JP3518444B2 - Electric motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor in which the center of gravity of a rotor is eccentric with respect to the center of rotation. 2. Description of the Related Art An electric motor for driving a load such as an oil pump in which a movable portion reciprocates linearly has an output shaft portion that is eccentric with respect to the rotation center of a rotor rotation shaft. A bearing such as a needle bearing or a ball bearing is attached to the output shaft portion, and the load is driven by transmitting the eccentric rotation of the output shaft to the movable portion of the load via the bearing. For example, in a plunger type pump, the eccentric rotation of the output shaft of the electric motor is transmitted to the plunger via a bearing attached to the output shaft portion. In some motors, the cross-sectional shape of the output shaft at the end of the rotary shaft is a D-cut shape in order to couple the load to the end of the rotor's rotary shaft with a non-rotating structure. An unbalanced portion may be formed, or a mass unbalanced portion may be formed in a portion other than the output shaft portion of the rotor for reasons of motor design. In such an electric motor, the center of gravity of the output shaft and other parts are eccentric with respect to the center of rotation, so that unbalance occurs when the rotor rotates, causing vibration and noise. In order to prevent this, a balance weight for adjusting the mass balance is attached to one end of the rotating shaft of the rotor. However, when the center of gravity position is decentered in the output shaft part or other parts, the center of gravity position and the center of gravity of the balance weight are decentered in opposite directions with respect to the rotation center of the rotor and rotate. Because it is separated by a certain distance in the axial direction of the shaft,
A bending moment is applied to the rotating shaft by the centrifugal force generated in the portion where the position of the center of gravity is eccentric and the balance weight. For this reason, it is impossible to completely remove the imbalance that occurs when the rotary shaft rotates, which may cause vibration and noise. In order to prevent this, in the conventional motor,
The example shown in FIG. 8 (the eccentric output shaft portion 1 of the rotary shaft 10 of the rotor
Eccentric direction of the center of gravity of the output shaft portion of the coil end of the armature coil 21 wound around the core 19 as in 0a and an example in which mass imbalance is caused by the bearing 13 fitted to the output shaft portion) The putty 22 is affixed at a position in the same direction as that of the output shaft portion so that the combined centrifugal force generated in the output shaft portion and the putty 22 and the centrifugal force generated in the balance weight 14 are offset. Further, in an electric motor having an eccentric output shaft proposed in Japanese Patent Laid-Open No. 7-231623, as shown in FIG. 9, a core sheet 19c for adjusting the mass balance is provided at both ends of the laminated core 19 constituting the rotor. And 19d are stacked to adjust the mass balance. In this case, the core sheet 19c disposed on the output shaft portion 10a side of the rotating shaft 10 is formed with a yoke portion (a slot near the rotating shaft) in a state of being positioned on the same side as the eccentric direction of the output shaft portion 10a. 1 to 5 holes 19 in the unexposed part)
The core sheet 19d provided with c1 and disposed on the opposite side of the output shaft portion 10a has one to five holes in the yoke portion in a state of being opposite to the eccentric direction of the output shaft portion 10a. 19d1 is provided. In this electric motor, the core sheets 19c and 1
9d is laminated in the number necessary for correcting the imbalance of the output shaft portion 10a (1 to 20), the combined centrifugal force generated in the eccentric output shaft portion 10a and the core sheet 19d, and the core sheet 19c The unbalance of the rotor is eliminated by offsetting the generated centrifugal force. Among the above conventional motors, as shown in FIG. 8, a putty for mass balance adjustment is attached to the coil end of the armature coil for mass balance adjustment of the rotor. For the attachment, the putty affixed during rotation was scattered and the balance could be lost, which was not preferable. Further, in the electric motor proposed in Japanese Patent Laid-Open No. 7-231623 (FIG. 9), it is necessary to laminate core sheets having different shapes when forming a laminated core, which makes the manufacture of the core troublesome. There was a problem. In particular, when punching and laminating a core sheet with a progressive laminating press die, two types of core sheets having different shapes between a core sheet with holes and a core sheet without holes are provided. In order to punch and stack each of the predetermined number of sheets, it is necessary to add a mechanism such as a jump cut, and there is a problem that the manufacture of the stacked mold is complicated