JP2001050830A - Torque sensor for power steering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the feeling of wrongness of steering and to reduce malfunction caused by the influence of noise by allowing a characteristic adjustment means to operate only if the output of a torque sensor is within the range of a dead zone. SOLUTION: The torque detection part of a torque sensor 1 for power steering is composed of a magnetostriction-type torque sensor consisting of a pair of detection coils 3a and 3a and a pair of excitation coils 4a and 4b. A characteristic-adjusting means is composed of a gain adjustment circuit 10, a middle point voltage adjustment circuit 13, and a CPU 12. The CPU 12 judges whether the output of the torque sensor 1 is within the range of a dead zone that becomes the non-execution region of power assist or not and allows the characteristic-adjusting means to operate only if the output is within the range of the dead zone, thus preventing the output characteristics of the torque sensor 1 from fluctuating when the power assist is being made and preventing steering from becoming heaving or lighter during the operation of a steering wheel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a torque sensor for power steering, and more particularly to an improvement for stabilizing output characteristic adjustment performed in response to a change in environmental temperature.

[0002]

2. Description of the Related Art A power steering torque sensor in which the output characteristic of a torque sensor is adjusted in accordance with a change in environmental temperature is already known. In particular, such a torque sensor as a magnetostrictive torque sensor depends on a change in environmental temperature. In the case of a power steering torque sensor in which the output characteristics of the torque sensor itself, for example, the midpoint voltage, the gain, etc. fluctuate significantly,
The adjustment of output characteristics according to the environmental temperature is an important issue.

In general, in this type of torque sensor for power steering, an environmental temperature is detected at a predetermined adjustment cycle, and each time, the output characteristic of the torque sensor is adjusted in accordance with the environmental temperature, and the difference in the environmental temperature is detected. By correcting the fluctuation of the output characteristics caused by the above, an appropriate power assist command corresponding to the steering force acting on the steering wheel (the steering wheel) is input to the power steering controller to drive and control the electric motor for the power assist. I have to.

[0004]

However, if the output characteristics of the torque sensor are adjusted in a situation where power assist is performed by an electric motor or the like, especially when the environmental temperature changes drastically, this adjustment processing is performed. As a result, the midpoint voltage and gain of the torque sensor may be significantly corrected.

In such a case, the power assist command output from the power steering torque sensor fluctuates in spite of the fact that the steering force acting on the steering wheel is constant, and the power from the electric motor or the like is correspondingly changed. A problem such as a change in assist force may occur, and a driver operating the steering wheel may feel uncomfortable, such as suddenly becoming lighter or lighter.

If the output characteristics of the torque sensor are adjusted when power assist is performed by an electric motor or the like, especially in a configuration in which this adjustment is performed by digital processing using a microprocessor, the driving state is not changed. There is a possibility that the noise of the electric motor or the like in the above may act as a disturbance, making it impossible to transmit appropriate data from the microprocessor to the characteristic adjustment means.

On the other hand, a mechanical torque detecting switch is provided on a steering shaft (handle shaft) for the purpose of accurately performing the zero point adjustment (midpoint voltage adjustment) of the power steering torque sensor. A torque sensor that adjusts the output characteristics of a torque sensor only when a zero state is detected is disclosed in
No. 159552, which is
Since it is necessary to provide an independent torque detection switch separately from the torque sensor, there are disadvantages that the structure is complicated and the manufacturing cost is increased.

Furthermore, in the conventional general torque sensor for power steering, the output characteristic of the torque sensor is always adjusted in a short adjustment cycle irrespective of the environmental temperature and the operating state of the device. The adjustment work is performed more frequently than necessary, and malfunctions are liable to occur, and power is wasted.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the disadvantages of the prior art and eliminate the feeling of strange steering feeling.
It is an object of the present invention to provide a power steering torque sensor that is less likely to malfunction due to the influence of noise and that can suppress power consumption.

[0010]

According to the present invention, there is provided a torque sensor for detecting a steering force acting on a steering wheel and outputting it as a power assist command, a temperature detecting means for detecting an environmental temperature, and a temperature detecting means for detecting an environmental temperature. Characteristic adjusting means for adjusting the output characteristic of the torque sensor at every predetermined adjustment cycle based on the environmental temperature.The torque sensor for power steering, wherein the output of the torque sensor is a non-execution region of the power assist. Output state determining means for determining whether the output is within the range; and characteristic adjusting means only when the output of the torque sensor is within the dead zone, receiving the determination result from the output state determining means. And an adjustment operation restricting means for permitting the operation of (1). According to this configuration, the output characteristic of the torque sensor is adjusted only when the output of the torque sensor is within the dead zone that is the non-execution region of the power assist. Therefore, the output characteristics of the torque sensor, such as the midpoint voltage and the gain, do not change while power assist is being performed, and the driver feels uncomfortable that the steering becomes heavy or light during the operation of the steering wheel. As a result, the steering feeling is improved. In addition, since the output characteristics of the torque sensor are adjusted in a state where the electric motor or the like serving as the power source of the power assist is inactive, abnormality in processing operation due to noise or disturbance, for example, when a microprocessor is used as the characteristic adjustment means This prevents abnormal data transmission.

