Combustion engine start-stop automatic control unit

Abstract

An internal combustion engine automatic start-stop control unit for executing an internal combustion engine idle reduction control that automatically stops an internal combustion engine when a predetermined automatic stop condition is met and restarts the internal combustion engine by driving a starter (18, 28) when a predetermined restart condition is met, the internal combustion engine automatic start-stop control unit comprising: - an idle reduction control microcomputer (14, 46) which controls a starter relay (17, 31, 32) to control an electric current supplied to the starter (18, 28); and - a monitoring circuit (13, 45) which monitors an operation of the idle reduction control microcomputer (14, 46) via a first signal line (22) and a second signal line (23), wherein - the idle reduction control microcomputer (14) and the monitoring circuit are integrated in a single electronic control unit (15), and characterized in that - the monitoring circuit (13, 45), when it detects an abnormality of the idle reduction control microcomputer (14, 46), switches off the starter relay (17, 31, 32) to prevent activation of the starter (18, 28) and resets the idle reduction control microcomputer (14, 46).

Description

[0001] The present invention relates to an internal combustion engine automatic start-stop control unit that executes idle reduction control in which an internal combustion engine is automatically stopped when a predetermined automatic stop condition is satisfied and restarted when a predetermined restart condition is satisfied.

[0002] In recent years, an idle reduction control system has been adopted in vehicles with an internal combustion engine (ICE) to reduce fuel consumption, emissions, and the like. In idle reduction control, the engine is automatically stopped when an automatic stop condition is met in accordance with a vehicle stop operation by the driver, a deceleration operation by the driver, or the like while the engine is operating. Furthermore, the engine is restarted by automatic cranking by a starter motor when a restart condition is met in accordance with a vehicle start operation by the driver or an acceleration operation by the driver while the engine is in an automatically stopped state, that is, while the engine is stopped by the idle reduction control.

[0003] Such an idle speed reduction control system uses an electronic control unit (ECU) for idle speed reduction control (hereinafter referred to as idle speed reduction ECU) and an electronic control unit for engine control (hereinafter referred to as engine ECU). A power supply relay is provided to turn on and off an electric power supply from a battery to the idle speed reduction ECU. The engine ECU monitors an operation of the idle speed reduction ECU. If the engine ECU determines that the idle speed reduction ECU has an abnormality, the engine ECU turns off the power supply relay to cut off the electric power supply from the battery to the idle speed reduction ECU. When the electric power supply to the idle speed reduction ECU is cut off, an electric current to the starter motor is cut off, and the starter motor is consequently stopped.Such an idle reduction control system is described, for example, in JP 2006-233917 A.

[0004] When the idle speed reduction ECU detects an abnormality, the starter motor is preferably stopped immediately. However, in the idle speed reduction control system described in JP 2006-233917 A, when the idle speed reduction ECU abnormality is detected, the power supply relay is turned off to cut off the power supply to the idle speed reduction ECU. When the power supply to the idle speed reduction ECU is cut off, the power to the starter motor is cut off, and the starter motor is consequently stopped. Accordingly, it takes time to stop the starter motor after the idle speed reduction ECU abnormality is detected. Therefore, it is difficult to stop the starter motor immediately when the idle speed reduction ECU abnormality is detected.

[0005] Furthermore, the power supply to the idle speed control ECU is stopped when the idle speed control ECU abnormality is detected. Therefore, to restart the starter motor, it is necessary to reset the idle speed control ECU to normal by resetting the idle speed control ECU CPU once. To reset the idle speed control ECU CPU, it is necessary to restart the power supply to the idle speed control ECU after the power supply to the idle speed control ECU has been stopped once. Therefore, it takes time to control the starter motor by resetting the idle speed control ECU to normal after the idle speed control ECU abnormality is detected. If it takes time to restart the engine during idle speed control, this may cause discomfort to the driver.

[0006] DE 10 2011 005 521 A1 discloses an internal combustion engine start-stop automatic control unit according to the preamble of claim 1. Advantageous further developments are the subject of the subclaims.

[0007] The present invention has been made in view of the above disadvantages, and it is an object of the present invention to provide an internal combustion engine automatic start-stop control unit which is adapted to immediately stop a starter when an abnormality is detected in an idle reduction control system, and which is adapted to smoothly restart the internal combustion engine by immediately returning the idle reduction control system to a normal state.

[0008] According to one aspect of the present invention, an internal combustion engine automatic start-stop control unit for executing engine idle reduction control includes an idle reduction control microcomputer and a monitoring circuit. The idle reduction control microcomputer controls a starter relay to control an electric current supplied to a starter. The monitoring circuit monitors an abnormality of the idle reduction control microcomputer via a first signal line and a second signal line. The idle reduction control microcomputer and the monitoring circuit are integrated into a single electronic control unit.When the monitoring circuit detects an abnormality of the idle reduction control microcomputer, the monitoring circuit turns off the starter relay to prevent the starter from being driven, and the monitoring circuit resets the idle reduction control microcomputer.

[0009] In the engine automatic start-stop control unit of the above configuration, the monitoring circuit monitors an abnormality of the idle reduction control microcomputer through two systems, such as the first signal line and the second signal line. Consequently, detection reliability of the monitoring circuit is improved. When the engine control microcomputer detects an abnormality of the idle reduction control microcomputer, the starter motor is prevented from being driven by directly turning off the starter relay. Consequently, the starter motor is immediately put into a stopped state. Furthermore, when the monitoring circuit detects the abnormality of the idle reduction control microcomputer, the idle reduction control microcomputer is immediately reset.Since the idle reduction control microcomputer is immediately returned to a normal state, the starter motor is immediately activated and the internal combustion engine is consequently restarted smoothly.

