Patent ID: 12228102

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment for implementing the present invention will be described in detail with reference to the accompanying drawings.

FIG.1shows an example of a vehicle to which the present invention is applicable. The following description will be made using a truck100as an example of such a vehicle. However, the vehicle is not limited to the truck100, and it may be another vehicle such as a bus, a passenger car, or a construction machine.

The truck100includes an engine200, an idle reduction system300, and a starting system400for the engine200. The engine200is configured to drive rear wheels120by means of a clutch and a transmission (not shown). A diesel engine may be used as the engine200for the truck100, but a gasoline engine may be used as the engine200for a passenger car or the like. The idle reduction system300is configured, for example, to detect a decrease in vehicle speed or the like and stop the engine, and then to detect a driver's vehicle start operation or the like and start (restart) the engine, so as to achieve fuel saving and emission reduction. The starting system400is configured to start the engine200from the engine stop.

As shown inFIG.2, the engine200includes a cylinder block205, pistons210, a crankshaft215, connecting rods220, a cylinder head225, a cylinder head cover230, and an oil pan235. The cylinder block205has cylinder bores205A into which the pistons210are reciprocally fitted. The crankshaft215is disposed below the cylinder block205with bearings (not shown) interposed therebetween so as to be rotatable relative to the cylinder block205. The pistons210are connected to the crankshaft215by means of the connecting rods220so as to be rotatable relative to the crankshaft215.

The cylinder head225has intake ports225A for introducing intake air and exhaust ports225B for discharging exhaust gas. When the cylinder head225is fastened to the upper surface of the cylinder block205, spaces are defined by the cylinder bores205A of the cylinder block205, the crown surfaces of the pistons210, and the lower surface of the cylinder head225. These spaces function as combustion chambers240. Intake valves250configured to be opened and closed by an intake camshaft245are disposed at open ends, facing the combustion chambers240, of the intake ports225A. Exhaust valves260configured to be opened and closed by an exhaust camshaft255are disposed at open ends, facing the combustion chambers240, of the exhaust ports225B. In addition, fuel injectors265for injecting high-pressure fuel into the combustion chambers240are mounted at predetermined positions, facing the combustion chambers240, of the cylinder head225. As the fuel injectors265, common rail fuel injectors may be used, for example.

The cylinder head cover230for covering the valvetrain including the intake camshaft245and the exhaust camshaft255is detachably fastened to the upper surface of the cylinder head225. The oil pan235is configured to store a predetermined amount of lubricating oil OIL for lubricating components such as the bearings of the crankshaft215, the pistons210, and the valvetrain. The oil pan235is detachably fastened to the lower surface of the cylinder block205.

As shown inFIG.3, the idle reduction system300includes an electronic idle reduction control unit310. When there is an idle reduction request, such as when the driver depresses the brake pedal and the vehicle speed falls to or below a predetermined vehicle speed, the electronic idle reduction control unit310outputs an engine stop command to the electronic engine control unit. Then, when there is an engine start request, such as when the driver releases the depression of the brake pedal, the electronic idle reduction control unit310outputs an engine start command (engine restart command) to an electronic engine start control unit480. As shown inFIG.4, the electronic idle reduction control unit310includes therein a processor310A such as a central processing unit (CPU), a non-volatile memory310B, a volatile memory310C, an input/output circuit310D, a communication circuit310E, and an internal bus310F for communicatively connecting these components with each other.

The processor310A is hardware that executes a set of instructions (e.g., for data transfer, arithmetic processing, data processing, and data control and management) described in an application program (control program). The processor310A includes an arithmetic unit, registers storing instructions and data, peripheral circuits, and the like. The non-volatile memory310B is formed, for example, of a flash read only memory (ROM), which is capable of retaining data even after it is powered off. The non-volatile memory310B retains an application program (control program) for implementing a control unit of the idle reduction system300. The volatile memory310C is formed, for example, of a dynamic random access memory (RAM), which loses data retained therein when it is powered off. The volatile memory310C serves as a temporary storage area for data from arithmetic operations of the processor310A.