Further, the adjustment cycle is maintained at the set value for the temperature fluctuation period until the power-on time to the torque sensor reaches a predetermined set value, while the power-on time to the torque sensor is predetermined. If the set value exceeds the set value, a power-on time corresponding adjustment period changing means for setting a set value for the temperature stabilization period longer than the set value for the temperature fluctuation period in the adjustment period is provided, thereby wasting power consumption. Will be resolved. That is, in the initial stage of turning on the power, the temperature of the device is often unstable, and it is necessary to adjust the output characteristics of the torque sensor relatively frequently. Therefore, the set value for the temperature fluctuation period, that is, a relatively short time While the output characteristics are adjusted with the adjustment period as the adjustment period, after the temperature of the device is stabilized, the set value for the temperature stabilization period, that is, by adjusting the output characteristics with the adjustment period of a relatively long time, , So as to eliminate unnecessary consumption of electric power.

[0012] Further, while the environmental temperature detected by the temperature detecting means is within a predetermined set range, the adjustment period is maintained at a set value for normal temperature, while the environmental temperature detected by the temperature detecting means is maintained at a predetermined value. By disposing an environmental temperature corresponding adjustment cycle changing means for setting a high / low temperature set value shorter than the normal temperature set value in the adjustment cycle when the temperature is out of the predetermined setting range, waste of power consumption is achieved in the same manner as described above. Can be eliminated. That is, when the environmental temperature is extremely high or low, there is a high possibility that the temperature change near the torque sensor becomes severe due to the influence of the cooling or heating of the automobile, and the output characteristics of the torque sensor are relatively frequently changed. Since it is necessary to adjust, setting values for high and low temperatures, in short, adjusting the output characteristics with a relatively short time as an adjustment cycle, and when the environmental temperature is within a predetermined setting range, By performing the output characteristic adjustment operation with the set value for normal temperature, that is, a relatively long time as the adjustment cycle, wasteful consumption of power is eliminated.

Further, a preceding-period environmental temperature storing means for sequentially updating and storing the environmental temperature detected by the temperature detecting means at the time when the characteristic adjusting means operates, and an environment stored in the preceding-period temperature storing means. Comparing the temperature with the environmental temperature detected by the temperature detecting means at the present time, when the difference exceeds a predetermined set value, and the adjusting operation restricting means permits the operation of the characteristic adjusting means; By providing the second adjusting operation restricting means that allows the operation of the characteristic adjusting means only, the abnormality of the processing operation due to noise or disturbance and the waste of power consumption can be more reliably eliminated. According to this configuration, when the environmental temperature changes to such an extent that the output characteristic of the torque sensor needs to be adjusted, that is, the environmental temperature at the time of the previous output characteristic adjustment stored in the previous cycle temperature storage means and the current temperature Adjustment of the output characteristics of the torque sensor is performed only when the difference from the environmental temperature exceeds a predetermined set value. Therefore, unnecessary adjustment operations are not performed unnecessarily, and waste of power consumption required for the adjustment operations is reliably eliminated. Further, since the number of times of adjusting the output characteristics of the torque sensor is substantially reduced, the probability of occurrence of a processing operation abnormality due to noise or disturbance is reduced, and the abnormality of the processing operation due to noise or disturbance is eliminated and the torque sensor is eliminated. Reliability is improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a simplified block diagram showing a main part of a circuit configuration of a torque sensor 1 for power steering according to an embodiment to which the present invention is applied.

The torque detector 2 of the power steering torque sensor 1 includes a pair of magnetically anisotropic members (shown in the figure) which are obliquely attached to the outer periphery of the steering shaft at an angle of about 45 degrees with respect to its axis. And a pair of detection coils 3a and 3 attached to each of the magnetic anisotropic members.
b, and a magnetostrictive torque sensor comprising a pair of exciting coils 4a, 4b provided corresponding to each of the detection coils 3a, 3b.

The exciting coils 4a and 4b are supplied with an exciting current via an oscillation circuit 5 serving as an AC power supply and a buffer 6 serving as a current amplifying circuit. Further, each of the detection coils 3a and 3b detects a small twist generated in the steering shaft due to the operation of the steering wheel as a change in the magnetic permeability of the magnetically anisotropic member, and outputs this as a voltage signal. The voltage signals output from the detection coils 3a and 3b are rectified by the rectifier circuits 7a and 7b and input to the comparison circuit 8, and the comparison circuit 8 calculates the deviation between the two voltage signals, that is, the steering force acting on the steering wheel. The magnitude and the steering direction are obtained, and the influence of noise is removed from the voltage deviation by a smoothing circuit 9 composed of a low-pass filter or the like, and is passed to a gain adjustment circuit 10.

