GB2120336A - Rotary flywheel skid sensing means for vehicle hydraulic braking systems - Google Patents

Abstract

A flywheel mechanism (5) rotatable with a shaft (4) comprises a flywheel (10), a thrust member (13), and an expander mechanism (15, 16, 17) comprising angularly spaced balls and ramps arranged to cause one of the members (10, 13) to move axially and actuate a brake pressure modulator (3) when the flywheel and the thrust member are relatively displaced from a predetermined angular alignment. The thrust member (13) is carried from the shaft (4) by a mounting (18) comprising a driving flange (19) coupled to the shaft (4), and a clutch plate (21) in frictional engagement with the thrust member (13) and driven from the flange by a coupling (20, 23; 36, 37) which enables the thrust member (13) to articulate and move radially with respect to the flywheel (10). A bias force is applied centrally to the movable member (10, 13) by lever (24), and the articulating mounting (18) ensures that the force is distributed substantially equally between the balls (15). Rotation of lever (24) actuates an anti-skid valve mechanism. A further embodiment (fig. 3, not shown) discloses a different lever and valve arrangement. <IMAGE>

Description

SPECIFICATION Rotary flywheel skid sensing means for vehicle hydraulic braking systems This invention relates to rotary flywheel skid sensing means for vehicle hydraulic systems of the kind comprising a flywheel mechanism rotatable with a shaft adapted to be driven from a wheel to be braked and including a flywheel member and a thrust member together with camming means responsive to relative angular movement between the two said members to cause one of the said members to move axially relative to the other between a first position in which the two members are in a predetermined angular alignment and a second position in which the said one axially movable member engages means to actuate brake pressure modulating means.

In known sensing means of the kind set forth, for example as disclosed in our G.B. Patent Specification No. 2 027 832, both members of the flywheel mechanism are mounted on, and are rotatable with respect to, the shaft so that they are both constrained against relative tilting movement, and the axially movable member acts on the brake-pressure modulating means through biassing means which bias the movable member towards the first position to determine a threshold setting of the flywheel mechanism, the camming means comprising balls which are located in complementary recesses in mating faces of the two members so that, upon relative angular movement between the two members, the balls tend to ride out of their recesses causing the movable member to move axially away from the other member.

In such a known construction it is difficult, due to concentricity tolerances of the two members of the flywheel mechanism, for us to arrange for all the balls to fit perfectly into their corresponding recesses and therefore be subjected to a uniform loading from the biassing means, which is desirable if the threshold setting of the sensing means is to be maintained within required limits.

Also, in such a known construction, a thrust member and a clutch are disposed between the flywheel mechanism and a housing which makes inspection of the parts and adjustment of the mechanism to determine the threshold setting difficult to achieve.

According to our invention in rotary flywheel skid sensing means of the kind set forth the members are carried from the shaft through mounting means, the mounting means for the axially movable member having a face for receiving a centrally applied bias force from biassing means, and the mounting means are so constructed and arranged to enable one of the members to articulate and move radially relative to the other member whereby the bias force from the biassing means is distributed substantially equally between angularly spaced balls located in corresponding recesses in adjacent faces of the two members.

The mounting means for the articulating member may comprise a driving flange coupled to the shaft, and a clutch plate in frictional engagement with the articulating member and driven from the flange by a coupling, the couplings being arranged to provide the articulation and radial movement.

Thus, if it is the axially movable member that is mounted for articulation and radial movement, the driving flange may be fast with the shaft, and the coupling between the flange and the clutch plate allows axial sliding movement as well as articulation and radial movement of the axially movable member.

Alternatively, if the fixed member is mounted for articulation, both couplings may be arranged to provide articulation and radial movement of the fixed member.

In one construction the flywheel member is journalled for rotation and is fixed axially with respect to the shaft, and the thrust member comprises the said axially movable member, the thrust member being mounted for articulation and radial movement, with a radial clearance being provided between overlapping faces of the flywheel member and the thrust member.

In this construction the driving flange is fast with the shaft; and the coupling between the clutch plate and the flange comprises axially projecting lugs on the flange sliding in notches in the clutch plate to provide axial movement of the thrust member as well as articulation and radial movement.

Conveniently the bias force is applied to the clutch plate through a single point forcetransmitting device in axial alignment with the axis of the shaft. The force-transmitting device may be axially adjustable to alter the clearance between the force-transmitting device and the modulating means and, in consequence, the amount of lostmotion of the skid sensing means.

Conveniently the flywheel mechanism is housed within a housing with the forcetransmitting device positioned at an outer end which is normally closed by a removable cover.

This has the advantage that the mechanism is fully protected by the housing from damage by objects flying in a radial direction, and removal of the cover enables the parts to be easily inspected and the force-transmitting device to be readily adjusted.

In another construction the flywheel comprises the axially movable member and the thrust member is fixed axially with respect to the shaft, the thrust member being mounted for articulation and radial movement, and a radial clearance being provided between overlapping faces of the flywheel member and the thrust member.

