JP7428593B2 - engine unit - Google Patents

Description

The present invention relates to an engine unit.

The engine unit disclosed in Patent Document 1 and Patent Document 2 includes a cooling water circuit having a switching valve that switches depending on the temperature of the cooling water.

When the cooling water of the engine unit of Patent Document 1 is at low temperature, it flows as follows due to the action of a thermostatic valve (switching valve). That is, the cooling water flows in the order of water pump → cylinder head → water pump. When the cooling water is at high temperature, it flows as follows due to the action of the thermostatic valve. That is, the cooling water flows in the order of water pump → cylinder head → cylinder body (cylinder block) → radiator → water pump. Since almost no cooling water flows into the cylinder body when the temperature is low, the temperature of the cylinder body rises relatively quickly during warm-up operation, and the viscosity of the lubricating oil decreases relatively quickly. Therefore, friction loss of the engine unit during warm-up operation is reduced.

When the cooling water of the engine unit of Patent Document 2 is at a low temperature, the cooling water flows as follows due to the action of a thermostatic valve (switching valve). That is, the cooling water flows in the order of water pump → cylinder head → water pump. When the cooling water is at high temperature, it flows as follows due to the action of the thermostatic valve. That is, the cooling water flows in the order of water pump → cylinder head → cylinder body (cylinder block) → radiator → water pump. Since cooling water is supplied to the cylinder body when the temperature is high, it is possible to lower the temperature of the cylinder body.

Patent No. 4278131 Japanese Patent Application Publication No. 2002-97959

The inventors of the present application have studied the engine units of Patent Documents 1 and 2. As a result, it has been found that problems occur in the engine units of Patent Documents 1 and 2 unless the device for cooling the coolant is made larger and/or more complicated. That is, it has been found that the engine units of Patent Documents 1 and 2 tend to cause knocking when the coolant is at a high temperature.

An object of the present invention is to provide an engine unit in which knocking is less likely to occur even when a device for cooling a coolant is not made large and complicated.

The inventors of the present application obtained the following knowledge by studying the engine units of Patent Documents 1 and 2. When the cooling water of the engine unit in Patent Documents 1 and 2 is at a high temperature, it flows out from the radiator and is then supplied to the cylinder body via the water pump and the cylinder head. In other words, the cooling water cooled by the radiator is warmed by the cylinder head and then supplied to the cylinder body. Therefore, it has been found that in the engine units of Patent Documents 1 and 2, the temperature of the cylinder body (particularly the cylinder bore) may not be sufficiently lowered by the cooling water flowing through the cylinder body. Therefore, the temperature of the intake air may increase significantly due to heat exchange between the intake air, which is air that has flowed into the cylinder bore during the intake stroke, and the cylinder bore. Therefore, the engine units of Patent Documents 1 and 2 tend to cause knocking.

For example, by increasing the amount of pressure that can be generated by the coolant pump device and/or by increasing the heat exchange function of the radiator, it becomes possible to lower the temperature of the cylinder body (cylinder bore) using the coolant. However, in this case, the coolant pump device and/or the radiator, which are devices for cooling the coolant, become larger and more complicated.

The inventors of the present application have noticed that cooling the cylinder body has a stronger correlation with the difficulty of knocking than cooling the cylinder head. Therefore, the inventors of the present invention came up with the idea of configuring the coolant circuit so that when the coolant is at a high temperature, the coolant flowing out of the radiator is supplied to the cylinder body without passing through the cylinder head. Thereby, the temperature of the cylinder body can be sufficiently lowered by the coolant without increasing the size and complexity of the device for cooling the coolant. As a result, the engine unit is less likely to knock without increasing the size and complexity of the device for cooling the coolant.

(1) The engine unit of the present invention includes a cylinder body in which at least one cylinder bore is formed, a cylinder head connected to the cylinder body, and at least a portion of which passes through the cylinder head and the cylinder body to cool the inside. a coolant passage section through which liquid circulates; a coolant pump device provided in the coolant passage section and configured to pump the coolant and circulate the coolant within the coolant passage section; A radiator provided in the section.
When the temperature of the coolant is in the first low temperature range, the coolant passes through the coolant pump device, the cylinder head, and the coolant pump device in this order, without passing through the radiator and the cylinder body. When the coolant flows and the temperature of the coolant is in a high temperature region higher than the first low temperature region, the coolant pump device, the cylinder head, the radiator, the cylinder body, and the coolant pump device are operated in the following order: The coolant flows within the coolant passage.

According to this configuration, when the temperature of the coolant is in the first low temperature range, the coolant does not flow into the cylinder body. Therefore, the temperature of the cylinder body rises relatively quickly while the engine unit is warming up.
Further, when the temperature of the coolant is in a high temperature range, the coolant cooled by the radiator flows directly to the cylinder body. In other words, the coolant cooled by the radiator is supplied to the cylinder body without passing through the coolant pump device and the cylinder head. In other words, the coolant cooled by the radiator is supplied to the cylinder body without being heated by the cylinder head. Therefore, without increasing the size and complexity of the coolant pump device and/or the radiator, which are devices for cooling the coolant, the coolant cooled by the radiator is transferred to the cylinder via the coolant pump device and the cylinder head. It is possible to further reduce the temperature of the cylinder body with the cooling liquid compared to when the cooling liquid is supplied to the body. That is, for example, it is possible to sufficiently reduce the temperature of the cylinder body (cylinder bore) without increasing the magnitude of the pressure that can be generated by the coolant pump device and/or the heat exchange function of the radiator. Therefore, it is possible to suppress the temperature of the intake air from increasing significantly due to heat exchange between the cylinder bore and the intake air that is air that has flowed into the cylinder bore while the engine unit is performing the intake stroke. Therefore, even if the coolant pump device and/or the radiator, which are devices for cooling the coolant, are not made large and complicated, knocking is unlikely to occur in the engine unit.

(2) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
When the temperature of the coolant is in the first low temperature range, the coolant flows into the coolant passage section in the order of the coolant pump device, the cylinder head, and the coolant pump device without passing through the radiator and the cylinder body. is in the first state where the coolant flows, and when the temperature of the coolant is in the high temperature range, the coolant pump device, the cylinder head, the radiator, the cylinder body, and the coolant A switching valve configured to be in a second state in which the coolant flows through the coolant passage in the order of the pump device is provided in the coolant passage.

According to this configuration, the switching valve controls the flow of the coolant depending on the temperature of the coolant. Therefore, knocking is less likely to occur in the engine unit without increasing the size and complexity of the coolant pump device and/or the radiator, which are devices for cooling the coolant.

(3) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration in addition to the configuration of (2) above.
The switching valve includes a first inlet into which the coolant flowing out from the cylinder head flows, a first outlet through which the coolant flows out toward the radiator, and a first outlet into which the coolant flowing out from the cylinder body flows. A four-way valve having a second inlet for inflow, and a second outlet for allowing the coolant to flow out towards the coolant pumping device.
The four-way valve causes the coolant that has flowed into the first inlet to flow out from the second outlet, and causes the coolant that has flowed into the second inlet to flow out from the first outlet and the second outlet. The first state is such that the cooling liquid that has flowed into the first inlet flows out from the first outlet, and the cooling liquid that has flowed into the second inlet flows out from the second outlet. The second state is configured to be switched to the second state.
When the temperature of the coolant is in the first low temperature range, the four-way valve is in the first state, so that the coolant pump device and the cylinder head do not pass through the radiator and the cylinder body. , the four-way valve, and the coolant pump device in this order, when the coolant circulates within the coolant passage section and the temperature of the coolant is in the high temperature region, the four-way valve As a result, the coolant flows through the coolant passage in the order of the coolant pump device, the cylinder head, the four-way valve, the radiator, the cylinder body, the four-way valve, and the coolant pump device. circulate within the department.

