EP1728976A1

EP1728976A1 - Internal combustion engine

Info

Publication number: EP1728976A1
Application number: EP06011297A
Authority: EP
Inventors: Tsunero Hamada; Yasuo Okamato
Original assignee: Yamaha Motor Co Ltd
Current assignee: Yamaha Motor Co Ltd
Priority date: 2005-05-31
Filing date: 2006-05-31
Publication date: 2006-12-06
Anticipated expiration: 2026-05-31
Also published as: EP1728976B1; US20060266315A1

Abstract

The present invention relates to an internal combustion engine, in particular multicylinder internal combustion engine (10), comprising a cam shaft (11,12) having at least one cam (13a-h,14a-h) for depressing a rocker arm (21,22), and at least one cam carrier (15), said cam carrier (15) being detachably mounted on a cylinder head (9), and being formed integrally with a cam shaft bearing portion (15m) and with a rocker shaft support section (15h), said rocker shaft support section (15h) independently supporting a rocker shaft (23,24) inserted in the rocker shaft support section.

Description

The present invention relates to an internal combustion engine, in particular a multi-cylinder internal combustion engine having rocker shafts for supporting for rotation rocker arms adapted to open/close valves in the multi-cylinder internal combustion engine and cam carriers on which these rocker shafts are supported.
Hitherto, opening/closing of valves in a multi-cylinder internal combustion engine has been carried out by rotating a cam shaft having the same number of cams as the valves corresponding to cylinders such that cam noses of the cams depress rocker arms supported on the rocker shaft and further valve stems depressed by the rocker arms move up and down. Inventions related to the multi-cylinder internal combustion engine provided with such a valve opening/closing mechanism include ones described in JP-A-2000-170506 and JP-B-2537205 .
It is stated in JP-A-2000-170506 that an intake side cam shaft and an exhaust side cam shaft are held by underlying lower cam holders and overlying upper cam holders therebetween and the lower cam holders in this condition are fastened to the cylinder head with first fastening members. The upper cam holder and lower cam holder are fastened to each other at a position further inward than the first fastening members, with second fastening members each having a smaller diameter than the first fastening member.
According to JP-A-2000-170506 , it is stated that size reduction of the cylinder head is possible and the first fastening member also serves as a turn-lock of the rocker shaft.
In addition, it is stated in JP-B-2537205 that a rocker arm holder is formed with a spark plug insert mouth, a rocker shaft is divided such that sub-divided rocker shafts are disposed overlapping each other in the axial direction of the cam shaft, and the rocker shaft is supported at its end on the rocker holder.
According to JP-B-2537205 , a narrow space above the cylinder head can be utilized effectively.
However, in the invention described in JP-A-2000-170506 , the rocker shafts are assembled to the cylinder head, each passing through their respective lower cam holders (cam carriers) and rocker arms. Therefore, their centering requires much time and assembling is complicated.
Further, to secure the positional accuracy of the rocker shaft support section formed on the lower cam holder (cam carrier) for supporting the rocker shaft, through-work machining is necessary after the lower cam holder (cam carrier) provided independently on each cylinder head is assembled to the cylinder head. Therefore, the scale of machining facilities for such through-work machining might become larger. In addition, since the rigidity of hole machining tools needs to be secured to secure the machining accuracy, size reduction of the tool diameter is difficult. Therefore, weight saving and size reduction of the rocker shaft are difficult and in turn, weight saving and size reduction of the rocker arm are also difficult.
In the invention as described in JP-B-2537205 , rocker shafts are configured such that they are supported on a plurality of holders (cam carriers) between adjacent holders (cam carriers). Therefore, when the holders (cam carriers) are assembled to the cylinder head, they need to be assembled in succession while rocker arms are fitted on the rocker shafts, causing complicated assembly work.
Further, since for the rocker shaft not to overlap the hole of the plug insert section, the support section for supporting the rocker shaft needs to be machined for each holder (cam carrier), the positional accuracy is difficult to secure.
In view of the foregoing, the object of this invention is to provide a multi-cylinder internal combustion engine provided with cam carriers in which centering of rocker shafts requires less time, assembly to a cylinder head is easy, weight saving and size reduction of the rocker shaft are effected, and further, small-scale machining facilities can be used satisfactory for machining rocker shaft support sections of the cam carriers, and accuracy of the position, at which the rocker arm is supported, is easily secured.
This objective is solved in an inventive manner by an internal combustion engine, in particular multi-cylinder internal combustion engine, comprising a cam shaft having at least one cam for depressing a rocker arm, and at least one cam carrier, said cam carrier being detachably mounted on a cylinder head, and being formed integrally with a cam shaft bearing portion and with a rocker shaft support section, said rocker shaft support section independently supporting a rocker shaft inserted in the rocker shaft support section.
Preferably, the rocker shaft, which is supported independently for each cam carrier, is inserted in the rocker shaft support section of the cam carrier and extends on both sides of or on one side of the cam shaft bearing section so as to be disposed parallel to the cam shaft, and wherein the rocker arm is supported for rotation by the rocker shaft on both sides of or on one side of the cam bearing section of the cam carrier.
Further, preferably the rocker shaft support section is provided extending on both sides of or on one side of the cam shaft bearing section in the same direction as the cam shaft and is formed with a slot for supporting the rocker arm, and wherein the rocker shaft support section is formed with a through-hole passing therethrough across the slot, and the rocker shaft is inserted in the through-hole.
Still further, preferably the cam carrier is mounted approximately directly above each cylinder, and all of the rocker arm supported on both sides of the cam shaft bearing section of the cam carrier, correspond to one cylinder.
Yet further, preferably the internal combustion engine is a multi-cylinder internal combustion engine, which includes cam shafts having a plurality of cams for depressing rocker arms formed thereon, a cam carrier for supporting the cam shafts, rocker shafts passing through a cam shaft bearing section formed in the cam carrier and extending on both sides thereof to be disposed parallel to the cam shafts, wherein the rocker arms are supported for rotation by the rocker shafts on both sides of the cam shaft bearing section of the cam shafts.
According to another embodiment, the cam carrier is mounted between adjacent cylinders, the rocker arm supported on one side of the cam shaft bearing section with respect to the cam shaft bearing section of the cam carrier is used for one of the adjacent cylinders, and the rocker arm supported on the other side of the cam shaft bearing section is used for the other of the adjacent cylinders.
According to yet another embodiment, the internal combustion engine further comprises a slipping-off prevention member mounted to the cam carrier for preventing the rocker shaft from slipping off the cam carrier.
Preferably, the slipping-off prevention member is a collar inserted in a hole of an ignition plug insert section formed in the cam carrier, wherein a notch, with which part of the collar is engaged, is formed in the rocker shaft for the prevention of slipping-off of the rocker shaft.
Further, preferably the slipping-off prevention member is a collar inserted in a hole for a fastening member with the cylinder head formed in the cam carrier, wherein a notch, with which part of the collar is engaged, is formed in the rocker shaft for the prevention of slipping-off of the rocker shaft.
Yet further, preferably a linear expansion coefficient of the collar is different from a linear expansion coefficient of the cam carrier.
Still further, preferably the cam carrier, the rocker shaft and the rocker arm have an oil passage supplied from the cylinder head, the rocker shaft is formed hollow inside and closed at both ends, and the notch is covered with the slipping-off prevention member.
According to a further embodiment, the oil passage is constituted by first, second and third oil passages, the cam carrier is provided with the first oil passage, the rocker shaft is provided with the second oil passage, the rocker arm is provided with the third oil passage, wherein an oil delivery port of the third oil passage is directed toward the contact face of the rocker arm with the cam, the rocker shaft is supported by the cam carrier without rotation, and a communication area between the second oil passage and the third oil passage changes to be increased or decreased, with the cam depressing the rocker arm.
In the following, the present invention is explained in greater detail with respect to several embodiments thereof in conjunction with the accompanying drawings, wherein:

