GB2322172A

GB2322172A - A tool for holding down a pedal of a vehicle for maintenance

Info

Publication number: GB2322172A
Application number: GB9720685A
Authority: GB
Inventors: Harold Nicholson Fell
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-02-07
Filing date: 1997-09-29
Publication date: 1998-08-19
Also published as: GB9702519D0; GB9720685D0

Abstract

A tool for holding down a vehicle brake pedal in a required position during maintenance, comprises telescopic elements 10, 11 for placement between the driver's seat (22, Fig.3) and a vehicle pedal (21). The tool has a spring 12 to maintain the brake pedal depressed as the pressure exerted by the pedal varies during maintenance. The tool has particular application to maintaining and repairing anti-lock braking systems in motor cars. The tool may be adapted for also depressing the accelerator pedal to obtain a correct engine speed by attaching arm 41 to element 11 by means of a clamp 31, and by turning screw 47 in screw hole 45 to depress the accelerator pedal by the required amount.

Description

Method and Device for Maintaining Vehicles The present invention relates to a method and device for the assistance of maintenance engineers, and particularly, but not exclusively, for use in maintaining and repairing anti-lock braking systems.

The anti-lock braking system differs from the standard brake system in that mechanical and or electronic means are provided to simulate so-called "cadence" braking, that is to say braking by applying and releasing the brakes. The principle of "cadence" braking is to apply the brakes until the wheels just lock and then to release them just until grip with the road is regained.

In the hands of an experienced driver this reduces overall stopping distances in most road surface conditions but avoids loss of steering ability, and the anti-lock braking system is a system that mimics this type of braking using electronic and mechanical components.

A typical system is shown in figure 1. Valves, typically solenoid valves, are attached to a modulator 1 to regulate the pressure of a brake fluid to the individual wheels 3 of the vehicle. The valves are operated by commands issued by an electronic control unit 2 in response to speed sensors 4 placed around the wheels. The speed sensors are typically inductive sensors positioned at a small gap from a toothed ring rotating with the wheel.

The electronics ensures that the brakes can be applied and released many times a second, thus greatly increasing the effect of this form of braking.

Anti-lock braking systems of the type described above are designed to be fail-safe. Thus if the valves or any of the pressurising means should fail then normal braking becomes available. However the brake pedal generally requires greater pressure to be exerted and/ or travels further up or down.

When the braking system is opened up for maintenance the brake pedal tends to behave as if in failsafe mode.

This gives rise to the following problem. When the system is being maintained it is necessary to keep the brake pedal depressed in order to force the modulator to self-seal. It is important that the modulator, which contains braking fluid, is not allowed to drain as it is difficult to bleed and expensive to replace.

However, as the system is opened up, the travel of the pedal increases or the back pressure of the pedal changes, so that any tool that has been jammed in against the pedal to keep it depressed is likely to fall out.

It is nevertheless necessary to keep the pedal depressed, sometimes for hours at a time, if the modulator is to be prevented from draining.

A further problem is that it is necessary on cars fitted with a catalytic converter to hold the accelerator down at a constant position to 'rev" the engine at a constant rate in order to test the catalytic converter. A simple stick fails to solve this problem because the back pressure of the accelerator pedal can also vary, causing the stick to fall away.

According to a first aspect of the invention there is thus provided a longitudinally tensioned telescopic device, for exerting a pressure, between two objects exerting a back pressure, which pressure is substantially maintained even if that back pressure varies.

According to a second aspect of the invention there is provided a tool for transmitting a forward pressure, from a first object having a fixed position to a second object having a variable position dependent on a backward pressure, in such a way that forward pressure is maintained when the position of the second object varies, the device comprising a first end for placing against the first object and a second end for placing against the second object and tensioning means to keep the first end apart from the second end.

An embodiment of this second aspect will include the tensioning means as part of a telescopic mounting which extends between the two ends. The tensioning means may be a coiled spring and a tension level of 4 to 6 kilogrammes (40-60 Newtons) would be adequate for most purposes.

