JP2020180566A - Control device of internal combustion engine - Google Patents

Abstract

To provide a control device of an internal combustion engine which can prevent a situation that the internal combustion engine becomes automatically restartable after the internal combustion engine is automatically stopped.SOLUTION: A control device of an engine comprises: a starter generator connected to a crankshaft; a MOSFET arranged at a drive circuit for connecting a second battery and the starter generator; a shunt resistor; a starter control part for controlling a drive current of the starter generator by operating the MOSFET on the basis of voltages of both ends of the shunt resistor; and an automatic stop/start control part for automatically stopping the engine when a prescribed condition is established, and after that, automatically restarting the engine by using the starter control part. When an element temperature value TM which becomes high according to a rise of temperatures of the MOSFET and the shut resistor is equal to a threshold th_m2 or higher which is lower than a MOSFET operation upper limit value th_m1 which is defined on the basis of an operation limit temperature of the MOSFET, the automatic stop/start control part prohibits an automatic stop.SELECTED DRAWING: Figure 5

Description

The present invention relates to a control device for an internal combustion engine. More specifically, the present invention relates to an internal combustion engine control device that automatically stops or automatically restarts an internal combustion engine.

Many vehicles equipped with an internal combustion engine have a so-called idle stop function in order to suppress fuel consumption in the internal combustion engine. The idle stop function automatically stops the internal combustion engine by stopping fuel injection when a predetermined condition is met, and then restarts fuel injection while cranking with a starter when the predetermined condition is met. This is a function that automatically restarts the internal combustion engine.

When the internal combustion engine is automatically restarted in this way, it is necessary to drive the starter by the starter control device. Further, if the temperature of the starter or the starter control device rises excessively due to heat generation, the starter may break down or the starter control device may not operate normally. Therefore, in many vehicles equipped with an idle stop function, when the temperature of the starter or starter control device exceeds the predetermined fail-safe temperature, the vehicle is automatically restarted by switching to the auxiliary starter prepared in advance. (For example, see Patent Document 1), fail-safe actions such as prohibiting automatic stop are performed.

Japanese Unexamined Patent Publication No. 2003-74447

By the way, the starter control device controls the drive current with respect to the starter by turning on / off the switching element based on the voltage of the shunt resistor for current detection provided in the vicinity of the switching element in the drive circuit of the starter. Therefore, the higher the temperature of the shunt resistor, the more the starter drive current varies. Further, if the drive current becomes excessively small, the starter cannot generate the torque required for cranking the internal combustion engine, and the internal combustion engine may not be automatically restarted. The event has not been fully considered.

An object of the present invention is to provide a control device for an internal combustion engine that can prevent a situation in which an internal combustion engine cannot be automatically restarted after being automatically stopped.

(1) The control device (for example, the control device 2 described later) of the internal combustion engine (for example, the engine 1 described later) according to the present invention is a starter (for example, a starter generator 4 described later) connected to the crank shaft of the internal combustion engine. A switching element (for example, MOSFET 401 described later) and a resistance element (for example, for example) provided in the drive circuit (for example, the drive circuit 40 described later) connecting the battery (for example, the second battery B2 described later) and the starter. A shunt resistor 403) described later, a starter control device (for example, a starter control unit 70c described later) that controls the drive current of the starter by operating the switching element based on the voltage across the resistance element, and the above. Element temperature parameter acquisition means (for example, diode temperature sensor 402 and temperature detection circuit 713 described later) for acquiring element temperature parameter values, which are values that increase as the temperature of the switching element and the resistance element rises, and predetermined conditions. The engine is provided with an automatic stop start control device (for example, an automatic stop start control unit 70b described later) that automatically stops the internal combustion engine and then automatically restarts the internal combustion engine using the starter control device. When the element temperature parameter value (TM) is equal to or greater than the first threshold value (th_m2) smaller than the operating limit value (th_m1) determined based on the operating limit temperature of the switching element, the automatic stop start control device is used. It is characterized in that the automatic stop is prohibited.

(2) In this case, the control device acquires a battery temperature parameter value which is a value that increases as the temperature of the battery rises (for example, the battery ECU 72 and the second sensor unit 79 described later). The automatic stop start control device further comprises the case where the battery temperature parameter value (TB2) is smaller than the second threshold value (th_b2) and the element temperature parameter value (TM) is equal to or higher than the first threshold value (th_m2). When the automatic stop is prohibited and the battery temperature parameter value (TB2) is equal to or higher than the second threshold value (th_b2) and the element temperature parameter value (TM) is smaller than the operating limit value (th_m1). It is preferable to allow the automatic stop.

(3) In this case, the control device includes a power line (for example, a third power line 36 described later) that connects the battery and an electric load different from the starter (for example, a second electric load 62 described later). The automatic stop start control device further includes a switch (for example, a third switch SW3 described later) provided on the power line, and the switch is on and the element temperature parameter value (TM) is the first. When it is equal to or higher than the threshold value (th_m2), the automatic stop is prohibited, and when the switch is off and the element temperature parameter value (TM) is smaller than the operating limit value (th_m1), the automatic stop is permitted. It is preferable to do so.

(4) In this case, the control device includes a power line (for example, a third power line 36 described later) that connects the battery and an electric load different from the starter (for example, a second electric load 62 described later). The automatic stop start control device further includes a switch provided on the power line (for example, a third switch SW3 described later), and the battery temperature parameter value (TB2) is smaller than the second threshold value (th_b2). When the switch is on and the element temperature parameter value (TM) is equal to or higher than the first threshold value (th_m2), the automatic stop is prohibited, and the battery temperature parameter value (TB2) is the second threshold value (TB2). When th_b2) or more and the element temperature parameter value (TM) is smaller than the operating limit value (th_m1), or when the switch is off and the element temperature parameter value (TM) is higher than the operating limit value (th_m1). If it is small, it is preferable to allow the automatic stop.

