JPH10310073A - Electric power steering - Google Patents

Abstract

(57) [Problem] To provide an electric power steering device capable of transmitting steering information of a vehicle to a driver through a steering operation while reducing a steering force required for the steering operation of the driver. thing. SOLUTION: A steering mechanism 2 for mechanically transmitting a steering torque T1 generated by an operation of a steering wheel 21 to steer a wheel 31, and a wheel 3 by applying an assist force F2 to the steering mechanism 2.
1, a steering torque sensor 52 for detecting a steering torque T1, a function for detecting a load torque T2 of the motor 41, and a steering mechanism 2 based on the detected steering torque T1 and load torque T2. The function of detecting the total load F applied, and the steering torque T1 for the detected full load F
An ECU 50 having a function of setting a target value of the load torque T2 so that the steering force F1 and the assist force F2 of the vehicle have a predetermined ratio, and a function of controlling the motor 41 so that the load torque T2 matches the target value. It is comprised including.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for a vehicle.

[0002]

2. Description of the Related Art Conventionally, as an electric power steering device for a vehicle, an electric power steering device described in Japanese Patent Application Laid-Open No. 63-28761 is known. In this electric power steering apparatus, as shown in FIG. 1 of the publication, a steering shaft, a torsion bar, and a pinion are mechanically connected to a steering wheel, which is a steering wheel (hereinafter, simply referred to as a “handle”). The steering force applied to the steering wheel is transmitted to the rack via the steering shaft, the pinion and the like. Further, a strain gauge for detecting a steering torque is installed on the steering shaft, and the controller operates the electric motor based on a detection signal of the strain gauge. Then, the steering of the steering wheel of the driver is reduced by assisting the steering force transmitted mechanically by operating the electric motor to steer the wheels.

[0003]

However, the conventional electric power steering system has a problem that it is difficult for a driver to recognize a running state through a steering wheel. For example, in the above-described electric power steering device, when a steered wheel receives a reaction force from a road surface or the like while the vehicle is traveling, the driver increases the steering torque by receiving the reaction force, so that the load torque of the electric motor is increased. Also increase accordingly.
At this time, the load torque of the electric motor is determined based only on the driver's steering torque, and is a larger force applied to the rack than the steering torque. For this reason, even if the reaction force from the road surface or the like slightly fluctuates, the driver can hardly sense the reaction force through the steering wheel, and cannot perform an appropriate steering operation according to a situation outside the vehicle.

Accordingly, the present invention has been made to solve the above problems, and aims at reducing the steering force required for the driver to operate the steering wheel while providing the driver with a vehicle through the steering operation. It is an object of the present invention to provide an electric power steering device capable of transmitting travel information of a vehicle.

[0005]

In order to achieve the above object, an electric power steering apparatus according to the present invention provides a steering mechanism for turning a wheel by mechanically transmitting a steering torque generated by operating a steering wheel. A motor that assists the turning of the wheels by applying an assist force to the steering mechanism; a steering torque detecting unit that detects a steering torque; a load torque detecting unit that detects a load torque of the motor; A full load detecting means for detecting a total load applied to the steering mechanism based on the load torque; and a target value of the load torque such that a steering ratio and an assist force by the steering torque have a predetermined ratio with respect to the detected total load. It is characterized by comprising a torque setting means for setting and a motor control means for controlling the motor so that the load torque matches the target value.

According to the present invention, when a wheel receives a reaction force from a road surface or the like, or when the reaction force fluctuates, a steering mechanism is provided from outside the vehicle on the basis of the detected steering torque and the motor load torque. The output of the motor is controlled such that the steering force and the assist force by the steering torque bear the entire load applied to the motor at a predetermined ratio. Therefore, the driver bears a part of the reaction force from the road surface or the like with the steering torque, and the driver can surely sense the reaction force through the operation of the steering wheel. Therefore, the driver can recognize the running state of the vehicle and can perform an appropriate steering operation according to the situation outside the vehicle.

