Head cover structure of engine and suspension structure thereof

Abstract

Provided is a head cover structure of an engine, which is capable of increasing supporting rigidity of a head cover. The engine includes a driving force transmission mechanism for transmitting a driving force of a crankshaft to a valve train, in which on one end side in a cylinder row direction of the head cover, a bulging portion for covering an upper side of the driving force transmission mechanism is provided, and an engine mounting portion is attached to the bulging portion. The bulging portion is provided with an inclined surface portion having an inclined surface inclined downwardly toward the other end side in the cylinder row direction, and the inclined surface is formed to rise upwardly from an intermediate position in the cylinder row direction so as to be continuous with a top surface of the bulging portion on the one end side in the cylinder row direction.

Claims

1. An engine cover mounting structure comprising: a cylinder head of an engine; a head cover which is provided on an upper portion of the cylinder head; an engine mounting portion which is provided on the head cover and supports the engine; and a cover member which is fastened to both the cylinder head and the head cover, wherein the cover member includes a head cover covering portion which is directly fastened to the head cover, and a cylinder head covering portion which is directly fastened to the cylinder head, wherein the cover member spans from a position below mating surfaces of the cylinder head and the head cover to a position above the mating surfaces of the cylinder head and the head cover, wherein a mounting surface for mounting the cover member on the head cover and the cylinder head is perpendicular to mating surfaces of the head cover and the cylinder head, wherein the cover member has a width dimension substantially equal to a full width of the mating surfaces located at a front end portion in a cylinder row direction of the engine, and wherein fastening points for fastening the cover member to the cylinder head are provided below both ends in a width direction of the mating surfaces, and fastening points for fastening the cover member to the head cover are provided above both ends in the width direction of the mating surfaces.

2. The engine cover mounting structure according to claim 1, wherein a lower portion of the cylinder head is coupled to a cylinder block via mating surfaces, and wherein a lower end of the cover member in a cylinder axis direction is located higher than the mating surfaces of the cylinder block and the cylinder head.

3. The engine cover mounting structure according to claim 1, wherein an opening portion of a substantially inverted triangular shape is formed on side walls of front ends of the cylinder head and the head cover, wherein the mounting surface has a shape surrounding the opening portion and is formed on a periphery of the opening portion, and wherein a plurality of fastening holes to which each fastening bolt is fastened are formed apart from each other by a substantially equal distance over an entire circumference of the mounting surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a front view of a V-type engine which is applied with a head cover structure and a cover mounting structure according to an embodiment of the present invention;

(2) FIG. 2 is an enlarged partial cross-sectional front view of a head cover and a cylinder head in a state where a part of a cover member is broken;

(3) FIG. 3 is an enlarged perspective view of a right bank including the cover member;

(4) FIG. 4 is an exploded perspective view of the right bank which is removed of the cover member from the state shown in FIG. 3;

(5) FIG. 5 is a plan view of the head cover shown in FIG. 4;

(6) FIG. 6 is a side view of the head cover seen from a direction of an arrow X in FIG. 5;

(7) FIG. 7 is a bottom view of the head cover shown in FIG. 5;

(8) FIG. 8 is an enlarged cross-sectional view taken along a line VIII-VIII in FIG. 5;

(9) FIG. 9 is an enlarged cross-sectional view taken along a line IX-IX in FIG. 3;

(10) FIG. 10 is a partially virtual perspective view showing a state in which an engine and a transmission are mounted on a vehicle body frame;

(11) FIG. 11 is a plan view of the engine and the transmission shown in FIG. 10;

(12) FIG. 12 is a side view of the engine and the transmission shown in FIG. 10; and

(13) FIG. 13 is a front view of the engine and the transmission shown in FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

(14) Next, an embodiment of the present invention will be described in detail with appropriate reference to accompanying drawings. FIG. 1 is a front view of a V-type engine which is applied with a head cover structure and a cover mounting structure according to the embodiment of the present invention, FIG. 2 is an enlarged partial cross-sectional front view of a head cover and a cylinder head in a state where a part of a cover member is broken, FIG. 3 is an enlarged perspective view of a right bank including the cover member, and FIG. 4 is an exploded perspective view of the right bank which is removed of the cover member from the state shown in FIG. 3.

