car

Abstract

This invention relates to automobiles. A control device for an automobile is configured to control an engine and a first electric motor such that, when a predetermined stop condition is met, the control device stops the engine, and while the engine stops as the predetermined stop condition is met, when a predetermined start condition is met, the control device starts the engine using the first electric motor, which uses power from a first energy storage device. When the engine does not start using the first electric motor despite the predetermined start condition being met, the control device starts the engine using a second electric motor and prevents the engine from stopping upon the subsequent meeting of a predetermined stop condition, wherein the second electric motor uses power from a second energy storage device.

Description

Technical Field

[0001] The present invention relates to an automobile, and more particularly to an automobile comprising a first motor configured to start an engine and a second motor configured to start an engine. Background Technology

[0002] In related technologies, an energy storage system has been proposed in which a main battery configured to supply power to a motor and an auxiliary battery configured to supply power to a starter motor are used together (see, for example, WO 2014 / 208028). The motor is configured to start an engine, and the starting mechanism causes the engine to start. In this system, a nickel-metal hydride battery or a lithium-ion battery is used as the main battery, and a lead-acid battery is used as the auxiliary battery. When the temperature of the main battery is higher than the set temperature at ignition start, the engine is started by supplying power from the main battery to the motor. When the temperature of the main battery is equal to or lower than the set temperature at ignition start, the engine is started by supplying power from the auxiliary battery to the starter motor. Summary of the Invention

[0003] In automobiles equipped with an electric storage system, when the so-called idle speed reduction is performed, the engine is started by supplying power from the main battery to the starter motor after the idle speed has decreased and the engine is about to start. In this situation, due to some inconvenience, even after the idle speed has decreased and power is supplied from the main battery to the starter motor, the engine may still fail to start. In such cases, it is conceivable to start the engine by supplying power from the auxiliary battery to the starter motor. However, if the engine is subsequently started by continuously supplying power from the auxiliary battery to the starter motor, the burden on the auxiliary battery increases. When a substandard product is used as the auxiliary battery, it may break down.

[0004] The main objective of the automobile of this invention is to reduce the burden on the auxiliary battery.

[0005] To achieve this primary objective, the automobile of the present invention adopts the following scheme.

[0006] The automobile of the present invention includes an engine, a first electric motor, a first energy storage device, a second electric motor, a second energy storage device, and a control device. The first electric motor causes the engine to start. The first energy storage device is configured to supply power to the first electric motor. The second electric motor causes the engine to start. The second energy storage device is configured to supply power to the second electric motor. The control device is configured to control the engine and the first electric motor such that when a predetermined stop condition is met, the control device stops the engine, and while the engine stops as the predetermined stop condition is met, when a predetermined start condition is met, the control device starts the engine using the first electric motor. When the engine does not start using the first electric motor when the predetermined start condition is met, the control device starts the engine using the second electric motor and prevents the engine from stopping when a subsequent predetermined stop condition is met.

[0007] In the automobile of the present invention, the engine and the first motor are controlled such that when a predetermined stop condition is met, the engine stops, and simultaneously, when a predetermined start condition is met, the engine starts using the first motor, which causes the first motor to receive power from the first energy storage device. When the engine cannot start using the first motor when the predetermined start condition is met, the engine starts using the second motor, which causes the second motor to receive power from the second energy storage device. Then, stopping the engine when a subsequent predetermined stop condition is met is prohibited. When the engine is started by the second motor when it cannot be started by the first motor, repeated stopping and starting of the engine is prohibited. This reduces the chances of the second motor starting the engine by receiving power from the second energy storage device. Thus, the burden on the second energy storage device is reduced. Of course, since the engine is started by the second motor when it cannot be started by the first motor, the automobile can continue to drive.

[0008] In the automobile of the present invention, the first energy storage device can be a lithium-ion battery or a nickel-metal hydride battery, and the second energy storage device can be a lead-acid battery. In this configuration, even if a substandard lead-acid battery is accidentally used as the second energy storage device, the burden on the second energy storage device can be reduced. Thus, the automobile can continue to operate.

[0009] In the vehicle of the present invention, when the system is activated, if the temperature of the first energy storage device is equal to or higher than a threshold temperature, the control device can start the engine using a first motor; however, if the temperature of the first energy storage device is lower than the threshold temperature, the control device can start the engine using a second motor. This configuration limits the engine to be started using the second motor. Attached Figure Description

[0010] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which the same reference numerals refer to the same elements, and wherein:

[0011] Figure 1 This is a structural diagram showing a general outline of the structure of a car 20 as an embodiment of the present invention; and

[0012] Figure 2 This is a flowchart illustrating an example of idle speed reduction control performed by the main ECU 70 of the vehicle 20 in this embodiment. Detailed Implementation

[0013] The mode for carrying out the present invention will now be described with reference to the embodiments.

