JP7481166B2 - Single cylinder engine unit - Google Patents

Description

The present invention relates to a single-cylinder engine unit.

The single-cylinder engine unit disclosed in Patent Document 1 has a coolant path and a mechanical pump device that pumps the coolant flowing through the coolant path. The mechanical pump device is connected to a camshaft. The pump mechanism of the mechanical pump device operates by receiving the rotational force of the camshaft. The camshaft is supported by a cylinder head, which is a component of the engine body. The mechanical pump device is fixed to the outer surface of the cylinder head. More specifically, the mechanical pump device is fixed to a surface located at the end of the cylinder head in the direction of the central axis of rotation of the camshaft.

The single-cylinder engine unit disclosed in Patent Document 2 has an electric pump device that pumps the coolant flowing through the coolant path. The electric pump device has an electric motor and a pump mechanism that is operated by the electric motor.

JP 2019-138227 A JP 60-142010 A

If the mechanical pump device of the single-cylinder engine unit of Patent Document 1 is replaced with the electric pump device of Patent Document 2, the electric pump device is fixed to the end face of the rotational center axis of the camshaft of the cylinder head, and in this case, there is no need to significantly change the design of the coolant path.
However, since the electric pump device has an electric motor, the size of the electric pump device in the direction of the rotational axis of the pump mechanism is larger than that of a mechanical pump device. Therefore, if the electric pump device is fixed to an end face of the cylinder head in the direction of the rotational axis of the camshaft, the electric pump device protrudes significantly in the direction of the rotational axis of the camshaft from the end face of the cylinder head in the direction of the rotational axis of the camshaft. In other words, the single-cylinder engine unit becomes larger in size in the direction of the rotational axis of the camshaft.

The present invention aims to provide a single-cylinder engine unit that is equipped with an electric pump device, yet can suppress an increase in size in the direction of the central axis of rotation of the camshaft of the single-cylinder engine unit, and can be used without making major design changes to the coolant path when a mechanical pump device is supported on the cylinder head.

In order to realize the object of the present invention, the inventors of the present invention studied single-cylinder engine units and electric pumps and came up with the idea of configuring a single-cylinder engine unit so that the electric pump device is supported by the head cover.

Since the electric pump device has an electric motor, it is not necessary to connect the electric pump device to the camshaft. Therefore, the electric pump device is not restricted by the placement position and the direction of the rotational axis of the pump mechanism. However, it is necessary to secure space for placing the electric pump device. Generally, a device (e.g., a vehicle) in which a single-cylinder engine unit is mounted is smaller than a device in which a multi-cylinder engine unit is mounted. Therefore, in a device in which a single-cylinder engine unit is mounted, there is less free space around the engine body. However, generally, it is easier to secure a space large enough to place the electric pump device around the head cover of a single-cylinder engine than around the cylinder head. Therefore, the electric pump device can be supported by the head cover. Moreover, when the electric pump device is supported by the head cover, the degree of freedom of layout of the electric pump device is higher than when the electric pump device is supported by the cylinder head. Therefore, the layout of the electric pump device supported by the head cover can be designed to suppress the enlargement of the direction of the rotational axis of the camshaft of the single-cylinder engine unit.

The distance from the cylinder head to the head cover is short. Therefore, the coolant path of a single-cylinder engine unit in which an electric pump device is supported on the head cover can be made to have a structure that is almost identical to the coolant path of a single-cylinder engine unit in which a mechanical pump device is supported on the cylinder head. Therefore, the coolant path in which a mechanical pump device is supported on the cylinder head can be used without major design changes.

(1) The single-cylinder engine unit of the present invention comprises a cylinder body that is a part of an engine body and has only one cylinder bore, a cylinder head that is a part of the engine body and is connected to an end of the cylinder body in the direction of the cylinder axis, which is the central axis of the cylinder bore, a head cover that is connected to the end of the cylinder head in the direction of the cylinder axis and is at the end of the engine body in the direction of the cylinder axis, a coolant path that is partially formed inside the engine body and through which a coolant circulates, a camshaft that is supported by the cylinder head and rotates around a cam axis that is perpendicular to a straight line parallel to the cylinder axis, and an electric pump device that has an electric motor and pumps the coolant flowing through the coolant path. At least a part of the electric pump device is located outside the engine body. The electric pump device is supported by the head cover so that the motor axis, which is the central axis of rotation of the output shaft of the electric motor, is not coaxial with the cam axis.

In general, it is easier to secure a space large enough to accommodate the electric pump device around the head cover of a single-cylinder engine unit than around the cylinder head. Therefore, by supporting the electric pump device on the head cover, the layout of the electric pump device is more flexible than when the electric pump device is supported on the cylinder head. Therefore, the layout of the electric pump device supported on the head cover can be designed to suppress an increase in size of the single-cylinder engine unit in the direction of the cam axis.
In addition, the distance from the cylinder head to the head cover is short, so the coolant path of the single-cylinder engine unit in which the electric pump device is supported on the head cover can have substantially the same structure as the coolant path of the single-cylinder engine unit in which the mechanical pump device is supported on the cylinder head. Therefore, the single-cylinder engine unit of the present invention can utilize the coolant path in which the mechanical pump device is supported on the cylinder head without making major design changes.
As described above, it is possible to prevent the size of the camshaft of a single-cylinder engine unit equipped with an electric pump device from increasing in size in the direction of the central axis of rotation, and it is possible to utilize the coolant path when a mechanical pump device is supported on the cylinder head without making major design changes.

(2) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration.
The electric pump device has a first portion aligned with the head cover in a first direction parallel to either the cam axis or the cylinder axis, and a second portion different from the first portion, aligned with the head cover in a second direction perpendicular to the first direction.

With this configuration, the single-cylinder engine unit can be prevented from becoming large in size in the direction of the cam axis, compared to a case in which the entire electric pump device is aligned with the cylinder head in a direction parallel to the cam axis.
Also, compared to a case in which the entire electric pump device is aligned with the cylinder head in a direction parallel to the cylinder axis, an increase in size of the single-cylinder engine unit in the direction of the cylinder axis can be suppressed.
Furthermore, compared to a case in which the entire electric pump device is aligned with the cylinder head in a direction parallel to a straight line perpendicular to both the cam axis and the cylinder axis, the size of the single-cylinder engine unit can be prevented from increasing in size in the direction perpendicular to both the cam axis and the cylinder axis.
In this way, it is possible to more reliably prevent an increase in size of a single-cylinder engine unit equipped with an electric pump device in the direction of the cam axis.

(3) According to one aspect of the present invention, in addition to the configuration of (2) above, the single-cylinder engine unit of the present invention preferably has the following configuration.
The first direction is parallel to the cylinder axis.

With this configuration, the electric pump device is positioned so that it has a portion aligned with the head cover in a direction parallel to the cylinder axis. This arrangement of the electric pump device is possible because the head cover is at the end of the engine body in the cylinder axis direction. Therefore, compared to when the electric pump device is supported by the cylinder head, it is possible to more reliably prevent the single-cylinder engine unit equipped with the electric pump device from becoming larger in the direction of the cam axis.

(4) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration in addition to the configuration of (2) or (3) above.
The electric pump device has a small diameter portion and a large diameter portion aligned with the small diameter portion in the direction of the motor axis and having a maximum radial dimension about the motor axis that is greater than a maximum radial dimension of the small diameter portion about the motor axis. A part of the large diameter portion is aligned with the head cover in a direction parallel to the motor axis and is the first portion or the second portion. At least a part of the small diameter portion is aligned with the head cover in a direction perpendicular to the motor axis and is the second portion when the part of the large diameter portion is the first portion, and is the first portion when the part of the large diameter portion is the second portion.

According to this configuration, the electric pump device has a large diameter portion and a small diameter portion that have different radial lengths centered on the motor axis. A part of the large diameter portion is aligned with the head cover in the direction of the motor axis. Generally, the length of an electric pump device in the direction of the motor axis is longer than the length in the direction perpendicular to the motor axis. Therefore, by aligning a part of the large diameter portion with the head cover in the direction of the motor axis, unnecessary space is less likely to be generated between the electric pump device and the head cover compared to a case in which the large diameter portion is not aligned with the head cover in the direction of the motor axis. Therefore, it is easier to prevent the single-cylinder engine unit equipped with an electric pump device supported by the head cover from becoming larger.

(5) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration in addition to the configuration of ( 4 ) above.
When viewed in a direction perpendicular to the motor axis, the large diameter portion does not overlap the head cover.

This configuration makes it difficult for unnecessary space to be generated between the electric pump device and the head cover. Therefore, it is easier to prevent the size of the single-cylinder engine unit equipped with the electric pump device supported by the head cover from increasing.

(6) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration in addition to the configuration of (4) or (5) above.
The electric pump device has a first cylindrical portion that houses the electric motor, a second cylindrical portion that houses at least a part of a pump mechanism that pressurizes and discharges a supplied cooling liquid, a first flange connected to an end of the first cylindrical portion, and a second flange connected to an end of the second cylindrical portion and fixed to the first flange in a state of contact with the first flange. The first flange or the second flange is the large diameter portion. At least a part of the first cylindrical portion or at least a part of the second cylindrical portion is the small diameter portion.

(7) According to one aspect of the present invention, in addition to the configuration of (6) above, the single-cylinder engine unit of the present invention preferably has the following configuration.
The cooling liquid path includes an external cooling liquid path located outside the engine body and connected to the second cylindrical portion, and when viewed in a direction perpendicular to the motor axis, a part of the first flange and a part of the second flange are located between the head cover and a part of the external cooling liquid path.

With this configuration, the first flange and the second flange are positioned using the gap between the head cover and the external coolant path. This makes it easier to prevent the single-cylinder engine unit equipped with the electric pump device supported by the head cover from becoming too large.

(8) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration.
The motor axis is parallel to the cam axis, parallel to the cylinder axis, or parallel to a straight line perpendicular to both the cam axis and the cylinder axis.

With this configuration, it is easier to efficiently place the electric pump device in the available space of the device (e.g., a vehicle) in which the single-cylinder engine unit is mounted, compared to when the motor axis is at an angle to the cam axis.

(9) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration.
The motor axis is parallel to a line perpendicular to the cylinder axis. The electric pump device has a third portion aligned with the head cover in a direction parallel to the cylinder axis and aligned with the head cover in a direction parallel to the line perpendicular to the cylinder axis.

According to this configuration, for example, the third portion of the electric pump device may be disposed to face an inclined surface formed on the head cover that is inclined with respect to a direction parallel to the cylinder axis. Also, for example, the third portion of the electric pump device may be integrally formed with the head cover so as to be aligned with the head cover in a direction parallel to the cylinder axis and aligned with the head cover in a direction parallel to a straight line perpendicular to the cylinder axis.
With the above configuration, the single-cylinder engine unit equipped with an electric pump device supported by a head cover can be prevented from becoming larger in the direction of the cylinder axis, compared to a case in which an electric pump device having a motor axis parallel to a line perpendicular to the cylinder axis does not have a portion aligned with the head cover in a direction parallel to the line perpendicular to the cylinder axis.
Furthermore, with the above configuration, an electric pump device having a motor axis parallel to a line perpendicular to the cylinder axis has a portion aligned with the head cover in a direction parallel to the line perpendicular to the cylinder axis, and compared to a case in which the portion is not aligned with the head cover in a direction parallel to the cylinder axis, the increase in size of a single-cylinder engine unit equipped with an electric pump device supported by the head cover in the direction perpendicular to the cylinder axis can be suppressed.

(10) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration.
The electric pump device includes a motor case that houses the electric motor, and a pump case that houses at least a part of a pump mechanism that pressurizes and discharges a supplied cooling liquid. The pump case is supported by the head cover via the motor case.

Generally, an electric motor has a greater weight per unit volume than a pump mechanism. Therefore, with the above configuration, the electric pump device can be stably supported on the head cover with a simpler support structure than when the motor case that houses the electric motor is connected to the head cover via the pump case.

(11) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration.
When viewed in the direction of the cam axis, the electric pump device is spaced apart from the cylinder axis.

(12) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration in addition to the configuration of (11) above.
The engine body has a combustion chamber in which an exhaust port and an intake port are formed. The exhaust port and the electric pump device are located in one of two spaces defined by a plane that is parallel to the cam axis and includes the cylinder axis.

(13) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration.
The electric pump device intersects a plane that is perpendicular to the cam axis and includes the cylinder axis.