(15) Note that, FRONT-REAR shown by an arrow in each FIG. refers to a front-rear direction of an engine, and one side of the engine, which is provided with a timing train mechanism in the front-rear direction, is referred to as a front side, and further the other side of the engine, which is coupled to a transmission, is referred to as a rear side. UP-DOWN refers to an up-down direction of the engine in a vehicle-mounted state, and coincides with an up-down direction of a vehicle (vertical up-down direction). LEFT-RIGHT refers to a left-right direction (vehicle width direction) with respect to a forward direction of the vehicle. In addition, the front-rear direction of the engine coincides with a cylinder row direction of the engine. The cylinder row direction coincides with an axial direction (a crankshaft direction) of a crankshaft. Further, since the engine is disposed longitudinally with respect to the vehicle, the front-rear direction of the engine coincides with the front-rear direction of the vehicle. Further, a reference sign A denotes a cylinder axis line (cylinder axis direction), and the reference signs M1, M2 denote mounting brackets, respectively. Furthermore, WIDTH DIRECTION shown in FIGS. 3 and 4 refers to a direction perpendicular to a cylinder axis line A and the cylinder row direction at a front end portion in the cylinder row direction.

(16) As shown in FIGS. 1 and 2, an engine 10, which is applied with a head cover structure and a cover mounting structure according to the embodiment of the present invention, is composed of a V-type multi-cylinder engine having V-shaped banks 12 on the left and right. In the engine 10, the crankshaft is disposed longitudinally in the front-rear direction of the vehicle. Behind the engine 10, a transmission 14 (see FIGS. 10 to 12), which has a plurality of gear stages (not shown) and serves as a transmission mechanism, is provided.

(17) The engine 10 is configured to include a cylinder head 16, a head cover 18 which is coupled to an upper portion of the cylinder head 16 with bolts 17 and is made of rigid metal (for example, made of aluminum alloy), a cylinder block 20 which is coupled to a lower portion of the cylinder head 16, and a cylinder block lower 22 which is provided on a lower portion of the cylinder block 20. Between the head cover 18 and the cylinder head 16, mating surfaces 24 for integrally coupling a lower surface of the head cover 18 and an upper surface of the cylinder head 16 to each other are provided. The mating surfaces 24 consist of surfaces which are substantially perpendicular to the cylinder axis line A, and are extended in the cylinder row direction (see FIGS. 3 and 4). Note that, each bank has a plurality of cylinders arranged in series, and the cylinder row direction refers to a row direction of the plurality of cylinders.

(18) The cylinder block 20 is provided with a crankcase and a cylinder bore (not shown). Inside the cylinder block 20, a crankshaft, connecting rods, pistons, and the like (not shown) are accommodated. Note that, in FIG. 1, a point O denotes a shaft center which is a center of the crankshaft.

(19) The cylinder head 16 constitutes a combustion chamber (not shown) together with the cylinder block 20. Inside the cylinder head 16, an intake port and an exhaust port (not shown) communicating with the combustion chamber are formed, and a valve train, which is composed of such as an intake valve and an exhaust valve (not shown) for opening or closing the intake port and the exhaust port, is provided. Further, as shown in FIG. 2, on an upper side of the cylinder head 16, two camshafts (not shown) composed of an intake camshaft 17a and an exhaust camshaft 17b are disposed. The two camshafts are extended in the front-rear direction of the vehicle, and are arranged in parallel so that shaft center lines thereof are parallel to each other.

(20) On a front edge portion of the engine 10, a pair of cover members 26 provided across both the cylinder head 16 and the head cover 18, and a timing train cover (chain cover) 28 provided on such as the cylinder block 20 and the cylinder block lower 22, are separately provided. A mounting surface 21 of the cover member 26 is located on the front side of the engine relative to the timing train cover 28 (see FIG. 12), while the cover member 26 is located on an upper side in the cylinder axis direction, and the timing train cover 28 is located on a lower side in the cylinder axis direction (see FIG. 1). Note that, since the pair of cover members 26 is formed in substantially the same shape with each other in the left and right, the cover member 26 on RIGHT side in FIG. 1 will be described in detail, and description of the cover member 26 on LEFT side will be omitted.

(21) The timing train cover 28 forms a timing train chamber together with the engine body, and covers a cam timing chain (not shown). The cam timing chain is disposed on one end side in the cylinder row direction of the engine 10, and serves as a driving force transmission mechanism. A rotational driving force of the crankshaft is transmitted to the valve train via the cam timing chain (not shown).

