JP2008280960A - Oil passage structure for engine with variable valve timing mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil passage structure for an engine with a variable valve timing mechanism capable of preventing communication between oil passages due to a blow hole and improving productivity. <P>SOLUTION: In the oil passage structure for the engine with the variable valve timing mechanism having a hydraulic actuator mounted on a camshaft, having a hydraulic control valve mounted on a chain case (engine cover) 18 formed by casting, having a boss part 31 joined on an engine main body projectingly provided on the chain case 18, and having an oil passage for controlling (oil passage for advancing 24) formed at the boss part 31, the oil passage for controlling (oil passage for advancing 24) is composed of a stepped hole comprising a deep bottomed large diameter part 24a opening at an end surface of the boss part 31 of the chain case 18 and a small diameter part 24b establishing communication between a hydraulic control valve and a bottom wall of the large diameter part 24a, and the large diameter part 24a of the stepped hole is formed by casting and the small diameter part 24b is formed by cutting. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oil passage structure for an engine with a variable valve timing mechanism that changes valve timing by supplying and discharging hydraulic oil to and from a hydraulic actuator attached to a camshaft.

In an engine with a variable valve timing mechanism, a hydraulic actuator that changes valve timing is attached to a camshaft, and a hydraulic control valve that supplies and discharges hydraulic oil to and from the hydraulic actuator is controlled according to the operating state of the engine to advance valve timing. Increase or decrease the angle by retarding or increasing the overlap amount of the intake / exhaust valves, improving the scavenging efficiency and improving fuel efficiency by improving internal EGR and NOX
This is intended to reduce the above.

  In such an engine with a variable valve timing mechanism, a hydraulic control valve is attached to an engine cover that is integrally formed by casting, and a boss portion that is joined to the engine body is projected from the engine cover, and the boss portion is used for control. An oil passage is formed. Here, the control oil passage includes a supply oil passage that supplies hydraulic oil to a hydraulic control valve from a hydraulic pump that is a hydraulic source, an advance oil passage that supplies and discharges hydraulic oil from the hydraulic control valve to a hydraulic actuator, and It is comprised with the oil path for retardation (for example, refer patent document 1).

  By the way, the control oil passage 123 is formed by drilling a hatched portion in the figure with respect to a pilot hole 118a formed by casting in the engine cover 118 as shown in FIG. 10 (a). It was formed as shown in

In addition, since a casting defect such as a casting hole inevitably occurs in a cast engine cover or the like, when a plurality of oil passages are formed in such an engine cover or the like by machining, the oil passages are short-circuited by the casting hole. It is pointed out in Patent Document 2 that so-called oil passage omission occurs.
Japanese Patent Laid-Open No. 11-324629 Japanese Patent Laid-Open No. 5-163917

  When a control oil passage is formed by machining in a cast engine cover as in the conventional case, a cast hole is likely to occur on the machined surface of the oil passage, and the oil passage communicates with the cast hole to leak oil, There arises a problem that the responsiveness of the variable valve timing mechanism is deteriorated. There is also a problem in that productivity is poor due to a large machining cost for forming the oil passage.

  Accordingly, the present invention has a variable valve timing mechanism that prevents communication between the oil passages by the cast hole and prevents the responsiveness of the variable valve timing mechanism from being lowered, and can improve productivity by reducing machining cost. An object is to provide an oil passage structure of an engine.

  In addition, in the conventional oil passage structure, when using hydraulic control valves with different shapes and dimensions of the insertion part to the engine cover, it is necessary to change the shape of the boss part according to the shape and dimension of the insertion part. As a result, the productivity of the engine cover was poor, and there was a problem that the cost was increased.

  Therefore, the present invention provides a common configuration without changing the shape and dimensions of the boss portion in accordance with each hydraulic control valve, even when hydraulic control valves having different shapes and dimensions of the insertion portion to the engine cover are used. It is an object of the present invention to provide an oil passage structure for an engine with a variable valve timing mechanism, in which each hydraulic control valve can be attached to the engine cover, and the productivity of the engine cover can be improved and the cost can be reduced.

