JP2023008128A - Electric power steering device and steering reaction force generating apparatus - Google Patents

Abstract

To provide a small-sized electric power steering device and a steering reaction force generating device which reduce the number of components.SOLUTION: An electric power steering device includes a rack bar, a pinion gear meshing with the rack bar, and an axial gap electric motor for rotating the pinion gear. The axial gap electric motor includes a motor stator including an exciting coil, a motor rotor for rotating in accordance with an excitation state of the exciting coil, and a shaft directly connected to the motor rotor and rotating in conjunction with the motor rotor. The motor rotor and the motor stator are opposed to each other in an axial direction along an extending direction of the shaft via a gap, and the shaft is directly connected to the pinion gear.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to an electric power steering device and a steering reaction force generation device.

Patent Literature 1 describes an electric power steering apparatus of a single pinion assist system or a dual pinion assist system. In the technique disclosed in Patent Document 1, an electric motor rotates a pinion via a worm speed reduction mechanism.

Japanese Patent Application Laid-Open No. 2007-039032

In the technique disclosed in Patent Document 1, since the worm reduction mechanism is interposed between the electric motor and the pinion, the inertia of the motor increases by the square of the reduction ratio of the worm reduction mechanism. Since the worm wheel is often made of a resin material in the worm speed reduction mechanism, the load capacity of the worm wheel must be ensured so that it can withstand the inertia of the motor. As a result, the worm speed reduction mechanism becomes large, and it is difficult to suppress the manufacturing cost.

On the other hand, if the worm reduction mechanism is removed, there is a possibility that the torque for rotating the pinion will be insufficient. Therefore, in the case of a radial gap type electric motor, it is necessary to increase the axial lengths of the stator core and rotor. As a result, the electric motor becomes large.

The present disclosure has been made in view of the above problems, and an object of the present disclosure is to reduce the number of parts and provide a compact electric power steering device and a steering reaction force generation device.

To achieve the above object, an electric power steering device according to one aspect includes a rack bar, a pinion gear that meshes with the rack bar, and an axial gap type electric motor that rotates the pinion gear. A type electric motor includes a motor stator having an exciting coil, a motor rotor that rotates according to the excitation state of the exciting coil, and a shaft that is directly connected to the motor rotor and rotates in conjunction with the motor rotor. The motor rotor and the motor stator face each other across a gap in the axial direction along the extending direction, and the shaft is directly connected to the pinion gear.

As a result, the axial gap type electric motor can rotate the pinion gear without using the worm speed reduction mechanism. Since the motor inertia receives the load from the rack-and-pinion structure, the steering system is expected to have improved load resistance. In addition, the steering device can be reduced in number of parts and made compact.

As a desirable aspect, the axial gap type electric motor includes a steering shaft connected to a steering wheel, and a pinion shaft that rotates in conjunction with the rotation of the steering shaft and is connected to the pinion gear. A shaft is connected to the pinion shaft.

This allows the axial gap type electric motor to transmit motor torque to the pinion shaft without a worm speed reduction mechanism. And the steering device, even if it is of the single pinion assist type, is compact.

As a desirable aspect, the axial gap type electric motor is arranged on the pinion end side of the pinion gear.

Since the axial gap type electric motor can reduce the control frequency more than the radial gap type electric motor, it is possible to design the control even with a low-frequency arithmetic element. As a result, the cost of the control device can be reduced.

As a desirable aspect, the pinion gear includes a first pinion gear attached at a different position, a steering shaft connected to a steering wheel, a steering shaft that rotates in conjunction with the rotation of the steering shaft, and the first pinion gear. a connecting pinion shaft, wherein said pinion gear is a second pinion gear, said shaft of said axial gap electric motor directly connecting with said second pinion gear.

This allows the axial gap type electric motor to transmit motor torque to the second pinion without a worm speed reduction mechanism. And the steering device, even if it is of the dual pinion assist type, is compact.

As a desirable aspect, a control device for controlling the operation of the axial gap type electric motor is attached to the axial end side of the shaft of the axial gap type electric motor.

The axial gap type electric motor can increase the motor torque by enlarging it in the radial direction. As a result, since the installation area in the radial direction is increased, the limitation on the size of the circuit board of the control device is reduced.

As a desirable aspect, the axial end of the shaft of the axial gap type electric motor is a radiation fin.

Heat generation of the axial gap type electric motor is suppressed.