According to this configuration, by using one switching valve (four-way valve), the coolant circulates within the coolant passage so as to sufficiently lower the temperature of the cylinder body. That is, by using one switching valve, the temperature of the intake air is prevented from increasing significantly due to heat exchange between the intake air and the cylinder bore. Therefore, knocking is less likely to occur in the engine unit without increasing the size and complexity of the coolant pump device and/or the radiator, which are devices for cooling the coolant.

(4) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration in addition to the configuration of (2) above.
The switching valve is located outside the cylinder head and the cylinder body, and is separate from the cylinder head and the cylinder body.

(5) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration in addition to the configuration of (2) above.
When the switching valve is in the first state, at least one of the coolant and air flows into the coolant passage formed in the cylinder body through the radiator.
The engine unit includes a bypass passage connected to the coolant passage in the cylinder body and connected to the coolant passage in the cylinder head.

When the switching valve is in the first state, a small amount of coolant and/or air may flow through the switching valve and into the coolant passage formed in the cylinder body via the radiator. This small amount of coolant and/or air then exerts pressure on at least one of the coolant and air within the coolant passage formed in the cylinder body. Therefore, at least one of the coolant and air in the coolant passage formed in the cylinder body flows into the coolant passage formed in the cylinder head through the internal space of the bypass passage.
When a small amount of coolant remains in the coolant passage formed in the cylinder body, the coolant receives heat from the cylinder body and rapidly becomes high in temperature. Also, air has a lower thermal conductivity than coolant. Therefore, when air remains in the coolant passage formed in the cylinder body, the cylinder body tends to become excessively hot. Therefore, if at least one of the coolant and the air is in such a state, the temperature of the cylinder body may become excessively high.
According to this configuration, even when the switching valve is in the first state, the coolant and air are unlikely to remain in the coolant passage formed in the cylinder body. Therefore, the temperature of the cylinder body can be maintained sufficiently when the switching valve is in the second state without increasing the size and complexity of the coolant pump device and/or the radiator, which are devices for cooling the coolant. It is possible to lower the Therefore, it is possible to suppress the temperature of the intake air from increasing significantly due to heat exchange between the intake air and the cylinder bore. Therefore, knocking is less likely to occur in the engine unit without increasing the size and complexity of the coolant pump device and/or the radiator, which are devices for cooling the coolant.

(6) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
The engine unit has a crankshaft.
The coolant pump device is configured to be switched between a stopped state and an activated state independently of movement of the crankshaft.

According to this configuration, for example, when the temperature of the coolant is lower than the first low temperature range and the engine unit is in the operating state, the coolant pump device is in the stopped state. As a result, the cylinder head and cylinder body become hot. For example, when the temperature of the coolant subsequently reaches a high temperature range, the coolant pump device is switched into operation. Then, the coolant cooled by the radiator flows into the cylinder body without passing through the cylinder head. Therefore, the temperature of the cylinder body can be sufficiently lowered without increasing the size and complexity of the coolant pump device and/or the radiator, which are devices for cooling the coolant. Therefore, it is possible to suppress the temperature of the intake air from increasing significantly due to heat exchange between the intake air and the cylinder bore. Therefore, knocking is less likely to occur in the engine unit without increasing the size and complexity of the coolant pump device and/or the radiator, which are devices for cooling the coolant.

(7) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration in addition to the configuration of (6) above.
The coolant pump device is configured to enter the stopped state when the temperature of the coolant is in a second low temperature range that is lower than the first low temperature range.

According to this configuration, when the temperature of the coolant is in the second low temperature range and the engine unit is in the operating state, the coolant pump device is in the stopped state. As a result, the cylinder head and cylinder body become hot. For example, when the temperature of the coolant subsequently reaches a high temperature range, the coolant pump device is switched into operation. Then, the coolant cooled by the radiator is supplied to the cylinder body without passing through the cylinder head. Therefore, the temperature of the cylinder body can be sufficiently lowered without increasing the size and complexity of the coolant pump device and/or the radiator, which are devices for cooling the coolant. Therefore, it is possible to suppress the temperature of the intake air from increasing significantly due to heat exchange between the intake air and the cylinder bore. Therefore, knocking is less likely to occur in the engine unit without increasing the size and complexity of the coolant pump device and/or the radiator, which are devices for cooling the coolant.

(8) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
The engine unit includes at least one piston that reciprocates within the at least one cylinder bore along a cylinder axis that is a central axis of the cylinder bore.
The diameter of the at least one cylinder bore is a first diameter, and the stroke of the piston that reciprocates within the cylinder bore having the first diameter is a first stroke longer than the first diameter.

According to this configuration, the engine unit is a long stroke engine unit.
If the displacement of a long-stroke engine unit and a short-stroke engine unit are the same, the length of the cylinder bore in the direction parallel to the cylinder axis, which is the central axis of the cylinder bore, is relatively longer for the long-stroke engine unit than for the short-stroke engine unit. long. Therefore, since the contact area between the inner surface of the cylinder bore and the intake air is wide, the amount of increase in temperature of the intake air in the long stroke engine unit is relatively larger than in the case of the short stroke engine unit. Further, when the engine rotation speeds of the long stroke engine unit and the short stroke engine unit are the same, the average piston speed of the long stroke engine unit is higher than that of the short stroke engine unit. Therefore, the intake speed of intake air is higher in the long stroke engine unit than in the short stroke engine unit. Therefore, the heat transfer coefficient, which increases in proportion to the magnitude of fluid turbulence, is greater in long-stroke engine units than in short-stroke engine units. Therefore, the amount of increase in temperature of the intake air is larger in the long stroke engine unit than in the short stroke engine unit.
According to this configuration, when the temperature of the coolant is in a high temperature range, the temperature of the cylinder body can be increased without increasing the size and complexity of the coolant pump device and/or radiator, which are devices for cooling the coolant. It is possible to sufficiently reduce the
Therefore, when the temperature of the coolant is in a high temperature range, it is possible to sufficiently reduce the temperature of the cylinder body of the long stroke engine unit by the coolant. As a result, it is possible to suppress heat exchange between the intake air and the cylinder bore during the intake stroke, and to reduce the amount of temperature rise of the intake air. Therefore, knocking is less likely to occur in the long stroke engine unit.

(9) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
The engine unit includes a combustion chamber in which an intake port is formed, a first intake passage portion formed in the cylinder head and connected to the intake port, and an upstream end of the first intake passage portion in an air flow direction. a second intake passage portion disposed outside the cylinder head, the second intake passage portion being connected to the cylinder head and having a throttle valve disposed therein; and a fuel injection device for injecting fuel within the first intake passage portion or within the second intake passage portion; has.