(14) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration.
The single-cylinder engine unit includes a temperature sensor that detects the temperature of the coolant flowing through the coolant path, and a control device that controls the electric pump device. The coolant path has an inlet formed on an outer surface of the engine body, through which the coolant passes when moving from the outside of the engine body to the inside of the engine body, and an outlet formed on the outer surface of the engine body, through which the coolant passes when moving from the inside of the engine body to the outside of the engine body, and is located above the inlet in the vertical direction of a vehicle on which the single-cylinder engine unit is mounted. In the coolant path, the distance between the temperature sensor and the outlet is shorter than the distance between the temperature sensor and the inlet. The control device stops the electric pump device when the temperature of the coolant detected by the temperature sensor is in a first low temperature region.

(15) According to one aspect of the present invention, in addition to the configuration of (14) above, the single-cylinder engine unit of the present invention preferably has the following configuration.
The single-cylinder engine unit includes a switching valve that forms part of the coolant path, is located outside the engine body, and is located downstream of the outlet in a coolant flow direction, and a radiator that is located outside the engine body, forms part of the coolant path, and is located in a position in the coolant path not between the switching valve and the inlet. The electric pump device is located downstream of the switching valve and upstream of the inlet in the coolant flow direction. The switching valve has an internal space that is part of the coolant path, a movable valve body that is located in the internal space and moves according to a temperature of the coolant in the internal space, a first inlet through which the coolant that has not passed through the radiator after flowing out from the outlet enters the internal space, a first outlet through which the coolant flowing from the internal space toward the radiator exits the internal space, a second inlet through which the coolant that has flowed out from the first outlet and passed through the radiator enters the internal space, and a second outlet through which the coolant flowing from the internal space toward the electric pump device exits the internal space. When the temperature of the cooling liquid in the internal space is in a second low temperature region higher than the first low temperature region, the movable valve element is located at a low temperature position where the cooling liquid that has flowed into the internal space from the first inlet flows to the second outlet, the cooling liquid that has flowed into the internal space from the first inlet flows to the first outlet, and the cooling liquid that has flowed into the internal space from the second inlet flows to the internal space.When the temperature of the cooling liquid in the internal space is in an intermediate temperature region higher than the second low temperature region, the movable valve element is located at an intermediate temperature position where the cooling liquid that has flowed into the internal space from the first inlet flows to the first outlet and the second outlet, the cooling liquid that has flowed into the internal space from the second inlet flows to the second outlet, and the cooling liquid that has flowed into the internal space from the second inlet flows to the first outlet. When the temperature of the cooling liquid in the internal space is in a high temperature region higher than the medium temperature region, the movable valve body is located at a high temperature position where the cooling liquid that has flowed into the internal space from the first inlet flows to the first outlet, the cooling liquid that has flowed into the internal space from the first inlet flows to the second outlet, and the cooling liquid that has flowed into the internal space from the second inlet flows to the second outlet. The control device operates the electric pump device when the temperature of the cooling liquid detected by the temperature sensor is in the second low temperature region, the medium temperature region, or the high temperature region.

In the above configuration, the switching valve is preferably a thermostat valve. The switching valve does not have to be a thermostat valve. For example, the switching valve may be configured such that the movable valve body is moved by the driving force of the actuator. In this case, the control device controls the actuator based on a signal from a temperature sensor that detects the temperature of the coolant flowing through the coolant path.

(16) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration.
The single-cylinder engine unit includes an ignition plug that ignites a mixture of air and fuel in a combustion chamber formed inside the engine body. The electric pump device includes a motor case that houses the electric motor and a pump case that houses at least a part of a pump mechanism that pressurizes and discharges a supplied cooling liquid. The shortest distance from the ignition plug to the motor case is shorter than the shortest distance from the ignition plug to the pump case.

With this configuration, the motor case of the electric pump device is close to the spark plug, and therefore the electric motor housed in the motor case is also close to the spark plug. Therefore, when bundling the wiring for supplying power from the battery to the spark plug and the wiring for supplying power from the battery to the electric motor, the length of the bundled wiring can be made longer. This makes it possible to reduce the space required to arrange the two wirings. This further prevents the single-cylinder engine unit equipped with the electric pump device supported by the head cover from becoming larger.

(17) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration.
The single-cylinder engine unit includes an intake valve that opens and closes an intake port of a combustion chamber formed in the engine body, an exhaust valve that opens and closes an exhaust port of the combustion chamber, and a variable valve timing mechanism that includes an electromagnetic or electric actuator, is connected to the camshaft, and changes at least one of the timing of opening and closing the intake port by the intake valve and the timing of opening and closing the exhaust port by the exhaust valve. The electric pump device includes a motor case that houses the electric motor, and a pump case that houses at least a part of a pump mechanism that pressurizes and discharges a supplied coolant. The shortest distance from the actuator to the motor case is shorter than the shortest distance from the actuator to the pump case.

With this configuration, the motor case of the electric pump device is close to the actuator of the variable valve timing mechanism, and the electric motor housed in the motor case is also close to the actuator of the variable valve timing mechanism. Therefore, when bundling the wiring for supplying power from the battery to the actuator of the variable valve timing mechanism and the wiring for supplying power from the battery to the electric motor, the length of the bundled wiring can be made longer. This makes it possible to reduce the space required to arrange the two wirings. This makes it possible to further prevent the single-cylinder engine unit equipped with the electric pump device supported by the head cover from becoming larger.

(18) According to one aspect of the present invention, the single-cylinder engine unit of the present invention preferably has the following configuration.
The single-cylinder engine unit includes a radiator that forms a part of the coolant path and is located outside the engine body. The electric pump device has a pump mechanism that pressurizes and discharges the supplied coolant. The entire radiator and the entire pump mechanism are located in one of two spaces that are partitioned by a plane that is perpendicular to the cam axis and includes the cylinder axis.

With this configuration, the pump mechanism of the electric pump device is close to the radiator. Therefore, if the pump mechanism and the coolant path from the radiator to the pump mechanism do not pass through the inside of the engine body, the coolant path from the pump mechanism to the radiator can be shortened. This makes it possible to further prevent the single-cylinder engine unit equipped with the electric pump device supported by the head cover from becoming larger.

(19) According to one aspect of the present invention, it is preferable that the single-cylinder engine unit of the present invention has the following configuration.
The single-cylinder engine unit has a radiator that forms a part of the coolant path and is located outside the engine body, and the radiator is located forward of the engine body in the front-rear direction of the vehicle on a plane perpendicular to the up-down direction of the vehicle on which the single-cylinder engine unit is mounted and that passes through the engine body and the radiator.

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

In this invention, a path means a space through which an object passes. This definition applies to coolant paths, internal intake paths, and internal exhaust paths.

In the present invention, "the electric pump device is supported by the head cover" means that the entire electric pump device is located outside the engine body and the electric pump device is fixed to the head cover. "The electric pump device is fixed to the head cover" means that the electric pump device is fixed to the head cover so that the electric pump device and the head cover are in contact with each other. "The electric pump device is fixed to the head cover" means that a member located between the electric pump device and the head cover is fixed to the electric pump device and the head cover. The fixation may be by a fastening member such as a bolt, or may be by welding.
In the present invention, "the electric pump device is supported by the head cover" means that at least a part of the electric pump device is located outside the engine body, and that a part of the electric pump device and at least a part of the head cover are integrally formed. The integral forming here is not limited to a manufacturing method using a mold. For example, it may be integral forming by casting, forging, or press molding.

In the present invention, the term "a cam axis perpendicular to a straight line parallel to a cylinder axis" includes both a cam axis perpendicular to the cylinder axis and a cam axis perpendicular to a straight line that is not perpendicular to the cylinder axis but is parallel to the cylinder axis. In other words, the cam axis does not have to intersect with the cylinder axis.

In the present invention, the "first portion aligned with the head cover in the first direction" may be separated from the head cover, may be in contact with the head cover, or may be integrally formed with the head cover. When the first portion is in contact with the head cover, the position at which the head cover and the electric pump device are fixed may or may not be the first portion. The same definition applies to the "second portion aligned with the head cover in the second direction" and the "third portion aligned with the head cover in a specified direction."

In the present invention, "the third portion is aligned with the head cover in a direction parallel to the cylinder axis, and is aligned with the head cover in a direction parallel to a straight line perpendicular to the cylinder axis" means that the portion aligned with the head cover in a direction parallel to the cylinder axis and the portion aligned with the head cover in a direction parallel to the straight line perpendicular to the cylinder axis are common.

In the present invention, the outline of the "small diameter portion" when viewed in the motor axial direction may or may not be circular. For example, it may be rectangular. The same applies to the "large diameter portion."

In the present invention, "the large diameter portion does not overlap with the head cover when viewed in a direction perpendicular to the motor axis" means that the large diameter portion does not overlap with the head cover when viewed in at least one of a plurality of directions perpendicular to the motor axis. This direction may be, for example, a direction perpendicular to both the motor axis and the cylinder axis. This direction may be, for example, a direction perpendicular to the motor axis and parallel to the cylinder axis. This direction may also be, for example, a direction perpendicular to both the motor axis and the cam axis. This direction may be, for example, a direction perpendicular to the motor axis and parallel to the cam axis.

When the electric pump device is fixed to the head cover, "the pump case is supported on the head cover via the motor case" means that the motor case is fixed to the head cover and the pump case is not fixed to the head cover.
When a part of the electric pump device and at least a part of the head cover are integrally molded, "the pump case is supported on the head cover via the motor case" means that at least a part of the motor case is integrally molded with at least a part of the head cover, and the pump case is not integrally molded with the head cover.

In the present invention and this specification, the vertical direction of the vehicle refers to the vertical direction when the vehicle is a lean vehicle including a two-wheeled vehicle, with all wheels in contact with the horizontal road surface and standing upright on the horizontal road surface. When the vehicle is not a lean vehicle including a four-wheeled vehicle, the vertical direction of the vehicle refers to the vertical direction when all wheels are in contact with the horizontal road surface. A lean vehicle is a vehicle in which the body frame tilts to the left of the vehicle when turning left and tilts to the right of the vehicle when turning right. When the vehicle is a jet ski, which is a saddle-type vehicle, the vertical direction of the vehicle refers to the vertical direction of the jet ski when it is floating on still water and is stationary.

In this invention and this specification, the end of a part means the combined part of the end of the part and its adjacent area.

In this specification, the end face in the A direction means the face at the end in the A direction.

In this specification, A being forward of B refers to the following state, unless otherwise specified: A is in the forward space of two spaces separated by a plane that passes through the front end of B and is perpendicular to the front-to-rear direction. A and B may or may not be side-by-side in the front-to-rear direction. When B is a plane or straight line perpendicular to the front-to-rear direction, the plane passing through the front-to-rear end of B is a plane that passes through B. When B is a straight line or plane with an infinite length in the front-to-rear direction, the front-to-rear end of B is not specified. A straight line or plane with an infinite length in the front-to-rear direction is not limited to a straight line or plane parallel to the front-to-rear direction.
The same definition applies to an expression that A is behind B under the same conditions for B. The same definition applies to an expression that A is above or below B, or to the right or left of B under the same conditions for B.

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

As used herein, use of the terms "comprising" or "having" and variations thereof identifies the presence of stated features, steps, operations, elements, components and/or equivalents thereof, but may include one or more of the steps, operations, elements, components and/or groups thereof.

In the present invention, the terms mounted, connected, coupled, and supported are used in a broad sense. Specifically, they include not only direct mounting, connection, coupling, and support, but also indirect mounting, 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/couplings.

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

In this specification, the term "preferable" is non-exclusive. "Preferable" means "preferable but not limited to." In this specification, a configuration described as "preferable" at least provides the above-mentioned effect obtained by the configuration (1) above. In this specification, the term "may" is non-exclusive. "may" means "may but not limited to." In this specification, a configuration described as "may" at least provides the above-mentioned effect obtained by the configuration (1) above.

When the number of a certain component is not clearly specified in the claims and is expressed in the singular when translated into English, the present invention may have a plurality of this component. The present invention may also have only one of this component. For example, the single-cylinder engine unit of the present invention may have two camshafts. For example, the combustion chamber of the present invention may have multiple exhaust ports and multiple exhaust valves. For example, the combustion chamber of the present invention may have multiple intake ports and multiple intake valves.

