JPH0320483Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to the camshaft support structure of an engine, particularly the camshaft of an overhead camshaft type engine in which the camshaft is disposed above the intake and exhaust valves in the cylinder head. Regarding support structures.

(Prior Art) In an overhead camshaft engine in which a camshaft placed above the intake and exhaust valves directly drives the intake and exhaust valves, a valve spring is used to bias the valves in the closing direction when the valves are opened. There is a problem in that the reaction force acts directly on the camshaft, causing the camshaft to deflect toward the side opposite to the cam drive transmission surface. In particular, this camshaft deflection is caused by the valve jump phenomenon that tends to occur as the engine speeds up, i.e. the phenomenon in which the upper end (or tappet) of the valve stem separates from the cam surface, or the bounce phenomenon, i.e. the valve seat after the valve is seated. This becomes more noticeable when the valve spring is strengthened to prevent the jump phenomenon, and the above-mentioned jump phenomenon becomes even more likely to occur due to the deflection of the camshaft.

This problem can be solved by increasing the number of bearings that support the camshaft, but especially in the case of overhead camshaft engines, there is not enough space to install multiple bearings in the cylinder head, so it is recommended to increase the number of bearings. This would increase the overall length of the engine. Furthermore, when the number of bearings is increased, the sliding resistance or driving torque of the camshaft increases, and the loss of engine output due to driving the camshaft increases.

By the way, according to Japanese Patent Application Laid-Open No. 57-2409, 1
Two intake valves and two exhaust valves are provided for each cylinder, and each intake valve and exhaust valve are driven respectively.
In a four-valve dual overhead camshaft engine equipped with two camshafts, an invention has been disclosed relating to a camshaft support structure in which bearings for these camshafts are provided between a pair of cams on the shaft. In this type of engine, the cylinder head bolt installed between adjacent cylinders is located below the camshaft. This is to deal with the problem that the engine must be placed outside the bolt and the width of the engine becomes wider as a result. However, when attempting to provide a bearing that completely sandwiches the camshaft between a pair of cams as in the present invention, such a bearing requires an oil groove for lubrication and seals on both sides of the camshaft. Since the width cannot be made too narrow, the dimension between the pair of cams inevitably becomes long, and in order to prevent the camshaft from deflecting, bearings are installed both between the pair of cams and between the adjacent cylinders. As a result, the dimensions of the camshaft and, by extension, the overall length of the engine become significantly longer.

(Purpose of the invention) The present invention addresses the above-mentioned actual situation in the camshaft support structure of an overhead camshaft engine. The purpose is to effectively suppress the deflection of the camshaft due to reaction force, thereby preventing the valve jump phenomenon and bounce phenomenon, the accompanying deterioration of intake and exhaust performance, and a decrease in engine output. In particular, the aim is to achieve this without increasing the overall length of the engine.

(Structure of the invention) In order to achieve the above object, the engine camshaft support structure according to the invention is characterized by the following structure.

That is, in an overhead camshaft engine in which a camshaft is disposed above the intake and exhaust valves in the cylinder head, at least two complete bearings that completely sandwich the camshaft from two directions are used for one camshaft. and a partial bearing that supports the shaft only from the side opposite to the cam drive transmission surface side, and a bearing cap that supports the camshaft in the complete bearing from the side opposite to the cam drive transmission surface side, and the partial bearing. Connect and integrate. An oil passage is provided in this connection portion to guide lubricating oil supplied to the complete bearing to the partial bearing side. According to such a configuration, the partial bearing is
Because it is located on the opposite side of the camshaft's cam drive transmission surface, it can absorb the reaction force of the valve spring that acts on the camshaft from the cam drive transmission surface side in the same way as the complete bearing described above. As in the case where the camshaft is provided, the deflection of the camshaft is effectively suppressed. In this case, since this partial bearing does not completely sandwich the camshaft, its sliding resistance is small, so the loss of camshaft drive torque or engine output does not increase significantly, and it is different from a complete bearing cap. Since it is integrated and has high rigidity, it is possible to reduce the wall thickness, and the provision of the partial bearing does not increase the overall length of the engine. This partial bearing cannot supply lubricating oil directly from the camshaft, and is often installed in locations where space is tight, such as between a pair of adjacent cams in each cylinder. The necessary lubrication is provided by the oil passage provided using the coupling part to increase the rigidity of the partial bearing.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

The present embodiment relates to a four-valve two-overhead camshaft engine equipped with a variable valve timing mechanism.

