Generator driven by engine

When an acceptance unit accepts an advance notice, a control unit, controls inflow amount of the air, an air fuel ratio derived from an injection amount of a fuel, and an advance of an ignition timing of an ignition device to temporarily increase a power that can be supplied by a generator. The control unit is determines whether a margin of an opening of a throttle is not less than a predetermined threshold. If the margin of the opening of the throttle is less than the predetermined threshold, the control unit inhibits a temporarily increase of the power. If the margin of the opening of the throttle is not less than the predetermined threshold, the control unit permits the temporarily increase of the power.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an engine generator comprising a generator driven by an engine.

Description of the Related Art

A portable generator including an internal combustion engine is used to supply power to an electric device at a construction site, an outdoor leisure, or a stall. PTL 1 proposes driving an engine at a rotation speed corresponding to the magnitude of a load at the time of activating the load.

SUMMARY OF INVENTION

The portable generator is sometimes used to supply power to an air conditioner mounted on an RV (recreational vehicle). Such an air conditioner includes a motor (induction motor) and a compressor. When activating the air conditioner, the motor needs starting power more than a rated value. Hence, even if a user prepares a generator of a power generation capacity corresponding to the rated value of the motor, the air conditioner cannot be activated. By the method of PTL 1, the rotation speed of the engine cannot immediately rise to the rotation speed corresponding to the starting power of the air conditioner, and after all, the engine stalls. Hence, the user needs to purchase a generator of a larger power generation capacity again, and the usability is poor. It is therefore an object of the present invention to provide an engine generator capable of supplying power, without stall, to a load that needs relatively large power at the time of activation.

According to the present invention, for example, there is provided an engine generator comprising: an engine: a throttle configured to adjust an inflow amount of air to be supplied to the engine; an injection device configured to inject fuel to the engine; an ignition device configured to ignite a gas mixture of the fuel and the air in the engine; a generator driven by the engine to generate power; a supply unit configured to supply the power generated by the generator to an external load; an acceptance unit configured to accept an advance notice representing that the power is supplied from the supply unmit to the external load; and a control unit configured to, when the acceptance unit accepts the advance notice, control the inflow amount of the air, an air fuel ratio derived from an injection amount of the fuel, and an advance of an ignition timing of the ignition device to temporarily increase the power that can be supplied by the generator, wherein the control unit is configured to determine whether a margin of an opening of the throttle is not less than a predetermined threshold, wherein if the margin of the opening of the throttle is less than the predetermined threshold, the control unit inhibits a temporarily increase of the power, and if the margin of the opening of the throttle is not less than the predetermined threshold, the control unit permits the temporarily increase of the power.

According to the present invention, there is provided an engine generator capable of supplying power, without stall, to a load that needs relatively large power at the time of activation.

Other features and advantages of the present invention will be apparent from the following descriptions taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