The present invention does not restrict the above-described preferred configurations from being combined with each other. Before describing the embodiments of the present invention in detail, it should be understood that the present invention is not limited to the details of the configuration and arrangement of the components described in the following description or illustrated in the drawings. The present invention is also possible in embodiments other than the embodiments described below. The present invention is also possible in embodiments with various modifications to the embodiments described below. The present invention can also be implemented by appropriately combining the embodiments and modifications described below.

Even though the single-cylinder engine unit of the present invention is equipped with an electric pump device, it is possible to suppress an increase in size in the direction of the central axis of rotation of the camshaft of the single-cylinder engine unit. Furthermore, the single-cylinder engine unit of the present invention can be used without making major design changes to the coolant path when a mechanical pump device is fixed to the cylinder head.

1 is a schematic configuration diagram of a single-cylinder engine unit according to an embodiment of the present invention; 1 is a diagram illustrating the layout of the cylinder head and electric pump device in specific examples 1 to 6 of an embodiment of the present invention. 1 is a diagram illustrating the layout of a cylinder head and an electric pump device in specific examples 7 and 8 of the embodiment of the present invention. FIG. 13 is a right side view of a motorcycle equipped with a single-cylinder engine unit according to a ninth embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a single-cylinder engine unit omitting an electric pump device. FIG. 13 is a schematic diagram illustrating the configuration of a single-cylinder engine unit of a ninth embodiment, viewed in a direction perpendicular to both the cam axis and the cylinder axis. FIG. 2 is a schematic right side view of the engine body and the radiator with the switching valve omitted. 4 is a schematic diagram of a single-cylinder engine unit for explaining the flow of the coolant when the temperature of the coolant is in a second low temperature region. FIG. FIG. 2 is a schematic diagram of a single-cylinder engine unit for explaining the flow of the coolant when the temperature of the coolant is in the medium temperature range. 1 is a schematic diagram of a single-cylinder engine unit for explaining the flow of a coolant when the temperature of the coolant is in a high temperature range. FIG. A schematic diagram viewed in a direction perpendicular to the rotational center axis of the camshaft and the cylinder axis to explain the configuration of a single-cylinder engine unit relating to a specific example 10 of an embodiment of the present invention. This is a schematic diagram viewed in a direction perpendicular to the rotational center axis of the camshaft and the cylinder axis to explain the configuration of a single-cylinder engine unit relating to a specific example 11 of an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1. The engine unit 11 of the embodiment of the present invention includes a cylinder body 20C, a cylinder head 20D, a head cover 20E, a coolant path 41, a camshaft 31, and an electric pump device 46. The cylinder body 20C, the cylinder head 20D, and the head cover 20E are included in the engine main body 20.

The cylinder body 20C has only one cylinder bore 20Ca. The cylinder head 20D is connected to the end of the cylinder body 20C in the direction of the cylinder axis 20X, which is the central axis of the cylinder bore 20Ca. Note that the cylinder axis 20X is not a line segment that exists only in the area where the cylinder bore 20Ca exists, but is a straight line that extends infinitely. The head cover 20E is connected to the end of the cylinder head 20D in the direction of the cylinder axis 20X. The head cover 20E is located at the end of the engine body 20 in the direction of the cylinder axis 20X.

A part of the coolant path 41 is formed inside the engine body 20. The coolant circulates through the coolant path 41. The camshaft 31 is supported by the cylinder head 20D. The camshaft 31 rotates around a cam axis 31X that is perpendicular to a straight line parallel to the cylinder axis 20X.

The electric pump device 46 has an electric motor 46A2. The electric pump device 46 pumps the coolant flowing through the coolant path 41. At least a part of the electric pump device 46 is located outside the engine body 20. The electric pump device 46 is supported by the head cover 20E so that the motor axis 46X, which is the rotational center axis of the output shaft of the electric motor 46A2, is not coaxial with the cam axis 31X. The motor axis 46X is not a line segment that exists only in the area where the output shaft of the electric motor 46A2 exists, but is a straight line that extends infinitely. The cam axis 31X is not a line segment that exists only in the area where the camshaft 31 exists, but is a straight line that extends infinitely.

In general, it is easier to secure a space large enough to accommodate the electric pump device around the head cover of a single-cylinder engine unit than around the cylinder head. Therefore, when the electric pump device 46 is supported by the head cover 20E, the layout of the electric pump device 46 has a higher degree of freedom than when the electric pump device 46 is supported by the cylinder head. Therefore, the layout of the electric pump device 46 supported by the head cover 20E can be designed to suppress an increase in size of the single-cylinder engine unit 11 in the direction of the cam axis 31X.
In addition, the distance from the cylinder head 20D to the head cover 20E is short. Therefore, the coolant path 41 of the single-cylinder engine unit when the electric pump device 46 is supported on the head cover 20E can be made to have substantially the same structure as the coolant path of the single-cylinder engine unit when the mechanical pump device is supported on the cylinder head 20D. Therefore, the single-cylinder engine unit 11 can utilize the coolant path when the mechanical pump device is fixed to the cylinder head 20D without making any major design changes.
As described above, it is possible to prevent the camshaft 31 of the single-cylinder engine unit 11 equipped with the electric pump device 46 from becoming larger in size in the direction of the central axis of rotation, and it is possible to utilize the cooling liquid path when a mechanical pump device is supported on the cylinder head 20E without making major design changes.

<Specific Examples 1 to 6 of the Embodiments of the Invention>
Next, specific examples 1 to 6 of the above-mentioned embodiment of the present invention will be described with reference to Fig. 2. In the following description, the description of the same parts as those in the above-mentioned embodiment of the present invention will be omitted. Specific examples 1 to 4 are included in the above-mentioned embodiment of the present invention.

In specific examples 1 to 3 and 5 shown in Fig. 2(a) to 2(c) and Fig. 2(e), respectively, the electric pump device 46 is disposed so that the motor axis 46X is perpendicular to a line parallel to the cam axis 31X. In specific examples 1 and 2, the motor axis 46X is parallel to the cylinder axis 20X. In specific examples 3 and 5, the motor axis 46X is perpendicular to a line parallel to the cylinder axis 20X. In specific examples 4 and 6 shown in Fig. 2(d) and Fig. 2(f), the electric pump device 46 is disposed so that the motor axis 46X is parallel to the cam axis 31X. As explained in the embodiment of the present invention, the cam axis 31X is perpendicular to a direction parallel to the cylinder axis 20X.

By having the motor axis 46X parallel to the cam axis 31X, parallel to the cylinder axis 20X, or parallel to a line perpendicular to both the cam axis 31X and the cylinder axis 20X, it is easier to efficiently arrange the electric pump device 46 in the available space of the device (e.g., a vehicle) in which the single-cylinder engine unit is mounted, compared to when the motor axis 46X is oblique to the cam axis 31X.

The electric pump device 46 of the first specific example has a portion 46b aligned with the head cover 20E in a direction parallel to the cylinder axis 20X, and a portion 46a aligned with the head cover 20E in a direction parallel to a straight line perpendicular to both the cylinder axis 20X and the cam axis 31X.

The electric pump device 46 of the second specific example has a portion 46a aligned with the head cover 20E in a direction parallel to the cam axis 31X, and a portion 46b aligned with the head cover 20E in a direction parallel to the cylinder axis 20X.

The electric pump device 46 of the third specific example has a portion 46a aligned with the head cover 20E in a direction parallel to the cylinder axis 20X, and a portion 46b aligned with the head cover 20E in a direction parallel to a straight line perpendicular to both the cylinder axis 20X and the cam axis 31X.

The electric pump device 46 of the fourth specific example has a portion 46a aligned with the head cover 20E in a direction parallel to the cylinder axis 20X, and a portion 46b aligned with the head cover 20E in a direction parallel to the cam axis 31X.

The electric pump device 46 of the fifth example has a portion 46a aligned with the head cover 20E in a direction parallel to the cam axis 31X, and a portion 46b aligned with the head cover 20E in a direction parallel to a straight line perpendicular to both the cam axis 31X and the cylinder axis 20X.

The electric pump device 46 of the sixth specific example has a portion 46b aligned with the head cover 20E in a direction parallel to the cam axis 31X, and a portion 46a aligned with the head cover 20E in a direction parallel to a straight line perpendicular to both the cam axis 31X and the cylinder axis 20X.

In this way, the electric pump device 46 of specific examples 1 to 6 has a first portion aligned with the head cover 20E in a first direction A1 parallel to either the cam axis 31X or the cylinder axis 20X, and a second portion different from the first portion aligned with the head cover 20E in a second direction A2 perpendicular to the first direction A1. One of the portions 46a and 46b corresponds to the first portion, and the other of the portions 46a and 46b corresponds to the second portion.

In specific example 1, the portion 46b corresponds to the first portion, and the direction parallel to the cylinder axis 20X is the first direction A1. In specific example 2, the portion 46a serves as both the first portion and the second portion. When the portion 46a is the first portion, the direction parallel to the cam axis 31X is the first direction A1, and when the portion 46b is the first portion, the direction parallel to the cylinder axis 20X is the first direction A1. In specific example 3, the portion 46a corresponds to the first portion, and the direction parallel to the cylinder axis 20X is the first direction A1. In specific example 4, the portion 46a serves as both the first portion and the second portion. When the portion 46a is the first portion, the direction parallel to the cylinder axis 20X is the first direction A1, and when the portion 46b is the first portion, the direction parallel to the cam axis 31X is the first direction A1. In the specific example 5, the portion 46a corresponds to the first portion, and the direction parallel to the cam axis 31X corresponds to the first direction A1. In the specific example 6, the portion 46b corresponds to the first portion, and the direction parallel to the cam axis 31X corresponds to the first direction A1.

By having such a first portion and a second portion, the electric pump device 46 of specific examples 1 to 6 can prevent the single-cylinder engine unit equipped with the electric pump device 46 from becoming larger. When the first direction A1 is parallel to the cylinder axis 20X, the single-cylinder engine unit equipped with the electric pump device 46 can be more reliably prevented from becoming larger in the direction of the cam axis compared to when the electric pump device is supported by the cylinder head.

The electric pump device 46 of the specific examples 1 to 6 has a small diameter portion 46m and a large diameter portion 46n. The large diameter portion 46n is aligned with the small diameter portion 46m in the direction of the motor axis 46X. The maximum radial dimension of the large diameter portion 46n about the motor axis 46X is larger than the maximum radial dimension of the small diameter portion 46m about the motor axis 46X. The electric pump device 46 of the specific examples 1 to 6 is arranged such that a part of the large diameter portion 46n is aligned with the head cover 20E in a direction parallel to the motor axis 46X, and at least a part of the small diameter portion 46m is aligned with the head cover 20E in a direction perpendicular to the motor axis 46X. The portion 46b is a part of the large diameter portion 46n, and the portion 46a is at least a part of the small diameter portion 46m. More specifically, the portion 46b is a part of the large diameter portion 46n in the circumferential direction. The portion 46a is at least a part of the small diameter portion 46m in the cylindrical axis direction.

By arranging the large diameter portion 46n and the small diameter portion 46m of the electric pump device 46 in specific examples 1 to 6 as described above, it becomes easier to prevent the single-cylinder engine unit equipped with the electric pump device 46 from becoming larger.

In specific examples 1 to 6, when the electric pump device 46 and the head cover 20E are viewed in a direction perpendicular to the motor axis 46X, the large diameter portion 46n does not overlap with the head cover 20E. This configuration makes it easier to prevent the single-cylinder engine unit equipped with the electric pump device 46 from becoming larger.

<Specific examples 7 and 8 of the embodiment of the present invention>
Specific examples 7 and 8 of the above-mentioned embodiment of the present invention will be described with reference to Fig. 3. In the following description, the description of the same parts as those in the above-mentioned embodiment of the present invention will be omitted. Specific examples 7 and 8 are included in the above-mentioned embodiment of the present invention.

In specific example 7 shown in FIG. 3(a) and specific example 8 shown in FIG. 3(b), the electric pump device 46 is arranged so that the motor axis 46X is parallel to a line perpendicular to the cylinder axis 20X. In specific example 7, the motor axis 46X is parallel to the cam axis 31X. In specific example 8, the motor axis 46X is perpendicular to a line parallel to the cam axis 31X.