In order to achieve the above object, an invention according to claim 1 is characterized in that a hydraulic actuator for changing valve timing is attached to a camshaft, and a hydraulic control valve for supplying and discharging hydraulic oil to and from the hydraulic actuator is formed by casting. A boss portion that is joined to the engine body, and a supply oil passage that supplies hydraulic oil from a hydraulic source to the hydraulic control valve and the hydraulic control valve. In an oil passage structure of an engine with a variable valve timing mechanism in which a control oil passage formed of an advance oil passage and a retard oil passage for supplying and discharging hydraulic oil to and from the hydraulic actuator is formed.
The control oil passage is a stepped hole comprising a deep bottom large-diameter portion that opens to an end surface of the boss portion of the engine cover, and a small-diameter portion that communicates the bottom wall of the large-diameter portion and the hydraulic control valve. In addition, the large diameter portion of the stepped hole is formed by casting, and the small diameter portion is formed by cutting.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the center of the small diameter portion of the stepped hole is offset in the radial direction with respect to the center of the large diameter portion.

  According to the first aspect of the present invention, the control oil passage formed in the boss portion of the engine cover is constituted by a stepped hole made up of a large diameter portion and a small diameter portion, and the deep large diameter portion is formed by casting. Because it is formed, the volume of the boss is reduced and the occurrence of a cast hole is suppressed, and the cast hole is hard to appear on the inner surface of the large diameter part, and communication between the oil passages by the cast hole is prevented and the variable valve High responsiveness is maintained in the timing mechanism.

  In addition, since the deep bottom large-diameter portion is formed by casting, the machining allowance for the small-diameter portion is kept small, and the productivity is increased.

  In addition, the control oil passage provided between the hydraulic control valve and the hydraulic actuator has a large-diameter portion with a large volume at the bottom, so that hydraulic fluctuations caused by the drive reaction force of the camshaft are attenuated at the large-diameter portion. Therefore, it is possible to improve the hydraulic controllability by preventing the propagation of the hydraulic pressure fluctuation to the hydraulic control valve.

  According to the second aspect of the present invention, when using a hydraulic control valve having a different shape and size of the insertion portion to the engine cover, the diameter of the center of the small diameter portion of the stepped hole is larger than the diameter of the center of the large diameter portion. By offsetting in the direction, each hydraulic control valve can be attached to a common engine cover without changing the shape and dimensions of the boss according to each hydraulic control valve, improving the productivity of the engine cover and reducing the cost Can be achieved.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a right side view of an engine with a variable valve timing mechanism having an oil passage structure according to the present invention, FIG. 2 is a perspective view showing the engine with its head cover and chain case removed, and FIG. 3 is a view of the chain case from the inside. 4 is a cross-sectional view taken along line AA in FIG. 3, FIG. 5 is a hydraulic path diagram of the variable valve timing mechanism, FIG. 6 is a view in the direction of arrow B in FIG. 4, and FIG. FIG.

  An engine with a variable valve timing mechanism (hereinafter simply referred to as an “engine”) 1 according to the present embodiment is a DOHC in-line four-cylinder engine for a vehicle. 1, the cylinder axis L is mounted on the vehicle in a state where the cylinder axis L is inclined forwardly with respect to the vertical line N by the angle θ shown in the drawing.

  As shown in FIGS. 1 and 2, the crankshaft 2 is rotatably supported by a cylinder block 3, and four cylinders (not shown) are arranged on the cylinder block 3 in the vehicle width direction (in the direction perpendicular to the plane of FIG. 1). ). Although not shown, pistons are slidably inserted into the cylinders of the cylinder block 3, and the pistons are connected to the crankshaft 2 via connecting rods along the cylinders of the pistons. The reciprocating linear motion is converted into rotational motion of the crankshaft 2 by the connecting rod.

  A cylinder head 4 is attached to the upper surface of the cylinder block 3, and an oil pan 5 is attached to the lower surface of the cylinder block 4. The cylinder head 4 has an intake port and an exhaust port (whichever Are also formed). As shown in FIG. 1, an intake manifold 6 connected to the intake port is connected to the intake side end surface (rear end surface) of the cylinder head 4. Here, the four intake manifolds 4 are gathered and connected to the surge tank 7. Although not shown, an air cleaner is connected to the upstream side of the surge tank 7 via a throttle body.

  On the other hand, as shown in FIG. 1, an exhaust manifold 8 connected to the exhaust port is connected to the exhaust side end face (front end face) of the cylinder head 4, and the four exhaust manifolds 8 are gathered to form a catalytic converter 9. It is connected to the. An exhaust pipe 10 is connected to the catalytic converter 9. The exhaust pipe 10 extends toward the rear of the vehicle body, and its rear end is open to the atmosphere.

