JP2017110579A - engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly secure the supporting rigidity of a supporting member while reducing the total length of a cylinder head.SOLUTION: A cylinder head 2 where an intake camshaft 5A and an exhaust camshaft 5B of an engine are arranged and a supporting member 10 which rotatably supports journal parts 53 on the most front sides of the intake and exhaust camshafts 5A, 5B are provided separately from each other. The cylinder head 2 has a front-side side wall 21 whose upper face 2a is cut out and on which the supporting member 10 is placed, and is fixed to a cylinder block with a plurality of head bolts 25 passing through the side wall 21 in its erecting direction and fastened thereto. On the other hand, the supporting member 10 is fixed to the side wall 21 at three sites sandwiching the two journal parts 53 above the head bolts 25 with fastening bolts 15. The supporting member 10 is formed so that heights Ha, Hb of left and right fixed parts 12 located outside the two journal parts 53 are each greater than a height Hc of a fixed part 12 located therebetween.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an engine in which a support member that rotatably supports a camshaft is provided separately from a cylinder head.

  A camshaft for driving an intake valve and an exhaust valve of an engine is supported by the cylinder head by holding a journal portion between a plurality of bearing portions formed on the cylinder head and a cam cap in a valve chamber of the cylinder head. Is done. The cylinder head is fixed to the cylinder block by fastening head bolts to a plurality of bolt holes penetrating the bottom surface of the valve operating chamber. In general, the plurality of bolt holes are provided between the side wall and the cylinder orthogonal to the cylinder row direction and between the cylinders adjacent in the same direction. The cylinder head is arranged with bearings, bolt holes, and the like so that its overall length (length in the cylinder row direction) is as short as possible. For example, a configuration has been proposed in which the front-side bearing portion is provided separately from the cylinder head, and the bearing portion is attached to the cylinder head so as to overlap the head bolt in a top view, thereby reducing the overall length of the cylinder head ( Patent Document 1).

JP 2001-304038 A

  By the way, the valve reaction force of the intake / exhaust valve is transmitted to the bearing portion via the camshaft and is transmitted to the cylinder head. Therefore, when the bearing portion is separated from the cylinder head, it is necessary to provide a bearing portion having a supporting rigidity that can sufficiently withstand the valve reaction force. In particular, in the case of a double overhead cam type (DOHC) engine, the outside is larger than the middle of the bearing part that supports the intake camshaft and the exhaust camshaft. Proposal of structure is desired.

  The present invention has been devised in view of such problems, and an object thereof is to provide an engine in which the support rigidity of the support member is appropriately secured while reducing the overall length of the cylinder head. The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

  (1) An engine disclosed herein includes a cylinder head on which an intake camshaft and an exhaust camshaft of the engine are disposed, a separate cylinder head from the cylinder head, and a most front side journal portion of the intake camshaft and the exhaust cam. And a support member that rotatably supports each of the most front journal portions of the shaft. The cylinder head has a front side wall on which an upper surface is cut off and on which the support member is placed, and a plurality of head bolts are fastened through the side wall in the standing direction to fasten the cylinder block. Fixed to. Further, the support member is fixed to the side wall by fastening bolts at three positions sandwiching the two journal portions above the head bolt, and left and right positions positioned on the outer sides of the two journal portions, respectively. The height dimension of the fixed part is formed larger than the height dimension of the intermediate fixed part located between the two journal parts.

(2) It is preferable that the support member is formed such that the lower surface of the intermediate fixing portion is positioned above the lower surfaces of the left and right fixing portions.
(3) It is preferable that the said supporting member is formed so that the height dimension of the said right and left fixing | fixed part may be the same.
(4) It is preferable that the cylinder head is provided so that an extension line of an axis of the head bolt intersects with each axis of the intake camshaft and the exhaust camshaft.

(5) The side wall has a recess that is recessed below the mounting surface on which the support member is mounted and is formed so as to penetrate in the axial direction of the intake camshaft and the exhaust camshaft. The head bolt is preferably fastened to the bottom surface of the recess.
(6) It is preferable that the support member has a rolling bearing built in a bearing portion that pivotally supports the journal portion.

