In-wheel motor system

An in-wheel motor system capable of maximizing the efficiency in using a wheel space by improving a mounting structure thereof, the in-wheel motor system installed at a wheel of a vehicle to transmit a rotational force including an axle installed at the wheel of the wheel and rotating together with the wheel, an in-wheel motor mounted inside the wheel and provided with a rotor and a stator that are used to generate a rotational force to drive the wheel, the rotor, and the stator disposed to face each other while having an accommodation space thereinbetween, a cycloid decelerator installed at a center of the in-wheel motor, and provided with an output shaft to transmit a rotational force at a reduced speed from the in-wheel motor to the axle and an input shaft that passes through the in-wheel motor and rotates together with the rotor, a disc installed at one end portion of the input shaft that protrudes by passing through the in-wheel motor, and a disc brake configured to provide a braking force by pressing the disc, wherein the in-wheel motor and the cycloid decelerator are disposed in a space formed inside the wheel.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 2011-0107811, filed on Oct. 21, 2011 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

Embodiments of the present disclosure relate to an in-wheel motor system, and more particularly, to an in-wheel motor system capable of maximizing a spatial efficiency by improving a mounting structure thereof.

2. Description of the Related Art

In general, an in-wheel motor is a technology used for an electric vehicle using electricity as a driving source, and differently from a gasoline vehicle or a diesel vehicle in which a wheel is rotated by a power sequentially transmitted through an engine, a transmission, and a driving shaft, is an apparatus enabling a power to be delivered to a wheel through a motor disposed inside a rim of the wheel.

By using the in-wheel motor, a power transmission apparatus, such as an engine, a transmission, or a differential gear, is omitted, the weight of the vehicle is reduced and a wheel is independently controlled, while the vehicle running performance is improved and the energy loss in a power transmission process is reduced.

FIG. 1is a perspective view illustrating a state of having a conventional in-wheel motor system installed at a wheel, andFIG. 2is an assembled cross-sectional view ofFIG. 1.

Referring toFIGS. 1 and 2, an in-wheel motor system is installed at a wheel10from an inside a vehicle to an outside the vehicle. In detail, the in-wheel motor system is provided with an axle20installed at the center of a wheel10and rotating together with the wheel10, a decelerator30transmitting a rotational force of an in-wheel motor40at a reduced speed, the in-wheel motor40connected to the decelerator30, and a disc brake60to generate a braking force by pressing a disc50provided between the wheel10and the axle20.

The in-wheel motor system needs to have the decelerator30to increase a torque of the in-wheel motor40, and in addition, a brake system, that is, the disc50and the disc brake60, needs to be installed inside the wheel10. Accordingly, if the in-wheel motor system as such is coupled on the wheel10, the spatial efficiency is lowered and an unsprung mass is increased, while degrading a vehicle running performance.

In particular, if the in-wheel motor system is mounted on the wheel10, the disc50, the disc brake60, and the decelerator30are disposed inside the wheel10. In this case, due to the spatial limitation of the inside the wheel10, the in-wheel motor40protrudes toward the outer side of the wheel10, that is, toward an interior of the vehicle, so that the in-wheel motor40may be broken by impact with an external object.

SUMMARY

Therefore, it is an aspect of the present disclosure to provide an in-wheel motor system capable of preventing a motor from being broken by maximizing the spatial efficiency inside a wheel, and capable of reducing an unsprung mass by having miniaturized and compact structure thereof, thereby improving the vehicle running performance.

In accordance with one aspect of the present disclosure, an in-wheel motor system installed at a wheel of a vehicle to transmit a rotational force, the in-wheel motor system includes an axle, an in-wheel motor, a cycloid decelerator, a disc, and a disc brake. The axle may be installed at the wheel of the wheel and rotating together with the wheel. The in-wheel motor may be mounted inside the wheel and provided with a rotor and a stator that are used to generate a rotational force to drive the wheel, and the rotor, and the stator may be disposed to face each other while having an accommodation space thereinbetween. The cycloid decelerator may be installed at a center of the in-wheel motor, and provided with an output shaft to transmit a rotational force at a reduced speed from the in-wheel motor to the axle and an input shaft that passes through the in-wheel motor and rotates together with the rotor. The disc may be installed at one end portion of the input shaft that protrudes by passing through the in-wheel motor. The disc brake may be configured to provide a braking force by pressing the disc. The in-wheel motor and the cycloid decelerator may be disposed in a space formed inside the wheel.