FIG. 1: is a plan view of a multi-cylinder internal combustion engine according to embodiment 1,
FIG. 2: is a plan view showing the construction of a cam carrier according to the same embodiment,
FIG. 3: is a front view showing the construction of the cam carrier according to the same embodiment,
FIG. 4: shows the construction of the cam carrier according to the same embodiment, in which FIG. 4 (a) is a sectional view taken along line B-B of FIG. 3 and FIG. 4 (b) is a sectional view taken along line D-D of FIG. 3,
FIG. 5: are sectional views of the cam carrier taken along line A-A of FIG. 2, showing the arrangement of oil passages according the same embodiment, in which FIG. 5 (a) is a sectional view showing a second oil passage and a third oil passage being in communication and FIG. 5 (b) is a sectional view showing the second oil passage and the third oil passage being not in communication,
FIG.6: is a plan view showing the construction of a cam carrier according to embodiment 2,
FIG. 7: is a front view showing the construction of the cam carrier according to the same embodiment,
FIG. 8: is a plan view of a multi-cylinder internal combustion engine according to embodiment 3,
FIG. 9: is a plan view showing the construction of a cam carrier according to the same embodiment,
FIG. 10: is a front view showing the construction of the cam carrier according to the same embodiment,
FIG. 11: is a sectional view taken along line C-C of FIG. 10, showing the construction of the cam carrier according to the same embodiment,
FIG. 12: shows the construction of cam carriers provided on a cylinder head at both ends according to the same embodiment, in which FIG. 12 (a) is a plan view of the cam carrier without a cam shaft bearing section and FIG. 12 (b) is a plan view of the cam carrier with a cam shaft bearing section, and
FIG. 13: shows the construction of the cam carriers provided on the cylinder head at both ends according to the same embodiment, in which FIG. 13 (a) is a sectional view of the cam carrier without a cam shaft bearing section and FIG. 13 (b) is a sectional view of the cam carrier with a cam shaft bearing section.

Description of Reference Numerals

9: cylinder head
10: multi-cylinder internal combustion engine
11: intake side cam shaft
12: exhaust side cam shaft
13a through 13h: intake side cam
14a through 14h: exhaust side cam
15: cam carrier
15m: cam shaft bearing section
15c: intake side cam shaft bearing hole
15d: exhaust side cam shaft bearing hole
15e: intake side rocker shaft through-hole (through-hole)
15f: exhaust side rocker shaft through-hole (through-hole)
15g: hole of ignition plug insert section (slipping-off prevention member)
15h: slot
15p; first oil passage
16: collar
17: ignition plug
21: intake side rocker arm
22: exhaust side rocker arm
21 a: shaft insert hole (through-hole)
22a: shaft insert hole (through-hole)
21 p,22p: third oil passage
21q,22q: oil delivery port
23: intake side rocker shaft
24: exhaust side rocker shaft
23a,24a: notch
23p,24p,23p-1,23p-2,24p-1,24p-2: second oil passage
215: hole for a fastening member (slipping-off prevention member)

[Embodiment 1]

