WO2007128031A1

WO2007128031A1 - Manufacture of hydraulic power steering sleeves

Info

Publication number: WO2007128031A1
Application number: PCT/AU2007/000543
Authority: WO
Inventors: Klaus Juergen Roeske
Original assignee: Bishop Innovation Limited
Priority date: 2006-05-03
Filing date: 2007-04-27
Publication date: 2007-11-15

Abstract

A method and apparatus for manufacturing partially finished sleeves for hydraulic power steering valves. The method comprises gripping and rotating a solid cylindrical bar in a spindle with a portion of the bar protruding from the spindle. A plurality of forming rolls engages with and feeds along the bar, whilst a rotating punch feeds into the end of the bar, to extrude the bar into a tubular form. A cutting tool parts off a portion of the tubular form to provide a partially finished sleeve.

Description

MANUFACTURE OF HYDRAULIC POWER STEERING SLEEVES

TECHNICAL FIELD

The present invention relates to a method and apparatus for manufacturing sleeves for hydraulic power steering valves.

BACKGROUND

Hydraulic power steering valves for automotive power steering typically comprise a sleeve and an input shaft that rotate relative to each other to control the flow of hydraulic fluid. Figs. 1 to 3 show a typical finished sleeve 1 for a hydraulic power steering valve. Sleeve 1 has a bore 2 with a plurality of arcuate slots 3. The outside diameter of sleeve 1 has a plurality of circumferential grooves 4 and 5. Grooves 4 are adapted to locate seals and grooves 5 allow hydraulic fluid to flow around sleeve 1. Bore 2 and slots 3 communicate with grooves 5 through a plurality of holes 8. One end of sleeve 1 has a skirt 6 with a hole 7 to accommodate a drive pin.

Sleeves for hydraulic power steering valves are typically manufactured from lengths of solid cylindrical steel bar. Partially finished sleeves, such as partially finished sleeve 1a shown in Fig. 13, are typically manufactured by machining the steel bar in an automatic bar feed lathe. The steel bar is drilled in the lathe to form rough bore 2a. The skirt 6 and cylindrical grooves 4 and 5 are machined using cutting tools in the lathe and then the partially finished sleeve is parted from the bar using a cutting tool. The bar is then fed though the spindle of the lathe and the process is repeated.

Arcuate slots 3 are typically machined in bore 2a of partially finished sleeve 1a using a "slotting machine" such as described in US Patent No. 5,328,309 (Bishop et al). Holes 7 and 8 are typically formed by drilling. Rough bore 2a may be finished by a boring process to produce finished bore 2, if bore 2 is to be left soft. Alternatively bore 2a may be hardened and ground to produce finished bore 2. A disadvantage of drilling to produce rough bore 2a is that significant material is wasted. An alternative method of making a sleeve is to start with a hollow cylindrical blank that has been forged from a short piece of solid bar. This overcomes the disadvantage of wasting material by drilling, but adds additional operations to the process.

An alternative method of manufacturing sleeve slots that has been used in the past is to firstly use a cutting tool to broach the slots through such that they are open at both ends. The slots may be blinded ended by press fitting a ring into a step in the bore at each end. Alternatively, the slots may be blind ended by deforming the end of the bore radially inwards, then machining the bore to remove excess material.

A method of forming hollow components, known as "spin extrusion", is disclosed in the paper "Spin Extrusion - A New Partial Forming Technology Based on 7 NC-Axes Machining" by R. Neugebauer, R. Glass, M. Hoffmann and M. Putz of the Fraunhofer Institute for Machine Tools and Forming Technology, Chemnitz, Germany, published in the Annals of the International Institution for Production Engineering Research (CIRP), Volume 54/1/2005. This method involves rotating a solid bar in a spindle. Three forming rolls are spaced around the axis of the spindle. These forming rolls are engaged with the bar and fed along the outside of the bar whilst a rotating punch is fed into the end of the bar to extrude the end of the bar into a tubular form. Longitudinal splines can be provided on the rotating punch to form corresponding splines in the bore of the tubular form.

The present invention seeks to ameliorate at least one of the disadvantages of the abovementioned prior art.

