CN110529271B - Engine unit and saddle-ride type vehicle - Google Patents

Abstract

An engine unit (300, 400) is provided that includes an engine (130), an intake passage member (110), and a communication passage member (363), wherein fuel vapor is introduced from a tank (161) to the intake passage member (110) through the communication passage member (363). The communication passage member (363) has a branch portion for each cylinder. A valve (170, 270) is provided at each branch portion. The valve (170, 270) is arranged such that the capacity of a portion of the communication passage member (363) extending from the downstream intake passage (110x) to the valve is less than half of the exhaust gas amount of the engine (130). The valve (170, 270) is controlled to vary in accordance with the negative pressure fluctuations generated in each four-stroke.

Description

Engine unit and saddle-ride type vehicle

Description of divisional applications

This application is a divisional application of the chinese invention patent application entitled "engine unit and saddle-ride vehicle" filed on 23/4/2015 with application number 201580042693.3.

Technical Field

The invention relates to an engine unit and a saddle-ride type vehicle.

Background

Some vehicles are provided with a tank. The canister contains therein an adsorbent that adsorbs fuel vapor generated in the fuel tank. There are techniques for actively introducing air containing fuel vapor from a canister into a combustion chamber to reduce the amount of fuel vapor adsorbed by the adsorbent and then vented from the canister to the atmosphere. This technique is widely used in an engine unit mounted on an automobile (four-wheeled vehicle). In patent document 1, a case having a large capacity is provided in a passage through which fuel vapor is introduced from a tank into an intake passage member.

Reference list

Patent document

Patent document 1: japanese unexamined patent publication No.2009-57844

Disclosure of Invention

Technical problem

It is desirable to apply the technique described in patent document 1 to an engine unit used in a saddle-ride type vehicle such as a motorcycle. As a result of technical studies conducted by the present inventors, the following facts were found. If the technique of patent document 1 is applied without change to an engine unit widely used in a saddle-ride type vehicle, disadvantages may be caused. That is, there is a possibility that a desired amount of fuel vapor cannot be introduced from the tank to the combustion chamber.

An object of the present invention is to provide an engine unit and a saddle-ride type vehicle each of which is capable of introducing a desired amount of fuel vapor into a combustion chamber.

Technical scheme for solving problems

According to an embodiment of the invention, a multi-cylinder four-stroke engine unit comprises: an engine including a combustion chamber; an intake passage member that is connected to the engine and allows air to be introduced into the combustion chamber; and a throttle valve provided at an intermediate portion of the intake passage member. A combustion chamber, an intake passage member, and a throttle valve are provided for each cylinder. The pressure in the downstream intake passage portion of the intake passage member downstream of the throttle valve varies in such a manner that the pressure varies: creating a smaller pressure drop at a smaller difference from atmospheric pressure and a larger pressure drop at a larger difference from atmospheric pressure in each four-stroke cycle; and, the smaller pressure drop and the larger pressure drop are repeatedly generated based on the four-stroke. The engine unit further includes: a canister connected to the fuel tank and containing therein a adsorbent configured to adsorb fuel vapor contained in intake air from the fuel tank; a communication passage member configured to establish communication between the interior of the tank and the downstream intake passage portion for each cylinder, the communication passage member including a branch portion for each cylinder, the branch portions being connected to the downstream intake passage portion, respectively; a valve provided at the branch portion of the communication passage member such that a capacity of a portion of the communication passage member extending from the intake passage member to the valve is less than half of an exhaust gas amount of the engine, an opening degree of the valve being changeable; and a controller configured to control operation of the valve based on a pressure variation pattern repeatedly generated by the four-stroke according to the smaller pressure drop and the larger pressure drop.

The present inventors have made an effort to find a reason why a desired amount of fuel vapor cannot be introduced from the canister into the combustion chamber when the technique of patent document 1 is applied without change to an engine unit widely used in a saddle-ride type vehicle. The amount of fuel vapor introduced from the canister into the combustion chamber changes in accordance with the amount of pressure drop in the downstream intake passage portion (i.e., the difference between the negative pressure in the downstream intake passage portion and the atmospheric pressure). The downstream intake passage portion is connected to a communication passage member extending from the tank. In view of the above, the present inventors compared the pressure drop generated in the downstream intake passage portion in an engine unit widely used in a saddle-ride type vehicle with the pressure drop in an engine unit widely used in an automobile. As a result of the comparison, the following differences were found.

In some engine units widely used in automobiles, pressure variation in the downstream intake passage portion is suppressed due to a surge tank provided downstream of a throttle valve. Further, in the automobile engine unit having the independent throttle body described in patent document 1, the pressure variation of each cylinder is suppressed by establishing communication between the downstream intake passage portions by providing one or more communicating pipes, for example.

Now, reference is made to an engine unit widely used in a saddle-ride type vehicle. In a saddle-ride type vehicle, a multi-cylinder engine unit having respective throttle bodies is widely used. In this engine unit for a saddle-ride type vehicle, the pressure in its downstream intake passage portion largely changes to be below atmospheric pressure, that is, a large pressure drop is generated in its downstream intake passage portion. The large pressure drop is generated in each four-stroke cycle, and the pressure drop is repeatedly generated based on the four strokes. In patent document 1, a tank having a relatively large capacity is provided to a passage through which fuel vapor is introduced into a downstream intake passage portion. It is assumed that the configuration in patent document 1 is applied without change to an engine unit widely used in a saddle-ride type vehicle in which the pressure in its downstream intake passage portion varies greatly. It has been found that this tends to easily cause a delay in the timing for introducing the fuel vapor into the combustion chamber, and therefore, there is a possibility that a desired amount of fuel vapor cannot be introduced.

In view of the above, in the present invention, the operation of the valve is controlled (more precisely, with pressure variation) on the premise that there is pressure variation. Specifically, the valve is disposed such that the capacity of a portion of the communication passage member between the downstream intake passage portion and the valve is less than half of the exhaust gas amount of the engine. Further, the control valve causes the amount of fuel vapor introduced to be changed in accordance with the smaller pressure drop and the larger pressure drop based on the pressure change pattern that is repeatedly generated by the four strokes.

With this configuration, the operating pressure of the valve is controlled according to the following pressure variation pattern: the large change in pressure is repeated based on the four-stroke. This makes it possible to control the valve in the following manner: so that an appropriate amount of fuel vapor is introduced into the combustion chamber. The capacity of a portion of the communication passage member extending from the intake passage portion to the valve is less than half of the exhaust gas amount of the engine. This reduces the delay in the timing at which the fuel vapor is introduced into the combustion chamber under the condition that the pressure in the downstream intake passage portion greatly changes. Therefore, in the engine unit in which the pressure greatly varies based on the four-stroke, this achieves introduction of a desired amount of fuel vapor into the combustion chamber.

Further, in the present invention, it is preferable that the engine unit further includes a sensor for each downstream intake passage portion, the sensor being configured to detect a negative pressure in the downstream intake passage portion; and the controller is configured to control the operation of the valve based on a detection result obtained by the sensor.

In this configuration, the pressure change is directly detected, and the operation of the valve is controlled based on the detection result. Thereby, the amount of the introduced fuel vapor can be appropriately adjusted according to the pressure change.

Further, in the present invention, preferably, the controller is configured to control the valve such that a ratio of an amount of fuel vapor introduced from the communication passage member into the downstream intake passage portion to an amount of combustion chamber-introduced air, which is an amount of air introduced from the downstream intake passage portion into the combustion chamber, increases as the amount of combustion chamber-introduced air increases, when the amount of combustion chamber-introduced air is equal to or smaller than a predetermined value.

In this configuration, the valve is controlled such that the ratio of the amount of fuel vapor introduced increases as the amount of air introduced into the combustion chamber increases. Therefore, the fuel vapor is introduced into the combustion chamber in such a manner that the fuel vapor has less influence on combustion in the combustion chamber. Therefore, when fuel is actively introduced into the combustion chamber, it is easier to control the engine.

Further, in the present invention, it is preferable that each valve be switchable from a closed state to an open state and from the open state to the closed state, the closed state being a state in which the valve prevents air from flowing between the interior of the tank body and the downstream intake passage portion, and the open state being a state in which the valve allows air to flow between the interior of the tank body and the downstream intake passage portion; and a controller configured to control the valve to perform a valve switching operation in association with a pressure variation pattern in which a smaller pressure drop and a larger pressure drop are repeatedly generated on the basis of a four-stroke, the valve switching operation being a set of an on operation and an off operation, one of the on operation and the off operation being performed first, and the other of the on operation and the off operation being performed, the on operation being an operation of switching the valve from a closed state to an open state, and the off operation being an operation of switching the valve from the open state to the closed state.

In this configuration, the amount of fuel vapor introduced is adjusted (more precisely, with the pressure change) on the premise that there is the above-described pressure change in the downstream intake passage portion. Specifically, the valve switching operation of introducing the fuel vapor is performed in association with the following pressure variation pattern: the smaller pressure drop and the larger pressure drop are repeatedly generated based on the four strokes in each four-stroke cycle. With this configuration, when the fuel vapor is actively introduced from the tank into the combustion chamber, the amount of the introduced fuel vapor is appropriately adjusted in a manner correlated with the pressure change pattern. In the present invention, the valve is disposed such that the capacity of a portion of the communication passage member extending between the downstream intake passage portion and the valve is less than half of the exhaust gas amount of the engine. Thereby, the pressure change in the downstream intake passage portion is transmitted to the valve in a shorter time. This promotes a smooth correlation between the operation of the valve and the pressure change, and reduces the delay in the timing of introducing the fuel vapor into the combustion chamber. Thereby, the amount of fuel vapor introduced into the combustion chamber is more appropriately adjusted.

Further, in the present invention, preferably, when each of the four strokes constituting the four-stroke cycle is counted as one stroke, the controller is configured to control each valve to perform the valve switching operation in association with n stroke periods, where n is a multiple of 4 or 1 or 2.

Both the control of performing the valve switching operation in association with one stroke period (i.e., based on one stroke period) and the control of performing the valve switching operation in association with two stroke periods (i.e., based on two stroke periods) are included in the control associated with the four-stroke cycle. In the case where n is a multiple of 4, when the valve switching operation is performed in association with n stroke periods (i.e., based on the n stroke periods), the operation is performed on a four-stroke cycle basis or in association with a four-stroke cycle spaced apart by one or more four-stroke cycles among the n stroke periods. Therefore, with the above configuration, in any of the above cases, the ventilation amount is adjusted in association with the pressure variation that is repeatedly generated in each four-stroke cycle on a four-stroke basis with a smaller pressure drop and a larger pressure drop.

Further, in the present invention, preferably, the controller is configured to control each valve to perform at least one of the on operation and the off operation in synchronization with n stroke periods, where n is a multiple of 4 or 1 or 2.

In this configuration, at least one of the switching operations is performed in synchronization with n stroke periods, where n is a multiple of 4 or 1 or 2. Therefore, the switching operation is easily controlled.

In the present invention, the controller may control each valve to perform an on operation every n stroke periods, where n is a multiple of 4 or 1 or 2, and then perform an off operation. In the present invention, the controller may control each valve to perform an off operation for every n stroke periods, where n is a multiple of 4 or 1 or 2, and then perform an on operation. In the present invention, the controller may control each valve to perform each of the on operation and the off operation once every n stroke periods, where n is a multiple of 4 or 1 or 2. In the present invention, the controller may control each valve to perform each of the on operation and the off operation once per stroke or every two stroke period. In the present invention, the controller may control each valve to perform each of the turning-on operation and the turning-off operation once in a four-stroke cycle every n stroke periods, where n is a multiple of 4. In the present invention, the controller may control each valve to perform each of the on operation and the off operation once every four stroke periods. In the present invention, the controller may control each valve to perform each of the turning-on operation and the turning-off operation two or more times per n stroke periods, where n is a multiple of 4. In the present invention, the controller may control each valve to perform one of the on operation and the off operation every n stroke periods, where n is a multiple of 4 or 1 or 2, and then perform the other, the timings at which the on operation and the off operation are performed in each period being different between the respective n stroke periods.

Further, in the present invention, it is preferable that each valve be able to be in an open state in which each valve allows air to communicate between the interior of the tank body and the intake passage member through the communication passage member, and the opening degree of each valve in the open state be able to be adjusted; and the controller is configured to control the opening degree of each valve in the open state according to a four-stroke-based pressure variation pattern included in pressure variation patterns in which a smaller pressure drop and a larger pressure drop are repeatedly generated based on the four strokes.

In this configuration, the amount of fuel vapor introduced is adjusted on the premise that the above-described pressure change is present in the downstream intake passage portion (more precisely, the pressure change is utilized). That is, the opening degree of the valve in the open state is controlled based on a four-stroke pressure variation pattern included in pressure variation patterns in which a small pressure drop and a large pressure drop are repeatedly generated based on four strokes. Thus, when the fuel vapor is actively introduced from the canister into the combustion chamber, the amount of the introduced fuel vapor can be appropriately adjusted in accordance with the pressure change pattern based on the four-stroke. In the present invention, the valve is provided such that the capacity of a portion of the communication passage member extending between the downstream intake passage portion and the valve is less than half of the exhaust gas amount of the engine. Therefore, the pressure change in the intake passage member is transmitted to the valve in a shorter time. This reduces the delay in the timing of introducing the fuel vapor into the combustion chamber when the valve is controlled based on the manner of pressure change. Thereby, the amount of fuel vapor introduced into the combustion chamber can be more appropriately adjusted.