As a desirable aspect, a component of a rotation angle sensor is attached to the axial end of the shaft of the axial gap type electric motor.

The size in the axial direction along the direction in which the shaft extends can be suppressed.

As a desirable aspect, the axial gap type electric motor is a first axial gap type electric motor, and a second axial gap type electric motor different from the first axial gap type electric motor and a steering wheel connected to a steering wheel are provided. and a shaft, wherein the shaft of the second axial gap electric motor rotates in conjunction with the steering shaft.

As a result, the possibility of occurrence of torque fluctuation and rattling noise at the time of starting or turning back due to the backlash of the worm speed reduction mechanism is reduced.

In order to achieve the above object, a steering reaction force generating device according to another aspect includes a steering shaft connected to a steering wheel, and an axial gap electric motor, the axial gap electric motor including an excitation coil. a motor rotor that rotates according to the excitation state of the excitation coil; and a shaft that is directly connected to the motor rotor and rotates in conjunction with the motor rotor, wherein the shaft extends in the axial direction along the direction in which the shaft extends. A motor rotor and the motor stator face each other across a gap, and the shaft rotates in conjunction with the steering shaft.

As a result, the reaction force generator does not transmit the reaction force from the electric motor to the steering wheel via the worm speed reduction mechanism. Therefore, the possibility of occurrence of torque fluctuation and rattling noise at the time of starting or turning back due to the backlash of the worm speed reduction mechanism is reduced.

According to the present disclosure, it is possible to reduce the number of parts and provide a compact electric power steering device and steering reaction force generation device.

FIG. 1 is a schematic diagram for explaining an electric power steering device according to Embodiment 1. FIG. FIG. 2 is a schematic diagram for explaining the axial gap type electric motor and the rack gear of the first embodiment. FIG. 3 is a schematic diagram for explaining a radial gap type electric motor of a comparative example. FIG. 4 is an explanatory diagram for conceptually explaining an example of the relationship between the motor rotation speed and the motor torque in the radial gap type electric motor of the comparative example. FIG. 5 is an explanatory diagram for conceptually explaining an example of the relationship between the motor rotation speed and the motor torque in the axial gap type electric motor of the first embodiment. FIG. 6 is a schematic diagram for explaining an axial gap type electric motor according to a modification of the first embodiment. FIG. 7 is a schematic diagram for explaining the axial gap type electric motor and the rack gear of the second embodiment. FIG. 8 is an explanatory diagram for explaining the axial end portion of the shaft of the axial gap type electric motor of Embodiment 2. FIG. FIG. 9 is a schematic diagram for explaining an axial gap type electric motor and a rack gear as a modification of the second embodiment. FIG. 10 is a schematic diagram for explaining the electric power steering device of the third embodiment. FIG. 11 is a schematic diagram for explaining the axial gap type electric motor and the rack gear of the third embodiment. FIG. 12 is a schematic diagram for explaining an axial gap type electric motor of a modified example of the third embodiment. FIG. 13 is a schematic diagram for explaining the electric power steering device of the fourth embodiment. FIG. 14 is a schematic diagram for explaining the axial gap type electric motor and the steering reaction force generating device of the fourth embodiment.

Hereinafter, the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited by the following modes for carrying out the invention (hereinafter referred to as embodiments). In addition, components in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that fall within a so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments can be combined as appropriate.

(Embodiment 1)
FIG. 1 is a schematic diagram for explaining an electric power steering device according to Embodiment 1. FIG. FIG. 2 is a schematic diagram for explaining the axial gap type electric motor and the rack gear of the first embodiment. As shown in FIG. 1, the steering device 80 includes a steering wheel 81, a steering shaft 82, a universal joint 84, a lower shaft 85, a universal joint 86, and a pinion shaft in the order in which the force applied by the operator is transmitted. 87 , a steering gear 88 and tie rods 89 . The steering device 80 also includes a control device (hereinafter referred to as an ECU (Electronic Control Unit)) 90 , a torque sensor 91 a and an axial gap type electric motor 1 . The vehicle speed sensor 91b is provided in the vehicle and outputs a vehicle speed signal V to the ECU 90 through CAN (Controller Area Network) communication.

The steering shaft 82 is connected at one end to the steering wheel 81 and at the other end to a universal joint 84 .

The lower shaft 85 is connected at one end to a universal joint 84 and at the other end to a universal joint 86 . The pinion shaft 87 is connected at one end to the universal joint 86 and at the other end to the torque sensor 91a. The torque sensor 91a has one end connected to the pinion shaft 87 and the other end connected to the shaft 25 (see FIG. 2) of the axial gap type electric motor 1 .

