JP2001157360A - Ground variation preventing device for electronic controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground variation preventing device preventing variation between grounds in an electronic controller of multi-ground constitution with two or more types of grounds including a power system ground and a signage ground. SOLUTION: This ground variation preventing device is formed, with an element restricting a voltage between a power system ground and a signage ground to be constant, so that the predetermined voltage value of the element restricting the voltage between the multi-grounds within a fixed voltage may be set at such a voltage value as preventing a DC component from passing through the multi-grounds, and the time of current flowing through the multi- grounds may be set significantly shorter than the filtering time of an input circuit from an external sensor with the signage ground as a reference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic control unit, and more particularly to an electronic control unit having a multi-ground configuration having two or more types of grounds and a device for preventing fluctuation between the grounds.

[0002]

2. Description of the Related Art A conventional electronic control unit of this type is grounded as shown in, for example, Japanese Patent Application Laid-Open No. 09-177597. That is, a signal ground for grounding a control block such as a regulator and a power ground for flowing a large current such as a solenoid drive are electrically separated and grounded. The reason why these grounds are separated is to prevent a large current flowing through the power system ground from adversely affecting a circuit connected to the signal system ground.

As shown in JP-A-09-177597, a diode is connected between the signal ground and the power ground in the direction from the signal ground to the power ground. This diode connects the anode side to the signal ground and the cathode side to the power ground to prevent current from flowing from the power ground to the signal ground, and at the same time, the signal ground cannot be grounded due to harness disconnection or the like. Even in this state, by grounding the signal system ground to the power system ground via the diode, the signal system ground potential level is suppressed to the signal system ground potential level = the power system ground potential level + the diode forward voltage, so that the signal system ground is maintained. Malfunction of the connected circuit is prevented.

[0004]

In the above technique, a large current flows to drive a solenoid or the like connected to the power system ground, so that a potential difference is generated between the power system ground and the signal system ground. . Further, when disturbance noise is mixed into the harness of the signal ground or the power ground, a potential difference is similarly generated between the power ground and the signal ground.

That is, the ground of the multi-ground electronic control device is separated into a power ground and a signal ground, and a diode is connected from the signal ground to the power ground. There is no longer the same potential between the grounds. Therefore, when the power system ground becomes higher in potential than the signal system ground, a potential difference occurs.

In normal operation, the potential difference does not become excessive. However, if the influence of a load operation or the like having a large current value is mixed into the power ground or the signal ground, the power ground becomes the signal ground. The potential becomes higher, and the positive bias from the CPU becomes reverse bias with respect to the drive element with respect to the drive element grounded to the power system ground, and there is a concern that the withstand voltage of the drive element may be insufficient.

Conversely, when the power system ground becomes lower in potential than the signal system ground, the potential difference is suppressed within the forward voltage of the diode by the diode connected from the signal system ground to the power system ground. By this, the potential difference between the power system ground and the signal system ground can be prevented below a certain voltage, but the signal system ground is pulled to the low potential of the power system ground,
The signal ground may fluctuate, and noise may be mixed into a sensor signal that uses the signal ground as a reference ground.

[0008]

Means for Solving the Problems At least a signal ground for grounding an element for flowing a small current, such as a control IC, and a power ground for grounding an element for flowing a large current, such as a solenoid drive element. In the electronic control device having a multi-ground configuration having both of the two types of grounds, it is characterized in that when an electric potential difference occurs between the multi-grounds, there is provided means for suppressing the voltage between the multi-grounds to be within a certain voltage.

Further, the voltage set value for keeping the voltage between the multi-grounds within a certain voltage is a voltage set value for preventing a DC component from passing between the multi-grounds.

Further, the voltage set value for keeping the voltage between the multi-grounds within a certain voltage is such that the time for flowing the current between the multi-grounds is sufficiently longer than the filter time of the input circuit from the external sensor with respect to the signal ground. It is characterized by being a short time.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
The engine control device will be described as an example with reference to FIGS.

FIG. 1 is a block diagram showing an engine control device as an example of an electronic control device having a ground fluctuation preventing device according to the present invention.

The engine controller 1 is controlled by a key switch 2 to supply power from a battery 3. That is, when the key switch 2 is turned on, the power of the battery 3 is supplied to the engine control device 1 via the harness 3a, the key switch 2, and the harness 2a. With the supplied power, the power control unit 5 in the engine control device 1 is activated, and power supply to the engine control device 1 is started. That is, the power control unit 5
Starts the control of the regulator 4, converts the power of the battery 3 to a power level 4a optimal for the CPU 6 and the like set in the engine control device 1, and starts the power supply in the engine control device 1.

