CN110397487A

CN110397487A - Engine

Info

Publication number: CN110397487A
Application number: CN201910327572.3A
Authority: CN
Inventors: 大场久绘
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2018-04-25
Filing date: 2019-04-23
Publication date: 2019-11-01
Also published as: JP2019190369A; US20190331007A1

Abstract

The present invention relates to a kind of engine, which includes: cylinder head；Cam shell is fastened in the cylinder head；Camshaft is rotatably supported by the cam shell and is supplied with lubricating oil；With the housing being fastened on the cam shell, wherein the cam shell includes the side wall extended along the camshaft, and the inner surface of the side wall includes the sunk area on gravity direction to lower recess.

Description

Engine

Technical Field

The present invention relates to an engine.

Background

An engine is known in which oil for lubrication is supplied to a sliding portion such as a camshaft (see, for example, japanese patent application laid-open No. 2012 and 167647).

In some cases, an engine includes a cylinder head, a cam housing secured to the cylinder head, and a head cover covering an upper side of the cam housing. These members are fastened via a seal member that inhibits oil leakage from the engine. Here, the temperature of the cylinder head is relatively high due to the combustion of the fuel. However, since the cam housing is spaced apart from the combustion chamber, the temperature of the cam housing is lower than that of the cylinder head. This results in a temperature difference between the cylinder head and the cam housing. In particular, when the engine is switched from the low load state to the high load state in a short time, the temperature difference increases. This temperature difference may cause an increase in the difference in thermal expansion between the cylinder head and the cam housing, which may cause oil leakage between the cylinder head and the cam housing.

Disclosure of Invention

Accordingly, an object of the present invention is to provide an engine in which oil leakage is suppressed.

An object of the present invention is to provide an engine, including: a cylinder head; a cam housing fastened to the cylinder head; a camshaft rotatably supported by the cam housing and supplied with lubricating oil; and a cover fastened to the cam housing, wherein the cam housing includes a side wall extending along the camshaft, and an inner side surface of the side wall includes a depressed region depressed downward in a gravity direction.

The lubricating oil supplied to the camshaft is warmed up by combustion of the engine, and splashes against the inside surface of the side wall of the cam housing in response to rotation of the camshaft. Since the inside surface of the side wall includes the depressed region depressed downward in the gravity direction, the oil is retained in the depressed region. This transfers the heat of the oil to the cam housing, promoting heat exchange between the oil and the cam housing. This increases the temperature of the cam housing, suppresses an increase in the temperature difference between the cam housing and the cylinder head, and also suppresses an increase in the difference in thermal expansion between the cam housing and the cylinder head. Oil leakage between the cylinder head and the cam housing can be suppressed.

The cylinder head may include a first sealing surface that cooperates with the side wall to sandwich a first sealing member, the side wall may include a second sealing surface that cooperates with the head cover to sandwich a second sealing member, and the recessed region may be disposed at a position closer to the first sealing surface than the second sealing surface.

The inner side surface of the side wall may include an upper region continuing from the depressed region to an upper side in a gravity direction, and the upper region may be located outside the cam housing with respect to a line connecting an inner edge of the first seal surface and an inner edge of the second seal surface when viewed in a cross section perpendicular to a direction in which the camshaft extends.

The inner side surface of the side wall may smoothly continue from the upper region to the depressed region when viewed in a cross section perpendicular to a direction in which the camshaft extends.

The recessed region may extend along the camshaft.

The side wall may include a rib partially protruding inside the cam housing.

The sidewall may include: an intake sidewall on an intake side; and a discharge sidewall on a discharge side, and the rib may be provided on the discharge sidewall.

Effects of the invention

According to the present invention, an engine in which oil leakage is suppressed can be provided.

Drawings

Fig. 1 is an explanatory diagram of an engine.