(7) It is preferable that the support member is provided with a holding part that supports the journal part from below and a cap part that supports the journal part from above separately.
(8) Alternatively, it is preferable that the support member is integrally provided with a hold portion that supports the journal portion from below and a cap portion that supports the journal portion from above.

  The support stiffness of the support member can be increased on the outside of each of the two journal portions, and the support stiffness can be appropriately ensured even on the outside where the valve reaction force is large. Thereby, noise and vibration that can be generated by the combustion excitation force of the engine can be suppressed, and the reliability of the engine can be improved. Further, since the head bolt is fastened through the side wall, the overall length of the cylinder head can be shortened as compared with a structure in which the head bolt is fastened at the bottom surface of the valve chamber of the cylinder head.

It is a disassembled perspective view of the engine which concerns on embodiment. It is a top view which shows the state in which the supporting member was attached to the cylinder head. It is a front view which decomposes | disassembles and shows the front side wall and support member of a cylinder head. It is AA arrow sectional drawing of FIG. It is an enlarged view of the side wall of the front side of FIG.

  An engine as an embodiment will be described with reference to the drawings. Each embodiment shown below is only an example, and there is no intention of excluding various modifications and application of technology that are not clearly shown in each of the following embodiments. Each configuration of the present embodiment can be implemented with various modifications without departing from the spirit thereof. Further, they can be selected as necessary, or can be appropriately combined.

[1. overall structure]
The engine 1 of this embodiment is disassembled and shown in FIG. The engine 1 is an inline three-cylinder double overhead cam type (DOHC) gasoline engine. On the front side of the engine 1 (in the lower left direction in FIG. 1), auxiliary machinery for the engine 1 and transmission members for transmitting power (crank pulley, timing pulley, sprocket, etc., not shown) are provided. A chain cover (not shown) is attached to the front side of the cylinder head 2 and the cylinder block 3. The transmission member is housed in a space between the cylinder head 2 and the cylinder block 3 and the chain cover. A drive plate and a flywheel are provided on the rear side of the engine 1 (upper right direction in FIG. 1), and are connected to various devices (for example, a transmission, a rotating electrical machine, etc.) on the downstream side of the power train.

  The engine 1 of this embodiment includes a cylinder head 2 with an exhaust manifold integrated. Below the cylinder head 2, a cylinder block 3 that houses a hollow cylindrical cylinder arranged in a row is provided. On the other hand, a head cover (not shown) that covers the entire upper surface 2 a of the cylinder head 2 is attached above the cylinder head 2. The head cover is fastened and fixed to the upper surface 2a of the cylinder head 2 via a gasket (not shown). A space surrounded by the upper surface 2a of the cylinder head 2 and the head cover is a valve operating chamber 4 in which a valve operating mechanism for driving the intake and exhaust valves of the engine 1 is built.

  In the following description, the side on which the cylinder block 3 is fixed with respect to the cylinder head 2 is defined as the lower side and the opposite side is defined as the upper side. Further, of the side surfaces of the cylinder head 2, the side where the upstream end opening of the intake port is located is called “intake side”, and the opposite side is called “exhaust side”. However, since the engine 1 may be installed in an inclined posture (non-horizontal posture) with respect to the vehicle, the vertical direction here does not necessarily correspond to the vertical vertical direction.

  A camshaft 5 extending along the direction in which the cylinders are arranged is disposed inside the valve train chamber 4. FIG. 1 shows an intake camshaft 5A for driving the intake valve and an exhaust camshaft 5B for driving the exhaust valve. Each camshaft 5 is provided with a plurality of cams 50 having a cam mountain shape corresponding to the opening / closing timing of the intake / exhaust valves and the valve lift amount. These cams 50 function to push down a tappet (not shown) provided at the upper end of the intake / exhaust valve to drive the intake / exhaust valve up and down. The cam 50 according to the present embodiment is provided as a combined cam in which a pair of cam lobes 51 are combined with a cylindrical cam journal 52 interposed therebetween. That is, two camshafts 5 having three cams 50 are arranged in parallel in the cylinder head 2 of the present embodiment.

