Cam Gears Limited

Trw Cam Gears Limited

Trw Limited

Frederick J Adams

Kenneth Chandler

Philip A Downing

Ralph M Lehman

Kenneth J Heap

A power assisted vehicle steering system of the speed responsive kind has a ram 6 fluid flow to chambers 4 and 5 of which from a pump 9 is directed by an open center steering valve 1. Communication between the chambers 4 and 5 is permissible through a by-pass valve 13 adjustable by a solenoid 17 in response to vehicle speed to open such communication as speed increases (and thereby decrease power assistance) and vice versa. The valve 13 has a spool 22 which is spring loaded relative to a control spindle 18 of the solenoid. Adjustment of the spool 22 in response to speed variations opens or closes by-pass ports 14 and 15 to opposite ends of a restrictor 32 which provides such fluid flow communication. A spring loaded spool 41 in the valve 13 is responsive through chambers 39 and 40 to fluid pressure at opposite sides of the restrictor 32. When the fluid pressure differential across the restrictor 32 exceeds a predetermined differential, the spool 41 is displaced to direct fluid pressure to spool chamber 55. This displaces the spool 22 against its spring biasing 27 and relative to the rod 18 thereby closing the ports 14 and 15 (and communication between the ram chambers) so that increased power assistance becomes available irrespective of the vehicle being at high speed.

Power assisted vehicle steering system

A vehicle power assisted steering system comprises a hydraulic pump 24 having a constant volume output communicating with an open center power assistance valve 40 which is adjustable from a neutral condition in response to a steering input torque during a steering maneuver to control fluid flow from the pump to opposed chambers of a ram 18b providing power assistance to assist the steering maneuver. A by-pass valve 25 communicates between the outlet of the pump 24 and a fluid reservoir 21 and is responsive to vehicle speed to increasingly open communication between the pump 24 and the reservoir 21 as vehicle speed increases and conversely. The valve 40 has valve members displaceable from a neutral condition in response to a steering input torque to direct hydraulic fluid to actuate the ram 18b for power assistance. In the neutral condition of the valve members, they provide intercommunication between the pump 24, the chambers 18a of the ram and the reservoir 21. The valve members are biassed to the neutral condition. In order to prevent large fluid flows occurring during severe steering maneuvers at high speed, a flow sensitive valve 100 is provided in the line 28,29 connecting the pump 24 to the reservoir 21 by way of the by-pass valve 25 whereby the flow sensitive valve 100 acts to reduce the flow of fluid through the by-pass valve 25 when the flow of fluid reaches a predetermined maximum flow.

Vehicle power assisted steering system

In a power assisted rack and pinion vehicle steering mechanism, a rack and a pinion engage within a housing. The pinion is mounted on a pinion shaft which is journalled in bearings in a cage. A lever is fixed to the cage and projects from the cage through the housing. The lever has a part-spherical seating portion which engages a part-spherical seat in the housing. Spring means biases the rack into engagement wiht the pinion, and through the cage biases the part-spherical seating portion of the lever into engagement with the seat on the housing. Steering torque imparted on the pinion moves the rack axially and causes a reaction on the pinion which rotates the cage about the center of the part-spherical seating portion. This rocks the lever to actuate power assistance means.

Power assistance vehicle steering mechanisms

A power assisted vehicle steering mechanism having a rack and pinion assembly, the pinion being mounted to be displaceable by reaction with the rack on the application of steering torque, including a lever mounted for pivotal movement in response to displacement of the pinion, movement of said lever actuating both an hydraulic valve for directing hydraulic fluid to augment steering torque and electrical sensor means for energizing a motor which drives a pump to supply hydraulic fluid to said valve.

Power assisted vehicle steering mechanism

Power assistance mechanism for a rack and pinion steering gear assembly and an assembly which includes such mechanism includes a main rack and pinion steering gear 1 mounted on which is an auxiliary rack and pinion unit 9. The unit 9 includes an auxiliary rack bar 11, the rack of which engages with an auxiliary pinion in an auxiliary housing 10. The auxiliary pinion is rotatable by an electric motor 23 in the housing 10 to drive the auxiliary rack bar 11. The housing 10 is bolted through brackets 14 to the housing 2a of the main gear 1 while the auxiliary rack bar is coupled through a bracket 16 to the rack bar of the main gear 1. The electric motor 23 is controlled by a switch 27 in the steering input 7 to the pinion of the main steering gear 1 so that when the main rack bar is driven by rotation of the main pinion, the switch 27 is actuated to energize the electric motor and drive the auxiliary rack bar 11 in a sense appropriate to assist the displacement of the main rack bar.