FIG. 2A is a top view of the cam housing, and FIG. 2B is a top view of the cylinder head;

FIG. 3A is a front view of the cylinder head and cam housing, and FIG. 3B is a rear view of the chain cover;

FIG. 4A is a cross-sectional view taken along line A-A of FIG. 2A, and FIG. 4B is an enlarged view of a recessed area;

FIG. 5 is a cross-sectional view taken along line B-B of FIG. 2A; and

fig. 6A is a partial top view of a cam housing according to a variation, and fig. 6B is a cross-sectional view taken along line C-C of fig. 6.

Detailed Description

Fig. 1 is an explanatory diagram of the engine 1. Fig. 1 shows X, Y and the Z direction orthogonal to each other. In fig. 1, the Z direction is parallel to the direction of gravity, and the Y direction is parallel to the direction in which the crankshaft 15, the camshaft 53 on the intake side, and the camshaft 54 on the exhaust side extend. The engine 1 includes a cylinder block 10, a cylinder head 20, a cam housing 30, and a head cover 40. The cylinder head 20 is fastened on the upper side of the cylinder block 10. The cam housing 30 is fastened on the upper side of the cylinder head 20. The cover 40 is fastened on the upper side of the cam housing 30, and the upper side of the cam housing 30 is covered by the cover 40.

A plurality of cylinders 12 are provided in the cylinder block 10, and the cylinders 12 are arranged in the depth direction of fig. 1. A piston 11 is accommodated in each cylinder 12 movably up and down. When the piston 11 moves up and down, the crankshaft 15 rotates. The cylinder 12, the piston 11, and the cylinder head 20 define a combustion chamber CH, the volume of which is increased or decreased by the up-and-down movement of the piston 11. An oil pan 16 for storing lubricating oil is fastened to the lower portion of the cylinder block 10. The oil is supplied to each sliding portion in the engine 1 via an oil passage formed in the engine 1 by an oil pump, and then recovered to the oil pan 16.

With the cylinder head 20, a right side wall 23 and a left side wall 24, which are located on the right and left sides, respectively, in fig. 1, extend in the Y direction, which is the direction in which the cylinders 12 are arranged. The intake port 21 and the exhaust port 22 are opened on the outer side surface of the right side wall 23 and the outer side surface of the left side wall 24, respectively. An intake pipe 81 and an exhaust pipe 82 are fastened to the right and left side walls 23 and 24, respectively, to communicate with the intake port 21 and the exhaust port 22. Therefore, the intake pipe 81 and the exhaust pipe 82 communicate with the combustion chamber CH through the intake port 21 and the exhaust port 22, respectively. In addition, the cylinder head 20 holds intake and exhaust valves for opening and closing the intake and exhaust ports 21 and 22 in response to rotation of the intake-side and exhaust-side camshafts 53 and 54, respectively. The camshafts 53 and 54 are rotatably supported by the cam housing 30.

Fig. 2A is a top view of the cam housing 30. The cam housing 30 includes a right side wall 33, a left side wall 34, a rear side wall 35, and a plurality of support walls 37. The rear side wall 35 extends continuously to the right side wall 33 and the left side wall 34 in the X direction, and is located at an end of the cam housing 30 in the-Y direction. A plurality of support walls 37, each extending in the X direction, are supported between the right side wall 33 and the left side wall 34 that face each other. The support wall 37 rotatably supports the camshafts 53 and 54 so as to be spaced apart at predetermined intervals in the X direction. An intake cam 53c and an exhaust cam 54c for driving an intake valve and an exhaust valve of each cylinder, respectively, are formed in the camshafts 53 and 54.

A sprocket 55 on the intake side and a sprocket 56 on the exhaust side are connected to the ends of the camshafts 53 and 54 in the + Y direction, respectively. A timing chain 65 for interlocking/linking the crankshaft 15 with the sprockets 55 and 56 is wound around the sprockets 55 and 56. As a result, when the crankshaft 15 rotates, the sprockets 55 and 56 also rotate via the timing chain 65. A chain cover 60 for housing a timing chain 65 is fastened on the cam housing 30 and the end of the cylinder head 20 in the + Y direction. Additionally, the illustration of chain cover 60 is simplified.

