JP2008144712A - Engine system and vehicle provided with same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost engine system capable of securely performing self ignition of air-fuel mixture, and provide a vehicle provided with the same. <P>SOLUTION: An engine 100 of the engine system 200 includes a cylinder 1, and an external container 21 for housing burned gas. The burned gas in the cylinder 1 is housed in the external container 21 through a communication hole 28. The burned gas housed in the external container 21 is supplied in the cylinder 1 through the communication hole 28. The communication hole 28 on a cylinder 1 side is opened and closed by an outer peripheral surface of the cylinder 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine system and a vehicle including the same.

  In order to improve engine thermal efficiency, there is a technique to reduce engine heat loss and pump loss by reducing the fuel concentration in the mixture (lean air-fuel ratio) or supplying exhaust gas into the cylinder. Are known.

  However, in a spark ignition type engine in which an air-fuel mixture is ignited using a spark plug, when the air-fuel ratio is made lean or when a large amount of exhaust gas is supplied, the combustion speed of the air-fuel mixture decreases, and the combustion state is reduced. It becomes unstable. For this reason, the thermal efficiency of the engine cannot be significantly improved.

  As a technique for preventing instability of the combustion state as described above, an HCCI (Homogeneous-Charge Compression-Ignition) system is known. In the HCCI method, the temperature of the cylinder is increased by compressing the air-fuel mixture, and the air-fuel mixture is self-ignited without performing spark ignition. According to the HCCI method, a combustion reaction occurs from a plurality of locations of the air-fuel mixture, so that the combustion speed does not decrease and stable combustion is possible. Moreover, since combustion temperature falls, generation | occurrence | production of NOx (nitrogen oxide) can be suppressed.

  As the HCCI method, for example, there is a method of increasing the temperature of the mixed gas by supplying combustion gas (burned gas) before one cycle into the cylinder (for example, refer to Patent Document 1).

In the four-stroke engine described in Patent Document 1, an accommodating portion that accommodates burned gas is provided outside the cylinder. The burned gas accommodated in the accommodating portion is supplied to the combustion chamber during the intake stroke or the compression stroke. Thereby, the temperature of the air-fuel mixture rises and the air-fuel mixture can be effectively self-ignited.
JP 11-343874 A

  By the way, in the engine of patent document 1, the cylinder and the combustion chamber are connected via the port. The port is provided with a valve. In such a configuration, the valve is controlled so that the burned gas flows into the housing portion during the expansion stroke, and the burned gas flows into the combustion chamber during the intake stroke or the compression stroke.

  That is, in the configuration of Patent Document 1, opening and closing of the valve must be controlled according to each stroke. In this case, a mechanism for controlling the opening and closing of the valve with high accuracy is required, and the manufacturing cost of the engine increases.

  An object of the present invention is to provide a low-cost engine system capable of reliably performing self-ignition of an air-fuel mixture and a vehicle including the same.

  (1) An engine system according to a first aspect of the present invention is an engine system for driving a mechanical device, and includes an engine capable of self-ignition combustion having a cylinder and a piston that reciprocates within the cylinder, A burned gas containing portion for containing burned gas, the cylinder has a communicating portion for communicating the inside of the cylinder and the burned gas containing portion, and the communicating portion is in a communication state and a shut-off state by a reciprocating motion of the piston. It is provided to become.

  In this engine system, the burned gas in the cylinder is housed in the burned gas housing portion. The burned gas stored in the burned gas storage unit is supplied again into the cylinder together with the intake air and fuel after the next cycle. Thereby, the mixture in the cylinder is stratified and the temperature of the mixture rises. As a result, the air-fuel mixture can be surely self-ignited.

  Moreover, the communication part which connects the inside of a cylinder and the burned gas accommodating part will be in a communication state and interruption | blocking state by the reciprocating motion of a piston. That is, the flow of burned gas between the cylinder and the burned gas storage unit is controlled by the reciprocating motion of the piston. In this case, there is no need to provide a valve for controlling the flow of burned gas, so the cost of the engine system can be reduced.

  As a result, the air-fuel mixture can be surely self-ignited with a low-cost engine system.

  (2) The communication portion may be in a closed state by closing the communication portion with the outer peripheral surface of the piston, and the communication portion may be in a communication state by removing the outer peripheral surface of the piston from the communication portion.

  In this case, since the communication portion can be closed and opened by the outer peripheral surface of the piston, the communication portion can be easily and reliably brought into a closed state and a communication state.

  (3) The communication portion may be provided so as to open when the piston is positioned near the bottom dead center.

  In this case, the communication portion is opened in a predetermined period before the end of the expansion stroke and after the start of the exhaust stroke. During the predetermined period before the end of the expansion stroke and after the start of the exhaust stroke, the burned gas in the cylinder flows into the burned gas storage portion via the communication portion due to the pressure generated during combustion.

  Further, the communication portion is opened before the intake stroke ends and during a predetermined period after the compression stroke starts. In the predetermined period before the end of the intake stroke and the predetermined period after the start of the compression stroke, the pressure in the cylinder is lower than that in the burned gas storage portion. Thereby, the burned gas in the burned gas storage part flows into the cylinder.

  As a result, it is possible to easily and surely store the burned gas in the burned gas storage unit and supply the burned gas into the cylinder.

  (4) The engine system includes a combustion timing measuring means for measuring the combustion timing of the air-fuel mixture in the cylinder, a storage unit for storing the optimal combustion timing of the air-fuel mixture, and a combustion timing measured by the combustion timing measuring means. Control means for controlling the operation of the engine may be further provided so that the difference from the optimal combustion timing stored in the storage unit becomes small.

  In this case, the operation of the engine is controlled by the control unit so that the combustion timing of the air-fuel mixture approaches the optimal combustion timing stored in the storage unit. Thereby, irregular combustion such as misfire can be prevented.

  (5) The engine system may further include a volume adjustment unit that adjusts the volume of the burned gas storage unit, and the control unit may adjust the combustion timing in the cylinder by controlling the volume adjustment unit.

  In this case, the amount of burned gas that can be stored in the burned gas storage unit can be adjusted by adjusting the volume of the burned gas storage unit by the volume adjusting means. Thereby, the quantity of the burned gas supplied from the burned gas storage part into the cylinder can be adjusted, and the temperature of the air-fuel mixture can be adjusted. As a result, the combustion timing of the air-fuel mixture can be easily adjusted.

