JPH03189271A - Power steering device - Google Patents

Abstract

PURPOSE:To eliminate the need of an extra steered angle detector by calculating the inside resistance of a motor with a motor temperature determined from the temperature of a motor drive element, determining back electromotive force by the inside resistance, applied voltage to the motor, and drive current, and moreover computing steering angular velocity. CONSTITUTION:In a device in which a motor 8 for generating steering auxiliary force is drive-controlled with a drive signal determined with a control part 7 based on the output signal of a torque sensor 6 and a vehicle speed detector 18, a PWM drive circuit 72, controlling, voltage supplied to the motor 8 by a duty ratio from a PID processing part 76, is provided in the control part 7. A temperature sensor 71G detecting the temperature of a power transistor 72a is provided in the vicinity of the power transistor 72a as a drive element in the drive circuit 72. A steered angle is calculated 71d from a motor 8 temperature, applied voltage, and drive current determined with a temperature sensor 71g, voltage detection circuit 71b, and current detection circuit 71c, and the drive current of the motor 8 is controlled by the steered angular velocity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electric power steering device (power steering) that uses the rotational force of a motor to supplement the force required to operate a steering wheel.

[Prior art]

The steering torque applied to the steering wheel is detected, and when the detected torque exceeds a predetermined dead zone, a drive current proportional to the detected torque is passed through a steering assist motor to drive the motor, and the motor is driven. 2. Description of the Related Art Electric power steering devices have been developed that provide a driver with a comfortable steering feeling by supplementing the force required for steering with the rotational force of the motor.

In such a power steering device, the rank axis.

The present applicant has proposed various systems in which a steering angle detector such as a rotation sensor or a stroke sensor is attached to a steering wheel shaft or a motor to perform steering angle control, steering angular velocity control, or steering angular acceleration control (Japanese Patent Application No. 63 -191844, Japanese Patent Application No. 63-189331, etc.).

These detect the midpoint of the steering angle and control the return of the steering wheel based on that, change the drive current of the motor during return according to the steering angle, and reduce the drive current of the motor according to the steering angular velocity. The damping control suppresses the unsteadiness and unnaturalness of the steering sensation, and also increases the drive current based on the steering angular acceleration to compensate for the inertia of the undercarriage and motor.

[Problem to be solved by the invention]

However, when controlling the steering assist force using the steering angle detector as described above, it is necessary to attach the steering angle detector to the rank shaft, the steering wheel shaft, or the motor. Therefore, there was a problem that the power steering device became expensive.

Additionally, a controller using a microcomputer, which serves as a control means, is usually installed in a location separate from the steering mechanism (for example, near the dash board in the car), which requires a long wiring from the steering angle detector to the controller. There was a problem that the wiring became complicated.

The present invention was made in view of the above circumstances, and detects the temperature of the motor drive element provided in the controller, determines the motor temperature based on it, and calculates the motor temperature from the motor temperature, the voltage applied to the motor, and the drive current. By determining the rotational angular velocity of An object of the present invention is to provide a power steering device that can detect the value of

[Means to solve the problem]

A power steering device according to the present invention is a power steering device equipped with a steering assist motor that is driven in accordance with a steering torque applied to a steering wheel. a voltage detection means for detecting a voltage applied to the motor, a current detection means for detecting a drive current of the motor, and a temperature of the motor based on the temperature detected by the temperature detection means; resistance calculating means for calculating the internal resistance of the motor based on the detected motor temperature, and calculating a back electromotive force of the motor based on the detected voltage and current and the calculated internal resistance, and steering the steering wheel based on the calculated back electromotive force. The present invention is characterized by comprising means for calculating a value related to the angle, and means for controlling a drive current of the motor based on the calculated value.

[Effect]

In the present invention, when the temperature of the drive element is detected, the temperature of the motor is determined from it, and the internal resistance of the motor is calculated based on it. The back electromotive force of the motor is calculated from the calculated internal resistance and the detected voltage and drive current applied to the motor.

