Electromagnetic drive unit and relay

Abstract

The present disclosure provides an electromagnetic drive unit and a relay. The electromagnetic drive unit includes a frame (4), a coil (5), a fixed adsorption member, and a movable adsorption member. The coil (5) is wound around the frame (4). The frame (4) is provided with an inner hole (41). The movable adsorption member is disposed in the inner hole (41). The fixed adsorption member is disposed at one end of the inner hole (41) and faces the movable adsorption member. Taking a plane perpendicular to the axial direction of the inner hole (41) as a projection plane, the orthographic projection area of the movable adsorption member on the projection plane is the first projection area, and the orthographic projection area of the fixed adsorption member on the projection plane is the second projection area. The second projection area is larger than the first projection area. In the present disclosure, since the fixed adsorption member can effectively absorb the leakage magnetic flux in the magnetic circuit, the electromagnetic attraction force of the electromagnetic drive unit is increased.

Description

Technical Field

[0001] The present disclosure relates to the technical field of relay manufacturing, and particularly relates to an electromagnetic drive unit and a relay.

Background Art

[0002] A relay is an electronic control element that has a control system (also called an input circuit) and a controlled system (also called an output circuit), and is usually applied to an automatic control circuit, playing roles such as automatic adjustment, safety protection, and conversion circuit in the circuit. With the expansion of the usage scenarios of relays, existing high-voltage DC relays generally require characteristics such as strong electromagnetic attraction force, low driving power, and miniaturization. A common method for improving the electromagnetic attraction force in this field is to increase the coil winding space and coil driving force of the magnetic circuit part of the relay, but this goes against the requirements of low driving power and miniaturization of the relay. Therefore, under the requirements of low driving power and miniaturization, how to improve the electromagnetic attraction force of the relay has become one of the urgent issues in this field.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Therefore, in response to the above problems, the present disclosure proposes an electromagnetic drive unit with an optimized structure, and also proposes a relay based on the electromagnetic drive unit.

Means for Solving the Problems

[0004] According to one aspect of the present disclosure, an electromagnetic drive unit includes a frame, a coil, a fixed suction member, and a movable suction member, wherein the coil is wound around the frame, the frame is provided with an internal bore, the movable suction member is positioned in the internal bore, and the fixed suction member is positioned at one end of the internal bore and faces the movable suction member. The plane perpendicular to the axial direction of the internal bore is a projection plane, the orthographic projection area of ​​the movable suction member on the projection plane is a first projection area, the orthographic projection area of ​​the fixed suction member on the projection plane is a second projection area, and the second projection area is larger than the first projection area.

[0005] According to one embodiment of the present disclosure, the fixed suction member includes a fixed core, the fixed core having a radially expanded portion whose radial dimension is greater than the radial dimension of the movable suction member, or the fixed suction member includes a fixed core and a magnetic ring sleeved around the outer circumference of the fixed core.

[0006] According to one embodiment of the present disclosure, the fixed adsorption member includes a fixed iron core and a magnetic ring sleeved around the outer circumference of the fixed iron core, wherein the orthogonal projected area of ​​the fixed iron core on the projection plane is the same as the first projected area of ​​the movable adsorption member.

[0007] According to one embodiment of the present disclosure, the present invention further includes a straight yoke plate, a U-shaped yoke, and a magnetic cylinder, wherein the yoke plate and the U-shaped yoke are fixedly connected to form a frame surrounding the coil, the magnetic cylinder is fixedly connected to the U-shaped yoke and extends toward the yoke plate, the length of the magnetic cylinder extending toward the yoke plate is less than the height of the U-shaped yoke, and a space is formed between the magnetic cylinder and the yoke plate, the magnetic cylinder is sleeved around the outer circumference of the movable adsorption member, and the radial expansion portion or magnetic ring is arranged in the space.

[0008] According to one embodiment of the present disclosure, the fixed core is an independent component, and the fixed core is fixedly connected to the yoke plate, or the fixed core and the yoke plate are integrally formed.

[0009] According to one embodiment of the present disclosure, the radially expanding portion is a tapered structure or stepped structure that contracts in a direction toward the movable suction member or toward the movable suction member.

[0010] According to one embodiment of the present disclosure, the magnetic ring has a tapered structure or a stepped structure that contracts in a direction toward the movable adsorption member or toward the movable adsorption member.