As shown in FIGS. 1 to 3, the cylinder head 1 is provided with two intake ports 2 ₁ , 2 ₂ and two exhaust ports 3 ₁ , 3 ₂ for one cylinder, respectively.
These valves 4 ₁ , 4 ₂ , 5 1 , 5 ₂ are connected to the combustion chamber 6 via the second intake valves 4 ₁ , 4 ₂ and the first and second exhaust valves 5 ₁ , 5 _{2 .} Always upward (closed direction) by valve spring 7...7
is energized by In addition, the above cylinder head 1
are fixed to the cylinder block 9 by a plurality of head bolts 8...8, and spark plugs 10...10 are disposed in the upper center of each combustion chamber 6...6 in the cylinder head 1, respectively. ing.

On the other hand, an intake camshaft 11 and an exhaust camshaft 12 are arranged in parallel on both sides of the upper part of the cylinder head 1. Each of these camshafts 11 and 12 has a
First and second intake cams 13 ₁ , 13 ₂ and first and second exhaust cams 14 ₁ , 14 ₂ are provided for each cylinder, and these cams 13 ₁ , 13 ₂ , 14 ₁ ,
14 ₂ and the upper end of the stem of each of the above-mentioned valves 4 ₁ , 4 ₂ , 5 ₁ , 5 ₂ are tapepets 15 ₁ ...15 ₁ , 15 ₂ ...1
The rotation of the intake camshaft 11 opens the first and second intake valves 4 ₁ and 4 2 of each cylinder at a predetermined timing, and the rotation of the exhaust camshaft 12 opens the first _and second intake valves 4 1 and 4 ₂ of each cylinder at a predetermined timing. 1st and 2nd of each cylinder
The exhaust valves 5 ₁ and 5 ₂ are opened and operated at predetermined timing. Here, both camshafts 11,
A timing pulley 16 is fixed to one end of the camshaft 12, and these camshafts 11,
12 is adapted to be rotationally driven in synchronization with the crankshaft.

In this embodiment, the journal portions 17, 17 between the first and second cylinders and between the third and fourth cylinders on the intake camshaft 11 (the portion between the third and fourth cylinders is not shown; the same applies hereinafter) ) and exhaust camshaft 12
In the journal portions 17...17 between the first and second cylinders and between the third and fourth cylinders, there are bucket boxes 18...18 and bucket boxes 18...
Bucket cap 19 connected to 18...19
The journal portions 17 of the camshafts 11 and 12...
Rotating members 20 . Two tappet fitting holes 18a, 18a are provided, and the tappets of the first intake valves ₄₁ , ₄₁ in the first and second cylinders are respectively adjacent to these four sets of eight fitting holes 18a...18a. 15 ₁ , 15 ₁ , tappets 15 1 , ₁₅ of the first intake valves 4 ₁ , 4 ₁ in the third and fourth cylinders
₁ , first exhaust valve 5 ₁ in the first and second cylinders,
5 ₁ tappets 15 ₁ , 15 ₁ and tappets 15 of the first exhaust valves 5 ₁ , 5 ₁ in the third and fourth cylinders.
₁ and 15 ₁ are slidably inserted. and,
As shown in FIG. 3, a gear 18b formed on the lower surface of the bucket box 18 in the rotating member 20 between the first and second cylinders on the intake camshaft 11 is disposed laterally on the cylinder head 1. drive shaft 2
The first gear 21a is meshed with the motor 22 for rotating the drive shaft 21, and the bucket cap 19 of the rotary member 20 and the third and fourth cylinders on the intake camshaft 11 are also provided with a motor 22 that rotates the drive shaft 21. Bucket cap 19 of rotating member 20 provided between
are connected via the connecting portion 19a, so that these rotating members 20, 20 are integrally rotated around the intake camshaft 11 as the motor 22 rotates. . Similarly, a rotating member 20 between the first and second cylinders and a rotating member 2 between the third and fourth cylinders are provided on the exhaust camshaft 12.
0 is also rotated around the exhaust camshaft 12. As a result, the tappets 15 1 ... 15 1 of the first intake valves 4 ₁ ... 4 ₁ and the first exhaust valves _{5 1} ... 5 ₁ of each cylinder rotate around the intake camshaft ₁₁ and the exhaust camshaft 12. and these camshafts 1
Each cam 13 for a predetermined rotation angle position of 1 and 12
₁ ...13 ₁ ,14 ₁ ...14 ₁ and tapepet 15 ₁ ...
By moving the contact position with 15 ₁ , the opening/closing timing of the first intake valves 4 ₁ ... 4 ₁ and the first exhaust valves 5 ₁ ... 5 ₁ is changed according to the operating state of the engine. It's becoming like that. Here, the second intake valve 4 ₂ ...4 ₂ of each cylinder and the second
Tappet of exhaust valve 5 ₂ ...5 ₂ 15 ₂ ...15 ₂
is the insertion hole 1a provided in the cylinder head 1...
It is inserted into 1a.