and the cost is increased. The object of the present invention is to reduce the imbalance that occurs when the rotor rotates without attaching a putty for adjusting the mass balance to the armature coil or using an apparatus having a complicated structure when forming the laminated core. An object of the present invention is to provide an electric motor that can be corrected. The present invention provides a rotor having a core made of a laminate of steel plates, the center of gravity of which is eccentric with respect to the center of rotation, and one end of the rotation shaft of the rotor. This relates to an electric motor having a balance weight for adjusting the mass balance on the side. In the present invention, a groove for adjusting the mass balance that extends along the axial direction of the core portion of the rotor is provided on the outer peripheral portion of the core portion of the rotor over the entire axial direction of the core portion of the rotor. Then, the mass balance of the rotor is corrected by the balance weight and the groove for adjusting the mass balance. With the above configuration, the center of gravity of the core portion is biased to the side opposite to the groove for adjusting the mass balance, the resultant centrifugal force generated in the eccentric output shaft portion and the core portion, and the balance weight Balance with the centrifugal force generated in
The rotor unbalance can be corrected. Since the groove for adjusting the mass balance formed in the rotor is formed over the entire axial direction of the core portion of the rotor, all the core sheets constituting the laminated core may be of the same shape. Even when a laminated core is manufactured by punching a core sheet (steel plate) having a concave-convex fitting portion with a feed-lamination type press and sequentially stacking and fitting the fitting portions of adjacent core sheets to each other. It does not require a complicated mechanism such as a jump cut mechanism. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 to FIG. 3 show a configuration example when the present invention is applied to a DC motor with a brush.
These are the longitudinal cross-sectional views which show the whole structure of this electric motor. FIG.
(A) and (B) show the rotor of the electric motor of FIG. 1, (A) is a side view showing a half of the section, (B)
Is a front view of the rotor. FIG. 3 is a front view showing a core sheet constituting the laminated core of the rotor. In FIG. 1, reference numeral 1 denotes a case in which an iron plate is formed in a substantially cup shape. Reference numeral 2 denotes an annular permanent magnet which is fixed to the inner periphery of the peripheral wall 1a of the case 1 and constitutes the field of the motor. 1 and the permanent magnet 2 constitute a stator of the electric motor. Reference numeral 3 denotes a front cover made of an iron plate, and the front cover is fixed to the case 1 with its outer peripheral portion being press-fitted into the inner periphery of the end portion on the opening side of the peripheral wall portion of the case 1. Reference numeral 4 denotes a brush holding plate made of an insulating material fixed to the inside of the front cover 3. The brush holding plate has a pair of brush holders 5 and 5 facing in one direction.
And another pair of brush holders (not shown) facing in a direction perpendicular to the facing direction of these brush holders. The two pairs of brush holders 5 hold the brushes 6 and are biased by the coil springs 7. Since the illustrated motor is a four-pole brush motor, two pairs of brushes 6 are provided as described above, and a pair of opposed brushes of these brushes are electrically connected to the front cover 3. The other pair of brushes is electrically connected to a female input terminal fitting 8 inserted in an insulating member 801 held by the front cover 3. Reference numeral 9 denotes a rotor of the electric motor, and a portion of the rotor 9 near the end on the output shaft portion 10a side of the rotary shaft 10 is fitted in a front side bearing holding portion 3a formed in the center portion of the front cover 3. The front ball bearing 11 is supported. A rear side ball bearing 12 fitted to a rear side bearing holding portion 1b formed at the center portion of the bottom wall portion of the case 1 has an end portion on the rear side (opposite side to the output shaft portion) of the rotation shaft of the rotor 9. Is supported by The output shaft portion 10a of the rotating shaft 10 of the rotor 9 passes through the front cover 3 and is led out to the outside. In the illustrated electric motor, the output shaft portion 10a is an eccentric shaft that is eccentric with respect to the rotation center axis of the rotary shaft 10, and a bearing 13 is fitted on the eccentric shaft. Further, a balance weight 14 for mass balance adjustment is attached to a portion adjacent to the output shaft portion 10a of the rotary shaft 10 by pressure fitting. The bush 1 for preventing the bearing 13 from coming off is provided at the tip of the rotary shaft 10 on the output shaft portion 10a side.
