GB2189322A

GB2189322A - Component for counter-mechanism

Info

Publication number: GB2189322A
Application number: GB08609583A
Authority: GB
Inventors: Mohammed Khaleel Chowdree
Original assignee: Lucas Electrical Electronics and Systems Ltd
Current assignee: Lucas Electrical Electronics and Systems Ltd
Priority date: 1986-04-18
Filing date: 1986-04-18
Publication date: 1987-10-21
Anticipated expiration: 2006-04-18
Also published as: GB8609583D0; GB2189322B

Abstract

A composite rotary component for use in an electro-magnetically actuated counter mechanism comprising a spindle (9) moulded of a thermoplastics material reinforced by carbon fibres and containing a lubricant. The spindle is attached at one end to a rotary magnetic member (4) which rotates in cup (3). The spindle has a worm gear (11) connected via a gear(12) and drive shaft (13) to gears (G) which turn rotary counters. <IMAGE>

Description

SPECIFICATION Composite rotary component The invention relates to a composite component in an electromagnetically actuated counter mechanism, such as an automotive speedometer and/or odometer or the like.

The machine includes a rotary component including a magnetic disc which is rotated according to the distance traveiled by the wheels, and which causes rotation of individual counter discs of a speedometer or odometer. The magnet is held at one end of a spindle by a piurality of bearing parts received in a hole in the magnet and engaged therewith. The conditions of use can be arduous, for example, much heat is generated. It is time consuming and costly to make the multipart component which does not always withstand the arduous condition of service; for example, the component may become noisy in use.

There is thus a need for a rotary component which is easier to make and which is better able to withstand the conditions of use.

According to one aspect of the invention there is provided a rotary component for use in a counter mechanism, the component comprising a magnetic disc having a hole therein, one end of a thermally stable spindle received in the disc hole and in engagement with the magnet, the spindle having a worm gear thereon for engagement with counter wheels, the spindle having been moulded of a thermoplastics material reinforced by carbon fibres and containing a lubricant.

The content of carbon fibre in the thermoplastic material is preferably at least about 25% by weight for thermal stability and preferably below about 33% since otherwise the spindle will tend to become brittle. The lubricant is preferably polytetrafluroethylene, which also lends thermal stability. The content of the polytetrafluroethylene is preferably from about 5 to about 20% by weight.

The carbon fibre content may be provided in high specific modulus or low specific modulus form. The fibres may be discrete and may be randomly or directionally orientated within the thermoplastic material.

The thermoplastic material is preferably a resin such as acetal or Nylon 6.6 or a polyester, a polycarbonate or a polysulphone.

The thermoplastic material preferably also contains up to about 2% by weight of silicone or like resin.

Molybdenum sulphide may be also used. Additives may be present such as glass fibres, colourants, lubricants, antiseizure agents etc.

In order that the invention may be well understood it will now be described by way of example only with reference to the accompanying diagrammatic drawings in which Figure 1 is a view of a odometer; and Figure 2 is a sectional view of a component of the invention drawn to an enlarged scale.

The odometer is incorporated in a speedometer housing 1 as shown in Figure 1. The housing incorporates a stationary circular field plate 2 within which is a non magnetic speed cup 3 which can rotate in bearings, not shown. A plate permanent magnet 4 of disc or plate form is present within the speed cup 3 and is connected to the vehicle drive cabie, not shown. The permanent magnet 4 is rotated at the same speed as the drive cable.

The rotating magnetic flux induces eddy currents in the cup 3 and the resultant field results in a torque being applied to the cup in direct ratio to the speed of rotation of the permanent magnet 4. A pin 5 extends forward from the cup, and a needle pointer 6 at the end thereof extends over a speedometer scale 7. As the speed of the vehicle increases the permanent magnet 4 increases the magnetic drag and pulls the speed cup 3 and pointer 6 further around the scale indicating faster speed A hairspring 8 is present about the pin 5 to urge the speed cup 3 and the pointer 6 towards the zero mark on the scale when the vehicle is at rest. The permanent magnet 4 is connected by a spindle 9 to the drive cable.The pin 5 has a rearward short extension 10 which extends through the hole in the magnet and into the adjacent end of the spindle.-The spindle 9 has a worm gear 11 which engages a gear 12 a wheel to drive a drive shaft 13 connected to one of a series of gears G connected to rotary counters W having a series of digit markings 0, 1,2 9 . . . .9 in the edge thereof making up the distance counter Dl. The counters Ware arranged in line so that a complete revolution of one wheel turns the next left hand counter one tenth of a revolution. The gears also actuate a parallel set of counters making up the trip odometer D2. The spindle also has recesses 14 to throw back lubricating oil.

The component of the invention comprises the assembly of the permanent magnet 4 and a one piece injection moulded spindle 9. As shown in Figure 2 the permanent magnet 4 is a relatively thick plate 20 generally elliptical in plan having a central hole 21. The spindle 9 has at one end a grommet like portion 22 which extends through the hole 21, and has flanges 23, 24 which lie on opposite side faces of the plate about the hole 21. The grommet has a recess 25 to receive the extension 10 of the pin 5 and also a moulding cavity 26 to ensure dimensional stability. The spindle is moulded with the grommet portion 22 about the magnet plate 20 which is placed in the injection tool. A passageway 27 of generally square cross-sectional shape is present at the other end of the spindle to receive the drive cable. The spindle is one piece moulding formed of a thermoplastic material reinforced with carbon fibre and lubricant. A specific formulation for the thermoplastic material is (parts by weight)

carbon fibre 30 polytetrafluoroethylene 15 silicone resin 1 Nylon 6.6 64 100 Our evaluations have shown that the spindle injection moulded of such a formulation has a high degree of thermal stability and non brittleness as a result ofwhich it can withstand prolonged use without distortion or damage. In particular the spindle does not change substantially in shape or size during use, so that it does not cause noise.

Claims

1. A thermally stable rotary component for use in a counter mechanism, the component comprising a magnetic disc having a hole therein, one end of a thermally stable spindle being received in the disc hole and in engagement with the disc, the spindle having a worm gear thereon for engagement with counter wheels, the spindle having been moulded of a composition comprising a thermoplastics material, carbon fibres and a lubricant.

2. A component according to Claim 1, in which the carbon fibres are discrete and randomly orientated within the thermoplastic material.

3. A component according to Claim 1 or 2, in which the content of carbon fibre in the composition is from about 25% to about 33% by weight.

4. A component according to any preceding Claim, in which the lubricant is selected to provide lubricity and thermal stability.

5. A component according to Claim 4, in which the lubricant is a polytetrafluoroethylene.

6. A component according to Claim 4 or 5, in which the content of the polytetrafluoroethylene lubricant is from about 5 to about 20% by weight.

7. A component according to any preceding Claim, in which the composition also contains up to about 2% by weight of silicone or like resin.

8. A component according to any preceding Claim, in which the thermoplastic material is selected from those specified herein.

9. A component according to Claim 8, in which the thermoplastic material is a Nylon.

10. A component according to any preceding Claim, in which the composition comprises (percent by weight) chopped carbon fibres (30), polytetrafluoroethylene (15), silicone resin (1) and Nylon 6.6 (64).

11. A rotary component substantially as described and with reference to the drawing.

12. An electromagnetically actuated counter mechanism incorporating a rotary component according to any preceding Claim.