Alcohol-containing fuel engine system and vehicle

Abstract

Provided are: an alcohol-containing fuel engine system capable of achieving both reproducibility of early combustion and target trackability of the engine rotation speed in an engine in which in-cylinder injection is not performed; and a vehicle comprising the alcohol-containing fuel engine system. The alcohol-containing fuel engine system comprises an alcohol-containing fuel engine, a starter motor, a control device, a combustion chamber, an intake passage, an intake valve, an air intake amount adjustment device, and an in-passage alcohol fuel injection device. In a first combustion cycle after causing the starter motor to start rotation of a crankshaft, the control device causes the intake air amount adjustment device to take in an amount of air smaller than an amount of air corresponding to a high idle state in the alcohol-containing fuel engine and causes an amount of an alcohol-containing fuel smaller than a maximum injection amount to be injected into the in-passage alcohol fuel injection device so that effective combustion occurs from a second combustion cycle following the first combustion cycle. In the second combustion cycle, the control device causes the intake air amount adjustment device to take in an amount of air smaller than the amount of air corresponding to the high idle state of the alcohol-containing fuel engine and causes an amount of the alcohol-containing fuel smaller than the maximum injection amount to be injected into the in-passage alcohol fuel injection device.

Description

Alcohol-containing fuel engine system and vehicle

[0001] The present invention relates to an engine system using an alcohol-containing fuel and a vehicle equipped with the same.

[0002] Patent Document 1 relates to an engine in which alcohol-containing fuel is supplied to an intake path (see, for example, claim 1 of Patent Document 1). The engine of Patent Document 1 has a main flow path with a throttle valve and a bypass flow path corresponding to the main flow path. Patent Document 1 discloses that a control means controls the bypass amount before the initial explosion to be less than the bypass amount after the initial explosion when the alcohol mixing ratio is equal to or greater than a predetermined value. According to the technology of Patent Document 1, the bypass amount before the initial explosion is less than the bypass amount after the initial explosion, thereby enriching the air-fuel ratio. This allows for a smooth initial explosion and improves the startability of the internal combustion engine (see, for example, paragraph

[0007] of Patent Document 1). Patent Document 1 also discloses controlling a fuel injection valve to increase the fuel injection amount before the initial explosion (see, for example, claim 7 of Patent Document 1).

[0003] JP 2009-74367 A

[0004] In an engine in which alcohol-containing fuel is supplied to the intake passage but direct injection is not performed, there are cases in which it is desired to achieve both reproducibility of early combustion and target tracking of the engine rotation speed during starting.

[0005] The object of the present invention is to provide an alcohol-containing fuel engine system that can achieve both the reproducibility of early combustion and the ability to track the target engine speed in an engine in which alcohol-containing fuel is supplied to the intake passage but in-cylinder injection is not performed, and a vehicle equipped with the same.

[0006] In view of the above-mentioned problems, the inventors of the present invention have conducted extensive research into how to achieve target engine speed tracking while ensuring the reproducibility of early combustion in an engine in which alcohol-containing fuel is supplied to the intake passage but direct cylinder injection is not performed, and have arrived at the following findings. When the engine is started, fuel is injected as a liquid into the intake passage. Some of the fuel is taken into the combustion chamber with the intake air following this injection, and some adheres to the intake passage wall and intake valve. Alcohol-containing fuel is less likely to vaporize. That is, alcohol-containing fuel tends to adhere more than non-alcohol-containing fuel. When injections are repeated, the amount of fuel that adheres to the intake passage wall and intake valve in the current injection is compensated for by the amount of fuel that adhered to the intake valve and wall in the previous injection and returns to the intake passage. However, since there is no previous injection in the first combustion cycle, the return of the fuel from the previous injection is not achieved. In contrast, in order to generate effective combustion from the combustion stroke of the second combustion cycle after the crankshaft starts to rotate, the amount of alcohol-containing fuel injected in the first combustion cycle is reduced below the maximum injection amount, and an amount of air less than that corresponding to a high idle state is taken in, and the amount of alcohol-containing fuel injected in the second combustion cycle is reduced below the maximum injection amount, and an amount of air less than that corresponding to a high idle state is taken in. This makes it possible to reproduce early combustion while also achieving target engine speed tracking. Based on this finding, the present invention was completed. Because the present invention is a technology related to the intake of alcohol-containing fuel from the intake passage into the combustion chamber, it is essentially different from technology related to engines with direct-cylinder injection.

[0007] The present invention can provide the following alcohol-containing fuel engine system.

[0008] (1) An alcohol-containing fuel engine system, comprising: an alcohol-containing fuel engine having a crankshaft and using an alcohol-containing fuel; a starter motor that drives the crankshaft to rotate the crankshaft; and a control device that controls at least the alcohol-containing fuel engine, wherein the alcohol-containing fuel engine has at least one cylinder, and each cylinder comprises: a combustion chamber; an intake passage through which air taken into the combustion chamber passes; an intake air amount adjustment device that adjusts the amount of air taken into the combustion chamber; and an in-passage alcohol fuel injection device configured to inject, into the intake passage, the entire amount of alcohol-containing fuel supplied into the combustion chamber, and the alcohol-containing fuel engine system is configured not to perform in-cylinder injection of the alcohol-containing fuel, and the control device controls, for at least one cylinder, In order to generate effective combustion from a second combustion cycle following the first combustion cycle, the in-passage alcohol fuel injection device is caused to inject an amount of alcohol-containing fuel smaller than the maximum injection amount, and the intake air amount adjustment device is caused to take in an amount of air smaller than the amount of air corresponding to a high idle state of the alcohol-containing fuel engine; and in the second combustion cycle, the in-passage alcohol fuel injection device is caused to inject an amount of alcohol-containing fuel smaller than the maximum injection amount, and the intake air amount adjustment device is caused to take in an amount of air smaller than the amount of air corresponding to the high idle state.