SUMMARY OF INVENTION

In a first aspect, the present invention consists of an apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve, said apparatus comprising a spindle adapted to grip and rotate a solid cylindrical bar with a portion of said bar protruding from said spindle, and a cutting tool movable radially and axially with respect to said portion, characterised in that said apparatus further comprises a plurality of forming rolls spaced around the axis of said spindle and a rotatable punch, said forming rolls being adapted to engage and feed along the outside diameter of said portion whilst said rotatable punch is simultaneously fed into the end of said portion thereby extruding said portion into a tubular form.

Preferably, said cutting tool is adapted to part a portion of said tubular form from said bar.

Preferably, said cutting tool is adapted to machine at least one feature of a finished sleeve for a power steering valve onto said tubular form.

Preferably, said apparatus further comprising a second cutting tool, said second cutting tool being movable radially and axially with respect to said tubular form, said second cutting tool being adapted to machine at least one feature of a finished sleeve for a power steering valve onto said tubular form.

Preferably, said apparatus further comprising a bar feed means adapted to repeatedly feed said bar through said spindle by a predetermined amount.

Preferably, said forming rolls are adapted to feed along the outside diameter of said portion by means of said forming rolls being movable towards said spindle, and said rotatable punch is adapted to feed into the end of said portion by means of said rotatable punch being movable towards said spindle.

Preferably, said plurality of forming rolls comprises three forming rolls.

Preferably, said forming rolls are movable radially with respect to said spindle.

Preferably, said rotatable punch has a plurality of longitudinal splines adapted to form the slots of said sleeve as said portion is extruded into said tubular form. Preferably, said rotatable punch has a cylindrical section between said splines and the free end of said rotatable punch, said slots thereby being formed as blind ended at one end of said sleeve.

Preferably, said splines are retractable into said rotatable punch.

In a second aspect, the present invention consists of a method of manufacturing a partially finished sleeve for a hydraulic power steering valve comprising the steps of

i. gripping and rotating a solid cylindrical bar in a spindle with a portion of said bar protruding from said spindle;

ii. engaging a plurality of forming rolls, spaced around the axis of said spindle, with said portion and feeding said forming rolls along the outside diameter of said portion, whilst simultaneously feeding a rotating punch into the end of said portion thereby extruding said portion into a tubular form;

iii. feeding a cutting tool into the outside diameter of said tubular form to part a portion of it from said bar, said partially finished sleeve comprising the parted portion of said tubular form.

Preferably, after step ii and before step iii, at least one feature of a finished sleeve is machined on said tubular form by moving a cutting tool radially and axially with respect to said tubular form.

Preferably, said feature comprises a plurality of circumferential grooves.

Preferably, said feature comprises the skirt of said finished sleeve.

Preferably, after step iii, said bar is fed through said spindle by a predetermined amount, and then steps i to iii are repeated.

Preferably, said plurality of forming rolls comprises three forming rolls. Preferably, during step ii, said forming rolls are fed along the outside diameter of said portion by means of moving said forming rolls towards said spindle, and said rotating punch is fed into the end of said portion by means of moving said rotating punch towards said spindle.

Preferably, after step i and before step ii, the free end of said portion is machined to a shape that assists the initial engagement of said forming rolls and said punch with said portion, by means of moving a cutting tool relative to said portion.

Preferably, said rotating punch has a plurality of longitudinal splines that form the slots of said sleeve as said portion is extruded into said tubular form.

Preferably, said rotating punch has a cylindrical section between said splines and the free end of said rotating punch, said slots thereby being formed as blind ended at one end of said sleeve.

Preferably, at least one end of said slots is blind ended by means of deforming the adjacent end of said sleeve.

Preferably, said splines are retractable into said rotating punch and said slots are formed as blind ended at both ends as said portion is extruded into said tubular form, said splines being retracted to remove said rotating punch.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is an elevation view of a typical finished sleeve for a hydraulic power steering valve.

Fig. 2 is a sectional elevation view of the sleeve shown in Fig. 1.

Fig. 3 is an end view of the sleeve shown in Fig. 1. Fig. 4 schematically shows a first preferred embodiment of an apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve, in accordance with the present invention.

Fig. 5 is an end view of the forming rolls and the spindle of the apparatus shown in Fig. 4.

