JP3477886B2 - Electric power steering device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering system that develops a force required to operate a steering wheel as a steering assist force by a rotational driving force of a steering assist motor, and more particularly to a rotating direction (current direction) of the steering assist motor. This is an improvement focusing on the magnitude of switching and steering assist force.

[0002]

2. Description of the Related Art Such conventional electric power steering
Of switching devices, especially by electrical switching elements
Electric power to switch the rotation direction (current direction) of the steering assist motor
As a dynamic power steering device, for example, FIG.
There is one as shown (hereinafter, also referred to as a first conventional example).
In this electric power steering device, FET (Field
-Effect Transistor) and other power devices
A so-called H-bridge is constructed by using four as children, and the torque sensor is
Sensor S_1aTorque detected by the vehicle speed sensor S _1bInspected
Vehicle speed and steering angle sensor S issued_1cSteering angle detected by
Two arithmetic processing units via the interface circuit I / F1
Read into the CPU1 and CPU2, and become the main one
The arithmetic processing unit CPU1 mainly consists of the steering torque, the vehicle
The steering assist force corresponding to the speed and steering angle (especially steering direction) is
So that it is generated as the rotational driving force of the motor.
S_i1Current flowing in the H-bridge detected by (
The motor current that actually flows in the motor is fed back.
However, the amount of current flowing in the motor and the current direction,
Is any of the switching elements consisting of the power element
How much power element is turned on when turned on / off
Whether or not to supply the current of
Force Therefore, means for controlling the rotation direction of the motor (below
Below, the motor current direction control means will be collectively referred to as)
Is it an H-bridge composed of switching elements and an arithmetic processing unit?
It is composed of these current commands. Also, while driving straight ahead
Steering applied to the steering wheel, such as disturbance
Steering assist force is generated when the torque itself is small
On the contrary, there is a possibility that the traveling stability may be deteriorated. So
With the motor current amount control means, the steering torque is small.
If it does, the steering assist force may not be expressed.
Current amount control, that is, control such that the motor current becomes zero
When the steering torque is larger than this,
The steering assist force according to the magnitude of the torque is expressed.
The motor current amount is controlled.

In addition, in the first conventional example, it becomes a sub.
The arithmetic processing unit CPU2 is mainly the H bridge.
Current detection to detect malfunction of steering and steering assist motor
Department S _i1And a current detection unit S different from that_i2H detected in
The motor current from the bridge, the motor current and each cell
Sensor S_1a~ S_1cBased on the detected value of
Monitors and compares the current command output from the CPU 1
In comparison, if there is a discrepancy in any of them, operation at the time of failure
To build compensation (hereinafter also referred to as fail-safe)
Supply the current supplied from the battery to the fail-safe relay of
Outputs a fail-safe command to shut off. Here, special
And the switching element of the H-bridge has failed due to short circuit
Or when the processor CPU1 fails,
Generation of steering assist force from motor independent of driver's intention
Is prevented. In addition, each sensor S_1a~ S_1cIs meaningless
Failure while outputting various detection signals, and as a result, the driver
The steering assist force is generated from the motor regardless of the intention of
To prevent this, an equivalent sensor S different from the above_2a~ S
_2cAnd the output of the second interface circuit I /
Via F2 to the sub-processing unit CPU2
Including the sensor S _1a~ S_1cCompare and monitor the output of
If there is a discrepancy, failsafe
In some cases, a fail-safe command is output to the relay. This
In the case of, the system up to the current command output (the current detection
(Including the feedback system by the department) is completely duplicated.
And trust in failsafe.
Sex is secured.

Further, as an electric power steering apparatus for switching the rotation direction (current direction) of a steering assist motor by a mechanical switch, for example, Japanese Utility Model Publication No. 5-192 is used.
No. 68 gazette (Actual disclosure No. 62-114876 gazette, hereinafter,
Some of them are simply described as the second conventional example), and some are described in JP-A-61-181933 (hereinafter, simply referred to as the third conventional example).

Regarding the specific motor current direction control means of the steering assist motor in the second conventional example and the third conventional example, the above publications are referred to, and each of the motor current direction control means is, for example, a steering wheel. A torsion bar is provided between the input shaft connected to the wheel and the output shaft connected to the steered wheels, and the twist amount between the input shaft and the output shaft including the twist angle and the twist displacement generated in the torsion bar, That is, the contact switching control of the two switches interposed between the steering assist motor and the power source is mechanically performed depending on whether the steering torque applied to the steering wheel is in the left or right direction. . In any case, the rotational driving force of the steering assist motor, that is, the steering assist force is controlled by controlling the magnitude of the command current supplied to the power element such as the FET so that the steering assist motor can be operated from the power element. Adjustment control is performed by controlling the amount of current flowing through. As described above, when the steering torque, that is, the amount of twist between the input shaft and the output shaft is small, the switch between the power source and the motor is maintained in the switching state immediately before that in the second conventional example. Then, the command current is controlled so that the amount of current from the power element to the steering assist motor becomes zero. In the third embodiment, in addition to this, the contact between the switch between the power source and the motor I am trying to switch to the open state which is not connected to. Also,
Instead of the mechanical switch in each of these conventional examples, an electrically controlled relay can be used to achieve exactly the same configuration. In this case, the motor current direction control means of each conventional example outputs a drive signal to the solenoid that switches the movable contact of the relay according to each of the assist states, thereby controlling the switching of the contact similar to that described above. Is executed.

Further, as an electric power steering apparatus different from the above-mentioned conventional examples, for example, Japanese Patent Publication No. 5-1559.
Some of them are described in JP-A No. 61-9371 (hereinafter, referred to simply as the fourth conventional example). In this electric power steering device, for example, a coil is wound around the outer circumference of an output shaft connected to the steered wheel side to form a commutator connected to the winding end of each coil on the output shaft, A magnet is provided in the outer case to apply a magnetic field in a fixed direction, and a pair of brushes is formed at the output shaft side end of the input shaft connected to the steering wheel side and outside the commutator. Then, the steering assist motor itself is composed of the input shaft, the brush, the coil, the magnet, the output shaft, and the like, and each of the brushes is connected to an external power source such as a battery. Therefore, in this electric power steering apparatus, when the input shaft is rotated together with the steering wheel, the commutator in contact with the brush changes, and accordingly, the direction of current flowing from the brush to the coil via the commutator changes. Then, along with that, a force (electromagnetic force) for rotationally driving the output shaft in the rotation direction of the input shaft is generated around the output shaft from the magnetic field in a certain direction by the magnet and the direction of the current flowing in the coil.
This rotational driving force is used as a steering assist force. When the steering torque, that is, the amount of twist between the input shaft and the output shaft is small, the rotational driving force of the motor is set by setting the arrangement positions of the brushes and the commutator so that the brushes and the commutator do not come into contact with each other. Is not generated as a steering assist force. Further, when the steering torque, that is, the amount of twist between the input shaft and the output shaft increases, the contact area between the brush and the commutator increases,
Along with this, the amount of electric current (the amount of electric charge) flowing through each coil increases, the rotational driving force by the motor increases, and a steering assist force corresponding to the steering torque is obtained.

[0007]

However, in the first conventional example, as the motor current direction control means, at least four switching elements including at least relatively expensive power elements must be used. The cost will be higher. Further, the cost is further increased by duplicating the input / output system of the control signal for fail-safe operation as described above, and especially by duplicating the sensors as detectors.