7 is fixed. The rotating shaft 10 includes an armature 15 and a commutator 1.
In this example, the rotary shaft 10, the armature 15 and the commutator 16, the balance weight 14 for adjusting the mass balance, the bearing 13, and the bush 17 constitute the rotor 9. The armature 15 is obtained by winding an armature coil on a core 19 formed by laminating a predetermined number of core sheets 18 of steel plates having a predetermined shape as shown in FIG. In the illustrated example, the core 1 has twelve salient poles 19a, 19a,.
9 and an armature coil 21 wound around the slot of the core via an insulating bobbin 20 constitute an armature 15, and the end of each winding of the armature coil is connected to the commutator 16. . The core 19 and the commutator 16 are fixed to the rotating shaft 10 by press-fitting. Balance weight 1 for mass balance adjustment
4 is arranged closer to the armature 15 than the output shaft portion 10a (unbalanced portion), and is press-fitted and fixed to a balance weight fitting shaft portion 10b that shares the axis with the rotation center line of the rotating shaft 10. Yes. For example, as shown in FIG. 5A, the balance weight 14 is made of a metal formed in a shape in which the center of the hole 14a fitted to the balance weight fitting shaft portion 10b is eccentric with respect to the center of the outer circumference circle. A bearing having a center of gravity of the annular body decentered in a direction opposite to the eccentric direction of the axis of the output shaft portion 10a with respect to the rotation center line of the rotation shaft 10; 13
The balance weight fitting shaft 10b is fixed to the balance weight with a slight gap between them. The shape of the balance weight 14 for adjusting the mass balance is arbitrary. For example, as shown in FIG. 5B, the balance weight fitting shaft portion 10b of the rotary shaft 10 is provided.
It is also possible to use a balance weight having a shape in which the thickness of the peripheral portion of the peripheral portion of the hole 14a to be fitted is different from the thickness of the other peripheral portion. The bush 17 is made of metal, and has a slight clearance from the bearing 13 so that the rotary shaft 1
Bush fitting shaft portion 10 sharing the axis with the rotation center line of 0
c is press-fitted. A front-side ball bearing 1 (not shown) is provided on the front bearing fitting shaft portion 10d of the rotary shaft 10.
1 is fitted. Front bearing fitting shaft portion 10d,
The outer diameter of each of the balance weight fitting shaft portion 10b and the eccentric output shaft portion 10a is such that the front side ball bearing 11, the balance weight 14 and the bearing 13 can be sequentially attached from one end side of the rotating shaft.
Each outer diameter is provided in a state of being sequentially reduced. The core 19 shown in the figure is formed by sequentially laminating core sheets 18 formed by punching, and by laminating fitting portions formed on the core sheets themselves with fitting portions of adjacent core sheets. It is a core manufactured by a known progressive lamination method in which sheets are sequentially bonded. FIG. 7 shows an example of a core coupling structure manufactured by a progressive lamination method.
It was shown to. As shown in FIG. 3, the core sheet 18 constituting the core 19 has a large number (12 in the illustrated example) of salient pole portions 18a, 18a,. A concave portion 18b is formed on the outer peripheral portion of one of the salient pole portions 18a, 18a,. The yoke portion of the core sheet 18 has a fitting portion 18c punched out on one side in the plate thickness direction (in the example shown in FIG. 7, it is composed of a punched portion exhibiting a substantially cup-like shape).
Is formed. A series of core sheets 18 constituting the laminated core 19 are all formed in the same shape, and the core sheets 18 sequentially formed by punching a steel plate are formed into the recesses 1.
As shown in FIG. 7, the fitting portions 18 c formed in the adjacent core sheets are laminated with the fitting portions 18 c provided in the laminated core sheets 18 as shown in FIG.
