JP2008095604A - Cam journal structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cam journal structure preventing the generation of air suction in an oil passage through which a hydraulic fluid for a variable valve timing mechanism flows. <P>SOLUTION: This cam journal structure is provided with a camshaft 21 extending along a center shaft 201 and having a lag angle side oil passage 56 communicating with the variable valve timing mechanism 200, and a journal bearing 30 rotatively supporting the camshaft 21 and having a lag angle side oil passage 51 communicating with the lag angle side oil passage 56. The camshaft 21 include a flange 26 spreading in a flange shape around the center shaft 201 and opposed to the journal bearing 30 in the axial direction of the center shaft 201 at an interval 35. The cam journal structure is further provided with an oil bath 30 storing oil and immersing the interval 35 in oil. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention generally relates to a cam journal structure, and more specifically, relates to a cam journal structure that is provided in an internal combustion engine equipped with a variable valve timing mechanism and distributes hydraulic oil of the variable valve timing mechanism.

  Regarding a conventional cam journal structure, for example, Japanese Unexamined Patent Publication No. 2000-73708 discloses a cam shaft thrust bearing structure for the purpose of shortening the overall length of the cam shaft and the engine (Patent Document 1). In Patent Document 1, a variable valve timing (VVT) mechanism is attached to the front end of the camshaft. The camshaft is rotatably supported by a first bearing portion including a first bearing base and a bearing cap.

  Japanese Laid-Open Patent Publication No. 11-315708 discloses a lubricating oil passage structure of a cylinder head for the purpose of increasing the degree of freedom of the layout of the thrust bearing member and lubricating the thrust bearing member easily. (Patent Document 2). In Patent Document 2, a thrust bearing member is provided on the cam shaft. A shaft end housing that supports a shaft end journal at an end portion of the cam shaft is provided with a positioning groove with which a thrust bearing member is engaged and an oil passage extending to the positioning groove.

  Japanese Laid-Open Patent Publication No. 9-273404 discloses a variable valve timing mechanism for an internal combustion engine for the purpose of improving the operability of the variable mechanism without increasing the overall length of the internal combustion engine (Patent Document). 3). In Patent Document 3, the camshaft is rotatably supported by a cylinder head and a bearing cap in the journal. A first oil groove and a second oil groove are formed on the inner peripheral surfaces of the cylinder head and the bearing cap over the entire circumference in the circumferential direction of the journal. In order to form an oil pressure in the hydraulic chamber of the variable valve timing mechanism, the camshaft is formed with a first oil passage and a second oil passage that respectively communicate with the first oil groove and the second oil groove. .

Japanese Laid-Open Patent Publication No. 8-246818 discloses a valve timing control device for an internal combustion engine for the purpose of improving the sealing performance in an oil passage for valve timing control without increasing the journal width. (Patent Document 4). In Patent Document 4, two flanges are provided so as to sandwich the cylinder head between the camshafts. A flange groove extending in the circumferential direction is formed on the thrust surface of the flange. A retard side head oil passage for supplying hydraulic oil to the retard side hydraulic chamber opens with respect to the flange groove.
JP 2000-73708 A JP 11-315708 A JP-A-9-273404 JP-A-8-246818

  In Patent Document 1 described above, a journal bearing that rotatably supports the camshaft is configured by the first bearing portion. An oil supply passage is formed in the journal bearing and the cam shaft. The hydraulic oil that operates the variable valve timing mechanism is transferred between the journal bearing and the camshaft through the oil supply passage.

  However, in such a cam journal structure, if there is a portion where the gap between the journal bearing and the cam shaft becomes locally large, when negative pressure is generated in the oil supply passage, air is introduced into the oil supply passage through the gap. Becomes easy to be inhaled. In this case, there is a possibility that proper operation of the variable valve timing mechanism may not be realized.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problem and to provide a cam journal structure that prevents air suction from occurring in an oil passage through which hydraulic oil of a variable valve timing mechanism flows.

  The cam journal structure according to the present invention is a cam journal structure that is provided in an internal combustion engine equipped with a variable valve timing mechanism and supplies hydraulic oil to the variable valve timing mechanism. The cam journal structure includes a camshaft extending along an axis, and a journal bearing that rotatably supports the camshaft. A first oil passage leading to the variable valve timing mechanism is formed in the camshaft. A second oil passage communicating with the first oil passage is formed in the journal bearing. The camshaft includes a first flange portion. The first collar extends in a bowl shape around the axis, and faces the journal bearing with a gap in the axis direction. The cam journal structure further includes an oil storage part that stores oil and that soaks the gap.