Since the rotational angular velocity of the motor related to the steering angle of the steering wheel changes according to the back electromotive force, the rotational angular velocity of the motor is determined from the calculated back electromotive force, and based on this, the angular acceleration of one rotation angle, etc. is determined, The drive current of the motor is controlled by them.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is a partially cutaway front view of a power steering device according to the present invention, and FIG. 2 is an enlarged sectional view taken along line nn in FIG. 1.

In the figure, 1 is a rank shaft, and a rack shaft case 2 is fixed to a part of the vehicle body and has a cylindrical shape, with the longitudinal direction being the left and right direction.
is interpolated concentrically with this. Reference numeral 3 denotes a pinion shaft, which is supported inside a pinion shaft case 4 connected to one end of the rack shaft case 2 with its axis obliquely intersecting with the rank shaft 1.

As shown in FIG. 2, the pinion shaft 3 consists of an upper shaft 3a and a lower shaft 3b coaxially connected via a torsion bar 5. The upper end thereof is operatively connected to the steering wheel via a universal joint (not shown). The lower shaft 3b is supported within the pinion shaft case 4 at a position near its upper end by a four-point contact ball bearing 41, with its lower portion protruding an appropriate length from the lower opening of the pinion shaft case 4. The four-point contact ball bearing 41 is fitted onto the lower shaft 3b from the lower end side, and is fixed by being caulked to the outer peripheral surface of the step portion formed near the upper end of the lower shaft 3b. After being positioned on the outside of the lower shaft 3b in the axial length direction with both sides of the inner ring held between the inner ring 42 and the lower shaft 3b, the pinion shaft case 4 is fitted into the pinion shaft case 4 from the lower opening along with the lower shaft 3b. Both sides of the outer ring are held between an annular shoulder formed at the lower part of the case 4 and a lock nut 43 screwed into the case 4 from the opening, and the pinion shaft is positioned inside the pinion shaft case 4 in the axial direction. A radial load and an axial load in both directions are applied to the lower shaft 3b.

The lower shaft 3b protrudes from the pinion shaft case 4 in the middle thereof, and has pinion teeth 3 extending over an appropriate length in the axial direction.
0 is formed, and the pinion teeth 30 are formed so that the pinion shaft case 4 is attached to the upper side of the rack shaft case 2 with a fixing bolt 4.
4, the lower shaft 3b meshes with the rack teeth 10 formed in the rack shaft case 2 at a position close to one end of the rank shaft 1 over an appropriate length in the shaft length direction. and the rack shaft 1 are engaged with each other with their axes obliquely intersecting each other. The lower shaft 3b extends further downward than the locking position with the rack shaft 1, and a large bevel gear 31 is fitted to the lower end of the lower shaft coaxially with the lower shaft 3b with its tooth forming surface facing downward. The large bevel gear 31 is supported by a needle roller bearing 33 in a bevel gear housing 20 that is connected to the lower side of the rack shaft case 2 so as to surround the large bevel gear 31. Therefore, the lower shaft 3b is supported by the four-point contact ball bearing 41 and the needle roller bearing 33 on both sides of the meshing position between the rack teeth 10 and the pinion teeth 30, and the lower shaft 3b is supported in the meshing position by the four-point contact ball bearing 41 and the needle roller bearing 33. The amount of deflection that occurs is kept within a predetermined tolerance.

Furthermore, at the meshing position between the rack teeth 10 and the binion teeth 30,
A rack guide 12 is provided that presses the rack shaft 1 by the urging force of a push spring 11 directed toward the pinion shaft 3 so that these are meshed without any gaps. The rack shaft case 2 is supported in a sandwiched manner from both sides in the radial direction by the shaft 3b, and the rack shaft case 2 is located opposite to the position where it is connected to the pinion shaft case 4.
It is supported by a bearing bush 13 fitted inside the end of the rack shaft case 2, and is movable in the axial direction inside the rack shaft case 2. Both left and right ends of the rack shaft 1 protruding from both sides of the rank shaft case 2 are connected to separate ball joints 14.
．． 14 to tie rods 15 and 15 connected to left and right wheels (not shown), respectively, and when the rack shaft 1 is moved in the axial direction, the wheels are moved to the left.

