JP2005247214A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device enabling high output at an inexpensive cost by arranging two electric motors for steering assist at different areas, easily controlling drive of the electric motors according to a traveling state, and improving steering performance. <P>SOLUTION: The electric power steering device steering assisting the rotation force of the motor for steering assist, comprises the two electric motors having different performance and arrange in the different areas in a steering system extending from a steering wheel to a turning wheel, and a controlling means for individually controlling the action of the two electric motors. The controlling means compensates the motor characteristics variation due to a load state of at least one of the two electric motors. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an improvement in an electric power steering device used for an automobile or an industrial vehicle.

  In general, the electric power steering device includes a column type that applies a steering assist force to the steering column by an electric motor, a pinion type that adds a steering assist force to the pinion shaft, and a rack shaft that is coaxial. There are a rack type that applies a steering assist force to the rack shaft by an electric motor arranged and a ball screw type that applies a steering assist force to the ball screw portion of the rack shaft.

  Such an electric power steering device has been widely used in automobiles in recent years because of the advantage that fine control according to traveling conditions is possible as compared with a hydraulic type.

  However, the electric power steering device has been difficult to apply to medium-sized and large-sized automobiles due to the disadvantage that the output is smaller than that of the hydraulic type. If the capacity of the electric motor is increased, high output can be obtained, but increasing the size of the electric motor is limited in terms of installation space, and it is not a good idea in terms of work and cost in the assembly process. There wasn't.

  Therefore, as a technology for increasing the output of the electric motor in the electric power steering device, two small electric motors are disclosed in Patent Document 1, Patent Document 2, and Patent Document 3, for example.

  In Patent Document 1, two motors for assisting steering are attached to a steering column, and the two motor rotational forces are loaded on a steering shaft and transmitted to a steering mechanism. A power steering device is disclosed.

  Patent Document 2 discloses a rack and pinion type in which two electric motors are attached to a rack and pinion section in addition to the column assist type electric power steering device.

  Furthermore, in Patent Document 3, the rotational force of a plurality of electric motors is transmitted to a steering mechanism through speed reducers having different reduction ratios, and the same steering assist force can be obtained by using a smaller rated electric motor. In addition, a larger steering assist force is applied to the steering mechanism using an electric motor having the same rating. In addition, the clutch connected to the speed reducer with a large reduction ratio is connected and disconnected according to the vehicle speed, thereby preventing the steering feeling from being lowered due to the moment of inertia of the electric motor during high speed running. .

JP-A-6-344927 Japanese Patent Laid-Open No. 7-172326 JP-A-8-258728

  However, in the electric power steering devices of Patent Document 1, Patent Document 2, and Patent Document 3, the two electric motors are all attached to the same part. When the electric motors are combined in the same part, both electric motors must be driven in appropriate synchronization. If the synchronization is inappropriate, the steering feeling will be uncomfortable and optimal steering will occur. It was difficult to assist.

  Moreover, in order to synchronize both electric motors, the respective rotation speeds and torques must be matched, and it is necessary to take countermeasures with sensors, control circuits, control software, etc., including individual differences of electric motors, The cost will increase.

  Furthermore, since two electric motors are attached to the same part, it is necessary to provide installation space in a concentrated manner, and as a result, the degree of freedom of mounting on a vehicle is limited.

  Therefore, an object of the present invention is to arrange two electric motors for assisting steering in different parts, thereby enabling high output at low cost and driving the electric motor according to the traveling state. An object of the present invention is to provide an electric power steering apparatus that can be easily controlled and has improved steering performance.

  The above object of the present invention is an electric power steering apparatus in which the rotational force of a steering assist motor is assisted by steering via a speed reduction mechanism, and has different performance and steering from a steering wheel of a vehicle to a steered wheel. Two electric motors arranged in different parts of the system, and a control means for individually controlling the operations of the two electric motors, at least one of the two electric motors being This is achieved by compensating for the motor characteristic fluctuation caused by the load state by the control means.

  Further, the above object is effectively achieved by the motor characteristic fluctuation being torque fluctuation of the electric motor.

  Further, the object is effectively achieved by the motor characteristic fluctuation being vibration generated in the steering system due to vehicle characteristics.

  Further, the above object is that one of the electric motors is a steering assist electric motor disposed in a steering column, and the other electric motor is a steering assist electric motor disposed in a steering pinion portion. It is achieved effectively by being.

  Further, the above object is that one of the electric motors is a steering assisting electric motor disposed in a steering column, and the other electric motor is a steering assisting electric motor disposed in a rack portion. This is achieved effectively.

  Further, the above object is that one of the electric motors is a steering assisting electric motor disposed in a steering column, and the other electric motor is a steering assisting electric motor disposed in a ball screw portion. It is achieved effectively by being.

  Further, the above object is that one of the electric motors is a steering assist electric motor disposed in a steering pinion portion, and the other electric motor is a steering assist electric motor disposed in a rack portion. It is achieved effectively by being.

  Further, the above object is that one of the electric motors is a steering assist electric motor disposed in a steering pinion portion, and the other electric motor is a steering assist electric motor disposed in a ball screw portion. This is effectively achieved.

  Further, the above object is that one of the electric motors is a steering assist electric motor disposed in a rack portion, and the other electric motor is a steering assist electric motor disposed in a ball screw portion. It is achieved effectively by being.

  Further, the object is that one of the electric motors is a gear ratio changing electric motor for changing a gear ratio of a steering gear ratio variable mechanism arranged in the steering system. Effectively achieved.

  Further, the above-described object is that the gear ratio changing electric motor is controlled by the control means based on an input value of a vehicle speed, a steering angle, a gear ratio, and an allowable maximum current value generated in the electric power steering. This is effectively achieved by controlling the gear ratio.