Power assistance means for a steering gear and a steering gear assembly

A power assisted vehicle steering mechanism having a rack and pinion assembly, including a pinion shaft adapted at one end to receive a steering wheel, a pinion on the steering shaft engaging a rack connected to effect steering of the vehicle, a bearing for the pinion shaft located between the pinion and said one end, said bearing permitting angular play of the pinion shaft, the pinion shaft having a portion thereof connected to transmit angular movement of the pinion shaft due to steering torque to a power assistance means to augment steering torque.

A power assisted vehicle steering system has a rack and pinion steering gear 6 incorporating a servo motor 6a controlled by a valve 22. A fluid pressure supply line 3 to the valve 22 includes a throttle or regulating valve 5 which is adjustable by a stepping motor 30 that is speed responsive to increase incrementally the restriction by the valve 5 to fluid flow to the valve 22 as vehicle speed increases. A flow control valve 7 is responsive to fluid pressure in the line 3 upstream of the valve 5 and to fluid pressure in the line 3 downstream of the valve 5 so that a pressure differential across the valve 5 is sensed by spool 9 which is displaced to open the supply line 3 upstream of the valve 5 and a reservoir 1. This latter opening reduces the supply of pressure fluid available for actuating the servo motor 6a and the available power assistance as the vehicle speed increases.

A steering system has annular pressure responsive electric components, such as piezo-electric transducers, mounted between thrust and restraining faces respectively, the transducers respond to a mechanical load applied to them by generating or determining electrical signals which are proportional to the load, the signals are supplied to a comparator by way of electrical connections. The transducers are arranged in pairs on the axially opposed faces of a bearing, so that in response to an axial thrust applied to the bearing by an input shaft of a steering gear incorporated in the system, the signals provided by the transducers will change from a predetermined comparative condition, one signal increasing in response to the increased compressive load on one transducer, the other signal decreasing in response to a decrease in compressive load on the other transducer in the pair. The predetermined comparative condition is established by compressing the transducer pair during installation by means of a retaining cap, which is screw threadedly connected to a housing. The changes in the electrical signal enable the comparator to determine the magnitude and direction of the thrust and to use this information for monitoring or control purposes.

Torque sensing vehicle steering system

A power assisted steering system of the rack and pinion type with a 'centre take-off' 7 has its rack bar 1 carrying a piston 17 at one end thereof. The rack bar 1 forms with the piston opposed pressurized faces 20 and 21 which present pressurized areas in the ratio 1:2. Valve means 22 controllable by rotational input to the pinion 4 directs fluid at the same pressure to both piston chambers 18 and 19 to assist in displacement of the piston rod 1 in a sense to contract the piston chamber 18 or directs fluid to the piston chamber 18 and exhausts the piston chamber 19 to assist in displacement of the piston rod 1 in a sense to contract the piston chamber 19--the power assistance to displacement of the piston rod being substantially the same in both senses of direction. The rack bar 1 is slidably mounted by and longitudinally displaceable relative to two bearings 10 and 11 of which bearing 10 biases the rack 5 into engagement with the pinion and the bearing 11 is in the form of a bush which partly seals an end of the piston chamber 18. The bearings 10 and 11 restrain the rack bar for lateral displacement.

Power assisted steering system

A power assistance steering system for a vehicle, particularly a heavy vehicle, having a first power assistance subsystem known per se and a second power assistance subsystem including a fluid pump for directing fluid pressure selectively to a movement assistance device to assist steering and a prime mover for driving the pump in accordance with signals generated by a sensor responsive to steering.

Power assistance steering system for a vehicle

A vehicle control system has a system part 5 with a pump 6 feeding an open centre valve 4 which controls power assistance for vehicle steering. A second system part 11 has a pump 16 feeding an accumulator 13 and a closed centre valve 10 which controls operation of a clutch or brake booster 2. The pumps 6 and 16 are simultaneously driven by a motor 18. A by-pass valve 21 in conduit 20 is responsive through a pressure transducer 22 and an electrical control unit 19 to pressure in the accumulator 13 so that when the accumulator pressure attains a predetermined value the by-pass valve 21 opens communication between the output from pump 16 and a reservoir 7 to relieve the load on the motor 18. A pressure regulating valve 23 is provided in the steering system part 5. The valve 23 is responsive to pressure from the output of the second pump 16 through conduit 28 and permits the output from the pump 6 to flow by way of conduits 24 and 9 to the reservoir 7 when the pressure from the pump 16 attains a predetermined value so that the pressure available to the valve 4 is less than the maximum pressure available from the output of the pump 6 and the load on the motor 18 which is attributable to it driving the pump 6 is relieved. The valve 23 is preferably a spring loaded spool valve displaceable by expansion of a chamber through the admission of fluid from conduit 28.

