JP2017043114A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of suppressing a steering load caused by a friction rise of a transmission section.SOLUTION: An electric power steering device includes: an electric motor 110; a speed reduction mechanism 111 for transmitting driving torque of the electric motor 110 as auxiliary force for steering a steering wheel 101 of a vehicle; and a control device 10 for controlling an operation of the electric motor 110 by taking into consideration torque corresponding to a friction rise by torque loss recognized on the basis of actual driving torque of the electric motor 110 and initial torque at the initial stage of the start of the use of the electric motor 110.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electric power steering apparatus.

2. Description of the Related Art In recent years, there has been proposed an electric power steering device that allows a vehicle to be driven comfortably by responding to a change in friction generated in a transmission unit that transmits a driving torque of an electric motor to a steering system.
For example, the electric power steering device described in Patent Document 1 is configured as follows. In other words, the control unit of the electric power steering device detects that the vehicle is traveling straight by the torque sensor, and the state where the input vehicle speed is within a predetermined friction detection speed range is predetermined. The system friction force is estimated by measuring the limit motor current value that determines whether or not the assist motor rotates when it continues for more than the standard straight running time, and the control characteristics of the assist control function according to the estimated system friction force To change.

JP 2004-168082 A

If the meshing of the gears constituting the transmission unit is poor and the friction increases, the steering load may increase.
An object of the present invention is to provide an electric power steering apparatus capable of suppressing a steering load caused by an increase in friction of a transmission unit.

  For this purpose, the present invention provides an electric motor, a transmission unit that transmits the driving torque of the electric motor as an auxiliary force for steering a vehicle steering wheel, the actual driving torque of the electric motor, and the electric motor. An electric power steering apparatus comprising: control means for controlling the operation of the electric motor in consideration of the torque of the friction increase due to the torque cross, which is grasped based on the initial torque at the beginning of use.

  From another point of view, the present invention relates to an electric motor, a transmission unit that transmits the driving torque of the electric motor as an assisting force for steering a steering wheel of a vehicle, and when the aging of the transmission unit is large. Control means for controlling the operation of the electric motor in consideration of a torque for an increase in friction due to the aging that is grasped based on an actual driving torque of the electric motor and an initial torque at the beginning of use of the electric motor; And an electric power steering device.

Here, the control means includes: an actual drive torque calculating means for calculating an actual drive torque that is an actual drive torque of the electric motor; an initial torque calculating means for calculating the initial torque; and the actual drive torque calculating means. Friction increase equivalent torque calculation means for subtracting the initial torque calculated by the initial torque calculation means from the calculated actual drive torque to calculate a friction increase equivalent torque that is a torque corresponding to an increase in friction due to deterioration over time. May be.
The actual driving torque calculating means further includes torque detecting means for detecting a steering torque of the steering wheel, and the actual driving torque calculating means is configured to determine the actual driving torque based on a reaction force from the road surface received by the rolling wheels and a steering torque detected by the torque detecting means. The driving torque may be calculated.
Further, the present invention further includes torque detection means for detecting a steering torque of the steering wheel, wherein the initial torque calculation means includes a predetermined correlation between the driving torque of the electric motor and the steering torque at the beginning of use, and the torque. The initial torque may be calculated based on the steering torque detected by the detecting means.
Further, the apparatus further includes an aging deterioration determining unit that determines aging deterioration of the transmission unit, and when the aging deterioration of the transmission unit detected by the aging deterioration determination unit is small, the electric motor is operated according to steering of the steering wheel. When the operation of the motor is controlled and the aging deterioration is large, the operation of the electric motor may be controlled in consideration of the torque of the friction increase due to the aging deterioration in addition to the steering of the steering wheel.

  According to the present invention, it is possible to suppress a steering load due to an increase in friction of the transmission unit.