(22) As shown in FIG. 4, on side walls 16a, 18a of front ends of the cylinder head 16 and the head cover 18, an opening portion 19 of substantially inverted triangular shape is formed. The opening portion 19 is formed in combination of an opening of the cylinder head 16 side and an opening of the head cover 18 side at the mating surfaces 24. The opening of the head cover 18 side is located on an upper side of the mating surfaces 24, and is formed in a substantially semi-elliptical shape. The opening of the cylinder head 16 side is located on a lower side of the mating surfaces 24, and is formed in a substantially triangular shape. On a periphery of the opening portion 19, the mounting surface 21, which has a shape surrounding the opening portion 19 and on which the cover member 26 is mounted from a direction described later, is formed. On the mounting surface 21, a plurality of fastening holes (second fastening portions) 23 to which each fastening bolt 30 is fastened are formed apart from each other by a substantially equal distance over an entire circumference thereof. The opening portion 19 is in communication with an upper portion of the timing train chamber which is provided on the front ends of the cylinder head 16 and the head cover 18. Note that, the side walls 16a, 18a have rigidities, because they are not formed in separate bodies from the cylinder head 16 and the head cover 18, but are respectively formed integrally with the cylinder head 16 and the head cover 18. When referring to all of the fastening holes, it is denoted by fastening holes 23, and when referring to a specific fastening hole, it is denoted by a reference numeral 23 with a suffix of a lowercase letter. Similarly, when referring to all of the fastening bolts, it is denoted by fastening bolts 30, and when referring to a specific fastening bolt, it is denoted by a reference numeral 30 with a suffix of a lowercase letter.

(23) On upper and lower positions of one end and the other end of the full width in the width direction of the mating surfaces 24, four fastening holes 23a, 23b, 23c, 23d are respectively provided. By fastening four fastening bolts 30a, 30b, 30c, 30d to the four fastening holes 23a, 23b, 23c, 23d, the cover member 26 is fixed to the cylinder head 16 and the head cover 18. In other words, the four fastening holes 23a, 23b, 23c, 23d are arranged closest to the mating surfaces 24 among the plural fastening holes 23, and the four fastening holes 23a, 23b, 23c, 23d are located outermost from the cylinder axis line A in a direction (in WIDTH DIRECTION shown in FIGS. 3 and 4) perpendicular to a cylinder axis line A direction, to be provided on the upper and lower positions of the mating surfaces 24. Note that, as shown in FIG. 1, a portion on a side of the mating surfaces 25 of the cylinder head 16 and the cylinder block 20 (on the lower side) in a side wall 16a of the front end of the cylinder head 16, is coupled (fastened) to the timing train cover 28 at the mating surfaces 25 with the timing train cover 28, in the width direction substantially perpendicular to the cylinder axis line A direction.

(24) As shown in FIGS. 3 and 4, the cover member 26 is made of a flat metallic plate of substantially inverted triangular shape, and is formed in a shape corresponding to the opening portion 19 so as to close the opening portion 19. On an outer peripheral edge portion of the cover member 26, curved portions 27, which are spaced from each other in a circumferential direction and project radially outwardly, are formed. The curved portions 27 are provided in plurality at substantially equal intervals in the circumferential direction. Each curved portion 27 is formed with a through-hole, which passes through the cover member 26, and through which the fastening bolt 30 is inserted.

(25) The cover member 26 is configured integrally with a head cover covering portion 26a fastened to the head cover 18 and a cylinder head covering portion 26b fastened to the cylinder head 16 at a boundary of the mating surfaces 24 (see FIGS. 3 and 4). When viewed from the front, the head cover covering portion 26a has a substantially semi-elliptical shape, and the cylinder head covering portion 26b has a substantially triangular shape, and then the cover member 26 is formed in a shape integrated with the both shapes.

(26) The cover member 26 is fastened across the mating surfaces 24 of the cylinder head 16 and the head cover 18 (see FIG. 3). Further, as shown in FIG. 4, the cover member 26 is mounted on the mounting surface 21, for example, with the fastening bolts (second fastening members) 30 such as a hexagonal bolt, from a direction perpendicular to the mating surfaces 24 of the cylinder head 16 and the head cover 18. Further, the cover member 26 has a width dimension W2 substantially equal to the full width W1 of the mating surfaces 24 (see FIG. 1). The full width W1 of the mating surfaces 24 is equal to the full width of the side walls 16a, 18a on the front ends of the cylinder head 16 and the head cover 18.

