JP2840950B2 - Electric power steering device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric steering apparatus that captures an ignition pulse of an engine as vehicle speed information and controls a power assist force based on the information.

(Prior Art) In the electric power steering apparatus shown in FIG. 6, a torque sensor 3 is connected to a steering wheel 1, and this torque sensor 3 is connected to a function generator 16 and a differentiating circuit 17. The function generator 16 is also connected to the vehicle speed sensor 4 so that the function generator 16 outputs a torque signal corresponding to the vehicle speed.

The output signal of the function generator 16 and the output signal of the differentiating circuit 17 are added and input to the steering angle correction circuit 18. The steering angle sensor 15 is connected to the steering angle correction circuit 18, and the difference between the actual steering angle and the steering angle of the steering wheel 1 is corrected.

The forward / reverse direction determination circuit 19 determines the forward / reverse direction of the steering angle signal corrected as described above, and is transmitted to the electric motor M. When a steering angle signal is transmitted to the electric motor M, the electric motor M is driven according to the signal, and the tire 14 is steered via the speed reducer 7.

(Problems to be Solved by the Present Invention) The conventional device constituted by the above-described circuit requires a vehicle speed sensor to convert the rotational speed of a mechanical axle or the like into an electric signal, which is expensive.

It is an object of the present invention to provide an electric power steering device that can set an assist force according to a running state of a vehicle without using a vehicle speed sensor.

(Means for Solving the Problems) The present invention is based on an electric power steering device that controls an electric motor according to running conditions of a vehicle.

While premised on the above device, the present invention provides a current sensor for detecting a current supplied to the electric motor, an ignition pulse detector for detecting an ignition pulse,
A torque sensor that detects a steering torque of a steering wheel, a motor control unit that controls a current supplied to the electric motor based on an output signal of the ignition pulse detector and an output signal of the torque sensor, and an output from the motor control unit. An input / output check circuit that compares the output signal from the current sensor with an output signal from the current sensor. The motor control unit includes a differentiation circuit that differentiates the output signal from the torque sensor, and an output signal from the differentiation circuit and the torque of the torque sensor. An input / output check circuit compares the output signal from the adder circuit with the output signal of the current sensor to determine whether the electric motor is operating according to the output signal of the motor control unit. And whether the output signal of the adder circuit and the output signal of the current sensor are in the normal range on the XY coordinates or in the dead band. It has a feature in that the determined configuration be in a Luke or output abnormal range.

(Operation of the Present Invention) The number of ignition pulses per time is proportional to the engine speed per time. The engine speed per time is almost proportional to the vehicle speed when the vehicle runs at a position other than the gear position where the reduction ratio is large. That is, it is considered that the number of ignition pulses per time is almost always proportional to the vehicle speed. Therefore, the present invention is of a vehicle speed sensitive type by detecting an ignition pulse of an engine and setting the power assist force as vehicle speed information.

Also, the input / output check circuit determines that the electric motor is operating according to the output signal of the motor control unit, but assimilation.

(Effect of the Present Invention) According to the electric power steering device of the present invention,
The ignition pulse can be used as engine speed information, and the ignition pulse, which is an electric signal, can be sent directly to the control circuit without using a vehicle speed sensor that converts the rotational speed of a mechanical axle or the like into an electric signal. The driving condition-sensitive power steering device can be provided at a low cost.

When the electric motor does not operate according to the output signal of the motor control unit due to the influence of a minute voltage such as noise, the input / output check circuit determines that the electric motor does not operate and stops the electric motor. Therefore, the device is switched to the manual steering state, and high safety can be secured as the electric power steering device.

In addition, it is possible to determine whether the output signal of the adder circuit and the output signal of the current sensor are in the normal range, the dead band, or the output abnormal range on the XY coordinates. Can be improved.

(Embodiment of the Present Invention) In the first embodiment shown in FIGS. 1 to 5, a pinion 9 is connected to the tip of a steering input shaft 2 connected to a steering wheel 1, and this pinion 9 is engaged with a rack 5. I have.
Both sides of the rack 5 are connected to knuckle arms 10 of tires 14 via side rods 11. Further, a speed reducer 7 is connected to the electric motor M which can be rotated forward and backward. The pinion 13 is connected to the tip of the output shaft of the speed reducer 7, and the pinion 13 is engaged with the rack 5.

