JPS62227859A - Electromotive power steering device - Google Patents

Abstract

PURPOSE:To prevent a careless steering operation, by stopping the electromotive power when the difference between the detected signals at two torque detecting devices is larger than a preset value, and making the weight of a steering wheel at the weight of the all manual steering without adding the auxiliary torque. CONSTITUTION:When the difference of the two torque detecting signals at strain gauges 40 and 43 is within a specific value, the Q output of the FF 55 is made L, and the Q bar output is made H, and, the power of a motor 8 is controlled at the CPU 47. In other words, CPU 47 reads the absolute value of the torque detecting signals in a specific angle and computes the difference, and when the difference is less than the preset value, it decides that the condition is normal and delivers a current to the motor 8 in a given duty. On the other hand, the difference of the torque detecting signals is out of the specific area, a relay 61 loses the power and cuts off the motor 8 from a power source 62, and the motor 8 receives no power regardless of the operation of CPU 47. Therefore, the output shaft is rotated by only the force imposed to the steering wheel.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a power steering device that reduces the force to be applied to a steering means such as a steering wheel for steering a vehicle. The present invention relates to an electric power steering device that detects a torque applied to a direction setting mechanism that determines the direction of vehicle travel, and applies a torque corresponding to the magnitude of this torque to the direction setting mechanism using an electric motor via a reduction gear.

(Prior Art) This type of device is disclosed in, for example, Japanese Patent Laid-Open No. 59-70257 and Japanese Patent Laid-Open No. 59-209964.

In the electric power steering device disclosed in Japanese Unexamined Patent Publication No. 59-70275, a strain gauge connected to the steering shaft detects the torque applied from the steering shaft to a toe board that sets the direction of the wheels, and determines the magnitude of this torque. A pulse current is applied to the electric motor connected to the steering shaft via a speed reducer at a duty corresponding to the current speed.

In the electric power steering device disclosed in Japanese Patent Application Laid-Open No. 59-209964, a steel plate with a strain gauge joined is inserted between the steering shaft and the direction setting mechanism, and the torsion of the steel plate due to steering is measured by the strain gauge. It detects the amount and energizes the electric motor that assists the steering force with power according to the detected amount.

(Problems to be solved by the invention) In any case, the direction of steering and the force applied for steering, that is, torque, are detected using a strain gauge, etc.
In response to this, the electric motor for steering assistance is energized,
In this type of electric power steering device, the steering assist torque applied by the electric motor varies from device to device and also varies depending on temperature, and due to these variations and fluctuations, the force applied by the vehicle driver to the steering wheel, i.e. The weight of steering changes, and the weight of left and right steering may differ. As a result, steering by auxiliary torque may work against the will of the vehicle driver, or
The auxiliary torque may not work against your will. If the auxiliary torque works or does not work, the steering will be different from what the vehicle driver had planned, resulting in unstable vehicle operation.

An object of the present invention is to prevent vehicle operation from becoming unstable.

[Structure of the invention]

According to the inventor's study, it has been found that variations in steering assist torque among individual devices and fluctuations due to temperature are caused by mechanical variations and wear over time in the 1-lux detection mechanism for detecting the steering torque applied by the vehicle driver. Causes include backlash due to vibration, fluctuations in the initial characteristics of each strain gauge, fluctuations in temperature characteristics, error detection due to vibration, etc., and temperature drift of the strain gauge and the signal processing circuit that processes its detection signal. I understand.

(Means for Solving the Problems) Therefore, in the present invention, at least two sets of
comprising first and second torque detection means;
The electric motor is energized with electric power corresponding to at least one of the detected torques of the torque detection means.

The motor energizing means is provided with a stop instructing means for instructing the motor energizing means to stop energizing when the difference between the detected torques of the first and second torque detecting means is greater than or equal to a set value.

(Function) According to this, the torque detection mechanism for detecting the steering torque and the first. Variations in mechanical settings with the second torque detection means, variations in initial characteristics of each strain gauge,
If the difference between the detection signals of the first and second torque detection means exceeds the set value due to variations in temperature characteristics or temperature drift of the strain gauge and the signal processing circuit that processes its detection signals, the motor is activated. When stopped, the steering wheel becomes fully manual steering with no auxiliary torque applied. Therefore, steering by the auxiliary torque does not work against the will of the vehicle driver during high-speed driving.

When the difference between the detection signals of the first and second torque detection means is less than the set value, that is, when mechanical variations and variations in characteristics are small (in this case, the auxiliary torque of the electric power steering is stable), the The auxiliary torque is controlled based on at least one of the torques detected by the first and second torque detection means, resulting in the intended light steering.

Conventionally, variations in auxiliary torque due to temperature drift in strain gauges and detection signal processing circuits had a large effect, but since the variation in temperature drift is particularly large in high and low temperature ranges, the above-mentioned difference signal becomes large, and this Since the auxiliary torque is cut off at this time, unstable application of the auxiliary torque due to temperature drift is prevented. Therefore, the vehicle speed range to which the auxiliary torque is applied can be expanded to the high speed side. Also,
Since two or more sets of torque detection means are provided and an abnormality is determined by relative comparison of their detection signals, the reliability of the electric power steering device is increased.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

(Example) FIG. 1 shows an outline of the structure of a mechanical section according to an embodiment of the present invention.

