Variable ratio rack and pinion power steering gear

• US 3,908,479 A
• Filed: 12/10/1973
• Issued: 09/30/1975
• Est. Priority Date: 12/10/1973
• Status: Expired due to Term

• Current Assignee: Stanley I. Macduff
• Original Assignee: Stanley I. Macduff
• Inventors: MacDuff, Stanley I.
• Primary Examiner(s): Gerin, Leonard H.
• Application Number:
  US05/423,106
• Time in Patent Office: 659 Days
• Field of Search: 74/422,498,388PS 91/375H
• US Class Current: 74/498
• CPC Class Codes: B62D 3/12 of rack-and-pinion type
• CPC Class Codes: B62D 5/22 for rack-and-pinion type

Abstract

A rack and pinion power steering gear for small sports type cars having a conventional rack and pinion with a ratio changing gear floating between them. The ratio changing gear is a conventional circular gear having an eccentrically positioned pin carried in bearings which are arranged to slide in slots centered on and aligned with a perpendicular to the rack passing through the center of the pinion. The ratio changing gear is proportioned to make one revolution for approximately full stroke of the rack. The pinion is proportioned to give the number of steering wheel turns desired from lock-to-lock. The eccentricity of the shaft predetermines the effective ratios at the center and at the locks. A modified form of the invention employs a swinging yoke to position the ratio changing gear on an arc which approximates the aforesaid perpendicular.

Claims

1. A vehicle steering gear comprising:

a housing having walls;

a pinion gear rotatable in said housing;

a rack spaced from the pinion gear and slidable in said housing; and

a ratio changing gear positioned between the rack and the pinion gear, said ratio changing gear having an eccentric pin, and means in engagement with said housing to constrain said eccentric pin to move in a path approximating a line perpendicular to the pitch line of said rack and passing through the center of said pinion gear.

2. The invention of claim 1 in which said means comprises slots in the walls of said housing.

3. The invention of clAim 1 in which said means comprises slots in the walls of said housing and bearing blocks journaled on said eccentric pin and slidable in said slots.

4. The invention of claim 3 in which the steering gear includes a power cylinder having a piston and a piston rod attached to said rack, an input shaft, and valve means for controlling flow of hydraulic fluid to said power cylinder interposed between said input shaft and said pinion gear.

5. The invention of claim 1 in which said means comprises a yoke having said eccentric pin journaled in one end and having the other end of the yoke swingably attached to said housing.

6. The invention of claim 5 in which said yoke constrains said eccentric pin to move in an arc having said perpendicular line forming a chord thereof.

7. The invention of claim 6 in which the steering gear includes a power cylinder having a piston and a piston rod attached to said rack, an input shaft, and valve means for controlling flow of hydraulic fluid to said power cylinder interposed between said input shaft and said pinion gear.

8. The invention of claim 1 in which the steering gear includes a power cylinder having a piston and a piston rod attached to said rack, an input shaft, and valve means for controlling flow of hydraulic fluid to said power cylinder interposed between said input shaft and said pinion gear.

9. The invention of claim 8 in which said valve means comprises:

the said housing being formed with a valve bore intersected by pump ports and cylinder ports;

a rotor formed integrally with said pinion gear and having longitudinal slots;

a sleeve in sealing engagement with said valve bore surrounding the rotor, said sleeve being formed with cooperating longitudinal slots forming selective fluid paths with the slots of said rotor, and having annular grooves on its outer surface communicating fluid to said pump ports and cylinder ports;

said sleeve and rotor having adjacent ends formed with aligned slots;

the said input shaft having a spline formed across its end in operative engagement with the slots of the sleeve and rotor;

a bearing seated in said valve bore and supporting said input shaft; and

a torsion bar interconnecting said valve rotor and said input shaft.

10. A steering gear comprising a housing, a rack positioned in the housing, a pinion positioned in the housing and spaced from said rack, and ratio varying means positioned between and in engagement with said rack and pinion.

11. The invention of claim 10 in which said ratio varying means is a gear having an eccentric rotational axis, and means to constrain said eccentric axis to move in a path approximating a line perpendicular to the pitch line of said rack and intersecting the center of said pinion.

12. The invention of claim 11 in which said means includes an element having linear sliding engagement with said housing.