JP6966951B2 - Electric power steering device - Google Patents

Description

The present invention relates to an electric power steering device.

Conventionally, in order to suppress an excessive impact load from being applied to a rack and pinion of an electric power steering device, cushioning elastic members such as rubber are provided at both ends of the rack shaft.
For example, in the rack and pinion type power steering device described in Patent Document 1, the rack shaft is an annular stopper rubber made of synthetic resin, rubber, or the like having a predetermined width at positions adjacent to ball joints at both left and right ends thereof. It is equipped with. The stopper rubber is attached to the end of the stopper piece that is fitted into the inner peripheral portion of the right-extending cylindrical housing of the gear housing at the moving end of the movement to the left in the stroke of moving forward and backward in the left-right direction of the rack shaft. Further, at the moving end of the movement to the right, the left end of the left housing is in contact with each other. As a result, it is possible to prevent an excessive impact load from being generated on the rack and pinion or the like due to the rack shaft hitting the housing. As described above, the stopper rubber plays a role of protecting the transmission mechanism (reduction gear mechanism) such as the rack and pinion that transmits the rotational operation force of the steering wheel (handle) to the wheel from the impact load.

Japanese Unexamined Patent Publication No. 2006-117221

When the rack end hits the housing or the like at the moving end of the rack shaft, the driver feels the impact of the hit through the steering wheel. However, if this impact becomes excessively large, the steering feeling may deteriorate. Further, if this impact is excessively small, it becomes difficult for the driver to detect the state in which the rack shaft reaches the moving end. That is, it is preferable that this impact does not fluctuate.
An object of the present invention is to provide an electric power steering device in which the impact when the rack end hits is less likely to fluctuate.

For this purpose, the present invention has a rack shaft that steers a wheel by linear movement in a housing, and a transmission mechanism that transmits one-way rotational operation force of the steering wheel as one-way rolling power of the wheel. And, through the transmission mechanism, an electric motor in which a one-way rotational driving force is applied as a one-way rotational force of the wheel, and a one-way rotational operation force when a one-way rotational operation force is applied to the steering wheel. and a control means for controlling the driving of the electric motor to produce a rotational driving force of said control means, when the front Symbol rack shaft abuts on the housing, in advance kinetic energy of the said rack shaft immediately before collision It is an electric power steering device that controls the rotational driving force of the electric motor at the moving end of the rack shaft so as to have a predetermined target amount.

According to the present invention, it is possible to provide an electric power steering device in which the impact when the rack end hits the housing is less likely to fluctuate.

It is a figure which shows the schematic structure of the electric power steering apparatus which concerns on embodiment. It is a schematic block diagram of a control device. It is a schematic block diagram of the target current calculation part. It is a model diagram which shows the relationship between the rack axis and energy when the rack axis moves to the right direction (plus direction). It is a figure which shows the relationship between the position of a rack shaft, and the energy given by a rack shaft.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing a schematic configuration of an electric power steering device 100 according to an embodiment.
The electric power steering device 100 (hereinafter, may be simply referred to as “steering device 100”) is a steering device for arbitrarily changing the traveling direction of the vehicle, and in the present embodiment, the automobile as an example of the vehicle. The configuration applied to No. 1 is illustrated. Note that FIG. 1 is a view of the automobile 1 as viewed from the front.

The steering device 100 includes a wheel-shaped steering wheel (steering wheel) 101 operated by the driver to change the traveling direction of the automobile 1 and a steering shaft 102 integrally provided on the steering wheel 101. There is. Further, 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.

Further, the steering device 100 includes a tie rod 104 connected to each of the left and right wheels 150 as rolling wheels, and a rack shaft 105 connected to the tie rod 104. Further, the steering device 100 includes a pinion 106a that constitutes a rack and pinion mechanism together with a rack tooth 105a formed on the rack shaft 105. The pinion 106a is formed at the lower end of the pinion shaft 106. These rack shafts 105, pinion shafts 106, and the like function as a transmission mechanism that transmits the rotational operation force of the steering wheel 101 as the rolling power of the wheels 150.