The steering gear 88 includes a first pinion gear 88a and a rack bar 88b. The first pinion gear 88 a is connected to the pinion shaft 87 . The rack bar 88b meshes with the first pinion gear 88a. The steering gear 88 converts the rotational motion transmitted to the first pinion gear 88a into linear motion by the rack bar 88b. The tie rod 89 is connected to the rack bar 88b. That is, the steering device 80 is of rack and pinion type.

The axial gap type electric motor 1 is, for example, a brushless motor, but may be a motor including brushes (sliders) and commutators (commutators). As shown in FIG. 2, the axial gap type electric motor 1 can rotate the first pinion gear 88a without using a worm reduction gear. That is, the steering device 80 is of a single pinion type.

The torque sensor 91a detects the driver's steering force transmitted to the steering shaft 82 via the steering wheel 81 as steering torque. The vehicle speed sensor 91b detects the traveling speed (vehicle speed) of the vehicle in which the steering device 80 is mounted. The axial gap type electric motor 1, the torque sensor 91a, and the vehicle speed sensor 91b are electrically connected to the ECU90.

The ECU 90 controls the operation of the axial gap electric motor 1 . The ECU 90 also acquires signals from the torque sensor 91a and the vehicle speed sensor 91b. That is, the ECU 90 acquires the steering torque T from the torque sensor 91a and acquires the vehicle speed signal V from the vehicle speed sensor 91b. The ECU 90 is supplied with electric power from a power supply device (for example, an in-vehicle battery) 99 when an ignition switch 98 is on. The ECU 90 calculates an assist steering command value of the assist command based on the steering torque T and the vehicle speed signal V. FIG. Then, the ECU 90 adjusts the power value X to be supplied to the axial gap type electric motor 1 based on the calculated assist steering command value. The ECU 90 acquires, as operation information Y, information about the induced voltage from the axial gap type electric motor 1 or information output from a rotation detecting device such as a resolver provided in the axial gap type electric motor 1 .

The operator's (driver's) steering force input to the steering wheel 81 is transmitted to the torque sensor 91a. At this time, the ECU 90 obtains the steering torque T from the torque sensor 91a and the vehicle speed signal V from the vehicle speed sensor 91b. The ECU 90 then controls the operation of the axial gap electric motor 1 . Auxiliary steering torque generated by the axial gap type electric motor 1 is transmitted to the first pinion gear 88a.

The steering force transmitted to the first pinion gear 88a is transmitted to the tie rod 89 via the steering gear 88 to displace the wheels.

As shown in FIG. 2 , the axial gap electric motor 1 includes a motor housing 15 , a motor stator 10 , bearings 16 , a shaft 25 and a motor rotor 20 . The motor housing 15 is connected with the pinion housing 88s and the rack housing 88h. The pinion housing 88s accommodates the first pinion gear 88a. The rack housing 88h accommodates the rack bar 88b. The motor stator 10 is arranged inside a motor housing 15 and fixed to the motor housing 15 . A motor stator 10 includes a stator core 11 and an exciting coil 12 . Stator core 11 is formed by stacking electromagnetic steel plates.

The shaft 25 is rotatably supported by the motor housing 15 via bearings 16 . The motor rotor 20 is fixed to a shaft 25, and as the motor rotor 20 rotates, the shaft 25 also rotates. The motor rotor 20 includes a rotor core 21 and magnets 22 . The rotor core 21 is formed by stacking electromagnetic steel plates. The rotor core 21 is disc-shaped. The magnet 22 is made of samarium cobalt, neodymium magnet, or the like. Although one motor rotor 20 is provided in the first embodiment, a plurality of motor rotors 20 may be arranged by alternately arranging the motor stator 10 and the motor rotor 20 in the axial direction. This increases the installation space, but by arranging a plurality of motor rotors 20, the torque increases.

Assuming that the direction along which the shaft 25 extends is the axial direction, the motor rotor 20 is sandwiched between the two motor stators 10, and the motor rotor 20 and the motor stator 10 face each other with a gap in the axial direction. According to such a structure, the phases of the magnetic fields excited by the motor stators 10 can be shifted from each other, or the magnets can be deformed in consideration of the skew. As a result, the axial gap electric motor 1 of the first embodiment can suppress fluctuations in the torque of the motor rotor 20 without adopting a complicated structure such as the skew grooves of the radial gap electric motor of the comparative example.

