JP4415819B2 - Camshaft bearing structure - Google Patents

Description

  The present invention relates to a bearing structure for a camshaft that drives a valve provided for each cylinder of a multi-cylinder internal combustion engine.

  As the cam shaft bearing structure, among the cam journal portions supporting the cam shaft, the clearances of the first and second cam journal portions from the front end side of the internal combustion engine where the timing belt or the chain is disposed are set to other cam journal portions. There is one in which the cam shaft is prevented from swinging due to the timing belt or chain tension (see Patent Document 1). Also, the bearings at both ends of the camshaft are rolling bearings, and the clearance of the rolling bearing is narrower than the clearance of other bearings, reducing friction loss at low speed rotation and suppressing camshaft deflection at high speed rotation. There is also a thing which aims at (patent document 2). In addition, there is Patent Document 3 as a prior art document related to the present invention.

JP 2004-124773 A Japanese Patent No. 2927360 Japanese Utility Model Publication No. 61-49004

  In the bearing structures described in these documents, since the bearings are provided between the cylinders adjacent to each other and at both ends of the cam shaft, and the cam shaft is supported by these bearings, the friction loss of the entire bearing structure is still maintained. large.

  Accordingly, an object of the present invention is to provide a camshaft bearing structure that can reduce the friction loss of the entire bearing structure.

A bearing structure according to the present invention includes a cam shaft that drives either one of an intake valve and an exhaust valve provided for each cylinder of a multi-cylinder internal combustion engine, and a cam journal portion formed on a cylinder head of the internal combustion engine. A camshaft bearing structure comprising a cam cap and a bearing means for rotatably supporting the camshaft, wherein the bearing means has a period during which it receives a reaction force from the valve means. In addition, the above-described problem is solved by the configuration in which the support rigidity of the cam shaft between the cylinders adjacent to each other is smaller than the support rigidity of the cam shaft between the other cylinders. 1).

  A reaction force from the valve means provided for each cylinder acts on the camshaft, and there is a case where the period for receiving the reaction force does not overlap between adjacent cylinders. Each of such cylinders is in a relationship in which the valve means of the other cylinder is opened after the valve means of one cylinder is completely closed. The reaction force from the means does not work at the same time. For this reason, the support strength (support rigidity) of the camshaft can be relatively weaker than the support rigidity between the other cylinders. According to the present invention, the cam shaft is supported by the bearing means configured such that the support rigidity of the cam shaft between the adjacent cylinders is smaller than that between the other cylinders, so the friction between the bearing means and the cam shaft The resistance can be reduced by reducing the support rigidity. As a result, the friction loss of the entire bearing structure can be reduced.

  In the bearing structure of the present invention, as a component of the bearing means, the camshaft is disposed between the cylinders whose support rigidity of the camshaft is reduced, and restricts displacement of the camshaft in a reaction force direction received from the valve means. A displacement restricting member, and the displacement restricting member has a clearance of a size such that the displacement restricting member and the cam shaft are not in contact with each other when the cam shaft is stationary or rotated at a predetermined rotation speed or less. It may be provided so as to be formed between the displacement regulating member and the cam shaft. According to this embodiment, it is possible to suppress deformation of the camshaft between the cylinders in which the camshaft support rigidity is relatively small, and thus, for example, torsion and vibration of the camshaft rotating at high speed can be prevented. Moreover, since a clearance is formed between the cam shaft and the cam shaft, the displacement regulating member and the cam shaft are held in a non-contact state unless the displacement exceeds the clearance. Therefore, the effect of reducing the friction loss of the entire bearing structure can be maintained while suppressing an increase in the frictional resistance as much as possible.

  The multi-cylinder internal combustion engine to which the bearing structure of the present invention is applied includes four cylinders arranged in one direction, and the first cylinder, the third cylinder, the fourth cylinder from the one end side of the camshaft. The valve means is configured to be opened and closed in the order of cylinder, second cylinder, or in the order of the first cylinder, the second cylinder, the fourth cylinder, and the third cylinder. The bearing means may be configured such that a support rigidity of the cam shaft between the second cylinder and the third cylinder is smaller than a support rigidity of the cam shaft between other cylinders. (Claim 3). Furthermore, in the multi-cylinder internal combustion engine of this aspect, the bearing means includes one end of the camshaft on the first cylinder side, between the first cylinder and the second cylinder, the third cylinder, and the A bearing portion may be arranged between the fourth cylinder and only at the other end of the cam shaft on the fourth cylinder side. Also in these forms, the effects of the present invention described above can be achieved.