  (6) The control means advances the combustion timing of the air-fuel mixture in the cylinder by increasing the volume of the burned gas storage unit, and reduces the volume of the fuel mixture in the cylinder by decreasing the volume of the burned gas storage unit. The combustion timing may be retarded.

  In this case, by increasing the volume of the burned gas storage unit, it is possible to reduce the pressure drop in the burnt gas storage unit due to the outflow of burnt gas into the cylinder. Thereby, the burned gas can be supplied into the cylinder while keeping the pressure in the burned gas storage portion high. Further, the amount of the burned gas in the burned gas storage unit increases as the volume of the burned gas storage unit increases. As a result, a sufficient amount of burned gas can be supplied into the cylinder. Thereby, the temperature of the air-fuel mixture rises and the combustion timing is advanced.

  Further, by reducing the volume of the burned gas storage unit, it is possible to increase the pressure drop in the burned gas storage unit due to the outflow of burnt gas into the cylinder. Further, since the volume of the burned gas storage unit is reduced, the stored amount of burned gas in the burned gas storage unit is reduced. As a result, the amount of burned gas supplied into the cylinder is reduced. Thereby, the temperature of the air-fuel mixture decreases and the combustion timing is retarded.

  (7) The engine system further includes an exhaust passage for discharging burned gas from the cylinder, an exhaust valve for opening and closing the exhaust passage, and an exhaust valve driving means for driving the exhaust valve, and the control means is driven by the exhaust valve. The combustion timing in the cylinder may be adjusted by controlling the means.

  In this case, the amount of burnt gas flowing out from the cylinder to the exhaust passage can be adjusted by adjusting the opening / closing timing of the exhaust valve by the exhaust valve driving means. Thereby, the quantity of the burned gas which flows into the burned gas storage part from the inside of a cylinder can be adjusted. As a result, the amount of burnt gas supplied into the cylinder can be adjusted, and the combustion timing of the air-fuel mixture can be easily adjusted.

  (8) The control means advances the combustion timing of the air-fuel mixture in the cylinder by delaying the opening timing of the exhaust valve, and delays the combustion timing of the air-fuel mixture in the cylinder by increasing the timing of opening the exhaust valve. You may make it horn.

  In this case, the amount of burnt gas flowing out from the cylinder to the exhaust passage is reduced by delaying the opening of the exhaust valve. Accordingly, the amount of burned gas flowing from the cylinder into the burned gas storage unit increases, and a sufficient amount of burned gas can be stored in the burned gas storage unit. Therefore, a sufficient amount of burned gas can be supplied from the burned gas storage portion into the cylinder. As a result, the temperature of the air-fuel mixture rises and the combustion timing is advanced.

  Further, by increasing the timing at which the exhaust valve opens, the amount of burned gas flowing out from the cylinder into the exhaust passage increases. As a result, the amount of burned gas flowing from the cylinder into the burned gas storage portion decreases, and the amount of burned gas stored in the burned gas storage portion 23 decreases. Therefore, the amount of burned gas supplied from the burned gas storage portion into the cylinder can be reduced. As a result, the temperature of the air-fuel mixture decreases and the combustion timing is retarded.

  (9) The engine further includes ignition means for spark-igniting the air-fuel mixture in the cylinder and opening / closing means for opening and closing the communicating portion, and when the air-fuel mixture in the cylinder is spark-ignited by the ignition means The communication part may be closed by the opening / closing means.

  In this case, when the state of the engine is not suitable for self-ignition combustion, the supply of burned gas from the burned gas storage portion into the cylinder can be interrupted by closing the communicating portion by the opening / closing means. . Thereby, the spark ignition of the air-fuel mixture by the ignition means can be performed reliably. As a result, engine combustion, generation of NOx, and irregular combustion such as misfire can be prevented.

  (10) The piston may have a flow rate reduction unit that reduces the flow rate of burned gas supplied from the communication unit into the cylinder.

  In this case, the flow velocity of the burned gas is lowered by the flow velocity reduction portion, so that the burnt gas flowing into the cylinder from the burned gas storage portion can be prevented from colliding with the wall surface of the cylinder at high speed. Thereby, it is possible to prevent the heat of the burned gas from being released from the wall surface of the cylinder. As a result, the temperature of the air-fuel mixture can be reliably increased, and the air-fuel mixture can be surely self-ignited.

  Moreover, since the flow of burned gas is controlled by the flow velocity reduction portion, the air-fuel mixture in the cylinder is sufficiently stratified. Thereby, the temperature of the air-fuel mixture can be further increased. As a result, the air-fuel mixture can be self-ignited more reliably.

  (11) The burned gas storage unit includes a plurality of burned gas storage units, and the communication unit includes a plurality of communication units that respectively connect the plurality of burned gas storage units and the inside of the cylinder, and the plurality of communication units. The burned gas may be formed so as to flow out toward the substantially central portion of the cylinder.

  In this case, a sufficient amount of burned gas can be supplied into the cylinder by the plurality of burned gas storage units. Thereby, the temperature of the air-fuel mixture can be reliably increased.

  Moreover, the burned gases supplied from the plurality of burned gas storage units merge at a substantially central portion of the cylinder. Therefore, the flow velocity of the burned gas flowing into the cylinder from the burned gas storage portion is reduced at the substantially central portion in the cylinder.

  In this case, it is possible to prevent the burned gas flowing into the cylinder from the burned gas storage portion from colliding with the wall surface of the cylinder at a high speed. Thereby, it is possible to prevent the heat of the burned gas from being released from the wall surface of the cylinder. As a result, the temperature of the air-fuel mixture can be reliably increased.

  As a result, the air-fuel mixture can be surely self-ignited.

  (12) A vehicle according to a second invention includes drive wheels, an engine system according to the first invention, and a transmission mechanism that transmits power generated by the engine system according to the first invention to the drive wheels. It is a thing.

  In this vehicle, power generated by the engine system according to the first aspect of the invention is transmitted to the drive wheels by the transmission mechanism, and the drive wheels are driven.