[0014] Figure 1 This is a structural diagram showing an overview of the construction of a car 20 as an embodiment of the present invention. As shown, the car 20 of this embodiment includes an engine 22, a starter 25, a motor 30, an inverter 32, an automatic transmission 40, a high-voltage battery 60, a low-voltage battery 67, a DC-DC converter 68, and a main electronic control unit (hereinafter referred to as "main ECU") 70.

[0015] Engine 22 is configured as a multi-cylinder internal combustion engine (with four cylinders, six cylinders, etc.), which generates power by using gasoline, light oil, etc. supplied from the fuel tank via the fuel supply system as fuel and by passing through the intake stroke, compression stroke, expansion (combustion) stroke, and exhaust stroke. The operation of engine 22 is controlled by engine electronic control unit (hereinafter referred to as "engine ECU") 24.

[0016] Although not shown here, the engine ECU 24 is constructed as a microprocessor mainly consisting of a CPU, and in addition to the CPU, it includes a ROM in which processing programs are stored, RAM in which data is temporarily stored, input and output ports, and a communication port. Signals from various sensors required to control the operation of the engine 22 are input to the engine ECU 24 via the input ports, and various control signals used to control the operation of the engine 22 are output from the engine ECU 24 via the output ports.

[0017] A starter 25, configured to start the engine 22, is connected to a crankshaft 23, which serves as the output shaft of the engine 22. Furthermore, the input side of a damper 28, which is a torsion element, is also connected to the crankshaft 23 of the engine 22. A pulley 23b is attached to the crankshaft 23 of the engine 22.

[0018] Motor 30 is configured, for example, as a synchronous generator motor. Pulley 30b is attached to the rotating shaft of motor 30. Belt 31 is placed on pulley 30b, causing pulley 23b, which is attached to crankshaft 23 of engine 22, to be rotated. Inverter 32 is used to drive motor 30 and is connected to high-voltage side power line 61. Motor 30 is rotated by multiple switching elements of inverter 32 controlled in a switching manner by main ECU 70.

[0019] The automatic transmission 40 includes a torque converter 43, a six-speed automatic transmission 45, and a hydraulic circuit (not shown). The torque converter 43 is configured as a general-purpose fluid transmission. The torque converter 43 is configured to transmit power from the input shaft 41, connected to the rotating shaft of the motor 30, to the intermediate rotating shaft 44, which serves as the input shaft of the automatic transmission 45, either by amplifying the torque or without amplifying the torque. The automatic transmission 45 is connected to the intermediate rotating shaft 44 and also to an output shaft 42, which is connected to a drive shaft 46. The automatic transmission 45 includes multiple planetary gears and multiple hydraulically driven friction engagement elements (clutches, brakes). Note that the drive shaft 46 is connected to the rear wheels 55a, 55b via an axle 56 and a rear differential gear 57. The automatic transmission 45 forms forward and reverse gears from a first speed to a sixth speed, for example, by engaging and disengaging the multiple friction engagement elements, and transmits power between the intermediate rotating shaft 44 and the output shaft 42.

[0020] For example, a lithium-ion battery or a nickel-metal hydride battery is used as the high-voltage battery 60 and connected to the high-voltage side power line 61, which is connected to the inverter 32. A lead-acid battery with a nominal voltage lower than that of the high-voltage battery 60 is used as the low-voltage battery 67 and connected to the low-voltage side power line 66, which is connected to the starter motor 25. A DC-DC converter 68 is connected to both the high-voltage side power line 61 and the low-voltage side power line 66. The DC-DC converter 68 is controlled by the main ECU 70, causing it to reduce the voltage of the power supplied to the high-voltage side power line 61 and supply power to the low-voltage side power line 66.