The electric pump device 46 of specific examples 7 and 8 has a third portion 46c that is aligned with the head cover 20E in a direction parallel to the cylinder axis 20X and is aligned with the head cover 20E in a direction parallel to a straight line perpendicular to the cylinder axis 20X. The third portion 46c of the electric pump device 46 of specific example 7 is aligned with the head cover 20E in a direction parallel to the cylinder axis 20X and is aligned with the head cover 20E in a direction parallel to a straight line perpendicular to both the cam axis 31X and the cylinder axis 20X. The third portion 46c of the electric pump device 46 of specific example 8 is aligned with the head cover 20E in a direction parallel to the cylinder axis 20X and is aligned with the head cover 20E in a direction parallel to the cam axis 31X.

The electric pump device 46 of specific examples 7 and 8 has such a third portion 46c, so that the single-cylinder engine unit including the electric pump device 46 can be prevented from becoming larger in the direction of the cylinder axis 20X compared to a case where the electric pump device has a motor axis parallel to a line perpendicular to the cylinder axis 20X and does not have a portion aligned with the head cover 20E in a direction parallel to the line perpendicular to the cylinder axis 20X. Also, the single-cylinder engine unit including the electric pump device 46 can be prevented from becoming larger in the direction perpendicular to the cylinder axis compared to a case where the electric pump device has a motor axis parallel to a line perpendicular to the cylinder axis 20X and has a portion aligned with the head cover 20E in a direction parallel to the line perpendicular to the cylinder axis 20X and the portion does not line up with the head cover 20E in a direction parallel to the cylinder axis 20X.

The electric pump device 46 of the specific examples 7 and 8 may have, in addition to the third portion 46c, a fourth portion that is different from the third portion 46c and is aligned with the head cover 20E in a direction parallel to a straight line perpendicular to the cylinder axis 20X. In this case, the third portion 46c corresponds to the first portion of the present invention, and the fourth portion corresponds to the second portion of the present invention. In Figures 3(a) and 3(b), an example of the fourth portion is shown by a two-dot chain line. For example, the electric pump device 46 of the specific examples 7 and 8 may have a fourth portion 46d that is aligned with the head cover 20E in a direction parallel to the cam axis 31X. Also, for example, the electric pump device 46 of the specific examples 7 and 8 may have a fourth portion 46e that is aligned with the head cover 20E in a direction parallel to a straight line perpendicular to both the cam axis 31X and the cylinder axis 20X.

The electric pump device 46 of the seventh embodiment may have a fifth portion different from the third portion 46c, which is aligned with the head cover 20E in a direction parallel to the cam axis 31X, and is aligned with the head cover 20E in a direction parallel to a straight line perpendicular to the cam axis 31X. In this case, the third portion 46c corresponds to the first portion of the present invention, and the fifth portion corresponds to the second portion of the present invention. In Fig. 3(a) and Fig. 3(b), an example of the fifth portion is shown by a two-dot chain line. For example, the electric pump device 46 of the seventh embodiment may have a fifth portion 46e aligned with the head cover 20E in a direction parallel to a straight line perpendicular to both the cam axis 31X and the cylinder axis 20X. For example, the electric pump device 46 of the seventh embodiment may have a fifth portion 46f aligned with the head cover 20E in a direction parallel to the cylinder axis 20X.

<Specific Example 9 of the embodiment>
Next, a specific example 9 of the embodiment of the present invention described above will be described with reference to FIGS. 4 to 10. In the following description, the same parts as those in the embodiment of the present invention described above will not be described. The specific example 9 is included in the embodiment of the present invention described above. The specific example 9 of the present embodiment is an example in which the present invention is applied to a motorcycle 1. In the following description, unless otherwise specified, the front-rear direction refers to the front-rear direction of the vehicle. The front-rear direction of the vehicle refers to the front-rear direction seen from a rider seated on a seat 5 of the motorcycle 1 described below. 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 seen from a rider seated on a seat 5 of the motorcycle 1 described below. The left-right direction of the vehicle is also the vehicle width direction of the motorcycle 1. In the following description, unless otherwise specified, the up-down direction refers to the up-down direction of the vehicle. The up-down direction of the vehicle refers to the up-down direction when the motorcycle 1, with all wheels in contact with the horizontal road surface, is upright on the horizontal road surface. The front-rear direction of the vehicle, the left-right direction of the vehicle, and the up-down direction of the vehicle are perpendicular to each other. Arrows F, B, U, and D shown in Figs. 4 and 5 indicate the front, rear, upper, and lower directions, respectively.

[1] Schematic configuration of motorcycle As shown in Fig. 4, 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 body frame 4. A single-cylinder engine unit 11A is mounted on the body frame 4. In the following description, the single-cylinder engine unit 11A is referred to as engine unit 11A. In addition, the body frame 4 is mounted with an ECU (Electronic Control Unit) 75 (described later) of the engine unit 11A, an electric pump device 46, and a battery (not shown) that supplies power to electronic devices such as various sensors.

[2] Configuration of Engine Unit The configuration of the engine unit 11A will be described below. Figures 5 and 6 are schematic diagrams showing the configuration of the engine unit 11A. The engine unit 11A has an engine body 20 and a cooling unit 40. The cooling unit 40 is located outside the engine body 20. As shown in Figure 5, the piston 22, the intake valve 25, the exhaust valve 26, the spark plug 27, at least a part of the fuel injector 28, and at least a part of the valve drive mechanism 30 are arranged inside the engine body 20. The engine unit 11A 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 has an oil pan 20A, a crankcase 20B, a cylinder body 20C, a cylinder head 20D, and a head cover 20E. These are connected in this order. Lubricating oil is stored in the oil pan 20A. An oil pump (not shown) for circulating the lubricating oil is disposed inside the engine body 20. The oil pump operates by receiving the rotational force of the crankshaft 21. The crankcase 20B supports the crankshaft 21. The central axis 21X of rotation of the crankshaft 21 is parallel to the left-right direction. The cylinder body 20C has a cylinder bore 20Ca.

As shown in Figs. 4 and 7, when the engine unit 11A is viewed in the left-right direction, the upper part of the cylinder axis 20X is located forward of the lower part. When the engine unit 11A is viewed in the left-right direction, the inclination angle of the cylinder axis 20X with respect to the up-down direction is greater than 0° and not greater than 45°. Hereinafter, the direction parallel to the cylinder axis 20X from the crankcase 20B toward the cylinder body 20C is defined as the cylinder upper direction. The direction parallel to the cylinder axis 20X from the cylinder body 20C toward the crankcase 20B is defined as the cylinder lower direction. The arrow Ua in Figs. 4 to 7 indicates the cylinder upper direction, and the arrow Da indicates the cylinder lower direction. The piston 22 is provided in the cylinder bore 20Ca so as to be able to reciprocate along the cylinder axis 20X. The piston 22 is connected to the crankshaft 21 via a connecting rod 23.

The engine body 20 has a combustion chamber 24, an internal intake path 20Da, and an internal exhaust path 20Db. The combustion chamber 24 is formed by a cylinder head 20D, a cylinder bore 20Ca, and a piston 22. An intake port 24a and an exhaust port 24b are formed in the combustion chamber 24. 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. The internal intake path 20Da is connected to the intake port 24a. The internal exhaust path 20Db is connected to the exhaust port 24b. The upstream end of the internal intake path 20Da is connected to an intake pipe 51 located outside the engine body 20. The downstream end of the internal exhaust path 20Db is connected to an exhaust pipe 61 located outside the engine body 20.

The intake valve 25 is provided in the cylinder head 20D to open and close the intake port 24a. The exhaust valve 26 is provided in the cylinder head 20D to open and close the exhaust port 24b. The intake valve 25 and the exhaust valve 26 are driven by a valve drive mechanism 30. The valve drive mechanism 30 in this embodiment is of a SOHC (Single Over Head Camshaft) type. The valve drive mechanism 30 may be of a rocker arm type or a direct-hit type (also called a direct-acting type). Furthermore, when the valve drive mechanism 30 is of a rocker arm type, the rocker arm may be of a seesaw type or a swing arm type.

As shown in FIG. 5, the valve drive mechanism 30 includes a camshaft 31 provided with at least one intake cam (not shown) and at least one exhaust cam (not shown). The camshaft 31 is supported by the cylinder head 20D. As shown in FIGS. 5 to 7, the camshaft 31 is located near the boundary between the cylinder head 20D and the head cover 20E. In other words, at least a portion of the camshaft 31 is located inside the cylinder head 20D. Note that the entire camshaft 31 may be located inside the cylinder head 20D.

The camshaft 31 rotates about the cam axis 31X in conjunction with the crankshaft 21. The cam axis 31X is parallel to the rotational center axis 21X of the crankshaft 21. The cam axis 31X is parallel to the left-right direction. The cam axis 31X is perpendicular to a straight line parallel to the cylinder axis 20X. The cam axis 31X intersects with the cylinder axis 20X.

When the camshaft 31 rotates, the intake valve 25 opens the intake port 24a. When the camshaft 31 rotates, the exhaust valve 26 opens the exhaust port 24b. The intake valve 25 is pressed by a spring (not shown) in a direction that closes the intake port 24a. The exhaust valve 26 is pressed by a spring (not shown) in a direction that closes the exhaust port 24b.

The valve drive mechanism 30 has a variable valve timing mechanism 35. As shown in FIG. 6, the variable valve timing mechanism 35 is connected to the camshaft 31. At least a part of the variable valve timing mechanism 35 is located outside the engine body 20. The variable valve timing mechanism 35 changes at least one of the timing of opening and closing the intake port 24a by the intake valve 25 and the timing of opening and closing the exhaust port 24b by the exhaust valve 26. The variable valve timing mechanism 35 has an actuator 36 located outside the engine body 20. The actuator 36 is operated by supplying electric power. The actuator 36 is an electromagnetic or electric actuator. The electromagnetic actuator is, for example, an electromagnetic solenoid. The electric actuator is, for example, an electric motor. The actuator 36 is controlled by the ECU 75. The ECU 75 controls the actuator 36 so as to change at least one of the timing of opening and closing the intake port 24a by the intake valve 25 and the timing of opening and closing the exhaust port 24b by the exhaust valve 26 according to, for example, the rotation speed of the crankshaft 21.

For example, assume that the valve drive mechanism 30 is of a direct-hit type, and one intake cam and one exhaust cam are fixed to the camshaft 31. In this case, the ECU 75 may control the variable valve timing mechanism 35 (actuator 36) so that the phase angle of the camshaft 31 relative to the crankshaft 21 changes according to the rotational speed of the crankshaft 21.
Also, for example, it is assumed that the valve drive mechanism 30 is of a direct-hit type, a plurality of intake cams and a plurality of exhaust cams are fixed to the camshaft 31, and the camshaft 31 is movable in the direction of the cam axis 31X relative to the engine body 20. The ECU 75 may control the variable valve timing mechanism 35 (actuator 36) in accordance with the rotational speed of the crankshaft 21 so that the camshaft 31 moves in the direction of the cam axis 31X relatively to the engine body 20.

As shown in Figures 5 and 6, a spark plug 27 is provided in the cylinder head 20D. The tip of the spark plug 27 is disposed in the combustion chamber 24. The spark plug 27 ignites the mixture containing fuel and air in the combustion chamber 24.

The fuel injection device 28 is provided in the cylinder head 20D so as to inject fuel into the internal intake path 20Da. The fuel injection device 28 may also be arranged so as to inject fuel into an intake pipe 51 connected to the internal intake path 20Da.

The head cover 20E is located at the end of the engine body 20 in the cylinder upward direction Ua. The head cover 20E is a one-piece molded product. As shown in Figures 5 and 7, the direction perpendicular to both the line parallel to the cylinder axis 20X and the line parallel to the cam axis 31X, and extending from the intake port 24a toward the exhaust port 24b, is defined as the cylinder forward direction. The opposite direction to the cylinder forward direction is defined as the cylinder rearward direction. The arrow Fa in Figure 7 indicates the cylinder forward direction, and the arrow Ba indicates the cylinder rearward direction.

The outer surface of the head cover 20E includes a right surface 20E1a, a left surface 20E1b, a top surface 20E2a, a front surface 20E2b, a rear surface 20E2c, and an inclined surface 20E3. The right surface 20E1a, the top surface 20E2a, the front surface 20E2b, the rear surface 20E2c, and the inclined surface 20E3 may not be composed of a single plane. For example, they may include a curved surface or may include irregularities. The top surface 20E2a is an end surface of the head cover 20E in the cylinder upward direction Ua. The front surface 20E2b is an end surface of the head cover 20E in the cylinder forward direction Fa. The rear surface 20E2c is an end surface of the head cover 20E in the cylinder rear direction Ba. The inclined surface 20E3 connects the end of the top surface 20E2a in the cylinder forward direction Fa and the end of the front surface 20E2b in the cylinder upward direction Ua. As shown in FIG. 7, the inclined surface 20E3 is inclined with respect to a straight line parallel to the cylinder axis 20X. The inclined surface 20E3 is inclined with respect to a straight line parallel to a straight line perpendicular to both the cylinder axis 20X and the cam axis 31X.