  According to the cam journal structure configured as described above, by providing the oil reservoir, the gap between the first flange and the journal bearing is immersed in oil, so that air is sucked into the oil passage through the gap. Can be prevented.

  Preferably, the camshaft further includes a second flange portion. The second flange extends in a bowl shape around the axis, and faces the journal bearing on the opposite side of the first flange in the axial direction. In the axial direction, the size of the gap provided between the first flange and the journal bearing is larger than the size of the gap provided between the second flange and the journal bearing. The oil storage part is provided only on the first collar part side of the first collar part and the second collar part. Note that the size of the gap provided between the second collar and the journal bearing may be zero.

  According to the cam journal structure configured as described above, there is a high possibility that air suction is generated between the first flange portion provided with a larger gap and the journal bearing. For this reason, an oil storage part is provided only in the 1st collar part side among a 1st collar part and a 2nd collar part.

  Preferably, a variable valve timing mechanism is connected to the end of the camshaft. The second collar portion is provided between the variable valve timing mechanism and the journal bearing. The first collar portion is provided on the opposite side of the variable valve timing mechanism with respect to the journal bearing. According to the cam journal structure configured as described above, it is relatively easy to secure a space on the opposite side of the side where the variable valve timing mechanism is provided across the journal bearing. For this reason, a first collar is provided on the opposite side of the variable valve timing mechanism, and an oil reservoir is provided.

  Preferably, when the variable valve timing mechanism fixes the valve timing, the oil is held in the hydraulic path including the first oil path and the second oil path. Positive pressure and negative pressure act alternately on the oil retained in the hydraulic path due to the fluctuation of the load from the valve to the camshaft. According to the cam journal structure configured as described above, air suction is likely to occur at the timing when negative pressure acts on the oil in the hydraulic path, and therefore the present invention for preventing the occurrence of air suction is more effectively applied. Can do.

  As described above, according to the present invention, it is possible to provide a cam journal structure that prevents air suction from occurring in the oil passage through which the hydraulic oil of the variable valve timing mechanism flows.

  Embodiments of the present invention will be described with reference to the drawings. In the drawings referred to below, the same or corresponding members are denoted by the same reference numerals.

  FIG. 1 is a perspective view of a variable valve timing mechanism to which a cam journal structure according to an embodiment of the present invention is applied. The variable valve timing mechanism shown in the figure is provided in an internal combustion engine such as a gasoline engine in order to change the opening / closing timing (valve timing) of the intake valve and the exhaust valve.

  Referring to FIG. 1, the cam journal structure in the present embodiment includes a camshaft 21. A variable valve timing mechanism 200 that is operated by hydraulic pressure is connected to the camshaft 21. The camshaft 21 extends in the axial direction of the central axis 201 that is a virtual axis. The variable valve timing mechanism 200 is connected to the end of the camshaft 21 extending in the axial direction.

  The variable valve timing mechanism 200 is provided on the cylinder head. The variable valve timing mechanism 200 includes a rotor 120 and a housing 110 that houses the rotor 120. The rotor 120 includes a vane part 121. The housing 110 is fixed to a sprocket 125 on which a timing chain is hung. The housing 110 rotates with the sprocket 125.

  A plurality of cams 23 are formed on the camshaft 21 at intervals in the axial direction. The cam 23 opens and closes an intake valve or an exhaust valve as the camshaft 21 rotates. The cam 23 is subjected to the elastic force of a valve spring provided in these valves. The rotor 120 is fixed to the camshaft 21. The rotor 120 rotates with the camshaft 21. The rotor 120 is provided so as to be rotatable relative to the housing 110.

  The housing 110 forms an advance chamber 111 and a retard chamber 112 which are hydraulic chambers. The advance chamber 111 and the retard chamber 112 are partitioned by the vane portion 121. An oil passage leading to an oil controller valve (OCV) (not shown) is independently connected to the advance chamber 111 and the retard chamber 112. When hydraulic oil is supplied to the advance chamber 111 or the retard chamber 112 through the oil passage, the vane portion 121 moves in the housing 110 while maintaining the airtightness between the advance chamber 111 and the retard chamber 112, The volumes of the advance chamber 111 and the retard chamber 112 are changed. At this time, the cam shaft 21 rotates together with the rotor 120, so that the phase of the cam 23 changes. The variable valve timing mechanism 200 is a vane type variable valve timing mechanism.