Further, the steering device 100 has a steering gear box (housing) 107 for accommodating the pinion shaft 106. The pinion shaft 106 is connected to the lower connecting shaft 108 in the steering gear box 107 via the torsion bar 112. Then, inside the steering gear box 107, the steering torque T applied to the steering wheel 101 is based on the relative rotation angle between the lower connecting 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 to detect the above.

The rack teeth 105a formed in the central portion of the rack shaft 105 are contained in the steering gear box 107, and both ends of the rack shaft 105 project from the steering gear box 107, respectively. At both ends of the rack shaft 105, protrusions 105b having an outer shape larger than the openings of both end faces 107a in the left-right direction in the steering gear box 107 as seen in FIG. 1 are provided. Further, the protrusion 105b is provided with a stopper rubber 105c, which is an example of a cushioning elastic member that cushions an impact when the rack shaft 105 hits the steering gear box 107. Then, the stopper rubber 105c abuts on the end surface 107a in the left-right direction of the steering gear box 107, so that the amount of movement of the rack shaft 105 is restricted.
In this configuration in which the stopper rubber 105c is configured on the protruding portion 105b, the stopper rubber 105c can also be referred to as the rack end of the rack shaft 105.
Further, the stopper rubber 105c may be provided on the end surface 107a of the steering gear box 107.

Further, the steering device 100 has an electric motor 110 supported by the steering gear box 107, and a deceleration mechanism 111 that decelerates the driving force of the electric motor 110 and transmits it to the pinion shaft 106. The electric motor 110 according to this embodiment is a three-phase brushless motor. 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.

Further, the steering device 100 includes a control device 10 as an example of a control means for controlling the operation of the electric motor 110. The output signal from the torque sensor 109 described above is input to the control device 10. Further, the control device 10 has a vehicle speed sensor that detects the vehicle speed Vc, which is the moving speed of the vehicle 1, via a network (CAN) that transmits signals for controlling various devices mounted on the vehicle 1. An output signal v or the like from 170 is input.

The steering device 100 configured as described above drives the electric motor 110 based on the steering torque T detected by the torque sensor 109, and transmits the driving force (generated torque) of the electric motor 110 to the pinion shaft 106. As a result, the driving force (generated torque) of the electric motor 110 assists the driver in steering applied to the steering wheel 101. In this way, the electric motor 110 applies an assist force (auxiliary force) to the steering of the driver's steering wheel 101.

〔Control device〕
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 logic operation circuit including a CPU, ROM, RAM, backup RAM, and the like.
The control device 10 has a torque signal Td in which the steering torque T detected by the torque sensor 109 described above is converted into an output signal, and a vehicle speed signal in which the vehicle speed Vc detected by the vehicle speed sensor 170 is converted into an output signal. v etc. are input.

Then, the control device 10 calculates the target auxiliary torque based on the torque signal Td and the vehicle speed signal v, and calculates the target current It required for the electric motor 110 to supply the target auxiliary torque. It has 20 and a control unit 30 that performs feedback control and the like based on the target current It calculated by the target current calculation unit 20.
Further, the control device 10 includes a motor rotation speed calculation unit 70 that calculates the rotation speed Nm of the electric motor 110, and a rack shaft position detection unit 80 that detects the position of the rack shaft 105. The motor rotation speed calculation unit 70 calculates the rotation speed Nm of the electric motor 110 based on the output signal from the resolver that detects the rotation position of the rotor of the electric motor 110, which is a three-phase brushless motor, and rotates the rotor. The rotation speed signal Nms in which the speed Nm is converted into an output signal is output. The rack shaft position detection unit 80 grasps the rotational position of the electric motor 110 based on the output signal from the resolver, and the rotational driving force of the electric motor 110 is mechanically transmitted via the reduction mechanism 111 and the pinion shaft 106. The position p of the rack shaft 105 is detected, and the rack shaft position signal Ps in which the position p of the rack shaft 105 is converted into an output signal is output.