  In the engine system according to the first aspect of the present invention, the burned gas in the cylinder is housed in the burned gas housing portion. The burned gas stored in the burned gas storage unit is supplied again into the cylinder together with the intake air and fuel after the next cycle. Thereby, the mixture in the cylinder is stratified and the temperature of the mixture rises. As a result, the air-fuel mixture can be surely self-ignited.

  Moreover, the communication part which connects the inside of a cylinder and the burned gas accommodating part will be in a communication state and interruption | blocking state by the reciprocating motion of a piston. That is, the flow of burned gas between the cylinder and the burned gas storage unit is controlled by the reciprocating motion of the piston. In this case, there is no need to provide a valve for controlling the flow of burned gas, so the cost of the engine system can be reduced.

  As a result, the running stability of the vehicle can be improved at a low cost.

  According to the present invention, the burned gas in the cylinder of the engine is accommodated in the burned gas storage portion. The burned gas stored in the burned gas storage unit is supplied again into the cylinder together with the intake air and fuel after the next cycle. Thereby, the mixture in the cylinder is stratified and the temperature of the mixture rises. As a result, the air-fuel mixture can be surely self-ignited.

  Moreover, the communication part which connects the inside of a cylinder and the burned gas accommodating part will be in a communication state and interruption | blocking state by the reciprocating motion of a piston. That is, the flow of burned gas between the cylinder and the burned gas storage unit is controlled by the reciprocating motion of the piston. In this case, there is no need to provide a valve for controlling the flow of burned gas, so the cost of the engine system can be reduced.

  Hereinafter, an engine system according to an embodiment of the present invention and a vehicle including the engine system will be described with reference to the drawings. The engine system according to the present embodiment performs combustion by an HCCI (Homogeneous-Charge Compression-Ignition) method and a spark ignition method. In the following description, a motorcycle will be described as an example of a vehicle.

(1) Configuration of Motorcycle FIG. 1 is a schematic diagram of a motorcycle according to an embodiment of the present invention.

  In the motorcycle 600 of FIG. 1, a head pipe 602 is provided at the front end of the main body frame 601. A front fork 603 is provided on the head pipe 602 so as to be swingable in the left-right direction. A front wheel 604 is rotatably supported at the lower end of the front fork 603. A handle 605 is attached to the upper end of the head pipe 602.

  An engine 100, an intake pipe 11, and an exhaust pipe 12 are provided at the center of the main body frame 601. A fuel tank 606 is provided at the top of the engine 100, and a seat 607 is provided behind the fuel tank 606. An ECU (Electronic Control Unit) 50 is provided below the seat 607.

  A rear arm 608 is connected to the main body frame 601 so as to extend rearward of the engine 100. The rear arm 608 rotatably holds the rear wheel 609 and the rear wheel driven sprocket 610. A three-way catalyst 616 is inserted in the exhaust pipe 12, and a muffler 612 is attached to the rear end of the exhaust pipe 12.

  A drive shaft 613 is attached to the engine 100, and a rear wheel drive sprocket 614 is attached to the drive shaft 613. The rear wheel drive sprocket 614 is connected to the rear wheel driven sprocket 610 via the chain 615.

(2) Configuration of Engine System FIG. 2 is a schematic diagram showing an engine system 200 according to the present embodiment. As shown in FIG. 2, the engine system 200 includes an accelerator opening sensor 31, a crank angle sensor 32, a throttle sensor 33, motors 34 and 35, an ECU 50, and the engine 100.

  Engine 100 includes a cylinder 1 and an outer container 21. The outer container 21 accommodates a part of the air-fuel mixture burned in the cylinder 1 (hereinafter referred to as burned gas). Details will be described later.

  A piston 2 is provided in the cylinder 1 so as to be movable up and down. The piston 2 is connected to the crankshaft 42 via a connecting rod 41 and a crank (not shown). A combustion chamber 3 is provided in the upper part of the cylinder 1. The combustion chamber 3 communicates with the outside of the engine 100 via the intake port 4 and the exhaust port 5.

  An intake valve 6 is disposed at the opening end on the downstream side of the intake port 4 so as to be opened and closed, and an exhaust valve 7 is disposed at the opening end on the upstream side of the exhaust port 5 so as to be opened and closed. An intake valve driving device 6 a for driving the intake valve 6 is provided at the upper end of the intake valve 6. An exhaust valve driving device 7 a for driving the exhaust valve 7 is provided at the upper end of the exhaust valve 7.

  An ignition plug 8 for performing spark ignition in the combustion chamber 3 is provided on the upper portion of the combustion chamber 3. A combustion timing measuring device 10 for measuring the combustion timing of the air-fuel mixture is provided at the side of the combustion chamber 3. An intake pipe 11 is attached to the upstream opening end of the intake port 4, and an exhaust pipe 12 is attached to the downstream opening end of the exhaust port 5.

  The outer container 21 is attached to the side surface of the cylinder 1. The outer container 21 is provided with partition plates 24 and 25 that divide the inside of the outer container 21 into two spaces 22 and 23. The burned gas in the cylinder 1 is accommodated in the space 23. Hereinafter, the space 23 is referred to as a burned gas storage unit 23.

  One end of the partition plate 24 is fixed to the upper surface in the outer container 21. A rotation shaft 26 is provided at the other end of the partition plate 24 so as to be rotatable with respect to the partition plate 24. The rotation shaft 26 is connected to the rotation shaft of the motor 34 and is rotated by the motor 34.

  One end of the partition plate 25 is fixed to the rotating shaft 26. As the rotation shaft 26 rotates, the partition plate 25 rotates about the rotation shaft 26. At this time, the other end of the partition plate 25 slides along the inner surface in the outer container 21. Thereby, the volume of the burned gas storage part 23 is adjusted. Therefore, the amount of burned gas accommodated in the burned gas storage portion 23 can be adjusted by rotating the rotation shaft 26.

  The burned gas storage unit 23 and the inside of the cylinder 1 are communicated with each other by a communication hole 28 having a square cross section formed in a side portion of the cylinder 1. The communication hole 28 is provided with an adjustment valve 29 for adjusting the flow rate of burnt gas passing through the communication hole 28.

  One end side of the adjustment valve 29 is fixed to a rotating shaft 30 provided in the outer container 21. The rotation shaft 30 is connected to the rotation shaft of the motor 35 and is rotated by the motor 35. The opening degree of the adjustment valve 29 can be adjusted by rotating the rotation shaft 30. Thereby, the flow rate of the burned gas passing through the communication hole 28 is adjusted.