Further, in the present invention, preferably, when the four strokes are counted as one cycle, the controller is configured to control the opening degree of each valve in the open state according to a four-stroke based pressure variation manner every n cycle periods, where n is a natural number.

In this configuration, the amount of fuel vapor introduced in every n cycle periods is adjusted according to the four-stroke based pressure variation pattern. This makes it easier to control the engine.

Further, in the present invention, the engine unit may further include a sensor for each downstream intake passage portion, the sensor being configured to detect a negative pressure in the downstream intake passage portion; and the controller may control the opening degree of each valve in the open state based on a detection result obtained by the sensor in each cycle included in the n cycle periods, the detection result being indicative of a four-stroke based pressure variation pattern in each of the n cycle periods. Further, in the present invention, when four strokes are counted as one cycle, the controller may control each valve in the following manner: after the controller keeps the opening degree of the valve in the open state constant for a plurality of cycles, the controller changes the opening degree of each valve in the open state according to a four-stroke-based pressure variation manner.

According to an embodiment of the present invention, a saddle-ride type vehicle includes: the engine unit of the above aspect of the invention; a vehicle body frame that supports an engine unit; a rider seat; a handle provided in front of a rider seat; and a fuel tank connected to a canister contained in the engine unit.

Thus, in a saddle-ride type vehicle having an engine unit in which the pressure largely changes based on the four-stroke, it is achieved that a desired amount of fuel vapor is introduced into the combustion chamber.

In the present invention, "a smaller pressure drop smaller than atmospheric pressure and a larger pressure drop larger than atmospheric pressure" means that there are two pressure drops, one of which is different from atmospheric pressure more than the other.

Drawings

Fig. 1 shows a side view of a motorcycle relating to a first embodiment of the present invention.

Fig. 2 shows a schematic view of the engine unit of the motorcycle in fig. 1 and its external devices. The figure includes a partial cross section of the engine in the engine unit and partially shows the internal structure of the engine.

Fig. 3 shows a schematic diagram representing: how the communication passage member extending from the tank to the downstream intake passage portion is connected; and a structure of a solenoid valve provided to an intermediate portion of the communication passage member. The figure includes a partial cross-sectional view of these components.

Fig. 4(a) and 4(b) show sectional views of the solenoid valve in fig. 3, respectively. Each cross-sectional view includes a portion of a front view of the internal structure of the valve.

Fig. 5 shows the following graph and line combinations: graphs showing open/close states of the intake valve, the exhaust valve, and the solenoid valve, respectively; and a graph showing a change in pressure in the downstream intake passage portion.

Fig. 6(a) and 6(b) show graphs of conditions for controlling the solenoid valve.

Fig. 7 shows a graph of changes in the inflow amount of fuel vapor when the electromagnetic valve is controlled according to various control methods.

Fig. 8 relates to a modification of the embodiment. Specifically, fig. 8 is a combination of the following figures and graphs: a graph showing an open/close state of the solenoid valve; and a graph showing a change in pressure in the downstream intake passage portion.

Fig. 9 relates to another modification of the embodiment. Specifically, fig. 9 is a combination of the following figures and graphs: a graph showing an open/close state of the solenoid valve; and a graph showing a pressure change in the downstream intake passage portion.

Fig. 10(a) and 10(b) each show a sectional view of a throttle valve used in the second embodiment of the present invention in place of the solenoid valve in the first embodiment. Each cross-sectional view includes a portion of a front view of the internal structure of the valve.

Fig. 11 shows a combination of the following figures and graphs: graphs showing open/close states of the intake valve and the exhaust valve, respectively; and a graph showing a pressure change in the downstream intake passage portion.

Fig. 12(a) and 12(b) are graphs showing conditions for controlling the flow rate adjustment valve.

Fig. 13 shows a combination of the following figures: a graph showing a change in the manner of pressure change in the downstream intake passage portion; and a graph showing an operation of changing the opening degree of the throttle valve under the control based on the change of the pressure change manner.

Fig. 14 is a schematic diagram showing a modification in which the present invention is applied to a multi-cylinder engine unit.

Fig. 15 is a graph showing a modification of the control method for the throttle valve.

Detailed Description

[ first embodiment ]

A first embodiment of the present invention will be described below with reference to a motorcycle 1 as an example. The motorcycle 1 is provided with an engine unit 100 embodying the engine unit of the present invention.

In the following description, the front-rear direction refers to the front-rear direction of the vehicle as viewed by a rider R riding on a rider seat 11 of the motorcycle 1. The rider seat 11 will be described later. The left-right direction refers to a left-right direction (vehicle width direction) of the vehicle as viewed by a rider R riding on the rider seat 11. Arrows F and B in the drawing indicate the forward direction and the backward direction, respectively. Arrows L and R in the drawing indicate the leftward direction and the rightward direction, respectively.

As shown in fig. 1, a motorcycle 1 includes a front wheel 2, a rear wheel 3, a vehicle body frame 4, and a rider seat 11. The handle unit 9 is provided to a portion of the vehicle body frame 4 located forward of the rider seat 11. The grip 9R is provided at the right end portion of the handle unit 9, and the grip 9L is provided at the left end portion of the handle unit 9. It should be noted that only grip 9L is shown in fig. 1. The grip 9R is located on the other side of the grip 9L in the left-right direction. The grip 9R is a throttle grip (throttle grip). The brake lever is mounted near the grip 9R. The clutch lever 10 is attached near the grip 9L. The upper end portion of the front fork 7 is fastened to the handle unit 9. The lower end of the front fork 7 supports the front wheel 2.

The swing arm 12 is swingably supported at its front end portion by a lower portion of the vehicle body frame 4. The rear end of the swing arm 12 supports the rear wheel 3. The rear suspension connects a portion of the swing arm 12 other than the swing arm pivot point to the body frame 4. The rear suspension absorbs vibration in the up-down direction.

The vehicle body frame 4 supports the single cylinder engine unit 100. The vehicle body frame 4 may directly support the engine unit 100, or may indirectly support the engine unit 100 via another member. The engine unit 100 includes a four-stroke engine 130. The detailed structure of the engine unit 100 will be described below. The air cleaner 31 is connected to the engine 130. The air cleaner 31 is configured to clean incoming outside or outside air. The air that has been cleaned by the air cleaner 31 is introduced into the engine 130. The muffler 41 is connected to the engine 130. The fuel tank 14 is disposed above the engine 130.

A transmission having a plurality of transmission gears is disposed rearward of the engine 130. The driving force of the engine 130 is transmitted to the rear wheel 3 via the transmission and the chain 26. A shift pedal 24 for changing the gear of the transmission is provided on the left side of the transmission. The foot boards 23 are provided on the left and right sides of the vehicle body frame 4. The footrest 23 is located slightly forward of the rear wheel 3. The footrest 23 is configured to support the feet of a rider R riding the motorcycle.

The front cover 15 is located above the front wheel 2 and in front of the grips 9R and 9L. The meter unit 16 is located between the front cover 15 and the grips 9R, 9L in the front-rear direction. The display surface of the meter unit 16 is configured to display thereon a vehicle speed, an engine speed, a vehicle state, a travel distance, a clock time, a measurement time, and the like.

The engine unit 100 will be described in detail below with reference to fig. 2. In addition to the engine 130, the engine unit 100 includes an intake passage member 110 and an exhaust passage member 120. The intake passage member 110 and the exhaust passage member 120 are connected to an engine 130. The engine Unit 100 further includes a tank 161 and an ECU (Electronic Control Unit) 150. The engine 130 is a four-stroke single cylinder engine. In the engine 130, a crankshaft 134 (to be described later) rotates twice in one engine cycle. One engine cycle includes four strokes, i.e., an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke. The ECU 150 includes hardware such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an ASIC (Application Specific Integrated Circuit), and software such as program data stored in the ROM and/or the RAM. The CPU executes various types of information processing based on software such as program data. The ASIC controls the components of the engine 130 based on the results of the above-described information processing. With this configuration, the ECU 150 controls the components of the engine 130 to smoothly perform the four strokes described above.

The engine 130 includes a cylinder 131, a piston 132, and a crankshaft 134. A piston 132 is disposed in the cylinder 131. The crankshaft 134 is connected to the piston 132 via a connecting rod 133. The combustion chamber 130a is provided in the cylinder 131. The combustion chamber 130a is formed by an outer surface 132a of the piston 132 and an inner wall surface 131a of the cylinder 131. The combustion chamber 130a is a space formed above the piston 132 at the top dead center in the cylinder 131. The combustion chamber 130a communicates the intake passage 110a and the exhaust passage 120 a. An intake passage 110a is located in the intake passage member 110, and an exhaust passage 120a is located in the exhaust passage member 120. The following description is based on the premise that: the space in the cylinder 131 and the intake passage 110a do not overlap each other; and the space inside the cylinder 131 and the exhaust passage 120a do not overlap each other.

An intake valve 141 is provided at a communication port between the intake passage 110a and the combustion chamber 130 a. An exhaust valve 142 is provided at a communication port between the exhaust passage 120a and the combustion chamber 130 a. The engine 130 is provided with a valve operating mechanism configured to operate in such a manner as to correlate the intake valve 141 and the exhaust valve 142 with the motion of the crankshaft 134. The valve operating mechanism includes members such as a camshaft, rocker arms, rocker arm shafts, and the like. These members transmit power generated by rotating crankshaft 134 to intake valve 141 and exhaust valve 142. This configuration enables the intake valve 141 and the exhaust valve 142 to repeatedly open/close respective communication ports between each of the intake passage 110a and the exhaust passage 120a and the combustion chamber 130a at appropriate timings. The timing of opening/closing the valve is associated with four strokes that make up one engine cycle. The ignition plug 143 is provided to ignite the air-fuel mixture in the combustion chamber 130 a. The tip of the ignition plug 143 is located in the combustion chamber 130 a. The ignition plug 143 is electrically connected to the ECU 150. ECU 150 controls ignition by ignition plug 143.

The intake passage 110a communicates with the combustion chamber 130a at one end of the intake passage member 110. The other end of the intake passage member 110 is connected to the air cleaner 31. Outside air is drawn through the air cleaner 31. The air cleaner 31 cleans the air passing through it. The air that has been cleaned by the air cleaner 31 is introduced into the intake passage member 110. The air that has been introduced into the intake passage member 110 from the air cleaner 31 flows toward the engine 130 through the throttle body 111. The throttle body 111 forms a part of the intake passage member 110. The throttle body 111 accommodates a throttle valve 112 therein such that a throttle opening degree thereof is variable. The throttle valve 112 is supported by the throttle body 111 such that the opening degree of a portion of the intake passage 110a located in the throttle body 111 changes in accordance with the throttle opening degree of the throttle valve 112. As the throttle opening of the throttle valve 112 changes, the flow rate of air passing through the throttle body 111 changes. The throttle body 111 is provided with an electric motor configured to change a throttle opening degree of the throttle valve 112. The motor is electrically connected to the ECU 150. The ECU 150 controls the degree to which the throttle valve 112 is rotated by the motor. Thus, the ECU 150 controls the amount of air flowing from the air cleaner 31 into the engine 130 through the intake passage member 110. As described above, the throttle valve used in the present embodiment is an electrically-driven throttle valve driven by an electric motor. Alternatively, a mechanical throttle may be used. The mechanical throttle valve is configured such that the operation of a throttle grip (throttle grip) is transmitted to the throttle valve through a transmission mechanism.

The intake passage member 110 is provided with a fuel injector 144. The fuel injector 144 is configured to inject fuel into the intake passage 110 a. The fuel injector 144 is connected to the fuel tank 14 via a fuel supply pipe 33. Fuel is supplied from the fuel tank 14 to the fuel injector 144 through the fuel supply pipe 33. The fuel injector 144 is electrically connected to the ECU 150. The ECU 150 controls the injection of fuel into the intake passage 110a through the fuel injector 144.

The exhaust passage 120a communicates with the combustion chamber 130a at one end of the exhaust passage member 120. The other end of the exhaust passage member 120 is connected to the muffler 41. Exhaust gas from the engine 130 is discharged to the muffler 41 through the exhaust passage member 120. A three-way catalyst is provided in the exhaust passage 120 a. The catalyst purifies exhaust gas flowing from the engine 130 into the exhaust passage member 120. The exhaust gas purified by the catalyst is discharged to the outside through the muffler 41.

The engine unit 100 is provided with various sensors. For example, the throttle body 111 is provided with an intake pressure sensor 151. The intake pressure sensor 151 detects the pressure in a portion of the intake passage 110a downstream of the throttle valve 112. The throttle body 111 is also provided with a throttle position sensor 152, and the throttle position sensor 152 detects the throttle opening degree of the throttle valve 112. The crankshaft 134 is provided with an rpm rotation speed sensor 153, and the rpm rotation speed sensor 153 detects the rpm rotation speed (revolutions per minute) of the crankshaft 134. The rpm speed sensor 153 also detects the position of the crankshaft 134. A signal of the detection result obtained by the sensor is transmitted to the ECU 150. The ECU 150 controls the operation of the components of the engine unit 100 based on the detection results transmitted by the sensors.

The engine unit 100 also includes a tank 161. Canister 161 is provided to inhibit the emission of fuel vapor from fuel tank 14 to the atmosphere by fuel vapor collected in fuel tank 14. The canister 161 contains therein an adsorbent such as activated carbon. The canister 161 is connected to the fuel tank 14 via a breather pipe 162. The fuel vapor in the fuel tank 14 flows into the canister 161 through the breather pipe 162. The fuel vapor introduced into the canister 161 is adsorbed by the adsorbent in the canister 161.

