GB2054860A

GB2054860A - Improvements relating to rotary speed transducers

Info

Publication number: GB2054860A
Application number: GB7925934A
Authority: GB
Original assignee: Probe Engineering Co Ltd
Current assignee: Probe Engineering Co Ltd
Priority date: 1979-07-25
Filing date: 1979-07-25
Publication date: 1981-02-18

Abstract

A transducer, designed for coupling to an automotive gearbox to give electrical pulses corresponding to the rotation of the gearbox output shaft, has a housing (1) made up from two matched halves (2a, 2b) forming a central chamber with two coaxial passages extending in opposite directions. A rotor has a shaft (12a, 12b) which rotates in these passages and a central disc (13) which spins freely between stator discs (7a, 7b) insulatedly mounted within the central chamber. The rotor and stator discs have circumferentially spaced electrically conductive zones and the stator discs are wired (10a, 10b) to the exterior where the changing capacitance due to the intervening rotor can be sensed. One end of the rotor shaft (12a) is formed as a spade (16) for engagement with a rotary element in the gearbox, and the attachment of the housing is by a union nut (18) retained by a circlip (17). <IMAGE>

Description

SPECIFICATION Improvements relating to rotary speed transducers This invention relates to rotary speed transducers, and it is particularly concerned with a device for use in conjunction with electronic taxi meters. These are tending to supersede meters with cable drive, and it is important to have a highly reliable and robust transducer to generate the pulses or other electrical information which the meter translates into the fare.

One of the major problems is heat. The gear boxes of London taxis have outlets for coupling to a taximeter, and it is desirable and convenient to fit a transducer directly to this outlet. However, their gear boxes are very much prone to overheating, and it is therefore necessary to provide a transducer that can withstand elevated temperatures.

According to the present invention there is provided a transducer for coupling to an automobile gear box to give an electrical pulse indication of speed/distance comprising a stator housing of two matched halves secured together with mirror symmetry with respect to a central transverse plane to form a central shallow cylindrical chamber and co-axial passages extending in opposite directions, normal to said plane, from said chamber; a stator assembly coaxially mounted within the chamber and having two stators spaced one on each side of the plane; a rotor having a shaft and a disc, the shaft being rotatably entered in said passages; the disc being coincident with said central plane, and the stators and rotor disc having electrically conductive zones regularly angularly spaced about their common axis; and cable connections to the conductive zones of said stators entering said chamber in and adjacent said central plane and being compression gripped between said halves; wherein one end of the rotor shaft and the associated passage are adapted to couple to a gear box outlet to mount the housing thereon with the rotor rotatable in correspondence with the gear box output speed.

The construction can be mostly of metal, with stator assembly insulatedly mounted within the central chamber by means of polytetrafluoroethylene (PTFE) rings. The cable will also generally be PTFE insulated. The shaft end that couples to the gear box may project a short distance and terminate in a spade end, to engage a slot in a rotary member within the gear box. The coupling is conveniently achieved by a union nut retained to the housing by a circlip in an external groove in a spigot forming the shaft passage. The opposite spigot may be plugged, although this plug could be removed and the opposite shaft end adapted to receive a speedometer cable.

For a better understanding of the invention one constructional form will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is an axial section of a rotary speed transducer, and Figure 2 is a diagram showing segmentation of the stators and rotor of the transducer.

The transducer has a housing 1 made up from two identical halves 2a and 2b. Each half-housing has a shallow cylindrical cup-like portion 3a, 3b and a spigot 4a, 4b extending co-axially from the centre of the portion 3a or 3b, the shape of each half in axial cross-section being generally a T.

These half-housings are fastened together by bolts 5 in mirror image symmetry with respect to a central transverse plane 6.

A stator assembly is housed in the central chamber formed by the portions 3a and 3b. It comprises two annular stators 7a and 7b which are screwed to PTFE rings Ba and 8b held spaced apart by a ring 9, the axial extent of the rings 8a, Bb and 9 matching the depth of the central chamber. PTFE insulated screened cables 1 0a and lOb enter this chamber together via cooperating recesses 1 1 a, 1 1b in the peripheral flanges of the portions 3a, 3b and when the housing is clamped together a compression grip is exerted on these cables to secure them firmly in place. The rings 8a and 8b are cut away at this zone of entry, where connections are made to the stators.