The input/output circuit310D includes an A/D converter, a D/A converter, a D/D converter, and the like. The input/output circuit310D provides functionality to input and output analog and digital signals to external devices. The communication circuit310E may include a controller area network (CAN) transceiver, for example. The communication circuit310E provides functionality to connect to an on-board network of the vehicle. The internal bus310F serves as a path for exchanging data between the components connected thereto. The internal bus310F includes an address bus for transferring addresses, data bus for transferring data, and a control bus for exchanging control information and information on when to actually perform input/output operations through the address bus and/or the data bus.

As shown inFIG.3, the electronic idle reduction control unit310receives, through the input/output circuit310D, output signals from an idle reduction switch320, a pedal stroke sensor330, a vehicle speed sensor340, and a state-of-battery sensor350. The idle reduction switch320for selection to activate or deactivate the idle reduction system300as necessary is mounted at a position facing the driver's seat of the truck100, for example. The idle reduction switch320outputs an “ON” signal to activate the idle reduction system300and outputs an “OFF” signal to deactivate the idle reduction system300. The pedal stroke sensor330is mounted, for example, near the brake pedal and outputs a brake pedal position POS. The vehicle speed sensor340is mounted, for example, to the output shaft of the transmission and outputs a vehicle speed VSP. The state-of-battery sensor350measures and outputs various conditions (state of battery) SBA of a battery470(seeFIGS.10to12). The state of battery SBA includes, but is not limited to, the charge rate, the discharge performance, and the state of charge of the battery470.

FIG.5shows an example of idle reduction control processing triggered by the activation of the electronic idle reduction control unit310and is repeatedly performed by the processor310A at predetermined time intervals in accordance with the application program (control program) stored in the non-volatile memory310B.

In step1(abbreviated as “S1” inFIG.5, the same applies to the other steps below), the processor310A reads the output signal from the idle reduction switch320and determines whether the idle reduction switch320is ON. When the processor310A determines that the idle reduction switch320is ON, i.e., determines activation of the idle reduction system300(Yes), the operation proceeds to step2. When the processor310A determines that the idle reduction switch320is OFF, i.e., determines deactivation of the idle reduction system300(No), the idle reduction control processing ends.

In step2, the processor310A reads the output signals from, for example, the pedal stroke sensor330, the vehicle speed sensor340, and the state-of-battery sensor350, and determines whether there is an idle reduction request to stop the engine200which is currently in operation. When the processor310A determines that there is an idle reduction request (Yes), the operation proceeds to step3. When the processor310A determines that there is no idle reduction request (No), the idle reduction control processing ends.

In step2, the processor310A determines that there is an idle reduction request and the truck100is in condition for idle reduction, when it determines that the following conditions (1) to (3) are satisfied, for example:(1) The brake pedal is depressed (The processor310A is able to determine whether the brake pedal is depressed, based on the brake pedal position POS);(2) The vehicle speed VSP is equal to or less than a predetermined vehicle speed (The predetermined vehicle speed is a threshold for determining whether the truck100has substantially stopped. For example, the predetermined vehicle speed may be defined in consideration of the resolution of the vehicle speed sensor340and/or the like. The predetermined vehicle speed may be set to zero); and(3) The state of battery SBA is sufficient to perform idle reduction.

In step3, the processor310A outputs the engine stop command to the electronic engine control unit. Upon receiving the engine stop command, the electronic engine control unit stops the engine200by, for example, controlling the fuel injectors265as appropriate.

In step4, the processor310A reads the output signals from, for example, the pedal stroke sensor330and the state-of-battery sensor350and determines whether there is an engine start request. When the processor310A determines that there is an engine start request (Yes), the operation proceeds to step5. When the processor310A determines that there is no engine start request (No), the processor310A waits until there is an engine start request.