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is a schematic block diagram of a control apparatus. It is a schematic block diagram of a target current calculation part. It is the schematic of the control map which shows a response | compatibility with detected torque and vehicle speed, and a base current. It is a schematic block diagram of a control part. It is a figure which shows the relationship between the thrust which moves a rack axis | shaft, and a driver | operator's steering torque. It is a figure which shows the relationship between a driver | operator's steering torque when the thrust of a rack axis | shaft is made constant, and the transmission torque which the drive torque of the electric motor was transmitted to the pinion shaft. It is a schematic block diagram of a friction compensation current setting part. It is a flowchart which shows the friction compensation current calculation process which a friction compensation current setting part performs. It is the schematic of the control map which shows a response | compatibility with the road surface reaction force which a vehicle speed, a steering angle, and a front wheel receive from a road surface.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an electric power steering apparatus 100 according to an embodiment.
Electric power steering device 100 (hereinafter, also simply referred to as “steering device 100”) is a steering device for arbitrarily changing the traveling direction of a vehicle, and in this embodiment, an automobile as an example of the vehicle. 1 illustrates the configuration applied to 1.

  The steering device 100 includes a wheel-like steering wheel 101 that is operated by a driver to change the traveling direction of the automobile 1, and a steering shaft 102 that is provided integrally with the steering wheel 101. Yes. The steering device 100 includes an upper connecting shaft 103 connected to the steering shaft 102 via a universal joint 103a, and a lower connecting shaft 108 connected to the upper connecting shaft 103 via a universal joint 103b. . The lower connecting shaft 108 rotates in conjunction with the rotation of the steering wheel 101.

  Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106 a is formed at the lower end portion of the pinion shaft 106. The rack shaft 105, the pinion shaft 106, and the like transmit the rotational operation force of the steering wheel 101 as the rolling force of the front wheel 150. The pinion shaft 106 applies a driving force to roll the front wheel 150 by rotating with respect to the rack shaft 105 that rolls the front wheel 150.

  The steering device 100 also has a steering gear box 107 that houses the pinion shaft 106. The pinion shaft 106 is connected to the lower connection shaft 108 via the torsion bar 112 in the steering gear box 107. The steering gear box 107 includes a steering torque applied to the steering wheel 101 based on the relative rotation angle between the lower connection shaft 108 and the pinion shaft 106, in other words, based on the twist amount of the torsion bar 112. A torque sensor 109 is provided as an example of torque detecting means for detecting disturbance torque transmitted to the pinion shaft 106 via the front wheel 150. In other words, the torque sensor 109 detects the torque acting on the torsion bar 112. Further, the torque sensor 109 detects torque that acts between the steering shaft 102 and the pinion shaft 106.

  Further, the steering device 100 includes an electric motor 110 supported by the steering gear box 107, and a reduction mechanism 111 as an example of a transmission unit that reduces the driving force of the electric motor 110 and transmits it to the pinion shaft 106. Yes. The speed reduction mechanism 111 includes, for example, a worm wheel (not shown) fixed to the pinion shaft 106, a worm gear (not shown) fixed to the output shaft of the electric motor 110, and the like. The electric motor 110 applies a driving force for rolling the front wheel 150 to the rack shaft 105 by applying a rotational driving force to the pinion shaft 106. The electric motor 110 according to the present embodiment can be exemplified as a three-phase brushless motor.

  In addition, the steering device 100 includes a steering angle sensor 180 as an example of a steering angle detection unit that detects a steering angle that is a rotation angle of the steering wheel (handle) 101. The steering angle sensor 180 is attached to the steering shaft 102 itself and rotates in synchronization with the steering shaft 102 (not shown), and a second rotating member (not shown) that rotates in conjunction with the rotation of the first rotating member. And a magnetoresistive element (not shown) for detecting a change in the magnetic field of the magnetized portion fixed to the second rotating member. The steering angle sensor 180 outputs sine wave and cosine wave signals corresponding to the rotation angle of the steering wheel 101.

  In addition, the steering device 100 includes a control device 10 that controls the operation of the electric motor 110. The control device 10 receives output signals from the torque sensor 109 and the steering angle sensor 180 described above. In addition, the control device 10 includes a vehicle speed sensor 170 that detects a vehicle speed Vc that is a moving speed of the automobile 1 via a network (CAN) that performs communication for transmitting signals for controlling various devices mounted on the automobile. The output signal from etc. is input. Further, the travel distance of the automobile 1 and the number of times the ignition switch provided in the automobile 1 is turned on are input to the control device 10 via the CAN.

