JP2020191358A - Electronic control device - Google Patents

Abstract

To provide an electronic control device that can detect a decrease in the rotation speed of a fan while reducing a load on a control microcomputer.SOLUTION: A control microcomputer 1b includes an abnormality diagnosis unit 1j (diagnosis unit) that detects a decrease in the rotation speed of a fan 1a from the output of the fan 1a via a low-pass filter 1c. The abnormality diagnosis unit 1j (diagnosis unit) determines, for example, that the rotation speed of the fan 1a has decreased when a digital value of a signal output from the low-pass filter 1c falls below a threshold value.SELECTED DRAWING: Figure 2

Description

The present invention relates to an electronic control device.

The ECU (Electronic Control Unit), which is a control device for controlling automatic operation, is equipped with a calculation processing device (microcomputer) that performs processing for recognizing the outside world, and the calculation load of the microcomputer changes greatly depending on the surrounding conditions. In order to prevent the microcomputer from malfunctioning due to the heat generated by the microcomputer itself due to the increase in the calculation load, it is necessary to release the heat of the microcomputer to the outside by a cooling structure such as a fan or a water cooling system. When cooling the ECU using a fan, it is necessary to monitor whether the rotation speed is reduced due to a fan failure.

Generally, a fan is equipped with a pulse output whose period changes according to the rotation speed, and the rotation speed can be obtained by a method of counting the pulse output signal with a counter or the like or a method of examining the period of the pulse output signal. .. Abnormal rotation speed can be detected by determining whether this rotation speed is equal to or less than a predetermined value. Such fan rotation speed abnormality detection is monitored in real time by a dedicated IC or a microcomputer.

In Patent Document 1, a pulse output signal output from a rotating body is counted by using a clock pulse having a period shorter than the rotation pulse output signal, and the number of counted clock pulses is compared with a predetermined value to obtain a rotation speed. A method for counting (rotational speed) is described.

Japanese Unexamined Patent Publication No. 2006-118960

The automatic driving system is composed of, for example, a vehicle control device that outputs a control command and a plurality of actuator control devices that individually perform engine control, brake control, power steering control, etc. based on the control command from the vehicle control device. To.

Here, the vehicle control device of the automatic driving system requires high computing power in order to realize automatic driving, and is composed of a high-performance computing device. A high-performance arithmetic processing unit generates heat during arithmetic processing, and the heat generation causes the temperature of the arithmetic processing unit to rise, which may cause the arithmetic processing unit to malfunction. In order to avoid such abnormal heat generation, it is necessary to release the heat of the vehicle control device with a fan or the like.

The fan rotates and sends air to the vehicle control device to release heat. To release the heat, the fan needs to rotate correctly, and it is necessary to monitor the rotation speed of the fan.

When Patent Document 1 is used as a means for solving the above problems, it is necessary to perform a process of counting the rotation speed of the fan with an arithmetic processing unit or to have a dedicated logic detection circuit.

When it is performed by the arithmetic processing unit, it is necessary to interrupt the arithmetic processing for automatic operation in order to execute the count and count of the clock pulse by the interrupt processing or the like, and there is a concern that the processing time of the arithmetic processing unit may increase.

If a detection circuit is provided, a clock pulse generation circuit, a counter circuit, a comparison circuit, and the like are required, and there is a concern about cost increase due to an increase in the number of parts and malfunction due to defective mounting of parts.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electronic control device capable of detecting a decrease in fan speed while suppressing a load on a control microcomputer (arithmetic processing unit). There is.

In order to achieve the above object, the present invention includes a diagnostic unit that detects a decrease in fan speed from the output of a fan via a low-pass filter.

According to the present invention, it is possible to detect a decrease in the rotation speed of the fan while suppressing the load on the control microcomputer. Issues, configurations and effects other than those described above will be clarified by the description of the following embodiments.

It is a schematic block diagram of the automatic driving system provided in the vehicle to which this invention is applied. It is a figure which shows the internal structure of the autonomous traveling control device (first ECU) in Example 1 of this invention. It is a figure which shows the process which detects the rotation speed abnormality in Example 1 of this invention. It is a figure which shows the internal structure of the autonomous traveling control device (first ECU) in Example 2 of this invention. It is a figure which shows the process which detects the rotation speed abnormality in Example 2 of this invention. It is a figure which shows the internal structure of the autonomous traveling control apparatus (first ECU) in Example 3 of this invention. It is a figure which shows the process of diagnosing the rotation state in Example 3 of this invention. It is a figure which shows the internal structure of the autonomous traveling control apparatus (first ECU) in Example 4 of this invention.