Now, embodiment 1 will be described below.
Embodiment 1 is shown in FIG. 1 through FIG. 6.
Referring first to the construction, in a multi-cylinder internal combustion engine 10, as shown in FIG. 1, a cylinder head 9 is disposed on a cylinder block (not shown), and a plurality of cam carriers 15 are provided on the cylinder head 9.
The cam carrier 15 supports an intake side cam shaft 11 and an exhaust side cam shaft 12 disposed parallel to each other, for rotation, as shown in FIG. 1, and is provided with a cam shaft bearing section 15m formed with cam shaft bearing holes 15c, 15d for supporting these cam shafts 11, 12, as shown in FIG. 3. As shown in FIG. 1, the intake side cam shaft 11 is formed with a plurality of cams 13a through 13h, and the exhaust side cam shaft 12 with a plurality of cams 14a through 14h. These pluralities of cams 13a through 13h, 14a through 14h are each adapted to depress their respective rocker arms 21, 22.
The cam carrier 15, as shown in FIG. 3, includes an upper holder 15a and a lower holder 15b, and the upper holder 15a is formed with upper recesses 15x, 15y and the lower holder 15b with lower recesses 15v, 15w so that the cam shafts 11, 12 can be held from above and below. Regarding these recesses 15x, 15y, 15v, 15w, the upper recess 15x and lower recess 15v are combined to form an intake side cam shaft bearing hole 15c, and the upper recess 15y and lower recess 15w are combined to form an exhaust side cam shaft bearing hole 15d. The intake side cam shaft 11 is fitted in the intake side cam shaft bearing hole 15c formed in this way for rotation, and the exhaust side cam shaft 12 is fitted in the exhaust side cam shaft bearing hole 15d for rotation. Thus, the cam shafts 11, 12 are supported by a cam shaft bearing section 15m having the cam shaft bearing holes 15c, 15d, as shown in FIG. 1.
Further, the lower holder 15b of the cam carrier 15 is formed with an intake side rocker shaft through-hole 15e and an exhaust side rocker shaft through-hole 15f in a rocker shaft support section 15n between the intake side cam shaft bearing section 15c and the exhaust side cam shaft bearing section 15d, as shown in FIG. 3.
Rocker shafts 23, 24 are supported by the rocker shaft support section 15n, as shown in FIG. 1, FIG. 2 and FIG. 4. The rocker shaft support section 15n is provided on both sides of the cam shaft bearing section 15m, extending in the same direction as the cam shafts 11, 12 (see FIG. 1). The rocker shaft through- holes 15e, 15f is formed in the cam carrier 15 as through-holes passing through the rocker shaft support section 15n, and the rocker shafts 23, 24 are inserted in these rocker shaft through- holes 15e, 15f.
Further, the lower holder 15b of the cam carrier 15 is formed with a hole 15g for an ignition plug insert section between the intake side rocker shaft through-hole 15e and the exhaust side rocker shaft through-hole 15f in the direction perpendicular to the axial direction of these shaft receiving sections 15e, 15f, as shown in FIG. 2 and FIG. 4. A cylindrical collar 16is fitted In the hole 15g for the ignition plug insert section formed in the cam carrier 15, as shown in FIG. 1, and an ignition plug 17 is disposed toward the cylinder head 9 through the collar 16.
The collar 16 is a member mounted to the cam carrier 15 and having the function of preventing the rocker shafts 23, 24 from slipping off the cam carrier 15. The rocker shafts 23, 24 are formed with notches 23a, 24a with which parts of the collar 16 are engaged, for the prevention of their slipping-off.
Further, the linear expansion coefficient of the collar 16 is different from that of the cam carrier 15 and it is larger than the linear expansion coefficient of the cam carrier 15 or smaller. This is because it is ensured that the collar 16 can be attached to and detached from the cam carrier 15 in a cold or a hot environment and the collar 16 is prevented from slipping off the cam carrier 15 at room temperature. Such an arrangement improves handling properties of the cam carrier 15, as well as its assembling properties, and a slipping-off prevention condition can be realized of a small amount of play compared with slipping-off prevention devices such as bolts.
The cam carrier 15 is formed with slots 15h, as shown in FIG. 2 and FIG. 4, and intake side rocker arms 21 and exhaust side rocker arms, 22 are inserted in these slots 15h. The rocker arms 21, 22 are formed with shaft insert holes 21 a, 22a, respectively.
With the intake side rocker arm 21 fitted in the slot 15h of the cam carrier 15, the intake side rocker shaft 23 is inserted in the intake side rocker shaft through-hole 15e and shaft insert hole 21 a. Likewise, with the exhaust side rocker arm 22 fitted in the slot 15h of the cam carrier 15, the exhaust side rocker shaft 24 is inserted in the exhaust side rocker shaft through-hole 15f and shaft insert hole 22a. The rocker shafts 23, 24 are supported independently for each cam carrier 15, pass through the rocker shaft support section 15n of the cam carrier 15 and extend on both sides of the cam shaft bearing section 15m so as to be disposed parallel to the cam shafts 11, 12. The rocker arms 21, 22 are supported for rotation by the rocker shafts 23, 24 on both sides of the cam shaft bearing section 15m of the cam carrier 15.
When the intake side cam shaft 11 and exhaust side cam shaft 12 are rotated, each of the intake side cams 13a through 13h and exhaust side cams 14a through 14h depresses each of the intake side rocker arms 21 and exhaust side rocker arms 22 or releases the depression.
The cam carrier 15 is mounted approximately directly above each cylinder and configured such that all of the plurality of rocker arms 21, 22 supported on both sides of the cam shaft bearing section 15m of the cam carrier 15, correspond to one cylinder. That is, all valve faces 32 (see FIG. 3) corresponding to one cylinder are adapted to be opened/closed by the movement of the four rocker arms 21, 22 supported on the two rocker shafts 23, 24 of one cam carrier 15.
The upper holder 15a is formed with bolt holes 15j and the lower holder 15b with bolt holes 15k (seed FIG. 2 and FIG. 4). When the upper holder 15a and lower holder 15b are combined, bolts 25 are inserted in the bolt holes 15j of the upper holder 15a and bolt holes 15k of the lower holder 15b from above, as shown in FIG. 2, so that the upper holder 15a and lower holder 15b are fastened. Bolts 26 are inserted in bolt holes 15t of the lower holder 15b so that the cam carrier 15 is fixed to the cylinder head 9.
Further, the cam carrier 15 is formed with an oil passage 15p, shown in FIG. 2 and FIG. 3, the intake side rocker shaft 23 and exhaust side rocker shaft 24 are formed with oil passages 23p, 24p, respectively, and the rocker arms 21, 22 are formed with oil passages 21 p, 22p, respectively.
The cam carrier 15, rocker shafts 23, 24 and rocker arms 21, 22 have oil passages 15p, 23p, 24p, 21 p, 22p for oil supplied from the cylinder head 9. The rocker shafts 23, 24 are each formed hollow inside and closed at both ends. Further, the rocker shafts 23, 24 have notches 23a, 24a (see FIG. 4) covered with the collar 16 as a slipping-off prevention member, respectively.
The cam carrier 15 is provided with the first oil passage 15p, the rocker shafts 23, 24 with the second oil passages 23p, 24p, 23p-1, 23p-2, 24p-1, 24p-2 and the rocker arms 21, 22 with the third oil passages 21p, 22p. Oil delivery ports 21q, 22q of the third oil passages 21 p, 22p are directed toward the contact faces of the rocker arms 21, 22 with the arms 13a through 13h, 14a through 14h, and the rocker shafts 23, 24 are supported on the cam carrier 15 without rotation.
The second oil passages in the rocker shafts 23, 24 are constituted by the oil passages 23p, 24p formed in the axial direction of the rocker shafts 23, 24; the oil passages 23p-1, 24p-1 formed in the direction perpendicular to the axial direction from the oil passages 23p, 24p and allowing oil in-flow from the first oil passage 15p; and the oil passages 23p-2, 24p-2 formed in the direction perpendicular to the axial direction from the oil passages 23p, 24p and allowing oil passage into the third oil passages 21 p, 22p.
With the cams 13a through 13h, 14a through 14h not depressing the rocker arms 21, 22, the rocker arms 21, 22 are rotatable, so that communication sections between the oil passages 23p-2, 24p-2 and the third oil passages 21 p, 22p decrease their size (see FIG. 5(a)), and with the cams 13a through 13h, 14a through 14h depressing the rocker arms 21, 22, communication sections between the oil passages 23p-2, 24p-2 and the third oil passages 21p, 22p increase their size (see FIG. 5(b)).
At this time, since whether or not the cams 13, 14 depress the rocker arms 21, 22, the rocker shafts 22, 24 don't rotate, the oil passages 23p-1, 24p-1 and the first oil passage 15p are in communication at all times.
