Electric power steering device

Abstract

An electric power steering device (100) is provided with a steering mechanism (10), an electric motor (20) for outputting assist force to the steering mechanism (10), a transmission mechanism (30) provided with toothed pulleys (31, 32) and a toothed belt (33) and transmitting the output of the electric motor (20) to the steering mechanism (10), and a torque limiter (40) for imposing a limit on the magnitude of the torque transmitted between the electric motor (20) and an output member (11) of the steering mechanism (10). In this electric power steering device (100), a variation lower-limit value of tooth-skipping torque, at which tooth skipping occurs between the toothed pulleys (31, 32) and the toothed belt (33), is set higher than a variation upper-limit value of limit torque in the torque limiter (40). Therefore, when torque occurs that exceeds the normal torque in the power transmission system between the electric motor (20) and the steering mechanism (10), the torque limiter (40) functions (actuates) before tooth skipping occurs in the transmission mechanism (30).

Description

technical field [0001] The present invention relates to an electric power steering device, in particular, an electric power steering device comprising: a steering mechanism; an electric motor which outputs an auxiliary force for assisting the steering mechanism; a pulley and a toothed belt, and transmits the output of the above-mentioned electric motor to the above-mentioned steering mechanism; Size is limited. Background technique [0002] Such an electric power steering system is disclosed, for example, in Patent Document 1 below. In the electric power steering device described in the following Patent Document 1, the problem of cogging (a phenomenon in which the teeth of the toothed belt pass over the teeth of the toothed pulley) that occurs between the toothed pulley and the toothed belt of the transmission mechanism There are deficiencies in consideration. [0003] Patent Document 1: Japanese Patent Laid-Open No. 2004-50884 [0004] In the electric power steering dev...

AI Technical Summary

Problems solved by technology

[0004] In the electric power steering device described in the aforementioned Patent Document 1, the creep torque (torque when creep occurs between the toothed pulley and the toothed belt, and is set in the transmission mechanism) is set to a ratio limit. When the torque (the maximum transmittable torque set in the torque limiter) is small, when a torque exceeding the normal torque is generated in the power transmission system between the electric motor and the output member of the steering mechanism, the Tooth creep occurs, so the torque limiter does not function (action)

In this case, there is a fear of loud noise due to gear creep of the transmission mechanism, and there is a concern of missing teeth in the transmission mechanism.

In addition, there is a concern that the generation of sound due to tooth crawling may give users a sense of uneasiness.

In addition, the lack of teeth in the transmission mechanism may cause the intrusion of the missing tooth piece between the toothed pulley and the toothed belt, and there is a concern that the durability of the transmission mechanism may be reduced.

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