Hereinafter, examples of the present invention will be described with reference to the accompanying drawings. This embodiment relates to detecting an abnormality in the rotation speed of a fan provided in an electronic control device included in an automatic operation system.

(Configuration example of automatic driving system)
First, the configuration of the automatic driving system (vehicle control system) to which the present invention is applied will be described.

FIG. 1 is a schematic configuration diagram of an automatic driving system provided in a vehicle to which the present invention is applied. In FIG. 1, the automatic driving system includes a camera (first sensor) 11, a radar (second sensor) 12, and a vehicle position sensor (third sensor), which are external world recognition sensors for recognizing the external world situation of the vehicle. ) 13.

Further, the automatic driving system includes an autonomous driving control device (first ECU) 1, a contraction control device (second ECU) 2, a brake control device (third ECU) 3, an engine control device (fourth ECU) 4, and power steering. It includes a control device (fifth ECU) 5. The brake control device 3, the engine control device 4, and the power steering control device 5 can be collectively referred to as actuator control devices that control the operation of the vehicle.

The camera 11, the radar 12, the vehicle position sensor 13, the autonomous driving control device 1, the contraction control device 2 as an auxiliary control device, the brake control device 3, the engine control device 4, and the power steering control device 5 are included in an in-vehicle network (for example, They are connected by CAN (Control Area Network), Sensornet (registered trademark), etc. so that they can communicate with each other.

The degeneracy control device 2 is a control device that operates to execute appropriate degeneracy control as a backup when the autonomous travel control device 1 fails, but even if the autonomous travel control device 1 fails, autonomous travel If the safety can be ensured by providing the degeneracy control function in the control device 1, the degeneration control device 2 is unnecessary.

The brake control device 3 is a control device that controls the brake of the vehicle (braking force control), and the engine control device 4 is a control device that controls the engine that generates the driving force of the vehicle. Further, the power steering control device 5 is a control device that controls the power steering of the vehicle.

The own vehicle position sensor 13 is a device that acquires the position of the own vehicle by using radio waves from a positioning satellite such as GPS (Global Positioning System). The own vehicle position sensor 13 outputs the acquired own vehicle position information to the autonomous travel control device 1. The own vehicle position sensor 13 may acquire the own vehicle position information by using a positioning system other than GPS.

In addition, the vehicle position sensor 13 has a memory for holding map data used in automatic driving, such as road width, number of lanes, slope, curve curvature, intersection shape, speed limit information, and the like. Map data is stored. The map data may be stored inside the autonomous travel control device 1.

Here, when the autonomous driving control device 1 receives the request for automatic driving, it calculates the trajectory on which the vehicle moves based on the information of the outside world acquired from the camera 11, the radar 12, the own vehicle position sensor 13, and the like, and autonomously travels. The control device 1 outputs a control command regarding a brake, a driving force, and the like to the brake control device 3, the engine control device 4, and the power steering control device 5 so as to move the vehicle according to the route described above.

The brake control device 3, the engine control device 4, and the power steering control device 5 receive a control command for automatic driving control from the autonomous driving control device 1 and output an operation signal to each control target (actuator).

(Example 1)
FIG. 2 is a diagram showing an internal configuration of the autonomous travel control device (first ECU) 1 according to the first embodiment of the present invention.

In FIG. 2, the signals of the camera 11 (first sensor), the radar 12 (second sensor), and the own vehicle position (third sensor) pass through the communication circuit 1e (communication circuit 2) and are the arithmetic processing unit of the control microcomputer 1b. It is input to 1m, and the arithmetic processing unit 1m executes arithmetic processing.

Here, the control microcomputer 1b is an outside world recognition microcomputer that performs arithmetic processing based on the signals of the outside world information sensors (first to third sensors) possessed by the vehicle. The fan 1a is attached so as to cool the control microcomputer 1b (outside world recognition microcomputer).

Although there is one microcomputer in the internal configuration of the autonomous travel control device (first ECU) shown in FIG. 2, two microcomputers may be used and the arithmetic processing unit 1 m may be another microcomputer.

The control microcomputer 1b sets the rotation speed in consideration of heat generation due to arithmetic processing by the rotation speed control 1i, and controls the fan 1a via the rotation speed control signal line 1f.

The fan 1a outputs a pulse signal corresponding to the rotation speed to the low-pass filter 1c via the pulse output signal line 1g, and outputs the output of the low-pass filter 1c to the control microcomputer 1b via the filter output signal line 1h.