  The steering device 100 configured as described above drives the electric motor 110 based on the detected torque detected by the torque sensor 109 and transmits the generated torque of the electric motor 110 to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the steering wheel 101.

Next, the control device 10 will be described.
FIG. 2 is a schematic configuration diagram of the control device 10.
The control device 10 is an arithmetic and logic circuit composed of a CPU, ROM, RAM, backup RAM, and the like.
The control device 10 includes a torque signal Td obtained by converting the detected torque T detected by the torque sensor 109 described above into an output signal, and a vehicle speed signal obtained by converting the vehicle speed Vc detected by the vehicle speed sensor 170 into an output signal. v, a steering angle signal θsd obtained by converting the steering angle θs detected by the steering angle sensor 180 into an output signal, and the like are input.

Then, the control device 10 calculates (sets) a target current It to be supplied to the electric motor 110 based on the torque signal Td and the vehicle speed signal v, and the target current It calculated by the target current calculation unit 20. And a control unit 30 that performs feedback control and the like based on the above.
In addition, the control device 10 includes a motor rotation speed calculation unit 70 that calculates the rotation speed Vm of the electric motor 110. The motor rotation speed calculation unit 70 calculates the rotation speed Vm of the electric motor 110 based on the output signal from the resolver that detects the rotation position of the rotor (rotor) of the electric motor 110 that is a three-phase brushless motor, and the rotation thereof. A rotation speed signal Vms in which the speed Vm is converted into an output signal is output.

Next, the target current calculation unit 20 will be described in detail.
FIG. 3 is a schematic configuration diagram of the target current calculation unit 20.
The target current calculation unit 20 includes a base current calculation unit 21 as an example of a base current calculation unit that calculates a base current Ib that is a base for setting the target current It, and an inertia for canceling the inertia moment of the electric motor 110. An inertia compensation current calculation unit 22 that calculates the compensation current Is and a damper compensation current calculation unit 23 that calculates a damper compensation current Id that limits the rotation of the electric motor 110 are provided.

  Further, the target current calculation unit 20 determines a temporary target current Itf that is a temporary target current based on the values calculated by the base current calculation unit 21, the inertia compensation current calculation unit 22, and the damper compensation current calculation unit 23. A temporary target current determination unit 25 is provided. In addition, the target current calculation unit 20 includes a phase compensation unit 26 that compensates for the phase of the detected torque T detected by the torque sensor 109.

The target current calculation unit 20 includes a friction compensation current setting unit 27 that sets a friction compensation current If, which will be described later. Further, the target current calculation unit 20 finally calculates the target current It based on the temporary target current Itf determined by the temporary target current determination unit 25 and the friction compensation current If set by the friction compensation current setting unit 27. A final target current determining unit 28 for determining is provided.
The target current calculation unit 20 receives a torque signal Td, a vehicle speed signal v, a steering angle signal θsd, a rotation speed signal Vms, and the like. In addition, the target current calculation unit 20 is input with the travel distance of the automobile 1 and the number of times the ignition is turned on, which is the number of times the ignition switch provided in the automobile 1 is turned on.

FIG. 4 is a schematic diagram of a control map showing the correspondence between the detected torque T and the vehicle speed Vc, and the base current Ib.
The base current calculation unit 21 calculates a base current Ib based on the torque signal Ts obtained by phase compensation of the torque signal Td by the phase compensation unit 26 and the vehicle speed signal v from the vehicle speed sensor 170. That is, the base current calculation unit 21 calculates the base current Ib corresponding to the phase-compensated detection torque T and the vehicle speed Vc. Note that the base current calculation unit 21 generates, for example, a phase compensated detection torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and base current, which are previously created based on empirical rules and stored in the ROM. The base current Ib is calculated by substituting the detected torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v) into the control map illustrated in FIG. 4 showing the correspondence with Ib.