  According to the electric power steering apparatus according to the present invention, two electric motors having different performances and disposed in different parts of the steering system from the steering wheel to the steered wheels, and the two electric motors Control means for controlling the rotational speed, rotational phase, or torque individually or simultaneously according to the load state, and at least one of the electric motors is subjected to torque fluctuations according to the load state by the control means, or Alternatively, the vibration generated in the steering system is compensated for by the vehicle characteristics. As a result, the load acting on the steering system can be distributed, the output can be increased, the electric motor can be reduced in size, and the installation space for arranging the electric motor can be reduced. As a result, the electric power steering apparatus can be applied not only to small vehicles but also to large vehicles.

  In addition, by using two electric motors with different output characteristics and individually controlling each electric motor according to the traveling state, for example, at high speed traveling, only the electric motor with a small output is used to assist steering, and at a relatively low speed. When the vehicle is traveling, it is possible to perform finer control such as assisting the steering with only the electric motor having a large output, and assisting the steering with both electric motors when the vehicle is stationary. As a result, the steering assist force can be easily controlled according to the traveling state of the vehicle, the motor inertia during traveling can be reduced, the steering performance can be improved, and the consumption per electric motor can be improved. Electric power can be reduced.

  In addition, when changing the size of the engine or the vehicle body, one electric motor is used in common, and the size of the other electric motor is changed so that it can be arranged in different parts of the steering system to reduce manufacturing costs. In addition, the electric motor can be miniaturized and installation can be simplified.

  In addition, by arranging two electric motors having different performances in different parts of the steering system, the degree of freedom in setting the assist characteristics is increased and the gain can be increased. In addition, by arranging the electric motor closer to the steered wheels, necessary kickback information can be properly transmitted to the control means, and unnecessary kickback information and high-frequency components of road surface unevenness information can be controlled. Can do.

  Furthermore, an electric motor for changing the gear ratio of the steering gear ratio variable mechanism arranged in the steering system is used for the vehicle speed, the steering angle of the steering system, the torque of the steering system, the gear ratio of the steering gear ratio variable mechanism, and the electric power steering. Based on the maximum allowable current value generated in the engine, control is made so that the optimum steering gear ratio is obtained. As a result, the steering gear ratio can be changed to an optimum gear ratio according to the traveling state, and it is not necessary to rotate the steering wheel much during low speed traveling such as in a garage, so that comfortable steering can be performed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating an electric power steering apparatus 1a according to a first embodiment of the present invention. In the figure, an electric power steering apparatus 1 a supports a steering shaft 2 rotatably in a steering column 3, and transmits a steering force of a steering wheel 4 to an intermediate shaft 6 via a universal joint 5. It has become.

  The intermediate shaft 6 is connected to a pinion shaft 8 via a universal joint 7 and is connected to a rack shaft 10 extending in the vehicle width direction by a steering gear portion 9. In the steering gear unit 9, the rotational motion of the pinion shaft 8 is converted into the linear motion of the rack shaft 10 by meshing the pinion teeth (pinion) of the pinion shaft 8 with the rack teeth (rack) of the rack shaft 10. ing.

  The steering column 3 is provided with an electric motor 11A. As shown in FIG. 2, a reduction gear 12A is rotatably supported by a pair of ball bearings 13 and 13 on the rear end side (left side in FIG. 2). Yes. The speed reducer 12 </ b> A includes a worm wheel 14 that is press-fitted and fixed to the steering shaft 2, and a worm gear 15 that meshes with the worm wheel 14. Thus, when the electric motor 11A is driven, the steering shaft 2 is assisted through the worm gear 15 and the worm wheel 14 connected to the drive shaft 16A.

  In addition, the steering gear portion (pinion portion) 9 is provided with an electric motor 11B, and assists the pinion shaft 8 via a reduction gear 12B similar to that described above. Here, the electric motor 11A that assists the steering shaft 2 that has higher strength than the pinion shaft 8 is larger in both output and capacity than the electric motor 11B. Therefore, in this embodiment, the electric motor 11A is the large motor 11A, and the electric motor 11B is the small motor 11B.

  A control unit (ECU) 17 that controls the driving of each of the electric motors 11A and 11B receives a signal based on the steering torque given by the operation of the steering wheel 4 from the torque sensor 18 attached to the steering shaft 2. Is done. Further, a vehicle speed signal is input to the ECU 17 from the vehicle speed sensor 19.

  As shown in FIG. 3, the ECU 17 includes a microprocessor 20 that controls the drive of the electric motors 11A and 11B according to a predetermined program, a ROM 21 that stores programs and predetermined constants, a work area of the microprocessor 20, RAM 22 used as temporary storage, motor drive circuits 23A and 23B for controlling the drive of each electric motor 11A and 11B, and motor current detection circuits 24A and 24B for detecting the supply current of each electric motor 11A and 11B And I / O interfaces (I / F) 25 and 25 for receiving signals from the torque sensor 18 and the vehicle speed sensor 19.

  Next, the operation of the drive control of the steering assist electric motors 11A and 11B in this embodiment will be described with reference to the flowchart of FIG.

  First, in step S <b> 1, the ECU 17 reads the steering torque T detected from the torque sensor 18 and the vehicle speed S detected from the vehicle speed sensor 19.

In step S2, it is determined whether or not the vehicle speed S exceeds a determined high speed reference value R _S1 . When the vehicle speed S exceeds the high speed reference value R _S1 , it is determined that the vehicle is traveling at high speed, and the process proceeds to step S3.