The voltage value of the filter output signal line 1h is detected by the voltage detection unit 1k inside the control microcomputer 1b, compared with the predetermined value inside the microcomputer by the abnormality diagnosis unit 1j, and if it exceeds the predetermined value, it is diagnosed as a rotation speed abnormality. To do. In other words, the control microcomputer 1b includes an abnormality diagnosis unit 1j (diagnosis unit) that detects a decrease in the rotation speed of the fan 1a from the output of the fan 1a via the low-pass filter 1c. As a result, it is not necessary to count the rotation speed of the fan 1a, so that it is possible to detect a decrease in the rotation speed of the fan 1a while suppressing the load on the control microcomputer.

When the abnormality diagnosis unit 1j diagnoses that the rotation speed is abnormal, the abnormality diagnosis unit 1j notifies the degeneration control microcomputer 2a of the degeneration control device 2 (second ECU) that the fan 1a has an abnormal rotation speed via the communication circuit 1d (communication circuit 1). To do.

FIG. 3 shows the magnitude relationship between the signal of the pulse output signal line 1g and the signal of the filter output signal line 1h and the predetermined value in the microcomputer (abnormality diagnosis unit) in the first embodiment of the present invention, and the frequency characteristics of the low-pass filter 1c. It is a figure which shows the relationship of the rotation speed of a fan.

The cutoff frequency of the low-pass filter 1c is set to a frequency (determination frequency) corresponding to the rotation speed for diagnosing an abnormality. When a pulse signal having a frequency higher than the determination frequency from the pulse output signal line 1g is input to the low-pass filter 1c, the low-pass filter 1c smoothes the pulse signal. That is, the low-pass filter 1c has a frequency characteristic (cutoff frequency) according to the rotation speed to be determined, and smoothes a signal having a frequency equal to or higher than the determination frequency. As a result, when a signal having a frequency higher than the determination frequency (cutoff frequency) is input to the low-pass filter 1c, the amplitude of the signal output from the low-pass filter 1c becomes small.

When a pulse signal having a frequency lower than the determination frequency is input to the low-pass filter 1c, the low-pass filter 1c passes the pulse signal and outputs the pulse signal to the filter output signal line 1h.

When the voltage value detected by the voltage detection unit 1k of the control microcomputer 1b is a pulse signal higher than the judgment frequency, the influence of the low-pass filter 1c is large, so that the fluctuation of the detected voltage becomes small and the pulse is lower than the judgment frequency. In the case of a signal, the influence of the low-pass filter 1c is small, so that the voltage fluctuation becomes large.

The abnormality diagnosis unit 1j of the control microcomputer 1b compares the voltage detection value with the predetermined value inside the microcomputer, and when the voltage detection value (peak value) exceeds the predetermined value (or the voltage detection value (bottom value) is predetermined). If it is below the value), it is diagnosed as an abnormal rotation speed.

In other words, the abnormality diagnosis unit 1j (diagnosis unit) is provided in the control microcomputer 1b having a function (AD converter function) of capturing the filter output signal as a voltage value. The abnormality diagnosis unit 1j diagnoses the rotation speed abnormality when the voltage value exceeds a predetermined value inside the microcomputer. As a result, it is possible to diagnose a decrease in the rotation speed of the fan 1a as a rotation abnormality by using an AD converter generally built in the control microcomputer. The low-pass filter 1c may be shared as a component for the AD converter. As a result, the manufacturing cost can be reduced.

Although only one predetermined value is shown in FIG. 3, it is possible to have a plurality of predetermined values and make a detailed diagnosis of the rotation speed abnormality.

The autonomous travel control device (first ECU) 1 which is an electronic control device includes at least a control microcomputer 1b that functions as a diagnostic unit, a fan 1a having a sensor that outputs a pulse signal according to the rotation of the fan 1a, and a sensor. It is provided with a low-pass filter 1c to which a pulse signal is input from. The control microcomputer 1b is composed of, for example, a processor, a memory, and the like. When the digital value of the signal output from the low-pass filter 1c falls below the threshold value, the control microcomputer 1b (processor) determines that the rotation speed of the fan 1a has decreased.

Here, the lower limit rotation speed of the fan 1a required for cooling the control microcomputer 1b is determined by, for example, simulation, experiment, or the like. The threshold value is determined from, for example, the bottom value of the signal output from the low-pass filter 1c when the pulse signal corresponding to the lower limit rotation speed is input to the low-pass filter 1c.