A first steering shaft 2 to which a steering wheel 1 is fixed has a first universal joint 4 and a second universal joint 4.
A steering shaft 5 is coupled. A rod 7 is connected to the second steering shaft 5 at a second universal joint 6. This rod 7 is connected to the reducer 9
is connected to the output shaft of the An input shaft of the reducer 9 is coupled to a rotating shaft of the electric motor 8. The output shaft of the reducer 9 meshes with a rack (11: FIG. 2) fixed to the toe board 1o. The toe board 1o is connected to the steering knuckle arm 16 of the wheel 12. A shock absorber 13 is coupled to the axle I2, and a suspension upper support 14 of the shock absorber 13 is coupled to a vehicle body (not shown). I5 is a coil spring for vibration damping between the upper support 14 and the axle, 18 is a lower suspension arm, and 19 is a stabilizer bar.

The internal structure of the reducer 9 is shown in FIGS. 2 and 3. The upper end of the rod 7 (Fig. 2) is connected to the second steering shaft 5 (Fig. 1) via the second universal joint 6 (Fig. 1).
Figure 1). An output shaft 21 of the reducer 9 is fixed to the lower end of the rod 7 (FIG. 2) with a pin 20. Pinion teeth 22 are formed at the lower end of the output shaft 21, and an output gear 23 is formed at the hollow upper end of the output shaft 21. The output shaft 21 is supported by a reduction gear case 24 . An intermediate gear 25 is shaft-supported by the case 24, and this gear 25 meshes with the output gear 23. Another intermediate gear 25 coaxial with and integral with the intermediate gear 25
is the input shaft gear 2 fixed to the output rotating shaft 28 of the electric motor 8.
It meshes with 7. When the output shaft 28 of the electric motor 8 rotates, the output shaft 28 passes through the gear train 27-26, 25-33.
1 rotates, and the rack 11 that meshes with the pinion teeth 22 formed on the output shaft 21 is driven in a direction perpendicular to the paper plane of FIG. 2 (the direction in which the toe board 10 extends in FIG. 1).

The orientation of the wheel 12 (FIG. 1) changes.

A sleeve 30 is fixed to the upper end of the rod 7 (FIG. 2) with a pin 29, and this sleeve 30 is attached to the reducer case 3.
1 is supported by the shaft. The rod 7 passes through the sleeve 30 and enters the output shaft 21, and is fixed to the output shaft 21 at the lower end by a pin 20. Therefore, when the steering wheel 1 (FIG. 1) rotates, the first steering shaft 2. 1st universal joint 4.
The output shaft 2 is connected to the output shaft 2 via the second steering shaft 5 and the second universal joint 6 and via the rod 7.
1 is rotationally driven, and as a result, the rack 11 that meshes with the pinion teeth 22 formed on the output shaft 21 is driven in a direction perpendicular to the paper plane of FIG. 2 (the direction in which the toe board 10 extends in FIG. 1), and the wheel 12 (Figure 1) changes direction.

In this way, the rotation of the output shaft 28 of the electric motor 8.

The direction of the wheels changes depending on the rotation of the steering wheel 1.

A wheel 32 is rotatably mounted on the sleeve 30. That is, the sleeve 30 passes through the wheel 32. As shown in FIG. 4, a round bottom groove 33 is formed on the outer surface of the sleeve 30 and is oblique to the central axis of the sleeve 30, and a ball 34 is fitted into this round bottom groove 33. This ball 34 is supported by the wheel 32.

A narrow groove 35 is formed in the wheel 32, and the upper end of a pin 36 fixed to the upper end of the output shaft 21 enters into this groove 35. This pin 36 restricts rotation of the wheel 32.

When the rod 7 rotates, the sleeve 30 and the output shaft 21 rotate.
is fixed to the lower end of rod 7.

When the load on the output shaft 21 is large, the rotation angles of the sleeve 30 and the output shaft 21 deviate by an amount equivalent to the amount of twist that causes the Rondo door to twist, and the wheel 32 rotates in the same manner as the output shaft 21 via the pin 36. Therefore, the rotation angle difference is a rotation angle difference between the sleeve 30 and the wheel 32. In other words, the sleeve 30 rotates an extra amount with respect to the wheel 32 by an amount corresponding to the deviation, and the groove 33 of the sleeve 30 is obliquely intersecting the central axis of the sleeve 30.

The ball 34 is pushed upward or downward by this groove 33,
The wheel 32 supporting the ball 34 moves upward or downward. The twist of the rod 7 corresponds to the steering torque applied to the steering wheel 1, and the wheel 32 moves to an upper or lower position corresponding to the amount of twist. Therefore, the vertical position W of the wheel 32 (more precisely, the amount moved upward or downward from the zero steering torque position) corresponds to the steering torque.

The wheel 32 has a ring-shaped groove 37. In the groove 32,
A first ball 39 and a second ball 42 are inserted. This situation is shown in FIG.

The first ball 39 is rotatably supported at one end of the first elastic plate 38, and the second ball 42 is supported at one end of the second elastic plate 41 at a position symmetrical to the first ball 39 with respect to the central axis of the rod 7. is rotatably supported. The other ends of the first and second elastic plates 38.41 are fixed at symmetrical positions with respect to the central axis of the rod 7, respectively.