(5) In this case, the automatic stop start control device prohibits the automatic stop when the battery temperature parameter value (TB2) is smaller than the third threshold value (th_b3) smaller than the second threshold value (th_b2). When the battery temperature parameter value (TB2) is equal to or higher than the third threshold value (th_b3) and the element temperature parameter value (TM) is smaller than the first threshold value (th_m2), the automatic stop may be permitted. preferable.

(1) In the present invention, the element temperature parameter acquisition means automatically acquires an element temperature parameter value that increases as the temperature of a switching element and a resistance element provided in a drive circuit connecting a battery and a starter rises. The stop start control device prohibits automatic stop of the internal combustion engine when the element temperature parameter value is equal to or higher than the first threshold value. Here, as described above, the range of variation in the drive current of the starter increases as the temperature of the resistance element increases. Therefore, when the temperature of the resistance element becomes higher than the predetermined temperature, the torque required for cranking the internal combustion engine by the starter is generated even if the temperature of the switching element does not exceed the operating limit temperature. This may prevent the internal combustion engine from being automatically restarted. Therefore, in the present invention, the first threshold value set for the element temperature parameter value in order to prohibit automatic stop is made smaller than the operating limit value determined based on the operating limit temperature of the switching element. Therefore, according to the present invention, after the internal combustion engine is automatically stopped, it is possible to prevent a situation in which automatic restart cannot be performed due to variations in the drive current.

(2) As will be described later with reference to FIGS. 6 and 7, in order to generate the torque required for cranking the internal combustion engine with the starter, the starter is operated under a current and voltage within a predetermined operating range. Need to drive. Further, if the internal resistance rises due to the battery temperature becoming lower than the predetermined temperature, the operating current deviates from the above operating range on the lower limit side of the variation range of the drive current, and the torque required for cranking cannot be generated. In some cases. Therefore, in the present invention, the battery temperature parameter acquisition means acquires the battery temperature parameter value that increases as the battery temperature rises, and the automatic stop start control device has the battery temperature parameter value smaller than the second threshold value and the element temperature. When the parameter value is equal to or higher than the first threshold value, automatic stop is prohibited. Therefore, according to the present invention, after the internal combustion engine is automatically stopped, it is possible to prevent a situation in which automatic restart cannot be performed due to variations in the drive current. Further, in the present invention, automatic stop is permitted when the battery temperature parameter value is equal to or higher than the second threshold value and the element temperature parameter is smaller than the operating limit value. Therefore, according to the present invention, the range in which automatic stop can be permitted can be widened as much as possible, so that fuel consumption in the internal combustion engine can be further suppressed.

(3) In the present invention, a battery that supplies electric power to the starter and an electric load different from the starter are connected by a power line, and a switch is provided on the power line. Thereby, by turning the switch on / off, the power of the battery can be supplied only to the starter, or both the starter and the electric load can be supplied. However, if the starter is driven and cranked while supplying the electric power of the battery to the electric load, the starter will be out of the above operating range on the lower limit side of the variation range of the drive current, and the torque required for cranking will be generated. May not be possible. Therefore, in the present invention, the automatic stop start control device prohibits automatic stop when the switch is on and the element temperature parameter value is equal to or higher than the first threshold value. Therefore, according to the present invention, after the internal combustion engine is automatically stopped, it is possible to prevent a situation in which automatic restart cannot be performed due to variations in the drive current. Further, in the present invention, automatic stop is permitted when the switch is off and the element temperature parameter value is smaller than the operating limit value. Therefore, according to the present invention, the range in which automatic stop can be permitted can be widened as much as possible, so that fuel consumption in the internal combustion engine can be further suppressed.

(4) As described above, when the battery temperature is lower than the predetermined temperature and the internal resistance is high, if the battery power is to be supplied to both the electric load and the starter, the lower limit of the variation range of the starter drive current is reached. On the side, it may be out of the above operating range, and it may not be possible to generate the torque required for cranking. Therefore, in the present invention, the automatic stop start control device prohibits automatic stop when the battery temperature parameter value is smaller than the second threshold value, the switch is on, and the element temperature parameter value is equal to or higher than the first threshold value. Therefore, according to the present invention, after the internal combustion engine is automatically stopped, it is possible to prevent a situation in which automatic restart cannot be performed due to variations in the drive current. Further, in the present invention, automatic stop is permitted when the battery temperature parameter value is equal to or higher than the second threshold value or the switch is off and the element temperature parameter value is smaller than the operating limit value. Therefore, according to the present invention, the range in which automatic stop can be permitted can be made as wide as possible, so that fuel consumption in the internal combustion engine can be further suppressed.

(5) If the temperature of the battery becomes excessively low, the starter may not be able to generate the torque required for cranking regardless of the presence or absence of variation in the drive current. Therefore, in the present invention, the automatic stop start control device prohibits automatic stop when the battery temperature parameter value is smaller than the third threshold value smaller than the second threshold value. Therefore, according to the present invention, after the internal combustion engine is automatically stopped, it is possible to prevent a situation in which automatic restart cannot be performed due to variations in the drive current. Further, in the present invention, when the battery temperature parameter is equal to or higher than the third threshold value and the element temperature parameter value is smaller than the first threshold value, automatic stop is permitted. Therefore, according to the present invention, the range in which automatic stop can be permitted can be made as wide as possible, so that fuel consumption in the internal combustion engine can be further suppressed.