According to this configuration, the engine unit includes a fuel injection device that injects fuel into the first intake passage or the second intake passage. Therefore, compared to a direct injection type engine unit that includes a fuel injection device that injects fuel into a combustion chamber, the cylinder head and cylinder body tend to reach high temperatures. Therefore, the effect of cooling the cylinder head and cylinder body by the coolant is large.

(10) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
The engine unit includes a spark plug that ignites a mixture of air and fuel within the combustion chamber.

(11) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
A cylinder axis that is a central axis of the cylinder bore is inclined with respect to a vertical direction of a vehicle in which the engine unit is mounted.
The engine unit includes a combustion chamber in which an exhaust port is formed, a first exhaust passage portion formed in the cylinder head and connected to the exhaust port, and a downstream end of the first exhaust passage portion in a gas flow direction. a second exhaust passage portion connected to the cylinder head and disposed outside the cylinder head.
When the up-down direction of the vehicle in which the engine unit is mounted is defined as the up-down direction, the downstream end of the first exhaust passage portion is formed on a downwardly facing outer surface of the cylinder head.

(12) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
Only one cylinder bore is formed in the cylinder body.

<Definition of terms>
In the present invention, the cooling liquid means a liquid having a cooling function. The coolant includes cooling water. Cooling water is a liquid containing water. The coolant may be a water-free liquid. The coolant does not contain lubricating oil for lubricating pistons and the like. The coolant may or may not contain oil other than lubricating oil.

In the present invention, "when the switching valve is in the first state, at least one of the coolant and air flows into the coolant passage formed in the cylinder body through the radiator" means that the switching valve is in the first state. When the cooling liquid flows through the switching valve and flows into the cylinder body through the radiator, a smaller amount of cooling liquid per unit time than the cooling liquid that flows through the switching valve and into the coolant pump device flows through the switching valve and into the cylinder body. When the switching valve is in the first state, less air per unit time passes through the switching valve than the air passing through the switching valve and into the coolant pump device. This means that the coolant passes through the radiator and flows into the coolant passage formed in the cylinder body.

In the present invention, "the coolant pump device is switched between the stopped state and the operating state independently of the movement of the crankshaft" means that the coolant pump device is switched between the stopped state and the operating state independently of the movement of the crankshaft. This means that it can be switched to the operating state. That is, when the crankshaft is not rotating, the coolant pump device can be in either a stopped state or an operating state. Further, while the crankshaft is rotating, the coolant pump device can be in either a stopped state or an activated state.

In the present invention and this specification, the vertical direction of the vehicle refers to the vertical direction of the watercraft when the watercraft is floating in still water and is in a stationary state, when the vehicle is a watercraft that is a straddle-type vehicle. be.

In the present invention and this specification, the expression that the cylinder axis intersects with the vertical direction of the vehicle in which the engine unit is mounted includes that the cylinder axis is horizontal.

In the present invention and this specification, rotation is not limited to rotation of 360° or more. Rotation herein also includes rotation of less than 360°. The definitions of forward rotation and reverse rotation are also similar to this definition of rotation. Rocking herein means rotation of less than 360°.

In the present invention and this specification, an end of a certain component means the sum of the end of the component and its vicinity.

As used herein, the term "and/or" includes any or all combinations of one or more of the associated listed components.

The passage section in the present invention refers to a wall or the like that surrounds and forms a passage. Moreover, a route means a space through which an object passes. For example, this definition is applied to a coolant passage, a bypass passage, an intake passage, and an exhaust passage.

In this specification, A is located in the front direction relative to B, unless otherwise specified, refers to the following conditions. A is located in the front space of two spaces partitioned by a plane that passes through the frontmost end of B and is perpendicular to the front and rear directions. A and B may or may not be lined up in the front-rear direction. When B is a plane or straight line orthogonal to the front-rear direction, a plane passing through the front end of B is a plane passing through B. If B is a straight line or plane with an infinite length in the front-back direction, the frontmost end of B is not specified. A straight line or plane having an infinite length in the front-back direction is not limited to a straight line or a plane parallel to the front-back direction.
Note that the same definition applies to the expression that A is behind B under the same conditions as B. Furthermore, under the same conditions for B, the same definition is applied to expressions such as A is above or below B, and A is to the right or left of B.

As used herein, the use of the terms "comprising" or "having" and variations thereof refer to the described features, steps, operations, elements, components and/or their Although equivalents are specified, they may include one or more of steps, acts, elements, components, and/or groupings thereof.

In the present invention, the terms mounted, connected, coupled, and supported are used broadly. Specifically, it includes not only direct attachment, connection, coupling, and support, but also indirect attachment, connection, coupling, and support. Furthermore, connected and coupled are not limited to physical or mechanical connections/couplings. They also include direct or indirect electrical connections/coupling.

Unless defined otherwise, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be construed to have meanings consistent with the relevant art and their meanings in the context of this disclosure, and are not explicitly defined herein. unless it is interpreted in an idealized or overly formal sense.

As used herein, the term "preferred" is non-exclusive. "Preferred" means "preferred, but not limited to." In this specification, configurations described as "preferable" exhibit at least the above effects obtained by configuration (1) above. Also, as used herein, the term "may" is non-exclusive. "You may" means "you may, but are not limited to this." In this specification, the configuration described as "may be performed" provides at least the above effect obtained by the configuration (1) above.

In the claims, if the number of a certain component is not clearly specified and is expressed in the singular when translated into English, the present invention may have a plurality of this component. . Moreover, the present invention may have only one such component.

The present invention does not limit the combination of the above-mentioned preferred configurations with each other. Before describing embodiments of the invention in detail, it is to be understood that the invention is not limited to the details of construction and arrangement of components that are described in the following description or illustrated in the drawings. The present invention is also possible in embodiments other than those described below. The present invention is also possible in embodiments in which various changes are made to the embodiments described below. Further, the present invention can be implemented by appropriately combining the embodiments and modifications described below.

In the engine unit of the present invention, knocking is less likely to occur in the engine unit even if the device for cooling the coolant is not made large and complicated.

1 is a schematic configuration diagram of an engine unit according to an embodiment of the present invention. FIG. 1 is a right side view of a motorcycle according to a specific example of an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the configuration of an engine unit. FIG. 3 is a schematic diagram of the engine unit for explaining the flow of the coolant when the temperature of the coolant is in a first low temperature range. FIG. 3 is a schematic diagram of the engine unit for explaining the flow of the coolant when the temperature of the coolant is in a high temperature range.

<Embodiments of the present invention>
Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1. The engine unit 11 according to the embodiment of the present invention includes a cylinder body 20B, a cylinder head 20C, a coolant passage section 41, a coolant pump device 42, and a radiator 44.

At least one cylinder bore 20Ba is formed in the cylinder body 20B. Cylinder head 20C is connected to cylinder body 20B. At least a portion of the coolant passage section 41 passes through the cylinder head 20C and the cylinder body 20B. Coolant can circulate inside the coolant passage section 41 . The coolant pump device 42 is provided in the coolant passage section 41 . The coolant pump device 42 pumps the coolant and circulates the coolant within the coolant passage section 41 . The radiator 44 is provided in the coolant passage section 41 .

