Mitsuba Corporation

Mitsuba Electric Manufacturing Co., Ltd.

Mitsuba Electric Mfg. Co., Ltd.

Tsugio Onodera

Tadao Kodaira

Yoshiaki Taniguchi

Susumu Aoki

Yasuhiro Kanai

Shigeru Takei

A power steering unit according to the invention scarcely transmits sounds and vibrations coming from the electric motor to the steering wheel of a motor vehicle. It comprises a rack-shaft,to be coupled to the guiding wheels of a vehicle, a housing A for slidably containing the rack-shaft,and holding therein a coupling section,for causing the teeth of the rack-shaft,to engage those of a pinion arranged on the steering column,linked to the steering handle of the vehicle and an electric motor,coaxially arranged around the rack-shaft,which the rotary force is transmitted to the rack-shaft,by way of a ball screw mechanism,as the steering assisting power. It further comprises another housing B, for rotatably supporting the nut section of the ball-and-screw mechanism,the housing B being provided with a fitting section to be secured to the vehicle main body. The housing A is secured to the vehicle main body by a bracket,while the housing B is secured to the vehicle main body by a fitting section

Electric power steering unit

An electric power steering unit comprises a rack-shaft,to be coupled to the guiding wheels of a vehicle, an electric motor,coaxially arranged around the rack-shaft,, a ball screw mechanism,for connecting a nut section,with a screw section,of the rack-shaft,by disposing ball,therebetween and for transmitting the rotary power of the motor,to the rack-shaft,as assisting power for steering, and a housing B comprising an angular bearing,for rotatably supporting the ball screw mechanism,. The angular bearing,comprising outer rings,pressed and fixed in an axial direction in the housing B by an outer ring fixing ring,, and balls,which is provided between the rings,and the nut,and which is in contact with the nut,at a position where a stress is not caused at the ball,by a pressure force applied to the rings

In an electric power steering device, a yoke made of a tubular member and carrying permanent magnets, and a hollow motor shaft coaxially and rotatably received in the yoke to carry a motor armature which cooperates with the permanent magnets to form an electric motor for the power steering device, a section of the yoke extending from an axial end thereof to a part thereof surrounding an axial end of the motor shaft defines an inner diameter which is greater than an outer diameter of the nut member so that the output torque of the electric motor can be measured during the course of assembling the power steering device by allowing a testing tool to be inserted from the open end of the yoke without any interference and to be applied to a suitable part of the nut member or the motor shaft. Thus, the performance of the electric motor can be directly evaluated before the power steering device is fully assembled so that any faulty electric motor can be either rejected or repaired before any further assembling work is conducted.

Electric power steering device

Armature structure for motor

An electric power steering unit comprises a rack-shaft 2 to be coupled to the guiding wheels of a vehicle, a housing A for slidably containing the rack-shaft 2 and holding therein a coupling section 6 for causing the teeth of the rack-shaft 2 to engage those of a pinion arranged on the steering column 5 linked to the steering handle of the vehicle and an electric motor 1 coaxially arranged around the rack-shaft 2, which the rotary force is transmitted to the rack-shaft 2 by way of a ball screw mechanism 3 as the steering assisting power. A nut section 19 of the ball-screw mechanism 3 is rotatably supported by a housing B separately formed from the housing A, in a state of supporting the armature shaft 11 of the electric motor 1. The rack-shaft 2 is axially movable and supported by two points of support, one at the coupling section and the other at the nut section supported by the housing B. Thus, the rack-shaft is not supported by three points such as the conventional power steering unit but supported by two points, the precision requirements for the components are eased and hence the manufacturing cost thereof is reduced.

An electric power steering unit includes a rack-shaft(2) to be coupled to the guiding wheels of a vehicle, a housing A for slidably containing the rack-shaft(2)and holding therein a coupling section(6)for causing the teeth of the rack-shaft(2)to engage those of a pinion arranged on the steering column(5)linked to the steering handle of the vehicle and an electric motor(1) coaxially arranged around the rack-shaft(2), which the rotary force is transmitted to the rack-shaft(2)by way of a ball screw mechanism 3 as the steering assisting power. A nut section(19)of the ball-screw mechanism(3)is rotatably supported by a housing(B) separately formed from the housing(A), in a state of supporting the armature shaft(11)of the electric motor(1). The rack-shaft(2) is axially movable and supported by two points of support, one at the coupling section and the other at the nut section supported by the housing(B). Thus, the rack-shaft is not supported by three points such as the conventional power steering unit but supported by two points, the precision requirements for the components are eased and hence the manufacturing cost thereof is reduced.

