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Motor with eccentric part and pump device using the sameRelated Patent Categories: Pumps, Motor Driven, Electric Or Magnetic Motor, Reciprocating Rigid Pumping MemberMotor with eccentric part and pump device using the same description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070020125, Motor with eccentric part and pump device using the same. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to a motor having an eccentric portion which includes a rotational shaft which has an axis and supports an armature and a commutator thereon, and an eccentric portion which is eccentrically configured with respect to the axis on the rotational shaft, wherein the eccentric portion constitutes an output portion for driving an external equipment such as a pump in a hydraulic brake system of an automobile, for example. Further, the present invention also relates to a pump device which uses such a motor. BACKGROUND ART [0002] Since this type of motor or pump device is mounted on the automobile, it is desirable that the motor or the pump is miniaturized and vibrations and operation sounds thereof are reduced. [0003] To focus on the eccentric portion of the motor, conventionally, a rotational shaft is machined so as to form an eccentric shaft portion on a portion thereof, and a needle bearing or a ball bearing is joined to an outer periphery of the eccentric shaft portion. The needle bearing withstands a high load compared to the ball bearing. However, the ball bearing is disadvantageous in the miniaturization and the reduction of weight of the motor or the reduction of the vibrations and operation sounds of the motor. For example, patent literature 1 discloses a motor which uses the needle bearing and patent literature 2 discloses a motor which uses a ball bearing. [Patent Literature 1] JP-A-11-252854 [Patent Literature 2] JP-A-2000-278904 DISCLOSURE OF THE INVENTION Task to be Solved by the Invention [0004] According to the present invention, while focusing their attentions to a current situation in which a diameter of a pump or the like which is driven by way of an eccentric portion is made small and a weight of the pump is reduced, inventors have extensively studied an effective use of a ball bearing which is relatively suitable for a low load. [0005] As a result, the inventors have found that, conventionally, there has been mainly adopted a design concept that, to obtain the eccentric portion, a portion of the rotational shaft is eliminated by applying cutting to a portion of the rotational shaft thus forming an eccentric shaft portion in the eliminated portion. It is inevitable that such shaft cutting pushes up a cost. Accordingly, the inventors have challenged a unique idea that instead of forming the rotational shaft per se in an eccentric manner, the eccentric structure is provided to the whole structure including the ball bearing. MEANS FOR SOLVING THE PROBLEM [0006] According to the present invention, an eccentric portion formed on a rotational shaft is constituted as follows. That is, in place of cutting a side of a rotational shaft, an eccentric ball bearing is directly joined to a shaft portion which is constituted of a portion of the straight rotational shaft so as to obtain an eccentric portion. In other words, the eccentric portion is constituted of a shaft portion (portion of the rotational shaft) having an axis equal to an axis of the rotational shaft and the eccentric ball bearing which is joined to the shaft portion. It is most preferable that an inner side of the eccentric ball bearing having a smaller diameter is formed in an eccentric configuration. This is because that compared to a case in which an outer side of the eccentric ball bearing is formed in an eccentric configuration, the above-mentioned provision is advantageous in view of the machining of parts as well as a strength of the eccentric ball bearing. The eccentric ball bearing is constituted of an inner lace which is arranged eccentric with respect to the axis of the rotational shaft, an outer lace which is positioned outside the inner lace and has an axis equal to the above-mentioned axis, and balls which are supported between the outer lace and the inner lace. [0007] On the rotational shaft having such an eccentric portion, an armature including a coil winding portion, a commutator for supplying electricity to the armature, and the eccentric portion which constitutes an output portion are arranged in this order. The eccentric portion is served for driving a pump for a hydraulic brake system of an automobile (an automatic brake served not only for a usual anti-skid control but also for a traction control and, further, for the safe traveling, the collision prevention and the like). Accordingly, in a usual case, the armature and the commutator are housed in a motor housing and the motor housing is mounted on one side of a control unit of the hydraulic brake system. [0008] The ball bearing has the simple constitution compared to a needle bearing (for example, while a stop bushing which supports a side is necessary in the needle bearing, the stop bushing is unnecessary in the ball bearing) and hence, frictions are small whereby a motor current is low. Further, structurally, a length of the ball bearing in the rotational axis direction is short and, at the same time, the ball-bearing becomes light-weighted (particularly, a mass of the eccentric portion becomes light-weighted) and hence, the vibrations and noises can be suppressed. [0009] When the eccentric ball bearing is joined to the shaft portion which constitutes a portion of the straight rotational shaft as in the case of this embodiment, to take the effectiveness of the product into consideration from a viewpoint of durability and the like, it is necessary to reduce an output of the motor. According to an experiment, it is preferable to restrict the output of the motor to 150 W or below, or it is preferable to apply the present invention to such an output. In this respect, as an external equipment such as a pump which is driven by way of the eccentric portion, it is necessary to select a low-load equipment such as a small-diameter pump or to miniaturize a motor per se. [0010] Further, when the present invention is grasped in a form of a pump device, the pump device is configured such that the above-mentioned particular motor is used as a drive source and a plunger is brought into contact with an outer periphery of the eccentric ball bearing (that is, an outer lace of the eccentric ball bearing). The pump device, along with a linear reciprocal motion of the plunger, repeats sucking and discharging of a working liquid. The plungers are usually provided in a pair and are arranged at positions which are spaced apart from each other by 180.degree. in the circumferential direction of the eccentric ball bearing. BRIEF EXPLANATION OF THE DRAWING [0011] FIG. 1 is a front view of a profile of an embodiment of a motor according to the present invention. [0012] FIG. 2 is a cross-sectional structural view of the motor shown in FIG. 1. [0013] FIG. 3 is a side view showing one example of an eccentric ball bearing. [0014] FIG. 4 is a cross-sectional view taken along a line 4-4 of FIG. 3. EXPLANATION OF SYMBOLS [0015] 10: motor [0016] 12: motor housing [0017] 30: rotational shaft [0018] 50: eccentric ball bearing [0019] 52: inner lace [0020] 54: outer lace [0021] 55: ball [0022] 70: armature [0023] 80: commutator [0024] 100: plunger pump Continue reading about Motor with eccentric part and pump device using the same... Full patent description for Motor with eccentric part and pump device using the same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Motor with eccentric part and pump device using the same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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