[0011] According to one embodiment of the present disclosure, the present invention further includes a sealing cylinder used to seal the movable suction member, the sealing cylinder having a flange at its opening, the flange being in contact with and fixed to the yoke plate, and the sealing cylinder being provided with a radially expanding section for housing the radially expanding portion or magnetic ring.

[0012] According to one embodiment of the present disclosure, the present invention further includes a sealing cylinder used to seal the movable suction member, wherein the sealing cylinder has a flange at its opening, the sealing cylinder is a straight cylinder with equal diameters in each axial cross-section, and the flange is in contact with and fixed to the radially expanding portion.

[0013] According to one embodiment of the present disclosure, the present invention further includes a sealing cylinder used to seal the movable suction member, wherein the sealing cylinder has a flange at its opening, the sealing cylinder is a straight cylinder with equal diameters in each axial cross-section, the flange is in contact with and fixed to the yoke plate, and the magnetic ring is sleeved and fixed to the sealing cylinder.

[0014] According to one embodiment of the present disclosure, the movable suction member has a cylindrical structure in which the diameters of each cross-section in the axial direction are equal.

[0015] According to another aspect of the present disclosure, the relay comprises a contact portion for realizing a switching function and an electromagnetic drive unit for driving the contact portion of the relay to perform a switching operation, wherein the electromagnetic drive unit is the electromagnetic drive unit described in the present disclosure.

[0016] The present disclosure has the following beneficial effects. That is, since the area of the orthographic projection of the fixed adsorption member on the projection plane perpendicular to the axial direction of the inner hole of the frame is larger than the area of the orthographic projection of the movable adsorption member on the projection plane perpendicular to the axial direction of the inner hole of the frame, the fixed adsorption member can effectively absorb the leakage magnetic flux in the magnetic circuit and increase the electromagnetic attraction force of the electromagnetic drive unit.

Brief Description of the Drawings

[0017] The above and other features and advantages of the present invention will become more apparent by describing its exemplary embodiments in detail with reference to the drawings. [Figure 1] It is a three-dimensional schematic diagram of Embodiment 1 of the electromagnetic drive unit of the present disclosure. [Figure 2] It is a cross-sectional view of Embodiment 1 of the electromagnetic drive unit of the present disclosure. [Figure 3] It is a structural development view of Embodiment 1 of the electromagnetic drive unit of the present disclosure. [Figure 4] It is a cross-sectional view of Embodiment 2 of the electromagnetic drive unit of the present disclosure. [Figure 5] It is a cross-sectional view of Embodiment 3 of the electromagnetic drive unit of the present disclosure. [Figure 6] It is a cross-sectional view of Embodiment 4 of the electromagnetic drive unit of the present disclosure. [Figure 7] It is a cross-sectional view of Embodiment 5 of the electromagnetic drive unit of the present disclosure. [Figure 8] It is a cross-sectional view of Embodiment 6 of the electromagnetic drive unit of the present disclosure. [Figure 9] It is a cross-sectional view of Embodiment 7 of the electromagnetic drive unit of the present disclosure. [Figure 10] It is a cross-sectional view of Embodiment 8 of the electromagnetic drive unit of the present disclosure. [Figure 11] It is a cross-sectional view of Embodiment 9 of the electromagnetic drive unit of the present disclosure. [Figure 12] It is a cross-sectional view of Embodiment 10 of the electromagnetic drive unit of the present disclosure. [Figure 13] It is a cross-sectional view of Embodiment 11 of the electromagnetic drive unit of the present disclosure.

Best Mode for Carrying Out the Invention

[0018] Next, with reference to the drawings, exemplary embodiments will be described in more detail. However, the exemplary embodiments can be implemented in various forms and should not be understood as being limited to the embodiments described herein. In this specification, relative terms such as "upper" and "lower" are used to describe the relative relationship between one component shown in the drawings and other components. These terms are used in this specification only for convenience, for example, in accordance with the exemplary directions shown in the drawings. It will be understood that if the device shown in the drawings is turned upside down, the component described as "upper" will become the "lower" component. Other relative terms such as "top" and "bottom" have similar meanings. When one structure is "above" another structure, it may mean that the structure is integrally formed on the other structure, or that the structure is "directly" disposed on the other structure, or that the structure is "indirectly" disposed on the other structure via another structure.