In step S3, whether the above atmospheric torque reference value R _T1 the steering torque T is determined, it determines whether. When the steering torque T exceeds the large torque reference value _RT1 , it is determined that a large steering torque is input from the steering wheel 4, and the process proceeds to step S4. When the steering torque T is equal to or less than the large torque reference value R _T1, it is determined that a large steering torque is not input from the steering wheel 4, and the process proceeds to step S5.

A high speed driving, when and inputted steering torque T exceeds the large torque reference value R _T1, at step S4, driving only large motor 11A, so that the assisting steering. A large steering torque is generated in the steering shaft 2 when the steering wheel is operated to avoid a collision during high-speed traveling. For this reason, even when the vehicle is traveling at high speed, when a large steering torque T is detected, the large motor 11A is driven to assist steering.

A high speed traveling, and when the input steering torque T is equal to or less than the high torque reference value R _T1 in step S5, by driving only the small motor 11B, so that the assisting steering. In steering during high-speed traveling, if the steering assist force is large, an excessive steering amount may occur. Therefore, it is preferable to suppress the steering assist force by the assist motor. Therefore, when the vehicle is traveling at high speed and a large steering torque T is not input, steering assist is performed only by the small motor 11B.

Next, when the vehicle speed S is equal to or less than the high speed reference value R _S1 in step S2, the process proceeds to step S6, whether or not the vehicle speed S exceeds the determined low speed reference value R _S2 (R _S2 <R _S1 ). Determine. When the vehicle speed S exceeds the low speed reference value _RS2 , it is determined that the vehicle is traveling at a medium speed, and the process proceeds to step S7.

In step S7, similarly to step S3, or exceeds the large torque reference value R _T1 the steering torque T is determined, determines whether. When the steering torque T exceeds the large torque reference value _RT1 , it is determined that a large steering torque is input from the steering wheel 4, and the process proceeds to step S8. When the steering torque T is equal to or less than the large torque reference value _RT1 , the process proceeds to step S9.

A medium-speed traveling, and when the input steering torque T exceeds the large torque reference value R _T1, at step S8, the large motor 11A, together drive the small motor 11B, so assisting steering ing. In this case, the speed S and the steering torque T are the speed and steering torque at the time of a U-turn or the like performed on a normal road, and a large torque is required. Therefore, both the large motor 11A and the small motor 11B are driven. Need steering assistance.

In step S9, it is determined whether or not the steering torque T exceeds the determined small torque reference value R _T2 (R _T2 > R _T1 ). When the steering torque T exceeds the small torque reference value R _T2 , it is determined that the steering torque T input from the steering wheel 4 is R _T2 <T ≦ R _T1 , and the process proceeds to step S10. When the steering torque T is less than or equal to the small torque reference value _RT2, it is determined that the steering torque input from the steering wheel 4 is small, and the process proceeds to step S11.

When the vehicle is traveling at medium speed and the input steering torque T is R _T2 <T ≦ R _T1 , only the large motor 11A is driven to assist steering in step S10. The speed S and the steering torque T in this case are the speed and the steering torque when a right turn or a left turn is performed on a normal road.

When the vehicle is traveling at medium speed and the input steering torque T is less than or equal to the small torque reference value _RT2 , only the small motor 11B is driven to assist steering in step S11. When the steering torque T is small while traveling at medium speed, a large steering assist force is not required, so that the steering assist using only the small motor 11B is sufficient.

If the vehicle speed S is equal to or lower than the low speed reference value R _{S2 in} step S6, it is determined that the vehicle is traveling at a low speed, and the process proceeds to step S12. In step S12, as in step S9, it is determined whether or not the steering torque T exceeds the determined small torque reference value _RT2 . When the steering torque T is less than or equal to the small torque reference value _RT2, it is determined that the steering torque input from the steering wheel 4 is not small, and the process proceeds to step S13. When the steering torque T is less than or equal to the small torque reference value _RT2, it is determined that the steering torque input from the steering wheel 4 is small, and the process proceeds to step S14.

When the vehicle is traveling at a low speed and the input steering torque T exceeds the small torque reference value _RT2 , both the large motor 11A and the small motor 11B are driven to assist steering in step S13. Yes. In this case, it is a handle operation mainly when entering a garage or parallel parking, and a large torque is required when the handle is stationary. Therefore, in this case, both the large motor 11A and the small motor 11B are driven to assist steering.

When the vehicle is traveling at low speed and the input steering torque T is less than or equal to the small torque reference value _RT2 , only the large motor 11B is driven to assist steering in step S14. When the vehicle is traveling at a low speed, a large steering assist force is required even when the steering torque T is small, and thus steering assist by the large motor 11A is necessary.

  As described above, in this embodiment, the rotational force of the electric motor 11A provided in the steering column 3 is assisted from the steering shaft 2 via the speed reducer 12A, and the electric motor 11B provided in the steering gear portion 9 is assisted. The rotational force is assisted through the speed reducer 12B. That is, the steering system of the electric power steering apparatus 1a is assisted separately from different parts by the two electric motors 11A and 11B. Thereby, each electric motor can be controlled individually according to the motor characteristic fluctuation. For example, based on the vehicle speed S and the steering torque T, only one electric motor 11 is driven during normal traveling, When high output acts like time, both the electric motors 11A and 11B can be driven. As a result, the steering assist force can be easily controlled according to the traveling state of the vehicle, and the power consumption can be reduced.

  Further, by providing two electric motors at different parts of the steering system, it is possible to more reliably detect motor characteristic fluctuations and activate the fail-safe function. As a result, when the electric motor fails, the steering wheel 4 suddenly becomes heavy and does not give the occupant a feeling of fatigue, thereby improving the safe operability of the vehicle. Also, by arranging the two electric motors in different parts, the synchronous controllability of the rotation of the two electric motors can be improved, and each electric motor can be reduced in size, and the installation space must be concentrated. There is also an effect of not.