Figs. 6 to 12 show the apparatus of Fig. 4 being used to implement a first preferred embodiment of a method of manufacturing a partially finished sleeve, in accordance with the present invention.

Fig. 13 shows a partially finished sleeve, manufactured by the method described with reference to Figs. 6 to 12.

Fig. 14 shows the rotating punch of a second preferred embodiment of an apparatus in accordance with the present invention.

Fig. 15 is an end view of the punch shown in Fig. 14.

Fig. 16 shows a partially finished sleeve manufactured by a second preferred embodiment of a method in accordance with the present invention using the punch of Fig. 14.

Figs. 17 and Fig. 18 show further manufacturing steps performed on the sleeve of Fig. 16.

Fig. 19 shows the rotating punch of a third preferred embodiment of an apparatus in accordance with the present invention.

Fig. 20 shows a partially finished sleeve manufactured by a third preferred embodiment of a method in accordance with the present invention using the punch of Fig. 19. BEST MODE OF CARRYING OUT THE INVENTION

Figs. 4 and 5 schematically show a first preferred embodiment of an apparatus 10 for manufacturing a partially finished sleeve for a hydraulic power steering valve, in accordance with the present invention. Details of the apparatus such as linear axes, bearings, servo systems, etc, are not shown as the implementation of these features is well understood by those skilled in the art of machine design.

Apparatus 10 comprises a spindle 11, driven to rotate about axis 12. Spindle 11 has a collet 14 to grip a solid cylindrical bar 13. Bar 13 is fed through spindle 11 , when collet 1.4 is released, by a commonly available bar feed device (not shown). Three forming rolls 17 are evenly spaced around spindle axis 12. Each forming roll is mounted in a carrier 18 and is freely rotatable about its axis 19, parallel to spindle axis 12. Forming rolls 17 are movable radially and axially with respect to spindle 11 by servo axes not shown. Each forming roll 17 has its own servo axis to control its radially movement. A single additional servo axis moves all three forming rolls 17 axially together as a group.

A cylindrical rotating punch 21 is coaxial with spindle 11. Punch 21 is driven to rotate at the same speed and in the same direction as spindle 11 , and is movable axially with respect to spindle 11 by a servo axis not shown.

Two cutting tools 22 and 24 are mounted on a cutting tool carrier 26 that is movable by two servo axes (not shown) such that cutting tools 22 and 24 are movable radially and axially with respect to spindle 11. Cutting tool 22 has a tip 23 that is shaped for parting-off and machining external features. Cutting tool 24 has a tip 25 shaped for boring.

Figs. 6 to 12 show the operation of apparatus 10 and a first preferred embodiment of a method of manufacturing a partially finished sleeve in accordance with the present invention. Initially, forming rolls 17, punch 21 and cutting tools 22, 24 are in their retracted positions as shown in Fig. 4. Solid cylindrical bar 13 is then fed through spindle 11 and gripped by collet 14 such that a portion 15 of bar 13 protrudes from spindle 11. Spindle 11 and punch 21 are then rotated at the same speed and in the same direction.

Forming rolls 17 are then moved radially inwards until they engage the outside diameter of the protruding portion 15 of bar 13, as shown in Figs. 6, 7 and 8. Freely rotatable forming rolls 17 are rotated by their engagement with portion 15. At the same time, punch 21 is moved axially towards spindle 11 until it contacts the end of portion 15. Fig. 8 shows the positions of forming rolls 17 and punch 21 in detail. Each forming roll 17 has a tapered portion 29 leading into a short cylindrical portion 28. As shown in Fig. 8, tapered portion 29 contacts bar portion 15 with cylindrical portion 28 radially overlapping bar portion 15.

Referring to Fig. 9, forming rolls 17 are then fed axially along the outside diameter of bar portion 15, by moving forming rolls 17 towards spindle 11 , whilst simultaneously punch 21 is fed into the end of bar portion 15, by moving punch 21 towards spindle 11. This extrudes the free end of portion 15 into a tubular form 31 , having an outside diameter smaller than bar 13. This process is known as "spin extrusion" as described above in the background.