In step4, the processor310A determines that there is an engine start request and the truck100is in condition for engine start, when it determines that at least one of the following conditions (4) and (5) is satisfied, for example:(4) The depression of the brake pedal is released (The processor310A is able to determine whether the depression of the brake pedal is released, based on the brake pedal position POS); and(5) The state of battery SBA indicates that the battery470requires immediate charging.

In step5, the processor310A outputs the engine start command (engine restart command) to the electronic engine start control unit480in the electronic engine control unit. Upon receiving the engine start command, the electronic engine start control unit480starts (restarts) the engine200by controlling the fuel injectors265and the starting system400as appropriate. After that, the idle reduction control processing ends.

According to the idle reduction control processing described above, when the idle reduction switch320is ON, the following operations are performed. When there is an idle reduction request while the engine is in operation, the engine stop command is output to the electronic engine control unit. Then, when there is an engine start request (engine restart request) after that, the engine start command (engine restart command) is output to the electronic engine start control unit480in the electronic engine control unit. As such, the idle reduction control processing described above enables fuel saving and emission reduction by stopping the engine200when the truck100is parked, stopped, or waiting for a traffic light. It should be noted that the above example of the idle reduction control processing is merely an illustrative example outlining the idle reduction control processing.

As shown inFIGS.6,7, and10to12, the starting system400includes an electric motor (starter motor)410, an air device420, an air reservoir (reservoir tank)440, the battery470, and an alternator475. The electric motor410is driven by electric power from the battery470. The battery470is configured to store electric power generated by the alternator475while the engine200is in operation. The electric power stored in the battery470may be supplied to various electrical loads. The air reservoir440is configured to store compressed air. The compressed air stored in the air reservoir440may be supplied to the brake booster, the air suspension system, and the like.

The air device420has two switchable operating modes: an air motor mode for operating as an air motor420′; and an air compressor mode for operating as an air compressor420″. In other words, the air device420is configured to operate as the air motor420′ when it is in the air motor mode, and also to operate as the air compressor420″ when it is in the air compressor mode. The air device420may be a reciprocating, vane, or axial air device, for example. The air device420, which is operable both as the air motor420′ and the air compressor420″, may be implemented using a well-known technique (see JP H02-298664 A, for example). As such, the configuration of the air device420will not be described in detail herein.

When the air device420operates as the air motor420′ at the start of the engine200, the air motor420′ is driven by compressed air from the air reservoir440. On the other hand, when the air device420operates as the air compressor420″ while the engine200is in operation, the air compressor420″ supplies compressed air into the air reservoir440. In other words, regarding the air device420, it can be understood that the air motor420′ is configured to function as the air compressor420″ while the engine200is in operation. Furthermore, regarding the air device420, it can be understood that the air compressor420″ is configured to function as the air motor420′ at the start of the engine200.

As shown inFIG.6, a ring gear275is fitted onto a flywheel270disposed at one end of the crankshaft215. When the engine200is started by the output of the electric motor410, which is a starter motor, a pinion415disposed at an end of the output shaft of the motor410advances and engages with the ring gear275. As a result, the rotational driving force of the electric motor410is transmitted to the crankshaft215through the pinion415, the ring gear275, and the flywheel270.

As shown inFIG.6, a gear280is attached at the one end of the crankshaft215so as to rotate integrally with the crankshaft215. A gear430is disposed at an end of a shaft425of the air motor420′. An idler gear285engages with the gears280,430. When the air device420operates as the air motor420′, the rotational driving force of the air motor420′ is transmitted to the crankshaft215through the shaft425, the gear430, the idler gear285, and the gear280. When the air device420operates as the air compressor420″, the rotational driving force of the engine200is transmitted to the shaft425of the air compressor420″ through the crankshaft215, the gear280, the idler gear285, and the gear430.