(27) Further, as shown in FIG. 2, a peripheral edge of the cover member 26 has an edge 34 which is substantially parallel to an axial direction T of fastening bolts 32 for fixing a mounting bracket M1 to the head cover 18. In other words, the edge 34 which is a part of the peripheral edge of the cover member 26 is formed in the axial direction T of the fastening bolts 32. The edge 34 is composed of a substantially straight line (see halftone dot part) connecting a center of a fastening bolt 30a on the upper side and a center of a fastening bolt 30e on the lower side among the plurality of fastening bolts 30 for fastening the cover member 26 (see FIGS. 3 and 4). On the mounting surface 21 corresponding to the edge 34 of the cover member 26, the plurality of fastening holes 23a, 23, 23e (see FIG. 4) or preferably three or more fastening holes 23 are provided. Note that, as shown in FIG. 2, the edge 34 which is the part of the peripheral edge of the cover member 26 provided on the left bank 12 is formed in the axial direction T of the fastening bolts 32, and the same effect as the right bank 12 is obtained.

(28) Furthermore, as shown in FIG. 1, a lower end of the cover member 26 in the cylinder axis line A direction is located higher than the mating surfaces 25 of the cylinder head 16 and the cylinder block 20. That is, a lower end portion of the cover member 26 does not cover a front surface of the cylinder block 20. The lower end of the cover member 26 in the cylinder axis line A direction does not reach the cylinder block 20, but is delimited by the lower portion of the cylinder head 16 in the cylinder axis line A direction. Note that, in the present embodiment, the hexagonal bolts formed with hexagonal head portions are shown as the fastening bolts 32, however, they are not limited thereto, stud bolts not provided with head portions may be used.

(29) As shown in FIGS. 3, 4 and 5, the head cover 18 is provided with a bulging portion 36, which is located on an upper portion of the front end thereof (on the upper portion of the timing train chamber) and protrudes upward more than a general portion located on a rear side in the cylinder row direction, and an inclined surface 37, which is continuous with the bulging portion 36 and is inclined downwardly toward the rear side in the cylinder row direction from the bulging portion 36. As shown in FIG. 9, the pair of bulging portions 36 is formed with a height dimension larger than that of other portions of the head cover 18, and the head cover 18 has rigidity and strength which are increased by the pair of bulging portions 36 and the inclined surfaces 37.

(30) As shown in FIG. 2 viewed from the front side of the vehicle, the bulging portion 36 includes a first flat surface 40a which is located on a valley portion 38 side between the left and right banks 12, 12 and over a location between the intake and exhaust camshafts 17a, 17b, an inclined surface 40b which is inclined downwardly outwardly in the left-right direction from the first flat surface 40a, and a second flat surface 40c which is located at a position lower than the first flat surface 40a in the up-down direction and extends outwardly in the left-right direction from the inclined surface 40b.

(31) The first flat surface 40a and the second flat surface 40c are formed with threaded-holes 42 into which threaded-portions of the fastening bolts 32 are screwed. One end portion of the mounting bracket M1 (an engine mounting portion) is fastened to the head cover 18 via the fastening bolts 32 which are screwed into the threaded-holes 42 of the first flat surface 40a and the second flat surface 40c. The other end portion of the mounting bracket M1 is fastened to a vehicle body frame 46a via a vibration isolator 44a (see FIG. 10).

(32) It is configured such that a fastening direction of the fastening bolts (first fastening members) 32 for fastening the mounting bracket M1 to the head cover 18 downwardly from the upper side, and a fastening direction of the fastening bolts (second fastening members) 30 for fastening the cover member 26 to the cylinder head 16 and the head cover 18 in a horizontal direction or in the cylinder row direction, are substantially perpendicular to each other.

(33) Further, as shown in FIG. 1 with reference to FIG. 2, the two fastening bolts 32 for fastening the mounting bracket M1 to the head cover 18 are provided spaced from each other in a direction intersecting the cylinder row direction, and the two fastening bolts 30c, 30d among the plurality of fastening bolts 30 for fastening the cover member 26 to the cylinder head 16 and the head cover 18 are provided so as to be located in a range between axis lines T, T of the pair of fastening bolts 32 adjacent to each other.

(34) With further reference to FIGS. 5 to 9, a structure of the head cover 18 will be described in detail. FIG. 5 is a plan view of the head cover shown in FIG. 4, FIG. 6 is a side view of the head cover seen from a direction of an arrow X in FIG. 5, FIG. 7 is a bottom view of the head cover shown in FIG. 5, FIG. 8 is an enlarged cross-sectional view taken along a line VIII-VIII in FIG. 5, and FIG. 9 is an enlarged cross-sectional view taken along a line IX-IX in FIG. 3.

(35) As shown in FIG. 5, on the one end side in the cylinder row direction of the head cover 18, the bulging portion 36 for covering an upper portion of the driving force transmission mechanism (not shown) is provided. On an upper surface of the bulging portion 36, an inclined surface portion 52 having the inclined surface 37 which is inclined downwardly toward the other end side in the cylinder row direction is provided.