The tank 161 is also coupled to the intake passage member 110 via a communication passage member 163. The inside of the tank 161 communicates with a communication passage 163a, which communication passage 163a is provided in the communication passage member 163 at one end of the communication passage member 163. The other end of the communication passage member 163 is connected to the downstream intake passage portion 110d of the intake passage member 110. The downstream intake passage portion 110d is a portion of the intake passage member 110 that is located downstream of the throttle valve 112. Thus, it is possible to provide

As shown in fig. 3, the connecting portion 113 is provided to the downstream intake passage portion 110 d. The communication passage member 163 is coupled to the downstream intake passage portion 110d via the connecting portion 113. The connection portion 113 has a communication passage 113a therein. The connecting portion 113 protrudes or protrudes outward with respect to the outer surface of the downstream intake passage portion 110 d. The communication passage member 163 is fixed to the connection portion 113 via a connection fitting 164. The outer surface of the connection fitting 164 and the inner surface of the connection portion 113 are formed with threads. When the connection fitting 164 formed with a thread is screwed into the thread portion of the connection portion 113, these members are fixed to each other. The communication passage 164a is provided in the connection fitting 164. The communication passage 163a in the communication passage member 163 communicates with the intake passage 110a in the downstream intake passage portion 110d via the communication passages 113a and 164 a. As a result, the interior of the tank 161 communicates with the downstream intake passage 110x of the intake passage 110a via the communication passages 163a, 164a, and 113 a. The downstream intake passage 110x is a portion of the intake passage 110a located in the downstream intake passage portion 110 d. In fig. 2, the downstream intake passage 110x is shown as a portion surrounded by a two-dot chain line. In order to replace the connection portion 113 and the connection fitting 164, a connection portion and a connection fitting having no threaded portion may be used. For example, the connection fitting may be a connection head, and may be inserted into a connection portion that does not have a threaded portion. In this case, the connection fitting may be inserted into the connection portion such that the leading end of the connection fitting protrudes into the downstream intake passage 110 x. Alternatively, the front end of the connection fitting is made not to protrude into the downstream intake passage 110 x. Alternatively, the leading end of the connection fitting may be flush with the inner wall surface of the downstream intake passage 110 x.

The solenoid valve 170 is provided to an intermediate portion of the communication passage member 163. As shown in fig. 4(a), the solenoid valve 170 includes: housing 171, core 172, plunger 173, coil 174, valve body 175, and spring 176. The housing 171 is fixed to the communication passage member 163. The core 172 is disposed in the housing 171. Further, a communication passage 163x is provided in the housing 171. The communication passage 163x is bent into an Ω (ohmic) shape. The communication passage 163x is a part of the communication passage 163 a. The communication passage 163x includes an opening 163 y. In fig. 4(a), spring 176 is biased downward toward valve body 175 such that valve body 175 holds opening 163y closed when no current flows through coil 174. The valve body 175 is fixed to the front end of the plunger 173. A state in which the valve body 175 shown in fig. 4(a) closes the opening 163y is hereinafter referred to as a closed state. In the closed state, the fuel vapor cannot flow from the tank 161 to the downstream intake passage portion 110d through the communication passage 163 a.

In this figure, plunger 173 moves upward in response to the flow of current through coil 174. The valve body 175 moves upward with the plunger 173 against the biasing force of the spring 176. Accordingly, the electromagnetic valve 170 is switched to the state shown in fig. 4 (b). This state is hereinafter referred to as "open state". When the solenoid valve 170 is in the open state, the valve body 175 opens the opening 163 y. This allows the fuel vapor to flow from the tank 161 to the downstream intake passage portion 110d through the communication passage 163 a.

The solenoid valve 170 is switchable between an open state and a closed state under the control of the ECU 150. Hereinafter, the operation of switching the electromagnetic valve 170 from the closed state to the open state under the control of the ECU 150 is referred to as "on operation". Meanwhile, an operation of switching the solenoid valve 170 from the open state to the closed state under the control of the ECU 150 is referred to as a "cut-off operation".

Switching the electromagnetic valve 170 to the open state establishes communication between the interior of the tank 161 and the downstream intake passage 110 x. At the same time, the pressure is transmitted from the combustion chamber 130a to the downstream intake passage 110 x. For example, during or during the intake stroke, the pressure in the downstream intake passage 110x is mostly sub-atmospheric. If the electromagnetic valve 170 is in the open state in the intake stroke, the pressure lower than the atmospheric pressure is transmitted from the downstream intake passage 110x to the tank 161 through the communication passage 163 a. Therefore, the fuel vapor in the tank 161 flows into the downstream intake passage 110x through the communication passage 163 a. The fuel vapor that has flowed into the downstream intake passage 110x also flows into the combustion chamber 130 a. The fuel vapor introduced into the combustion chamber 130a is ignited in the combustion chamber 130 a. Therefore, the fuel vapor in the canister 161 is introduced into the combustion chamber 130a, and this reduces the emission of the fuel vapor in the canister 161 to the atmosphere.

Now, in the field of automobiles (four-wheeled vehicles), the following techniques are known. A valve is provided to a passage through which fuel vapor is introduced from the tank into the intake system. The amount of fuel vapor introduced into the air intake system from the canister can be controlled by the valve. The present inventors have conducted technical studies and found the following facts. Disadvantages may be caused if the above-described technology for an automobile is applied without change to an engine unit widely used in a saddle-ride type vehicle. That is, there is a possibility that a desired amount of fuel vapor cannot be introduced from the tank into the combustion chamber. Thus, the present inventors have made an effort to find a technique of ensuring that a desired amount of combustion steam is introduced from the tank into the combustion chamber. As a result of intensive studies, the present inventors arrived at the following configuration.

First, the present inventors configured such that the volume of the passage for the vapor fuel from the opening 163y to the downstream intake passage 110x is less than half of the exhaust gas amount of the engine 130. The opening 163y can be closed by the valve body 175 of the solenoid valve 170. The above-described passage is a passage surrounded by a two-dot chain line in fig. 3. The passage surrounded by the two-dot chain line in fig. 3 is formed by: a part of the communication passage 163 a; a communication passage 113 a; and a communication passage 164 a. The portion of the communication passage 163a is connected to the connection fitting 164 from the opening 163y to one end of the passage 163 a. The displacement of the engine 130 is equal to the difference in volume: the volume of the space above the piston 132 at the bottom dead center in the cylinder 131; the volume of the combustion chamber 130.

Further, the present inventors have arrived at a control method regarding the solenoid valve 170. The control method is described with reference to fig. 5 and 6.

Each line segment L1 in fig. 5 shows a period of time during which the intake valve 141 is opened in the four-stroke cycle. Each line segment L2 illustrates the period of time for which the exhaust valve 142 is open in the four-stroke cycle. Curves P1 and P2 show pressure changes in the downstream intake passage 110 x. The numerical values plotted on the abscissa in fig. 5 represent crank angles in degrees. In this embodiment, the crank angle of 0 degrees corresponds to a timing at about the midpoint of the period from the timing of opening the intake valve 141 to the timing of closing the exhaust valve 142. The vertical axis in fig. 5 represents pressure values for illustrating a graph of pressure changes in the downstream intake passage 110 x.

The curve P1 represents the pressure change under the condition that the crankshaft 134 rotates at a predetermined rpm. Curve P2 represents the pressure variation under the following conditions: the throttle opening degree of the throttle valve 112 is the same as that for the curve P1; and crankshaft 134 rotates at a higher rpm than that of curve P1. As shown in the curves P1 and P2, the pressure in the downstream intake passage 110x starts to decrease from atmospheric pressure in a short time after the intake valve 141 starts to open. For curve P1, the pressure reaches a minimum point or value at about 180 crank angle degrees and then rises in turn. After the intake valve 141 is closed, the pressure returns to the vicinity of the atmospheric pressure at a crank angle of about 360 degrees. Then, the pressure slightly fluctuates around the atmospheric pressure and gradually becomes substantially constant. Meanwhile, for the curve P2, after the pressure reaches the lowest point or minimum value at about 200 crank angle degrees, the pressure returns to the atmospheric pressure in a more gradual manner than the pressure change of the curve P1. Further, the minimum pressure value in the curve P2 is smaller than the minimum pressure value in the curve P1.

Accordingly, a large pressure drop (depression) that is a large difference from atmospheric pressure and a small pressure drop that is a small difference from atmospheric pressure are sequentially or sequentially generated in each four-stroke cycle in response to the opening and closing of the intake valve 141. In curves P1 and P2, the larger pressure drop occurs around the range from 180 degrees to 200 degrees. In curve P1, a smaller pressure drop occurs around the range from 360 degrees to 720 degrees, and in curve P2 a smaller pressure drop occurs around the range from 540 degrees to 720 degrees. The pressure change is repeatedly generated in the downstream intake passage 110x when the four-stroke cycle is repeated. Thus, the pressure varies in the following manner of pressure variation: the larger pressure drop and the smaller pressure drop are repeatedly generated on a four-stroke basis. This pressure variation pattern can be observed in engine units widely used in four-stroke saddle-ride type vehicles. The offset from curve P1 to curve P2 results from an increase in the rpm of the crankshaft, as described above. The curve P1 also shifts in the same manner when the throttle opening of the throttle valve 112 is reduced without changing the rpm of the crankshaft. That is, the smaller the throttle opening degree of the throttle valve 112, the larger the pressure change amount.

The present inventors conceived the following methods for controlling the electromagnetic valve 170 by the ECU 150: the control solenoid valve 170 performs switching operation in association with the above-described pressure variation pattern observed in the engine unit widely used in the four-stroke saddle-ride type vehicle. Note that "associated with the pressure variation manner" means that the switching operation is controlled with reference to the timing at which the pressure drop is generated.

More specifically, the present inventors used a control method based on the time charts C1 to C3 in the lower part of fig. 5. The graphs C1 to C3 correspond to control methods different from each other. Any one of the control methods based on the graphs C1 to C3 may be used as a method of controlling the valves by the ECU 150. Alternatively, a combination of any two or more control methods based on the graphs C1 to C3 may be used. In each of the graphs C1-C3, the line at the horizontal line labeled "open" in fig. 5 represents the period of time for which the solenoid valve 170 is in the open state. The line in fig. 5 at the horizontal line labeled "off" represents the period of time for which the solenoid valve 170 is in the closed state.

In each of the control methods based on the graphs C1 to C3, each of the on operation and the off operation is performed once in each four-stroke cycle. The on operation is an operation of switching the solenoid valve 170 from the closed state to the open state. The opening operation is an operation of switching the solenoid valve 170 from the open state to the closed state. As a result of the above operation, in each four-stroke cycle, when the electromagnetic valve 170 is in the open state, fuel vapor flows from the communication passage 163a into the downstream intake passage 110 x. The period during which the solenoid valve 170 is in the open state may be hereinafter referred to as "an open period of the solenoid valve 170". The length of the opening period of the solenoid valve 170 may be adjusted by changing at least one of the timings of the on operation and the off operation.

In the present embodiment, the timing of the on operation is fixed in the four-stroke cycle. The length of the opening period of the solenoid valve 170 is adjusted by changing the timing of the opening operation. Now, the timings of the on operation and the off operation in each four-stroke cycle are expressed in crank angles from 0 degrees to 720 degrees. As shown in fig. 5, at the time T1 of the on operation in plot C1, at 660 degrees crank angle, in each four-stroke cycle. The moment of the switch-on operation is the same in all four-stroke cycles. The key-on operation in the graph C1 is timed immediately before the time at which the intake valve 141 is opened in each cycle. The timing at which the intake valve 141 is opened is indicated by the left end of each line segment L1 in fig. 5. The timing of the on operation in plot C2 is at 90 crank angle degrees in each four-stroke cycle. The on operation in the graph C2 is timed during the pressure drop in the downstream intake passage 110x and before the pressure reaches a minimum. The timing of the on operation in plot C3 is 270 crank angle degrees in each four-stroke cycle. The on operation in the graph C3 is timed after the pressure in the downstream intake passage 110x reaches a minimum and during the pressure rise to atmospheric pressure.

Each of the graphs C1 to C3 in fig. 5 shows a case where the length of the open period of the solenoid valve 170 is half the length of the period corresponding to the four-stroke cycle. In other words, assuming that the length of the period corresponding to the four-stroke cycle is 100%, the length of the open period of the solenoid valve 170 is 50% in each of the graphs C1 to C3 in fig. 5. Hereinafter, when the length of the opening period of the solenoid valve 170 is expressed as a percentage, the expression is premised on the length of the period corresponding to the four-stroke cycle being 100%.

The length of the opening period of the solenoid valve 170 is adjusted by changing the timing of the opening operation. For example, in the graph C1, the timing of the opening operation may be changed from T2(300 degrees) to T3(120 degrees). Thereby, the length of the opening period of the solenoid valve 170 is changed from 50% to 25%. In plot C1, the turn-off operation is performed first, followed by the turn-on operation, in each four-stroke cycle. In contrast, in plots C2 and C3, in each four-stroke cycle, the on operation is performed first, and then the off operation is performed. Therefore, it is not important in which order the on operation and the off operation are performed in each four-stroke cycle.

The above-described timings (crank angles) of the on operation and the off operation are controlled based on the crank position of the crankshaft 134 detected by the rpm rotation speed sensor 153.