In automotive products, it is a practice to design system redundancy rather than the requirement for continuous functioning. In the radial gap type electric motor of the comparative example, due to the restriction of the structure controlled by the three-phase current, redundancy is achieved by making the coils multipolar in multiples of three. In addition, in the radial gap electric motor of the comparative example, multiple (redundant 3-phase currents) flow through one stator, so it is necessary to consider the influence of mutual inductance in the design of each current control. In contrast, in the axial gap type electric motor 1 of Embodiment 1, two motor stators 10 act on one motor rotor 20, so even if one motor stator 10 fails, the other motor If the stator 10 functions, it can continue to function. Furthermore, in the axial gap type electric motor 1 of Embodiment 1, each of the plurality of motor stators 10 can be controlled independently. Therefore, in the axial gap type electric motor 1 of Embodiment 1, the influence of mutual inductance is small compared to the radial gap type electric motor of the comparative example.

In the axial gap type electric motor 1 of Embodiment 1, the resolver 30 detects rotation of the shaft 25 . The resolver 30 includes a resolver rotor 31 and a resolver stator 32 . A resolver rotor 31 is attached around the shaft 25 . The resolver rotor 31 is radially opposed to the resolver stator 32 attached to the support member 35 via a gap.

The resolver stator 32 has an annular laminated core in which a plurality of stator magnetic poles are formed at equal intervals in the circumferential direction, and a resolver coil is wound around each stator magnetic pole. The resolver rotor 31 is composed of a hollow annular laminated core. When the motor rotor 20 rotates, the shaft 25 rotates together with the motor rotor 20, and the resolver rotor 31 rotates accordingly. Thereby, the reluctance between the resolver rotor 31 and the resolver stator 32 continuously changes, and the rotation of the shaft 25 is detected.

The ECU 90 is located between the axial gap electric motor 1 of the first embodiment and the torque sensor 91a. The resolver 30, the circuit board 90a of the ECU 90, and the torque sensor 91a are housed in a housing 95 of the ECU 90. As shown in FIG. As a result, the housing of the torque sensor 91a can be simplified, and the number of parts can be reduced. Moreover, since the harness connecting the circuit board 90a and the resolver 30 and the harness connecting the circuit board 90a and the torque sensor 91a can be shortened, resistance to electromagnetic noise is improved. Since it is not necessary to dispose the housing 95 of the ECU 90 on the side surface of the worm speed reduction mechanism as in Patent Document 1, the layout of the steering device 80 of the first embodiment is improved. In FIG. 2, the resolver 30, which is a rotation detection device, is not limited to being placed between the torque sensor 91a and the motor housing 15, but is placed between the first pinion gear 88a and the bearing 16, or between the first pinion gear 88a and the bearing 16. It may be the pinion end side of 88a.

FIG. 3 is a schematic diagram for explaining a radial gap type electric motor of a comparative example. FIG. 4 is an explanatory diagram for conceptually explaining an example of the relationship between the motor rotation speed and the motor torque in the radial gap type electric motor of the comparative example. FIG. 5 is an explanatory diagram for conceptually explaining an example of the relationship between the motor rotation speed and the motor torque in the axial gap type electric motor of the first embodiment. The relationship between the motor rotation speed and the motor torque shown in FIGS. 4 and 5 is an ideal curve, and shows a curve conceptually representing the relationship.

As shown in FIG. 3, in the radial gap type electric motor 200 of the comparative example, the motor rotor and the motor stator face each other across a gap in the radial direction. When obtaining the same output with the radial gap type electric motor 200 of the comparative example and the axial gap type electric motor 1 of the first embodiment, if the amount of magnet used is the same, the performance is higher than that of the radial gap type electric motor 200 of the comparative example. The axial gap type electric motor 1 of form 1 can reduce the volume by about 30%. In particular, assuming that the size in the axial direction of the axial gap type electric motor 1 of Embodiment 1 can be reduced to half that of the radial gap type electric motor 200 of the comparative example, it is equivalent to the radial gap type electric motor 200 of the comparative example. The axial gap type electric motor 1 of Embodiment 1, which has an axial dimension, can obtain an output torque approximately double that of the radial gap type electric motor 200 of the comparative example.

