GB2194392A

GB2194392A - A miniature motor fitted with a speed governor

Info

Publication number: GB2194392A
Application number: GB08713473A
Authority: GB
Inventors: Kazuo Okada; Keisuke Ebihara
Original assignee: Mabuchi Motor Co Ltd
Current assignee: Mabuchi Motor Co Ltd
Priority date: 1986-06-09
Filing date: 1987-06-09
Publication date: 1988-03-02
Also published as: KR880001419U; JPS62198860U; GB8713473D0; KR900008924Y1; CN87104183A

Abstract

The open end of the motor case 1 is closed by a cover 2 having a hole 3 at a predetermined location for access to adjustment reactor on circuit hoard 4, and a vibration-damping and insulating member 10 is adapted to be fitted to the cover 2 so that one of a plurality of notches 11 is aligned with the hole on the cover, to enable the passage of an adjusting tool therethrough to adjust the governor in the motor. The plurality of notches 11 are provided at predetermined positions in the vibration-damping and insulating member on the perimeter of a circle to minimise the need to specifically orient the member to achieve such alignment. <IMAGE>

Description

SPECIFICATION Miniature motor fitted with speed governor This invention relates generally to miniature motors, particularly electric motors, with speed governors. Specifically, it relates to a miniature motor fitted with a speed governor in which a vibration-damping and insulating member to be fitted to the inside of a cover is provided.

In general, a governor circuit for a miniature motor fitted with a speed governor (hereinafter referred to as a governor motor) is mounted on a cover or shield case. A vibration-damping and insulating member is provided between the printed circuit board and the cover or shield case for vibration-damping and insulating purposes. A very soft and resilient material, such as sponge rubber, is usually used as the material of the vibration-damping and insulating member.

The governor circuit of a typical governor motor is adjusted, after the motor has been assembled, by inserting the tip of a screw driver or like instrument through a hole in the cover to adjust a semi-fixed resistor mounted on a printed circuit board. In order to reach a resistance-adjusting position on the printed circuit board the screw driver tip has to be passed through a notch provided on the vibration-damping and insulating member interposed between the printed circuit board and the cover. It is necessary, therefore, to match the position of the hole in the cover with the position of the notch on the vibration-damping and insulating member and the resistance-adjusting position on the printed circuit board.

Known vibration-damping and insulating members of the conventional type, however, have a single notch provided at a predetermined location. Thus, when fitting the vibrationdamping and insulating member on the cover, the hole on the cover has to be adjusted with the notch on the vibration-damping and insulating member. This involves an additional assembly step, leading to lower assembly efficiency and various unwanted problems, including the risk of misma,tching after assembly.

According to the present invention, a miniature motor comprises a motor case substantially closed at the end; a motor shaft extending from said one end towards the opposite open end; a cover clpsing said open end; a vibration-damping and insulating member fitted on the inside of the cover; and a speed governor disposed within the motor with the damping and insulating member between the governor and the end of the cover, wherein the end of the cover is formed with an opening therein at a predetermined location, and the damping and insulating member has a plurality of notches arranged on the circumference of a circle around the centre of the cover of radius equal to spacing of said opening from the cover centre.Normally, the notches in the damping and insulating member comprise a plurality of circumferential slots and a plurality of radial slots which intersect the circumferential slots.

In preferred embodiments of the invention, the damping and insulating member comprises a disc with an irregular outer circumferential surface, irregularities on said surface making contact with an inner circumferential surface of the cover. This facilitates mounting of the damping and insulating member in the cover, and the attachment of the cover in assembly of the motor.

The invention will now be described by way of example and with reference to the accompanying drawings wherein: Figure 1A is a cross-sectional side view of a motor embodying this invention; Figure 1B is an end view of the motor cover of Fig. 1A; Figure 2 is a perspective view of the motor of Figs. 1A and 1B illustrating how the governor thereof is adjusted; Figure 3A is a perspective view of a printed circuit board for use in the motor of Figs. 1A and 1 B; Figure 3B is a perspective view of the vibration-damping member shown in Fig. 1B; and Figure 4 is an end view of a vibration-damping member of the type used prior to this invention.