As shown inFIG.7, a pneumatic system405, which constitutes the starting system400, includes a first pipe450, a second pipe455, a first switching valve460, and a second switching valve465, in addition to the air device420(air motor420′/air compressor420″) and the air reservoir440described above. Each of the first switching valve460and the second switching valve465is a three-way valve, such as a 3-port solenoid valve.

The first pipe450connects an air inlet420A of the air device420to the air reservoir440. The first switching valve460is disposed at some midpoint of the first pipe450. Specifically, connection ports460A,460B of the first switching valve460are connected to the first pipe450.

The second pipe455connects an air outlet420B of the air device420to the air reservoir440. The second switching valve465is disposed at some midpoint of the second pipe455. Specifically, connection ports465A,465B of the second switching valve465are connected to the second pipe455.

To cause the air device420to operate as the air motor420′, the first switching valve460is positioned such that communication is established between the connection ports460A,460B, and a port460C open to the atmosphere is closed. In addition, the second switching valve465is positioned such that communication is established between the connection port465A and a port465C open to the atmosphere, and the connection port465B is closed. As a result, compressed air is supplied from the air reservoir440to the air device420, which thus operates as the air motor420′. After being used by the air motor420′, the air is discharged to the atmosphere through the second switching valve465. At that time, communication between the second switching valve465and the air reservoir440is disconnected.

To cause the air device420to operate as the air compressor420″, the first switching valve460is positioned such that communication is established between the connection port460A and the port460C open to the atmosphere, and the connection port460B is closed. In addition, the second switching valve465is positioned such that communication is established between the connection ports465A,465B, and the port465C open to the atmosphere is closed. When the engine200is in operation under the above conditions, air entering through the port460C is drawn into the air device420through the air inlet420A, and is compressed by the air device420(air compressor420″). Then, the compressed air discharged through the air outlet420B flows through the connection ports465A,465B of the second switching valve465, and is introduced into the air reservoir440.

As shown inFIG.3, the starting system400includes the electronic engine start control unit480(electronic control unit) for controlling the electric motor410, the air device420(air motor420′/air compressor420″), the first switching valve460, and the second switching valve465. As shown inFIG.8, the electronic engine start control unit480includes therein a processor480A such as a CPU, a non-volatile memory480B, a volatile memory480C, an input/output circuit480D, a communication circuit480E, and an internal bus480F for communicatively connecting these components with each other. Note that the configuration of the electronic engine start control unit480is basically the same as that of the electronic idle reduction control unit310, and thus, will not be further described herein so as to avoid redundant description. Please also refer to the above description for the electronic idle reduction control unit310, if necessary.

As shown inFIG.3, the electronic engine start control unit480receives, through the input/output circuit480D, an output signal from a pressure sensor490configured to measure an air pressure PCA in the air reservoir440. Through the communication circuit480E that provides connection, for example, to a CAN (controller area network)500, the electronic engine start control unit480is communicatively connected to the electronic idle reduction control unit310and the like.

The electronic engine start control unit480controls the air motor420′ (air device420), the first switching valve460, the second switching valve465, and/or the electric motor410such that the engine200is started by at least one, determined in accordance with the air pressure PCA in the air reservoir440measured by the pressure sensor490, of the output of the air motor420′ (air device420) and the output of the electric motor410.

FIG.9shows an example of engine start control processing for starting the engine200performed by the processor480A in accordance with the application program (control program) stored in the non-volatile memory480B. The processor480A is triggered to perform the engine start control processing when the electronic engine start control unit480receives the engine start command (engine restart command) output in step5in the above example of the idle reduction control processing. Here, at the start of the engine start control processing, the air device420is in the air compressor mode, i.e., the air device420is set to be operable as the air compressor420″.

In step11, the processor480A determines whether the pressure sensor490operates properly by using, for example, a self-diagnostic function implemented in the electronic engine start control unit480. When the processor480A determines that the pressure sensor490operates properly (Yes), the operation proceeds to step12. When the processor480A determines that the pressure sensor490does not operate properly (No), the operation proceeds to step15.