As shown in FIG. 4, when the radial gap electric motor 200 of the comparative example generates motor torque via the worm speed reduction mechanism, the motor rotation speed is, for example, 1000 rpm to 2500 rpm. The motor rotor of the motor 200 is rotated at high speed. In order for the radial gap type electric motor 200 of the comparative example to rotate at a high speed, it is effective to make the magnet 22 have multiple pole pairs. As the number of pole pairs of the magnet 22 increases, the control frequency is required to be at least 4 to 10 kHz. However, there are few arithmetic elements (especially arithmetic elements for automobile products) on the market that can satisfactorily operate this control frequency, and the cost tends to increase.

On the other hand, as shown in FIG. 5, the axial gap electric motor 1 generates a large motor torque at a lower rotation speed than the radial gap electric motor 200 of the comparative example without using the worm speed reduction mechanism. The axial gap type electric motor 1 can reduce the control frequency to 1/10 to 1/20. Since this enables control design even with low-frequency arithmetic elements, cost reduction of the ECU 90 (see FIG. 1) is also expected. In the axial gap type electric motor 1, a further increase in torque can be expected by various measures such as the material of the magnets and the layout of the magnetic poles.

As described above, the steering device 80 includes the rack bar 88b, the first pinion gear 88a that meshes with the rack bar 88b, and the axial gap electric motor 1 that rotates the first pinion gear 88a. The axial gap type electric motor 1 includes a motor stator 10 having an exciting coil 12 , a motor rotor 20 that rotates according to the excitation state of the exciting coil 12 , and a shaft 25 that is directly connected to the motor rotor 20 and rotates in conjunction with the motor rotor 20 . ,including. The motor rotor 20 and the motor stator 10 face each other across a gap in the axial direction along the direction in which the shaft 25 extends. Further, the shaft 25 is directly connected to the first pinion gear 88a. The shaft 25 rotates coaxially with the first pinion gear 88a.

As a result, the axial gap type electric motor 1 can rotate the first pinion gear 88a without using the worm speed reduction mechanism. Since the motor inertia receives the load from the rack-and-pinion structure, the steering device 80 is expected to have improved load resistance. Further, the steering device 80 can be reduced in the number of parts and made compact.

Since the axial gap type electric motor 1 has a gap in a plane perpendicular to the shaft 25, the design requirements for the coaxiality between the motor stator 10 and the motor rotor 20 are lower than in the radial gap type electric motor 200 of the comparative example. . Therefore, the pinion housing 88s and the motor housing 15 can be integrally molded, and the gap between the motor stator 10 and the motor rotor 20 can be managed and assembled.

(Modification of Embodiment 1)
FIG. 6 is a schematic diagram for explaining an axial gap type electric motor according to a modification of the first embodiment. The same reference numerals are assigned to the same components as those described in the first embodiment, and overlapping descriptions are omitted. In the axial gap type electric motor 1A of the modified example of the first embodiment, there are a plurality of motor rotors 20, and the two motor rotors 20 sandwich the motor stator 10 with a gap in the axial direction. By increasing the motor rotor 20 in the axial direction, the motor torque can be increased.

(Embodiment 2)
FIG. 7 is a schematic diagram for explaining the axial gap type electric motor and the rack gear of the second embodiment. In addition, the same reference numerals are assigned to the same components as those described in the first embodiment and the modified example, and overlapping descriptions are omitted.

The axial gap type electric motor 1B of Embodiment 2 is arranged on the pinion end side of the first pinion gear 88a. The torque sensor 91a has one end connected to the pinion shaft 87 and the other end connected to the first pinion gear 88a. As a result, one end of the shaft 25 is connected to the first pinion gear 88a, and the other shaft end is not connected to the torque sensor 91a. As a result, the ECU 90 can be fixedly arranged on the other shaft end side of the motor housing 15 .

The radial gap type electric motor of the comparative example can increase the motor torque by increasing the shaft length. However, since there is a weight limit, it tends to be narrower in the radial direction in order to keep the volume down. Therefore, if the ECU 90 is arranged at the shaft end of the motor, the size of the circuit board 90a is limited. As a result, in many cases, the circuit board 90a of the ECU 90 must be three-dimensionally designed, and the circuit design conditions are very strict. On the other hand, the axial gap type electric motor 1B can increase the motor torque by enlarging it in the radial direction. In other words, since the installation area of the ECU 90 can be widened, the restriction on the size of the circuit board 90a is relaxed.