  When the camshaft 21 is rotated in the advance direction indicated by the arrow 101 (the same direction as the rotation direction of the camshaft 21), the advance chamber 111 is increased and the retard chamber 112 is decreased. In this case, the hydraulic oil is supplied to the advance chamber 111 such that the hydraulic pressure in the advance chamber 111 is larger than the hydraulic pressure in the retard chamber 112. On the other hand, when the camshaft 21 is rotated in the retardation direction indicated by the arrow 102 (the direction opposite to the rotation direction of the camshaft 21), the advance chamber 111 is reduced and the retard chamber 112 is increased. In this case, the hydraulic oil is supplied to the retard chamber 112 so that the hydraulic pressure in the retard chamber 112 is greater than the hydraulic pressure in the advance chamber 111.

  The housing 110 may be provided on both the intake side and the exhaust side, or may be provided on either one. The number of vane portions 121 included in the rotor 120 is four in FIG. 1, but is not limited to this, and may be a different number. The vane portion 121 may be provided with a lock pin for fixing the vane portion 121 at a predetermined position when the internal combustion engine is stopped.

  The hydraulic pressure in the advance chamber 111 and the retard chamber 112 is controlled by the OCV. Specifically, an engine control unit (ECU) sends a control signal suitable for the operating state of the internal combustion engine to the OCV based on signals received from the sensors. Based on this control signal, the OCV controls the hydraulic pressure applied to the advance chamber 111 and the retard chamber 112 to adjust the sizes of the advance chamber 111 and the retard chamber 112. Thereby, the phase of the cam 23 can be continuously changed.

  FIG. 2 is a view for explaining an advanced state of the variable valve timing mechanism in FIG. FIG. 2A is a perspective view showing a hydraulic chamber, and FIG. 2B is a diagram schematically showing the flow of hydraulic oil. Referring to FIG. 2, an advance side hydraulic path 160 is formed between the advance chamber 111 of the housing 110 and the OCV 300. A retard side hydraulic path 150 is formed between the retard chamber 112 of the housing 110 and the OCV 300. The OCV 300 functions as a switching valve that switches the oil flow in the advance side hydraulic path 160 and the retard side hydraulic path 150. The OCV 300 includes a spool valve 133. When the spool valve 133 receives a signal from the ECU 350, the oil flow is controlled.

  When the camshaft 21 is rotated in the advance direction, the oil supplied to the OCV 300 flows into the advance chamber 111 through the advance side hydraulic path 160. Further, the oil in the retard chamber 112 is discharged from the OCV 300 through the retard side hydraulic path 150. As a result, the advance chamber 111 expands and the retard chamber 112 shrinks, so that the camshaft 21 rotates in the advance direction.

  FIG. 3 is a view for explaining a retarded state of the variable valve timing mechanism in FIG. FIG. 3A is a perspective view showing the hydraulic chamber, and FIG. 3B is a diagram schematically showing the flow of hydraulic oil. Referring to FIG. 3, when the camshaft 21 is rotated in the retarding direction, the oil supplied to the OCV 300 flows into the retarding chamber 112 through the retarding-side hydraulic path 150. Further, the oil in the advance chamber 111 is discharged from the OCV 300 through the advance side hydraulic path 160. As a result, the retard chamber 112 expands and the advance chamber 111 contracts, so that the camshaft 21 rotates in the retard direction.

  FIG. 4 is a view for explaining a holding state of the variable valve timing mechanism in FIG. FIG. 4A is a perspective view showing a hydraulic chamber, and FIG. 4B is a diagram schematically showing the flow of hydraulic oil. Referring to FIG. 4, ECU 350 calculates a target advance angle according to the traveling state and performs control. After the target timing is set by the steps shown in FIGS. 2 and 3, the timing is maintained by making the OCV 300 neutral unless the running state changes. This state is when holding.

  In this case, the spool valve 133 of the OCV 300 is positioned at a position where both the advance side hydraulic path 160 and the retard side hydraulic path 150 are closed. Accordingly, the hydraulic pressure in the advance angle chamber 111 and the retard angle chamber 112 is maintained, and oil from the OCV 300 is not supplied to any of the advance angle hydraulic path 160 and the retard angle hydraulic path 150. As a result, the valve timing can be maintained at an arbitrary target position, and at the same time, unnecessary loss of engine oil can be suppressed.

  FIG. 5 is a cross-sectional view showing a cam journal structure for supporting the camshaft in FIG. FIG. 6 is a cross-sectional view of the cam journal structure along the line VI-VI in FIG.