Further, in the second conventional example and the third conventional example, an abnormal operation due to seizure or contact failure is caused by an increase in the number of contacts of a mechanically switchable switch and an electrically switchable relay. There is a possibility that a failure will occur, the motor current will not flow in the necessary direction, and the steering assist force will not be developed. Further, in order to construct the above-mentioned fail-safe in these conventional examples, at least the potential of each contact or the potential difference (voltage drop) between them.
It is necessary to detect and compare it with a predetermined state value.Therefore, the number of contacts of the switch or relay increases, so the number of detected potentials and potential differences increases, and at the same time, arithmetic processing for comparison is also performed. It becomes complicated, the structure becomes complicated, and the cost becomes high.

On the other hand, in the fourth conventional example, such a problem can be said to be relatively small, but the input shaft connected to the steering wheel can be continuously rotated for several revolutions within a so-called lock-to-lock range. Because there is
In order to keep the brush rotating with this input shaft connected to an external power source such as a battery, it is necessary to interpose a rotation allowance contact such as a slip ring between the brush and the external power source. However, the number of contacts increases and the possibility of failure increases, and the structure for fail-safe construction becomes complicated and the cost increases.

The present invention was developed in order to solve these problems, and makes it possible to reduce the cost by reducing the use amount of power elements and the like, and to reduce the number of contacts as much as possible. It is therefore an object of the present invention to provide an electric power steering device that can reduce the possibility of failure and can also simplify the structure and reduce the cost.

[0011]

In order to achieve the above object, an electric power steering apparatus according to claim 1 of the present invention comprises an input shaft connected to a steering wheel and an output shaft connected to steered wheels. And a torsion bar interposed between the input shaft and the output shaft, and drives a motor connected to the output shaft according to the relative twist amount between the input shaft and the output shaft generated in the torsion bar to assist the steering of the rotational driving force. The motor includes at least a rotor provided with a commutator connected to each coil and a plurality of coils in a predetermined winding direction divided in the rotation direction, and switching the energization to each coil; An electrically driven pad including magnetic field applying means for applying a magnetic field in a fixed direction around the coil, and a brush for contacting the commutator of the rotor and energizing the coil at a predetermined position. In the steering device, the rotational driving force of the rotor generated between the current of the coil energized from the commutator and the magnetic field of the magnetic field applying means in response to an increase in the relative twist amount between the input shaft and the output shaft. Is provided with a brush moving mechanism for moving the brush relative to at least the magnetic field applying means.

The electric power steering apparatus according to a second aspect of the present invention is characterized in that the rotor and the input shaft and the output shaft are arranged coaxially. The electric power steering apparatus according to claim 3 of the present invention controls the energization current to the motor to zero when the relative twist amount between the input shaft and the output shaft is zero or substantially zero. It is characterized by adding a control device.

In the electric power steering apparatus according to a fourth aspect of the present invention, the brush does not come into contact with the commutator when the relative twist amount between the input shaft and the output shaft is zero or substantially zero. It is characterized in that a guide mechanism for guiding the brush is added to.

[0014]

Therefore, in the electric power steering apparatus according to claim 1 of the present invention, the brush moving mechanism responds to an increase in the relative twist amount between the input shaft and the output shaft.
For example, in the uniform magnetic field strength by the magnetic field applying means,
By moving the brush, the position of the coil through which the current flows is increased in the direction in which the component force in the rotating direction of the rotor increases due to the current (charge amount) flowing in the coil, that is, the direction in which the rotational driving force of the rotor increases. By changing the value, it is possible to obtain the relative twist amount between the input shaft and the output shaft, that is, the twist amount of the torsion bar, and at the same time, obtain the steering assist force according to the magnitude of the steering torque applied to the steering wheel. At this time, the number of contacts in the motor is only the number of contacts between the brush and the commutator, which is the minimum number of contacts in a normal motor. The possibility of is suppressed to a minimum. Further, the potential or the potential difference of the contact to be detected when constructing the operation compensation (fail safe) at the time of failure is only the so-called motor terminal potential or the potential difference,
To that extent, the structure of the fail-safe becomes simple, the comparison judgment with the normal operation becomes simple, and the cost is reduced.

In the electric power steering apparatus according to a second aspect of the present invention, the rotor and the input shaft and the output shaft are coaxial with each other by, for example, making the rotor also serve as the input shaft or the output shaft. If placed on top,
By reducing the space required by such a power steering device in the space under the driver's seat or in the engine room, the degree of freedom in layout is improved.

When the relative twist amount between the input shaft and the output shaft, that is, the steering torque is zero or substantially zero, the control is performed as in the electric power steering apparatus according to claim 3 of the present invention. The device controls the current supplied to the motor to zero, or the electric power steering device according to claim 4 of the present invention is configured so that the guide mechanism guides the brush and does not contact the commutator. This prevents the generation of an inadvertent steering assist force during straight traveling or near straight traveling, and ensures traveling stability of the vehicle. Further, particularly in the electric power steering apparatus according to the fourth aspect, since this can be achieved mechanically, it is possible to reduce the amount of use of the power element such as the FET, and the cost is correspondingly reduced. It is possible to reduce the cost.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the electric power steering apparatus of the present invention will be described with reference to the drawings. First, the structure will be described. As shown in FIG. 1, the steering wheel 1 is connected to an upper end portion of a steering shaft 2, and the steering shaft 2 extends downward. The lower end of the steering shaft 2 is connected to the pinion shaft 3 via a twist amount conversion unit 12 described later. The lower end of the pinion shaft 3, that is, the pinion 3a
Engages with a rack 4 arranged horizontally in the vehicle width direction, and the rack 4 and the pinion shaft 3 constitute a steering gear. Therefore, the rotational movement of the steering wheel 1 around the steering shaft 2 is converted into the linear movement (translational movement) of the rack 4.

Both ends of the horizontally extending rack 4 are connected to the knuckle and the steered wheels 6 through tie rods 5, respectively, and the rack 4 moves horizontally (translational movement) to rotate left and right. The steering wheel 6 is adapted to steer. A ring gear 11 constituting a speed reducer is coaxially fixed to the upper part of the pinion shaft 3, and a pinion gear 10 attached to a drive shaft 9 of a steering assist motor 8 meshes with the ring gear 11. There is. The rotational driving force and the rotational direction of the steering assist motor 8 are obtained by using the storage battery (battery) 14 as a power source and the twist amount conversion unit 1
Adjustment is controlled according to the relative twist amount between the steering shaft 2 and the pinion shaft 3, that is, between the input shaft and the output shaft, and the direction thereof, which is transmitted from the second ring outer gear 21a to the brush moving mechanism 15 described later. Further, the twist amount conversion unit 12, the pinion shaft 3, the rack 4, the steering assist motor 8, the brush moving mechanism 15, and the pinion gear 1 are provided.
0 and the like are installed inside one casing 13.