  The intake pipe 11 is provided with an injector 9 for supplying fuel into the cylinder 1. The intake pipe 11 is provided with an electronically controlled throttle valve (ETV) 14. When the driver operates an accelerator grip (not shown), the ECU 50 adjusts the opening of the ETV 14 (hereinafter referred to as the throttle opening). Thereby, the amount of air (intake air) sucked into the cylinder 1 is adjusted.

  The accelerator opening sensor 31 detects the amount of operation of the accelerator grip by the driver (hereinafter referred to as the accelerator opening) and gives the detected value to the ECU 50. The crank angle sensor 32 detects a rotation angle of the crankshaft 42 (hereinafter referred to as a crank angle), and gives the detected value to the ECU 50. The throttle sensor 33 detects the throttle opening and gives the detected value to the ECU 50.

  The ECU 50 includes an I / F (interface) 51, a CPU (central processing unit) 52, a ROM (read only memory) 53, and a RAM (random access memory) 54. The detected values of the sensors 31 to 33 and the combustion timing measuring instrument 10 are given to the CPU 52 via the I / F 51.

  The CPU 52 controls the intake valve driving device 6a, the exhaust valve driving device 7a, the spark plug 8, the injector 9, the ETV 14, and the motors 34 and 35 based on the detected values of the sensors 31 to 33 and the combustion timing measuring device 10. Details of the control operation of the CPU 52 will be described later. The ROM 53 stores a control program for the CPU 52 and the like. The RAM 54 stores various data and functions as a work area for the CPU 52.

(3) Engine Operation Next, the operation of the engine 100 will be described. In the present embodiment, the operation of each part is controlled by the CPU 52 so that combustion by the HCCI method (hereinafter referred to as HCCI combustion) and combustion by the spark ignition method (hereinafter referred to as spark ignition combustion) are selectively performed. Is done. Hereinafter, HCCI combustion and spark ignition combustion will be briefly described.

(3-1) HCCI combustion First, the state of the engine 100 during HCCI combustion will be described. In the present embodiment, a 4-stroke engine is used as engine 100.

  FIG. 3 is a schematic diagram showing a state of engine 100 during HCCI combustion. In FIG. 3A, the air-fuel mixture is self-ignited. At this time, the upper surface of the piston 2 is located above the upper surface of the communication hole 28. Thereby, the piston 2 side of the communication hole 28 is closed by the side surface of the piston 2.

  As shown in FIGS. 3A and 3B, the piston 2 of the engine 100 descends from TDC (Top Dead Center) to BDC (Bottom Dead Center) in the expansion stroke. Thereafter, as shown in FIGS. 3B and 3C, the piston 2 rises from BDC to TDC in the exhaust stroke.

  Here, in the engine 100, as shown in FIG. 3B, the upper surface of the piston 2 is positioned below the upper surface of the communication hole 28 before and after BDC. Thereby, the piston 2 side of the communication hole 28 is opened. That is, the burned gas storage unit 23 and the inside of the cylinder 1 communicate with each other through the communication hole 28 in a predetermined period before the end of the expansion stroke and in a predetermined period after the start of the exhaust stroke. At this time, a part of the air-fuel mixture (burned gas) burned in FIG. 3A flows into the burned gas storage unit 23 by the pressure generated during combustion.

  3C, the upper surface of the piston 2 is positioned above the upper surface of the communication hole 28 before and after TDC. Thereby, the piston 2 side of the communication hole 28 is closed by the side surface of the piston 2. In this case, the movement of the burned gas between the cylinder 1 and the burned gas storage unit 23 is blocked. Thereby, the burned gas is held in the burned gas storage unit 23.

  Next, as shown in FIGS. 3C and 3D, the piston 2 descends from TDC to BDC in the intake stroke. Thereafter, as shown in FIGS. 3D and 3A, the piston 2 rises from BDC to TDC in the compression stroke. Thereby, the air-fuel mixture self-ignites.

  Also in the predetermined period before the end of the intake stroke and the predetermined period after the start of the compression stroke, as shown in FIG. 3D, the upper surface of the piston 2 is more than the upper surface of the communication hole 28 as in the expansion stroke and the exhaust stroke. Located below. That is, the burned gas storage unit 23 and the inside of the cylinder 1 are communicated with each other through the communication hole 28 in a predetermined period before the end of the intake stroke and in a predetermined period after the start of the compression stroke. At this time, since the inside of the cylinder 1 is at a lower pressure than the inside of the burned gas storage unit 23, the burned gas in the burnt gas storage unit 23 flows into the cylinder 1. Thereby, the mixture in the cylinder 1 is stratified and the temperature of the mixture rises. As a result, HCCI combustion can be performed reliably.

  In the present embodiment, it is assumed that the upper surface of the piston 2 and the lower surface of the communication hole 28 are flush with each other in the BDC (see FIGS. 3B and 3D). That is, in the BDC, the piston 2 side of the communication hole 28 is completely opened.

(3-2) Spark Ignition Combustion FIG. 4 is a schematic diagram showing a state of engine 100 during spark ignition combustion.

  As shown in FIG. 4, the communication hole 28 is closed by the adjustment valve 29 during the spark ignition combustion. Thereby, the movement of the burned gas between the cylinder 1 and the burned gas storage unit 23 is prevented. In this state, normal spark ignition combustion using the spark plug 8 is performed.

(3-3) Operation Region As described above, in the present embodiment, HCCI combustion and spark ignition combustion are selectively performed under the control of the CPU 52 (FIG. 2). CPU 52 selects one of HCCI combustion and spark ignition combustion based on the relationship between the rotational speed of engine 100 and the load on engine 100. The load on engine 100 is detected by a detection device (not shown) provided on engine 100. Further, the rotational speed of the engine 100 is calculated by the CPU 52 based on the detection value of the crank angle sensor 32.