  Referring to FIGS. 5 and 6, the cam journal structure in the present embodiment further includes a journal bearing 30 and an oil bath 36. The camshaft 21 is supported by the journal bearing 30 so as to be rotatable about the central axis 201. In the axial direction of the central shaft 201, a journal bearing 30 is disposed between the variable valve timing mechanism 200 and the cam 23 in FIG.

  The journal bearing 30 includes a receiving portion 33 as a first divided body and a cap portion 31 as a second divided body, which are combined with each other. The camshaft 21 is sandwiched by the receiving portion 33 and the cap portion 31 from the outer periphery thereof. The camshaft 21 includes an outer peripheral surface 21a. The receiving part 33 and the cap part 31 are arrange | positioned so that the outer peripheral surface 21a may be surrounded. The receiving portion 33 includes an inner peripheral surface 33b that is in sliding contact with the outer peripheral surface 21a. The cap portion 31 includes an inner peripheral surface 31b that is in sliding contact with the outer peripheral surface 21a. The inner peripheral surfaces 33b and 31b extend in a semicircular arc shape around the central axis 201. The receiving portion 33 is disposed vertically below the cap portion 31 so that the weight of the camshaft 21 is loaded on the receiving portion 33.

  In the present embodiment, the receiving portion 33 is formed on the cylinder head of the internal combustion engine on which the variable valve timing mechanism 200 is mounted. The receiving portion 33 may be provided on a camshaft support member that is provided separately from the cylinder head and is fixed to the cylinder head. The cap part 31 is fixed to the receiving part 33 by a bolt 32. An OCV 300 is installed on the cap unit 31.

  The receiving part 33 and the cap part 31 are formed from an aluminum alloy. The camshaft 21 is made of steel. The receiving portion 33 is formed from a material having a smaller hardness than the material forming the camshaft 21.

  The journal bearing 30 is formed with an advance side oil passage 61 and a retard side oil passage 51. The advance side oil passage 61 and the retard angle side oil passage 51 are formed in the cap portion 31. The advance side oil passage 61 and the retard angle side oil passage 51 lead to the OCV 300. An advance angle side oil passage 66 and a retard angle side oil passage 56 are formed in the camshaft 21. The advance side oil passage 66 and the retard angle side oil passage 56 communicate with the variable valve timing mechanism 200. The advance side oil passage 61 and the advance side oil passage 66 communicate with each other on the sliding surface of the journal bearing 30. The retard angle side oil passage 51 and the retard angle side oil passage 56 communicate with each other on the sliding surface of the journal bearing 30. The advance angle side oil passage 61 and the advance angle side oil passage 66 constitute an advance angle side hydraulic passage 160 in FIG. The retard angle side oil passage 51 and the retard angle side oil passage 56 constitute a retard angle side hydraulic passage 150 in FIG.

  The advance side oil passage 66 includes a groove portion 67. The groove 67 is recessed from the outer peripheral surface 21 a of the camshaft 21 and extends in the circumferential direction about the central axis 201. The advance side oil passage 61 opens in the inner peripheral surface 31 b so as to overlap the groove portion 67. The retard side oil passage 56 includes a groove portion 57. The groove 57 is recessed from the outer peripheral surface 21 a of the camshaft 21 and extends in the circumferential direction about the central axis 201. The retard side oil passage 51 opens in the inner peripheral surface 31 b so as to overlap the groove portion 57. A groove part 67 is formed between the variable valve timing mechanism 200 and the groove part 57 in the axial direction of the central shaft 201. Part of the oil flowing through the grooves 67 and 57 is supplied between the outer peripheral surface 21a and the inner peripheral surfaces 31b and 33b, and functions as the lubricating oil for the journal bearing 30.

  The camshaft 21 includes a flange portion 26 and a flange portion 27. The collar portions 26 and 27 spread in a bowl shape around the central axis 201. The flange portions 26 and 27 protrude from the outer peripheral surface 21 a and spread in the radial direction with the central axis 201 as the center. The flange part 26 and the flange part 27 are formed with a space therebetween in the axial direction of the central axis 201. Groove portions 57 and 67 are formed between the flange portion 26 and the flange portion 27. The flange portion 26 and the flange portion 27 are provided so as to sandwich the journal bearing 30 in the axial direction of the central shaft 201.