It is a figure which shows the structure of the internal combustion engine and its control device which concerns on one Embodiment of this invention. It is a figure which shows the structure of the drive circuit of the starter generator and the starter control part. It is a flowchart which shows the specific procedure of the automatic stop permission determination process. It is a figure which shows an example of the automatic stop permission determination map for the 2nd battery (when the load is low). It is a figure which shows an example of the automatic stop permission determination map for the 2nd battery (at the time of a high load). It is a figure which shows the operating range of a starter generator. It is a figure which superposed and plotted the discharge characteristic of the 2nd battery on the figure which shows the operating range of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine (hereinafter, referred to as “engine 1”) and a control device 2 thereof according to the present embodiment. The engine 1 and the control device 2 are mounted on at least a vehicle (not shown) whose power source is the engine 1.

The control device 2 is a power supply system S that transfers electric power between the starter generator 4 and its drive circuit 40 connected to the crankshaft of the engine 1 and the starter generator 4 and the first battery B1 and the second battery B2. And the FI-ECU 70, which is a computer that controls the engine 1 and the starter generator 4.

The starter generator 4 is connected to the crankshaft of the engine 1 via a power transmission mechanism such as a belt or a pulley. As the starter generator 4, for example, what is called an ISG (Integrated Starter Generator) is used. That is, the starter generator 4 has a function as a generator that generates electricity when it is rotationally driven by the crankshaft of the operating engine 1 and a function as an electric motor that rotationally drives the crankshaft of the stopped engine 1. .. The starter generator 4 is connected to the power supply system S via a drive circuit 40, and uses the electric power supplied from the power supply system S to rotationally drive the crankshaft of the engine 1 and transfers the generated electric power to the power supply system S. To supply.

The power supply system S includes a first battery B1 and a second battery B2, a first electric load 61 and a second electric load 62, a starter motor 5 connected to the crank shaft of the engine 1, a first battery B1 and a second battery. It includes a switch circuit 3 that connects the battery B2, the starter generator 4, and the second electric load 62, and a battery ECU 72 that controls the switch circuit 3.

The first electric load 61 mainly includes electric devices mounted on the vehicle that are not essential for running the vehicle, such as audio equipment. On the other hand, the second electric load 62 mainly includes electric devices mounted on the vehicle that are indispensable for driving the vehicle, such as an electric power steering drive device, an FI-ECU 70, and a battery ECU 72. included.

The first battery B1 is a secondary battery capable of both discharging that converts chemical energy into electrical energy and charging that converts electrical energy into chemical energy. Hereinafter, a case where a so-called lead storage battery using lead as an electrode is used as the first battery B1 will be described, but the present invention is not limited to this.

The first battery B1 is connected to the starter generator 4 and the second electric load 62 via the switch circuit 3. The first battery B1 can transfer and receive electric power to and from the starter generator 4 via the switch circuit 3, and can supply electric power to the second electric load 62. Further, a starter motor 5, a first electric load 61, and the like are connected to the first battery B1. The first battery B1 can appropriately supply electric power to the starter motor 5, the first electric load 61, and the like.

The first battery B1 is provided with a first sensor unit 78 that detects values of various physical quantities necessary for estimating the internal state of the first battery B1 and transmits a signal corresponding to the detected values to the battery ECU 72. There is. The first sensor unit 78 includes, for example, a voltage sensor that detects the terminal voltage of the first battery B1, a current sensor that detects the current flowing through the first battery B1, and a temperature sensor that detects the temperature of the first battery B1. To be equipped. In the battery ECU 72, the temperature of the first battery B1 and the charge rate of the first battery B1 (the ratio of the remaining capacity of the secondary battery to the battery capacity are expressed as a percentage based on the signal transmitted from the first sensor unit 78. It is also called SOC).

The second battery B2 is a secondary battery capable of both discharging and charging, like the first battery B1 described above. Hereinafter, a case where a so-called lithium ion storage battery that charges and discharges by moving lithium ions between the electrodes is used as the second battery B2 will be described, but the present invention is not limited to this. It is preferable that the first battery B1 and the second battery B2 have different characteristics. More specifically, it is preferable to use a second battery B2 having a higher output density and a larger battery capacity than the first battery B1.

The second battery B2 is connected to the starter generator 4 and the second electric load 62 via the switch circuit 3. The second battery B2 is capable of transmitting and receiving electric power to and from the starter generator 4 via the switch circuit 3 and supplying electric power to the second electric load 62.

The second battery B2 is provided with a second sensor unit 79 that detects values of various physical quantities necessary for estimating the internal state of the second battery B2 and transmits a signal corresponding to the detected values to the battery ECU 72. There is. The second sensor unit 79 includes, for example, a voltage sensor that detects the terminal voltage of the second battery B2, a current sensor that detects the current flowing through the second battery B2, and a temperature sensor that detects the temperature of the second battery B2. To be equipped. In the battery ECU 72, based on the signal transmitted from the second sensor unit 79, the temperature of the second battery B2 and the charge rate of the second battery B2 (the ratio of the remaining capacity of the secondary battery to the battery capacity are expressed as a percentage. It is also called SOC).

The switch circuit 3 includes a first input / output terminal 31, a second input / output terminal 32, an output terminal 33, a first power line 34, a second power line 35, a third power line 36, and a fourth power line 37. It includes a first switch SW1, a second switch SW2, a third switch SW3, and a fourth switch SW4.

The starter generator 4 and its drive circuit 40 are connected to the first input / output terminal 31. The first battery B1, the first electric load 61, and the starter motor 5 are connected in parallel to the second input / output terminal 32. A second electric load 62 is connected to the output terminal 33.

The first power line 34 connects the first input / output terminal 31 and the second battery B2. The second power line 35 connects the second input / output terminal 32 and the merging portion 38 of the first power line 34. The third power line 36 connects the output terminal 33 and the merging portion 39 of the first power line 34 on the second battery B2 side of the merging portion 38. The fourth power line 37 connects the second power line 35 and the output terminal 33.