The arrangement of the casing 13 is shown in FIG. As is clear from the figure, a torsion bar 16 is interposed between the steering shaft 2 and the pinion shaft 3 which are rotatably supported by the casing 13 via bearings 51 and 52, respectively. At the same time, the twist amount converter 12 is arranged around the torsion bar 16. The twist amount conversion unit 12 is composed of two planetary gear mechanisms, and the steering shaft 2 of the planetary gear mechanism will be described in detail later.
Side ring inner gear (to be exact, a ring-shaped internal gear (internal gear)) 20a formed outside the ring outer gear (to be exact, a ring-shaped external gear (external gear)) The brush moving gear 30 of the brush moving mechanism 15 is engaged with 21a. The brush moving gear 30 is rotatably supported on the drive shaft 9 of the steering assist motor 8 via a bearing 53. A pair of brush holders 31a and 31b made of an insulating material are provided at positions facing each other in the diametrical direction of the gear 30.
Are provided upright, and brushes 32a, 32b project inwardly from the facing surfaces of the brush holders 31a, 31b. The brushes 32a, 32b are elastically expandable and contractible to the electrodes of the battery 14 which is an external power source. It is connected via wirings 33a and 33b.

On the other hand, the drive shaft 9 of the steering assist motor 8
A rotor 17 is formed around the. The rotor 17 of this embodiment has a bearing 5 with respect to the casing 13.
Those which are divided into eight around the drive shaft 9 which is rotatably supported via 4, 55 and which face each other in the diametrical direction are coils 34a to 34h (in FIG. Four coils 34a-34d are shown),
Eight-divided commutators 35a to 35h (four commutators 35a to 35d among them are shown in FIG. 2) to which the winding ends of the coils facing each other in the diametrical direction are connected, Any two commutators 35a to 35d facing each other in the direction are provided in the pair of brushes 3
It is always in contact with either 2a or 32b. Further, permanent magnets (magnetic field applying means) 36N and 36S forming a pair are arranged inside the casing 13 so as to be opposed to each other on the outer circumference of the coils 34a to 34h in the diametrical direction of the rotor 17 and to the rotor 17. A constant magnetic field is applied. The actual brushes 32a and 32b of this embodiment are different from those shown in FIG. 2 in a state in which the torsion bar 16 is not twisted, that is, the steering torque is not applied to the steering wheel 1 and the steering shaft 2 and the pinion. Shaft 3
In the state where there is no relative twist between the permanent magnet 36 and
N and 36S are arranged to face each other in a direction orthogonal to the facing direction. The windings of the coils 34a to 34h are the same.

Next, the structure of the twist amount conversion unit 12 will be described with reference to FIG. This twist amount conversion unit 1
2, the two planetary gear mechanisms are arranged side by side in series between the steering shaft 2 and the pinion shaft 3. Of these, as is apparent from FIG. 3, the planetary gear mechanism on the steering shaft 2 side is A for each component and b for each component of the planetary gear mechanism on the pinion shaft 3 side.
Are attached as subscripts to the members constituting each planetary gear mechanism. Here, the steering shaft 2 is integrated with a carrier 22a on the side of the steering shaft, and the carrier 22a includes three planet gears 23.
Each planet gear 22a supports the ring inner gear 20a and the sun gear 24. On the other hand, similarly, the pinion shaft 3 is also integrated with the carrier 22b on the pinion shaft side.
Supports three planet gears 23b, and each planet gear 23b meshes with the ring (inner) gear 20b and the sun gear 24. The two sun gears 24 of the planetary gear mechanism are integrally connected to each other, and are rotatably fitted to the outer periphery of the pinion shaft 3 in this embodiment. Further, the ring (inner) gear 20 b on the pinion shaft 3 side is fixed to the casing 13.

Next, the structure inside the casing 13, that is, the twist amount conversion portion 12 including the torsion bar 16, the brush moving mechanism 15, the steering assist motor 8, the pinion gear 1
The operation of the 0 and the ring gear 11 will be described with reference to FIG. Although FIG. 4 is a schematic diagram of each configuration in the casing 13, for convenience of description, for example, the layout of the brush moving mechanism 15 and the steering assist motor 8 is reversed to cause the steering assist motor 8 to move to the pinion gear 10. Place on the side. Further, the outer diameter of the ring outer gear 21a of the planetary gear mechanism on the steering shaft side and the outer diameter of the brush moving gear 30 are drawn equally. Further, in the pinion gear 10 and the ring gear 11, which are originally reduction gears, the outer diameter of the pinion gear 10 must be smaller than the outer diameter of the ring gear 11, but both are drawn equally in FIG. In addition, the reference numerals of the coils and commutators that actually rotate as the rotor 17 are 8 as described above.
It shall be given to the coil and commutator existing at each divided position.

When no steering torque is applied to the steering wheel 1 as shown in FIG. 4A, the torsion bar 16 is not twisted, so that each member (gear) of the two planetary gear mechanisms is initialized. In this state, the brush holders 31a and 31b on the brush moving gear 30 are in the positions shown in the figure, and as a result, both brushes 32a and 32b are moved to the pair of permanent magnets 36.
The commutator existing in the direction orthogonal to the facing direction of N and 36S, specifically, the brush 32a connected to the high-potential side electrode (hereinafter, also simply referred to as the positive electrode) of the battery 14 comes into contact with the uppermost commutator 35a in the drawing, The brush 32b connected to the low potential side electrode (hereinafter, also simply referred to as a negative electrode) of the battery 14 comes into contact with the commutator 35e at the lowermost portion in the drawing,
As a result, a current flows through the uppermost coil 34a connected to the uppermost commutator 35a in the figure toward the other side of the drawing as shown in the figure, and the lowermost commutator 35 in the figure is shown.
It is assumed that a current flows through the lowermost coil 34e connected to e as shown in the drawing on the front side of the drawing. On the other hand, by the permanent magnets 36N and 36S facing each other outside the rotor 17, a uniform magnetic field is applied in the vicinity of the coils 34a to 34h of the rotor 17 in the arrow α direction from left to right in the figure. It has been done. Therefore, in accordance with the so-called Fleming's left-hand rule, an electromagnetic force Fa that passes through the axis of the drive shaft 9 and goes directly downward in the figure acts on the uppermost coil 34a or in the vicinity thereof, and the lowermost coil 34e or the lowermost coil 34e. In the vicinity, an electromagnetic force Fb that passes through the axis of the drive shaft 9 and goes directly upward in the figure acts, but an electromagnetic field generated by a uniform magnetic field and the same current (charge amount) in the coils 34a and 34e having the same number of turns. Since the magnitudes of the forces Fa and Fb are the same and the lines of action are the same but opposite to each other, the electromagnetic forces Fa and Fb cancel each other out, and the electromagnetic forces F toward the axis of the drive shaft 9 are also cancelled.
Since a and Fb originally have no component force in the rotation direction of the rotor 17, as a result, the rotational drive force is not transmitted to the drive shaft 9, the pinion gear 10 and the ring gear 11, and the steering assist force is also expressed. Not done.