The cylinder head 9 is provided below of the carriers 15 and a valve mechanism 31 is provided inside the cylinder head 9, as shown in FIG. 3. In the valve mechanism 31, the top of a valve stem 33 having a valve face 32 is fixed with an upper retainer 34 and the top of a valve spring 33 is fixed to the upper retainer 34.
The valve spring 35 is disposed between the upper retainer 34 and a spring seat 36, and when the cams 13a through 13h, 14a through 14h depress the rocker arms 21, 22, the valve stems 33 are depressed by the rocker arms 21, 22 to be lowered so that the valve springs 35 are compressed. On the contrary, when the cams 13a through 13h, 14a through 14h release the depression of the rocker arms 21, 22, the contracted valve springs 35 expand so that the rocker arms 21, 22 are raised, as well as the rocker stems 33. As such, raising and lowering the valve stems 33 causes up and down movements of the valve faces 32.
Now, reference will be made to the function of the multi-cylinder internal combustion engine 10 according to the embodiment.
When the cam shafts 11, 12 rotate, the plurality of cams 13a through 13h, 14a through 14h also rotate, and when the cams 13a through 13h, 14a through 14h depress the rocker arms 21, 22, the valve stems 33 are lowered and the valve faces 32 are lowered inside the cylinder (not shown), so that air is taken in on the intake side and combustion gas is exhausted on the exhaust side.
When the cams 13a through 13h, 14a through 14h are not in the condition of depressing the rocker arms 21, 22, the valve stems 33 are raised and the valve faces 32 are also raised inside the unillustrated cylinder, so that no air will be taken in on the intake side and no exhaust gas will be exhausted on the exhaust side.
While the cam shafts 11, 12 are rotating, lubricating oil flows in from the first oil passage 15p in the cam carrier 15, and the lubricating oil flows through the second oil passages 23p, 24p in the rocker shafts 23, 24 and further through the third oil passages 21 p, 22p in the rocker arms 21, 22 to be delivered from delivery ports 21q, 22q. The delivered lubricating oil is splashed on the contact faces of the cams 13a through 13h, 14a through 14h with the rocker arms 21, 22.
In the foregoing multi-cylinder internal combustion engine 10, there are provided cam shafts 11, 12 having a plurality of cams 13a through 13h, 14a through 14h for depressing rocker arms 21, 22, formed thereon; a plurality of cam carriers 15 each formed integrally with cam shaft bearing section 15m for supporting the cam shafts 11, 12 and a rocker shaft support section 15n for supporting rocker shafts 23, 24; the rocker shafts 23, 24 being supported independently for each cam carrier 15, inserted in the rocker shaft support section 15n of the cam carrier 15 and extending on both sides of the cam shaft bearing section 15m so as to be disposed parallel to the cam shafts 11, 12; and the rocker arms 21, 22 being supported for rotation on the rocker shafts 23, 24 on both sides of the cam bearing section 15m of the cam carrier 15.
Therefore, since a plurality of cam carriers 15 are provided and the rocker shaft 23, 24 are adapted to pass independently through each of the rocker shaft support sections 15n of the cam carriers 15, not all the plurality of rocker shafts 23, 24 provided need be centered such that their axes are arranged in the direction of the cam shaft, facilitating assembly work. Further, since the rocker shaft 23, 24 are divided for each cam carrier 15 and small in length, weight saving and size reduction (smaller diameter and shorter length) of the rocker shaft 23, 24 can be effected. Further, small-scale, machining facilities of the cam carrier 15 can be used satisfactory. Furthermore, the positional accuracy of the holes for supporting rocker shafts 23, 24 to the cam shaft bearing section 15m can be secured easily, so that improvement in reliability due to improvement in the behavior of the valve drive system can be realized. Moreover, the scale of the mounting work of the rocker shafts 23, 24 to the arm carrier 15 can be decreased.
Further, the rocker shaft support section 15n is provided extending on both sides of the cam shaft bearing section 15m in the same direction as the cam shafts 11, 12 and is formed with slots 15h for supporting the rocker arms 21, 22, the rocker shaft support section 15n is formed with through- holes 15e, 15f passing therethrough across the slots 15h, and the rocker shafts 23, 24 are inserted in the through- holes 15e, 15f. Therefore, since the rocker arms 21, 22 are held by the slots 15h on both sides in the vicinity of the shaft insert holes 21a, 22a, supporting rigidity of the rocker arms 21, 22 can be secured, as well as accurate movements of the rocker arms 21, 22, effecting higher rotation and improvement in reliability.
Further, the cam carrier 15 is mounted approximately directly above each cylinder, and all of the plurality of rocker arms 21, 22 supported on both sides of the cam shaft bearing section 15m of the cam carrier 15, correspond to one cylinder. If the cam carriers 15 are each provided between cylinders, additional cam carriers 15 need to be provided to support rocker arms 21, 22 disposed at both ends of the cam shafts 11, 12. On the contrary, such cam carriers 15 are dispensed with in this case, so that the number of parts can be decreased, as well as the number of types of parts.
Further, a collar 16 is mounted to the cam carrier 15 to prevent the rocker shafts 23, 24 from slipping off the cam carrier 15. Therefore, the rocker shafts 23, 24 are fixed to the cam carrier 15 with the collar 16. Thus, the rocker arms 21, 22 can be prevented from slipping off during their rocking movement.
Further, the collar 16 is a collar inserted in a hole 15g of an ignition plug insert section formed in the cam carrier 15, and notches 23a, 24a with which parts of the collar 16 are engaged, are formed in the rocker shaft 23, 24 for the prevention of slipping-off of the rocker shafts 23, 24. Therefore, by using the collar 16 in the hole 15g of the ignition plug insert section, the rocker shafts 23, 24 can be prevented from slipping off the cam carrier 15 within a narrow space.
Further, the cam carrier 15, the rocker shafts 23, 24 and the rocker arms 21, 22 have passages 15p, 23p, 24p, 21p, 22p for oil supplied from the cylinder head 9, the rocker shaft 23, 24 are each formed hollow inside and closed at both ends, and the notches 23a, 24a are covered with the collar 16. Therefore, leakage of oil passing through the rocker shafts 23, 24 from the notches 23a, 24a can be suppressed. This structure allows the hollow portions inside the rocker shaft 23, 24 to be increased in size, effecting weight saving of the rocker shafts 23, 24.
Furthermore, the cam carrier 15 is provided with the first oil passage 15p, the rocker shafts 23, 24 with the second oil passages 23p, 24p and the rocker arms 21, 22 with the third oil passages 21 p, 22p, oil delivery ports 21 q, 22q of the third oil passages 21 p, 22p are directed toward the contact faces of the rocker arms 21, 22 with the cams 13, 14, the rocker shafts 23, 24 are supported by the cam carrier without rotation, and communication areas between the second oil passages 23p, 24p and the third oil passages 21p, 22p change to be increased or decreased, with the cams 13, 14 depressing the rocker arms 21, 22. Since, rotation of the rocker shafts 23, 24 are restricted at this time through slipping-off prevention action of a small amount of play, change in the communication area can be set accurately. This cause oil to be delivered accurately and intermittently, allowing restriction of the oil flow. Therefore, a stirring loss due to delivered oil can be decreased, as well as the oil pump capacity, effecting reduction in the driving loss horsepower of the oil pump.
Although in the multi-cylinder internal combustion engine 10 according to the embodiment 1, the rocker shafts 23, 24 also pass through the rocker shaft support section 15n, the teaching of the invention is not limited to the foregoing embodiment if the rocker shafts 23, 24 can be supported. That is, it is possible that the rocker shafts 23, 24 are configured such that they pass at one ends through the rocker shaft support section 15n and don't pass at the other ends through the rocker shaft support section 15n, and both of the rocker shafts 23, 24 need not necessarily pass each at both ends through the rocker shaft support section 15n at both ends.
Although in the multi-cylinder internal combustion engine 10 according to the embodiment 1, the rocker shafts 23, 24 are provided extending on both sides of the cam shaft bearing section 15m to be disposed parallel to the cam shafts 11, 12, the teaching of the invention is not limited to the foregoing embodiment. That is, the rocker shafts 23, 24 can be configured such that they extend only on one side of the cam shaft bearing section 15m. For example, it is possible that the cam carrier 15 is configured so as to be provided with the cam shaft bearing section 15m extending only on one side thereof in plan view. By way of example, a cam carrier 215 is shown in FIG. 11 and FIG. 12 illustrating embodiment 3.