In the axial gap type electric motor 1</b>B of Embodiment 2, the resolver 30 detects rotation of the shaft 25 . The resolver 30 includes a resolver rotor 31 and a resolver stator 32 . A resolver rotor 31 is attached to the other axial end of the shaft 25 . The resolver rotor 31 is radially opposed to the resolver stator 32 attached to the support member 35 via a gap. With this structure, the size of the steering device 80 in the axial direction is suppressed. Further, since the distance between the torque sensor 91a and the resolver 30 is increased compared to the first embodiment, the torque sensor 91a and the resolver 30 are less likely to interfere with each other. 7, the resolver 30, which is a rotation detection device, may be arranged between the torque sensor 91a and the first pinion gear 88a and between the first pinion gear 88a and the bearing 16. As shown in FIG.

The first pinion gear 88a is rotatably supported by the bearings 17 inside the pinion housing 88s and the two bearings 16 of the axial gap electric motor 1B of the second embodiment. This structure suppresses variation in meshing engagement between the first pinion gear 88a and the rack bar 88b.

FIG. 8 is an explanatory diagram for explaining the axial end portion of the shaft of the axial gap type electric motor of Embodiment 2. FIG. It is desirable that the shaft end portion of the shaft 25 in the axial direction has high heat dissipation. As shown in FIG. 8, the shaft 25 of the second embodiment includes a groove 25S and a projection 25P axially protruding from the bottom of the groove 25S at the axial end. The grooves 25S and the projections 25P constitute heat radiation fins to enhance heat radiation.

As described above, the steering device 80 includes the rack bar 88b, the second pinion gear 88e that meshes with the rack bar 88b, and the axial gap electric motor 1B that rotates the second pinion gear 88e. The axial gap type electric motor 1B includes a motor stator 10 having an exciting coil 12, a motor rotor 20 that rotates according to the excitation state of the exciting coil 12, and a shaft 25 that is directly connected to the motor rotor 20 and rotates in conjunction with the motor rotor 20. ,including. The motor rotor 20 and the motor stator 10 face each other across a gap in the axial direction along the direction in which the shaft 25 extends. Further, the shaft 25 is directly connected to the second pinion gear 88e.

As a result, the axial gap type electric motor 1B can rotate the second pinion gear 88e without using the worm speed reduction mechanism. Since the motor inertia receives the load from the rack-and-pinion structure, the steering device 80 is expected to have improved load resistance. Further, the steering device 80 can be reduced in the number of parts and made compact.

(Modification of Embodiment 2)
FIG. 9 is a schematic diagram for explaining an axial gap type electric motor and a rack gear as a modification of the second embodiment. The same reference numerals are assigned to the same components as those described in the second embodiment, and overlapping descriptions are omitted. In the axial gap type electric motor 1</b>C of the modified example of the second embodiment, the shaft 25 has a rotation detection magnet 90 m at the end of the shaft 25 . Half of the rotation detection magnet 90m is magnetized to the south pole, and half is magnetized to the north pole.

A rotation angle sensor 90s mounted on a sensor substrate 90b is arranged at a position facing the rotation detection magnet 90m in the axial direction. The rotation angle sensor 90s should be able to detect the rotation of the rotation detection magnet 90m. The rotation angle sensor 90s is, for example, a spin valve sensor. A spin-valve sensor is an element in which a non-magnetic layer is sandwiched between a ferromagnetic pinned layer whose magnetization direction is fixed by an antiferromagnetic layer, etc., and a ferromagnetic free layer, and detects changes in the direction of magnetic flux. It is a sensor that can Spin valve sensors include GMR (Giant Magneto Resistance) sensors and TMR (Tunnel Magneto Resistance) sensors. For example, an AMR (Anisotropic Magneto Resistance) sensor or a Hall sensor may be used.

According to the structure described above, the size in the axial direction along the shaft 25 is suppressed. As a result, the layout of the steering device 80 is improved.

(Embodiment 3)
FIG. 10 is a schematic diagram for explaining the electric power steering device of the third embodiment. FIG. 11 is a schematic diagram for explaining the axial gap type electric motor and the rack gear of the third embodiment. The same components as those described in the first embodiment, the second embodiment, and their modifications are given the same reference numerals, and overlapping descriptions are omitted.

The steering device 80 of Embodiment 3 includes a second pinion gear 88e in addition to the first pinion gear 88a. The steering device 80 of Embodiment 3 is of a dual pinion assist type. The torque sensor 91a is attached to the first pinion gear 88a. The torque sensor 91a outputs to the ECU 90 the steering torque transmitted to the first pinion gear 88a.

