Electric motor

An electric motor having a rotor having permanent magnets and a first gear arranged on an inner surface of the rotor, a stator having electromagnetic coils wound around sections of the rotor, a shaft arranged to be rotatably supported in the electric motor, the shaft having a second gear arranged on an outer surface of the shaft, and at least one rotary gear member arranged in a space between the first gear and the second gear. A number of the permanent magnets is the same as a number of the electromagnetic coils, and both the permanent magnets and the electromaqnetic coils are evenly spaced apart in a circumferential manner. The rotor further having a plurality of non-magnetic sections positioned between the plurality of permanent magnets to form an outermost layer of the rotor.

This Application is a US National Phase application filed under 35 USC § 371 of PCT Application PCT/GB2018050429, filed Feb. 19, 2018, which claims priority to RU Application 2017105408, filed Feb. 20, 2017, which is incorporated herein by reference.

FIELD

This specification relates to an electric motor, particularly but not exclusively to an electric motor which operates without requiring use of rotor position sensors or computer processors.

BACKGROUND

In part due to concerns regarding air pollution and instability of petroleum prices, there has been increasing growth in interest in electric vehicles, in particular electric vehicles which adopt advanced drive systems and vehicle power systems using induction motors. These electric vehicles require motors which are small in size, lightweight, and low-cost with high efficiency.

A number of different types of electric motors have been used to provide the power requirements of the electric vehicles. In currently known electric motor configurations, at least one rotor and one stator are provided, wherein the rotor is mounted on a shaft axially relative to the stator. The flux generates a magnetic field in an air gap between the stator and the rotor and induces a voltage which produces current through the rotor bars. The rotor circuit is shorted and current flows in the rotor conductors. The action of the rotating flux and the current produces a force that generates a torque to start the motor.

SUMMARY

In a first aspect, this specification describes an electric motor comprising: a rotor having at least one permanent magnet and a first gear arranged on an inner surface of the rotor; a stator comprising at least one electromagnetic coil wound around a section of the rotor; a shaft arranged to be rotatably supported in the electric motor, the shaft comprising a second gear arranged on an outer surface of the shaft; at least one rotary gear member arranged in a space between the first gear and the second gear, wherein the at least one rotary gear member is in meshing engagement with the first gear and the second gear, wherein when current passes through the at least one electromagnetic coil, a magnetic field is generated to cause the rotor to rotate, thereby transferring torque to the shaft through meshing between the first gear and the at least one rotary gear member, and meshing between the second gear and the at least one rotary gear member.

The space between the first gear of the rotor and the second gear of the shaft may be a circumferential space.

The first gear may comprise a plurality of teeth formed on the inner surface of the rotor, each of the teeth projecting towards the centre of the rotor radially, and the second gear may comprise a plurality of teeth formed on the outer surface of the shaft, each of the teeth extending radially from a centre of the shaft.

The rotor may comprise a plurality of permanent magnets spaced apart evenly in a circumferential manner, and the stator may comprise a plurality of electromagnetic coils wound around sections of the rotor. The plurality of electromagnetic coils may be spaced apart evenly in a circumferential manner.

The number of the plurality of permanent magnets in the rotor may be the same as the number of the plurality of electromagnetic coils.

Current may be passed through the plurality of electromagnetic coils simultaneously.

The direction of the current passing through the plurality of electromagnetic coils may be the same in each coil.

Current may be passed through each of the plurality of electromagnetic coils sequentially.

The rotor may further comprise a plurality of non-magnetic sections positioned between the plurality of permanent magnets.

The plurality of permanent magnets may each comprise opposite magnetic poles, and the opposite magnetic poles in each of the plurality of permanent magnets may be arranged such that they correspond rotationally along the circumference of the rotor.

The rotor may further comprise a non-magnetic layer arranged between the at least one permanent magnet and the first gear.

