JP7276384B2 - idle stop vehicle - Google Patents

Description

The present invention relates to an idle stop vehicle.

As described in Patent Literature 1, there is known a control device that prohibits execution of idle stop based on the lowest voltage value of the battery when the engine is started for the first time.

JP 2012-246867 A

By the way, among idling stop vehicles, there is known one in which the engine is started by a different motor at the time of initial starting and at the time of restarting from idling stop. In such an idling stop vehicle, if the execution of idling stop control itself is prohibited based on the lowest voltage value of the battery at the time of the first start, idling stop is prohibited even in a situation where idling stop can be executed. There is a possibility that it will hinder the improvement of fuel efficiency.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an idle stop vehicle capable of improving fuel efficiency by increasing the frequency of idle stop.

In order to solve the above problems, the present invention provides an idle stop vehicle that automatically stops the engine when a predetermined automatic stop condition is satisfied and restarts the engine when a predetermined restart condition is satisfied, comprising at least A first motor for starting the engine when the engine is first started, a second motor for restarting the engine from an automatic stop state, a first battery for supplying electric power to the first motor, and the second motor. Restart control for prohibiting restart of the engine by the first motor when the lowest voltage value of a second battery that supplies electric power and the first battery at the time of initial start of the engine is equal to or less than a restart prohibition threshold. , wherein the restart control unit responds to a parameter indicating a change in engine friction when the engine is started by the first motor or a parameter indicating a change in the internal resistance value of the first battery. changing the restart prohibition threshold, and restarting the engine by the first motor when restarting the engine by the second motor is not permitted or when restarting the engine fails; It is a thing .

Thus, according to the present invention, the frequency of idle stop can be increased to improve fuel efficiency.

FIG. 1 is a configuration diagram of an idle-stop vehicle according to one embodiment of the present invention. FIG. 2 is a diagram showing changes in the voltage of the first battery when the engine is started when the minimum voltage of the idle-stop vehicle is equal to or lower than the restart prohibition threshold value according to one embodiment of the present invention. FIG. 3 is a diagram showing changes in the voltage of the first battery when the engine is started when the minimum voltage of the idle-stop vehicle is greater than the restart prohibition threshold value according to one embodiment of the present invention. FIG. 4 is a diagram showing changes in the restart prohibition threshold depending on the engine water temperature of the idling stop vehicle according to one embodiment of the present invention. FIG. 5 is a diagram showing changes in the restart prohibition threshold depending on the battery temperature of the idle-stop vehicle according to one embodiment of the present invention. FIG. 6 is a diagram showing changes in the restart prohibition threshold depending on the soak time of the idling stop vehicle according to one embodiment of the present invention. FIG. 7 is a diagram showing an idle stop vehicle according to an embodiment of the present invention, and is a flow chart showing the processing procedure. FIG. 8 is a diagram showing an idling stop vehicle according to an embodiment of the present invention, and is a flow chart showing the processing procedure thereof.

An idle stop vehicle according to an embodiment of the present invention is an idle stop vehicle that automatically stops an engine when a predetermined automatic stop condition is satisfied and restarts the engine when a predetermined restart condition is satisfied. a first motor that starts the engine at least when the engine is first started; a second motor that restarts the engine from an automatic stop state; a first battery that supplies electric power to the first motor; a second battery that supplies power, and a restart control unit that restarts the engine by the first motor when restarting the engine by the second motor is not permitted or when restarting the engine fails. is configured to have As a result, the frequency of idle stop can be increased to improve fuel efficiency.

BEST MODE FOR CARRYING OUT THE INVENTION An idle stop vehicle according to an embodiment of the present invention will be described in detail below with reference to the drawings.

An idling stop vehicle 1 according to an embodiment of the present invention automatically stops the engine when a predetermined idling stop condition is satisfied, and restarts the engine when a predetermined restarting condition is satisfied. It has functionality.

1, an idle stop vehicle 1 according to an embodiment of the present invention includes an engine 2 as an internal combustion engine, a first motor 3, a second motor 4, a first battery 5, a second battery 6, It includes an MCU (Motor Control Unit) 7 and an ECU (Electronic Control Unit) 8 as a restart control section.

A plurality of cylinders are formed in the engine 2 . In this embodiment, the engine 2 is constructed so that each cylinder performs a series of four strokes consisting of an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke.