It is designed to be steered to the right.

Reference numeral 6 in FIG. 2 is a torque sensor that detects the steering torque applied to the steering wheel, and is fitted onto the upper shaft 3a and rotates together with it, and has a lower end face centered on the axis of the upper shaft 3a. a resistor holding member 60 formed of an annular resistor;
A potentiometer is constituted by a detector holding member 61 that is fitted onto the lower shaft 3b and rotates together with the lower shaft 3b, and has a detector on its upper end surface that slides into contact with one point in the radial direction on the resistor. This is what happens. Upper shaft 3a of pinion shaft 3
rotates around its axis in response to rotation of the steering wheel, but road resistance acting on the wheels acts on the lower shaft 3b via the rack shaft 1, and a torsion bar interposed between the two shafts acts on the lower shaft 3b. 5, twisting occurs in response to the steering torque applied to the steering wheel. The torque sensor 6 outputs the relative displacement in the circumferential direction that occurs between the upper shaft 3a and the lower shaft 3b due to the torsion of the torsion bar 5 as a potential corresponding to the sliding contact position between the detector and the resistor. It is initially adjusted so that a predetermined reference potential is output when the torsion bar 5 is not twisted, in other words, when the steering wheel is not operated.

The output signal of the torque sensor 6 is manually input to the control unit 7 in a time-series manner, and the control unit 7 compares this signal with the reference potential to recognize the direction and magnitude of the steering torque, and as described below. A drive signal is issued to the provided steering assist motor 8.

The steering assist motor 8 transmits its rotational force to the lower shaft 3b via an electromagnetic clutch 16, a planetary gear reduction device 9, and a small bevel gear 32 having a smaller diameter than the large bevel gear 31 and meshing with the large bevel gear 31. It is.

The electromagnetic clutch 16 has an annular shape, and is fitted onto one side of the rotating shaft 80 of the motor 8 coaxially with a coil portion 161 fixed to the intermediate case 81 of the motor 8, and rotates together with the rotating shaft 80. and a disc-shaped engagement/disengagement part 163 that faces the main drive part 162 and engages with the main drive part 162 by electromagnetic force caused by energizing the coil part 161. Engages and disengages rotational force.

The planetary gear reduction device 9 is fitted into the engaging/disengaging part 163, rotates, and has a sun gear, one end of which is supported by a bearing fitted into the main moving part, and the other end fitted into a planetary carrier 93, which will be described later. a sun shaft 90 supported on a bearing, and the motor 8
an annular outer ring 91 coaxially fixed to the casing end face 82 of the rotating shaft 80; A plurality of planetary gears 92,92... that rotate about the axis of the sun gear and revolve around the axis of the sun gear, and a planetary carrier 9 that respectively supports the planetary gears 92,92...
The motor 8 and the electromagnetic clutch 1 are arranged on one side of the rotating shaft 80, and have a smaller outer diameter than the motor 8.
It is integrated with 6. Output shaft 9 of planetary gear reduction device 9
Numeral 4 is fitted and fixed at the axial center position of the planetary carrier 93 located coaxially with the rotating shaft 80 of the motor 8, and protrudes to the outside of the casing by an appropriate length. The small bevel gear 32 is fitted to the tip of the output shaft 94 with its tooth forming surface facing toward the tip. It is designed to rotate according to the revolution of...