[0009] According to the alcohol-containing fuel engine system (1) above, the control device controls the alcohol-containing fuel engine to generate effective combustion starting from the second combustion cycle following the first combustion cycle after the crankshaft starts rotating. Specifically, the control device injects an amount of alcohol-containing fuel from the in-passage alcohol fuel injection device in the first combustion cycle less than the maximum injection amount and causes the alcohol-containing fuel engine to take in an amount of air less than the amount corresponding to a high idle state of the alcohol-containing fuel engine. A portion of the alcohol-containing fuel injected in the first combustion cycle, which is less than the maximum injection amount, adheres to the wall surface and the intake valve. As a result, the amount of alcohol-containing fuel taken into the combustion chamber is further reduced from the injection amount of the first injection. As a result, the alcohol-containing fuel injected in the first combustion cycle is used for combustion in the second combustion cycle. The control device reduces the amount of alcohol-containing fuel injected in the second combustion cycle less than the maximum injection amount and causes the engine to take in an amount of air less than the amount corresponding to a high idle state. A portion of the alcohol-containing fuel injected in the second combustion cycle also adheres to the wall surface and the intake valve. However, when the remaining unattached alcohol-containing fuel is introduced into the combustion chamber together with the air, it is mixed with the alcohol-containing fuel derived from the portion of the alcohol-containing fuel injected in the first combustion cycle that adhered to the wall surface and the intake valve. Furthermore, the intake passage pressure is reduced by narrowing the intake air volume, which increases the amount of alcohol-containing fuel evaporation. Furthermore, the concentration of alcohol-containing fuel in the combustion chamber is increased because the intake air volume is reduced. This increases the probability of effective combustion occurring in the combustion stroke of the second combustion cycle. In other words, the reproducibility of early combustion is further improved. Furthermore, since effective combustion in the first combustion cycle may be suppressed, the amount of alcohol-containing fuel injected in the first combustion cycle can be combined with the alcohol-containing fuel injected in the second combustion cycle to be used for effective combustion in the second combustion cycle. This prevents, for example, the amount of alcohol-containing fuel carried over to the second combustion cycle and thereafter from exceeding the target range when effective combustion is targeted in the combustion stroke of the first combustion cycle, or, conversely, prevents the alcohol-containing fuel from being carried over to the second combustion cycle.In other words, the rotation speed in the next combustion cycle is prevented from falling outside the target range. Therefore, the ability of the engine rotation speed to track the target at startup is further improved. In this way, in an engine in which alcohol-containing fuel is supplied to the intake passage but direct injection is not performed, it is possible to achieve both the reproducibility of early combustion and the ability of the engine rotation speed to track the target.

[0010] An alcohol-containing fuel is a fuel composition containing alcohol as a primary component. The term "primary component" here means that the alcohol is not an impurity or an unavoidable mixture, and includes, for example, at least 1% by volume. An alcohol-containing fuel may also contain a hydrocarbon fuel. A hydrocarbon fuel may also be included as a primary component. Examples of alcohols include, but are not limited to, methanol, ethanol, propanol, and butanol. The alcohol concentration (volume concentration) may be greater than 0% by volume or substantially 100% by volume. Examples of hydrocarbon fuels include, but are not limited to, gasoline. E3, E10, E15, E20, E25, E85, and E100 may be used. E indicates the volume percentage of ethanol in a gasoline-ethanol mixture. A mixture with a different composition but equivalent concentration may also be used. The composition and alcohol concentration of the alcohol-containing fuel are not particularly limited, as long as they are applicable to an alcohol-fueled engine.

[0011] An alcohol-containing fuel engine is not particularly limited as long as the upper limit of the alcohol concentration of the applicable alcohol-containing fuel is greater than 0% by volume. Examples of such upper limits include, by volume, 3, 10, 15, 20, 25, 85, and 100. An upper limit of 20% by volume means that the alcohol-containing fuel engine can use alcohol-containing fuels with alcohol concentrations up to 20% by volume. The higher the upper limit, the higher the alcohol-containing fuel concentration that can be used. An alcohol-containing fuel engine may be configured so that the lower limit of the alcohol concentration of the applicable alcohol-containing fuel is 0% by volume. In other words, an alcohol-containing fuel engine may be able to use hydrocarbon fuels (e.g., gasoline) that do not contain alcohol. The alcohol concentration of the applicable alcohol-containing fuel is not particularly limited as long as it is within the above-mentioned upper and lower limit ranges. Furthermore, with regard to the number of cylinders, alcohol-containing fuel engines include, for example, single-cylinder engines and engines with two or more cylinders. The alcohol-containing fuel engine may be, for example, a single-cylinder engine, a two-cylinder engine, a variable-interval combustion three-cylinder engine, or a variable-interval combustion four-cylinder engine. When the alcohol-containing fuel engine has multiple cylinders, the control according to the present invention does not necessarily need to be performed on all cylinders. As long as the control according to the present invention is performed on any one cylinder, the engine system corresponds to the alcohol-containing fuel system according to the present invention.

[0012] The starter motor is, for example, a motor connected to the crankshaft via a gear. The starter motor is not particularly limited, and may be connected to the crankshaft via a clutch. Alternatively, the starter motor may be directly connected to the crankshaft. The starter motor may have, for example, a power generation function.

[0013] The control device is composed of a computer having a processor, RAM, and ROM. The control device may be an ECU (Engine Control Unit). The processor performs arithmetic processing based on a control program. The processor receives data from multiple sensors provided in the system and outputs commands to control various devices in the system. The RAM functions as a memory area for temporary data storage. Examples of temporary data include data currently being processed and data from the sensors. The data from the sensors includes data related to the dynamic state of the vehicle. The ROM stores a control program and a control map. The control device controls an alcohol-fueled engine. The control device controls an in-passage alcohol fuel injection device and an alcohol-fueled ignition device in the engine. The control device may also control devices other than the alcohol-fueled engine. The control device may be composed of a single device or multiple devices physically separated from each other. Because the control device controls an alcohol-fueled engine, different values ​​are used to adjust, for example, the fuel injection amount, intake air amount, and fuel mixture ratio compared to a gasoline engine. The present invention solves problems specific to alcohol-fueled engines.

[0014] The in-passage alcohol fuel injection device is a device that injects alcohol-containing fuel into an intake passage. The device is, for example, an injector. The device may be a device dedicated to alcohol-containing fuel, or a general-purpose device that is also used for gasoline fuel. The device can be selected depending on the alcohol concentration of the alcohol-containing fuel. Note that in-cylinder injection is not performed in an alcohol-containing fuel engine.

