JPH0893538A - Waveform shaping device - Google Patents

Abstract

PURPOSE: To easily set the threshold level by providing a comparing means for comparing the threshold level converted into an analog value by a D/A converting means, and inputting a signal whose waveform is shaped. CONSTITUTION: A detecting signal to be outputted from an engine rotational sensor 1 is compared with the threshold level by a comparator 311, and the output of the comparator 311 is H until it exceeds the threshold level VTHh and it is changed to L when it exceeds the threshold level VTHh . A logic circuit 33 closes a switch S2 by the change to L, and a digital value V...m stored in a VTH1 resister 342 is selected. This digital value VTH1 is converted into an analog value by a D/A converter 32 and set as the threshold level VTH1 . Waveform shaping not to be easily affected by noise can be performed by switching of the threshold level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform shaping device for shaping an input signal.

[0002]

2. Description of the Related Art Conventionally, as a waveform shaping device of this type,
JP-B-1-18604, JP-B-3-36146, JP-A-60-8444, JP-A-3-118
Various proposals have been made as seen in Japanese Patent Publication No. 478, etc. These are configured as shown in FIG. 8, and a signal from the sensor 11 is compared with a predetermined threshold level by a comparator 13 via a low pass filter 12, and a pulse signal is output. Further, the threshold level is set by the threshold level setting circuit 14.

This threshold level is changed according to the state, characteristics, etc. of noise countermeasures or application targets. For example, the threshold level V _TH is switched between two threshold levels V _THh and V _THl for the sensor detection signal N + as shown in FIG. 3 to prevent chattering due to noise. Further, when the detection signal generated at each predetermined crank angle of the engine is subjected to waveform shaping,
As shown in, the threshold level is changed by the battery voltage + B, and the characteristic of V _THh is switched at the time of starting the engine and after the engine starts. Furthermore, FIG.
As shown in, the threshold level may be increased in proportion to the engine speed obtained from the waveform-shaped engine speed signal.

[0004]

Conventionally, the threshold level setting circuit 14 is constructed by a discrete circuit in which all analog circuit elements are combined.
Therefore, when the threshold level is changed as shown in FIGS. 4 and 5, the circuit for setting the threshold level becomes complicated, and when changing the characteristic, it is necessary to change the element of the circuit, etc. However, there is a problem that the characteristics cannot be changed.

The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to easily set a threshold level.

[0006]

In order to achieve the above object, the present invention provides a waveform shaping device for shaping the input signal (N +) according to the first aspect of the invention, in which the threshold level is stored as a digital value. Storing means (34), D / A converting means (32) for converting the threshold level stored in the storing means (34) into an analog value, the threshold level converted into the analog value and the input signal ( N +) and a comparison means (311) for outputting a signal whose waveform has been shaped are provided.

According to a second aspect of the present invention, in the first aspect of the present invention, the storage means (34) stores a plurality of threshold levels and is output from the comparison means (311). Based on the signal level
It is characterized by comprising a selecting means (33) for selecting one of the plurality of threshold levels. The invention according to claim 3 is characterized in that, in the invention according to claim 1 or 2, there is provided setting means (37 to 39) for changing the setting of the threshold level stored in the storage means (34). There is.

The symbols in parentheses for the above means are as follows:
It shows a correspondence relationship with a specific means described in the embodiments described later.

[0009]

According to the first aspect of the invention, the threshold level is stored as a digital value, the digital value is converted into an analog value, and the threshold level is set. Therefore, by setting the threshold level as a digital value, a desired threshold level can be easily set.

According to the second aspect of the present invention, since a plurality of threshold levels are stored and which of the threshold levels is used is selected according to the comparison result of the comparing means, the threshold level can be changed. It is possible to perform waveform shaping that is not easily affected by noise or the like superimposed on the input signal. According to the invention described in claim 3, by providing the setting means for setting and changing the threshold level stored in the storage means, the characteristic of the threshold level is changed,
For example, it is possible to easily change the setting of the threshold level suitable for various states as shown in FIGS.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration diagram of an engine rotation input device according to a first embodiment of the present invention. The engine rotation sensor 1 uses a magnetic detection element to output a detection signal that is an engine rotation signal generated at each predetermined crank angle of the engine. This detection signal is input to the waveform shaping circuit 31 incorporated in the microcomputer 3 (hereinafter referred to as MCU) via the low pass filter 2.