  A cam sprocket 6 wound around a timing chain and a phase actuator 7 (variable valve mechanism) are provided at the end of the camshaft 5 on the front side of the engine 1. The phase actuator 7 is a hydraulic device that changes the phase of the rotation angle of the camshaft 5 with respect to the rotation angle of the crankshaft, and is formed integrally with the cam sprocket 6, for example. A mechanism for moving the phase angle of the cam shaft 5 in the advance direction or the retard direction with respect to the cam sprocket 6 is built in the phase actuator 7, and based on a control signal from an electronic control device (not shown) The phase of 5 is freely controlled.

  Each camshaft 5 has three cam journals 52 supported rotatably between the sliding bearing portion 26 of the cylinder head 2 and the sliding bearing portion 8 a of the cam cap 8. The cam cap 8 is formed in a small size that can support only one of the intake camshaft 5A and the exhaust camshaft 5B. The cam cap 8 is formed in a semicircular concave shape capable of supporting only the cam journal 52 of the camshaft 5 disposed in the vicinity of the center of the cylinder in a top view of the engine 1.

  Each camshaft 5 has a journal portion 53 disposed adjacent to the phase actuator 7. The journal portion 53 is rotatably supported by a support member 10 provided separately from the cylinder head 2. The support member 10 is formed to a size that can support both the intake camshaft 5A and the exhaust camshaft 5B. That is, the support member 10 of the present embodiment also has a bearing function for two cam caps 8. The support member 10 has a size that covers a range from the vicinity of the phase actuator 7 in the intake camshaft 5A to the vicinity of the phase actuator 7 in the exhaust camshaft 5B.

  As shown in FIG. 2, the cylinder head 2 has a plurality of head bolt holes 23 through which head bolts 25 for fastening and fixing the cylinder head 2 to the cylinder block 3 are inserted. The head bolt holes 23 are provided on the intake side and the exhaust side of the cylinder head 2 side by side in the direction in which the cylinders are arranged. The cylinder head 2 of the present embodiment includes a head bolt hole 23 formed in the lower surface portion 20 that forms the bottom surface of the valve operating chamber 4, and a side wall 21 on the front side of the cylinder head 2 (hereinafter referred to as "front wall 21"). And a head bolt hole 23 (see FIG. 3). Hereinafter, when the latter head bolt hole 23 is distinguished from the former, it is referred to as a “front head bolt hole 23 f”. The head bolt hole 23 of the present embodiment is disposed at a position overlapping the intake camshaft 5A and the exhaust camshaft 5B in the vertical direction. In FIG. 2, the axis 5c of each camshaft 5A, 5B is indicated by a one-dot chain line.

  As shown in FIG. 1, the cylinder head 2 includes an oil control valve 9 (OCV, Oil Control Valve) that controls the pressure of oil (operating oil) supplied to the phase actuator 7. One oil control valve 9 is provided for each of the intake side and exhaust side phase actuators 7. The oil control valve 9 is disposed below the phase actuator 7 in a state where the camshaft 5 is fixed to the cylinder head 2. As shown in FIG. 4, mounting holes 21 h into which the oil control valve 9 is inserted are formed in the front wall 21 of the cylinder head 2 on the intake side and the exhaust side, respectively. Each oil control valve 9 is inserted and fixed in these mounting holes 21h.

[2. Main part configuration]
As shown in FIGS. 1, 3 and 4, the cylinder head 2 according to the present embodiment has a top surface 2a of the front wall 21 cut out of the top surface 2a, and its height dimension is smaller than that of the other side walls. Formed as follows. The support member 10 is placed on the cut-out upper surface of the front wall 21 and fastened with bolts. Further, the cylinder head 2 is fixed to the cylinder block 3 by a plurality of (two in this embodiment) head bolts 25 passing through the front wall 21 in the standing direction and being fastened. 3 and 4, the structure inside the valve operating chamber 4 is omitted for convenience.