The electric motor may comprise a plurality of rotary gear members arranged in the space between the first gear of the rotor and the second gear of the shaft.

The plurality of rotary gear members may be spaced apart evenly in the space between the first gear of the rotor and the second gear of the shaft.

Each of the plurality of rotary gear members may have its own stationary axis of rotation.

The shaft may comprise a hollow centre.

DETAILED DESCRIPTION

In known types of synchronous brushless motors, the rotor comprises permanent magnets with magnetic poles arranged to be spaced apart circumferentially such that when current passes through the stator electromagnetic coils, the rotor rotates incrementally from one magnetic pole to another to drive a central motor shaft. These types of known electric motors require the use of a rotor position sensor so as to accurately switch on and off the current in the stator electromagnetic coils as well as a central processing unit (CPU) to control the switching. In addition, it is required in these known types of electric motors to create specific software for the CPU to effectively manage the switching control.

The aspects described below provide an improved electric motor in terms of overall electrical and mechanical performance. In particular, these aspects provide an electric motor with increased power efficiency as well as improved dynamic and traction properties, while having a reduced size due to absence of any rotor position sensors (e.g. Hall sensor, resolver, etc.) and computer processors. Moreover, for this reason, the costs for manufacturing the electric motor according to these aspects are reduced.

FIGS. 1A, 1B, and 1Care respectively a front view of a rotor of an electric motor, a front view of the electric motor, and the side cross-sectional view of the electric motor.FIG. 2is a perspective view of the electric motor ofFIG. 1B, andFIG. 3is a perspective view of the electric motor ofFIG. 1Bwith the stator removed.

The rotor110, as illustrated inFIG. 1Aindividually and separate from the other components of the electric motor, comprises a first permanent magnet112a, a second permanent magnet112b, a third permanent magnet112c, a plurality of intermediate sections114, a non-magnetic layer116, and a first gear118. A perspective side view of the rotor110is more clearly shown inFIG. 3.

The first, second, and third permanent magnets112a,112b,112ceach comprises opposite magnetic poles (i.e. north pole and south pole), wherein the opposite magnetic poles in each of the first, second and third permanent magnets are arranged such that they correspond rotationally along the circumference of the rotor110. Therefore, the plurality of permanent magnets112a,112b,112cof the rotor110all have the same magnetic orientation within the rotor110as the rotor110rotates.

Each of the plurality of intermediate sections114of the rotor110comprises non-magnetic material. These sections114serve as buffer zones in the rotor110between the plurality of permanent magnets112a,112b,112cin order to prevent the magnetic fields at the magnetic poles of the different permanent magnets from influencing each other. The plurality of sections114are respectively positioned between the first permanent magnet112aand the second permanent magnet112b, between the second permanent magnet112band the third permanent magnet112c, and between the third permanent magnet112cand the first permanent magnet112a, as illustrated inFIG. 1A. In other words, the first, second, and third permanent magnets112a,112b,112cand the plurality of sections114form an outermost layer of the rotor110.

The non-magnetic layer116of the rotor110is located between the outermost layer of the rotor (i.e. the layer comprising the first, second, and third permanent magnets112a,112b,112cand the plurality of sections114) and a first gear118. The non-magnetic layer116serves to prevent magnetic fields at the magnetic poles of each of the permanent magnets from forming a loop within the rotor110, which may produce an undesired effect on the operation of the electric motor100. For example, a magnetic field loop formed in an inner layer of the rotor110would potentially counteract magnetic fields generated by the electromagnetic coils in the electric motor thus reducing the efficiency of the electric motor.

The first gear118comprises a plurality of teeth formed on an inner surface of the rotor110, each of the teeth projecting towards the centre of the rotor radially. As shown inFIG. 1B, the first gear118is in a meshing engagement with a plurality of rotary gear members130a,130b,130cso as to transfer torque from the rotor110to a shaft140. This will be explained in further detail below.

