WO2007090231A1

WO2007090231A1 - Method and apparatus for enhancing automobile power steering performance

Info

Publication number: WO2007090231A1
Application number: PCT/AU2007/000118
Authority: WO
Inventors: Kenneth John Dennis
Original assignee: Truck Whisperer Limited
Priority date: 2006-02-06
Filing date: 2007-02-06
Publication date: 2007-08-16

Abstract

A method of improving car steering performance is disclosed. The method comprises modifying the size of the flow path for supply of hydraulic fluid from a pump to a steering unit so that the flow path is of a size greater than the size prior to modification. The modification can be made by increasing the size of a bore (61) of a bolt (63) forming a restriction (45) in the pump or by modifying a fitting (47) to increase fluid flow through the fitting (47).

Description

METHOD AND APPARATUS FOR ENHANCING AUTOMOBILE POWER STEERING PERFORMANCE

Field of the Invention

This invention relates to a method and apparatus for enhancing car performance and, in particular, to reducing problems associated with performance due to hydraulic power steering systems used in cars . For the purpose of this specification, the word "car" or "cars" means passenger cars and passenger 4-wheel drive vehicles for transporting people.

Background of the Invention

Many cars from various problems under particular driving conditions, which include general rough ride, vibration and shuddering on rough roads, steering feedback, pulling consistently in one direction, understeer while cornering, heavy excessive tyre wear, heaving steering, wander across the road and the need for constant steering corrections whilst the car is being driven.

These problems can make it difficult to drive a car and, in particular, in some conditions, which can result in driver fatigue, accident and also significant wear on tyres and other steering components .

Summary of the Invention

The present inventor has found that the above problems relate directly to hydraulic steering systems and, in particular, to the amount of hydraulic fluid which is able to flow to a steering box to control steering. In particular, it has been found that the forces created on the steering box when a steering change is made by rotating a steering wheel and which are provided by hydraulic fluid, is often insufficient to counteract forces on the car wheels caused by travel of the car over the terrain on which the vehicle is driving. This in turn can result in greater momentary forces being applied to the wheels by the terrain than by the hydraulic fluid. Thus, although the car does turn in response to movement of the steering wheel and the application of hydraulic fluid to the steering box, the momentary forces cause feedback into the steering system which create the rough ride, vibration and shuddering and the other problems referred to above.

The present inventor has found that by increasing the amount of fluid which can be supplied to the steering box, the above problems are greatly reduced, if not eliminated altogether, thereby providing much better car steering performance, less wear on steering components and tyres and therefore greater driving satisfaction from the point of view of comfort and safety, and also in relation to the need for maintenance of the steering system.

Thus, the present invention is based on the concept of increasing the amount of hydraulic fluid which is supplied to the steering box during operation of the vehicle.

The invention in a first aspect provides a method of improving car performance of a car which has a hydraulic power steering system comprising a hydraulic fluid reservoir, a pump for pumping hydraulic fluid from the reservoir and a steering unit operably connected to a mechanical steering system and to be activated by supply of hydraulic fluid by the pump to the unit, the hydraulic power steering system having a flow path for supply of hydraulic fluid by the pump to the unit of a first size which is provided at manufacture of the steering system, said method comprising: modifying the size of the flow path for the supply of hydraulic fluid from the pump to the unit so that the flow path is of a size greater than the said first size so as to increase the amount of flow of fluid to the steering unit compared to that which occurs with the flow path having the said first size to thereby improve steering performance of the car.

Since the flow path is of increased size, the amount of fluid which flows to the steering unit is increased, thereby creating greater force to maintain the wheels in position, as set by rotation of the steering wheel so that the force created by contact of the wheels over terrain does not overcome the force created by the hydraulic fluid and therefore maintains the wheels in their correct orientation. This therefore reduces all of the problems referred to above, thereby greatly improving car performance .

In one embodiment the step of modifying the flow path comprises changing a component of the flow path to increase the size of the flow path.

In another embodiment the step of modifying the size of the flow path comprises altering a component of the flow path to increase the size of the flow path.

Thus , the flow path can be altered by either removing an old part and inserting a new part, or by altering an existing part, such as by enlarging orifice sizes or the like to increase the size of the flow path.

Preferably the steering system includes a fitting having a bore and/or outlet orifice for allowing fluid to flow through the fitting, the fitting being located in the pump or on the pump, and the step of modifying comprises enlarging the bore and/or orifice .

In one embodiment the fitting is a banjo fitting on the pump .

In another embodiment the fitting is an oil flow restriction in the pump .

Again, this modification can taken place by altering the bore size or orifice by increasing the bore size or orifice size of the fitting or completely replacing the fitting with a fitting having a larger bore size or orifice size.

The invention also provides a method of enhancing steering performance of a car which has a hydraulic power steering system comprising a hydraulic fluid reservoir, a pump for pumping hydraulic fluid from the reservoir and a steering unit operably connected to a mechanical steering system and to be activated by supply of hydraulic fluid by the pump to the unit, the hydraulic power steering system having a flow path for supply of hydraulic fluid by the pump to the unit, said method comprising: increasing the size of the flow path for the supply of hydraulic fluid from the pump to the unit.