[Embodiment 2]

The embodiment 2 will be described hereinafter.
FIG. 6 and FIG. 7 show the embodiment 2. In FIG. 6 and FIG. 7, same parts as in the embodiment 1 are designated by same reference numerals and description will not be repeated.
A cam carrier 115 in the embodiment 2 is different from the cam carrier 15 of the embodiment 1 in that as shown in FIG. 7, rocker shaft through- holes 115e, 115f are formed in a rocker shaft support section 115n outside the cam shaft bearing section 115m to be disposed parallel to the cam shafts 11, 12, respectively, and as shown in FIG. 6, the rocker arms 21, 22 rotate for up and down movement at the sides of an ignition plug insert hole 115g, respectively.
As shown in FIG. 6, the cam carrier 115 includes a cam shaft bearing section 115m having cam shaft bearing holes 115c, 115d, and a rocker shaft support section 115n extending on both sides of the cam shaft bearing section 115m, and the rocker shaft support section 115n formed with shaft through- holes 115e, 115f for the rocker shafts 11, 12 to be inserted therein.
Other effects and functions are approximately the same as in the cam carrier 15 of the embodiment 1 of this invention, except that while the rocker shafts 23, 24 on which the rocker arms 21, 22 rotate, are disposed inwardly in the embodiment 1, they are dispose outwardly in the embodiment 2.

[Embodiment 3]

