Patent Grant
7768175
The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2007-206775, filed on Aug. 8, 2007, and to Japanese Patent Application No. 2007-201928, filed on Aug. 2, 2007. The content of these applications is incorporated herein by reference in their entirety.
The present invention relates to a brush manufacturing method, a motor manufacturing method, a brush, a motor, and an electromotive power steering device that can reduce vibration caused by contact with the commutator.
Electromotive power steering devices have a steering shaft that is configured by connecting an input shaft and an output shaft through a torsion bar. A steering wheel is connected to the input shaft side of the steering shaft, and a steering mechanism is connected to the output shaft side. Then, when rotating the steering wheel in one direction, steering torque applied to the input shaft is detected by the relative angular displacement in the rotational direction of the input shaft and output shaft produced by the intervention of the torsion bar, and the motor generates rotational force corresponding to the size of the steering torque in the direction of application of the steering torque. The device is configured such that this rotational force is transmitted to the output shaft, and output force augmented in the same direction as the direction of rotation of the steering wheel is transmitted from the output shaft to the steering mechanism.
The steering assist motor has a rotational shaft and an armature winding around the rotational shaft. Then, by supplying current to the armature winding, the rotational shaft rotates by electromagnetic action and rotational force is produced. In addition, the motor has a brush and a commutator that the brush contacts; and electric power is transmitted and supplied to the armature winding through the commutator by sending electric power from an outside source to the brush and the brush making contact with the commutator.
In this kind of motor, if the contact area between the brush and commutator is large, then a large volume of frictional noise is produced from the contact surface parts causing discomfort to the operator, and therefore a motor that reduces the noise caused by the frictional noise has been disclosed in Japanese Patent Application Publication No. 2006-311639 (“JP '639”). The motor described in JP '639 sets the contact area between the brush and the commutator based on the brush and the current flowing in the brush.
The motor described in JP '639 can reduce the frictional noise, but the present inventors discovered that, compared to the conventional method of cutting away the central part of one surface of the brush and making the part other than the cut-away central part be the contact surface part, making the contact surface part be an even smaller area could reduce the frictional noise with the commutator without hindering the supply of current.
The present invention is based on this discovery, and an object of the present invention is to provide a brush manufacturing method, a motor manufacturing method, a brush, a motor, and an electromotive power steering device that reduce the contact area between the brush and the commutator, which is a conductive rotating body, and that can reduce the frictional noise at the contact surface part.
The brush manufacturing method of the present invention is a manufacturing method of a brush in which the central part of the one surface that is to make pressure contact with a rotating commutator is cut away to form contact surface parts, which make sliding contact with the aforementioned commutator on the related one surface, and a non-contact surface part, which does not make contact with the aforementioned commutator, having the steps of: molding a conductive member, in which both margins of the aforementioned one surface that are to be margins in the direction of the axis of rotation of the aforementioned commutator, are made into forms that slant away from the commutator and face a direction other than that of the aforementioned direction of the axis of rotation; and cutting away the aforementioned central part to form the aforementioned contact surface parts between the aforementioned margins.
The motor manufacturing method of the present invention is a motor manufacturing method that provides a brush in which the central part of the one surface that is to make pressure contact with a rotating commutator is cut away to form contact surface parts, which make sliding contact with the aforementioned commutator on the related one surface, and a non-contact surface part, which does not make contact with the aforementioned commutator, having the steps of: molding a conductive member to have a shape such that both margins of the aforementioned one surface, which are to be the margins in the direction of the axis of rotation of the aforementioned commutator, are made into forms that slant away from the commutator and face a direction other than that of the aforementioned direction of the axis of rotation; cutting away the aforementioned central part to form the aforementioned contact surface parts between the aforementioned margins; and installing the brush molded by the aforementioned molding process.
Moreover, the brush of the present invention is a brush that has the central part of the one surface that is to make contact with a rotating commutator cut away to have contact surface parts by which the related one surface makes sliding contact with the aforementioned commutator, and non-contact surface parts that do not make contact with the aforementioned commutator, wherein both margins of the aforementioned one surface in the direction of the axis of rotation of the aforementioned commutator are slanted away from the commutator and face a direction other than that of the aforementioned direction of the axis of rotation, and the aforementioned contact surface parts are formed between the aforementioned slanted margins and the aforementioned cut-away central part.
