Patent Description:
In general, a vehicle includes a starter motor for driving an engine and an alternator for generating electricity using torque of the engine.

In the starter motor, an ignition switch is connected to a battery power source through an operation of a driver when the vehicle is started, and thus driving force generated by supply of power to the starter motor rotates the engine so that the vehicle start.

On the other hand, the alternator is connected to a drive portion of the engine to generate alternating current power by rotation of a rotor in a state in which a magnetic field is formed through the driving force of the engine, and the alternating current power is converted using a rectifying device so as to charge the battery.

Both of the starter motor and the alternator have a structure configured of a stator and a rotor. Accordingly, since the starter motor and the alternator have a very similar structure, the starter motor and the alternator may function as either a generator or a motor according to application of force or power thereto.

In recent years, a belt-driven starter-generator (BSG) structure which can serve as both of a stator motor and an alternator by one structure has been actively studied.

Meanwhile, in the belt-driven starter-generator, a pulley belt is coupled to an upper end of a rotary shaft rotated by a motor. Specifically, after a woodruff key is laterally inserted into the rotary shaft, the pulley belt is assembled and fixed by fastening a nut thereto.

However, when the motor is driven at a high speed, the fixed coupling of the nut to the pulley belt is loosened, thereby causing troubles. For this reason, there is a problem in that operation reliability is deteriorated.

In addition, there is a problem in that the pulley belt is not easily assembled since the woodruff key is laterally inserted into the rotary shaft.

<CIT>, <CIT>, <CIT> and <CIT> disclose motors and/or generators of state of the art.

The present invention is directed to a belt-driven starter-generator capable of improving operation reliability and assembly convenience even though a motor having high power and torque is driven, by stably fixing a pulley belt to a rotary shaft.

According to an aspect of the present invention, a belt-driven starter-generator includes a rotary shaft, a bearing supporting the rotary shaft; a pulley belt coupled to the rotary shaft and configured such that one end of the rotary shaft is exposed therethrough, a pocket formed between the rotary shaft and the pulley belt, a key arranged in the pocket, and a coupling member coupled to one end of the rotary shaft, wherein the pulley belt includes a receiving groove to which one end of the rotary shaft is exposed, and a through-hole formed on a bottom surface of the receiving groove so that the rotary shaft is inserted into the through-hole, and the receiving groove has a diameter greater than a diameter of the through-hole and a maximum linear width of the coupling member, wherein the pocket comprises a first slit formed on a side wall of the through-hole and a second slit formed on an outer peripheral surface of the rotary shaft, and wherein the key is press-fitted into the pocket such that the rotary shaft is fixed to the pulley belt, characterized in that the first slit is extended to a portion where the pulley belt supports an upper surface of the bearing, and a length of the first slit is longer than a length of the second slit so that a space portion is formed between the first slit and the rotary shaft.

The belt-driven starter-generator may further include a housing, a stator arranged in the housing, and a rotor rotated along with the rotary shaft.

The housing may include a first housing accommodating the stator and the rotor, a second housing accommodating the first housing, and a fixing portion to fix the first and second housings.

The belt-driven starter-generator may further include a cooling channel formed between the first housing and the second housing.

One end of the rotary shaft coupled to the coupling member may have a thread.

The coupling member may include a nut portion coupled to one end of the rotary shaft, and a fixed portion connected to the nut portion so as to come into contact with the bottom surface of the receiving groove of the pulley belt.

The pocket may have a length greater than that of the key.

The pocket may have a length equal to or less than that of the key.

The belt-driven starter-generator may further include a ring-shaped tension washer inserted between the key and the coupling member.

The key may have a tapered portion formed on at least one of upper and lower end portions thereof.

According to another aspect of the present invention, a belt-driven starter-generator includes a rotary shaft rotated by a motor, a pulley belt coupled on an outer peripheral surface of the rotary shaft, and a coupling member coupled to a thread formed on the outer peripheral surface of the rotary shaft so as to support one side of the pulley belt, wherein at least one protrusion is formed on the outer peripheral surface of the rotary shaft and a pocket corresponding to the protrusion is formed on an inner peripheral surface of the pulley belt.