The embodiment 3 will be described hereinafter.
FIG. 8 through FIG. 11 show the embodiment 3. In FIG. 8 through FIG. 11, same parts as in the embodiment 1 are designated by same reference numerals and description will be omitted.
A multi-cylinder internal combustion engine 200 in the embodiment 3 is different from the multi-cylinder internal combustion engine 10 of the embodiment 1 in the following aspects.
That is, in the multi-cylinder internal combustion engine 200, first as shown in FIG. 8, cam carriers 215 are each disposed between adjacent cylinders, rocker arms 21, 22 supported on a cam shaft bearing section 215m at one side with respect to the cam shaft bearing section 215m (see FIG. 10) having cam shaft bearing holes 215c, 215d of the cam carrier 215, are held by the inside walls of slots 215h formed in a rocker shaft support section 215n of the cam carrier 215 and used for one of the adjacent cylinders, and rocker arms 21, 22 supported on the cam shaft bearing section 215m at the other side are held by the slots 215h formed in the rocker shaft support section 215n of the cam carrier 215 and used for the other of the adjacent cylinders.
In addition, in the multi-cylinder internal combustion engine 200, as shown in FIG. 11, a collar 216 as a slipping-off prevention member is inserted in a hole 215s for a fastening member with the cylinder head 9 formed in the cam carrier 215. Further, rocker shafts 223, 224 are formed with notches 223a, 224a with which parts of the collars 216 are engaged, for the prevention of slipping-off of the rocker shafts 223, 224.
As shown in FIG. 8, at the left and right ends of the cylinder head 9, a cam carrier 220a (see FIG. 12(b) and FIG. 13(b)) and a cam carrier 220b (see FIG. 12(a) and FIG. 13(a)) are provided to support the rocker arms 21, 22 for cylinders provided at the left and right ends of the cylinder head 9. These cam carriers 220a, 220b, as shown in FIG. 12 and FIG. 13, are each formed in the same shape as part of the cam carrier 215, but they have shapes each lacking the other part of the cam carrier 215. This is because when four valve mechanisms 31 are provided for each cylinder in a four-cylinder engine as shown in FIG. 8, four rocker arms 21, 22 at the both ends on the cylinder head 9 are left unfastened and it is satisfactory if they can be supported. Further, in the cam carrier 220a, rocker shafts 323, 324 are smaller in length than the rocker shafts 23, 24. Also, in the cam carrier 220b, rocker shafts 423, 424 are smaller in length than the rocker shafts 23, 24, and each formed with the hole 215s for a fastening member in which the collar 216 is inserted. The rocker shafts 423, 424 are also formed with notches 423a, 424a.
In the multi-cylinder internal combustion engine 200 as described above, the cam carrier 215 are each mounted between adjacent cylinders, the rocker arms 21, 22 supported on one side of the cam shafts bearing section 215m with respect to the cam shaft bearing section 215m, are used for one of the adjacent cylinders, and the rocker arms 21, 22 supported on the other side of the cam shaft bearing section 215m are used for the other of the adjacent cylinders. Therefore, even in the multi-cylinder internal combustion engine 200 having an ignition plug 17 dispose above each cylinder, the cam carriers 215 can be configured such that they don't obstruct the disposition of ignition plugs 17. Thus, the degree of freedom in designing can be increased for the disposition of cam carriers 215 in the multi-cylinder internal combustion engine 200.
The collar 216 is inserted in the hole 215s formed in the cam carrier 215 for a fastening member with the cylinder head 9, the rocker shafts 223, 224 are formed with the notches 223a, 224a with which parts of the collars 216 are engaged, for the prevention of the slipping-off of the rocker shafts 223, 224. Therefore, by using the collar 216 inserted in the hole 215s for a fastening member with the cylinder head 9, the rocker shafts 223, 224 can be prevented from slipping off the cam carrier 215 within a narrow space.
The description above discloses (amongst others) in order to achieve the foregoing object, an embodiment (first aspect) of a multi-cylinder internal combustion engine including: a cam shaft having at least one cam for depressing a rocker arm, formed thereon; at least one cam carrier formed integrally with a cam shaft bearing section for supporting the cam shaft and a rocker shaft support section for supporting a rocker shaft and mounted detachably on a cylinder head; the rocker shaft being supported independently for each cam carrier, inserted in the rocker shaft support section of the cam carrier and extending on both sides or on one side of the cam shaft bearing section so as to be disposed parallel to the cam shaft; and the rocker arm being supported for rotation by the rocker shaft on both sides or on one side of the cam bearing section of the cam carrier.
A further embodiment (second aspect) is directed to the arrangement of the first aspect, in which the rocker shaft support section is provided extending on both sides or on one side of the cam shaft bearing section in the same direction as the cam shaft and is formed with a slot for supporting the rocker arm, the rocker shaft support section is formed with a through-hole passing therethrough across the slot, and the rocker shaft is inserted in the through-hole.
A further embodiment (third aspect) is directed to the arrangement of the first or second aspect, in which the cam carrier is mounted approximately directly above each cylinder, and all of the rocker arm supported on both sides of the cam shaft bearing section of the cam carrier, correspond to one cylinder.
A further embodiment (fourth aspect) is directed to the arrangement of the first or second aspect, in which the cam carrier is mounted between adjacent cylinders, the rocker arm supported on one side of the cam shaft bearing section with respect to the cam shaft bearing section of the cam carrier is used for one of the adjacent cylinders, and the rocker arm supported on the other side of the cam shaft bearing section is used for the other of the adjacent cylinders.
A further embodiment (fifth aspect) is directed to the arrangement of one of the first to fourth aspects, further including a slipping-off prevention member mounted to the cam carrier for preventing the rocker shaft from slipping off the cam carrier.
A further embodiment (sixth aspect) is directed to the arrangement of the fifth aspect, in which the slipping-off prevention member is a collar inserted in a hole of an ignition plug insert section formed in the cam carrier, and a notch with which part of the collar is engaged, is formed in the rocker shaft for the prevention of slipping-off of the rocker shaft.
A further embodiment (seventh aspect) is directed to the arrangement of the fifth aspect, in which the slipping-off prevention member is a collar inserted in a hole for a fastening member with the cylinder head formed in the cam carrier, and a notch with which part of the collar is engaged, is formed in the rocker shaft for the prevention of slipping-off of the rocker shaft.
A further embodiment (eight aspect) is directed to the arrangement of the sixth or seventh aspect, in which the linear expansion coefficient of the collar is different from that of the cam carrier.
A further embodiment (ninth aspect) is directed to the arrangement of the sixth or seventh aspect, in which the cam carrier, the rocker shaft and the rocker arm have passages for oil supplied from the cylinder head, the rocker shaft is formed hollow inside and closed at both ends, and the notch is covered with the slipping-off prevention member.
A further embodiment (tenth aspect) is directed to the arrangement of the ninth aspect, in which the oil passage is constituted by a first through a third oil passages, the cam carrier is provided with the first oil passage, the rocker shaft is provided with the second oil passage, the rocker arm is provided with the third oil passage, an oil delivery port of the third oil passage is directed toward the contact face of the rocker arm with the cam, the rocker shaft is supported by the cam carrier without rotation, and communication area between the second oil passage and the third oil passage changes to be increased or decreased, with the cam depressing the rocker arm.
According to the embodiment according to the first aspect, there are provided a cam shaft having at least one cam for depressing a rocker arm, formed thereon; at least one cam carrier formed integrally with a cam shaft bearing section for supporting the cam shaft and a rocker shaft support section for supporting a rocker shaft and mounted detachably on a cylinder head; the rocker shaft being supported independently for each cam carrier, inserted in the rocker shaft support section of the cam carrier and extending on both sides or on one side of the cam shaft bearing section so as to be disposed parallel to the cam shaft; and the rocker arm being supported for rotation by the rocker shaft on both sides or on one side of the cam bearing section of the cam carrier.
Therefore, since at least one cam carrier is provided and a rocker shaft is inserted independently in each of the rocker shaft support sections of the cam carrier, not all the rocker shaft provided, need be centered such that their axes are arranged in the direction of the cam shaft, facilitating assembly work. Further, since the rocker shaft is divided for each cam carrier and small in length, weight saving and size reduction of the rocker shaft can be effected, and small-scale, cam carrier machining facilities can be used satisfactory. Furthermore, the positional accuracy of the hole for supporting a rocker shaft in the rocker shaft support section is secured easily.
According to the embodiment of the second aspect, the rocker shaft support section is provided extending on both sides or on one side of the cam shaft bearing section in the same direction as the cam shaft and is formed with a slot for supporting the rocker arm, the rocker shaft support section is formed with a through-hole passing therethrough across the slot, and the rocker shaft is inserted in the through-hole. Therefore, since the rocker arm is held by the slot 15h on both sides, supporting rigidity of the rocker arm can be secured, as well as accurate movements of the rocker arm, effecting higher rotation and improvement in reliability.
