JP7512980B2 - Sensor Signal Processing Device - Google Patents

Description

The present invention relates to a device that processes a voltage signal output from a magnetic pickup type rotation sensor that detects the crank angle of an internal combustion engine.

Conventionally, to detect the crank angle of an internal combustion engine, a magnetic pickup type rotation sensor has been used in which a disk-shaped rotary pulser with multiple protrusions formed on its outer circumference is attached to the crankshaft, and the multiple protrusions that are displaced by the rotation are detected by a magnetic sensor to generate a rotation signal. The rotation state of the crankshaft is detected by comparing the magnitude of the electromotive force output by this rotation sensor with a threshold value using a comparator. Hereinafter, this rotation sensor is referred to as an MPU sensor.

Since the MPU sensor has magnetic properties, the electromotive force varies according to the angular velocity. When the angular velocity slows down, the electromotive force becomes smaller, and when the angular velocity increases, the electromotive force becomes larger. Therefore, it is necessary to respond by varying the threshold value set in the comparator according to the angular velocity.

Patent No. 4239775

In addition, MPU sensors can detect mechanical vibrations that occur when the vehicle engine is started and generate electromotive forces, which can manifest as high-frequency noise. In recent years, many vehicles have adopted idling stop systems, which has created a demand for improved engine starting performance. The challenge is how to balance this demand with improved responsiveness of the MPU sensor.

The present invention was made in consideration of the above circumstances, and its purpose is to provide a sensor signal processing device that can improve responsiveness by eliminating erroneous detection by a rotation sensor due to mechanical vibrations that occur when an internal combustion engine starts.

According to the sensor signal processing device of claim 1, the comparator compares a voltage signal output by a magnet pickup type rotation sensor that detects the rotation of the internal combustion engine with a threshold value, and the signal processing unit detects the rotation state of the internal combustion engine by processing the output signal of the comparator. The output interval detection unit detects the output interval of the output signal, and the threshold setting unit variably sets the threshold value of the comparator according to the output interval. Then, the abnormality determination unit determines that an abnormality has occurred when the output interval of the voltage signal exceeds the abnormality determination time.

When the voltage signal output by the rotation sensor changes in a noise-like manner, the threshold setting unit increases the comparator threshold in accordance with the extremely short occurrence interval of the signal. As a result, the comparator output signal no longer changes appropriately in response to changes in the rotation sensor output signal, but the abnormality determination unit determines that an abnormality has occurred when the output interval of the comparator output signal exceeds the abnormality determination time. This makes it possible to eliminate the inappropriate setting of the threshold based on the result of the determination, and improves responsiveness to changes in the sensor signal.

Specifically , when the abnormality determination unit determines an abnormality, the threshold setting unit lowers the threshold of the comparator.
In addition, as in the sensor signal processing device according to claim 2 , the threshold setting unit initializes the setting of the threshold when the abnormality determination unit determines an abnormality. With this configuration, the increased threshold can be lowered, and the output signal of the comparator can be restored to an appropriate change in response to a change in the output signal of the rotation sensor.

FIG. 1 is a functional block diagram showing a configuration of a sensor signal processing device according to an embodiment; Timing chart showing each signal when operation is normal Timing chart showing each signal when operation is abnormal Timing chart showing the output timing of the lifting prohibition signal in detail 1 is a timing chart showing how a ramp generating circuit provides dynamic hysteresis characteristics. 1 is a flowchart illustrating an operation of a sensor signal processing device.

As shown in FIG. 1, the sensor signal processing device 1 of this embodiment includes a comparator 3 in an analog circuit section 2. A voltage signal output from a rotation sensor (not shown) is input to the non-inverting input terminal of the comparator 3 via the input terminal NEI of the analog circuit section 2 and a resistor element 4. The rotation sensor is a magnetic pickup type, and detects, for example, the crank angle of a vehicle engine. A series circuit of resistor elements 5a and 5b is connected between the power supply and ground, and the common connection point of resistor elements 4a and 4b is connected to the inverting input terminal of the comparator 3 via a resistor element 6. A predetermined threshold voltage is applied to the inverting input terminal of the comparator 3 by these resistor elements 5 and 6.

The output terminal of the 6-bit D/A converter 7 is connected to the non-inverting input terminal of the comparator 3 via the V-I conversion unit 8 and analog switch 9. Hereinafter, "D/A converter" will be abbreviated as "DAC." The output terminal of the 7-bit DAC 10 is connected to the inverting input terminal of the comparator 3 via the V-I conversion unit 11. In addition, the inverting input terminal is connected to the output terminal of the V-I conversion unit 8 via the analog switch 12.

The input terminal of DAC7 receives 6-bit data from a ramp generation circuit 13, which is a 6-bit counter. The input terminal of DAC10 receives 7-bit data from a threshold voltage generation circuit 14, which is a 7-bit counter. The analog switches 9 and 12 are controlled by an analog switch control circuit 16 in an analog control circuit section 15.

The output terminal of the comparator 3 is connected to the input terminals of the lift-prohibition signal generating circuit 17 and the NEI edge detection circuit 18 of the analog control circuit section 15. The output terminal of the comparator 3 is also connected to the terminal NEO of the analog circuit section 2 via a NOT gate 19.