  The inertia compensation current calculation unit 22 calculates an inertia compensation current Is for canceling the moment of inertia of the electric motor 110 and the system based on the torque signal Ts and the vehicle speed signal v. That is, the inertia compensation current calculation unit 22 calculates the inertia compensation current Is according to the detected torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v). Note that the inertia compensation current calculation unit 22 generates, for example, the detected torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the inertia compensation current Is, which are previously created based on empirical rules and stored in the ROM. The inertia compensation current Is is calculated by substituting the detected torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v) into a control map indicating the correspondence between the two.

  The damper compensation current calculation unit 23 calculates a damper compensation current Id that limits the rotation of the electric motor 110 based on the torque signal Ts, the vehicle speed signal v, and the rotation speed signal Vms of the electric motor 110. That is, the damper compensation current calculation unit 23 calculates the damper compensation current Id corresponding to the detected torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the rotational speed Vm (rotational speed signal Vms) of the electric motor 110. calculate. The damper compensation current calculation unit 23 is, for example, a detection torque T (torque signal Ts), a vehicle speed Vc (vehicle speed signal v), and a rotation speed Vm (rotation) that are previously created based on empirical rules and stored in the ROM. By substituting the detected torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the rotational speed Vm (rotational speed signal Vms) into a control map indicating the correspondence between the speed signal Vms) and the damper compensation current Id. A damper compensation current Id is calculated.

The temporary target current determination unit 25 includes a base current Ib calculated by the base current calculation unit 21, an inertia compensation current Is calculated by the inertia compensation current calculation unit 22, and a damper calculated by the damper compensation current calculation unit 23. A temporary target current Itf is determined based on the compensation current Id. For example, the temporary target current determination unit 25 determines the current obtained by adding the inertia compensation current Is to the base current Ib and subtracting the damper compensation current Id as the temporary target current Itf.
The friction compensation current setting unit 27 will be described in detail later.

  The final target current determination unit 28 finally determines the target current It based on the temporary target current Itf determined by the temporary target current determination unit 25 and the friction compensation current If set by the friction compensation current setting unit 27. To do. The final target current determination unit 28 according to the present embodiment adds the friction compensation current If set by the friction compensation current setting unit 27 to the temporary target current Itf determined by the temporary target current determination unit 25. The obtained current is determined as the target current It.

Next, the control unit 30 will be described in detail.
FIG. 5 is a schematic configuration diagram of the control unit 30.
As shown in FIG. 5, the control unit 30 includes a motor drive control unit 31 that controls the operation of the electric motor 110, a motor drive unit 32 that drives the electric motor 110, and an actual current Im that actually flows through the electric motor 110. And a motor current detection unit 33 for detection.
The motor drive control unit 31 is based on a deviation between the target current It finally determined by the target current calculation unit 20 and the actual current Im supplied to the electric motor 110 detected by the motor current detection unit 33. A feedback (F / B) control unit 40 that performs feedback control, and a PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110.

  The feedback control unit 40 includes a deviation calculating unit 41 for obtaining a deviation between the target current It finally determined by the target current calculating unit 20 and the actual current Im detected by the motor current detecting unit 33, and the deviation is A feedback (F / B) processing unit 42 that performs feedback processing so as to be zero.

The feedback (F / B) processing unit 42 performs feedback control so that the target current It and the actual current Im match. For example, the feedback (F / B) processing unit 42 is proportional to the deviation calculated by the deviation calculating unit 41. Is proportionally processed, integrated by an integral element, and these values are added by an addition operation unit.
The PWM signal generation unit 60 generates a PWM signal for driving the electric motor 110 by PWM (pulse width modulation) based on the output value from the feedback control unit 40, and outputs the generated PWM signal.

The motor drive unit 32 is a so-called inverter, and includes, for example, six independent transistors (FETs) (not shown) as switching elements, and three of the six transistors are connected to the positive-side line of the power source and each phase. The other three transistors are connected to the electric coil of each phase and the negative side (ground) line of the power source. Then, the driving of the electric motor 110 is controlled by driving the gates of two transistors selected from the six and switching the transistors.
The motor current detection unit 33 detects the value of the actual current Im flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor connected to the motor drive unit 32.