[Target current calculation unit]
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 that calculates a base current Ib that is a reference for setting the target current, and an inertia compensation current calculation unit 22 that calculates a current for canceling the inertial moment of the electric motor 110. And a damper compensation current calculation unit 23 that calculates a current that limits the rotation of the motor. Further, the target current calculation unit 20 determines the tentative target current Itf, which is a tentative 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 provisional target current determination unit 25 is provided. Further, the target current calculation unit 20 includes an energy compensation current calculation unit 27 that calculates an energy compensation current Ir, which is a current that adjusts the energy given by the rack shaft 105 based on the position and moving state of the rack shaft 105, and a provisional target current. The provisional target current Itf determined by the determination unit 25 and the final target current determination unit 28 that finally determines the target current It based on the energy compensation current Ir calculated by the energy compensation current calculation unit 27 are provided. ing.
A torque signal Td, a vehicle speed signal v, a rotation speed signal Nms, a rack shaft position signal Ps, and the like are input to the target current calculation unit 20.

The base current calculation unit 21 calculates the base current Ib based on the torque signal Ts whose phase compensation is the torque signal Td by the phase compensation unit 26 (see FIG. 3) and the vehicle speed signal v from the vehicle speed sensor 170. That is, the base current calculation unit 21 calculates the phase-compensated steering torque T and the base current Ib according to the vehicle speed Vc. The base current calculation unit 21 has, for example, phase-compensated steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and base current stored in the ROM, which are created in advance based on empirical rules. The base current Ib is calculated by substituting the steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v) into the control map showing the correspondence with Ib.

The inertia compensation current calculation unit 22 calculates the 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 steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v). The inertia compensation current calculation unit 22 includes, for example, steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and inertia compensation current Is, which are created in advance based on empirical rules and stored in the ROM. The inertia compensation current Is is calculated by substituting the steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v) into the control map showing the correspondence between the above.

The damper compensation current calculation unit 23 calculates the 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 Nms of the electric motor 110. That is, the damper compensation current calculation unit 23 obtains the damper compensation current Id according to the steering torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the rotation speed Nm (rotational speed signal Nms) of the electric motor 110. calculate. The damper compensation current calculation unit 23 has, for example, steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and rotation speed Nm (rotation), which are created in advance based on empirical rules and stored in the ROM. By substituting the steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and rotation speed Nm (rotational speed signal Nms) into the control map showing the correspondence between the speed signal Nms) and the damper compensation current Id. The damper compensation current Id is calculated.

The tentative 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. The tentative target current Itf is determined based on the compensation current Id. The tentative target current determination unit 25 determines, for example, the current obtained by adding the inertia compensation current Is and subtracting the damper compensation current Id to the base current Ib as the tentative target current Itf.
The energy compensation current calculation unit 27 will be described in detail later.

The final target current determination unit 28 finally determines the target current Itf based on the provisional target current Itf determined by the provisional target current determination unit 25 and the energy compensation current Ir calculated by the energy compensation current calculation unit 27. do. The final target current determination unit 28 according to the present embodiment is obtained by adding the energy compensation current Ir calculated by the energy compensation current calculation unit 27 to the provisional target current Itf determined by the provisional target current determination unit 25. The current is determined as the target current It.

[Control unit]
The control unit 30 detects a motor drive control unit (not shown) that controls the operation of the electric motor 110, a motor drive unit (not shown) that drives the electric motor 110, and an actual current Im that actually flows through the electric motor 110. It has a motor current detection unit (not shown).

The motor drive control unit feeds back based on the 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 20. It has a feedback (F / B) control unit (not shown) that controls. Further, the motor drive control unit has a PWM signal generation unit (not shown) that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110.

The motor drive unit is a so-called inverter, for example, six independent transistors (FETs) are provided as switching elements, and three of the six transistors are the positive electrode side line of the power supply and the electric coil of each phase. Connected between them, the other three transistors are connected to the electric coils of each phase and the negative electrode side (earth) line of the power supply. Then, the drive of the electric motor 110 is controlled by driving the gates of two transistors selected from the six and switching these transistors.
The motor current detecting unit detects the value of the actual current Im flowing through the electric motor 110 from the voltage generated across the shunt resistor connected to the motor driving unit.

[Energy compensation current calculation unit]
Next, the energy compensation current calculation unit 27 will be described in detail.
The final target current determination unit 28 according to the above-described embodiment is based on the provisional target current Itf determined by the provisional target current determination unit 25 and the energy compensation current Ir calculated by the energy compensation current calculation unit 27. To determine the target current It. As will be described in detail later, this is given by the rack shaft 105 at the time of hitting by adjusting the assist performed based on the steering torque T before the stopper rubber 105c of the rack shaft 105 hits the end surface 107a of the steering gear box 107. The intention is to adjust the energy so that the energy at the time of hitting is a predetermined amount.