In the analog control circuit section 15, the output signal of the NEI edge detection section 18 is input to the ramp generation circuit 13 as a 6-bit data load signal. The lift-prohibition signal generation circuit 17 is equipped with a filter 20 and a logic section 21, and the output signal Sc of the comparator 3 is input to both. The filter 20 has a time constant that slightly delays the above-mentioned output signal, and the logic section 21 logically combines the two input signals to generate control signals for the analog switches 9 and 12. The output signal of the filter 20 is also input to the NEI falling edge detection section 22.

The output signal of the NEI falling edge detection unit 22 is input to the first edge detection unit 24 of the NEI period measurement unit 23. The first edge detection unit 24 masks the first edge when the signal STA is enabled, and passes the second and subsequent edges to the next stage, the NEI period counter 25. The NEI period counter 25 is a counter that measures the interval between the first edges detected by the first edge detection unit 24. The count value of the NEI period counter 25 is stored sequentially in the NEI period registers 26 and 27 connected in series, and is also input to the missing tooth determination unit 28. The data values stored in the NEI period registers 26 and 27 are both input to the NEI average period calculation unit 28.

The NEI average period calculation unit 28 calculates the average value of the edge occurrence periods from the second onwards of the output signal Sc by adding up the count data values stored in the NEI period registers 26 and 27 and dividing the result in half. Here, the above average value is referred to as the "NEI average period." The NEI average period is input to the missing tooth determination unit 29 and the clamp circuit 32. The NEI period measurement unit 23 corresponds to the output interval detection unit.

The missing tooth determination unit 29 performs missing tooth detection using the missing tooth detection circuit 30 by referring to the count value of the NEI period counter 25, and performs abnormality determination using the abnormality determination circuit 31. The missing tooth detection circuit 30 compares the above count value with α times the NEI average period using a magnitude comparator. α can be set in increments of multiples of 0.125, for example, from 0.125 to 7.875, but is not limited to this. The output signal of the magnitude comparator becomes a missing tooth detection signal, which is input to the NEI period registers 26 and 27 as a signal that masks the data latch. Similarly, the abnormality determination circuit 31 compares the above count value with 4α times the NEI average period using a magnitude comparator.

The clamp circuit 32 outputs the initial value of the count data to the ramp generation circuit 13 and the threshold voltage generation circuit 14 based on the input NEI average period. Note that the hold or down decision unit 14A is interposed between the clamp circuit 32 and the threshold voltage generation circuit 14. The abnormality determination signal output by the abnormality determination circuit 31 is input to the hold or down decision unit 14A as a down switching signal. The abnormality determination circuit 31 corresponds to the abnormality determination unit.

The reference clock generating circuit 33 supplies two clock signals CLK1 and CLK2 to the ramp generating circuit 13 and the threshold voltage generating circuit 14, respectively. The period of the clock signal CLK2 is, for example, 3.2 ms, and the period of the clock signal CLK1 is set shorter than that. The portion of the sensor signal processing device 1 excluding the analog circuit unit 2 corresponds to the signal processing unit. The clamp circuit 32 and the threshold voltage generating circuit 14 correspond to the threshold setting unit.

Next, the operation of this embodiment will be described. The timing chart during normal operation shown in Figure 2 is for the case where α = 1. Note that signal STA, not shown in Figure 1, is an enable signal that enables the operation of the sensor signal processing device 1, and while this signal indicates a low level, the NEI period registers 26 and 27 and the register in which the NEI average period built into the clamp circuit 32 is stored are initialized. The change in the threshold of the comparator 3 set by the ramp generation circuit 13 is also zero, and is the initial value set only by the resistance elements 5a and 5b.

The NEI period counter 25 counts the falling edge intervals T1, T2, T3, ... of the signal NEI. When the first average value {(initial value) + T1}/2 is input to the clamp circuit 32, the threshold voltage generation circuit 14 updates the threshold in synchronization with the rising edge of the next clock signal CLK2. When the missing tooth part of the rotary pulser is reached, the output signal Sc of the comparator 3 stops changing, and the missing tooth detection circuit 30 outputs a missing tooth detection signal. As described above, the register values are not updated during the period when this missing tooth detection signal is output.

As shown in FIG. 4, when chattering occurs at the rising or falling edge of the signal Sc, the analog switches 9 and 12 are controlled by the lift prohibition signal generating circuit 17. The filter 20 outputs the output signal of the comparator 3 with a predetermined delay. The logic unit 21 logically combines two signals to generate lift prohibition signals for the threshold and input. A load signal is output to the ramp generating circuit 13 in response to an edge detected in response to the occurrence of chattering. During the rising period of the output signal, a threshold lift prohibition signal is output to turn off the analog switch 12, and during the falling period of the same signal, an input lift prohibition signal is output to turn off the analog switch 9. This eliminates the effects of chattering.