Next, the friction compensation current setting unit 27 will be described in detail.
The speed reduction mechanism 111 described above includes, for example, a resin worm wheel (not shown) fixed to the pinion shaft 106 and a metal worm gear (not shown) fixed to the output shaft of the electric motor 110. Yes. In the speed reduction mechanism 111 configured as described above, for example, it is conceivable that the engagement between the worm wheel and the worm gear is deteriorated due to aged deterioration of the resin worm wheel, and the friction is increased. When the friction of the speed reduction mechanism 111 increases, when the road surface reaction force received by the front wheels 150 from the road surface and the drive torque of the electric motor 110 are the same, the driver's steering torque applied to the steering wheel 101 of the steering device 100 is Increased by the amount of the friction increase phase.

FIG. 6 is a diagram showing the relationship between the thrust for moving the rack shaft 105 and the steering torque Tu of the driver in the steering device 100.
FIG. 7 is a diagram illustrating a relationship between the driver's steering torque Tu and the transmission torque Tt transmitted from the drive torque Tm of the electric motor 110 to the pinion shaft 106 when the thrust of the rack shaft 105 is constant. .
In FIG. 6, the relationship between the steering torque Tu of the driver at the beginning of use of the steering apparatus 100 including the electric motor 110 and the speed reduction mechanism 111 and the thrust of the rack shaft 105 is indicated by a solid line, and the friction of the speed reduction mechanism 111 is increased. In this case, the relationship between the driver's steering torque Tu and the thrust of the rack shaft 105 is indicated by a broken line.
In FIG. 7, the relationship between the steering torque Tu and the transmission torque Tt of the driver at the beginning of use of the steering device 100 including the electric motor 110 and the speed reduction mechanism 111 (no increase in friction of the speed reduction mechanism 111) is indicated by a solid line. The relationship between the driver's steering torque Tu and the transmission torque Tt when the friction of the mechanism 111 increases is indicated by a broken line.

  As shown in FIG. 6, when the thrust of the rack shaft 105 is the same, the value of the broken line is larger than the value of the steering torque Tu of the driver shown by the solid line in FIG. The difference between the solid-line steering torque Tu value and the broken-line steering torque Tu value is considered to be an increase in the driver's steering torque Tu due to an increase in the friction of the speed reduction mechanism 111.

  The friction compensation current setting unit 27 uses the assist force corresponding to the increase in the friction of the speed reduction mechanism 111 in order to prevent the driver's steering torque Tu from increasing due to the increase in the friction of the speed reduction mechanism 111. A friction compensation current If for increasing is set. In other words, the friction compensation current If is a current applied to the electric motor 110 in order to offset an increase in the driver's steering torque Tu due to an increase in friction due to deterioration over time of the speed reduction mechanism 111. The absolute value of the target current It is largely corrected by the friction compensation current If, so that the driver's steering torque Tu is reduced, and the broken line shown in FIG. 6 overlaps the solid line.

FIG. 8 is a schematic configuration diagram of the friction compensation current setting unit 27.
The friction compensation current setting unit 27 includes an aging deterioration determination unit 271 that determines the aging deterioration of the speed reduction mechanism 111, a current motor torque calculation unit 272 that calculates the current drive torque Tmn of the electric motor 110, and an electric motor at the beginning of use. And an initial motor torque calculation unit 273 that calculates a drive torque Tmf of 110. Further, the friction compensation current setting unit 27 is based on the current driving torque Tmn calculated by the current motor torque calculating unit 272 and the initial driving torque Tmf calculated by the initial motor torque calculating unit 273, and the speed reduction mechanism 111. The friction increase equivalent torque calculation unit 274 calculates the friction increase equivalent torque Tf, which is the torque corresponding to the increase in the friction. Further, the friction compensation current setting unit 27 calculates the friction compensation current If necessary to cancel the friction increase equivalent torque Tf calculated by the friction increase equivalent torque calculation unit 274 with the drive torque of the electric motor 110. A current calculation unit 275 is included.