The potential level generated by the power control unit 5 is determined with reference to the signal ground 7.

The engine control device 1 fetches signals from various sensors attached to the engine unit and performs an optimal calculation by the CPU 6 to optimize the engine, and optimizes at least the injector 14 for supplying fuel to the engine. Controlling.

Reference numeral 9 denotes a water temperature sensor for detecting the temperature of cooling water of the engine, which is one of the sensors attached to the engine for optimal control of the engine. The water temperature sensor 9 is a thermistor type sensor whose resistance value changes according to the detected temperature, and has an input voltage 10 (=) to the A / D converter of the CPU 6 based on a ratio with a pull-up resistor 8 set in the engine control device 1. Input voltage 13) is determined.

That is,

[0018]

(Equation 1)

Is determined.

The input voltage 10 is supplied to the A / D
Input to the converter and use as calculation parameters in CPU6. The reference ground of the input voltage 10 is an analog ground 7 ′ that is short-circuited to the signal ground 7 in the engine control device 1. Further, in order to remove the AC noise component of the input voltage 10, the A
Resistor 11 and capacitor 1 before input to the / D converter
2. A low-pass filter circuit composed of 2 is set. The time constant of this low-pass filter is calculated by the following equation

[0021]

## EQU2 ## Time constant: τ = resistance 11 × capacitor 13 The time constant τ is a value optimized for each input sensor.

As described above, the water temperature sensor 9 for detecting the state of the engine and the control elements such as the CPU 6 are grounded to the signal ground 7.

The CPU 6 outputs a control signal 15a to a drive element 15 that drives an injector 14 that supplies fuel to the engine based on the calculation result of the CPU 6, thereby determining the amount of fuel to be supplied into the cylinder of the engine. Adjusts and controls the engine optimally. The driving element 15 is used to supply a large current to the
In this configuration, the current flowing through the injector 14 flows out to the power ground 16 so that a large current does not affect the signal ground 7.

Reference numeral 17 denotes a ground fluctuation preventing device of the present invention, which is set between the signal ground 7 and the power ground 16 to prevent a potential fluctuation between the signal ground 7 and the power ground 16.

FIG. 2 is a diagram showing a mechanism in which a potential change occurs between the power system ground 16 and the signal system ground 7.

The power system ground 16 and the signal system ground 7 are each grounded to the engine block 25 via a harness. However, each harness has an impedance component (harness impedance 21 for signal ground, harness impedance 2 for power ground).
If 2) exists and the drive current 24 of the injector 14 flows in the power system ground, a voltage 23 is generated in the power system ground 16 with respect to the signal system ground 7.

However, the harness impedance is 10 m
Since the resistance is about Ω / m, the harness length is 5 m and the current 24 is 2
Assuming 0 A, the potential difference generated in the power system ground 16 with respect to the signal system ground 7 is:

[0028]

[Formula 3] 10mΩ / m × 5m × 20A = 1V However, this level of signal ground 7
The potential difference between the power system ground 16 and the power system ground 16 causes no particular problem.

However, when a low potential 23a is generated in the power ground 16 based on the signal ground 7, a current 28b flows from the signal ground 7 to the power ground 16, and the signal ground 7 is lowered by the power ground 16. Is varied. JP-A-09-177597
In the technique described in (1), when a potential difference equal to or more than the forward voltage VF of the diode occurs, the current 28b flows and the fluctuation of the signal system ground 7 occurs.

In the ground fluctuation preventing device according to the present invention, the potential difference generated by the current 28b is set to the forward voltage VF of the diode.
The voltage VZ2 of the ground fluctuation preventing device 17a having the above voltage is set to prevent the fluctuation of the signal ground 7.

In the technique disclosed in Japanese Patent Application Laid-Open No. 09-177597, when disturbance noise is mixed into the power ground 16 via a harness, the signal ground is used as a reference.
A large potential is generated in the power system ground. Conversely, if disturbance noise is mixed in the signal ground 7 via the harness, a large potential will be generated in the power ground based on the signal ground.

In the ground fluctuation preventing device of the present invention, the large potential generated in the power ground with reference to the signal ground is suppressed to the voltage VZ1 of the ground fluctuation preventing device 17b, and the power ground 16 and the signal ground 7 are suppressed. This prevents potential fluctuations between them.