[0015] The intake air amount adjusting device is, for example, a fast idle (FID) controller provided in a bypass passage of a throttle valve. However, the intake air amount adjusting device is not particularly limited, and may be, for example, the throttle valve or an idling speed controller (ISC) provided in a bypass passage of the throttle valve.

[0016] A combustion cycle is a cycle corresponding to 720° rotation of the crankshaft of a four-stroke alcohol-fueled engine. The combustion cycle is based on the start of fuel injection. The combustion cycle includes the injection and the subsequent ignition timing. For example, if the first fuel injection crank angle is reached after the starter motor starts rotating the crankshaft, but fuel injection is not performed at that fuel injection crank angle, the 720° crank angle cycle including that crank angle does not qualify as a combustion cycle. If fuel injection is performed in the next cycle, that cycle would qualify as the first combustion cycle.

[0017] The maximum injection quantity is the maximum injection quantity that can be set during the starting period and the idling period. In other words, it is the maximum injection quantity that can be set in the combustion cycle when the driver is not operating the accelerator. The maximum injection quantity is, for example, the quantity injected by the in-passage alcohol fuel injection device during the intake valve opening period. The intake valve is provided in an alcohol-containing fuel engine and opens to take air from the intake passage into the combustion chamber. "Injecting less than the maximum injection quantity" can be achieved, for example, by the in-passage alcohol fuel injection device injecting alcohol-containing fuel for a period shorter than the period corresponding to the maximum injection quantity.

[0018] For example, if the intra-passage alcohol fuel injection device is capable of adjusting not only the injection duration but also the injection amount per unit time in the injection state, the maximum injection amount is the amount injected during the intake valve opening period when the injection amount per unit time in the injection state is at its maximum. The injection amount per unit time in the injection state is adjusted, for example, by the voltage applied to the intra-passage alcohol fuel injection device for injection. It is controlled by the supply pressure of the alcohol-containing fuel being supplied. In this case, "reducing the injection amount below the maximum injection amount" can be achieved, for example, by the intra-passage alcohol fuel injection device injecting for a short period or by injecting an injection amount per unit time less than the maximum injection amount. Furthermore, "reducing the injection amount below the maximum injection amount" can be achieved, for example, by the intra-passage alcohol fuel injection device injecting for a short period or by injecting an injection amount per unit time less than the maximum injection amount.

[0019] The high idle state is the idling state of an alcohol-containing fuel engine during cold start. The engine speed during high idle is higher than the idling speed during normal operating conditions. For example, if the intake air amount during idling is adjusted using a throttle valve, the throttle valve opening corresponds to the high idle state, thereby introducing an amount of air corresponding to the high idle state. Also, by controlling the throttle valve opening to be smaller than that during high idle, an amount of air less than that corresponding to the high idle state can be introduced. In contrast, for example, if the intake air amount during idling is adjusted using a bypass valve provided in the intake path that bypasses the throttle valve, the bypass valve opening corresponds to the high idle state, thereby introducing an amount of air corresponding to the high idle state. The high idle state is the state in which the engine speed is at its highest when the engine is started at normal outside temperature without operating the accelerator.

[0020] Effective combustion includes initial combustion and complete combustion. In this specification, complete combustion refers to a state in which combustion can continue without the need for an external driving force such as a starter motor. Complete combustion in this specification does not mean that all oxidizable components of the alcohol-containing fuel are completely oxidized. Initial combustion refers to a state in which the rotational speed of the crankshaft increases, but the combustion cannot continue without the need for an external driving force. Effective combustion may be either complete combustion or initial combustion, as long as it increases the rotational speed of the crankshaft. Combustion that does not increase the rotational speed of the crankshaft is not effective combustion.

[0021] When "effective combustion is generated from the second combustion cycle," effective combustion does not occur in the first combustion cycle. However, combustion that does not reach effective combustion may occur in the first combustion cycle. Also, effective combustion may rarely occur in the first combustion cycle. The possibility of effective combustion occurring is at most 5%. Ignition itself may not occur in the first combustion cycle.

[0022] (2) In the alcohol-containing fuel engine system of (1), the control device injects an amount of alcohol-containing fuel smaller than the maximum injection amount into the intra-passage alcohol fuel injection device so that, at least in the first and second combustion cycles, a portion of the period during which the intra-passage alcohol fuel injection device injects the alcohol-containing fuel overlaps with the opening period of the intake valve, and the start of injection of the alcohol-containing fuel occurs before the start of opening of the intake valve.

[0023] According to the alcohol-containing fuel engine system of (2) above, when an amount of alcohol-containing fuel less than the maximum injection amount is injected by the intra-passage alcohol fuel injection device, the mixture containing the injected alcohol-containing fuel is efficiently introduced into the combustion chamber, thereby improving the reproducibility of early combustion and the target tracking ability of the engine rotation speed while reducing the injection amount of alcohol-containing fuel.

[0024] (3) In the alcohol-containing fuel engine system of (1) or (2), the control device injects an amount of alcohol-containing fuel into the in-passage alcohol fuel injection device that is less than the maximum injection amount in the second combustion cycle, and injects an amount of alcohol-containing fuel into the in-passage alcohol fuel injection device in the first combustion cycle that is less than the amount of alcohol-containing fuel injected from the in-passage alcohol fuel injection device in the second combustion cycle.

[0025] According to the alcohol-containing fuel engine system of (3) above, an amount of alcohol-containing fuel less than the maximum injection amount is injected in the second combustion cycle, and an even smaller amount of alcohol-containing fuel is injected in the first combustion cycle than the amount injected in the second combustion cycle. This increases the possibility of effective combustion occurring in the second combustion cycle. Therefore, the alcohol-containing fuel injected in the first combustion cycle is used to prepare for increasing the possibility of effective combustion in the second combustion cycle, thereby achieving both the reproducibility of early combustion and the ability to track the target engine rotation speed, while further reducing the amount of alcohol-containing fuel injected in the first combustion cycle that is discharged from the combustion chamber.

[0026] In the alcohol-containing fuel engine system described above in (3), the injection period of the alcohol-containing fuel overlaps with the valve-open period, and the injection starts before the intake valve starts to open, so that the air-fuel mixture containing the alcohol-containing fuel is efficiently introduced into the combustion chamber. This makes it possible to achieve both the reproducibility of early combustion and the ability to control the engine rotation speed to track the target while further reducing the injection amount of the alcohol-containing fuel.