The lubricating oil stored in the oil pan 16 is supplied to the camshafts 53 and 54 via a plurality of paths. For example, oil is supplied between the camshafts 53 and 54 and the journal bearings via oil passages formed in the camshafts 53 and 54. Journal bearings are provided in the support wall 37 and hold the camshafts 53 and 54 in rotation. Further, oil is supplied from the cam shower to the intake cam 53c and the exhaust cam 54 c.

Sealing surfaces 33s, 34s, and 35s are formed on upper portions of the right, left, and rear side walls 33, 34, and 35, respectively. The sealing surfaces 33s, 34s, and 35s are continuous with each other and substantially parallel to the XY plane. Fig. 2A shows the seal member CL3 on the seal surfaces 33s, 34s, and 35 s. The sealing member CL3 is a gasket made of rubber having oil resistance, particularly acrylic rubber, but is not limited thereto, and may be a liquid gasket described later. On the seal surfaces 33s, 34s, and 35s, a plurality of bolt holes, not denoted with reference numerals, are formed for respective bolts for fastening the cam housing 30 to the head cover 40 to be inserted thereinto. The seal member CL3 is located outside the plurality of bolt holes.

The cam housing 30 and the head cover 40 are fastened to each other in a state where the seal member CL3 is sandwiched between the seal surfaces 33s, 34s, and 35s and the seal surface of the head cover 40. This suppresses the generation of a gap between the cam housing 30 and the head cover 40. The sealing surfaces 33s, 34s, and 35s are one example of second sealing surfaces that sandwich the sealing member CL3 in cooperation with the head cover 40. Further, as will be described later in detail, sealing surfaces 37s and 38s substantially parallel to the YZ plane are formed on the right and left side walls 33 and 34, respectively, in the vicinity of the chain cover 60. Further, the inner side surface of the right side wall 33 and the inner side surface of the left side wall 34 include recessed regions 330 and 340, respectively, which are described in detail later.

Fig. 2B is a plan view of the cylinder head 20. The cylinder head 20 includes a rear side wall 25 in addition to the above-described right side wall 23 and left side wall 24. The rear side wall 25 extends continuously to the right side wall 23 and the left side wall 24 in the X direction, and is located at an end of the cylinder head 20 in the-Y direction. The cylinder head 20 is provided in its portion surrounded by the right side wall 23, the left side wall 24, and the rear side wall 25 with a holding hole 210 that holds a corresponding ignition plug for a corresponding cylinder, a guide hole 211 that guides a corresponding intake valve, and a guide hole 212 that guides a corresponding exhaust valve. Sealing surfaces 23s, 24s, and 25s are formed on upper portions of the right, left, and rear side walls 23, 24, and 25, respectively. The sealing surfaces 23s, 24s and 25s are continuous with each other and substantially parallel to the XY plane.

Fig. 2B shows the seal member CL2 on the seal surfaces 23s, 24s, and 25 s. The seal member CL2 is made of rubber having oil resistance, and is a form-in-place gasket (FIPG). The FIPG in a liquid state is applied to the sealing surfaces 23s, 24s, and 25s of the cylinder head 20 before the cam housing 30 is fastened, and then hardened by heating or absorbing moisture in the air, thereby becoming an elastomer. Thus, FIPG is a liquid cushion. In addition, the sealing member CL2 is not limited thereto, and may be a gasket made of acrylic rubber or the like as described above. On the seal surfaces 23s, 24s, and 25s, a plurality of bolt holes, not denoted by reference numerals, are formed therein for bolts for fastening the cam housing 30 to the cylinder head 20. The seal member CL2 is located outside the plurality of bolt holes. The cylinder head 20 and the cam housing 30 are fastened to each other in a state where the seal members CL2 are sandwiched between the seal surfaces 23s, 24s, and 25s and the seal surface of the cam housing 30 in the-Z direction. This suppresses the formation of a gap between the cylinder head 20 and the cam housing 30. The seal surfaces 23s, 24s, and 25s are examples of first seal surfaces that cooperate with the right side wall 33, the left side wall 34, and the rear side wall 35 to sandwich the seal member CL 2. As will be described later, sealing surfaces 27s and 28s substantially parallel to the YZ plane are formed on the right and left side walls 23 and 24, respectively, near the chain cover 60.