[0019] The terms "one," "a," "said," and "the" are used to indicate the presence of one or more elements / components, etc. The terms "comprising" and "having" are used to indicate an open inclusion and mean that there may be additional elements / components, etc. in addition to the listed elements / components, etc. The terms "first," "second," etc. are used only as markers and are not used as quantitative limitations on the object.

[0020] Example 1: The electromagnetic drive unit, also called the magnetic circuit part when applied to a relay, drives the contact part of the relay to perform a switching operation and is used to realize the switching function of the relay.

[0021] Referring to Figures 1-3, the electromagnetic drive unit includes a yoke plate 1, a U-shaped yoke 2, a magnetic cylinder 3, a frame 4, a coil 5, a sealing cylinder 6, a fixed suction member, and a movable suction member. In this embodiment, the fixed suction member is a fixed core 7, and the movable suction member is a movable core 8. The coil 5 is wound around the frame 4, and the frame 4 is provided with an inner hole 41. The movable core 8 is slidably positioned in the inner hole 41, and the fixed core 7 is fixedly positioned at one end of the inner hole 41 and faces the movable core 8. When current is passed through the coil 5, the fixed core 7 generates an electromagnetic attractive force toward the movable core 8, causing the movable core 8 to move toward the fixed core 7 and an operating action to occur. Furthermore, a reaction spring (not shown) is provided between the fixed core 7 and the movable core 8 to provide an elastic force to reset the movable core 8. The sealing cylinder 6 is used to seal the movable core 8.

[0022] The yoke plate 1 and the U-shaped yoke 2 are fixedly connected to form a frame-shaped magnetic yoke, which surrounds the coil 5 and closes the magnetic field lines generated by the coil 5, thereby increasing the electromagnetic attractive force. The magnetic cylinder 3 is fixed to the U-shaped yoke 2 and extends toward the yoke plate 1. The frame 4 is sleeved around the outer circumference of the magnetic cylinder 3, and the magnetic cylinder 3 is sleeved in an annular manner around the outer circumference of the movable iron core 8, meaning that the movable iron core 8 is also slidably positioned in the inner bore of the magnetic cylinder 3, allowing for further transmission of magnetic field lines through the magnetic cylinder 3. Here, the length of the magnetic cylinder 3 extending toward the yoke plate 1 (i.e., the height of the magnetic cylinder 3) is smaller than the height of the U-shaped yoke 2. Since the height of the magnetic cylinder 3 is between 1 / 2 and 4 / 5 of the height of the U-shaped yoke 2, it is preferable that a space P is formed between the magnetic cylinder 3 and the yoke plate 1.

[0023] In this embodiment, the movable core 8 has a cylindrical structure with equal diameters in each axial cross-section, and the fixed core 7 has a radially expanding portion 71 whose radial dimension is larger than that of the movable core 8. The orthographic projection area of ​​the fixed core 7 (second projection area) in a projection plane perpendicular to the inner bore 41 is larger than the orthographic projection area of ​​the movable core 8 (first projection area) in a projection plane perpendicular to the axial direction of the inner bore 41. The radially expanding portion 71 increases the diameter of the fixed core 7, which can effectively absorb leakage flux in the magnetic circuit and increase the electromagnetic attractive force of the electromagnetic drive unit.

[0024] Furthermore, in this embodiment, the radial expansion portion 71 is located in the space P between the magnetic cylinder 3 and the yoke plate 1, further absorbing leakage flux caused by the high magnetic resistance of space P and reducing magnetic flux loss. Moreover, the radial expansion portion 71 effectively utilizes the space P between the magnetic cylinder 3 and the yoke plate 1, and based on the principle of reducing magnetic flux loss, it does not increase the overall volume of the electromagnetic drive unit, thus realizing a design concept that kills two birds with one stone.

[0025] In this embodiment, the radial expansion portion 71 is a cylindrical structure that expands uniformly in the radial direction of the fixed core 7, thereby increasing the radial dimension of the fixed core 7. In other embodiments, the radial expansion portion 71 may be irregular and non-uniform, as long as the second projected area of ​​the fixed core 7 in the projection plane perpendicular to the axial direction of the inner bore 41 is larger than the first projected area of ​​the movable core 8 in the projection plane perpendicular to the axial direction of the inner bore 41.