As shown in Figures 6 and 7, a base 20F for fixing the electric pump device 46 is connected to the end of the top surface 20E2a in the cylinder forward direction Fa. The base 20F is part of the head cover 20E. The base 20F protrudes from the top surface 20E2a in the cylinder upward direction Ua.

The engine unit 11A has a coolant path 41 through which the coolant circulates. The coolant path 41 includes a first internal coolant path 41a, a second internal coolant path 41b, an inlet path 41c, and an outlet path 41d, each of which is formed inside the engine body 20. A portion of the coolant path 41 is located outside the engine body 20 and is included in the cooling unit 40.

As shown in Figures 6 and 8 to 10, the first internal coolant path 41a is formed inside the cylinder body 20C. The first internal coolant path 41a is located radially outside the cylinder bore 20Ca. The first internal coolant path 41a is formed so as to surround the entire circumference of the cylinder bore 20Ca. The second internal coolant path 41b is formed in the cylinder head 20D. The shape of the end of the second internal coolant path 41b in the cylinder downward direction Da is the same as or approximately the same as the shape of the end of the first internal coolant path 41a in the cylinder upward direction Ua.

6 and 8 to 10, the inlet path 41c and the discharge path 41d are formed inside the cylinder head 20D. The downstream end of the inlet path 41c is connected to the second internal coolant path 41b. The upstream end of the inlet path 41c is the inlet 20D1 formed on the outer surface of the cylinder head 20D. The upstream end of the discharge path 41d is connected to the second internal coolant path 41b. The downstream end of the discharge path 41d is the outlet 20D2 formed on the outer surface of the cylinder head 20D. The inlet 20D1 and the outlet 20D2 are included in the coolant path 41. The coolant passes through the outlet 20D2 when moving from the inside of the engine body 20 to the outside of the engine body 20. The coolant passes through the inlet 20D1 when moving from the outside of the engine body 20 to the inside of the engine body 20. As shown in FIG. 7, the outlet 20D2 is located above the inlet 20D1.

As shown in FIG. 6, the coolant path 41 is provided with a temperature sensor 38 that detects the temperature of the coolant flowing through the coolant path 41. The temperature sensor 38 is located inside the engine body 20. The temperature sensor 38 is located near the outlet 20D2. The temperature sensor 38 is positioned so that it can detect the temperature of the coolant just before it passes through the outlet 20D2. As is clear from FIG. 6, in the coolant path 41, the distance between the temperature sensor 38 and the outlet 20D2 is shorter than the distance between the temperature sensor 38 and the inlet 20D1.

As shown in Figures 6 and 8 to 10, the cooling unit 40 has a switching valve 42, a first tube 43, a second tube 44, a radiator 45, an electric pump device 46, a third tube 47, and a fourth tube 48. A portion of the coolant path 41 is formed by the switching valve 42, the first tube 43, the second tube 44, the radiator 45, the electric pump device 46, the third tube 47, and the fourth tube 48.

As shown in FIG. 6, the switching valve 42 is fixed to the outer surface of the engine body 20. The switching valve 42 is fixed to the outer surface of the cylinder head 20D. As shown in FIGS. 8 to 10, the switching valve 42 has a valve case 42a and a movable valve body 42c. The internal space 42a1 of the valve case 42a forms a part of the coolant path 41. The switching valve 42 is a thermostatic valve. The movable valve body 42c is disposed in the internal space 42a1 and moves according to the temperature of the coolant in the internal space 42a1. A temperature detection unit 42c1 that detects the temperature of the coolant is provided at the end of the movable valve body 42c. The temperature detection unit 42c1 is provided at the end of the movable valve body 42c in the direction linearly going from the first outlet 42b3 to the second outlet 42b4. The movable valve body 42c moves in the internal space 42a1 according to the temperature of the coolant detected by the temperature detection unit 42c1. The switching valve 42 may be any type of thermostatic valve. For example, the switching valve 42 may be a mechanical thermostatic valve using a bimetal. The switching valve 42 may be an expansion type thermostatic valve using wax. The valve case 42a has a first inlet 42b1, a second inlet 42b2, a first outlet 42b3, and a second outlet 42b4. That is, the switching valve 42 is a four-way valve.

When the temperature of the cooling liquid in the internal space 42a1 is in the first low temperature region or the second low temperature region, the movable valve body 42c is located in the low temperature position shown in FIG. 8. The second low temperature region is a temperature region higher than the first low temperature region. When the movable valve body 42c is in the low temperature position, the cooling liquid that has flowed into the internal space 42a1 from the first inlet 42b1 is allowed to flow to the second outlet 42b4. When the movable valve body 42c is in the low temperature position, the cooling liquid that has flowed into the internal space 42a1 from the first inlet 42b1 is prevented from flowing to the first outlet 42b3. When the movable valve body 42c is in the low temperature position, the cooling liquid is prevented from flowing into the internal space 42a1 from the second inlet 42b2.

When the temperature of the cooling liquid in the internal space 42a1 is in the medium temperature region, which is higher than the second low temperature region, the movable valve body 42c is located at the medium temperature position shown in FIG. 9. When the movable valve body 42c is in the medium temperature position, the cooling liquid that flows into the internal space 42a1 from the first inlet 42b1 is allowed to flow to the first outlet 42b3 and the second outlet 42b4. When the movable valve body 42c is in the medium temperature position, the cooling liquid that flows into the internal space 42a1 from the second inlet 42b2 is allowed to flow to the second outlet 42b4. When the movable valve body 42c is in the medium temperature position, the cooling liquid that flows into the internal space 42a1 from the second inlet 42b2 is less likely to flow to the first outlet 42b3. In other words, this flow may be completely blocked, or a small amount of flow may be allowed.

When the temperature of the cooling liquid in the internal space 42a1 is in the high temperature region, which is higher than the medium temperature region, the movable valve body 42c is located in the high temperature position shown in FIG. 10. When the movable valve body 42c is in the high temperature position, the cooling liquid that has flowed into the internal space 42a1 from the first inlet 42b1 is allowed to flow to the first outlet 42b3. When the movable valve body 42c is in the high temperature position, the cooling liquid that has flowed into the internal space 42a1 from the first inlet 42b1 is prevented from flowing to the second outlet 42b4. When the movable valve body 42c is in the high temperature position, the cooling liquid that has flowed into the internal space 42a1 from the second inlet 42b2 is allowed to flow to the second outlet 42b4. When the movable valve body 42c is in the high temperature position, the cooling liquid that has flowed into the internal space 42a1 from the second inlet 42b2 is less likely to flow to the first outlet 42b3. In other words, this flow may be completely blocked, or a small amount of flow may be allowed.

As shown in FIG. 6 and FIG. 8 to FIG. 10, the first inlet 42b1 of the valve case 42a communicates with the outlet 20D2 of the cylinder head 20D. The upstream end of the first tube 43 is connected to the first outlet 42b3 of the switching valve 42. The downstream end of the first tube 43 is connected to the radiator 45 provided outside the engine body 20. The upstream end of the second tube 44 is connected to the radiator 45. The downstream end of the second tube 44 is connected to the second inlet 42b2 of the switching valve 42. In other words, the radiator 45 is disposed at a position not between the switching valve 42 and the inlet 20D1 in the cooling liquid path 41. After flowing out from the outlet 20D2, when the cooling liquid that has not passed through the radiator 45 enters the internal space 42a1, the cooling liquid passes through the first inlet 42b1. When the cooling liquid flowing from the internal space 42a1 toward the radiator 45 leaves the internal space 42a1, the cooling liquid passes through the first outlet 42b3. After flowing out of the first outlet 42b3, the coolant passes through the radiator 45 and enters the internal space 42a1, and then passes through the second inlet 42b2.

As shown in FIG. 7, a plane Sf that is perpendicular to the up-down direction and passes through the engine body 20 passes through the radiator 45. In the plane Sf, the radiator 45 is located forward of the engine body 20. Although not shown, when viewed in the front-rear direction, the radiator 45 overlaps with the cylinder axis 20X. Note that FIG. 6 shows the position of the radiator 45 diagrammatically.

6, the electric pump device 46 has a motor case 46A1 that houses the electric motor 46A2 and a pump case 46B1 that houses at least a part of the pump mechanism 46B2. When power is supplied from the battery to the electric motor 46A2, an output shaft (not shown) of the electric motor 46A2 rotates around the electric motor 46A2. The output shaft is connected to the pump mechanism 46B2. When the output shaft rotates, the pump mechanism 46B2 operates. The pump mechanism 46B2 pressurizes the supplied cooling liquid and discharges it. The electric pump device 46 may be any type of electric pump device. For example, the electric pump device 46 may be a non-positive displacement electric pump device. Also, the electric pump device 46 may be a positive displacement electric pump device.

The electric pump device 46 is arranged so that the motor axis 46X is parallel to the cam axis 31X. The motor case 46A1 and the pump case 46B1 are aligned in the direction of the motor axis 46X. The electric motor 46A2 and the pump mechanism 46B2 are aligned in the direction of the motor axis 46X. The pump case 46B1 is located on the left side of the electric pump device 46.

The motor case 46A1 has a first cylindrical portion 46A1a, a first flange 46A1b, and an attachment portion 46A1c. The pump case 46B1 has a second cylindrical portion 46B1a and a second flange 46B1b. The first cylindrical portion 46A1a houses the electric motor 46A2. The second cylindrical portion 46B1a houses at least a part of the pump mechanism 46B2. The first cylindrical portion 46A1a and the second cylindrical portion 46B1a are cylindrical with one end closed. The first cylindrical portion 46A1a and the second cylindrical portion 46B1a may be cylindrical or rectangular, for example. The maximum radial dimension of the first cylindrical portion 46A1a about the motor axis 46X is smaller than the maximum radial dimension of the second cylindrical portion 46B1a about the motor axis 46X. The maximum radial dimension of the first cylindrical portion 46A1a about the motor axis 46X may be the same as or larger than the maximum radial dimension of the second cylindrical portion 46B1a about the motor axis 46X.

The first flange 46A1b is connected to the left end (open end) of the first cylindrical portion 46A1a. That is, the first flange 46A1b is connected to the first cylindrical portion 46A1a so as to be aligned with the first cylindrical portion 46A1a in the direction of the motor axis 46X. The maximum radial dimension of the first flange 46A1b around the motor axis 46X is larger than the maximum radial dimension of the first cylindrical portion 46A1a around the motor axis 46X. The second flange 46B1b is connected to the right end (open end) of the second cylindrical portion 46B1a. The maximum radial dimension of the second flange 46B1b around the motor axis 46X is larger than the maximum radial dimension of the second cylindrical portion 46B1a around the motor axis 46X. The shapes of the outer circumferential ends of the first flange 46A1b and the second flange 46B1b are not particularly limited. For example, they may be circular or rectangular. The maximum radial dimension of the first flange 46A1b about the motor axis 46X is the same as or approximately the same as the maximum radial dimension of the second flange 46B1b about the motor axis 46X. The first flange 46A1b is fixed to the second flange 46B1b by, for example, a plurality of bolts while in contact with the second flange 46B1b.

As shown in Fig. 7, the mounting portion 46A1c is connected to the outer circumferential surface of the first cylindrical portion 46A1a . The mounting portion 46A1c is fixed to the base 20F of the head cover 20E by, for example, a plurality of bolts or the like, thereby fixing (supporting) the electric pump device 46 to the head cover 20E. In other words, the pump case 46B1 is supported by the head cover 20E via the motor case 46A1. With this configuration, the electric pump device 46 can be stably supported by the head cover 20E with a simpler support structure than when the motor case 46A1 is connected to the head cover 20E via the pump case 46B1.

As shown in FIG. 6, the upstream end of the third tube 47 and the downstream end of the fourth tube 48 are connected to the pump case 46B1 (second cylindrical portion 46B1a). The downstream end of the third tube 47 is connected to the inlet 20D1 of the cylinder head 20D. The upstream end of the fourth tube 48 is connected to the second outlet 42b4 of the switching valve 42. The electric pump device 46 is located downstream of the switching valve 42 and upstream of the inlet 20D1 in the flow direction of the cooling liquid. When the cooling liquid flowing from the internal space 42a1 of the switching valve 42 toward the electric pump device 46 leaves the internal space 42a1, the cooling liquid passes through the second outlet 42b4.