[0027] (4) In the alcohol-containing fuel engine system of any one of (1) to (3), the control device causes the intake air amount adjustment device to take in an amount of air that is less than an amount of air that corresponds to a high idle state of the alcohol-containing fuel engine in the first and second combustion cycles, and when the effective combustion occurs in both the second combustion cycle and the third combustion cycle, causes the intake air amount adjustment device to take in an amount of air that corresponds to the high idle state of the alcohol-containing fuel engine in at least one combustion cycle of the fourth to sixth combustion cycles that follows the third combustion cycle.

[0028] According to the alcohol-containing fuel engine system described above in (4), when effective combustion continues in both the second combustion cycle and the third combustion cycle, an amount of air equivalent to the maximum amount of air during idling is taken in, so that a smooth transition to a high idle state can be achieved while suppressing abrupt changes in rotation speed. This allows for both the reproducibility of early combustion and the ability to track the rotation speed target, including the transition to a high idle state.

[0029] Furthermore, in the alcohol-containing fuel engine system described in (4) above, if the injection period of the alcohol-containing fuel overlaps with the valve-open period and the injection starts before the intake valve starts to open, the air-fuel mixture containing the alcohol-containing fuel is efficiently introduced into the combustion chamber. This makes it possible to achieve both the reproducibility of early combustion and the ability to track the target rotation speed, including the transition to a high idle state, while further reducing the injection amount of the alcohol-containing fuel.

[0030] Furthermore, in the alcohol-containing fuel engine system of (4) above, when an amount of alcohol-containing fuel less than the maximum injection amount is injected in the second combustion cycle, and an amount of alcohol-containing fuel less than the amount in the second combustion cycle is injected in the first combustion cycle, it is possible to further reduce the amount of alcohol-containing fuel injected in the first combustion cycle that is discharged from the combustion chamber, while achieving both the reproducibility of early combustion and the ability to track the target rotational speed, including the transition to a high idle state.

[0031] (5) The alcohol-containing fuel engine system according to any one of (1) to (4), further comprising a three-way catalyst provided in an exhaust passage of the alcohol-containing fuel engine.

[0032] According to the alcohol-containing fuel engine system described above in (5), the reproducibility of early combustion and the ability of the engine rotation speed to follow the target are further improved, and therefore the ability of the catalyst temperature to follow the target for the three-way catalyst to purify the exhaust gas of the alcohol-containing fuel engine is also further improved.

[0033] The present invention can provide the following vehicle.

[0034] (6) A vehicle equipped with an alcohol-containing fuel engine system according to any one of (1) to (5).

[0035] According to the vehicle of (6) above, it is possible to achieve both the reproducibility of early combustion and the ability of the engine rotation speed to follow the target.

[0036] A vehicle is a device for transportation. A vehicle is configured to operate in a manned or unmanned (automated) manner. A vehicle can be a personal transportation vehicle. For example, a vehicle may be a public transportation vehicle such as a bus. Examples of personal transportation vehicles include automobiles and saddle-type vehicles. A vehicle may or may not have wheels. Examples of vehicles without wheels include ships with propellers, drones and helicopters with propellers, snowmobiles, and watercraft. A vehicle may or may not have a cabin. Examples of vehicles with a cabin include automobiles and helicopters. One example of a vehicle is a saddle-type vehicle. A saddle-type vehicle is a vehicle equipped with a saddle-type seat. A saddle-type vehicle is a vehicle configured so that a rider sits astride the seat. The saddle-type vehicle is not limited to scooter-type, moped-type, off-road-type, and on-road-type motorcycles, but also includes snowmobiles, watercraft, all-terrain vehicles (ATVs), etc. The saddle-type vehicle may have at least one front wheel and at least one rear wheel. The saddle-type vehicle is not limited to motorcycles, but may be a three-wheeled vehicle having a pair of front or rear wheels, or a four-wheeled vehicle having a pair of front and rear wheels, respectively. The saddle-type vehicle may be configured to be able to turn in a lean position toward the center of a curve. Since a saddle-type vehicle that can turn in a lean position requires agility, small size and light weight are important. In a saddle-type vehicle configured to be able to turn in a lean position, it is important to achieve both the reproducibility of early combustion during starting and the ability to track a target engine rotation speed without the need for additional devices such as a device for promoting the vaporization of alcohol-containing fuel or a device for in-cylinder fuel injection. The alcohol-containing fuel engine system of the present invention can achieve both the reproducibility of early combustion and the ability of the engine rotation speed to track a target by controlling the injection and air amount, and therefore can be suitably applied to a saddle-type vehicle that is configured to be able to turn in a lean position. A saddle-type vehicle that is configured to be able to turn in a lean position is suitable as the vehicle of the present invention.Other examples of vehicles include golf cars, caterpillar-type snow vehicles, and snow plows.

[0037] The terminology used herein is for the purpose of defining particular embodiments only and is not intended to limit the invention. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed components. As used herein, the use of the terms "including," "comprising," or "having," and variations thereof, identifies the presence of stated features, steps, operations, elements, components, and / or equivalents thereof, but may include one or more of the steps, operations, elements, components, and / or groups thereof. As used herein, the terms "attached," "connected," "coupled," and / or equivalents thereof are used broadly and encompass both direct and indirect attachments, connections, and couplings. Furthermore, "connected" and "coupled" are not limited to physical or mechanical connections or couplings, but can include direct or indirect electrical connections or couplings. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms, such as those defined in commonly used dictionaries, should be interpreted to have a meaning consistent with the relevant technology and meaning in the context of this disclosure, and should not be interpreted in an idealized or overly formal sense unless explicitly defined herein. It is understood that numerous techniques and processes are disclosed in the description of the present invention. Each of these has distinct advantages, and each can also be used with one or more, or in some cases all, of the other disclosed technologies. Therefore, for the sake of clarity, this description will refrain from unnecessarily repeating all possible combinations of individual steps. Nevertheless, the specification and claims should be read with the understanding that all such combinations are within the scope of the present invention and claims. Novel alcohol-containing fuel engine systems and vehicles are described herein. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention.However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. The present disclosure is to be considered as an example of the present invention and is not intended to limit the invention to the specific embodiments illustrated by the following drawings or description.