  FIG. 5 is a diagram showing an operation region (hereinafter referred to as HCCI combustion region) by HCCI combustion of engine 100 and an operation region (hereinafter referred to as spark ignition combustion region) by spark ignition combustion. In FIG. 5, the horizontal axis indicates the rotation speed of engine 100, and the vertical axis indicates the load of engine 100. The region surrounded by the solid line H1 indicates the HCCI combustion region, and the region surrounded by the solid line H2 indicates the spark ignition combustion region. The relationship shown in FIG. 5 is stored in the ROM 53 or RAM 54 of the ECU 50.

  As shown in FIG. 5, in the present embodiment, HCCI combustion is performed in a medium to low load region excluding a part of the low load region in a region where the rotation speed of engine 100 is lower than a predetermined value. The reason will be briefly described below.

  When HCCI combustion is performed in a state where a large load is applied to the engine 100, the combustion speed of the air-fuel mixture increases. Therefore, when HCCI combustion is performed at a high load, an impact is generated due to combustion that propagates rapidly, and engine 100 may be damaged.

  Further, when the rotational speed of the engine 100 is high, the number of times the air-fuel mixture burns increases, and heat from the combustion reaction is accumulated in the cylinder 1. The amount of NOx (nitrogen oxide) generated by the combustion of the air-fuel mixture depends on the combustion temperature in the cylinder 1. Therefore, as the rotational speed of engine 100 increases, the concentration of generated NOx increases.

  Moreover, the temperature of the burned gas accommodated in the outer container 21 is low when the engine 100 is started and when the load is low. Therefore, even if burned gas in the outer container 21 flows into the cylinder 1, the temperature of the air-fuel mixture may not rise sufficiently. Thereby, the air-fuel mixture may not be able to self-ignite.

  Therefore, in the present embodiment, when the rotation speed of engine 100 is high, normal spark ignition combustion is performed when engine 100 is at a high load, when engine 100 is started, and when engine 100 is at a low load. Thereby, irregular combustion such as breakage of engine 100, generation of NOx, and misfire can be prevented.

(4) CPU Control Next, the control operation of the CPU 52 (FIG. 2) will be described.

  FIG. 6 is a flowchart showing the control operation of the CPU 52.

  First, as shown in FIG. 6, the CPU 52 obtains driving information (step S1). The driving information is information related to the operating state of the engine system 200. The operation information includes, for example, the accelerator opening, the rotation speed of the engine 100, the load of the engine 100, the oil temperature, the water temperature, the throttle opening, the crank angle, the opening / closing timing of the intake valve 6 and the exhaust valve 7, and the like.

  Next, the CPU 52 determines whether or not the engine 100 is in the HCCI combustion region (see FIG. 5) based on the operation information acquired in step S1 (step S2). When the engine 100 is in the HCCI combustion region, the CPU 52 performs an HCCI combustion process (step S3). Then, it returns to step S1. Details of the HCCI combustion process will be described later.

  In step S2, when the engine 100 is not in the HCCI combustion region, that is, in the spark ignition combustion region (see FIG. 5), the CPU 52 performs a spark ignition combustion process (step S4). In this case, normal spark ignition combustion control is performed. Then, it returns to step S1. In the spark ignition combustion process, the CPU 52 controls the motor 34 (FIG. 2) to set the opening of the adjustment valve 29 to zero. That is, the communication hole 28 is closed.

(4-1) HCCI Combustion Process In the HCCI combustion process, a target combustion timing (hereinafter referred to as a target combustion timing) is determined in advance according to the rotational speed of the engine 100. The CPU 52 controls each unit so that the combustion timing detected by the combustion timing measuring instrument 10 (FIG. 2) is equal to the target combustion timing. The target combustion timing is an ignition timing at which thermal efficiency and combustion stability are most improved when HCCI combustion is performed based on the acquired operation information. The target combustion timing is stored as a map in the ROM 53 or the RAM 54 so as to correspond to arbitrary operation information.

(A) Combustion time First, the combustion time will be described.

  As described above, the combustion timing is detected by the combustion timing meter 10. For example, the combustion time is the time when the heat generation rate in the cylinder 1 is maximized (the time when dQ / dθ is maximized), or the time when the pressure change rate in the cylinder 1 due to combustion is maximized (dP / dθ is It can be detected as one of the maximum times). Q indicates the amount of heat generated in the cylinder 1, P indicates the pressure in the cylinder 1, and θ indicates the crank angle.

  Moreover, you may use the time when a combustion mass ratio (ratio of the mass of the burned part with respect to the mass of the whole air-fuel mixture) becomes 50% as a combustion timing. FIG. 7 shows an example of the relationship between the crank angle and the heat generation rate in the cylinder 1 and the relationship between the crank angle and the combustion mass ratio. The time when the combustion mass ratio becomes 50% is slightly retarded compared to the time when dP / dθ is maximum, but as shown in FIG. 7, the time when the combustion mass ratio becomes 50% and dQ / The time when dθ is maximized is almost the same. Therefore, the time when the combustion mass ratio becomes 50% may be set as the combustion time.

  Further, when the ion current in one cycle of engine 100 is integrated, the timing when the integrated value becomes 50% of the ion current for one cycle is substantially the same as the timing when the combustion mass ratio becomes 50%. Therefore, the time when the integrated value of the ion current becomes 50% of the ion current for one cycle may be set as the combustion time.

  In the present embodiment, as the combustion timing measuring instrument 10, for example, an apparatus that can measure an ion current using an ion probe or the like is used. And the time when the integrated value of the measured ion current becomes 50% of the ion current for one cycle is defined as the combustion time.

(B) CPU Control Operation During HCCI Combustion Process Next, the control operation of the CPU 52 (FIG. 2) during the HCCI combustion process will be described.

  FIG. 8 is a flowchart showing details of the HCCI combustion process shown in step S3 of FIG.

  As shown in FIG. 8, the CPU 52 reads the target combustion timing corresponding to the operation information (rotation speed of the engine 100) acquired in step S1 of FIG. 6 from the ROM 53 or RAM 54 (step S11).

  Next, the CPU 52 determines the fuel injection timing, the fuel injection amount, and the air amount based on the operation information acquired in step S1 of FIG. 6 (step S12). Note that the combustion injection timing is determined, for example, so that the fuel injected from the injector 9 is supplied into the cylinder 1 during the intake stroke. Further, the fuel injection amount is determined based on the accelerator opening, for example. Further, the amount of air is determined so that the air-fuel ratio of the air-fuel mixture becomes the theoretical air-fuel ratio (about 14.5: 1), for example.