[0026] In this embodiment, the sealing cylinder 6 has a flange 62 at its opening, which is welded to the yoke plate 1 in contact with it. The sealing cylinder 6 is further provided with a radial expansion section 61 to accommodate the radial expansion portion 71, thereby making the electromagnetic drive unit more compact.

[0027] This embodiment improves the electromagnetic attraction force while maintaining the requirements for low power consumption and miniaturization of the electromagnetic drive unit by improving the structure of the fixed iron core 7, thereby effectively utilizing the internal space of the electromagnetic drive unit.

[0028] The electromagnetic drive unit provided in this embodiment can be applied to relays and can also be applied to other electronic components such as solenoid valves that need to convert electromagnetic energy into mechanical energy.

[0029] Example 2: Referring to Figure 4, the electromagnetic drive unit provided in this embodiment is basically the same as in Embodiment 1 and has the same structure and the same technical effects. The difference is that in Embodiment 1, the fixed core 7 and the yoke plate 1 are two separate parts, and the fixed core 7 is fixedly assembled to the yoke plate 1, whereas in this embodiment, the fixed core 7A and the yoke plate 1A are an integrated structure, and the fixed core 7A is formed to protrude outward from the lower surface of the yoke plate 1A. According to this embodiment, the assembly process of the fixed core 7A and the yoke plate 1A can be omitted, and costs can be reduced.

[0030] Example 3: Referring to Figure 5, the electromagnetic drive unit provided in this embodiment is basically the same as in Embodiment 1 and has the same structure and the same technical effects. The difference is that in this embodiment, the radially expanding portion 71B of the fixed core has a tapered structure that contracts toward the direction of the movable core 8B. According to this embodiment, leakage flux can be absorbed and the amount of material used for the fixed core can be reduced, thereby reducing costs.

[0031] Example 4: Referring to Figure 6, the electromagnetic drive unit provided in this embodiment is basically the same as in Embodiment 3 and has the same structure and the same technical effects. The difference is that in this embodiment, the fixed core 7C is integrally formed with the yoke plate 1C. According to this embodiment, the assembly process between the fixed core 7C and the yoke plate 1C can be omitted, and costs can be reduced.

[0032] Example 5: Referring to Figure 7, the electromagnetic drive unit provided in this embodiment is basically the same as in Embodiment 1 and has the same structure and the same technical effects. The difference is that in this embodiment, the radially expanding portion 71D of the fixed core has a tapered structure that contracts in the direction away from the movable core 8D. According to this embodiment, leakage flux can be absorbed and the amount of material used for the fixed core can be reduced, thereby reducing costs.

[0033] Example 6: Referring to Figure 8, the electromagnetic drive unit provided in this embodiment is basically the same as in Embodiment 1 and has the same structure and the same technical effects. The difference is that in this embodiment, the radially expanding portion 71E of the fixed core has a stepped structure that contracts toward the direction of the movable core 8E. According to this embodiment, leakage flux can be absorbed and the amount of material used for the fixed core can be reduced, thereby reducing costs.

[0034] Example 7: Referring to Figure 9, the electromagnetic drive unit provided in this embodiment is basically the same as in Embodiment 1 and has the same structure and the same technical effects. The difference is that in this embodiment, the radially expanding portion 71F of the fixed core has a stepped structure that contracts in the direction away from the movable core 8F. According to this embodiment, leakage flux can be absorbed and the amount of material used for the fixed core can be reduced, thereby reducing costs.

[0035] Example 8: Referring to Figure 10, the electromagnetic drive unit provided in this embodiment is basically the same as in Embodiment 1 and has the same structure and the same technical effects. The difference is that in this embodiment, the fixed suction member includes two parts, a fixed core 7G and a magnetic ring 9, the radial dimensions of the fixed core 7G and the movable core 8G are equivalent, the magnetic ring 9 is sleeved and fixed around the outer circumference of the fixed core 7G, and the sum of the orthogonal projected areas of the fixed core 7G and the magnetic ring 9 in a projection plane perpendicular to the axial direction of the inner bore of the frame (i.e., the second projected area of ​​the fixed suction member) is larger than the first projected area of ​​the movable core 8G in a projection plane perpendicular to the axial direction of the inner bore of the frame. The magnetic ring 9 can effectively absorb more leakage flux, reduce flux loss, and thereby increase the electromagnetic attractive force.