[0038] According to the present invention, an alcohol-containing fuel engine system can be provided that is capable of achieving both the reproducibility of early combustion and the ability of the engine rotation speed to track a target during startup in an engine in which alcohol-containing fuel is supplied to the intake passage but in-cylinder injection is not performed, and a vehicle equipped with the same.

[0039] Fig. 1 is a diagram illustrating an alcohol-containing fuel engine system according to one embodiment. Fig. 2 is a diagram illustrating an example of implementing the alcohol-containing fuel engine system shown in Fig. 1.

[0040] 1 is a diagram illustrating an alcohol-containing fuel engine system according to one embodiment, with part (a) of FIG. 1 being a block diagram that schematically illustrates the alcohol-containing fuel engine system.

[0041] The alcohol-containing fuel engine system 1 includes an alcohol-containing fuel engine 2, a starter motor M, and an ECU 3.

[0042] The alcohol-containing fuel engine 2 uses an alcohol-containing fuel. In this embodiment, the alcohol-containing fuel engine system 1 is mounted on a vehicle 20. The alcohol-containing fuel engine system 1 has a crankshaft 2a. The alcohol-containing fuel engine system 1 is configured to output power generated by the alcohol-containing fuel engine 2 to the outside of the alcohol-containing fuel engine system 1. The alcohol-containing fuel engine system 1 outputs power through rotation of the crankshaft 2a. The rotational speed of the crankshaft 2a is also referred to as the rotational speed of the alcohol-containing fuel engine 2. The vehicle 20 is configured to be able to run using the power generated by the alcohol-containing fuel engine 2. Although not shown, the vehicle 20 is configured so that power is transmitted from the crankshaft 2a of the alcohol-containing fuel engine 2 to wheels via a powertrain. The alcohol-containing fuel engine 2 is a four-stroke internal combustion engine. The alcohol-containing fuel engine 2 has an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke. The alcohol-containing fuel engine 2 repeats a combustion cycle. In this specification, the criterion for starting a combustion cycle is fuel injection.

[0043] The starter motor M drives the crankshaft 2 a to rotate the crankshaft 2 a, and the starter motor M starts the alcohol-containing fuel engine 2 by rotating the crankshaft 2 a.

[0044] The ECU 3 corresponds to a control device. The ECU 3 controls at least the alcohol-containing fuel engine 2. The ECU 3 includes a processor 3 a, a RAM 3 b, a ROM 3 c, and a communication I / F (interface) 3 d. The communication I / F 3 d is hardware configured to communicate with sensors and devices within the system 1.

[0045] The alcohol-containing fuel engine 2 includes at least one cylinder 5. In this embodiment, the alcohol-containing fuel engine 2 is a single-cylinder engine. However, the number of cylinders of the alcohol-containing fuel engine 2 is not particularly limited.

[0046] The alcohol-containing fuel engine 2 includes, for each cylinder, a combustion chamber 6, an intake passage 7, an intake valve 12, an intake amount regulator 4, and an in-passage alcohol fuel injection device 9.

[0047] The combustion chamber 6 is configured to combust an alcohol-containing fuel mixture therein. The alcohol-containing fuel is not injected (so-called in-cylinder injection) into the combustion chamber 6. The combustion chamber 6 is in communication with both an intake passage 7 and an exhaust passage 8.

[0048] The intake valve 12 is provided between the combustion chamber 6 and the intake passage 7. When the intake valve 12 opens, air is taken in from the intake passage 7 into the combustion chamber 6. The alcohol-containing fuel engine 2 also includes an exhaust passage 8. An exhaust valve 13 is provided between the combustion chamber 6 and the exhaust passage 8.

[0049] Air taken into the combustion chamber 6 passes through the intake passage 7 .

[0050] The intake air amount regulator 4 adjusts the amount of air taken into the combustion chamber 6. The intake air amount regulator 4 adjusts the amount of air under the control of the ECU 3. During the starting period, the intake air amount regulator 4 can adjust the amount of air within a range from an air amount corresponding to a low idle state to an air amount corresponding to a high idle state. The intake air amount regulator 4 shown in part (a) of FIG. 1 is shown as a single device provided in the intake passage 7. For example, a throttle valve that operates under the control of a control device based on the rider's acceleration request may perform the function of the intake air amount regulator 4 during the starting period. Alternatively, the intake air amount regulator 4 may be provided in a bypass passage of the throttle valve, as will be described later. The bypass passage may be, for example, a fast idle (FID) controller, or an idling speed controller (ISC) provided in a bypass passage separate from the FID controller.

[0051] The intra-passage alcohol fuel injection device 9 is connected to an alcohol-containing fuel tank 11, and is configured to inject the entire amount of alcohol-containing fuel supplied to the inside of the combustion chamber 6 into the intake passage 7. The alcohol-containing fuel injected into the intake passage 7 becomes a mixture with air, and is taken into the combustion chamber 6. The intra-passage alcohol fuel injection device 9 is controlled by the ECU 3.

[0052] The ignition device 10 is configured to ignite the alcohol-containing fuel mixture introduced into the combustion chamber 6. The ignition device 10 is controlled by the ECU 3.

[0053] Next, the control executed by the ECU 3 when starting the alcohol-containing fuel engine 2 will be described.

[0054] When starting the alcohol-containing fuel engine 2, the ECU 3 controls the starter motor M to rotate the crankshaft 2a of the alcohol-containing fuel engine 2. This initiates the starting period. After the crankshaft 2a starts rotating, the ECU 3 starts injecting the alcohol-containing fuel into the intake passage 7 using the intra-passage alcohol fuel injection device 9. The ECU 3 injects the alcohol-containing fuel from the intra-passage alcohol fuel injection device 9 for each combustion cycle of the alcohol-containing fuel engine 2. The ECU 3 controls the amount of alcohol-containing fuel injected by the intra-passage alcohol fuel injection device 9. The ECU 3 also controls the intake air amount regulator 4 to adjust the amount of air passing through the intake passage 7. Based on the control of the ECU 3, the amount of air passing through the intake passage 7 is adjusted, and the alcohol-containing fuel is injected into the intake passage 7 to generate an alcohol-containing fuel mixture. The alcohol-containing fuel mixture is introduced into the combustion chamber 6. The ECU 3 also controls the ignition device 10 to ignite the alcohol-containing fuel mixture introduced into the combustion chamber 6. The alcohol-containing fuel mixture burns depending on the amount and concentration of the alcohol-containing fuel in the alcohol-containing fuel mixture. The starting period is the period from when the crankshaft 2 a starts to rotate until complete combustion, during which the combustion operation can continue by burning the alcohol-containing fuel mixture without driving the starter motor M.