The electric power steering apparatus according to the present invention includes a steering mechanism for mechanically transmitting a steering torque generated by operating a steering wheel to steer a wheel, and applying an assist force to the steering mechanism to steer the wheel. And a steering torque detecting means for detecting the steering torque, and a steering torque and a steering torque so that the steering force and the assist force by the steering torque bear at a predetermined ratio with respect to a total load applied to the steering mechanism from outside the vehicle. Torque setting means for setting a new target value of the motor load torque based on the target value of the motor load torque set at the present time; and driving the motor so that the motor load torque matches the new target value. And a motor control means for controlling.

According to the present invention, when the wheel receives a reaction force from the road surface or the like, or when the reaction force fluctuates, the target value of the motor load torque is set based on the detected steering torque by the steering operation. The drive of the motor is controlled so that the steering load and the assisting force by the steering torque bear the entire load applied to the steering mechanism from outside the vehicle at a predetermined ratio.
Therefore, the driver bears a part of the reaction force from the road surface or the like with the steering torque, and the driver can surely sense the reaction force through the operation of the steering wheel. Therefore, the driver can recognize the running state of the vehicle and can perform an appropriate steering operation according to the situation outside the vehicle.

Further, the electric power steering apparatus according to the present invention includes a steering position detecting means for detecting a steering position of the steering wheel, and a steering wheel when the steering wheel is at a predetermined steering position when no steering torque is applied. Steering wheel angular velocity control means for controlling rotation in a direction at a predetermined angular velocity.

According to the present invention, when the steering torque becomes zero due to the driver releasing the steering wheel, the steering wheel is controlled to rotate at a predetermined angular velocity. Therefore, if the steered wheels are receiving a reaction force from the road surface,
The reaction force prevents the steering wheel from turning suddenly,
Stable vehicle traveling becomes possible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same elements are denoted by the same reference numerals, and the description is omitted. Also,
The dimensional ratios in the drawings do not always match those described.

(First Embodiment) FIG. 1 shows a schematic diagram of an electric power steering apparatus according to the present embodiment. In FIG. 1, a power steering device 1 includes a steering mechanism 2 that mechanically transmits a steering torque T1 (steering force) generated by operating a steering handle 21 to steer the wheels 31, 31. The steering mechanism 2 has a structure in which a steering shaft 22 is connected to a handle 21, and the steering torque T 1 of the handle 21 is transmitted into the steering gear box 23 through the steering shaft 22. A pinion 2 is provided at the lower end of the steering shaft 22.
2 a is provided and meshes with a rack bar 24 installed in the steering gear box 23. Rack bar 2
Reference numeral 4 denotes a bar member that moves linearly in the horizontal direction by the rotation of the pinion 22a, and is disposed toward the left and right wheels 31, 31. Both ends of the rack bar 24 extend from the steering gear box 23, and a tie rod 25 and a knuckle arm 26 are attached thereto. According to such a steering mechanism 2, the steering torque T 1 is increased by the driver's operation of the steering wheel 21.
To the steering force F1 via the pinion rack mechanism.
And transmitted to the rack bar 24. Then, the steering force F1 is applied to the tie rod 25 and the knuckle arm 2.
6 and mechanically transmitted to the wheels 31, 31 via
The wheels 31, 31 are steered. The handle 21
Not only the steering mechanism 2 but also other mechanisms may be used as long as the wheels 31 can be mechanically steered according to the steering torque.

The power steering device 1 is provided with a motor 41 which applies an assist force F2 to the steering mechanism 2 to assist the steering mechanism 2 in turning the wheels 31, 31. Motor 4
1 is provided in a steering gear box 23, and its load torque (output torque) T2 is converted into an assist force F2 via a predetermined gear or the like and transmitted to the rack bar 24. As the motor 41, for example, a DC motor is used. In this case, by controlling the rotation drive by the voltage control, the current value or the number of rotations when the motor 41 is driven can be measured, and the load torque T2 of the motor 41 can be detected. As the motor 41, any motor other than the DC motor may be used as long as the load torque T2 can be detected from the supply voltage value, the supply current value, the number of revolutions, or the like. In some cases, the motor 41 is provided so as to transmit the load torque T2 to the steering shaft 22 to assist in turning the wheels 31.