According to a further aspect of the present invention, a belt-driven starter-generator includes a rotary shaft rotated by a motor, a pulley belt coupled on an outer peripheral surface of the rotary shaft, and a coupling member coupled to a thread formed on the outer peripheral surface of the rotary shaft so as to support one side of the pulley belt, wherein at least one pocket is formed on the outer peripheral surface of the rotary shaft and a protrusion, which is inserted into the pocket, is formed on an inner peripheral surface of the pulley belt.

The above and other objects, features, and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which:.

Exemplary embodiments of the present invention will be described below in more detail with reference to the accompanying drawings.

<FIG> is a cross-sectional view illustrating a belt-driven starter-generator according to an embodiment of the present invention. <FIG> is an enlarged view of portion A in <FIG>. <FIG> is a perspective view of portion A in <FIG>. <FIG> is a cross-sectional view illustrating a rotary shaft and a pulley belt when viewed from the top, in the belt-driven starter-generator according to the embodiment of the present invention.

Referring to <FIG>, the belt-driven starter-generator according to the embodiment of the present invention includes a housing <NUM>, a stator <NUM>, a rotor <NUM>, a rotary shaft <NUM>, a pulley belt <NUM>, a key <NUM>, a tension washer <NUM>, and a coupling member <NUM>.

The housing <NUM> has a cylindrical shape and has a space defined therein such that the stator <NUM> and the rotor <NUM> may be mounted in the space. In this case, the housing <NUM> may be formed in various shapes or of various materials, but a metal material having high thermal resistance may be selected due to characteristics of the housing mounted on a vehicle.

The housing <NUM> includes a first housing <NUM> and a second housing <NUM>. The first housing <NUM> accommodates the stator <NUM> and the rotor <NUM>, and the second housing <NUM> accommodates a portion of the first housing <NUM>. The first housing <NUM> is fixed to the second housing <NUM> by a fastening portion <NUM>. Through coupling of the first and second housings <NUM> and <NUM>, the stator <NUM> and the rotor <NUM> are blocked from the outside.

A cooling channel <NUM> is formed between an outer side of the first housing <NUM> and an inner side of the second housing <NUM>. The stator <NUM> and the rotor <NUM> may be cooled by circulation of coolant in the cooling channel <NUM>. Since the cooling channel <NUM> is integrally formed in the housing <NUM>, the structure thereof is simplified and the size of a motor may be reduced. However, the present invention is not limited thereto, and an air-cooled structure or a water-cooled structure may be properly selected as the cooling structure. The housing <NUM> may have a properly modified structure according to a cooling method.

The stator <NUM> is inserted into the inner space of the housing <NUM> and has a space portion defined therein. The stator <NUM> may be a fixed structure including coils and a plurality of cores around which the coils are wound, and may be formed by stacking plate-shaped stator plates having the same shape to a predetermined height.

The rotor <NUM> is inserted into the space portion provided in the stator <NUM>, and coupled on an outer peripheral surface of the rotary shaft <NUM>. The rotor <NUM> may be formed by stacking a plurality of core plates having a disc shape. A plurality of magnets mounted on the rotor <NUM> are arranged so as to face the stator <NUM>, and each magnet may be inserted and coupled to the rotor <NUM> through a hole formed in the rotor <NUM>.

Upper and lower magnet support plates <NUM> and <NUM> may be tightly arranged at the top and bottom of the rotor <NUM>, respectively. The magnet support plates <NUM> and <NUM> are tightly arranged at the top and bottom of the rotor <NUM> in order to prevent the magnets from being separated from the rotor <NUM> when the rotor <NUM> rotates at a high speed.

The rotary shaft <NUM> is formed at a central portion of the rotor <NUM> so as to pass through the same. Accordingly, when the rotary shaft <NUM> rotates, the rotor <NUM> rotates along with the rotary shaft <NUM>. On the contrary, when the rotor <NUM> rotates, the rotary shaft <NUM> may rotate along with the rotor <NUM>. In this case, the rotary shaft <NUM> may be coupled into the housing <NUM> so as to be rotatable by a bearing <NUM>. A thread is formed on one end <NUM> of the rotary shaft.