  Next, the CPU 52 determines the amount of burned gas supplied from the external container 21 (FIG. 2) into the cylinder 1 (FIG. 2) based on the target combustion timing read in step S11 and the air amount determined in step S12. Is determined (step S13). The temperature in the cylinder 1 can be adjusted by adjusting the amount of burnt gas.

  Next, the CPU 52 determines whether or not a correction coefficient has been calculated in the process one cycle before (step S14). The correction coefficient is calculated in the process of step S20 described later.

  When the correction coefficient is calculated one cycle before, the CPU 52 multiplies the burned gas amount determined in step S13 by the correction coefficient (step S15).

  Next, based on the fuel injection timing, fuel injection amount, air amount determined in step S12, and the burned gas amount calculated in step S15, the CPU 52 opens and closes the intake valve 6 (FIG. 2), exhaust valve 7 (FIG. 2), the burned gas storage unit 23 (FIG. 2) volume, and the throttle opening are determined (step S16).

  When the correction coefficient is not calculated in step S14, the CPU 52 takes in the intake air based on the fuel injection timing, the fuel injection amount, the air amount determined in step S12, and the burned gas amount determined in step S13. The opening / closing timing of the valve 6, the opening / closing timing of the exhaust valve 7, the volume of the burned gas storage unit 23, and the throttle opening are determined.

  Next, the CPU 52 self-ignites and burns the air-fuel mixture based on the opening / closing timing of the intake valve 6, the opening / closing timing of the exhaust valve 7, the volume of the burned gas storage unit 23, and the throttle opening determined in step S <b> 16. The actual combustion timing is acquired from the combustion timing measuring instrument 10 (FIG. 2) (step S17).

  Next, the CPU 52 calculates an error between the target combustion timing read in step S11 and the actual combustion timing acquired in step S17 (step S18). Next, the CPU 52 determines whether or not the absolute value of the error calculated in step S18 is greater than or equal to a preset threshold value (step S19).

  When the absolute value of the error is less than or equal to the threshold value, the CPU 52 calculates a correction coefficient for the burned gas amount (step S20). Thereafter, the CPU 52 returns to step S1 in FIG.

  When the absolute value of the error is larger than the threshold value in step S19, the CPU 52 performs the spark ignition combustion process after closing the communication hole 28 with the adjusting valve 29 (step S21). Then, it returns to step S1 of FIG. By providing the processing of step S19 and step S21, when the actual combustion timing is significantly different from the target combustion timing, spark ignition combustion can be performed without performing HCCI combustion. Thereby, irregular combustion such as early ignition and misfire of the air-fuel mixture can be prevented.

(C) Correction coefficient The correction coefficient for the burned gas amount calculated in step S20 is calculated so that an error between the target combustion timing and the actual combustion timing is small.

  Specifically, when the actual combustion timing is later than the target combustion timing, the correction coefficient is calculated so that the ratio of burned gas in the cylinder 1 (FIG. 2) increases. As the ratio of burned gas in the cylinder 1 increases, the temperature of the air-fuel mixture rises. Thereby, the combustion timing of the air-fuel mixture advances.

  When the actual combustion timing is earlier than the target combustion timing, the correction coefficient is calculated so that the ratio of burned gas in the cylinder 1 becomes small. As the ratio of burned gas in the cylinder 1 decreases, the temperature of the air-fuel mixture decreases. Thereby, the combustion timing of the air-fuel mixture is retarded.

  The amount of burnt gas in the cylinder 1 can be adjusted by, for example, any one of the following methods or a combination of the following methods.

(D) Method for adjusting the amount of burnt gas in the cylinder (d-1) Adjustment by the burnt gas storage unit The volume of the burnt gas storage unit 23 (FIG. 2) is adjusted to be supplied into the cylinder 1. The amount of burnt gas can be adjusted. When adjusting the volume of the burned gas storage unit 23, the CPU 52 rotates the partition plate 25 by controlling the motor 35 (FIG. 2).

  When the volume of the burnt gas storage unit 23 is increased, the pressure drop in the burnt gas storage unit 23 caused by the burnt gas flowing out into the cylinder 1 is reduced. In this case, the burned gas can be supplied into the cylinder 1 while keeping the pressure in the burned gas storage unit 23 high. Further, since the volume of the burned gas storage unit 23 increases, the amount of burned gas stored in the burned gas storage unit 23 increases. Therefore, a sufficient amount of burned gas can be supplied into the cylinder 1. Thereby, the temperature of the air-fuel mixture rises and the combustion timing is advanced.

  On the other hand, when the volume of the burnt gas storage unit 23 is reduced, the pressure drop in the burnt gas storage unit 23 caused by the burnt gas flowing out into the cylinder 1 increases. In this case, the pressure drop in the burned gas storage part 23 when the burned gas is supplied into the cylinder 1 becomes large. Further, since the volume of the burned gas storage unit 23 is reduced, the stored amount of burned gas in the burned gas storage unit 23 is reduced. Accordingly, the amount of burned gas supplied into the cylinder 1 is reduced. Thereby, the temperature of the air-fuel mixture decreases and the combustion timing is retarded.

(D-2) Adjustment by Exhaust Valve The amount of burnt gas supplied into the cylinder 1 can be adjusted by adjusting the time (opening period) during which the exhaust valve 7 (FIG. 2) is open.

  When the opening period of the exhaust valve 7 is shortened, the amount of burned gas flowing out from the cylinder 1 to the exhaust port 5 decreases. As a result, the amount of burned gas flowing from the cylinder 1 into the burned gas storage unit 23 increases.

  In this case, a sufficient amount of burned gas is stored in the burned gas storage unit 23. Accordingly, a sufficient amount of burned gas can be supplied from the burned gas storage portion 23 into the cylinder 1. As a result, the temperature of the air-fuel mixture rises and the combustion timing is advanced.

  On the other hand, when the opening period of the exhaust valve 7 is lengthened, the amount of burnt gas flowing out from the cylinder 1 to the exhaust port 5 increases. Accordingly, the amount of burned gas flowing from the cylinder 1 into the burned gas storage unit 23 is reduced.