Fig. 3A is a front view of the cylinder head 20 and the cam housing 30. Fig. 3A shows a lower side wall 29 of the cylinder head 20, which extends in the X direction between the right side wall 23 and the left side wall 24. The sealing surface 29s of the lower side wall 29 in the + Y direction is continuous with the above-described sealing surfaces 27s and 28 s. The sealing surfaces 27s, 28s and 29s are substantially parallel to the XZ plane. In a state where the cylinder head 20 and the cam housing 30 are fastened to each other, the sealing surfaces 27s and 28s of the cylinder head 20 and the sealing surfaces 37s and 38s of the cam housing 30 are continuous with each other, and these sealing surfaces 27s, 28s, 29s, 37s, and 38s are substantially parallel in the XZ plane. Fig. 3A shows the seal member CL5 on the seal surfaces 27s, 28s, 29s, 37s, and 38 s. The sealing member CL5 is the same as the sealing member CL2 described above, but is not limited thereto.

Fig. 3B is a rear view of chain cover 60. Fig. 3B shows a portion of chain cover 60 when viewed in the + Y direction. Chain cover 60 includes sealing surfaces 68s that cooperate with sealing surfaces 27s, 28s, 29s, 37s, and 38s to sandwich sealing member CL 5. On the sealing surfaces 27s, 28s, 29s, 37s, and 38s and the sealing surface 68s, a plurality of bolt holes, to which no reference numeral is given, are formed for insertion of bolts for fastening the chain cover 60 to the cylinder head 20 and the cam housing 30. The seal member CL5 is located outside the plurality of bolt holes. The chain cover 60 is fastened to the cylinder head 20 and the cam housing 30 in a state where the seal member CL5 is sandwiched between the seal surfaces 27s, 28s, 29s, 37s, and 38s and the seal surface 68 s. This suppresses the generation of a gap between the chain cover 60 and the cylinder head 20 and the cam housing 30.

As described above, the gap between cylinder head 20 and cam housing 30, the gap between cam housing 30 and head cover 40, and the gap between chain cover 60 and cylinder head 20 and cam housing 30 are sealed. Therefore, for example, the lubricating oil supplied to the camshafts 53 and 54 is prevented from leaking to the outside.

Next, the right side wall 33 of the cam housing 30 shown in fig. 2A will be described. Fig. 4A is a sectional view taken along line a-a of fig. 2A. The cross section is perpendicular to the direction in which the camshafts 53 and 54 extend. Right sidewall 33 includes a recessed region 330, a curved region 331, and a linear region 332. The curved region 331 continues from the depressed region 330 to the upper side in the direction of gravity. The linear region 332 extends from the curved region 331 to the upper side in the direction of gravity. The curved region 331 and the linear region 332 are one example of an upper region extending from the recessed region 330 to the upper side in the direction of gravity. Both the recessed region 330 and the curved region 331 are curved and have substantially the same radius of curvature. The inner side surface of the right sidewall 33 is curved so as to be gradually close to vertical from the concave area 330 to the curved area 331. The linear region 332 is slightly inclined with respect to the direction of gravity in cross section, but extends substantially linearly.

The recessed region 330 is recessed downward in the direction of gravity. Fig. 4B is an enlarged view of the recessed region 330. Fig. 4B shows a horizontal line segment HL parallel to the X direction. Here, the lubricating oil supplied to the camshafts 53 and 54 is splashed by the rotation of the camshafts 53 and 54. At least a part of the splashed oil adheres to the linear region 332 and the curved region 331 of the inner side surface of the right sidewall 33, then flows downward in the gravity direction, and is held in the recessed region 330. This ensures that the oil comes into contact with the right sidewall 33 until the time when the oil overflows from the depressed area 330. The newly splashed oil is always held in the depressed area 330.

