GB1597902A - Ignition distributors for internal combustion engines - Google Patents

Description

(54) IGNITION DISTRIBUTORS FOR INTERNAL COMBUSTION ENGINES (71) We, FORD MOTOR COMPANY LIMITED, of Eagle Way, Brentwood, Essex CM13 3BW, a British Company, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to ignition distributors for internal combustion engines.

In recent years there has been many proposals for replacing the contact breaker points traditionally used in ignition distributors with "breakerless" systems which act to detect engine timing by means of magnetic or optical pick-ups cooperating with slots or other discontinuities in a member driven by a distributor shaft. Several such systems are in commercial use and provide a satisfactory performance; however, these are largely based on minimal modification of conventional distributor designs, and the possibility of exploiting the advent of breakerless systems to simplify and cheapen distributor design has not been exploited.

There have also been proposals for a more radical approach to i.c. engine ignition by using electronic sensors and processing to replace centrifugal and vacuum mechanisms in the variation of timing. The cost and complexity of such an approach is at present unacceptably high for volume production.

A primary object of this invention is therefore to provide a breakerless distributor which is simple and cheap to manufacture and service.

The present invention accordinglpro- vides an ignition distributor including a base, a distributor cap closing the base and having a central h.t. input and spaced peripheral h.t. outputs, a rotor assembly for sequentially providing an h.t. path between said input and said outputs, a shaft rotatable by an engine and extending within the base, a rotary member arranged to be rotated by the shaft, electronic means cooperating with the rotary member to provide timing pulses, and centrifugal means interposed between the shaft and the rotary member to advance the rotary member relative to the shaft as the shaft speed increases, the centrifugal means comprising a pair of weights each eccentrically mounted on a respective pivot on top of the rotary member the rotor assembly being secured to rotate with the rotary member by means of a pair of screws each received in a screwthreaded bore of a respective pivot.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of a distributor embodying the invention; Figure 2 is an assembled view of certain parts of Figure 1, shown in longitudinal cross-section; Figure 3 is a plan view of a shaft assembly on the line III-III of Fig. 1; and Figure 4 is a scrap sectional view on the line IV-IV of Figure 1.

The distributor includes a base 10, a shaft assembly 16, a rotor assembly 18, a distributor cap 20, a vacuum actuator 22, a sensor unit 24, and an electronics module 26.

The distributor operates in conjunction with a conventional ignition coil (not shown). The low tension side of the coil is controlled by the electronics module 26 which derives its timing information from the sensor unit 24. The sensor unit 24 as will be described in more detail, is a magnetic sensor cooperating with a rotating slotted vane 28.

With particular reference to Figure 2 which shows the relationship of the body 10, shaft assembly 16 and rotor assembly 18, the shaft assembly comprises a shaft 30 journalled in the body 10 by a bearing 32. A drive pinion 34 is secured to the lower end of the shaft 30 by a pin 36. The lower end of the housing 10 is secured to an engine in known manner, and the drive pinion 34 is driven from the engine in the usual way. The slotted vane 28 is rotatably mounted on the shaft 30 by means of a bearing 38. Centrifugal weights 40 see also Figure 3) are mounted on pivots 42 secured by peening to a plate 44 which is also carried by the bearing 38. The weights 40 have cam surfaces 40a which bear on an arm 45 secured to the shaft 30.Outward movement of the weights 40 is restrained by a primary and a secondary return spring 46, 48 respectively each exerting tension between a post on the arm 45 and an upturned tab on the plate 44.

Thus, as the speed of the shaft 30 rises, the weights 40 move outwardly against the bias of the return springs and, by a camming action of the surfaces 40a against the arm 45, advance the vane 28 relative to the shaft 30.

This construction is simple and cheap to manufacture, and the position of the centrifugal weights and springs on top of the vane gives ease of access for lubrication.