The first switch SW1 is provided on the merging portion 38 side of the second power line 35 from the portion to which the fourth power line 37 is connected. When the first switch SW1 is turned on, the first battery B1 and the starter generator 4 are connected, and electric power can be exchanged between the first battery B1 and the starter generator 4. When the first switch SW1 is turned off, the first battery B1 and the starter generator 4 are shut off. The first switch SW1 is turned on / off in response to a command signal from the battery ECU 72. For example, the battery ECU 72 presses the first switch SW1 when charging the first battery B1 with the electric power obtained by the starter generator 4 or when driving the starter generator 4 with the electric power output from the first battery B1. turn on.

The second switch SW2 is provided between the merging portion 38 and the merging portion 39 of the first power line 34. When the second switch SW2 is turned on, the second battery B2 and the starter generator 4 are connected, and electric power can be exchanged between the second battery B2 and the starter generator 4. When the second switch SW2 is turned off, the second battery B2 and the starter generator 4 are shut off. The second switch SW2 is turned on / off in response to a command signal from the battery ECU 72. The battery ECU 72 presses the second switch SW2, for example, when charging the second battery B2 with the electric power obtained by the starter generator 4 or when driving the starter generator 4 with the electric power output from the second battery B1. turn on.

The third switch SW3 is provided on the third power line 36. When the third switch SW3 is turned on, the second battery B2 and the second electric load 62 are connected, and electric power can be supplied from the second battery B2 to the second electric load 62. When the third switch SW3 is turned off, the second battery B2 and the second electric load 62 are cut off. The third switch SW3 is turned on / off in response to a command signal from the battery ECU 72. The battery ECU 72 turns on the third switch SW3, for example, when driving the second electric load 62 with the electric power output from the second battery B2.

The fourth switch SW4 is provided on the fourth power line 37. When the fourth switch SW4 is turned on, the first battery B1 and the second electric load 62 are connected, and electric power can be supplied from the first battery B1 to the second electric load 62. When the fourth switch SW4 is turned off, the first battery B1 and the second electric load 62 are cut off. The fourth switch SW4 is turned on / off in response to a command signal from the battery ECU 72. The battery ECU 72 turns on the fourth switch SW4, for example, when driving the second electric load 62 with the electric power output from the first battery B1.

The battery ECU 72 is a computer that mainly manages the batteries B1 and B2. More specifically, the battery ECU 72 estimates the SOC of each battery B1 and B2 based on the signals transmitted from the sensor units 78 and 79, and the SOC of each battery B1 and B2 is within a predetermined target range. The switches SW1, SW2, SW3, and SW4 of the switch circuit 3 are turned on / off so as to be maintained at. The battery ECU 72 selectively turns on the first switch SW1 and the second switch SW2 so that at least one of the first battery B1 and the second battery B2 is connected to the starter generator 4. Further, the battery ECU 72 selectively turns on the third switch SW3 and the fourth switch SW4 so that at least one of the first battery B1 and the second battery B2 is connected to the second electric load 62.

Further, the battery ECU 72 is a second battery temperature which is a temperature value of the first battery temperature value TB1 and the second battery B2 which is a temperature value of the first battery B1 acquired based on the signals transmitted from the sensor units 78 and 79. The value TB2 is transmitted to the FI-ECU 70. Therefore, in the present embodiment, the battery temperature parameter acquisition means for acquiring the second battery temperature value TB2, which increases as the temperature of the second battery B2 rises, is composed of the second sensor unit 79 and the battery ECU 72.

The drive circuit 40 is provided on a power line connecting the first input / output terminal 31 of the switch circuit 3 and the starter generator 4. The drive circuit 40 is, for example, a PWM inverter by pulse width modulation including a bridge circuit configured by bridging a plurality of switching elements (for example, MOSFETs).

Returning to FIG. 1, the FI-ECU 70 includes an engine control unit 70a, which is a control module responsible for fuel injection control and ignition timing control of the engine 1, and an automatic stop start control unit 70b, which is a control module responsible for idle stop control of the engine 1. A computer including a starter control unit 70c, which is a control module responsible for operating the drive circuit 40 of the starter generator 4.

The starter control unit 70c supplies power supplied from the switch circuit 3 to the starter generator 4 or is supplied from the starter generator 4 by turning on / off a plurality of MOSFETs in the drive circuit 40 at predetermined timings. Power is supplied to the switch circuit 3.

FIG. 2 is a diagram showing a partial configuration of the drive circuit 40 of the starter generator 4 and the starter control unit 70c. The drive circuit 40 is provided with a plurality of MOS modules 400 configured by integrally modularizing the MOSFET 401, the diode temperature sensor 402, and the shunt resistor 403 as chips. FIG. 2 illustrates only one of the plurality of MOS modules 400.

The starter control unit 70c includes a microcomputer 710, a pre-driver 711, a current detection circuit 712, and a temperature detection circuit 713.

The current detection circuit 712 detects the voltage across the shunt resistor 403, generates a current detection signal according to the magnitude of the current flowing through the starter generator 4 based on this voltage, and transmits this to the microcomputer 710. .. The microcomputer 710 generates a gate drive signal of the MOSFET 401 so that the current flowing through the starter generator 4 becomes a predetermined target based on a known feedback control algorithm based on the current detection signal transmitted from the current detection circuit 712. This is transmitted to the predriver 711. The pre-driver 711 operates the MOSFET 401 on / off by PWM control based on the gate drive signal transmitted from the microcomputer 710. As a result, a current corresponding to a predetermined target flows through the starter generator 4.

