JPWO2018051677A1 - Electronic control unit - Google Patents

Abstract

We propose an electronic control system that can reduce the failure of the main relay and reduce the cost. In an electronic control unit in which current from a battery is input to an input terminal of a power supply IC through a contact of a main relay and a UB line continuing to the contact, the electronic control unit has one end connected to the UB line and the other end Has a capacitor connected to ground and one end connected upstream of the capacitor on the UB line and the other end connected to the battery, and the inrush current prevention unit switches the main relay to ON. Before the battery is charged, the capacitor is charged by inputting the current from the battery from the other end and outputting it from one end, and when the predetermined condition is satisfied, the charging of the capacitor is stopped by stopping the input of the current from the battery.

Description

  The present invention relates to an electronic control device, and is particularly suitable for application to an electronic control device that controls the operation of an engine.

  Conventionally, a battery related circuit is disposed between an ECU (Electronic Control Unit) for controlling the operation of the engine and the battery, and a relay (hereinafter referred to as "main relay") is provided in the battery related circuit. ing. The main relay is required to handle a large current and reliably disconnect the ECU from the battery when the ignition is off. However, in the main relay, the contact may stick and fail due to inrush current flowing when voltage is supplied from the battery to the ECU. The amount of such inrush current is determined mainly in accordance with the capacitance in the vehicle harness and the ECU (see Patent Document 1).

JP, 2006-316639, A

  By the way, in recent years, since the ESR (Equivalent Series Resistance) of the electrolytic capacitor is suppressed to low power consumption, the rush current may be further increased. And, the risk of the contact of the main relay being fixed by such inrush current also increases. On the other hand, although a main relay having a high allowable current may be used to prevent the sticking of the contacts, the main relay having a high allowable current is expensive, resulting in a new problem that the manufacturing cost is increased.

  The present invention has been made in consideration of the above points, and proposes an electronic control device capable of reducing the failure of the main relay and suppressing the cost.

  In order to solve such problems, in the present invention, the electronic control unit is an electronic control unit in which a current from a battery is inputted to an input terminal of a power supply IC through a contact of a main relay and a UB line continuing to the contact. And a rush current preventing portion having one end connected to the UB line and the other end connected to the capacitor, and one end connected to the upstream side of the UB line from the capacitor and the other end connected to the battery. A CPU for controlling the rush current control unit, wherein the rush current prevention unit inputs current from the battery from the other end and outputs it from the one end before the main relay is switched to ON. Charge the capacitor, and stop charging of the capacitor by stopping the input of current from the battery when a predetermined condition is satisfied. And wherein the Rukoto.

  According to the present invention, the failure of the main relay can be reduced and the cost can be suppressed.

It is a schematic block diagram of the electronic control system by a 1st embodiment. It is a flow chart which shows starting processing. It is a schematic block diagram of the electronic control system by a 2nd embodiment. It is a figure which shows a current characteristic. It is a schematic block diagram of the electronic control system by a 3rd embodiment. It is a figure which shows a voltage characteristic.

  An embodiment of the present invention will be described with reference to the drawings. The following description does not limit the present invention, and can be appropriately modified within the scope of the present invention.

(1) First Embodiment FIG. 1 shows a schematic configuration of an electronic control system according to a first embodiment. In the electronic control system according to the first embodiment, an electronic control unit (hereinafter referred to as "ECU") 100 is connected to a battery 35 as a power supply via an ignition switch 31 and a relay (hereinafter referred to as "main relay") 32. ing.

  The negative terminal of the battery 35 is grounded, and the positive terminal is connected to the ignition switch 31, the main relay 32, and the sources of a capacitor charging FET 41 described later. The ignition switch 31 is a type of switch for starting or stopping the power supply from the battery 35 to the ECU 100.

  Main relay 32 is provided between battery 35 and ECU 100. The main relay 32 controls the supply of power from the battery 35 to the ECU 100 by turning on and off the contact 32A by the exciting force of the inductance 32B.

  The ECU 100 includes resistors 33 and 34, a power supply IC 37, capacitors 38 and 39, an inductance 36, and an inrush current prevention unit 50. Details of the inrush current prevention unit 50 will be described later.

  The power supply IC 37 includes an ignition switch input terminal 37A, an MR output terminal 37B, and a battery voltage input terminal 37C. The ignition switch input terminal 37A is connected to the ignition switch 31 via a resistor 34. The battery voltage of the battery 35 when the ignition switch 31 is turned on is applied to the ignition switch input terminal 37A. An inductance 32B of the main relay 32 is connected to the MR output terminal 37B. A UB line 44 continuous with the contact 32A of the main relay 32 is connected to the battery voltage input terminal 37C via an inductance 36.