In this construction the driving flange is coupled to the shaft by a transverse pin, and a rocking coupling is provided between the driving flange and the clutch plate, so that both couplings provide articulation and radial movement.

The bias force is preferably applied to the flywheel member by means of a bifurcated lever, which also actuates the brake pressure modulating means.

Two embodiments of our invention are illustrated in the accompanying drawings in which Figure 1 is an end view of rotary flywheel skid sensing means with the cover removed for clarity; Figure 2 is a section on the line 2-2 of Figure 1; Figure 3 is a transverse section through a modified rotary flywheel skid sensing means; Figure 4 is an end view of the fixed member of Figure 3; and Figure 5 is an underneath view of the fixed member of Figure 4.

The sensing means illustrated in Figures 1 and 2 of the drawings comprises a housing 1 incorporating an hydraulic pump 2 and a combined pressure dump valve and modulator assembly 3. A longitudinally extending shaft 4 projecting at opposite ends from the housing 1 is coupled at one end to the wheel and at the other end carries skid sensing means 5 in the form of a flywheel assembly which is enclosed within a cylindrical radial portion 6 of the housing 1 of which the open, outer, end is closed by a detachable cover 7. The radial portion 6 protects the mechanism from radially directed flying debris and other objects.

The flywheel assembly 5 comprises a flywheel 10 which is fixed axially but freely rotatable on mounting means comprising spaced bearings 11 and 12 adjacent to one end of the shaft 4, and an annular rotatable thrust member 13 which is axially movable, and is at least partially accommodated within an annular recess 14 in the end of the flywheel which faces the outer end of the radial portion 6. A clearance is provided between the outer edge of the thrust member 1 3 and the outer wall of the recess 14, and between the inner edge of the thrust member 13 and the inner wall of the recess 14.

Three angularly spaced balls 1 5 are located in complementary recesses 16, 1 7 in mating faces of the flywheel 10 and the thrust member 13.

The thrust member 1 3 is carried from the free end of the shaft 4 by mounting means 1 8 which enables the thrust member 13 to move axially, as well as to articulate and move radially relative to the flywheel 10. The mounting means 18 comprises a radial driving flange 1 9 which is fast with the free end of the shaft 4, and is provided at its peripherai edge with a pair of diametrically arranged parallel-sided lugs 20 which project axially towards the outer end of the radial portion 6, and a clutch plate 21 of dished outline which engages frictionally at its outer peripheral edge with a radial clutch face 22 on the thrust member 13 and in which is provided a pair of diametrically spaced notches 23 which slidably receive the lugs 20.The dished form in the clutch plate 21 provides a clearance with respect to the free end of the shaft 4.

The thrust member 1 3 is urged towards the flywheel 10 by a force from a bias spring (not shown) applied to the clutch plate 21. This force is transmitted to the thrust member 13 through the clutch plate 21 and an angularly movable lever 24 mounted in the housing 1. The lever 24 acts on the clutch plate 21 in a position in axial alignment with the rotational axis of the shaft 4 through an adjustable single-point force-transmitting member 25 which is screwed through the lever 24 so that the biassing force is applied centrally to the mounting means 18. Since the thrust member 13 can articulate and move radially with respect to the flywheel 10, the load from the bias spring is distributed and shared substantially equally between the three balls 1 5.

In operation, relative movement between the flywheel 10 and the thrust member 13, due to excessive deceleration of the wheel and the shaft, with the flywheel 10 running on due to its inertia, causes the balls 1 5 to tend to ride out of the recesses 1 6 and 1 7 thereby urging the thrust member 13 and the clutch plate 21 axially away from the flywheel 10 move the lever 24 angularly, in turn to operate the combined modulator and dump valve assembly 3. The clutch plate 21 slides on the lugs 20. Thereafter the flywheel 10 and the thrust member 13 run on against the frictional force of engagement between the clutch plate 21 and the clutch face 22 of which the threshold is determined by the loading in the bias spring.

The clearance between the lever 24 and the dump valve 3 can be readily adjusted or otherwise set by adjusting the axial position of the member 25 relative to the lever 24, after removal of the cover 7.

The embodiment shown in Figures 3 to 5 is a modification of that shown in Figures 1 and 2, and corresponding reference numerals have been applied to corresponding parts.

In Figure 3 the flywheel 10 is the axially movable member, while the thrust member 1 3 is axially fixed. The flywheel 10 is mounted by a collar 26 which is rotatable on the shaft 4, and has sufficient clearance to enable it to move axially with respect to the shaft. The collar 26 has a radial flange 27, and a bearing 28 is interposed between adjacent radial surfaces of the flange 27 and the flywheel 1 0.

A bias force from a biassing spring 29 located in the housing 1 is applied to the flywheel 10 through a bifurcated lever 30 and the collar 26.