When the temperature of the coolant is in the first low temperature range, the engine unit 11 supplies the coolant to the coolant pump device 42, the cylinder head 20C, and the coolant pump device 42 in this order, without passing through the radiator 44 and the cylinder body 20B. The cooling liquid is configured to flow within the passage portion 41 . When the temperature of the coolant in the engine unit 11 is in a high temperature region higher than the first low temperature region, the coolant is pumped in the order of the coolant pump device 42, the cylinder head 20C, the radiator 44, the cylinder body 20B, and the coolant pump device 42. The cooling liquid is configured to flow within the passage portion 41 .

When the temperature of the coolant of the engine unit 11 according to the embodiment of the present invention is in the first low temperature range, the coolant does not flow into the cylinder body 20B. Therefore, when the engine unit 11 performs a warm-up operation, the temperature of the cylinder body 20B rises relatively quickly.

Further, when the temperature of the coolant is in a high temperature range, the coolant cooled by the radiator 44 flows directly to the cylinder body 20B. In other words, the coolant cooled by the radiator 44 is supplied to the cylinder body 20B without going through the coolant pump device 42 and the cylinder head 20C. In other words, the coolant cooled by the radiator 44 is supplied to the cylinder body 20B without being heated by the cylinder head 20C. Therefore, the coolant cooled by the radiator 44 can be transferred to the coolant pump device 42 and the cylinder head without increasing the size and complexity of the coolant pump device 42 and/or the radiator 44, which are devices for cooling the coolant. Compared to the case where the coolant is supplied to the cylinder body 20B via the coolant 20C, the temperature of the cylinder body 20B can be further lowered by the coolant. That is, for example, it is possible to sufficiently reduce the temperature of the cylinder body 20B (cylinder bore 20Ba) without increasing the pressure that can be generated by the coolant pump device 42 and/or the heat exchange function of the radiator 44. Become. Therefore, it is possible to suppress the temperature of the intake air from increasing significantly due to heat exchange between the intake air, which is the air that has flowed into the cylinder bore 20Ba while the engine unit 11 is performing the intake stroke, and the cylinder bore 20Ba.

Therefore, knocking is less likely to occur in the engine unit 11 without increasing the size and complexity of the coolant pump device 42 and/or the radiator 44, which are devices for cooling the coolant.

<Specific example of embodiment>
Next, specific examples of the embodiments of the present invention described above will be explained using FIGS. 2 to 5. In the following description, description of the same parts as in the embodiment of the present invention described above will be omitted. Specific examples are included in the embodiments of the invention described above. The specific example of this embodiment is an example in which the present invention is applied to a motorcycle 1. In the following description, unless otherwise specified, the longitudinal direction refers to the longitudinal direction of the vehicle. The longitudinal direction of the vehicle refers to the longitudinal direction as viewed from a rider seated on a seat 5 of the motorcycle 1, which will be described later. In the following description, the left-right direction refers to the left-right direction of the vehicle. The left-right direction of the vehicle refers to the left-right direction as seen from a rider seated on a seat 5 of the motorcycle 1, which will be described later. The left-right direction of the vehicle is also the width direction of the motorcycle 1. below. The vertical direction of the vehicle is the vertical direction when the motorcycle 1 is standing upright on a horizontal road surface with all wheels in contact with the horizontal road surface. The vehicle longitudinal direction, the vehicle lateral direction, and the vehicle vertical direction are orthogonal to each other. In the description of FIG. 2, unless otherwise specified, the vertical direction refers to the vertical direction of the vehicle. represents.

[1] Schematic configuration of motorcycle As shown in FIG. 2, the motorcycle 1 includes a front wheel 2, a rear wheel 3, and a body frame 4. A seat 5 is supported on the upper part of the vehicle body frame 4. An engine unit 11 is supported on the vehicle body frame 4. The vehicle body frame 4 also supports a battery (not shown) that supplies power to electronic devices such as an ECU (Electronic Control Unit) 80, a coolant pump device 42, and various sensors, which will be described later in the engine unit 11.

[2] Configuration of Engine Unit The configuration of the engine unit 11 will be described below. FIG. 3 is a schematic diagram showing the configuration of the engine unit 11. The engine unit 11 includes an engine main body 20, a cooling unit 40, an external intake passage section 51, and an external exhaust passage section 61. The cooling unit 40, the external intake passage section 51, and the external exhaust passage section 61 are located outside the engine body 20. At least a portion of a crankshaft 21, a piston 22, an intake valve 25, an exhaust valve 26, a spark plug 27, and a fuel injection device 28 are arranged inside the engine body 20. Engine unit 11 is a single cylinder engine unit. The engine unit 11 is a four-stroke engine that repeats an intake stroke, a compression stroke, a combustion stroke (expansion stroke), and an exhaust stroke.

The engine body 20 includes a crankcase 20A, a cylinder body 20B, a cylinder head 20C, and a head cover 20D. These are connected in this order. Crankshaft 21 is rotatably provided in crankcase 20A. The rotation center axis of the crankshaft 21 is parallel to the left-right direction. The crankcase 20A has an oil pan that stores lubricating oil. An oil pump (not shown) that pumps lubricating oil is arranged inside the crankcase 20A. The oil pump is operated by the rotational force of the crankshaft 21. Note that the head cover 20D may be integrated with the cylinder head 20C.

Cylinder body 20B has a cylinder bore 20Ba. A cylinder axis 20X, which is the central axis of the cylinder bore 20Ba, is inclined with respect to the vertical direction. As shown in FIG. 2, when the engine unit 11 is viewed in the left-right direction, the upper part of the cylinder axis 20X is located further forward than the lower part. When the engine unit 11 is viewed in the left-right direction, the inclination angle of the cylinder axis 20X with respect to the vertical direction is greater than 0° and less than 45°. Note that the cylinder axis 20X is not a line segment that exists only in the area where the cylinder bore 20Ba exists, but is a straight line that extends infinitely. The piston 22 is provided within the cylinder bore 20Ba so as to be able to reciprocate along the cylinder axis 20X. Piston 22 is connected to crankshaft 21 via connecting rod 23. As shown in FIG. 3, the first stroke St, which is the stroke during the reciprocating movement of the piston 22, is longer than the first diameter Db, which is the diameter of the cylinder bore 20Ba. That is, the engine unit 11 of the specific example is a long stroke engine unit.

The engine body 20 has a combustion chamber 24, a cylinder head intake passage section 20Ca, and a cylinder head exhaust passage section 20Cb. Note that in this specification, a passage section means a structure that forms a path. Combustion chamber 24 is formed by cylinder head 20C, cylinder bore 20Ba, and piston 22. The combustion chamber 24 has an intake port 24a and an exhaust port 24b formed in the cylinder head 20C. Air is supplied to the combustion chamber 24 from the intake port 24a. Exhaust gas generated in the combustion chamber 24 is exhausted from the exhaust port 24b. A cylinder head intake passage section 20Ca and a cylinder head exhaust passage section 20Cb are formed in the cylinder head 20C. The cylinder head intake passage section 20Ca is connected to the intake port 24a. Cylinder head exhaust passage section 20Cb is connected to exhaust port 24b.

The upstream end of the cylinder head intake passage section 20Ca in the air flow direction is connected to the external intake passage section 51. A throttle valve 52 is arranged within the external intake passage section 51 . Air in the atmosphere is supplied to the combustion chamber 24 through the external intake passage section 51 and the cylinder head intake passage section 20Ca.

