rotor rotates, the encoder or circular grating 41 rotates accordingly and reflects the rotation dynamics of the outer rotor. The reading head 42 reads the dynamic signal from the rotation of the encoder or circular grating 41, obtains the rotation data of the outer rotor, and is used to provide the rotation data of the outer rotor to the controller, and the controller controls the rotating magnetic field of the inner stator to control the rotation of the outer rotor.

[0050] The machine tool power head of this embodiment, when grinding a workpiece (such as a lead screw), installs the shaft end of the workpiece (such as a lead screw) on the head of the positioning device 5. Since the positioning device is fixedly connected to the inner stator, the rotation runout error of the positioning device is almost 0 when the vibration factor of the machine tool is ignored. The workpiece (such as a lead screw) is clamped by a fixture and driven to rotate. The outer rotor and the inner stator constitute a direct drive motor with precise rotation accuracy, which meets the accuracy requirements of the lead screw.

[0051] Example 2

[0052] like Figure 4 As shown, the machine tool power head also includes a base 2, an outer rotor 1, an inner stator 3, a sensor 4 and a positioning device 5 as in Example 1. Compared with Example 1, this embodiment has the following differences:

[0053] In this embodiment, the base 2 has a barrel 23, the center of which has a base tapered hole 21, and the positioning device 5 is assembled to the base tapered hole 21 of the base 2 through a tapered handle 52, and the central axis 22 of the base tapered hole 21 of the base coincides with the rotation centerline 11 of the outer rotor 1. The inner stator 3 is sleeved on the radial outer side of the barrel 23 and is directly fastened and assembled to the vertical surface of the base through its end face, that is, the inner stator 3 is axially fixed to the base 2. In this structure, the inner stator 3 is radially positioned and installed on the vertical surface 24 of the base through the radial outer side of the skirt 34 at its end, ensuring the concentricity of the inner stator 3 and the barrel 23, indirectly ensuring the concentricity of the positioning device 5 and the outer rotor 1, reducing the assembly error of the machine tool power head, and ensuring the processing accuracy.

[0054] In this embodiment, there is a gap 35 between the inner stator 3 and the barrel 23 of the base to facilitate heat dissipation of the inner stator; at the same time, the barrel and the base body are integrated into one design to increase the rigidity of the overhanging barrel and avoid micro-vibration errors that may occur after the positioning device is installed on the barrel.

[0055] In this embodiment, the reading head 42 is fixed directly or indirectly to the base.

[0056] The rest of the structure of this embodiment is the same as that of Embodiment 1 and will not be described in detail.

[0057] The machine tool power head of this embodiment also installs the shaft end of the workpiece (such as a lead screw) on the head of the positioning device 5 when grinding the workpiece (such as a lead screw). Since the positioning device is fixedly connected to the base, the rotation runout error of the positioning device is almost 0 when the vibration factor of the machine tool is ignored. The workpiece (such as a lead screw) is clamped by a fixture and driven to rotate. The outer rotor and the inner stator constitute a direct drive motor with precise rotation accuracy, which meets the accuracy requirements of the lead screw.

[0058] In the aforementioned embodiments, the center is used as an example to illustrate the support and positioning of the workpiece by the positioning device. In other embodiments, positioning devices of other structural forms equivalent to the center can be selected to support and position the workpiece.

Claims

1. A machine tool power head, comprising a base (2), an outer rotor (1), an inner stator (3), a sensor (4) and a positioning device (5), wherein the outer rotor (1) is mounted on the radially outer side of the inner stator (2) to rotate around the inner stator (2) by virtue of the rotating magnetic field of the inner stator (2), and wherein: A clamp (6) for clamping a workpiece and driving the workpiece (7) to rotate is arranged at one axial end of the outer rotor (1); the inner stator (3) is fixed to the base (2) at the other axial end of the outer rotor (1); the sensor (4) is arranged between the outer rotor (1) and the inner stator (3); the positioning device (5) is directly or indirectly fixed to the base (2) or the inner stator (3); and the positioning center line (53) of the positioning device (5) coincides with the rotation center line (11) of the outer rotor (1).

2. The machine tool power head according to claim 1, characterized in that: The inner stator (3) is directly or indirectly fixedly assembled on the base (2) in the axial direction and / or radial direction.

3. The machine tool power head according to claim 1 or 2, characterized in that: The inner stator (3) has a stator tapered hole (31) at its center, and the positioning device (5) is assembled in the stator tapered hole (31) via a tapered handle (51).

4. The machine tool power head according to claim 1 or 2, characterized in that: The base (2) has a cylindrical portion (23), the center of which has a base tapered hole (21), the positioning device (5) is assembled in the base tapered hole (21) via a tapered handle (52), and the inner stator (3) is sleeved on the radial outer side of the cylindrical portion (23).

5. The machine tool power head according to claim 1, characterized in that: The outer rotor (1) and the inner stator (3) form a direct drive motor, and the controller controls the direct drive motor according to the feedback signal of the sensor.

6. The machine tool power head according to claim 1, characterized in that: The positioning device (5) is a tip, and the head (51) of the tip is an outward convex structure or an inward concave structure.

7. The machine tool power head according to claim 6, characterized in that: The positioning device (5) is provided with a handle (52) having a taper; the handle (52) is positioned by being installed in a base tapered hole (21) of a base (2) or a stator tapered hole (31) of an inner stator through static fit.

8. The machine tool power head according to claim 7, characterized in that: The central axis (22) of the base tapered hole (21) of the base (2) or the central axis (32) of the stator tapered hole (31) of the inner stator (3) coincides with the rotation center line of the outer rotor (1).

9. The machine tool power head according to any one of claims 6 to 8, characterized in that: The positioning center line (53) of the positioning device (5) is the geometric axis center line of the top.

10. The machine tool power head according to claim 1, characterized in that: The sensor (4) comprises a reading head (42) and an encoder or circular grating (41) for the reading head (42) to read dynamic signals, wherein the reading head (42) is directly or indirectly fixed to the inner stator (3) and / or the base (2), and the encoder or circular grating (41) is directly or indirectly fixed to the outer rotor (1).

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