  In addition, by arranging two electric motors having different performances in different parts of the steering system, the degree of freedom in setting the assist characteristics is increased and the gain can be increased. As a result, continuous assist characteristic setting can be realized, and steering performance can be improved.

  Furthermore, it is possible to cope with the problem by simply changing the size of the other electric motor while using one electric motor in common, and the electric motor can be reduced in size and can be easily attached. Thereby, the manufacturing cost and the labor required for mounting the electric motor can be reduced.

  FIG. 5 is a schematic configuration diagram illustrating an electric power steering apparatus 1b according to the second embodiment of the present invention. The same members as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the figure, the rack shaft 10 is assisted by the pinion shaft 8 through the reduction gear 12A with the driving force of the electric motor 11A provided on the steering column 3.

  Further, the intermediate shaft 6 is provided with a steering gear ratio variable mechanism 26 that can arbitrarily change the characteristic of the steering angle with respect to the rotation angle of the steering wheel 4. The steering gear ratio variable mechanism 26 includes a gear ratio changing motor 11 ′ for changing the steering gear ratio. The gear ratio changing motor 11 ′ is a control means (ECU) 17 provided in the steering column 3. The drive is controlled by '.

  A signal based on the steering torque and the steering angle given by the operation of the steering wheel 4 is input to the ECU 17 ′ from the torque sensor 18 and the steering angle sensor 27 attached to the steering shaft 2. Further, a vehicle speed signal is input from the vehicle speed sensor 19 to the ECU 17 ′.

  As shown in FIG. 6, the ECU 17 ′ includes a microprocessor 20 that controls driving of the electric motor 11A and the gear ratio changing motor 11 ′ according to a predetermined program, an allowable maximum current value of the program and the electric power steering device 1b, and the like. ROM 21 storing predetermined constants, RAM 22 used as a work area or temporary storage of microprocessor 20, motor drive circuit 23A for controlling the drive of electric motor 11A, and gear ratio changing motor 11 23 'for controlling the drive of', a motor current detection circuit 24A for detecting the supply current of the electric motor 11A, and a motor terminal voltage detection circuit 24 'for detecting the motor terminal voltage of the gear ratio changing motor 11' , I receive signals from the torque sensor 18, the vehicle speed sensor 19, and the steering angle sensor 27. And an O interface (I / F) 25,25 Prefecture.

  The ECU 17 'controls the driving of the steering assisting electric motor 11A based on signals from the torque sensor 18, the vehicle speed sensor 19, and the current value supplied to the electric motor 11A. On the other hand, the gear ratio changing motor 11 ′ is controlled by the ECU 17 ′ with signals from the torque sensor 18, the vehicle speed sensor 19, and the rudder angle sensor 27, the motor terminal voltage value of the gear ratio changing motor 11 ′, Based on the allowable maximum current value of the electric power steering apparatus 1b, the gear ratio is changed by comprehensively determining the state of the vehicle.

  7 and 8 are cross-sectional views of the main part of the steering gear ratio variable mechanism 26. FIG. In FIG. 7, the housing 28 of the steering gear ratio variable mechanism 26 includes a housing main body 28A and a lid member 28C fixed to the housing main body 28A with bolts 28B. An input shaft 6A connected to the steering shaft 2 is rotatably supported on the housing main body 28A via bearings 29 and 30. The input shaft 6A has a substantially annular input side disk 31 attached to one end (right end in FIG. 7) in an eccentric state from the axis of the input shaft 6A. The external gear 33 is rotatably supported via the.

  The external gear 33 meshes with an internal gear 34 fixed to the housing main body 28A, and the external gear 33 and the internal gear 34 constitute a hypocycloid reduction mechanism. Further, the external gear 33 is connected to the guide plate 36 via the Oldham coupling 35. As shown in the exploded perspective view of the Oldham coupling 35 in FIG. 9, the tracks 33A and 37A are formed on the mutually facing surfaces of the external gear 33 and the disc-shaped intermediate member 37, respectively. A plurality of balls 38 are arranged between the track 37A and the track 37A. On the other hand, the tracks 37B and 36B are formed on the mutually facing surfaces of the intermediate member 37 and the guide plate 36 so as to be orthogonal to the track 37A, and a plurality of balls are provided between the track 37B and the track 36B. 39 is arranged. As a result, the Oldham coupling 35 can transmit rotational force even when the axis of the guide plate 36 and the axis of the external gear 33 are deviated. In FIG. 9, the ball cage is omitted.

Moreover, in FIG.7 and FIG.8, the code | symbol 40 is a substantially cylindrical moving case. The moving case 40 passes through holes 40A and 40A formed in the protruding portion on the left side of FIG. 8 and extends along the shaft 41 fixed to the housing 28 in the vertical direction (arrow ZZ ′ in FIG. 8). It can be moved freely. Further, the moving case 40 is moved in the vertical direction by a drive shaft 42 having a screw portion 42A screwed into a screw hole 40B formed in the protruding portion on the right side of FIG.
One end (upper side in FIG. 8) of the drive shaft 42 is connected to a rotation shaft 11′A of a gear ratio changing motor (drive motor) 11 ′, and is rotatably supported by the housing 28 via a bearing 43. The other end (the lower side in FIG. 8) is rotatably supported by the housing 28 via a bearing 44.