In step12, the processor480A reads the air pressure PCA in the air reservoir440from the pressure sensor490.

In step13, the processor480A determines whether or not the air pressure PCA is below a predetermined threshold P0. The predetermined threshold P0 is previously defined to determine whether the engine200can be started by the output of the air motor420′. When the processor480A determines that the air pressure PCA is not below the predetermined threshold P0 (Yes), the operation proceeds to step14. When the processor480A determines that the air pressure PCA is below the predetermined threshold P0 (No), the operation proceeds to step15.

In step14, the processor480A switches the air device420from the air compressor mode to the air motor mode so that the air device420becomes operable as the air motor420′ and uses the output of the air motor420′ to start the engine200. Specifically, the processor480A controls the first switching valve460such that communication is established between the connection ports460A,460B, and the port460C open to the atmosphere is closed. In addition, the processor480A controls the second switching valve465such that communication is established between the connection port465A and the port465C open to the atmosphere, and the connection port465B is closed. This causes compressed air to be supplied from the air reservoir440to the air motor420′, thereby activating the air motor420′. Thus, in step14, by controlling the first switching valve460and the second switching valve465, the processor480A controls the air motor420′ such that the engine200is started by the output of the air motor420′. In step14, the electric motor410is turned off. Then, (by controlling the first switching valve460and the second switching valve465,) the processor480A switches the air device420from the air motor mode to the air compressor mode so that the air device420becomes operable as the air compressor420″. After that, the engine start control processing ends.

In step15, the processor480A uses the output of the electric motor410to start the engine200. In other words, in step15, the processor480A controls the electric motor410such that the engine200is started by the output of the electric motor410. In step15, the air device420is maintained in the air compressor mode. After that, the engine start control processing ends.

According to the engine start control processing described above, the output of the air motor420′ may be used to start the engine200. This reduces the frequency of charging and discharging the battery470, thus extending the service life of the battery470.

FIG.10shows an illustrative example of how torque, electric current, and compressed air flow while the engine200is in operation.FIG.11shows an illustrative example of how torque, electric current, and compressed air flow when the engine200is started by the output of the air motor420′ (air device420).FIG.12shows an illustrative example of how torque, electric current, and compressed air flow when the engine200is started by the output of the electric motor410. In each ofFIGS.10to12, the blank arrow indicates a torque flow, the dashed arrow indicates an electric current flow, and the dashed-dotted arrow indicates a compressed air flow.FIGS.11and12correspond to steps14and15described above, respectively.

As shown inFIG.10, while the engine200is in operation, the output of the engine200is used not only to drive the truck100, but also to put the alternator475and the air compressor420″ (air device420) into operation. While the alternator475is in operation, it charges the battery470. While the air compressor420″ (air device420) is in operation, it supplies compressed air into the air reservoir440.

As shown inFIG.11, when the engine200is being started by the output of the air motor420′ (air device420), the air motor420′ (air device420) operates using compressed air from the air reservoir440.

As shown inFIG.12, when the engine200is being started by the output of the electric motor410, the electric motor410operates using electric power from the battery470.

FIG.13shows another example of engine start control processing for starting the engine200performed by the processor480A in accordance with the application program (control program) stored in the non-volatile memory480B. The processor480A is triggered to perform the engine start control processing when the electronic engine start control unit480receives the engine start command (engine restart command) output in step5in the above example of the idle reduction control processing. Here, at the start of the engine start control processing, the air device420is in the air compressor mode, i.e., the air device420is set to be operable as the air compressor420″.

In step21, the processor480A determines whether the pressure sensor490operates properly by using, for example, a self-diagnostic function implemented in the electronic engine start control unit480. When the processor480A determines that the pressure sensor490operates properly (Yes), the operation proceeds to step22. When the processor480A determines that the pressure sensor490does not operate properly (No), the operation proceeds to step27.

In step22, the processor480A reads the air pressure PCA in the air reservoir440from the pressure sensor490.