As shown inFIGS. 1B, 1C, and 2, the electric motor100(herein referred to as “the motor”) comprises the rotor110ofFIG. 1A, a plurality of electromagnetic coils120a,120b,120c, a plurality of rotary gear members130a,130b,130c, and a shaft140.

The first electromagnetic coil120a, the second electromagnetic coil120b, and the third electromagnetic coil120care individually wound around the rotor110, and in an initial state the plurality of electromagnetic coils120a,120b,120care positioned such that they correspond to the plurality of sections114between the permanent magnets112a,112b,112ccircumferentially. This initial state is illustrated inFIG. 1B. Each of the plurality of electromagnetic coils120a,120b,120ccomprises a plurality of windings. When current passes through an electromagnetic coil, a magnetic field is generated which passes through the centre of the electromagnetic coil. A permanent magnet positioned in the vicinity of the generated magnetic field would be caused to move under the influence of the magnetic field.

For example, starting from the initial state as shown inFIG. 1B, current may pass through the first electromagnetic coil120aso as to generate a first magnetic field which causes the first permanent magnet112ato move towards and through the centre of the first electromagnetic coil120a. The movement of the first permanent magnet112acauses the rotor110to rotate in a clockwise direction. At the same time, current also passes through the second and third electromagnetic coils120b,120cso as to respectively generate a second magnetic field and a third magnetic field, wherein the directions of the first, second, and third magnetic field are all substantially aligned along the circumference of the electric motor100. Under the second and third magnetic fields, the second permanent magnet112band the third permanent magnet112crespectively move towards and through the centre of the second electromagnetic coil120band of the third electromagnetic coil120c, thereby increasing the efficiency of the rotation of the rotor110. As explained above, the plurality of permanent magnets112a,112b,112cof the rotor110all have the same magnetic orientation within the rotor110as the rotor110rotates. Accordingly, the direction of rotation of the rotor110is dependent on direction of the current passing through the plurality of electromagnetic coils120a,120b,120c. For maximum efficiency, the direction of the current passing through the plurality of electromagnetic coils120a,120b,120cshould be the same (i.e. clockwise or anticlockwise through the coils).

As shown inFIG. 1B, a first rotary gear member130a, a second rotary gear member130b, and a third rotary gear member130care positioned within a circumferential space between the rotor110and the shaft140. Specifically, the plurality of rotary gear members130a,130b,130care positioned between the first gear118of the rotor110and a second gear142located on the shaft140. Each of the plurality of rotary gear members130a,130b, and130ccomprises a plurality of teeth which allow them to be in a meshing engagement with both the first gear118and the second gear142such that torque can be transferred from the rotor110to the shaft140. In addition, each of the plurality of rotary gear members130a,130b, and130chas its own stationary axis of rotation.

The shaft140is a hollow cylinder positioned axially relative to the rotor110and is rotatably supported in the electric motor100. As outlined above, the shaft140comprises a second gear142which is arranged on an outer surface of the shaft140. The shaft140may, for example, be made of steel or other suitable magnetic material. The second gear142comprises a plurality of teeth formed on the outer surface of the shaft140, each of the teeth extending radially from a centre of the shaft140. As explained above, the plurality of rotary gear members130a,130b,130ccan mesh with the second gear142so as to transfer torque from the rotor110to the shaft140.

The first electromagnetic coil120a, the second electromagnetic coil120b, the third electromagnetic coil120c, together with the first rotary gear member130a, the second rotary gear member130b, and the third rotary gear member130cform the stator of the electric motor100. Although the plurality of rotary gear members130a,130b, and130cform part of the stator, it is noted that each of the plurality of rotary gear members is able to rotate within the stator. As mentioned above, each of the plurality of rotary gear members has its own stationary axis of rotation within the stator.

A sequence of the operation of the electric motor100is described below:

Current is passed through the first, second, and third electromagnetic coils at the same time, such that the first magnetic field, the second magnetic field, and the third magnetic field are respectively generated at the electromagnetic coils. The directions of the first, second, and third magnetic field are all substantially aligned along the circumference of the electric motor100.