According to the embodiment of the third aspect, the cam carrier is mounted approximately directly above each cylinder, and all of the rocker arm supported on both sides of the cam shaft bearing section of the cam carrier, correspond to one cylinder. If cam carriers are each provided between cylinders, additional cam carriers need to be provided to support rocker arms disposed at both ends of the cam shaft. On the contrary, such cam carriers are dispensed with in this case, so that the number of parts can be decreased, as well as the number of types of parts.
According to the embodiment of the fourth aspect, the cam carrier is mounted between adjacent cylinders, the rocker arm supported on one side of the cam shaft bearing section with respect to the cam shaft bearing section of the cam carrier is used for one of the adjacent cylinders, and the rocker arm supported on the other side of the cam shaft bearing section is used for the other of the adjacent cylinders. Therefore, in the case of a multi-cylinder internal combustion engine having an ignition plug disposed above each cylinder, cam carriers can be configured such that they doesn't obstruct proper disposition of the ignition plugs. Thus, the degree of freedom in designing can be increased for the disposition of cam carriers in the multi-cylinder internal combustion engine.
According to the embodiment of the fifth aspect, a slipping-off prevention member is mounted to the cam carrier to prevent the rocker shaft from slipping off the cam carrier. Therefore, the rocker shaft is fixed to the cam carrier with the slipping-off prevention member. Thus, the rocker arm can be prevented from slipping off during its rocking movement.
According to the embodiment of the sixth aspect, the slipping-off prevention member is a collar inserted in a hole of an ignition plug insert section formed in the cam carrier, and a notch with which part of the collar is engaged, is formed in the rocker shaft for the prevention of slipping-off of the rocker shaft. Therefore, by using the collar in the hole of the ignition plug insert section, the rocker shaft can be prevented from slipping off the cam carrier within a narrow space.
According to the embodiment of the seventh aspect, the slipping-off prevention member is a collar inserted in a hole for a fastening member with the cylinder head formed in the cam carrier, and a notch with which part of the collar is engaged, is formed in the rocker shaft for the prevention of slipping-off of the rocker shaft. Therefore, by using the collar inserted in the hole for a fastening member with the cylinder head, the rocker shaft can be prevented from slipping off the cam carrier within a narrow space.
According to the embodiment of eight aspect, the linear expansion coefficient of the collar is different from that of the cam carrier. That is, the linear expansion coefficient of the collar is larger than that of the cam carrier or smaller. Therefore, the collar can be attached to and detached from the cam carrier in a cold or hot environment and it doesn't slip off the cam carrier at room temperature. Thus, handling properties of the cam carrier can be improved, as well as its assembling properties, and a slipping-off prevention condition can be realized of a small amount of play compared with slipping-off devices such as bolts.
According to the embodiment of the ninth aspect, the cam carrier, the rocker shaft and the rocker arm have a passage for oil supplied from the cylinder head, the rocker shaft is formed hollow inside and closed at both ends, and the notch is covered with the slipping-off prevention member. Therefore, leakage of oil passing through the rocker shaft from the notch can be suppressed. This structure allows the hollow section inside the rocker shaft to be increased in size, effecting weight saving of the rocker shaft.
According to the embodiment of the tenth aspect, the cam carrier is provided with the first oil passage, the rocker shaft is provided with the second oil passage, the rocker arm is provided with the third oil passage, an oil delivery port of the third oil passage is directed toward the contact face of the rocker arm with the cam, the rocker shaft is supported by the cam carrier without rotation, and communication area between the second oil passage and the third oil passage changes to be increased or decreased, with the cam depressing the rocker arm. Since, rotation of the rocker shaft is restricted at this time by the slipping-off prevention action of a small amount of play, change in the communication area can be set accurately. This causes oil to be delivered accurately and intermittently, allowing restriction of the oil flow. Therefore, a stirring loss due to delivered oil can be decreased, as well as the oil pump capacity, effecting reduction in the driving loss horsepower of the oil pump.
The description above discloses as a particularly preferred embodiment in order to provide a multi-cylinder internal combustion engine provided with cam carriers assembly work of which requires less time and each having a rocker shaft allowing its weight saving and size reduction, a multi-cylinder internal combustion engine 10 includes cam shafts 11, 12 having a plurality of cams 13a through 13h, 14a through 14h for depressing rocker arms 21, 22 formed thereon; a cam carrier 15 for supporting the cam shafts 11, 12; rocker shafts 23, 24 passing through a cam shaft bearing section 15m formed in the cam carrier 15 and extending on both sides thereof to be disposed parallel to the cam shafts 11, 12; and the rocker arms 21, 22 being supported for rotation by the rocker shafts 23, 24 on both sides of the cam shaft bearing section 15m of the cam shafts 11, 12.
As discussed above, there is disclosed as a first aspect an embodiment of a multi-cylinder internal combustion engine comprising: a cam shaft having at least one cam for depressing a rocker arm, formed thereon; at least one cam carrier formed integrally with a cam shaft bearing section for supporting the cam shaft and a rocker shaft support section for supporting a rocker shaft and mounted detachably on a cylinder head; the rocker shaft being supported independently for each cam carrier, inserted in the rocker shaft support section of the cam carrier and extending on both sides or on one side of the cam shaft bearing section so as to be disposed parallel to the cam shaft; and the rocker arm being supported for rotation by the rocker shaft on both sides or on one side of the cam bearing section of the cam carrier.
Further, as a second aspect, there is disclosed an embodiment of the multi-cylinder internal combustion engine, wherein the rocker shaft support section is provided extending on both sides or on one side of the cam shaft bearing section in the same direction as the cam shaft and is formed with a slot for supporting the rocker arm, the rocker shaft support section is formed with a through-hole passing therethrough across the slot, and the rocker shaft is inserted in the through-hole.
Further, as a third aspect, there is disclosed an embodiment of the multi-cylinder internal combustion engine, wherein the cam carrier is mounted approximately directly above each cylinder, and all of the rocker arm supported on both sides of the cam shaft bearing section of the cam carrier, correspond to one cylinder.
Further, as a fourth aspect, there is disclosed an embodiment of the multi-cylinder internal combustion engine, wherein the cam carrier is mounted between adjacent cylinders, the rocker arm supported on one side of the cam shaft bearing section with respect to the cam shaft bearing section of the cam carrier is used for one of the adjacent cylinders, and the rocker arm supported on the other side of the cam shaft bearing section is used for the other of the adjacent cylinders.
Further, as a fifth aspect, there is disclosed an embodiment of the multi-cylinder internal combustion engine, further comprising a slipping-off prevention member mounted to the cam carrier for preventing the rocker shaft from slipping off the cam carrier.
Further, as a sixth aspect, there is disclosed an embodiment of the multi-cylinder internal combustion engine, wherein the slipping-off prevention member is a collar inserted in a hole of an ignition plug insert section formed in the cam carrier, and a notch with which part of the collar is engaged, is formed in the rocker shaft for the prevention of slipping-off of the rocker shaft.
Further, as a seventh aspect, there is disclosed an embodiment of the multi-cylinder internal combustion engine, wherein the slipping-off prevention member is a collar inserted in a hole for a fastening member with the cylinder head formed in the cam carrier, and a notch with which part of the collar is engaged, is formed in the rocker shaft for the prevention of slipping-off of the rocker shaft.
Further, as an eight aspect, there is disclosed an embodiment of the multi-cylinder internal combustion engine, wherein the linear expansion coefficient of the collar is different from that of the cam carrier.
Further, as a ninth aspect, there is disclosed an embodiment of the multi-cylinder internal combustion engine, wherein the cam carrier, the rocker shaft and the rocker arm have a passage for oil supplied from the cylinder head, the rocker shaft is formed hollow inside and closed at both ends, and the notch is covered with the slipping-off prevention member.
Further, as a tenth aspect, there is disclosed an embodiment of the multi-cylinder internal combustion engine, wherein the oil passage is constituted by a first through a third oil passages, the cam carrier is provided with the first oil passage, the rocker shaft is provided with the second oil passage, the rocker arm is provided with the third oil passage, an oil delivery port of the third oil passage is directed toward the contact face of the rocker arm with the cam, the rocker shaft is supported by the cam carrier without rotation, and communication area between the second oil passage and the third oil passage changes to be increased or decreased, with the cam depressing the rocker arm.