According to a third aspect of the invention there is provided a tool for depressing a vehicle pedal, comprising a telescopic tube having a first end for placing against the driver's seat and a second end for placing against the pedal, and a resilient bias member for maintaining the pedal depressed as the back pressure on the pedal varies.

In any of the above aspects of the invention the ends of the tool may comprise pads or feet to rest against the brake pedal of the vehicle and against the driver's seat or other convenient surface respectively. The pad for resting against the brake pedal will typically be smaller than the pad for resting against the car seat.

The distance between the two ends of the tool under tension will typically be the distance between the car seat and the brake pedal for any given motor vehicle.

As this does not vary greatly, being dependent on the length of the driver's legs, no further adjustment means is generally considered necessary to render the tool as being applicable to all vehicles. In any event, the position of the car seat can normally be adjusted.

In embodiments, an accelerator pedal engagement fitting is provided for holding the accelerator pedal of a vehicle depressed. This may be needed to test the catalytic converter of the vehicle. Preferably, the accelerator pedal engagement fitting has a spar extending laterally from the brake pedal end of the tool. An accelerator pedal adjustment member for adjusting the position of the accelerator pedal separately from the brake pedal is also preferably provided. This adjustment member can be a screw screwed into a screw thread in the spar, the outer end of the screw being for engagement with the accelerator pedal, so that turning the screw adjusts the longitudinal position of the screw and hence the position of the accelerator pedal. The accelerator pedal engagement fitting is preferably releaseably attached to the rest of the tool, for example by a clamp.

In a fourth aspect of the invention there is provided a method of closing the valves of the modulator of an anti-lock braking system of a motorised vehicle by inserting a tensioned telescopic tool between a fixed surface of the vehicle and the brake pedal, such that pressure is exerted by the tool on the brake pedal, the tension of the tool being such that pressure is maintained by the tool on the brake pedal when the position of the pedal varies.

The fixed surface of the vehicle may be the driver's seat, and the tool would be inserted between the pedal and the seat. This would be followed by a step of moving the seat forwards to wedge the tool downwards tightly against the brake pedal. Then later on, during maintenance, for example during replacement of brake pads or calipers, when there is a loss of pressure in the modulator and hence the brake pedal moves downward, the tightness of the fit is maintained because of the pressure still exerted by the tension means. Thus the brake pedal can be used to keep the modulator sealed whilst the pads or calipers are being serviced and the only loss of fluid is the initial loss when the component under maintenance is removed from the hydraulic system.

The invention also encompasses a method of adjusting the position of an accelerator pedal. This may be done by fitting the tool between the brake pedal and vehicle seat as described above, and then adjusting the adjustment member on the accelerator pedal depressing device. Alternatively, the tool may simply be fitted between the vehicle seat and accelerator pedal. The accelerator pedal can thus be maintained depressed, for example to check the catalytic converter of the vehicle or to maintain the engine speed during cleaning of contamination from the fuel injectors or fuel system.

For a better understanding of the invention and to show how the invention may be carried into effect reference will now be made, purely by way of example, to the accompanying drawings in which: Fig 1 shows a schematic diagram of a generalised antilock braking system, Fig 2 shows a tool according to embodiments of the invention, Fig 3 shows the tool of Fig 2 in use in a vehicle, Fig 4 shows an embodiment of a accelerator pedal engagement fitting for attachment to the rest of the tool, and Fig 5 shows a side view of part of the accelerator pedal engagement fitting.

Figure 1 shows a schematic diagram of a generalised anti-lock braking system and has briefly been discussed above. In principle the system may be thought of as a standard hydraulic circuit to which high specification actuator valves have been added. The actuator valves are operated through the modulator 1 and will be closed when the brake pedal is depressed except in those instances when the electronic control unit 2 detects a locking condition. If the brake pedal is not depressed, the unbraked condition, then the valves will always be open.