The gain adjustment circuit 10 has a gain adjustment function for adjusting an output gain so as to obtain a proper power assist command Ts by absorbing a characteristic change in sensitivity of the torque detector 2 caused by a change in environmental temperature. , A microprocessor provided in the control circuit 11 for the torque sensor (hereinafter, referred to as a microprocessor)
The value of the output gain is controlled by a CPU 12. The midpoint voltage adjustment circuit 13 absorbs a voltage drift generated in the torque detector 2 due to a change in environmental temperature, and outputs the output from the power steering torque sensor 1 when the steering force acting on the steering wheel is “0”. Has a midpoint voltage adjusting function of adjusting the midpoint voltage of the power assist command Ts such that the value of the power assist command Ts matches the predetermined set voltage.
CPU 12 provided in control circuit 11 for torque sensor
Controls the value of the midpoint voltage. That is, the characteristic adjusting means in the present embodiment is constituted by the gain adjusting circuit 10, the midpoint voltage adjusting circuit 13, and the microprocessor 12.

The power assist command Ts output from the midpoint voltage adjusting circuit 13 is input to a power steering controller (hereinafter, referred to as an EPS controller) (not shown). The feedback control of the driving amount of the power assisting motor determined from the above is performed, and the motor of the power steering device (not shown) is operated with the steering force of the driver by the driver and the force corresponding to the steering amount.

Accordingly, the driving force applied to the power steering device is a force proportional to the steering force applied to the steering wheel by the driver, and the turning operation of the automobile is assisted by the power assisting force.

In this embodiment, when the steering force acting on the steering wheel at normal temperature is "0", the value of the power assist command Ts output from the midpoint voltage adjustment circuit 13 is 2.5 volts at the midpoint voltage. , And this 2.5 volt output corresponds to a substantial power assist command “0”. That is, when the output Ts from the midpoint voltage adjustment circuit 13 is 2.5 volts, which is the same as the midpoint voltage, the substantial drive command value given to the electric motor for power assist from the EPS controller that has received the output Ts is “0”. ". In this state, the power assisting force of the electric motor does not act on the power steering device.
Power assist by the power steering device is not performed.

In order to prevent the power steering device from being operated carelessly due to a disturbance acting on the steering wheel, in the present embodiment, as shown in FIG. A dead zone of Vm / 2 volts is provided above and below the voltage to make the power assist non-execution region, and the power assist command Ts is 2.5 + Vm
/ 2 volts, the electric motor for power assist is driven to perform power assist in the right-turn direction, and when the power assist command Ts falls below 2.5-Vm / 2 volts, The motor for power assist is driven to perform power assist in the left turning direction.

Accordingly, the power assist command Ts output from the power steering torque sensor 1 becomes 2.5-
When it is in the range of the dead zone of Vm / 2 volts to 2.5 + Vm / 2 volts, substantially no power assist is performed as in the case of the above-mentioned midpoint voltage of 2.5 volts. The set value Vm volt of this dead zone is set on the side of the EPS controller.

The analog voltage generating circuit 14 uses a Hi (for example, 5 volt) or Lo (for example, 0 volt) voltage as an abnormality detection signal in place of the power assist command Ts when an abnormality occurs in the power steering torque sensor 1. The voltage monitor circuit 15 provided in the torque sensor control circuit 11 is used to notify the EPS controller side of the occurrence of an abnormality by outputting the voltage. When the output abnormality is detected, it is automatically driven by the CPU 12 to output a Hi or Lo fail signal.

The voltage monitoring circuit 15 can read a temperature detection signal and the like from a temperature sensor (temperature detecting means) 16 for detecting an ambient temperature Tn around the torque detecting section 2.

The memory 17 has a correction value for adjusting the gain of the gain adjustment circuit 10 and the midpoint voltage adjustment circuit 1.
The relationship between the correction value for adjusting the midpoint voltage of No. 3 and the ambient temperature is stored in advance. Then, the CPU 12 selects an appropriate correction value from the memory 17 in accordance with the value of the environmental temperature detected via the temperature sensor 16 and the voltage monitoring circuit 15 and sets the correction value in the gain adjustment circuit 10 and the midpoint voltage adjustment circuit 13. It is supposed to.

FIG. 4 is a timing chart for determining the adjustment period inc of the characteristic adjustment means based on the power-on time to the power steering torque sensor 1, that is, the elapsed time Tabs after power-on and the current value of the environmental temperature Tn. It is a flowchart which shows an example of an adjustment cycle setting process, This process is repeated every predetermined process cycle of a millisecond by CPU12 which also serves as a power-on time adjustment cycle change means and an environmental temperature adjustment cycle change means. Be executed.

CPU 12 that has started the adjustment cycle setting process
First, it is determined whether or not 0 is set in the timekeeping processing execution flag F, that is, the power steering torque sensor 1
Then, it is determined whether or not the process for measuring the power-on time has already been started (step c1).

Here, if the result of the determination in step c1 is true and the value of the timekeeping processing execution flag F is held at the initial value 0, the processing in this cycle is the first one immediately after the power is turned on. Means that the processing for measuring the power-on time has not been started yet.