From this state, when the steering wheel 1 is rotated to the right as shown in FIG. 4b, the torsion bar 16 is rotated in a state where the pinion shaft 3 cannot rotate or is difficult to rotate due to tire load or the like.
Is twisted, which is equivalent to the magnitude of the steering torque applied to the steering wheel 1, and the steering shaft 2 rotates to the right. On the other hand, since the sun gear 24 does not rotate or rotates with a delay, the planet gear 23a connected to the steering shaft 2 rotates by the amount of twist of the torsion bar 16 in the direction of the arrow in FIG. The ring inner gear 20a and the ring outer gear 21a revolve, and rotate in the right direction of the arrow. As a result, the ring outer gear 21
The brush moving gear 30 meshing with a rotates in the leftward direction of the arrow in the drawing, and the brush holders 31a and 31b on the brush moving gear 30 rotate in the opposite direction of the drawing around the axis of the drive shaft 9. It rotates about 45 degrees clockwise, and as a result, the brush 32a connected to the positive electrode of the battery 14
Is in contact with the commutator 35h in the upper left of the figure, and the brush 32b connected to the negative electrode of the battery 14 is in contact with the commutator 35d in the lower right of the figure. It is assumed that a current flows through the coil 34d on the lower right side of the drawing as shown in the drawing. Also here, assuming that the magnetic fields generated by the permanent magnets 36N and 36S are uniform in the direction of the arrow α, the coil 34h on the upper left side or in the vicinity thereof does not pass through the axis of the drive shaft 9 and goes directly below in the drawing. An electromagnetic force Fa acts, and an electromagnetic force Fb that does not pass through the axis of the drive shaft 9 and goes directly upward in the drawing acts on the coil 34d on the lower right side or in the vicinity thereof. Even at this time, the magnitudes of both electromagnetic forces Fa and Fb are equal, but these electromagnetic forces F
The action lines of a and Fb are different from each other and opposite to each other. Therefore, the component force of each electromagnetic force Fa and Fb in the rotation direction of the rotor 17 is used as a couple force and the counterclockwise rotation is performed around the axis of the drive shaft 9. A moment is generated, and this moment rotates the drive shaft 9 and the pinion gear 10 counterclockwise as an arrow as a rotational driving force, and at the same time, rotates the ring gear 11 and the pinion shaft 3 clockwise, so that a steering assist force is generated. When the planet gear 23b on the side of the pinion shaft 3 revolves while rotating rightward along with this, the sun gear 24 relatively rotates counterclockwise,
As a result, the planet gear 23a on the steering shaft 2 side revolves while rotating leftward, so that the ring inner gear 20a and the ring outer gear 21a also rotate leftward, and the torsion amount of the torsion bar 16 becomes zero. Each component of each planetary gear mechanism returns to the state of FIG. 4a.

When the steering wheel 1 is rotated to the left as shown in FIG. 4c from the neutral state to the left steering state, the torsion bar 16 is equivalent to the magnitude of the steering torque applied to the steering wheel 1. Twisting occurs and the steering shaft 2 rotates to the left. On the other hand, since the sun gear 24 does not rotate or rotates with a delay, the planet gear 23a connected to the steering shaft 2 rotates by the amount of twist of the torsion bar 16 in the direction of the arrow in FIG. Revolving, the ring inner gear 20a and the ring outer gear 21a rotate in the left direction of the arrow. As a result, the brush moving gear 30 meshing with the ring outer gear 21a rotates in the right direction of the arrow in the drawing, and the brush holders 31a, 31 on the brush moving gear 30 are rotated.
b rotates about 45 degrees clockwise in the figure around the axis of the drive shaft 9, and as a result, the brush 32a connected to the positive electrode of the battery 14 contacts the commutator 35b in the upper right of the figure, The brush 32b connected to the negative electrode of the battery 14 comes into contact with the commutator 35f at the lower left of the drawing, whereby a current flows through the coil 34b at the upper right of the drawing toward the other side of the drawing as shown in the drawing, and the coil at the lower left of the drawing. It is assumed that a current flows through 34f on the front side of the drawing as shown in the figure. Again, the permanent magnets 36N, 36S
Assuming that the magnetic field due to is uniform in the direction of the arrow α, an electromagnetic force Fa that does not pass through the axis of the drive shaft 9 and goes directly downward in the figure acts on the coil 34b on the upper right side or in the vicinity thereof, and The electromagnetic force F that does not pass through the axis of the drive shaft 9 and goes directly above in the drawing is applied to the one coil 34f or in the vicinity thereof.
b acts. Even at this time, the magnitudes of the two electromagnetic forces Fa and Fb are equal, but since the lines of action of the electromagnetic forces Fa and Fb are different from each other and opposite to each other, the electromagnetic forces Fa and Fb in the rotation direction of the rotor 17 are the same. A clockwise moment is generated around the axis of the drive shaft 9 by using the component force of Fb as a couple, and this moment rotates the drive shaft 9 and the pinion gear 10 rightward as an arrow as a rotational drive force, and at the same time, the ring gear 11 and The steering assist force is developed by rotating the pinion shaft 3 counterclockwise. When the planet gear 23b on the side of the pinion shaft 3 revolves while revolving to the left while revolving, the sun gear 24 rotates relatively to the right, whereby the planet gear 23a on the side of the steering shaft 2 rotates to the right. While revolving, the ring inner gear 20a
Also, the ring outer gear 21a also rotates to the right, and when the torsion amount of the torsion bar 16 becomes zero, each component of each planetary gear mechanism returns to the state shown in FIG. 4a.

Next, the relationship between the steering torque and the steering assist force in each of the steering states of this embodiment will be described with reference to FIG. 5 shows only the steering assist motor 8 and the battery 14 in FIG. 4,
5A shows the same state as FIG. 4B, and the details of its operation are the same as those described above, so a detailed description thereof will be omitted. Here, the electromagnetic forces Fa, F generated at this time are omitted.
Pay attention to each component of b. In FIG. 5a, the right steering torque is assumed to be medium. In this way, the electromagnetic force Fa acting on the coil 34h on the upper left side in the figure and the electromagnetic force Fb acting on the coil 34d on the lower right side in the figure are generated by the respective coils 34h.
h, 34d and the diametrical direction passing through the axis of the drive shaft 9 and about 45
When the degree is made, the diametrical force components Fa _D , Fb _D and the circumferential force components Fa _C , Fb _C are divided into equal or almost equal parts. Of these, the diametrical force components Fa _D , Fb _D are Since the lines of action are the same but opposite to each other, they are offset, and the remaining circumferential component components Fa _C and Fb _C are used as couples, and a clockwise moment acts around the drive shaft 9 as described above. Since it becomes the driving force, the rotational driving force that is the steering assist force at this time is the circumferential component force F of the electromagnetic forces Fa and Fb.
It can be seen that it is proportional to a _C and Fb _C.