Referring to <FIG>, the pulley belt <NUM> is coupled on the outer peripheral surface of the rotary shaft <NUM> which rotatably supports the rotor <NUM>, and is configured such that a belt moving according to engine power is coupled to the pulley belt <NUM> so as to rotate the rotary shaft <NUM> and the rotor <NUM>. On the other hand, the pulley belt <NUM> may also be configured to rotate external parts (for instance, an engine) by the rotation of the rotor <NUM>. A plurality of grooves <NUM> are formed on an outer peripheral surface of the pulley belt <NUM> so that a groove belt (not shown) may be fastened to the grooves.

When the belt-driven starter-generator according to the embodiment functions as an alternator, the rotor <NUM> is rotated while the pulley belt <NUM> is rotated by driving of the engine, thereby generating an alternating current. The generated alternating current may be converted into a direct current to be supplied to external parts (for instance, a battery).

On the other hand, when the belt-driven starter-generator according to the embodiment functions as a starter motor, the pulley belt <NUM> connected to the rotary shaft <NUM> is rotated while the rotor <NUM> is rotated by a drive current, thereby enabling external parts (for instance, an engine) to be driven.

The pulley belt <NUM> includes a receiving groove <NUM> to which the one end <NUM> of the rotary shaft is exposed, and a through-hole <NUM> which is formed on a bottom surface <NUM> of the receiving groove <NUM> so that the rotary shaft <NUM> is inserted into the through-hole <NUM>. The one end <NUM> of the rotary shaft <NUM> passes through the through-hole <NUM> and is exposed to the receiving groove <NUM>.

The coupling member <NUM> is coupled to the exposed one end <NUM> of the rotary shaft. The coupling member <NUM> includes a nut portion <NUM> coupled to the one end <NUM> of the rotary shaft and a fixed portion <NUM> which is connected to the nut portion <NUM> to come into contact with the bottom surface <NUM> of the receiving groove <NUM>. A hole, which is screw-coupled with a thread 410a formed at the one end <NUM> of the rotary shaft, is formed at a center of the nut portion <NUM>. When the nut portion <NUM> is coupled to the one end <NUM> of the rotary shaft, the fixed portion <NUM> presses the bottom surface <NUM> of the receiving groove <NUM>. The fixed portion <NUM> may have a disc shape and have a flat contact surface.

The receiving groove <NUM> has a diameter D3 greater than a diameter D1 of the through-hole <NUM> and a maximum linear width D2 of the coupling member <NUM>. Accordingly, the coupling member <NUM> is easily inserted into the receiving groove <NUM>.

Referring to <FIG>, a pocket <NUM> is formed between the rotary shaft <NUM> and the pulley belt <NUM>. Specifically, the pocket <NUM> may be defined by a first slit <NUM> formed on a side wall of the through-hole <NUM> and a second slit <NUM> formed on the outer peripheral surface of the rotary shaft <NUM>. The key <NUM> is press-fitted into the pocket <NUM>, thereby enabling the rotary shaft <NUM> to be fixed to the pulley belt <NUM>. The rotary shaft <NUM> and the pulley belt <NUM> may be stably fixed by the press-fit of the key <NUM> even though the motor is rotated at a high speed.

When the pocket <NUM> has a length equal to or less than that of the key <NUM>, the flat surface of the fixed portion <NUM> presses an upper end portion of the key <NUM>.

At least one of upper and lower end portions of the key <NUM> is tapered such that a cross-sectional area is decreased toward an end. Consequently, the key <NUM> may be smoothly press-fitted into the pocket <NUM>.

In addition, a height h and a thickness t of the key <NUM> may be variously selected within a suitable range according to a designer's intention and a product specification. Especially, the thickness t of the key <NUM> may be determined by the following equation <NUM>. <MAT> where k refers to a proportional constant and may be <NUM> × <NUM>-<NUM>, S refers to a safety factor, I refers to rotational moment of inertia of the rotor <NUM> rotated along with the rotary shaft <NUM>, T refers to rotational torque generated by rotation, and α refers to angular acceleration.