A first strain gauge 40 (an electric element whose resistance value changes according to strain) consisting of a total of four strain detection elements, two on the front surface of the first elastic plate 38 and two on the back surface, is attached to the first elastic plate 38. It is joined. Similarly, a second strain gauge 43 (an electric element whose resistance value changes depending on the strain) consisting of a total of four strain detection elements, two on the front surface of the second elastic plate 41 and two on the back surface, is connected to the second elastic plate 41. 41. 1st ball 39. a first displacement detection means consisting of a first elastic plate 38 and a first strain gauge 40; a second ball 42. The second displacement detection means consisting of the second elastic plate 41 and the second I-rain gauge 43 have exactly the same structure, and only differ in their arrangement positions. In each displacement detection means, four strain detection elements are bridge-connected, and the difference between the resistance values of the elements on the front and back surfaces (one receives compressive stress and the other receives tensile stress, and the signals have different polarities, so
The voltage corresponding to the numerical difference (the level is twice the detection level for only one side) is extracted as a torque detection signal.

When the wheel 32 moves upward or upward in response to the twisting of the rod 7, the first and second elastic plates 38.41 bend upward or downward, and the first and second displacement detection means detect the wheel. 32 (deviation ff1 from the zero steering torque position), that is, the amount of twist of the rod 7, that is, the steering torque is generated.

Since the first and second displacement detection means are arranged symmetrically, the wheel 32 is ring-shaped, and the wheel 32 is supported on both sides by the first and second elastic plates. Therefore, the vertical movement of the wheel 32 is smooth and tilting of the posture is less likely to occur, so that fluctuations in the detection values of the first and second displacement detection means due to variations or play in the mechanical coupling mechanism between the sleeve 30 and the wheel 32 are avoided. is small and the detected value is stable. If the wheel 32 is tilted, the detection signal level of one of the first and second displacement detection means will be high and the detection signal level of the other will be low, but if the average value of these is used as the torque detection value, it will be more accurate. A detected value will be obtained.

FIG. 5 shows the configuration of an electric control device that biases the electric motor 8 to rotate based on detection signals from the first and second displacement detection means.

Motor 8 is connected to switching transistors 63 - 66 of motor energizing circuit 80 . When both the transistors 63 and 65 are on, the motor 8 rotates in the normal direction, and the output shaft 21 is rotated clockwise (this corresponds to clockwise rotation of the steering wheel 1). transistor 64
and 66 are both on, the motor 8 reverses and the output shaft 21
is rotated counterclockwise (this corresponds to counterclockwise rotation of the steering wheel 1: left rotation). The transistors 65 and 66 are for determining the rotation direction of the motor 8, and the transistors 63 and 64 turn on and off the current flowing through the motor 8 at a specified duty to determine the effective current value (time-series average value of the energizing current: the motor's current). This is to control the output torque (the output torque is determined).

The collectors of the transistors 1 to 3 and 64 are connected to the positive terminal of the on-board battery via the relay 61.

The emitters of transistors 65 and 66 are connected to the negative terminal of the onboard battery (equipment ground) via a current detection resistor 72.
It is connected to the.

The switching driver (transistor on/off activation circuit) 67 turns on the transistor 6 when there is a high level H input.
5 is turned on, and when the input is at a low level L, the transistor 65 is restricted to be turned off.

The switching driver 68 turns on the transistor 66 when there is an input at a high level H, and restricts the transistor 66 to turn off when there is an input at a low level L.

The switching driver 70 turns on the transistor 63 when the output of the pulse width modulator 71 is H and the input to the driver 67 is H, and restricts the transistor 63 to OFF when one of them is L.

The switching driver 69 turns on the transistor 64 when the output of the pulse width modulator 71 is I] and the input to the driver 68 is F(, and constrains the transistor 64 to turn off when one of them is L.

Relay driver 60 energizes relay 61 to connect the collectors of transistors 63 and 64 to battery 62 when the output of AND gate 59 is 1].

When the output of the AND gate 59 is L, the relay 61 is deenergized and the collectors of the transistors 63 and 64 are connected to the battery 6.
Block from 2. In the AND gate 59, the microprocessor 47 controls the relay on (energized: H)/off (deenergized: L).
) A stop instruction circuit 9o, which will be described later, also provides an instruction signal.
gives a relay on (energized: H)/off (deenergized: L) instruction signal A. Therefore, the microprocessor 47 instructs the relay 61 to turn on, and the stop instruction circuit 9
It is energized only when 0 indicates relay on.

In this embodiment, the pulse width modulator 71 is a digital timer consisting of a preset counter, a clock pulse oscillator, and a controller, and loads data Hd into the counter so that the counter generates a carry (Hd count over). Until then, the output is high level H (transistor on instruction), and when a carry occurs, the output is low
(transistor off instruction), Ld is loaded into the counter, and when the counter generates a carry, data Hd is loaded into the counter and the output is set to H, and the operation is repeated. That is, the pulse modulator 71 has a duty of H during the time interval indicated by the data Hd, a duty of H during the next time interval indicated by the data Ld, and a duty of H during the next time interval indicated by the data Hd. /(Hd+Ld) pulse is generated. Note that when Hd is data indicating zero, L
Continue output.

Data Hd and Ld indicating the duty are generated by the microprocessor 47.

A stop instruction circuit 90 is connected to the first and second strain gauges 40 and 43.

The torque detection signal of the first strain gauge 40 is subjected to linearization amplification processing for filtering and level calibration in an amplifier 44 and is provided to an absolute value circuit 45 . Absolute value circuit 4
5 generates a signal (positive polarity) indicating the absolute value level of the output of the amplifier 44, that is, a signal indicating the absolute value of the detected torque, and inputs the input channel C112 of the A/D converter 46.
to be applied. The polarity of the detected torque (signal plus or minus: this corresponds to the rotation direction of the wheel 1; plus corresponds to clockwise rotation, and minus corresponds to counterclockwise rotation) is determined by the polarity discrimination circuit 50, and if the polarity is positive ( A direction signal C of level 4 is generated when the rotation is clockwise (clockwise rotation), and L level is generated when the rotation is negative (counterclockwise rotation), and this is applied to the AND gate 82.