[0036] In this embodiment, the magnetic ring 9 is sleeved and fixed to the outer circumference of the fixed core 7G, which makes the assembly and installation of the fixed adsorption member more flexible and improves its applicability. In this embodiment, the radial dimensions of the fixed core 7G and the movable core 8G are the same, which simplifies manufacturing and installation. In other embodiments, the radial dimension of the fixed core 7G may be slightly smaller than that of the movable core 8G, as long as the sum of the orthographic areas of the fixed core 7G and the magnetic ring 9 (second projection area) in a projection plane perpendicular to the axial direction of the inner bore of the frame is greater than the orthographic area of ​​the movable core 8G (first projection area) in a projection plane perpendicular to the axial direction of the inner bore of the frame. Similarly, the magnetic ring 9 effectively utilizes the space P between the magnetic cylinder 3 and the yoke plate 1G, reducing magnetic flux loss without increasing the overall volume of the electromagnetic drive unit.

[0037] In this embodiment 8, the sealing cylinder 6G is a straight cylinder with equal diameters in each axial cross-section, and the flange 62G at the mouth of the sealing cylinder 6G is in contact with and fixed to the yoke plate 1G. The magnetic ring 9 is sleeved and fixed to the sealing cylinder 6G, thereby sleeved around the outer circumference of the fixed iron core 7G. The sealing cylinder 6G of this embodiment has a simpler structure, is easier to manufacture and install, and is less expensive.

[0038] Example 9: Referring to Figure 11, the electromagnetic drive unit provided in this embodiment is basically the same as in Embodiment 8 and has the same structure and the same technical effects. The difference is that in this embodiment, the magnetic ring 9H has a tapered structure that narrows towards the movable core 8H. According to this embodiment, leakage flux can be absorbed and the amount of material used for the fixed core can be reduced, thereby reducing costs.

[0039] In other embodiments, the magnetic ring may have a tapered structure similar to the radially expanded portion of Embodiment 5, or it may have a stepped structure similar to the radially expanded portion of Embodiments 6 and 7.

[0040] Example 10: Referring to Figure 12, the electromagnetic drive unit provided in this embodiment is basically the same as in Embodiment 8 and has the same structure and the same technical effects. The difference is that in Embodiment 8, the magnetic ring 9 is sleeved and fixed to the sealing cylinder 6G, whereas in this embodiment, the magnetic ring 9M is sleeved and fixed to the fixed iron core 7M, and the sealing cylinder 6M is provided with a radial expansion section 61M similar to the radial expansion section 61 of the sealing cylinder 6 in Embodiment 1 to accommodate the magnetic ring 9M.

[0041] Example 11: Referring to Figure 13, the electromagnetic drive unit provided in this embodiment is basically the same as in Embodiment 1 and has the same structure and the same technical effects. The difference is that in this embodiment, the sealing cylinder 6N is a straight cylinder with equal diameters in each axial cross-section, and the flange 62N at the mouth of the sealing cylinder 6N is in contact with the radially expanded portion 71N of the fixed iron core 7N. The sealing cylinder 6N in this embodiment has a simpler structure, is easier to manufacture and install, and is less expensive.

[0042] Example 12: This embodiment provides a relay comprising a contact portion that realizes a switching function and an electromagnetic drive unit (or magnetic circuit portion) for driving the contact portion of the relay to perform a switching operation, wherein the electromagnetic drive unit is any of the electromagnetic drive units of Embodiments 1 to 11 above and has the same technical effects as the corresponding structure.

[0043] It should be understood that this disclosure is not limited in its application to the detailed structure and arrangement of the components described herein. Other embodiments of this disclosure are possible and can be realized and carried out in various ways. The aforementioned variations and modifications are included within the scope of this disclosure. It will be understood that the disclosure disclosed and limited herein covers all alternative combinations of two or more individual features mentioned or evident in the text and / or drawings. All of these different combinations constitute multiple alternative aspects of this disclosure. The embodiments described herein represent the best known modes for carrying out the invention and are intended to make the invention available to those skilled in the art.

[0044] This disclosure claims priority to the Chinese patent application No. 202210818439.X filed on 13 July 2022, the entirety of which is incorporated herein by reference.