[0010] The objects, features, and advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings. In the drawings: Fig. 1 is a schematic diagram of an internal combustion engine start-stop automatic control unit according to a first embodiment of the present invention; Fig. 2 is a diagram illustrating a relationship between outputs of an engine control microcomputer and an idle reduction control microcomputer and an output of a starter terminal according to the first embodiment; Fig. 3 is a flowchart illustrating a control process executed by the engine control microcomputer according to the first embodiment; Fig. 4 is a schematic diagram of an internal combustion engine start-stop automatic control unit according to a second embodiment of the present invention; Fig. 5 is a schematic diagram of an internal combustion engine start-stop automatic control unit according to a third embodiment of the present invention; Fig. 6 is a schematic diagram of an internal combustion engine start-stop automatic control unit according to a fourth embodiment of the present invention; and Fig. 7 is a schematic diagram of an internal combustion engine start-stop automatic control unit according to a fifth embodiment of the present invention.

[0011] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. (First embodiment)

[0012] A first embodiment is described with reference to the Fig. 1 to 3 described.

[0013] First, a control system of an internal combustion engine start-stop automatic control unit according to the first embodiment will be described with reference to Fig. 1 described.

[0014] The combustion engine start-stop automatic control unit generally has, as in Fig. 1, a power supply IC 12 connected to a battery (power source) 11, an engine control microcomputer (ENG MC) 13 for controlling an internal combustion engine (internal combustion engine), and an idle reduction control microcomputer (IDLE RDC MC) 14. The power supply IC 12, the engine control microcomputer 13, and the idle reduction control microcomputer 14 are integrated into a single electronic control unit (ECU) 15.

[0015] The ECU 15 has a CAN (Controller Area Network) port connected to a plurality of electronic control units 16 to send and receive information to and from the electronic control units 16 via CAN communication. The ECU 15 has a starter (STA) port connected to a starter relay 17. The STA port corresponds to a control port of the starter relay 17. The starter relay 17 connects and disconnects an electrical connection between the battery 11 and a starter motor 19 of a starter motor 18. That is, an electric current from the battery 11 to the starter motor 19 is controlled by the starter relay 17.

[0016] The ECU 15 executes idle reduction control. That is, the ECU 15 automatically stops the engine when an automatic stop condition is met in accordance with a vehicle stop operation by the driver or a deceleration operation by the driver while the engine is running, and restarts the engine by cranking the starter motor 18 by automatically controlling the starter motor 18 when a restart condition is met in accordance with a vehicle start operation by the driver or an acceleration operation by the driver while the engine is automatically stopped (i.e., during an idle stop).

[0017] The engine control microcomputer 13 controls the fuel injection amount, ignition timing, air intake amount (throttle opening degree), and the like of the engine. The idle reduction control microcomputer 14 controls the on / off state of the starter relay 17 to control the starter motor 18.

[0018] The engine control microcomputer 13 provides a starter relay drive permission signal DA to a NAND gate 20. The idle reduction control microcomputer 14 provides a starter relay drive signal DB to the NAND gate 20. The NAND gate 20 provides an output signal DC to a transistor 21. The transistor 21 is a MOSFET, for example. The transistor 21 is connected between the battery 11 and the starter relay 17. When the transistor 21 is turned on and off, the starter relay 17 is turned on and off.

[0019] NAND gate 20, transistor 21, and the like serve as a logic multiplier circuit. When starter relay drive permission signal DA is high (starter relay drive permission level) and starter relay drive signal DB is high (starter relay drive level), NAND gate 20 outputs low-level DC to transistor 21. When transistor 21 is turned on, starter relay 17 is turned on, that is, electric current is supplied from battery 11 to starter motor 19. Thus, starter 18 is driven.

[0020] When the starter relay drive permission signal DA is at a low level (starter relay drive prohibition level) or the starter relay drive signal DB is at a low level (starter relay drive stop level), the NAND gate 20 outputs the DC output signal at a high level to turn off the transistor 21. When the transistor 21 is turned off, the starter relay 17 is turned off, that is, the electric power supply from the battery 11 to the starter motor 19 is interrupted. Consequently, the drive of the starter motor 18 is stopped.

[0021] The engine control microcomputer 13 serves as a monitoring IC that monitors an abnormality of the idle reduction control microcomputer 14. In the present embodiment, the ECU 15 includes a direct line (such as a connecting line) 22 as a first signal line and a communication line 23 as a second signal line. The direct line 22 transmits a watchdog signal from the idle reduction control microcomputer 14 to the engine control microcomputer 13. The communication line 23 transmits monitoring information intended for a monitoring operation between the idle reduction control microcomputer 14 and the engine control microcomputer 13.

[0022] The communication line 23 communicatively connects the idle reduction control microcomputer 14 and the engine control microcomputer 13 in a 1:1 relationship without using a transceiver IC. In this case, a communication load increases due to the communication of monitoring information. However, bus communication, such as CAN, between the electronic control units is not used. Consequently, the influence of external noise is reduced. Furthermore, high-speed communication is enabled without using a transceiver IC, such as a CAN transceiver IC. Consequently, communication can be realized at low cost.

[0023] Furthermore, communication between the idle reduction control microcomputer 14 and the engine control microcomputer 13 can be performed in a 1:1 relationship. Since the communication between the idle reduction control microcomputer 14 and the engine control microcomputer 13 does not receive information from the other electronic control units 16, it does not affect the other electronic control units 16 even if the communication load increases.

[0024] The engine control microcomputer 13 monitors an abnormality of the idle reduction control microcomputer 14 as follows via two systems such as the direct line 22 and the communication line 23. (1) Monitoring the idle reduction control microcomputer 14 using the direct line 22

[0025] The engine control microcomputer 13 includes a watchdog timer (not shown) for monitoring the operation of the idle reduction control microcomputer 14. In a state where the idle reduction control microcomputer 14 is operating normally, the idle reduction control microcomputer 14 outputs a watchdog signal for clearing the watchdog timer at a predetermined interval via the direct line 22.