Claims

Internal combustion engine, in particular multi-cylinder internal combustion engine, comprising a cam shaft having at least one cam for depressing a rocker arm, and at least one cam carrier, said cam carrier being detachably mounted on a cylinder head, and being formed integrally with a cam shaft bearing portion and with a rocker shaft support section, said rocker shaft support section independently supporting a rocker shaft inserted in the rocker shaft support section.
Internal combustion engine according to claim 1, wherein the rocker shaft, which is supported independently for each cam carrier, is inserted in the rocker shaft support section of the cam carrier and extends on both sides of or on one side of the cam shaft bearing section so as to be disposed parallel to the cam shaft, and wherein the rocker arm is supported for rotation by the rocker shaft on both sides of or on one side of the cam bearing section of the cam carrier.
Internal combustion engine according to claim 1 or 2, wherein the rocker shaft support section is provided extending on both sides of or on one side of the cam shaft bearing section in the same direction as the cam shaft and is formed with a slot for supporting the rocker arm, and wherein the rocker shaft support section is formed with a through-hole passing therethrough across the slot, and the rocker shaft is inserted in the through-hole.
Internal combustion engine according to one of the claims 1 or 3, wherein the cam carrier is mounted approximately directly above each cylinder, and all of the rocker arm supported on both sides of the cam shaft bearing section of the cam carrier, correspond to one cylinder.
Internal combustion engine according to one of the claims 1 to 4, being a multi-cylinder internal combustion engine (10), which includes cam shafts (11, 12) having a plurality of cams (13a to 13h, and 14a to 14h) for depressing rocker arms (21, 22) formed thereon, a cam carrier (15) for supporting the cam shafts (11, 12), rocker shafts (23, 24) passing through a cam shaft bearing section (15m) formed in the cam carrier (15) and extending on both sides thereof to be disposed parallel to the cam shafts (11, 12), wherein the rocker arms (21, 22) are supported for rotation by the rocker shafts (23, 24) on both sides of the cam shaft bearing section (15m) of the cam shafts (11, 12).
Internal combustion engine according to one of the claims 1 or 3, wherein the cam carrier is mounted between adjacent cylinders, the rocker arm supported on one side of the cam shaft bearing section with respect to the cam shaft bearing section of the cam carrier is used for one of the adjacent cylinders, and the rocker arm supported on the other side of the cam shaft bearing section is used for the other of the adjacent cylinders.
Internal combustion engine according to one of the claims 1 to 6, further comprising a slipping-off prevention member mounted to the cam carrier for preventing the rocker shaft from slipping off the cam carrier.
Internal combustion engine according to claim 7, wherein the slipping-off prevention member is a collar inserted in a hole of an ignition plug insert section formed in the cam carrier, wherein a notch, with which part of the collar is engaged, is formed in the rocker shaft for the prevention of slipping-off of the rocker shaft.
Internal combustion engine according to claim 7, wherein the slipping-off prevention member is a collar inserted in a hole for a fastening member with the cylinder head formed in the cam carrier, wherein a notch, with which part of the collar is engaged, is formed in the rocker shaft for the prevention of slipping-off of the rocker shaft.
Internal combustion engine according to claim 8 or 9, wherein a linear expansion coefficient of the collar is different from a linear expansion coefficient of the cam carrier.
Internal combustion engine according to one of the claims 8 to 10, wherein the cam carrier, the rocker shaft and the rocker arm have an oil passage supplied from the cylinder head, the rocker shaft is formed hollow inside and closed at both ends, and the notch is covered with the slipping-off prevention member.
Internal combustion engine according to claim 11, wherein the oil passage is constituted by first, second and third oil passages, the cam carrier is provided with the first oil passage, the rocker shaft is provided with the second oil passage, the rocker arm is provided with the third oil passage, wherein an oil delivery port of the third oil passage is directed toward the contact face of the rocker arm with the cam, the rocker shaft is supported by the cam carrier without rotation, and a communication area between the second oil passage and the third oil passage changes to be increased or decreased, with the cam depressing the rocker arm.