More specifically, the control device 10 basically drives the electric motor 110 so as to generate a one-way rotational driving force when a one-way rotational operation force is applied to the steering wheel 101. Control. However, depending on the position p of the rack shaft 105, the moving speed of the rack shaft 105, and the like, the control device 10 of the electric motor 110 so as to make the energy given by the rack shaft 105 at the moving end of the rack shaft 105 a predetermined amount. Controls the rotational driving force. In this case, the moving end of the rack shaft 105 is a position where the stopper rubber 105c provided on the rack shaft 105 and the end surface 107a of the steering gear box 107 come into contact with each other. In this embodiment, it can be said that the moving end of the rack shaft 105 is a stopper rubber 105c provided on the rack shaft 105, and is a place where the stopper rubber 105c and the end surface 107a of the steering gear box 107 come into contact with each other. can.

Therefore, the energy compensation current calculation unit 27 calculates the energy compensation current Ir based on the position p of the rack shaft 105 and the moving state.
The energy compensation current calculation unit 27 basically calculates the energy given by the rack shaft 105 based on the speed of the rack shaft 105, and sets the energy compensation current Ir required for adjusting the energy.

Next, a method of calculating the energy given by the rack shaft 105 will be described.
In the following description, when the steering wheel (handle) 101 is rotated clockwise, the rack shaft 105 moves to the right as seen in FIG. 1, and the wheel 150 rotates clockwise, and the steering wheel (handle) 101 It is assumed that when the wheel is rotated counterclockwise, the rack shaft 105 moves to the left as seen in FIG. 1 and the wheel 150 rotates counterclockwise. Then, the case where the rack shaft 105 moves to the right as seen in FIG. 1 is defined as a positive direction, and the case where the rack shaft 105 moves to the left is defined as a negative direction.

FIG. 4 is a model diagram showing the relationship between the rack shaft 105 and energy when the rack shaft 105 moves to the right (plus direction). In this case, consider the case where the steering gear box 107 is fixed and the rack shaft 105 moves in the right direction (plus direction).
At this time, the energy F given by the rack shaft 105 can be calculated by the following equation (1). In the formula (1), m represents the mass of the rack shaft 105, and V represents the speed of the rack shaft 105. That is, here, the energy F given by the rack shaft 105 is used as the kinetic energy of the rack shaft 105. The velocity V of the rack shaft 105 can be obtained, for example, by time-differentiating the position p of the rack shaft 105.

Further, it is preferable to further add the driving energy applied from the electric motor 110 to the rack shaft 105 as the energy F given by the rack shaft 105. In this case, the energy F given by the rack shaft 105 can be calculated by the following equation (2). In formula (2), M represents the driving energy applied to the rack shaft 105 from the electric motor 110. That is, the formula (2) is a formula in which the driving energy applied to the rack shaft 105 from the electric motor 110 is added to the right side of the formula (1). This driving energy can be obtained from, for example, the rotation speed Nm of the electric motor 110.

Further, as the energy F given by the rack shaft 105, it is preferable to further add the driving energy applied from the steering wheel 101 to the rack shaft 105. In this case, the energy F given by the rack shaft 105 can be calculated by the following equation (3). In formula (3), H represents the driving energy applied from the steering wheel 101 to the rack shaft 105. That is, the equation (3) is an equation obtained by adding the driving energy applied from the steering wheel 101 to the rack shaft 105 to the right side of the equation (2). This driving energy can be obtained from, for example, the steering torque T.

Further, the energy compensation current calculation unit 27 controls the energy given by the rack shaft 105 at the moving end of the rack shaft 105 to a predetermined amount as follows, based on the energy F obtained as described above. To do.

First, the energy compensation current calculation unit 27 presets desirable energy when the stopper rubber 105c abuts on the end surface 107a of the steering gear box 107 at the moving end of the rack shaft 105. In the present embodiment, this desirable energy is set as the set energy Fr. This set energy Fr is a target amount of energy given by the rack shaft 105 at the moving end of the rack shaft 105. Then, the energy compensation current calculation unit 27 calculates the difference Fd between the above-mentioned energy F and the set energy Fr by the following equation (4).