Therefore, in this case, the CPU 12 as the power-on time-corresponding adjustment cycle changing means stores the set value of the adjustment cycle to be used in the initial stage after the power is turned on in the reference adjustment cycle storage register tinc, that is, for the temperature fluctuation period. Is set (step c2), and the absolute elapsed time measurement timer Tab is set.
s is started to start measuring the power-on time to the power steering torque sensor 1 (step c3), and the value 1 indicating that the timekeeping process is being executed is set to the timekeeping process execution flag F (step c4).

The current processing cycle is the second processing cycle after the power is turned on.
If it is the first time or later, the timekeeping processing execution flag F
Since a value other than the initial value 0 has already been set, the determination result of step c1 is false. In this case, the CPU 12
Further determines whether or not 1 is set in the clocking process execution flag F (step c10).

Then, if 1 has been set to the clock processing execution flag F, it is further determined whether or not the measured value of the absolute elapsed time measuring timer Tabs exceeds a predetermined set value T1 ( Step c11) If the measured value does not exceed the set value T1, the set value a1 for the temperature fluctuation period is held in the reference adjustment cycle storage register tinc as it is.

That is, in the present embodiment, the time period until the elapsed time Tabs from the power-on time reaches the set value T1 is regarded as the temperature fluctuation period at the time of starting the system. The set value a1 for the temperature fluctuation period, that is, a relatively short time period a1 is applied as the adjustment period of the characteristic adjustment unit.

In the initial stage immediately after the power is turned on, it is expected that the ambient temperature around the torque detector 2 will fluctuate relatively largely. In the present embodiment, a predetermined set time T1 elapses after the power is turned on. Is regarded as a temperature fluctuation period, and during this period, the characteristic adjusting means is operated at a relatively short time period a1, and the torque sensor 1 for power steering is operated.
Therefore, even if the environmental temperature changes suddenly, as shown in FIG. 5, the midpoint voltage of the torque sensor 1 for the power steering is set to a reference value. It can be properly maintained around 0.5 volts.

The cause of the large fluctuation in the ambient temperature around the torque detector 2 in the initial stage immediately after the power is turned on is the heat generated by turning on the power to the power assist motor.

When it is confirmed in the determination processing in step c11 that the measured value of the absolute elapsed time measurement timer Tabs has reached the set value T1 while the adjustment cycle setting processing is repeatedly executed, the CPU 12 determines the absolute elapsed time. Measurement timer Tab
s is stopped and reset (step c12).

Next, the CPU 12 as a power-on time-corresponding adjustment cycle changing means includes a reference adjustment cycle storage register t.
The set value a2 for the temperature stable period having a value larger than the set value a1 for the temperature fluctuation period is set in inc (step c13), and the value 2 indicating the completion of the timekeeping process is set in the timekeeping process execution flag F. Set (step c14).

As a result of setting 2 in the timekeeping processing execution flag F, in the adjustment cycle setting processing after the next cycle, the determination results of step c1 and step c10 are always false.
Therefore, no further change is made to the reference adjustment period storage register tinc, and the value of the set value a2 for the temperature stable period is held as it is.

That is, in the present embodiment, at the stage where the elapsed time from the power-on time exceeds the set value T1 and the ambient temperature around the torque detector 2 is stabilized, the set value a1 for the temperature fluctuation period is set lower. Set value a for large temperature stable period
2 is applied as an adjustment cycle of the characteristic adjustment means, thereby preventing the gain and the midpoint voltage of the power steering torque sensor 1 from being adjusted more frequently than necessary, and reducing the power consumption required for the adjustment work. I try to eliminate waste. At the same time, by reducing the number of times correction values are written from the memory 17 to the gain adjustment circuit 10 and the midpoint voltage adjustment circuit 13, the probability of occurrence of processing malfunction due to noise or disturbance is reduced.

In this way, step c4, step c10 (if the determination result is false), step c11 (if the determination result is false),
Alternatively, the CPU 12 that has finished the processing of step c14,
Next, the current value Tn of the environmental temperature is read via the temperature sensor 16 and the voltage monitoring circuit 15 (step c5),
The present value Tn of the environmental temperature is a predetermined set temperature range T
It is determined whether it is within the range of L to TH, that is, whether it is within the range of normal temperature (step c6).

Then, if the current value Tn of the environmental temperature is TL to T
If the temperature is within the temperature range of H, that is, the normal temperature range, the CPU 12 as the environmental temperature corresponding adjustment cycle changing means sets the normal temperature coefficient b2 in the adjustment coefficient storage register Kt (step c7). Is outside the set temperature range TL-TH, the high / low temperature coefficient b smaller than the normal temperature coefficient b2 is stored in the adjustment coefficient storage register Kt.
1 is set (step c8).

Next, a CPU as a power-on time corresponding adjustment cycle changing means and an environmental temperature corresponding adjustment cycle changing means is provided.
12 multiplies the set value stored in the reference adjustment cycle storage register tinc by the current value of the adjustment coefficient storage register Kt to determine the value of the adjustment cycle inc to be actually used (step c8).