As shown in FIG. 6, a portion of the first flange 46A1b is aligned with the left surface 20E1b of the head cover 20E in a direction parallel to the motor axis 46X and the cam axis 31X. In other words, the first flange 46A1b has a portion aligned with the left surface 20E1b of the head cover 20E in a direction parallel to the motor axis 46X and the cam axis 31X. As shown in FIG. 7, a portion of the cylinder axis direction of the first cylindrical portion 46A1a is aligned with the inclined surface 20E3 of the head cover 20E in a direction parallel to a straight line perpendicular to both the cylinder axis 20X and the cam axis 31X. In other words, the first cylindrical portion 46A1a has a portion aligned with the inclined surface 20E3 of the head cover 20E in a direction parallel to a straight line perpendicular to both the cylinder axis 20X and the cam axis 31X. The portion of the first flange 46A1b corresponds to the first portion of the present invention, the portion of the first cylindrical portion 46A1a corresponds to the second portion of the present invention, and the direction parallel to the cylinder axis 20X corresponds to the first direction of the present invention. The first flange 46A1b corresponds to the large diameter portion of the present invention, and the first cylindrical portion 46A1a corresponds to the small diameter portion of the present invention. Furthermore, the portion of the first cylindrical portion 46A1a is aligned with the inclined surface 20E3 of the head cover 20E in the direction parallel to the cylinder axis 20X. The portion of the first cylindrical portion 46A1a corresponds to the third portion of the present invention.

As shown in FIG. 6, when viewed in a direction perpendicular to the motor axis 46X, the first flange 46A1b (large diameter portion), the second flange 46B1b, and the pump case 46B1 do not overlap with the head cover 20E. The electric pump device 46 intersects with a plane PL1 that is perpendicular to the cam axis 31X and includes the cylinder axis 20X. The plane PL1 intersects with the motor case 46A1 of the electric pump device 46.

As shown in FIG. 7, when viewed in the direction of the cam axis 31X, the entire electric pump device 46 is spaced apart from the cylinder axis 20X. More specifically, when viewed in the direction of the cam axis 31X, the entire electric pump device 46 is spaced apart from the cylinder axis 20X in the cylinder forward direction Fa. As shown in FIG. 7, the entire exhaust port 24b and the entire electric pump device 46 are located in one of two spaces separated by a plane PL2 that is parallel to the cam axis 31X and includes the cylinder axis 20X.

As shown in FIG. 6, when viewed in a direction perpendicular to the motor axis 46X, a portion of the first flange 46A1b and a portion of the second flange 46B1b are located between the left surface 20E1b of the head cover 20E and a portion of the fourth tube 48. This configuration makes it easier to prevent the engine unit 11A, which includes the electric pump device 46 supported by the head cover 20E, from becoming larger. The internal space of the fourth tube 48 corresponds to the external coolant path of the present invention.

As shown in FIG. 6, the shortest distance from the spark plug 27 to the motor case 46A1 of the electric pump device 46 is L1, and the shortest distance from the spark plug 27 to the pump case 46B1 of the electric pump device 46 is L2. The shortest distance L1 is shorter than the shortest distance L2. Therefore, the electric motor 46A2 is closer to the spark plug 27 than when the shortest distance L1 is equal to or greater than the shortest distance L2. Therefore, when bundling the wiring for supplying power from the battery to the spark plug 27 and the wiring for supplying power from the battery to the electric motor 46A2, the length of the bundled wiring can be made longer. Therefore, the space required to arrange the two wirings can be made smaller. This can further prevent the engine unit 11A from becoming larger.

As shown in FIG. 6, the shortest distance from the actuator 36 of the variable valve timing mechanism 35 to the motor case 46A1 of the electric pump device 46 is L3, and the shortest distance from the actuator 36 to the pump case 46B1 of the electric pump device 46 is L4. The shortest distance L3 is shorter than the shortest distance L4. Therefore, the electric motor 46A2 is closer to the actuator 36 than when the shortest distance L3 is equal to or greater than the shortest distance L4. Therefore, when bundling the wiring for supplying power from the battery to the actuator 36 of the variable valve timing mechanism 35 and the wiring for supplying power from the battery to the electric motor 46A2, the length of the bundled wiring can be made longer. Therefore, the space required to arrange the two wirings can be made smaller. This can further prevent the engine unit 11A from becoming larger.

The ECU 75 (see FIG. 4) controls the operation of the engine unit 11A. The ECU 75 controls, for example, the spark plug 27, the fuel injector 28, the variable valve timing mechanism 35, and the electric pump device 46. The ECU 75 includes a processor (arithmetic processing unit) and a memory. The ECU 75 may be composed of multiple devices arranged at separate locations.

The ECU 75 controls the electric pump device 46 based on the detection result transmitted from the temperature sensor 38. The ECU 75 controls the electric motor 46A2 of the electric pump device 46. When the temperature of the coolant detected by the temperature sensor 38 is in the first low temperature region, the ECU 75 stops the electric pump device 46. When the temperature of the coolant detected by the temperature sensor 38 is higher than the first low temperature region, the ECU 75 operates the electric pump device 46. The ECU 75 may be capable of controlling the rotation speed of the output shaft (not shown) of the electric pump device 46.

For example, during a cold start of the engine unit 11A, the temperature of the coolant detected by the temperature sensor 38 and the temperature of the coolant detected by the temperature detection unit 42c1 of the movable valve body 42c of the switching valve 42 are in the first low temperature region. Therefore, the electric pump device 46 is in a stopped state under the control of the ECU 75. The movable valve body 42c of the switching valve 42 is in the low temperature position shown in FIG. 8.

After the engine unit 11A is cold started, the temperatures of the cylinder body 20C and the cylinder head 20D rise. Then, the heat of the cylinder body 20C and the cylinder head 20D is transferred to the coolant. Therefore, the coolant moves by convection. As a result, the coolant circulates through the coolant path 41 by convection. The outlet 20D2 is located above the inlet 20D1. Therefore, the coolant circulating by convection flows from the inside of the engine body 20 to the outside of the engine body 20 through the outlet 20D2 instead of the inlet 20D1. Therefore, the coolant circulates through the coolant path 41 by convection. The coolant circulates through the coolant path 41 in the direction of the arrow in FIG. 9. That is, the coolant circulates in the following order: first internal coolant path 41a and second internal coolant path 41b → exhaust path 41d → outlet 20D2 → switching valve 42 (first inlet 42b1 → internal space 42a1 → second outlet 42b4) → fourth tube 48 → electric pump device 46 → third tube 47 → inlet 20D1 → inlet path 41c → first internal coolant path 41a and second internal coolant path 41b.

For example, after a certain time has passed since the engine unit 11A was started in a cold state, the temperature of the coolant detected by the temperature sensor 38 and the temperature of the coolant detected by the temperature detector 42c1 of the movable valve body 42c of the switching valve 42 reach the second low temperature region. Then, the ECU 75 switches the electric pump device 46 from a stopped state to an operating state. The movable valve body 42c of the switching valve 42 is still in the low temperature position. Therefore, the coolant pumped by the electric pump device 46 circulates through the coolant path 41 along the direction of the arrow in FIG. 8. That is, the coolant circulates in the order of the electric pump device 46 → the third tube 47 → the inlet 20D1 → the inflow path 41c → the first internal coolant path 41a and the second internal coolant path 41b → the discharge path 41d → the outlet 20D2 → the switching valve 42 (the first inlet 42b1 → the internal space 42a1 → the second outlet 42b4) → the fourth tube 48 → the electric pump device 46.

As described above, the outlet 20D2 is located above the inlet 20D1. Therefore, when the temperature of the coolant is in the first low temperature region, the coolant circulating by convection flows out from inside the engine body 20 to the outside of the engine body 20 through the outlet 20D2, and flows from the outside of the engine body 20 to the inside of the engine body 20 through the inlet 20D1. Therefore, the temperature of the coolant at the outlet 20D2 is close to the average temperature of the coolant flowing inside the engine body 20. The temperature of the coolant drops when it flows outside the engine body 20. Therefore, the temperature of the coolant at the inlet 20D1 is lower than the temperature of the coolant at the outlet 20D2. If the temperature sensor 38 is disposed near the inlet 20D1, even if the temperature of the coolant inside the engine body 20 rises to such an extent that the temperature of the coolant at the outlet 20D2 reaches the second low temperature region, the electric pump device 46 is not switched to an operating state by the ECU 75 and remains in a stopped state. This may cause the cylinder body 20C and the cylinder head 20D to become excessively hot. By locating the temperature sensor 38 near the outlet 20D2, the electric pump device 46 can be switched from a stopped state to an operating state at the appropriate timing, preventing the cylinder body 20C and cylinder head 20D from becoming excessively hot.

For example, when a certain amount of time has passed since the temperature of the cooling liquid detected by the temperature sensor 38 reached the second low temperature region, the temperature of the cooling liquid detected by the temperature sensor 38 may rise and reach the high temperature region. In this case, the cooling liquid in the high temperature region flows into the internal space 42a1 from the first inlet 42b1. Therefore, the movable valve body 42c moves from the low temperature position toward the first inlet 42b1. As a result, a part of the cooling liquid that has flowed into the internal space 42a1 from the first inlet 42b1 flows to the first outlet 42b3. The cooling liquid that flows out from the internal space 42a1 through the first outlet 42b3 is cooled by the radiator 45, then flows into the internal space 42a1 from the second inlet 42b2 and flows toward the temperature detection portion 42c1 of the movable valve body 42c. Hereinafter, the cooling liquid that flows through the internal space 42a1 from the second inlet 42b2 to the temperature detection portion 42c1 is referred to as the first cooling liquid CL1. The first cooling liquid CL1 is the cooling liquid after passing through the radiator 45. Therefore, when the temperature of the cooling liquid that flows into the internal space 42a1 from the first inlet 42b1 is in the high temperature region, the temperature of the first cooling liquid CL1 may become in the second low temperature region.

Another part of the cooling liquid in the high temperature region that flows into the internal space 42a1 from the first inlet 42b1 flows toward the temperature detection portion 42c1 of the movable valve body 42c. Hereinafter, the cooling liquid flowing through the internal space 42a1 from the first inlet 42b1 to the temperature detection portion 42c1 is referred to as the second cooling liquid CL2. The first cooling liquid CL1 in the second low temperature region and the second cooling liquid CL2 in the high temperature region merge around the temperature detection portion 42c1. The temperature of the merged cooling liquid becomes a medium temperature region that is higher than the second low temperature region and lower than the high temperature region. Therefore, the movable valve body 42c is located at the medium temperature position shown in FIG. 9. This cooling liquid in the medium temperature region flows out from the internal space 42a1 through the second outlet 42b4 and then flows into the electric pump device 46. Therefore, the cooling liquid circulates through the cooling liquid path 41 along the direction of the arrow in FIG. 9 .

For example, when the temperature of the coolant detected by the temperature sensor 38 is in the high temperature range and the temperature of the coolant around the temperature detection unit 42c1 is in the medium temperature range, if the rotation speed of the crankshaft 21 increases, the temperature of the first coolant CL1 may rise to the high temperature range. In this case, the first coolant CL1 in the high temperature range and the second coolant CL2 in the high temperature range merge around the temperature detection unit 42c1. The temperature of the merged coolant is in the high temperature range. Therefore, the movable valve body 42c moves to the high temperature position shown in FIG. 10. At this time, the temperature of the coolant detected by the temperature sensor 38 is in the high temperature range, so the electric pump device 46 is still in operation under the control of the ECU 75. Therefore, the coolant circulates through the coolant path 41 in the direction of the arrow in FIG. 10. That is, the coolant circulates through the coolant path 41 in the following order: electric pump device 46 → third tube 47 → inlet 20D1 → inflow path 41c → first internal coolant path 41a, second internal coolant path 41b → discharge path 41d → outlet 20D2 → switching valve 42 (first inlet 42b1 → internal space 42a1 → first outlet 42b3) → first tube 43 → radiator 45 → second tube 44 → switching valve 42 (second inlet 42b2 → internal space 42a1 → second outlet 42b4) → fourth tube 48 → electric pump device 46.