The lever 30 has domed contact points 31 which contact the collar 26. One end of the lever 30 is mounted in the housing 1, by an adjustable screw arrangement 32, to provide a fulcrum, and the other end of the lever 30 is adapted to actuate the dump valve 3, with the spring 29 and the contact points 31 acting at intermediate locations. The screw arrangement 32 enables the clearance between the flywheel 10 and the valve 3 to be adjusted.

The thrust member 1 3 is fixed to the shaft 4 by mounting means 1 8 which allows the thrust member 13 to articulate and move radially relative to flywheel 10. As in Figure 2, the mounting means 1 8 comprises a driving flange 19 and a clutch plate 21. The driving flange 1 9 is fixed to the free end of the shaft 4 by a transverse pin 33 through which the drive is transmitted to the thrust member 13. The flange 1 9 is permitted a limited amount of pivotal movement about the pin 33.The clutch plate 21 is annular, with an inner face 34 engaging frictionally with the face 22 of the thrust member 13, and an outer face 35 provided with two pairs of spaced lugs 36, between which opposed radial arms 37 of the flange 1 9 are accommodated (see Figure 4). The engagement between the arms 37 and the lugs 36 provide a rocking coupling, since, as can be seen in Figure 5, there is a clearance between the arms 37 and the lugs 36, and the arms 37 have a curved contact surface 38, so that a limited amount of rocking movement of the clutch plate 21 relative to the flange 19 is allowed. Thus, the pivotal pin coupling and the rocking coupling provide the articulation and radial movement of the thrust member 1 3 with respect to the flywheel 10, so that the load from the spring 29 is distributed and shared substantially equally between the balls 15.

Operation of the embodiment of Figures 3 to 5 is substantially similar to that described in relation to Figures 1 and 2, except the flywheel 10, rather than the thrust member 13, moves axially, and operates the dump valve 3 via the lever 30.

The skid sensing means described above are suitable for use with motor cycles or other light motor vehicles such as light passenger cars.

Claims (14)

1. Rotary flywheel skid sensing means of the kind set forth in which the members are carried from the shaft through mounting means, the mounting means for the axially movable member having a face for receiving a centrally applied bias force from biassing means, and the mounting means are so constructed and arranged to enable one of the members to articulate and move radially relative to the other member whereby the bias force from the biassing means is distributed substantially equally between angularly spaced balls located in corresponding recesses in adjacent faces of the two members.

2. Means as claimed in claim 1 , in which the mounting means for the articulating member comprises a driving flange coupled to the shaft, and a clutch plate in frictional engagement with the articulating member and driven from the flange by a coupling, the couplings being arranged to provide the articulation and radial movement.

3. Means as claimed in claim 2, in which the axially movable member is mounted for articulation and radial movement, the driving flange being fast with the shaft, and the coupling between the flange and the clutch plate allowing axial sliding movement as well as articulation and radial movement of the axially movable member.

4. Means as claimed in claim 2, in which the fixed member is mounted for articulation and radial movement, both couplings being arranged to provide articulation and radial movement of the fixed member.

5. Means as claimed in any of claims 1 to 3, in which the flywheel member is journalled for rotation and is fixed axially with respect to the shaft, and the thrust member comprises the said axially movable member the thrust member being mounted for articulation and radial movement, with a radial clearance being provided between overlapping faces of the flywheel member and the thrust member.

6. Means as claimed in claim 5, in which the driving flange is fast with the shaft, and the coupling between the clutch plate and the flange comprises axially projecting lugs on the flange sliding in notches in the clutch plate to provide axial movement of the thrust member as well as articulation and radial movement.

7. Means as claimed in claim 6, in which the clutch plate is of dished form to provide a clearance with respect to the end of the shaft.

8. Means as claimed in any of claims 5 to 7, in which the bias force is applied to the clutch plate through a single point force-transmitting device in axial alignment with the axis of the shaft.

9. Means as claimed in claim 8, in which the force transmitting device is axially adjustable to alter the clearance between the force-transmitting device and the modulating means and, in consequence, the amount of lost-motion of the skid sensing means.

10. Means as claimed in claim 8 or claim 9, in which the flywheel mechanism is housed within a housing with the force-transmitting device positioned at an outer end which is normally closed by a removable cover.

11. Means as claimed in any of claims 1, 2 and 4, in which the flywheel member comprises the axially movable member, and the thrust member is fixed axially with respect to the shaft, the thrust member being mounted for articulation and radial movement, and a radial clearance being provided between overlapping faces of the flywheel and the thrust member.

12. Means as claimed in claim 11, in which the driving flange is coupled to the shaft by a transverse pin, and a rocking coupling is provided between the driving flange and the clutch plate, so that both couplings provide articulation and radial movement.

13. Means as claimed in claim 10 or claim 11, in which the bias force is applied to the flywheel member by means of a bifurcated lever, which also actuates the brake pressure modulating means.

14. Rotary flywheel skid sensing means substantially as described herein with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.

1 5. Rotary flywheel skid sensing means substantially as described herein with reference to and as illustrated in Figures 3 to 5 of the accompanying drawings.