[0026] If the idle reduction control microcomputer 14 has an abnormality in its operation, the monitoring timer is not cleared. Therefore, when the monitoring timer counts a predetermined time, that is, the predetermined time elapses (timeout), the engine control microcomputer 13 determines that the idle reduction control microcomputer 14 has an abnormality in its operation. Accordingly, the engine control microcomputer 13 sends a reset signal to the idle reduction control microcomputer 14 to reset (restart) the idle reduction control microcomputer 14. (2) Monitoring the idle reduction control microcomputer 14 using the communication line 23

[0027] The engine control microcomputer 13 outputs a calculation request to the idle reduction control microcomputer 14 via the communication line 23. The idle reduction control microcomputer 14 outputs a result (response) of the calculation request to the engine control microcomputer 13 via the communication line 23.

[0028] The engine control microcomputer 13 checks the result of the calculation request from the idle reduction control microcomputer 14 and determines whether the calculation of the idle reduction control microcomputer 14 has an abnormality.

[0029] The method for monitoring the idle reduction control microcomputer 14 via the communication line 23 is not limited to the above example, but can be modified in various ways. For example, an identical signal is input to both the engine control microcomputer 13 and the idle reduction control microcomputer 14, and is converted from an analog signal to a digital signal in both the engine control microcomputer 13 and the idle reduction control microcomputer 14. The engine control microcomputer 13 compares a digital value obtained from the engine control microcomputer 13 and a digital value obtained from the idle reduction control microcomputer 14, and determines whether the analog-to-digital conversion of the idle reduction control microcomputer 14 is abnormal.

[0030] In the monitoring method (1) described above, the engine control microcomputer 13 determines whether the idle reduction control microcomputer 14 has an abnormality in its operation, such as an abnormality in a processing timing, by monitoring the monitor signal. In this case, however, if an abnormality occurs only in a part of a routine of a control program of the idle reduction control microcomputer 14, the monitor signal is output at the predetermined interval and the monitor timer is reset. Furthermore, if the regular process of the idle reduction control microcomputer 14 is in a normal state, even if the calculation process of the idle reduction control microcomputer 14 has an abnormality, the abnormality is not indicated by the monitor signal.

[0031] Consequently, it is technically difficult to determine that the idle reduction control microcomputer 14 is in a normal operating state solely by means of the monitor signal. Therefore, if the above-described monitoring method (2) is applied in addition to the above-described monitoring method (1), the abnormality of the idle reduction control microcomputer 14, such as a calculation abnormality that cannot be detected solely by monitoring the monitor signal, can be detected. In such a case, the detection reliability of the engine control microcomputer 13, that is, the reliability in detecting an abnormality of the idle reduction control microcomputer 14, is improved.

[0032] In the present embodiment, the engine control microcomputer 13 performs a Fig. 3 to prohibit the activation of the starter 18 and reset the idle reduction control microcomputer 14 when an abnormality of the idle reduction control microcomputer 14 is detected. Specifically, when an abnormality of the idle reduction control microcomputer 14 is detected, the starter relay activation permission signal DA is set to a low level (starter relay activation prohibition level) to turn off the transistor 21. This turns off the starter relay 17, that is, interrupts the electric current to the starter motor 19, thus preventing the activation of the starter 18. Further, the engine control microcomputer 13 outputs the reset signal to the idle reduction control microcomputer 14 to reset the idle reduction control microcomputer 14.

[0033] Accordingly, when an abnormality of the idle reduction control microcomputer 14 is detected, the starter 18 is immediately put into a stopped state and the idle reduction control microcomputer 14 is immediately reset.

[0034] Even if the idle reduction control microcomputer 14 is in a normal state when the engine is running, that is, when the engine is not stopped, the engine control microcomputer 13 determines that it is not necessary to drive the starter motor 18. Consequently, the engine control microcomputer 13 changes the starter relay drive permission signal DA to the low level to turn off the starter relay 17 and prohibit the drive of the starter motor 18.

[0035] The engine control microcomputer 13 has a function for monitoring the STA terminal. In this case, the engine control microcomputer 13 can check the actual activation state of the starter relay 17 based on the state of the STA terminal. If the starter relay 17 is not activated due to a circuit failure or the like, the engine control microcomputer 13 can immediately detect the abnormality of the starter relay 17.

[0036] The idle reduction control microcomputer 14 monitors the engine control microcomputer 13 in the following manner to determine an abnormality of the engine control microcomputer 13.

[0037] The idle reduction control microcomputer 14 includes a watchdog timer (not shown) for monitoring the operation of the engine control microcomputer 13. When the engine control microcomputer 13 is in a normal state, the engine control microcomputer 13 outputs a watchdog signal for resetting the watchdog timer of the idle reduction control microcomputer 14 to the idle reduction control microcomputer 14 at a predetermined interval via a direct line (such as a connecting line).

[0038] When the engine control microcomputer 13 has an abnormal operation, the monitoring timer of the idle reduction control microcomputer 14 is not cleared. Therefore, when the monitoring timer counts a predetermined time, that is, the predetermined time elapses (timeout), the idle reduction control microcomputer 14 determines that the engine control microcomputer 13 has an abnormal operation. In this case, the idle reduction control microcomputer 14 sends a reset signal to the engine control microcomputer 13 to reset (restart) the engine control microcomputer 13.

[0039] The power supply IC 12 monitors the engine control microcomputer 13 as follows to determine an abnormality of the engine control microcomputer 13.