The motor 8, the electromagnetic clutch 16, and the planetary gear reduction device 9
This means that the small bevel gear 32 is fitted into the bevel gear housing 20 with the small bevel gear 32 inside with the axes thereof being substantially parallel to the axis of the rack shaft 1. 32 is meshed with a large bevel gear 31 fitted to the lower end of the lower shaft 3b, and is fixed to a bracket 2a provided on the outside of the rack shaft case 2. The bank clamping adjustment between the large bevel gear 31 and the small bevel gear 32 is carried out at the butt portion between the casing of the planetary gear reduction device 9 and the bevel gear housing 20 when the planetary gear reduction device 9 is fitted into the bevel gear housing 20. This can be easily achieved by changing the thickness and/or number of shims interposed in the shims.

In addition to the output signal of the torque sensor 6 described above, the output signal of a vehicle speed detector 18 that detects the vehicle speed is also input to the control section 7, and the control section 7 performs the control described later and generates a drive signal for driving the motor 8. Output.

Next, control by the control section 7 will be explained.

FIG. 3 is a block diagram showing the configuration and control operation of the control section.

The torque detection signal of the torque sensor 6 advances its phase,
a phase compensator 71a and a torque T for stabilizing the system;
The midpoint θ of the relative steering angle θ7 based on the vehicle speed ■ and the steering angular velocity ω7. It is given to the midpoint calculation unit 73d which calculates . The phase compensator 71a provides a compensated detection torque 'rc obtained by phase-compensating the torque detection signal to an instruction current function section 73a that generates an instruction current (2) for the motor 8.

On the other hand, the vehicle speed detection signal of the vehicle speed detector 18 is given to an instruction current function section 73a, a midpoint calculation section 73d, a steering wheel return control calculation section 73e, an angular acceleration control calculation section 73c, and a damping control calculation section 73b, which will be described later.

Further, the voltage e1 applied to the motor 8 is detected by the voltage detection circuit 71b based on the terminal voltage VIIAa of the battery 75, which is the power source of the motor 8, and the duty ratio from the PID arithmetic processing section 76, which will be described later. id is detected by a current detection circuit 71c in which a current detection resistor (not shown) is inserted into the motor line. The PID calculation processing unit 76 performs PID control on the input current and outputs a predetermined duty ratio.

The output duty ratio is given to the voltage detection circuit 71b as described above, and is
thModulation (pulse width modulation) is applied to the drive circuit 72. The PWM drive circuit 72 controls the voltage supplied to the motor 8 from the battery 75 connected thereto by pulse width control based on the duty ratio from the PID calculation processing unit 76, and uses a power transistor as a drive element such as a MOSFET. 72a is used.

A temperature sensor 71g is provided near the power transistor 72a to detect its temperature.

Heat capacity between power transistor 72a and motor 8.

By considering the difference in heat dissipation, it is possible to show the correlation between both temperatures.

FIG. 4 is a graph showing the relationship between the temperature of the power transistor 72a and the temperature of the motor 8. The horizontal axis shows the temperature of the power transistor 72a, and the vertical axis shows the temperature of the motor 8. power transistor 72
By detecting the temperature of a, the temperature of the motor 8 can be determined.

The detection results of the temperature sensor 71g, the voltage detection circuit 71b, and the current detection circuit 71c are respectively given to the steering angular velocity calculation section 71d, and the steering angular velocity calculation section 71d calculates the steering angular velocity of the motor 8 by calculations described later based on these detection results. ω7 is calculated, and the calculated result ω1 is the vehicle speed ■ and the steering angular speed ω. A damping control calculation unit 73b that outputs the subtraction current I, a midpoint calculation unit 73d, a steering angle calculation unit 71f that calculates the relative steering angle θ7, and a steering angle calculation unit 71f that calculates the steering angular acceleration αゎ. The calculated steering angular acceleration α7 is provided to an angular acceleration control calculation unit 73c that outputs a correction current 1c according to the inertia force of the motor and the inertia force of the undercarriage. The relative steering angle θ7 is calculated by a midpoint calculation unit 73d and a subtractor 7 that calculates the steering angle Δθ from the relative steering angle θ7 and the steering angle midpoint θ.
4d. The obtained steering angle Δθ is given to the rudder return control calculation unit 73e, which outputs a variable current I for return control that becomes larger as the steering angle Δθ increases due to the vehicle speed ■ and the steering angle Δθ. .

