초록

A slack adjuster for a vehicle drum brake includes a pinion that rotates about a worm axis whenever the slack adjuster pivots. Excess clearance is taken up upon commencement of the apply stroke, at an accelerated rate. This enables a larger amount of initial clearance to be built into the brake.

대표청구항 ▼

Having described the invention, we claim: 1. A method of operating a vehicle drum brake in response to actuation of the vehicle brake, said method comprising the steps of: pivoting a slack adjuster body in an apply direction about a camshaft axis, in response to actuation of the brake; moving a wor

Having described the invention, we claim: 1. A method of operating a vehicle drum brake in response to actuation of the vehicle brake, said method comprising the steps of: pivoting a slack adjuster body in an apply direction about a camshaft axis, in response to actuation of the brake; moving a worm that is in the slack adjuster body in an arc about the camshaft axis in response to the pivoting of the slack adjuster body; transmitting torque from the moving worm to a worm wheel thereby to apply a first torque to the worm wheel to effect rotation of the worm wheel about the camshaft axis in an apply direction; rotating a pinion mechanism about a pinion axis in an apply direction during the initial period of pivoting of the slack adjuster body in the apply direction, in response to the pivoting of the slack adjuster body in the apply direction and during the step of moving the worm in the slack adjuster body; rotating the worm in an apply direction about a worm axis in response to rotational force of the pinion mechanism; transmitting torque from the rotating worm to the worm wheel thereby to apply a second torque to the worm wheel to effect rotation of the worm wheel about the camshaft axis at an increased speed in the apply direction; rotating a brake camshaft with the worm wheel thereby to operate the vehicle drum brake; rotating a control member with the worm during the initial period of pivoting of the slack adjuster body in the apply direction to take up initial clearance and excess clearance, the control member being rotatable about the worm axis for helping to control the rotation of the worm about the worm axis; blocking rotation of the control member after a predetermined amount of rotation; and thereafter rotating the worm further in the apply direction to take up additional excess clearance until brake resistance blocks further worm rotation. 2. A method as set forth in claim 1 wherein the first torque and the second torque are additive so that the worm wheel rotates faster than it would rotate if it were being driven only by the first torque. 3. A method as set forth in claim 1, said method including the steps of: blocking rotation of the control member and the worm and the worm wheel during a first period of pivoting of the slack adjuster body in a release direction; enabling rotation of the control member and the worm and the worm wheel in a release direction during a second period of pivoting of the slack adjuster body in the release direction; and enabling rotation of the worm wheel but not the worm and the control member during a third period of pivoting of the slack adjuster body in the release direction. 4. A method as set forth in claim 1 wherein said step of rotating the pinion mechanism is commenced substantially immediately upon pivoting of the slack adjuster body in the apply direction. 5. A method as set forth in claim 1 wherein the pinion mechanism is in meshing engagement with a link that is supported in the slack adjuster body but that is not movable with the slack adjuster body, and wherein the slack adjuster body and the pinion mechanism move relative to the link upon commencement of and in response to the pivoting of the slack adjuster body in the apply direction. 6. A method as set forth in claim 5 wherein the link is in engagement with the control member that does not move when the slack adjuster body pivots, and the link does not move relative to the control member. 7. A method as set forth in claim 6 wherein the link has an end portion in engagement in a notch in the control member without a gap therebetween. 8. A method as set forth in claim 1 wherein said step of applying a first torque to the worm wheel effects take-up of the initial clearance in the drum brake, said step of applying a second torque to the worm wheel effects take-up of the excess clearance, and further including the step of rotating the pinion mechanism about the worm axis whenever the slack adjuster body is pivoting about the camshaft axis. 9. A method of operating a vehicle drum brake having a designed-in initial clearance between the brake shoe and drum and having excess clearance between the brake shoe and drum, said method comprising the steps of: pivoting a slack adjuster body in an apply direction about a camshaft axis, in response to actuation of the vehicle brake; taking up initial clearance upon commencement of said pivoting step; and taking up additional clearance immediately upon commencement of said pivoting step; rotating a control member with a worm in the slack adjuster body during the initial period of pivoting of the slack adjuster body in the apply direction to take up initial clearance and excess clearance, the control member being rotatable about a worm axis for helping to control the rotation of the worm about the worm axis; blocking rotation of the control member after a predetermined amount of rotation; and thereafter rotating the worm further in the apply direction to take up additional excess clearance until brake resistance blocks further worm rotation. 10. A method as set forth in claim 9 including the step of rotating a pinion mechanism in the slack adjuster body about a pinion axis whenever the slack adjuster body is pivoting about the camshaft axis. 11. A method as set forth in claim 9 wherein: said step of taking up initial clearance comprises rotating a worm wheel in the slack adjuster body in an apply direction about a camshaft axis to apply a first torque to a camshaft; and said step of taking up excess clearance comprises rotating the worm that is in engagement with the worm wheel about the worm axis to apply a second torque to the camshaft, the first and second torques being additive. 12. A method as set forth in claim 9 further including the steps of: after actuation of the brake, pivoting the slack adjuster body in a release direction to release the brake; providing initial clearance subsequent to commencement of said step of pivoting the slack adjuster body in the release direction; and providing an increased amount of initial clearance simultaneously with said step of providing initial clearance. 13. A method as set forth in claim 12 wherein: said step of providing initial clearance comprises pivoting a slack adjuster body in a release direction about a camshaft axis to apply a first torque to a camshaft; and said step of providing an increased amount of initial clearance comprises rotating a worm to rotate a worm wheel to apply a second torque to the camshaft, the first and second torques being additive. 