Forming rolls 17 and punch 21 are then retracted as shown in Fig. 10. Cutting tool carrier 26 is then moved axially and radially such that the tip 25 of cutting tool 24 machines the free end of tubular form 31 into the shape of a skirt 6 of finished sleeve 1. Next, as shown in Fig. 11 , cutting tool carrier 26 is moved axially and radially such that the tip 23 of cutting tool 22 machines circumferential grooves on the outside diameter of tubular form 31 having the shape of grooves 4 and 5 of finished sleeve 1.

Referring to Fig. 12, cutting tool carrier 26 is then moved radially inwards such that the tip 23 of cutting tool 22 is fed into the outside diameter of tubular form 31 , parting a portion of it from bar 13. The parted portion is a partially finished sleeve 1a, as shown in Fig. 13. Bar 13 is then fed through spindle 11 by a predetermined amount, by means of the bar feed device, and the sequence is repeated to make another partially finished sleeve. In another not shown embodiment, prior to engaging forming rolls 17 with bar portion 15, the free end of portion may be machined using cutting tool 22 or 24 to a shape that assists the initial engagement of the forming rolls 17 and punch 21 with bar portion 15. Such a shape may comprise a taper and a shallow bore on the end of bar portion 15, similar to that which remains on bar 13 after partially finished sleeve 1a is parted off in the embodiment described above. This additional machining may only be necessary when starting a new bar having a squared off end, as shown in Fig. 4.

In other not shown embodiments, an apparatus may be used that has only one cutting tool, or more than two cutting tools. Furthermore, less or more features than shown in the described embodiment may be machined on the tubular form before parting it off. For instance, only the circumferential grooves, or only the skirt of the sleeve, may be machined before parting off.

Figs. 14 and 15 show the rotating punch 21a of a second preferred embodiment of an apparatus in accordance with the present invention. The other components of the apparatus are the same as shown in Fig. 4 and the apparatus operates in the same manner. Rotating punch 21a has eight evenly spaced longitudinal splines 33, each extending to the free end of punch 21a.

Fig. 16 shows a partially finished sleeve 1b manufactured by a second preferred embodiment of a method in accordance with the present invention using the apparatus described above having rotating punch 21a. This method is the same as described with reference to Figs. 6 to 12 except that as bar portion 15 is extruded into a tubular form by the spin extrusion process, longitudinal slots 3b, corresponding to splines 33, are formed in the bore of the tubular form. Also, prior to parting off partially finished sleeve 1b, a cylindrical protrusion 34 is machined at each end of the bore 2b of sleeve 1b by moving a cutting tool axially and radially, in a similar manner to which grooves 4 and 5, and skirt 6 are machined.

In a subsequent operation, cylindrical protrusions 34 are then deformed radially inwards by swaging, or any other suitable method, to form partially finished sleeve 1c as shown in Fig. 17. Slots 3b are thus blinded ended by deformed cylindrical protrusions 34a. The bore and ends of partially finished sleeve 1c are then machined to remove excess material from deformed cylindrical protrusions 34a to form partially finished sleeve 1d as shown in Fig. 18. The sleeve is then finished using conventional operations with formed slots 3b becoming the hydraulic slots of the finished sleeve, having the same function as slots 3 of sleeve 1.

Fig. 19 shows the rotating punch 21b of a third preferred embodiment of an apparatus in accordance with the present invention. The only difference between this punch and punch 21a shown in Fig. 14 is that the longitudinal splines 33a of punch 21b do not extend all the way to the free end of the punch. Instead, there is a short cylindrical section 35 between the splines 33a and the free end of the punch.

Fig. 20 shows a partially finished sleeve 1e manufactured by a third preferred embodiment of a method in accordance with the present invention using an apparatus having rotating punch 21b. Punch 21b operates in the same manner as punch 21a except that since splines 33a do not extend all the way the end of punch 21b, the slots 3c formed thereby in partially finished sleeve 1e are blinded end at one end. However, slots 3c must be open ended at the other end of the sleeve so that punch 21b can be removed. A cylindrical protrusion 34 is machined at the end of sleeve 1e adjacent the open ends of slots 3c. Cylindrical protrusion 34 is subsequently deformed to blind end slots 3c in the same manner as described with reference to Figs. 16 to 18.

In other not shown embodiments, the slots formed by splines on the rotating mandrel may be blind ended by press fitting rings into a step in the bore at one or both ends of the sleeve.