(36) As shown in FIG. 6, the inclined surface 37 is formed so as to rise upwardly from an intermediate position in the cylinder row direction of the head cover 18, to be continuous with the first flat surface 40a and the second flat surface 40c of the bulging portion 36 at the one end side in the cylinder row direction. Note that, the first flat surface 40a and the second flat surface 40c of the bulging portion 36 respectively serve as a top surface and a first fastening portion.

(37) Note that, the inclined surface 37 is composed of a first inclined surface 37a with a tilt angle 1 with respect to a lower surface 18a of the head cover 18, a second inclined surface 37b with a tilt angle 2 with respect to the lower surface 18a, and a substantially flat surface 37c which is interposed between the first inclined surface 37a and the second inclined surface 37b. By interposing the substantially flat surface 37c between the first inclined surface 37a and the second inclined surface 37b, the tilt angles 1, 2 of the first inclined surface 37a and the second inclined surface 37b can be easily set to be different from each other. Note that, the tilt angles 1, 2 of the first inclined surface 37a and the second inclined surface 37b may be set to be equal or substantially equal to each other.

(38) It is preferred that the intermediate position where the inclined surface 37 rises in the cylinder row direction of the head cover 18 is a position closer to the one end side than a middle position between the one end side and the other end side in the cylinder row direction of the head cover 18. Further, the tilt angles 1, 2 of the first inclined surface 37a and the second inclined surface 37b are preferably set such that components in a vertically downward direction of a mount input load, which are respectively received by the first flat surface 40a and the second flat surface 40c of the bulging portion 36, are maximized.

(39) Further, as shown in FIG. 5, the head cover 18 is formed with a pair of first ribs 54 extending in the cylinder row direction in plan view. The pair of first ribs 54 extends linearly in parallel to each other. One end side of the pair of first ribs 54 is formed continuously with the bulging portion 36.

(40) Further, as shown in FIG. 8, inside the pair of first ribs 54, hollow oil passages 56 which are sealed at the one end side in the cylinder row direction are formed. By dropping or discharging lubricating oil through a plurality of small holes (not shown) communicating with the oil passage 56, it is possible to improve lubricating properties of the intake cam shaft 17a and the exhaust cam shaft 17b which are provided on the upper side of the cylinder head 16.

(41) Furthermore, returning to FIG. 5, the head cover 18 is formed with three openings 58 for inserting ignition plugs (not shown) which pass through front and rear surfaces of the head cover 18 to be held by the cylinder head 16, and is provided with second ribs 60 for coupling together the three openings 58 in the cylinder row direction. The second ribs 60 are arranged in inclined states to intersect an axis line B of the head cover 18 in plan view (see FIG. 5), and are formed of vertical walls projecting upward in a cross-sectional view (see FIG. 8).

(42) The bulging portion 36 is formed with a pair of openings (through-holes) 64 through which oil control valves (hereinafter referred to as OCVs) 62 are inserted (see FIGS. 3 and 4). The pair of openings 64 has substantially elliptical shapes in plan view, and is disposed spaced from each other by a predetermined distance in a direction perpendicular to the cylinder row direction.

(43) The OCV 62 is mounted on a cam holder (not shown) which is fastened to the cylinder head 16. The cam holder (not shown) is formed in a separate body from the cylinder head 16. The OCV 62 is provided without contacting with an inner peripheral edge of the opening 64, and such that a part thereof is exposed to the outside from the opening 64. Since the OCV 62 is mounted on (supported by) the cam holder on the cylinder head 16 side, it is configured such that transmission of vibration of the head cover 18 to the OCV 62 is prevented. Note that, the cam holder (not shown), on which the OCV 62 is mounted, is preferably configured to be a separate body from the head cover 18.

(44) As shown in FIG. 7, on the one end side in the cylinder row direction at an inner wall of the head cover 18 facing the cylinder head 16, a plurality of boss portions 66 formed by bulging are provided. The fastening bolts 30 are screwed into the boss portions 66. The head cover 18 is provided with third ribs 68 for coupling the boss portions 66 and peripheral edge portions 64a of the through-holes 64.

(45) FIG. 10 is a partially virtual perspective view showing a state in which the engine and the transmission are mounted on the vehicle body frame, FIG. 11 is a plan view of the engine and the transmission shown in FIG. 10, FIG. 12 is a side view of the engine and the transmission shown in FIG. 10, and FIG. 13 is a front view of the engine and the transmission shown in FIG. 10.

