GB2270760A

GB2270760A - A fuel level sender assembly

Info

Publication number: GB2270760A
Application number: GB9219840A
Authority: GB
Inventors: Steven Shortis
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1992-09-19
Filing date: 1992-09-19
Publication date: 1994-03-23
Also published as: GB9219840D0

Abstract

A level sender assembly for a vehicle fuel tank has a float arm 22 which performs a pivoting movement as the fuel level changes. The pivoting movement causes two contact members 40, 42 to move over respective resistor tracks 32, 34 printed on a card 26 which is received in a main housing 24 of the assembly. The contact members are mounted on the float arm through a carrier 68. The contact members may be either electrically connected or electrically isolated form one another by the presence or absence of a conductive shoe 72 placed on the, otherwise insulating, carrier 68 before the contact members are put in position. The carrier is the mounted on the float arm, being a slide fit in a socket 70 of a head moulding 52. The float arm has a pivot portion 54 which passes through the head moulding and through an earthing strap 56 and the main housing 24, where it is retained by a clip 60 <IMAGE>

Description

A FUEL SENDER ASSEMBLY This invention relates to a fuel sender assembly for use in a motor vehicle fuel tank.

Fuel sender assemblies are known (see for example EP 0 007 072) in which a resistor card is mounted in a sender housing, a contact is mounted on the float arm and the contact moves over the resistor card track as the float arm moves up and down in accordance with the fuel level in the tank. By passing a current through the resistor track, a varying output will be obtained depending on the position of the contact along the track. This output can be used to drive an indicating instrument which will indicate the fuel level in the tank, for the information of the driver.

Where a vehicle is fitted with a fuel computer, a separate output is required from the sender assembly to provide a signal to the computer, and it is conventional to provide a second resistor track on the same resistor card, to provide a second contact which travels on the second track, and to electrically connect the first and second contacts with one another.

According to the present invention there is provided a fuel sender assembly for a motor vehicle fuel tank, the assembly comprising a float arm pivoted on a sender housing, a resistor card mounted in the housing with two independent resistor tracks thereon and two separate contact members connected to the float arm and movable over the resistor tracks as the float arm pivots; characterised inthat the contact members are both mounted on a separate carrier which is adapted to fit into a socket on the float arm to connect the contact members to the float arm.

By mounting the two contact members on a separate carrier, it becomes possible to pre-assemble the two contact members and then to assemble them as a single unit onto the float arm. Furthermore it is desirable to be able to make fuel sender assemblies where the two contact members are insulated from one another and other assemblies where the two contact members are electrically connected to one another. To facilitate this, the separate carrier can be assembled either with or without a contact shoe which makes an electrical connection between the two contact members and in this way the same assembly process and substantially the same components can be used to assemble two different sender assembly configurations.

The carrier is preferably a plastics moulding which has two pairs of tracks, one for each of the contact members, and a conductive shoe may or may not be fitted on the carrier.

When the shoe is fitted it makes electrical contact between the two contact members; when it is omitted the two contact members are electrically isolated from one another.

The float arm preferably includes a head moulding and a limb which carries a float. One of the contact members can carry an alignment tongue which locates in an alignment feature on the head moulding. This then ensures correct alignment of the carrier with the float arm.

The two resistor tracks may be angularly offset relative to one another to reduce the space requirements on the resistor card and thus to reduce the overall size of the fuel sender assembly. When the tracks are offset from one another in this way, the two contact members have their contact points correspondingly offset relative to one another.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a simplified cross-sectional view through a fuel tank of a motor vehicle which incorporates a fuel sender assembly in accordance with the invention; Figure 2 is an electrical circuit diagram representing the electrical circuit of the sender of Figure 1; Figure 3 is a simplified cross-sectional view of a fuel tank with an alternative configuration, including two fuel sender assemblies in accordance with the invention; Figure 4 is an electrical circuit diagram of the two senders of Figures 3 and 4; Figure 5 is an exploded view of a fuel sender assembly in accordance with the invention; Figure 6 is an enlarged end view of a head moulding for a float arm; Figure 7 is an enlarged section through a carrier for the electrical contacts; and Figure 8 is a plan view showing the electrical contacts and resistor card of a sender assembly in accordance with the invention.