By fitting (pressure fitting) to each core sheet 1
8 is bonded to the adjacent core sheet 18 to form a core 19. A core 19 made of a laminate of core sheets 18
A groove 19b for adjusting the mass balance is formed in the outer peripheral portion of the core by the recess 18b (see FIG. 2) extending over the entire axial direction of the core. The core 19 has a groove 19 for adjusting the mass balance.
b is positioned on the same side as the direction of deviation of the center of gravity of the balance weight 14, and the output shaft portion 10a and the eccentric output shaft portion 10a are offset by the balance weight 14 and the core mass balance adjusting groove 19b. The imbalance of the mass of the rotor by the needle bearing 13 fitted to the output shaft portion is corrected. As described above, according to the present invention, the core 19 can be formed by laminating only core sheets having the same shape. Therefore, when the core sheets are continuously punched and laminated by the progressive laminating method. In addition, a complicated mechanism such as a jump cut mechanism is not required. When the core is press-fitted and fixed to the rotating shaft of the rotor, it is necessary to position the groove 19b for mass balance adjustment in a predetermined direction with respect to the rotating shaft.
This positioning can be easily performed by using the mass balance adjusting groove 19b (for example, by fitting a positioning jig into the groove 19b), so that a special mechanism for positioning the core is provided. The rotor can be assembled without the need. Therefore, according to the present invention, it is possible to easily manufacture the rotor of the electric motor and reduce the cost of the electric motor. FIG. 4 is an explanatory diagram of a mechanical concept for explaining the mass balance of the rotor of the illustrated example. In FIG. 4, the mass unbalance of the armature 15 portion of the rotor is only due to the mass balance adjusting groove 19b formed in the core 19, and there is no mass unbalance due to the armature coil. Assume that Further, the core 19 has a mass of an unbalanced mass portion 19b ′ (part indicated by a broken line in FIG. 4) having a volume corresponding to the volume of the groove 19b imaginary at a position symmetrical to the groove 19b with respect to the rotation center of the rotation axis. Considered to be added as an unbalanced mass. In FIG. 4, the unbalanced mass generated in the rotor is the one eccentric output shaft portion 10a, the needle bearing 13, the two balance weights 14, and the three-core unbalanced mass portion 19b '. Let us consider the balance conditions by setting the mass, the center of gravity position, the amount of eccentricity of the center of gravity position, the axial distance between the positions of the center of gravity, and the eccentric load (centrifugal force) during rotation of the rotor as shown in Table 1. [Table 1] Here, if the rotational angular velocity of the rotor is ω, the eccentric load (centrifugal force) of each part is given by the following equation. Fe = Me · re · ω ² (2) Fb = Mb · rb · ω ² (3) Fc = Mc · rc · ω ² (4) The balance condition is expressed by the following equation. Fe + Fc = Fb (5) Fe · le = Fc · lc (6) In the rotor in which the value of the mass Me · re and the distance between the centers of gravity le and lc are determined, the imbalance is corrected. The value of Mb · rb of the balance weight 14 and the value of Mc · rc of the unbalanced mass portion 19b ′ corresponding to the core mass balance adjusting groove 19b are expressed by the above equation (5).
And from (6), it becomes as follows. Mb.rb = Me.re (1 + le / lc) (7) Mc.rc = Me.re.times.le / lc (8) Accordingly, the shape and dimensions of the balance weight 14 and the specific gravity of the material and the core If the dimensions of the mass balance adjusting groove 19b are selected so as to satisfy the above equation, the unbalance during rotation of the rotor 9 can be corrected. In the above example, the groove 1 for adjusting the mass balance is used.
Although only one 9b is provided, the present invention is not limited to this. If necessary, as shown in FIG. 6, a plurality of core sheets 18 (three in the example shown in FIG. 6) are provided. A recess 18b may be formed on the outer peripheral portion of each salient pole portion 18a, and a plurality of mass balance adjusting grooves 19b may be formed on the outer peripheral portion of the core. Thus, when providing the several groove | channel 19b for mass balance adjustment, this several groove | channel 19b
May be formed respectively on the outer peripheral portions of a plurality of adjacent salient pole portions, or may be formed on the outer peripheral portions of the plurality of salient pole portions at separate positions. In the above example, the balance weight 14 is an unbalanced portion (in the above example, the eccentric output shaft portion 10a).