(46) Inside the vibration isolator 44a shown in FIG. 10, for example, a cylindrical bush (not shown) made of an elastic body is provided, and the front side of the engine 10 is floated and supported by the bush. Note that, the vibration isolator 44a is preferably a liquid sealed type active vibration isolator. In this manner, the front side in the vehicle front-rear direction of the engine 10 is suspended and supported via a pair of mounting brackets M1 and the vibration isolators 44a which are fastened to the vehicle body frame 46a (see FIG. 10). Note that, the pair of mounting brackets M1 and the vibration isolators 44a are adapted to function as a first engine mounting portion.

(47) As shown in FIGS. 10 to 13, on the transmission 14 which is provided in a linked manner on a vehicle rear side of the engine 10, via fastening bolts 50, a pair of mounting brackets M2 is mounted, on both the left and right sides in the vehicle width direction at lower rear end portions of the vehicle. The pair of mounting brackets M2 is, for example, floated and supported by vehicle body frames 46b via vibration isolators 44b having cylindrical bushes (not shown). Note that, the pair of mounting brackets M2 and the vibration isolators 44b are adapted to function as a second engine mounting portion.

(48) The engine 10 is suspended such that the first engine mounting portion (the vibration isolators 44a and the pair of mounting brackets M1 on the front side which are provided on the head cover 18) and the second engine mounting portion (the vibration isolators 44b and the pair of mounting brackets M2 on the rear side which are mounted on the transmission 14) are located on a principal axis of inertia PAI of the engine 10. Note that, the principal axis of inertia PAI is a specific axis having an origin of the gravity center G of the engine 10.

(49) That is, as shown in side view in FIG. 12, a fastening point P1 of the mounting bracket M1 for the head cover 18 is provided on a front side of the principal axis of inertia PAI, and a fastening point P2 of the mounting bracket M2 for the transmission 14 is provided on a rear side of the principal axis of inertia PAI.

(50) In this manner, by arranging the fastening points P1, P2 in the front-rear direction of the engine 10 on the principal axis of inertia PAI, a driving stability can be improved. Further, by considering the principal axis of inertia PAI, it is possible to set a mounting position of the engine 10 in an appropriate position capable of reducing engine vibration.

(51) The engine 10, which is applied with the head cover structure according to the present embodiment, is basically configured as described above, and operation and effects thereof will be described below.

(52) In a case of attaching the vibration isolator 44a and the mounting bracket M1 for supporting the engine 10 to the head cover 18, a vibration during travel of the vehicle, a centrifugal force during turning, a load in the front-rear direction during acceleration or deceleration, and the like are inputted to the head cover 18 from the mounting bracket M1. In comparison with a conventional head cover of simple rectangular shape, in the present embodiment, since the mounting bracket M1 is attached to the bulging portion 36 which projects to cover the driving force transmission mechanism, a rigidity of the bulging portion 36 is relatively high without thickening the head cover. Further, by forming the inclined surface 37 so as to be continuous with the bulging portion 36, a height dimension is gradually increased toward the one end side in the cylinder row direction owing to the inclined surface 37, and thus the entire inclined surface 37 functions as a rib (partially rigid rib). In the present embodiment, in the bulging portion 36 where the mount input load corresponding to a weight of the engine 10 is inputted, the inclined surface 37 forms the partially rigid rib, and thus it is possible to ensure high rigidity against the mount input load from multiple directions.

(53) Further, in the present embodiment, in the bulging portion 36 where the mount input load is inputted, by providing the pair of first ribs 54 extending in the cylinder row direction, it is possible to prevent deformation in the cylinder row direction of the head cover 18, thereby ensuring sealing performance of the head cover 18.

(54) Further, in the present embodiment, by substantially orthogonalizing the fastening direction of the fastening bolts 32 for fastening the mounting bracket M1 to the head cover 18 with respect to the fastening direction of the fastening bolts 30 for fastening the cover member 26 to the cylinder head 16 and the head cover 18, and by providing the fastening holes 23 (mounting surface 21) for fastening the cover member 26 in proximity to the first flat surface 40a and the second flat surface 40c of the bulging portion 36 so that the fastening holes 23 (mounting surface 21) for fastening the cover member 26 are arranged around the first flat surface 40a and the second flat surface 40c of the bulging portion 36, it is possible to partially thicken the head cover (see FIG. 9). As a result, the rigidity of the head cover 18 around the first flat surface 40a and the second flat surface 40c of the bulging portion 36 can be increased. Further, since the threaded-holes 42 (the fastening boss portion of the first fastening portion) for the fastening bolts 32 and the fastening holes 23 (the fastening boss portion of the second fastening portion) for the fastening bolts 30 are formed in directions substantially perpendicular to each other, the rigidity around the first flat surface 40a and the second flat surface 40c of the bulging portion 36 is increased not only in one direction but also in multiple directions. Therefore, it is possible to sufficiently increase the rigidity against loads in multiple directions which are inputted from the mounting bracket M1, while suppressing an increase in engine weight.