Moreover, the motor of the present invention is a motor containing a brush that has the central part of the one surface that is to make contact with a rotating commutator cut away to have contact surface parts by which the related one surface makes sliding contact with the aforementioned commutator, and non-contact surface parts that do not make contact with the aforementioned commutator, wherein both margins of the aforementioned one surface in the direction of the axis of rotation of the aforementioned commutator are slanted away from the commutator and face a direction other than that of the aforementioned direction of the axis of rotation, and the contact surface parts of the aforementioned brush are formed between the aforementioned slanted margins and the aforementioned cut-away central part.
Moreover, the electromotive power steering device of the present invention is an electromotive power steering device containing a motor having a brush that has the central part of the one surface that is to make contact with a rotating commutator cut away to have contact surface parts by which the related one surface makes sliding contact with the aforementioned commutator, and non-contact surface parts that do not make contact with the aforementioned commutator, and a transmission mechanism that transmits the rotation of the aforementioned motor to a steering member, wherein both margins of the aforementioned one surface in the direction of the axis of rotation of the aforementioned commutator are slanted away from the commutator and face a direction other than that of the aforementioned direction of the axis of rotation, and the contact surface parts of the aforementioned brush are formed between the aforementioned slanted margins and the aforementioned cut-away central part.
According to the present invention, the margins, which are slanted away from the commutator and face a direction other than that of the direction of the axis of rotation of the commutator, do not contact the commutator. Consequently, once the central part of the one surface that makes pressure contact with the commutator is cut away making the cut-away central part a non-contact surface part, when compared to the conventional method that takes everything other than the central part as contact surface parts, it is possible to make the area of the contact surface part smaller by the portion of the margins that have been made non-contact surface parts. For the brush and the motor that has the brush, the frictional noise with the commutator at the contact surface part can thereby be decreased by the portion that the surface area was reduced. Moreover, by reducing the frictional noise, it is possible to make an electromotive power steering device that does not make the operator feel uncomfortable because of the frictional noise.
Moreover, according to the present invention, when manufacturing the brush, a conductive member is molded such that both margins of the one surface of the brush have a shape slanted away from the commutator and face a direction other than that of the direction of the axis of rotation. A brush with a smaller contact surface area can thereby be manufactured without changing the number of processing steps compared to the conventional brush manufacturing process that takes everything other than the cut-away central part as contact surface parts.
a) is a perspective view diagram of a brush related to the present invention, and FIG. 5(b) is a top view diagram of the brush.
Preferred embodiments of the present invention will be explained in detail below using diagrams.
Both ends of the rack shaft 10 that protrudes to the exterior from both sides of the rack housing 11 are connected through separate tie rods 12 to right and left front wheels 13 as the wheels for steering. Moreover, the upper end of the pinion shaft 2 that protrudes to the exterior from the pinion housing 19 is connected through a steering shaft 3 to a steering wheel 16 as a steering member. The pinion, not indicated in the diagram, is formed as a single unit on the lower part of the pinion shaft 2 extending into the interior of a pinion housing 19, and at the part that intersects with the rack housing 11, the pinion meshes with the rack at the suitable length midway on the rack shaft 10.
The steering shaft 3 is configured by connecting an input shaft 3a and an output shaft 3b through a torsion bar 3c. The steering shaft 3 is supported so as to rotate freely in the interior of the cylindrical housing 31, and through the housing 31, is assembled to maintain an inclined position dropping to the front in the interior of the passenger compartment, which is not indicated in the diagram. The pinion shaft 2 is connected to the lower end of the output shaft 3b of the steering shaft 3 that protrudes to below the housing 31, and the steering wheel 16 is fixed on the upper end of the input shaft 3a of the steering shaft 3 that protrudes to above the housing 31.
According to the configuration above, the steering shaft 3 rotates based on the rotational operation of the steering wheel 16; this rotation is transferred to the pinion shaft 2; the rotation of the pinion shaft 2 is converted to an axial-lengthwise movement of the rack shaft 10 at the meshing part of the pinion and the rack; and this movement of the rack shaft 10 is transferred to and steers the left and right front wheels 13 through separate tie rods 12.
A torque sensor 15 that detects the steering torque applied to the steering shaft 3 by the rotational operation of the steering wheel 16 is provided midway in the housing 31 that supports the steering shaft 3. A steering-assist motor 5 is installed in a position lower than the torque sensor 15.