(Example 2)
FIG. 4 is a diagram showing an internal configuration of an autonomous travel control device (first ECU) 1 that performs a rotation speed abnormality diagnosis according to a second embodiment of the present invention using a comparator circuit.

The autonomous traveling control device (first ECU) 1 which is the electronic control device of this embodiment includes a comparator 1o (comparator circuit) connected to the output of the low-pass filter 1c, and is compared with a voltage corresponding to a specified value by the comparator 1o. , The comparator output is input to the control microcomputer 1b.

Specifically, a comparator 1o capable of comparing voltages is provided between the low-pass filter 1c and the control microcomputer 1b. The comparator 1o compares the voltage value of the filter output signal line 1h with the voltage value of the threshold voltage signal line 1p that can be arbitrarily set, and when it falls below (or exceeds) the threshold voltage, it signals High. (Or Low signal) is output to the comparator output signal line 1q.

The signal from the comparator output signal line 1q is input to the abnormality diagnosis unit 1j inside the control microcomputer 1b. When the input signal becomes a High signal (or Low signal), the abnormality diagnosis unit 1j diagnoses the rotation speed abnormality and notifies the outside (degeneration control device 2 or the like).

That is, the control microcomputer 1b sends a signal indicating that the fan 1a has an abnormal rotation speed when the voltage value of the filter output signal line 1h exceeds a predetermined value (voltage value of the threshold voltage signal line 1p). It is transmitted to the backup microcomputer (reduction control device 2, etc.). This makes it possible to back up the system.

FIG. 5 shows the magnitude relationship between the signal of the pulse output signal line 1g, the signal of the filter output signal line 1h and the threshold voltage signal 1p (threshold voltage) in the second embodiment of the present invention, and the comparator output signal line 1q. It is a figure which shows the signal.

The cutoff frequency of the low-pass filter 1c is set to the determination frequency as in the first embodiment. The low-pass filter 1c smoothes the pulse signal when a pulse signal having a frequency higher than the determination frequency is input. When a pulse signal having a frequency lower than the determination frequency is input to the low-pass filter 1c, the low-pass filter 1c passes the pulse signal and outputs the pulse signal to the filter output signal line 1h.

The comparator 1o (judgment circuit unit) compares the voltage values of the threshold voltage signal line 1p and the filter output signal line 1h, and when the voltage of the filter output signal line 1h is lower than the threshold voltage signal line 1p, the comparator A High signal is output to the output signal line 1q.

When the High signal is input from the comparator output signal line 1q, the abnormality diagnosis unit 1j of the control microcomputer 1b diagnoses that the rotation speed is abnormal.

That is, the autonomous travel control device (first ECU) 1 which is an electronic control device includes at least a control microcomputer 1b that functions as a diagnostic unit, a fan 1a having a sensor that outputs a pulse signal according to the rotation of the fan 1a, and a sensor. A low-pass filter 1c to which a pulse signal is input from the low-pass filter 1c and a comparator 1o (comparator circuit) for comparing a voltage value of a signal output from the low-pass filter 1c with a threshold voltage are provided. The control microcomputer 1b (processor) detects a decrease in the rotation speed of the fan 1a from the signal output from the comparator 1o.

Since a comparator is used instead of the AD converter, there is no sampling delay and the fan abnormality (low speed) can be determined in real time.

(Example 3)
FIG. 6 is a diagram showing an internal configuration of an autonomous travel control device (first ECU) 1 that detects a rotational state using a plurality of low-pass filters according to a third embodiment of the present invention.

In this embodiment, the low-pass filter is connected to the control microcomputer 1b by configuring a plurality of filters having different frequency characteristics in parallel. That is, the control microcomputer 1b includes a low-pass filter 1r having a cutoff frequency different from that of the low-pass filter 1c shown in Examples 1 and 2. The signal of the pulse output signal line 1g is input to the low-pass filter 1r, and the low-pass filter 1r outputs the signal to the filter output signal line 1s.

The voltage detection unit 1k inside the control microcomputer detects the voltage values of the filter output signal lines 1h and 1s, and the rotation state diagnosis unit 1t compares the predetermined values inside the microcomputer to diagnose the rotation state and notify the outside.

FIG. 7 shows the magnitude relationship between the pulse output signal 1g signal, the filter output signal line 1h, 1s signal and the predetermined value in the microcomputer (rotational state diagnosis unit) in the third embodiment of the present invention, and the low-pass filters 1c and 1r. It is a figure which shows the relationship between the frequency characteristic of, and the rotation speed of a fan.