The cycloid decelerator may include a pair of eccentric bearings, a pair of cycloid discs, a ring gear housing, and the output shaft. The pair of eccentric bearings is connected to the input shaft rotating together with the rotor to eccentrically transmit a rotation. The pair of cycloid discs each may be installed at the eccentric bearings, respectively, to have the eccentric bearing positioned at a center thereof, each of the pair of cycloid discs provided with a plurality of through holes in a radial direction from a center thereof and configured to eccentrically rotate. The ring gear housing may be installed to surround the pair of cycloid discs and have a roller installed along an inner circumferential surface thereof, the roller making contact with an outer circumferential surface of the cycloid disc such that the cycloid disc performs a revolution and a rotation. The output shaft may be rotatably coupled to the axle, and having a plurality of output pins installed thereto, the plurality of output pins inserted into the plurality of through-holes, respectively, to compensate for an eccentricity of a center of the cycloid disc.

An output housing having a hollowness allowing the output shaft to pass therethrough and an input housing having a hollowness allowing the input shaft to pass therethrough may be further provided at a front side of the output shaft and a rear side of the ring gear housing, respectively.

The output housing, the input housing and the ring gear housing may be coupled to one another through a fastening bolt, and the fastening bolt may be fastened to the in-wheel motor to prevent the ring gear housing from being rotated.

A hub bearing may be installed between the output housing and the axle.

The input shaft may be provided in a predetermined length, and have a middle portion thereof inserted into the rotor so as to rotate together with the rotor by an input shaft fixing nut that is installed at each of a front side and a rear side of the rotor while being in close contact.

The other end portion of the input shaft may be provided with a key protruding from an outer circumferential surface thereof, and the eccentric bearing may be provided with a key groove matching to the key in shape.

A tip of the other end portion of the input shaft may be provided with a connecting ring to prevent the eccentric bearing from being separated from the input shaft.

The disc may be fixed to a tip of the one end portion of the input shaft by a disc fixing nut such that the disc rotates together with the input shaft.

A ball bearing may be provided between the input shaft and the output shaft.

The output shaft may be provided in a predetermined length and have a shaft portion coupled to the axle and a flange portion radially extending from an end portion of the shaft portion, and the plurality of output pins may be installed at a rear side of the flange portion.

A rubber ring may be interposed between the pair of cycloid discs.

The roller may be installed at a ring pin rotatably installed at the ring gear housing, so as to make contact with the outer circumferential surface of the cycloid disc.

The in-wheel motor may include, a front housing, a rear housing, a rotor, a stator and a three-phase power port. The front housing may be provided at a center thereof with an opening portion. The rear housing may be assembled to the front housing through a bolt to form an accommodation space therein. The rotor may be disposed in the accommodation space, and have a plurality of magnets installed along an outer circumferential surface thereof while being spaced apart from each other by a predetermined interval. The stator may be spaced apart from the outer circumferential surface of the rotor to surround the rotor. The stator is wound by a coil. The three-phase power port may be provided at a rear side wall of the rear housing to supply the coil with a power.

The rear side wall of the rear housing may be provided with an installation portion at which the disc brake is installed.

The input shaft may pass through the installation portion, and a bearing may be installed between the installation portion and the input shaft.

As described above, the design flexibility is improved by guaranteeing a space for a cycloid decelerator and a motor.

In addition, a motor is mounted to be installed at an inner side of the wheel, so that the motor is prevented from being broken while being protected from an impact of an external substance.

In addition, the in-wheel motor system has a miniaturized and compact structure so as to reduce an unsprung mass, thereby improving the safety in driving a vehicle.

DETAILED DESCRIPTION

FIG. 3is an exploded perspective view illustrating an in-wheel motor system in accordance with an embodiment of the present disclosure.FIG. 4is an assembled cross-sectional view ofFIG. 3.

Referring toFIGS. 3 and 4, an in-wheel motor system includes an axle120rotating together with a wheel110, an in-wheel motor130to generate a rotational force to drive the wheel110, a cycloid decelerator140to transmit a rotational force at a reduced speed, a disc160rotated by the in-wheel motor130and a disc brake170to provide a braking force by pressing the disc160.