As shown in FIG. 1, the steering shaft 22
A steering position sensor 51 and a steering torque sensor 52 are provided in the upper part of FIG. The steering position sensor 51 is a sensor for detecting the steering position of the steering wheel 21. The steering torque sensor 52 is a sensor for detecting the steering torque of the steering wheel 21.

Further, the power steering device 1 is provided with an ECU 50 for electrically controlling the entire device. This EC
Output signals of the steering position sensor 51 and the steering torque sensor 52 are input to the ECU 50 at U50. The power steering device 1 is provided with a vehicle speed sensor 53, a vehicle behavior sensor 54, a vehicle weight sensor 55, and the like, and various kinds of vehicle information are input to the ECU 50 as needed.

The ECU 50 determines the load torque T of the motor 41.
It functions as a load torque detecting means for detecting 2. For example, when the steering wheel 21 receives a turning reaction force from the road surface due to the operation of the steering wheel 21 or when the turning reaction force changes, the ECU 50 responds to the change in the total load applied to the steering mechanism 2 by
The load torque T2 of the motor 41 is detected based on the voltage value, current value, rotation speed, and the like of the motor 41.

Further, as shown in FIG.
It functions as full load detecting means for detecting an external total load applied to the steering mechanism 2. For example, when the steering wheel 21 receives a turning reaction force from the road surface due to the operation of the steering wheel 21 or when the turning reaction force fluctuates, the generated and fluctuating turning reaction force is defined as a full load F applied to the steering mechanism 2. The ECU 50 detects the steering torque T1 of the steering wheel 21 and the load torque T2 of the motor 41 on the basis of the output signal of the steering torque sensor 52 and the voltage value, current value, rotation speed, etc. of the motor 41, and calculates the steering torque T1 and the load torque T2. Steering force F1 and assist force F2 applied to the steering mechanism 2 based on the gear ratio and the gear ratio.
Is calculated, and the total load F applied to the steering mechanism 2 is calculated based on the sum of the steering force F1 and the assist force F2.

The ECU 50 functions as torque setting means for setting a target value of the load torque T2 of the motor 41. That is, the ECU 50 controls the steering force F1 by the steering torque T1 and the assist force F2 by the motor 41 to a predetermined ratio with respect to the total load F calculated based on the steering torque T1, the load torque T2, the gear ratio, and the like. , The target value Tm of the load torque T2 is set.

The target value Tm of the load torque T2 is set, for example, as follows. First, the equation of motion of the rotating shaft system of the handle 21 is as follows: the angular acceleration of the steering position (steering angle) θ of the handle 21 is β, the moment of inertia of the handle 21 is I, and the gear ratio between the rack bar 24 and the pinion 22a is α. Then, it is represented by the following equation 1.

I · β = α (F− (F1 + F2))） (1)

Here, assuming that the steering wheel 21 does not rotate by accelerating due to external force, the angular acceleration β of the steering position θ becomes zero. Therefore, the following equation (2) holds.

F = F1 + F2 ‥‥ (2)

In this equation (2), the total load F of the steering mechanism 2 due to the reaction force from the road surface and the like received through the wheels 31
In contrast, the steering force F1 due to the steering torque T1 of the steering wheel 21
Assuming that the ratio (distribution ratio) borne by K is K, the following expression 3 holds.

F1 = K · F ‥‥ (3)

The steering force F is calculated according to the equations (2) and (3).
When 1 is deleted, the following equation (4) holds.

F = K · F + F2 ‥‥ (4)

Here, the gear ratio for converting the steering torque T1 to the turning force F1 is α1, the load torque T2 of the motor 41 is
Assuming that the gear ratio for converting the torque into the assist force F2 is α2, F1 = α1 · T1 ‥‥ (5) F2 = α2 · T2 ‥‥ (6), and this equation (6) is substituted into the equation (4). Then, T2 = ((1−K) · F) / α2 ‥‥ (7). That is, the motor 41 is controlled so that the equation (7) holds.