  The front wall 21 has a surface on which the support member 10 is mounted (hereinafter referred to as “mounting surface 21a”) between the two camshafts 5A and 5B and outside of the camshafts 5A and 5B. Is provided. The three placement surfaces 21a are formed by cutting the upper surface 2a of the front wall 21 into a flat shape, and are provided in parallel with the upper surfaces 2a of the other side walls. The cylinder head 2 of the present embodiment is formed such that the height positions of the three placement surfaces 21a are not all the same, and the intermediate placement surface 21a is higher than the left and right placement surfaces 21a. The height positions of these placement surfaces 21a are determined according to the position of the lower surface 12d of the fixing portion 12 of the support member 10 described later. The front wall 21 is provided with a hole portion 21d drilled downward from each mounting surface 21a. A fastening bolt 15 for fixing the support member 10 is screwed into each hole 21d.

  The front wall 21 has two recesses 21b that are recessed below the placement surface 21a and that penetrate through the camshaft 5 in the axial direction (the direction in which the cylinders are arranged). As shown in FIGS. 3 and 4, these recesses 21 b are formed directly under the intake camshaft 5 </ b> A and the exhaust camshaft 5 </ b> B, and with the bearing portion 11 described later in a state where the support member 10 is placed. The shape forms a space between them. The head bolt 25 is fastened to the bottom surface 21c of the recess 21b. In the concave portion 21b of the present embodiment, a seat surface 21e with which the head of the head bolt 25 abuts is projected on the bottom surface 21c. The front head bolt hole 23f is formed to penetrate from the seat surface 21e to the lower surface of the front wall 21 in the standing direction of the front wall 21. The cylinder head 2 is provided such that an extension line of the axis 25 c of the head bolt 25 intersects each axis 5 c of the camshaft 5.

  The front wall 21 of the present embodiment is provided with two types of bolt holes extending in the standing direction. That is, the front head bolt hole 23f for fastening the head bolt 25 and the hole 21d into which the fastening bolt 15 is screwed. As shown in FIGS. 2 and 5, the cylinder head 2 of the present embodiment has a hole portion 21 d formed on the inner side (the valve operating chamber 4 side) of the front head bolt hole 23 f. That is, the hole 21d and the front head bolt hole 23f are not arranged in a straight line when viewed from above, and the former is arranged closer to the valve operating chamber 4 than the latter. The front wall 21 is formed thicker than the other side walls, and has a thickness that allows the head bolt 25 to be fastened. Furthermore, the position of the hole 21d in the front wall 21 is overlaid.

  As shown in FIGS. 1 and 3, in the cylinder head 2 of the present embodiment, since the recess 21b is provided through the front wall 21, the valve operating chamber 4 is provided in a space for accommodating the transmission member via the recess 21b. It is open. For this reason, the oil accumulated in the valve operating chamber 4 is discharged from the recess 21b on the front side of the cylinder head 2, and is coupled to the lower side of the cylinder block 3 through the outside of the front wall 21 (the storage space for the transmission member). Drops into an oil pan (not shown). That is, the recess 21b has a function as a front side oil passage as shown by a white arrow in FIG. 1 in addition to a function as a portion to which the head bolt 25 is fastened. The oil control valve 9 is inserted obliquely downward from the outside toward the bottom surface 21c of the recess 21b. In other words, the bottom surface 21 c of the recess 21 b is disposed so as to be positioned at the tip of the oil control valve 9. As a result, the oil in the oil control valve 9 leaks from the tip of the oil control valve 9 to the bottom surface 21c and can be circulated to the oil pan.

The support member 10 is fixed to the front wall 21 by the fastening bolts 15 at three positions sandwiching the two journal portions 53 above the head bolt 25. As shown in FIG. 3, the support member 10 of the present embodiment includes an intake support portion 10 _IN that supports the journal portion 53 of the intake camshaft 5A, and an exhaust support portion 10 _EX that supports the journal portion 53 of the exhaust camshaft 5B. And are integrated. The support member 10 includes two bearing portions 11 that respectively support the two journal portions 53, and three fixing portions 12 for fixing the support member 10 to the cylinder head 2.

  In the support member 10 of the present embodiment, a holding part 10H that supports the journal part 53 from below and a cap part 10C that supports the journal part 53 from above are provided separately, and these are assembled from the cylinder head 2. Also assembled before or at the same time as assembly. The support member 10 is divided into a holding portion 10H and a cap portion 10C by a straight line (a dashed line E in FIG. 3) connecting the shaft centers 5c of the two camshafts 5. The axis 5c of the camshaft 5 is set at the same height as the upper surface 2a of the cylinder head 2.