Here, the camshafts 53 and 54 are supplied with oil from a plurality of paths, and the oil is warmed up by combustion in the engine 1 while flowing through these paths. Accordingly, such high temperature oil held in the depressed region 330 transfers heat from the oil to the right side wall 33 of the cam housing 30, thereby promoting heat exchange between the oil and the cam housing 30. Further, the recessed region 330 is formed to extend in the X direction in which the camshafts 53 and 54 extend. This ensures a contact area between the oil and the inner side surface of the right sidewall 33 of the cam housing 30, promoting heat exchange between the oil and the cam housing 30. In addition, fig. 4A shows splashed oil.

In this way, heat exchange between the high-temperature oil and the cam housing 30 is promoted, whereby the temperature of the cam housing 30 rises. This suppresses an increase in the temperature difference between the cylinder head 20 and the cam housing 30, and suppresses an increase in the difference in thermal expansion between the cylinder head 20 and the cam housing 30 due to the temperature difference. Here, if the difference in thermal expansion between the cylinder head 20 and the cam housing 30 increases, the sealing surfaces 23s, 24s, and 25s of the cylinder head 20 may be positionally offset relative to the sealing surface of the cam housing 30 opposite thereto. As a result, the seal member CL2 interposed between the seal surfaces may be damaged, and then oil may leak between the cylinder head 20 and the cam housing 30. In the present embodiment, an increase in the difference in thermal expansion is suppressed as described above, so that such oil leakage is suppressed.

Further, as shown in fig. 4A, the recessed region 330 is formed at a position closer to the sealing surface 23s than the sealing surface 33s (a position closer to the sealing surface 23s than the sealing surface 33 s). Therefore, it is possible to raise the temperature of the sealing surface 23s of the cylinder head 20 and the cam housing 30 around the sealing surface of the cam housing 30, which face each other and may become a leak oil gap. This appropriately suppresses oil leakage.

Incidentally, unlike the sealing surface of the cam housing 30 that faces the sealing surface 23s of the cylinder head 20, the peripheries of the sealing surface 33s of the cam housing 30 and the sealing surface of the head cover 40 that face each other are away from the cylinder head 20. Therefore, in this periphery, the temperature difference and the difference in thermal expansion between the cam housing 30 and the head cover 40 hardly increase, and oil leakage hardly occurs. Therefore, in the present embodiment, the recessed region 330 is formed in the periphery of the sealing surface 23s of the cylinder head 20 in which oil leakage is likely to occur.

Fig. 4A shows a line segment CL connecting between the inner edge of the sealing surface 23s and the inner edge of the sealing surface 33 s. The curved region 331 and the linear region 332 are located outside the cam housing 30 with respect to the line segment CL. In other words, the curved region 331 and the linear region 332 protrude from the line segment CL to the outside of the cam housing 30. Therefore, the length of the inner side surface of the right side wall 33 is ensured, compared to the case where the side wall has a straight shape along the line segment CL in the sectional view. Here, as described above, the oil splashes the bending region 331 and the linear region 332 and then flows toward the depressed region 330. Since the length of the inner surface of the right sidewall 33 is ensured, the time for which the oil is in contact with the curved region 331 and the linear region 332 is ensured. Therefore, even if this configuration is adopted, heat exchange between the oil and the right side wall 33 of the cam housing 30 is promoted. In addition, as with the recessed region 330, the curved region 331 and the linear region 332 also extend along the camshaft 53.

As shown in FIG. 4A, linear region 332 smoothly continues to recessed region 330 via curved region 331. Therefore, the oil adhered to the linear region 332 and the curved region 331 rapidly flows to the depressed region 330. Therefore, the oil is held in the depressed region 330 before a large amount of heat is absorbed to the linear region 332 and the curved region 331 of the right sidewall 33, and thus a large amount of heat of the oil is transferred to the depressed region 330. This makes it possible to increase the temperature of the sealing surface 23s of the cylinder head 20 and the cam housing 30 around the sealing surface of the cam housing 30 which face each other. This appropriately suppresses oil leakage.