A rotor assembly comprises a shaft with portions 1 2a, 1 2b, and disc 13, the latter being symmetrically disposed between the stators, and the shaft being rotatably entered in the spigots 4a and 4b. The central portion of the shaft is thickened at 14 to provide shoulders, and between these and the housing there are thrust washers 1 spa and 1 sub.

The shaft portion 1 2a extends beyond its associated spigot 4a to terminate in a spade end 1 6. This engages a rotary member in a gear box.

The spigot 4a is formed externally with a groove near its end which receives a circlip 1 7. This retains a union nut 1 8 by which the transducer is secured to the gear box housing. The corresponding groove in the opposite spigot 4b is unused, and the outer end of the passage through that spigot is closed by a plug 1 9.

Figure 2 shows a possible segmentation of the stators and the rotor disc, each taking the form of an electrically conductive disc with five frusto segments 20 removed at regular angularly spaced intervals leaving similarly shaped land areas 21 joined at outer and inner peripherals.

The electrical arrangements will generally be the rotor grounded with an alternating voltage applied to one of the stators. The other stator is coupled to pulse detection circuitry. The action of the rotor as it spins between the stators will be to modulate the alternating voltage at a frequency corresponding to the output speed of the gear box.

It will be seen that the transducer is simple and robust, with principal parts duplicated as far as possibie for economy of manufacture.

1. A transducer for coupling to an automotive gear box to give an electrical pulse indication of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements relating to rotary speed transducers This invention relates to rotary speed transducers, and it is particularly concerned with a device for use in conjunction with electronic taxi meters. These are tending to supersede meters with cable drive, and it is important to have a highly reliable and robust transducer to generate the pulses or other electrical information which the meter translates into the fare. One of the major problems is heat. The gear boxes of London taxis have outlets for coupling to a taximeter, and it is desirable and convenient to fit a transducer directly to this outlet. However, their gear boxes are very much prone to overheating, and it is therefore necessary to provide a transducer that can withstand elevated temperatures. According to the present invention there is provided a transducer for coupling to an automobile gear box to give an electrical pulse indication of speed/distance comprising a stator housing of two matched halves secured together with mirror symmetry with respect to a central transverse plane to form a central shallow cylindrical chamber and co-axial passages extending in opposite directions, normal to said plane, from said chamber; a stator assembly coaxially mounted within the chamber and having two stators spaced one on each side of the plane; a rotor having a shaft and a disc, the shaft being rotatably entered in said passages; the disc being coincident with said central plane, and the stators and rotor disc having electrically conductive zones regularly angularly spaced about their common axis; and cable connections to the conductive zones of said stators entering said chamber in and adjacent said central plane and being compression gripped between said halves; wherein one end of the rotor shaft and the associated passage are adapted to couple to a gear box outlet to mount the housing thereon with the rotor rotatable in correspondence with the gear box output speed. The construction can be mostly of metal, with stator assembly insulatedly mounted within the central chamber by means of polytetrafluoroethylene (PTFE) rings. The cable will also generally be PTFE insulated. The shaft end that couples to the gear box may project a short distance and terminate in a spade end, to engage a slot in a rotary member within the gear box. The coupling is conveniently achieved by a union nut retained to the housing by a circlip in an external groove in a spigot forming the shaft passage. The opposite spigot may be plugged, although this plug could be removed and the opposite shaft end adapted to receive a speedometer cable. For a better understanding of the invention one constructional form will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is an axial section of a rotary speed transducer, and Figure 2 is a diagram showing segmentation of the stators and rotor of the transducer. The transducer has a housing 1 made up from two identical halves 2a and 2b. Each half-housing has a shallow cylindrical cup-like portion 3a, 3b and a spigot 4a, 4b extending co-axially from the centre of the portion 3a or 3b, the shape of each half in axial cross-section being generally a T. These half-housings are fastened together by bolts 5 in mirror image symmetry with respect to a central transverse plane 6. A stator assembly is housed in the central chamber formed by the portions 3a and 3b. It comprises two annular stators 7a and 7b which are screwed to PTFE rings Ba and 8b held spaced apart by a ring 9, the axial extent of the rings 8a, Bb and 9 matching the depth of the central chamber. PTFE insulated screened cables 1 0a and lOb enter this chamber together via cooperating recesses 1 1 a, 1 1b in the peripheral flanges of the portions 3a, 3b and when the housing is clamped together a compression grip is exerted on these cables to secure them firmly in place. The rings 8a and 8b are cut away at this zone of entry, where connections are made to the stators. A rotor assembly comprises a shaft with portions 1 2a, 1 2b, and disc 13, the latter being symmetrically disposed between the stators, and the shaft being rotatably entered in the spigots 4a and 4b. The central portion of the shaft is thickened at 14 to provide shoulders, and between these and the housing there are thrust washers 1 spa and 1 sub. The shaft portion 1 2a extends beyond its associated spigot 4a to terminate in a spade end 1 6. This engages a rotary member in a gear box. The spigot 4a is formed externally with a groove near its end which receives a circlip 1 7. This retains a union nut 1 8 by which the transducer is secured to the gear box housing. The corresponding groove in the opposite spigot 4b is unused, and the outer end of the passage through that spigot is closed by a plug 1 9. Figure 2 shows a possible segmentation of the stators and the rotor disc, each taking the form of an electrically conductive disc with five frusto segments 20 removed at regular angularly spaced intervals leaving similarly shaped land areas 21 joined at outer and inner peripherals. The electrical arrangements will generally be the rotor grounded with an alternating voltage applied to one of the stators. The other stator is coupled to pulse detection circuitry. The action of the rotor as it spins between the stators will be to modulate the alternating voltage at a frequency corresponding to the output speed of the gear box. It will be seen that the transducer is simple and robust, with principal parts duplicated as far as possibie for economy of manufacture. CLAIMS