[0040] The power supply IC 12 includes a watchdog timer (not shown) for monitoring the operation of the engine control microcomputer 13. When the engine control microcomputer 13 is in a normal state, the engine control microcomputer 13 outputs a watchdog signal for clearing the watchdog timer of the power supply IC 12 to the power supply IC 12 at a predetermined interval via a direct line 25.

[0041] When the engine control microcomputer 13 is in an abnormal state, the monitoring timer of the power supply IC 12 is not cleared. Therefore, when the monitoring timer of the power supply IC 12 counts a predetermined time, that is, the predetermined time elapses (timeout), the power supply IC 12 determines that the engine control microcomputer 13 is in an abnormal state. Consequently, the power supply IC 12 outputs a reset signal to the engine control microcomputer 13 to reset (restart) the engine control microcomputer 13.

[0042] The idle reduction control microcomputer 14 resets the engine control microcomputer 13 as described above when it detects that the engine control microcomputer 13 has an abnormality. Furthermore, the idle reduction control microcomputer 14 is also reset until the engine control microcomputer 13 is started normally after the engine control microcomputer 13 is reset.

[0043] When the engine control microcomputer 13 is reset, the output of the engine control microcomputer 13 is in a high-impedance (HiZ) state. Consequently, the starter relay drive permission signal DA is at a low level (starter relay drive inhibit level) via a pull-down resistor 26. When the idle reduction control microcomputer 14 is reset, the output of the idle reduction control microcomputer 14 is in a high-impedance (HiZ) state. Consequently, the starter relay drive signal DB is at a low level (starter relay drive stop level) via a pull-down resistor 27.

[0044] When the output of the engine control microcomputer 13 is in the high resistance state (HiZ), that is, when the engine control microcomputer 13 is reset, the starter relay drive permission signal DA, as shown in Fig. 2, the low level (starter relay drive inhibit level). In this case, the starter relay 17 is turned off to inhibit the drive of the starter 18, regardless of the output of the idle reduction control microcomputer 14. That is, the starter relay 17 is turned off to inhibit the drive of the starter 18 when the starter relay drive signal DB is at the high level and when the starter relay drive signal DB is at the low level.

[0045] In contrast, when the output of the idle reduction control microcomputer 14 is in the high-impedance state (HiZ), that is, when the idle reduction control microcomputer 14 is reset, the starter relay drive signal DB is at the low level (starter relay drive stop level). In this case, the starter relay 17 is turned off to prevent the starter 18 from being driven, regardless of the output of the engine control microcomputer 13. That is, the starter relay 17 is turned off to prevent the starter 18 from being driven when the starter relay drive permission signal DA is at the high level and when the starter relay drive permission signal DA is at the low level.

[0046] If the engine control microcomputer 13 is not operating, the vehicle cannot be driven. Therefore, the ECU 15 has a configuration in which the engine control microcomputer 13 serves as a main microcomputer. That is, if the engine control microcomputer 13 is not operating, the operation of the idle reduction control microcomputer 14 is inhibited, and the control of the starter motor 18 is inhibited.

[0047] The control routine executed by the engine control microcomputer 13 will be described below with reference to Fig. 3 described.

[0048] The Fig. The control routine shown in Figure 3 is executed at a predetermined interval while the power supply to the engine control microcomputer 13 is turned on. When the control routine is started, the engine control microcomputer 13 executes (starts) monitoring of the idle reduction control microcomputer 14 using the direct line 22 and monitoring of the idle reduction control microcomputer 14 using the communication line 23 in step S101.

[0049] In step S102, the engine control microcomputer 13 determines whether an abnormality of the idle reduction control microcomputer 14 has been detected in the monitoring of the idle reduction control microcomputer 14 using the direct line 22 and / or the monitoring of the idle reduction control microcomputer 14 using the communication line 23.

[0050] If it is determined in step S102 that the abnormality has been detected in the idle reduction control microcomputer 14, the process proceeds to step S103. In step S103, the starter relay activation permission signal DA is set to the low level (starter relay activation prohibition level). Consequently, the starter relay 17 is turned off, that is, the electric current to the starter motor 19 is interrupted, thus preventing the activation of the starter motor 18.

[0051] In step S104, the engine control microcomputer 13 outputs the reset signal to the idle reduction control microcomputer 14 to reset the idle reduction control microcomputer 14.

[0052] In step S105, the engine control microcomputer 13 waits until a predetermined time (such as 50 milliseconds) required to restart the idle reduction control microcomputer 14 elapses. Then, the engine control microcomputer 13 terminates the control routine.

[0053] If it is determined in step S102 that the abnormality has not been detected in the idle reduction control microcomputer 14, that is, it is determined that the idle reduction control microcomputer 14 is in a normal state, the process proceeds to step S106. In step S106, the engine control microcomputer 13 determines whether the engine is in a stopped state.

[0054] If it is determined in step S106 that the engine is stopped, the process proceeds to step S107. In step S107, the starter relay drive permission signal DA is set to the high level (starter relay drive permission level). Thus, the drive of the starter 18 is permitted. In this case, when the idle reduction control microcomputer 14 sets the starter relay drive signal DB to the high level (starter relay drive level), the starter relay 17 is turned on. Consequently, electric current is supplied to the starter motor 19, and the starter 18 is driven.

[0055] If it is determined in step S106 that the engine is not stopped, that is, the engine is operating, the process proceeds to step S108. In step S108, the engine control microcomputer 13 determines that it is not necessary to drive the starter motor 18, and the engine control microcomputer 13 changes the starter relay drive permission signal DA to the low level (starter relay drive prohibition level). Consequently, the starter relay 17 is turned off. This cuts off the electric current to the starter motor 19 and prevents the drive of the starter motor 18. Accordingly, the starter motor 18 is less likely to be erroneously driven.