FIG. 1is a schematic view showing an engine system100. The engine system100may be called an electronically controlled fuel injection control system. An internal combustion engine1is a 4-stroke engine. A crankshaft19is stored in a crankcase2. When the crankshaft19rotates, a piston4connected to a connecting rod3moves in the vertical direction in a cylinder. A recoil starter5used to start the internal combustion engine1is connected to the crankshaft19. A recoil operator grasps and pulls the handle of the recoil starter5, thereby rotating the crankshaft19. A generator6is connected to the crankshaft19. When the crankshaft19rotates, the rotor of the generator6rotates and generates power. The crank angle of the crankshaft19is detected by a crank angle sensor7. The crank angle sensor7may be, for example, a Hall element configured to detect the magnetism of a magnet41provided on a flywheel40connected to the crankshaft19. The detection result of the crank angle sensor7may be used to calculate the engine speed. A power supply circuit8includes an inverter that converts an AC generated by the generator6into an AC of a predetermined frequency, a circuit that converts the AC into a DC, a circuit that converts the level of the DC voltage, and the like. The power supply circuit8supplies the power generated by the generator6to a control unit9. Note that when the crankshaft19is rotated by the recoil starter5, the generator6generates sufficient power for the control unit9to operate. The control unit9is an engine control unit (ECU) and controls the power supplied from the power supply circuit8to an ignition device11, a fuel pump14, an injector15, a throttle motor16, and the like. The ignition device11supplies ignition power to cause a spark plug12to cause spark discharge. A fuel tank13is a container that stores fuel. The fuel pump14is a pump that supplies fuel stored in the fuel tank13to the injector15. Referring toFIG. 1, the fuel pump14is provided in the fuel tank. The throttle motor16is a motor configured to control the inflow amount of air flowing into the cylinder via an intake path50. An intake valve17is a valve to be opened/closed by a cam configured to convert the rotary motion of the crankshaft19into a vertical motion, and the like. The intake valve17is opened in an intake stroke and is basically closed in a compression stroke, an expansion stroke, and an exhaust stroke. An exhaust valve18is a valve to be opened/closed by a cam configured to convert the rotary motion of the crankshaft19into a vertical motion, and the like. The exhaust valve18is opened in the exhaust stroke and is basically closed in the compression stroke, the expansion stroke, and the intake stroke. For smooth transition from exhaust to intake, a period in which the intake valve17and the exhaust valve18are simultaneously opened may be provided (overlap). An02sensor42is a sensor that detects an oxygen concentration in an exhaust gas discharged from the cylinder to an exhaust path51. A temperature sensor43is a sensor that detects the temperature of the internal combustion engine1.

<Control Unit and Power Supply Circuit>

FIG. 2shows the function of the control unit9and the function of the power supply circuit8. The function of the control unit9may be implemented by hardware such as an ASIC or FPGA, or may be implemented by executing a control program stored in a memory by a CPU. ASIC is an abbreviation for an application specific integrated circuit. FPGA is an abbreviation for a field programmable gate array. CPU is an abbreviation for a central processing unit. The control unit9may be call as a controller, a control circuit or a processor.

A setting unit20is a unit that sets the control parameters of the internal combustion engine1. The setting unit20controls the throttle motor16via a throttle control unit23to adjust the inflow amount of air. The engine speed is thus controlled. The setting unit20controls the ignition device11via an ignition control unit24. The ignition control unit24adjusts the advance of the ignition timing based on the detection result of the crank angle sensor7. The setting unit20may decide a target air fuel ratio in accordance with the temperature of the internal combustion engine1detected by the temperature sensor43, the load of the generator6, ON/OFF of a workout switch25, and the like. The setting unit20may convert the detection result of the02sensor42into an air fuel ratio, drive the fuel pump14via a pump control unit27, and adjust the supply amount of fuel such that the air fuel ratio becomes the target air fuel ratio. The setting unit20may discriminate the engine stroke based on the detection result of the crank angle sensor7, and control the injection timing of the injector15via an injector control unit26in accordance with the engine stroke. The workout switch25is a switch configured to give an advance notice of connection of an external load (start of supply of large power) before connection of the external load to an AC outlet33. When the advance note is accepted by the workout switch25, the setting unit20raises the rotation speed of the internal combustion engine1up to a workout rotation speed in advance so the internal combustion engine1does not stall even if the external load is connected. The workout rotation speed is higher than an upper limit value in normal driving. Hence, the generator6can temporarily increase the output. The setting unit20makes the internal combustion engine1transition to a workout state in accordance with a workout instruction input from the workout switch25or a workout instruction received from a remote controller, a smartphone, or the like via a communication circuit21. The workout state is a state in which the internal combustion engine1is operating at the workout rotation speed. A timer28is a timer used to monitor the duration of the workout state so the duration does not exceed a limit time. This protects the internal combustion engine1. A determination unit29determines whether the internal combustion engine1can transition to the workout state. An output unit37outputs a warning if the internal combustion engine1cannot transition to the workout state. This is because if an air conditioner or the like is connected when the internal combustion engine1cannot transition to the workout state, the internal combustion engine1stalls. Note that the output unit37may output a notification representing that the internal combustion engine1can transition to the workout state (that is, an air conditioner or the like can be connected). This allows the user to connect an external load60such as an air conditioner to the AC outlet33without worries.