A crankshaft 21 of the engine 2 is connected to the transmission 10 via the clutch 9 . The transmission 10 changes the speed of rotation output from the engine 2 and drives the driving wheels 12 via the differential mechanism 11 .

The clutch 9 and the transmission 10 are configured such that an actuator (not shown) controlled by the ECU 8 switches gears in the transmission 10 and engages and disengages the clutch 9 .

The differential mechanism 11 transmits power output by the transmission 10 to the drive wheels 12 .

A first motor 3 and a second motor 4 are connected to the engine 2 . The first motor 3 rotates when supplied with electric power, thereby rotating the crankshaft 21 and giving the engine 2 a rotational force at the time of starting. The first motor 3 starts the engine 2 at least when the engine 2 is started for the first time.

The second motor 4 is connected to a crankshaft 21 of the engine 2 via a belt 22 or the like. The second motor 4 has a function of an electric motor that starts the engine 2 by rotating when supplied with electric power, and a function of a generator that converts rotational force input from the crankshaft 21 into electric power. The second motor 4 starts the engine 2 at least when restarting from a stopped state by the idling stop function.

By functioning as an electric motor, the second motor 4 can assist the power of the engine 2 and can drive the idle stop vehicle 1 only with the power of the second motor 4 .

The first battery 5 is composed of, for example, a lead-acid battery. The first battery 5 is electrically connected to an electrical load such as the first motor 3 and vehicle electrical components 14 . A first battery state sensor 51 is connected to the first battery 5 . The first battery state sensor 51 detects charge/discharge current, voltage and battery temperature of the first battery 5 . The first battery state sensor 51 is connected to the ECU 8 . The ECU 8 can detect the battery voltage of the first battery 5 based on the output of the first battery state sensor 51 . The output voltage of the first battery 5 is, for example, about 12V.

The second battery 6 is composed of, for example, a lithium ion storage battery. This second battery 6 is electrically connected to the second motor 4 . A second battery state sensor 61 is connected to the second battery 6 . A second battery state sensor 61 detects charge/discharge current, voltage, and battery temperature of the second battery 6 . The second battery state sensor 61 is connected to the ECU8. The ECU 8 can detect the state of charge and discharge current of the second battery 6 from the output of the second battery state sensor 61 . The output voltage of the second battery 6 is, for example, approximately 48V.

The first battery 5 and the second battery 6 are connected via a DC (direct current) DC converter 13 . The DCDC converter 13 can step down the power generated by the second motor 4 and charge the first battery.

Each of the MCU 7 and the ECU 8 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, an input port, and an output port. It consists of a computer unit equipped with

The ROMs of these computer units store programs for causing the computer units to function as the MCU 7 and the ECU 8, along with various constants, various maps, and the like.

That is, these computer units function respectively as the MCU 7 and the ECU 8 in this embodiment by the CPU executing the programs stored in the ROM using the RAM as a work area.

The MCU 7 and the ECU 8 are connected by an in-vehicle LAN (Local Area Network) conforming to a standard such as a CAN (Controller Area Network), and can communicate with each other.

A second motor 4 is connected to an output port of the MCU 7 . The MCU 7 controls the second motor 4 according to instructions from the ECU 8 to restart the engine 2 and control the output torque of the second motor 4 .

Various sensors including the engine water temperature sensor 23 are connected to the input port of the ECU 8 in addition to the first battery state sensor 51 and the second battery state sensor 61 described above. An engine water temperature sensor 23 detects the temperature of cooling water for the engine 2 .

An output port of the ECU 8 is connected to various control objects including actuators for controlling the first motor 3, the clutch 9 and the transmission 10, injectors (not shown), spark plugs, and throttle valves.

The ECU 8 automatically stops the engine 2 when a preset automatic stop condition is satisfied, and executes idle stop control for restarting the engine 2 when a preset restart condition is satisfied.

The automatic stop condition is, for example, that the vehicle speed is equal to or less than a predetermined vehicle speed, that the brake pedal is depressed, and that the charge capacity of the second battery 6 is equal to or greater than a predetermined value. do. On the other hand, as the restart condition, for example, the condition is that any one or any combination of the shift position suitable for starting and the brake pedal not being depressed is satisfied.