  In the axial direction of the central shaft 201, the flange portion 26 is opposed to the journal bearing 30 with a gap 35. In the present embodiment, the collar portion 26 is opposed to the receiving portion 33 with a gap 35. The receiving part 33 includes an end face 33c. The end surface 33c extends in a plane orthogonal to the central axis 201. A gap 35 is provided between the flange portion 26 and the end surface 33c. The collar part 26 and the cap part 31 are in sliding contact.

  In the axial direction of the central shaft 201, the flange portion 27 faces the journal bearing 30. The collar portion 27 and the journal bearing 30 are in sliding contact. The collar part 27, the receiving part 33, and the cap part 31 are in sliding contact. In the axial direction of the central shaft 201, a journal bearing 30 is disposed between the flange portion 26 and the flange portion 27. The collar portion 27 is provided between the variable valve timing mechanism 200 and the journal bearing 30. The collar portion 26 is provided on the opposite side of the variable valve timing mechanism 200 with respect to the journal bearing 30. The collar portion 26 is provided between the journal bearing 30 and the cam 23 in FIG.

  During the assembly process of the internal combustion engine, the camshaft 21 is installed on the receiving portion 33. At this time, since the camshaft 21 needs to be pressed against the cylinder head against the elastic force of a valve spring (not shown), the work at the time of assembly is difficult. On the other hand, in this embodiment, since the gap 35 is provided between the flange portion 26 and the receiving portion 33, the assembling property of the camshaft 21 to the cylinder head is ensured.

  The oil bath 36 stores oil. Oil supplied to the journal bearing 30 as lubricating oil flows into the oil bath 36 as needed. The oil bath 36 has a concave shape that opens vertically upward so that the oil can be stored. The oil bath 36 is formed so as to surround the flange portion 26 at a position overlapping the receiving portion 33 when viewed from the axial direction of the central shaft 201. A gap 35 formed between the flange portion 26 and the receiving portion 33 is immersed in the oil stored in the oil bath 36.

  The oil bath 36 is formed in the cylinder head. That is, in the present embodiment, the oil bath 36 and the receiving portion 33 are provided integrally. An end surface 33 c of the receiving portion 33 forms a part of the inner wall of the oil bath 36. The oil bath 36 may be provided separately from the receiving portion 33 without being limited to such a form.

  The collar portion 26 includes an outer peripheral surface 26a. The oil bath 36 includes an inner wall 36h facing the outer peripheral surface 26a with a gap. The inner wall 36h extends in a semicircular arc shape around the central axis 201. The distance between the inner wall 36h and the outer peripheral surface 26a is constant in the circumferential direction around the central axis 201. The inner wall 36h is formed by a curved surface.

  When the variable valve timing mechanism 200 is in the holding state shown in FIG. 4, the advance force chamber 111 and the retard chamber 112 are repeatedly expanded and contracted by the elastic force of the valve spring acting on the cam 23 continuously. As a result, positive pressure and negative pressure act alternately on the oil retained in the advance side hydraulic path 160 and the retard side hydraulic path 150. In this case, there is a possibility that air is sucked into the retarded-side hydraulic path 150 through the gap 35 at the timing when the negative pressure is generated in the groove portion 57 of the retarded-side oil path 56 adjacent to the gap 35. On the other hand, in this embodiment, the oil gap 36 can be forcibly immersed in the oil by providing the oil bath 36. Thereby, it is possible to prevent the retard angle side hydraulic path 150 from sucking air through the gap 35.

  Further, in the axial direction of the central shaft 201, the gap 35 provided between the flange portion 26 and the journal bearing 30 is larger than the size of the gap provided between the flange portion 27 and the journal bearing 30. In the present embodiment, the oil bath 36 is provided only on the side where the collar part 26 is provided in the collar part 26 and the collar part 27 because air suction is more likely to occur at a position where a larger gap is provided. It has been. In the present embodiment, the size of the gap provided between the collar portion 27 and the journal bearing 30 is zero. However, the present invention is not limited to this, and the gap 35 is provided between the collar portion 27 and the receiving portion 33. Even when a small gap is provided, the oil bath 36 is provided on the side where the flange 26 is provided. Moreover, when a clearance gap exists in both the side in which the collar part 26 was provided, and the side in which the collar part 27 was provided, it is good also as a structure which provides an oil bath in both.

  Further, when comparing the side on which the variable valve timing mechanism 200 is provided with respect to the journal bearing 30, the opposite side to the side on which the variable valve timing mechanism 200 is provided is somewhat more secure. Easy. For this reason, by providing the gap 35 on the side opposite to the side where the variable valve timing mechanism 200 is provided, it is possible to reduce the space limitation when the oil bath 36 is provided.