The tension washer <NUM> having a ring shape may be inserted between the key <NUM> and the coupling member <NUM>. In this case, the length of the pocket <NUM> may be greater than that of the key <NUM> by an insertion distance of the tension washer <NUM>.

As such, according to the embodiment, since the pulley belt <NUM> is stably fixed to the rotary shaft <NUM>, operation reliability may be improved even though the motor having high power and torque is driven. In addition, since the key <NUM> is press-fitted into the pocket <NUM> formed between the rotary shaft <NUM> and the pulley belt <NUM>, assembly convenience may be improved.

<FIG> is a cross-sectional view illustrating a rotary shaft and a pulley belt when viewed from the top, in a belt-driven starter-generator according to another embodiment of the present invention.

Meanwhile, the structure in which the key <NUM> is press-fitted into the pocket <NUM> formed between the rotary shaft <NUM> and the pulley belt <NUM> and the rotary shaft <NUM> is fixed to the pulley belt <NUM> is described in the above-mentioned embodiment.

However, as shown in <FIG>, a rotary shaft <NUM> may also be fixed to a pulley belt <NUM> by forming at least one protrusion <NUM> on an outer peripheral surface of the rotary shaft <NUM> and forming a pocket corresponding to the protrusion <NUM> on an inner peripheral surface of the pulley belt <NUM>. According to such a configuration, a separate key <NUM> may not be manufactured.

<FIG> is a cross-sectional view illustrating a rotary shaft and a pulley belt when viewed from the top, in a belt-driven starter-generator according to a further embodiment of the present invention.

The configuration in which the rotary shaft <NUM> is fixed to the pulley belt <NUM> by forming at least one protrusion <NUM> on the outer peripheral surface of the rotary shaft <NUM> and forming the pocket corresponding to the protrusion <NUM> on the inner peripheral surface of the pulley belt <NUM> is described in the above-mentioned embodiment. However, the configuration may also be made in reverse.

That is, as shown in <FIG>, a rotary shaft <NUM> may also be fixed to a pulley belt <NUM> by forming at least one pocket on an outer peripheral surface of the rotary shaft <NUM> and forming at least one protrusion <NUM>, which is inserted into the pocket, on an inner peripheral surface of the pulley belt <NUM>.

In accordance with a belt-driven starter-generator according to exemplary embodiments of the present invention, since a pulley belt is stably fixed to a rotary shaft, operation reliability can be improved even though a motor having high power and torque is driven.

Claim 1:
A belt-driven starter-generator comprising:
a rotary shaft (<NUM>);
a bearing (<NUM>) supporting the rotary shaft (<NUM>);
a pulley belt (<NUM>) coupled to the rotary shaft (<NUM>) and configured such that one end of the rotary shaft (<NUM>) is exposed therethrough;
a pocket (<NUM>) formed between the rotary shaft (<NUM>) and the pulley belt (<NUM>);
a key (<NUM>) arranged in the pocket (<NUM>); and
a coupling member (<NUM>) coupled to one end of the rotary shaft (<NUM>),
wherein the pulley belt (<NUM>) comprises a receiving groove (<NUM>) to which one end of the rotary shaft (<NUM>) is exposed, and
a through-hole (<NUM>) formed on a bottom surface of the receiving groove (<NUM>) so that the rotary shaft (<NUM>) is inserted into the through-hole (<NUM>); and
wherein the receiving groove (<NUM>) has a diameter greater than a diameter of the through-hole (<NUM>) and a maximum linear width of the coupling member (<NUM>), and
wherein the pocket (<NUM>) comprises a first slit (<NUM>) formed on a side wall of the through-hole (<NUM>) and a second slit (<NUM>) formed on an outer peripheral surface of the rotary shaft (<NUM>), and wherein the key (<NUM>) is press-fitted into the pocket (<NUM>) such that the rotary shaft (<NUM>) is fixed to the pulley belt (<NUM>),
characterized in that the first slit (<NUM>) is extended to a portion where the pulley belt (<NUM>) supports an upper surface of the bearing (<NUM>), and
a length of the first slit (<NUM>) is longer than a length of the second slit (<NUM>) so that a space portion is formed between the first slit (<NUM>) and the rotary shaft (<NUM>).