The modulator is a dual system device. The system described above is a high pressure system and operates only when the motor is able to provide power to the electronic control unit 2. When the motor is switched off or the electronic control unit is disconnected then the failsafe system operates. This simply uses the pressure of the driver exerted on the brake pedal to operate the brake system. Generally during maintenance this will be the system in operation. Under this system the brake pedal has far more travel. The only circumstances when the high pressure system would be on during maintenance would be during fault diagnosis.

This is because at the present time ABS modulators are not user serviceable, at least not without specialist tools which are not generally available or are specific to individual models. However it is envisaged that in the near future the situation will change as such brake systems become more widespread.

At the far end of the hydraulic circuit are the standard brake components such as brake pads and callipers. As these are removed fluid will leak from the hydraulic circuit. As mentioned above it is important that the modulator is isolated at this time.

The best way of achieving this is to have the brake pedal depressed as this will shut the modulator valves directly. However, as the pressure is changing within the whole hydraulic system at this time the maximum downward travel of the brake pedal is liable to increase. Devices used to jam the pedal in the depressed position are thus liable to fall off as back pressure from the pedal falls away.

The solution to this problem is to use the tool shown in figure 2. The tool consists of two longitudinal sections at least a first of which 10 is hollow and a second of which 11 is able to slide within the hollow and which extends outwardly therefrom along the same axis. Thus the two sections 10 and 11 form a telescopic arrangement. Within the hollow is placed a coiled spring 12 which serves to keep the two sections apart. A gauge may be inserted within the hollow.

The spring is approximately 300mm long and the arrangement is designed to provide about 150mm of travel. The spring should ideally exert a force of 20 to 30 Newtons. The tool may be 450mm along when compressed and 600mm long when extended. It may be made of plastic or metal.

At the end of the section 10 is a large pad 13 which is designed to rest against the front of the driver's seat. At the end of the section 11 is a smaller pad 14 which is designed to rest against the brake pedal.

The first stage of the maintenance operation is to disconnect the wiring harness so as to disable the pump motor and electronic control unit. Then, as shown in figure 3, the tool 20 is placed between the front of the driver's seat 22 and the brake pad 21. The driver's seat is moved forward about 150mm until the tool is tightly pressed against the brake pad 21 which is forced downwards to the limit of its travel.

Maintenance can then be carried out on the brake calipers, hoses, cylinders, metal pipes, switches, proportioning valves and other brake components.

At this point maintenance work can commence on the brake system and the brake pedal will remain securely held even though its limit of travel increases.

A skilled operator with the correct specialised tools can use the tool for bleeding the modulator and for other operations involving the ABS braking system.

Embodiments of the invention include an accelerator pedal engagement fitting, as shown in figures 4 and 5.

All or some of the parts of the fitting may be formed from moulded plastics.

The fitting has a clamp part 31 shaped to fit around the second section 11 of the tool. A clamp screw 37 is provided to compress the clamp part together to firmly clamp the fitting onto the second section 11.

An arm 41 is attached to the clamp part 31 by a hinge 43. The arm 41 defines a screw hole 45 at the opposite end to the hinge. By adjusting the hinge 43 the distance between the clamp part 31 and the screw hole 45 can be adjusted to fit different vehicles.

Referring to figure 5, an accelerator screw 47 is fitted in the screw hole 45. One end 49 of the screw has a pad for engagement with the accelerator pedal, the other end 51 has a handle.

In use, the accelerator pedal engagement fitting is clamped onto the second section 11 and the tool fitted between the brake pedal and vehicle seat as described above. The end 49 of the accelerator screw 47 is then brought into position against the accelerator pedal by adjustment of the hinge 43 and screw 47. If necessary, the clamp screw 37 can be loosened to reposition the clamp part 31 and then retightened. The accelerator screw 47 can then be turned so as to depress the accelerator pedal by the correct amount to obtain the correct engine speed.

The tool can be used to clean contamination in the fuel injectors and fuel system. After checking and cleaning the air filter element, the water and the fan switch, fuel system cleaner is added to the fuel tank. The engine is switched on, and the tool fitted as described above. The engine speed can then be adjusted to 2000 rpm, or other predetermined speed, by adjusting the screw 47, and the engine is left running at this speed for 15 to 20 minutes to clean the injectors and fuel systems.