The torque detection signal of the second strain gauge 43 is also transmitted to the amplifier 4.
8 and absolute value circuit 49, and a signal (positive polarity) indicating the absolute value of the detected torque is sent to the A/D converter 4.
6 input channel C113. In addition, the polarity of the torque detection signal is determined by the circuit 79, and the polarity is positive (
A direction signal is applied to the AND gate 83, which is at H level when the rotation is clockwise (clockwise rotation) and at L level when the rotation is negative (counterclockwise rotation).

A signal indicating the torque detected by the first strain gauge 40 (positive, negative) and a signal indicating the torque detected by the second strain gauge 43 (positive, negative) are applied to the differential amplifier 51, and a signal indicating the difference between the two (positive, negative) is applied to the differential amplifier 51. , negative) are provided to comparators 52 and 53.

The correlation between No. 4B indicating the difference and the outputs of the comparators 52 and 53 is as follows.

(1) When the level of the signal indicating the difference is equal to or higher than the upper limit level UL (positive), the output of the comparator 52 is H (the difference value is too large: abnormal), and the output of the comparator 53 is L.

(2) When the level of the signal indicating the difference is less than the upper limit level UL and exceeds the lower limit level LL (negative),
The outputs of comparators 52 and 53 are both L (the difference value is small:
normal).

(3) When the level of the signal indicating the difference is below the upper limit level UL and below the lower limit level LL, the output of the comparator 52 is L and the output of the comparator 53 is H (the difference value is too large: abnormal).

The outputs of comparators 52 and 53 are applied to the S input terminal of flip-flop 55 via OR gate 54. When the power supply (Vc) is on, a pulse is applied to the flop-flop 55 at the R input terminal, and it is reset at the rising point of the pulse, producing a Q output at L level and an output at H level. When an H signal (indicating an abnormality) is added,
It is set at the rising point to H, switching the Q output from ■ to H, and switching the output from H to L.

=9-output signal A is applied to AND gate 59.

Therefore, the signal indicating the difference between the signal indicating the torque detected by the first strain gauge 40 and the signal indicating the torque detected by the second strain gauge 43 is within the setting range LL.
-When it is within the UL, that is, in (2) above,
The Q output of the flip-flop 55 is H, and the signal A (Q) given to the anti-game I-59 is H.
When the microprocessor 47 outputs the relay 61 ON (auxiliary torque application instruction: power steering mode instruction), the electric motor 8 is energized.

When the signal indicating the difference is out of the setting range LL-UL, that is, in the case of (1) or (3) above, the output Q of the flip-flop 55 is H, -9, and the output is L, so that the output is low. Even if the microprocessor 47 turns on the relay 61 (auxiliary torque application instruction: power steering mode instruction) in response to the signal A (Q) given to −1 to 59, the output of the AND gate 59 remains L. ,
Relay 61 is not energized and motor 8 is not energized. When the steering wheel 1 is steered, the output shaft 21 rotates, and this rotation mechanically rotates the rotor of the electric motor 8. The force required to idle the rotor requires a higher steering force than in the case of a steering device without power support.

Since the Q output of the flip-flop 55 is applied to the OR gate 56 and the microprocessor 47, when the signal indicating the difference is outside the setting range LL-UL, that is, in (1) or (3) above, the Q output is applied to the OR gate 56 and the microprocessor 47. Since is H,
The LED (light emitting diode) driver 57 is energized and the light emitting diode 58 lights up. This light emitting diode 5
8 is attached to the front panel of the driver's seat of the vehicle. The microprocessor 47 has a signal indicating a difference that is outside the set range. When it is determined that this is the case, I4 is also applied to the OR gate 56, and the light emitting diode 58 is turned on.

The absolute value of the signal indicating the torque detected by the first strain gauge 40 and the detection 1- by the second strain gauge 43
A comparator 53 compares the absolute value of the signal indicating the current value.

The comparator 53 generates an H level signal when the former is greater than or equal to the latter, and an L level signal when the former is less than the latter, and applies this signal as it is to the anime game 1-82.
An inverted signal is applied to the AND gate 83. The outputs of AND gates 82 and 83 are provided to microprocessor 84 via OR gate 84. The contents of the output B of the OR gate 84 are as follows.

(,1) The absolute value of the detected torque of the first gauge 40 is
When the detected torque of the gauge 43 is greater than the absolute value, the output of the comparator 81 is ■, the AND gate 82 is on, the AND gate 83 is off, the output C of the polarity discrimination circuit 50 is given to the OR gate 84, and the output of the OR gate 84 is Output B is signal C. That is, the signal C indicating the polarity of the torque detected by the first gauge 4o
is provided to microprocessor 47.

(5) When the absolute value of the detected torque of the first gauge 40 is less than the absolute value of the detected torque of the second gauge 43, the comparator 8
1 is output, 82 is off and 83 is on, and the output of the polarity determining circuit 79 is given to the OR gate 84, and the output B of the OR gate 84 is a signal. That is, a signal indicating the polarity of the torque detected by the second gauge 43 is given to the microprocessor 47.

As will be described later, when the difference between the detected torque of the first gauge 40 and the detected torque of the second gauge 43 is within the setting range LL-UL (normal), the average value of both detected torques is calculated and the average value is calculated. The value is used as the detected torque value.