[0056] In the first embodiment described above, the engine control microcomputer 13 monitors an abnormality of the idle reduction control microcomputer 14 via two lines, that is, the direct line 22 and the communication line 23. Consequently, a detection reliability of the engine control microcomputer 13 for detecting an abnormality of the idle reduction control microcomputer 14 is improved.

[0057] When an abnormality of the idle reduction control microcomputer 14 is detected, the starter motor 18 is prevented from being driven by directly turning off the starter relay 17 instead of turning off the power supply relay. Consequently, the starter motor 18 can be immediately stopped. Furthermore, when the abnormality of the idle reduction control microcomputer 14 is detected, the idle reduction control microcomputer 14 is immediately reset instead of stopping the power supply to the idle reduction control microcomputer 14. Consequently, the idle reduction control microcomputer 14 is immediately returned to a normal operating state, and the starter motor 18 is driven. Accordingly, the engine is immediately restarted.

[0058] The engine control microcomputer 13, which knows a driving state of the vehicle, serves as the monitoring IC. Consequently, the control of the starter 18 can be immediately inhibited in accordance with the driving state, such as a starter start operation inhibition during vehicle travel and a malfunction of an engine device.

[0059] The idle reduction control microcomputer 14 monitors an abnormality of the engine control microcomputer 13. That is, the idle reduction control microcomputer 14 can detect an abnormality of the engine control microcomputer 13, such as an abnormality in an electronic throttle control. Consequently, it is less likely that the activation of the starter motor 18 will be erroneously inhibited when the engine control is in an abnormal state.

[0060] In the first embodiment, NAND gate 20 and transistor 21 serve as the logic multiplier circuit. When an abnormality of the idle reduction control microcomputer 14 is detected, the starter relay drive permission signal DA is set to the low level (starter relay drive prohibition level). This turns off the starter relay 17 to cut off the electric current to the starter motor 19, thus preventing the starter 18 from being driven. Consequently, with a low-cost structure, the starter relay 17 can be turned off to prevent the starter 18 from being driven. (Second embodiment)

[0061] A second embodiment of the present invention will be described below with reference to the Fig. 4 described.

[0062] In the first two embodiments, substantially identical components are provided with the same reference numerals, and the following mainly focuses on the features different from the first embodiment.

[0063] In the second embodiment, a starter 28, as shown in Fig. 4, a solenoid 29 for pushing out a gear (not shown) and a starter motor 30 for rotating the gear. Furthermore, a first starter relay 31 and a second starter relay 32 are provided to operate independently of each other. The first starter relay 31 switches the electric current from the battery 11 to the solenoid 29 on and off. The second starter relay 32 switches the electric current from the battery 11 to the starter motor 30 on and off.

[0064] A first transistor 33 is connected between the battery 11 and the first starter relay 31. A second transistor 34 is connected between the battery 11 and the second starter relay 32. The first transistor 33 is turned on and off in accordance with the starter relay drive permission signal DA from the engine control microcomputer 13. The second transistor 34 is turned on and off in accordance with the starter relay drive signal DB from the idle reduction control microcomputer 14. The first starter relay 31 may also be referred to as a magnetic relay or solenoid relay, and the second starter relay 32 may also be referred to as a motor relay.

[0065] In this case, when the starter relay drive permission signal DA is at a low level (first starter relay drive permission level), the first transistor 33 is turned on. This turns on the first starter relay 31 to supply electric current to the solenoid coil 29. When the starter relay drive signal DB is at a low level (second starter relay drive level), the second transistor 34 is turned on. This turns on the second starter relay 32 to supply electric current to the starter motor 30.

[0066] In the second embodiment, the first transistor 33 and the second transistor 34 serve as the logic multiplier circuit. When the starter relay drive permission signal DA and the starter relay drive signal DB are both low, the first starter relay 31 and the second starter relay 32 are both turned on, so that electric current is supplied to both the solenoid coil 29 and the starter motor 30. When the first starter relay 31 and the second starter relay 32 are both turned on, the starter motor 28 is normally driven.

[0067] When the engine control microcomputer 13 detects an abnormality of the idle reduction control microcomputer 14, the engine control microcomputer 13 changes the starter relay drive permission signal DA to a high level (first starter relay drive prohibition level) to turn off the first transistor 33. When the first starter relay 31 is turned off, the electric current to the solenoid coil 29 is interrupted. Therefore, the drive of the starter 28 is prohibited. Furthermore, the engine control microcomputer 13 outputs the reset signal to the idle reduction control microcomputer 14 to reset the idle reduction control microcomputer 14.

[0068] When the engine control microcomputer 13 is reset, the output of the engine control microcomputer 13 is in the high-impedance (HiZ) state. Consequently, the starter relay drive permission signal DA is at a high level (starter relay drive inhibit level) via a pull-up resistor 35. When the idle reduction control microcomputer 14 is reset, the output of the idle reduction control microcomputer 14 is in the high-impedance (HiZ) state. Consequently, the starter relay drive signal DB is at a high level (second starter relay drive stop level) via a pull-up resistor 36.

[0069] In the second embodiment described above, the starter 28 includes the solenoid 29, and the starter motor 30 is controlled by controlling the first starter relay 31 and the second starter relay 32. When an abnormality of the idle reduction control microcomputer 14 is detected, the starter 28 is prevented from being driven by turning off the first starter relay 31, that is, by cutting off the electric current to the solenoid 29. Consequently, advantageous effects similar to the first embodiment can be achieved.

[0070] In the second embodiment, when an abnormality of the idle reduction control microcomputer 14 is detected, the activation of the starter 28 is prohibited by turning off the first starter relay 31. According to another example, when the abnormality of the idle reduction control microcomputer 14 is detected, the activation of the starter 28 can be prohibited by turning off the second starter relay 32. (Third embodiment)

[0071] A third embodiment will be described below with reference to the Fig. 5 described.