14. A method as set forth in claim 13 including the step of rotating a pinion mechanism in the slack adjuster body about the axis of the worm whenever the slack adjuster body is pivoting about the camshaft axis. 15. Apparatus for adjusting a vehicle drum brake in response to actuation of the vehicle brake, said apparatus comprising: a slack adjuster body with a stop surface within a notch, the slack adjuster body pivotable in an apply direction about a camshaft axis in response to actuation of the brake; first means for transmitting torque from the slack adjuster body to a worm wheel thereby to apply a first torque to the worm wheel to effect rotation of the worm wheel about the camshaft axis in an apply direction, the first means comprising a worm; second means for transmitting torque to the worm wheel during an initial period of pivoting of the slack adjuster body in the apply direction thereby to apply a second torque to the worm wheel, additive to the first torque, to effect rotation of the worm wheel about the camshaft axis at an increased speed in the apply direction, a brake camshaft rotatable with the worm wheel thereby to adjust the vehicle brake; a control member rotatably supported in the slack adjuster body and rotatable with the worm during the initial period of pivoting of the slack adjuster body in the apply direction to take up initial clearance and excess clearance, the control member being rotatable about a worm axis for helping to control the rotation of the worm about the worm axis; wherein the control member is blocked from rotating by the stop surface after a predetermined amount of rotation; and thereafter the worm is further rotatable by the second means in the apply direction to take up additional excess clearance until brake resistance blocks further worm actuation. 16. Apparatus as set forth in claim 15 wherein: said first means comprises the worm in the slack adjuster body movable in an arc about the camshaft axis in response to the pivoting of the slack adjuster body, the worm being in engagement with the worm wheel; and said second means comprises a pinion mechanism rotatable on a pinion axis in an apply direction during the initial period, in response to the pivoting of the slack adjuster body in the apply direction and during the step of moving the worm in the slack adjuster body, the worm rotating in the apply direction about a worm axis in response to rotational force applied from the pinion mechanism. 17. A slack adjuster for an actuatable vehicle drum brake that includes a rotatable drum and a brake shoe expandable into engagement with the drum by rotation of a camshaft, said slack adjuster comprising: a base; a body with a stop surface within a notch, the body supported on said base for pivoting movement relative to said base about a camshaft axis in an apply direction and a release direction, said body receiving braking force to rotate said body about said camshaft axis; a worm wheel supported on said body for rotation about said camshaft axis; a worm in meshing engagement with said worm wheel and supported on said body for rotation about a worm axis; a pinion mechanism supported on said body for rotation about said worm axis; a first clutch selectively coupling said worm for rotation with said pinion mechanism; a link in meshing engagement with said pinion mechanism; a worm control member supported on said body for rotation about said worm axis for helping to control the rotation of the worm about the worm axis, the control member rotating with the worm during the initial period of pivoting the slack adjuster body in the apply direction to take-up initial clearance and excess clearance; a second clutch selectively coupling said worm control member for rotation with said worm; wherein said pinion mechanism is rotatable about said worm axis whenever said body rotates relative to said base; wherein the control member is blocked from rotating by the stop surface after a predetermined amount of rotation; and wherein the worm is further rotatable by the pinion mechanism in the apply direction to take up additional excess clearance until brake resistance blocks further worm rotation. 18. A slack adjuster as set forth in claim 17 wherein said worm control member is supported on said body for limited rotation about said worm axis, and wherein the rotational position of said control member is a factor in determining the condition of said second clutch and thereby the rotational state of said worm. 19. A slack adjuster as set forth in claim 18 wherein said slack adjuster has a zero stroke position, when the drum brake is not actuated, in which a portion of said link is in engagement with said base in a manner to effect substantially immediate movement of said pinion mechanism relative to said link upon commencement of pivoting of said body. 20. A slack adjuster as set forth in claim 18 wherein said slack adjuster body and said pinion mechanism move relative to said link upon commencement of and in response to pivoting of said body in the apply direction. 21. A method of adjusting a vehicle drum brake in response to actuation of the vehicle brake, said method comprising the steps of: pivoting a slack adjuster body in an apply direction about a camshaft axis, in response to actuation of the brake; moving a worm that is in the slack adjuster body in an arc about the camshaft axis in response to the pivoting of the slack adjuster body; transmitting torque from the moving worm to a worm wheel thereby to apply a first torque to the worm wheel to effect rotation of the worm wheel about the camshaft axis in an apply direction; rotating a pinion mechanism about a worm axis in an apply direction during the initial period of pivoting of the slack adjuster body in the apply direction, in response to the pivoting of the slack adjuster body in the apply direction and during the step of moving the worm in the slack adjuster body; rotating the worm in an apply direction about the worm axis in response to rotational force of the pinion mechanism; transmitting torque from the rotating worm to the worm wheel thereby to apply a second torque to the worm wheel to effect rotation of the worm wheel about the camshaft axis at an increased speed in the apply direction; rotating a brake camshaft with the worm wheel thereby to adjust the vehicle brake; rotating a control member with the worm during the initial period of pivoting of the slack adjuster body in the apply direction to take up initial clearance and additional clearance, the control member being rotatable about the worm axis for helping to control the rotation of the worm about the worm axis; blocking rotation of the control member after a predetermined amount of rotation; and thereafter rotating the worm further in the apply direction to take up additional excess clearance until the brake resistance blocks further worm rotation. 22. A method as set forth in claim 21 wherein the pinion mechanism is in meshing engagement with a link that is supported in the slack adjuster body but that is not movable with the slack adjuster body, and wherein the slack adjuster body and the pinion mechanism move relative to the link upon commencement of and in response to the pivoting of the slack adjuster body in the apply direction. 23. A method as set forth in claim 22 wherein the link is in engagement with a control member that does not move when the slack adjuster body pivots, and the link does not move relative to the control member. 24. A method as set forth in claim 23 wherein the link has an end portion in engagement in a notch in the control member without a gap therebetween.