Fd = F-Fr ... (4)

The energy compensation current calculation unit 27 calculates this difference Fd at a control start point set at a predetermined distance between the moving end and the moving end.

The energy compensation current calculation unit 27 calculates using the equation (4) in, for example, a control map showing the correspondence between the difference Fd and the energy compensation current Ir, which is created in advance based on an empirical rule and stored in the ROM. The energy compensation current Ir is calculated by substituting the difference Fd. The relationship between the difference Fd and the energy compensation current Ir is, for example, a relationship in which the energy compensation current Ir increases in the minus direction as the difference Fd increases in the plus direction.

FIG. 5 is a diagram showing the relationship between the position of the rack shaft 105 and the energy F given by the rack shaft 105. In the figure, the horizontal axis represents the position of the stopper rubber 105c as the position of the rack shaft 105, and the vertical axis represents the energy F.
The solid lines shown by P1 to P3 in the figure indicate the change in energy F with respect to the position of the stopper rubber 105c.

Of these, the solid line P1 shows an example in which the energy F at the control start point is larger than the set energy Fr. In this case, the difference Fd calculated by the equation (4) becomes a positive value, and the energy compensation current Ir output from the energy compensation current calculation unit 27 becomes a negative value. Therefore, the target current It determined by the final target current determination unit 28 is smaller than the temporary target current Itf determined by the provisional target current determination unit 25, and the assist force is reduced. Therefore, as the rack shaft 105 approaches the end surface 107a of the steering gear box 107 from the control start point, the energy F decreases. When the stopper rubber 105c of the rack shaft 105 hits the end surface 107a of the steering gear box 107, the energy F becomes the set energy Fr.

Further, the solid lines P2 and P3 show an example in which the energy F at the control start point is smaller than the set energy Fr. In this case, the difference Fd calculated by the equation (4) becomes a negative value, and the energy compensation current Ir output from the energy compensation current calculation unit 27 becomes a positive value. Therefore, the target current It determined by the final target current determination unit 28 becomes larger than the temporary target current Itf determined by the provisional target current determination unit 25, and the assist force increases. Therefore, the energy F increases as the rack shaft 105 approaches the end surface 107a of the steering gear box 107 from the control start point. When the stopper rubber 105c of the rack shaft 105 hits the end surface 107a of the steering gear box 107, the energy F becomes the set energy Fr. Normally, as the wheel 150 approaches the moving end of the rack shaft 105, the twist of the wheel 150 increases and the repulsive force from the wheel 150 increases, so that the driver tends to feel that the steering wheel 101 has become heavier (the assist force is increased). It is easy to run out). In this case, the driver needs to apply a large rotational operation force to the steering wheel 101. However, by increasing the assist force and increasing the energy F, the shortage of the assist force is eliminated, so that the steering feeling is less likely to change even when approaching the moving end of the rack shaft 105.

At this time, since the difference Fd is smaller in the case of the solid line P3 than in the case of the solid line P2 (the difference Fd is a negative value and therefore becomes larger as an absolute value), the energy compensation current Ir becomes larger. , Greater assist power is given.

As described above, in the present embodiment, the energy compensation current Ir is determined based on the difference Fd at the control start point, and the target current It is adjusted accordingly. As a result, the assist force is adjusted, and the energy when the stopper rubber 105c of the rack shaft 105 hits the end surface 107a of the steering gear box 107 can be adjusted. As a result, the impact when the stopper rubber 105c hits the end surface 107a of the steering gear box 107 is less likely to fluctuate.

In the above example, the energy compensation current Ir is determined from the difference Fd at the control start point, but the difference Fd is further calculated on the side closer to the end face 107a of the steering gear box 107 from the control start point, and a new energy compensation current is obtained. Ir may be determined, and the target current It may be obtained based on this. That is, in this case, the energy compensation current Ir is calculated a plurality of times. Thereby, the energy F can be controlled with higher accuracy. Then, the energy F when the stopper rubber 105c of the rack shaft 105 hits the end surface 107a of the steering gear box 107 becomes easier to approach the set energy Fr.