  The moving case 40 supports the guide plate 36 via a bearing 45 so as to be rotatable. The guide plate 36 has a rectangular guide hole 35C whose cross section is elongated in the radial direction. The guide hole 35C engages with a prismatic part 46A of the slide member 46 and is slidable along the guide hole 35C. is there. On the other hand, the cylindrical portion 46B of the slide member 46 is rotatably supported in a hole 48A formed in a substantially annular output side disk 48 attached to one end of the output shaft 6B via a needle bearing 47. The output shaft 6B is rotatably supported by the housing 28 via bearings 49 and 50, and transmits a rotational force to the pinion shaft 8 via the universal joint 7. Reference numeral 51 denotes a movement amount detector (such as a potentiometer) for detecting the movement amount of the movement case 40.

  In short, the gear ratio changing means of the steering gear ratio variable mechanism 26 includes a guide plate 36 as an input member, a slide member 46, and an output side disk 48 as an output member. When the rotational force is transmitted from the input shaft 6A to the guide plate 36 through the Oldham coupling 35, the axes of the guide plate 36 and the output side disk 48 coincide (state shown in FIG. 10A). Then, the slide member 46 does not move with respect to the guide hole 35 </ b> C, and the rotation of the guide plate 36 is directly transmitted to the output side disk 48.

On the other hand, when the guide plate 36 is moved with respect to the output side disk 48 by the drive motor 42, as shown in FIG. 10B, the axis O ₃₆ of the guide plate ₃₆ and the output side disk 48. the axis O ₄₈ of the offset (shift) the offset (shift) amount delta. Also in this case, the ball 38 reduces the friction in the radial direction between the external gear 33 and the intermediate member 37, and the ball 38 reduces the friction between the intermediate member 37 and the guide plate 36. Is transmitted from the external gear 33 to the guide plate 36. At this time, if the guide plate 36 is rotated by the angle θ1 due to the rotation from the input shaft 6A, the slide member 46 slides along the guide hole 35C as shown in FIG. The disk 48 rotates at an angle θ2 (θ1> θ2). Therefore, the rotation angle ratio is θ2 / θ1 according to the offset amount Δ. Thus, even during traveling, by operating the drive motor 42, it can be arbitrarily set the offset amount Δ of the axis O ₃₆ of the guide plate 36 and the axis O ₄₈ of the output side disk 48. As a result, the characteristics of the steering angle with respect to the rotation angle of the steering wheel 4 can be arbitrarily changed, so that the optimum steering gear ratio according to the traveling state can be determined based on various parameters such as the vehicle speed, the steering force, and the steering angle. Can be obtained.

  Next, the operation of the drive control of the gear ratio changing motor 11 ′ in this embodiment will be described with reference to the flowchart of FIG.

First, in step S21, the current steering gear ratio _{G r,} is set as the gear ratio initial value _{G 0.}

  In step S 22, the ECU 17 ′ reads the steering torque T detected from the torque sensor 18, the vehicle speed S detected from the vehicle speed sensor 19, and the steering angle θ detected from the rudder angle sensor 26.

In step S23, it is determined whether or not the read vehicle speed S is equal to or higher than _{0 and} equal to or lower than a predetermined vehicle speed S0. This step, which running state is determined whether a low speed, the predetermined speed S ₀ may be arbitrarily changed in accordance with the design.

When the vehicle speed S is equal to or greater than _{0 and} equal to or less than the predetermined vehicle speed S ₀ , the process proceeds to step S24, and the read absolute value of the steering angle θ is equal to or greater than the absolute value of the predetermined steering angle θ _0. It is determined whether or not. This step determines whether or not the amount of steering by the driver is large, and the predetermined steering angle θ ₀ can be arbitrarily changed according to the design.

If the vehicle speed S is less than 0 or greater than the predetermined vehicle speed S ₀ , the process proceeds to step S25, where the absolute value of the read steering angle θ is less than or equal to the absolute value of the predetermined steering angle θ _0. It is determined whether or not. This step also determines whether the amount of steering by the driver in the low-speed traveling state is large.

If the steering angle θ is greater than or equal to the predetermined steering angle θ ₀ in step S24, and if the absolute value of the steering angle θ is less than or equal to the absolute value of the predetermined steering angle θ ₀ in step S25, step S26. Then, it is determined whether or not the steering torque T is _{equal to} or greater than a predetermined steering torque T0. In this step, it is determined whether or not the steering torque T applied to the steering system is large. The predetermined steering torque T ₀ can be arbitrarily changed according to the design.

If the steering torque T is greater than or equal to the predetermined steering torque T ₀ in step S26, if the steering angle θ is smaller than the predetermined steering angle θ ₀ in step S24, or if the vehicle is in a low-speed traveling state, and in step S25, When the absolute value of the steering angle θ is larger than the absolute value of the predetermined steering angle θ ₀ , the process proceeds to step S27, the steering gear ratio G _r is increased by a predetermined gear ratio displacement amount ΔG _r , and the process again returns to step S26. It is determined whether or not the steering torque T is _{equal to} or greater than a predetermined steering torque T0.

In step S26, when the steering torque T is predetermined steering torque _{T 0} is less than, at step S28, the current value _{I e} of the steering assist electric motor 11A, which is detected from the motor drive current circuit 24A is preliminarily ROM21 in the storage It is determined whether or not the allowable maximum current value I ₀ M or less. This step determines whether or not the current value I _e supplied to the steering assist electric motor exceeds the upper limit, and the allowable maximum current value I ₀ M can be arbitrarily changed according to the design. is there.

In step S28, it is greater than the current value _{I e} is the allowable maximum current value _{I 0} M, the process proceeds to step S29, to reduce the steering gear ratio _{G r} by a predetermined gear ratio displacement .DELTA.G _r, to step S27 again It is determined whether or not the steering torque T is _{equal to} or greater than a predetermined steering torque T0.

If the current value _Ie is equal to or smaller than the allowable maximum current value I ₀ M in step S26, it is determined that the optimal steering gear ratio has been set without exceeding the allowable maximum current value I ₀ M, and the process proceeds to step S21. return the current steering gear ratio G _r, it is set as the gear ratio initial value G _0, repeated strokes of step S22 and subsequent steps.