(55) In a case where the mounting bracket M1 is attached to the bulging portion 36 of the head cover 18, by the mount input load which is inputted from the mounting bracket M1, a force to separate the mating surfaces 24 (coupling surfaces) of the cylinder head 16 and the head cover 18 from each other, is generated. In the present embodiment, when the mount input load is applied to the mating surfaces 24 of the cylinder head 16 and the head cover 18, since the cover member 26 for covering both the cylinder head 16 and the head cover 18 across the mating surfaces 24 thereof serves as a rigid member, it is possible to suitably avoid that the mating surfaces 24 of the cylinder head 16 and the head cover 18 are separated from each other to generate a gap between the mating surfaces 24.

(56) In other words, since the cover member 26 is fastened across the mating surfaces 24 of the cylinder head 16 and the head cover 18, a force to couple together the mating surfaces 24 of the cylinder head 16 and the head cover 18 is applied so that a coupling state of the mating surfaces 24 can be firmly held.

(57) Further, in the present embodiment, when the mount input load is applied in the range between axis lines T of the pair of fastening bolts 32 adjacent to each other, since the two fastening bolts 30c, 30d for fastening the cover member 26 are provided in the range (see FIG. 1), because of the threaded-holes 42 (the fastening boss portion of the first fastening portion) for the fastening bolts 32 and the fastening holes 23 (the fastening boss portion of the second fastening portion) for the fastening bolts 30, it is possible to increase the rigidity by locally (partially) thickening a thickness of a portion to which the mount input load is inputted. Therefore, it is possible to suppress deformation of the head cover 18, thereby supporting the engine in a stable manner.

(58) Further, in the present embodiment, even in a case where the head cover 18 is formed to have three openings 58 for inserting members such as the ignition plugs, which are inserted through the head cover 18 and are held by the cylinder head 16, the rigidity is not reduced thanks to the second ribs 60 for coupling together the three openings 58 in the cylinder row direction, and a desired rigidity can be ensured.

(59) Further, in the present embodiment, even in a case where the bulging portion 36 for supporting the mounting bracket M1 is formed to have the openings 64 through which the OCVs 62 are inserted, the rigidity is not reduced thanks to the third ribs 68 for coupling together the boss portions 66 and the peripheral edge portions 64a of the openings 64, and the desired rigidity can be ensured.

(60) Furthermore, when the mounting bracket M1 serving as the engine mounting portion is attached to the head cover 18, by the mount input load which is inputted from the mounting bracket M1, a force to separate the mating surfaces 24 (coupling surfaces) of the cylinder head 16 and the head cover 18 from each other is generated. However, in the present embodiment, since the cover member 26 is provided so as to cover both the cylinder head 16 and the head cover 18 across the mating surfaces 24 thereof, the force to couple together the mating surfaces 24 of the cylinder head 16 and the head cover 18 is applied, so that the coupling state of the mating surfaces 24 can be firmly held.

(61) As a result, in the present embodiment, when the mount input load is applied to the mating surfaces 24 of the cylinder head 16 and the head cover 18, since the cover member 26 which is fastened across the mating surfaces 24 of the cylinder head 16 and the head cover 18 serves as the rigid member, it is possible to suitably avoid that the mating surfaces 24 of the cylinder head 16 and the head cover 18 are separated from each other to generate the gap between the mating surfaces 24.

(62) In the case where the mounting bracket M1 serving as the engine mounting portion is attached to the head cover 18, by the load (mount input load) which is inputted from the mounting bracket M1, the force to separate the mating surfaces 24 (coupling surfaces) of the cylinder head 16 and the head cover 18 from each other is generated. However, in the present embodiment, since the cover member 26 is provided so as to cover both the cylinder head 16 and the head cover 18, the force to couple together the mating surfaces 24 of the cylinder head 16 and the head cover 18 is applied, so that the coupling state of the mating surfaces 24 can be firmly held.