1. A transducer for coupling to an automotive gear box to give an electrical pulse indication of speed/distance, comprising a stator housing of two matched halves secured together with mirror symmetry with respect to a central transverse plane to form a central shallow cylindrical chamber and co-axial passages extending in opposite directions, normal to said plane, from said chamber; a stator assembly co-axially mounted within the chamber and having two stators spaced symmetrically one on each side of said plane; and a rotor having a shaft and a disc, the shaft being rotatably entered in said passages, the disc being coincident with said central plane and spaced from said stators, and the stators and rotor disc having electrically conductive zones regularly angularly spaced about their common axis with electrical connections to the conductive zones of said stators from the exterior of the housing; wherein one end of the rotor shaft and the associated passage are adapted to couple to a gearbox outlet to mount the housing thereon with the rotor rotatable in correspondence with the gearbox output speed.

2. A transducer as claimed in Claim 1 , wherein the electrical connections to the stators enter the chamber in and adjacent the central plane and are compression gripped between said halves.

3. A transducer as claimed in Claim 1 or 2, wherein the stators are mounted on polytetrafluoroethylene rings, electrically insulating them with respect to the housing.

4. A transducer as claimed in Claim 1, 2 or 3, wherein the coupling to the gearbox is by means of a projecting spade end of the rotor shaft and a union nut retained by a circlip in a groove in the exterior of a cylindrical formation providing the shaft passage.

5. A transducer as claimed in any preceding claim, wherein the passage end remote from the gearbox is plugged.

6. A transducer as claimed in Claim 5, wherein the plug is removable and the adjacent shaft end is adapted to couple to a speedometer cable.

7. A transducer as claimed in any preceding claim, wherein the conductive zones are substantially sectors of circles separated by nonconductive zones of similar arc, the rotor matching both stators.

8. A transducer for coupling to an automotive gearbox substantially as hereinbefore described with reference to the accompanying drawing.