Brake device for motor vehicle seat

A brake device for a motor vehicle seat, comprising:

• a braking section structured to hold a pinion shaft in a braked and locked state to resist an external torque inputted through the pinion shaft;
• and
• an operating section structured to release the pinion shaft from the braked and locked state, and rotate the pinion shaft, wherein the braking section and the operating section are arranged in an axial direction;
• wherein:
• the braking section includes:
• a housing including an inner periphery including a braking surface;
• the pinion shaft arranged at a central position of the housing;
• a first braking component structured to hold the pinion shaft in the braked and locked state, and including:
• first and second lock plates arranged opposite to each other with respect to the pinion shaft in the housing, wherein each of the first and second lock plates has a substantially semicircular shape, and includes first and second ends, and wherein each of the first and second ends includes a braking and locking surface structured to be in contact with the braking surface of the housing;
• and
• a lock spring disposed between the second end of the first lock plate and the second end of the second lock plate, and structured to apply a biasing force to bias the second end of the first lock plate and the second end of the second lock plate away from each other;
• and
• a drive wheel structured to be operated by the operating section to rotate one of the first and second lock plates in a direction to release the pinion shaft from the braked and locked state against the biasing force of the lock spring, and rotate the pinion shaft;
• the pinion shaft includes a rectangular shaft part disposed between the first and second lock plates, wherein the rectangular shaft part includes an acting surface structured to be in contact with the first lock plate;
• the first lock plate includes an inner peripheral surface including first and second protrusions structured to be in contact with the acting surface of the rectangular shaft part of the pinion shaft at corresponding ones of two contact points that are opposite to each other along a center line with respect to a center of the pinion shaft, wherein the center line is a line evenly dividing a space between the first lock plate and the second lock plate;
• the first lock plate is structured to hold the pinion shaft in the braked and locked state by pressing contact between the braking and locking surfaces of the first lock plate and the braking surface of the housing and pressing contact between the first protrusion of the first lock plate and the acting surface of the rectangular shaft part of the pinion shaft, under the biasing force of the lock spring;
• the acting surface of the rectangular shaft part of the pinion shaft includes a crest line corresponding in position to the center of the pinion shaft, and an inclined surface that descends from the crest line toward a radially outward end of the rectangular shaft part;
• and
• the inclined surface is set to satisfy a mathematical expression of θ1<θ2, wherein:
• θ1 represents an angle between the center line and a first line, wherein the first line connects the center of the pinion shaft with an initial contact point between the braking and locking surface of the second end of the first lock plate and the braking surface of the housing when the braking and locking surface of the second end of the first lock plate is pushed by the acting surface of the rectangular shaft part of the pinion shaft;
• and
• θ2 represents an angle between the center line and a direction of a resultant force of a pressing force, a first restoring force, and a second restoring force, wherein the pressing force is a force applied from the acting surface of the rectangular shaft part of the pinion shaft to the first protrusion of the first lock plate under the external torque inputted to the pinion shaft, wherein the first restoring force is a force applied from the braking surface of the housing to the braking and locking surface of the first end of the first lock plate under application of the pressing force, and wherein the second restoring force is a force applied from the braking surface of the housing to the braking and locking surface of the second end of the first lock plate under application of the pressing force.