Now, the amount of fuel vapor flowing from the communication passage 163a into the downstream intake passage 110x is considered according to the control method based on the graphs C1 to C3. The amount of fuel vapor introduced depends on the relationship between the opening period of the electromagnetic valve 170 and the pressure in the downstream intake passage 110 x. For example, in the graph C1, the period from T1 to T2 is the opening period of the solenoid valve 170. During this period, a large pressure drop that is relatively large in difference from atmospheric pressure is generated in both the curves P1 and P2, as shown by the portion surrounded by the two-dot chain line a1 in fig. 5. During this time, the fuel vapor flows from the communication passage 163a into the downstream intake passage 110x, and the amount of the fuel vapor changes as the magnitude of the pressure drop changes.

As described above, in the present embodiment, the timing of the disconnection operation is variable. When the timing of the shutoff operation is changed, the relationship between the opening period of the electromagnetic valve 170 and the pressure in the downstream intake passage 110x is changed. For example, assume that in the graph C1, the timing of the disconnection operation changes from T2 to T3 (see the broken line shown in the graph C1). By this change, the length of the opening period of the solenoid valve 170 is changed from 50% to 25%. Then, a portion of each of the curves P1 and P2, which represents a large pressure drop generated during the opening period of the solenoid valve 170, changes from the portion surrounded by the two-dot chain line a1 to the portion surrounded by the two-dot chain line a 2. Therefore, the amount of fuel vapor flowing from the communication passage 163a into the downstream intake passage 110x decreases.

Therefore, in the control method based on the graphs C1 to C3 included in the control method of the present embodiment, the ECU 150 can change the timing of the off operation and fix the timing of the on operation. Thus, in these control methods, the on operation is performed in synchronization with the four-stroke cycle (four-stroke period). The expression "synchronized with the four-stroke cycle" means that the moment of operation in each four-stroke cycle is the same among the respective four-stroke cycles. By changing the timing of the switch-off operation in each four-stroke cycle, the relationship between the opening period of the solenoid valve 170 and the pressure change in each four-stroke cycle changes. Alternatively, the reverse configuration to that described above may be employed: the moment of the switch-off operation may be synchronized with the four-stroke cycle, while the moment of the switch-on operation is variable. The opening period of the solenoid valve 170 can be changed by this configuration.

The amount of fuel vapor flowing from the communication passage 163a into the downstream intake passage 110x can be adjusted by changing the opening period of the electromagnetic valve 170 in the manner described above. The control method of the embodiment makes it unlikely that the amount of fuel vapor flowing from the communication passage 163a into the downstream intake passage 110x will change undesirably unless the manner of pressure change in each four-stroke cycle is changed greatly.

For example, in the graph C1, it is assumed that the opening period of the solenoid valve 170 is fixed to 50%. In this case, the portion of the curve P1 that represents the large pressure drop generated during the opening period of the solenoid valve 170 is the portion surrounded by the two-dot chain lines a1 and a 1' in fig. 5. As can be seen by a comparison between the portions of the curve P1 enclosed by the two-dot chain lines a1 and a 1', there is no substantial difference in the manner of pressure change between these portions. That is, as long as the opening period is fixed, unless the manner of pressure variation is largely changed, the relationship between the opening period of the solenoid valve 170 and the pressure variation is unlikely to be changed. Therefore, the amount of fuel vapor flowing from the communication passage 163a into the downstream intake passage 110x is less likely to change.

Meanwhile, if the running state of the motorcycle 1 changes, the manner of pressure change in the downstream intake passage 110x also changes. For example, if the rpm speed of the engine 130 is changed, the manner of pressure change in the downstream intake passage 110x is changed from that shown by the curve P1 to that shown by the curve P2. Therefore, for example, under control based on the graph C1, even if the opening period of the electromagnetic valve 170 is fixed, the variation in the rpm rotation speed causes a difference in the amount of fuel vapor flowing from the communication passage 163a into the downstream intake passage 110 x. Specifically, there is a difference in the fuel vapor amount between the case where the engine 130 runs at the rpm speed in the curve P1 and the case where the engine 130 runs at the rpm speed in the curve P2. Also, the change in rpm of the engine 130 also causes the amount of air flowing into the combustion chamber 130a to change. Therefore, the change in the rpm causes the change in the inflow amount of fuel vapor and the inflow amount of air. This changes the degree of influence of the fuel vapor on the air-fuel ratio of the air-fuel mixture in the combustion chamber 130 a. For this reason, introducing fuel vapor into the combustion chamber 130a may prevent the air-fuel mixture in the combustion chamber 130a from being stably combusted at a desired air-fuel ratio.

Therefore, in order to stabilize the combustion of the fuel in the combustion chamber 130a, the ECU 150 of the present embodiment is configured to control the amount of fuel vapor introduced into the combustion chamber 130a as follows. The ECU 150 controls the length of the open period of the electromagnetic valve 170 based on the following detection values. The detection values are: a detection value of the rpm rotation speed of the engine 130; and a detected value of the pressure in the downstream intake passage 110x or a detected value of the throttle opening degree of the throttle valve 112. These detection values are obtained from the detection results obtained by the sensors 151 to 153. Which of the detection values (the detection value of the pressure in the downstream intake passage 110x and the detection value of the throttle opening degree of the throttle valve 112) is used is determined based on the running state. For example, when the rpm rotation speed of the engine 130 is low, a detection value of the pressure in the downstream intake passage 110x may be used, and when the rpm rotation speed of the engine 130 is high, a detection value of the throttle opening degree of the throttle valve 112 may be used. Each detection value used for control may be an average value of values detected within a predetermined period of time. Alternatively, a periodically detected value may be used for the control. The frequency of such detection may be once every four-stroke cycle, or once for a plurality of four-stroke cycles.

The ECU 150 performs control such that the ratio of the inflow amount of fuel vapor per four-stroke cycle to the amount of air taken into the engine satisfies the relationship shown in fig. 6 (a). Note that the amount of air taken into the engine may be referred to as "engine intake air amount". The engine intake air amount corresponds to "the amount of intake air to the combustion chamber" in the present invention. The abscissa of the graph in fig. 6(a) represents the engine intake air amount. The engine intake air amount is the amount of air flowing into the combustion chamber 130a per four-stroke cycle. The air amount can be obtained from the following values: rpm speed of engine 130; and the throttle opening degree of the throttle valve 112 or the pressure in the downstream intake passage 110 x. The ordinate of the graph in fig. 6(a) represents the ratio of the inflow amount of fuel vapor to the engine intake air amount. Hereinafter, this ratio is referred to as "fuel-vapor ratio". The fuel vapor ratio is the percentage of the amount of fuel vapor flowing from the communication passage 163a into the downstream intake passage 110x per four-stroke cycle to the engine intake air amount.

As shown in fig. 6(a), when the engine intake air amount is smaller than the first value q1, control is performed such that the fuel vapor ratio simply increases as the engine intake air amount increases. The larger the engine intake air amount is, the smaller the influence of the fuel vapor introduced into the combustion chamber 130a on the fuel combustion is. Therefore, by increasing the amount of fuel vapor introduced into the combustion chamber 130a as the engine intake air amount increases, a larger amount of fuel vapor is introduced into the combustion chamber 130a while having less influence on the combustion of the fuel. When the engine intake air amount exceeds the first value q1, control is performed so that the fuel vapor ratio is kept constant at a predetermined value R%. This is because if the percentage of the fuel vapor amount to the engine intake air amount exceeds R%, it is difficult to control combustion in the engine 130. When the engine intake air amount is further increased (for example, when the engine intake air amount exceeds the second value q2 that is larger than the first value q 1), the fuel vapor ratio is decreased as the engine intake air amount is increased. This is because if the engine intake air amount exceeds the second value q2, the fuel-vapor ratio decreases as the engine intake air amount increases even if the length of the opening period of the electromagnetic valve 170 is set to 100%. The reason why the fuel vapor ratio is reduced is as follows. When the engine intake air amount is increased at a constant rpm, the pressure difference between the pressure in the downstream intake passage 110x and the atmospheric pressure is reduced. The pressure difference decreases so that the fuel vapor hardly flows into the downstream intake passage 110 x. This makes the increase in the inflow amount of fuel vapor smaller than the increase in the intake air amount of the engine.

In order to adjust the fuel vapor ratio to satisfy the relationship shown in fig. 6(a), it is necessary to control the introduction amount of fuel vapor at a desired value with respect to the engine intake air amount. The amount of fuel vapor flowing from the communication passage 163a to the downstream intake passage 110x depends on the pressure in the downstream intake passage 110 x. Then, the ECU 150 controls the electromagnetic valve 170 so that the length of the opening period of the electromagnetic valve 170 is changed in accordance with the pressure in the downstream intake passage 110x so as to satisfy the relationship shown in fig. 6 (b). For example, the pressure in the downstream intake passage 110x corresponds to a value detected by the intake air pressure sensor 151. As shown in fig. 6(b), the length of the open period of the electromagnetic valve 170 is adjusted so as to increase when the pressure in the downstream intake passage 110x approaches the atmospheric pressure. By increasing the length of the opening period of the electromagnetic valve 170 when the pressure in the downstream intake passage 110x approaches the atmospheric pressure, a desired inflow amount of fuel vapor is ensured.

As described below, the ECU 150 of the present embodiment is configured to control the length of the opening period of the electromagnetic valve 170 without calculating any of the engine intake air amount and the fuel-vapor ratio. The ECU 150 includes a storage unit. The storage unit stores therein: information on the length of the open period of the solenoid valve 170; and information about the rpm of the engine 130 and the pressure in the downstream intake passage 110 x. These information items are related to each other. The storage unit of the ECU 150 further stores therein: information on the length of the open period of the solenoid valve 170; and information on the rpm rotational speed of the engine 130 and the throttle opening degree of the throttle valve 112. These information items are related to each other. These information items are related to each other by: such that the control performed by the ECU 150 when the ECU 150 controls the electromagnetic valve 170 based on the stored information and the detected values satisfies the relationship shown in fig. 6(a) and 6 (b). The ECU 150 acquires information on the length of the open period of the electromagnetic valve 170 from the storage unit. The information entry is obtained based on the following values: a detection value of the rpm rotation speed of the engine 130; and a detected value of the pressure in the downstream intake passage 110x or a detected value of the throttle opening degree of the throttle valve 112. The ECU 150 controls the switching operation of the electromagnetic valve 170 such that the length of the open period of the electromagnetic valve 170 in each four-stroke cycle is equal to the length represented by the information obtained from the storage unit. In the present embodiment, as described above, the timing of the off operation is adjusted in each four-stroke cycle, while the timing of the on operation is fixed, based on the graphs C1 to C3.

Fig. 7 is a graph showing a change in the inflow amount of fuel vapor as a function of the length of the opening period of the electromagnetic valve 170 under the control of the electromagnetic valve 170 based on the graphs C1 to C3. The curve Q1 shows the change in the inflow amount of fuel vapor under control based on the graphs C1 to C3 in the case where the throttle opening degree of the throttle valve 112 is relatively small or the rpm rotation speed of the engine 130 is relatively high. When the throttle opening degree of the throttle valve 112 is relatively small or the rpm speed of the engine is relatively high, for example, as shown by a curve P2 in fig. 5, the pressure in the downstream intake passage 110x is normally kept lower than the atmospheric pressure for the period of four strokes. Therefore, regardless of the control based on which of the graphs C1 to C3, the inflow amount of fuel vapor increases substantially linearly with the length of the opening period of the electromagnetic valve 170, as shown by the curve Q1.

Meanwhile, when the throttle opening degree of the throttle valve 112 is relatively large or the rpm speed of the engine is relatively low, the manner of increase in the inflow amount of fuel vapor differs depending on which of the graphs C1 to C3 the control is based on. The curve Q2 shows the change in the inflow amount of fuel vapor under control based on the graph C1 when the throttle opening of the throttle valve 112 is relatively large or the rpm speed of the engine is relatively low. The curve Q2 shows that the inflow amount of fuel vapor increases substantially steadily over the entire range from 0% to 100%. However, the increased linearity of curve Q2 is less than the increased linearity of curve Q1. Also, the difference in inflow amount between the curves Q1 and Q2 is small. Curves Q3 and Q4 show changes in the inflow amount of fuel vapor under control based on the graphs C2 and C3, respectively, when the throttle opening degree of the throttle valve 112 is relatively large or the rpm rotation speed of the engine is relatively low. As shown by these curves, the inflow amount of fuel vapor is smaller in the most part in the range of 0% to 100% than in the case shown by the curves Q1 and Q2 under control based on the graph C2 or C3. Moreover, the manner of increasing the inflow amount is not stable.

The reason for the difference between the curves showing the change in the inflow amount of fuel vapor caused by the change in the rpm is as follows. For example, as shown by curves P1 and P2 in fig. 5, the manner of pressure change in the downstream intake passage 110x changes according to the rpm. Particularly under control based on the graphs C2 and C3, the switch-on operation is timed after the pressure in the downstream intake passage 110x starts to drop greatly below the atmospheric pressure. As shown in fig. 5, the difference in the manner of pressure change due to the difference in rpm rotation speed mainly occurs in a period after the time at which the pressure in the downstream intake passage 110x reaches its minimum value. For this reason, under control based on the graphs C2 and C3, the difference in rpm rotation speed causes a large difference in inflow amount of fuel vapor. Meanwhile, the key-on operation in the graph C1 is timed immediately before the intake valve 141 is opened. That is, for both curves P1 and P2, the switch-on operation in plot C1 is timed shortly before the pressure in the downstream intake passage 110x begins to drop significantly below atmospheric pressure. For this reason, under control based on the graph C1, the difference in rpm rotation speed causes a small difference in the inflow amount of fuel vapor.