Accordingly, the target value Tm of the load torque T2 to be set is expressed by the following equation (8).

Tm = ((1−K) · (α1 · T1 + α2 · T2)) / α2 ‥‥ (8)

That is, the target value Tm is set based on the detected steering torque T1 and load torque T2, and the load torque T2 of the motor 41 is controlled so as to become the new target value Tm.

The distribution ratio K at the target value Tm is:
It is determined based on vehicle information such as the steering position θ, the vehicle speed V, the fluctuation frequency f of the external load, and the full load F, and is represented by the following equation (9).

K = G (θ, V, f, F,...) (9)

On the other hand, the ECU 50 also functions as motor control means for controlling the driving of the motor 41. That is,
The ECU 50 compares the detected load torque T2 of the motor 41 with the set target value Tm,
It is detected whether or not 2 matches the target value Tm. When the load torque T2 does not match the target value Tm, the driving of the motor 41 is controlled so that the load torque T2 matches the target value Tm. The drive control of the motor 41
For example, a control signal is output from the ECU 50 and the applied voltage of the motor 41 is increased or decreased based on the control signal. The control signal for the motor 41 is provided to the motor 41 and is input to a power unit for driving a large power provided outside the motor 41.

Further, the ECU 50 operates the steering wheel 2 during traveling.
It functions as a handle angular velocity control means for controlling the rotation speed of the handle 21 when, for example, the hand 1 is released. That is, when the steering wheel 21 is released during traveling, the ECU 50 does not control the load torque T2 of the motor 41, and controls the vehicle speed V and the steering position θ of the steering wheel 21.
The rotation speed of the steering wheel 21 is controlled based on vehicle information such as the vehicle information. For example, the ECU 50 stores the target steering speed ωm
Is set as a function of vehicle information as represented by the following equation (10).

Ωm = H (θ, V, f, F,...) (10)

The ECU 50 has a steering position sensor 51.
Is calculated based on the output of the steering wheel 21.
Then, the voltage applied to the motor 41 is appropriately increased or decreased so that the angular velocity ω of the steering wheel 21 becomes the target steering speed ωm. With such a steering wheel angular velocity control, when the steering wheel receives a reaction force from a road surface or the like when the driver releases the steering wheel, the steering wheel does not suddenly rotate due to the reaction force and the vehicle is stable. Traveling becomes possible.

Next, the operation of the power steering device 1 will be described.

FIG. 2 is a flowchart showing the operation of the power steering device 1. In FIG. 2, the power steering device 1 starts operating when an ignition switch of the vehicle is turned on. First, in step S10, the steering torque T1 due to the operation of the steering wheel 21 is detected. The detection of the steering torque T1 is performed by the steering torque sensor 52. The output signal of the steering torque sensor 52 is input to the ECU 50, and the process proceeds to step S12, where the ECU 50 outputs the steering torque T.
It is determined whether 1 is zero. When it is determined in step S12 that the steering torque T1 is zero, the process proceeds to step S30, and when it is determined that the steering torque T1 is not zero, the process proceeds to step S14.

In step S14, vehicle information such as the steering position θ, the vehicle speed V, the fluctuation frequency f of the external load, and the full load F is detected by various sensors provided in the vehicle.
Then, the process proceeds to step S16, and the vehicle information is input to the ECU 50 as output signals of various sensors and the like, and the distribution ratio K is calculated based on the information. The distribution ratio K is set so as to be appropriately changed depending on the state of running of the vehicle and the like, whereby the operation stability of the steering wheel 21 is maintained. The calculation of the distribution ratio K may be performed using a part of the vehicle information described above, for example, the vehicle speed V and the steering position θ. The calculation of the distribution ratio K may be performed using information other than the vehicle information described above.

After calculating the distribution ratio K, step S18
Then, the load torque T2 of the motor 41 is detected.
The load torque T2 is detected, for example, by measuring the current value or the rotation speed of the motor 41 when the motor 41 is driven.
It is input to the CU 50, and is calculated and detected based on the measurement signal of the current value or the rotation speed.