  The aging degradation determination unit 271 causes aging degradation when the travel distance of the automobile 1 equipped with the steering device 100 is equal to or greater than a predetermined specified distance and the number of ignition ON times is equal to or greater than a predetermined specified number of times. It is determined that

The current motor torque calculator 272 substitutes the actual current Im supplied to the electric motor 110 detected by the motor current detector 33 and a predetermined motor torque constant Kt into the following equation (1) to The drive torque Tmn of the electric motor 110 is calculated.
Tmn = Im × Kt (1)

  The initial motor torque calculation unit 273, for example, generates the initial characteristics before the start of use based on an empirical rule and stores them in the ROM, and the driver's steering torque Tu and transmission as shown by the solid line in FIG. The transmission torque Tt is calculated by substituting the steering torque Tu of the driver detected by the torque sensor 109 into the control map indicating the correspondence with the torque Tt. The initial motor torque calculation unit 273 is based on an empirical rule and is stored in the ROM in advance, and the driver's steering torque Tu detected by the torque sensor 109 is calculated based on the relational expression between the driver's steering torque Tu and the transmission torque Tt. The transmission torque Tt may be calculated by substituting the steering torque Tu. In the initial stage of use, the torque cross due to friction of the speed reduction mechanism 111 due to aging degradation is zero, and the transmission torque Tt is the same as the drive torque Tmf of the electric motor 110 in the initial stage of use. The torque Tt is set as the driving torque Tmf of the electric motor 110 at the beginning of use.

The friction increase equivalent torque calculation unit 274 calculates the current drive torque Tmn of the electric motor 110 calculated by the current motor torque calculation unit 272, and the drive torque Tmf of the electric motor 110 at the start of use calculated by the initial motor torque calculation unit 273. Is substituted into the following equation (2) to calculate the friction increase equivalent torque Tf.
Tf = Tmn−Tmf (2)

The reason for calculating the friction increase equivalent torque Tf using the equation (2) is as follows.
The relationship between the transmission torque Tt transmitted from the drive torque Tm of the electric motor 110 to the pinion shaft 106, the driver's steering torque Tu, and the road surface reaction force TR is expressed by the following equation (3).
TR = Tu + Tt (3)

If the torque cross due to the friction of the speed reduction mechanism 111 is zero, the transmission torque Tt becomes the same as the driving torque Tm of the electric motor 110. Therefore, the driving torque Tm of the electric motor 110, the steering torque Tu of the driver, and the road surface reaction force The relationship with TR is as the following formula (3) ′.
TR = Tu + Tm (3) ′
Therefore, when the road surface reaction force TR at the beginning of use of the steering device 100 is the road surface reaction force TR0, when the drive torque Tm of the electric motor 110 is the drive torque Tmf and the driver's steering torque Tu is the steering torque Tu0, Equation (4) is obtained.
TR0 = Tu0 + Tmf (4)

On the other hand, when the road surface reaction force TR at which the friction of the speed reduction mechanism 111 is increased is the road surface reaction force TR1, the driving torque Tm of the electric motor 110 is the driving torque Tmn, and the steering torque Tu of the driver is the steering torque Tu1. Since the transmission torque Tt is a value obtained by subtracting the friction increase equivalent torque Tf from the drive torque Tmn (Tt = Tmn−Tf), the following equation (5) is obtained.
TR1 = Tu1 + (Tmn−Tf) (5)

In the equations (4) and (5), if the road surface reaction force TR0 and the road surface reaction force TR1 are the same, the following equation (6) is obtained.
Tu0 + Tmf = Tu1 + (Tmn−Tf) (6)
Further, in the equation (6), when Tu0 = Tu1 is set so that the driver's steering torque Tu at the beginning of use is the same as when the friction of the speed reduction mechanism 111 is increased, the above equation (2) is obtained.