Therefore, the value of the adjustment cycle inc actually used is determined by the combination of the elapsed time Tabs after the power is turned on and the environmental temperature Tn, a1 × b1 (minimum value), a1 × b1.
2, a2 × b1, a2 × b2 (maximum value).

As an example, a relatively short adjustment cycle a1 × b
FIG. 5 in which a section A of a time zone to which 1 or a1 × b2 is applied and a section B of a time zone to which a relatively long adjustment cycle a2 × b1 or a2 × b2 is applied have origins at power-on times.
Is shown on the number line.

Note that only the elapsed time Tabs after the power is turned on is
Alternatively, the value of the adjustment cycle inc may be alternatively determined based only on the environmental temperature Tn. In order to realize the former, a process similar to steps c1 to c4 and steps c10 to c14 is performed, and a relatively short time set value is set to the adjustment cycle inc in the process of step c2. In the process of c13, a set value for a relatively long time is set to the adjustment cycle inc. In order to realize the latter, a process approximate to steps c5 to c8 is performed, a relatively long time set value is set in the adjustment cycle inc in the process of step c7, and the process is performed in the process of step c8. Adjustment cycle in
Set a relatively short time setting to c.

FIG. 2 shows the simplest adjustment operation limiting process for determining whether or not the output of the power steering torque sensor 1 is within the range of the dead zone to determine the operation / non-operation of the characteristic adjustment means. FIG. 4 is a flowchart showing an example of this process. This process is repeatedly executed by the CPU 12 serving as an output state determining unit and an adjusting operation limiting unit as a task independent of the process of FIG. 4 at a predetermined processing cycle of milliseconds. Is done.

CPU 12 that has started the adjustment operation restriction process
First, it is determined whether or not the execution cycle measurement flag f is set to 0, that is, whether or not a process for measuring the adjustment cycle inc for performing the characteristic adjustment has already been started (step a1). .

Here, if the result of the determination in step a1 is true and the value of the execution cycle measurement flag f is held at the initial value 0, the processing in this cycle is the first one immediately after the power is turned on. Means that the process for measuring the adjustment cycle has not been started yet.

Therefore, in this case, the CPU 12 sets the execution cycle measurement flag f to a value 1 indicating that the measurement of the adjustment cycle has started (step a2), and then resets and starts the operation cycle measurement timer Tinc (step a2). Step a
3), the processing of this cycle ends.

The current processing cycle is the second processing cycle after the power is turned on.
If it is the first time or later, the execution cycle measurement flag f
Since the value 1 indicating that the adjustment cycle is being measured has already been set, the determination result in step a1 is necessarily false. In this case, the CPU 12 further operates the operation cycle measurement timer Tin.
Whether the measured value of c has reached the value of the adjustment cycle inc set in the above-described adjustment cycle setting processing, that is, whether the gain adjustment or the midpoint voltage adjustment processing by the characteristic adjustment means should be performed at this time It is determined whether or not it is (step a4).

If the result of the determination in step a4 is false, that is, if it is determined that the value measured by the operation cycle measurement timer Tinc has not reached the value of the adjustment cycle inc, the CPU 12 proceeds to the next step. End the processing of the cycle,
The determination process of step a1 and step a4 is repeatedly executed in the process after the next cycle, and the process waits until the determination result of step a4 becomes true.

Then, the elapsed time Tinc from the time when the first measurement is started or the time when the adjustment process executed immediately before is completed and the determination result of step a4 becomes true is set to the adjustment cycle inc.
Is reached, the CPU 12 as the output state determination means reads the current value of the power assist command Ts of the torque sensor 1 for power steering via the voltage monitoring circuit 15, and the value reads the current value of the power assist. Within the range of the dead zone serving as the non-execution region, that is, 2.5-Vm '/
It is determined whether it is in the range of 2 volts to 2.5 + Vm '/ 2 volts (step a5).

The width of the actual dead zone set on the EPS controller is 2.5-Vm / 2 volts.
Although it is in the range of 5 + Vm / 2 volts, in the determination processing in step a5, the aforementioned Vm is considered in consideration of a certain margin.
The value Vm ', which is slightly smaller than that, is used as the width of the dead zone. This is because the power assist command Ts is 2.5-V
slightly greater than m / 2 volts, or 2.5
When the gain and the midpoint voltage of the power steering torque sensor 1 are adjusted in a state slightly smaller than + Vm / 2 volts, the value of the power assist command Ts becomes 2.5-Vm / 2 volts as an adjustment result. This is a measure to prevent the power steering apparatus from inadvertently operating, for example, when the power steering apparatus is smaller than the above or when it is larger than 2.5 + Vm / 2 volts.

If the result of the determination at step a5 is true, the power steering apparatus is not currently performing power assist, and even if the adjustment processing is performed in this state, the power steering apparatus will not perform. Means that there is no fear of suddenly starting the operation. Therefore, the CPU 12 as the adjusting operation restricting means permits the operation of the characteristic adjusting means, and outputs the current value of the environmental temperature via the temperature sensor 16 and the voltage monitoring circuit 15. Tn is read (step a6), and a gain adjustment process and a midpoint voltage adjustment process similar to those of the related art are performed based on the environmental temperature Tn (step a7). Then, in order to start measuring the timing of the next adjustment processing, the operation cycle measurement timer Tinc is reset and started (step a3), and the processing of this cycle is ended.