Further, the input shaft 2 is provided with a torque sensor 3 for detecting a steering torque acting on the input shaft 2. Also,
An ignition pulse sensor 46 for detecting an ignition pulse of the engine of the vehicle is provided, and these sensors are connected to a motor control device 6 corresponding to a motor control unit of the present invention.

The torque signal Tin detected by the torque sensor 3 is input to a torque signal processing circuit 41 provided in the motor control device 6 and a torque sensor abnormality detection circuit 45.

The torque signal output from the torque signal processing circuit 41
V ₁ is a forward / reverse direction determination circuit 19 for determining the direction of the torque
When, an absolute value circuit 43 is input to each of the differentiating circuit 17 which converts the differential value C _{1 1} by differentiating the torque signal V _1. The torque normal signal T ₀ which is output from the determination circuit 19 is inputted to the input port A ₁ microprocessor 49 striking the function generator circuit of the present invention.

The signal V ₁ input to the absolute value conversion circuit 43 is converted into an absolute value there. The absolute value | V ₁ | is converted into a digital value by the A / D conversion circuit 44. The torque level signal T ₁ which is converted into the digital value is input to the input port A ₂ of the microprocessor 49, the torque level signal T ₁ is
For example, in the case of 8 bits, | V ₁ | = 0 is zero, | V ₁ | = max is 255
To respond to.

The ignition pulse signal V detected by the ignition pulse 46 is input to a pulse signal processing circuit 47. The pulse signal V _S processed by the pulse signal processing circuit 47 is input to the interrupt port INT1 of the microprocessor 49. The pulse signal processing circuit 47 outputs a pulse train corresponding to the engine speed, for example, a pulse train of 0 pulses / sec when the engine speed is 0 rpm, 100 pulses / sec at 3000 rpm, and 200 pulses / sec at 6000 rpm. I am trying to be. When the pulse signal rises or falls, an interrupt is generated at the interrupt port INT1.

Further, the output signal of the above-described abnormality detection circuit 45 is supplied to the interrupt port IN of the microprocessor 49 via the OR gate 48.
Input to T2.

From the output port C ₁ of the microprocessor 49,
Output by the forward and reverse signals M ₀ to identify the rotational direction of the electric motor M, from the output port C _2, the output level signal M ₁ of the digital value is output, these output level signals M _0, M ₁ is
The torque output signal V ₂ is converted into an analog signal by the D / A conversion circuit 50 and output. The output signal V ₂ is input to the first adding circuit 54.

That is, the torque output signal output from the D / A conversion circuit 50 changes according to the steering torque and the engine speed. For example, such as shown in FIG.

Differential circuit output signal voltage from 17 C _{1 1} and the D / A conversion circuit after the vehicle speed sensitive sent from 50 torque signal voltage V ₂
It is added in the first addition circuit 54 to obtain a voltage _{V 3 = C 1 1 + V} 2.

Then, from the first adding circuit 54, a motor driving circuit
52 the signal V ₃ to control the output, in this signal V ₃ in which the electric motor M is controlled.

Further, from the output port C _3, or outputs a pulse indicating the the the program is running normally, the output signal is to be input to the OR gate 48 via the watchdog processor 51.

The differentiating circuit 17 is connected to a second adding circuit 57 separately from the first adding circuit 54. The torque signal processing circuit 41 is also connected to the second adding circuit 57, The output signal V ₁ of the processing circuit 41 is input to the second adding circuit 57. Therefore, the second adder circuit 57
From, the signal V ₁ and the differential signal C _{1 1} and the sum signal
V ₄ is output.