As described later, this average value is calculated after A/D conversion of the absolute values of both detected torques, so the polarity of the detected torques is unknown. Microscopically, the polarity of the rain detection torque may be different, so it is necessary to determine the polarity of the average value (polarity of the detection torque: corresponding to the rotation direction of the wheel 1). Therefore, in this embodiment, as in (4) and (5) above, a signal C indicating the polarity of both detected torques is used.
and D, the one with the larger absolute value indicating the polarity of the detected torque is selected and supplied to the microprocessor 47.

The voltage across the resistor 72 is smoothed by an amplifier circuit 73, amplified for level calibration, and applied to channel C of the A-/D converter 46.

While the microprocessor 47 is outputting the relay 61 ON signal to the AND gate 59, the microprocessor 47 turns on A at a predetermined timing.
Instruct the /D converter 46 to manually perform A/D conversion on channel C81, read the voltage of the resistor 72, that is, the smoothed value of the current of the motor 8, as digital data, and use the duty instruction data Hd and Ld output at that time. Compared with the determined average current value, abnormalities (
If there is an abnormality, the relay 61 is turned off (no auxiliary torque is applied by the electric motor 8), H is applied to the OR gate 56, and the control operation is stopped there. Note that after stopping in this manner, the microprocessor 47 cannot be reset unless the key switch 78 is turned off and then turned on again.

An amplification waveform shaping circuit 76 is connected to a reed switch 74 that opens and closes according to the rotation of a permanent magnet gear 75 fixed to a vehicle speed meter cable (a wire that rotates in conjunction with the rotation of the output shaft of a transmission). A pulse (vehicle speed detection pulse) which is at L level when 74 is closed and at H level when it is open (vehicle speed detection pulse) is applied from waveform shaping circuit 76 to an interrupt port of microprocessor 47 .

A battery 62f! is connected to the constant voltage power supply circuit 77 via a key switch 78. A voltage is applied and circuit 77 provides the required constant voltage to each part of the circuit shown in FIG.

FIG. 6 shows the main electric power steering control operations performed by the microprocessor 47.

When the power is turned on (when the key switch 78 is closed and the power supply circuit 77 generates the required constant voltage), the microprocessor 47 initializes the input/output board, registers, timers, flags, etc. That is, it is set to the content required in the standby state.

Through this initialization, the output to the AND gate 59 is set to L, and the relay 61 is set to off (although it was originally off) (Step 2: Hereinafter, the word "step" will be omitted in parentheses).

Next, the microprocessor 47 allows interrupts (3)
. As a result, interrupt processing is executed every time the interrupt port input switches from I (to L).One of the interrupt ports is interrupt 1.When the input of this port switches from H to L. FIG. 8 shows the interrupt processing that is sometimes executed.

Now, to explain the processing of interrupt 1 with reference to FIG.
Update the register contents n to a number larger by 1.22), n
It is checked whether the content n of the register is 4 (23). If it is not 4, return to the main routine. 4, the count data CKC of the clock pulse counter (program counter) CKC is sent to tx
m register memory (24) and clears the counter CKC (25). This causes the counter CKC to count up again from 0. txm register contents t
x corresponds to the elapsed time between the successive arrivals of four vehicle speed detection pulses.

Next, the n register is cleared (26). Next, the contents of the M3 register for calculating the average value of vehicle speed values are transferred to the M4 register, the contents of the M2 register to the M3 register, and the contents of the Mm register to the Mm register (27), and /lx is transferred to the Mm register. (28). tx is the content of the txm register, K is a constant, and is a conversion constant for obtaining the frequency of the vehicle speed detection pulse, that is, the vehicle speed, from the 4 cycles (tx) of the output pulse of the shaping circuit 76, and K/lx is the vehicle speed data. It is. Next, the average vehicle speed Vm=(4M1+2M2+M3+Ma)/8 is calculated and stored in the Vm register (29), and the process returns to the main routine. M 1 r M2 t M3 and M4
are the Mm register and M2 register, respectively.

These are the contents of the M3 register and M4 register.

The reason why the weighted average is taken is to reduce the probability of incorrect vehicle speed detection due to noise or the like.

Through the above-described interrupt 1 processing, the vehicle speed data is constantly stored in the Vm register, and the vehicle speed data is updated to the latest data every time four consecutive vehicle speed detection pulses occur.

Referring again to FIG. When the interrupt is permitted (3), the microprocessor 4 sets a T timer for determining the detected torque reading cycle (4), and instructs the A/D converter 46 to manually perform A/D conversion of channel CH2. Conversion data (absolute value of torque detected by gauge 40: Tq
l) and store it in the TQI register 5), then instruct channel CH3 manual A/D conversion, and convert the conversion data (absolute value of torque detected by gauge 43: T
q2) and stores it in the TCI2 register (6
).

Next, calculate the absolute value Td of the difference between the detected torques Tql and Tq2 (7), and compare it with the set value Ta (8).

Ta has a value comparable to (Ur,, -LL)/2, but Ta is not necessarily exactly equal to (UL-LL)/2.

If T d < Ta, the absolute value T91 of the torque detected by the gauge 40 and the torque Tq detected by the gauge 43
Since the difference from the absolute value of 2 is less than the set value Ta (normal), the light emitting diode 58 is turned off (9).

Average absolute value of detected torque Tm=(Tql+Tq2)/2 (10).