Then, the flow shifts to step S20, where the load torque T2 for driving the motor 41 is calculated using the detected steering torque T1, load torque T2 and calculated distribution ratio K.
Is calculated. The target value Tm is obtained by calculating the steering torque T1, the load torque T2, and the distribution ratio K in the above equation (8).
Calculated by substituting

Then, in step S22, it is determined whether or not the calculated target value Tm and the detected load torque T2 match. When it is determined that the target value Tm and the load torque T2 match, it is determined that the steering torque T1 by operating the steering wheel 21 and the load torque T2 by the motor 41 are acting on the steering mechanism 2 at a desired distribution ratio K. Become. Therefore, in this case, the process returns to step S10,
The detection of the steering torque T1 is performed again.

On the other hand, in step S22, the target value Tm
If it is determined that the load torque T2 is large,
In step S24, to reduce the output of the motor 41, E
When a control signal is input from the CU 50 to the motor 41 and the motor 4
The voltage applied to 1 is reduced. Then, the process returns to step S14 to detect the vehicle information, and the calculations in steps S16, S18, S20, and S22 are sequentially performed to obtain the target value Tm and the load torque T2.
Is repeated until a match is found. Although not shown in the flowchart of FIG. 2, the full load F
Is very large and exceeds a predetermined threshold value, it is desirable to control so that a load equal to or more than a predetermined value out of the total load F is not applied to the steering wheel 21 through the steering mechanism 2. According to such control, the stability of the vehicle is reliably maintained, for example, when a large impact is applied to the wheels 31.

In step S22, the target value Tm
If it is determined that the load torque T2 is smaller than
In step S26, to increase the output of the motor 41, E
When a control signal is input from the CU 50 to the motor 41 and the motor 4
The voltage applied to 1 is increased. Then, the process returns to step S14 to detect the vehicle information, and the calculations in steps S16, S18, S20, and S22 are sequentially performed to obtain the target value Tm and the load torque T2.
Is repeated until a match is found.

On the other hand, if it is determined in step S12 that the steering torque T1 is zero and the process proceeds to step S30, the steering position (steering angle) θ of the steering wheel 21 is detected by the steering position sensor 51 in step S30. The output signal of the steering position sensor 51 is input to the ECU 50, and the process proceeds to step S32, where the ECU 50 drives the motor 41 based on the steering position θ to control the steering mechanism 2.
It is determined whether or not assistance is required. This motor 4
The necessity of the assist by 1 is determined based on, for example, whether or not the steering position θ is zero. In this case, the wheel 31
When the vehicle is not steered, the assist by the motor 41 is unnecessary, and when the wheel 31 is steered, the assist by the motor 41 is required. If it is determined in step S32 that the assist is not required, the process returns to step S10 to detect the steering torque T1. On the other hand, when it is determined in step S32 that assistance is required, the process proceeds to step S34 to detect vehicle information.

In step S34, the vehicle information such as the steering position θ, the vehicle speed V, the fluctuation frequency f of the external load, and the full load F is detected by various sensors provided in the vehicle.
Then, the process proceeds to step S36, and the vehicle information is input to the ECU 50 as output signals of various sensors and the like, and the target steering speed ωm is calculated based on the output signals. The target steering speed ωm is set so as to appropriately change depending on the running state of the vehicle and the like. Note that the calculation of the target steering speed ωm is a part of the above-described vehicle information,
For example, the determination may be performed using the vehicle speed V and the steering position θ. The calculation of the target steering speed ωm may be performed using information other than the vehicle information described above.