The input / output check circuit 58 is connected to the second addition circuit 57, or the input / output check circuit 58 is connected to the current sensor 55 via the current signal processing circuit 56. Then, this current sensor 55 detects a current supplied to the electric motor M, a current signal processing circuit 56 outputs a signal V ₅ in accordance with the output signal of the current sensor 55. Output check circuit 58 as described above, the output signal V ₄ the input signal x of the second adder circuit 57, the output signal of the current signal processing circuit 56
Let _V5 be the output signal y, and as shown in FIG.
Coordinate points determines whether or not there in any of the normal range N _1, N _2, dead band F _1, F _2, the first output abnormal range U _1, U ₂ or the second output abnormal range U _3, U ₄ .

The dead zones F ₁ and F ₂ are respectively in the _second quadrant,
Those appearing in the quadrant IV, dead band F ₁ of the quadrant II is
The input signal x is x> 0, the output signal y is in the range of 0 <y ≦ <y _0, dead band F ₂ of the IV quadrant, the input signal x is x <
0, the output signal y is in the range of 0> y ≧ -y _0.

Further, U ₁ and U ₂ appear in the first output abnormal region in the _second and fourth quadrants, respectively. In the region where the dead zones F ₁ and F ₂ are excluded from the entire second and fourth quadrants. is there.

That is, the first output abnormal range U _1, the input signal x is x <
0, in the range output signal y is y> y _0, the first output abnormal range U ₂ different from the input signal x is x> 0, the output signal y is y <-y ₀
In the range.

Second output abnormal range U _3, U ₄ is a quadrant I, in the region where the input of the III quadrant appears to near zero showing the vicinity of the neutral position of the steering wheel, the second output abnormal range U _3, the input signal x is 0 <X <x ₀ ,
In the range of the output signal y is y> y _1, the second output abnormal range of different
U _4, the input signal x is 0>x> -x _0, the output signal y is y <-
in the range y. X As described above, the coordinate point of y is, when in any of the first and second output abnormal range U ₁ ~U _4, the output y for the input x is determined to be abnormal circumstances, OR gate The motor drive circuit 52 is controlled via 59 to stop the electric motor M. When the input / output coordinate points x and y are outside the first and second output abnormal areas U _{1 to} U ₄ , it is not determined to be abnormal and the power steering state is continued.

Further, from the output port C ₃ , a pulse is output to notify that the program is operating normally, and this output signal is sent to the OR gate through a word processing circuit 51.
48 is entered.

Thus, the signal V ₄ = x obtained by adding the output signal C _{1 1} from the differentiation circuit 17 to the signal V ₁ output from the torque output signal processing circuit 41, the signal V ₅ = y detected by the current sensor 55 ,
Check input and output check circuit 58, to the direction of the input signal x, when the direction of the output signal y is different, in other words, input coordinates x, y is the first output abnormal range U _1, to U ₂ At a certain time, the motor OFF signal H is output to control the motor drive circuit 52 and stop the electric motor M.

When the input signal x is near zero, the output signal is abnormally high, and the direction is the same, in other words, when the input signal x is in the second output abnormal region U ₃ , U ₄ , the motor OFF signal By outputting H, the motor drive circuit 52 is controlled to stop the electric motor M.

The program configuration of the microprocessor 49 will be described with reference to FIG.

That is, when the ignition switch for starting the engine is turned on, the program starts in synchronization with the ignition switch.

When the program is started as described above, the output level signal M ₁ = 0 is output from the output port C ₂ in step 1.

Then by outputting the motor ON signal from the output port C ₄ in step 2, and sets the maximum value of the ignition pulse count register R of the engine in Step 3 (equivalent to the rotation speed ≒ 0), to complete the operation preparation.

When the preparation is completed as described above, the process moves from step to step 6 in order. Then, the torque level signal T ₁ in step 4 is input to the input port A _2, Step 5
In the data input by entering the torque forward and reverse signals T ₀ to the input port A ₁ is completed. In step 6, but comparing the values R and the constant C ₀ of the pulse count register of the engine speed, when R ≦ C _0, the routine proceeds to step 7 it is determined to be normal.