  As described above, in this embodiment, the intermediate shaft 6 is provided with the steering gear ratio variable mechanism 26 that can change the steering gear ratio, the gear ratio changing motor 11 ′ of the steering gear ratio variable mechanism 26, and the steering assist. The drive motor is controlled individually. As a result, it is possible to set the optimum steering gear ratio as well as to obtain the same operational effects as in the first embodiment, and it is not necessary to rotate the steering wheel much during low speed traveling such as in a garage, for example. Can be steered.

  In the present embodiment, the steering gear ratio variable mechanism 26 is provided on the intermediate shaft 6. However, the present invention is not limited thereto, and may be provided on the steering shaft 2, for example.

  FIG. 12 is a schematic configuration diagram illustrating an electric power steering apparatus 1c according to the third embodiment of the present invention. The same members as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the figure, the rack shaft 10 is assisted by the drive force of the electric motor 11A provided in the steering column 3 from the pinion shaft 8 via the speed reducer 12A, and on the other steered wheel side (right side in FIG. 12), It is connected to the electric motor 11C via a power transmission means (reduction gear) 12'C that engages with the ball screw, and is assisted by the electric motor 11C.

  FIG. 13 is a longitudinal sectional view of the rack and pinion mechanism. In the figure, a member denoted by reference numeral 52 is a rack and pinion housing, and holds a rack shaft 10 and a pinion shaft 8 constituting a rack and pinion mechanism. The rack shaft 10 has a rack 53 on the left side in the drawing that meshes with the pinion of the pinion shaft 8.

  The speed reducer 12'C is a gear housing 54 bolted to the right end of FIG. 13 of the rack and pinion housing 52, and is bolted to the gear housing 54 to form a steering gear case together with the rack and pinion housing 52 and the gear housing 54. A ball screw housing 55 is used as an outer shell.

  The gear housing 54 includes an electric motor 11 </ b> C at a lower portion thereof, and houses a drive gear 57 fixed to the drive shaft 56 of the electric motor 11 </ b> C and a driven gear 58 that meshes with the drive gear 57. Reference numeral 59 in the drawing indicates a bearing that rotatably supports the drive gear 57, and reference numeral 60 indicates a bearing that rotatably supports the driven gear 58.

  A ball nut 61 is rotatably held in the ball screw housing 55 via a double-row angular ball bearing 62. The rack shaft 10 is formed with a male screw groove 63, while the ball nut 61 is formed with a female screw groove 64, and a large number of circulating balls are provided between the male screw groove 63 and the female screw groove 64. Steel balls 65 are interposed.

  The driven gear 58 has a hollow portion 66 through which the rack shaft 10 is inserted, and the driven gear 58 and the ball nut 61 are relatively loosely fitted to each other at the right end of the hollow portion 66 in the drawing. It can be freely slid relative to each other.

  The electric motor 11 </ b> C rotates in either the forward or reverse direction based on a signal from the ECU 17, and the rotation is decelerated to the ball nut 61 that is spline-engaged with the driven gear 58 via the drive gear 57 and the driven gear 58. Is transmitted. When the ball nut 61 rotates, a thrust force acts on the male screw groove 63 of the rack shaft 10 via the steel ball 65 engaged with the female screw groove 64, thereby realizing steering assistance.

  Further, the electric motor 11C that assists the rack shaft 10 having higher strength than the steering shaft 2 is larger in both output and capacity than the electric motor 11A. Therefore, in this embodiment, the electric motor 11C is the large motor 11C, and the electric motor 11A is the small motor 11A. The operation of the electric motor drive control in this embodiment is the same as that of the first embodiment shown in FIG.

  Thus, in the present embodiment, the driving force of the electric motor 11A provided in the steering column 3 is assisted through the speed reducer 12A, and the driving force of the electric motor 11C engaged with the ball screw of the rack shaft 10 is increased. Assist is provided via the speed reducer 12'C. Thereby, the capacity of the electric motor 11 </ b> A provided in the steering column 3 having not much room for installation space can be reduced as well as obtaining the same operational effects as the first embodiment. As a result, it is possible to cope with a vehicle type in which the installation space of the steering device is limited. Further, the load acting on the steering gear portion 9 can be dispersed, the load acting on the rack and pinion portion in the pinion shaft 8 and the ball screw portion can be equalized, and high output can be achieved.

  FIG. 14: is a schematic block diagram which shows the electric power steering apparatus 1d based on Example 4 of this invention, and attaches | subjects the same code | symbol to the same member as Example 1, and abbreviate | omits the description. In the figure, a rack shaft 10 is assisted by a drive force of an electric motor 11A provided on a steering column 3 from a pinion shaft (first pinion shaft) 8 via a speed reducer 12A and on the other steered wheel side ( 14), the second pinion shaft 8D is engaged with the second pinion shaft 8D. The second pinion shaft 8D is connected to the electric motor 11D via the speed reducer 12D and is assisted by the electric motor 11D. .

  Further, the electric motor 11D that assists the rack shaft 10 having higher strength than the steering shaft 2 has a larger output and capacity than the electric motor 11A. Therefore, in this embodiment, the electric motor 11D is the large motor 11D, and the electric motor 11A is the small motor 11A. The operation of the electric motor drive control in this embodiment is the same as that of the first embodiment shown in FIG.