(63) As a result, in the present embodiment, when the mount input load is applied to the mating surfaces 24 of the cylinder head 16 and the head cover 18, since the cover member 26 which is provided across both the cylinder head 16 and the head cover 18 serves as the rigid member, it is possible to suitably avoid that the mating surfaces 24 of the cylinder head 16 and the head cover 18, which constitute a part of the engine 10, are separated from each other to generate the gap between the mating surfaces 24.

(64) Further, in the present embodiment, the mounting surface 21 for mounting the cover member 26 to the cylinder head 16 and the head cover 18 is set to be perpendicular to the mating surfaces 24 of the cylinder head 16 and the head cover 18. As a result, in the present embodiment, the mounting surface 21 (coupling surface) of the cylinder head 16 and the head cover 18, on which the cover member 26 is mounted, can be in a direction substantially parallel to the mount input load (a direction along the mount input load), and thus it is possible to suppress opening between the cylinder head 16 and the head cover 18. Further, by mounting the cover member 26 from a direction which is perpendicular to a direction to open the mating surfaces 24, the mounting workability can be improved.

(65) Further, in the present embodiment, by setting the width dimension W2 of the cover member 26 to be substantially equal to the full width W1 of the mating surfaces 24, it is possible to cover the mating surfaces 24 (full width of the mating surfaces 24) from one end to the other end in the width direction thereof, thereby suppressing opening of the mating surfaces 24 in a substantially full range in the width direction of the mating surfaces 24.

(66) Further, in the present embodiment, by setting the width dimension W2 of the cover member 26 to be substantially equal to the full width W1 of the mating surfaces 24, it is possible to allow separation (dispersion) of the fastening points (30a, 30b, 30c, 30d) from one end to the other end of the full width in the width direction of the cover member 26 to prevent the opening by the cover member 26, thereby firmly fixing the cover member 26 to the mounting surfaces 21 of the cylinder head 16 and the head cover 18, and thereby suppressing the opening of the mating surfaces 24. Assuming that the width dimension W2 of the cover member 26 is set to be smaller than the full width W1 of the mating surfaces 24 (W1>W2), it is required to couple together portions of the mating surfaces 24 which are not covered by the cover member 26, for example, with fastening members or the like, and thus the number of components is increased, while there is a possibility that the opening occurs at the portions of the mating surfaces 24 which are not covered with the cover member 26.

(67) Further, in the present embodiment, on the upper and lower positions of one end and the other end of the full width in the width direction of the mating surfaces 24, the fastening bolts 30a, 30b, 30c, 30d for respectively fastening the cover member 26 to the cylinder head 16 and the head cover 18 are provided (see FIG. 4), and thus it is possible to firmly fix the cover member 26 across the full width of the mating surfaces 24 which have a possibility to open.

(68) Further, in the present embodiment, by setting the edge 34 provided on the cover member 26 to be in substantially parallel to an input direction of the mount input load from the mounting bracket M1, it is possible to increase a holding force of the mating surfaces 24 by the cover member 26.

(69) Further, in the present embodiment, since the lower portion of the cylinder head 16 is coupled to the cylinder block 20 via the mating surfaces 25, it is possible to increase the rigidity of the cylinder head 16. By increasing the rigidity of the cylinder head 16, it is possible to suppress deformation of the cylinder block 20 even when the mount input load is inputted to the cylinder block 20.

(70) Further, in the present embodiment, since the lower end of the cover member 26 is located higher than the mating surfaces 25 of the cylinder block 20 and the cylinder head 16, and does not cover the front surface of the cylinder block 20, it is possible to improve a joining accuracy between the cylinder head 16 and the head cover 18, thereby increasing a coupling strength therebetween.

(71) Furthermore, in the present embodiment, since the side walls 16a, 18a provided on the front ends in the cylinder row direction of the cylinder head 16 and the head cover 18 are not formed in separate bodies from the cylinder head 16 and the head cover 18, but are respectively formed integrally with the cylinder head 16 and the head cover 18, they can have rigidity. Further, a lower end of the cylinder head 16 is integrally fastened to an upper end of the cylinder block 20 by fastening means such as bolts, so that a bag-like space portion (upper portion of the timing train chamber) can be formed between the cylinder head 16 and the side wall 16a of the cylinder head 16. In this case, by providing the side wall 16a of the cylinder head 16 for forming the space portion together with the cylinder head 16, it is possible to provide the mating surfaces 25 (fastening surfaces) with the cylinder block 20 (timing train cover 28) on the lower portion of the cylinder head 16.

(72) Note that, the present embodiment is described by use of the cover member 26 provided on the V-type engine, however, the present invention is not limited thereto, but can be, for example, applied to a cover member provided on an in-line engine (not shown).