The axle120is coupled to the wheel110to rotate together with the wheel110. The axle120as such is provided with a plurality of axle bolts122radially installed from a center thereof. The axle bolt122, after passes through the wheel110, is coupled to the wheel110by a wheel nut112.

The in-wheel motor130is an electric motor provided with a rotor134and a stator135, and is installed inside the wheel110to generate a driving force to drive a wheel. In detail, the in-wheel motor130includes a front housing131and a rear housing132assembled to each other through a bolt133, and has the rotor134and the stator disposed to face each other in an accommodation space131bformed through the assembly of the front housing131and the rear housing132. A plurality of magnets134′ are installed while being spaced apart from each other by a predetermined interval along an outer circumferential surface of the rotor134. The stator135configured to surround the rotor134while being spaced apart from the rotor134is wound by a coil (not shown). If a power is applied to the coil, a repulsive force and an attractive force act between the magnet134′ and the coil, so that the rotor134is rotated.

Meanwhile, the front side housing131is provided at a center thereof with an opening portion131a. The opening portion131aserves to expose a portion of the cycloid decelerator140, which is to be described later, when the cycloid decelerator140is installed in the accommodation space131bof the in-wheel motor130.

A three-phase power port136is provided at a rear side wall of the rear housing132to supply the coil with a power. In addition, an installation portion138is provided at the rear side wall of the rear housing136such that the disc brake170is installed at the installation portion138. The installation portion138protrudes from the rear side wall, and has an input shaft141, which is to be described later, passing therethrough and installed thereto. That is, as shown in the drawings, the disc160is installed at one end portion of the input shaft141passing through the installation portion138, so the disc brake170is installed adjacent to an upper side of the installation portion138so as to press the disc160. In this case, a bearing137is installed between the input shaft141and the installation portion138. In addition, the disc160installed at the one end portion of the input shaft141is fixed by a pair of disc fixing nuts161, which are installed at a front side and at a rear side of the disc160, respectively, so that the disc160rotates together with the input shaft141.

Meanwhile, the disc160and the disc brake170correspond to a brake apparatus that is generally used for braking a vehicle, and thus a detailed description thereof will be omitted. Reference numeral ‘172’ represents a pad configured to provide a braking force by pressing both lateral sides of a disc.

The cycloid decelerator140in accordance with one embodiment of the present disclosure includes the input shaft141coupled to the rotor134, a pair of eccentric bearings142connected to the input shaft141to eccentrically transmit a rotation, a pair of cycloid discs143configured to be eccentrically rotated by the eccentric bearing142, a ring gear housing144to which a roller145is installed such that the cycloid disc143is revolved or rotated, and an output shaft151having a plurality of output pins153installed thereto, the plurality of output pins153inserted into a plurality of through-holes143′, respectively (seeFIG. 5).

The cycloid decelerator140as such is configured to amplify a rotational torque of the in-wheel motor130, and is disposed in the accommodation space131bof the in-wheel motor130.

The input shaft141is provided in a predetermined length, and is installed by passing through the rotor134. As shown in the drawings, the input shaft141has a center portion thereof inserted into the rotor134, and is fixed by an input shaft fixing nut139, which is installed at a front side and at a rear side of the rotor134, respectively, while being in close contact, so as to rotate with the rotor134. One end portion of the input shaft141passes through the rear housing132of the in-wheel motor130such that the disc160is installed at the one end portion of the input shaft141as described above. The other end portion of the input shaft141is coupled to the pair of eccentric bearings142. A key141aprotrudes from an outer circumferential surface of the other end portion of the input shaft14, and a key groove142′ matching to the key141ain shape is formed in the eccentric bearing142.

Meanwhile, a connection ring141bis installed at a tip of the other end portion of the input shaft141to prevent the eccentric bearing142from being separated from the input shaft141.

The pair of eccentric bearings142is provided at a position away from the center thereof with a hole to which the input shaft141is insertedly coupled, so as to enable an eccentric rotation. The eccentric bearings142are connected to the input shaft141while being spaced apart from each other.

The cycloid disc143is installed to the eccentric bearing142to have the eccentric bearing142positioned at a center thereof. That is, the pair of cycloid discs143is configured to be eccentrically rotated by the eccentric bearing142.