After calculating the target steering speed ωm,
In step S38, the actual rotational angular velocity ω of the handle 21 is calculated. The rotational angular velocity ω of the handle 21
Is calculated based on the temporal change of the detected steering position θ. Next, the process proceeds to step S40, and it is determined whether the calculated target steering speed ωm matches the calculated rotational angular speed ω. If it is determined that the target steering speed ωm and the rotational angular speed ω match, it means that the steering wheel 21 is rotating at a desired angular speed. Therefore, in this case, the process returns to step S10, and the steering torque T1 is returned again.
Is detected. On the other hand, if it is determined in step S40 that the rotational angular speed ω is higher than the target steering speed ωm, the voltage applied to the motor 41 is reduced to reduce the output of the motor 41 in step S42. Then, the process returns to step S34, and the vehicle information is detected. The calculations in steps S36, S38, and S40 are sequentially performed, and the calculation is repeated until the target steering speed ωm matches the rotational angular speed ω.

If it is determined in step S40 that the rotational angular speed ω is smaller than the target steering speed ωm, the voltage applied to the motor 41 is increased to increase the output of the motor 41 in step S44. Then, the process returns to step S34, and the vehicle information is detected. The calculations in steps S36, S38, and S40 are sequentially performed, and the calculation is repeated until the target steering speed ωm and the rotational angular speed ω match.

As described above, according to the power steering apparatus 1 according to the present embodiment, when the wheel 31 receives a reaction force from the road surface or the like, or when the reaction force fluctuates, the detected operation of the steering wheel 21 is performed. On the basis of the steering torque T1 and the load torque T2 of the motor 41 so that the steering load F1 and the assist force F2 by the steering torque T1 bear the entire load F applied to the steering mechanism 2 from the outside of the vehicle at a predetermined ratio. The output of 41 is controlled. For this reason, the driver bears a part of the reaction force from the road surface or the like with the steering torque T1, and the driver can surely sense the reaction force through the operation of the steering wheel 21. Therefore, the driver can recognize the running state of the vehicle and can perform an appropriate steering operation according to the situation outside the vehicle.

When the steering torque T1 becomes zero due to the driver releasing the steering wheel 21, the steering wheel 21 is controlled to rotate at a predetermined angular velocity. Therefore, when the wheel 31 receives a reaction force from the road surface or the like,
Due to the reaction force, the steering wheel 21 can be prevented from suddenly rotating, and the vehicle can run stably.

(Second Embodiment) Next, an electric power steering apparatus according to a second embodiment will be described.

The power steering device 1a according to the present embodiment has the same structure as the power steering device 1 shown in FIG. This power steering device 1a performs E control for electrically controlling the entire device.
Although the CU 50 is provided, the ECU 50 functions as torque setting means for setting a new target value Tm of the load torque T2 of the motor 41. That is, the ECU 50
The steering torque T1, the steering force F1 by the steering torque T1 and the assist force F2 by the motor 41 with respect to the total load F calculated based on the target value Tm of the load torque T2 at the present time, the gear ratio, etc. A new target value Tm of the load torque T2 is set so as to be the ratio. The new target value Tm of the load torque T2 is calculated by substituting each value into the above equation (8). At this time, as for the load torque T2 of the motor 41, the actual load torque T2 of the motor 41 is not detected, and the target value T
m is substituted as the load torque T2 of the motor 41.
At this time, the initial value of the target value Tm may be set to zero.

On the other hand, the ECU 50 also functions as motor control means for controlling the driving of the motor 41. That is,
The ECU 50 outputs a drive signal to the motor 41 so that the new target value Tm is set, and controls the drive of the motor 41 based on the drive signal. The power steering device 1
In the ECU 50 a of FIG.
The detection function 2 and the full load detection function may not be provided.

Next, the operation of the power steering device 1a will be described.

FIG. 3 is a flowchart showing the operation of the power steering device 1a. In FIG. 3, when the ignition switch of the vehicle is turned on, the power steering device 1a starts operating. First, in step S10, the steering torque T1 due to the operation of the steering wheel 21 is detected.
The CU 50 determines whether the steering torque T1 is zero. When it is determined in step S12 that the steering torque T1 is zero, the process proceeds to step S30, and when it is determined that the steering torque T1 is not zero, the process proceeds to step S14.