The internal ROM of the microprocessor 47 stores duty instruction data HdO+LdO assigned to each absolute value of the detected torque Tm and auxiliary torque application rate Kv assigned to each vehicle speed. These values are shown in section 7a.
Qualitatively shown in Figures 7b and 7b. Note that since digital data is stored in the ROM, the curves shown in FIGS. 7a and 7b are actually one step.

In step 11, the microprocessor 47 calculates the calculated T
The data Hd o + I-d O corresponding to m is internally RO
The data Kv corresponding to the contents Vm of the Vm register are read from the internal ROM, and ν is set to Hd=.
- Calculate Hdo and store this Hd in the lower 4 bits of the PWM register, and store the read LdO in the upper 4 pins 1- of the PIi1M register. Next, referring to output B of the OR gate 84 (12), if it is H (detected torque is positive: wheel 1 is being driven clockwise), the direction register is set to forward rotation (output shaft 21 is driven clockwise). 13) If B is L (detected torque is negative: the wheel is being driven counterclockwise), set the data that instructs the direction of rotation of the electric motor (8 rotation direction) in the direction register.
(8 rotational directions of the electric motor that drives the output shaft 21 clockwise)
(14). Then turn on the relay 61 (set H to the output port to the AND gate 59) L, (15), set the contents of the PWM register to the output ports OP1 to OP8, and set the contents of the direction register to the output ports OP9, 0 PIO. (16). PWM
The assignment of register contents and direction register contents to output ports is shown in FIG. 7C.

With this output set (16), when Tm is greater than or equal to a predetermined value near 0, Hd > 0 and the motor 8 receives Hd/(
A current is passed through the duty of Hd+Ld), and the current is applied in the direction in which the steering wheel 1 is trying to turn. l! The I1 machine 8 attempts to rotate the output shaft 21.

The output torque of the electric motor 8 is proportional to Hd/(Hd+Ld). That is, the value corresponds to the detected torque Tm and the vehicle speed Vm, and the larger the detected torque Tm, the greater the torque, and the lower the vehicle speed Vm, the greater the torque that the electric motor 8 applies to the output shaft 21. After setting the contents of the PWM register and direction register to the output ports OP1-f) PIO (16), the microprocessor 47 checks whether the T timer has exceeded (17). That is, it is checked whether the elapsed time from step 4 is greater than or equal to T. If it has exceeded (T elapsed), the process returns to step 4, and if it has not exceeded, it waits until it has exceeded and returns to step 4.

In this way, in T periods, steps 4-8-9-17
, detected torque reading (5, 6), detected torque difference calculation (
7), abnormality determination (8), average value calculation of detected torque (10)
), calculation of the energizing current duty of the motor 8 (1, 1),
Then, the motor energization instructions (12 to 16) are repeatedly executed.

When the difference Td between the absolute values Tql and Tq2d of the detected torque is greater than or equal to the set value Ta, or when Td becomes greater than or equal to Ta, the process proceeds from step 8 to step 18, and relay 6 is activated.
1 to turn off the motor 8 from the power supply (62), output I to the OR gate 56 to light the light emitting diode 58 (1.9), initialize the PWM register, and set the contents of the PWM register to 0. ) to the output port (
20). As a result, the output of the pulse width modulator 71 also becomes L, and the transistors 63 and 64 are constrained to be turned off. Microprocessor 47 then selects Q of flip-flop 55.
Check the output 21), and if it is H (the stop instruction circuit 90 has also detected an abnormality), the Q output will be L.
wait until it becomes In other words, the controller waits with the steering assist torque application control stopped.

When the Q output of the flip-flop 55 is low (the stop instruction circuit 90 detects normality), the process from step 21 to step 1 is performed.
6, and return to step 4 via steps 16 and 17. In this case, steps 4-8-18-21-
16-17-4, the electric motor 8 is not energized. During this cycle, if T d < Ta, the control returns to the normal state, and if T d < Ta does not occur and the Q output of the flip-flop 55 also becomes 1 (if it becomes 1, the process waits in step 21, The electric motor 8 remains deenergized.

The operation and advantages of the embodiments described above will now be summarized.

(1) Torque detection of the first strain gauge 40 No. 7g (
Correct.

The difference (positive, negative: equipment ground level when the difference is O) between the torque detection signal of the second strain gauge 43 (positive, negative: equipment ground level when the difference is O) is predetermined. When within the range LL (negative) to UL (positive), the Q output of the flip-flop 55 is high and the Q output is H, and the energization of the electric motor 8 is controlled by the microprocessor 47.

The microprocessor 47 calculates the absolute value Tql of the torque detection signal of the first strain gauge 40 and the second strain I- in T periods.
The absolute value Tq2 of the 1-lux detection signal of the rain gauge 43 is read, the difference Td is calculated, and if Td is less than the set value, it is considered normal, and the average value Tm of T(II and Tq2, etc., determined by the vehicle speed Vm The electric motor 8 is energized at duty! (d/(Hd+Ld). The rotation direction of the electric motor 8 is determined by the output of the comparator 81, and when Tql is Tq2 or more, the rotation direction of the electric motor 8 is energized according to the polarity of the detection signal of the first strain gauge 40. , if it is positive, it will be clockwise, and if it is negative, it will be counterclockwise.When Tql is smaller than Tq2, depending on the polarity of the detection signal of the second strain gauge 40, if it is positive, it will be clockwise. If negative, the direction is counterclockwise.

If Td is greater than the set value, it is determined that there is an abnormality, the light emitting diode 58 is turned on, the relay 61 is turned off, the pulse width modulator 71 is set to L, and the motor 8 is not energized (the microprocessor 47 detects an abnormality). protective action when detected).