The waveform shaping circuit 31 is composed of a Zener diode 312, a comparator 311 and the like.
Compares the detection signal clamped by the Zener diode 312 with a predetermined threshold level, and outputs an engine rotation signal Ne. A threshold level setting dedicated register 34 is provided for setting the threshold level. The threshold level setting dedicated register 34 includes a V _THh register 341 and a V _THl register 3
42, in which two threshold levels V _THh and V _THl are set and stored as digital values.
The logic circuit 33 selects which of the two registers 341 and 342 is to be used, the selected digital value is converted into an analog value by the D / A converter 32, and the converted value is compared with the comparator 311. Is entered as a threshold level.

Based on the signal level output from the comparator 311, the logic circuit 33 operates so as to close the switch S1 when the output is at a high level, as shown in FIG. 3, to set the V _THh register 341. Select and comparator 311
When the output of is at a low level, it operates so as to close the switch S2 and selects the V _THl register 342. CP
The U 37 executes various controls based on the control program stored in the ROM 38 and various data stored in the RAM 39. For example, with respect to the setting of the threshold level, the arithmetic processing shown in FIG. 2 is executed based on the engine rotation signal Ne input via the input port 36 and the voltage VB of the vehicle-mounted battery input via the A / D converter 35. Then, the threshold levels V _THh and V _THl are set in the registers 341 and 342, respectively.

The operation of the above structure will be described. When starting the operation of this device, the CPU 37 outputs a reset signal to the logic circuit 33, and the logic circuit 33 closes the switch S1. Therefore, in the initial state, V
Digital value V stored in _THl register 342
_THh is converted into an analog value by the D / A converter 32, which is used as the threshold level V _THh in the comparator 31.
Input to 1.

The engine rotation sensor 1 outputs a detection signal N + which is an engine rotation signal generated at each predetermined crank angle of the engine. The detection signal N + is input to the comparator 311 and compared with the threshold level. Here, the detection signal N + 4 to over the threshold level V _THh output of the comparator 311 is at a high level, the detection signal N + is exceeds the threshold level V _THh, changes to a low level. By this change to the low level, the logic circuit 33 closes the switch S2,
The digital value V _THl stored in the V _THl register 342 is selected. Therefore, the digital value V _THl is converted into an analog value by the D / A converter 32 and set as the threshold level V _THl .

Thereafter, when the detection signal N + becomes lower than the threshold level V _THl , the output of the comparator 311 changes to the high level, and the threshold level V _{THh accordingly.}
Is changed to. As described above, the operation of the logic circuit 33 according to the output level of the comparator 311 causes the comparator 311 to operate.
The threshold level set to V _THh is switched between V _THh and V _THl , and the comparator 311 outputs the engine rotation signal Ne by comparing it with the detection signal N +. Therefore, by switching between the two threshold levels, it is possible to perform waveform shaping that is less likely to be affected by noise superimposed on the detection signal.

Next, the above two registers 341 and 342.
Digital values V _THh and V _THl set in Fig. 2
It will be described based on the flowchart shown in FIG. CPU 37
The arithmetic processing shown in FIG. 2 is executed according to the control program stored in the ROM 38. First, at step 100, the engine speed NE obtained from the engine speed signal Ne
And the battery voltage VB. Next Step 1
In 01, it is determined whether or not the engine is starting based on the engine speed based on the engine speed signal NE. For example, it is determined that the engine is starting when the engine speed is 500 rpm or less.

When the determination at step 101 is YES at the time of starting, the _routine proceeds to step 102, where V _{THh is set} by the engine speed NE and the battery voltage VB according to the starting characteristic shown in FIG. 4 and the rotational speed characteristic shown in FIG. Ask for. If the determination in step 101 is NO after the start, the process proceeds to step 103, and V _THh is similarly obtained according to the post-start characteristic shown in FIG.