An electric power steering unit has an armature shaft that is free from axial forces and hence may have less rigorous requirements for its strength so that it may be manufactured more efficiently at reduced cost. It comprises a rack-shaft 2 to be coupled to the guiding wheels of a vehicle, a housing A for slidably containing the rack-shaft 2 and holding therein a coupling section 6 for causing the teeth of the rack-shaft 2 to engage those of a pinion arranged on the steering column 5 linked to the steering handle of the vehicle and an electric motor 1 coaxially arranged around the rack-shaft 2, which the rotary force is transmitted to the rack-shaft 2 by way of a ball screw mechanism 3 as the steering assisting power. A nut section 19 is linked to the armature shaft 11 of the electric motor 1 and rotatably supported by the housing B. The reaction force from the rack-shaft 2 generated by the inertia of the armature shaft 11 is transmitted to the housing B by way of the nut section 19 so that the armature shaft 11 is free from any axial force.

In a yoke arrangement for electric motors which are particularly suitable for use in electric power steering devices, the yoke comprises a first tubular portion, a second tubular portion which has a smaller diameter than the first tubular portion, and a tapered section connecting the two tubular portions. The length of the tapered sections is desired to be minimized so that the overall length of the electric motor may be minimized. Reducing the length of the tapered section and thereby increasing the taper angle of the tapered section leads to the reduction in the mechanical strength of the yoke against an axial force. To compensate for this reduction in mechanical strength, the wall thickness of the tapered section is made larger than that of the first portion. Thus, the overall mechanical strength of the yoke can be ensured with a minimum increase in the material cost and manufacturing cost. The yoke may be formed by plastic deformation such as swaging and expansion.

Yoke arrangement for an electric motor having an improved mechanical

In a method for forming the coils passed through the core slots of a motor rotor so as to keep the coils fully received in the core slots, a motor rotor, in which coils are wound around the core thereof, is received in a metallic mold die which has a die surface spaced from the outer circumferential surface of the core by a certain gap, and resin material is injected from an injection inlet provided in an axial end of the upper metallic mold die. As the resin material is injected into the cavity of the metallic mold die, the resin material first fills the gap, and then flows into the core slots from the outer periphery thereof. The flow and the pressure of the resin material causes the coils to be pushed toward the bottom regions of the core slots, and once the filled resin material is cured, the coils are firmly secured well inside the core slots. Thereby, the cost of the component parts is reduced, and the fabrication process in forming coils of motor rotors is simplified, in contrast to the conventional method which uses wedges to retain the coils in the core slots.

Method for forming coils of motor rotors

The starter motor power cables for the starter motor, having a relatively large cross sectional area and therefore involving a very little voltage drop, are used as a part of the motor drive power cables for the electric power steering system, and the length of the motor drive power cables can be thereby reduced with the net result that the overall voltage drop can be reduced, and a sufficient power output can be produced from the electric power steering system. Also, the reduction in the length of the motor drive power cables reduces the possibility of producing electromagnetic interferences.

Wiring structure for an electric power steering system

In an arrangement for testing air-tightness of an electric device having an enclosed housing, and an electric connector fitted into an opening provided in the housing, the electric connector is provided with a communication hole for communicating the interior of the electric device with the exterior, and the communication hole is adapted to close when two halves of the connector are coupled with each other. Thus, the air-tightness of electric device can be conducted when the assembly work is substantially finished whereas the conventional arrangements require an additional assembly work step which could be a potential cause for loss of air tightness. Furthermore, the present invention can be implemented simply by providing a small communication hole in the electric connector and an associated sealing arrangement without requiring any change to the existing device to be tested.

Air-tightness testing arrangement for electric devices

A composition for the copper armature coil of a electric motor which can withstand crack generation due to great temperature differentials by setting the coefficient of thermal expansion of the composition to a value between the coefficients of thermal expansion of both iron and copper.

Coating material for an armature coil of an electrical motor

A labyrinth ring having a section of L-shape is radially, inwardly and integrally projected from the inner periphery of a brush holder stay of a motor. This labyrinth ring provides a labyrinth construction in a space portion extending from brushes and a ball and roller bearing in cooperation with the brush holder stay, a commutator, a bearing holder and a distance ring. The thickness of this labyrinth ring is determined to be so thin as to increase the volume of a carbon accumulating space portion formed between the bearing holder and itself as large as possible.

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Azumamura, Japan

Tsugio Onodera