Since the groove 19b for adjusting the mass balance is provided at a position deviated in the same direction as the direction of deviation of the center of gravity of the balance weight 14, the balance weight 14 is used as an unbalanced portion. On the other hand, when provided in a state of being positioned on the opposite side of the core 19 (when the balance weight 14 is attached to the right side of the output shaft portion 10a in FIG. 1), the mass balance adjusting groove 19b is provided with the center of gravity of the balance weight 14. It is provided at a position that is biased in the direction opposite to the bias direction. In the above description, the case where the present invention is applied to a DC motor with a brush is taken as an example. However, the center of gravity of a rotor having a core made of a laminate of steel plates is at a position eccentric to the rotation center. In the above example, the present invention can be applied to an electric motor in which a balance weight for adjusting the mass balance is attached to one end of the rotating shaft of the rotor, for example, a brushless electric motor. The balance weight for adjusting the mass balance and the outer periphery of the rotor are formed by the shaft portion and the needle bearing fitted to the output shaft portion when the center of gravity of the rotor is in an eccentric position with respect to the rotation center. The balance of the mass of the rotor is corrected by the groove for adjusting the mass balance, but it is directly connected to the axis of the output shaft portion provided on one end side of the rotation shaft of the rotor. Since the cross section is D-cut so as to exhibit a D shape, the center of gravity of the output shaft portion is eccentric, or there is an unbalance in mass in the design of the other part of the rotor. The present invention can also be applied when the center of gravity is in an eccentric position with respect to the center of rotation. When the rotor has a mass unbalance due to a manufacturing error, the unbalance is corrected separately. As described above, according to the present invention, a rotor for adjusting the mass balance is formed on the outer periphery of the core of the rotor so as to extend over the entire axial direction of the rotor. Since the design mass imbalance that occurs during the rotation of the core is corrected, it is possible to easily configure the core by stacking only the core sheets having the same shape. Therefore, according to the present invention, there is an advantage that the assembly of the rotor can be facilitated and the cost of the electric motor can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing a configuration example of an electric motor to which the present invention is applied. 2A and 2B show a rotor used in the electric motor of FIG. 1, in which FIG. 2A is a side view showing the upper half section and FIG. 2B is a front view. 3 is a front view showing an example of the shape of a core sheet constituting the core of the rotor shown in FIG. 2. FIG. FIG. 4 is a mechanical conceptual explanatory diagram of the mass balance of the rotor shown in FIG. 2; FIGS. 5A and 5B are front views showing different examples of balance weights used in the electric motor targeted by the present invention. FIG. 6 is a front view showing another example of the shape of the core sheet constituting the core of the rotor shown in FIG. 2; FIG. FIG. 7 is a cross-sectional view illustrating a coupling structure of progressive laminated cores. FIG. 8 is a side view showing a cross section of an upper half of a rotor of a conventional electric motor. FIG. 9 is a side view showing a rotor of another conventional motor, with its upper half section cut away. [Description of Symbols] 1 ... Case, 2 ... Permanent magnet, 9 ... Rotor, 10 ... Rotating shaft, 10a ... Output shaft, 10b ... Balance weight fitting shaft, 10c ... Bush fitting shaft, 10d ... Front bearing Fitting shaft portion, 11 ... front side ball bearing, 12 ... rear side ball bearing, 13 ... needle bearing, 14 ... balance weight, 15 ... armature, 1
8 ... Core sheet, 18b ... Recess, 19 ... Core, 19a ...
Salient pole part, 19b ... Groove for adjusting the mass balance.

──────────────────────────────────────────────────── ─── Continuation of Front Page (56) Reference Japanese Patent Laid-Open No. 6-6944 (JP, A) Shokai Sho 54-57402 (JP, U) Shokai Sho 59-47268 (JP, U) Shokai Sho 51- 143096 (JP, U) Shoko 49-37125 (JP, Y1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02K 15/16

Claims (1)

(57) [Claims] [Claims] [Claim 1] The center of gravity of a rotor provided with a core portion made of a laminate of steel plates is in an eccentric position with respect to the center of rotation, and one end of the rotation shaft of the rotor In the electric motor to which a balance weight for adjusting the mass balance is attached, a groove for adjusting the mass balance extending along the axial direction of the rotor on the outer peripheral portion of the core portion of the rotor is entirely in the axial direction of the core portion of the rotor. An electric motor in which an unbalance of the mass of the rotor is corrected by the balance weight and a groove for mass balance adjustment.