Therefore, the graph C1 is suitable for controlling the inflow amount of fuel vapor. In the graph C1, the key-on operation is timed immediately before the intake valve 141 is opened. The control based on the graph C1 is also validated at the following timing. After the intake valve 141 is switched from the closed state to the open state, the pressure in the downstream intake passage 110x starts to decrease. In view of the above, the electromagnetic valve 170 is opened in advance before the end of the period in which the intake valve 141 is closed. This enables the fuel vapor to flow from the tank 161 into the downstream intake passage 110x quickly in response to the pressure in the intake passage 110a starting to drop. Note that there may be a time lag between the timing of the key-on operation and the timing of opening the intake valve 141. For example, as long as the timing of the switch-on operation is in the latter half of the period in which the intake valves 141 are closed, the timing of the switch-on operation may be before the timing in the graph C1.

The electromagnetic valve 170 may be controlled according to an engine intake air amount calculated based on the detection value. The detection values are: a detection value of the rpm rotation speed of the engine 130; and a detected value of the pressure in the downstream intake passage 110x or a detected value of the throttle opening degree of the throttle valve 112. For example, the ECU 150 may be configured as follows. The storage unit of the ECU 150 stores therein data representing the graphs of fig. 6(a) and 6 (b). The ECU 150 calculates the engine intake air amount using the detection value. Then, the ECU 150 obtains the fuel-vapor ratio corresponding to the thus calculated engine intake air amount, with reference to the map of fig. 6 (a). Next, the ECU 150 obtains the length of the opening period of the electromagnetic valve 170 corresponding to the pressure in the downstream intake passage 110x estimated from the detected value, with reference to the graph of fig. 6 (b). Also, the ECU 150 switches the electromagnetic valve 170 based on the thus obtained length of the open period of the electromagnetic valve 170.

It should be noted that the graphs of fig. 6(a) and 6(b) are only ideal examples referred to in the control of the ECU 150. It is merely preferable to implement the control in such a manner as to satisfy the relationship shown in these graphs as much as possible. Note that the control need not be implemented such that the control result strictly satisfies the relationship shown in these drawings.

Unlike the case where the configuration for the automobile is applied to the saddle-ride type vehicle without change, according to the above-described embodiment, a desired amount of combustion vapor can be introduced into the combustion chamber 130. The reason for introducing the desired amount of combustion steam will be described below.

The present inventors compared the pressure drop generated in the intake passage in the engine unit widely used in the saddle-ride type vehicle with the pressure drop in the engine unit widely used in the automobile. As a result of comparison, the present inventors found the following differences between the saddle-riding vehicle and the automobile. In some engines widely used in automobiles, for example, a pressure variation in a downstream intake passage portion is suppressed by means of a pressure equalizing tank provided downstream of a throttle valve. Further, in an engine unit of an automobile having an independent throttle body, a pressure change in each cylinder is suppressed, for example, by providing one or more communication pipes to establish communication between downstream intake passage portions. In this case, the pressure in the downstream intake passage portion(s) is relatively stable. Thus, when the communication passage is provided to establish communication between the tank and the downstream intake passage portion(s), the pressure in the communication passage is also relatively stable. This makes it easy to stabilize the amount of combustion vapor introduced into the intake passage through the communication passage.

In contrast, in the motorcycle 1 as an example of the saddle-ride type vehicle, a large negative pressure change by four strokes is generated in the downstream intake passage 110 x. This is illustrated by curves P1 and P2 in fig. 5. In the above case, as in the related art for automobiles, it is assumed that a tank having a large volume is provided in a passage through which fuel vapor is introduced from a canister into a downstream intake passage. This makes it difficult for the pressure in the passage for introducing the fuel vapor to quickly follow the pressure change in the downstream intake passage. It is found that the above configuration may cause a delay in the timing at which the fuel vapor is introduced into the downstream intake passage, and therefore there is a possibility that a desired amount of fuel vapor cannot be introduced.

In order to solve this problem, in the present embodiment, the introduction amount of the fuel vapor is adjusted on the premise that the above-described pressure variation exists (more precisely, the pressure variation is utilized). That is, the solenoid valve 170 is controlled based on the following pressure variation pattern: a smaller differential pressure with a smaller difference from atmospheric pressure and a larger differential pressure with a larger difference from atmospheric pressure are generated in each four-stroke cycle; and a smaller differential pressure and a larger differential pressure are repeatedly generated based on the four strokes. Specifically, the control of the switching operation of the electromagnetic valve 170 is performed in association with the following pressure variation pattern: creating a smaller pressure drop at a smaller difference from atmospheric pressure and a larger pressure drop at a larger difference from atmospheric pressure in each four-stroke cycle; and repeatedly generates a smaller pressure drop and a larger pressure drop based on the four-stroke.

Meanwhile, in the control of the solenoid valve 170 associated with the above-described pressure variation manner (in which the pressure largely varies in each four-stroke cycle), the pressure variation in the communication passage 163a must promptly follow the operation of the valve. If a portion of the communication passage from the solenoid valve 170 to the intake passage 110a has a large capacity, it is difficult for the pressure in the communication passage 163a to quickly react to a pressure change in the downstream intake passage 110 x. This may cause a delay in the timing of introducing the fuel vapor into the combustion chamber 130a, since the pressure change cannot promptly follow the operation of the solenoid valve 170.

In order to solve the above problem, the following configuration is made in this embodiment. In order to achieve control in the high degree of followability as required above, the electromagnetic valve 170 (valve body 175) is provided such that the capacity of the passage for fuel vapor from the opening 163y to the downstream intake passage 110x is less than half of the exhaust gas amount of the engine 130. The above-described passage is a passage surrounded by a two-dot chain line in fig. 3. Since the capacity of the passage from the downstream intake passage 110x to the opening 163y is small as described above, the pressure change in the downstream intake passage 110x is transmitted to the opening 163y in a shorter time. This promotes a smooth correlation between the operation of the solenoid valve 170 and the pressure change, and reduces the delay in the timing of introducing the fuel vapor into the combustion chamber 130 a. With the above configuration, in the engine 100 in which the pressure variation largely varies based on the four-stroke, it is achieved that a desired amount of fuel vapor is introduced into the combustion chamber 130 a.

In the present embodiment, in the control of the solenoid valve 170 associated with the pressure variation manner, the timing of the off operation of the solenoid valve 170 is adjusted while synchronizing the timing of the on operation of the solenoid valve 170 with the four-stroke cycle. This makes it possible to adjust the length of the period during which the solenoid valve 170 is in the open state. Thereby, the solenoid valve 170 is controlled in association with a four-stroke based pressure variation pattern. This configuration makes it easier to control the amount of fuel vapor introduced from the communication passage 163a into the downstream intake passage 110x at a desired level in each four-stroke cycle.

It should be noted that the timing of the on operation may be changed as follows. Specifically, rather than synchronizing with the four-stroke cycle, the timing of the on operation may be advanced as the rpm speed of the engine 130 increases. In other words, the crank angle at which the switch-on operation is performed may decrease as the rpm increases. There is a short time lag between the time when the fuel vapor actually starts to flow from the communication passage 163a into the downstream intake passage 110x and the time of the on operation. Meanwhile, as the rpm speed increases, the absolute length of the period of the four-stroke cycle decreases. Therefore, when the rpm rotation speed increases, the time delay between the timing of the on operation and the timing at which the fuel vapor starts to flow in increases with respect to the length of the period of the four-stroke cycle. To address this problem, the timing of the on operation in each four-stroke cycle may be advanced as the rpm speed increases. This results in a reduction in the influence caused by the above-described time delay.

As described above, the timings of the on operation and the off operation are controlled based on the crank position (crank angle) of the crankshaft 134 detected by the rpm rotation speed sensor 153. However, the on operation and the off operation may be performed based on a detection result obtained by the intake air pressure sensor 151 or the like. That is, these operations may be performed at respective timings in direct association with pressure changes that are generated in the downstream intake passage 110x in each four-stroke cycle and detected by the intake pressure sensor 151 or the like.

Control methods other than those based on the graphs C1 to C3 will be described below with reference to fig. 8 and 9. In fig. 8 and 9, a curve P3 shows how the pressure in the downstream intake passage 110x changes under the condition that the rpm rotation speed of the engine 130 is constant. Like curves P1 and P2, curve P3 also shows the pressure variation pattern such that the larger pressure drop and the smaller pressure drop are repeated on a four-stroke basis.

In the control method based on the graphs C1 to C3 described above, each of the on operation and the off operation of the solenoid valve 170 is performed once in each four-stroke cycle. Further, in the control method based on the graphs C4 to C6 in fig. 8, each of the on operation and the off operation is performed two or more times in each four-stroke cycle. The graph C4 shows a case where each of the on operation and the off operation is performed once in each stroke period. Each of the graphs C5 and C6 shows that each of the on operation and the off operation is performed once every two stroke periods. As shown in these tables, the solenoid valve 170 may be controlled in association with one stroke period or two stroke periods. It should be noted that the control associated with one stroke period or two stroke periods is included in the control associated with the four stroke cycle. That is, within the control associated with the four-stroke cycle, the control is further subdivided into control over each stroke period or over every two stroke periods. Therefore, the control method based on the graphs C4 to C6 is included in the control associated with the four-stroke based pressure variation pattern.

In the control based on the graph C4, the timing of the on operation may be synchronized with one stroke period. In other words, the timing of the on operation in each stroke period may be the same in each one stroke period. Further, in the control based on the graph C5 or C6, the timing of the on operation may be synchronized with the two stroke periods. In other words, the moment of the switch-on operation in every two stroke periods may be the same in the respective two stroke periods. When the timing of the on operation is synchronized with one stroke period or two stroke periods (as described above), the length of the open period of the solenoid valve 170 is changed by changing the timing of the off operation. Alternatively, when the timing of the off operation is synchronized with one stroke period or two stroke periods, the length of the opening period of the solenoid valve 170 may be changed by changing the timing of the on operation. In addition, control associated with a two stroke period may be performed, as shown by plot C6. That is, the period from the on operation to the off operation may cross the boundary between the two strokes.

A plot C7 shown in fig. 9 illustrates control associated with a time period corresponding to two four-stroke cycles (rather than one four-stroke cycle). That is, plot C7 illustrates control associated with eight stroke periods. Plots C8 and C9 each illustrate control associated with time periods corresponding to three four-stroke cycles (i.e., twelve stroke time periods). Thus, control may be performed in association with n stroke periods, where n is a multiple of 4. Under this control, fuel vapor is introduced into the downstream intake passage 110x in a four-stroke cycle of n stroke periods, where n is a multiple of 4, but no fuel vapor is introduced in the remaining four-stroke cycle(s). In each of the four-stroke cycles in which the fuel vapor is introduced, the solenoid valve 170 is controlled in association with the manner of pressure change in each four-stroke cycle.

Plot C10 shows an example of control associated with, but not synchronized with, a four-stroke cycle. As shown by plot C10, neither the timing of the on operation nor the off operation is synchronized with the four-stroke cycle. Thus, the expression "associated with … …" in the present invention includes the case where the timing of the operation is synchronized with the four-stroke cycle and the case where the timing of the operation is not synchronized with the four-stroke cycle. For example, assume that it is desired to keep the amount of fuel vapor introduced into the downstream intake passage 110x at a desired level in each four-stroke cycle. In this case, the opening period of the solenoid valve 170 need not be the same in all four-stroke cycles. As shown by plot C10, the open period may be different in all four-stroke cycles, provided that the following conditions are met. That is, as a result of the control of the on operation and the off operation of the electromagnetic valve 170 being associated with the four-stroke-based pressure variation pattern, it is only necessary to keep the amount of fuel vapor introduced into the downstream intake passage 110x at a desired value in each four-stroke cycle.

[ second embodiment ]

A second embodiment will be described below as a further embodiment of the present invention. Some components in the second embodiment are the same as those in the first embodiment. The following description mainly relates to components in the second embodiment that are different from those in the first embodiment. Further, the same components as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted as appropriate.

In the second embodiment, an ECU250 is provided in place of the ECU 150 of the first embodiment. The ECU250 is configured to control each component of the motorcycle relating to the second embodiment. The control by the ECU250 is similar to the control by the ECU 150, except for the control relating to components different from those in the first embodiment.

Further, in the second embodiment, a throttle valve 270 is provided in place of the electromagnetic valve 170 of the first embodiment. As shown in fig. 10(a), the throttle valve 270 includes: a housing 271, a stepper motor 272, a rotor shaft 273, a valve body 275, and a spring 276. The housing 271 is fixed to the communication passage member 163. The stepping motor 272 is provided in the housing 271. Further, a communication passage 163x is provided in the housing 271. The communication passage 163x is bent in an Ω (ohm) shape. The communication passage 163x is a part of the communication passage 163 a. In fig. 10(a), the spring 276 is biased downward toward the valve body 275. The valve body 275 has a front end 275 a. In fig. 10(a), the front end 275a is in the shape of a truncated cone that tapers toward its lower end. In the state shown in fig. 10(a), the front end 275a of the valve body 275 completely closes the opening 163 y. The opening 163y is included in the communication passage 163 x. The valve body 275 has a threaded hole 275 b. In fig. 10(a), the rotor shaft 273 is inserted into the screw hole 275b from above. The rotor shaft 273 has a threaded portion 273a at a front end portion thereof. The threaded portion 273a is screwed into the threaded hole 275 b.