Starting from the initial position as shown inFIG. 1B, each of the first magnetic field, the second magnetic field, and the third magnetic field cause permanent magnets112a-clocated adjacent to the coils120a-cto move along a magnetic direction of each of the magnetic fields. For example, the first magnetic field generated by the first electromagnetic coil causes the first permanent magnet112ato move towards and through the centre of the first electromagnetic coil120a. At the same time, the second and third magnetic fields generated respectively by the second and third electromagnetic coils respectively cause the second and third permanent magnets112b,112cto respectively move towards and through the centres of the second and third electromagnetic coils120b,120c.

The movement of the first, second, and third permanent magnets causes the rotor110to rotate, and in the particular configuration as shown inFIG. 1B, the rotor110is caused to rotate in a clockwise direction. The collective magnetic effect provided by the first, second, and third electromagnetic coils120a,120b,120cincreases the efficiency of the rotation of the rotor110.

Due to the arrangement of the first gear118of the rotor110, the first, second, and third rotary gears130a,130b,130c, and the second gear142of the shaft140, rotation of the rotor110causes torque to be transferred from the rotor110, through meshing between the first gear118and the plurality of rotary gears130a,130b,130c, to the shaft140, through meshing between the plurality of rotary gears130a,130b,130cand the second gear142of the shaft140. Therefore, the shaft140is caused to rotate. The shaft140can be used to drive a component mechanically connected to the shaft140, such as a vehicle axle.

Since current is passed through the first, second, and third electromagnetic coils120a,120b,120cat the same time in the operation of the electric motor100, there is no requirement for any rotor position sensors in the electric motor100for the purpose of detecting a position of the rotor and controlling switching of current in response. In addition, due to the same reason, there is also no requirement for a processing unit to control switching of the current in these electromagnetic coils. The elimination of these components from the electric motor allows for a more compact and lightweight configuration.

Although it is described above that the rotor comprises a first, second, and third permanent magnets, in alternative embodiments a different number of permanent magnet(s) may be provided. For example, in some alternative embodiments, the rotor may comprise six permanent magnets in relatively reduced size arranged along the circumference in the outer layer of the rotor. In these alternative embodiments, the electric motor may comprise an equivalent number of electromagnetic coils so as to achieve a high efficiency of operation. In some embodiments, the electric motor may comprise at least one permanent magnet and at least one electromagnetic coil.

Although it is described above that current passes through the first electromagnetic coil, the second electromagnetic coil, and the third electromagnetic coil at the same time, in alternative embodiments, current may not pass through all the electromagnetic coils simultaneously. In some alternative embodiments in which the electric motor comprises a plurality of electromagnetic coils, the electric motor may be configured such that the current only passes through one or some of the electromagnetic coils at any one time. In some alternative embodiments in which the electric motor comprises a plurality of electromagnetic coils, the electric motor may be configured such that current passes through each of the plurality of electromagnetic coils sequentially.

Although it is described above that the electric motor comprises first, second, and third rotary gear members, in alternative embodiments a different number of rotary gear members may be provided, depending on the dimensions, power requirements, and cost requirements of the electric motor.

Although it is described above that the plurality of intermediate sections in the electric motor comprises non-magnetic material, in alternative embodiments, the plurality of sections may comprise magnetic material.

Although it is described above that the electric motor comprises a non-magnetic layer, in alternative embodiments the electric motor may not comprise such a non-magnetic layer. In these alternative embodiments, the first gear of the electric motor may comprise non-magnetic material so as to minimise undesired magnetic effects on the plurality of permanent magnets and the plurality of electromagnetic coils.

Although the various aspects of the present disclosure are set out in the independent claims, other aspects of the present disclosure comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

It is also noted herein that while the above describes various examples, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.