In step S14, vehicle information such as the steering position θ, the vehicle speed V, the fluctuation frequency f of the external load, and the full load F is detected by various sensors provided in the vehicle.
Then, the process proceeds to step S16, and the vehicle information is input to the ECU 50 as output signals of various sensors and the like, and the distribution ratio K is calculated based on the information. The distribution ratio K is set so as to be appropriately changed depending on the state of running of the vehicle and the like, whereby the operation stability of the steering wheel 21 is maintained. The calculation of the distribution ratio K may be performed using a part of the vehicle information described above, for example, the vehicle speed V and the steering position θ. The calculation of the distribution ratio K may be performed using information other than the vehicle information described above.

After calculating the distribution ratio K, step S19
And the calculation of the load torque T2 is performed. That is, the motor 41 currently set in the ECU 50
Is read, and the target value Tm of the load torque is read out.
m is stored as the load torque T2 of the motor 41. In this case, it is not necessary to detect the actual load torque T2 of the motor 41, and it is not necessary to equip a device such as a current detector necessary for detecting the load torque T2. Therefore, the power steering device 1a has a simple configuration.

Then, the flow shifts to step S21, where the detected steering torque T1, the load torque T2 at which the current load torque target value Tm is substituted, and the calculated distribution ratio K, the load torque T2 for driving the motor 41 is used. Is calculated as a new target value Tm. The new target value Tm is calculated by substituting the steering torque T1, the distribution ratio K, and the like into the above equation (8).

Then, in step S23, the driving of the motor 41 is controlled so as to reach the calculated target value Tm. That is, a drive signal is output from the ECU 50 to the motor 41 so that the load torque T2 becomes the calculated target value Tm, and the drive of the motor 41 is controlled based on the drive signal. At this time, the load torque T2 of the motor 41 is controlled so as to satisfy the equation (8), so that the steering torque T1 is applied to the entire load applied to the steering mechanism 2 from outside the vehicle.
Steering force F1 and assist force F2 due to load torque T2
Will be borne at a predetermined rate.

Then, the process returns to step S10 to detect the steering torque T1.
12, etc. are performed.

On the other hand, if it is determined in step S12 that the steering torque T1 is zero and the process proceeds to step S30, the steering position (steering angle) θ of the steering wheel 21 is detected by the steering position sensor 51 in step S30. The output signal of the steering position sensor 51 is input to the ECU 50, and the process proceeds to step S32, where the ECU 50 drives the motor 41 based on the steering position θ to control the steering mechanism 2.
It is determined whether or not assistance is required. If it is determined in this step S32 that the assist is not required, the process returns to step S10 to change the steering torque T1.
Is detected. On the other hand, if it is determined in step S32 that assistance is required, the process proceeds to step S32.
The process proceeds to 34, where vehicle information is detected.

In step S34, vehicle information such as the steering position θ, the vehicle speed V, the fluctuation frequency f of the external load, and the full load F is detected by various sensors provided in the vehicle.
Then, the process proceeds to step S36, and the vehicle information is input to the ECU 50 as output signals of various sensors and the like, and the target steering speed ωm is calculated based on the output signals. After calculating the target steering speed ωm, the process proceeds to step S38, and the actual rotational angular speed ω of the steering wheel 21 is calculated. The calculation of the rotational angular velocity ω of the steering wheel 21 is performed based on a temporal change in the detected steering position θ. Next, the process proceeds to step S40, and it is determined whether the calculated target steering speed ωm matches the calculated rotational angular speed ω. If it is determined that the target steering speed ωm and the rotational angular speed ω match, it means that the steering wheel 21 is rotating at a desired angular speed. Therefore, in this case, the process returns to step S10, and the steering torque T1 is detected again. On the other hand, if it is determined in step S40 that the rotational angular speed ω is higher than the target steering speed ωm, the voltage applied to the motor 41 is reduced to reduce the output of the motor 41 in step S42. Then, the process returns to step S34, and the vehicle information is detected. The calculations in steps S36, S38, and S40 are sequentially performed, and the calculation is repeated until the target steering speed ωm matches the rotational angular speed ω.