Further, as shown in fig. 4A, the inclination angle of the linear region 332 located above the recessed region 330 in the direction of gravity is steeper than the inclination angle at any point on the recessed region 330. In other words, the linear region 332 is inclined at an angle of approximately 90 degrees with respect to the horizontal direction. Therefore, the oil attached to the linear region 332 rapidly flows to the depressed region 330. This also appropriately suppresses oil leakage.

Fig. 5 is a sectional view taken along line B-B of fig. 2A. The left side wall 34 is substantially symmetrical to the right side wall 33 about the YZ plane. Therefore, as with the right side wall 33, the inner side surface of the left side wall 34 also includes a recessed region 340, a curved region 341, and a linear region 342. This promotes heat exchange between the oil and the left side wall 34 of the cam housing 30, and also suppresses oil leakage between the sealing surface 24s of the cylinder head 20 and the sealing surface of the left side wall 34 of the cam housing 30.

As described above, an increase in the difference in thermal expansion between the cylinder head 20 and the cam housing 30 due to the temperature difference therebetween is suppressed, which also suppresses oil leakage between the sealing surfaces 37s and 38s of the cam housing 30 and the sealing surface 68s of the chain cover 60. In addition, the heat exchange between the oil and the cam housing 30 suppresses an excessive increase in the oil temperature. This suppresses the deterioration of the oil and lowers its lubricity due to an excessive decrease in its viscosity.

Further, the surface areas of the respective inner side surfaces of the right side wall 33 and the left side wall 34 are ensured, which also ensures the areas of the surfaces contacted by the blowby gas generated in the engine 1. Accordingly, the blowby gas comes into contact with the inner side surfaces of the right and left side walls 33, 34, which promotes separation of oil from the blowby gas. This suppresses an increase in oil consumption and generation of white smoke due to the introduction of blow-by gas into the intake system.

In the present embodiment, the rear side wall 35 is different from the right side wall 33 and the left side wall 34, but the rear side wall 35 may be similarly configured. With this configuration, heat exchange can be performed between substantially the entire cam housing 30 and the oil, which further suppresses an increase in the temperature difference between the cam housing 30 and the cylinder head 20.

In the present embodiment, the recessed region 330 is formed on substantially the entire region of the right sidewall 33 extending in the Y direction, but is not limited thereto. For example, the above-described recessed region 330 may be formed only in a part of the region of the right sidewall 33 extending in the Y direction. For example, such recessed area 330 may be formed at a location closer to chain cover 60 than rear sidewall 35. This raises the temperature of the right side wall 33 of the cam housing 30 near the chain cover 60, properly suppressing oil leakage between the cam housing 30 and the chain cover 60. The same applies to the recessed region 340 of the left sidewall 34.

Next, the cam housing 30a according to a modification will be described. Fig. 6A is a partial plan view of the cam housing 30a according to this modification. Fig. 6B is a sectional view taken along line C-C of fig. 6A. The cam housing 30a is formed with a rib 347 on the inner surface of the left side wall 34 a. The rib 347 extends downward along the inner side surface of the left side wall 34a in the gravity direction, and protrudes inside the cam housing 30 a. The ribs 347 are provided between the adjacent support walls 37. Providing the ribs 347 in this manner increases the area of the inside surface of the left side wall 34 a. That is, the amount of oil that can adhere to the inner side surface of the left side wall 34a is ensured. This promotes heat transfer from the oil to the left sidewall 34a, suppressing oil leakage.

In addition, providing the rib 347 in the left side wall 34a increases the volume of the left side wall 34a, which ensures rigidity thereof. Ensuring the rigidity of the left sidewall 34a on the exhaust side suppresses the vibration of the left sidewall 34a due to combustion in the engine. This suppresses vibration noise of the cover 40 due to vibration transmission from the left side wall 34a to the cover 40.