[0055] Part (b) of Fig. 1 is a diagram for explaining control executed in the alcohol-containing fuel engine system 1. Parts (c) to (e) of Fig. 1 are time charts for explaining an example of control executed in the alcohol-containing fuel engine system 1. Part (c) of Fig. 1 shows the operation of a starter motor. Part (d) of Fig. 1 shows the intake air amount. Part (e) of Fig. 1 shows the injection amount and combustion state of the alcohol-containing fuel. The horizontal axis of parts (c) to (e) of Fig. 1 represents a common time.

[0056] For example, at time t1 shown in part (c) of FIG. 1 , the ECU 3 places the starter motor M in the drive state Mon and causes the starter motor M to start rotating the crankshaft 2a. In the first combustion cycle C1 after the starter motor M starts rotating the crankshaft 2a, the ECU 3 controls the intake air amount regulator 4 and the intra-passage alcohol fuel injection device 9 so that effective combustion occurs from the second combustion cycle C2 following the first combustion cycle C1. The ECU 3 places the starter motor M in the drive-off state Moff when complete combustion occurs, such that combustion can continue by burning the alcohol-containing fuel mixture without driving the starter motor M. More specifically, the ECU 3 places the starter motor M in the drive-off state Moff when the rotational speed of the crankshaft 2a exceeds the speed corresponding to the complete combustion.

[0057] In the first combustion cycle C1, the ECU 3 injects an amount of alcohol-containing fuel from the intra-passage alcohol fuel injector 9 that is less than the maximum injection amount Fmax, and causes the intake air amount regulator 4 to take in an amount of air that is less than the air amount (high idle air amount) Amax corresponding to a high idle state. That is, the ECU 3 controls the amount of alcohol-containing fuel injected from the intra-passage alcohol fuel injector 9 in injection F1 in the first combustion cycle C1 to be less than the maximum injection amount Fmax. The amount of alcohol-containing fuel injected from the intra-passage alcohol fuel injector 9 is controlled, for example, by the injection time from the intra-passage alcohol fuel injector 9. However, for ease of viewing, the injection amount in part (e) of FIG. 1 is shown on the vertical axis rather than the horizontal axis, which represents time. The maximum injection amount Fmax of the alcohol-containing fuel is an amount corresponding to injection over the opening period of the intake valve 12.

[0058] The second combustion cycle C2 follows the first combustion cycle C1. The second injection F2 after the start of rotation of the crankshaft 2a is performed in the second combustion cycle C2, which follows the first combustion cycle C1 to which the first injection F1 belongs. In the second combustion cycle C2, the ECU 3 controls the intra-passage alcohol fuel injector 9 to inject an amount of alcohol-containing fuel that is less than the maximum injection amount Fmax, and controls the intake air amount regulator 4 to take in an amount of air that is less than the air amount Amax corresponding to a high idle state.

[0059] Under control of the ECU 3, the amount of alcohol-containing fuel injected in injection F1 of the first combustion cycle C1 is less than the maximum injection amount Fmax. Furthermore, the amount of air taken into the combustion chamber 6 is less than the air amount Amax corresponding to the high idle state. A portion of the alcohol-containing fuel injected in injection F1 of the first combustion cycle C1 adheres to the wall surface of the intake passage 7 and the intake valve 12. Therefore, the amount of alcohol-containing fuel taken into the combustion chamber 6 is further reduced from the injection amount in the first combustion cycle C1. Therefore, even if ignition is performed by the ignition device 10, for example, at time t2 after injection F1 of the first combustion cycle C1, effective combustion of the alcohol-containing fuel in the combustion chamber 6 is suppressed.

[0060] The alcohol-containing fuel injected in injection F1 of the first combustion cycle C1 is used for combustion in the second combustion cycle C2 (time t3), i.e., the combustion following injection F2 in the second combustion cycle C2 (time t3). The ECU 3 reduces the amount of alcohol-containing fuel injected in injection F2 of the second combustion cycle C2 to less than the maximum injection amount Fmax and causes less air to be introduced than the air amount Amax corresponding to a high idle state. A portion of the alcohol-containing fuel injected in injection F2 of the second combustion cycle C2 also adheres to the wall surface and the intake valve 12. However, when the remaining unadhered alcohol-containing fuel is introduced into the combustion chamber 6 together with air, it is mixed with the alcohol-containing fuel derived from the portion of the alcohol-containing fuel injected in the first combustion cycle C1 that adhered to the wall surface and the intake valve 12. Because the pressure in the intake passage 7 decreases due to the small amount of air being introduced, the amount of evaporation of the alcohol-containing fuel that adhered to the wall surface and the intake valve 12 in injection F1 of the first combustion cycle C1 increases. Furthermore, since the amount of air taken in is small, the concentration of alcohol-containing fuel in the combustion chamber 6 is high. This increases the probability of effective combustion occurring in the combustion stroke of the second combustion cycle C2. In other words, the reproducibility of early combustion is further improved. Furthermore, since effective combustion in the combustion stroke of the first combustion cycle C1 (time t2) may be suppressed, the amount of alcohol-containing fuel injected in the first combustion cycle C1 can be set to an amount that increases the possibility of effective combustion when combined with the alcohol-containing fuel injected F2 in the second combustion cycle C2. This prevents, for example, situations in which the amount of injected alcohol-containing fuel carried over to the second combustion cycle C2 and thereafter exceeds the target range when effective combustion is targeted in the combustion stroke of the first combustion cycle C1, or, conversely, the alcohol-containing fuel is not carried over to the second combustion cycle C2. In other words, situations in which the rotational speed resulting from combustion in the combustion cycle falls outside the target range are suppressed. Therefore, the target tracking ability of the engine rotational speed at startup is further improved. In this way, in the alcohol-containing fuel engine 2 in which alcohol-containing fuel is supplied to the intake passage 7 but direct injection is not performed, it is possible to achieve both the reproducibility of early combustion and the ability of the engine rotation speed to follow the target.In addition, since the amount of alcohol-containing fuel injected in the first combustion cycle C1 is small and some of the alcohol-containing fuel adheres to the wall surface and the intake valve 12, the amount of alcohol-containing fuel emitted from the alcohol-containing fuel engine 2 is reduced even if effective combustion does not occur in the first combustion cycle C1.