  Capacitors 38 and 39 have one end connected to UB line 44 between main relay 32 and battery voltage input terminal 37C of ECU 100, and the other end grounded. Hereinafter, the capacitor 38 will be mainly described and described.

  The rush current prevention unit 50 includes a reverse current prevention diode 40 and a capacitor charging FET 41. The backflow prevention diode 40 is a diode for supplying current from the battery 35 only to the UB line 44, but preventing current from flowing in the opposite direction.

  One end of the capacitor charging FET 41 is connected to the UB line 44 between the main relay 32 and the capacitor 38, and the other end is connected to the positive terminal of the battery 35. The capacitor charge FET 41 has a function of charging the capacitor 38 by supplying the current from the battery 35 to the UB line 44 via the backflow prevention diode 40 by on / off control by the CPU 200 and stopping the charge. That is, the capacitor charge FET 41 corresponds to a capacitor charge switching unit for controlling whether or not the capacitor 38 is charged by the power supply of the battery 35.

  FIG. 2 shows the start-up process. When the ignition switch 31 is turned on (step S101), the CPU 200 first switches the capacitor charge FET 41 to the on state (step S102). That is, the CPU 200 switches the capacitor charging FET 41 to start charging the capacitor 38 immediately before the main relay 32 is turned on. Thus, current can be prevented from flowing into the capacitor 38.

  Thereafter, the CPU 200 switches the capacitor charge FET 41 to the off state in response to the satisfaction of a predetermined condition described later, and stops the charging of the capacitor 38 (step S103). As this predetermined condition, for example, it can be mentioned that a predetermined time has elapsed.

  Next, the power supply IC 37 turns on the MR output terminal 37B to energize the inductance 32B (step S104). Then, in the main relay 32, the contact 32A is closed by the exciting force of the inductance 32B and switched from the off state to the on state, and the battery voltage is supplied from the battery 35 to the ECU 100 (step S105). Thereafter, engine control is started.

  According to the present embodiment, when the ignition switch 31 is turned on, the inrush current flows in, whereby the contact 32A is fixed and the failure of the main relay 32 can be reduced. Furthermore, since it is not necessary to adopt an expensive high-permissible current relay as the main relay 32, it is possible to provide an electronic control system capable of suppressing the cost as a whole.

(2) Second Embodiment The electronic control system according to the second embodiment has substantially the same configuration and operation as the electronic control system according to the first embodiment. Description will be made focusing on the points different from the embodiment of FIG.

  FIG. 3 shows a schematic configuration of the electronic control system according to the second embodiment. The second embodiment differs from the first embodiment in the configuration of the inrush current prevention unit 50A. The inrush current preventing unit 50A has substantially the same configuration as the inrush current preventing unit 50 in the first embodiment, except that the shunt resistor 45A and the current detection circuit 45 are newly provided in the first embodiment. It is different from

  One end of the shunt resistor 45A is connected to the anode of the backflow prevention diode 40 and the other end is connected to the drain of the capacitor charging FET 41.

  On the other hand, the current detection circuit 45 is connected in parallel to the shunt resistor 45A, and measures the current flowing through the shunt resistor 45A.

  In the second embodiment, assuming that the CPU 200 fulfills the above-described predetermined condition, for example, the current flowing through the shunt resistor 45A connected downstream of the capacitor charge FET 41 causes the ignition switch 31 to be off (as shown in FIG. Turn to the on state (corresponding to “IG ON” in the figure) from “IG OFF” to become larger as the charging of the capacitor 38 proceeds and then decreases and becomes a timing T that falls below the predetermined threshold current It At the same time, the capacitor charging FET 41 is switched to stop charging the capacitor 38.

  According to the present embodiment, by stopping charging of the capacitor 38 at a more appropriate timing T based on the current actually flowing through the shunt resistor 45A, it is possible to perform determination in a fixed time as in the first embodiment. In addition, since the inrush current can be made more difficult to flow through the main relay 32, the failure of the main relay 32 due to the inrush current can be further reliably prevented.

(3) Third Embodiment The electronic control system according to the third embodiment has substantially the same configuration and operation as the electronic control system according to the first embodiment. Description will be made focusing on the points different from the embodiment of FIG.

  FIG. 5 shows a schematic configuration of an electronic control system according to the third embodiment. Unlike the first embodiment, the monitoring voltage detection unit 51 is provided in the third embodiment. The monitoring voltage detection unit 51 is provided between the CPU 200 and the UB line 44. The monitoring voltage detection unit 51 includes resistors 52 and 53 and an analog-to-digital converter (hereinafter, abbreviated as “ADC”) 42.