[0021] Although not shown here, the main ECU 70 is configured as a microprocessor primarily consisting of a CPU, and includes, in addition to the CPU, a ROM in which processing programs are stored, RAM in which data is temporarily stored, input and output ports, and a communication port. Signals from various sensors are input to the main ECU 70 via the input ports. Examples of signals input to the main ECU 70 include, for example, the rotational position φm of the rotor of the motor 30 from a rotary position sensor (not shown), the rotational speed Np of the drive shaft 46 from a speed sensor 46a, which is configured to detect the rotational position of the rotor of the motor 30 and is attached to the drive shaft 46. Furthermore, examples of signals include the battery temperature Tb from a temperature sensor 60a attached to the high-voltage battery 60, the voltage Vh of the high-voltage battery 60 detected by a voltage sensor (not shown) attached between the terminals of the high-voltage battery 60, the current Ih of the high-voltage battery 60 detected by a current sensor (not shown) attached to the output terminals of the high-voltage battery 60, and the voltage Vb of the low-voltage battery 67 detected by a voltage sensor (not shown) attached between the terminals of the low-voltage battery 67. In addition, examples of signals include an ignition signal from an ignition switch 80, a shift position SP from a shift position sensor 82 configured to detect the operating position of a shift lever 81, an accelerator operation amount Acc from an accelerator pedal position sensor 84 configured to detect the amount of pressure applied to an accelerator pedal 83, a brake pedal position BP from a brake pedal position sensor 86 configured to detect the amount of pressure applied to a brake pedal 85, and a vehicle speed V from a vehicle speed sensor 88.

[0022] Various control signals are output from the main ECU 70 via an output port. Examples of signals output from the main ECU 70 include control signals sent to the starter 25, control signals sent to the inverter 32, control signals sent to the automatic transmission 40, and control signals sent to the DC-DC converter 68. The main ECU 70 is connected to the engine ECU 24 via a communication port.

[0023] In the vehicle 20 constructed in this embodiment, when the ignition switch 80 is on, and the battery temperature Tb detected by the temperature sensor 60a attached to the high-voltage battery 60 is equal to or greater than the threshold temperature Tref, power is supplied from the high-voltage battery 60 to the motor 30, causing the motor 30 to start the engine 22. The starting of the engine 22 is performed by drive control of the motor 30 by the main ECU 70, intake air volume control and fuel injection control by the engine ECU 24 (which has received a start control signal from the main ECU 70), and engine start control (e.g., ignition control). Simultaneously, when the ignition switch 80 is on, and the battery temperature Tb is less than the threshold temperature Tref, power is supplied from the low-voltage battery 67 to the starter motor 25, causing the starter motor 25 to start the engine 22. At this time, the starting of the engine 22 is performed by drive control of the starter motor 25 by the main ECU 70 and engine start control by the engine ECU 24 (which has received a start control signal from the main ECU 70). Here, the threshold temperature Tref is the temperature at which the engine 22 is started when cold, and can be, for example, -10°C, -5°C, 0°C, etc. When a lithium-ion battery is used as the high-voltage battery 60, the output limit (maximum permissible output limit) Wout when cold may be very small, making it difficult to start the engine 22 using the motor 30 powered by the high-voltage battery 60. Therefore, engine starting is performed by the starter motor 25 using power from the low-voltage battery 67 (lead-ion battery), which is capable of successfully starting the engine 22 when cold.

[0024] In the vehicle 20 of this embodiment, idle speed reduction control is performed to improve fuel efficiency. This idle speed reduction control stops the operation of engine 22 when a predetermined stop condition is met, and then starts engine 22 when a predetermined start condition is met. The predetermined stop condition can be that all of the following conditions are met: for example, the vehicle speed V is 0, and the brake pedal pressure is equal to or greater than a first threshold. The predetermined start condition can be that the brake pedal pressure is less than a second threshold, which is less than the first threshold. In this embodiment, restarting from idle speed reduction, that is, starting engine 22 when the predetermined start condition is met, is typically performed by starting engine 22 using a motor 30 powered by electricity from the high-voltage battery 60.

[0025] Next, the operation in the vehicle 20 of this embodiment when restarting from idle speed reduction (starting the engine 22) fails will be described. As a phenomenon of restarting from idle speed reduction failure, there is a situation where the output limit Wout of the high-voltage battery 60 is reduced due to some abnormality, and the torque required to start the engine 22 cannot be output from the motor 30. Figure 2This is a flowchart illustrating an example of idle speed reduction control performed by the main ECU 70 of the vehicle 20 in this embodiment. This control is performed repeatedly.

[0026] When idle speed reduction control is executed, the main ECU 70 first determines whether the idle speed reduction prohibition flag F has a value of 0 (step S100). With the ignition switch 80 on and the system started, the idle speed reduction prohibition flag F is set to a value of 0 through the initialization process. When idle speed reduction is prohibited, the idle speed reduction prohibition flag F is set to a value of 1. When the idle speed reduction prohibition flag F is determined to be a value of 1, idle speed reduction is determined to be prohibited, and this control ends without performing idle speed reduction.