In another not shown embodiment, the splines on the rotating punch may be radially retractable into the punch. This allows the slots to be formed as blind ended at both ends during the spin extrusion process with the slots having the same length as the splines. After spin extrusion, the splines are retracted into the punch to allow the punch to be removed. In other not shown embodiments, the rotating punch may have other than eight splines and the splines may have uneven spacing or varying width corresponding to the slot arrangements of various sleeve designs. The splines may also have varying axial length. For example, some splines may extend to the end of the punch whilst others do not such that some of the slots are open ended, whilst the others are blind ended.

The term "comprising" as used herein is used in the inclusive sense of "including" or "having" and not in the exclusive sense of "consisting only of.

Claims

1. An apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve, said apparatus comprising a spindle adapted to grip and rotate a solid cylindrical bar with a portion of said bar protruding from said spindle, and a cutting tool movable radially and axially with respect to said portion, characterised in that said apparatus further comprises a plurality of forming rolls spaced around the axis of said spindle and a rotatable punch, said forming rolls being adapted to engage and feed along the outside diameter of said portion whilst said rotatable punch is simultaneously fed into the end of said portion thereby extruding said portion into a tubular form.

2. An apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 1 wherein said cutting tool is adapted to part a portion of said tubular form from said bar.

3. An apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 1 wherein said cutting tool is adapted to machine at least one feature of a finished sleeve for a power steering valve onto said tubular form.

4. An apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 1 further comprising a second cutting tool, said second cutting tool being movable radially and axially with respect to said tubular form, said second cutting tool being adapted to machine at least one feature of a finished sleeve for a power steering valve onto said tubular form.

5. An apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 1 further comprising a bar feed means adapted to repeatedly feed said bar through said spindle by a predetermined amount.

6. An apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 1 wherein said forming rolls are adapted to feed along the outside diameter of said portion by means of said forming rolls being movable towards said spindle, and said rotatable punch is adapted to feed into the end of said portion by means of said rotatable punch being movable towards said spindle.

7. An apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 1 wherein said plurality of forming rolls comprises three forming rolls.

8. An apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 1 wherein said forming rolls are movable radially with respect to said spindle.

9. An apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 1 wherein said rotatable punch has a plurality of longitudinal splines adapted to form the slots of said sleeve as said portion is extruded into said tubular form.

10. An apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 9 wherein said rotatable punch has a cylindrical section between said splines and the free end of said rotatable punch, said slots thereby being formed as blind ended at one end of said sleeve.

11. An apparatus for manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 9 wherein said splines are retractable into said rotatable punch.

12. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve comprising the steps of

13. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 12 wherein, after step ii and before step iii, at least one feature of a finished sleeve is machined on said tubular form by moving a cutting tool radially and axially with respect to said tubular form.

14. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 13 wherein said feature comprises a plurality of circumferential grooves.

15. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 13 wherein said feature comprises the skirt of said finished sleeve.

16. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 12 wherein after step iii, said bar is fed through said spindle by a predetermined amount, and then steps i to iii are repeated.

17. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 12 wherein said plurality of forming rolls comprises three forming rolls.

18. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 12 wherein during step ii, said forming rolls are fed along the outside diameter of said portion by means of moving said forming rolls towards said spindle, and said rotating punch is fed into the end of said portion by means of moving said rotating punch towards said spindle.

19. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 12 wherein after step i and before step ii, the free end of said portion is machined to a shape that assists the initial engagement of said forming rolls and said punch with said portion, by means of moving a cutting tool relative to said portion.

20. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 12 wherein said rotating punch has a plurality of longitudinal splines that form the slots of said sleeve as said portion is extruded into said tubular form.

21. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 20 wherein said rotating punch has a cylindrical section between said splines and the free end of said rotating punch, said slots thereby being formed as blind ended at one end of said sleeve.

22. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 20 wherein at least one end of said slots is blind ended by means of deforming the adjacent end of said sleeve.

23. A method of manufacturing a partially finished sleeve for a hydraulic power steering valve as claimed in claim 20 wherein said splines are retractable into said rotating punch and said slots are formed as blind ended at both ends as said portion is extruded into said tubular form, said splines being retracted to remove said rotating punch.