  As described above, in this embodiment, the driving force of the electric motor 11A provided in the steering column 3 is assisted through the speed reducer 12A, and the driving force of the electric motor 11D provided in the second pinion shaft 8D is decelerated. Assist is provided via the machine 12D. Thereby, the capacity of the electric motor 11 </ b> A provided in the steering column 3 having not much room for installation space can be reduced as well as obtaining the same operational effects as the first embodiment. As a result, it is possible to cope with a vehicle type in which the installation space of the steering device is limited. Further, the load acting on the steering gear portion 9 can be dispersed, the load acting on the rack and pinion portion in the first pinion shaft 8 and the second pinion shaft 8d can be equalized, and high output can be achieved. .

  FIG. 15: is a schematic block diagram which shows the electric power steering apparatus 1e which concerns on Example 5 of this invention, attaches | subjects the same code | symbol to the member same as Example 1, and abbreviate | omits the description. In the figure, a rack shaft 10 is assisted by a driving force of an electric motor 11B provided in a steering gear portion (pinion portion) 9 from a pinion shaft (first pinion shaft) 8 via a speed reducer 12B. Is engaged with the second pinion shaft 8D on the steered wheel side (right side in FIG. 15), and the second pinion shaft 8D is connected to the electric motor 11D via the speed reducer 12D and assisted by the electric motor 11D. It is like that.

  Further, the electric motor 11D that assists the rack shaft 10 having higher strength than the pinion shaft 8 is larger in both output and capacity than the electric motor 11B. Therefore, in this embodiment, the electric motor 11D is the large motor 11D, and the electric motor 11C is the small motor 11C. The operation of the electric motor drive control in this embodiment is the same as that of the first embodiment shown in FIG.

  Thus, in the present embodiment, the driving force of the electric motor 11B provided in the pinion unit 9 is assisted through the speed reducer 12B, and the electric motor provided in the second pinion shaft 8d engaged with the rack shaft 10 is used. The driving force of the motor 11D is assisted through the speed reducer 12D. As a result, the capacity of the electric motor 11B provided in the pinion portion 9 can be obtained without providing the electric motor on the steering column 3 having not much room for installation space as well as obtaining the same operational effects as the first embodiment. Can be reduced. As a result, it is possible to cope with a vehicle type in which the installation space of the steering device is limited. Further, the load acting on the steering gear portion 9 can be dispersed, the load acting on the rack and pinion portion in the first pinion shaft 8 and the second pinion shaft 8d can be equalized, and high output can be achieved. .

  FIG. 16: is a schematic block diagram which shows the electric power steering device 1f which concerns on Example 6 of this invention, and attaches | subjects the same code | symbol to the member same as Example 1, and abbreviate | omits the description. In the figure, a rack shaft 10 is assisted by a driving force of an electric motor 11B provided in a steering gear portion (pinion portion) 9 from a pinion shaft (first pinion shaft) 8 via a speed reducer 12B. On the steered wheel side (the right side in FIG. 16), it is connected to an electric motor 11C through a power transmission means (reduction gear) 12'C engaged with a ball screw, and is assisted by the electric motor 11C. .

  In addition, the electric motor 11C that assists the rack shaft 10 having higher strength than the pinion shaft 2 has a larger output and capacity than the electric motor 11B. Therefore, in this embodiment, the electric motor 11C is the large motor 11C, and the electric motor 11B is the small motor 11B. The operation of the electric motor drive control in this embodiment is the same as that of the first embodiment shown in FIG.

  Thus, in the present embodiment, the electric motor 11B provided in the pinion unit 9 assists the driving force of the electric motor 11B via the speed reducer 12B and is arranged to engage with the ball screw of the rack shaft 10. The driving force of 11C is assisted through the speed reducer 12'C. As a result, the capacity of the electric motor 11B provided in the pinion portion 9 can be obtained without providing the electric motor on the steering column 3 having not much room for installation space as well as obtaining the same operational effects as the first embodiment. Can be reduced. As a result, it is possible to cope with a vehicle type in which the installation space of the steering device is limited. Further, by using the ball screw transmission mechanism 12'C having high durability against a high load, the load acting on the steering gear portion 9 is dispersed, and the load acting on the rack and pinion portion in the pinion shaft 8 and the ball screw portion is reduced. While being able to equalize, high output can be achieved.

  FIG. 17: is a schematic block diagram which shows the electric power steering apparatus 1g which concerns on Example 7 of this invention, attaches | subjects the same code | symbol to the member same as Example 1, and abbreviate | omits the description. In the figure, a rack shaft 10 is assisted by the steering force of the steering wheel 4 from a pinion shaft (first pinion shaft) 8 and is engaged with the second pinion shaft 8D on the other steered wheel side (right side in FIG. 17). The second pinion shaft 8D is connected to the electric motor 11D via the speed reducer 12D, is assisted by the electric motor 11D, and is connected to the power transmission means (speed reducer) 12'C engaged with the ball screw. It is connected to the electric motor 11C through and is assisted by the electric motor 11C.

  In addition, the electric motor 11C that assists the rack shaft 10 via a ball screw having higher strength than the second pinion shaft 8D has a larger output and capacity than the electric motor 11D. Therefore, in this embodiment, the electric motor 11C is the large motor 11C, and the electric motor 11D is the small motor 11D. The operation of the electric motor drive control in this embodiment is the same as that of the first embodiment shown in FIG.

  As described above, in this embodiment, the driving force of the electric motor 11D provided on the second pinion shaft 8D engaged with the rack shaft 10 is assisted through the speed reducer 12D, and the ball screw of the rack shaft 10 is engaged. The driving force of the electric motor 11C to be combined is assisted through the speed reducer 12'C. Thereby, the capacity of the electric motor 11 </ b> A provided in the steering column 3 having not much room for installation space can be reduced as well as obtaining the same operational effects as the first embodiment. As a result, it is possible to cope with a vehicle type in which the installation space of the steering device is limited. Further, by using the ball screw transmission mechanism 12'C having high durability against a high load, the load acting on the steering gear portion 9 is dispersed, and the load acting on the rack and pinion portion in the pinion shaft 8 and the ball screw portion is reduced. It is possible to equalize and increase the output.