Figure 1 shows a fuel tank 10 containing fuel up to a level 12 and with a fuel sender assembly 14 positioned in the tank. The assembly is introduced into the tank through an aperture 16 in the upper face of the tank, and this aperture is subsequently closed by a closure plate 18. The sender assembly has a float 20 mounted at the end of a float arm 22. The sender also has a housing 24 which contains a resistor card 26. As the fuel level 12 in the tank varies, the float 20 will follow the changing fuel level and the arm 22 will rotate, causing electrical contacts which move with the arm to move relative to the resistor card 26. As a result, a varying electrical output will be sent along electrical conductors 28, 29, 30 to a remote fuel level indicating device.

It will be seen in Figure 1 that there are two resistor tracks 32 and 34 on the resistor card 26. One track is provided to pass a signal to a fuel level indicating device 36 (Figure 2) and the other track is provided to pass a signal to a fuel computer 38.

The float arm 22 carries two contacts, one of which travels on the resistor track 32 and the other of which travels on the track 34. In the embodiments shown in Figures 1 and 2, these two contacts (which are indicated in Figure 2 as 40 and 42) are electrically connected to one another. The output signals produced on the conductors 28 and 29 therefore have a common earth connection via the contacts 40 and 42 and the shoe 72, but provide different resistive signals to suit the fuel gauge 36 and the fuel computer 38.

The circuit shown in Figure 2 also provides a third output on the conductor 30 to a low fuel level warning lamp 44.

Figure 3 shows an alternative fuel tank 110 which is divided by a central ridge 46 into two tank regions 48 and 50. The tank is formed in this way to provide space for the driveshaft 54 and exhaust pipe 56 used, for example, on a four wheel drive vehicle. The tank is further protected by a shield 52. Because the tank can extend on both sides of the transmission tunnel, optimum fuel capacity is obtained.

When the tank is full, the regions 48 and 50 communicate with one another but when the fuel level drops below the height of the ridge 46, then the two tank regions become substantially independent of one another. In order to produce a valid indication of the quantity of fuel left in the tank, it is necessary to place a sender assembly 14, 14a in each of the tank regions 48, 50. The sender assembly 14 will be exactly as already described with reference to Figure 1. The sender assembly 14a has one small but significant difference in that the contacts 40 and 42 are electrically isolated from one another.

This will become more apparent from Figure 4 which shows how the two sender assemblies 14 and 14a of Figure 3 are electrically connected together.

In Figure 4, the tracks 32 of the two sender assemblies are connected in series and provide an output on a line 28a to the fuel computer 38. The tracks 34 are also connected in series and are connected via a line 29a to a fuel level indicating device 36. The low fuel level warning light 44 is connected by a line 30a to the tracks 34.

To enable the sender assembly to be prepared either with the contacts 40 and 42 connected or with the contacts isolated, whilst using the same basic structure, the constructional features shown in Figure 5 are adopted. Figure 5 shows the main housing 24 of the fuel sender assembly in which a resistor card is fitted. The resistor card has tracks 32 and 34 printed on it (see also Figure 8) and the card is fitted into the housing 24 so that the surface of the card lies at right angles to the axis of pivoting 50 of the float arm 22.

The float arm 22 has a head moulding 52. The float arm also has a rod 122 with a bent end at 54. The bent end 54 passes through a hole 51 in the head moulding 52, through a hole 53 in an earth contact strap 56, through a hole 58 in the housing 24 and through a hole 59 in a retaining clip 60.

The main portion of the rod 22 is clipped into guide lugs 62 on the moulding 52.