The ECU 8 restarts the engine 2 by the second motor 4 when the restart condition is satisfied and the engine 2 is restarted. When restarting the engine 2 by the second motor 4, the ECU 8 prohibits restarting the engine 2 by the second motor 4 if the charge capacity of the second battery 6 is equal to or less than a predetermined capacity. The ECU 8 restarts the engine 2 by the first motor 3 when restarting the engine 2 by the second motor 4 is prohibited.

The ECU 8 restarts the engine 2 with the second motor 4 , but restarts the engine 2 with the first motor 3 when the restart of the engine 2 fails. For example, when restarting the engine 2 by the second motor 4 is retried a predetermined number of times and the engine 2 cannot be restarted, the ECU 8 determines that the restarting of the engine 2 has failed.

When the lowest voltage value of the first battery 5 is equal to or less than a predetermined restart prohibition threshold when the engine 2 is first started by the first motor 3, the ECU 8 controls the first motor 3 to restart from a stopped state by the idling stop function. Prohibit starting of the engine 2.

When the engine 2 is started by the first motor 3, the voltage of the first battery 5 decreases as shown in FIG. As shown in FIG. 2, when the minimum voltage value of the voltage drop of the first battery 5 when the engine 2 is started is equal to or less than the restart prohibition threshold, the ECU 8 determines the first Start-up of the engine 2 by the motor 3 is prohibited.

A load to be protected is connected to the first battery 5 as a vehicle electrical component 14 , and the load to be protected is supplied with power from the first battery 5 . The engine 2 is restarted by the first motor 3 in order to prevent unstable power supply to the load to be protected due to a significant drop in the voltage of the first battery 5 when the engine 2 is restarted. permission is being determined.

As shown in FIG. 3, when the lowest voltage value of the voltage of the first battery 5 when the engine 2 is started by the first motor 3 exceeds the restart prohibition threshold, the ECU 8 prevents the vehicle from being stopped by the idling stop function. Start-up of the engine 2 by the first motor 3 is permitted at the time of restart.

The ECU 8 may change the restart prohibition threshold using a parameter correlated with the voltage drop of the first battery 5 when the engine 2 is started by the first motor 3 . If the parameter indicates that the voltage drop of the first battery when starting the engine 2 is small, the restart prohibition threshold is set high (strict), and the parameter indicates that the voltage drop of the first battery when starting the engine 2 is If it indicates that it is large, the restart prohibition threshold is set low (loosely). By doing so, even if the voltage drop of the first battery 5 is large when the engine 2 is started due to the state of the engine 2 or the first battery 5, the restart prohibition threshold is set according to the degree of the voltage drop. It is possible to ensure the operation of the protected load while ensuring automatic restart of the engine 2 as much as possible.

The ECU 8 uses, for example, the engine water temperature indicating the temperature of the engine 2 as this parameter. The voltage drop of the first battery 5 when the engine 2 is started by the first motor 3 decreases as the temperature of the engine 2 increases. As shown in FIG. 4, the ECU 8 increases the restart prohibition threshold as the engine coolant temperature increases.

Even if the voltage of the first battery 5 drops to, for example, 7 V, the protected load is affected, and the voltage of the first battery 5 drops to 7 V when the engine 2 is started when the engine temperature is high. This has a different meaning than that the voltage of the first battery 5 drops to 7 V when the engine 2 is started when the engine temperature is low.

In the former case, there is a high possibility that the voltage of the first battery 5 will similarly drop to 7 V at the time of restart, and if this happens, the power supply to the unprotected devices may become unstable.

On the other hand, in the latter case, the reason why the voltage of the first battery 5 dropped to 7 V is considered to be largely due to the influence of engine friction. It can be expected that the voltage will not drop to 7V.

Therefore, in the former case, it is considered effective to set the restart prohibition threshold value to 7.1 V to prohibit the restart of the engine 2 by the first motor 3 . However, if the restart prohibition threshold is similarly set to 7.1 V in the latter case, even though the voltage of the first battery 5 does not drop to 7 V when the engine 2 is restarted when it is warm, the voltage at the first start is The descent prohibits the restart of the engine 2 by the first motor 3 .

By changing the restart prohibition threshold according to the parameter, the state of the first battery 5 that requires prohibition of the restart of the engine 2 by the first motor 3 can be determined when the engine 2 is started for the first time.