The stepper motor 272 is configured to rotate the rotor shaft 273. The stepping motor 272 can control the rotation angle of the rotor shaft 273 in a stepwise manner. The valve body 275 has a restriction portion 275 c. The restricting portion 275c protrudes or protrudes outward from the main body of the valve body 275. When the restricting portion 275c contacts the inner surface of the communication passage 163x, the restricting portion 275c restricts the rotation of the valve body 275. As described above, the threaded portion 273a of the rotor shaft 273 is screwed into the threaded hole 275b of the valve body 275. Therefore, when the rotor shaft 273 is rotated in the first direction, the valve body 275 moves upward in fig. 10(a) against the spring 276 that biases the valve body 275. When the valve body 275 reaches the upper limit position, the front end portion 275a of the valve body 275 opens the valve 163y by the maximum opening degree, as shown in fig. 10 (b). Further, when the rotor shaft 273 is rotated in a second direction opposite to the first direction, the valve body 275 moves downward in fig. 10 (b). When the valve body 275 reaches the lower limit position, the front end portion 275a completely closes the opening 163y again, as shown in fig. 10 (a).

Referring to fig. 10(a), in fig. 10(a), the valve body 275 completely closes the opening 163 y. In this state, the fuel vapor cannot communicate between the tank 161 and the downstream intake passage portion 110 d. Meanwhile, when the valve body 275 opens the opening 163y, the fuel vapor is allowed to communicate between the tank 161 and the downstream intake passage portion 110d via the opening 163 y. The amount of fuel vapor that can pass through the opening 163y depends on the opening degree of the opening 163y that is opened by the valve body 275. In the state of fig. 10(b), the valve body 275 opens the opening 163y by the maximum opening degree. In this state, the amount of fuel vapor that can pass through the opening 163y is the maximum.

The ECU250 controls the opening degree of the opening 163y opened by the valve body 275 by controlling the rotation angle of the rotor shaft 273 in a stepwise manner by the stepping motor 272. Thus, the ECU250 controls the opening degree of the opening 163y in the throttle valve 270. Hereinafter, this opening degree is referred to as "opening degree of the throttle valve 270". The amount of fuel vapor introduced from the canister 161 into the combustion chamber 130a depends on: the opening degree of the throttle valve 270; and the pressure in the downstream intake passage 110 x. By adjusting the opening degree of the throttle valve 270 to correspond to one of the plurality of levels, the amount of fuel vapor introduced can be changed to one of the plurality of levels.

The embodiment is also configured such that the capacity of the passage for fuel vapor from the opening 163y to the downstream intake passage 110x is less than half of the exhaust gas amount of the engine 130. The valve body 275 of the throttle valve 270 can close the opening 163 y.

Now, the control of the throttle valve 270 by the ECU250 will be described in more detail with reference to fig. 11 and 12. Note that the line segments L1 and L2 and the curves P1 and P2 are similar to those in the graph in fig. 4.

The ECU250 acquires the pressure in the downstream intake passage 110x at a specific timing in each four-stroke cycle (each cycle) based on the detection results obtained by the sensors 151 to 153. For example, the specific timing is timing T4 in fig. 11. Time T4 corresponds to a crank angle of about 210 degrees. Then, the ECU250 controls the opening degree of the throttle valve 270 to be an appropriate degree matching the pressure in the downstream intake passage 110x based on at least the obtained pressure. Based on the pressure detected in the downstream intake passage 110x, the ECU250 maintains or changes the opening degree of the throttle valve 270. The timing of changing the opening degree of the throttle valve 270 may be within the four-stroke cycle, or may correspond to the boundary between the four-stroke cycles, i.e., at 0 or 720 degrees of crank angle.

The ECU250 may control the throttle valve 270 based on the pressure changes in the downstream intake passage 110x detected at a plurality of times in the four-stroke cycle. For example, the ECU250 may control the throttle valve 270 as follows: the ECU250 obtains the pressure values at times T4, T5, and T6 in fig. 11, and calculates the average value of the obtained pressure values. Then, the ECU250 controls the valve 270 based on the average value thus obtained. Time T5 corresponds to a crank angle of about 120 degrees. Time T6 corresponds to a crank angle of approximately 300 degrees. The times T4 to T6 are described by way of example, and can be freely set. Further, pressure values detected at two or four or more times may also be used for the control. The timings T4 to T6 (crank angle) are obtained based on the crank position of the crankshaft 134 detected by the rpm speed sensor 153.

As described above, if the running state of the motorcycle 1 changes, a change in the manner of pressure change in the downstream intake passage 110x is caused. For example, if the rpm speed of the engine 130 is changed, the pressure variation pattern in the downstream intake passage 110x is changed from the pattern shown by the curve P1 to the pattern shown by the curve P2. It is assumed that the opening degree of the throttle valve 270 is fixed. Based on this premise, the amount of fuel vapor flowing from the communication passage 163a into the downstream intake passage 110x differs between the case where the engine 130 is rotating at the rpm of the curve P1 and the case where the engine 130 is rotating at the rpm of the curve P2. Further, the rpm rotation speed change of the engine 130 also causes a change in the amount of air flowing into the combustion chamber 130 a. Therefore, the change in rpm changes the inflow amount of fuel vapor and the inflow amount of air. This changes the degree of influence of the fuel vapor on the air-fuel ratio of the air-fuel mixture in the combustion chamber 130 a. Thus, the fuel vapor introduced into the combustion chamber 130a may hinder the air-fuel mixture in the combustion chamber 130a from being stably combusted at a desired air-fuel ratio.

Therefore, in order to stably combust the fuel in the combustion chamber 130a, the ECU250 of the present embodiment is configured to control the amount of fuel vapor introduced into the combustion chamber 130a as follows. The ECU250 controls the opening degree of the throttle valve 270 based on the detected value of the rpm rotation speed of the engine 130 and the detected value of the pressure in the downstream intake passage 110 x. These detection values are obtained from the detection results obtained by the sensors 151 to 153. The detection result obtained by the intake air pressure sensor 151 may be directly used as the detection value of the pressure in the downstream intake passage 110 x. Alternatively, the value of the pressure in the downstream intake passage 110x may be derived from the detection results obtained by the throttle position sensor 152 and the rpm rotation speed sensor 153. Which of the above-described modes is used is determined according to the running state. That is, whether to use the detection result obtained by the intake air pressure sensor 151 or the pressure value derived from the detection results obtained by the throttle position sensor 152 and the rpm rotation speed sensor 153 is selected according to the running state. For example, when the rpm rotation speed of the engine 130 is low, the detection result obtained by the intake air pressure sensor 151 may be used, and when the rpm rotation speed of the engine 130 is high, the pressure values derived from the detection results obtained by the throttle position sensor 152 and the rpm rotation speed sensor 153 may be used. As described above, the detection value of the pressure in the downstream intake passage 110x may be the pressure value at a specific timing within each four-stroke cycle, or may be the average value of the pressure values at a plurality of timings within each four-stroke cycle.

Similar to the ECU 150, the ECU250 executes control such that the relationship between the fuel vapor ratio and the engine intake air amount forms a curve shown in fig. 12 (a). Further, the ECU250 controls the throttle valve 270 so that the opening degree of the throttle valve 270 satisfies the relationship shown in fig. 12(b) with respect to the pressure in the downstream intake passage 110 x. As shown in fig. 12(b), the opening degree of the throttle valve 270 is adjusted such that when the detected value of the pressure in the downstream intake passage 110x approaches the atmospheric pressure, the opening degree increases toward its fully open state. A desired inflow amount of fuel vapor is ensured by increasing the opening degree of the throttle valve 270 when the detected value of the pressure in the downstream intake passage 110x approaches the atmospheric pressure.

The ECU250 of the present embodiment is configured to control the opening degree of the throttle valve 270 without calculating any of the engine intake air amount and the fuel-vapor ratio, as described below. The ECU250 includes a storage unit. The storage unit of the ECU250 stores therein: information on the rpm rotational speed of the engine 130 and the throttle opening degree of the throttle valve 112; and information about the pressure in the downstream intake passage 110 x. These information items are related to each other. Referring to the stored information, the ECU250 derives the pressure in the downstream intake passage 110x from the rpm of the engine 130 and the throttle opening of the throttle valve 112. Alternatively, the ECU250 directly obtains the pressure in the downstream intake passage 110x from the detection result obtained by the intake air pressure sensor 151. The storage unit of the ECU250 also stores therein: information on the opening degree of the throttle valve 270; and information about the rpm speed of the engine 130 and about the pressure in the downstream intake passage 110 x. These information items are related to each other. These information items are related to each other by: when the ECU250 controls the throttle valve 270 based on the stored information and the detected value, the control performed by the ECU250 satisfies the relationship shown in fig. 12(a) and 12 (b). The ECU250 obtains information on the opening degree of the throttle valve 270 in relation to a detection value on the rpm rotation speed of the engine 130 and a detection value on the pressure in the downstream intake passage 110 x. Then, the ECU250 controls the throttle valve 270 so that the opening degree of the throttle valve 270 is equal to the value of the information obtained from the storage unit.

The running state such as the rpm rotation speed of the engine 130 is smoothly changed. Unlike the smooth change, the ECU250 controls the throttle valve 270 such that the opening degree of the valve 270 changes in a stepwise manner. For example, when the throttle opening of the throttle valve 112 is not changed and the rpm rotation speed is increased, the manner of pressure change in the downstream intake passage 110x does not rapidly change greatly in response to the increase in the rpm rotation speed. In contrast, the pressure variation pattern gradually changes over a plurality of four-stroke cycles (over a plurality of cycles), as shown by a curve P4 in fig. 13. When the manner of pressure change in the downstream intake passage 110x is slightly changed, the ECU250 does not immediately change the opening degree of the throttle valve 270. As shown by a line D1 in fig. 13, the ECU250 maintains the opening degree of the throttle valve 270 at α 1 in a plurality of four-stroke cycles. Then, the ECU250 changes the opening degree of the valve 270 from α 1 to α 2 only after the amount of change in the pressure change manner in the downstream intake passage 110x exceeds a predetermined value. Therefore, under the control of the ECU250, the opening degree of the throttle valve 270 is kept constant over a plurality of four-stroke cycles; and the opening degree is changed in a stepwise manner in association with the change in the rpm rotation speed and the change in the pressure change manner in the downstream intake passage 110 x.

The above is an example of controlling the opening amount of the throttle valve 270 without calculating either of the engine intake air amount and the fuel-vapor ratio. Alternatively, the throttle valve 270 may be controlled based on an engine intake air amount calculated from the following detection values. These measured values are: a detection value regarding the rpm rotation speed of the engine 130; and a detection value regarding the pressure in the downstream intake passage 110x or a detection value regarding the throttle opening degree of the throttle valve 112. For example, the ECU250 may be configured as follows. The storage unit of the ECU250 stores therein data representing the graphs of fig. 12(a) and 12 (b). The ECU250 calculates the engine intake air amount using the detection value. Then, the ECU250 obtains the fuel-vapor ratio corresponding to the thus calculated engine intake air amount, with reference to the map of fig. 12 (a). Next, the ECU250 obtains the opening degree of the throttle valve 270 corresponding to the pressure in the downstream intake passage derived from the detected value, with reference to the graph of fig. 12 (b). Further, the ECU250 controls the throttle valve 270 based on the thus obtained opening degree.

The ECU250 may be configured to control the throttle valve 270 without deriving the pressure in the downstream intake passage 110 x. For example, the following configuration may be made. The storage unit of the ECU250 stores therein information on the rpm rotation speed of the engine 130 and the throttle opening degree of the throttle valve 112 and information on the opening degree of the throttle valve 270. These information items are related to each other. Then, the ECU250 directly acquires information on the opening degree of the throttle valve 270 from the storage unit, the opening degree of the throttle valve 270 being associated with values on the rpm rotation speed of the engine 130 and the throttle opening degree of the throttle valve 112. In this configuration, the ECU250 does not need to derive the pressure in the downstream intake passage 110 x. Then, the ECU250 controls the throttle valve 270 so that the opening degree of the flow rate adjustment valve 270 becomes equal to the value of the information obtained from the storage unit. In this case, the storage unit of the ECU250 does not have to store information on the pressure in the downstream intake passage 110x in association with information on the rpm rotation speed of the engine 130 and the throttle opening degree of the throttle valve 112. That is, in the above case, the storage unit of the ECU250 only needs to store information on the opening degree of the throttle valve 270 in association with information on the rpm rotation speed of the engine 130 and the throttle opening degree of the throttle valve 112. Further, in the above case, it is not necessary to provide a detector configured to directly detect the pressure in the downstream intake passage 110 x. That is, in the above case, the intake pressure sensor 151 may be omitted.

It should be noted that the graphs of fig. 12(a) and 12(b) are merely ideal examples in the control by the ECU 250. It is preferable to perform the control in such a manner as to satisfy the relationship shown in these graphs as much as possible. Note that this control need not be implemented so that the results thereof strictly satisfy the relationships shown in these graphs.