If it is determined in step S40 that the rotational angular speed ω is smaller than the target steering speed ωm, the voltage applied to the motor 41 is increased to increase the output of the motor 41 in step S44. Then, the process returns to step S34, and the vehicle information is detected. The calculations in steps S36, S38, and S40 are sequentially performed, and the calculation is repeated until the target steering speed ωm and the rotational angular speed ω match.

As described above, according to the power steering apparatus 1a according to the present embodiment, when the wheel 31 receives a reaction force from the road surface or the like, or when the reaction force fluctuates, the steering by the detected steering operation is performed. The target value Tm of the load torque T2 of the motor 41 is set based on the torque T1 and the like, and the total load F applied to the steering mechanism 2 from outside the vehicle is determined by the steering force F1 by the steering torque T1 and the assist force F2 by the load torque T2. The drive of the motor is controlled so as to bear the ratio. For this reason, the driver bears a part of the reaction force from the road surface or the like with the steering torque T1, and the driver can surely sense the reaction force through the operation of the steering wheel 21. Therefore, the driver can recognize the running state of the vehicle and can perform an appropriate steering operation according to the situation outside the vehicle.

In the power steering device 1a, desired drive control of the motor 41 can be performed without actually measuring the load torque T2 of the motor 41. Therefore, the device can be simplified.

Further, when the steering torque T1 becomes zero due to the driver releasing the steering wheel 21, the steering wheel 21 is controlled so as to rotate at a predetermined angular velocity. Therefore, when the wheel 31 receives a reaction force from the road surface or the like,
Due to the reaction force, the steering wheel 21 can be prevented from suddenly rotating, and the vehicle can run stably.

[0067]

As described above, according to the present invention, the following effects can be obtained.

When the wheel receives a reaction force from the road surface or the like, or the reaction force fluctuates, the driver can sense a part of the reaction force by operating the steering wheel. Therefore, the driver can perform an appropriate steering operation according to a situation outside the vehicle while operating the steering wheel with the reduced steering force.

Further, even when the driver releases the steering wheel, the steering wheel is prevented from suddenly turning, and the vehicle can be stably driven.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an electric power steering device.

FIG. 2 is a flowchart showing an operation of the electric power steering device.

FIG. 3 is a flowchart showing an operation of the electric power steering device according to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Power steering device, 2 ... Steering mechanism, 21 ... Steering wheel, 3
DESCRIPTION OF SYMBOLS 1 ... Wheel, 41 ... Motor, 50 ... ECU, 52 ... Steering torque sensor

Claims (3)

[Claims] 1. A steering mechanism for mechanically transmitting a steering torque generated by a steering wheel operation to steer a wheel, a motor for assisting the steering of the wheel by applying an assist force to the steering mechanism, and the steering torque. A torque detection means for detecting a load torque of the motor; a full load detection means for detecting a total load applied to the steering mechanism based on the detected steering torque and the load torque. A torque setting means for setting a target value of the load torque such that the steering force and the assist force by the steering torque have a predetermined ratio with respect to the detected total load; and the load torque is the target value. And a motor control means for controlling the motor so as to conform to the above. 2. A steering mechanism for mechanically transmitting a steering torque generated by a steering wheel operation to steer a wheel, a motor for assisting the steering of the wheel by applying an assist force to the steering mechanism, and the steering torque. A steering torque detecting means for detecting the steering torque and the steering torque and the current setting such that the steering force and the assist force by the steering torque bear at a predetermined ratio with respect to a total load applied to the steering mechanism from outside the vehicle. Based on the target value of the load torque of the motor being
An electric type comprising: a torque setting unit that sets a new target value of the load torque of the motor; and a motor control unit that drives and controls the motor so that the load torque of the motor matches the new target value. Power steering device. 3. A steering position detecting means for detecting a steering position of the steering wheel, wherein when the steering torque is not applied and the steering wheel is at a predetermined steering position, the steering wheel is rotated at a predetermined angular velocity in a predetermined direction. The electric power steering apparatus according to claim 1 or 2, further comprising: a steering wheel angular velocity control means for controlling rotation.