As shown in FIG. 11, the axial gap type electric motor 1D can rotate the second pinion gear 88e without using a worm reduction gear. The second pinion gear 88e may be arranged orthogonally to the rack bar 88b, or may be arranged obliquely with respect to the rack bar 88b.

The operator's (driver's) steering force input to the steering wheel 81 is transmitted to the torque sensor 91a. At this time, the ECU 90 obtains the steering torque T from the torque sensor 91a and the vehicle speed signal V from the vehicle speed sensor 91b. The ECU 90 then controls the operation of the axial gap electric motor 1 . Auxiliary steering torque generated by the axial gap type electric motor 1 is transmitted to the second pinion gear 88e. The second pinion gear 88e can also be said to be an assist pinion gear.

Since the axial gap type electric motor 1D is not connected to the pinion shaft 87, there are few restrictions on its arrangement around the rack housing 88h. The second pinion gear 88e may be arranged perpendicular to the extending direction of the rack bar 88b or perpendicular to the extending direction of the rack bar 88b.

The axial gap type electric motor 1D can rotate the second pinion gear 88e without using a worm reduction gear. Therefore, it is possible to reduce the number of parts of the worm reduction gear.

(Modification of Embodiment 3)
FIG. 12 is a schematic diagram for explaining an axial gap type electric motor of a modified example of the third embodiment. The same reference numerals are assigned to the same components as those described in the above-described first and second embodiments, their modifications, and the third embodiment, and duplicate descriptions are omitted. Also in the axial gap type electric motor 1E of the modified example of the third embodiment, the second pinion gear 88e can be rotated without using the worm reduction gear.

One end of the shaft 25 is connected to the first pinion gear 88a, and the other shaft end is not connected to the torque sensor 91a. As a result, the ECU 90 can be fixedly arranged on the other shaft end side of the motor housing 15 .

(Embodiment 4)
FIG. 13 is a schematic diagram for explaining the electric power steering device of the fourth embodiment. FIG. 14 is a schematic diagram for explaining the axial gap type electric motor and the steering reaction force generating device of the fourth embodiment. The same components as those described in Embodiment 1, Embodiment 2, Embodiment 3, their modifications, and Embodiment 3 are denoted by the same reference numerals, and overlapping descriptions are omitted.

The steering device 80 has a steering reaction force generation device (FFA: Force Feedback Actuator) 40 for steering by the driver, and a tire steering device (RWA: Road Wheel Actuator) 60 for steering the vehicle. The steering reaction force generating device 40 and the tire steering device 60 are mechanically separated. The steering reaction force generating device 40 and the tire turning device 60 are electrically connected via the ECU 90, and control between the steering reaction force generating device 40 and the tire turning device 60 is performed by an electric signal. For this reason, the steering device 80 of the fourth embodiment is called a steer-by-wire (SBW) system.

The tire steering device 60 includes a steering gear 88 and an axial gap electric motor 1D (first axial gap electric motor). As described in the third embodiment, the axial gap type electric motor 1D shown in FIG. 11 can rotate the second pinion gear 88e without using a worm reduction gear.

The steering reaction force generating device 40 includes a torque sensor 91a, a steering angle sensor 91c, and an axial gap electric motor 1F (second axial gap electric motor). A steering angle sensor 91 c detects a steering angle θ of the steering wheel 81 .

The operator's (driver's) steering force input to the steering wheel 81 is transmitted to the torque sensor 91a and the steering angle sensor 91c. At this time, the ECU 90 acquires the steering torque T from the torque sensor 91a, the steering angle θ from the steering angle sensor 91c, and the vehicle speed signal V from the vehicle speed sensor 91b. The ECU 90 controls operations of the axial gap electric motor 1D and the axial gap electric motor 1F. Auxiliary steering torque produced by the axial gap type electric motor 1D is transmitted to the second pinion gear 88e.

The ECU 90 is supplied with electric power from a power supply device (for example, an in-vehicle battery) 99 when an ignition switch 98 is on. The ECU 90 calculates an assist steering command value of the assist command based on the steering torque T, the steering angle θ and the vehicle speed signal V. FIG. Then, the ECU 90 adjusts the electric power value X to be supplied to the axial gap type electric motor 1D based on the calculated assist steering command value. The ECU 90 acquires, as operation information Y, information about the induced voltage from the axial gap type electric motor 1D or information output from a rotation detecting device such as a resolver provided in the axial gap type electric motor 1D.