Claims

1. An electromagnetic drive unit comprising a frame, a coil, a fixed suction member, and a movable suction member, wherein the coil is wound around the frame, the frame is provided with an internal hole, the movable suction member is positioned in the internal hole, and the fixed suction member is positioned at one end of the internal hole and faces the movable suction member, The projection plane is defined as a plane perpendicular to the axial direction of the internal bore, the orthographic projection area of ​​the movable suction member on the projection plane is the first projection area, the orthographic projection area of ​​the fixed suction member on the projection plane is the second projection area, and the second projection area is larger than the first projection area. The fixed suction member includes a fixed iron core, and the fixed iron core has a radially expanded portion whose radial dimension is larger than the radial dimension of the movable suction member. The electromagnetic drive unit further includes a straight yoke plate, a U-shaped yoke, and a magnetic cylinder, wherein the yoke plate and the U-shaped yoke are fixedly connected to form a frame surrounding the coil, the magnetic cylinder is fixedly connected to the U-shaped yoke and extends toward the yoke plate, the length of the magnetic cylinder extending toward the yoke plate is less than the height of the U-shaped yoke, forming a space between the magnetic cylinder and the yoke plate, the magnetic cylinder is sleeved around the outer circumference of the movable adsorption member, and the radially expanding portion is arranged in the space. The electromagnetic drive unit further includes a sealing cylinder used to seal the movable suction member, wherein the sealing cylinder has a flange at its opening, the sealing cylinder is a straight cylinder with equal diameters in each axial cross-section, and the flange is in contact with and fixed to the radially expanding portion.

2. An electromagnetic drive unit comprising a frame, a coil, a fixed suction member and a movable suction member, wherein the coil is wound around the frame, the frame is provided with an internal hole, the movable suction member is positioned in the internal hole, and the fixed suction member is positioned at one end of the internal hole and faces the movable suction member, The projection plane is defined as a plane perpendicular to the axial direction of the internal bore, the orthographic projection area of ​​the movable suction member on the projection plane is the first projection area, the orthographic projection area of ​​the fixed suction member on the projection plane is the second projection area, and the second projection area is larger than the first projection area. The fixed adsorption member includes a fixed iron core and a magnetic ring sleeved around the outer circumference of the fixed iron core. The electromagnetic drive unit further includes a straight yoke plate, a U-shaped yoke, and a magnetic cylinder, wherein the yoke plate and the U-shaped yoke are fixedly connected to form a frame surrounding the coil, the magnetic cylinder is fixedly connected to the U-shaped yoke and extends toward the yoke plate, the length of the magnetic cylinder extending toward the yoke plate is less than the height of the U-shaped yoke, forming a space between the magnetic cylinder and the yoke plate, the magnetic cylinder is sleeved around the outer circumference of the movable adsorption member, and the magnetic ring is arranged in the space. The electromagnetic drive unit further includes a sealing cylinder used to seal the movable suction member, wherein the sealing cylinder has a flange at its opening, the sealing cylinder is a straight cylinder with equal diameters in each axial cross-section, the flange is in contact with and fixed to the yoke plate, and the magnetic ring is sleeved and fixed to the sealing cylinder.

3. The electromagnetic drive unit according to claim 2, characterized in that the orthographic projection area of ​​the fixed iron core on the projection surface is the same as the first projection area of ​​the movable suction member.

4. The electromagnetic drive unit according to claim 1 or 2, characterized in that the fixed core is an independent component, and the fixed core is fixedly connected to the yoke plate, or the fixed core and the yoke plate are integrally formed.

5. The electromagnetic drive unit according to claim 1, characterized in that the radially expanding portion has a tapered structure or a stepped structure that contracts in a direction toward the movable suction member or toward the movable suction member.

6. The electromagnetic drive unit according to claim 2, characterized in that the magnetic ring has a tapered structure or a stepped structure that contracts in a direction toward the movable adsorption member or toward the movable adsorption member.

7. The electromagnetic drive unit according to claim 1 or 2, characterized in that the movable suction member has a cylindrical structure in which the diameters of each cross-section in the axial direction are equal.

8. A relay comprising a contact portion for realizing a switching function and an electromagnetic drive unit for driving the contact portion of the relay to perform a switching operation, wherein the electromagnetic drive unit is the electromagnetic drive unit described in any one of claims 1 to 3, 5, or 6.

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