On the other hand, if the result of the determination in step a5 is false and it is found that the power assist is being performed by the power steering device, the CPU 12 as the adjusting operation restricting means inhibits the operation of the characteristic adjusting means. And
The processing of the cycle ends as it is.

In the processing after the next cycle, step a
Steps a4 and a5 only are repeatedly performed, and when the determination processing in step a5 becomes true, that is, when power assist by the power steering device is not performed, the above-described steps are repeated. Steps a6 to a7 and step a3, that is, the gain adjustment processing and the midpoint voltage adjustment processing by the characteristic adjustment unit, and the restart processing of the operation cycle measurement timer Tinc are performed.

In this embodiment, as described above, only when the output Ts from the torque sensor 1 for power steering is within the dead zone in which the power assist is not executed, the adjustment processing of the gain and the midpoint voltage is performed. Since the operation is performed, an uncomfortable feeling such as suddenly becoming heavy or light during the operation of the steering wheel is eliminated, and the steering feeling can be improved. At the same time, the adjustment process of the gain and the midpoint voltage is performed in a state where the motor or the like which is the power source of the power assist is inactive, so that the adjustment process does not become unstable due to noise or disturbance caused by the motor or the like. The reliability of the entire device is also increased.

As an example, FIG. 5 shows sections A and B of the time zone in which the adjustment process is performed according to the adjustment cycle and section C of the time zone in which the adjustment process is not executed.

FIG. 3 shows another adjustment operation limiting process for determining whether or not the output of the power steering torque sensor 1 is within the range of the dead zone to determine the operation / non-operation of the characteristic adjustment means. It is a flowchart which shows an example.
This process is repeatedly executed as an independent task by the CPU 12 serving as the adjusting operation restricting means and the second adjusting operation restricting means at a predetermined processing cycle of milliseconds. Note that the adjustment cycle setting process described with reference to FIG. 4 can be directly applied to the process of generating the adjustment cycle inc required in the adjustment operation restriction process of FIG.

The difference from the above-described embodiment (FIG. 2) is that the environmental temperature at the time of the last adjustment processing is stored, and the temperature change from that time exceeds the set value. The point is that the adjustment process of the gain and the midpoint voltage is executed again.

CPU 12 that has started the adjustment operation restriction process
First, the current value Tn of the environmental temperature is read and temporarily stored via the temperature sensor 16 and the voltage monitoring circuit 15 (step b1), and whether the execution cycle measurement flag f is set to 0, that is, Adjustment cycle inc for performing adjustment
It is determined whether or not the process for measuring is already started (step b2).

Here, if the determination result of step b2 is true and the value of the execution cycle measurement flag f is held at the initial value 0, the processing of this cycle is the first one immediately after the power is turned on. Means that the process for measuring the adjustment cycle has not been started yet.

Therefore, in this case, the CPU 12 first
The current value Tn of the environmental temperature read in the processing of step b1
Is stored in the environmental temperature storage register Tp as an initial value (step b3), a value 1 indicating that the measurement of the adjustment cycle has been started is set in the execution cycle measurement flag f (step b4), and the operation cycle measurement timer is set. Tinc is reset and started (step b5), and the processing of this cycle ends.

The current processing cycle is the second processing cycle after the power is turned on.
If it is the first time or later, the execution cycle measurement flag f
Since the value 1 indicating that the adjustment cycle is being measured has already been set, the determination result of step b2 is false. in this case,
The CPU 12 as the second adjustment operation restricting means subtracts the value of the environmental temperature storage register Tp from the current value Tn of the environmental temperature read in the processing of step b1, from the time when the power is turned on or the time when the adjustment processing was last performed The amount of change in the environmental temperature up to the present time is obtained, and it is determined whether or not the value has reached a preset set value Ts (step b6).

If the result of the determination in step b6 is false, that is, if the amount of change in the environmental temperature from the time when the adjustment process was last performed to the present time is small, the torque detection is performed. Since the influence of the temperature change on the section 2 is small and the gain and the midpoint voltage set by the characteristic adjusting means in the adjustment processing performed last time are used without any problem, there is no problem. The CPU 12 as the restricting unit prohibits the operation of the characteristic adjusting unit, terminates the processing of the cycle as it is, repeatedly executes the determination processing of step b1, step b2, and step b6 in the processing of the next cycle and thereafter. It waits until the determination result of b6 becomes true.

That is, in the present embodiment, if the amount of change in the environmental temperature from the time when the adjustment process was last performed to the present time is small, regardless of other conditions, the gain and the midpoint No adjustment related to voltage is performed.

On the other hand, if the result of the determination in step b6 is true and it is determined that the amount of change in the environmental temperature from the time when the adjustment process was last performed to the present time has exceeded the set value, the CPU 12 Further determines whether the measured value of the operation cycle measurement timer Tinc has reached the value of the adjustment cycle inc,
That is, it is determined whether or not the gain or midpoint voltage adjustment processing by the characteristic adjustment means should be performed at the present time (step b7).