The temperature detection circuit 713 detects the current flowing through the diode temperature sensor 402 provided at a position closer to the MOSFET 401 than the shunt resistor 403 in the MOS module 400, and based on this current, the element temperature value TM which is the temperature value of the MOSFET 401. Is transmitted to the FI-ECU 70. Here, the MOSFET 401, the diode temperature sensor 402, and the shunt resistor 403 are integrated as a chip. Therefore, when the temperature of the MOSFET 401 rises, the temperature of the shunt resistor 403 also rises. Further, the temperature difference between the MOSFET 401 and the shunt resistor 403 at this time can be specified by conducting a test in advance. Therefore, in the present embodiment, the element temperature parameter acquisition means for acquiring the element temperature value TM, which is a value that increases as the temperature of the MOSFET 401 and the shunt resistor 403 rises, is composed of the diode temperature sensor 402 and the temperature detection circuit 713. ..

Returning to FIG. 1, the engine control unit 70a controls the fuel injection amount and the fuel injection timing by the fuel injection valve (not shown) provided in the engine 1 based on a known algorithm, and the engine 1 The ignition timing control for controlling the ignition timing by the spark plug (not shown) provided in the above is executed.

The automatic stop start control unit 70b determines whether or not a predetermined automatic stop condition is satisfied while the engine 1 is operating under the control of the engine control unit 70a, and if the automatic stop condition is satisfied, the engine The engine 1 is automatically stopped by stopping the fuel injection control and the ignition timing control by the control unit 70a. Here, the automatic stop conditions include, for example, basic conditions such as the speed of the vehicle being equal to or less than a predetermined value, the accelerator pedal of the vehicle not being depressed, and the brake pedal of the vehicle being depressed. This includes the fact that the automatic stop of the engine 1 is permitted by the automatic stop permission determination process shown in FIG. 3, which will be described later. That is, the automatic stop start control unit 70b automatically stops the engine 1 only when the basic conditions are satisfied and the automatic stop of the engine 1 is permitted by the automatic stop permission determination process. Further, the automatic stop start control unit 70b does not automatically stop the engine 1 even if the basic conditions are satisfied, if the automatic stop of the engine 1 is prohibited by the automatic stop permission determination process.

Further, the automatic stop start control unit 70b determines whether or not a predetermined automatic restart condition is satisfied after automatically stopping the engine 1 as described above, and if the automatic restart condition is satisfied, starter control is performed. The engine 1 is automatically started by transmitting a command signal to the unit 70c, cranking the engine 1 under the control of the starter generator 4 by the starter control unit 70c, and restarting the fuel injection control and the ignition timing control by the engine control unit 70a. Restart. Here, the automatic restart condition includes, for example, that the accelerator pedal has been depressed, that the brake pedal has been released, and the like.

FIG. 3 is a flowchart showing a specific procedure of the automatic stop permission determination process. This automatic stop permission determination process is repeatedly executed by the automatic stop start control unit 70b under a predetermined control cycle while the engine 1 is operating.

First, in S1, the automatic stop start control unit 70b acquires the element temperature value TM, which is the temperature value of the MOSFET 401, and moves to S2. In S2, the automatic stop start control unit 70b acquires the first battery temperature value TB1 which is the temperature value of the first battery B1 and the second battery temperature value TB2 which is the temperature value of the second battery B2, and moves to S3.

In S3, the automatic stop start control unit 70b determines whether or not the second switch SW2 is on. When the determination result of S3 is YES, that is, when the second switch SW2 is on and the starter generator 4 and the second battery B2 are connected, the automatic stop start control unit 70b moves to S4.

In S4, the automatic stop start control unit 70b determines whether or not the third switch SW3 is on. When the determination result of S4 is NO, that is, the second switch SW2 and the fourth switch SW4 are on (as described above, the third switch SW3 and the fourth switch SW4 are selectively turned on). 2 When only the starter generator 4 is connected to the battery B2 and the second electric load 62 is connected to the first battery B1, the automatic stop start control unit 70b moves to S5.

In S5, the automatic stop start control unit 70b automatically stops the engine 1 by searching the automatic stop permission determination map for the second battery B2 shown in FIG. 4 based on the element temperature value TM and the second battery temperature value TB2. It is determined whether to allow or prohibit the stop, and the automatic stop permission determination process of FIG. 3 is terminated.

FIG. 4 shows the automatic operation for the second battery B2, which is referred to when the load of the second battery B2 is low, that is, when the third switch SW3 is off and only the starter generator 4 is connected to the second battery B2. It is a figure which shows an example of the stop permission determination map. The automatic stop start control unit 70b is used when the operating points of the drive circuit 40 and the second battery B2 specified by the element temperature value TM and the second battery temperature value TB2 are within the automatic stop prohibition region shown by hatching in FIG. Prohibits the automatic stop of the engine 1 and permits the automatic stop of the engine 1 when the operating point is within the automatic stop permission area shown in white in FIG.

More specifically, the automatic stop start control unit 70b automatically stops the engine 1 when the third switch SW3 is off and the second battery temperature value TB2 is equal to or higher than the predetermined battery operation upper limit threshold value th_b1. Ban. If the automatic stop of the engine 1 is permitted in such an area, sufficient power cannot be supplied from the second battery B2 to the starter generator 4 at the time of the subsequent automatic restart, and the engine 1 may not be cranked. 2 The temperature of the battery B2 may rise further, and the second battery B2 may deteriorate.

Further, the automatic stop control unit 70b is an engine when the third switch SW3 is off and the second battery temperature value TB2 is smaller than the battery operation lower limit threshold value th_b3 defined to be smaller than the above-mentioned battery operation upper limit threshold value th_b1. Prohibit the automatic stop of 1. If the automatic stop of the engine 1 is permitted in such a region, sufficient power cannot be supplied from the second battery B2 to the starter generator 4 at the time of the subsequent automatic restart, and the engine 1 may not be cranked.