In the power supply circuit8, an inverter30is a conversion circuit that converts an AC generated by the generator6into an AC of a predetermined frequency. A rectifying circuit31is a circuit that rectifies the AC generated by the AC generated by the generator6. A smoothing circuit32is a circuit that generates a DC by smoothing a pulsating current generated by the rectifying circuit31. Accordingly, a DC voltage of for example, 12 V is generated. The control unit9may PWM-control the power supplied to the fuel pump14in accordance with the load of the generator6or the internal combustion engine1. A DC/DC converter35is a circuit that converts the level of the DC voltage. For example, the DC/DC converter35converts the DC voltage of 12 V into a DC voltage of 5 V or 3.3 V. The DC/DC converter35supplies the DC voltage from a DC outlet34to an external load.

The inverter30supplies an AC voltage to an external load via the AC outlet33. In particular, a switch36(option) to be turned on/off by the setting unit20may be provided between the inverter30and the AC outlet33. The switch36may be a semiconductor switch, a relay circuit, or the like. When a workout instruction is accepted, the setting unit20may keep the switch36off until transition to the workout state is possible, and may turn on the switch36when it is possible to transition to the workout state. Stall of the internal combustion engine1may thus be suppressed.

An output monitoring unit52monitors the output of the generator6. For example, if the AC outlet33includes a plurality of outlet receptacles, power can be supplied to a plurality of external loads. Hence, when an air conditioner is to be connected to an outlet receptacle, it can be considered that another external load is already connected to another outlet receptacle. Hence, if the sum of the starting power of the air conditioner and the power supplied to the other external load exceeds workout power, the generator6cannot supply the starting power to the air conditioner. Hence, the determination unit29may determine, based on the monitoring result of the output monitoring unit52, whether transition to the workout state is possible (whether it is possible to supply starting power to the air conditioner). It is assumed here that the generation capability of the generator6and the starting power of the air conditioner in the workout state almost match.

FIG. 3is a flowchart for explaining a workout operation.

In step S301, the setting unit20determines whether a workout instruction is accepted. When a workout instruction is accepted via the workout switch25or the communication circuit21, the setting unit20advances to step S302. The workout instruction may be, for example, switching the workout switch25from OFF to ON.

In step S302, the determination unit29acquires the state of the internal combustion engine1and the state of the generator6. For example, the determination unit29may acquire the engine temperature from the temperature sensor43. The determination unit29may acquire information representing the current output of the generator6from the output monitoring unit52. The determination unit29may acquire the opening (a throttle opening or throttle margin) of the throttle motor16via the throttle control unit23.

In step S303, the determination unit29may determine, based on the state of the internal combustion engine1and the state of the generator6, whether the internal combustion engine1can work out. Conditions to enable workout (workout conditions) are, for example, as follows.

The engine temperature is equal to or less than a temperature threshold.

The current output of the generator6is equal to or less than an output threshold.

The throttle margin is equal to or more than a threshold.

If the workout conditions are satisfied, the determination unit29advances to step S304. If the workout conditions are not satisfied, the determination unit29advances to step S310. In step S310, the determination unit29outputs, to the output unit37, a warning representing that workout is impossible. For example, the output unit37may light a red LED representing that workout is impossible. Alternatively, the output unit37may include a display device that displays a message representing that workout is impossible. The output unit37may transmit a warning to a remote controller or a smartphone via the communication circuit21.

In step S304, the determination unit29or the setting unit20resets the timer28and starts counting. The timer28measures the duration of the workout operation.

In step S305, the setting unit20reads out control parameters for the workout operation from a memory22, and sets them in the throttle control unit23, the ignition control unit24, the pump control unit27, and the like. The control parameters include, for example, a target rotation speed, an air fuel ratio, the advance of an ignition timing, and the like.