However, when R ≧ C ₀ , the output motor M is prevented from being driven when the engine is not running, and the engine pulse is not input due to a harness disconnection or the like. Then, the process proceeds to step 9 to execute power-off for fail-safe. That motor M via the OR gate 59 and output from the output port C ₄ a motor OFF signal H in step 9
Is turned off, and in step 10, the output level M ₁ =
0 is outputted from the output port C ₂ and the same state as the normal steering. As a result, the steering wheel becomes appropriately heavy even when the harness is broken during high-speed running, and safety is ensured. In Step 6, when the value R of the pulse counting register is less than the constant C _0, it is determined to be operating normally, the routine proceeds to step 7 as described above. In step 7 and subsequent steps, a calculation for making the output torque sensitive to the engine speed is performed.

That is, in step 7, in response to the torque level signal T _1, to select the address of the torque constant table, pulling out the torque constant C _T at that address.

In step 8, select the address of the engine speed constant table corresponding to the value of the vehicle speed pulse register V, elicit engine speed constant C _R at that address.

In step 11, a torque constant C _T and engine rotational speed constant C _R to the vehicle speed sensitive output torque multiplied,
Shift right by n bits. To thus shifted to the right n bits as _{^{(1/2 n) × C R ×}} C T, obtaining the output level M _1.

If no shifted right by n bits as described above, for example, C _R is 4 bits, the C _T is 8 bits, D / A Konbada is 8 bits, a result of their multiplication becomes 12 bits, D The capacity of the / A converter is exceeded. Therefore, in this case, n = 4 bits are shifted to the right, and a maximum of 8
The number of bits is set so as not to exceed the capability of the D / A converter.

In step 12, an output forward and reverse signals M _0, the torque forward and reverse signals
The same Lay the T _0, is outputted from the output port C ₁ its output forward and reverse signal M ₀ in step 13. Then, the output level signal M ₁ is outputted from the output port C ₂ in step 14, these output forward and reverse signal M ₀ and the output level signal M _1, controls the electric motor M.

Further, in step 15, is outputted from the output port C ₃ a watchdog pulse, when it discovers abnormal, OR
The motor ON-OFF signal H is input to INT2 via the gate 48.

In this embodiment, the second adder circuit 57 is provided so that V ₄ = V ₁
= Seeking C _{1 1,} the value of this V _4, had to be compared with the signal V ₅ on the output side, adds the signal V ₃ is already differentiated signal C _{1 1} output from the first adder circuit 54 It is in order to balance it.

[Brief description of the drawings]

1 to 4 show an embodiment of the present invention.
2 is a circuit diagram, FIG. 2 is a circuit diagram, FIG. 3 is a graph showing a relationship between output level and steering torque, and FIG. 4 is an input signal x.
FIG. 5 is a flow chart showing the operation in the microprocessor 49, and FIG. 6 is a circuit diagram of a conventional device. DESCRIPTION OF SYMBOLS 1 ... Handle, 2 ... Steering input shaft, 3 ... Torque sensor, 6 ... Motor control unit, M ... Electric motor, 46 ... Ignition pulse sensor, 47 ... Pulse signal processing circuit, 49 ... Micro Processor, 55 …… Current sensor,
58 ... Input / output check circuit.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B62D 6/00 B62D 5/04

Claims (1)

(57) [Claims] 1. An electric power steering apparatus for controlling an electric motor according to a running condition of a vehicle, a current sensor for detecting a current supplied to the electric motor, an ignition pulse detector for detecting an ignition pulse, and a steering wheel. A torque sensor for detecting the steering torque of
A motor control unit that controls a current supplied to the electric motor based on the output signal of the ignition pulse detector and the output signal of the torque sensor, and an output signal from the motor control unit and an output signal of the current sensor. An input / output check circuit for comparison, wherein the motor control unit includes a differentiation circuit for differentiating an output signal from the torque sensor, and an addition circuit for adding the output signal of the differentiation circuit and the torque signal of the torque sensor. The input / output check circuit compares the output signal from the addition circuit with the output signal of the current sensor to determine whether the electric motor is operating according to the output signal of the motor control unit, It is determined whether the output signal and the output signal of the current sensor are in a normal range, a dead zone, or an output abnormal range on the XY coordinates. Electric power steering apparatus being characterized in that the.