In step23, the processor480A determines whether or not the air pressure PCA is below a first predetermined threshold P1. The first predetermined threshold P1 is previously defined to determine whether the engine200can be started solely by the output of the air motor420′. When the processor480A determines that the air pressure PCA is not below the first predetermined threshold P1 (Yes), the operation proceeds to step24. When the processor480A determines that the air pressure PCA is below the first predetermined threshold P1 (No), the operation proceeds to step25.

In step24, the processor480A switches the air device420from the air compressor mode to the air motor mode so that the air device420becomes operable as the air motor420′ and uses the output of the air motor420′ to start the engine200. Specifically, the processor480A controls the first switching valve460and the second switching valve465as in step14described above. This causes compressed air to be supplied from the air reservoir440to the air motor420′, thereby activating the air motor420′. Thus, in step24, by controlling the first switching valve460and the second switching valve465, the processor480A controls the air motor420′ such that the engine200is started by the output of the air motor420′. In step24, the electric motor410is turned off. Then, (by controlling the first switching valve460and the second switching valve465) the processor480A switches the air device420from the air motor mode to the air compressor mode so that the air device420becomes operable as the air compressor420″. After that, the engine start control processing ends.

In step25, the processor480A determines whether or not the air pressure PCA is below a second predetermined threshold P2. The second predetermined threshold P2 is previously defined to determine whether the engine200can be started by the output of the air motor420′ with the assistance of the output of the electric motor410. The second predetermined threshold P2 is set to a value lower than that of the first predetermined threshold P1. When the processor480A determines that the air pressure PCA is not below the second predetermined threshold P2 (Yes), the operation proceeds to step26. When the processor480A determines that the air pressure PCA is below the second predetermined threshold P2 (No), the operation proceeds to step27.

In step26, the processor480A switches the air device420from the air compressor mode to the air motor mode so that the air device420becomes operable as the air motor420′ and uses the combination of the output of the air motor420′ and the output of the electric motor410to start the engine200. Specifically, the processor480A controls the first switching valve460and the second switching valve465as in step14described above. This causes compressed air to be supplied from the air reservoir440to the air motor420′, thereby activating the air motor420′. Thus, in step26, by controlling the first switching valve460, the second switching valve465, and the electric motor410, the processor480A controls the air motor420′ and the electric motor410in parallel such that the engine200is started by both the output of the air motor420′ and the output of the electric motor410. Then, (by controlling the first switching valve460and the second switching valve465,) the processor480A switches the air device420from the air motor mode to the air compressor mode so that the air device420becomes operable as the air compressor420″. After that, the engine start control processing ends.

In step27, the processor480A uses the output of the electric motor410to start the engine200. In other words, in step27, the processor480A controls the electric motor410such that the engine200is started by the output of the electric motor410. In step27, the air device420is maintained in the air compressor mode. After that, the engine start control processing ends.

According to the engine start control processing described above, the output of the air motor420′ alone or the combination of the output of the air motor420′ and the output of the electric motor410may be used to start the engine200. This reduces the frequency of charging and discharging the battery470and/or the amount of discharge from the battery470, thus extending the service life of the battery470.

FIG.14shows an illustrative example of how torque, electric current, and compressed air flow when the engine200is started by both the output of the air motor420′ (air device420) and the output of the electric motor410. InFIG.14, the blank arrow indicates a torque flow, the dashed arrow indicates an electric current flow, and the dashed-dotted arrow indicates a compressed air flow.FIG.14corresponds to step26described above.

As shown inFIG.14, when the engine200is being started by both the output of the air motor420′ (air device420) and the output of the electric motor410, the air motor420′ (air device420) operates using compressed air from the air reservoir440and the electric motor410operates using electric power from the battery470in a parallel manner.