The friction compensation current calculation unit 275, when the friction increase equivalent torque Tf calculated by the friction increase equivalent torque calculation unit 274 is equal to or greater than a predetermined specified torque, corresponds to the friction increase corresponding to the friction increase equivalent torque calculation unit 274. The friction compensation current If is calculated by substituting the torque Tf and a predetermined motor torque constant Kt into the following equation (7).
If = Tf / Kt (7)

Next, the procedure of the friction compensation current calculation process performed by the friction compensation current setting unit 27 will be described using a flowchart.
FIG. 9 is a flowchart showing a friction compensation current calculation process performed by the friction compensation current setting unit 27.
The friction compensation current setting unit 27 repeatedly executes the friction compensation current calculation process shown in FIG. 9 at regular time intervals (for example, 4 milliseconds).

  The friction compensation current setting unit 27 determines whether or not the travel distance of the automobile 1 on which the steering device 100 is mounted is equal to or greater than a specified distance (step (hereinafter simply referred to as “S”) 101). When the travel distance of the automobile 1 is equal to or greater than the specified distance (Yes in S101), the friction compensation current setting unit 27 determines whether or not the number of ignition ON is equal to or greater than the specified number (S102). If it is determined that the number of times the ignition is ON is equal to or greater than the specified number (Yes in S102), the friction compensation current setting unit 27 executes the processes after S103. The processes of S101 and S102 are processes performed by the aging deterioration determination unit 271. The aged deterioration determination unit 271 determines that the traveling distance of the automobile 1 is equal to or greater than the specified distance in S101 and determines that the ignition ON number of times is equal to or greater than the specified number of times in S102. Is determined to have occurred.

  In the process of S103, the friction compensation current setting unit 27 calculates the current drive torque Tmn of the electric motor 110 (S103). This is a process performed by the current motor torque calculation unit 272. The current motor torque calculation unit 272 substitutes the actual current Im supplied to the electric motor 110 detected by the motor current detection unit 33 and a predetermined motor torque constant Kt into the above-described equation (1), thereby The drive torque Tmn of the electric motor 110 is calculated.

  In the process of S104, the friction compensation current setting unit 27 calculates the drive torque Tmf of the electric motor 110 at the beginning of use (S104). This is a process performed by the initial motor torque calculation unit 273. The initial motor torque calculation unit 273 displays, for example, a driver's steering torque Tu detected by the torque sensor 109 in a control map indicating the correspondence between the driver's steering torque Tu and the transmission torque Tt as shown by a solid line in FIG. Is substituted to calculate the transmission torque Tt. At the beginning of use, the torque cross due to the friction of the speed reduction mechanism 111 is zero, and the transmission torque Tt is the same as the drive torque Tmf of the electric motor 110 at the beginning of use, so the calculated transmission torque Tt is used. The initial driving torque Tmf of the electric motor 110 is assumed.

  In the process of S105, the friction compensation current setting unit 27 calculates the friction increase equivalent torque Tf by subtracting the drive torque Tmf of the electric motor 110 at the beginning of use from the current drive torque Tmn of the electric motor 110 (S105). . This is a process performed by the friction increase equivalent torque calculation unit 274.

  Thereafter, the friction compensation current setting unit 27 determines whether or not the friction increase equivalent torque Tf calculated in S105 is equal to or greater than a specified torque (S106). If the friction increase equivalent torque Tf is equal to or greater than the specified torque (Yes in S106), the friction compensation current If is calculated. This is a process performed by the friction compensation current calculation unit 275, and the friction compensation current is calculated by substituting the friction increase equivalent torque Tf calculated in S105 and a predetermined motor torque constant Kt into the above equation (7). If is calculated (S107).

The friction compensation current setting unit 27 stores the friction compensation current If calculated by the above-described method in a storage area such as a RAM.
Then, the final target current determination unit 28 determines a value obtained by adding the temporary target current Itf and the friction compensation current If stored in a storage area such as a RAM as the target current It.

  In the steering device 100 configured as described above, the friction compensation current If that generates the assist force that cancels out the steering torque Tu of the driver that increases due to the increase in the friction of the speed reduction mechanism 111 is the target. It is added to the current It. As a result, even if the friction of the speed reduction mechanism 111 increases, the driver's steering torque is suppressed from increasing. That is, the steering device 100 configured as described above can suppress an increase in the driver's steering load due to an increase in friction of the speed reduction mechanism 111.