  By the way, the intake port and the exhaust port formed in the cylinder head 4 for each cylinder are opened and closed at appropriate timings by an unillustrated intake valve and exhaust valve, respectively, thereby performing a required gas exchange in each cylinder. The

  Thus, as shown in FIG. 2, the intake valve and the exhaust valve are composed of an intake cam shaft 11 rotatably supported on the cylinder head 4 and an intake cam 11a integrally formed with the exhaust cam shaft 12, respectively. It is opened and closed by the exhaust cam 12a. Here, the intake camshaft 11 and the exhaust camshaft 12 are arranged in parallel in the left-right direction on the intake side (rear side of the vehicle body) and the exhaust side (front side of the vehicle body) of the cylinder head 4. An intake cam sprocket 13 and an exhaust cam sprocket 14 are respectively attached to the right end portion of the exhaust camshaft 12.

  As shown in FIG. 2, a crank sprocket 15 having a small diameter is attached to the right end portion of the crankshaft 2, and an endless timing chain is connected to the crank sprocket 15, the intake cam sprocket 13, and the exhaust cam sprocket 14. 16 is wound. As shown in FIG. 1, a head cover 17 is attached to the upper portion of the cylinder head 4, and an intake camshaft 11, an exhaust camshaft 12, and an intake cam sprocket 13 are placed in a cam chamber formed in the head cover 17. And a part of the exhaust cam sprocket 14 and the like are accommodated.

  Thus, the rotation of the crankshaft 2 is decelerated via the crank sprocket 15, the timing chain 16, the intake cam sprocket 13 and the exhaust cam sprocket 14 and transmitted to the intake camshaft 11 and the exhaust camshaft 12, respectively. When the camshaft 11 and the exhaust camshaft 12 are rotationally driven at a speed half that of the crankshaft 2, as described above, the intake valve and the exhaust valve are opened and closed at appropriate timings, respectively, and the required values are set in each cylinder. Gas exchange is performed.

  Here, the timing chain 16 is covered with a chain case 18 as an engine cover attached to each right end surface of the cylinder block 3 and the cylinder head 4, and in this chain case 18, the timing chain 16 is connected to a chain guide 19. , And rotates with a predetermined tension applied by the tensioner 20.

  By the way, in this embodiment, a variable valve timing mechanism (VVT) that changes the opening / closing timing of the intake valve in accordance with the engine speed or the like is provided. As shown in FIGS. 2 and 5, the variable valve timing mechanism includes a hydraulic actuator 21 attached to one end of the intake camshaft 11 and a hydraulic control valve (OCV) 22 that supplies and discharges hydraulic oil to the hydraulic actuator 21. As shown in FIGS. 1 and 4, the hydraulic control valve 22 is attached to the chain case 18.

  As shown in FIG. 5, the variable valve timing mechanism includes a supply oil passage 23 for supplying hydraulic oil from the oil pan 5 as a hydraulic source to the hydraulic control valve 22, and a hydraulic actuator from the hydraulic control valve 22. 21 is provided with an advance oil passage 24 and a retard oil passage 25 for supplying and discharging the hydraulic oil, and a drain passage 26 for returning the hydraulic oil from the hydraulic control valve 22 to the oil pan 5. The advance oil passage 24 and the retard oil passage 25 constitute a control oil passage. An oil pump 27 and an oil filter 28 are provided in the supply oil passage 23.

  Here, as shown in FIG. 2, a head-side boss portion 29 is integrally protruded in a region adjacent to the hydraulic actuator 21 on the right end surface of the cylinder head 4 and surrounded by the timing chain 16. The head-side boss 29 is formed with the supply oil passage 23, the advance oil passage 24, and the retard oil passage 25.

  On the other hand, as shown in FIG. 4, a control valve mounting cylinder 30 is integrally formed on the upper inner surface of the chain case 18, and the control valve mounting on the inner surface of the chain case 18 is formed as shown in FIGS. A boss portion 31 is integrally protruded from a portion overlapping the cylinder 30. The chain case 18 is formed by casting an aluminum alloy.