[0061] Fig. 2 is a diagram for explaining an example of implementing the alcohol-containing fuel engine system shown in Fig. 1. Part (a) of Fig. 2 is a block diagram that schematically shows the alcohol-containing fuel engine system. Part (b) of Fig. 2 is a diagram for explaining control executed in the alcohol-containing fuel engine system. Part (c) of Fig. 2 shows the operation of a starter motor. Part (d) of Fig. 2 shows the intake amount. Part (e) of Fig. 2 shows the injection amount of alcohol-containing fuel. For ease of understanding, elements in Fig. 2 that are common to Fig. 1 will be described using the same reference numerals as in Fig. 1.

[0062] In the example shown in part (a) of FIG. 2 , the intake passage 7 includes a passage having a throttle valve 4a and a bypass passage 7b for the throttle valve 4a. The bypass passage 7b is provided with an intake air amount adjuster 4b. The intake air amount adjuster 4b is, for example, an FID controller. The intake air amount adjuster 4b adjusts the amount of air taken into the combustion chamber 6 through the bypass passage 7b under the control of the ECU 3. For example, during the starting and idling periods, the throttle valve 4a sets the air amount to zero, and the FID controller serving as the intake air amount adjuster 4b adjusts the air amount within a range from an air amount corresponding to a low idle state to an air amount corresponding to a high idle state under the control of the ECU 3. In this case, the throttle valve 4a may be connected to the accelerator by a mechanical cable, for example, without the ECU 3. Although not shown in part (a) of FIG. 2 , a configuration may also be adopted in which, in addition to the bypass passage 7b, a passage for ISC is provided as a second bypass passage.

[0063] Part (e) of Figure 2 shows the opening period V of the intake valve 12. The opening of the intake valve 12 corresponds to the rotation of the crankshaft 2a. The ECU 3 causes the intra-passage alcohol fuel injection device 9 to inject an amount of alcohol-containing fuel that is smaller than the maximum injection amount Fmax. At this time, the ECU 3 may control the intra-passage alcohol fuel injection device 9 so that, in the first combustion cycle C1 and the second combustion cycle C2, a part of the period during which the intra-passage alcohol fuel injection device 9 injects the alcohol-containing fuel overlaps with the opening period V of the intake valve 12, and the start of injection of the alcohol-containing fuel occurs before the start of opening of the intake valve 12.

[0064] Because the injection of the alcohol-containing fuel begins before the intake valve 12 begins to open, the injected alcohol-containing fuel is contained in the air in the intake passage 7 at the time when air begins to be taken from the intake passage 7 into the combustion chamber 6. Therefore, a mixture containing the injected alcohol-containing fuel is taken into the combustion chamber 6 with high efficiency. This makes it possible to further improve the reproducibility of early combustion and the ability of the engine rotation speed to track the target while reducing the injection amount of the alcohol-containing fuel.

[0065] 2B, the ECU 3 causes the intra-passage alcohol fuel injection device 9 to inject an amount of alcohol-containing fuel that is smaller than the maximum injection amount Fmax in the second combustion cycle C2. Then, the ECU 3 may cause the intra-passage alcohol fuel injection device 9 to inject, in the injection F1 in the first combustion cycle C1, an amount of alcohol-containing fuel that is smaller than the amount of alcohol-containing fuel injected in the second combustion cycle C2.

[0066] The alcohol-containing fuel injected in the first combustion cycle C1 can be used to prepare for increasing the possibility of effective combustion (time t3) in the second combustion cycle C2, while suppressing the amount of unburned alcohol-containing fuel discharged from the combustion chamber 6 due to the injection F1 in the first combustion cycle C1.

[0067] The ECU 3 causes the intake air amount regulator 4b to take in an amount of air less than the amount of air corresponding to the high idle state in the first combustion cycle C1 and the second combustion cycle C2. If effective combustion occurs in both the second combustion cycle C2 and the third combustion cycle C3, the ECU 3 may cause the intake air amount regulator 4 to take in an amount of air Amax corresponding to the high idle state in at least one of the fourth through sixth combustion cycles (C4, C5, C6). By taking in the amount of air Amax corresponding to the high idle state, the alcohol-containing fuel engine 2 enters a high idle state. The ECU 3 then adjusts the amount of air based on the temperature of the alcohol-containing fuel engine 2, the temperature of the exhaust gas passing through the exhaust passage 8, the temperature of the three-way catalyst 15, or a combination of these temperatures. More specifically, the ECU 3 gradually reduces the amount of air taken in by the intake air amount regulator 4b as the temperature rises due to the combustion operation of the alcohol-containing fuel engine 2. Finally, when the temperature exceeds a reference value, the ECU 3 causes the intake air amount regulator 4b to take in an amount of air Amin corresponding to the low idle state.

[0068] When effective combustion continues in the second combustion cycle C2 and the third combustion cycle C3, the maximum amount of air Amax during idling is taken in, so that a sudden change in rotation speed can be suppressed and a smooth transition to a high idling state can be made.

[0069] The ECU 3 may take in an air amount that is less than the air amount Amax corresponding to the high idle state and the median air amount Amid corresponding to the low idle state, at least in both the first combustion cycle C1 and the second combustion cycle C2.

[0070] Because the pressure in the intake passage 7 is reduced, the amount of evaporation of the alcohol-containing fuel increases compared to when an amount of air greater than the median value Amid is taken in. This increases the probability that effective combustion will occur in the combustion stroke of the second combustion cycle C2.

[0071] The alcohol-containing fuel engine system 1 may further include a three-way catalyst 15 provided in the exhaust passage 8 of the alcohol-containing fuel engine 2 .