Assume that the temperature of the coolant detected by the temperature sensor 38 is in the high temperature range and the temperature of the first coolant CL1 is in the high temperature range. When the rotation speed of the crankshaft 21 decreases in this state, the temperature of the first coolant CL1 may drop and reach the second low temperature range while the temperature of the coolant detected by the temperature sensor 38 remains in the high temperature range. Since the temperature detection section 42c1 of the movable valve body 42c detects the temperature of the first coolant CL1, the movable valve body 42c moves from the high temperature position toward the second inlet 42b2. As a result, the first coolant CL1 in the second low temperature range and the second coolant CL2 in the high temperature range merge around the temperature detection section 42c1. The temperature of the merged coolant becomes the medium temperature range, which is higher than the second low temperature range and lower than the high temperature range. Therefore, since the temperature detection section 42c1 of the movable valve body 42c detects that the temperature of the coolant is in the medium temperature range, the movable valve body 42c is located at the medium temperature position shown in FIG. 9 . Therefore, the coolant circulates through the coolant path 41 in the direction of the arrow in FIG .

Assume that the temperature of the coolant detected by the temperature sensor 38 is in the medium temperature region, and the temperature of the first coolant CL1 is in the second low temperature region. In this state, if the rotation speed of the crankshaft 21 is further decreased, the temperature of the second coolant CL2 may become the medium temperature region, and the temperature of the first coolant CL1 may become the first low temperature region. In this case, the first coolant CL1 in the first low temperature region and the second coolant CL2 in the medium temperature region merge around the temperature detection unit 42c1. The temperature of the merged coolant is in the second low temperature region. Therefore, the movable valve body 42c moves to the low temperature position shown in FIG. 8. Therefore, the coolant circulates through the coolant path 41 along the direction of the arrow in FIG. 8 .

When the temperature of the coolant detected by the temperature sensor 38 is in the first low temperature region, the electric pump device 46 is stopped under the control of the ECU 75. Therefore, immediately after the engine unit 11A is started when the temperature of the coolant is low, the coolant does not circulate through the coolant path 41 by the electric pump device 46. Therefore, after the engine unit 11A is started, the temperature of the cylinder body 20C and the cylinder head 20D rises quickly, and the temperature of the lubricating oil flowing inside the engine body 20 rises quickly. When the temperature of the lubricating oil is high, the viscosity of the lubricating oil is low. The lower the viscosity of the lubricating oil, the lower the friction loss between the parts lubricated by the lubricating oil. When the friction loss is low, the fuel efficiency (fuel consumption rate) of the engine unit 11A is low. Therefore, in the specific example 9, the fuel efficiency of the engine unit 11A is improved when the engine unit 11A is started when the temperature of the coolant is low.

The switching valve 42 is configured so that the temperature detection section 42c1 can come into contact with the cooling liquid resulting from the merging of the first cooling liquid CL1 and the second cooling liquid CL2. This stabilizes the temperature of the cooling water that comes into contact with the temperature detection section 42c1. This makes it difficult for the movable valve body 42c to move back and forth between the low temperature position and the medium temperature position, or between the medium temperature position and the high temperature position, in a short period of time.

<Example 10 of the embodiment>
Next, a specific example 10 of the embodiment of the present invention described above will be described with reference to Fig. 11. In the following description, the same parts as those in the specific example 9 of the embodiment of the present invention described above will not be described. The specific example 10 of the embodiment of the present invention is included in the embodiment of the present invention described above.

Engine unit 11B of specific example 10 differs from engine unit 11A of specific example 9 in the arrangement of radiator 45 and electric pump device 46. The other configuration of engine unit 11B of specific example 10 is the same as engine unit 11A of specific example 9. Engine unit 11B of specific example 10 can be mounted on, for example, a scooter-type motorcycle.

The motor case 46A1 and pump case 46B1 of specific example 10 are substantially symmetrical to the motor case 46A1 and pump case 46B1 of specific example 9. The first flange 46A1b has a portion aligned with the right surface 20E1a of the head cover 20E in a direction parallel to the motor axis 46X. As in specific example 9, the first cylindrical portion 46A1a has a portion aligned with the inclined surface 20E3 of the head cover 20E in a direction parallel to a straight line perpendicular to both the cylinder axis 20X and the cam axis 31X. Furthermore, the portion of the first cylindrical portion 46A1a is aligned with the inclined surface 20E3 of the head cover 20E in a direction parallel to the cylinder axis 20X.

As in Specific Example 9, when viewed in a direction perpendicular to the motor axis 46X, the first flange 46A1b (large diameter portion), the second flange 46B1b, and the pump case 46B1 do not overlap with the head cover 20E. As in Specific Example 9, the electric pump device 46 intersects with a plane PL1 that is perpendicular to the cam axis 31X and includes the cylinder axis 20X. The plane PL1 intersects with the motor case 46A1 of the electric pump device 46.

Although not shown, as in specific example 9, when viewed in the direction of the cam axis 31X, the entire electric pump device 46 is spaced away from the cylinder axis 20X in the cylinder forward direction Fa. Although not shown, as in specific example 9, the entire internal exhaust path 20Db and the entire electric pump device 46 are located in one of two spaces separated by a plane (see plane PL2 in FIG. 7) that is parallel to the cam axis 31X and includes the cylinder axis 20X.

As with Example 9, when viewed in a direction perpendicular to the motor axis 46X, a portion of the first flange 46A1b and a portion of the second flange 46B1b are located between the right surface 20E1a of the head cover 20E and a portion of the fourth tube 48.

When viewed in the front-to-rear direction, the radiator 45 of Example 10 does not overlap with the cylinder axis 20X. The entire radiator 45 and the entire pump mechanism 46B2 are located in one of two spaces separated by a plane PL1 that is perpendicular to the cam axis 31X and includes the cylinder axis 20X. The radiator 45 and the pump mechanism 46B2 are located in the space to the right of the plane PL1.

<Example 11 of the embodiment>
Next, the above-mentioned specific example 11 of the embodiment of the present invention will be described with reference to Fig. 12. In the following description, the same parts as those in the above-mentioned specific example 9 of the embodiment of the present invention will not be described. The above-mentioned specific example 11 of the embodiment of the present invention is included in the above-mentioned embodiment of the present invention.

As shown in FIG. 12, the engine unit 11C of the specific example 11 differs from the engine unit 11A of the specific example 9 in the shape of the head cover 20E and the arrangement of the electric pump device 46. Note that the third tube 47 and the fourth tube 48 are omitted from FIG. 12. Also, the variable valve timing mechanism 35 is omitted from FIG. 12.

The outer surface of the head cover 20E of the eleventh example has an inclined surface 20E4. The inclined surface 20E4 connects the end of the top surface 20E2a in the cylinder right direction R to the end of the right surface 20E1a in the cylinder upward direction Ua. The inclined surface 20E4 is inclined with respect to a straight line parallel to the cylinder axis 20X. The inclined surface 20E4 is inclined with respect to a straight line parallel to the cam axis 31X. The base 20F fixed to the mounting portion 46A1c of the electric pump device 46 is connected to the right end of the top surface 20E2a.

The electric pump device 46 of Example 11 is arranged so that the motor axis 46X is parallel to a straight line perpendicular to both the cam axis 31X and the cylinder axis 20X.

The first flange 46A1b of the electric pump device 46 has a portion aligned with the rear surface 20E2c of the head cover 20E in a direction parallel to the motor axis 46X. The motor axis 46X is parallel to a straight line perpendicular to both the cam axis 31X and the cylinder axis 20X. The first cylindrical portion 46A1a has a portion aligned with the inclined surface 20E4 of the head cover 20E in a direction parallel to the cam axis 31X. Furthermore, the portion of the first cylindrical portion 46A1a is aligned with the inclined surface 20E4 of the head cover 20E in a direction parallel to the cylinder axis 20X. The portion of the first cylindrical portion 46A1a corresponds to the first portion of the present invention, and the portion of the first flange 46A1b corresponds to the second portion of the present invention. The direction parallel to the cylinder axis 20X corresponds to the first direction of the present invention, and the direction parallel to the cam axis 31X also corresponds to the first direction of the present invention. The first flange 46A1b corresponds to the large diameter portion of the present invention, and at least a part of the first cylindrical portion 46A1a corresponds to the small diameter portion of the present invention. Also, the above-mentioned portion of the first cylindrical portion 46A1a corresponds to the third portion of the present invention.

Although not shown in the figure, when viewed in the direction of the cam axis 31X (i.e., when viewed in a direction perpendicular to both the motor axis 46X and the cylinder axis 20X), the first flange 46A1b (large diameter portion), the second flange 46B1b, and the pump case 46B1 do not overlap with the head cover 20E.

Although not shown in the figure, the electric pump device 46 is perpendicular to the cam axis 31X and does not intersect with a plane that includes the cylinder axis 20X. When viewed in the direction of the cam axis 31X, the electric pump device 46 intersects with the cylinder axis 20X.

When viewed in a direction perpendicular to the motor axis 46X, a portion of the first flange 46A1b and a portion of the second flange 46B1b may be located between the rear surface 20E2c of the head cover 20E and a portion of the fourth tube 48.

<Example of change>
Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment and its specific examples, and various modifications are possible within the scope of the claims. Modifications of the embodiment of the present invention will be described below.

In the present invention, the shortest distance from the spark plug to the motor case may be the same as or longer than the shortest distance from the spark plug to the pump case.

In the present invention, the shortest distance from the actuator of the variable valve timing mechanism to the motor case may be the same as or longer than the shortest distance from the actuator of the variable valve timing mechanism to the pump case.

In specific examples 9 and 10, when viewed in the direction of the cam axis 31X, the entire electric pump device 46 is spaced from the cylinder axis 20X in the cylinder forward direction Fa. However, in the present invention, when viewed in the direction of the cam axis, the entire electric pump device may be spaced from the cylinder axis in the cylinder rear direction.

In specific example 11, the radiator 45 and the pump mechanism 46B2 are located in a space to the right of the plane PL1. In the present invention, the radiator and the pump mechanism may be located in the left space in the left-right direction of the vehicle on which the single-cylinder engine unit is mounted, of the two spaces separated by a plane that is perpendicular to the cam axis and includes the cylinder axis.

In the present invention, the entire exhaust port may be located in the first of two spaces separated by a plane that is parallel to the cam axis and includes the cylinder axis, and at least a portion of the electric pump device may be located in the second of the two spaces.

In the present invention, at least a part of the radiator may be located in a first space of two spaces separated by a plane that is perpendicular to the cam axis and includes the cylinder axis, and at least a part of the pump mechanism may be located in a second space of the two spaces.

In the present invention, the motor case may be supported on the head cover via the pump case.

In the present invention, the motor axis may be oblique to the cam axis. For example, the motor axis may be parallel to a line perpendicular to the cam axis, and may not be parallel to the cylinder axis. For example, the motor axis may be parallel to a line perpendicular to the cylinder axis, and may not be parallel to the cam axis. For example, the motor axis may not be parallel to a line perpendicular to the cam axis, and may not be parallel to a line perpendicular to the cylinder axis.

In the present invention, when viewed in a direction perpendicular to the motor axis, a portion of the first flange and a portion of the second flange do not have to be located between the external coolant path connected to the second cylindrical portion and the head cover. In the present invention, when viewed in a direction perpendicular to the motor axis, the large diameter portion may overlap the head cover.

In the present invention, the large diameter portion of the electric pump device may not be either the first flange or the second flange. In the present invention, the small diameter portion of the present invention may not be included in either the first cylindrical portion or the second cylindrical portion.

In the present invention, when the electric pump device has a first portion aligned with the head cover in a first direction parallel to either the cam axis or the cylinder axis, and a second portion different from the first portion aligned with the head cover in a second direction perpendicular to the first direction, the motor axis may be parallel to a straight line perpendicular to both the first and second directions. In other words, in the present invention, when the electric pump device has the first and second portions, the electric pump device does not need to have a large diameter portion aligned with the head cover in a direction parallel to the motor axis.

In the present invention, the coolant is preferably supplied to the electric pump device from inside the engine body through a path located outside the engine body. In the present invention, the coolant may be supplied to the electric pump device from inside the engine body without passing through a path located outside the engine body.