  Resistors 52 and 53 are connected in series between the UB line 44 and the ground. That is, one end of the resistor 52 is connected to the UB line 44 and the other end is connected to one end of the resistor 53 (a connection point between the resistor 52 and the resistor 53 is referred to as a "specific connection point"). The other end of the resistor 53 is grounded.

  The ADC 42 has one end connected to the CPU 200 and the other end connected to the specific connection point. The ADC 42 measures the voltage at the UB line 44 according to the voltage dividing ratio by the resistors 52 and 53, performs analog-to-digital conversion, and provides the voltage value to the CPU 200.

  In the third embodiment, it is assumed that the CPU 200 divides the voltage of the UB line 44 by the plurality of resistors 52 and 53 and outputs the voltage from the ADC 42 as shown in FIG. The capacitor charging FET 41 triggered by the timing T exceeding the predetermined threshold voltage Vt after being turned on (corresponding to "IG ON" in the drawing) from the off state (corresponding to "IG OFF" in the drawing) To stop charging the capacitor 38.

  According to the present embodiment, in addition to the effects of the first embodiment, charging of capacitor 38 is stopped at more appropriate timing T based on the voltage on UB line 44, thereby achieving the first embodiment. Since the inrush current can be made more difficult to flow through the main relay 32 more reliably than in the case where it is determined in a fixed time as in the embodiment, the failure of the main relay 32 due to the inrush current can be prevented more reliably.

  On the other hand, in the present embodiment, the CPU 200 divides the voltage of the UB line 44 by the plurality of resistors 52 and 53, for example, and measures the voltage output by the ADC 42 at constant intervals as the predetermined condition described above. When the difference between the voltage and the voltage at this measurement falls below a predetermined threshold voltage Vt, the capacitor charging FET 41 may be switched to stop the charging of the capacitor 38.

  In this way, in addition to the effects of the first embodiment, charging of capacitor 38 is stopped at a more appropriate timing based on the temporal voltage difference in UB line 44, thereby achieving the first embodiment. Since the inrush current can be made more difficult to flow through the main relay 32 more reliably than in the case where it is determined in a fixed time as in the embodiment, the failure of the main relay 32 due to the inrush current can be prevented more reliably.

  31: ignition switch, 32: main relay, 35: battery, 37: power supply IC, 41: FET for capacitor charge, 50, 50A: rush current prevention unit, 51: monitoring voltage detection unit, 100 ...... ECU, 200 ... CPU.

Claims (5)

The current from the battery (35) is input to the input terminal (37C) of the power supply IC (37) through the contact (32A) of the main relay (32) and the UB line (44) continuous with the contact (32A). In the electronic control unit (100),
The electronic control unit (100)
A capacitor (38) having one end connected to the UB line (44) and the other end grounded;
And a rush current prevention unit (50) having one end connected upstream of the capacitor (38) of the UB line (44) and the other end connected to the battery (35),
The inrush current prevention unit (50) is
Before the main relay (32) is turned on, the current from the battery (35) is input from the other end and output from the one end to charge the capacitor (38), and a predetermined condition is satisfied. In this case, the charging of the capacitor (38) is stopped by stopping the input of the current from the battery (35). The inrush current prevention unit (50) is
The electronic control device according to claim 1, wherein charging of the capacitor (38) is stopped when a predetermined time has elapsed as the establishment of the predetermined condition. The inrush current prevention unit (50) is
The capacitor (38) is triggered by the fact that the current flowing through the inrush current prevention unit (50A) decreases as the charging of the capacitor (38) proceeds and falls below a predetermined threshold current (It) as the establishment of the predetermined condition. The electronic control device according to claim 1, wherein charging of the battery is stopped. The inrush current prevention unit (50) is
The capacitor (38) is charged when the voltage obtained by dividing the voltage of the UB line (44) by a plurality of resistors (52, 53) exceeds a predetermined threshold voltage as the predetermined condition is met. The electronic control device according to claim 1, which stops. The inrush current prevention unit (50) is
As the establishment of the predetermined condition, the voltage obtained by dividing the voltage of the UB line (44) by a plurality of resistors (52, 53) is measured at regular intervals, and the difference between the voltage at the previous measurement and the voltage at the current measurement is The electronic control device according to claim 1, wherein charging of the capacitor (38) is stopped in response to the voltage falling below a predetermined threshold voltage.

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