The command current function section 73a has the compensation torque Tc as described above.
, vehicle speed V and changing current 1 are given, and within the dead zone where the predetermined torque range occurs during steering, the indicated current I is set according to the changing current I, as shown by the broken line in Fig. 3, and outside the dead zone, the vehicle speed is changed. Outputs an instruction current I according to V and torque T.

Further, in the damping control calculation unit 73b, the relationship between the steering angular velocity ω7 and the subtraction current is converted into a function according to the vehicle speed V, and the steering angular velocity ω is expressed as a function. Subtract current from and vehicle speed V■1
is determined and given to the subtractor 74b. The subtracter 74b is supplied with the instruction current I output from the instruction current function section 73a, and subtracts the subtraction current I from the instruction current I.

This subtraction result is given to the adder 74a, and the correction current outputted from the angular acceleration control calculation section 73c! . is added,
The addition result is given to a subtracter 74c.

The subtracter 74c subtracts the feedback signal from the current detection circuit 71c, and the subtraction result is provided to the PID arithmetic processing section 76 and then provided to the motor 8 via the PWM drive circuit 72. This current detection circuit 71c is configured to detect current including the flywheel current of the motor, and the current loop is stabilized.

Next, the control operation of the control section 7 will be explained.

FIG. 5 is a flowchart showing the calculation control of the steering angular velocity calculation section 71d, which is the gist of the present invention. First, timer processing is performed to determine the sampling period TS for steering angular velocity calculation (step #10), and the following processing is performed in the sampling period TS. Initially, the terminal voltage V M of the battery 575
Detect AT (step 111). The duty ratio is read (step $112), and the voltage e applied to the motor 8 is calculated by the voltage detection circuit 71b as follows: e, = vllAy XD (step #13). Next, the current detection circuit 71c detects the drive current i, the step port 14), and the power transistor 72 detected by the temperature sensor 71g.
The temperature of a is converted into the temperature tM of the motor 8 based on the relationship shown in FIG. 4 (step 115).

Then, the internal resistance r of the motor 8 is determined from the motor temperature 1 using the following formula (step port 16).

r,”re+α(tM-to)°t.

However, to: reference temperature ro: internal resistance of the motor at the reference temperature t0 α: temperature coefficient of resistance at the reference temperature t0 From the determined internal resistance r, the back electromotive force of the motor (ea-
ra·id) is obtained, and the steering angular velocity ω7 is obtained from the following formula (step #17).

However, kv: proportional constant and the obtained steering angular velocity ω7 is calculated by the damping control calculation unit 7.
3b, and the subtracted current ■1 according to the vehicle speed is applied to the subtracter 7.
4b, the subtraction current (2) is subtracted from the instruction current I in order to suppress the feeling of wobbling of the steering wheel when the steering angular velocity ω7 is large at high speed.

Further, the steering angular acceleration calculating section 71e calculates the steering angular acceleration α7 using the following formula from the calculated steering angular velocity ω1 and the steering angular velocity ω7-1 calculated immediately before. The obtained steering angular acceleration αゎ is given to the angular acceleration control calculation unit 73c, which generates a correction current (■) according to the vehicle speed (■) to compensate for the inertial force of the undercarriage and the motor. is generated and provided to the adder 74a.

Next, a procedure for calculating the relative steering angle θ7 will be explained.

FIG. 6 is a flowchart showing the steering direction determination procedure;
The figure is a flowchart showing a procedure for calculating the relative steering angle θ7 based on the determination result. In FIG. 6, it is determined whether the motor rotation instruction direction is to the left or not (step #20), and when the motor rotation instruction direction is to the left, the current i of the addition result of the adder 74a is
Step 1122), i≧i.