The steering conducted as described above is assisted, for example, by a configuration in which: the shaft core of the steering-assist motor 5 is installed roughly orthogonally to the outside to the housing 31; a worm 33 (refer to
The assist controller 6 contains a CPU (central processing unit), a ROM (read only memory), and a RAM (random access memory), and is configured such that assist control is conducted by the operation of the CPU following the control program stored in the ROM. The steering torque value detected by the torque sensor 15 and the vehicle velocity value detected by a vehicle velocity sensor 8, the motor current detection value output by a motor current sensor 50 to detect the current flowing in the steering-assist motor 5, the battery voltage value detected by a battery sensor 9 set up on the vehicle battery 90, and the like are given to the assist controller 6, and the steering-assist motor 5 is driven through the motor drive circuit 7 based on the various values.
Next, the steering-assist motor 5 will be described in detail.
In
A cylindrically shaped stator 22 is fitted and fixed into the motor housing 20, and the cylindrically shaped rotor 23 is arranged rotatably inside the stator 22. The rotor 23 has a rotor shaft 23a, and an armature winding 23b is provided around the shaft of the rotor shaft 23a. A commutator 24 is cylindrically shaped, is coaxially fitted outside the rotor shaft 23a and rotates in a single unit with the rotor shaft 23a, and multiple commutator pieces 24a are provided interposed with insulation. The commutator pieces 24a are connected to the armature wiring 23b.
As indicated in
a) is a perspective view diagram of a brush related to the present invention; and
On the top of the brush 4 are non-contact surface part 4b and non-contact surface parts 4c, which do not contact the commutator. The non-contact surface part 4b is formed between the contact surface parts 4a, and the central part of the top surface of the brush 4 is a recession curved toward the back surface (direction opposite that of the commutator to which pressure contact is made) that deepens from the contact surface parts 4a toward the center of the top surface. Moreover, the non-contact parts 4c are formed at the intersection of the top surface and the surface perpendicular to the direction of the axis of rotation of the brush 4. This region of intersection is at both margins of the top surface in the direction of the axis of rotation, and both margins bend toward the back surface and have a shape like the curvature of a removed surface.
Next, the manufacturing method of the brush 4 of the present invention will be explained.
The groove 4A has roughly the same curvature as the outer periphery of the commutator, and is a round groove formed on the top surface along the direction of the axis of rotation of the commutator. Specifically, the width and curvature of the groove 4A are set based on the shape and size, etc., of the commutator. Moreover, the groove 4A is formed roughly in the center of the top surface when viewed perpendicularly to the direction of the axis of rotation. The groove margins 4B are roughly rectangular, and are formed on both sides of the top surface when viewed perpendicularly to the direction of the axis of rotation, and the groove 4A is interposed between the groove margins 4B. The groove margins 4B are formed by forming the groove 4A on the top surface of the molded body 40.
The margins 4C are formed on both margins in the direction of the axis of rotation on the top surface, and both margins bend or slanted or are slanted toward the back surface and have a shape like the curvature of a removed surface. Specifically, the shape of the peripheral margin of both margins 4C in a direction perpendicular to the top surface is an arc facing the direction of the axis of rotation as its center, and the shape of the peripheral margin of the cross-section of both margins 4C in the direction of the axis of rotation is also an arc. When the top surface of the molded body 40 in this state makes pressure contact with the commutator, the groove 4A contacts the peripheral surface of the commutator, and the margins 4C do not make contact with the commutator. Further, as described above, the curvature of the margins 4C is set so that the margins 4C are further to the back surface side than is the groove 4A.
Next, a grinding stone 44 is used to cut away the central part of the top surface of the molded body 40 facing the axis of rotation. The grinding stone 44 is a truncated cone having a small-diameter peripheral surface and a large-diameter peripheral surface, and is moved perpendicularly to the direction of the axis of rotation from one side to the other of the top surface on which the groove margins 4B are formed (called the “cutting direction” below). Further, because of the formation of the groove 4A and the groove margins 4B, the molded body 40 gradually deepens toward the back surface in the cutting direction going from both sides of the molded body 40 toward the center. Then, the grinding stone is arranged in relation to the molded body 40 such that the peripheral surface of the small-diameter side cuts the groove margins 4B, and the peripheral surface of the large-diameter side cuts the groove 4A, which is recessed more toward the back surface than are the groove margins 4B.
As indicated in
Then, the grinding stone 44 is moved further in the cutting direction, and when cutting is ended, as indicated in
In addition, in order to have the necessary current density, the area of the contact surfaces 4a is determined in accordance with the types and amounts of materials that the brush 4 contains and the current that must be supplied to the commutator, etc. Then, in the manufacturing process of the brush 4, the diameter of the grinding stone 44 and the curvatures and sizes of the groove 4A and both margins 4C, etc., are selected so as to provide the determined area and dimensions.