The downstream end of the cylinder head exhaust passage section 20Cb in the exhaust gas flow direction is an opening (not shown) formed in the front surface 20C3 of the cylinder head 20C. The front surface 20C3 is a downwardly facing outer surface of the cylinder head 20C. The downstream end of the cylinder head exhaust passage section 20Cb in the flow direction of exhaust gas is connected to the external exhaust passage section 61. A catalyst (not shown) for purifying exhaust gas is disposed within the external exhaust passage section 61. Exhaust gas generated in the combustion chamber 24 passes through the cylinder head exhaust passage section 20Cb and the external exhaust passage section 61 and is exhausted to the atmosphere.

The intake valve 25 is provided in the cylinder head 20C to open and close the intake port 24a. The exhaust valve 26 is provided in the cylinder head 20C to open and close the exhaust port 24b. The intake valve 25 and the exhaust valve 26 are driven by a valve drive mechanism (not shown).

As shown in FIG. 3, the tip of the spark plug 27 is disposed within the combustion chamber 24. The spark plug 27 ignites a mixture containing fuel (for example, gasoline) and air in the combustion chamber 24 . The fuel injection device 28 is provided in the cylinder head 20C to inject fuel within the cylinder head intake passage 20Ca. Note that the fuel injection device 28 may be arranged to inject fuel within the external intake passage section 51.

A part of the coolant passage section 41 is formed inside the engine body 20. The coolant circulates through the coolant passage section 41 . The coolant passage section 41 includes a cylinder head coolant passage section 41b, a cylinder body coolant passage section 41f, and a bypass passage section 41g, which are formed inside the engine body 20. The cylinder head coolant passage portion 41b is formed inside the cylinder head 20C. The upstream end of the cylinder head coolant passage portion 41b in the flow direction of the coolant is a first opening 20C1 (see FIGS. 4 and 5) formed on the outer surface of the cylinder head 20C. The downstream end of the cylinder head coolant passage 41b is a second opening 20C2 (see FIGS. 4 and 5) formed on the outer surface of the cylinder head 20C. The cylinder body coolant passage portion 41f is formed inside the cylinder body 20B. The upstream end of the cylinder body coolant passage 41f in the flow direction of the coolant is a third opening 20B1 (see FIGS. 4 and 5) formed on the outer surface of the cylinder body 20B. The downstream end of the cylinder body coolant passage 41f is a fourth opening 20B2 (see FIGS. 4 and 5) formed on the outer surface of the cylinder body 20B. Bypass passage portion 41g is formed inside cylinder body 20B and cylinder head 20C. The upstream end of the bypass passage section 41g in the flow direction of the coolant is connected to the cylinder body coolant passage section 41f. A downstream end of the bypass passage section 41g in the flow direction of the coolant is connected to the cylinder head coolant passage section 41b. The cylinder head 20C is provided with a coolant temperature sensor 29 that detects the temperature of the coolant flowing through the coolant passage section 41.

As shown in FIGS. 2 to 5, the cooling unit 40 of the engine unit 11 includes a coolant pump device 42, a switching valve 43, a radiator 44, and a fan (not shown). Furthermore, the cooling unit 40 includes a part of the cooling liquid passage section 41 .

The coolant pump device 42 is an electric coolant pump device. The coolant pump device 42 can be fixed to any part of the engine body 20. In the example of FIG. 3, the coolant pump device 42 is fixed to the outer surface of the crankcase 20A. The coolant pump device 42 includes an electric motor and a pump that rotates by the driving force of the electric motor. The electric motor rotates when power from the battery is supplied. The coolant pump device 42 is switched between a stopped state and an operating state independently of the movement of the crankshaft 21 and the camshaft that rotates in conjunction with the crankshaft 21. That is, when the crankshaft 21 is not rotating, the coolant pump device 42 can be in either a stopped state or an operating state. Further, while the crankshaft 21 is rotating, the coolant pump device 42 can be in either a stopped state or an operating state.

The switching valve 43 is a thermostatic valve. The switching valve 43 is fixed to the outer surface of at least one of the cylinder body 20B and the cylinder head 20C. The switching valve 43 is separate from the cylinder body 20B and cylinder head 20C. As shown in FIGS. 4 and 5, the case 43a of the switching valve 43 is formed with a first inlet 43b1, a second inlet 43b2, a first outlet 43c1, and a second outlet 43c2. That is, the switching valve 43 is a four-way valve. A movable valve body 43d that is movable between a low temperature position and a high temperature position is provided inside the case 43a. The movable valve body 43d moves from a low temperature position to a high temperature position or from a high temperature position to a low temperature position depending on the temperature of the coolant flowing through the switching valve 43.

When the temperature of the coolant is in the first low temperature range and in the second low temperature range lower than the first low temperature range, the movable valve body 43d is located at the low temperature position shown in FIG. 4. That is, when the temperature of the coolant in the case 43a is in either the first low temperature range or the second low temperature range, the movable valve body 43d is located at the low temperature position shown in FIG. 4. The state of the switching valve 43 at this time is the first state. When the temperature of the coolant is in a high temperature region higher than the first low temperature region, the movable valve body 43d is located at the high temperature position shown in FIG. 5. That is, when the temperature of the coolant in the case 43a is in the high temperature range, the movable valve body 43d is located at the high temperature position shown in FIG. The state of the switching valve 43 at this time is the second state. The switching valve 43 may be any type of thermostatic valve. For example, the switching valve 43 may be a mechanical thermostatic valve using bimetal. The switching valve 43 may be an expansion type thermostatic valve using wax. As shown in FIG. 2, the radiator 44 is located forward of the upper part of the engine body 20. As shown in FIG. A fan (not shown) is provided between the engine body 20 and the radiator 44.

The first inlet 43b1 of the switching valve 43 is connected to the second opening 20C2, which is the downstream end of the cylinder head coolant passage 41b. The second inlet 43b2 of the switching valve 43 is connected to the fourth opening 20B2, which is the downstream end of the cylinder body coolant passage 41f.

The cooling unit 40 has a first passage section 41a, a second passage section 41c, a radiator feed passage section 41d, and a radiator return passage section 41e. The first passage section 41a, the second passage section 41c, the radiator feed passage section 41d, and the radiator return passage section 41e are included in the coolant passage section 41. An upstream end of the first passage portion 41 a in the flow direction of the coolant is connected to a coolant pump device 42 . The downstream end of the first passage section 41a is connected to the first opening 20C1, which is the upstream end of the cylinder head coolant passage section 41b. The upstream end of the second passage portion 41c in the flow direction of the coolant is connected to the second outlet 43c2 of the switching valve 43. A downstream end of the second passage section 41c is connected to the coolant pump device 42. The upstream end of the radiator feed passage portion 41d in the flow direction of the coolant is connected to the first outlet 43c1 of the switching valve 43. A downstream end of the radiator feed passage section 41d is connected to the radiator 44. The upstream end of the radiator return passage portion 41e in the flow direction of the coolant is connected to the radiator 44. The downstream end of the radiator return passage 41e is connected to the third opening 20B1, which is the upstream end of the cylinder body coolant passage 41f.