According to the above-described embodiment, the amount of fuel vapor introduced is adjusted on the premise that the pressure is changed in the above-described pressure change manner or with the pressure change manner. The pressure variation mode is as follows: creating a smaller pressure drop at a smaller difference from atmospheric pressure and a larger pressure drop at a larger difference from atmospheric pressure in each four-stroke cycle; and the smaller pressure drop and the larger pressure drop are repeatedly generated based on the four-stroke. That is, in the present embodiment, the throttle valve 270 is provided. The throttle valve 270 is configured such that the amount of fuel vapor introduced can be changed by adjusting the opening degree of the valve to correspond to one of a plurality of levels. Further, the amount of the introduced fuel vapor is controlled by adjusting the opening degree of the throttle valve 270 with the valve kept open. The opening degree of the throttle valve 270 is controlled according to a four-stroke-based pressure variation pattern included in a pressure variation pattern that repeatedly generates a small pressure drop and a large pressure drop based on a four-stroke. Specifically, the opening degree of the throttle valve 270 is controlled based on the pressure value(s) in the downstream intake passage 110x at a specific time or times in each four-stroke cycle. Therefore, the control is performed according to the pressure variation pattern based on the four-stroke. Therefore, appropriate control is performed to follow the change in the pressure change pattern in which the pressure greatly changes based on the four-stroke.

In the present embodiment, as shown in fig. 13, when the pressure change pattern in the downstream intake passage 110x is changed due to a change in the running state such as the rpm speed of the engine 130, the opening degree of the throttle valve 270 is changed in a stepwise manner. That is, the opening degree of the throttle valve 270 does not immediately change in response to a smooth change in the rpm rotational speed of the engine 130 during a plurality of four-stroke cycles. In contrast, the opening degree of the throttle valve 270 is changed only after the amount of change in the manner of pressure change in the downstream intake passage 110x exceeds the predetermined value. Therefore, the opening degree of the throttle valve 270 does not change frequently in response to each change in the manner of pressure change in the downstream intake passage 110 x. This makes the amount of the introduced fuel vapor stable. Therefore, the control is performed to appropriately follow the change in the pressure change manner while stably introducing the fuel vapor into the combustion chamber 130 a. It should be noted that the opening degree of the throttle valve 270 may be changed immediately in response to a change in the running state such as the rpm rotation speed of the engine 130. For example, the opening of the throttle valve 270 may be varied during each four-stroke cycle.

Therefore, also in the present embodiment, the throttle valve 270 (the valve body 175) is set such that the capacity of the passage for fuel vapor from the opening 163y to the intake passage 110a is less than half of the exhaust gas amount of the engine 130, and then control is implemented in accordance with the four-stroke-based pressure variation manner. This reduces the delay in the timing of introducing the fuel vapor into the combustion chamber 130a under the above-described control of the opening degree of the throttle valve 270. Therefore, the valve is appropriately controlled to follow a pressure change pattern in which the pressure greatly changes on the four-stroke basis. This causes a desired amount of fuel vapor to be introduced into the combustion chamber.

As described above, it has been desired to apply the technology for automobiles to engine units used in saddle-ride type vehicles including the motorcycle 1. This is the background of the study of the first and second embodiments. It has been found that disadvantages may be caused if the technology for automobiles is applied without change to an engine unit widely used in saddle-ride type vehicles. That is, there is a possibility that a desired amount of fuel vapor cannot be introduced from the tank into the combustion chamber. Namely, the following facts were found: in an engine unit that repeatedly generates a small pressure drop and a large pressure drop based on a four-stroke cycle, there is a possibility that a desired amount of fuel vapor cannot be introduced from the canister into the combustion chamber. Therefore, the first and second embodiments have been developed for the following purposes: in an engine that repeatedly generates a small pressure drop and a large pressure drop based on a four-stroke cycle, a desired amount of fuel vapor is introduced into a combustion chamber.

The preferred embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the above-described embodiments, and various changes can be made within the scope of the claims. Further, a combination of the above-described embodiment and the following modifications may be used as necessary. Note that the term "preferably" as used herein is non-exclusive and means "preferably, but not limited to. Note that the term "may … …" as used herein is non-exclusive and means "may … …, but is not limited thereto".

In the first embodiment described above, the present invention is applied to the single cylinder engine unit 100. Alternatively, the present invention may be applied to a multi-cylinder engine unit 300 shown in fig. 14 (a). The engine unit 300 includes four engines 130, four intake passage members 110, a tank 161, an ECU 350, and a communication passage member 363. The four intake passage members 110 are connected to four engines 130, respectively. The fuel vapor is introduced from the tank 161 into the intake passage member 110 through the communication passage member 363. The air cleaner 331 is configured to clean air. The clean air is supplied to the four intake passage members 110. A throttle valve 112 is provided in each of the intake passage members 110, respectively. That is, the engine unit 300 is an engine unit having respective throttle bodies. In this engine unit having the respective throttle bodies, the pressure in each downstream intake passage portion 110d also downstream of the corresponding throttle valve 112 changes in the same manner as described above. That is, the pressure in each downstream intake passage portion 110d changes in the following pressure change manner: creating a smaller pressure drop at a smaller difference from atmospheric pressure and a larger pressure drop at a larger difference from atmospheric pressure in each four-stroke cycle; and the smaller pressure drop and the larger pressure drop are repeatedly generated based on the four-stroke. Due to the above structure, the communication passage member 363 has four branch portions connected to the downstream intake passage portion 110d, respectively. A solenoid valve 170 is provided to each branch portion. Each branch portion of the communication passage member 363 is arranged such that the capacity of the passage for fuel vapor from the opening 163y of its electromagnetic valve 170 to the corresponding downstream intake passage 110x is less than half of the exhaust gas amount of the corresponding engine 130. The ECU 350 controls each of the four solenoid valves 170 in association with the pressure change in the corresponding downstream intake passage portion 110 d. The control method for each solenoid valve 170 is similar to that of the ECU 150 in the first embodiment. The above arrangement reduces the delay in the timing of introducing the fuel vapor into each combustion chamber 130 a. Thus, with the above arrangement, it is also possible to achieve the introduction of a desired amount of fuel vapor into each combustion chamber 130a in the engine 300 having the respective throttle bodies in which the pressure greatly varies based on the four-stroke. In this modification, the engine unit 300 has four cylinders. It should be noted that the present invention may be applied to a two-cylinder engine unit, a three-cylinder engine unit, or a five-cylinder or more engine unit.

The above-described first embodiment describes the case where the solenoid valve 170 is controlled in association with one stroke, two strokes, four strokes, eight strokes, or twelve stroke periods. However, the solenoid valve 170 may be controlled in association with n stroke periods, where n is a multiple of 4 and equal to or greater than 16.

The above-described first embodiment describes the case where each of the on operation and the off operation of the solenoid valve 170 is performed once, twice, or four times in each four-stroke cycle. However, each of the on operation and the off operation may be performed three or five or more times per four-stroke cycle.

Further, in the first embodiment described above, the ECU 150 controls the electromagnetic valve 170 to satisfy the conditions shown in fig. 6(a) and 6 (b). However, the ECU may control the solenoid valve 170 to satisfy conditions different from those shown in fig. 6(a) and 6 (b).

Also, in the first embodiment described above, the storage unit of the ECU 150 stores therein: information on the length of the open period of the solenoid valve 170; and information about the rpm of the engine 130 and the pressure in the downstream intake passage 110 x. These information items are related to each other. In addition, the storage unit of the ECU 150 stores therein: information on the length of the open period of the solenoid valve 170; and information on the rpm rotational speed of the engine 130 and the throttle opening degree of the throttle valve 112. These information items are related to each other. When the length of the opening period of the electromagnetic valve 170 is obtained based on the information stored in the storage device, the detected value of the pressure in the downstream intake passage 110x or the detected value of the throttle opening degree of the throttle valve 112 is used. Which of them to use is determined based on the running state. Therefore, the detected value of the throttle opening degree of the throttle valve 112 can be used at all times regardless of the running state. In this case, the storage unit of the ECU 150 may store only information on the length of the open period of the solenoid valve 170 and information on the rpm rotation speed of the engine 130 and the throttle opening degree of the throttle valve 112 in association with the length information. That is, the storage unit does not have to store information on the rpm of the engine 130 and the downstream intake passage 110x in association with information on the length of the open period of the electromagnetic valve 170. Also, in the above case, it is not necessary to provide a detector configured to directly detect the pressure in the downstream intake passage 110 x. That is, in the above case, the intake pressure sensor 151 may be omitted.

The arrangement of the second embodiment can also be applied to a multi-cylinder engine unit 400 shown in fig. 14 (b). Some components of the engine unit 400 are the same as those of the engine unit 300 shown in fig. 14 (a). Components different from those of the engine unit 300 will be mainly described below. Further, the same components as those of the engine unit 300 are denoted by the same reference numerals, and repeated description thereof is omitted as appropriate. Similar to the engine unit 300, the engine unit 400 includes four engines 130, four intake passage members 110, a tank 161, and a communication passage member 363. The four intake passage members 110 are connected to four engines 130, respectively. Fuel vapor is introduced from the tank 161 into the intake passage member 110 through the communication passage member 363. That is, the engine unit 400 is also an engine unit having respective throttle bodies. A throttle valve 270 is provided to each branch portion of the communication passage member 363. Each branch portion is connected to a corresponding intake passage member 110. Each branch portion of the communication passage member 363 is arranged such that the capacity of the passage for fuel vapor from the opening 163y of its throttle valve 270 to the corresponding downstream intake passage 110x is less than half the exhaust gas amount of the corresponding engine 130. Further, the ECU 450 controls the components of the engine unit 400.

The ECU 450 controls each of the four throttle valves 270 according to the four-stroke-based pressure variation pattern in the downstream intake passage portion 110d corresponding to the throttle valve. The control method for each throttle valve 270 is similar to the control method performed by the ECU250 in the second embodiment. The four-stroke based pressure variation pattern is obtained based on the results obtained by the sensor. Specifically, the result is obtained by an intake air pressure sensor and a throttle position sensor each provided to each downstream intake passage portion 110d, and an rpm rotation speed sensor each provided to each engine 130. The above arrangement reduces the delay in the timing of introducing the fuel vapor into each combustion chamber 130 a. Thus, with the above arrangement, the introduction of a desired amount of fuel vapor into each combustion chamber 130a is also achieved in the engine unit 400 having the respective throttle bodies in which the pressure greatly varies based on the four-stroke. In this modification, the engine unit 400 has four cylinders. It should be noted that the present invention may be applied to a two-cylinder engine unit, a three-cylinder engine unit, or a five-cylinder or more engine unit.

In the second embodiment described above, the opening amount of the throttle valve 270 is controlled based on the pressure in the downstream intake passage 110x detected in each four-stroke cycle. The detection frequency and the control method may be different from those in the above-described embodiments. For example, fig. 15 shows a modification in which the pressure is detected on the basis of n cycles (i.e., in every n cycle periods). Here, n is a natural number equal to or greater than 2. In this modification, the pressure in the downstream intake passage 110x is not detected for the period from the first cycle to the (n-1) th cycle in every n cycle periods. In every n cycle periods, the pressure in the downstream intake passage 110x is detected at a specific timing or timings in the nth cycle to serve as the value(s) indicating the manner of pressure change based on the four-stroke. The opening degree of the throttle valve 270 is controlled based on the detected pressure value(s). The above control is repeated based on n cycles. Therefore, the throttle valve 270 is appropriately controlled according to the four-stroke based pressure variation pattern every n cycle periods.

The above modification can also be arranged as follows: the pressure is detected at a specific timing in two or more cycles every n cycle periods, and a value obtained by calculating the detected pressure value may be used as a pressure value representing the four-stroke-based pressure variation pattern every n cycle periods. For example, the pressure may be detected at a particular moment in each of two or more four-stroke cycles in each n cycle duration, and an average of the detected pressure values may be calculated. The average value is then used to control the throttle valve 270 as a value representing the four-stroke based pressure variation pattern for each n cycle length.

Further, in the second embodiment described above, the ECU 150 controls the throttle valve 270 to satisfy the conditions shown in fig. 12(a) and 12 (b). However, the ECU may control the throttle valve 270 to satisfy conditions different from those shown in fig. 12(a) and 12 (b).

Further, in order to replace the throttle valve 270 used in the above-described second embodiment, various valves that narrow the passage with different structures may be used. Further, the valve configured to change the amount of fuel vapor in the present invention may change the flow rate discretely, or may change the flow rate continuously.

Note that, in this specification, "control associated with the pressure variation pattern based on the four-stroke" means that control is performed such that the valve is operated at a timing associated with the pressure variation pattern in which a pressure drop is repeatedly generated based on the four-stroke. The control may be performed by taking a time point of a current time in the four-stroke cycle and based on the time point. The above time points may be obtained in any manner. For example, in the above-described embodiment, the crank position (crank angle) of the crankshaft 134 is detected by the rpm rotation speed sensor 153. Based on the detection result, the on operation and the off operation of the electromagnetic valve 170 are performed at specific crank angles, respectively. Further, "control associated with the four-stroke-based pressure variation pattern" includes control performed based on the detection result of the repetitive pressure variation based on the four strokes. Examples of such control include control directly associated with a pressure change indicated by a detection result obtained by the intake air pressure sensor 151 or the like. For example, when the pressure value detected by the intake air pressure sensor 151 or the like is equal to a predetermined value, the on operation or the off operation may be performed.

There are various control modes associated with the four-stroke based pressure variation mode. Examples of controls associated with a four-stroke based pressure variation pattern include: a control associated with one stroke period, a control associated with two stroke periods, and a control associated with n stroke periods, where n is a multiple of 4. Examples of the control associated with one stroke period include: the control of the on operation is performed in each stroke period and the control of the off operation is performed in each stroke period, as shown by a graph C4. Examples of controls associated with two stroke periods include: the control of the on operation is performed in every two stroke periods and the control of the off operation is performed in every two stroke periods, as shown by graphs C5, C6 in fig. 7. Examples of the control associated with the n stroke periods (where n is a multiple of 4) include control of performing an on operation in each four stroke cycle and control of performing an off operation in each four stroke cycle, as shown by graphs C1 to C3 in fig. 4. Examples of the control associated with the n stroke periods (where n is a multiple of 4) also include control of performing the on operation and/or the off operation every eight strokes or every twelve stroke periods, as shown by graphs C7 to C10 in fig. 8. Examples of the control associated with the n stroke periods (where n is a multiple of 4) also include control that performs the on and/or off operation every sixteen strokes or every twenty stroke periods. The multiple of 4 may be equal to or greater than 16.