  In the present invention, “the support rigidity of the cam shaft is“ small ”” means that the support rigidity is reduced, and includes the case where the support rigidity is zero, that is, the support is omitted.

  As described above, according to the present invention, the periods during which the reaction force is received from the valve means do not overlap, and the camshaft support stiffness between adjacent cylinders is greater than the camshaft support stiffness between other cylinders. Since the bearing means is configured to be small, the friction loss of the entire bearing structure can be reduced.

(First embodiment)
FIG. 1 shows a first embodiment in which the bearing structure of the present invention is applied to a four-cycle internal combustion engine. The internal combustion engine 1 has four cylinders 2 and is an in-line four-cylinder engine in which these cylinders are arranged in one direction. Each cylinder 2 is given a cylinder number # 1 to # 4 in order from the front A of the internal combustion engine 1 to be distinguished from each other. Each cylinder 2 is provided with two intake valves 3 as valve means. Each intake valve 3 is biased upward (in the closing direction) by a valve spring 4 and is driven to open and close by a cam shaft 11 via a valve lifter 5.

  A plurality of (eight in FIG. 1) cams 12 </ b> A to 12 </ b> D are provided on the cam shaft 11 so as to be integrally rotatable with the cam shaft 11. Cams 12 </ b> A to 12 </ b> D (which may be represented by reference numeral 12) have the intake valves 3 of # 1 to # 4 corresponding to the rotation of a crankshaft (not shown) of the internal combustion engine 1 being # 1, # 3, the camshaft 11 is provided to be opened and closed in the order of # 4, # 2. The cam 12 is provided on the camshaft 11 so that the two intake valves 3 provided in each cylinder 2 perform substantially the same operation. For example, the cams 12A and 12A are provided on the camshaft 11 so that the nose contacts the valve lifters 5 and 5 of the cylinder # 2 at the same time. A sprocket 6 is provided on one end side of the camshaft 11, and the rotation of the crankshaft is transmitted to the camshaft 11 via a chain (not shown) wound around the sprocket 6.

  The cam shaft 11 is rotatably supported by a plurality (four in FIG. 1) of bearing portions 13 to 16. Each bearing part 13-16 is comprised including the cam journal part and cam cap which were formed in the cylinder head although detailed illustration was abbreviate | omitted. A bearing portion 13 is disposed on one end side of the cam shaft 11 and a bearing portion 16 is disposed on the other end side, and a bearing is provided between the cam 12A and the cam 12B (between the cylinders # 1 and # 2). The bearing portion 15 is disposed between the cam 12C and the cam 12D (between the cylinders # 3 and # 4). In this embodiment, since the support of the cam shaft 11 is omitted between the cam 12B and the cam 12C (between the cylinders # 2 and # 3), the support rigidity of the cam shaft 11 at this point is the other cylinder. It is made smaller than the support rigidity between two. In this embodiment, the bearing means of this invention is comprised by the above bearing parts 13-16.

  FIG. 2 schematically shows changes in the driving reaction force with respect to the crank angle (° CA) between the bearing portions 13 and 14, between the bearing portions 14 and 15, and between the bearing portions 15 and 16. As is clear from this figure, the drive reaction force of the cam 12A is between the bearing portions 13 and 14, and the drive reaction force of the cam 12B and the cam 12C is between the bearing portions 15 and 16. The driving reaction force of the cam 12D acts respectively. A driving reaction force acts on each cam 12 in the order (# 1, # 3, # 4, # 2) in which the intake valve 3 is driven to open and close. Here, among the cylinders 2 adjacent to each other, there are periods T during which the cam 12 receives the driving reaction force simultaneously between # 1, # 2 and between # 3, # 4. There is no overlap between the periods for receiving the driving reaction force. That is, the driving reaction force acting on each of the cam 12B and the cam 12C does not act on the bearing portion 14 or the bearing portion 15 at the same time. For this reason, the support between # 2 and # 3 is omitted, and the load between these is received by the bearing portion 14 and the bearing portion 15. Even in this case, the support rigidity of the entire camshaft 11 is not lowered more than necessary.