[0027] When the idle speed reduction prohibition flag F is set to 0 in step S100, the main ECU 70 waits until a predetermined stop condition is met (step S110). When the predetermined stop condition is met, the main ECU 70 stops the operation of the engine 22 (step S120), and waits until a predetermined start condition is met (step S130). When the predetermined start condition is met, the main ECU 70 starts the engine 22 by using the motor 30 powered by the high-voltage battery 60 (step S140). Then, the main ECU 70 determines whether the engine 22 has failed to start (step S150). This control ends when the engine 22 starts successfully.

[0028] When the main ECU 70 determines in step S150 that the engine 22 has failed to start, the main ECU 70 starts the engine 22 by using the starter 25 powered by the low-voltage battery 67 (step S160). Then, the idle speed reduction prohibition flag F is set to a value of 1 to prohibit subsequent idle speed reduction (step S170), and this control ends. When the ignition switch 80 is turned off to stop the system, and then turned on to start the system, the idle speed reduction prohibition flag F is initialized to a value of 0. Therefore, the prohibition of idle speed reduction is used as a system switchover (until the system stops).

[0029] In the vehicle 20 of the above embodiment, when a predetermined stop condition for idling speed reduction is met, the operation of the engine 22 stops, and then when a predetermined start condition for idling speed reduction is met, the engine 22 is started by using the motor 30 powered by electricity from the high-voltage battery 60. When starting the engine 22 by the motor 30 fails, the engine 22 is started by using the starter motor 25 powered by electricity from the low-voltage battery 67, and subsequent idling speed reduction is prohibited. This reduces the chances of starting the engine 22 using the starter motor 25 powered by the low-voltage battery 67. Thus, the burden on the low-voltage battery 67 is reduced. In particular, even when a low-quality lead-acid battery is used as the low-voltage battery 67, the reduced burden on the low-voltage battery 67 helps to suppress inconveniences such as so-called terminal corrosion.

[0030] The vehicle 20 of this embodiment is configured such that it is feasible to start the engine 22 using a motor 30 powered by electricity from a high-voltage battery 60 and a starter motor 25 powered by electricity from a low-voltage battery 67. However, the vehicle 20 can have any configuration, as long as engine starting can be performed using different motors powered by different batteries. That is, the vehicle 20 is also applicable to various hybrid electric vehicles.

[0031] The following describes the correspondence between the main elements of the embodiment and the main elements of the present invention described in the field of the invention. In this embodiment, engine 22 corresponds to "engine", motor 30 corresponds to "first motor", high-voltage battery 60 corresponds to "first energy storage device", starter 25 corresponds to "second motor", "low-voltage battery 67" corresponds to "second energy storage device", and main electronic control unit 70 and engine electronic control unit 24 correspond to "control device".

[0032] It should be noted that the correspondence between the main elements of this embodiment and the main elements of the invention described in the field of the invention description is an example of a specific embodiment for carrying out the mode of the invention described in the field of the invention description. Therefore, the correspondence is not limited to the elements of the invention described in the field of the invention description. That is, the invention described in the field of the invention description should be interpreted based on the description in that field, and this embodiment is merely a specific example of the invention described in the field of the invention description.

[0033] The embodiments for carrying out the present invention have been described above with reference to examples. However, the present invention is not limited to such embodiments, and needless to say, the present invention can be implemented in various forms without departing from the spirit of the invention.

[0034] This invention can be used in the manufacturing industry of automobiles and other similar products.

Claims

1. A car, comprising: engine; A first motor, configured to start the engine; A first energy storage device, configured to supply power to the first motor; A second motor, configured to start the engine; A second energy storage device is configured to supply power to the second motor; as well as A control device configured to control the engine and the first electric motor to perform idle speed reduction control, such that... When the predetermined stopping condition is met, the control device stops the engine, and As the engine stops upon the fulfillment of the predetermined stop condition, the control device starts the engine by using the first motor when the predetermined start condition is met. When the engine is not started by using the first motor during the execution of idle speed reduction control as the predetermined start condition is met, the control device starts the engine by using the second motor and prohibits the engine from stopping as the predetermined stop condition is met thereafter, so as to reduce the chance of the second motor starting the engine by receiving power from the second energy storage device.

2. The automobile according to claim 1, wherein: The first energy storage device is a lithium-ion battery or a nickel-metal hydride battery; and The second energy storage device is a lead-acid battery.

3. The automobile according to claim 1 or 2, wherein, When the system is activated, if the temperature of the first energy storage device is equal to or higher than the threshold temperature, the control device starts the engine by using the first motor; however, if the temperature of the first energy storage device is lower than the threshold temperature, the control device starts the engine by using the second motor.

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