  Although the present invention has been specifically described above, the present invention is not limited thereto, and various modifications can be made without departing from the spirit of the present invention. For example, the steering gear ratio variable mechanism 26 of the second embodiment can be changed. The steering shaft 2 and the pinion shaft 8 may be provided, and the electric power steering apparatus according to the first embodiment and the third to seventh embodiments may include the steering gear ratio variable mechanism 26.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of an electric power steering device according to a first embodiment of the present invention in which two electric motors for steering assistance are arranged in a steering column portion and a pinion portion. It is a longitudinal cross-sectional view of the said steering column part. It is a block diagram which shows the structure of the control circuit of the said electric motor. It is a flowchart figure which shows the drive control of the electric motor for steering assistance of the said Example 1. FIG. FIG. 6 is a schematic configuration diagram of an electric power steering apparatus including a steering gear ratio variable mechanism according to a second embodiment of the present invention in which a steering assist electric motor is arranged in a steering column portion and an intermediate shaft has a gear ratio changing electric motor. . It is a block diagram which shows the structure of the control circuit of the said electric motor for gear ratio change. It is sectional drawing of the said steering gear ratio variable mechanism. It is sectional drawing along the VIII-VIII line of FIG. It is a disassembled perspective view of the Oldham coupling of the steering gear ratio variable mechanism. It is the figure which looked at the guide plate and output side disk of the said steering gear ratio variable mechanism in the axial direction. It is a flowchart figure which shows drive control of the said electric motor for gear ratio change. It is a schematic block diagram of the electric power steering apparatus which has arrange | positioned two electric motors for steering assistance based on Example 3 of this invention to the steering column part and the ball screw part. It is a longitudinal cross-sectional view of the rack and pinion mechanism of the electric power steering apparatus. It is a schematic block diagram of the electric power steering apparatus which has arrange | positioned the two electric motors for steering assistance based on Example 4 of this invention to the steering column part and the rack part. It is a schematic block diagram of the electric power steering apparatus which has arrange | positioned two electric motors for steering assistance based on Example 5 of this invention to the rack part and the pinion part. It is a schematic block diagram of the electric power steering apparatus which has arrange | positioned the two electric motors for steering assistance based on Example 6 of this invention to the pinion part and the ball screw part. It is a schematic block diagram of the electric power steering apparatus which has arrange | positioned the two electric motors for steering assistance based on Example 7 of this invention to the rack part and the ball screw part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering device 3 Steering column 4 Steering wheel 8 Pinion shaft 9 Steering gear part (pinion part)
10 Rack shaft 11A Electric motor (for steering shaft assist)
11B Electric motor (for pinion shaft assist)
11C Electric motor (for ball screw assist)
11D electric motor (for rack shaft assist)
11 'Electric motor (for changing gear ratio)
12A Reducer (located in the steering column)
12B Reducer (located in the pinion part)
12'C Reducer (power transmission mechanism), (located in the ball screw)
12D reducer (located in the rack)
17 Control means (ECU)
26 Steering gear ratio changing mechanism 61 Ball nut 63 Male thread groove 64 Female thread groove

Claims (11)

In the electric power steering apparatus configured to assist the steering through the speed reduction mechanism of the steering assist motor,
Two electric motors having different performance and arranged in different parts of the steering system from the steering wheel of the vehicle to the steered wheels;
Control means for individually controlling the operation of the two electric motors,
An electric power steering apparatus, wherein at least one of the two electric motors is compensated for a motor characteristic variation caused by a load state by the control means. The electric power steering apparatus according to claim 1, wherein the motor characteristic fluctuation is a torque fluctuation of the electric motor. 3. The electric power steering apparatus according to claim 1, wherein the motor characteristic fluctuation is vibration generated in the steering system due to vehicle characteristics. 4. One of the electric motors is a steering assisting electric motor disposed in a steering column, and the other electric motor is a steering assisting electric motor disposed in a steering pinion portion. The electric power steering device according to any one of the above. 4. One of the electric motors is a steering assist electric motor disposed in a steering column, and the other electric motor is a steering assist electric motor disposed in a rack portion. The electric power steering apparatus according to any one of the above. 4. One of the electric motors is a steering assisting electric motor disposed in a steering column, and the other electric motor is a steering assisting electric motor disposed in a ball screw portion. The electric power steering device according to any one of the above. 4. One of the electric motors is a steering assist electric motor disposed in a steering pinion portion, and the other electric motor is a steering assist electric motor disposed in a rack portion. The electric power steering device according to any one of the above. One of the electric motors is a steering assist electric motor disposed in a steering pinion portion, and the other electric motor is a steering assist electric motor disposed in a ball screw portion. The electric power steering device according to any one of claims 3 to 4. 4. One of the electric motors is a steering assist electric motor disposed in a rack portion, and the other electric motor is a steering assist electric motor disposed in a ball screw portion. The electric power steering device according to any one of the above. 4. The gear ratio changing electric motor according to claim 1, wherein one of the electric motors is a gear ratio changing electric motor for changing a gear ratio of a steering gear ratio variable mechanism arranged in the steering system. 5. Electric power steering device. The gear ratio changing electric motor is generated by the control means in the vehicle speed, the steering angle of the steering system, the torque of the steering system, the gear ratio of the steering gear ratio variable mechanism, and the electric power steering. The electric power steering apparatus according to claim 10, wherein the electric power steering apparatus is controlled so as to achieve an optimum steering gear ratio based on an input value of a maximum current value.

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