  In this case, the amount of burned gas stored in the burned gas storage unit 23 decreases. Accordingly, the amount of burned gas supplied from the burned gas storage unit 23 into the cylinder 1 is reduced. As a result, the temperature of the air-fuel mixture decreases and the combustion timing is retarded.

  The opening period of the exhaust valve 7 can be shortened by, for example, retarding the opening time (opening time) of the exhaust valve 7 or advancing the closing time (closing time) of the exhaust valve 7. . Further, the opening period of the exhaust valve 7 can be extended by, for example, advancing the opening timing of the exhaust valve 7 or delaying the closing timing of the exhaust valve 7.

(5) Effects of the present embodiment (a) In the engine system 200 according to the present embodiment, the communication hole 28 is opened and closed on the outer peripheral surface of the piston 2 as the piston 2 moves up and down. Specifically, the communication hole 28 is opened during a predetermined period in which the piston 2 is located near the BDC. Further, in the period excluding the predetermined period, the communication hole 28 is closed by the outer peripheral surface of the piston 2.

  In this case, during the predetermined period in the expansion stroke and the exhaust stroke, the burned gas in the cylinder 1 flows into the burned gas storage portion 23 through the communication hole 28 due to the pressure generated during combustion. Further, during the predetermined period in the intake stroke and the compression stroke, the burned gas in the burned gas storage unit 23 flows into the cylinder 1 due to the low pressure in the cylinder 1.

  Thus, in the present embodiment, without providing a valve for controlling the flow of burned gas, the burned gas is stored in the burned gas storage section 23 and the burned gas is stored in the cylinder 1. Supply can be made at an appropriate time. Thereby, the air-fuel mixture can be surely self-ignited with a low-cost engine system.

  (B) Moreover, in this Embodiment, the volume of the burned gas accommodating part 23 can be adjusted. Thereby, the quantity of the burned gas supplied in the cylinder 1 can be adjusted. As a result, the combustion timing of the air-fuel mixture can be adjusted, and stable HCCI combustion becomes possible.

  (C) Further, the communication hole 28 can be closed by the adjustment valve 29. In this case, when the engine 100 is not suitable for HCCI combustion, the communication hole 28 can be closed by the regulating valve 29 and spark ignition combustion can be performed. That is, in the present embodiment, HCCI combustion and spark ignition combustion can be selectively performed according to the state of engine 100. Thereby, the output of engine 100 can be stabilized.

  (D) In the present embodiment, the amount of burned gas accommodated in the burned gas accommodating portion 23 can be adjusted by adjusting the opening / closing timing of the exhaust valve 7. Thereby, the quantity of the burned gas supplied in the cylinder 1 can be adjusted. As a result, the combustion timing of the air-fuel mixture can be adjusted, and stable HCCI combustion becomes possible.

  (E) In this embodiment, each part of engine system 200 is controlled so that self-ignition combustion is performed at the set target combustion timing. Thereby, knocking and misfire can be prevented, and stable operation of engine 100 becomes possible.

  (F) Further, when the error between the target combustion timing and the actual combustion timing is large, spark ignition combustion is performed. Thereby, irregular combustion such as early ignition and misfire of the air-fuel mixture can be surely prevented.

  (G) In this embodiment, when the rotation speed of engine 100 is high, normal spark ignition combustion is performed when engine 100 is at a high load, when engine 100 is started, and when engine 100 is at a low load. Thereby, irregular combustion such as breakage of engine 100, generation of NOx, and misfire can be prevented.

(6) Other Embodiments (6-1) Example of Installation of External Container In the above embodiment, a case where one external container 21 is provided in one cylinder 1 has been described. The outer container 21 may be provided.

  9 and 10 are diagrams showing an example of the engine 100 including the two outer containers 21. FIG. 10 is a cross-sectional view taken along line AA in FIG.

  As shown in FIGS. 9 and 10, in this example, two outer containers 21 are provided on both side surfaces of the cylinder 1 so as to face each other. In this configuration, as shown by arrows in FIGS. 9 and 10, the burned gas flowing into the cylinder 1 from the two outer containers 21 joins at the center of the cylinder 1. For this reason, the flow rate of the burned gas flowing into the cylinder 1 from the external container 21 decreases at the central portion in the cylinder 1.

  In this case, the burned gas that has flowed into the cylinder 1 can be prevented from colliding with the wall surface of the cylinder 1 at a high speed. Thereby, it is possible to prevent the heat of the burned gas from being released from the wall surface of the cylinder 1. As a result, the temperature of the air-fuel mixture can be reliably increased.

  Further, in this example, since the burned gas can be stored in the two external containers 21, a sufficient amount of burned gas can be supplied into the cylinder 1.

  As a result, the air-fuel mixture can be surely self-ignited.

  Note that three or more external containers 21 may be provided in one cylinder 1. In this case, each communication hole 28 is formed so that the burned gas flowing into the cylinder 1 from each outer container 21 joins at the center of the cylinder 1. In this case, the flow rate of the burned gas flowing into the cylinder 1 from the external container 21 decreases at the central portion in the cylinder 1. Thereby, it is possible to prevent the heat of the burned gas from being released from the wall surface of the cylinder 1.

(6-2) Other Examples of Piston Piston 2 having a shape described below may be used.

  FIG. 11 is a diagram illustrating another example of the piston 2. The piston 2 in FIG. 11 has a protrusion 2a formed on the upper surface so as to extend upward. In this configuration, as shown by an arrow in FIG. 11, the burnt gas flowing into the cylinder 1 from the outer container 21 collides with the protrusion 2 a. At this time, the flow direction of the burned gas changes upward and the flow velocity decreases.

  In this case, it is possible to prevent the burned gas flowing into the cylinder 1 from the external container 21 from colliding with the wall surface of the cylinder 1 at a high speed. Thereby, it is possible to prevent the heat of the burned gas from being released from the wall surface of the cylinder 1. As a result, the temperature of the air-fuel mixture can be reliably increased. Therefore, the air-fuel mixture can be surely self-ignited.

  Moreover, since the flow of burned gas is controlled by the protrusion 2a, the air-fuel mixture in the cylinder 1 is sufficiently stratified. Thereby, the temperature of the air-fuel mixture can be further increased. As a result, the air-fuel mixture can be self-ignited more reliably.