In an aspect according to this embodiment, a starting system control method for controlling a starting system400of an engine200mounted on a truck100, which is an example of a vehicle, is provided. Here, the starting system400includes an air reservoir440, an air motor420′ driven by compressed air supplied from the air reservoir440, a battery470, an electric motor410driven by electric power from the battery470, and an electronic engine start control unit480(electronic control unit). The method includes the step (steps13to15and23to27), performed by the electronic engine start control unit480, of: controlling the air motor420′ and/or the electric motor410so that the engine200is started by at least one, determined in accordance with an air pressure PCA in the air reservoir440, of an output of the air motor420′ and an output of the electric motor410. The method allows reducing the frequency of charging and discharging the battery470and/or the amount of discharge from the battery470, thus extending the service life of the battery470.

Furthermore, in another aspect according to this embodiment, in the step of controlling the air motor420′ and/or the electric motor410(steps13to15): when the air pressure PCA in the air reservoir440is equal to or greater than a predetermined threshold P0, the air motor420′ is controlled so that the engine200is started by the output of the air motor420′ (steps13and14); and when the air pressure PCA in the air reservoir440is less than the predetermined threshold P0, the electric motor410is controlled so that the engine200is started by the output of the electric motor410(steps13and15). This reduces the frequency of charging and discharging the battery470, thus extending the service life of the battery470.

Furthermore, in another aspect according to this embodiment, in the step of controlling the air motor420′ and/or the electric motor410(steps23to27): when the air pressure PCA in the air reservoir440is equal to or greater than a first predetermined threshold P1, the air motor420′ is controlled so that the engine200is started by the output of the air motor420′ (steps23and24); when the air pressure PCA in the air reservoir440is less than a second predetermined threshold P2 that is lower than the first predetermined threshold P1, the electric motor410is controlled so that the engine200is started by the output of the electric motor410(steps23,25, and27); and when the air pressure PCA in the air reservoir440is less than the first predetermined threshold P1 and equal to or greater than the second predetermined threshold P2, the air motor420′ and the electric motor410are controlled so that the engine200is started by both the output of the air motor420′ and the output of the electric motor410(steps23,25, and26). This reduces the amount of discharge from the battery470of charging and discharging the battery470, thus extending the service life of the battery470.

Furthermore, in another aspect according to this embodiment, the air motor420′ is configured, when the engine200is in operation, to function as an air compressor420″ that supplies compressed air to the air reservoir440. In other words, the air device420is configured to operate as the air motor420′ when it is in the air motor mode, and also to operate as the air compressor420″ when it is in the air compressor mode. Thus, the starting system400uses fewer components than other comparable systems each including an air motor and an air compressor separated from each other.

Furthermore, in another aspect according to this embodiment, a truck100, which is an example of a vehicle, is equipped with an idle reduction system300, and the engine200is stopped by the idle reduction system300before the engine200is started (steps3to5). This reduces the frequency of charging and discharging the battery470in the truck100equipped with the idle reduction system300.

Furthermore, in another aspect according to this embodiment, the idle reduction system300includes an idle reduction switch320(switch) for selecting whether to activate or deactivate the idle reduction system300, and the step of controlling the air motor420′ and/or the electric motor410(steps13to15, and23to27) is performed by the electronic engine start control unit480(electronic control unit) when the idle reduction switch320is operated to select to activate the idle reduction system300(step1). This allows the driver to select whether to activate idle reduction control.

Furthermore, in another aspect according to this embodiment, the air pressure PCA in the air reservoir440is measured by a pressure sensor490. The step of controlling the air motor420′ and/or the electric motor410(steps13to15, and23to27) is performed by the electronic engine start control unit480(electronic control unit) when the pressure sensor490operates properly (steps11and21). When the pressure sensor490does not operate properly, the electric motor410may be controlled so that the engine200is started by the output of the electric motor410.