FIG. 4shows the relationship between a rotation speed, a shaft output, and an output torque. The shaft output of the internal combustion engine1is the product of the torque and the rotation speed. For example, if a predetermined torque is set for the rotation speed, the shaft output increases in proportion to the rotation speed. That is, the output of the generator6also increases in proportion to the rotation speed. If power is to be abruptly supplied to an external load, the rotation speed of the internal combustion engine1lowers. In addition, the internal combustion engine1that is operating at an idle rotation speed stalls when a workout condition is connected to the generator6. Hence, before an air conditioner is connected to the generator6, the control unit9raises the rotation speed of the internal combustion engine1up to a workout rotation speed. When the air conditioner is connected, the rotation speed of the internal combustion engine1becomes lower than the workout rotation speed. However, stall can be prevented. As described above, if the rotation speed of the internal combustion engine1reaches the workout rotation speed, the control unit9may start supplying power to the external load.

FIG. 5shows the relationship between an air fuel ratio (A/F ratio) and a shaft output. In general, it is known that when the A/F ratio is 12.0 to 12.5, the shaft output of a gasoline engine is maximized. On the other hand, when hydrocarbon contained in gasoline and oxygen contained in air are made to react, H2O and CO2are generated. It is also known here that the A/F ratio (stoichiometric ratio) at which neither of air and oxygen becomes excess is 14.7. If focus is placed on exhaust gas emission, the A/F ratio is generally set to 14.7 (stoichiometric control). If focus is placed on suppression of fuel consumption, the A/F ratio is increased up to about 18 (lean burn control). In this case, since the shaft output considerably lowers, the load driving capability of the generator6also lowers. However, this state suffices for the generator6to drive a light load. When a workout instruction is input, the control unit9stops stoichiometric control or lean burn control, and sets the A/F ratio to a value from 12.0 (inclusive) to 12.5 (inclusive). As shown inFIG. 5, within the A/F ratio range from 12.0 (inclusive) to 12.5 (inclusive), the shaft output is expected to be maximized.

FIG. 6shows the relationship between a rotation speed and an output torque. The ignition timing in which the maximum output torque can be expected is called an MBT (Minimum-advanced for Best Torque). However since priority is given to stabilization of the rotation of the internal combustion engine1, the ignition timing is not set to the MBT in most cases. Hence, when a workout instruction is input, the setting unit20sets the ignition timing to the MBT. Accordingly, the output expected value is maximized.

In step S306, the determination unit29acquires the state of the internal combustion engine1, the state of the generator6, and the count value (timer value) of the timer28.

In step S307, the determination unit29determines whether the internal combustion engine1can continue the workout operation. Conditions to enable continuation of the workout operation (continuation conditions) are, for example, as follows.

The engine temperature is equal to or less than a temperature threshold.

The current output of the generator6is equal to or less than the maximum output value.

The throttle margin is equal to or more than a threshold.

The workout duration measured by the timer28is equal to or less than a limit time.

Upon determining that the internal combustion engine1can continue workout, the determination unit29returns to step S306. On the other hand, upon determining that the internal combustion engine1cannot continue the workout operation, the determination unit29advances to step S308.

In step S308, the setting unit20reads out control parameters for a normal operation from the memory22, and sets them in the throttle control unit23, the ignition control unit24, the pump control unit27, and the like. The control parameters include, for example, a target rotation speed, an air fuel ratio, the advance of an ignition timing, and the like.

According to the present invention, the engine system100is an example of an engine generator. The throttle motor16is an example of a throttle configured to adjust the inflow amount of air to be supplied to the internal combustion engine1. The fuel pump14and the injector15are an example of an injection device configured to inject or supply fuel to the internal combustion engine1. The ignition device11is an example of an ignition device configured to ignite a gas mixture of the fuel and the air in the internal combustion engine1. The generator6is an example of a generator driven by the internal combustion engine1to generate power. The AC outlet33is an example of a supply unit configured to supply the power generated by the generator6to an external load (RV air conditioner or the like). The workout switch25or the communication circuit21is an example of an acceptance unit configured to accept an advance notice representing that the power is supplied from the supply unit to the external load. As described above, the advance notice suggests the start of supply of large power. When the acceptance unit accepts the advance notice, the control unit9controls the inflow amount of air, the air fuel ratio derived from the injection amount of fuel, and the advance of the ignition timing of the ignition device to temporarily increase the power that can be supplied by the generator6. This provides an engine generator that hardly stalls while supplying power to a load that needs relatively large power at the time of activation.