ECU 80 (see FIG. 2) controls the operation of engine unit 11. ECU 80 controls spark plug 27, fuel injection device 28, coolant pump device 42, and the like. ECU 80 includes a processor (arithmetic processing unit) and memory. ECU 80 may be composed of a plurality of devices located at separate locations. The ECU 80 is electrically connected to various sensors such as the coolant temperature sensor 29.

[3] Flow of Coolant in Cooling Unit When the engine unit 11 starts, the ECU 80 controls the coolant pump device 42 based on the detection result sent from the coolant temperature sensor 29. When the temperature of the coolant detected by the coolant temperature sensor 29 is in the second low temperature range, battery power is not supplied to the coolant pump device 42 under the control of the ECU 80. Therefore, when the temperature of the coolant detected by the coolant temperature sensor 29 is in the second low temperature range, the coolant pump device 42 is in a stopped state. At this time, the movable valve body 43d of the switching valve 43 is located at the low temperature position shown in FIG. At this time, the movable valve body 43d allows the coolant to flow from the first inlet 43b1 to the second outlet 43c2. When the engine unit 11 starts, the temperatures of the cylinder body 20B and cylinder head 20C rise. Then, the heat of the cylinder body 20B and cylinder head 20C is transferred to the coolant. Therefore, a small amount of coolant flows through the coolant pump device 42 → first passage portion 41a → cylinder head coolant passage portion 41b → first inlet 43b1 → second outlet 43c2 → second passage portion 41c → coolant pump device 42. Convection occurs within the coolant passage section 41 in this order. On the other hand, at this time, the movable valve body 43d almost prevents the coolant from flowing from the first inlet 43b1 to the first outlet 43c1, and also prevents the coolant from flowing from the second inlet 43b2 to the first outlet 43c1 and the second outlet 43c2. prevent it from flowing. However, at this time, at least one of the cooling liquid and air flows slightly from the first inlet 43b1 to the first outlet 43c1.
When the temperature of the coolant is in the second low temperature range as described above, the coolant inside the cylinder body 20B and the cylinder head 20C hardly flows. Therefore, when the engine unit 11 is started, the temperatures of the cylinder body 20B and the cylinder head 20C rise relatively quickly, and the viscosity of the lubricating oil flowing through the engine body 20 decreases relatively quickly. Therefore, the friction loss of the engine unit 11 is reduced when the engine unit 11 is started.

Further, when the temperature of the coolant is in the second low temperature range, the coolant convecting in the radiator return passage 41e flows into the cylinder body coolant passage 41f provided inside the cylinder body 20B. Then, due to the pressure of the coolant flowing into the cylinder body coolant passage 41f, at least one of the coolant and air existing in the cylinder body coolant passage 41f passes through the bypass passage 41g to cool the cylinder head. The liquid flows to the liquid passage section 41b. If the coolant passage section 41 does not include the bypass passage section 41g, there is a risk that a small amount of the coolant in the cylinder body coolant passage section 41f will boil due to the heat of the cylinder body 20B. However, since the coolant passage section 41 in the specific example includes the bypass passage section 41g, the coolant in the cylinder body coolant passage section 41f flows to the cylinder head coolant passage section 41b through the bypass passage section 41g. Therefore, there is little risk that the coolant in the cylinder body coolant passage section 41f will boil. Furthermore, if the coolant passage section 41 does not include the bypass passage section 41g and air exists within the coolant passage section 41, there is a risk that air may remain within the cylinder body coolant passage section 41f. Air has a lower thermal conductivity than coolant. Therefore, if air remains in the cylinder body coolant passage portion 41f, the cylinder body 20B becomes difficult to be cooled. However, since the coolant passage section 41 of the specific example includes the bypass passage section 41g, no air remains in the cylinder body coolant passage section 41f. Therefore, the cylinder body 20B can be cooled by the coolant in the cylinder body coolant passage section 41f. Note that even when the temperature of the coolant is in the first low temperature range and the high temperature range, at least one of the coolant and air in the cylinder body coolant passage 41f passes through the bypass passage 41g and flows into the cylinder head coolant passage. It flows to section 41b.

When the temperature of the coolant detected by the coolant temperature sensor 29 is in the first low temperature range, battery power is supplied to the coolant pump device 42 under the control of the ECU 80 . Therefore, the coolant pump device 42 operates to pump the coolant in the coolant passage section 41. Furthermore, the movable valve body 43d of the switching valve 43 is located at the low temperature position shown in FIG. Therefore, the coolant circulates within the coolant passage section 41 along the direction of the arrow in FIG. That is, the coolant flows in the order of coolant pump device 42 → first passage section 41a → cylinder head coolant passage section 41b → first inlet 43b1 → second outlet 43c2 → second passage section 41c → coolant pump device 42. The coolant circulates within the coolant passage section 41. As described above, at this time, the movable valve body 43d almost prevents the coolant from flowing from the first inlet 43b1 to the first outlet 43c1. Therefore, the coolant in the switching valve 43 hardly flows to the radiator feed passage 41d, the radiator 44, the radiator return passage 41e, and the cylinder body coolant passage 41f. When the temperature of the coolant is in the first low temperature range as described above, almost no coolant flows into the cylinder body 20B. Therefore, when the engine unit 11 is started, the temperature of the cylinder body 20B rises relatively quickly, and the viscosity of the lubricating oil in the engine body 20 decreases relatively quickly. Therefore, the friction loss of the engine unit 11 is reduced when the engine unit 11 is started.

When the temperature of the coolant detected by the coolant temperature sensor 29 is in the high temperature range, battery power is supplied to the coolant pump device 42 under the control of the ECU 80. Therefore, the coolant pump device 42 operates to pump the coolant in the coolant passage section 41. Furthermore, the movable valve body 43d of the switching valve 43 is located at the high temperature position shown in FIG. Therefore, the coolant circulates within the coolant passage section 41 along the direction of the arrow in FIG. That is, the coolant flows through the coolant pump device 42→first passage section 41a→cylinder head coolant passage section 41b→first inlet 43b1→first outlet 43c1→radiator feed passage section 41d→radiator 44→radiator return passage section 41e. The coolant circulates within the coolant passage 41 in the following order: → cylinder body coolant passage 41f → second inlet 43b2 → second outlet 43c2 → second passage 41c → coolant pump device 42.
When the temperature of the coolant is in the high temperature range as described above, the coolant cooled by the radiator 44 is supplied to the cylinder body 20B without going through the coolant pump device 42 and the cylinder head 20C. Therefore, the temperature of the cylinder body 20B can be lowered by the cooling fluid. Therefore, knocking is less likely to occur in the engine unit 11. Knocking is a phenomenon in which abnormal combustion occurs within a combustion chamber, resulting in the generation of a metallic striking sound or striking vibration.

Specific examples of the embodiments of the present invention have been described above. A specific example of the embodiment of the present invention provides the following effects in addition to the effects of the embodiment of the present invention described above.

The engine unit 11 of the specific example uses one switching valve 43 to circulate the coolant within the coolant passage 41 so as to sufficiently lower the temperature of the cylinder body 20B. That is, by using the single switching valve 43, the temperature of the intake air, which is the air taken into the combustion chamber 24, is prevented from increasing significantly due to heat exchange between the intake air and the cylinder bore. Therefore, knocking is less likely to occur in the engine unit 11 without increasing the size and complexity of the coolant pump device 42 and/or the radiator 44, which are devices for cooling the coolant.