  According to the above bearing structure, the friction loss of the entire bearing structure can be reduced according to omission of support between # 2 and # 3. Further, since the overall length of the camshaft 11 and the interval between the cylinders # 2 and # 3 can be shortened as compared with the configuration in which the space between # 2 and # 3 is supported, the overall length of the internal combustion engine can be shortened. Furthermore, since the amount of oil supply related to the bearing portion can be reduced by at least 1/5, the capacity of the oil pump can be reduced and the drive loss of the oil pump can be reduced. Furthermore, the number of parts can be reduced and the internal combustion engine can be reduced in weight.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. About the structure which is common in 1st Embodiment, the same code | symbol is attached | subjected to FIG.3 and FIG.4, and the overlapping description is abbreviate | omitted. As shown in FIG. 3, in this type of bearing structure, a stopper 20 as a displacement regulating member is provided between the # 2 and # 3 cylinders as a component of the bearing means of the present invention. As shown in FIG. 4, the stopper 20 is arranged along the upper side of the cam shaft 11 (the direction of the driving reaction force), and a clearance C is formed between the stopper 20 and the cam shaft 11. . The clearance C is appropriately set to a size that allows the camshaft 11 to be held in a non-contact state when the camshaft 11 is stationary or rotated at a low speed (when rotating at a predetermined rotation speed or less). The stopper 20 is made of a resin material having a smaller coefficient of friction than metal and does not require forced lubrication.

  According to this form, at the time of low speed rotation, the cam shaft 11 and the stopper 20 are in a non-contact state, which is equivalent to a form in which the support between # 2 and # 3 is omitted. For this reason, the support rigidity of the camshaft 11 between # 2 and # 3 is smaller than that between the other cylinders 2, and as a result, the friction loss of the entire bearing structure is reduced. During high-speed rotation, the displacement of the cam shaft 11 in the driving reaction force direction is restricted by the stopper 20, so that deformation of the cam shaft 11 can be suppressed, and twisting and vibration of the cam shaft 11 can be prevented.

  The present invention is not limited to the above embodiment, and may be implemented in various forms. As a multi-cylinder internal combustion engine, the number of cylinders is not particularly limited, and there is no particular limitation on the arrangement direction of cylinders such as in-line type, V type, and horizontally opposed type. In short, the present invention can be applied to any internal combustion engine in which the periods of receiving the reaction force from the valve means do not overlap and there are adjacent cylinders.

  Further, the combustion order of each cylinder 2 of the internal combustion engine 1 (the opening / closing drive order of the intake valve 3) may be # 1, # 2, # 4, and # 3. In the embodiment described above, the cam shaft that opens and closes the intake valve 3 is illustrated as the cam shaft 11, but a cam shaft that opens and closes the exhaust valve may be used. In this case, the exhaust valve corresponds to the valve means of the present invention.

The figure which showed 1st Embodiment to which the bearing structure of this invention is applied. Explanatory drawing which showed typically the change of the driving reaction force with respect to a crank angle about each between each bearing parts. The figure which showed the 2nd Embodiment of this invention. Sectional schematic regarding the III-III line | wire of FIG.

Explanation of symbols

1 Internal combustion engine 2 Cylinder 3 Intake valve (valve means)
11 Camshaft 13-16 Bearing part (bearing means)
20 Stopper (Displacement restricting member)
C Clearance

Claims (4)

A camshaft that drives either one of an intake valve or an exhaust valve provided for each cylinder of the multi-cylinder internal combustion engine ; a cam journal portion formed on a cylinder head of the internal combustion engine; and a cam cap. A bearing structure for a camshaft comprising: bearing means configured to rotatably support the camshaft;
The bearing means is configured so that the periods for receiving the reaction force from the valve means do not overlap, and the support rigidity of the camshaft between the cylinders adjacent to each other is smaller than the support rigidity of the camshaft between the other cylinders. A camshaft bearing structure characterized by being configured.   As a component of the bearing means, there is provided a displacement regulating member that is disposed between the cylinders in which the support rigidity of the camshaft is reduced and that regulates the displacement of the camshaft in the reaction force direction received from the valve means. The displacement regulating member has a clearance large enough to cause the displacement regulating member and the cam shaft to be in a non-contact state when the cam shaft is stationary or rotated at a predetermined rotation speed or less. The camshaft bearing structure according to claim 1, wherein the camshaft bearing structure is provided between the shaft and the shaft. The multi-cylinder internal combustion engine includes four cylinders arranged in one direction, and in order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder from one end side of the camshaft. Alternatively, the valve means is configured to be opened and closed in the order of the first cylinder, the second cylinder, the fourth cylinder, and the third cylinder.
The bearing means is configured such that the support rigidity of the cam shaft between the second cylinder and the third cylinder is smaller than the support rigidity of the cam shaft between other cylinders. 3. A bearing structure for a camshaft according to claim 1, wherein the bearing structure is a camshaft.   The bearing means includes one end of the camshaft on the first cylinder side, between the first cylinder and the second cylinder, between the third cylinder and the fourth cylinder, and The camshaft bearing structure according to claim 3, wherein a bearing portion is arranged only at the other end of the camshaft on the fourth cylinder side.

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