  The boss portion 31 is provided with a supply oil passage 23, an advance oil passage 24, and a retard oil passage 25. When the chain case 18 is attached to the end faces of the cylinder block 3 and the cylinder head 4, the chain The boss 31 protruding from the case 18 is joined to the head-side boss 29 (see FIG. 2) protruding from the cylinder head 4, and the supply oil passage 23 formed in the boss 31 and the advance angle are formed. The oil passage 24 and the retard oil passage 25 are joined to the supply oil passage 23, the advance oil passage 24, and the retard oil passage 25 formed in the head-side boss portion 29, respectively. As shown in FIG. 3, the drain passage 26 is opened on both sides of the boss portion 31 on the inner surface of the chain case 18.

  Thus, in the variable valve timing mechanism shown in FIG. 5, when hydraulic oil is supplied from the oil pan 5 to the hydraulic control valve 22 through the supply oil passage 23 by the oil pump 27 driven by the crankshaft 2. The hydraulic control valve 22 controls the distribution of the hydraulic oil to drive the hydraulic actuator 21 and appropriately controls the opening / closing timing of the intake valve according to the engine speed or the like.

  That is, when hydraulic oil is supplied from the advance oil passage 24 to the oil chamber S1 on the advance side of the hydraulic actuator 21, the rotational phase of the intake camshaft 11 is advanced to advance the opening / closing timing of the intake valve, At this time, hydraulic oil returns from the retarded oil chamber S2 in the hydraulic actuator 21 to the oil pan 5 through the drain passage 26.

  Similarly, when hydraulic fluid is supplied from the retard oil passage 25 to the retarded oil chamber S2 of the hydraulic actuator 21, the rotational phase of the intake camshaft 11 is retarded and the opening / closing timing of the intake valve is delayed. At this time, the hydraulic oil returns from the oil chamber S 1 on the advance side in the hydraulic actuator 21 to the oil pan 5 through the drain passage 26.

  As shown in detail in FIG. 6, the supply oil passage 23, the advance oil passage 24, and the retard oil passage are provided in the boss portion 31 protruding integrally with the inner surface of the chain case 18 as described above. 25, for example, the advance oil passage 24 is formed as shown in FIG.

  That is, the advance oil passage 24 has a deep bottom large-diameter portion 24a that opens to the end face of the boss portion 31 of the chain case 18, a small-diameter portion that communicates the bottom wall of the large-diameter portion 24a and the hydraulic control valve 22. The large diameter portion 24a of the stepped hole is formed by casting when the chain case 18 is cast, and the small diameter portion 24b has a large diameter by cutting such as drilling. It is formed concentrically with the portion 24a. Similarly, as shown in FIG. 6, other supply oil passages 23 and retarding oil passages 25 are composed of large-diameter portions 23a, 25a and small-diameter portions 23b, 25b, similarly to the advance oil passage 24. It consists of stepped holes.

  As described above, in the present embodiment, the supply oil passage 23, the advance oil passage 24, and the retard oil passage 25 formed in the boss 31 of the chain case 18 are divided into the large diameter portions 23a, 24a, 25a and small-diameter portions 23b, 24b, and 25b, and the deep-bottom large-diameter portions 23a, 24a, and 25a are formed by casting, so that the volume of the boss portion 31 is reduced and cast. The formation of nests is suppressed, and the cast holes are less likely to appear on the inner surfaces of the large diameter portions 23a, 24a, 25a, and the supply oil passage 23, the advance oil passage 24, and the retard oil passage 25 communicate with each other by the cast holes. This prevents the variable valve timing mechanism from maintaining high responsiveness.

  In addition, since the large-diameter portions 23a, 24a, and 25a at the bottom of each stepped hole are formed by casting, the machining allowance of the small-diameter portions 23b, 24b, and 25b is reduced, and the productivity is increased.

  Further, large-diameter portions 23a, 24a, 25a having a deep bottom and a large volume are provided in a supply oil passage 23, an advance oil passage 24 and a retard oil passage 25 provided between the hydraulic control valve 22 and the hydraulic actuator 21. Therefore, the hydraulic pressure fluctuation generated by the driving reaction force of the intake camshaft 11 can be attenuated by the large diameter portions 23a, 24a, and 25a, and the propagation of the hydraulic pressure fluctuation to the hydraulic control valve 22 can be prevented to be hydraulically controllable. Can be increased.