If the result of the determination at step b7 is false, that is, if it is determined that the value measured by the operation cycle measurement timer Tinc has not reached the value of the adjustment cycle inc, the CPU 12 keeps the current state. End the processing of the cycle,
In the processing after the next cycle, the determination processing of step b1, step b2, step b6, and step b7 is repeatedly executed, and the process waits until the determination result of step b7 becomes true. In other words, even if the environmental temperature changes drastically, the adjustment process is not performed more times than necessary.

The elapsed time Tinc from the time when the first measurement is started or the time when the immediately preceding adjustment process is completed is determined by the adjustment cycle inc.
Is reached, the CPU 12 as the output state determination means reads the current value of the power assist command Ts of the torque sensor 1 for power steering via the voltage monitoring circuit 15, and the value reads the current value of the power assist. Within the range of the dead zone serving as the non-execution region, that is, 2.5-Vm '/
It is determined whether it is in the range of 2 volts to 2.5 + Vm '/ 2 volts (step b8).

If the result of the determination in step b8 is true, the power steering apparatus is not being executed at this time, and even if the adjustment processing is performed in this state, the power steering apparatus is not used. Means that there is no fear of suddenly starting the operation. Therefore, the CPU 12 as the adjusting operation restricting means and the second adjusting operation restricting means allows the operation of the characteristic adjusting means, and is read in the processing of step b1. Based on the current value of the environmental temperature Tn, a gain adjustment process and a midpoint voltage adjustment process are performed as in the related art (step b9).

The CPU 12 as the preceding-period environmental temperature storage means updates and stores the current value of the environmental temperature Tn read and temporarily stored in the processing of step b1 in the environmental temperature storage register Tp (step b10). )
In order to start measuring the timing of performing the next adjustment processing, the operation cycle measurement timer Tinc is reset and started (step b5), and the processing of this cycle ends.

The value of the environmental temperature updated and stored in the environmental temperature storage register Tp in the processing of step b10 is the determination processing of step b6 performed in the adjustment cycle setting processing after the next cycle. It will be referred to as the environmental temperature at the time of execution.

On the other hand, if the determination result of step b8 is false and it is found that the power assist device is performing the power assist, the CPU 12 as the adjusting operation restricting means prohibits the operation of the characteristic adjusting means. And
The processing of the cycle ends as it is. In other words, no matter how much the environmental temperature changes, in situations where the power steering device operates excessively and causes the driver to feel uncomfortable with the operation of the steering wheel, the gain and the midpoint voltage may be reduced. No related adjustment processing is performed.

Then, in the processing after the next cycle, only the determination processing of step b1, step b2, step b6, step b7, and step b8 is repeatedly executed, and when the determination processing of step b8 becomes true, that is, the power At the stage where the power assist by the steering device is not executed, the processes of step b9 to step b10 and step b5, that is, the gain adjustment process and the midpoint voltage adjustment process by the characteristic adjustment unit, and the environmental temperature storage register Tp The data rewriting process and the restarting process of the operation cycle measurement timer Tinc are performed.

In this embodiment, as described above, the most important determination condition is whether or not the amount of change in the environmental temperature from the time when the adjustment process was last performed to the present time exceeds the set value. If the amount of change in the environmental temperature does not exceed the set value, that is, if the gain and the midpoint voltage set in the past can be used as they are, no adjustment processing related to the gain or the midpoint voltage is performed. Not performed. Therefore, as compared with the first embodiment (the processing in FIG. 2), the number of times the adjustment processing is performed is significantly reduced, and a malfunction operation due to noise or disturbance is prevented, and power saving required for the adjustment processing is reduced. With regard to the formation of a film, a higher effect can be exhibited.
As for the improvement of the steering feeling, the same effects as those of the first embodiment can be achieved.

Further, the torque detecting unit 2 cooled in the cold weather
Is warmed by the effect of the start of heating in the vehicle, the ambient temperature rises sharply, or conversely, the torque detector 2 that has been warmed by a high outside temperature is cooled by the effect of cooling in the vehicle. Often causes a sudden drop in the environmental temperature, but in such a case, the temperature change is so severe that the discrimination process of step b6 does not hinder the execution of the adjustment process. It is possible to accurately adjust the output gain and the midpoint voltage of the power steering torque sensor 1 in a short adjustment cycle in response to a change in the environmental temperature.

Also, instead of setting the current value Tn of the environmental temperature in the environmental temperature storage register Tp in the process of step b3, if the maximum value or the minimum value that can be set for the register is set, the process in the next cycle is always performed. Since the determination result of step b6 becomes true, the first correction process can be reliably executed in the initial stage of the operation start.

Although the case where the gain and the midpoint voltage are corrected in accordance with the environmental temperature has been described above, other characteristics that change in accordance with the environmental temperature, such as correction of the linearity and hysteresis of the torque / output voltage, are also described. Execution and non-execution can be determined based on the same criteria as described above.