Note that the engine oil temperature may be used as the parameter indicating the engine temperature. As for the engine oil temperature, as shown in FIG. 4, the higher the engine oil temperature, the higher the restart prohibition threshold.

The ECU 8 may increase the restart prohibition threshold as the temperature of the first battery 5 increases, as shown in FIG. This is because the higher the temperature of the first battery 5, the smaller the internal resistance and the smaller the voltage drop.

As shown in FIG. 6, the ECU 8 may lower the restart prohibition threshold as the soak time, which is the elapsed time from when the ignition switch is turned off, increases. This is because it is predicted that the temperature of the engine 2 is higher as the soak time is shorter.

The ECU 8 may increase the restart prohibition threshold as the outside air temperature increases. This is because the outside air temperature affects the temperature of the first battery 5 , and similarly to the temperature of the first battery 5 , the higher the outside air temperature, the smaller the voltage drop of the first battery 5 .

The restart prohibition determination process by the ECU 8 of the idle stop vehicle according to the present embodiment configured as described above will be described with reference to FIG. The restart prohibition determination process described below is started when the ECU 8 starts operating, and is executed at preset time intervals.

In step S1, the ECU 8 determines whether or not the first motor 3 is starting the engine for the first time. When determining that the engine is not started for the first time, the ECU 8 repeats the process.

When it is determined in step S1 that the engine is started for the first time, in step S2, the ECU 8 acquires the lowest voltage V1 of the first battery 5 when the engine is started.

In step S3, the ECU 8 calculates the restart prohibition threshold value Vf based on the parameters described above.

In step S4, the ECU 8 determines whether or not the minimum voltage V1 is greater than the restart prohibition threshold value Vf. When determining that the lowest voltage V1 is greater than the restart prohibition threshold value Vf, the ECU 8 permits the restart of the engine 2 by the first motor 3 in step S5.

If it is determined in step S4 that the minimum voltage V1 is not greater than the restart prohibition threshold value Vf, the ECU 8 prohibits the restart of the engine 2 by the first motor 3 in step S6.

Next, restart control processing by the ECU 8 of the idle stop vehicle according to this embodiment will be described with reference to FIG. The restart control process described below is started when the engine 2 is automatically stopped, and is executed at preset time intervals.

In step S11, the ECU 8 determines whether or not the restart condition described above is satisfied. When determining that the restart condition is not satisfied, the ECU 8 terminates the process.

When it is determined in step S11 that the restart condition is satisfied, the ECU 8 determines in step S12 whether restarting of the engine 2 by the second motor 4 is permitted. When it is determined that the restart of the engine 2 by the second motor 4 is permitted, the ECU 8 restarts the engine 2 by the second motor 4 in step S13.

In step S14, the ECU 8 determines whether or not the restart of the engine 2 by the second motor 4 has succeeded. When determining that the engine 2 has been successfully restarted, the ECU 8 terminates the process.

If it is determined in step S14 that the restart of the engine 2 has not succeeded, or if it is determined in step S12 that the second motor 4 is not permitted to restart the engine 2, in step S15, the ECU 8 , determines whether restarting of the engine 2 by the first motor 3 is permitted. When determining that restarting of the engine 2 by the first motor 3 is not permitted, the ECU 8 terminates the process.

When it is determined in step S15 that the restart of the engine 2 by the first motor 3 is permitted, the ECU 8 restarts the engine 2 by the first motor 3 in step S16, and ends the process.

As described above, in the above-described embodiment, the ECU 8 prohibits restarting of the engine 2 by the first motor 3 when the lowest voltage value of the first battery 5 when the engine 2 is started for the first time is equal to or lower than the restart prohibition threshold. Prepare.

As a result, when the lowest voltage value of the first battery 5 that supplies electric power to the first motor 3 when the engine 2 is started for the first time is equal to or less than the restart prohibition threshold value, only the restart by the first motor is prohibited. Therefore, when restart by the second motor 4 is possible, the restart is executed, and restart by the first motor 3 is prohibited. The operation of the protected load connected to the first battery 5 can be ensured.