The plurality of through holes143′ are radially formed from the center of the cycloid disc143. As shown in the drawings, the cycloid disc143has eight through-holes143′ spaced apart from each other by a predetermined interval. Here, the number of the through-holes143′ may be selectively increased/decreased depending on the capacity, and the output pin153is inserted into the through-hole to compensate for the eccentricity of the center of the cycloid disc143.

Meanwhile, a lobe having a cycloid curve is formed at an outer circumferential surface of the cycloid disc143in a continuous manner. A rubber ring147is disposed between the pair of cycloid discs143to have the pair of cycloid discs143spaced apart from each other.

The ring gear housing144is configured to surround the cycloid disc143while being spaced apart from the cycloid disc143by a predetermined interval. A plurality of rollers145, which make contact with the outer circumferential surface of the cycloid disc143, that is, the lobe, are installed at an inner circumferential surface of the ring gear housing144, so that the cycloid disc143performs a revolution and a rotation. In detail, the rollers145are installed at ring pins145′ that are rotatably installed along the inner circumferential surface of the ring gear housing144while being spaced apart from each other by a predetermined interval, and make contact with the outer circumferential surface of the pair of cycloid disc143. In this case, the ring gear housing144is prevented from being rotated while being fixed to the in-wheel motor130through a fastening bolt148, which is to be described later.

The output shaft151receives a rotational force at a reduced speed from the cycloid disc143, and transmits the rotational force to the axle120. The output shaft151is provided in a predetermined length, and has a shaft portion151acoupled to the axle120and a flange portion151bradially extending from an end portion of the shaft portion151a. In this case, the plurality of output pins153are installed at a rear side of the flange portion141, such that the plurality of output pins153are inserted into the plurality of through-holes143′, respectively. The plurality of output pins153are provided in the same number as that of the through-holes143′.

In addition, an output housing152having a hollowness allowing the output shaft151to pass therethrough and an input housing146having a hollowness allowing the input shaft141to pass therethrough are further provided at a front side of the output shaft151and a rear side of the ring gear housing144, respectively. The output housing152and the input housing146serve to protect the components of the cycloid decelerator140. In this case, the output housing152, the input housing146and the ring gear144are coupled to one another through a fastening bolt148. The fastening bolt149is coupled to the front housing131of the in-wheel motor130, thereby preventing the ring gear housing144from being rotated.

Meanwhile, reference numeral ‘149’ represents a ball bearing that is provided between the input shaft141and the output shaft151to prevent a rotational force of the input shaft141from being directly transmitted to the output shaft151. Reference numeral ‘155’ represents a hub bearing installed between an output housing152and the axle120. Reference numeral ‘115’ represents a flange nut coupled to an end portion of the output shaft151.

As for the cycloid decelerator140, if the pair of eccentric bearings142connected to the input shaft141, which rotates together with the rotor134, is rotated, the pair of cycloid discs143performs a revolution and a rotation while making contact with the roller145at an inside of the ring gear housing144. For example, if the eccentric bearing142transmits a rotational force to the cycloid disc143in a clockwise direction, the cycloid disc143revolves in a clockwise direction while rotating in a counter-clockwise direction in an interlocked manner with the roller145. That is, a torque of the cycloid disc143corresponds to a rate of rotation of the cycloid disc143that is output at a reduced speed. Accordingly, the reduction in speed is transmitted to the axle120through the output shaft151. In this case, the output pin153is connected to the through-hole143′ of the cycloid disc143to compensate for the vibration due to the revolution, so that the axle120having received the rotational force through the output shaft151rotates in the same line with the shaft portion151a.

As a result, a structure to transmit a driving force of the in-wheel motor130, which is being amplified through the cycloid decelerator140to the axle120, is provided in a serial scheme, and the cycloid decelerator140is mounted at an inside the in-wheel motor130, and the in-wheel motor130is positioned at an inside the wheel110, thereby reducing the entire size of the in-wheel motor system when compared to the conventional in-wheel motor. Accordingly, the in-wheel motor130is prevented from being broken due to external impact, an unsprung mass is reduced to improve the vehicle driving performance, an easy installation is ensured, and the efficiency in using an installation space is enhanced to improve the design flexibility.