  As shown in FIG. 3, when the engine 1 is viewed from the front side, the overall shape of the support member 10 is provided with fixed portions 12 between two substantially cylindrical bearing portions 11 and outside each. Can match the shape of glasses. Rolling bearings 14 are built into the two bearing portions 11. In the camshaft 5, the largest load acts on the end portion on the front side close to the timing chain. Therefore, the journal portion 53 located on the most front side is pivotally supported by the rolling bearing 14 to effectively reduce the friction. The In addition, since the support member 10 is provided with the hold portion 10H and the cap portion 10C as separate bodies, the rolling bearing 14 is assembled when these are assembled.

  The three fixing portions 12 each have a top surface 12e and a bottom surface 12d formed in a planar shape, and have bolt holes 13 penetrating in the vertical direction. Each bolt hole 13 is for inserting the fastening bolt 15, and is provided at a position overlapping the hole 21 d in a state where the support member 10 is placed on the front wall 21. As shown in FIGS. 3 and 5, the support member 10 has a straight line (a dashed line L in FIGS. 2 and 5) in which the bearing portion 11 connects the centers of the bolt holes 13 of the three fixing portions 12 in a top view. ) With respect to the outer side. That is, the support member 10 is formed in a non-linear shape that is bent in a top view. The bearing portion 11 is provided at a position overlapping the head bolt 25 in the vertical direction in a state where the support member 10 is placed on the front wall 21.

  Further, in the support member 10 of the present embodiment, the height dimensions of the three fixing parts 12 are not all the same, and the height dimensions Ha and Hb of the left and right fixing parts 12 positioned outside the bearing part 11 are the bearing parts. The height dimension Hc of the intermediate fixing part 12 positioned between the two is formed larger than the height dimension Hc. Here, the height dimensions Ha and Hb of the left and right fixing portions 12 are formed identically. Further, in the support member 10 of the present embodiment, the height positions of the upper surfaces 12e of the three fixing portions 12 are formed to be the same. Therefore, the support member 10 is formed such that the lower surface 12d of the intermediate fixing portion 12 is positioned above the lower surfaces 12d of the left and right fixing portions 12.

[3. Action, effect]
(1) In the engine 1 described above, the support member 10 is formed such that the height dimensions Ha and Hb of the left and right fixing parts 12 are larger than the height dimension Hc of the intermediate fixing part 12. For this reason, the support rigidity of the support member 10 can be increased on the outside of each of the two journal portions 53, and the support rigidity can be appropriately ensured even on the outside where the valve reaction force is large. Thereby, noise and vibration that can be generated by the combustion excitation force of the engine 1 can be suppressed, and the reliability of the engine 1 can be improved. Further, since the head bolt 25 is fastened through the front wall 21, the most front head bolt 25 is fastened at the bottom surface (lower surface portion 20) of the valve operating chamber 4 in the same manner as the other head bolts 25. As compared with the above, the total length of the cylinder head 2 can be shortened.

  (2) Further, the support member 10 described above is formed such that the lower surface 12d of the intermediate fixing portion 12 is positioned above the lower surfaces 12d of the left and right fixing portions 12. For this reason, the support member 10 is well placed and the stability can be improved. Further, by increasing the height position of the lower surface 12d of the intermediate fixing portion 12C, the height position of the intermediate mounting surface 21a among the three mounting surfaces 21a of the front wall 21 is changed to the intermediate fixing portion 12. Together, it gets higher. That is, the height dimension of the front wall 21 on which the intermediate fixing part 12 is placed is larger than the height dimension of the part on which the left and right fixing parts 12 are placed. For this reason, the support rigidity of the front wall 21 can be improved in the intermediate part.

(3) Furthermore, the above-described support member 10 is formed such that the left and right fixing portions 12 have the same height dimension Ha, Hb. For this reason, the support rigidity of the support member 10 can be made equal on the left and right sides, and the support member 10 can be more firmly installed, so that the stability of the support member 10 can be further improved.
(4) Further, since the cylinder head 2 is provided so that the extension line of the axis 25c of the head bolt 25 intersects each axis 5c of the camshaft 5, a moment due to the valve reaction force acts on the head bolt 25. Without stress concentration can be avoided.