Further, when the engine 2 cannot be restarted by the second motor 4, the ECU 8 restarts the engine 2 by the first motor 3 so that the lowest voltage value of the first battery 5 when the engine 2 is started for the first time is If it is equal to or less than the restart prohibition threshold, the restart of the engine 2 by the first motor 3 is prohibited even if the restart by the second motor 4 cannot be performed.

As a result, if the lowest voltage value of the first battery 5 that supplies electric power to the first motor 3 at the initial start of the engine 2 is equal to or less than the restart prohibition threshold, the restart of the engine 2 by the second motor 4 fails. The restart of the engine 2 by the first motor 3 is prohibited. Therefore, it is possible to secure the operation of the protected load connected to the first battery 5 while increasing the frequency of idling stop to improve fuel consumption.

Further, the ECU 8 changes the restart prohibition threshold in accordance with a parameter correlated with the voltage drop amount of the first battery 5 when the engine 2 is started by the first motor 3 .

As a result, the restart prohibition threshold is changed according to the parameter correlated with the voltage drop amount of the first battery 5 when the engine 2 is started by the first motor 3 . Therefore, the restart prohibition threshold can be changed in accordance with the change in the amount of voltage drop of the first battery 5 indicated by the parameter. Operation of the connected protected load can be secured.

Further, the ECU 8 uses at least one of the water temperature of the engine 2, the oil temperature of the engine 2, the temperature of the first battery 5, and the soak time as parameters.

As a result, depending on whether the temperature of the engine 2 indicates a change in engine friction, or the temperature of the first battery 5 indicates a change in the internal resistance value of the first battery 5, or the engine temperature. Since the restart prohibition threshold is determined according to the length of the soak time that indicates the change, it is necessary to ensure the operation of the protected load connected to the first battery 5 while ensuring automatic restart of the engine 2 as much as possible. can be done.

In the present embodiment, the prohibition of restarting the engine 2 by the first motor 3 is determined based on the voltage drop of the first battery 5 when the engine 2 is first started. , the voltage drop of the first battery 5 when the engine 2 is started by an arbitrary first motor 3 may be used for determination.

In addition, restarting the engine 2 by the first motor 3 takes into account the charging amount of the first battery 5 performed from the lowest voltage of the first battery 5 when the engine 2 is first started to the automatic stop of the engine 2. may be determined to be prohibited.

Also, although the output voltage of the second battery 6 is about 48V, it is not limited to this, and a similar effect can be obtained with about 12V.

Further, in the description of FIG. 8, it is described that when it is determined in step S14 that the engine 2 has not been successfully restarted, the process proceeds to step S15. Even if it is determined, the process returns to step S13 to repeat restarting by the second motor 4 a predetermined number of times, or returns to step S12 to determine whether restarting by the second motor 4 is permitted a predetermined number of times and the second motor 4 in step S13. The configuration may be such that the restart by the motor 4 is repeated. With such a configuration, even if restarting with the first motor 3 is not permitted, restarting with the second motor 4 is performed as much as possible, so that automatic restarting of the engine 2 is further ensured. be able to.

Although embodiments of the present invention have been disclosed, it will be apparent that modifications may be made by those skilled in the art without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims.

1 idle stop vehicle 2 engine 3 first motor 4 second motor 5 first battery 6 second battery 8 ECU (restart control unit)
23 engine water temperature sensor 51 first battery state sensor

Claims (2)

An idle stop vehicle that automatically stops an engine when a predetermined automatic stop condition is satisfied and restarts the engine when a predetermined restart condition is satisfied,
a first motor that starts the engine at least when the engine is started for the first time;
a second motor for restarting the engine from an automatically stopped state;
a first battery that supplies power to the first motor;
a second battery that supplies power to the second motor;
a restart control unit that prohibits restarting of the engine by the first motor when the lowest voltage value of the first battery at the initial start of the engine is equal to or less than a restart prohibition threshold,
The restart control unit sets the restart prohibition threshold according to a parameter indicating a change in engine friction when the engine is started by the first motor or a parameter indicating a change in the internal resistance value of the first battery. The idle stop vehicle restarts the engine by the first motor when restarting the engine by the second motor is not permitted or when restarting the engine fails. 2. The idle stop vehicle according to claim 1, wherein the restart control unit prohibits restarting of the engine by the second motor when the charge amount of the second battery is equal to or less than a predetermined amount.

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