[0078]

According to the torque sensor for power steering of the present invention, the output characteristic is adjusted in accordance with the environmental temperature only when the output of the torque sensor is within the dead zone which is the non-execution region of the power assist. Like that.
Therefore, the uncomfortable feeling that the output characteristic of the torque sensor fluctuates during power assist and the steering becomes heavy or light is eliminated, and the steering feeling is improved. In addition, since the output characteristics of the torque sensor are adjusted when the electric motor, etc., which is the power source of the power assist, is in an inactive state, abnormalities in the processing operation due to noise or disturbance are less likely to occur, and the device becomes stable The performance is improved.

Further, the output characteristics of the torque sensor are adjusted in a relatively short cycle in an initial stage in which the environmental temperature is apt to change, and in a relatively long cycle thereafter in a state where the temperature is stable, in accordance with the power-on time to the torque sensor. Further, while the environmental temperature is within a predetermined set range (normal temperature range), a relatively long adjustment cycle is applied, while the environmental temperature is extremely low and high, that is, the cooling and heating of the automobile is performed. Is used to adjust the output characteristics of the torque sensor in a relatively short adjustment cycle in situations where the ambient temperature around the torque sensor may change greatly, so that the environmental temperature does not change Under such circumstances, the output characteristic adjustment work is not performed with excessive frequency, and waste of power consumption is eliminated.

Furthermore, the environmental temperature at the time of the last adjustment work is stored, and the readjustment work is performed only when a large change occurs in the environmental temperature.
The probability of occurrence of an abnormality in the processing operation due to noise or disturbance can be greatly reduced, and waste of power consumption can be reliably eliminated.

[Brief description of the drawings]

FIG. 1 is a simplified block diagram showing a main part of a circuit configuration of a torque sensor for power steering according to an embodiment to which the present invention is applied.

FIG. 2 is a flowchart illustrating a simple example of an adjustment operation restriction process.

FIG. 3 is a flowchart illustrating another example of the adjustment operation restriction process.

FIG. 4 is a flowchart illustrating an example of an adjustment cycle setting process.

FIG. 5 is a conceptual diagram showing an example of a change in a power assist command output from a power steering torque sensor in response to an elapsed time since power-on and an operation of a steering wheel.

[Explanation of symbols]

Reference Signs List 1 Torque sensor for power steering 2 Torque detector (magnetostrictive torque sensor) 3a, 3b Detector coil 4a, 4b Exciter coil 5 Oscillator circuit 6 Buffer 7a, 7b Rectifier circuit 8 Comparison circuit 9 Smoothing circuit 10 Gain adjustment circuit (characteristic adjustment means) 11) Control circuit 12 Microprocessor (adjustment operation limiting means, power-on time adjustment cycle change means, environmental temperature adjustment cycle change means, second adjustment operation limit means) 13 Midpoint voltage adjustment circuit (characteristic adjustment) 14) Analog voltage generation circuit 15 Voltage monitoring circuit 16 Temperature sensor (temperature detection means) 17 Memory

Claims (4)

[Claims] 1. A torque sensor for detecting a steering force acting on a steering wheel and outputting it as a power assist command, temperature detecting means for detecting an environmental temperature, and a predetermined value based on the environmental temperature detected by the temperature detecting means. And a characteristic adjusting means for adjusting an output characteristic of the torque sensor for each adjustment cycle of the power steering, wherein an output of the torque sensor falls within a dead zone which is a non-execution region of power assist. Output state determination means for determining whether or not the torque adjustment is performed, and receiving the determination result from the output state determination means, only when the output of the torque sensor is within the range of the dead zone, A torque sensor for power steering, comprising: an adjustment operation restricting unit that permits operation. 2. A power-on time for the torque sensor while maintaining the adjustment cycle at a set value for a temperature fluctuation period until a power-on time for the torque sensor reaches a predetermined set value. A power-on time corresponding adjustment period changing means for setting a set value for a temperature stabilization period longer than the set value for the temperature fluctuation period in the adjustment period when the set value exceeds the predetermined set value. The torque sensor for power steering according to claim 1, wherein 3. An environment detected by the temperature detecting means while the adjustment cycle is maintained at a set value for normal temperature while an environmental temperature detected by the temperature detecting means is within a predetermined set range. An environment-temperature-adjustable adjustment cycle changing means for setting a high / low temperature set value shorter than the normal temperature set value in the adjustment cycle when the temperature is out of the predetermined set range. The torque sensor for power steering according to claim 1 or 2. 4. A pre-period environmental temperature storage means for sequentially updating and storing the environmental temperature detected by said temperature detecting means at the time when said characteristic adjusting means operates, and Comparing the current environmental temperature with the environmental temperature currently detected by the temperature detecting means, the difference exceeds a predetermined set value, and the adjusting operation restricting means permits the operation of the characteristic adjusting means. And a second adjusting operation restricting unit that permits the operation of the characteristic adjusting unit only when the operation is being performed. Power steering torque sensor.