The distributor cap 20 is of conventional form, having a central high tension input and equispaced peripheral h.t. outputs. The rotor assembly 18 comprises a plastics rotor 70 carrying a metallic strip 72 for conducting h.t. current from the cap input to its outputs sequentially. The rotor assembly is arranged for movement with the vane 28, and for this purpose is secured thereto by means of screws 74 passing through the assembly 18 to engage in screw threads formed m the weight pivots 42. The use of the pivots to receive the screws 74 saves space on the top of the shaft assembly 16, and this allows larger centrifugal weights to be used for a given overall size of distributor and consequently a better control of advance and retard characteristics.

The sensor unit (Figure 4) comprises a permanent magnet 50 and a Hall effect device sensor 52 positioned radially outwardly of the magnet 50. Pole pieces 54 are provided to form a magnetic return path.

The vane 28 rotates between the magnet 50 and the sensor 52. As each slot of the vane 28 passes between them, the magnetic flux passing through the sensor 52 increases sharply, producing an output pulse which is processed by amplifying and switching circuits in the electronics module 26 to control the l.t. supply to the coil. Such processing circuitry is well known in the art and will not be described.

The sensor unit 24 is mounted to the underside of a mounting plate 56 in the position indicated in broken lines in Figure 1.

The mounting plate 56 is journalled for movement through an arc on the outer peripheral surface of the bearing 32 and is secured thereon by a washer 58 and circlip 60. The mounting plate 56, and thus the sensor unit 24, is moved in advance and retard directions around the shaft 30 by the vacuum actuator 22.

The base 10 has a flat transverse portion 12 adjacent the bearing 32, which portion is apertured at 62. The aperture 62 is aligned with the rest position of the sensor unit 24 and has a shape commensurate with but slightly larger than the underneath plan view of the sensor unit 24. The latter may therefore be inserted into and removed from the base in a direction parallel to the shaft 28 without removing any of the other parts, and secured in position for example by screws (not shown) driven into tapped bores 64 in the mounting plate, or by means of a snap fit. The electronics module 26 is suitably fastened to the base portion 12 to cover the aperture 62.

Thus, in the event of a malfunction in the electronics parts, these may be removed and replaced without disassembly of any other part of the distributor and hence without disturbance of the ignition timing.

The sensor unit 24 and module 26 are interconnected by cables 64 passing through the aperture 62.

The invention may, of course, equally be applied to a distributor in which the sensor unit and vane or other rotary member take different forms. The essential feature is that an engine-driven member rotates between a transmitter and a sensor of radiation, said member having discontinuities for identifying engine timing. Thus, the transmitter may be a light source and the receiver a lightsensitive device, the rotary member being slotted or formed with opaque and transparent portions.

Further features of the distributor illustrated in the drawings are disclosed and claimed in our British Patent Application No. 1201/78 (Serial No. 1 597 903).

WHAT WE CLAIM IS: 1. An ignition distributor including a base, a distributor cap closing the base and having a central h.t. input and spaced peripheral h.t. outputs, a rotor assembly for sequentially providing an h.t. path between said input and said outputs, a shaft rotatable by an engine and extending within the base, a rotary member arranged to be rotated b the shaft, electronic means cooperating with the rotary member to produce timing pulses, and centrifugal means interposed between the shaft and the rotary member to advance the rotary member relative to the shaft as the shaft speed increases, the centrifugal means comprising a pair of weights each eccentrically mounted on a respective pivot on top of the rotary member, the rotor assembly being secured to rotate with the rotary member by means of a pair of screws each received in a screw-threaded bore of a respective pivot.

2. A distributor according to claim 1, in which the rotary member is of inverted cup shape, a mounting plate is provided above the rotary member, the mounting plate and rotary member are secured to a bearing encompassing the shaft, and the pivots

