Hitachi Automotive Systems, Ltd.

Hitachi Astemo Ltd.

Nissan Motor Company Limited

Hiroshi Shigeta

Naoki Shirakawa

Masami Abe

Mitsuhiro Endo

Takuya Usui

Atsushi Odaira

Hideaki Ishii

Kazumoto Sano

Kunihiro Matsunaga

Ryoichi Yagi

Ryozo Ikeuchi

Daichi Nomura

Ryo Sekiya

Satohiro Koi

Masayuki Yoshimoto

A disk brake that includes, between an internal gear () and a first housing portion () of a housing (), each of protrusion portions () provided on the internal gear side and engagement recessed portions () provided on the first housing side that are engaged with each other to restrict a relative rotation. Each of these protrusion portions on the internal gear side and engagement recessed portions on the first housing portion side are disposed along a direction perpendicular to a straight line connecting a radial center of a second speed reduction gear () and a radial center of a first speed reduction gear (). Due to this configuration, the disk brake can improve the precision of the position of the internal gear of the planetary gear speed reduction mechanism () while reducing the cost.

Disk brake

An electric booster includes an input member configured to be moved forward or rearward according to an operation on a brake pedal, a thrust force transmission member provided movably relative to the input member, an electric actuator configured to move the thrust force transmission member forward or rearward, and an output member connected to the thrust force transmission member and configured to transmit a thrust force provided from the electric actuator to the thrust force transmission member to a piston of a master cylinder. The electric actuator includes an electric motor, at least two threaded shaft members configured to be rotationally driven by the electric motor, and nut members respectively meshed with the threaded shaft members. Each of the nut members is connected to the thrust force transmission member. The thrust force transmission member is swingably connected to at least one of the nut members and the output member.

Electric booster

An electric motor () is controlled according to the stroke of an input rod () moved in response to an operation of a brake pedal. The rotation of the electric motor is transmitted through a belt transmission mechanism () to a ball-screw mechanism () to propel a primary piston (), thereby generating a brake hydraulic pressure in a master cylinder (). The belt transmission mechanism has pulleys (A,B), one of which is secured to an output shaft of the electric motor. The output shaft and a nut member () of the ball-screw mechanism are held by bearings (A,B andC) secured to a rear housing (B) which is a single member. Thus, before an electric motor-driven booster () is assembled, the belt transmission mechanism can be subassembled to the rear housing. Therefore, a belt () can be adjusted for tension in the state of a subassembly.

Electric motor-driven booster

An electric motor is controlled according to the back and forth movement of an input rod, which is caused by brake pedal operation; a primary piston is propelled to generate hydraulic brake pressure in a master cylinder; and the hydraulic brake pressure is fed back to the input rod through an input piston. The input piston is resiliently held by springs with respect to the primary piston. A jump-in clearance is created between the input piston and the input rod by a rearward spring. At the initial stage of braking, hydraulic brake pressure is not transmitted to the input rod due to the jump-in clearance, which provides jump-in characteristics. The jump-in clearance can be set, regardless of the amount of a relative displacement between the primary piston and the input piston, so that the range of adjustment for regenerative braking can be set larger than the jump-in clearance.

In an electric motor-driven booster, a sharp change of reaction force to an operation of a brake pedal is reduced to improve the brake pedal operation feeling. Operation of the brake pedal causes an input rod () and an input piston () to advance, and an electric motor () is driven according to the movement of the input piston to propel a primary piston () through a ball-screw mechanism, thereby generating a desired brake hydraulic pressure in a master cylinder. At this time, the input piston receives the hydraulic pressure in the master cylinder to feed back a part of reaction force during braking to the brake pedal. When the brake pedal is further depressed after the output of the electric motor has reached a maximum output and the primary pistonhas stopped, a lock nut abuts against a movable spring retainer and compresses a reaction force spring.

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Kai, Japan

Hiroshi Shigeta