The position of the rib 347 is not limited to the position shown in fig. 6A, but may be provided at a position distant from the bolts used to fasten the cylinder head 20 and the cam housing 30 a. The reason for this is as follows: in the vicinity of the bolts, an increase in the difference in thermal expansion between the cylinder head 20 and the cam housing 30a is regulated to some extent by the fastening force of the bolts, and such a fastening force may not be sufficient at a position distant from the bolts. Therefore, providing the rib 347 at the position distant from the bolt ensures the surface area of the left side wall 34a of the cam housing 30a at the position distant from the bolt, which suppresses an increase in the difference in thermal expansion between the cylinder head 20 and the cam housing 30a at the position distant from the bolt.

A rib similar to the rib 347 may also be provided in the right side wall 33 on the intake side. This further suppresses oil leakage. Moreover, the vibration of the right side wall 33 can be suppressed. However, the provision of such ribs may lead to an increase in weight of the housing and deterioration in fuel consumption. Therefore, it is desirable to set the position, size, and number of the ribs in consideration of an increase in the weight of the case, an effect of suppressing oil leakage, an effect of reducing vibration, and the like. For example, vibrations caused by combustion of the engine tend to be transmitted to the left sidewall 34a on the exhaust side, as compared with the right sidewall 33 on the intake side. Therefore, in this modification, the rib 347 is provided only in the left side wall 34a in view of reducing the vibration of the left side wall 34a on the exhaust side while suppressing the increase in weight of the cam housing 30 a.

Although some embodiments of the present invention have been described in detail, the present invention is not limited to the specific embodiments, but may be changed or modified within the scope of the claimed invention.

In the above-described embodiment and modifications, the depressed region 330 smoothly continues to the curved region 331, but is not limited to this shape. For example, the recessed region may be formed in a groove shape on a substantially horizontal region of the inner surface of the side wall when viewed in a cross section perpendicular to a direction in which the camshaft extends. Further, the inner side surface of the side wall may be curved such that the inclination angle gradually approaches to the horizontal from the upper portion to the lower portion in the gravity direction, and the recessed region may be defined by a shape protruding upward from the inner edge of the curved region of the housing under the gravity so as to block the oil from flowing to the inside of the housing. In the above-described embodiments and modifications, the linear region 332 is formed to be substantially straight, but is not limited thereto, and may be formed in a curved shape.

Claims

1. An engine, comprising:

a cylinder head;

a cam housing fastened to the cylinder head;

a camshaft rotatably supported by the cam housing and supplied with lubricating oil; and

a cover secured to the cam housing,

wherein,

the cam housing includes a side wall extending along the cam shaft, and

the inside surface of the side wall includes a depressed region depressed downward in the direction of gravity.

2. The engine according to claim 1,

the cylinder head including a first sealing surface that cooperates with the sidewall to sandwich a first sealing member,

the side wall includes a second sealing surface that cooperates with the cover to sandwich a second sealing member, an

The recessed region is disposed at a position closer to the first sealing surface than the second sealing surface.

3. The engine according to claim 2,

the inner side surface of the side wall includes an upper region continuing from the depressed region to an upper side in the gravity direction, and

the upper region is located outside the cam housing with respect to a line connecting an inner edge of the first seal surface and an inner edge of the second seal surface when viewed in a cross section perpendicular to a direction in which the camshaft extends.

4. The engine according to claim 3,

the inner side surface of the side wall smoothly continues from the upper region to the depressed region when viewed in a cross section perpendicular to a direction in which the camshaft extends.

5. An engine according to any of claims 1 to 4, wherein the recessed region extends along the camshaft.

6. The engine of any of claims 1-5, wherein the side wall includes a rib that projects partially inside the cam housing.

7. The engine according to claim 6,

the side wall includes:

an intake sidewall on an intake side; and

an exhaust sidewall on the exhaust side, and

the ribs are disposed on the exhaust sidewall.