The two contacts 40 and 42 are provided in the form of conductive buttons mounted at the end of sprung metal arms 64 and 66. The terminal end portions of these arms 64 and 66 are shaped so as to be slide fitted onto a carrier 68 (which also has a hole, hole 61, for receiving the bent end 54 of the float arm), and the carrier 68 is adapted to be a slide fit into a socket 70 on the head moulding. The head moulding 52 and the carrier 68 are moulded of plastics and therefore are electrically non-conductive. A conductive metal shoe 72 is also provided, and the difference between the sender assemblies 14 and 14a relates to the presence or absence of the shoe 72. In order to prepare a connected assembly 14, a shoe 72 is placed onto the carrier 68 before the contact arms 64 and 66 are put into place.The shoe slides over the central bridge of the carrier 68 and the arms 64, 66 are received in slots on the opposite faces of the carrier. This can be seen most clearly in Figure 7. If the shoe 72 is present, then there is a conductive path between the arms 64 and 66. If it is absent then there is no such conducting path.

This assembly can be used in an installation as shown in Figures 1 and 2 (with the shoe present) as well as in an installation as shown in Figures 3 and 4, where one assembly 14 will have the shoe present and the other 14a will have the shoe absent.

When the carrier 68 is fitted in the slot 70 on the head moulding, and when the components on the axis 50 are all properly assembled then the arm 66 makes contact with the earth strap 56 through a tongue 74. If the shoe 72 is absent, then the arm 64 is connected to an earth strap through the tang 76.

In order to properly align the contacts 40 and 42, the arm 64 carries a tongue 78 which locates in a groove 80 on the head moulding. Furthermore slots 82, 84 and 86 on, respectively, the arms 64 and 66 and the carrier 68, all engage with a rib 88 which is moulded into the head member.

In a further feature shown in Figure 6, it can be seen that the arc A occupied by the inner resistor track 34 is angularly offset from the arc B occupied by the outer resistor track 32. A similar offset exists between the positions of the contacts 40, 42. This offset allows the necessary tracks to be accommodated on a resistor card 26 which is smaller than would otherwise be required, and also provides space for the positioning of contact pads 90, 92, 94 by which electrical conductors can be connected to the resistor tracks 32, 34.

The combination of the features described here allows one set of components to be assembled to form a double resistor track sender assembly either with the contacts electrically connected or with the contacts electrically insulated.

Claims

1. A fuel sender assembly for a motor vehicle fuel tank, the assembly comprising a float arm pivoted on a sender housing, a resistor card mounted in the housing with two independent resistor tracks thereon and two separate contact members connected to the float arm and movable over the resistor tracks as the float arm pivots; characterised in that the contact members are both mounted on a separate carrier which is adapted to fit into a socket on the float arm.

2. A fuel sender assembly as claimed in Claim 1, wherein the separate carrier maintains the two contact members electrically isolated from one another.

3. A fuel sender assembly as claimed in Claim 1, wherein the separate carrier maintains the two contact members electrically connected to one another.

4. A fuel sender assembly as claimed in any preceding claim, wherein the separate carrier is a plastics moulding adapted to slide into the socket on the float arm.

5. A fuel sender assembly as claimed in Claim 4 when appendant to Claim 3, wherein the carrier is fitted with an electrically conductive shoe to provide electrical connection between the contact members.

6. A fuel sender assembly as claimed in any preceding claim, wherein the separate carrier has two pairs of tracks, and the contact members are slide fitted in respective pairs of tracks.

7. A fuel sender assembly as claimed in any preceding claim, wherein the float arm comprises a head moulding and a limb which carries a float.

8. A fuel sender assembly as claimed in Claim 7, wherein one of the contact members carries an alignment tongue which locates in an alignment feature on the head moulding.

9. A fuel sender assembly as claimed in any preceding claim, wherein the two resistor tracks are angularly offset relative to one another on the resistor card and the two contact members have their contact points correspondingly offset relative to one another.

10. A fuel sender assembly substantially as herein described with reference to the accompanying drawings.