The valve drive mechanism of the single cylinder engine unit of the present invention may be of the DOHC (Double Over Head Camshaft) type. In this case, the single cylinder engine unit of the present invention may have a variable valve timing mechanism having an electric or electromagnetic actuator. The valve drive mechanism of the single cylinder engine unit of the present invention may be of the OHV (Over Head Valve) type in which a camshaft is disposed in the cylinder body. In this case, the single cylinder engine unit of the present invention may have a variable valve timing mechanism having an electric or electromagnetic actuator. The single cylinder engine unit of the present invention may not have a variable valve timing mechanism having an electric or electromagnetic actuator.

The single-cylinder 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 single-cylinder engine unit of the present invention may not have a spark plug. The single-cylinder engine unit of the present invention may be a two-stroke engine unit. The engine unit of the present invention may be a supercharged engine equipped with a supercharger. The supercharger is a device that compresses air supplied to the combustion chamber. The supercharger may be a mechanical supercharger or an exhaust turbine supercharger (so-called turbocharger).

When the single-cylinder engine unit of the present invention is mounted on a vehicle, the cam axis is not limited to being parallel to the left-right direction of the vehicle. For example, the cam axis may be parallel to the front-rear direction of the vehicle.
When the single-cylinder engine unit of the present invention is mounted on a vehicle, the direction of the cylinder axis is not limited to the directions of specific examples 9 to 11. When the single-cylinder 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 single-cylinder 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° and less than or equal to 90°.

The vehicle on which the single-cylinder engine unit of the present invention is mounted is not limited to a motorcycle. The single-cylinder engine unit of the present invention may be mounted on a saddle-type vehicle other than a motorcycle. A saddle-type vehicle refers to any vehicle on which a rider rides while straddling a saddle. Examples of saddle-type vehicles on which the single-cylinder engine unit of the present invention is mounted include motorcycles, three-wheeled vehicles, four-wheeled buggies (ATV: All Terrain Vehicle), jet skis, snowmobiles, etc. Examples of motorcycles include scooter types, off-road types, moped types, etc. The single-cylinder engine unit of the present invention may be mounted on a vehicle other than a saddle-type vehicle. For example, the single-cylinder engine unit of the present invention may be mounted on a four-wheeled vehicle (automobile) or a ship that is not a saddle-type vehicle. The vehicle on which the single-cylinder engine unit of the present invention is mounted may be a hybrid vehicle having a single-cylinder engine unit and an electric motor as a driving source. The single-cylinder engine unit of the present invention may also be mounted on a device other than a vehicle.

1. Motorcycles (vehicles)
11, 11A, 11B, 11C Single cylinder engine unit 20 Engine body 20B Crankcase 20C Cylinder body 20Ca Cylinder bore 20D Cylinder head 20D1 Inlet 20D2 Outlet 20E Head cover 20X Cylinder axis 20Da Internal intake path 20Db Internal exhaust path 22 Piston 24 Combustion chamber 24a Intake port 24b Exhaust port 25 Intake valve 26 Exhaust valve 27 Spark plug 31 Camshaft 31X Cam axis 35 Variable valve timing mechanism 36 Actuator 38 Temperature sensor 41 Cooling liquid path 42 Switching valve 42a1 Internal space 42b1 First inlet 42b2 Second inlet 42b3 First outlet 42b4 Second outlet 42c Movable valve body 45 Radiator 46 Electric pump device 46A1 Motor case 46A1a First cylindrical portion (small diameter portion)
46A1b First flange (large diameter portion)
46A2 Electric motor 46X Motor axis 46B1 Pump case 46B1a Second cylindrical portion 46B1b Second flange 46B2 Pump mechanism 48 Fourth tube (external coolant path)
75 ECU (control unit)

Claims (13)

A cylinder body that is a part of an engine body and has only one cylinder bore;
a cylinder head that is a part of the engine body and is connected to an end of the cylinder body in a direction of a cylinder axis that is a central axis of the cylinder bore;
a head cover connected to an end of the cylinder head in a direction of the cylinder axis and located at an end of the engine body in a direction of the cylinder axis;
a coolant passage, a portion of which is formed inside the engine body, through which a coolant circulates;
a camshaft supported by the cylinder head and rotating about a cam axis perpendicular to a line parallel to the cylinder axis;
an electric pump device having an electric motor for pumping the cooling liquid flowing through the cooling liquid path;
Equipped with
At least a portion of the electric pump device is located outside the engine body,
the electric pump device is supported by the head cover such that a motor axis, which is a rotational center axis of an output shaft of the electric motor, is not coaxial with the cam axis,
a part of the cooling liquid path is formed by a piping member connected to the electric pump device,
The electric pump device is
a first portion that does not include the piping member and is aligned with the head cover in a first direction that is parallel to either the cam axis or the cylinder axis;
a second portion that does not include the piping member, is different from the first portion, and is aligned with the head cover in a second direction perpendicular to the first direction;
A single cylinder engine unit comprising: The single cylinder engine unit according to claim 1, characterized in that the first direction is parallel to the cylinder axis. The electric pump device is
A small diameter portion;
a large diameter portion arranged next to the small diameter portion in the direction of the motor axis and having a maximum radial dimension about the motor axis that is greater than a maximum radial dimension about the motor axis of the small diameter portion;
having
The motor axis is parallel to the cam axis or perpendicular to a straight line parallel to the cam axis,
A part of the large diameter portion is aligned with the head cover in a direction parallel to the motor axis, and the first portion or the second portion is
3. The single-cylinder engine unit according to claim 1, characterized in that at least a portion of the small diameter portion is aligned with the head cover in a direction perpendicular to the motor axis, and the portion of the large diameter portion is the second portion when the portion of the large diameter portion is the first portion, and the portion of the large diameter portion is the first portion when the portion of the large diameter portion is the second portion. The single-cylinder engine unit according to claim 3, characterized in that the large diameter portion does not overlap the head cover when viewed in a direction perpendicular to the motor axis. The electric pump device is
a first cylindrical portion in which the electric motor is housed;
a second cylindrical portion that accommodates at least a part of a pump mechanism that pressurizes and discharges the supplied cooling liquid;
A first flange connected to an end of the first cylindrical portion;
a second flange connected to an end of the second tubular portion and fixed to the first flange in a state of contact with the first flange;
having
The first flange or the second flange is the large diameter portion,
5. The single-cylinder engine unit according to claim 3, wherein at least a part of the first cylindrical portion or at least a part of the second cylindrical portion is the small diameter portion. the coolant passage includes an external coolant passage located outside the engine body and connected to the second cylindrical portion,
6. The single-cylinder engine unit according to claim 5, wherein when viewed in a direction perpendicular to the motor axis, a portion of the first flange and a portion of the second flange are located between the head cover and a portion of the external coolant path. A cylinder body that is a part of an engine body and has only one cylinder bore;
a cylinder head that is a part of the engine body and is connected to an end of the cylinder body in a direction of a cylinder axis that is a central axis of the cylinder bore;
a head cover connected to an end of the cylinder head in a direction of the cylinder axis and located at an end of the engine body in a direction of the cylinder axis;
a coolant passage, a portion of which is formed inside the engine body, through which a coolant circulates;
a camshaft supported by the cylinder head and rotating about a cam axis perpendicular to a line parallel to the cylinder axis;
an electric pump device having an electric motor for pumping the cooling liquid flowing through the cooling liquid path;
Equipped with
At least a portion of the electric pump device is located outside the engine body,
the electric pump device is supported by the head cover such that a motor axis, which is a rotational center axis of an output shaft of the electric motor, is not coaxial with the cam axis,
2. A single-cylinder engine unit, comprising: a cylinder axis; a cylinder head; and a pump unit for receiving the pump; The engine body has a combustion chamber in which an exhaust port and an intake port are formed,
8. The single-cylinder engine unit according to claim 7, wherein the exhaust port and the electric pump device are entirely located in one of two spaces defined by a plane that is parallel to the cam axis and includes the cylinder axis. A single-cylinder engine unit mounted on a vehicle,
A cylinder body that is a part of an engine body and has only one cylinder bore;
a cylinder head that is a part of the engine body and is connected to an end of the cylinder body in a direction of a cylinder axis that is a central axis of the cylinder bore;
a head cover connected to an end of the cylinder head in a direction of the cylinder axis and located at an end of the engine body in a direction of the cylinder axis;
a coolant passage, a portion of which is formed inside the engine body, through which a coolant circulates;
a camshaft supported by the cylinder head and rotating about a cam axis perpendicular to a line parallel to the cylinder axis;
an electric pump device having an electric motor for pumping the cooling liquid flowing through the cooling liquid path;
a temperature sensor for detecting a temperature of the cooling liquid flowing through the cooling liquid path;
A control device for controlling the electric pump device;
Equipped with
At least a portion of the electric pump device is located outside the engine body,
the electric pump device is supported by the head cover such that a motor axis, which is a rotational center axis of an output shaft of the electric motor, is not coaxial with the cam axis,
The cooling fluid path is
an inlet formed on an outer surface of the engine body through which a coolant passes when moving from the outside of the engine body to the inside of the engine body;
an outlet formed on an outer surface of the engine body, through which the coolant passes when moving from inside the engine body to outside the engine body, and which is located above the inlet in the vertical direction of the vehicle ;
having
In the cooling liquid path, a distance between the temperature sensor and the outlet is shorter than a distance between the temperature sensor and the inlet,
the control device stops the electric pump device when the temperature of the coolant detected by the temperature sensor is in a first low temperature region;
a switching valve that forms a part of the coolant path, that is located outside the engine body, and that is located downstream of the outlet in a flow direction of the coolant;
a radiator located outside the engine body, forming a part of the coolant passage, and disposed in a position in the coolant passage other than between the switching valve and the inlet;
Equipped with
the electric pump device is located downstream of the switching valve and upstream of the inlet in a flow direction of the coolant,
The switching valve,
An internal space that is a part of the cooling liquid path;
a movable valve body disposed in the internal space and moving in response to a temperature of the cooling liquid in the internal space;
a first inlet through which the coolant that has flowed out of the outlet and has not passed through the radiator passes when entering the interior space;
a first outlet through which the coolant flowing from the internal space toward the radiator passes when exiting the internal space;
a second inlet through which the coolant flows after flowing out of the first outlet and passing through the radiator before entering the internal space;
a second outlet through which the coolant flowing from the internal space toward the electric pump device exits the internal space;
having
when the temperature of the cooling liquid in the internal space is in a second low temperature region that is higher than the first low temperature region, the movable valve body is positioned at a low temperature position that allows the cooling liquid that has flowed into the internal space from the first inlet to flow to the second outlet, prevents the cooling liquid that has flowed into the internal space from the first inlet from flowing to the first outlet, and prevents the cooling liquid from flowing into the internal space from the second inlet,
when the temperature of the cooling liquid in the internal space is in an intermediate temperature region higher than the second low temperature region, the movable valve body is located at an intermediate temperature position which allows the cooling liquid that has flowed into the internal space from the first inlet to flow to the first outlet and the second outlet, allows the cooling liquid that has flowed into the internal space from the second inlet to flow to the second outlet, and prevents the cooling liquid that has flowed into the internal space from the second inlet from flowing to the first outlet,
when the temperature of the cooling liquid in the internal space is in a high temperature region higher than the intermediate temperature region, the movable valve body is positioned at a high temperature position which allows the cooling liquid that has flowed into the internal space from the first inlet to flow to the first outlet, prevents the cooling liquid that has flowed into the internal space from the first inlet from flowing to the second outlet, and allows the cooling liquid that has flowed into the internal space from the second inlet to flow to the second outlet,
The control device operates the electric pump device when the temperature of the coolant detected by the temperature sensor is in the second low temperature region, the medium temperature region, or the high temperature region. A single-cylinder engine unit according to any one of claims 1 to 9, characterized in that the motor axis is parallel to the cam axis, parallel to the cylinder axis, or parallel to a straight line perpendicular to both the cam axis and the cylinder axis. The motor axis is parallel to a straight line perpendicular to the cylinder axis,
The single-cylinder engine unit according to any one of claims 1 to 10, characterized in that the electric pump device has a third portion that is aligned with the head cover in a direction parallel to the cylinder axis and is aligned with the head cover in a direction parallel to a straight line perpendicular to the cylinder axis. The electric pump device is
a motor case in which the electric motor is housed;
a pump case that accommodates at least a part of a pump mechanism that pressurizes and discharges a supplied cooling liquid;
having
12. The single-cylinder engine unit according to claim 1, wherein the pump case is supported by the head cover via the motor case. A single-cylinder engine unit as described in any one of claims 1 to 12, characterized in that the electric pump device is perpendicular to the cam axis and intersects with a plane including the cylinder axis.

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