JPS61229638A - Electronic control device for car - Google Patents

Abstract

PURPOSE:To prevent an erroneous operation of a controlled circuit due to an abnormality of an earth line for a control circuit by providing a diode between the both each lines independently provided for the control circuit and the control circuit respectively. CONSTITUTION:An electronic control device for a car has a control circuit 4 outputting control signals to control the operation of actuators based on information signals from sensors and an output circuit 5 to output the control signals to actuators. Individual circuits 4, 5 have earth lines 21, 22 respectively. In this case, an and is connected to the earth line 21, and a diode connected with cathode is provided to the earth line 21, and a diode connected with a cathode is provided on the earth line 22. If an imperfect contact occurs in a connector (not shown in the figure) for removably connecting the electronic control device and a hardness for car, the potential difference between both earth lines 21, 22 can be reduced to the forward down from voltage of the diode 62.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a malfunction prevention structure that prevents malfunction of an electronic control device for a vehicle when a temporary contact failure occurs in the electronic control device. .

[Prior Art] Conventionally, there is a vehicle electronic control device as shown in FIG. 2, for example.

In FIG. 2, 1 is a vehicle electronic control device I that controls actuators, etc., and 2 is this vehicle electronic control device 1.
A vehicle harness 3 connects a battery, sensors, actuators (not shown), and a connector 3 connects the vehicle electronic control device 1 and the vehicle harness 2 in a 1112-way connection. 4 is a control circuit that outputs a control signal for controlling the operation of actuators based on information signals from sensors, and 5 is an output circuit for outputting the control signal from control circuit 4 to the actuators. . 21
22 is a ground line of the control circuit 4, and 22 is a ground line of the output circuit 5. These ground lines 21 and 22 are separated in the vehicle electronic control unit 1 and the vehicle harness 2, and are drawn in common at the negative terminal of the battery or the ground point of the engine. This can be achieved by reducing the common impedance of the ground lines 21 and 22.
This is to prevent the control circuit 4 from being affected by voltage effects or the like due to a relatively large current flowing through the control circuit 2.

FIG. 3 specifically shows the vehicle electronic control device 1. As shown in FIG. In FIG. 3, 41 is an electronic circuit including a voltage regulator, a microcomputer, a resistor, and the like.

42 is a capacitor disposed on the power supply line, and 43 is a field effect transistor that transmits a control signal to the output circuit 5 based on information signals from sensors. 51 is a transistor on the output circuit side that receives the control signal, and 52 is an electronic circuit that drives actuators (not shown) based on the control signal received by the transistor 51.

[Problems to be Solved by the Invention] By the way, in the conventional vehicle electronic control device 1 described above, when the connector 3 has a temporary contact failure, the ground line 21 for the control circuit and the ground line 21 for the output circuit are connected to each other. There is a problem that a potential difference occurs between the ground line 22 and the vehicle electronic control device malfunctions.

In other words, even if the connector 3 has a temporary contact failure and the ground line 21 is disconnected, the
Due to the effect of J7I2, the electronic circuit 41 normally generates control signals for a short time.

However, when looking at the potential of the ground line 21 of the control circuit 4 using the ground line 22 of the output circuit 5 as a reference, it becomes as shown in FIG. In other words, if it is assumed that a disconnection occurs between 11 and 1 U, then the ground line 21 of the control circuit 4
The potential immediately rises from the same level as the potential of the ground line 22 of the output circuit 5, creating a large potential difference.

Therefore, when viewed from the ground line 21, the base voltage V^ of the 1-transistor 51 increases by the change in (Vp, y). Here, VDS is the voltage between the denoid and the source of the field effect transistor 43.

Therefore, if such a state occurs when the field effect transistor /I3 is on and \l8 is at the 1-level, the transistor 51 may malfunction from on to A5.

[Means for Solving the Problems] 31 The present invention has been made to solve the above-mentioned problems of the conventional art. The purpose is to provide a vehicle electronic control device that can prevent malfunctions of transistors in the circuit, and the technical means for this purpose is to provide independent ground lines for the control circuit and the controlled circuit. In addition, in a vehicle electronic control device that controls energization in a predetermined path to a ground line in a controlled circuit using a control voltage from the control circuit based on the ground potential of the control circuit, the ground potential of the control circuit is This is done by a vehicle electronic control device including a diode whose anode is connected to the line and whose cathode is connected to the ground line of the controlled circuit.

[Example code] Hereinafter, the present invention will be described in detail based on the accompanying drawings.

FIG. 1 shows a vehicle electronic control device according to an embodiment of the present invention. This electronic control device for a vehicle 1 has substantially the same configuration as a conventional electronic control device for a vehicle, and 4 is a control signal for controlling the operation of actuators based on information signals from sensors. 5 is an output circuit for outputting a control signal from the control circuit 4 to actuators. 21 is a ground line of the control circuit 4, and 22 is a ground line of the output circuit 5. Also,
Reference numeral 43 indicates a field effect transistor 1 to a transistor that transmits a control signal to the output circuit 5 based on information signals from sensors, and 51 indicates a transistor on the output circuit 5 side that receives the control signal.