  (5) In the cylinder head 2 described above, the front wall 21 is provided with the recess 21b to which the head bolt 25 is fastened. Since the recess 21 b is formed so as to penetrate the front wall 21 in the axial direction of the camshaft 5, it functions as an oil passage for discharging the oil accumulated in the valve operating chamber 4. That is, since the concave portion 21b has both a function as a portion to which the head bolt 25 is fastened and a function as an oil passage on the front side, the front wall 21 is formed with a hole or a notch dedicated to the oil passage. Therefore, the configuration of the cylinder head 2 can be simplified. Further, since the oil accumulated in the valve operating chamber 4 is discharged from the recess 21b and returns to the oil pan through the storage space of the transmission member, the oil lubrication becomes active and the cooling performance by the oil is improved. Can do.

(6) In the above-described support member 10, the rolling bearing 14 is built in the bearing portion 11. Since the largest load is applied to the front end near the timing chain, the camshaft 5 incorporates the rolling bearing 14 in the journal 53 located closest to the front, thereby effectively reducing the friction of the valve mechanism. Can be reduced.
(7) Since the holding member 10H and the cap portion 10C are provided separately, the above-described support member 10 is easy to manufacture and can reduce manufacturing costs. Also, when the rolling bearing 14 is built in, it can be easily assembled.

  (8) Further, in the engine 1 of the present embodiment, the fastening positions of the head bolts 25 and the fastening bolts 15 are not provided in a straight line, but are intentionally shifted. Thereby, stress concentration can be avoided and the rigidity of the cylinder head 2 can be increased. Further, by disposing the fastening bolt 15 on the inner side (the valve operating chamber 4 side) than the head bolt 25, the oil control valve 9 can be incorporated in the front wall 21 of the cylinder head 2 while avoiding the fastening bolt 15. . Thereby, in order to arrange | position and incorporate the oil control valve 9, it is not necessary to carry out an excessive build-up in the cylinder head 2, and the weight of the cylinder head 2 can be reduced and the shape can be simplified.

  (9) The support member 10 of the present embodiment is a straight line in which the bearing portion 11 that pivotally supports the journal portion 53 connects the centers of the bolt holes 13 of the fixing portion 12 (as indicated by the alternate long and short dash line L in FIG. 5). Is provided at a position offset to the outside. That is, the support member 10 is formed in a shape such that the bearing portion 11 overlaps the head bolt 25 in the vertical direction while being placed on the front wall 21. Thereby, the distance of the bearing part 11 and the cam 50 can be set to the minimum necessary, and the cylinder head 2 can be made further compact.

  For example, in the case where the support member 10 is formed in a straight line shape when viewed from above, assuming that the positional relationship between the fastening bolt 15 and the head bolt 25 is the state shown in FIG. It will overlap in the up-and-down direction, and the cam 50 and the bearing part 11 will interfere. Further, if the front wall 21 is shifted to the front side in order to dispose the bearing portion 11 so as not to overlap the intake port and the exhaust port, the overall length of the cylinder head 2 is increased. On the other hand, with the support member 10 of the present embodiment, the bearing portion 11 does not overlap the intake port and the exhaust port in the vertical direction, and the overall length of the cylinder head 2 can be shortened.

[4. Modified example]
The shape of the support member 10 described above is an example, and is not limited to the above. For example, the support member 10 may be one in which the hold portion 10H and the cap portion 10C are provided integrally. In the case where the support member 10 is integral, the intake camshaft 5A and the exhaust camshaft 5B may be inserted into each bearing portion 11 of the support member 10 and assembled to the cylinder head 2 in an assembled state. With such a configuration, the camshafts 5A and 5B can be easily centered, displacement of the camshafts 5A and 5B can be prevented, and friction can be further reduced.