In the period during which the signal NEO is at a high level relative to the input signal of the comparator 3 shown by the thick line at the top of Figure 5, the threshold of the comparator 3 shown by the dashed line changes so as to gradually decrease from the state in which a predetermined value is added. Also, in the period during which the signal NEO is at a low level, the input signal of the comparator 3 shown by the thin line is raised so as to reliably exceed the threshold. The counter of the ramp generating circuit 14 is loaded with a count value of "0" in response to both edges of the signal Sc, and counts up in response to the clock signal CLK1. When the count value reaches "61", it hits the ceiling. Note that the input signal raising process is not reflected in the timing charts of Figures 2 and 3.

As shown in FIG. 3, immediately after the rise of the signal STA, the rotation sensor is affected by mechanical vibrations caused when the vehicle engine is started, causing the signal NEI to change like high-frequency noise, that is, multiple times within a short period of time. The dashed line superimposed on the signal NEI is the threshold of the comparator 3. The clamp circuit 32 increases the threshold of the comparator 3 in one go in response to the NEI average period being set to a short period. As an example, the NEI period counter 25 is set so that the count value becomes full after about 130 ms has elapsed. Therefore, in the abnormality determination circuit 31, the 4α multiplied value of the NEI average period is set to correspond to 130 ms. The above 4α multiplied value corresponds to the abnormality determination time.

As the threshold rises, the signal NEI, which is the inversion of the output signal of the comparator 3, stops changing thereafter, so a missing tooth detection signal is output, and then, after about 130 ms, an abnormality detection signal is output. In response to this, the hold or down decision unit 14A switches the threshold voltage generation circuit 14 to down-count operation. Then, the threshold gradually decreases in response to the clock signal CLK2.

Figure 6 shows an outline of the operation of the sensor signal processing device 1. When the signal STA changes to a high level to permit reception of the rotation sensor signal (S1), the first NEI average period is determined when the falling edge of the signal Sc is detected three times (S2). Subsequently, when the next falling edge of the signal Sc is detected without the output of an abnormality detection signal (S4; YES), the edge signal is captured and processed (S5) before returning to step S3.

On the other hand, if the falling edge of the next signal Sc is not detected and an abnormality detection signal is output (S4; NO), the hold or down decision unit 14A switches the threshold voltage generation circuit 14 to down-count operation to lower the threshold value.

As described above, according to this embodiment, in the sensor signal processing device 1, the comparator 3 compares the voltage signal output by the magnet pickup type rotation sensor with a threshold value, and the signal processing unit detects the engine rotation state by processing the output signal Sc of the comparator 3. The NEI period measurement unit 23 detects the output interval of the signal Sc, and the clamp circuit 32 and the threshold voltage generation circuit 14 variably set the threshold value of the comparator 3 according to the output interval. Then, the abnormality determination circuit 31 determines that an abnormality has occurred when the output interval of the signal Sc exceeds the abnormality determination time.

This makes it possible to resolve the problem of the threshold of the comparator 3 being set inappropriately when the output signal NEI of the rotation sensor detects mechanical vibrations that occur when the vehicle engine starts and changes like high-frequency noise. Specifically, the clamp circuit 32 and the threshold voltage generation circuit 14 lower the threshold of the comparator 3 when the abnormality determination circuit 31 determines an abnormality, so that the output signal of the comparator 3 can be restored to change in response to changes in the output signal NEI of the rotation sensor. In other words, the responsiveness to changes in the sensor signal NEI can be improved.

Other Embodiments
When the abnormality determination circuit 31 determines an abnormality, the threshold value of the comparator 3 may be set to an initial setting value.
The abnormality determination time may be changed as appropriate according to individual designs.
Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also encompasses various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

In the drawing, 1 indicates a sensor signal processing device, 3 indicates a comparator, 13 indicates a ramp generating circuit, 14 indicates a threshold voltage generating circuit, 15 indicates an analog control circuit section, 23 indicates an NEI period measuring section, 29 indicates a missing tooth determining section, and 31 indicates an abnormality determining circuit.

Claims (2)

a comparator (3) that receives a voltage signal output from a magnetic pickup type rotation sensor that detects rotation of an internal combustion engine and compares the voltage signal with a threshold value;
a signal processing unit (13 to 15, 23, 29, 32) for detecting a rotation state of the internal combustion engine by processing an output signal of the comparator;
an output interval detection unit (23) for detecting an output interval of the output signal;
a threshold setting unit (14, 32) that variably sets the threshold in accordance with the output interval;
an abnormality determination unit (31) that determines that an abnormality has occurred when the output interval exceeds an abnormality determination time ;
The threshold setting unit reduces the threshold when the abnormality determination unit determines that an abnormality has occurred. a comparator (3) that receives a voltage signal output from a magnetic pickup type rotation sensor that detects rotation of an internal combustion engine and compares the voltage signal with a threshold value;
a signal processing unit (13 to 15, 23, 29, 32) for detecting a rotation state of the internal combustion engine by processing an output signal of the comparator;
an output interval detection unit (23) for detecting an output interval of the output signal;
a threshold setting unit (14, 32) that variably sets the threshold in accordance with the output interval;
an abnormality determination unit (31) that determines that an abnormality has occurred when the output interval exceeds an abnormality determination time;
The threshold setting unit initializes a setting of the threshold when the abnormality determination unit determines that an abnormality has occurred .

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