Disc brake

Patent metadata

Field	Value
Publication number	US-9568058-B2
Application number	US-201514804422-A
Country	US
Kind code	B2
Filing date	Jul 21, 2015
Priority date	Jul 31, 2014
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

A rotary-to-linear conversion mechanism includes a rotation transmission member, a shaft member threadedly fitted to the rotation transmission member so that a rotation and linear motion of the shaft member are enabled, and a ball-and-ramp mechanism threadedly fitted to the shaft member, which is configured to apply a thrust in the axial direction to a piston through the rotation of the shaft member. The shaft member includes a first thread formed on one end side thereof, and a second thread formed on the other end side thereof. A rotation friction torque of the first thread is larger than a rotation friction torque of the second thread.

First claim

What is claimed is:

1. A disc brake, comprising:
a pair of pads arranged on both sides of a rotor in an axial direction of the rotor;
a piston configured to press one of the pair of pads against the rotor:
a caliper main body including a cylinder in which the piston is movably arranged;
an electric motor installed on the caliper main body; and
a rotary-to-linear conversion mechanism installed on the caliper main body, which is configured to thrust the piston so as to hold the piston in a braking position, wherein:
the rotary-to-linear conversion mechanism comprises:
a rotation transmission member to which a rotation of the electric motor is transmitted;
a shaft member threadedly fitted to the rotation transmission member so that a rotation and linear motion of the shaft member are enabled; and
a ball-and-ramp mechanism threadedly fitted to the shaft member, which is configured to apply a thrust in the axial direction to the piston through the rotation of the shaft member;

the shaft member comprises a first thread threadedly fitted to the rotation transmission member, which is formed on one end side of the shaft member, and a second thread threadedly fitted to the ball-and-ramp mechanism, which is formed on another end side of the shaft member; and
a rotation friction torque of the first thread is larger than a rotation friction torque of the second thread.

2. A disc brake according to claim 1 , wherein a diameter of the first thread is larger than a diameter of the second thread.

3. A disc brake according to claim 1 , wherein:
the rotary-to-linear conversion mechanism comprises a first one-way clutch configured to apply a rotation resistance torque against a rotation in one direction; and
the first one-way clutch applies the rotation resistance torque against a rotation of the shaft member with respect to the rotation transmission member in a release direction in which the piston is moved backward.

4. A disc brake according to claim 3 , wherein:
the rotary-to-linear conversion mechanism comprises a second one-way clutch configured to apply a rotation resistance torque against a rotation in one direction; and
the second one-way clutch applies the rotation resistance torque against a rotation of the shaft member with respect to the piston in an application direction in which the piston is thrusted.

5. A disc brake according to claim 3 , wherein when the piston is moved backward in the release direction, a rotation resistance torque in a thread fitting part between the shaft member and the ball-and-ramp mechanism is smaller than a rotation resistance torque acquired by adding a rotation resistance torque in a thread fitting part between the shaft member and the rotation transmission member to the rotation resistance torque applied by the first one-way clutch.

6. A disc brake according to claim 4 , wherein when the piston is moved backward in the release direction, a rotation resistance torque in a thread fitting part between the shaft member and the ball-and-ramp mechanism is smaller than a rotation resistance torque acquired by adding a rotation resistance torque in a thread fitting part between the shaft member and the rotation transmission member to the rotation resistance torque applied by the first one-way clutch.

7. A disc brake according to claim 1 , further comprising a one-way clutch configured to apply a rotation resistance torque against a rotation of the shaft member in one direction,
wherein the one-way clutch comprises a coil part, and the coil part is wound around a thread groove of a male thread formed in a thread fitting part of the shaft member with respect to the rotation transmission member.

8. A disc brake according to claim 7 , wherein:
the one-way clutch comprises a distal end part extending outward in a radial direction of the shaft member; and
the distal end part is fitted to a lock groove formed on the rotation transmission member.

9. A disc brake according to claim 7 , wherein the one-way clutch applies a rotation resistance torque against a rotation of the rotation transmission member upon release, and permits the rotation of the rotation transmission member upon application.

Assignees

• Hitachi Automotive Systems Ltd

Inventors

• Sakashita Takayasu
• Naito Yuki

Classifications

• F16D2125/50

  with parallel non-stationary axes, e.g. planetary gearing · CPC title

• F16D65/18 Primary

  adapted for drawing members together {, e.g. for disc brakes} · CPC title

• F16D2125/48

  with parallel stationary axes, e.g. spur gears · CPC title

• F16D2125/36

  Helical cams, Ball-rotating ramps · CPC title

• F16D2125/40

  Screw-and-nut · CPC title