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

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. a plate 44 which is also carried by the bearing 38. The weights 40 have cam surfaces 40a which bear on an arm 45 secured to the shaft 30. Outward movement of the weights 40 is restrained by a primary and a secondary return spring 46, 48 respectively each exerting tension between a post on the arm 45 and an upturned tab on the plate 44. Thus, as the speed of the shaft 30 rises, the weights 40 move outwardly against the bias of the return springs and, by a camming action of the surfaces 40a against the arm 45, advance the vane 28 relative to the shaft 30. This construction is simple and cheap to manufacture, and the position of the centrifugal weights and springs on top of the vane gives ease of access for lubrication. The distributor cap 20 is of conventional form, having a central high tension input and equispaced peripheral h.t. outputs. The rotor assembly 18 comprises a plastics rotor 70 carrying a metallic strip 72 for conducting h.t. current from the cap input to its outputs sequentially. The rotor assembly is arranged for movement with the vane 28, and for this purpose is secured thereto by means of screws 74 passing through the assembly 18 to engage in screw threads formed m the weight pivots 42. The use of the pivots to receive the screws 74 saves space on the top of the shaft assembly 16, and this allows larger centrifugal weights to be used for a given overall size of distributor and consequently a better control of advance and retard characteristics. The sensor unit (Figure 4) comprises a permanent magnet 50 and a Hall effect device sensor 52 positioned radially outwardly of the magnet 50. Pole pieces 54 are provided to form a magnetic return path. The vane 28 rotates between the magnet 50 and the sensor 52. As each slot of the vane 28 passes between them, the magnetic flux passing through the sensor 52 increases sharply, producing an output pulse which is processed by amplifying and switching circuits in the electronics module 26 to control the l.t. supply to the coil. Such processing circuitry is well known in the art and will not be described. The sensor unit 24 is mounted to the underside of a mounting plate 56 in the position indicated in broken lines in Figure 1. The mounting plate 56 is journalled for movement through an arc on the outer peripheral surface of the bearing 32 and is secured thereon by a washer 58 and circlip 60. The mounting plate 56, and thus the sensor unit 24, is moved in advance and retard directions around the shaft 30 by the vacuum actuator 22. The base 10 has a flat transverse portion 12 adjacent the bearing 32, which portion is apertured at 62. The aperture 62 is aligned with the rest position of the sensor unit 24 and has a shape commensurate with but slightly larger than the underneath plan view of the sensor unit 24. The latter may therefore be inserted into and removed from the base in a direction parallel to the shaft 28 without removing any of the other parts, and secured in position for example by screws (not shown) driven into tapped bores 64 in the mounting plate, or by means of a snap fit. The electronics module 26 is suitably fastened to the base portion 12 to cover the aperture 62. Thus, in the event of a malfunction in the electronics parts, these may be removed and replaced without disassembly of any other part of the distributor and hence without disturbance of the ignition timing. The sensor unit 24 and module 26 are interconnected by cables 64 passing through the aperture 62. The invention may, of course, equally be applied to a distributor in which the sensor unit and vane or other rotary member take different forms. The essential feature is that an engine-driven member rotates between a transmitter and a sensor of radiation, said member having discontinuities for identifying engine timing. Thus, the transmitter may be a light source and the receiver a lightsensitive device, the rotary member being slotted or formed with opaque and transparent portions. Further features of the distributor illustrated in the drawings are disclosed and claimed in our British Patent Application No. 1201/78 (Serial No. 1 597 903). WHAT WE CLAIM IS:

1. An ignition distributor including a base, a distributor cap closing the base and having a central h.t. input and spaced peripheral h.t. outputs, a rotor assembly for sequentially providing an h.t. path between said input and said outputs, a shaft rotatable by an engine and extending within the base, a rotary member arranged to be rotated b the shaft, electronic means cooperating with the rotary member to produce timing pulses, and centrifugal means interposed between the shaft and the rotary member to advance the rotary member relative to the shaft as the shaft speed increases, the centrifugal means comprising a pair of weights each eccentrically mounted on a respective pivot on top of the rotary member, the rotor assembly being secured to rotate with the rotary member by means of a pair of screws each received in a screw-threaded bore of a respective pivot.

2. A distributor according to claim 1, in which the rotary member is of inverted cup shape, a mounting plate is provided above the rotary member, the mounting plate and rotary member are secured to a bearing encompassing the shaft, and the pivots

extend upwardly from the mounting plate.

3. A distributor according to claim 2, in which each weight has a cam surface bearing on an arm secured to the shaft, and the centrifugal means includes return springs each extending between the mounting plate and the arm.

4. An ignition distributor as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.