Based on the motion information Y, the ECU 90 calculates a reaction torque according to the motion state of the vehicle. The ECU 90 adjusts the electric power value Z to be supplied to the axial gap type electric motor 1D based on the reaction torque. The axial gap type electric motor 1F operates according to the electric power value Z, and the reaction force of the steering wheel 81 is transmitted to the operator.

The steering shaft 82 and the shaft 25 of the axial gap type electric motor 1F are connected without a worm reduction gear. Therefore, the axial gap type electric motor 1F can rotate the second pinion gear 88e without using the worm reduction gear. Thus, the shaft 25 rotates in conjunction with the steering shaft 82 .

In the steering reaction force generating device 40, the reaction force from the electric motor is not transmitted to the steering wheel 81 via the worm speed reduction mechanism. Therefore, the possibility of occurrence of torque fluctuation and rattling noise at the time of starting or turning back due to the backlash of the worm speed reduction mechanism is reduced. In the steering reaction force generating device 40, the reaction force from the axial gap type electric motor 1F is directly transmitted to the operator, so that the driver is less likely to feel discomfort.

1, 1A, 1B, 1C, 1D, 1E, 1F Axial Gap Electric Motor 10 Motor Stator 11 Stator Core 12 Exciting Coil 15 Motor Housing 16, 17 : Bearing 20 Motor Rotor 21 Rotor Core 22 Magnet 25 Shaft 40 Steering Reaction Force Generating Device 60 Tire steering device 80 steering device 81 steering wheel 82 steering shaft 87 pinion shaft 88 steering gear 88a first pinion gear 88b rack bar 88e second pinion gear 88h rack housing 88s pinion housing 89 tie rod 90 ECU
90a circuit board 90b sensor board 90m rotation detection magnet 90s rotation angle sensor 91a torque sensor 91b vehicle speed sensor 91c steering angle sensor

Claims (9)

a rack bar;
a pinion gear meshing with the rack bar;
an axial gap type electric motor that rotates the pinion gear,
The axial gap type electric motor includes a motor stator having an exciting coil, a motor rotor that rotates according to the excitation state of the exciting coil, and a shaft that is directly connected to the motor rotor and rotates in conjunction with the motor rotor,
the motor rotor and the motor stator face each other across a gap in the axial direction along the direction in which the shaft extends;
An electric power steering device, wherein the shaft is directly connected to the pinion gear. a steering shaft connected to the steering wheel;
a pinion shaft that rotates in conjunction with the rotation of the steering shaft and is connected to the pinion gear;
the shaft of the axial gap type electric motor is connected to the pinion shaft;
The electric power steering device according to claim 1. The axial gap type electric motor is arranged on the pinion end side of the pinion gear,
The electric power steering device according to claim 1 or 2. A first pinion gear mounted at a position different from the pinion gear;
a steering shaft connected to the steering wheel;
a pinion shaft that rotates in conjunction with the rotation of the steering shaft and is connected to the first pinion gear;
The pinion gear is a second pinion gear, and the shaft of the axial gap electric motor is directly connected to the second pinion gear,
The electric power steering device according to claim 1. A control device for controlling the operation of the axial gap type electric motor is attached to the shaft end side of the shaft of the axial gap type electric motor.
The electric power steering device according to any one of claims 1 to 4. The axial end of the shaft of the axial gap type electric motor is a heat radiating fin,
The electric power steering device according to claim 5. A rotation angle sensor component is attached to the axial end of the shaft of the axial gap type electric motor,
The electric power steering device according to claim 5 or 6. The axial gap electric motor is a first axial gap electric motor,
a second axial gap electric motor different from the first axial gap electric motor;
a steering shaft coupled to the steering wheel;
a shaft of the second axial gap type electric motor rotates in conjunction with the steering shaft;
The electric power steering device according to claim 1. A steering shaft connected to a steering wheel and an axial gap type electric motor,
The axial gap type electric motor includes a motor stator having an exciting coil, a motor rotor that rotates according to the excitation state of the exciting coil, and a shaft that is directly connected to the motor rotor and rotates in conjunction with the motor rotor,
the motor rotor and the motor stator face each other across a gap in the axial direction along the direction in which the shaft extends;
The steering reaction force generating device, wherein the shaft rotates in conjunction with the steering shaft.

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