  Further, when the camshaft 21 rotates, the flange portion 26 agitates the oil stored in the oil bath 36. On the other hand, in the present embodiment, since the oil bath 36 has the inner wall 36h extending in a semicircular arc shape, the foaming and scattering of oil caused by stirring can be suppressed. Thereby, the clearance gap 35 provided between the collar part 26 and the receiving part 33 can be oil-immersed more reliably.

  FIG. 7 is a sectional view showing a modification of the cam journal structure in FIG. With reference to FIG. 7, in this modification, the oil bath 36 has a substantially rectangular cross-sectional shape. The distance between the inner wall 36h and the outer peripheral surface 26a changes in the circumferential direction around the central axis 201. Also with the oil bath 36 having such a configuration, the gap 35 can be immersed in oil, and the occurrence of air suction can be prevented. The oil bath 36 may have, for example, a circular cross-sectional shape such as an ellipse or an ellipse, or a polygonal cross-sectional shape, without being limited to the forms illustrated in FIGS. 6 and 7.

  The cam journal structure according to the embodiment of the present invention includes a camshaft 21 that extends along a central axis 201 as an axis, and that has a retarded-side oil passage 56 as a first oil passage that communicates with the variable valve timing mechanism 200. The journal shaft 30 is provided with a retard angle side oil passage 51 as a second oil passage that rotatably supports the camshaft 21 and communicates with the retard angle side oil passage 56. The camshaft 21 includes a flange 26 as a first flange that extends in a bowl shape around the central axis 201 and faces the journal bearing 30 with a gap 35 in the axial direction of the central axis 201. The cam journal structure further includes an oil bath 36 as an oil storage part that stores oil and soaks the gap 35.

  According to the cam journal structure in the embodiment of the present invention thus configured, it is possible to prevent air from entering the hydraulic path when the variable valve timing mechanism 200 is in the holding state. Thereby, the retention property of valve timing can be improved and desired engine characteristics can be realized.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a perspective view of a variable valve timing mechanism to which a cam journal structure according to an embodiment of the present invention is applied. It is a figure for demonstrating the advance state of the variable valve timing mechanism in FIG. It is a figure for demonstrating the retardation state of the variable valve timing mechanism in FIG. It is a figure for demonstrating the holding state of the variable valve timing mechanism in FIG. It is sectional drawing which shows the cam journal structure which supports the cam shaft in FIG. It is sectional drawing of the cam journal structure along the VI-VI line in FIG. It is sectional drawing which shows the modification of the cam journal structure in FIG.

Explanation of symbols

  21 camshaft, 26, 27 collar, 30 journal bearing, 35 clearance, 36 oil bath, 51 advance side oil path, 56 retard side oil path, 150 retard side hydraulic path, 200 variable valve timing mechanism, 201 center axis.

Claims (4)

A cam journal structure that is provided in an internal combustion engine equipped with a variable valve timing mechanism and supplies hydraulic oil to the variable valve timing mechanism,
A camshaft extending along an axis and having a first oil passage leading to the variable valve timing mechanism;
A journal bearing that rotatably supports the camshaft and has a second oil passage communicating with the first oil passage;
The camshaft includes a first brim that spreads in a bowl shape around the axis and faces the journal bearing with a gap in the axis direction;
A cam journal structure comprising an oil reservoir that stores oil and soaks the gap. The camshaft further includes a second collar portion that extends in a bowl shape around the axis and faces the journal bearing on the opposite side of the first collar portion in the axial direction.
In the axial direction, the size of the gap provided between the first flange and the journal bearing is larger than the size of the gap provided between the second flange and the journal bearing,
2. The cam journal structure according to claim 1, wherein the oil storage portion is provided only on the first flange portion side of the first flange portion and the second flange portion. The variable valve timing mechanism is connected to an end of the camshaft;
The second flange is provided between the variable valve timing mechanism and the journal bearing, and the first flange is provided on the opposite side of the variable valve timing mechanism with respect to the journal bearing. The cam journal structure according to claim 2.   When the variable valve timing mechanism fixes the valve timing, the oil is held in the hydraulic path including the first oil path and the second oil path, and the load from the valve to the camshaft fluctuates. 4. The cam journal structure according to claim 1, wherein positive pressure and negative pressure act alternately on the oil retained in the hydraulic path. 5.

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