By the way, even in the same right steering state, when the steering torque applied to the steering wheel 1 increases, the amount of twist generated in the torsion bar 16 also increases, and in the present embodiment, it is connected to the steering shaft 2. The planet gear 23a thus rotated revolves while rotating large and fast, and the ring inner gear 20a and the ring outer gear 21a thereof also rotate large and fast.
Therefore, the brush moving gear 30 meshing with the ring outer gear 21a also rotates largely and quickly, and as a result, the brush 32a connected to the positive electrode of the battery 14 is at the leftmost position in the figure as shown in FIG. 5b. Commutator 35
brush 3 that contacts g and is connected to the negative electrode of the battery 14.
2b comes into contact with the commutator 35c on the rightmost side in the drawing, whereby a current flows through the coil 34g on the leftmost side in the drawing on the other side of the drawing as shown in the drawing, and the coil 3 on the rightmost side in the drawing
It is assumed that an electric current flows through 4c on the front side of the drawing as shown in the figure. Also here, assuming that the magnetic fields generated by the permanent magnets 36N and 36S are uniform in the direction of the arrow α, the leftmost coil 34g or its vicinity does not pass through the axis of the drive shaft 9 and is located directly below in the drawing. An electromagnetic force Fa that acts is applied, and an electromagnetic force Fb that does not pass through the axis of the drive shaft 9 and that is directed directly above in the figure acts on the rightmost coil 34c or in the vicinity thereof. At this time, since the diametrical force components Fa _D and Fb _D as described above are not split from the two electromagnetic forces Fa and Fb, the electromagnetic force components Fa and Fb themselves are circumferential force components Fa _C and Fb _C.
Becomes Circumferential component force Fa _C at this time, Fb _C is circumferential component force Fa _C when the electromagnetic force Fb shown in FIG. 5a forms an approximately diameter direction about 45 degrees, obviously compared to Fb _C Therefore, the clockwise moment acting around the drive shaft 9 as described above, that is, the rotational driving force serving as the steering assisting force, using the circumferential component forces Fa _C and Fb _C as couples, is the electromagnetic force Fa. , Fb increase in proportion to the circumferential component components Fa _C and Fb _C.

Here, the steering torque is zero, the right steering torque is medium, and the right steering torque is larger, respectively, but the brushes for the permanent magnets 36N and 36S are described in a fragmentary manner. Considering that the relative movement of 32a and 32b continuously occurs according to the magnitude and direction of the steering torque, the rotational driving force from the steering assist motor 8, that is, the steering assist force, is increased as the steering torque increases. It can be seen that it increases continuously in a cosine curve, and the direction of its occurrence is forcibly matched with the direction of the steering torque. Therefore, switching of contacts by a mechanical switch or electrical relay or a motor by a power element such as FET No current control is required, and the structure can be simplified and the cost can be reduced accordingly. In addition, the maximum movement amount of the brushes 32a and 32b, specifically, the maximum rotation angle around the shaft center of the drive shaft 9, is assumed to be the maximum steering torque of the driver, the lateral elastic coefficient of the torsion bar 16, and the cross section. The secondary polar moment, the reduction ratio of the planetary gear mechanism in the twist amount conversion unit 12, the gear ratio between the ring outer gear 21a and the brush moving gear 30, and the ratio of the rotational driving force of the motor to the desired steering assist force. The corresponding reduction ratio between the pinion gear 10 and the ring gear 11,
Since the number of poles of the magnet and the number of brushes can be appropriately set according to the set rotational driving force of the motor, for example, the maximum rotation angle of either brush in the left and right directions is 180 °.
If it is made smaller, by using the elastic wiring as described above for the wiring between the brush and the casing, the displacement of each brush can be allowed, and the special rotation allowance of the slip ring or the like can be allowed. There is no need to use contacts. Therefore, the number of contacts of the electric power steering apparatus of the present embodiment is equal to the number of contacts between the brush and commutator of a normal motor, and it is possible to prevent the occurrence of failures such as seizure and contact failure by the corresponding amount. it can.

Next, a second embodiment of the electric power steering apparatus of the present invention will be described with reference to FIGS. Among the constituent members of the electric power steering apparatus of the present embodiment, those which are the same as or substantially the same as those of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.
More specifically, as shown in FIG. 6, the above-described speed reducer is removed and the drive shaft 9 of the steering assist motor 8 is directly connected to the pinion shaft 3 or serves both as the steering shaft and the steering assist motor 8 described later. The brush moving mechanism for moving the brush and the twist amount converting unit for converting the relative twist amount between the input and output shafts are assigned to the relative twist amount converting unit and the brush moving mechanism 115, and the relative twist amount converting unit and the brush moving mechanism are combined. 11
5 is arranged in series with the input side of the steering assist motor 8, more specifically, coaxially. Then, as in the case of the first embodiment, the relative twist amount conversion unit / brush movement mechanism 11 is used.
5, steering assist motor 8, pinion shaft 3, rack 4
Etc. are housed in a single casing. However, since the shape of this casing is obviously different from that of the first embodiment, the reference numeral “11” is different for the casing of this embodiment.
Add 3 ".

FIG. 7 shows the arrangement of the casing 113.
Shown in. As described above, the pinion shaft 3 which also serves as the drive shaft 9 of the steering assist motor 8 is provided with the bearing 52, and the steering shaft 2 is provided with the bearing 51 as in the first embodiment with respect to the casing 113. It is rotatably supported, and both are connected via a torsion bar 16. The twist amount conversion unit / brush moving mechanism 115 is arranged around the torsion bar 16. Of these, the structure corresponding to the twist amount conversion unit is composed of a double planetary gear mechanism as in the first embodiment. Specifically, specifically, the ring inner gear 20a on the steering shaft 2 side and the pinion shaft. The structure of the ring inner gear 20b on the third side is the same as the first
It differs from that of the embodiment. That is, the ring inner gear 20a on the steering shaft 2 side is not formed with the ring outer gear as in the first embodiment, but the ring inner gear 20a is fixed to the casing 113. On the other hand, the ring inner gear 20b on the pinion shaft 3 side has a blank (material) formed in a cylindrical shape, and a gear as a ring inner gear is formed on the inner surface of the end portion on the steering shaft 2 side. A pair of brush holders 31a, 31b made of an insulating material is provided to project inward at the diametrically opposed positions of the side ends, and the brushes 32a, 31b are inwardly projected from the facing surfaces of the brush holders 31a, 31b. 32b is provided in a protruding manner, and the brushes 32a and 32b are connected to the respective electrodes of the battery 14 which is an external power source via elastic elastic wires 33a and 33b. The other structure is the same as or substantially the same as that of the first embodiment, and the details of its operation will be described later.

Further, the drive shaft 9 of the steering assist motor 8
There is a rotor 17 around the pinion shaft 3, which is also used as
Are formed. The rotor 17 of this embodiment is the first
Similar to the embodiment, those which are divided into eight around the pinion shaft 3 and face each other in the diametrical direction are coils 34a to 34h (in FIG. 7, four coils 34a to 34d among them are constituted by a single winding). 8) and eight-divided commutators 35a to 35h (in FIG. 7, four commutators 35a to 35d among them are shown) to which the winding ends of the coils facing each other in the diametrical direction are connected. ) And any two commutators 35a to 35d facing each other in the diametrical direction are provided in the pair of brushes 32a, 32a.
Always in contact with any of b. In addition, as in the first embodiment, the rotor 17 is attached to the outer circumference of the coils 34a to 34h.
A pair of permanent magnets (magnetic field applying means) 36N and 36S which are opposed to each other in the diametrical direction and are located inside the casing 13 are provided to apply a constant magnetic field to the rotor 17. The actual brushes 32a and 32b of this embodiment are
7 is different from the one shown in FIG. 7, a state in which the torsion bar 16 is not twisted, that is, the steering wheel 1
In the state where there is no relative twist between the steering shaft 2 and the pinion shaft 3 regardless of the steering torque, the permanent magnets 36N and 36S are arranged to face each other in a direction orthogonal to the facing direction. In addition, each of the coils 34 a to 34
The winding of h is the same.

Next, the structure of the casing 113, that is, the operation of the twisting amount converting portion / brush moving mechanism 115 including the torsion bar 16 and the steering assist motor 8 is basically the same as that of the first embodiment. Although the operation is almost the same, the operation of the twisting amount converting portion / brush moving mechanism 115 is slightly different. Therefore, the operation of that portion will be described in detail, and the operation of the other portions will be briefly described.