  Moreover, in the integral support member 10, the rolling bearing 14 may be press-fitted and incorporated. Alternatively, regardless of whether the support member 10 is an integral body or a separate body, the rolling bearing 14 may be omitted and function as a sliding bearing. Further, the fastening bolt 15 and the head bolt 25 may be arranged in a straight line when viewed from above. In this case, the configuration can be simplified if the shape of the support member 10 is a linear shape in a top view. Moreover, the height dimension of the three fixing | fixed part 12 of the supporting member 10 should just be larger than the middle on either side, and the height dimensions Ha and Hb of both right and left sides may mutually differ. Further, the height position of the lower surface 12d and the height position of the upper surface 12e of the fixing portion 12 are arbitrary and can be set according to the height dimension. In addition, what is necessary is just to set the three mounting surfaces 21a of the cylinder head 2 according to the height position of the lower surface 12d of the fixing | fixed part 12. FIG.

  The configuration and shape of the camshaft 5 described above are examples, and are not limited to those described above. For example, the cam 50 may be a cam with a roller having a roller rotatably attached to the tip of each cam lobe 51. In this case, if the support member 10 is integrated, the centering is easy and the positional accuracy is increased as described above. Therefore, the friction can be further reduced by combining with a cam with a roller.

  The engine 1 may not be the above-described inline three-cylinder double overhead cam type (DOHC) gasoline engine. For example, a cylinder engine other than three cylinders may be used, or a single cylinder engine may be used. Further, it may be a single overhead cam type (SOHC) engine or a diesel engine.

DESCRIPTION OF SYMBOLS 1 Engine 2 Cylinder head 2a Upper surface 3 Cylinder block 5 Cam shaft 5A Intake cam shaft 5B Exhaust cam shaft 10 Support member 10 _IN Intake support portion 10 _EX Exhaust support portion 10C Cap portion 10H Hold portion 11 Bearing portion 12 Fixing portion 12d Lower surface 12e Upper surface 13 Bolt hole 14 Rolling bearing 15 Fastening bolt 20 Lower surface 21 Front wall (front side wall)
21a Mounting surface 21b Recessed portion 21c Bottom surface 21d Hole portion 21e Seat surface 21h Mounting hole 23 Head bolt hole 23f Front head bolt hole 25 Head bolt 25c Shaft center 26 Sliding bearing portion 50 Cam 53 Journal portion E Straight line connecting the shaft centers 5c L Straight line connecting the centers of bolt holes 13
Ha, Hb Height dimensions of the left and right fixed parts 12
Hc Height of middle fixed part 12

Claims (8)

A cylinder head on which an intake camshaft and an exhaust camshaft of the engine are disposed;
A support member that is provided separately from the cylinder head and rotatably supports each of the most front journal portion of the intake camshaft and the most front journal portion of the exhaust camshaft,
The cylinder head has a front side wall on which an upper surface is cut off and on which the support member is placed, and a plurality of head bolts are fastened through the side wall in the standing direction to fasten the cylinder block. Fixed to
The support member is fixed to the side wall by fastening bolts at three positions sandwiching the two journal parts above the head bolt, and is fixed to the left and right sides of the two journal parts. The engine is characterized in that a height dimension of the portion is formed larger than a height dimension of an intermediate fixing portion located between the two journal portions. 2. The engine according to claim 1, wherein the support member is formed such that a lower surface of the intermediate fixing portion is positioned higher than lower surfaces of the left and right fixing portions. The engine according to claim 1, wherein the support member is formed such that the left and right fixing portions have the same height. 4. The cylinder head according to claim 1, wherein the cylinder head is provided so that an extension line of an axis of the head bolt intersects with each axis of the intake camshaft and the exhaust camshaft. The engine according to claim 1. The side wall has a recess that is recessed below the mounting surface on which the support member is mounted and is formed so as to penetrate in the axial direction of the intake camshaft and the exhaust camshaft,
The engine according to any one of claims 1 to 4, wherein the head bolt is fastened to a bottom surface of the recess. The engine according to any one of claims 1 to 5, wherein the support member includes a rolling bearing built in a bearing portion that pivotally supports the journal portion. The support member according to any one of claims 1 to 6, wherein a holding part that supports the journal part from below and a cap part that supports the journal part from above are provided separately. The engine according to item. 7. The support member according to claim 1, wherein a holding portion that supports the journal portion from below and a cap portion that supports the journal portion from above are integrally provided. Engine described in.

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