If so, left steering is determined in step #24, and if i<i4, right steering is determined in step #23, and the process returns. Also, if the motor rotation instruction direction is right, step #2
1 determines whether the result of subtracting the current i and the drive current i is positive or negative, and when i≧i4, it is determined that the steering is to the right in step #23,
When i<i, it is determined in step #24 that steering is to the left, and the process returns.

Using this determination result, in FIG.
When the steering direction is determined at 0 and right steering is determined at step #23 in FIG. 6, the relative steering angle θ7=θn-1+
Find ω,・TS (step #31), step #24
θ when left steering is determined. =θ,, -I -ω7
- Obtained by TS (step #32).

When the relative steering angle θ is calculated by the steering angle calculation unit 71f in this way, it is calculated by the midpoint calculation unit 73d and the subtractor 74.
given to d.

FIG. 8 is a flowchart showing the midpoint calculation procedure, in which a timer is set and the midpoint calculation is performed based on the time-up. First, in step #40, it is determined whether the timer has expired, and when the timer has finished, the vehicle speed V, torque T, and steering angular velocity ω7 are read, respectively, and the torque T and steering angular velocity ω are read out in steps #41 to #43. is a predetermined threshold T.

and ω are smaller and the vehicle speed ② is larger than a predetermined threshold value V, it is determined that the vehicle is traveling straight, and the relative steering angle θ° at that time is read out in step #44. Then, integrate it as shown in the formula below and average it (step #45)
.

m m Then repeat this N times, and when the count is finished (step 1146), the obtained steering angle is set to the midpoint θ. A binding midpoint update process is performed (step I47). As a result, the midpoint θ of the steering angle. is required. And the found midpoint θ. is sent to the subtractor 74d, and the steering angle Δθ is calculated according to the processing procedure shown in the flowchart of FIG. The instruction current I within the dead zone when the steering wheel is returned is controlled by the changing current ■1. 9th
In the figure, the relative steering angle θ7 and the midpoint θ calculated by the steering angle calculation unit 71f in steps #50 and #51. are read out and subtracted by the subtractor 74d to obtain the steering angle Δθ (step #52).

〔effect〕

As detailed above, in the present invention, the internal resistance of the motor is calculated by determining the motor temperature from the temperature of the drive element of the motor, the back electromotive force is determined from this, the voltage applied to the motor, and the driving current, and the steering angular velocity is Since the value related to the steering angle can be detected at low cost within the control unit without using a special steering angle detector, it is sufficient to simply detect the temperature of the drive element provided within the control unit. This has excellent effects such as eliminating the need for wiring to the control unit and simplifying it.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view showing an embodiment of a power steering device according to the present invention, FIG. 2 is an enlarged sectional view taken along line nn in FIG. 1, and FIG. FIG. 4 is a block diagram showing the operation, FIG. 4 is a graph showing the relationship between the temperature of the power transistor and the motor temperature, and FIGS. 5 to 9 are flowcharts showing the processing procedure of each part. 6...Torque sensor 8...Motor 71b...
Voltage detection circuit 71c...Current detection circuit 71d...
- Steering angular velocity calculation section 71g-1 - Temperature sensor 72a
...Power transistor 73a...Instruction current function section 73b...Damping control calculation section 73c...
Angular acceleration control calculation section 73e... Steering wheel return control calculation section Patent Applicant: Koyo Seiko Co., Ltd.

Claims (1)

[Scope of Claims] 1. In a power steering device equipped with a steering assist motor that is driven in accordance with a steering torque applied to a steering wheel, there is provided a temperature detection means for detecting the temperature of a drive element that drives the motor; , voltage detection means for detecting the voltage applied to the motor; current detection means for detecting the drive current of the motor; and determining the temperature of the motor based on the temperature detected by the temperature detection means. resistance calculating means for calculating an internal resistance of the motor based on the temperature of the motor; calculating a back electromotive force of the motor from the detected voltage and current and the calculated internal resistance; and adjusting the steering angle of the steering wheel based on the back electromotive force of the motor; A power steering device comprising: means for calculating a related value; and means for controlling a drive current of the motor based on the calculated value.