(2) When the difference between the torque detection signal of the first strain gauge 40 and the torque detection signal of the second strain L/in gauge 43 is outside the predetermined range LL (negative) to UL (positive), the Q output of the flip-flop 55 is H,Q Ant Gate 59
is tied off, the relay 61 is deenergized and the motor 8 is cut off from the power supply (62), and the motor 8 is not energized (stop command circuit 90) regardless of the operation of the microprocessor 47. protective operation when an abnormality is detected).

Similar to steering devices without torque assistance, the output shaft 2
1 is rotationally driven only by the force applied to the steering wheel 1.

In addition, in this state, the microprocessor 47 is also abnormal (Td
≧Ta), the microprocessor 47 stops the control operation and performs vehicle speed calculation (distribution) until the stop instruction circuit 90 detects normality or the power supply (key switch 78) is turned off and then turned on again. (1: Figure 8) only.

(3) According to (1) and (2) above, if at least one of the stop instruction circuit 90 and the microprocessor 47 detects an abnormality, the electric motor 8 is not energized.

(4) The stop instruction circuit 90 is connected to the first strain gauge 40
When the difference between the torque detection signal of the second strain gauge 43 and the torque detection signal of the second strain gauge 43 is out of a predetermined range LL (negative) to tJL (positive), the relay 61 is turned off as an abnormality.

The microprocessor 47 has a first . Absolute value TQI of the detected torque of the second strain gauges 40, 43, "rq2
When the difference Td of
(Hd=0), and the transistors 63 and 64 are also constrained to be turned off.

The predetermined range LL (negative) - UL (positive) and Ta are set independently and do not exactly match. However, all of these are set in association with unacceptable detection differences.

If there is an unacceptable abnormality in the torque detection mechanism related to the combination of the rod 7, elastic plates (38, 41), strain gauge (40° 43), output shaft 21, etc., such as play, vibration, breakage, etc. If there is an unacceptable abnormality in the strain gauge (40, 43) and the signal processing circuit connected to it, such as a partial disconnection, short circuit, or temperature drift, the first strain gauge 40 system and the second strain gauge There is virtually no possibility that the system of gauges 43 and the system of gauges 43 simultaneously generate torque detection signals with an acceptable difference. For example, even with regard to temperature drift, which becomes a problem at high temperatures, there are variations depending on the element and circuit, and the drift difference due to this variation becomes larger as the temperature increases.
Even if there are two torque detection signals, it is virtually impossible to generate torque detection signals at the same time with a difference within an allowable range.

Therefore, through the above-described abnormality protection operation, an abnormality in the torque detection system is sufficiently determined, and a protective operation corresponding to the abnormality (stopping of energization of the electric motor 8) is performed.

The weight of steering the steering wheel without auxiliary torque during low-speed running is much greater than when the auxiliary torque is present, but since the vehicle is running at low speed, there is no particular danger. The weight of steering the steering wheel without auxiliary torque while driving at high speed is only slightly heavier than with auxiliary torque. This is because the steering force is originally low at high speeds, so a low auxiliary torque is applied. Therefore, even if there is no auxiliary torque due to the protective operation, the safety of vehicle operation is not impaired. Since the steering wheel is light when driving at high speeds, and the direction of the vehicle changes quickly with a slight rotation, incorrect steering torque assistance could result in unintentional steering, which is very dangerous. Since the auxiliary torque is cut off, safety is increased. This is a so-called fail-safe.

〔Effect of the invention〕

As described above, the present invention includes a torque detection mechanism for detecting steering torque and a first . Variations in the mechanical settings with the second torque detection means, variations in the initial characteristics of each strain gauge, variations in temperature characteristics, or disconnections in the strain gauges and the signal processing circuit that processes their detection signals, - due to temperature drift, etc., the first and second
When the difference between the detection signals of the torque detection means is greater than the set value,
The electric motor energization is deactivated and the steering wheel becomes fully manual steered with no auxiliary torque applied. Therefore, steering by the auxiliary torque does not work against the will of the vehicle driver during high-speed driving.

When the difference between the detection signals of the first and second torque detection means is less than the set value, that is, when the mechanical variations and variations in characteristics are small (in this case, the auxiliary torque of the i! dynamic power steering is stabilized), , the auxiliary torque is controlled based on at least one of the torques detected by the first and second torque detection means, resulting in the intended light steering.

Conventionally, the variation in temperature drift of strain gauges and detection signal processing circuits was particularly large in high and low temperature ranges.
Fluctuations in the auxiliary torque due to temperature drift in high and low temperature ranges are particularly dangerous when driving at high speeds, so the vehicle speed range in which the auxiliary torque is applied has been limited to low speeds, but according to the present invention.