Further, in the "control associated with the four-stroke-based pressure variation pattern", it does not matter whether or not the period from the on operation to the off operation crosses the boundary between the strokes or the boundary between the four-stroke cycles. For example, as shown by the graph C1 in fig. 4 and the graph C6 in fig. 7, the period of time from the on operation to the off operation may cross the boundary between strokes or the boundary between four-stroke cycles. Alternatively, as shown by plots C2 and C3 in fig. 4 and plots C4 and C5 in fig. 7, the period from the on operation to the off operation may fall within one stroke period or a four-stroke cycle.

Also, in the "control associated with the four-stroke based pressure variation pattern", it does not matter whether or not the timing of the on operation and/or the timing of the off operation is synchronized with the time period of one or more strokes or with the four-stroke cycle. For example, the control shown in the graph C10 is also included in the "control associated with the four-stroke based pressure variation pattern". In the control shown by the graph C10, the timing of the on operation and the timing of the off operation are not synchronized with the four-stroke cycle. Note that "synchronized with n stroke periods" means that the timing of the operation within each n stroke periods (i.e., the position of the time point of the operation with respect to the length of the n stroke periods) is the same among the respective n stroke periods. Meanwhile, "synchronized with the four-stroke cycle" means that the timing of the operation within each four-stroke cycle (i.e., the position of the time point of the operation with respect to the length of the four-stroke cycle) is the same in each four-stroke cycle.

In the present specification, "the opening degree of the valve is controlled in accordance with a pressure variation pattern based on a four-stroke cycle, the pressure variation pattern being included in a pressure variation pattern in which a small pressure drop and a large pressure drop are repeatedly generated based on a four-stroke cycle" means that the following control is performed. As described in the above embodiments by way of example, the pressure variation manner changes as the rpm of the engine 130 changes, for example. The pressure change pattern is represented by the shape of a curve representing the pressure change (such as curves P1 and P2 in fig. 11). Each of the curves P1 and P2 is formed with a trough in each four-stroke cycle. The trough shows the drop in pressure. As shown in FIG. 13, the pressure drop trough in each four-stroke cycle becomes lower as the rpm speed of the engine 130 increases. Now, "controlling the opening degree of the valve according to a four-stroke-based pressure variation pattern included in a pressure variation pattern repeatedly generating a small pressure drop and a large pressure drop based on a four stroke" includes controlling the opening degree of the valve in association with a variation of the above-described four-stroke-based pressure variation pattern. For example, in the above-described embodiment, the following control is performed. The four-stroke based pressure variation pattern changes as the rpm of the engine 130 increases. Specifically, the shape of the valleys in the curve representing the pressure change changes as the rpm rotation speed increases. Control is performed to increase the opening degree of the throttle valve 270 in response to the change.

In the above control, the opening degree of the valve may be controlled based on a pressure value derived from the detection result(s) of the sensor(s), or may be controlled based on a pressure value directly obtained by the sensor. For example, in the above-described embodiment, the opening degree of the throttle valve 270 is controlled based on the pressure in the downstream intake passage 110x derived from the detection results regarding the rpm rotation speed of the engine 130 and the throttle opening degree of the throttle valve 112. However, the opening amount of the throttle valve 270 may be controlled based on the pressure in the downstream intake passage 110x obtained by the detection result directly obtained by the intake pressure sensor 151.

Further, it is not necessary to directly perform control of the opening degree of the valve based on the pressure value. For example, the valves may be controlled without deriving the value of the pressure in the downstream intake passage 110x from the values of the rpm rotation speed of the engine 130 and the throttle opening of the throttle valve 112, and without directly obtaining the value of the pressure in the downstream intake passage 110x from the detection result obtained by the intake pressure sensor 151. For example, the valve may be controlled based on information stored in the memory unit. Specifically, the storage unit stores therein: information on the rpm rotational speed of the engine 130 and the throttle opening degree of the throttle valve 112; and information on the opening degree of the throttle valve 270, and these information items are related to each other. Information on the opening degree of the throttle valve 270, which is related to the values of the rpm rotational speed of the engine 130 and the value of the throttle opening degree of the throttle valve 112, is obtained from the storage unit. The valve can be controlled based on these items of information obtained.

In the present specification, "the opening degree of the valve in the open state is adjustable" means that the opening degree of the valve in the open condition is adjustable to two or more levels. This means that the number of levels to which the opening degree of the valve can be adjusted is three or more in the case of a level including a zero opening degree at which the valve closes the communication passage to prevent air from communicating between the tank and the intake passage. The valve may be configured such that its opening degree varies discretely, or may be configured such that its opening degree varies continuously.

In addition to this, "the smaller pressure drop and the larger pressure drop are repeatedly generated based on four strokes" herein means that there are two pressure drops in each four-stroke cycle, and that one of the pressure drops has a pressure difference with atmospheric pressure that is greater than the other pressure drop. In other words, there are two pressure drops in each four-stroke cycle, which are different from each other in pressure difference from atmospheric pressure.

Further, in the present specification, the valve whose opening degree is variable includes: a valve capable of switching from an open state to a closed state and from a closed state to an open state; and a valve configured such that an opening degree of the valve in an open state is adjustable. That is, in the first and second embodiments, the above-described valve includes both the valves 170 and 270.

It should be noted that the saddle-ride type vehicle of the invention is not limited to the motorcycle 1 described above. A ride-on vehicle may be any vehicle that a rider straddles to ride on. The riding vehicle may be any other type of two-wheeled motor vehicle, such as off-road motorcycles, scooters, and scooters. In addition, the saddle-ride type vehicles in the present invention include three-wheeled vehicles and four-wheeled vehicles (all-terrain vehicles (ATVs)).

List of reference numerals

1: motorcycle with a motorcycle body

14: fuel tank

100: engine unit

110: intake passage member

110 a: air intake passage

110 d: downstream air intake passage part

112: air throttle

120: exhaust passage member

120 a: exhaust passage

130: engine

130 a: combustion chamber

141: air inlet valve

142: exhaust valve

150：ECU

151: air inlet pressure sensor

152: throttle position sensor

153: rpm revolution speed sensor

161: tank body

163: communication passage member

163 a: communication path

170: electromagnetic valve

200: engine unit

263: communication passage member

270: throttle valve

300: engine unit

350：ECU

363: communication passage member

400: engine unit

450：ECU

Claims (20)

1. A multi-cylinder four-stroke engine unit, comprising:

an engine including a combustion chamber; an intake passage member that is connected to the engine and allows air to be introduced into the combustion chamber; and a throttle valve provided at an intermediate portion of the intake passage member, the combustion chamber, the intake passage member, and the throttle valve being provided for each cylinder, wherein a pressure in a downstream intake passage portion of the intake passage member downstream of the throttle valve varies in such a manner that: creating a smaller pressure drop at a smaller difference from atmospheric pressure and a larger pressure drop at a larger difference from atmospheric pressure in each four-stroke cycle; and the smaller pressure drop and the larger pressure drop are repeatedly generated based on a four-stroke cycle, the engine unit further comprising:

a canister connected to a fuel tank and containing therein a adsorbent configured to adsorb fuel vapor contained in intake air from the fuel tank;

a communication passage member configured to establish communication between the interior of the tank and the downstream intake passage portion for each cylinder, the communication passage member having branch portions for each cylinder, the branch portions being connected to the downstream intake passage portion, respectively;

a valve provided to each branch portion of the communication passage member such that a capacity of a portion of the communication passage member extending from the intake passage member to the valve is less than half of an exhaust gas amount of the engine, wherein an opening degree of the valve is changeable; and

a controller configured to control operation of the valve based on a pattern of pressure changes that are repeatedly generated based on a four-stroke cycle as a function of the smaller pressure drop and the larger pressure drop, wherein

The controller is configured to control the valve such that a ratio of an amount of fuel vapor introduced from the communication passage member into the downstream intake passage portion to a combustion chamber intake air amount, which is an amount of air introduced from the downstream intake passage portion into the combustion chamber, increases as the combustion chamber intake air amount increases.

2. The engine unit according to claim 1, further comprising a sensor for each downstream intake passage portion, the sensor being configured to detect a negative pressure in the downstream intake passage portion, wherein

The controller is configured to control the operation of the valve based on a detection result obtained by the sensor.

3. The engine unit according to claim 1, wherein the controller is configured to control the valve such that a ratio of an amount of fuel vapor introduced from the communication passage member into the downstream intake passage portion to the combustion chamber introduced air amount increases as the combustion chamber introduced air amount increases, when the combustion chamber introduced air amount is equal to or smaller than a predetermined value.

4. The engine unit according to claim 2, wherein the controller is configured to control the valve such that a ratio of an amount of fuel vapor introduced from the communication passage member into the downstream intake passage portion to the combustion chamber intake air amount increases as the combustion chamber intake air amount increases, when the combustion chamber intake air amount is equal to or smaller than a predetermined value.

5. The engine unit according to any one of claims 1 to 4, wherein:

each of the valves is switchable from a closed state, in which the valve prevents air from flowing between the interior of the tank and the downstream intake passage portion, to an open state, in which the valve allows air to flow between the interior of the tank and the downstream intake passage portion, and from the open state to the closed state; and

the controller is configured to control the valve to perform a valve switching operation in association with the pressure variation pattern in which the smaller pressure drop and the larger pressure drop are repeatedly generated on a four-stroke basis, the valve switching operation being a set of an on operation and an off operation, one of the on operation and the off operation being performed first, and the other of the on operation and the off operation being performed, the on operation being an operation of switching the valve from the closed state to the open state, and the off operation being an operation of switching the valve from the open state to the closed state.

6. The engine unit according to claim 5, wherein, when counting each of the four strokes constituting a four-stroke cycle as one stroke, the controller is configured to control each of the valves to perform the valve switching operation in association with n stroke periods, where n is a multiple of 4 or 1 or 2.

7. The engine unit according to claim 6, wherein the controller is configured to control each of the valves to perform at least one of the on and off operations in synchronization with n stroke periods, where n is a multiple of 4 or 1 or 2.

8. An engine unit as claimed in claim 7, wherein the controller is configured to control each of the valves to perform the on operation and then the off operation every n stroke periods, where n is a multiple of 4 or 1 or 2.

9. An engine unit as claimed in claim 7, wherein the controller is configured to control each of the valves to perform the switch-off operation and then the switch-on operation every n stroke periods, where n is a multiple of 4 or 1 or 2.

10. The engine unit according to claim 7, wherein the controller is configured to control each of the valves to perform each of the on and off operations once every n stroke periods, where n is a multiple of 4 or 1 or 2.

11. The engine unit according to claim 10, wherein the controller is configured to control each of the valves to perform each of the on operation and the off operation once per one stroke period or once every two stroke periods.

12. The engine unit according to claim 10, wherein the controller is configured to control each of the valves to perform each of the on and off operations once within a four-stroke cycle every n stroke periods, where n is a multiple of 4.

13. The engine unit according to claim 12, wherein the controller is configured to control each of the valves to perform each of the on and off operations once every four stroke period.

14. The engine unit according to claim 7, wherein the controller is configured to control each of the valves to perform each of the on and off operations two or more times per n stroke periods, where n is a multiple of 4.

15. An engine unit according to claim 6, wherein the controller is configured to control each of the valves to perform one of the on and off operations and then the other in every n stroke periods, where n is a multiple of 4 or 1 or 2, the instants at which the on and off operations are performed in each period being different among the respective n stroke periods.

16. The engine unit according to any one of claims 1 to 4, wherein:

each of the valves may be in an open state in which the valve allows air to communicate between the interior of the tank and the intake passage member through the communication passage member, and an opening degree of each of the valves in the open state may be adjusted; and

the controller is configured to control the opening degree of each of the valves in the open state according to a four-stroke-based pressure variation pattern included in pressure variation patterns in which the smaller pressure drop and the larger pressure drop are repeatedly generated on a four-stroke basis.

17. The engine unit according to claim 16, wherein when four strokes are counted as one cycle, the controller is configured to control the opening degree of each of the valves in the open state according to the four-stroke based pressure variation pattern for every n cycle periods, where n is a natural number.

18. The engine unit according to claim 17, further comprising a sensor for each downstream intake passage portion, the sensor being configured to detect a negative pressure in the downstream intake passage portion, wherein

The controller is configured to control the opening degree of each of the valves in the open state based on a detection result obtained by the sensor in each cycle included in the n cycle periods, the detection result being indicative of the four-stroke based pressure variation pattern in the every n cycle periods.

19. An engine unit as claimed in claim 17 or 18, wherein when four strokes are counted as one cycle, the controller is configured to control each of the valves in the following manner: the controller changes the opening degree of the valve in the open state according to the four-stroke based pressure variation manner after the controller keeps the opening degree of the valve in the open state constant in each cycle.

20. A saddle-ride type vehicle, comprising:

an engine unit according to any one of claims 1 to 19;

a vehicle body frame that supports the engine unit;

a rider seat;

a handle disposed forward of the rider seat; and

a fuel tank connected to a canister contained in the engine unit.

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