[0072] In the first three embodiments, substantially identical components are provided with the same reference numerals, and the following mainly focuses on the features different from the first two embodiments.

[0073] A transistor 37 and a first transistor 38 are, as in Fig. 5, is connected in series between the battery 11 and the first starter relay 31. Further, the transistor 37 and a second transistor 39 are connected in series between the battery 11 and the second starter relay 32. The transistor 37 is turned on and off in accordance with the starter relay drive permission signal DA from the engine control microcomputer 13. The first transistor 38 is turned on and off in accordance with a first starter relay drive signal DB1 output from the idle reduction control microcomputer 14. Further, the second transistor 39 is turned on and off in accordance with a second starter relay drive signal DB2 output from the idle reduction control microcomputer 14.

[0074] When the starter relay drive permission signal DA is at a low level (drive permission level for the first and second starter relays), the transistor 37 is turned on. When the first starter relay drive signal DB1 is at a low level (drive level for the first starter relay), the first transistor 38 is turned on. When the transistor 37 and the first transistor 38 are both turned on, the first starter relay 31 is turned on to supply electric current to the solenoid coil 29.

[0075] When the starter relay drive permission signal DA is at a low level (drive permission level for the first and second starter relays), the transistor 37 is turned on. When the second starter relay drive signal DB2 is at a low level (drive level for the second starter relay), the second transistor 39 is turned on. When the transistor 37 and the second transistor 39 are both turned on, the second starter relay 32 is turned on to supply electric current to the starter motor 30.

[0076] In the third embodiment, transistor 37, first transistor 38, and second transistor 39 serve as the logic multiplier circuit. When the starter relay drive permission signal DA is at a low level and the first and second starter relay drive signals DB1, DB2 are both at a low level, the first starter relay 31 and the second starter relay 32 are both turned on, so that electric current is supplied to both the solenoid coil 29 and the starter motor 30. Therefore, the starter 28 is normally driven.

[0077] When the engine control microcomputer 13 detects an abnormality of the idle reduction control microcomputer 14, the engine control microcomputer 13 changes the starter relay drive permission signal DA to a high level (drive prohibition level for the first and second starter relays) to turn off the transistor 37. This turns off the first starter relay 31 and the second starter relay 32, that is, the electric current to the solenoid coil 29 and the electric current to the starter motor 30 are both cut off, thus preventing the drive of the starter 28. Furthermore, the engine control microcomputer 13 outputs the reset signal to the idle reduction control microcomputer 14 to reset the idle reduction control microcomputer 14.

[0078] When the engine control microcomputer 13 is reset, the output of the engine control microcomputer 13 is in the high-impedance (HiZ) state. Consequently, the starter relay drive permission signal DA is at a high level (drive prohibition level for the first and second starter relays) via a pull-up resistor 40. When the idle reduction control microcomputer 14 is reset, the output of the idle reduction control microcomputer 14 is in the high-impedance (HiZ) state. Consequently, the first starter relay drive signal DB1 and the second starter relay drive signal DB2 are at a high level (drive stop level for the first and second starter relays) via pull-up resistors 41 and 42.

[0079] In the third embodiment, the starter 28 including the solenoid 29 and the starter motor 30 is controlled by controlling the first starter relay 31 and the second starter relay 32. When an abnormality of the idle reduction control microcomputer 14 is detected, the first starter relay 31 and the second starter relay 32 are both turned off, so that the electric current to the solenoid 29 and the electric current to the starter motor 30 are both cut off. Thus, the driving of the starter 28 is prevented. Accordingly, advantageous effects similar to the above-described embodiments are achieved.

[0080] In the third embodiment, the transistor 37 and the first transistor 38 are connected in series between the battery 11 and the first starter relay 31. Therefore, even if one of the transistor 37 and the first transistor 38 has an ON-state failure, the first starter relay 31 can be turned off by blocking the other.

[0081] Furthermore, the transistor 37 and the second transistor 39 are connected in series between the battery 11 and the second starter relay 32. Consequently, even if one of the transistor 37 and the second transistor 39 has an ON-state fault, the second starter relay 32 can be turned off by blocking the other.

[0082] In a vehicle without an idle speed reduction function, a configuration is usually provided that prohibits starter motor activation when a transmission shift position (gear position) is different from a neutral (N) position and a park (P) position. In contrast, in the vehicle with an idle speed reduction function, it is necessary to control the starter motor to restart the engine from the idle speed reduction state even when the transmission shift position is different from the N position and the P position. Consequently, it is necessary to design the configuration so that the starter motor can be controlled even when the transmission shift position is different from the N position and the P position. Therefore, a starter motor control circuit requires further safety design.In such a case, it is effective to connect two transistors in series as proposed in the third embodiment.

[0083] In the third embodiment, transistor 37 is controlled by the starter relay drive permission signal DA provided by the engine control microcomputer 13. Transistor 37 is shared between the two starter relays 31 and 32. Consequently, costs can be reduced. (Fourth embodiment)

[0084] A fourth embodiment will be described below with reference to the Fig. 6 described.

[0085] In the fourth embodiment, components substantially the same as those of the second embodiment are denoted by the same reference numerals, and the following mainly describes the features different from the second embodiment.

[0086] The engine control microcomputer 13 controls the starter relay 31 to bring the gear into engagement with a gear ring of the engine when an engine speed is less than or equal to a predetermined speed (such as 100 rpm).