Further, the set energy Fr may be set in advance as a constant value, but may be determined based on the vehicle state. In this case, examples of the vehicle state include the vehicle speed Vc, the speed of the wheels 150, the yaw rate, the acceleration of the vehicle, the temperature of the rack shaft 105, the outside air temperature in the vicinity of the rack shaft 105, and the like. That is, the value of the set energy Fr is determined for each of these vehicle states, and the energy compensation current calculation unit 27 selects the set energy Fr according to the vehicle state.

Further, in the above-mentioned example, the relationship between the position of the rack shaft 105 and the energy F given by the rack shaft 105 when the rack shaft 105 moves in the right direction (plus direction) has been described, but the rack shaft 105 is in the left direction (in the left direction). The same is true when moving in the negative direction). That is, when the rack shaft 105 moves to the left (minus direction), the protruding portion 105b of the rack shaft 105 located on the right side in FIG. 1 is the steering gear box 107 located on the right side in FIG. This is the case when it hits the end face 107a of. In this case as well, the energy F can be obtained in the same manner.
Further, in the above-mentioned example, the case where the stopper rubber 105c is provided on the protruding portion 105b of the rack shaft 105 has been described, but the stopper rubber 105c may not be provided. In this case as well, the above-mentioned matters can be applied in the same manner. In this case, the moving end becomes the protruding portion 105b, and the protruding portion 105b can be referred to as a rack end.

Although the rack and pinion type is exemplified in the above embodiment, it can be similarly adopted for other rack assist type, dial pinion type and the like.

Further, the components of the control device 10 in each of the above-described embodiments may be realized by hardware or software. Further, when a part or all of the components of the present invention are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. The "computer-readable recording medium" is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but is an internal storage device in a computer such as various RAMs or ROMs, or an external storage device such as a hard disk. Also includes.

10 ... Control device, 20 ... Target current calculation unit, 21 ... Base current calculation unit, 22 ... Initial compensation current calculation unit, 23 ... Damper compensation current calculation unit, 25 ... Temporary target current determination unit, 27 ... Energy compensation current calculation unit , 28 ... Final target current determination unit, 30 ... Control unit, 100 ... Electric power steering device, 105 ... Rack shaft, 107 ... Steering gear box, 110 ... Electric motor

Claims (7)

A transmission mechanism that has a rack shaft that steers the wheels by linear movement in the housing and transmits the rotational operation force of the steering wheel in one direction as the rolling power in one direction of the wheels.
An electric motor in which a one-way rotational driving force is applied as a one-way rolling power of the wheel via the transmission mechanism.
A control means for controlling the driving of the electric motor so as to generate the rotation driving force in one direction when the rotation operating force in one direction is applied to the steering wheel.
Equipped with
Wherein, when the front Symbol rack shaft abuts the housing, so that the target amount of kinetic energy predetermined to have said rack shaft immediately before the collision, the rotation of the electric motor at the moving end of said rack shaft An electric power steering device that controls the driving force. The kinetic energy, electric power steering apparatus according to claim 1 wherein is an electric motor obtained by pressurizing taste drive energy applied to the rack shaft. The kinetic energy, electric power steering apparatus according to claim 2 from the steering wheel is obtained by pressurizing taste drive energy applied to the rack shaft. The electric power steering device according to claim 1, wherein the control means controls based on the difference between the kinetic energy and the target amount. The electric power steering device according to claim 4 , wherein the target amount is determined based on a vehicle condition. The electric power steering device according to claim 4 , wherein the control means controls based on the difference between the moving end and a control start point set at a predetermined distance from the moving end. A tentative target current determination unit that determines a tentative target current as a tentative target current that drives an electric motor so as to generate the one-way rotational driving force when a unidirectional rotational operation force is applied to the steering wheel. ,
When the rack shaft to steer the wheels by linear movement in the housing abuts the housing, so that the target amount of kinetic energy predetermined to have said rack shaft immediately before the collision, the energy to calculate the energy compensation current Compensation current calculation unit and
A final target current determination unit that determines the final target current as the final target current for driving the electric motor based on the provisional target current and the energy compensation current.
An electric power steering device equipped with.

Images