GB2308578A

GB2308578A - Input shaft rotation blocking control valve assembly.

Info

Publication number: GB2308578A
Application number: GB9621495A
Authority: GB
Inventors: Jong Sig Byeon; Byung Yun Choi
Original assignee: Mando Machinery Corp
Current assignee: Mando Machinery Corp
Priority date: 1995-12-27
Filing date: 1996-10-15
Publication date: 1997-07-02
Anticipated expiration: 2016-10-15
Also published as: JPH09188267A; CN1155487A; KR970036864U; GB2308578B; CN1058457C; DE19642398A1; JP2828959B2; GB9621495D0

Description

2308578 CONTROL VALVE ASSEMBLY FOR AUTOMOTIVE VEHICLE The present

invention relates to a power assisted rack-pinion steering system. More particularly, it relates to a control valve assembly having a ring-shaped plate spring applying pressure to a roller which is seated in a groove formed in the valve body of the pinion valve assembly.

A hydraulic power steering system for an automotive vehicle 1.5 a steering control mechanism in which an auxiliary power source assists the driver by providing the majority of force required to direct the road wheels. It controls the application of powered assistance to the manual steering effort applied to the pinion through the steering wheel by regulating the flow of oil jetted out by an engine-driven oil pump. FIG. 6 depicts a conventional power steering system. Oil filled in a tank 80 is pumped to a control valve assembly 60 through a fluid supply line I as the pump 70 is actuated by the engine (not illustrated). In accordance with the direction of the fluid's supply in the control valve assembly 60, the oil is. alternatively supplied to the left or right: chamber 91 or 93 of the power cylinder 90. through a fluid discharge line ( designated by the leCter R or L The position of the piston 92 inside thepower cylinder 90 is determined by the relative amounts of fluid supplied to the left or right chamber 91 or 93. Thus, when the steering wheel 200 turns in the direction of the arrow LI, the piston 92 is moved in the L2 direction by the fluid pumped into the left chamber. 93.

1 Thereby, each of the wheels 10OR and 100L makes a turn to the left L3.

On the contrary, if the steering wheel 200 turns in the opposite direction Rl, the fluid flows into the right chamber 91 and the piston 92 is moved in the R2 direction resulting in each of the wheels 10OR and 100L turning to the right R3. The pressure applied to the power steering system is instantaneously increased by unexpected road shock created when an automotive vehicle equipped with such a power steering system travels over irregularities in the road.

The road shock is delivered from the vehicle wheel 100L or 10OR to a rack 94 thereby causing the rack's 94 undesired movement. This movement of the rack 94 causes the pinion 64 of the output shaft 63 to turn, which causes the connected input shaft 61 to also rotate. This increases the amount of fluid provided to the power cylinder 90 from the control valve assembly 60, thereby making the steering wheel 200 rock from side to side or from front to back.

In the case where the vehicle is traveling at intermediate or highway speeds, even a small torque generated by the output shaft is enough to precipitate the above phenomenon.

This phenomenon represents the driver's loss of sensitivity to operating the steering wheel when driving a car at intermediate or highway speeds, and gives rise to an unstable steering feel. Therefore, the conventional system makes a driverOs manual steering effort harder and increases driver fatigue and irritation while driving the car.

2 The present invention eliminates the above-mentioned problems of the conventional art by introducing a control valve assembly for an automotive vehicle.

The first objective of the present invention is to provide a control valve assembly for an automotive vehicle which permits a large amount of torque to be administrated to the steering wheel within a predetermined angle of rotation while the vehicle is driven at intermediate or highway speeds.

The second objective of the present invention is to provide a control valve assembly for an automotive vehicle which enables the steering wheel to be free from sudden road shock when the vehicle is travelling at intermediate or highway speeds.

In order to achieve the above objectives and advantages, and in accordance with the purpose of the present invention as embodied and broadly described, the present invention's control valve assembly for an automotive vehicle includes an input shaft and output shaft connected to either end of a torsion bar, and a pinion on the output shaft's lower section.

This control valve assembly possesses blocking means which prevents the input shaft from turning below a predetermined angle of rotation, and a housing which accommodates the input: shaft, output shaft and blocking means.

The blocking mean includes at least. one groove formed lengthwise on the outer circumferential surface of the input shaft, at least one roller located along the longitudinal axis of the input shaft and partially seated in the groove, and elastic means provided to encompass the roller so as to make it roll along the outer 3 circumferential surface of the input shaft. This elastic means is a ring- shaped plate spring with a slit which facilitates easy mounting around the outer circumference of the input shaft.

This control valve assembly further includes a washer having two projections inserted into the space in which the rollers lie, and a third projection designed to be inserted into the slit of the elastic means.