[0087] The engine control microcomputer 13 includes a signal receiving section (signal determining section, SG RCV) 130 that receives a signal from an engine speed sensor (ENG SP SEN) 100 regarding an engine speed, such as a rotation angle of a crankshaft or a camshaft, and detects the engine speed, such as the rotation angle of the crankshaft or the camshaft. The other structures are the same as in the second embodiment.

[0088] When the engine stops and the engine speed detected by the signal output from the engine speed sensor 100 is equal to or lower than the predetermined speed (such as 100 rpm), the engine control microcomputer 13 changes the starter relay drive permission signal DA to the low level to turn on the first transistor 33. This turns on the first starter relay 31, so that electric current is supplied to the solenoid coil 29 and the gear is engaged with the engine ring gear. In this case, the first starter relay 31 functions as a solenoid relay for pushing out the gear.

[0089] When the engine stops, the engine speed is likely to drop rapidly or become unstable. Consequently, the gear is preferably pushed out such that the gear engages the ring gear immediately before the engine stops.

[0090] In the present embodiment, when the engine speed becomes less than or equal to the predetermined speed, the first starter relay 31 is turned on to engage the gear with the ring gear. That is, the gear is engaged with the ring gear immediately before the engine stops, that is, before the engine is restarted. Consequently, even if the idle reduction control microcomputer 14 enters an abnormal state immediately after the engine is stopped, the gear is maintained in the engaged state. Consequently, the engine can be restarted smoothly after the idle reduction control microcomputer 14 is recovered from the abnormal state.

[0091] In order to reduce emissions, the engine control microcomputer 13 needs to appropriately control the fuel injection timing, the ignition timing, and the like by accurately detecting the rotation angle of the crankshaft or the camshaft. Therefore, the engine control microcomputer 13 usually includes the signal receiving section (signal determining section) 130 for accurately detecting the rotation angle of the crankshaft or the camshaft. The timing to bring the gear into engagement with the ring gear in the idle reduction control can be determined based on the information provided by the signal receiving section (SG RCV) 130, which is used to detect the rotation angle of the crankshaft or the camshaft. That is, it is not necessary to newly add a section or element for detecting the rotation angle of the crankshaft or the camshaft for determining the locking or unlocking point.To record the moment of engagement of the gear.

[0092] In the fourth embodiment, the control operation of the engine control microcomputer 13 for determining the locking or engagement timing of the gear is carried out with respect to the configuration similar to that shown in the Fig. 4. The same control operation can be used for the configuration of the Fig. 5 shown third embodiment can be applied.

[0093] In the first to fourth embodiments described above, the engine control microcomputer 13 serves as the monitoring IC that monitors an abnormality of the idle reduction control microcomputer 14. However, the monitoring IC for monitoring an abnormality of the idle reduction control microcomputer 14 may be provided separately from the engine control microcomputer 13. (Fifth embodiment)

[0094] A fifth embodiment will be described below with reference to the Fig. 7 described.

[0095] In the fifth embodiment, components substantially the same as those of the third embodiment are denoted by the same reference numerals, and the following mainly describes the features different from the third embodiment.

[0096] In the fifth embodiment, the ECU 15, as shown in Fig. 7, an engine and idle reduction control microcomputer (ENG & IDLE RDC MC) 46 and a monitoring IC (MNT IC) 45. The idle reduction control microcomputer 46 has a function of the engine control microcomputer and a function of the idle reduction control microcomputer. The monitoring IC 45 has a function of monitoring an abnormality of the engine and the idle reduction control microcomputer 46.

[0097] In the system of the fifth embodiment, the monitoring IC 45 is used instead of the engine control microcomputer 13 of the third embodiment ( Fig. 5) and the idle reduction control microcomputer 46 is provided instead of the idle reduction control microcomputer 14 of the third embodiment ( Fig.5). In this case, the idle reduction control microcomputer 46 includes the signal receiving section (signal determination section) 130. The signal receiving section (signal determination section) 130 receives the signal from the engine speed sensor 100 and detects the engine speed, the crankshaft angle, or the camshaft angle based on the signal from the engine speed sensor 100. The other structures of the present embodiment are the same as the third embodiment.

[0098] When the engine is stopped and the engine speed detected based on the signal from the engine speed sensor 100 is less than or equal to the predetermined speed (such as 100 rpm), the idle reduction control microcomputer 46 changes the first starter relay drive signal DB1 to the low level to turn on the first transistor 38, and the monitoring IC 45 changes the starter relay drive permission signal DA to the low level to turn on the transistor 37. This turns on the first starter relay 31. Consequently, electric current is supplied to the solenoid coil 29, and the gear is pushed out to engage the gear of the engine.

[0099] Also in the fifth embodiment, advantageous effects similar to those of the third embodiment can be produced.

[0100] An internal combustion engine start-stop automatic control unit is described above.

[0101] An internal combustion engine automatic start-stop control unit includes an idle reduction control microcomputer 14 and a monitoring circuit 13, 45. The idle reduction control microcomputer 14 controls a starter relay 17, 31, 32 to control an electric current supplied to a starter 18, 28. The monitoring circuit 13, 45 monitors an abnormality of the idle reduction control microcomputer 14 via a first signal line 22 and a second signal line 23. The idle reduction control microcomputer 14 and the monitoring circuit 13, 45 are integrated into a single electronic control unit.When the monitoring circuit 13, 45 detects an abnormality of the idle reduction control microcomputer 14, the monitoring circuit 13, 45 turns off the starter relay 17, 31, 32 to prevent the starter 18, 28 from being driven, and the monitoring circuit resets the idle reduction control microcomputer 14.