Further, the automatic stop control unit 70b is the engine 1 when the third switch SW3 is off and the element temperature value TM is equal to or higher than the MOSFET operating upper limit threshold value th_m1 determined based on the operating limit temperature of the MOSFET 401 of the drive circuit 40. Prohibit the automatic stop of. If the automatic stop of the engine 1 is permitted in such a region, the temperature of the MOSFET 401 may further rise and the MOSFET 401 may fail when the MOSFET 401 of the drive circuit 40 is turned on / off during the subsequent automatic restart. Further, if the automatic stop of the engine 1 is permitted in such a region, the MOSFET 401 of the drive circuit 40 may not operate normally at the time of the subsequent automatic restart, and the engine 1 may not be cranked by the starter generator 4.

Therefore, in the automatic stop control unit 70b, the third switch SW3 is off, the element temperature value TM is smaller than the MOSFET operating upper limit threshold value th_m1, the second battery temperature value TB2 is smaller than the battery operating upper limit threshold value th_b1, and the second battery temperature. When the value TB2 is equal to or higher than the battery operating lower limit threshold value th_b3, the automatic stop of the engine 1 is permitted.

Returning to FIG. 3, when the determination result of S4 is YES, that is, the second switch SW2 and the third switch SW3 are on, and the second electric load 62 and the starter generator 4 are connected in parallel to the second battery B2. If so, the automatic stop start control unit 70b moves to S6.

In S6, the automatic stop start control unit 70b automatically stops the engine 1 by searching the automatic stop permission determination map for the second battery B2 shown in FIG. 5 based on the element temperature value TM and the second battery temperature value TB2. It is determined whether to allow or prohibit the stop, and the automatic stop permission determination process of FIG. 3 is terminated.

FIG. 5 is referred to when the second battery B2 is under heavy load, that is, when the third switch SW3 is on and the starter generator 4 and the second electric load 62 are connected in parallel to the second battery B2. It is a figure which shows an example of the automatic stop permission determination map for the 2nd battery B2. The automatic stop start control unit 70b is used when the operating points of the drive circuit 40 and the second battery B2 specified by the element temperature value TM and the second battery temperature value TB2 are within the automatic stop prohibition region shown by hatching in FIG. Prohibits the automatic stop of the engine 1 and permits the automatic stop of the engine 1 when the operating point is within the automatic stop permission range shown in white in FIG.

More specifically, the automatic stop start control unit 70b prohibits the automatic stop of the engine 1 when the third switch SW3 is on and the second battery temperature value TB2 is equal to or higher than the battery operation upper limit threshold value th_b1. .. This is for the same reason as explained with reference to FIG.

Further, the automatic stop start control unit 70b prohibits the automatic stop of the engine 1 when the third switch SW3 is on and the second battery temperature value TB2 is smaller than the battery operation lower limit threshold value th_b3. This is for the same reason as explained with reference to FIG.

Further, the automatic stop start control unit 70b prohibits the automatic stop of the engine 1 when the third switch SW3 is on and the element temperature value TM is equal to or higher than the MOSFET operation upper limit threshold value th_m1. This is for the same reason as explained with reference to FIG.

As is clear from the comparison between FIGS. 5 and 4, two threshold values th_b2 and th_m2 are newly defined in the automatic stop permission determination map referred to at the time of high load shown in FIG. The threshold value th_b2 is a threshold value for the second battery temperature value TB2, and is set to a value slightly larger than the battery operation lower limit threshold value th_b3 between the battery operation upper limit threshold value th_b1 and the battery operation lower limit threshold value th_b3. The threshold value th_m2 is a threshold value with respect to the element temperature value TM, and is set to a value slightly smaller than the MOSFET operation upper limit threshold value th_m1.

Under the definition of the threshold values th_b2 and th_m2 as described above, in the automatic stop start control unit 70b, the third switch SW3 is on, the second battery temperature value TB2 is smaller than the threshold value th_b2, and the element temperature value TM is the threshold value th_m2 or more. If this is the case, the automatic stop of the engine 1 is prohibited. The reason for prohibiting the automatic stop of the engine 1 in such a case will be described with reference to FIGS. 6 to 7.

FIG. 6 is a diagram showing an operating range of the starter generator 4. Here, the operating range of the starter generator 4 means a range of current (horizontal axis) -voltage (vertical axis) in which the engine 1 can be cranked by the starter generator 4. The broken line in FIG. 6 is a curve obtained by plotting the minimum torque curve of the starter generator 4, that is, the operating point that generates the minimum torque required for cranking the engine 1. Therefore, in order to crank the engine 1 with the starter generator 4, it is necessary to drive the starter generator 4 under the current and voltage within the operating range indicated by the hatching on the upper side of the minimum torque curve in FIG. In other words, even if the starter generator 4 is driven under a current and a voltage outside the operating range below the minimum torque curve in FIG. 6, the engine 1 may not be cranked.

FIG. 7 is a diagram in which the discharge characteristics of the second battery B2 are superimposed and plotted on a diagram showing the operating range of FIG. In FIG. 7, the thick solid line shows that when the second battery B2 has a high load and a low temperature, the third switch SW3 is turned on, and the second battery B2 has the starter generator 4 and the second electric load 62. Shows the discharge characteristics of the second battery B2 when and are connected in parallel and the second battery temperature value TB2 is smaller than the threshold th_b2. Further, in FIG. 7, the alternate long and short dash line shows that when the second battery B2 has a low load or a normal temperature, the third switch SW3 is turned off, and only the starter generator 4 is connected to the second battery B2. The discharge characteristics of the second battery B2 are shown when the second battery temperature value TB2 is equal to or higher than the threshold value th_b2.