  Here, the correspondence in the case of using a hydraulic control valve in which the shape and size of the insertion portion to the chain case 18 are different will be described based on FIGS. 8 is a view similar to FIG. 6 when another hydraulic control valve is used, and FIG. 9 is a cross-sectional view taken along the line DD of FIG.

  As shown in FIG. 8, when using a hydraulic control valve 22 ′ having a small diameter that is different from the hydraulic control valve 22 in the shape and size of the insertion portion to the chain case 18, for example, the supply oil passage 23 and the retarded angle are retarded. If the centers of the small diameter portions 23b, 25b of the oil passage 25 are offset in the radial direction with respect to the centers of the large diameter portions 23a, 25a, the shape and dimensions of the boss portion 31 are changed according to the hydraulic control valve 22 ′. Since the hydraulic control valve 22 ′ can be attached to the common chain case 18 without any problem, the productivity of the chain case 18 can be improved and the cost can be reduced. FIG. 9 shows a state where the small-diameter portion 25b of the retarding oil passage 25 is offset from the center of the large-diameter portion 25a by the ε shown.

  In the embodiment described above, the present invention has been described with respect to an engine in which the variable valve timing mechanism is provided on the intake side. However, the present invention is not limited to the exhaust valve or the intake side and the exhaust side. Of course, the present invention can be similarly applied to engines provided on both sides.

It is a right view of an engine with a variable valve timing mechanism. It is a perspective view which removes and shows the head cover and chain case of an engine with a variable valve timing mechanism. It is the internal view which looked at the chain case of the engine with a variable valve timing mechanism from the inner side. FIG. 4 is a sectional view taken along line AA in FIG. 3. FIG. 5 is a hydraulic path diagram of a variable valve timing mechanism. It is a figure of the arrow B direction of FIG. It is CC sectional view taken on the line of FIG. It is a figure similar to FIG. 6 which shows another form of this invention. It is the DD sectional view taken on the line of FIG. (A), (b) is sectional drawing which shows the processing method of the conventional control oil path.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine with variable valve timing mechanism 2 Crankshaft 3 Cylinder block 4 Cylinder head 5 Oil pan 6 Intake manifold 7 Surge tank 8 Exhaust manifold 9 Catalytic converter 10 Exhaust pipe 11 Intake camshaft 11a Intake cam 12 Exhaust camshaft 12a Exhaust cam 13 Intake Cam sprocket 14 Exhaust cam sprocket 15 Crank sprocket 16 Timing chain 17 Head cover 18 Chain case (engine cover)
19 Chain guide 20 Tensioner 21 Hydraulic actuator 22, 22 'Hydraulic control valve 23 Supply oil passage 23a Large diameter portion of supply oil passage 23b Small diameter portion of supply oil passage 24 Advance oil passage 24a Advance oil passage 24a Large-diameter portion 24b Small-diameter portion of the advance oil passage 25 Delay oil passage 25a Large-diameter portion of the retard oil passage 25b Small-diameter portion of the delay oil passage 26 Drain passage 27 Oil pump 28 Oil filter 29 Head side boss Part 30 Control valve mounting cylinder 31 Boss part S1 Oil chamber on the advance side of the hydraulic actuator S2 Oil chamber on the retard side of the hydraulic actuator

Claims (2)

A hydraulic actuator that changes the valve timing is attached to the camshaft, and a hydraulic control valve that supplies and discharges hydraulic oil to and from the hydraulic actuator is attached to an engine cover molded by casting, and is joined to the engine body by the engine cover. An oil passage for supply that supplies a hydraulic oil from a hydraulic pressure source to the hydraulic control valve and an oil passage for an advance angle that supplies and discharges the hydraulic oil from the hydraulic control valve to the hydraulic actuator. And an oil passage structure of an engine with a variable valve timing mechanism in which a control oil passage formed of a retarding oil passage is formed,
The control oil passage is a stepped hole comprising a deep bottom large-diameter portion that opens to an end surface of the boss portion of the engine cover, and a small-diameter portion that communicates the bottom wall of the large-diameter portion and the hydraulic control valve. An oil passage structure for an engine with a variable valve timing mechanism, characterized in that the large diameter portion of the stepped hole is formed by casting and the small diameter portion is formed by cutting. 2. The oil passage structure for an engine with a variable valve timing mechanism according to claim 1, wherein the center of the small diameter portion of the stepped hole is offset in the radial direction with respect to the center of the large diameter portion.

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