FIG. 1 is a perspective view of a pinion valve assembly which it equipped with input shaft rotation blocking means in accordance with the first preferred embodiment of the present invention; FIG. 2 is a plan view as taken by an arrow X of FIG. 1; FIG. 3 is a perspective view of the pinion valve assembly which further includes a washer in accordance with the second preferred embodiment of the present invention; FIGS. 4A through 4C respectively depict three positions of the roller in relation to various degrees of the input shaft's rotation; FIG. 5 graphically shows torsional angle and torque of the input shaft in accordance with embodiments of the present invention; and FIG. 6 depicts a. power steering system equipped. with a conventional pinion valve assembly.

The preferred embodiments of the present invention will now be discussed in detail with reference to the accompanying drawings. Similar reference numerals designate similar elements throughout 4 the drawings and the specification. Furthermore, redundant explanations of features common between the conventional art and preferred embodiments of this invention are omitted.-

FIG. 1 illustrates a perspective view of a pinion valve assembly 300 equipped with input shaft rotation - blocking means in accordance with the first preferred embodiment of the present invention.

The Pinion valve 300 accommodates one and of the torsion bar 62. It also includes an input shaft 10 which is passed through and fixed in place by a pin 11,. and an output shaft 63 connected it a serration to the other end of the torsion bar 62. The output shaft 63 has a pinion 64 on its lower section. A valve body 65 which is rotatable within its housing 67 is attached to the outer circumferential surface of the input shaft 10.

Two grooves 12 are formed lengthwise on the outer circumferential surface of the input shaft 10 adjacent to the upper section of the valve body 65, and 180o from each other with respect to the longitudinal axis of the input shaft 10, as depicted FIG. 2.

Continuning with FIG. 1, rollers 22 are introduced parallel to the input shaft's 10 longl'tudl"ml axis- and upon its circumferential surface in such a manner that they sit in the grooves 12. A roller cage 24. is installed around the outer circumferential surface of the input shaft-10 so as to control the movement of the roller 22 ( i.e. to make the roller 22 revolve on its axis while rolling along the rotating input shaft 10 Since there are two rollers 22 corresponding to the grooves 12 in this embodiment of the present invention, a pair of roller cages 24 are provided thereto.

A plate spring 26 is fitted onto the circumferential surfaces of the roller cages 24 so as to encompass the rollers 22. A slit 28 is formed in the plate spring 26 to facilitate its mounting on the outer surfaces of the roller cages 24. A snap-ring 30 is tightly inserted in the slot 32 of the input shaft 10 in order to be joined with the upper surfaces 24U of the roller cage 24, which prevents the roller cages 24 from being disjoined between the input shaft 10 and the plate spring 26.

FIG. 3 depicts, as the second preferred embodiment of the invention, the pinion valve assembly 300 which further has a washer 40 disposed between the plate spring 26 and the snap-ring 30, the washer 40 consists of two projections 41 aligned with its inner circumference extending downward, and a third projection 48 originating at its outer circumference and extending downward. The first two projections 41 are mounted close to the upper surfaces 22U of the rollers 22 in order to prevent the roller cages 24 and the plate spring 26 from slipping out toward the washer 40. The second projection 48 inserts into the slit 28 of the plate spring 26.

As the rollers 22 revolve around their centers with the rotation of the input shaft 10, the plate spring 26 ( which contacts them) rotates in the opposite direction of the rotating input shaft 10. Consequently, when slit 28 of the plate spring 26 moves towards one of the rollers 22, the roller 22 may move out of its original position along the groove 12 via the slit 28. To preclude this problem, the third projection 48 is formed at a predetermined distance from each of the first two projections 41, and maintains the spacing between the slit 28 and the respective 6 rollers 22 at all times.

The following description relates to the operation of the control valve assembly for an automotive vehicle having such an input shaft rotation blocking means.

FIGS. 4A to 4C respectively depict the movement of the roller 22 with the rotation of the input shaft 10.

As shown in FIG. 4A, when the automotive vehicle is travelling on a straight road at intermediate or highway speeds, the roller 22 is held in place in the groove 12 on the input shaft 10 by compression force of the plate spring 26. This allows the steering wheel to lie in a straightahead position.

Shock delivered to the vehicle through the wheels 100L and 10OR as they move over irregularities in the road rotates the rack 94 which then rotaty the pinion. This causes the output shaft to the turn and apply torque to the input shaft 10. The elastic force of the plate spring 26, which is transmitted to the input shaft 10 through the rollers 22 acts as blocking torque Td as shown in FIG. 5. The torsional angle e of the input shaft 10 becomes zero, therefore preventing the steering wheel 200 from turning.