The coolant pump device 42 is an electric coolant pump device configured to be able to switch between a stopped state and an operating state independently of the movement of the crankshaft 21. Therefore, when the temperature of the coolant is in the second low temperature range and the engine unit 11 is in the operating state, it is possible to bring the coolant pump device 42 into the stopped state. Therefore, when the engine unit 11 is started, the temperature of the cylinder body 20B and the cylinder head 20C rises relatively quickly, and the viscosity of the lubricating oil in the engine body 20 decreases relatively quickly. Therefore, the friction loss of the engine unit 11 is reduced when the engine unit 11 is started.

The engine unit 11 of the specific example is a long stroke engine unit. If the displacement of a long-stroke engine unit and a short-stroke engine unit are the same, the length of the cylinder bore in the direction parallel to the cylinder axis, which is the central axis of the cylinder bore, is relatively longer for the long-stroke engine unit than for the short-stroke engine unit. long. Therefore, since the contact area between the inner surface of the cylinder bore and the intake air is wide, the amount of increase in temperature of the intake air in the long stroke engine unit is relatively larger than in the case of the short stroke engine unit. Further, when the engine rotation speeds of the long stroke engine unit and the short stroke engine unit are the same, the average piston speed of the long stroke engine unit is higher than that of the short stroke engine unit. Therefore, the intake speed of intake air is higher in the long stroke engine unit than in the short stroke engine unit. Therefore, the heat transfer coefficient, which increases in proportion to the magnitude of fluid turbulence, is greater in long-stroke engine units than in short-stroke engine units. Therefore, the amount of increase in temperature of the intake air is larger in the long stroke engine unit than in the short stroke engine unit. The engine unit 11 of the specific example can be used without increasing the size and complexity of the coolant pump device 42 and/or the radiator 44, which are devices for cooling the coolant, when the temperature of the coolant is in a high temperature range. , it is possible to sufficiently lower the temperature of the cylinder body 20B. Therefore, when the temperature of the coolant is in a high temperature range, it is possible to sufficiently lower the temperature of the cylinder body 20B of the engine unit 11, which is a long stroke engine unit, by the coolant. As a result, it is possible to suppress heat exchange between the intake air and the cylinder bore 20Ba during the intake stroke, and reduce the amount of temperature rise of the intake air. Therefore, knocking is less likely to occur in the engine unit 11, which is a long stroke engine unit.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and specific examples thereof, and various changes can be made within the scope of the claims. Modifications of the embodiment of the present invention will be described below.

The engine unit of the present invention may include a coolant pump device other than an electric coolant pump device. This coolant pump device may be a mechanical coolant pump device operated by the rotational force of a crankshaft. A mechanical coolant pump device may be connected to the camshaft. A mechanical pump device connected to the camshaft is operated by the rotational force of the camshaft when the camshaft rotates in conjunction with the rotation of the crankshaft. A mechanical coolant pump device may be connected to the crankshaft. The mechanical coolant pump device may be connected to a rotatable shaft that is different from the crankshaft and camshaft.

The coolant pump device of the present invention may be a magnet-driven pump device. In a magnet-driven pump device, a permanent magnet is provided in the pump. This permanent magnet exerts a magnetic force on a rotatable shaft made of magnetic material. For example, assume that a permanent magnet is fixed to the impeller of a pump and the shaft is a camshaft. In this case, when the camshaft rotates, the impeller rotates together with the camshaft due to the magnetic force generated by the permanent magnet.

The coolant pump device of the present invention may be provided at a location other than the crankcase of the engine body. For example, the coolant pump device of the present invention may be provided in a cylinder body.

The diameter of the cylinder bore of the engine unit, which is a single cylinder engine unit of the present invention, may be larger than the stroke of the piston. That is, the single cylinder engine unit of the present invention may be a short stroke engine unit.

The engine unit of the present invention may have a plurality of intake ports for one combustion chamber. The engine unit of the present invention may have a plurality of exhaust ports for one combustion chamber.

The engine unit of the present invention may be a multi-cylinder engine unit having a plurality of cylinder bores. In this case, the diameters of all cylinder bores may be the first diameter, and the strokes of all the pistons reciprocating within each cylinder bore may be the first stroke longer than the first diameter. Further, in this case, the diameter of some of the cylinder bores may be the first diameter, and the stroke of the piston that reciprocates within each cylinder bore having the first diameter may be the first stroke longer than the first diameter. Further, in this case, the diameters of all cylinder bores may be larger than the stroke of the piston that reciprocates within each cylinder bore.

When the engine unit of the present invention is a multi-cylinder engine unit, or when the engine unit of the present invention has a plurality of intake ports for one combustion chamber, the engine unit includes a plurality of cylinders each connected to the plurality of intake ports. a first intake passage section, a plurality of branch intake passage sections respectively connected to the upstream ends of the plurality of first intake passage sections, and one collective intake passage section connected to the upstream ends of the plurality of branch intake passage sections. It may have. The second intake passage section has a plurality of branch intake passage sections and a surge tank. The throttle valve may be arranged inside each branch intake passage. The throttle valve may be arranged in the collective intake passage. In this case, the throttle valve is arranged in the surge tank of the collective intake passage. The throttle valve does not have to be located in the surge tank.

When the engine unit of the present invention is a multi-cylinder engine unit, or when the engine unit of the present invention has a plurality of intake ports for one combustion chamber, the first intake passage portion is connected to each of the plurality of intake ports. The air intake passage may have a plurality of branched intake passages, and one collective intake passage connected to the upstream ends of the plurality of branched intake passages.

When the engine unit of the present invention is a multi-cylinder engine unit, or when the engine unit of the present invention has a plurality of exhaust ports for one combustion chamber, the engine unit includes a plurality of exhaust ports each connected to the plurality of exhaust ports. and a plurality of second exhaust passages respectively connected to the downstream ends of the plurality of first exhaust passages.

When the engine unit of the present invention is a multi-cylinder engine unit, or when the engine unit of the present invention has a plurality of exhaust ports for one combustion chamber, the first exhaust passage portion is connected to each of the plurality of exhaust ports. It may have a plurality of independent exhaust passage sections, and one collective exhaust passage section connected to the downstream ends of the plurality of independent exhaust passage sections.

The engine unit of the present invention may be a direct injection engine unit. A direct injection engine unit is a type of engine unit in which fuel is injected into the combustion chamber. The engine unit of the present invention may be a two-stroke engine unit. The engine unit of the present invention may be a diesel engine unit. Diesel engine units do not have spark plugs. The engine unit of the present invention may be a supercharged engine equipped with a supercharger. A supercharger is a device that compresses air supplied to a combustion chamber. The supercharger may be a mechanical supercharger or an exhaust turbine supercharger (so-called turbocharger).

The engine unit of the present invention may include a switching valve disposed inside the cylinder head or cylinder body and provided in the coolant passage.

The switching valve of the present invention does not have to be a thermostatic valve. For example, the switching valve may be an electromagnetic valve or an electric valve having a movable valve body that can move between a low temperature position and a high temperature position depending on the temperature of the coolant detected by a coolant temperature sensor.