In the next step 104, the engine speed NE and the battery voltage V are measured according to the characteristics shown in FIGS.
_Calculate V _THl from B. Then, in step 105, V _{TH h} and V _THl are set in the registers 341 and 342, respectively. Therefore, by performing the above processing, V _THh and V _THl are set by the engine speed NE and the battery voltage VB at that time.

Next, a second embodiment of the present invention will be described. When noise is superimposed on the detection signal of the engine rotation sensor 1 (especially when noise is superimposed in the vicinity where the threshold level is crossed), it is possible to erroneously output a pulse due to fluctuations in the output signal level due to this noise. There is a nature. Therefore, in the second embodiment, the threshold level is sufficiently shifted from the original value for a certain period of time after the output signal is inverted, in the direction opposite to the direction in which the detection signal of the engine rotation sensor is increased, and the influence of the above noise I try to get rid of.

Therefore, as shown in FIG. 6, the comparator 31
A time constant circuit 4 including a resistor and a capacitor is provided between the output line 1 and the “+” terminal of the comparator 311. When the output level of the comparator 311 changes, the time constant circuit 4 changes the voltage of the capacitor by the voltage of the comparator 311.
The “+” terminal voltage of 11, that is, the threshold level changes, and then changes toward the output level of the D / A converter 32 with the time constant of the time constant circuit 4. That is, the threshold voltage changes as shown in FIG. 7 according to the change in the output level of the comparator 311.

In the above embodiment, the CPU 37 executes the control program stored in the ROM 38 to set V _THl and V _{THh in} the registers 341 and 342, but the threshold level is constant. Yes, and if it is not necessary to change the set value, V is stored in the non-volatile memory (EPROM, PROM, etc.).
_You may make it memorize _THl and V _THh .

According to the above embodiment, V _THl and V _THh can be changed by changing the control program.
Even if the specification of the engine speed sensor 1 is changed, it is possible to respond to the specification change without requiring a major circuit change.
Product cost can be reduced. Further, by storing the threshold level in a rewritable non-volatile memory such as an EEPROM so that it can be rewritten after the manufacturing process or the market distribution, it is possible to deal with a plurality of vehicle types and after vehicle assembly.

Further, each step shown in FIG. 2 is understood as a function realizing means for realizing each function. For example, step 101 is a signal input means, step 101 is a start time determination means, and steps 102 and 103. Is the first threshold (V _THh ) computing means, step 104
Is the second threshold (V _THl ) computing means, step 1
Reference numeral 05 is understood as a threshold setting means.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an engine rotation input device showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing a process of setting a threshold level.

[FIG. 3] Detection signal N + and threshold levels V _THl , V
₆ is a timing chart showing the relationship between _THh and the engine rotation signal Ne.

FIG. 4 is a characteristic diagram showing a threshold level characteristic with respect to a battery voltage.

FIG. 5 is a characteristic diagram showing threshold level characteristics with respect to engine speed.

FIG. 6 is a partial configuration diagram of an engine rotation input device showing a second embodiment of the present invention.

7 is a threshold level V according to the configuration shown in FIG.
₆ is a timing chart showing changes in _THl and V _THh .

FIG. 8 is a configuration diagram showing a configuration of a conventional waveform shaping device.

[Explanation of symbols]

1 ... Engine rotation sensor, 2 ... Low-pass filter,
3 ... MCU, 31 ... Waveform shaping circuit, 311 ... Comparator, 32 ... D / A converter, 33 ... Logic circuit, 34 ... Threshold level setting dedicated register, 3
7 ... CPU, 38 ... ROM, 39 ... RAM.

Claims (3)

[Claims] 1. A waveform shaping device for shaping a waveform of an input signal, comprising: storage means for storing the threshold level as a digital value; and D / A conversion means for converting the threshold level stored in the storage means into an analog value. A waveform shaping device comprising: a comparison unit that compares the threshold level converted into the analog value with the input signal and outputs a waveform-shaped signal. 2. The storage means stores a plurality of threshold levels, and comprises a selection means for selecting one of the plurality of threshold levels based on the signal level output from the comparison means. The waveform shaping device according to claim 1, wherein 3. The waveform shaping device according to claim 1, further comprising setting means for setting and changing a threshold level stored in the storage means.