Vehicle control system

In a sealing arrangement for a rotary fluid pressure control valve, such as a power steering control valve, a resilient sealing ring is located in a ring groove for sealing engagement with an outer cylindrical member. Frictional losses and a tendency for the sealing assembly to jam are reduced by equalization of the fluid pressure on opposite faces of the sealing ring. This is achieved by virtue of a tapered ring cross-sectional profile and other ring profiles disclosed herein, or by provision of a relieved zone in the ring groove for transmission of fluid pressure.

Valve assemblies

A power assistance steering system 10 for a vehicle comprises steering gear 12 having an internal hydraulic ram supplied with hydraulic fluid by a pump 14 from a reservoir 16 via a solenoid valve 18 controlled by a micro-processor 20 which also controls an electric motor 22 for driving pump 14. Steering input torque is sensed by a torque sensor 36 and steering direction is sensed by a direction switch 34. Output signals from these devices are fed to micro-processor 20 which controls solenoid valve 18 and pump motor 22 accordingly, varying the motor speed in accordance with the pressure requirements of the steering ram as sensed by the torque sensor. In a further embodiment the pump is driven at a constant speed and a proportional control valve 74 is controlled by a micro-processor 78 to vary the fluid pressure supply.

Power assistance steering systems for vehicles

A power assisted steering system and a steering assembly for such a system. The steering assembly has a steering output comprising an arm 6 displaceable through a toothed sector 7 by a racked piston nut 3 drivingly engaging a worm shaft 7 rotatable by a steering input shaft 12. The piston 3 and its cylinder 2 provides a first servomotor for power assisting the steering output. The first servomotor is powered by a first hydraulic system 16 comprising a rotary valve 10 which is responsive to the steering input to control fluid pressure to the first servomotor. The steering system also includes a second hydraulic system 25 comprising an axially responsive spool valve 21 which controls fluid pressure to operate a second servomotor 28 coupled to the steering output arm 6. The rotary and axially responsive valves 10 and 21 are axially coupled together by the shaft 7 which is axially displaceable to control operation of the valve 21. Axial biasing springs 34 and 35 axially spring load the shaft 7 to a neutral condition for the valve 21. During use of the steering assembly the resistance to displacement of the piston 3 by the drive imparted thereto from the worm shaft 7 serves to provide a reaction on the shaft 7 which displaces the shaft against its spring biasing to operate the valve 21 and provide power assistance through the system 25 and ram 28. This power assistance may be effected prior to, simultaneously with or subsequent to power assistance provided by the servomotor comprising the piston 3 powered by operation of the rotary valve and from the hydraulic system 16. If required, both hydraulic systems 16 and 25 can be used to power a single and common servomotor.

Power assisted steering system and a steering assembly for such a system

A rotary valve and a method of forming a sleeve for such a valve. The valve for controlling fluid pressure to a power assisted steering gear has a rotor 3 mounted in the bore 2 of a sleeve 1 so that relative rotation between the rotor and sleeve controls fluid flow through ports 5, 6a, 6b and 7 to actuate the power assistance means. The port 7 is in the form of an axially extending slot in the bore 2, one end 18 of the slot 7 terminating within the bore and the other end opening into an end face 19 of the sleeve to alleviate the requirement for an annular recess (such as 8, 9 or 10) on the sleeve for supply of fluid to the slot 7 and thereby permitting a reduction in length of the sleeve. The slot 7 may be flat bottomed and inclined relative to the sleeve axis and the method comprises rectilinearly machining such a slot--preferably as a single pass with a broaching tool inclined relative to the sleeve axis. In a modification two diametrically opposed slots 7 are provided which open into opposite end faces 19, 27 of the sleeve and have parallel and inclined flat bottoms, and the method comprises forming both said slots simultaneously or consecutively by rectilinear broaching as a single machining operation with the broaching tool inclined relative to the sleeve axis.

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Clevedon, United Kingdom

Frederick J Adams