In the above-described embodiment, the friction compensation current setting unit 27 calculates the friction increase equivalent torque Tf based on the equation (2). However, the present invention is not particularly limited to this mode. For example, the friction compensation current setting unit 27 may calculate the friction increase equivalent torque Tf as follows.
FIG. 10 is a schematic diagram of a control map showing a correspondence relationship between the vehicle speed Vc, the steering angle θs, and the road surface reaction force TR received by the front wheels 150 from the road surface.
The friction compensation current setting unit 27 first determines the current road surface reaction force TR1 at which the friction of the speed reduction mechanism 111 has increased based on the vehicle speed signal v from the vehicle speed sensor 170 and the steering angle signal θsd from the steering angle sensor 180. calculate. For example, the friction compensation current setting unit 27 adds the vehicle speed Vc (vehicle speed signal v) and the steering angle θs (steering angle signal) to the control map illustrated in FIG. The current road reaction force TR1 is calculated by substituting θsd).
Then, the friction compensation current setting unit 27 calculates the calculated road surface reaction force TR1, the driver's steering torque Tu1 detected by the torque sensor 109, and the current driving torque Tmn of the electric motor 110 calculated using the equation (1). Then, the friction increase equivalent torque Tf is calculated by substituting it into the above equation (5) (Tf = Tu1 + Tmn-TR1).

  In the above-described embodiment, the case where the control for correcting the steering torque Tu of the driver that increases due to the increase in the friction of the speed reduction mechanism 111 is applied to the pinion type electric power steering is described. There is no particular limitation. The present invention may be applied to other types of electric power steering devices such as a double pinion type and a rack assist type.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Target current calculation part, 21 ... Base current calculation part, 25 ... Temporary target current determination part, 27 ... Friction compensation current setting part, 28 ... Final target current determination part, 30 ... Control part, 100 ... Electric power steering device, 110 ... electric motor

Claims (6)

An electric motor;
A transmission unit for transmitting the driving torque of the electric motor as an auxiliary force for steering the steering wheel of the vehicle;
Control means for controlling the operation of the electric motor in consideration of the torque of the friction increase due to the torque cross, which is grasped based on the actual driving torque of the electric motor and the initial torque at the beginning of use of the electric motor;
An electric power steering apparatus comprising: An electric motor;
A transmission unit for transmitting the driving torque of the electric motor as an auxiliary force for steering the steering wheel of the vehicle;
When the aging deterioration of the transmission unit is large, considering the torque of the friction increase due to the aging that is grasped based on the actual driving torque of the electric motor and the initial torque at the beginning of use of the electric motor. Control means for controlling the operation of the electric motor;
An electric power steering apparatus comprising: The control means includes
Actual driving torque calculating means for calculating an actual driving torque that is an actual driving torque of the electric motor;
Initial torque calculating means for calculating the initial torque;
By subtracting the initial torque calculated by the initial torque calculating means from the actual driving torque calculated by the actual driving torque calculating means, a friction increase equivalent torque is calculated which is a friction increase torque due to aged deterioration. Torque calculating means;
The electric power steering apparatus according to claim 2, further comprising: A torque detecting means for detecting a steering torque of the steering wheel;
The electric power according to claim 3, wherein the actual drive torque calculating means calculates the actual drive torque based on a reaction force from the road surface received by the rolling wheels and a steering torque detected by the torque detecting means. Steering device. A torque detecting means for detecting a steering torque of the steering wheel;
The initial torque calculation means calculates the initial torque based on a predetermined correlation between the driving torque of the electric motor and the steering torque at the beginning of use and the steering torque detected by the torque detection means. The electric power steering apparatus according to claim 3 or 4, characterized in that: Further comprising aging deterioration determining means for determining aging deterioration of the transmission unit,
When the aging deterioration of the transmission unit detected by the aging deterioration determining means is small, the operation of the electric motor is controlled according to the steering of the steering wheel, and when the aging deterioration is large, the steering wheel 6. The electric power steering apparatus according to claim 2, wherein the operation of the electric motor is controlled in consideration of a torque corresponding to an increase in friction due to the aging in addition to the steering of the motor.

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