62 is a diode whose anode is connected to the ground line of the control circuit 4 and whose cathode is connected to the ground line 22 of the output circuit 5 which is the controlled circuit; The potential difference between the two ground lines 21 and 22 is reduced to the forward voltage drop of the diode 62. Further, in this embodiment, a connection line C connecting the control circuit 4 and the output circuit 5 is
A diode 61 is provided above.

Next, the operation of this vehicle electronic control device 1 will be explained.

First, if the connection between the ground line 21 for the control circuit and the connector 3 is normal, the current flowing through the control circuit 4 passes through the ground line 21 and returns to the negative terminal of the battery (not shown)! do.

If the current flowing through the earth line 21 is 10° and the current flowing through the earth line 22 is to, then 1. This is because Vll<Vu2 because the forward voltage drop of the diode 62 is vF:.

Therefore, in this case, the output circuit 5 operates normally as in the conventional case.

Next, a case will be described in which a momentary disconnection (temporary poor contact) occurs between the ground line 21 of the control circuit 4 and the connector 3.

In this case, V21 is the potential of the ground line 21 at the connection point with the diode 62, Vll is the potential of the ground line 22 at which connection point of the diode 62, and vD8 is the potential between the denoid and the source when the field effect transistor 43 is on. The electric current fE and VA between the field effect transistors 43 and
, VC is the base potential of the transistor 51, VF is the forward drop voltage of the diode 61, 62, and the voltage when the transistors 1 to 51 are turned on is VBE.
shall be. When a momentary power outage occurs, the voltage level V, L- of the ground line 21 for the control circuit rises to a very high level compared to the voltage level V2 of the ground line 22 for the output circuit. (See Figure 3). However, Vl
Due to the effect of the diode 62, l cannot be higher than V210 VF. Also, this (D time, VA HaV
21+Vos, that is, Vl)-+VF+Vbs. Since the voltage VBB when the transistor 51 is turned on is previously set to Vos<Vlla, VBE is normally smaller than VF+VDS, but due to the effect of the diode 61, the base voltage Vc of the transistor 51 is (VA - V
F ) −(Vxz+Vps), and transistor 5
1 cannot be turned on. Therefore, even if there is a temporary contact failure between the ground line 21 for the control circuit and the connector 3, the current path for the control circuit can be routed without affecting the control signal from the control circuit 4 to the output circuit 5. can be ensured. In the above embodiment, the diode 61 was provided on the connection line C connecting the control circuit 4 and the output circuit 5, but it is not necessary to provide such a diode in the present invention. Even in such a case, according to the present invention, since the diode 62 is provided between the ground line 21 of the control circuit 4 and the ground line 22 of the output circuit 5, the potential difference between the two ground lines is caused by the forward drop of the diode 62. down to the voltage. Therefore, compared to conventional electronic control devices, malfunction of the transistor 51 of the output circuit 5 can be prevented as much as possible. Also, both ground lines 21.2
2 becomes smaller, the control circuit 4 and the output circuit 5
Measures to eliminate malfunctions of the transistor 51 can also be taken by installing a diode 61 on the connection line C of the transistor 51 so as to cancel out the change in the voltage level of the control circuit ground from the control signal. It becomes easy.

[Effects of the Invention] As explained above, according to the present invention, since the diode is provided between the ground line of the control circuit and the ground line of the controlled circuit, the potential difference between the two ground lines is reduced to the forward voltage drop of the diode. down to Therefore, compared to conventional electronic control devices, malfunctions of the controlled circuit can be prevented as much as possible. In addition, since the potential difference between the ground lines provided independently between the control section and the controlled section is reduced, a diode is provided on the connection line between the control circuit and the controlled circuit to compensate for changes in the voltage level of the ground for the control circuit. This has the effect of making it easier to take measures to eliminate malfunctions in any controlled path, such as by configuring the control signal to cancel the error.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a vehicle electronic control device according to an embodiment of the present invention, FIGS. 2 and 3 are circuit diagrams showing a conventional vehicle electronic control device, and FIG. 4 is a circuit diagram showing a control circuit. 1 is a graph showing the voltage change of the ground line for the control circuit when a temporary contact failure occurs with the =1 connector. 1...Vehicle electronic control device 3...Connector 4...Control circuit 5...Output circuit 21...Ground line 22 for control circuit...Ground line 43 for output circuit... Field effect transistor 51...1 to transistor 1.62...diode Patent applicant Nissan Motor Co., Ltd. Figure 1

Claims (1)

[Claims] In addition to providing independent ground lines for the control circuit and the controlled circuit, the control voltage from the control circuit with reference to the ground potential of the control circuit controls the energization in a predetermined path to the ground line in the controlled circuit. 1. A vehicle electronic control device comprising a diode having an anode connected to a ground line of a control circuit and a cathode connected to a ground line of a controlled circuit.