First, when the steering torque is not applied to the steering wheel 1, since the torsion bar 16 is not twisted, each member (gear) of the two planetary gear mechanisms is in the initial setting state. In this state, the two brushes 32a and 32b have the pair of permanent magnets 36N,
A commutator 3 existing in the direction orthogonal to the facing direction of 36S
The coils 34a to 34h, which are in contact with any two of the motors 5a to 35h and are connected between the commutators 35a to 35h, pass through the axis of the pinion shaft 3 which is the motor drive shaft 9 and are mutually connected. Reverse electromagnetic force F
a and Fb (see FIG. 4a) act on each other, but these electromagnetic forces Fa and Fb cancel each other out, and the electromagnetic forces Fa and Fb toward the axial center of the drive shaft 9 (pinion shaft 3) are essentially Since there is no component force in the rotating direction of the rotor 17, as a result, the rotational drive force is not transmitted to the drive shaft 9, the pinion gear 10 and the ring gear 11, and the steering assist force is not expressed.

From this state, when the steering wheel 1 is turned to the right steering state, the pinion shaft 3 cannot rotate or is difficult to rotate due to tire load or the like. Twisting equivalent to the magnitude of the applied steering torque occurs, and the steering shaft 2 rotates to the right. On the other hand, since the ring inner gear 20a fixed to the casing 113 does not rotate, the planet gear 23a connected to the steering shaft 2 via the carrier 22a rotates by the amount of twist of the torsion bar 16 while rotating. An attempt is made to revolve to the right, and the sun gear 24 is rotated to the right due to the frictional force between the planet gear 23a and the sun gear 24. On the other hand, the carrier 22 fixed to the pinion shaft 3
Since b cannot rotate or is difficult to rotate, the planet gear 23b does not revolve, but rotates leftward on the spot, and the ring inner gear 20b accordingly rotates leftward. As a result, the brush holders 31a, 31b fixed to the ring inner gear 20b and the brushes 32a, 32b at the tips thereof rotate counterclockwise about the axis of the pinion shaft 3 (driving shaft 9), As a result, the two brushes 32a and 32b are located in the counterclockwise direction from the neutral state, and the commutator 35a is present in the position.
Coils 35a to 3h which are respectively in contact with any two of the commutators 35a to 35h.
Electromagnetic forces Fa and Fb (see FIG. 4b, but the directions of currents are opposite) that do not pass through the axis of the pinion shaft 3 that is the motor drive shaft 9 and act in the opposite direction act on 4h. Even at this time, the magnitudes of the two electromagnetic forces Fa and Fb are equal, but since the lines of action of the electromagnetic forces Fa and Fb are different from each other and opposite to each other, the electromagnetic forces Fa and Fb in the rotation direction of the rotor 17 are the same. A clockwise moment is generated around the axis of the motor drive shaft 9 by using the component force of Fb as a couple, and this moment rotates the pinion shaft 3 which is also the motor drive shaft 9 as a rotational drive force to assist steering. Power is expressed. When the amount of twist of the torsion bar 16 becomes zero accordingly, each component of each planetary gear mechanism returns to the neutral state.

When the steering wheel 1 is rotated to the left from the neutral state to the left steering state, the torsion bar 16 is twisted in the same amount as the steering torque applied to the steering wheel 1 and the steering shaft is rotated. 2 rotates to the left. On the other hand, the ring inner gear 2 fixed to the casing 113
0a does not rotate, so the planet gear 23a tries to revolve to the left while rotating on its own axis.
Is relatively rotated to the right. The planet gear 23b does not revolve, but rotates leftward on the spot, and the ring inner gear 20b accordingly rotates leftward. Thereby, the brush holders 31a, 31b
And the brushes 32a and 32b are the pinion shaft 3
Rotate counterclockwise around the axis of (drive shaft 9),
The two brushes 32a and 32b are located at positions counterclockwise from the neutral state, and are commutators 35a to 35b.
The coils 34a to 34h which are respectively in contact with any two of the h and are connected between the commutators 35a to 35h do not pass through the axial center of the pinion shaft 3 which is the motor drive shaft 9 and have opposite electromagnetic fields. Forces Fa and Fb (see FIG. 4c) act. Since these electromagnetic forces Fa and Fb have different lines of action and are in opposite directions, the component force of each electromagnetic force Fa and Fb in the rotation direction of the rotor 17 is used as a couple force to rotate the motor drive shaft 9 around its axis. A counterclockwise moment is generated on the shaft, and this moment rotates the pinion shaft 3, which is also the motor drive shaft 9, counterclockwise as a rotational drive force, and a steering assist force is generated. Incidentally, when the planet gear 23b tries to revolve to the left while rotating on the basis of this, the ring inner gear 20b rotates relatively to the right, and the sun gear 24 rotates to the left with this, whereby the steering shaft is rotated. The planet gear 23a on the second side revolves to the right while rotating, and when the torsion amount of the torsion bar 16 becomes zero, each component of each planetary gear mechanism returns to the neutral state.

Here, similarly to the first embodiment, it is found that the rotational driving force from the steering assist motor 8, that is, the steering assist force, continuously increases in a cosine curve as the steering torque increases. Since the direction of generation is forcibly matched with the direction of the steering torque, the same effect as in the first embodiment can be obtained. Further, in the present embodiment, since the brush moving mechanism which also serves as the twisting amount converting portion and the steering assist motor are coaxially arranged, such a power steering device is originally required in the foot space of the driver's seat or in the engine room. Since the space to be used can be reduced, the degree of freedom in layout is improved.

When the rotational driving force of the steering assisting motor is used as the steering assisting force as in this embodiment, in consideration of the expected steering torque and the rotational driving force of the motor. It is necessary to set the specifications of the motor, specifically, the number of coils themselves, the number of turns of the coil, the magnetic field strength, etc., but if necessary, for example, make the inside of the pinion shaft hollow, and inside the hollow portion of the pinion shaft. It is also possible to interpose a speed reducer composed of, for example, a planetary gear mechanism between the motor drive shaft inserted into the motor drive shaft so that the necessary steering assist force can be obtained by the torque amplifying action of the speed reducer.

Next, a third embodiment of the electric power steering apparatus of the present invention will be described with reference to FIGS. Since the basic configuration of the electric power steering apparatus of the present embodiment is the same as or substantially the same as that of the first embodiment, the first embodiment among the components of the electric power steering apparatus of the present embodiment is the same. The same or substantially equivalent parts as those in the example are designated by the same reference numerals, detailed description thereof will be omitted, and only different parts will be described here.

In the electric power steering apparatus of this embodiment, the ring outer gear 21 of the twist amount conversion section 12 is used.
a is a rotational displacement sensor 20 including a potentiometer and the like.
0 pinion gear 201 mounted on the rotary shaft 200a
Are in mesh. The rotational displacement sensor 200 is provided with the rotation angle of the ring outer gear 21a, that is, the torsion bar 1
The rotational displacement θ corresponding to the twist angle of 6 is output. In addition,
The rotational displacement θ detected by this rotational displacement sensor 200 is
The relative twisting direction between the steering shaft 2 and the pinion shaft 3, that is, the twisting direction of the torsion bar 16 is a positive value when the steering wheel 1 is in the right direction, which is generated when steering the steering wheel 1 to the right, and a negative value when it is in the reverse direction. It shall be a value.