In one embodiment the step of increasing the size of the flow path comprises changing a component of the flow path to increase the size of the flow path.

In another embodiment the step of increasing the size of the flow path comprises altering a component of the flow path to increase the size of the flow path.

Preferably the steering system includes a fitting having a bore and/or outlet orifice for allowing fluid to flow through the fitting, the fitting being located in the pump or on the pump, and the step of modifying comprises enlarging the bore and/or orifice.

The invention also provides a car hydraulic power steering system comprising: a hydraulic fluid reservoir; a steering unit coupled to a mechanical actuating part of a mechanical steering system for control by rotation of a steering wheel to turn wheels of the car; a pump for pumping hydraulic fluid from the reservoir to the steering unit; a pressure supply conduit between the pump and the steering unit for the supply of fluid pumped by the pump from the reservoir to the steering unit; a return conduit for supplying hydraulic fluid from the steering unit to the reservoir; and wherein the pump, supply conduit and steering unit define a flow path having a size which is set to supply hydraulic fluid to the steering unit so as to substantially eliminate one or more of the following unwanted conditions:

(a) erratic deviations from a steered path;

(b) excessive feedback to the steering wheel caused by road unevenness;

(c) excessive understeer by cornering; (d) excessive heavy steering;

(e) excessive slow response of power assist of the steering system;

(f) excessive tyre wear;

(g) cabin noise and vibration or shudder; (h) rough ride on uneven surfaces.

In one embodiment the size of the flow path before increasing the size has a minimum cross-sectional dimension of 4 to 8 mm and the size is increased by an amount in the range of 0.3 to 0.7 mm.

Most preferably the increase is 0.5 mm.

In terms of percentage preferably the change in the size of the flow path is produced by changing a fitting of the flow path so the minimum cross-sectional area of the flow path provided by that fitting is increased in size from 3 to 15% and most preferably about 5 to 10%.

In the preferred embodiment the fitting which is altered comprises a fitting in or attached to the pump. In the case of a passenger 4-wheel drive, the fitting comprises a banjo fitting and the fitting includes a central bore and at least one outlet orifice arranged transverse to the central bore for supplying fluid to the supply line, and preferably the outlet orifice is increased in size. The banjo fitting may include two or four outlet orifices.

In the case of a passenger car, the fitting is an internal restriction within the pump, the fitting having a central bore and the size of the central bore is increased to provide the increase in fluid flow.

Brief Description of the Drawings

A preferred embodiment of the invention will be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a passenger car steering system according to the preferred embodiment of the invention ;

Figure 2 is a schematic diagram of a steering system for a 4-wheel drive/

Figure 3 is a cross-sectional view of a fitting used in the embodiment of Figure 1 ; and

Figure 4 is a cross-sectional view of a fitting used in the embodiment of Figure 2.

Detailed Description of the Preferred Embodiment Figure 1 shows in semi-schematic form a hydraulic circuit of a hydraulically operated power steering system 1 for passenger cars . From a reservoir 2 , hydraulic fluid is drawn into an engine-driven pump 3 via a supply line 35.

The pump 3 is of fixed-displacement type, and is typically of the sliding-vane type that is well known in the art. From the pump 3, hydraulic fluid is delivered through a pressure line 4 to a power steering unit 5. A return line 40 from pump 3 is provided to return fluid to reservoir 2 in the event of an integral relief valve (not shown) in pump 3 being opened.

The unit 5 has an input shaft 6 which is coupled via a coupling 7 to shaft 8 of a steering wheel 9 of the passenger car (not shown) . The purpose of the unit 5 is to cause rotation of a pitman arm 10 in response to inputs from the steering wheel 9, with torque applied to the steering wheel 9 being magnified hydraulically . The pitman arm 10 is connected to other mechanical components (not shown) which in turn steer road wheels (not shown) of the car in a known manner. A line 11 is provided to return hydraulic fluid from the steering unit 5 to the reservoir 2.

System 1 is simplified and illustrative only, as many variations occur in practice .

Figure 2 is a schematic diagram of a steering system of a passenger 4-wheel drive. In Figure 2, much of the componentry is the same as Figure 1. Only the pump 3 is shown and the supply line 4. The pump 3 receives a banjo bolt 47 which is shown in more detail in Figure 4. Oil supplied from the pump 3 flows through bore 49 of the banjo bolt out of outlet orifices 51 and into supply line 4.

Returning to Figure 1 , oil is supplied from pump 3 to supply line 4 via a threaded oil flow restriction 45 which may also be in the form of an internal bolt or fitting, as shown in Figure 3. The restriction 60 is provided with a central bore 61 which passes through shaft 63 of the fitting and also through head 64. Typically, the diameter of the bore 61 prior to modification is anywhere from 0.75 mm to 2.5 mm.