As depicted in FIG 4B, in the case that torque T is acting on the input shaft 10 in excess of the aforementioned blocking torque Td (about 8kgfcm in the present invention) as the input shaft 10 turns in the direction of arrow R8, the inclined surface of the groove 12 contacting the roller 22 pushes the roller 22 away from the input shaft 10. The outward movement R9 of the roller 22 is restrained by the plate spring 26, and the torsional angle of the input shaft 10 becomes small.

In other words, as shown in FIG. 5, even if torque Tb (indicated 7 by a solid line) greater than the conventional artfs torque Tp (indicated by a dotted line) is applied to the input shaft 10, the present invention requires an input shaft-'s 10 torsional angle eb which is equal to that of the conventional art.

Turning now to FIG. 4C, in the case that greater torque is applied to the input shaft 10 as the steering wheel 200 makes a big turn, the roller 22 becomes completely disloged from the groove 12 and is resituated on the circumferential surface of the input shaft 10. Referring to FIG. 5, when torque Tc is applied to the input shaft 10 (about 40kgfcm in the present invention), the torsional angle of the input shaft 10 (approximately 3o in the present invention) equals ec.

When the torsional angle of the input shaft 10 exceeds ec, the roller 22 rolls along the circumferential surface of the input shaft 10 and the input shaft 10 rotates on its axis. Therefore, the torsional angle of the present invention indicated by the solid line increases to be slightly larger than that of the conventional art shown by the dotted line.

The above description concerns the case where the input shaft 10 turns clockwise (in the directions of the arrow R8 of FIGS. 4B, 4C) due to the road shock generated when the vehicle is running. When the input shaft 10 makes a counterclockwise rotation, the conventional and inventive torsional angles of the input shaft 10 may be respectively indicated by lines in the third guadrant of the FIG. 5 graph. Further descriptions concerning the case in which the input shaft 10 turns counterclockwise are omitted because it is complientary to the above clockwise-rotation discussion.

8 FIG. 5 illustrates the characteristics of torque produced by the rotation of the automotive vehicle's steering wheel 200 employing the control valve body with the inventive input shaft rotation blocking means while the vehicle is running at intermediate or highway speeds. When the torsional angle e of the input shaft 10 is less than a predetermined angle ec, the conventional art requires a small amount of torque Tp; the present invention needs torque Th relatively greater than Tp in order to attain the same torsional angle eb.

Regarding the control valve assembly. with the present invention't input shaft rotation blocking means, when the steering wheel t urn s within a predetermined torsional angle while the vehicle is running at moderate or highway speeds, greater torque may act on the steering wheel because the resistance of the plate spring holds the rollers in the their respective grooves. Therefore, the present invention provides a driver with a firm and stable steering feel. When the road shock is delivered to the input shaft by way of the vehicle wheels, the elastic force of the plate spring prevents the input shaftIs rotation from being transmitted to the steering wheel, thereby emhancing steering feel and alleviating driver fatigue and irritation caused.by the unstable operation of the steering wheel -While- the invention has been described in conjunction with specific embodiments thereof, it is evidenC that several alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations the fall within the broad scope of the following cl-aims.

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Claims

CLAIMS: 1. A control valve assembly comprising:

for an automotive vehicle an input shaft connected to one end of a torsion bar; an output shaft connected to the other end of the torsion bar and having a pinion on its lower section; blocking means acting to prevent the input shaft from turning at angles of rotation below a predetermined angle of rotation; and a housing accommodating the input shaft, output shaft and: blocking means.
2. A control valve assembly for an automotive vehicle as set forth in claim 1, wherein said blocking means comprises: at least one groove formed lengthwise on the outer circumferential surface of the input shaft; at least one roller disposed along the longitudinal axis of the input shaft and adapted to be partially seated in the groove; and resilient means provided to encompass the roller such as to enable the roller to roll along the outer circumferential surface of the input shaft.
3. A control valve assembly for an automotive vehicle as set forth in claim 2, wherein said blocking means further comprises at least one roller cage for directing the or each roller along the outer circumferential surface of the input shaft when rotating.
4. A control valve assembly for an automotive vehicle as set forth in claim 2 or claim 3, wherein said resilient means is a ring-shaped plate spring which has a slit adapted to facilitate its mounting around the outer circumference of the input shaft.
5. A control valve assembly for an automotive vehicle as set forth in claim 3, or claim 4 where dependent on claim 3, further comprising a washer having two projections inserted into the spaces between the roller cages surrounded by the resilient means and contacting the upper surface of the roller.
6. A control valve assembly for an automotive vehicle as set forth in claim 5 where dependent on claim 4 wherein said washer includes a third projection designed to be inserted into the slit of the resilient means.
7. A control valve assembly for an automotive device substantially as described herein with reference to Figures 1 to 4, and with or without reference to Figure 5, of the accompanying drawings.

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