Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1984-08-27
1987-05-05
Salce, Patrick R.
Electrical generator or motor structure
Dynamoelectric
Rotary
310256, H02K 7106, H02K 102
Patent
active
046635505
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an electric motor with a DC brake having a brake mechanism which is disengaged upon being excited by a direct current, more particularly to an improvement of the shaft structure of the motor.
BACKGROUND ART
A motor with built-in brake having a brake mechanism associated with the rotor shaft has conventionally been used. The brake mechanism of a motor with a built-in brake is constituted so that the rotation of the rotor is braked by pressing a brake pad with a spring pressure against a brake disk secured to the rotor shaft. The rotor is released by disengaging the brake pad from the brake disk through the excitation of a DC electromagnet. Such a brake mechanism includes a brake disk, a brake pad, a braking spring or springs, and a DC electromagnet for disengaging the brake is disposed coaxially with the rotor within a case at the front end or at the rear end of the motor. In such a brake mechanism, the DC electromagnet is disposed near the rotor shaft. Therefore, a leakage flux flows as far as to the part of the rotor shaft extending outside the motor when the rotor shaft is formed of a material, such as a carbon steel, which is easily workable and has high mechanical strength and magnetic conductivity. Consequently, when such an electric motor with a DC brake is employed as the driving source of a machine tool, powder of magnetic materials, such as iron powder, adheres to the projecting part of the rotor shaft, adversely affecting the mechanical connection between the projecting part of the rotor shaft and the associated driven body. When a revolution detector is provided on the rotor shaft of the motor for the servocontrol of the motor, the leakage flux adversely affects the revolution detector by causing errors in detecting revolutions and deteriorating the detecting accuracy. Accordingly, in some cases, a rotor shaft of a nonmagnetic material, such as a stainless steel, is employed in an electric motor with a DC brake. However, nonmagnetic materials, including stainless steels, in general are hard to work. It is difficult and costly to work such a material to form a rotor shaft. In addition, nonmagnetic materials are comparatively expensive.
DISCLOSURE OF THE INVENTION
Accordingly, it is an object of the present invention to provide an electric motor with a DC brake eliminating the above-mentioned disadvantages, having a rotor shaft formed of two parts, namely, a part formed of a nonmagnetic material and a part formed of a free cutting metal, joined together by a recently developed pressure welding method.
According to the present invention, there is provided an electric motor with a DC brake equipped on the rotor shaft thereof with a brake mechanism adapted to be disengaged when excited by DC current, in which part of the rotor shaft extending through and outward from the brake mechanism is formed of a nonmagnetic material and the other part, i.e., the part extending within the rotor, is formed of a free cutting metal material and both the parts of the rotor shaft are connected coaxially and integrally. The free cutting metal material applicable to the rotor shaft is a machine structural carbon steel or a chromium-molybdenum steel, and the nonmagnetic material is a stainless steel.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of an electric motor with a DC brake, embodying the present invention, showing the general constitution of the same;
FIG. 2 is a sectional view of an electric motor with a DC brake embodying the present invention, showing the constitution of the same; and
FIG. 3 is a schematic diagram of another electric motor with a DC brake embodying the present invention, showing the general constitution of the same.
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows the general constitution of a preferred embodiment of an electric motor with a DC brake of the present invention equipped with a DC electromagnetic brake disposed in the front part of the motor. Referring to FIG. 1, a DC electromagnetic brake 10 an
REFERENCES:
patent: 3037133 (1962-05-01), Peach
patent: 3711009 (1973-01-01), Kuzuya et al.
patent: 4491753 (1985-01-01), Kumatani
Amemiya Yoichi
Kawada Shigeki
Sogabe Masatoyo
Sugahara Katsuya
Fanuc Ltd
Rebsch D. L.
Salce Patrick R.
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