In order to improve steering performance, the bore 61 is enlarged by 0.2 mm to 0.6 mm and most preferably by an amount of 0.4 mm to 0.5 mm. Thus, the minimum cross- sectional flow area of the flow passage from the pump 3 to the steering box 5 is set by the size of the bore 61 and is preferably increased in the range of 30% to 190%, and most preferably 44% to 176%.

Figure 4 is a cross-sectional view of the banjo bolt 47 of Figure 2. As is apparent from Figure 4, the banjo bolt has a central bore 49 in stem 71 and a solid head 73. Two outlet orifices 75 and 76 supply oil from the pump into the supply line 4. In some embodiments, two orifices 75 and 76 are provided and in others (not shown) , four orifices can be provided by drilling a further bore perpendicular to the inlet bore 46 and the orifices 76 and 75.

In the case of two orifices 75 and 76, the size of the orifices are increased in diameter by 0.5 mm and if four orifices are provided, each orifice is increased by 0.25 mm.

Since modifications within the spirit and scope of the invention may readily be effected by persons skilled within the art, it is to be understood that this invention is not limited to the particular embodiment described by way of example hereinabove .

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise", or variations such as "comprises" or "comprising", is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

1. A method of improving car performance of a car which has a hydraulic power steering system comprising a hydraulic fluid reservoir, a pump for pumping hydraulic fluid from the reservoir and a steering unit operably connected to a mechanical steering system and to be activated by supply of hydraulic fluid by the pump to the unit, the hydraulic power steering system having a flow path for supply of hydraulic fluid by the pump to the unit of a first size which is provided at manufacture of the steering system, said method comprising: modifying the size of the flow path for the supply of hydraulic fluid from the pump to the unit so that the flow path is of a size greater than the said first size so as to increase the amount of flow of fluid to the steering unit compared to that which occurs with the flow path having the said first size to thereby improve steering performance of the car .

2. The method of claim 1 wherein the step of modifying the flow path comprises changing a component of the flow path to increase the size of the flow path.

3. The method of claim 1 wherein the step of modifying the size of the flow path comprises altering a component of the flow path to increase the size of the flow path .

4. The method of claim 1 wherein the steering system includes a fitting having a bore and/or outlet orifice for allowing fluid to flow through the fitting, the fitting being located in the pump or on the pump, and the step of modifying comprises enlarging the bore and/or orifice.

5. The method of claim 4 wherein the fitting is a banjo fitting on the pump.

6. The method of claim 4 wherein the fitting is an oil flow restriction in the pump.

7. A method of enhancing steering performance of a car which has a hydraulic power steering system comprising a hydraulic fluid reservoir, a pump for pumping hydraulic fluid from the reservoir and a steering unit operably connected to a mechanical steering system and to be activated by supply of hydraulic fluid by the pump to the unit, the hydraulic power steering system having a flow path for supply of hydraulic fluid by the pump to the unit, said method comprising: increasing the size of the flow path for the supply of hydraulic fluid from the pump to the unit.

8. The method of claim 7 wherein the step of increasing the size of the flow path comprises changing a component of the flow path to increase the size of the flow path.

9. The method of claim 7 wherein the step of increasing the size of the flow path comprises altering a component of the flow path to increase the size of the flow path.

10. The method of claim 7 wherein the steering system includes a fitting having a bore and/or outlet orifice for allowing fluid to flow through the fitting, the fitting being located in the pump or on the pump, and the step of modifying comprises enlarging the bore and/or orifice.

11. A car hydraulic power steering system comprising: a hydraulic fluid reservoir; a steering unit coupled to a mechanical actuating part of a mechanical steering system for control by rotation of a steering wheel to turn wheels of the car; a pump for pumping hydraulic fluid from the reservoir to the steering unit; a pressure supply conduit between the pump and the steering unit for the supply of fluid pumped by the pump from the reservoir to the steering unit; a return conduit for supplying hydraulic fluid from the steering unit to the reservoir; and wherein the pump, supply conduit and steering unit define a flow path having a size which is set to supply hydraulic fluid to the steering unit so as to substantially eliminate one or more of the following unwanted conditions :

(a) erratic deviations from a steered path;

(b) excessive feedback to the steering wheel caused by road unevenness;

(c) excessive understeer by cornering;

(d) excessive heavy steering;

(e) excessive slow response of power assist of the steering system; (f) excessive tyre wear;

(g) cabin noise and vibration or shudder; (h) rough ride on uneven surfaces .

12. The system of claim 11 wherein the size of the flow path before increasing the size has a minimum cross- sectional dimension of 4 to 8 mm and the size is increased by an amount in the range of 0.3 to 0.7 mm.

13. The system of claim 12 wherein the increase is 0.5 mm.

14. The system of claim 11 wherein in terms of percentage preferably the change in the size of the flow path is produced by changing a fitting of the flow path so the minimum cross-sectional area of the flow path provided by that fitting is increased in size from 3 to 15% and most preferably about 5 to 10% .

15. The system of claim 11 wherein the fitting which is altered comprises a fitting in or attached to the pump.