A switching element 203, which is a power element such as the FET, is interposed between the battery 14 and the steering assist motor 8. The switching element 203 is a control unit 202 described later.
ON / OFF is controlled by the drive signal D _AST from
Current flows through the steering assist motor 8 when the switching element 203 is in the ON state.

[0041] The control unit 20 2 is provided with a microcomputer 204 as best shown in FIG. 9 and the drive circuit 205. Here, the microcomputer 204 includes an arithmetic processing unit (CPU) 2 including an input side interface circuit 204a having at least an A / D conversion function and the like, a microprocessor unit MPU and the like.
04b, a storage device 204c including a RAM, a ROM and the like, and an output side interface circuit 2 having a D / A conversion function.
With 04d. Then, the rotational displacement θ from the rotational displacement sensor 200 is input to the input side interface circuit 204a, and the output side interface circuit 204d.
Outputs a control signal S _AST for ON / OFF controlling the switching element 203.

Further, the arithmetic processing unit 204b executes the arithmetic processing of FIG. 10 described later at every predetermined sampling time ΔT (for example, 5 msec.), And the rotational displacement sensor 20.
The rotational displacement θ from 0 is read and the absolute value of this rotational displacement |
When θ | is equal to or greater than a predetermined threshold value θ ₀ , the switching element 203 is configured so that a current flows through the steering assist motor 8.
Is turned on, and if not, a control signal S _AST that _turns off the switching element 203 is output.

Further, the storage device 204c stores in advance maps, arithmetic expressions, programs, etc. necessary for the arithmetic processing of the arithmetic processing device 204b, and the arithmetic processing device 2
The calculation results required in the calculation process of 04b are sequentially stored. In the drive circuit 205, the control signal S _AST output from the microcomputer 204 has a logical value "1".
When the control signal _SAST has a logical value "0", the drive signal _{DAST for turning on the} switching element 203 is output.
The drive signal D _AST for turning off the switch is output.

Next, the arithmetic processing executed by the arithmetic processing unit 204b of the microcomputer 204 will be described with reference to the flowchart of FIG. This arithmetic processing is processed as a timer interrupt executed at each predetermined sampling time ΔT, and first, in step S1, the rotational displacement θ detected by the rotational displacement sensor 200 is read. Next, in step S2, it is determined whether or not the absolute value of the rotational displacement | θ | read in step S1 is equal to or larger than a threshold value θ ₀ set to a relatively small positive value in advance, and the rotation is determined. If the absolute value of displacement | θ | is greater than or equal to this threshold θ ₀ , the process proceeds to step S3, and if not, step S4.
Move to.

In step S3, the control signal _SAST is set to the logical value "1", and then the process proceeds to step S5.
On the other hand, in step S4, the control signal _SAST is set to the logical value "0", and then the process proceeds to step S5. In the step S5, the step S3 or the step S
After outputting the control signal S _AST set in step 4, the process returns to the main program.

Next, the operation of the electric power steering apparatus of this embodiment will be described. In the electric power steering apparatus of the present embodiment, the mechanical and electromagnetic actions up to the generation of the steering assist force when the steering torque is larger than a certain level are exactly the same as those of the first embodiment, and at least the above The same effect as that of the first embodiment can be obtained, but the following points are further different. That is, according to the arithmetic processing of FIG. 10, the absolute value | θ | of the rotational displacement of the ring outer gear 21a on the steering shaft 2 side is equal to the predetermined threshold value θ.
When it is smaller than ₀ , that is, when the torsion angle of the torsion bar 16 is small, and therefore the steering torque itself is small, step S3 to step S4 and step S5 are performed.
Then, the control signal S _AST having the logical value “0” is output, so that the drive signal D output from the drive circuit 205 is output.
_The switching element 203 is turned off by _AST , and any of the coils 34 from the brushes 32a and 32b is removed.
No current flows in a to 34h. In such a state where the steering torque is small, the steering assist force is not originally required, and in the first embodiment, the steering assist force is not developed as described with reference to FIG. 4A. In this state, no current flows through the coils 34a to 34h, so that electric energy can be saved accordingly.

In the electric power steering apparatus having the above-described power element, the motor current itself can be controlled in addition to the above-mentioned mechanical steering assist force setting. In that case, for example, P for the drive circuit
A WM (Pulse Width Modulation) function may be added to control the duty ratio of the power element.
For example, while suppressing the feeling of wobbling when traveling at high speed,
In order to improve the response of the steering assist force during constant speed running,
In addition to the calculation process of FIG. 10, the vehicle speed is detected, and the control gain is reduced in a quadratic curve as the vehicle speed increases,
The steering assist force that is output as a result may be reduced as the vehicle speed increases under a constant steering torque.
Of course, it is possible to control the magnitude of the steering assist force according to other control inputs.

Further, in this embodiment, only the case where the control unit is constructed by the microcomputer is described in detail, but the control unit may be constructed by using an equivalent arithmetic circuit or theoretical circuit. Next, a fourth embodiment of the electric power steering apparatus of the present invention will be described with reference to FIGS. Since the basic configuration of the electric power steering apparatus of the present embodiment is the same as or substantially the same as that of the first embodiment, the first embodiment among the components of the electric power steering apparatus of the present embodiment is the same. The same or substantially equivalent parts as those in the example are designated by the same reference numerals, detailed description thereof will be omitted, and only different parts will be described here.

In the electric power steering system of this embodiment, as shown in FIGS. 11 and 12, the commutator 3 is used.
A brush guide plate 301 is added to the inside of the casing 13 around 5a to 35h. The brush guide plate 301 has an elliptical guide groove 301a.
However, it is formed by aligning the minor axis with the arrangement direction of the permanent magnets 36N and 36S and the major axis with the orthogonal direction.

On the other hand, the brushes 32a and 32b are as shown in FIG.
2, the brushes 31a and 31b are attached to the brush holders 31a and 31b so that they can move toward and away from each other.
Are pressed by the brushes 32a, 32b toward the inside of the guide groove 301a of the brush guide plate 301.
02 is projected. Therefore, each brush 32a, 32
b will slide along the inner elliptical arc surface of the guide groove 301a at least when it does not contact the commutators 35a to 35h.

Next, the operation of the electric power steering apparatus of this embodiment will be described. In the electric power steering apparatus of the present embodiment, the mechanical and electromagnetic actions up to the generation of the steering assist force when the steering torque is larger than a certain level are exactly the same as those of the first embodiment, and at least the above The same effect as that of the first embodiment can be obtained, but the following points are further different. That is, according to the electric power steering apparatus of the present embodiment, when the torsion angle of the torsion bar 16 is small and therefore the steering torque itself is zero or almost zero, which is small to some extent (the state of FIG. 4a in the first embodiment). 12b), as shown in FIG. 12b, both brushes 32a, 32b facing in the direction orthogonal to the facing direction of the permanent magnets 36N, 36S, that is, in the major axis direction of the elliptical guide groove 301a are The springs 303 make contact with the inner elliptical arc surface of the guide groove 301a, respectively, and at this time, the brushes 32a and 32b do not contact any of the commutators 35a to 35h, so that no current flows through any of the coils 34a to 34h.