As the load on the second battery B2 increases and the current flowing through the second battery B2 increases, the voltage drop increases. Further, as the temperature of the second battery B2 becomes lower, the internal resistance of the second battery B2 becomes larger and the voltage drop becomes larger. Therefore, as shown in FIG. 7, the discharge characteristics (thick solid line) when the second battery B2 has a high load and a low temperature are the discharge characteristics (thick one-dot chain line) when the second battery B2 has a low load or a normal temperature. It becomes the lower voltage side than.

When cranking the engine 1 with the starter generator 4, the starter control unit 70c sets the drive current of the starter generator 4 to a target set within the operating range by feedback control based on the voltage across the shunt resistor 403. The MOSFET 401 is turned on / off so as to be. Therefore, when the temperature of the MOSFET 401 rises and the temperature of the shunt resistor 403 rises, the drive current realized by the feedback control by the starter control unit 70c becomes uneven.

Here, the range indicated by the arrow 7a in FIG. 7 indicates the variation range of the drive current when the element temperature value TM is smaller than the MOSFET operating upper limit threshold value th_m1 and equal to or higher than the threshold value th_m2. Further, the range indicated by the arrow 7b in FIG. 7 indicates the variation range of the drive current when the element temperature value TM is smaller than the threshold value th_m2.

As shown by the alternate long and short dash line in FIG. 7, when the second battery B2 has a low load or normal temperature, the starter generator 4 is operated within the operating range even if the driving current fluctuates within the variation range indicated by the arrow 7a. It is possible to drive. On the other hand, as shown by the thick solid line in FIG. 7, when the second battery B2 has a high load and a low temperature, if the drive current fluctuates within the variation range indicated by the arrow 7a, the voltage is on the lower limit side of the variation range. It may be out of the operating range. Therefore, when the second battery B2 has a high load and a low temperature, even if the element temperature value TM is smaller than the MOSFET operating upper limit threshold value th_m1 and the MOSFET 401 operates normally, due to the variation in the drive current, There is a risk that the engine 1 cannot be cranked. Therefore, when the second battery B2 has a high load and a low temperature, it is necessary to limit the variation range of the drive current to the range indicated by the arrow 7b. Therefore, when the third switch SW3 is on, the second battery temperature value TB2 is smaller than the threshold value th_b2, and the element temperature value TM is equal to or higher than the threshold value th_m2, the automatic stop start control unit 70b is within the range indicated by the arrow 7a. The automatic stop of the engine 1 is prohibited in order to prevent the cranking from being impossible due to the variation in the drive current. Further, in the automatic stop start control unit 70b, when the third switch SW3 is on and the second battery temperature value TB2 is smaller than the threshold value th_b2, the element temperature value TM is smaller than the threshold value th_m2 and the variation of the drive current is arrow 7b. Only when it falls within the range indicated by, the automatic stop of the engine 1 is permitted.

Returning to FIG. 5, in the automatic stop start control unit 70b, when the third switch SW3 is on, the second battery temperature value TB2 is equal to or higher than the threshold value th_b2, and the element temperature value TM is smaller than the MOSFET operating upper limit threshold value th_m1. , Allows automatic stop of engine 1. Further, in the automatic stop start control unit 70b, when the third switch SW3 is on, the second battery temperature TB2 is equal to or higher than the battery operating lower limit threshold value th_b3, and the element temperature value TM is smaller than the threshold value th_b2, the engine 1 is automatically started. Allow suspension.

Returning to FIG. 3, when the determination result of S3 is NO, that is, the first switch SW1 is on (as described above, the first switch SW1 and the second switch SW2 are selectively turned on), and the starter. When the generator 4 and the first battery B1 are connected, the automatic stop start control unit 70b moves to S7.

In S7, the automatic stop start control unit 70b searches for a predetermined automatic stop permission determination map (not shown) for the first battery based on the element temperature value TM and the first battery temperature value TB1. It is determined whether to allow or prohibit the automatic stop of the engine 1, and the automatic stop permission determination process of FIG. 3 is terminated.

According to the control device 2 of the engine 1 as described above, the following effects are obtained.
(1) The automatic stop start control unit 70b prohibits the automatic stop of the engine 1 when the element temperature value TM is equal to or higher than the threshold value th_m2. As described above, the range of variation in the drive current of the starter generator 4 increases as the temperature of the shunt resistor 403 increases. Therefore, when the temperature of the shunt resistor 403 becomes higher than the predetermined temperature, the starter generator 4 generates the torque required to crank the engine 1 even if the temperature of the MOSFET 401 does not exceed the operating limit temperature. It may not be possible to restart the engine 1 automatically. Therefore, in the control device 2, the threshold value th_m2 set for the element temperature value TM in order to prohibit automatic stop is made smaller than the MOSFET operation upper limit threshold value th_m1 determined based on the operation limit temperature of the MOSFET 401. Therefore, according to the control device 2, it is possible to prevent a situation in which automatic restart cannot be performed due to variations in the drive current after the engine 1 is automatically stopped.

(2) As described above, in an attempt to supply the electric power of the second battery B2 to both the second electric load 62 and the starter generator 4 in a state where the temperature of the second battery B2 is lower than the predetermined temperature and the internal resistance is high. Then, the lower limit side of the variation range of the drive current of the starter generator 4 may be out of the operating range of the starter generator 4, and the torque required for cranking may not be generated. Therefore, the automatic stop start control unit 70b automatically stops the engine 1 when the second battery temperature value TB2 is smaller than the threshold value th_b2, the third switch SW3 is on, and the element temperature value TM is the threshold value th_m2 or more. Is prohibited. Therefore, according to the control device 2, it is possible to prevent a situation in which automatic restart cannot be performed due to variations in the drive current after the engine 1 is automatically stopped. Further, in the control device 2, when the second battery temperature value TB2 is equal to or higher than the threshold value th_b2, the third switch SW3 is off, and the element temperature value TM is smaller than the MOSFET operating upper limit value th_m1, automatic stop is permitted. Therefore, according to the control device 2, the range in which automatic stop can be permitted can be widened as much as possible, so that the fuel consumption in the engine 1 can be further suppressed.