Therefore, the intake camshaft 11 and the exhaust camshaft 1
2 is a bearing 2 between both ends and the second and third cylinders.
Although it is rotatably supported by 3...23,
These bearings 23...23 are mounted on the end wall 1b of the cylinder head 1 and the partition wall 1 between the second and third cylinders, respectively.
A semicircular recess is formed in c, and bearing caps 24 . With these bearings 23...23, the camshafts 11, 12
The main journal portions 26...26 provided at both ends and between the second and third cylinders are completely sandwiched from the entire periphery.

In addition, the main journal portion 26...2 as described above
Bearing that completely holds 6 (complete bearing) 23...2
3, the camshafts 11 and 12 are arranged between the first and second intake cams 13 1 and 13 ₂ of each cylinder and between the first and second intake cams 13 ₁ and 13 2 of each cylinder.
Also between the exhaust cams 14 ₁ and 14 ₂ , the bearing 27...
27. This bearing 27...27 is connected to a bearing cap 29... fixed to the cylinder head 1 by bolts 28...28.
29, semicircular bearing recesses 29a...29a formed in the bearing caps 29...29 connect the first and second intake cams ₁₃₁ , 13 _2nd interval and 1st,
It is fitted into the upper half of the auxiliary journal parts 30...30 provided between the second exhaust cams 14 ₁ and 14 ₂ from above, that is, from the opposite side of the cam drive transmission surface.

As shown in FIG. 1, a complete bearing 23 ₁ is provided at the end of the exhaust camshaft 12 on the first cylinder side.
The bearing cap 24 that constitutes the exhaust camshaft 12, the bearing cap 29 that constitutes the partial bearing ₂₇₁ between the first and second exhaust cams ₁₄₁ and ₁₄₂ of the first cylinder, and the The bearing cap that constitutes a complete bearing at the end on the fourth cylinder side and the bearing cap that constitutes a partial bearing between the first and second exhaust cams of the fourth cylinder are connected to connecting portions 31 and 31, respectively. Therefore, the bearing cap 24 is connected and integrated into a single cap member 32 ₁ , 32 ₁ , and constitutes a complete bearing 23 ₂ between the second and third cylinders of the exhaust camshaft 12. , the bearing cap 29 of the partial bearing 27 ₂ between the first and second exhaust cams 14 ₁ and 14 ₂ of the second cylinder located on both sides thereof, and the first and second exhaust cam 1 of the third cylinder.
The bearing cap 29 of the partial bearing 27 ₃ between the bearings _{4 1} and 14 ₂ is also connected and integrated by the connecting portions 31 . . . 31 to form a single cap member 32 ₂ .
Furthermore, although not shown, each bearing of the intake camshaft 11 is similarly configured.