[0072] As described above, the alcohol-containing fuel engine system 1 improves the reproducibility of early combustion and the target tracking ability of the engine rotation speed. This also improves the target tracking ability of the catalyst temperature, which affects the ability of the three-way catalyst 15 to purify exhaust gas from the alcohol-containing fuel engine 2.

[0073] The present invention is not limited to the above-described embodiment. The present invention can be implemented in other embodiments, and various modifications can be added. In addition, as an example of this embodiment, any one of the features described above with reference to FIG. 2 or a combination of any two or more features may be provided.

[0074] 2 , an example has been described in which the intra-passage alcohol fuel injection device 9 is controlled so that the start of injection of the alcohol-containing fuel occurs before the start of opening of the intake valve 12. However, the start of injection of the alcohol-containing fuel is not particularly limited, and may be, for example, after the start of opening of the intake valve 12.

[0075] 2 , for example, it has been described that in injection F1 of the first combustion cycle C1, the amount of alcohol-containing fuel injected from the intra-passage alcohol fuel injector 9 is smaller than the amount of alcohol-containing fuel injected from the intra-passage alcohol fuel injector 9 in injection F2 of the second combustion cycle C2. However, the relationship between the injection amounts in the first combustion cycle C1 and the second combustion cycle C2 is not particularly limited, and for example, the injection amount in the first combustion cycle C1 may be greater than or equal to the injection amount in the second combustion cycle C2.

[0076] 2, for example, it has been explained that when effective combustion occurs in the second combustion cycle C2 and the third combustion cycle C3, the ECU 3 causes the intake air amount regulator 4b to introduce the amount of air Amax corresponding to the high idle state in at least one of the fourth to sixth combustion cycles. However, the conditions for introducing the amount of air Amax corresponding to the high idle state are not particularly limited, and for example, when effective combustion occurs in the second combustion cycle C2, the ECU 3 may introduce the amount of air Amax corresponding to the high idle state.

[0077] 2, for example, it has been described that the air amount taken in is less than the median value Amid in both the first combustion cycle C1 and the second combustion cycle C2. However, the air amounts in the first combustion cycle and the second combustion cycle are not particularly limited as long as they are less than the air amount Amax corresponding to the high idle state, and the air amount taken in may be greater than the median value Amid.

[0078] 2, an example in which the three-way catalyst 15 is provided in the exhaust passage 8 has been described. However, the location and type of catalyst are not particularly limited.

[0079] In the alcohol-containing fuel engine system 1, the reproducibility of early combustion and the target tracking ability of the engine rotation speed are further improved, and therefore the target tracking ability of the catalyst temperature for the three-way catalyst 15 to purify the exhaust gas of the alcohol-containing fuel engine 2 is also further improved.

[0080] 1: Alcohol-containing fuel engine system 2: Alcohol-containing fuel engine 2a: Crankshaft 4, 4b: Intake amount adjustment device 5: Cylinder 6: Combustion chamber 7: Intake passage 8: Exhaust passage 9: In-passage alcohol fuel injection device 12: Intake valve 15: Three-way catalyst 20: Vehicle C1: First combustion cycle C2: Second combustion cycle C3: Third combustion cycle Fmax: Maximum injection amount M: Starter motor V: Valve opening period

Claims

1. An alcohol-containing fuel engine system, wherein the alcohol-containing fuel engine system includes an alcohol-containing fuel engine having a crankshaft and using alcohol-containing fuel, a starter motor that rotates the crankshaft by driving the crankshaft, and a control device that controls at least the alcohol-containing fuel engine. The alcohol-containing fuel engine includes at least one cylinder, and for each cylinder, a combustion chamber, an intake passage through which air taken into the combustion chamber passes, an intake air amount adjusting device that adjusts the amount of air taken into the combustion chamber, and an in-passage alcohol fuel injector configured to inject the entire amount of alcohol-containing fuel supplied into the combustion chamber in the intake passage. The alcohol-containing fuel engine is configured not to perform in-cylinder injection of alcohol-containing fuel. The control device, for at least one cylinder, in a first combustion cycle after starting the rotation of the crankshaft by the starter motor, causes the in-passage alcohol fuel injector to inject an amount of alcohol-containing fuel less than the maximum injection amount so as to cause effective combustion starting from a second combustion cycle following the first combustion cycle, and causes the intake air amount adjusting device to take in an amount of air less than the amount of air corresponding to the high idle state of the alcohol-containing fuel engine. In the second combustion cycle, the in-passage alcohol fuel injector is caused to inject an amount of alcohol-containing fuel less than the maximum injection amount, and the intake air amount adjusting device is caused to take in an amount of air less than the amount of air corresponding to the high idle state.

2. The alcohol-containing fuel engine system according to claim 1, wherein the control device causes the in-passage alcohol fuel injector to inject an amount of alcohol-containing fuel less than the maximum injection amount such that, in at least the first and second combustion cycles, a part of the period during which the alcohol-containing fuel is injected overlaps with the valve opening period of the intake valve, and the start of injection of the alcohol-containing fuel precedes the start of valve opening of the intake valve.

3. The control device causes the in-passage alcohol fuel injector to inject an amount of alcohol-containing fuel that is less than the maximum injection amount in the second combustion cycle, and in the first combustion cycle, causes the in-passage alcohol fuel injector to inject an amount of alcohol-containing fuel that is less than the amount of alcohol-containing fuel injected from the in-passage alcohol fuel injector in the second combustion cycle. The alcohol-containing fuel engine system according to claim 1 or 2.

4. The control device causes an air amount less than the air amount corresponding to the high idle state of the alcohol-containing fuel engine to be taken in during the first and second combustion cycles. When effective combustion occurs in both the second combustion cycle and the third combustion cycle, in at least one combustion cycle of the fourth to sixth combustion cycles after the third combustion cycle, the intake air amount adjustment device is caused to take in the air amount corresponding to the high idle state in the alcohol-containing fuel engine. The alcohol-containing fuel engine system according to any one of claims 1 to 3.

5. The alcohol-containing fuel engine system according to any one of claims 1 to 4, further comprising a three-way catalyst provided in an exhaust passage of the alcohol-containing fuel engine.

6. A vehicle equipped with the alcohol-containing fuel engine system according to any one of claims 1 to 5.

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