On the other hand, for example, when the steering torque is increased to some extent in the right steering state (corresponding to the state of FIG. 4b or 5a in the first embodiment), as shown in FIG. The guide groove 30
Both of the brushes 32a and 32b, which are moved while slidingly contacting the inner elliptic arc surface of 1a, are moved to the minor axis side of the guide groove 301a. 35h, respectively, and apart from the inner elliptic arc surface of the guide groove 301a, the current flows from the commutators 35a to 35h at the positions where the brushes 32a and 32b come into contact with the coils 34a to 34h. Similarly to the first embodiment, the rotational driving force of the steering assist motor 8 is expressed as the steering assist force.

Further, for example, when the steering torque is further increased in the right steering state (corresponding to the state of FIG. 5b in the first embodiment), the guide groove 301 is set as described above.
Both brushes 32a, 32b spaced from the inner elliptical arc surface of a
14 is moved by sliding contact with the outer peripheral surface formed by the commutators 35a to 35h by the spring 303, as shown in FIG. 14, until it coincides with the minor axis direction of the guide groove 301a, that is, the facing direction of the permanent magnets 36N, 36S. Within the range of, the two commutators 35a to 35h facing each other in the diametrical direction are respectively contacted, and the commutator 3 concerned
Current flows from the coils 5a to 35h to the coils 34a to 34h, and the rotational driving force of the steering assist motor 8 is expressed as a larger steering assist force as in the first embodiment.

In this way, when the steering torque is small,
Originally, no steering assist force is required, and in the first embodiment,
Although the steering assist force is not developed as described with reference to FIG. 4a, in the present embodiment, as in the third embodiment, since no current flows through the coils 34a to 34h in such a state, the electric power is reduced accordingly. Energy can be saved. Incidentally, in each of the above-mentioned embodiments, it is possible to suppress the failure such as seizure or contact failure at each contact to the minimum as described above, but when further constructing the fail-safe as described above, for example, In the case where a fail-safe relay is provided between the battery and the steering assist motor to detect the terminal potential of the steering assist motor or the potential difference between the terminals, and the terminal potential or the potential difference between the terminals assumed in each steering state does not match. In this case, the fail safe relay may be cut off.

Further, in each of the above-mentioned embodiments, only the case where the permanent magnet is used as the magnetic field applying means has been described in detail, but it is of course possible to use an electromagnet or the like for the magnetic field applying means.

[0056]

As described above, according to the electric power steering device of the present invention, the number of contacts in the device can be reduced to the minimum number of contacts of a normal motor.
It is possible to minimize the possibility of failure due to operation abnormality such as seizure or poor contact in the mechanical contact.
Further, by arranging the rotor of the steering assist motor and the steering input shaft and the steering output shaft on the same axis, the space under the driver's seat and the space required in the engine room can be reduced to improve the layout. The degree of freedom is improved. Further, when the relative twist amount between the input shaft and the output shaft, that is, the steering torque is zero or substantially zero, the electric current is prevented from flowing to the motor, so that carelessness during straight traveling or near straight traveling is inadvertent. It is possible to prevent the generation of a large steering assist force, ensure the traveling stability of the vehicle, and reduce the electrical energy loss.

[Brief description of drawings]

FIG. 1 is a first part of an electric power steering device according to the present invention.
It is a whole lineblock diagram showing an example.

FIG. 2 is a detailed view of a main part of the electric power steering device of FIG.

3 is an overall configuration diagram of a twist amount conversion unit in FIG.

FIG. 4 is an operation explanatory view of a main part of the electric power steering device of FIG.

5 is an operation explanatory view of a steering assist motor of the electric power steering apparatus of FIG.

FIG. 6 is a second electric power steering device according to the present invention.
It is a whole lineblock diagram showing an example.

7 is a detailed view of a main part of the electric power steering apparatus of FIG.

FIG. 8 is a third electric power steering device according to the present invention.
It is a whole lineblock diagram showing an example.

9 is a detailed view of a main part of the electric power steering apparatus of FIG.

10 is a flowchart showing a calculation process executed by the microcomputer of FIG.

FIG. 11 shows an electric power steering device according to the present invention.
It is a detailed view of the principal part showing 4 examples.

12 is a detailed view of the steering assist motor and brush moving mechanism of FIG.

FIG. 13 is an operation explanatory view of the brush moving mechanism of FIG.

FIG. 14 is an operation explanatory view of the brush moving mechanism of FIG.

FIG. 15 is an electrical configuration diagram of a conventional electric power steering device.

[Explanation of symbols]

1 is the steering wheel 2 is the steering shaft 3 is a pinion shaft 4 is a rack 6 is a steered wheel 8 is a steering assist motor 9 is a drive shaft 10 is a pinion gear 11 is a ring gear 12 is a twist amount conversion unit 14 is a battery (power supply) 15 is a brush moving mechanism 17 is a rotor 20a and 20b are ring inner gears 21a is a ring outer gear 22a and 22b are carriers 23a and 23b are planet gears 24 is sun gear 30 is a gear for brush movement 31a and 31b are brush holders 32a and 32b are brushes 33a and 33b are elastic wiring 34a to 34h are coils 35a to 35h are commutators 36N and 36S are permanent magnets (magnetic field applying means) Denoted at 115 is a twist amount conversion unit and a brush moving mechanism. 200 is a rotational displacement sensor 202 is a control unit 203 is a switching element 204 is a microcomputer 205 is a drive circuit 301 is a brush guide plate 302 is a guide bar 303 is a spring

Continuation of the front page (56) Reference JP-A-6-344928 (JP, A) JP-A-61-9373 (JP, A) JP-A-6-293265 (JP, A) JP-A-61-181933 (JP , A) JP 619371 (JP, A) Actual development 62-114876 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B62D 5/00-5/32 B62D 6/00-6/06

Claims (4)

(57) [Claims] 1. A torsion bar is provided between an input shaft connected to a steering wheel and an output shaft connected to steered wheels, and a relative twist amount between the input shaft and the output shaft generated in the torsion bar is calculated. Accordingly, the motor connected to the output shaft is driven to generate the rotational driving force as a steering assisting force, and the motor has at least a plurality of coils in a predetermined winding direction divided in the rotation direction and each coil. A rotor provided with a commutator that is connected and switches energization to each coil, magnetic field applying means for applying a magnetic field in a constant direction around the coil of the rotor, and a predetermined position in contact with the commutator of the rotor. In an electric power steering device including a brush for energizing a coil, according to an increase in the relative twist amount between the input shaft and the output shaft,
Brush movement that moves the brush relative to at least the magnetic field applying means in a direction in which the rotational driving force of the rotor generated between the current of the coil supplied from the commutator and the magnetic field of the magnetic field applying means increases. An electric power steering device having a mechanism. 2. The electric power steering apparatus according to claim 1, wherein the rotor and the input shaft and the output shaft are coaxially arranged. 3. A control device is added to control the energization current to the motor to zero when the relative twist amount between the input shaft and the output shaft is zero or substantially zero. Alternatively, the electric power steering device according to item 2. 4. A guide mechanism is added for guiding the brush so that the brush does not come into contact with the commutator when the relative twist amount between the input shaft and the output shaft is zero or substantially zero. The electric power steering device according to claim 1.