(6-3) Adjustment of the amount of burned gas in the cylinder Adjusting the length of the intake pipe 11 (FIG. 2) or adjusting the opening of the adjustment valve 29 (FIG. 2) Adjustments may be made. Further, the amount of burned gas in the cylinder 1 may be adjusted by combining some of the plurality of methods described above.

(6-4) Application to Other Vehicles In the above-described embodiment, the motorcycle 100 has been described as an example of the vehicle. However, the engine system according to the present invention can be applied to other vehicles such as an automatic tricycle and an automatic four-wheel vehicle. Can be applied to.

(6-5) Cylinder shape The cylinder 1 and the outer container 21 may be formed as separate bodies or may be formed integrally.

(7) Correspondence between each constituent element of claims and each element of the embodiment Hereinafter, an example of correspondence between each constituent element of the claims and each element of the embodiment will be described. It is not limited to.

  In the above embodiment, the communication hole 28 is an example of a communication part, the combustion timing measuring instrument 10 is an example of a combustion timing measuring means, the ROM 53 or the RAM 54 is an example of a storage part, and the CPU 52 is an example of a control means. Yes, the partition plate 25 is an example of volume adjusting means, the exhaust port 5 is an example of an exhaust passage, the exhaust valve driving device 7a is an example of an exhaust valve driving means, and the spark plug 8 is an example of an ignition means. The adjustment valve 29 is an example of an opening / closing means, the projecting portion 2a is an example of a flow velocity reduction portion, the rear wheel 609 is an example of a drive wheel, a rear wheel driven sprocket 610, a drive shaft 613, a rear wheel drive sprocket. 614 and chain 615 are examples of transmission mechanisms.

  As each constituent element in the claims, various other elements having configurations or functions described in the claims can be used.

  The present invention can be used for various vehicles, ships, generators and the like equipped with an engine.

1 is a schematic diagram of a motorcycle according to an embodiment of the present invention. It is a mimetic diagram showing an engine system concerning this embodiment. It is a schematic diagram which shows the state of the engine at the time of HCCI combustion. It is the schematic diagram which showed the state of the engine at the time of spark ignition combustion. It is a figure which shows the operation area | region by HCCI combustion of an engine, and the operation area | region by spark ignition combustion. It is a flowchart which shows the control operation of CPU. An example of the relationship between the crank angle in a cylinder and a heat release rate, and the relationship between a crank angle and a combustion mass ratio is shown. It is a flowchart which shows the detail of HCCI combustion processing. It is a figure which shows an example of the engine provided with two external containers. FIG. 10 is a sectional view taken along line AA in FIG. 9. It is a figure which shows the other example of a piston.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 2a Protruding part 4 Intake port 5 Exhaust port 6 Intake valve 6a Intake valve drive device 7 Exhaust valve 7a Exhaust valve drive device 8 Spark plug 9 Injector 10 Combustion timing measuring instrument 11 Intake pipe 12 Exhaust pipe 14 Throttle valve 21 External container 23 Burned gas storage part 28 Communication hole 29 Regulating valve 50 ECU
100 Engine 200 Engine System 609 Rear Wheel 610 Rear Wheel Driven Sprocket 613 Drive Shaft 614 Rear Wheel Drive Sprocket 615 Chain

Claims (12)

An engine system for driving a mechanical device,
An engine having a cylinder and a piston that reciprocates within the cylinder, and capable of self-ignition combustion;
A burned gas storage section for storing the burned gas in the cylinder,
The cylinder has a communication portion for communicating the inside of the cylinder and the burned gas storage portion,
The engine system is characterized in that the communication portion is provided so as to be in a communication state and a cutoff state by a reciprocating motion of the piston. The communication portion is closed by the outer peripheral surface of the piston being closed, and the communication portion is in a communication state by removing the outer peripheral surface of the piston from the communication portion. Item 1. The engine system according to Item 1. 3. The engine system according to claim 1, wherein the communication portion is provided so as to be opened when the piston is positioned near a bottom dead center. Combustion timing measuring means for measuring the combustion timing of the air-fuel mixture in the cylinder;
A storage unit for storing an optimal combustion timing of the air-fuel mixture;
And a control means for controlling the operation of the engine so that a difference between the combustion timing measured by the combustion timing measuring means and the optimum combustion timing stored in the storage unit is reduced. The engine system according to any one of claims 1 to 3. A volume adjusting means for adjusting the volume of the burned gas storage unit;
The engine system according to claim 4, wherein the control means adjusts the combustion timing in the cylinder by controlling the volume adjusting means. The control means advances the combustion timing of the air-fuel mixture in the cylinder by increasing the volume of the burned gas storage unit, and reduces the volume of the burned gas storage unit to reduce the mixing in the cylinder. 6. The engine system according to claim 5, wherein the combustion timing of the gas is retarded. An exhaust passage for discharging burned gas from the cylinder;
An exhaust valve for opening and closing the exhaust passage;
An exhaust valve driving means for driving the exhaust valve;
The engine system according to any one of claims 4 to 6, wherein the control means adjusts the combustion timing in the cylinder by controlling the exhaust valve driving means. The control means advances the combustion timing of the air-fuel mixture in the cylinder by delaying the opening timing of the exhaust valve, and advances the combustion timing of the air-fuel mixture in the cylinder by increasing the opening timing of the exhaust valve. The engine system according to claim 7, wherein the angle is retarded. The engine is
Ignition means for spark ignition of the air-fuel mixture in the cylinder;
Opening and closing means for opening and closing the communication portion;
The engine system according to any one of claims 1 to 8, wherein when the air-fuel mixture in the cylinder is spark-ignited by the ignition means, the communication section is closed by the opening / closing means. The engine system according to any one of claims 1 to 9, wherein the piston has a flow velocity reduction portion that reduces the flow velocity of burned gas supplied into the cylinder from the communication portion. The burned gas storage unit includes a plurality of burned gas storage units,
The communication part includes a plurality of communication parts for communicating the plurality of burned gas storage parts and the inside of the cylinder, respectively.
The engine system according to any one of claims 1 to 10, wherein the plurality of communication portions are formed such that the burned gas flows out toward a substantially central portion of the cylinder. Drive wheels,
The engine system according to any one of claims 1 to 11,
A vehicle comprising: a transmission mechanism that transmits power generated by the engine system to the drive wheels.

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