Claims

[1] An internal combustion engine start-stop automatic control unit for executing an internal combustion engine idle reduction control that automatically stops an internal combustion engine when a predetermined automatic stop condition is met and restarts the internal combustion engine by driving a starter (18, 28) when a predetermined restart condition is met, the internal combustion engine start-stop automatic control unit comprising: - an idle reduction control microcomputer (14, 46) which controls a starter relay (17, 31, 32) to control an electric current supplied to the starter (18, 28); and - a monitoring circuit (13, 45) which monitors an operation of the idle reduction control microcomputer (14, 46) via a first signal line (22) and a second signal line (23), wherein - the idle reduction control microcomputer (14) and the monitoring circuit are integrated in a single electronic control unit (15), and characterized by , that - the monitoring circuit (13, 45), when it detects an abnormality of the idle reduction control microcomputer (14, 46), switches off the starter relay (17, 31, 32) to prevent activation of the starter (18, 28) and resets the idle reduction control microcomputer (14, 46). [2] Internal combustion engine start-stop automatic control unit according to claim 1, characterized by , that - the monitoring circuit is provided by an internal combustion engine control microcomputer (13) which controls the internal combustion engine; and - the idle reduction control microcomputer (14) monitors an operation of the internal combustion engine control microcomputer (13). [3] Internal combustion engine start-stop automatic control unit according to claim 2, characterized by , that - the starter relay (17, 31, 32) comprises a first starter relay (31) and a second starter relay (32) which are operated independently of each other to control the starter (28); - the first starter relay (31) is controlled by the internal combustion engine control microcomputer (13); and - the second starter relay (32) is controlled by the idle reduction control microcomputer (14). [4] Internal combustion engine start-stop automatic control unit according to one of claims 1 to 3, characterized by , that - the starter relay (17, 31, 32) comprises a first starter relay (31) and a second starter relay (32); - the first starter relay (31) serves as a magnetic relay to supply an electric current to a magnetic coil (29) of the starter (28) for pushing out a gear of the starter (28); - the second starter relay (32) serves as a motor relay to supply an electric current to a motor (30) of the starter (28) to rotate the gear; - an engine control microcomputer (13, 46) has a signal receiving section (130) that receives a signal from an engine speed sensor (100) and detects an engine speed based on the signal; and - when the engine speed is less than or equal to a predetermined speed, the first starter relay (31) brings the gear into engagement with a gear ring of the engine. [5] Internal combustion engine start-stop automatic control unit according to one of claims 2 to 4, characterized by , that - the idle reduction control microcomputer (14) resets the engine control microcomputer (13) when an abnormality of the engine control microcomputer (13) is detected; - the idle reduction control microcomputer (14) is reset when the engine control microcomputer (13) is reset until the engine control microcomputer (13) is started normally; - the engine control microcomputer (13) provides a starter relay activation permission signal (DA) having a starter relay activation prohibition level when the engine control microcomputer (13) is reset; and - the idle reduction control microcomputer (14) provides a starter relay drive signal (DB, DB1, DB2) having a starter relay drive stop level when the idle reduction control microcomputer (14) is reset. [6] Internal combustion engine start-stop automatic control unit according to one of claims 2, 3 or 5, characterized bythat the engine control microcomputer (13) provides a starter relay drive permission signal (DA) having a starter relay drive prohibition level when the engine is not in a stopped state. [7] Internal combustion engine start-stop automatic control unit according to one of claims 1 to 6, characterized by , that - the first signal line (22) is a direct line which transmits a monitoring signal from the idle reduction control microcomputer (14, 46) to the monitoring circuit (13, 45); and - the second signal line (23) is a communication line which allows transmission of monitoring information between the idle reduction control microcomputer (14) and the monitoring circuit (13, 45). [8] Internal combustion engine start-stop automatic control unit according to claim 7, characterized bythat the communication line establishes a connection between the idle reduction control microcomputer (14) and the monitoring circuit (13, 45) in a 1:1 relationship without using a transceiver circuit. [9] Internal combustion engine start-stop automatic control unit according to one of claims 1 to 8, characterized by that it also has: - a logic multiplier circuit (20, 21, 33, 34, 37, 38, 39) which switches on the starter relay (17, 31, 32) when a starter relay drive permission signal (DA) from the monitoring circuit (13, 45) has a starter relay drive permission level and when a starter relay drive signal (DB, DB1, DB2) from the idle reduction control microcomputer (14, 46) has a starter relay drive level, wherein - when the monitoring circuit (13, 45) detects an abnormality of the idle reduction control microcomputer (14, 46), the monitoring circuit (13, 45) provides the starter relay drive permission signal (DA) having a starter relay drive prohibition level to turn off the starter relay (17, 31, 32). [10] Internal combustion engine start-stop automatic control unit according to claim 9, characterized by , that - the logic multiplier circuit comprises a plurality of transistors (37, 38, 39) connected in series between a power source (11) and the starter relay (31, 32); - one (37) of the plurality of transistors (37, 38, 39) is controlled by the starter relay control permission signal (DA) provided by the monitoring circuit (13, 45); and - another one (38, 39) of the plurality of transistors (37, 38, 39) is controlled by the starter relay control signal (DB1, DB2) provided by the idle reduction control microcomputer (14). [11] Internal combustion engine start-stop automatic control unit according to claim 10, characterized by , that - the starter relay comprises a plurality of starter relays (31, 32) which are operated independently of one another to control the starter (28); - one of the plurality of transistors (37, 38, 39) controlled by the starter relay control permission signal (DA) is provided in common for the plurality of starter relays (31, 32); and - the other of the plurality of transistors (37, 38, 39) which is driven by the starter relay drive signal (DB1, DB2) provided by the idle reduction control microcomputer (14) is provided for each of the plurality of starter relays (31, 32). [12] Internal combustion engine start-stop automatic control unit according to one of claims 1 to 11, characterized by that the monitoring circuit (13, 45) monitors a control connection (STA, STA1, STA2) of the starter relay (17, 31, 32).

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