The switching valve of the present invention does not have to be a four-way valve. For example, the switching valve of the present invention may be a three-way valve, and a plurality of three-way valves may be provided in the coolant passage. Also in this case, when the temperature of the coolant is in the first low temperature range, the coolant flows into the coolant passage in the order of the coolant pump device, the cylinder head, and the coolant pump device, without passing through the radiator and the cylinder body. be circulated. Further, when the temperature of the coolant is in a high temperature range, the coolant is circulated through the coolant passage in the order of the coolant pump device, the cylinder head, the radiator, the cylinder body, and the coolant pump device.

The engine unit of the present invention does not need to include a bypass passage section.

When the engine unit of the present invention is mounted on a vehicle, the rotation center axis of the crankshaft of the engine unit is not limited to being parallel to the left-right direction of the vehicle. For example, the rotation center axis of the crankshaft may be parallel to the longitudinal direction of the vehicle.
When the engine unit of the present invention is mounted on a vehicle, the direction of the cylinder axis, which is the central axis of the cylinder bore of the engine body, is not limited to the direction shown in the specific example. When the engine unit is viewed in the left-right direction of the vehicle, the cylinder axis may be parallel to the vertical direction of the vehicle. When the engine unit is viewed in the left-right direction of the vehicle, the inclination angle of the cylinder axis with respect to the vertical direction may be greater than 45 degrees and less than 90 degrees.

Vehicles equipped with the engine unit of the present invention are not limited to motorcycles. The present invention may be mounted on a saddle type vehicle other than a motorcycle. A straddle-type vehicle refers to any vehicle in which a passenger rides while straddling a saddle. Straddle-type vehicles equipped with the engine unit of the present invention include, for example, motorcycles, tricycles, four-wheeled buggies (ATVs: All Terrain Vehicles), personal watercraft, snowmobiles, and the like. Examples of motorcycles include scooter types, off-road types, and moped types. The engine unit of the present invention may be mounted on a vehicle other than a straddle-type vehicle. For example, the engine unit of the present invention may be mounted on a four-wheeled vehicle (automobile) or a ship that is not a straddle-type vehicle. A vehicle to which the present invention is applied may be a hybrid vehicle having an engine unit and an electric motor as a drive source. Moreover, the engine unit of the present invention may be mounted on a device other than a vehicle.

11 Engine unit 20 Engine body 20A Crank case 20Ba Cylinder bore 20Ba
20C Cylinder head 20Ca Cylinder head intake passage section (first intake passage section)
20Cb Cylinder head exhaust passage section (first exhaust passage section)
20X Cylinder axis 22 Piston 41 Coolant passage section 41g Bypass passage section 42 Coolant pump device (electric coolant pump device)
43 Switching valve 43b1 First inlet 43b2 Second inlet 43c1 First outlet 43c2 Second outlet 43d Movable valve body 44 Radiator 51 External intake passage section (second intake passage section)
61 External exhaust passage section (second exhaust passage section)
St First stroke Db First diameter

Claims (10)

a cylinder body formed with at least one cylinder bore;
a cylinder head connected to the cylinder body;
a coolant passage portion through which at least a portion passes through the cylinder head and the cylinder body and in which coolant circulates;
a coolant pump device that is provided in the coolant passage and that pumps the coolant and circulates the coolant within the coolant passage;
a radiator provided in the coolant passage section;
A switching valve provided in the coolant passage section, when the temperature of the coolant is in a first low temperature range, the coolant pump device and the cylinder head do not pass through the radiator and the cylinder body. , when the coolant pump device enters a first state in which the coolant is allowed to flow through the coolant passage, and the temperature of the coolant is in a high temperature region higher than the first low temperature region; is configured to be in a second state in which the coolant is allowed to flow within the coolant passage in the order of the coolant pump device, the cylinder head, the radiator, the cylinder body, and the coolant pump device. a switching valve,
Equipped with
The switching valve is
A first inlet into which the coolant flowing out from the cylinder head flows, a first outlet allowing the coolant to flow out toward the radiator, and a second inlet into which the coolant flowing out from the cylinder body flows. and a second outlet for allowing the coolant to flow out toward the coolant pumping device;
The four-way valve is
The cooling liquid flowing into the first inlet flows out from the second outlet, and the cooling liquid flowing into the second inlet does not flow out from the first outlet and the second outlet. 1 state and
the second state in which the coolant that has flowed into the first inlet flows out from the first outlet, and the coolant that has flowed into the second inlet flows out from the second outlet;
configured so that it can be switched to
When the temperature of the coolant is in the first low temperature range, the four-way valve is in the first state, so that the coolant pump device and the cylinder head do not pass through the radiator and the cylinder body. , the coolant circulates within the coolant passage in the order of the four-way valve and the coolant pump device,
When the temperature of the coolant is in the high temperature range, the four-way valve is in the second state, so that the coolant pump device, the cylinder head, the four-way valve, the radiator, the cylinder body, An engine unit characterized in that the coolant circulates within the coolant passage section in the order of the four-way valve and the coolant pump device . The engine unit according to claim 1 , wherein the four-way valve is located outside the cylinder head and the cylinder body, and is separate from the cylinder head and the cylinder body. When the four-way valve is in the first state, at least one of the coolant and air flows into the coolant passage formed in the cylinder body through the radiator,
3. The engine unit according to claim 1 , further comprising a bypass passage connected to the coolant passage in the cylinder body and connected to the coolant passage in the cylinder head. the engine unit has a crankshaft,
4. The coolant pump device according to claim 1 , wherein the coolant pump device is configured to be switched between a stopped state and an activated state independently of movement of the crankshaft. engine unit. The engine unit according to claim 4 , wherein the coolant pump device is configured to enter the stopped state when the temperature of the coolant is in a second low temperature region lower than the first low temperature region. . The engine unit has at least one piston that reciprocates within the at least one cylinder bore along a cylinder axis that is a central axis of the cylinder bore,
the diameter of the at least one cylinder bore is a first diameter;
The engine unit according to any one of claims 1 to 5 , wherein the stroke of the piston that reciprocates within the cylinder bore having the first diameter is a first stroke longer than the first diameter. . The engine unit is
a combustion chamber in which an intake port is formed;
a first intake passage portion formed in the cylinder head and connected to the intake port;
a second intake passage portion disposed outside the cylinder head, the second intake passage portion being connected to an upstream end of the first intake passage portion in the air flow direction and having a throttle valve disposed therein;
a fuel injection device that injects fuel into the first intake passage or the second intake passage;
The engine unit according to any one of claims 1 to 6 , characterized in that it has: The engine unit is
The engine unit according to claim 7 , further comprising a spark plug that ignites a mixture of air and fuel in the combustion chamber. a cylinder axis that is a central axis of the cylinder bore is inclined with respect to a vertical direction of a vehicle in which the engine unit is mounted;
The engine unit is
a combustion chamber in which an exhaust port is formed;
a first exhaust passage portion formed in the cylinder head and connected to the exhaust port;
a second exhaust passage section disposed outside the cylinder head and connected to a downstream end of the first exhaust passage section in the gas flow direction;
has
The downstream end of the first exhaust passage portion is formed on a downwardly facing outer surface of the cylinder head, when the vertical direction of the vehicle in which the engine unit is mounted is the vertical direction. The engine unit according to any one of items 1 to 8 . The engine unit according to claim 1 , wherein only one cylinder bore is formed in the cylinder body.

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