Furthermore, in another aspect according to this embodiment, the electronic engine start control unit480(starting system controller) for controlling the starting system400may be configured to perform the step according to any of the above aspects. In another aspect according to this embodiment, a starting system control program for controlling the starting system400may include a program code which, when executed on a computer, causes the computer to perform the step according to any of the above aspects. In another aspect according to this embodiment, a computer-readable medium carrying a starting system control program for controlling the starting system400may include a program code which, when executed on a computer, causes the computer to perform the step according to any of the above aspects.

Furthermore, in another aspect according to this embodiment, a starting system400of an engine200mounted on a truck100, which is an example of a vehicle, includes: an air reservoir440; an air motor420′ driven by compressed air supplied from the air reservoir440; a battery470; an electric motor410driven by electric power from the battery470; and an electronic engine start control unit480(electronic control unit) configured to control the air motor420′ and/or the electric motor410so that the engine200is started by at least one, determined in accordance with an air pressure PCA in the air reservoir440, of an output of the air motor420′ and an output of the electric motor410. The configuration allows reducing the frequency of charging and discharging the battery470, thus extending the service life of the battery470.

The application program (control program) may be stored in a computer-readable medium such as an SD (secure digital) card or a USB (universal serial bus) memory and sold commercially. As an alternative, the application program (control program) may be stored in a storage at a node connected to the Internet or the like and distributed from this node. In this case, the storage at the node is understood to be an example of the computer-readable medium.

It should be noted that one skilled in the art can easily understand that some of the technical features in the above embodiment may be omitted, replaced with one or more well-known technical features, and/or combined with one or more well-known technical features to provide various alternative embodiments.

For example, although the electronic engine start control unit480is incorporated in the electronic engine control unit in the above embodiment, the electronic engine start control unit480may be incorporated in an electronic control unit other than the electronic engine control unit. As another alternative, the electronic engine start control unit480may be a separate unit from the electronic engine control unit.

Furthermore, the idle reduction control processing may further include, before step2, an additional step in which the processor310A determines whether the air pressure PCA in the air reservoir440measured by the pressure sensor490is not below a predetermined threshold P3. In this alternative idle reduction control processing, when the processor310A determines that the air pressure PCA is not below the predetermined threshold P3 (Yes), the operation may proceed to step2. When the processor310A determines that the air pressure PCA is below the predetermined threshold P3 (No), the idle reduction control processing may end. It is preferable that the predetermined threshold P3 be substantially equal to or lower than the predetermined threshold P0 described above. Furthermore, it is also preferable that the predetermined threshold P3 be substantially equal to or lower than the second predetermined threshold P2.

Alternatively or additionally, the idle reduction control processing may further include, before step2, an additional step in which the processor310A determines whether the pressure sensor490operates properly by using, for example, a self-diagnostic function implemented in the electronic idle reduction control unit310. In this alternative idle reduction control processing, when the processor310A determines that the pressure sensor490operates properly (Yes), the operation may proceed to step2. When the processor310A determines that the pressure sensor490does not operate properly (No), the idle reduction control processing may end.

Furthermore, the air motor420′ included in the starting system400does not have to have the functionality to operate as the air compressor420″. In other words, the air motor420′ and the air compressor420″ may be separate devices from each other.

Furthermore, instead of reading the brake pedal position POS from the pedal stroke sensor330and the vehicle speed VSP from the vehicle speed sensor340, the electronic idle reduction control unit310may acquire the brake pedal position POS and the vehicle speed VSP through, for example, communication with another electronic control unit.

Furthermore, the starting system400and the engine start control processing described above may not only be used to start (restart) the engine200after the engine200is stopped by the idle reduction system300, but may also be applied to normal startup of the engine200.

REFERENCE SIGNS LIST

100Truck (Vehicle)200Engine300Idle reduction system310Electronic idle reduction control unit320Idle reduction switch400Starting system405Pneumatic system410Electric motor420Air device420′ Air motor420″ Air compressor440Air reservoir450First pipe455Second pipe460First switching valve465Second switching valve470Battery475Alternator480Electronic engine start control unit (Electronic control unit)490Pressure sensor