The general construction of the motor shown in Fig. 1A is essentially the same as that of known governor motors, and will not be described in detail. A motor case has a cover 2, and supports a rotor 13 on a bearing 14 at either end thereof. One bearing 14 is mounted directly in the case 1; the other in an end bell cap 18. The rotor is mounted on a shaft 20 which also carries a commutator 15 engaged by brushes 19 connected to terminals 16. The rotor rotates between magnets 12 mounted in the case 1 in the usual way, and the cover is formed with a window 17.

In the illustrated embodiment of the invention, the cover 2 has a resistance-adjusting hole 3 through which access may be had to a printed circuit board 4 by a screw driver 5, as shown in Fig. 2. The screw driver 5 passes through an adjusting hole 7 in the circuit board 4, and can adjust a resistor 6 which is part of a governor circuit 8. A vibration-damping and insulating member 10 is fitted to the cover 2 and serves as a means to stabilise and insulate the governor circuit mounted on the printed circuit board 4.

As shown in Fig. 1B, the vibration-damping and insulating member 10 has a plurality of notches 11 at predetermined positions on a circle, whose radius corresponds to the distance of the resistance-adjusting hole 3 from the centre of the cover 2. In the embodiment shown, the notches are formed by circumferential slots in the member 10, and a plurality of radial slots which intersect therewith.

Fig. 2 shows how the governor circuit of the governor motor is adjusted, after as- sembly, by inserting the tip of the screw driver 5 into the resistance-adjusting hole 3 provided on the cover 2. As will be apparent from Figs. 3A and 3B, the tip of the screw driver 5 inserted into the hole 3 on the cover 2 is first passed through any of the notches 11 on the vibration-damping and insulating member 10. The tip of the screw driver 5 can then reach through the resistance-adjusting hole 7 on the printed circuit board 4 to adjust the semi-fixed resistor 6 provided thereon.

The damping and insulating member 10 shown Figs. 1B and 3B has an irregular outer circumferential surface which engages the inner surface of the cover 2 and serves to hold the member 10 in place in the cover 2.

The surface defines an undulating curve in plan view, as shown in Fig. 1B, successive peaks making contact with the inner periphery of the cover. Normally the outer diameter de fined by these peaks is slightly larger than the inner diameter of the cover to ensure a fric tion fit which holds the member 10 in posi tion.

Fig. 4 shows a known damping and insulat -ing member 10 with a single notch 9. The use of this member requires it to be specifi cally positioned during assembly of the motor to align the notch 9 with the hole 3, which involves additional assembly time.

As will be apparent from the above, the invention substantially reduces and can even eliminate the need to orient the damping and insulating member during assembly of the mo tor to enable adjustment of the governor cir cuit. In Fig. 1B four circumferential slots are shown, with small regions of the member 10 therebetween. Thus, the screw driver 5 or like instrument can easily penetrate the member 10 unless the hole 3 is disposed directly over one of these small regions. However, it should be appreciated that these small regions may be very small indeed, to the extent of being breakabJe by reasonable pressure on the screw driver 5 if the hole 3 is disposed di rectly thereover. In the assemble motor of course, the member 10 is sandwiched be tween- the circuit board 4 and the end of the cover 2, so the actual separation of the mem ber 10 into a central disc and an outer annu lus is of little consequence.

Claims

1. A miniature motor comprising a motor case substantially closed at one end; a motor shaft extending from said one end towards the opposite open end; a cover closing said open end; a vibration-damping and insulating member fitted on the inside of the cover; and a speed governor disposed within the motor with the damping and insulating member be tween the governor and the end of the cover, wherein the end of the cover is formed with an opening therein at a predetermined location, and the damping and insulating member has a plurality of notches arranged on the circumference of a circle around the centre of the cover of radius equal to spacing of said opening from the cover centre.

2. A miniature motor according to Claim 1 wherein the notches in the damping and insulating member comprise a plurality of circum -ferential slots and a plurality of radial slots which intersect the circumferential slots.

3. A miniature motor according to Claim 1 or Claim 2 wherein the speed governor comprises a governor circuit mounted on a printed circuit board, which board has a hole through which to adjust the resistance of a resistor of said governor circuit on the other side thereof, the hole being aligned with the opening in the cover.

4. A miniature motor according to any preceding claim the damping and insulating member comprises a disc with an irregular outer circumferential surface, irregularities on said surface making contact with an inner circumferential surface of the cover.

5. A miniature electric motor substantially as described herein with reference to Figs. 1 A to 3B of the accompanying drawings.