Here, as shown in FIGS. 4 to 7, each cap member 32 ₁ (the illustrated cap member is at the end of the first cylinder side of the intake camshaft 11, but the same applies to other cap members) , a first passage 33 whose one end opens to the inner peripheral surface of the semicircular recess 24a in the bearing cap 24 of the complete bearing 23;
a second passage 35 whose one end communicates with the other end, passes through the one connecting portion 31, and whose other end opens into the bolt insertion hole 34 in the bearing cap 29 of the partial bearing 27;
An oil passage is formed with one end opening into the bolt insertion hole 34 and the other end opening into the inner peripheral surface of the semicircular recess 29a in the bearing cap 29 of the partial bearing 27. . As shown in FIG. 6, one end of the first passage 33 is connected to a circumferential groove 37 formed in the main journal portion 26 of the camshafts 11, 12 and a radial hole 3 through which the circumferential groove 37 communicates.
8, the axial center portions of the shafts 11 and 12 are communicated with an oil supply passage 39 which is bored in the axial direction, and as shown in FIG. It communicates with a crescent-shaped oil groove 40 formed in the inner peripheral surface of the semicircular recess 29a in the bearing cap 29 of the bearing 27. In this embodiment, a thin wall 1d is provided upright from the cylinder head 1 below each of the partial bearings 27...27, and together with the bearing cap 29 of the partial bearing 27, this constitutes a bearing. Rather, it is to prevent the cutter from escaping downward when the bearing recess 29a is machined with the bearing cap 29 assembled to the cylinder head.

According to the above configuration, the rotation of the intake camshaft 11 and the exhaust camshaft 12 causes the intake valves 4 ₁ , 4 ₂ and the exhaust valves 5 ₁ , 5 ₂ to be connected to the valve springs 7 .
When the camshafts 11 and 12 are opened downward against the
The reaction force of the valve springs 7...7 acting upward on each cam 13 ₁ , 13 ₂ , 14 ₁ , 14 ₂ supports both ends of the camshafts 11 and 12 and between the second and third cylinders. The camshafts 11 and 12 are received by the complete bearings 23...23, but if the valve springs 7...7 are particularly strong, these bearings 23...23 alone will not allow the camshafts 11, 12 to move upward in the middle of the complete bearings 23, 23. There is a possibility of bending. However, the camshaft 11,
12 is a first and second intake cam 13 ₁ for each cylinder;
13 ₂ and between the first and second exhaust cams 14 ₁ and 14 ₂ are supported by partial bearings 27 . . . 27 from above, that is, from the opposite side of the cam drive transmission surface. Bearing 27...
... 27 is also adapted to receive the above reaction force. In other words, valve spring 7...
7, the camshafts 11 and 12 are supported not only between both ends and the second and third cylinders, but also between the pair of cams in each cylinder. , 12 is suppressed,
Suction and exhaust valves 4 due to flexure of camshafts 11 and 12
₁ , 4 ₂ , 5 ₁ , and 5 ₂ jump phenomena and bounce phenomena are prevented. In that case, since the partial bearings 27...27 support the auxiliary journal parts 30...30 of the camshafts 11, 12 only from above, the complete bearings 23...23 completely sandwich them from both the upper and lower directions. The driving torque of the camshafts 11, 12 is significantly increased by providing the partial bearings 27...27 in order to prevent the camshafts 11, 12 from deflecting. There is no.