(3) The automatic stop start control unit 70b prohibits automatic stop when the second battery temperature value TB2 is smaller than the battery operation lower limit threshold value th_b3, which is smaller than the threshold value th_b2. Therefore, according to the control device 2, it is possible to prevent a situation in which automatic restart cannot be performed due to variations in the drive current after the engine 1 is automatically stopped. Further, in the control device 2, when the second battery temperature value is equal to or higher than the battery operating lower limit threshold value th_b3 and the element temperature value TM is smaller than the threshold value th_m2, automatic stop is permitted. Therefore, according to the control device 2, the range in which automatic stop can be permitted can be widened as much as possible, so that the fuel consumption in the engine 1 can be further suppressed.

Although one embodiment of the present invention has been described above, the present invention is not limited to this. Within the scope of the gist of the present invention, the detailed configuration may be changed as appropriate.

For example, in the above embodiment, the automatic stop start control unit 70b automatically stops when the second battery temperature value TB2 is smaller than the threshold value th_b2, the third switch SW3 is on, and the element temperature value TM is the threshold value th_m2 or more. However, the present invention is not limited to this. As described with reference to FIG. 7, the voltage drop increases as the load on the second battery B2 increases, that is, as the current flowing through the second battery B2 increases, and as the temperature of the second battery B2 decreases, the voltage drop increases. Therefore, there is a high risk that the voltage will deviate from the operating range of the starter generator 4 due to the variation in the drive current. Therefore, in the automatic stop start control unit, when the second battery temperature value TB2 is smaller than the threshold value th_b2 and the element temperature value TM is the threshold value th_m2 or more, or the third switch SW3 is on and the element temperature value TM is the threshold value th_m2 or more. Even in the case of, the automatic stop may be prohibited.

1 ... Engine (internal combustion engine)
2 ... Control device 4 ... Starter generator (starter)
40 ... Drive circuit 401 ... MOSFET (switching element)
402 ... Diode temperature sensor (element temperature parameter acquisition means)
403 ... Shunt resistance (resistor element)
S ... Power supply system B2 ... Second battery (battery)
3 ... Switch circuit 36 ... Third power line (power line)
SW3 ... 3rd switch (switch)
62 ... Second electric load 70 ... FI-ECU
70a ... Engine control unit 70b ... Automatic stop start control unit (automatic stop start control device)
70c ... Starter control unit (starter control device)
713 ... Temperature detection circuit (element temperature parameter acquisition means)
72 ... Battery ECU (battery temperature parameter acquisition means)
79 ... Second sensor unit (battery temperature parameter acquisition means)

Claims (5)

With a starter connected to the crankshaft of an internal combustion engine,
Switching elements and resistance elements provided in the drive circuit that connects the battery and the starter,
A starter control device that controls the drive current of the starter by operating the switching element based on the voltage across the resistance element.
An element temperature parameter acquisition means for acquiring an element temperature parameter value which is a value that increases as the temperature of the switching element and the resistance element rises.
A control device for an internal combustion engine, comprising an automatic stop start control device that automatically stops the internal combustion engine when a predetermined condition is satisfied and then automatically restarts the internal combustion engine using the starter control device.
The automatic stop start control device is characterized in that the automatic stop is prohibited when the element temperature parameter value is equal to or greater than the first threshold value smaller than the operating limit value determined based on the operating limit temperature of the switching element. Internal combustion engine control device. Further provided with a battery temperature parameter acquisition means for acquiring a battery temperature parameter value which is a value that increases as the temperature of the battery rises.
When the battery temperature parameter value is smaller than the second threshold value and the element temperature parameter value is equal to or higher than the first threshold value, the automatic stop start control device prohibits the automatic stop, and the battery temperature parameter value is the battery temperature parameter value. The control device for an internal combustion engine according to claim 1, wherein when the element temperature parameter value is equal to or more than a second threshold value and the element temperature parameter value is smaller than the operating limit value, the automatic stop is permitted. A power line connecting the battery and an electric load different from the starter,
A switch provided on the power line is further provided.
The automatic stop start control device prohibits the automatic stop when the switch is on and the element temperature parameter value is equal to or higher than the first threshold value, and the switch is off and the element temperature parameter value. The control device for an internal combustion engine according to claim 1, wherein when is smaller than the operating limit value, the automatic stop is permitted. A power line connecting the battery and an electric load different from the starter,
A switch provided on the power line is further provided.
The automatic stop start control device prohibits the automatic stop when the battery temperature parameter value is smaller than the second threshold value, the switch is on, and the element temperature parameter value is equal to or higher than the first threshold value. When the battery temperature parameter value is equal to or higher than the second threshold value and the element temperature parameter value is smaller than the operating limit value, or when the switch is off and the element temperature parameter value is smaller than the operating limit value. The control device for an internal combustion engine according to claim 2, wherein the automatic stop is permitted. The automatic stop start control device prohibits the automatic stop when the battery temperature parameter value is smaller than the third threshold value smaller than the second threshold value, and the battery temperature parameter value is equal to or higher than the third threshold value. The control device for an internal combustion engine according to claim 2 or 4, wherein when the element temperature parameter value is smaller than the first threshold value, the automatic stop is permitted.

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