Since the variation in temperature drift is particularly large in the high temperature range and the low temperature range, the above-mentioned difference signal becomes large and the auxiliary torque is cut off at this time, so that unstable application of the auxiliary torque due to excessive temperature drift is prevented. Therefore, the vehicle speed range to which the auxiliary torque is applied can be expanded to the high speed side. Also,
Since two or more sets of 1-lux detection means are provided and an abnormality is determined by relative comparison of their detection signals, the reliability of the electric power steering device is increased.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an outline of a mechanical structure according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view of the reducer 9 shown in FIG. 1, and is a sectional view taken along the line II--II in FIG. 3. FIG. 3 is a sectional view taken along the line ■--■ in FIG. 2. FIG. 4 is a plan view showing the outer surface of the sleeve 30 shown in FIGS. 2 and 3. FIG. FIG. 5 is a block diagram showing the configuration of the electrical control system of this embodiment. FIG. 6 is a flowchart showing an overview of the control operation of the microprocessor 47 shown in FIG. 7a and 7b are graphs schematically showing data stored in the internal ROM of the microprocessor 47. FIG. FIG. 7c is a plan view showing the correlation between the data in the internal registers of the microprocessor 47 and the ports to which it is output. FIG. 8 is a flow chart showing the interrupt processing operation of the microprocessor 47. 1 Steering wheel 2, 5 Steering shaft 4.6: Universal joint (1 to 6
: ffl rudder means) 7: Rod 8
: Electric motor 9: Reducer 10: l--board 11 (7, 1, 0, 11
, 16, 22: Running direction setting mechanism) 12: Wheel
13: Shock absorber 14: Suspension upper support 15: Coil spring 16: Steering knuckle arm 17: Tie rod 18: Lower suspension arm 19 Stabilizer bar 2
0: Pin 21: Output shaft 22
: Pinion gear 23: Output gear 24
:Reduction gear case 25:Second reduction gear 2
6: 1st reduction gear 27: Input gear 2
8: Rotating shaft 29: Pin 30 sleeve 31: Reducer case 32
: Wheel 33: Round bottom groove 34: Ball 35: Groove 36: Connecting pin
37: Ring groove 38: First elastic plate
39: First ball 40: First strain gauge (38, 39, 40: First displacement detector) (7, 30, 32, 38, 39, 408 first torque detection means) 41: Second elastic plate 42: 2nd ball 43: 2nd ball 1
Herrein gauge (41, 42, 43: 2nd displacement detector)
(7, 30, 32, 41, 42, 7I3: second torque detection means) 44: Linearization amplifier 45:
Absolute value circuit 46: A/D converter 47: Microprocessor (energization instruction means, stop instruction means) 48 Bilinear amplifier 49: Absolute value circuit 50: Polarity discrimination circuit 51: Differential amplifier 52.53. Comparator 54 Nior gate 55: Flip-flop 56: Or gate 57: LED driver
58 Two light emitting diodes 59: AND gate
60: Relay driver 61: Relay
62 2nd car upper battery 63.64: PW
M switching transistor 65: Forward switching transistor 66: Reverse switching transistor 67 to 70 Ni switching driver 71: Pulse width converter 72: @ Current detection resistor 73: Smoothing amplifier circuit 74: Reed switch 75: Permanent magnet gear 76: Waveform shaping circuit 77: Constant voltage power supply circuit 78:
Key Inochi 79: Polarity discrimination circuit 80: Motor energizing circuit (motor energizing means) 81: Comparator 82.83: AND gate 84 Nior gate 90: Stop instruction circuit (stop instruction means) Door 3 Diagram Voice 4 Diagram City 8 Procedure Amendment c method) % formula % Director General of the Patent Office Mr. Michibu Uga Beni 1, Indication of case 1985 Patent Application No. 071963 2゜ Title of invention Electric power steering device 3, Relationship with the amended person case Patent Applicant Address 2-1 Asahicho, Kariya City, Aichi Prefecture Name
(001) Aisin Seiki Co., Ltd. Representative Kiyoshi Ito 4, Agent Address: 103 Phone: 03-864-6052
Address: 2-27-6 Higashi Nihonbashi, Chuo-ku, Tokyo, Showa 6
May 7, 1 year (shipment date: May 27 of the same year) 6. Subject of amendment Drawing 7. Contents of amendment

Claims (3)

[Claims] (1) A running direction setting mechanism that determines the orientation of the wheels with respect to the vehicle body; A steering means that is coupled to the running direction setting mechanism and drives the running direction setting mechanism; A running direction setting mechanism that has an output shaft coupled to the running direction setting mechanism; a reduction gear that drives; an electric motor that rotationally drives the input shaft of the reduction gear; a motor energizing means that energizes the electric motor in forward and reverse directions; first and second motors that detect the torque that the steering means applies to the direction setting mechanism
Torque detection means; energization instruction means for instructing the motor energization means to energize the motor with electric power corresponding to at least one of the detected torques of the first and second torque detection means; and the first and second torque detection means. An electric power steering device comprising: stop instruction means for instructing the motor energizing means to stop energizing when the difference in torque detected by the means is greater than or equal to a set value. (2) The steering means includes a steering wheel and a steering shaft that connects the steering wheel and a travel direction setting mechanism; the first torque sensing means has one end connected to the steering shaft and the other end connected to the output shaft of the speed reducer. a first displacement detector that generates an electric signal corresponding to the amount and direction of displacement of a displacement member that moves in a direction along the central axis of the rod in response to the torsion of the rod; the second torque detection means , corresponding to the amount and direction of displacement of a displacement member that is disposed at a position symmetrical to the position of the first displacement detector with respect to the rod and moves in a direction along the central axis of the rod in response to the torsion of the rod. The electric power steering device according to claim 1, which is a second displacement detector that generates an electric signal. (3) The first displacement detector includes a first elastic plate with one end supported by the displacement member and the other end fixed, and a first strain gauge joined to the first elastic plate; , one end of the first elastic plate is supported by a displacement member at a position symmetrical to the one end of the first elastic plate with respect to the rod;
Claim (2): comprises a second elastic plate whose other end is fixed at a position symmetrical to the other end of the elastic plate; and a second strain gauge joined to the second elastic plate; The electric power steering device described.