In addition, since the partial bearings 27...27 are composed only of the bearing caps 29...29 located above the camshafts 11 and 12, which have sufficient space,
By providing these partial bearings 27...27, there is no need to increase the dimension between the first and second cams of each cylinder. 31 , 31 are integrally connected to the bearing cap 24 of the adjacent complete bearing 23 to form a single cap member 32 , respectively.
₁ , 32 ₂ , the bearing cap 29 of the partial bearing 27 is more rigid than if it were separated from the bearing cap 24 of the complete bearing 23; ) can be made thinner. As a result, the first and second intake cams 13 1 and ₁ of the camshafts 11 and 12 on which the partial bearings 27...27 are provided
3 ₂ and the dimensions between the first and second exhaust cams 14 ₁ and 14 ₂ can be further narrowed.
It is possible to provide a plurality of partial bearings 27 (four in this embodiment) for each of the camshafts 11 and 12 without increasing the overall length of the camshafts 2 or the engine.

In addition, the main journal portions 26 of the camshafts 11 and 12...
. . 26 and the auxiliary journal portion 30 . The radial holes 38 of the camshafts 11 and 12 lead to the circumferential grooves 37 provided on the circumferential surfaces of the camshafts 11 and 12, and once the main journal portion 26 is lubricated here, the bearing of the complete bearing 23 is A first passage 33 bored in the cap 24, a second passage 35 bored in the connecting part 31, and a partial bearing 2.
The inner periphery of the semicircular recess 27a of the bearing cap 29 is passed through the circumference of the bolt 28 in the bolt insertion hole 34 provided in the bearing cap 29 of No. The oil reaches a crescent-shaped oil groove 40 formed on the surface and lubricates the auxiliary journal portion 30. In that case, the auxiliary journal part 3 whose lower half is open
The lubrication of No. 0 is performed after the main journal portion 26 is lubricated, and since the oil groove 40 is shaped like a crescent and both ends 40' and 40' (see Fig. 7) are closed, the lubricating oil is not lubricated. Hydraulic pressure drop due to leakage can be prevented.

(Effects of the invention) As described above, according to the invention, in an overhead camshaft engine in which a camshaft is disposed above the intake and exhaust valves, at least two camshafts are provided that completely sandwich the camshaft from two directions. Since we have provided a complete bearing and a partial bearing that supports the camshaft only from the opposite side of the cam drive transmission surface, it is possible to reduce the deflection of the camshaft due to the reaction force of the valve spring without increasing the drive torque of the camshaft. It can be prevented. In particular, in the present invention, since the bearing cap of the complete bearing and the partial bearing are connected and integrated through the connecting part, the rigidity of the complete bearing and the partial bearing is increased, and the camshaft is affected by the reaction force. The deflection of the exhaust valve is more effectively suppressed, thereby preventing suction caused by deflection of the camshaft, jump phenomenon or bounce phenomenon of the exhaust valve, deterioration of suction and exhaust performance caused by these, and reduction in engine output. Furthermore, by increasing the rigidity of the partial bearing, it is possible to reduce the thickness of the partial bearing, without increasing the overall length of the camshaft or the engine. A large number of partial bearings can be provided to receive the reaction force, and even when the partial bearings are installed in locations where space is limited, such as between a pair of adjacent cams in each cylinder, the required lubrication for the partial bearings can be maintained. It becomes possible to do this.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a plan view of the main part of the cylinder head, FIG. 2 is a vertical sectional side view of the main part of the cylinder head, and FIG.
FIG. 3 is a longitudinal sectional front view cut along a line. Also, Fig. 4 is a plan view showing the connection state between the bearing cap of a complete bearing and the bearing cap of a partial bearing, and Figs. 5, 6, and 7 are cross sections taken along lines -, -, and - in Fig. 4, respectively. It is a diagram. 11, 12...Camshaft, 23...Complete bearing, 2
7...Partial bearing, 31...Connection part, 33, 35,
36...Oil passage.

Claims (1)

[Scope of utility model registration request] Bearings that support the camshaft include at least two complete bearings that completely sandwich the camshaft from two directions, and a portion that supports the shaft only from the side opposite to the cam drive transmission surface. The partial bearing is connected and integrated with a bearing cap that supports the camshaft in the complete bearing from the side opposite to the cam drive transmission surface side, and lubricating oil supplied to the complete bearing is supplied to the connecting part. An engine camshaft support structure characterized by having an oil passage leading to the partial bearing side.