<Low speed>
When the cutoff frequencies of the two low-pass filters 1c and 1r are f1c and f1r and the fan rotation speed is low (fan rotation frequencies a <f1c and f1r), the signals of the filter output signal lines 1h and 1s are of the filter. The effect is small and the detected voltage fluctuation is large. Therefore, both the signals of the filter output signal lines 1h and 1s are lower than the predetermined values of the rotation state diagnosis unit 1t.

<Medium speed>
When the rotation speed of the fan is medium (f1c <rotation frequency b <f1r), the signal of the filter output signal line 1h is greatly affected by the filter and the voltage fluctuation is small, but the voltage fluctuation of the filter output signal line 1s is small. Is large, so only the filter output signal 1s falls below the predetermined value of the rotation state diagnosis unit 1t.

<High speed>
When the rotation speed of the fan is high (f1c <f1r <rotation frequency c), the signals of the filter output signal lines 1h and 1s are both greatly affected by the filter and the voltage fluctuation becomes small. It does not fall below the predetermined value of 1t.

By using a plurality of low-pass filters as described above, it is possible to diagnose the rotational state.

That is, the autonomous travel control device (first ECU) 1 which is an electronic control device includes at least a control microcomputer 1b that functions as a diagnostic unit, a fan 1a having a sensor that outputs a pulse signal according to the rotation of the fan 1a, and a sensor. A pulse signal is input from the low-pass filter 1c (first low-pass filter) having a cutoff frequency f1c (first cutoff frequency), and a pulse signal is input from the sensor, and the cutoff frequency is higher than the cutoff frequency f1c. A low-pass filter 1r (second low-pass filter) having f1r (second cutoff frequency) is provided.

When the value indicated by the signal output from the low-pass filter 1c (first low-pass filter) falls below the first threshold value, the control microcomputer 1b (processor) transfers the function of the control microcomputer 1b to another control microcomputer. Let me take over. Further, in the control microcomputer 1b, the value (digital value or voltage value) indicated by the signal output from the low-pass filter 1c (first low-pass filter) exceeds the first threshold value, and the low-pass filter 1r (first low-pass filter) When the value (digital value or voltage value) indicated by the signal output from the low-pass filter (2) falls below the second threshold value, the calculation amount (load) of the control microcomputer 1b is reduced.

(Example 4)
FIG. 8 is a diagram showing an internal configuration of an autonomous travel control device (first ECU) 1 capable of changing an abnormal rotation speed according to the rotation speed control in the fourth embodiment of the present invention.

In FIG. 8, a variable low-pass filter 1u is provided in order to change the cutoff frequency according to the rotation speed of the fan.

The rotation speed control unit 1i of the control microcomputer controls the rotation speed of the fan and passes the rotation speed information to be controlled to the variable filter control unit 1v. The filter control unit 1v sets the variable low-pass filter so that the determination frequency becomes the cutoff frequency (1w), and also passes the predetermined value setting information indicating the predetermined value corresponding to the determination frequency to the abnormality diagnosis unit 1j (1x). ..

The signal of the pulse output signal line 1g output from the fan 1a is input to the control microcomputer 1b via the variable filter 1u. The voltage value detection unit 1k detects the voltage value of the pulse output signal line 1g. The abnormality diagnosis unit 1j detects a rotation speed abnormality when the voltage value of the pulse output signal line 1g falls below a predetermined value.

Here, the autonomous traveling control device (first ECU) 1, which is an electronic control device, controls the rotation speed of the fan 1a from the control microcomputer 1b, and determines the rotation speed according to the rotation speed control by the variable filter 1u. The frequency can be set, and the rotation speed of the fan 1a can be controlled / monitored by the amount of heat generated.

In FIG. 8, a variable low-pass filter is provided outside the control microcomputer 1b, but a digital filter may be configured inside the control microcomputer 1b. That is, the low-pass filter may be digitally processed by the control microcomputer 1b. As a result, for example, the number of parts can be reduced, so that the manufacturing cost can be reduced.

The present invention is not limited to the above-mentioned examples, and includes various modifications. For example, the above-described examples have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

The low-pass filter is, for example, an "RC filter", a filter using an operational amplifier, etc., but in the latter, the output value changes sharply at the cutoff frequency, so that the fan is normal (desired speed) and abnormal (low speed). The distinction is good.