FIG. 3 shows a power system ground 16 and
FIG. 4 is a diagram comparing ground fluctuation waveforms generated in a power system ground 16 based on the signal system ground 7 due to noise mixed in the signal system ground 7 before and after application of the present invention.

The ground fluctuation waveform 31 is a waveform before the application of the ground fluctuation prevention device. As described above, when the power system ground 16 is monitored with the signal system ground 7 as a reference, a large potential difference is generated on the plus side, and the forward voltage VF of the diode is generated on the minus side by the diode shown in JP-A-09-177597. It has become.

The ground fluctuation waveform 32 is a waveform after the application of the ground fluctuation prevention device. By the application of the present invention, the plus side is the voltage VZ1 determined by the ground fluctuation prevention device 17b.
In addition, the minus side can be suppressed to the voltage VZ2 determined by the ground fluctuation preventing device 17a which is larger than the forward voltage VF of the diode.

FIG. 4 is a graph showing the noise mixing time into the signal system ground 7 with respect to the ground fluctuation preventing voltage on the plus side of the power system ground 16 based on the signal system ground 7 by the ground fluctuation preventing device.

If the ground fluctuation prevention voltage is set low,
The current 28a shown in FIG. 2 flows from the power system ground 16 in the direction of the signal system ground 7,
Fluctuates longer. Conversely, if the ground fluctuation preventing voltage is set high, the time during which the current 28a flows from the power ground 16 toward the signal ground 7 is shortened, and the time during which the signal ground 13 fluctuates is shortened. The ground fluctuation preventing voltage of the ground fluctuation preventing device 17b is 41, that is, the time 42 during which the circuit connected to the signal ground 7 is not affected, that is, the filter of the input processing circuit of the sensor for detecting the operating state of the engine. The ground fluctuation prevention voltage 43 is set so as to be within a time sufficiently shorter than the time or the like.

FIG. 4 is a graph showing the noise mixing time into the signal ground 7 with respect to the ground fluctuation preventing voltage on the plus side 17b of the power ground 16 with respect to the signal ground 7 by the ground fluctuation preventing device. However, the same applies to the noise mixing time into the signal ground 7 with respect to the ground fluctuation preventing voltage on the minus side 17a of the power ground 16 with reference to the signal ground 7.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and a design may be made without departing from the spirit of the invention described in the appended claims. Various changes can be made.

[0040]

According to the ground fluctuation preventing apparatus of the present invention, at least two grounds such as a power ground and a signal ground are provided.
In an electronic control unit with a multi-ground configuration that combines several types of grounds, the voltage between the power system ground and the signal system ground can be kept within a certain voltage, thus preventing adverse effects on the electronic control unit circuit due to ground voltage fluctuations. Can be.

[Brief description of the drawings]

FIG. 1 is a diagram showing an engine control device including a ground fluctuation preventing device.

FIG. 2 is a diagram illustrating a mechanism in which a potential difference between a power ground and a signal ground occurs.

FIG. 3 is a view showing a ground fluctuation waveform generated in a power system ground due to noise mixed in a power system ground and a signal system ground before and after application of the present invention.

FIG. 4 is a graph showing a noise mixing time into a signal system ground with respect to a ground fluctuation preventing voltage by a ground fluctuation preventing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine control device, 2 ... Key switch, 3 ... Battery, 4 ... Regulator, 5 ... Power supply control unit, 6 ... CPU,
7: Signal ground, 7 ': Analog ground,
9: water temperature sensor, 14: injector, 15: injector driving element, 16: power system ground, 17: ground fluctuation preventing element, 25: engine block.

Claims (3)

[Claims] 1. A signal ground for grounding an element for passing a small current, such as a control IC, and a solenoid drive element.
A power system ground that grounds an element that flows a large current,
An electronic control device having a multi-ground configuration having at least the two types of grounds, further comprising: a unit configured to suppress a voltage between the multi-grounds within a predetermined voltage when a potential difference occurs between the multi-grounds. . 2. The ground fluctuation preventing device according to claim 1, wherein the voltage set value for suppressing the voltage between the multi-grounds to a predetermined voltage is a voltage set value for preventing a DC component from passing between the multi-grounds. Ground fluctuation prevention device. 3. The ground fluctuation preventing device according to claim 1, wherein the voltage set value for keeping the voltage between the multi-grounds within a certain voltage is based on a signal flowing time between the multiple grounds. A ground fluctuation prevention device characterized in that the time is sufficiently shorter than a filter time of an input circuit from an external sensor.