The tool can also be used to test catalytic converters.

A vacuum gauge is fitted to the inlet manifold, and the reading on the vacuum gauge is then noted whilst the engine is ticking over. The tool is then fitted as previously described and the engine speed adjusted using the screw to 2500 rpm or other predetermined speed. The reading on the vacuum gauge is monitored, and if the air filter or catalytic converter is blocked the pressure read on the vacuum gauge will fall off after 15-20 seconds.

The tool is suitable for all kinds of vehicle, and in particular all kinds of throttle and accelerator controls, including manual, electric, electronic and drive by wire controls in petrol or diesel vehicles.

Claims

1. A tool for depressing a pedal of a motor vehicleZcomprising a telescopic tube having a first end adapted for placing against a fixed or fixable part of the vehicle and a second end adapted for placing against the pedal, and a resilient bias member provided between the first and second ends for maintaining the pedal depressed under variations of pressure on the tool exerted by the pedal.

2. A tool according to claim 1 having pads at the first and second ends for resting against the driver's seat or fixed part of the vehicle, and against a brake pedal of the vehicle, respectively.

3. A tool according to claim 2 in which the pad for resting against the brake pedal is smaller than the pad for resting against the car seat.

4. A tool according to claim 2 or 3, further comprising an accelerator pedal engagement fitting for holding an accelerator pedal of the vehicle depressed.

5. A tool according to claim 4 in which the accelerator pedal engagement fitting has a spar extending laterally from the second end of the tool.

6. A tool according to claim 5 wherein said accelerator pedal engagement fitting further comprises an accelerator pedal adjustment member for adjusting the position of the accelerator pedal separately from the brake pedal.

7. A tool according to claim 6 in which the accelerator pedal adjustment member is a screw screwed into a screw thread in the spar, the outer end of the screw being for engagement with the accelerator pedal, so that turning the screw adjusts the longitudinal position of the screw and hence the position of the accelerator pedal.

8. A tool according to claim 7 in which the accelerator pedal engagement fitting is releaseably attached to the rest of the tool by mounting at or adjacent said second end.

9. A tool substantially as herein described with reference to and as shown in Figures 2 and 3 or 4 and 5 of the accompanying drawings.

10. A tool used in motor vehicle maintenance, for transmitting a pressure from a part of the vehicle having a fixed position to a movable part having a variable position, in such a way that pressure is maintained when the position of the movable part varies, the device comprising a first end adapted for placing against the fixed part and a second end adapted for placing against the movable part and tensioning means to maintain a compression force between the first and second ends.

11. A tool according to claim 10 in which the tensioning means is housed within a telescopic mounting which extends between the two ends.

12. A tool according to claim 10 or 11 in which the tensioning means is a coiled spring.

13. A method of maintaining a pedal of a motor vehicle depressed, comprising placing one end of a telescopic tube against a fixed or fixable part of the vehicle, placing the other end of the telescopic tube against the pedal, and maintaining the pedal depressed by the action of a resilient bias member provided between the first and second ends.

14. A method of closing the valves of the modulator of an anti-lock braking system of a motor vehicle by inserting a tensioned telescopic tool between a fixed part of the vehicle and the brake pedal, such that pressure is exerted by the tool on the brake pedal, the tension of the tool being such that pressure is maintained by the tool on the brake pedal when the position of the pedal varies.

15. A method of adjusting the position of an accelerator pedal of a vehicle having brake and accelerator pedals comprising the steps of: providing a tool according to claim 8, positioning the tool between the brake pedal and the vehicle seat with the first end resting against the driver's seat and the second end resting against the brake pedal, clamping the spar to the second end of the tool so that the screw is in alignment with the accelerator pedal, and adjusting the screw to engage the accelerator pedal and adjust it to the desired position.

16. A method of adjusting the position of a vehicle pedal substantially as herein described with reference to Figures 2 and 3, or Figures 4 and 5 of the accompanying drawings.