As shown inFIG. 2, the timer28is an example of a timer configured to start counting time when the advance notice is accepted. When the advance notice is accepted, the control unit9increases the inflow amount of the air, enriches the air fuel ratio derived from the injection amount of the fuel, and increases the advance of the ignition timing of the ignition device to increase the power that can be supplied by the generator6. When the time counted by the timer28becomes not less than a predetermined time, the control unit9returns the inflow amount of the air, the air fuel ratio derived from the injection amount of the fuel, and the advance of the ignition timing of the ignition device to original values (e.g., parameters for a normal operation). An external load using an induction motor, such as an air conditioner, needs large power at the time of activation. However, the time in which the large power is necessary is not so long. Hence, fuel consumption can be reduced by limiting the time for operating the internal combustion engine1at the workout rotation speed. In addition, a mechanical burden on the internal combustion engine1is also reduced.

The determination unit29is an example of an output determination unit for determining, when the advance notice is accepted, whether the output of the generator6exceeds a predetermined threshold. If the output of the generator6exceeds the predetermined threshold, the control unit9inhibits a temporarily increase of the power. On the other hand, if the output of the generator6does not exceed the predetermined threshold, the control unit9permits the temporarily increase of the power. This suppresses stall of the internal combustion engine1. It is also considered that the generator6already supplies power to another external load before an external load such as an air conditioner is connected. In this case, it may be impossible to supply sufficient activation power to an external load such as an air conditioner. Hence, the temporarily increase of the power is inhibited or permitted in accordance with the current output of the generator6, thereby suppressing stall of the internal combustion engine1.

The temperature sensor43is an example of a temperature sensor configured to detect the temperature of the internal combustion engine1. The determination unit29is an example of a temperature determination unit for determining, when the advance notice is accepted, whether the temperature of the internal combustion engine1is a temperature at which a temporarily increase of the power can be permitted. If the temperature of the internal combustion engine1is not the temperature at which the temporarily increase of the power can be permitted, the control unit9inhibits the temporarily increase of the power. If the temperature of the internal combustion engine1is the temperature at which the temporarily increase of the power can be permitted, the control unit9permits the temporarily increase of the power. This suppresses the stall of the internal combustion engine1.

The determination unit29is an example of a throttle determination unit for determining whether a margin of an opening of the throttle is not less than a predetermined threshold. If the margin of the opening of the throttle is less than the predetermined threshold, the control unit9inhibits a temporarily increase of the power, and if the margin of the opening of the throttle is not less than the predetermined threshold, the control unit9permits the temporarily increase of the power. This suppresses the stall of the internal combustion engine1while ensuring the controllability of the throttle.

The output unit37is an example of an output unit for outputting a notification warning about connection of an excessive external load to the supply unit when the temporarily increase of the power should be inhibited. This prevents the user for connecting an excessive external load.

The workout switch25is an example of a switch configured to switch between a state in which the temporarily increase of the power is requested and a state in which the temporarily increase of the power is canceled. The communication circuit21is an example of a communication unit for receiving an instruction to switch between a state in which the temporarily increase of the power is requested and a state in which the temporarily increase of the power is canceled.

The control unit9may set the air fuel ratio to a value within a range between 12.0 (inclusive) and 12.5 (inclusive) to temporarily increase the power that can be supplied by the generator6. This is because at the air fuel ratio of 12.0 (inclusive) to 12.5 (inclusive), the shaft output is expected to be maximized, as shown inFIG. 5.

The control unit9may set the ignition timing of the ignition device11to an MBT (Minimum-advanced for Best Torque) to temporarily increase the power that can be supplied by the generator6. This is because with the MBT, the output torque is expected to be maximized.