In addition, each of the above configurations, functions, and the like may be realized by hardware, for example, by designing a part or all of them with an integrated circuit. Further, each of the above configurations, functions, and the like may be realized by software by the processor (microcomputer) interpreting and executing a program that realizes each function. Information such as programs, tables, and files that realize each function can be stored in a memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.

1 ... Autonomous driving control device 2 ... Retraction control device 3 ... Brake control device 4 ... Engine control device 5 ... Power steering control device 11 ... Camera 12 ... Radar 13 ... Own vehicle position sensor, map information 1a ... Fan 1b ... Control microcomputer 1c ... Low pass filter 1d, 1e ... Communication circuit 1f ... Rotation speed control signal line 1g ... Pulse output signal line 1h ... Filter output signal line 1i ... Rotation speed control unit 1j ... Abnormality diagnosis unit 1k ... Voltage value detection unit 1m ... Arithmetic processing unit 1o ... comparator 1p ... threshold voltage signal line 1q ... comparator output signal line 1r ... low pass filter 1s ... filter output signal line 1t ... rotation speed determination unit 1u ... variable low pass filter 1v ... filter control unit 1w ... filter control signal line 1x ... Predetermined value control signal 2a ... Reduction control microcomputer 2b ... Communication circuit

Claims (12)

An electronic control device equipped with a diagnostic unit that detects a decrease in fan speed from the output of the fan via a low-pass filter.
This The electronic control device according to claim 1, wherein the low-pass filter has a frequency characteristic (cutoff frequency) according to a rotation speed to be determined, and smoothes a signal having a frequency equal to or higher than the determination frequency. The diagnostic unit is provided in a control microcomputer having a function of capturing a filter output signal as a voltage value.
The electronic control device according to claim 2, wherein the diagnosis unit diagnoses a rotation speed abnormality when the voltage value exceeds a predetermined value inside the microcomputer. The electronic control device according to claim 3, wherein the low-pass filter is digitally processed by the control microcomputer. The electronic control device according to claim 3, wherein the low-pass filter comprises a plurality of filters having different frequency characteristics in parallel and is connected to the control microcomputer. A comparator circuit connected to the output of the low-pass filter is provided.
The electronic control device according to claim 1, wherein the comparator circuit compares the voltage corresponding to a specified value and inputs the comparator output to the control microcomputer. Equipped with an external world recognition microcomputer that performs arithmetic processing based on the signal of the external world information sensor of the vehicle
The electronic control device according to any one of claims 1 to 6, wherein the fan is attached so as to cool the external recognition microcomputer. The electronic control device according to claim 7, wherein the external world recognition microcomputer transmits a signal indicating that the fan has an abnormal rotation speed to the backup microcomputer when the voltage value of the output exceeds a predetermined value. By controlling the rotation speed of the fan from the control microcomputer, the rotation speed according to the rotation speed control can be set as the determination frequency.
The electronic control device according to claim 4, wherein the rotation speed of the fan can be controlled / monitored by the amount of heat generated. A control microcomputer that functions as the diagnostic unit,
The fan having a sensor that outputs a pulse signal according to the rotation of the fan, and the fan.
The low-pass filter to which a pulse signal is input from the sensor is provided.
The control microcomputer is
The electronic control device according to claim 1, wherein when the digital value of the signal output from the low-pass filter falls below the threshold value, it is determined that the rotation speed of the fan has decreased. A control microcomputer that functions as the diagnostic unit,
The fan having a sensor that outputs a pulse signal according to the rotation of the fan, and the fan.
The low-pass filter to which a pulse signal is input from the sensor and
A comparator circuit for comparing the voltage value of the signal output from the low-pass filter with the threshold voltage is provided.
The control microcomputer is
The electronic control device according to claim 1, wherein a decrease in the rotation speed of the fan is detected from a signal output from the comparator circuit. A control microcomputer that functions as the diagnostic unit,
The fan having a sensor that outputs a pulse signal according to the rotation of the fan, and the fan.
A pulse signal is input from the sensor, and a first low-pass filter having a first cutoff frequency and
A second low-pass filter, which receives a pulse signal from the sensor and has a second cutoff frequency higher than the first cutoff frequency, is provided.
The control microcomputer is
When the value indicated by the signal output from the first low-pass filter falls below the first threshold value, the function of the control microcomputer is taken over by another control microcomputer.
The value indicated by the signal output from the first low-pass filter exceeds the first threshold value, and the value indicated by the signal output from the second low-pass filter exceeds the second threshold value. The electronic control device according to claim 1, wherein if the value is lower than that, the calculation amount of the control microcomputer is reduced.

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