Moreover, margins 4C are formed by slanting both margins of the top surface of the molded body 40 in order to reduce the surface area of the contact surfaces 4a, but the cutting process for forming the margins can be omitted by conducting the process to form both margins 4C when molding the molded body 40. Consequently, the number of steps of the manufacturing process can be reduced, and the surface area of the contact surfaces 4a can also be decreased. Moreover, in order to further reduce the contact surface, the contact surface may be cut away after cutting the central part, but in the present embodiment, the process of cutting the contact surface to make the surface areas of the contact surfaces 4a even smaller can be omitted, and the surface area of the contact surfaces 4a can still be reduced, by making the top-surface shapes of both margins 4C into arcs facing the direction of the axis of rotation as their center so that the contact surfaces 4a become long curving bands in the sliding direction.
The electromotive power steering device described in detail above is constituted such that when steering torque is applied to the steering wheel 16 by rotating the steering wheel 16 in one direction: the torque sensor 15 detects the steering torque by the amounts of relative displacement of the input shaft 3a and the output shaft 3b in the direction of rotation; the motor 5 generates rotational force corresponding to the size of steering torque in the direction of steering torque action based on the detection results of the torque sensor 15; the rotational force of the motor 5 is transmitted to the worm 33 and the worm 33 rotates; the rotational force is amplified and transmitted to the output shaft by the worm wheel 32 rotating in conjunction with the rotation of the worm 33; and the amplified rotational force is transmitted from the output shaft 3b to the steering mechanism 1 in the same direction as the direction of rotation of the steering wheel 16.
At this time, the generation of rotational moment on the brush 4 is prevented by the two contact surfaces 4a being respectively provided in the axial direction of the commutator 24 and the contact surfaces 4a contacting the peripheral surface of the commutator 24, and therefore the contact between the commutator 24 and the brush 4 is stable and vibration of the brush 4 can be reduced.
Moreover, frictional force generated on the peripheral surface of the commutator 24 can be reduced by using a brush 4 that provides non-contact surface 4b and non-contact surfaces 4c and makes the contact surface area with the commutator 24 (total surface area of the contact surfaces 4a) smaller than when the entire surface makes contact, and therefore, brush 4 vibration caused by frictional force can be reduced.
By reducing the vibration of the brush 4 in this way, the generation of vibration noise due to the vibration, the instability of contact between the commutator 24 and the brush 4, the generation of gripping vibration, and the generation of gripping noise caused by gripping vibration can all be reduced.
As described above, the brush 4, which is a part of the steering-assistance motor 5 of the electromotive power steering device, has a molded body 40 that is molded from carbon material containing, for example, copper. Then, the groove 4A, which runs along the direction of the axis of rotation on the top surface of the molded body 40, and curved margins 4C, which are on both ends of the top surface in the direction of the axis of rotation, are formed during molding. Further, by cutting away the central part of the top surface of the molded body 40 facing the direction of the axis of rotation along the direction of cutting, the brush 4 comes to have contact surfaces 4a, which contact the periphery of the commutator 24, and non-contact part 4b and non-contact parts 4c, which do not have contact with the periphery of the commutator 24.
Further, as long as the brush 4 slants at both margins of the top surface in the direction of the axis of rotation and the contact surfaces 4a are between the slanted margins and the cut-away central part, the shape, dimensions and surface area of the contact surfaces 4a are not particularly limited. For example, in the present embodiment, the contact surfaces 4a are curved as indicated in
An embodiment of a suitable example of the present invention was concretely described above, but the present invention is not limited to the embodiment described above, and the various configurations and manufacturing processes, etc., may be suitably modified.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-201928 | Aug 2007 | JP | national |
| 2007-206775 | Aug 2007 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6731040 | Tanaka et al. | May 2004 | B1 |
| 7154203 | Nakajima et al. | Dec 2006 | B2 |
| Number | Date | Country |
|---|---|---|
| 8808697 | Aug 1988 | DE |
| 102004051463 | Apr 2006 | DE |
| 102005047083 | Apr 2007 | DE |
| 813649 | May 1959 | GB |
| 55109155 | Aug 1980 | JP |
| 2006-311639 | Nov 2006 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20090033172 A1 | Feb 2009 | US |
