Patent Grant
8573169
The present invention relates to a variable valve device for an internal combustion engine, in which a movable cam is variable in phase on the basis of a reference cam.
In the case of a reciprocal engine (internal combustion engine) for automobiles, for the purpose of improving measures against engine exhaust gas and reducing pumping loss, a variable valve device is more and more often installed in its cylinder head.
In some of such variable valve devices, an inner camshaft is turnably encased in an outer camshaft formed of a pipe member to function as a shaft member driven by crank output of the engine. In the outer periphery of the outer camshaft, there are provided a fixed reference cam and a movable cam that is turnable around the shaft axis. A pin-like member that is inserted in between the movable cam and the inner camshaft from a shaft-diametrical direction is used to connect the outer camshaft and the inner camshaft while allowing relative displacement. Due to this structure, the inner camshaft is relatively displaced by output of the outer camshaft, and the movable cam is varied in phase relative to the reference cam by output from the pin-like member connected to the inner camshaft, to thereby change the duration for which the valve is open (split variable) (see Patent Documents 1 and 2).
In the variable valve device, it is required to connect the inner camshaft and the movable cam, which are located in the inside and outside, respectively, of the outer camshaft with simple work. To that end, it has been proposed that a press-fit pin be used as the pin-like member for connecting the movable cam and the inner camshaft, and that the press-fit pin be pressed in along the shaft-diametrical direction to connect the movable cam and the inner camshaft located in the inside and outside, respectively, of the outer camshaft. It has also been proposed that a bolt member be used as the pin-like member, and that this bolt member be screwed into the inner camshaft to connect the movable cam and the inner camshaft located in the inside and outside, respectively, of the outer camshaft.
In the case of the former structure in which the press-fit pin is pressed into the movable cam and the inner camshaft, a large load has to be applied to press the press-fit pin into the movable cam and the inner camshaft lest the press-fit pin come off due to amplitude load of valve driving. The press-fit load deforms or bends the movable cam or the inner camshaft or causes a positional displacement of the inner shaft in the direction of the press-fit pin. Moreover, the outer camshaft formed of the pipe member has low rigidity. For that reason, if deformation, bending or positional displacement occurs in the movable cam or the inner camshaft, this increases friction between the outer camshaft and the movable cam or inner camshaft or produces additional friction due to contact therebetween.
On top of that, as the result of the deformation or bending, even an outer pipe is deformed or bent, too. If the deformation or bending of the outer pipe affects the straightness of the cam shaft axis and the cylindricality of an outer diameter, this might lead to an increase in friction of a journal bearing between the camshaft and the cylinder head or friction between the cam and a tappet attributable to an increase in misalignment.
In the case of the latter structure in which the screw member is screwed in, a fastening force is applied to a threaded portion of the inner camshaft, so that the inner camshaft is deformed or bent, causing friction as in the above-mentioned case. Furthermore, the structure is a cantilever structure, and therefore induces stress concentration. It is then necessary to improve the strength of adjacent areas of the threaded portion, which causes another problem that compact design cannot be achieved.
Such friction not only deteriorates the response of the variable valve device but also increases friction in the entire engine, thus degrading fuel consumption and causing abnormal wear of components.
It is an object of the invention to provide a variable valve device for an internal combustion engine, in which the movable cam on the outer periphery of the outer camshaft and the inner camshaft in the outer camshaft can be connected together, and at the same time, friction is prevented from being generated between components.
In order to achieve the above object, the first aspect of the invention has a structure in which, as connecting means for connecting a movable cam located in an outer periphery of an outer camshaft and an inner camshaft located inside the outer camshaft, there are provided a pin-like member that is movably inserted so as to penetrate the movable cam, the outer camshaft and the inner camshaft along a diametrical direction of a shaft member that is formed by turnably encasing the inner camshaft in the outer camshaft, and an escape-preventing portion for restricting the pin-like member from escaping. The movable cam and the inner camshaft are connected together by using the above structure while preventing press-fit load and axial force from acting on components.
According to the second aspect of the invention, the escape-preventing portion for restricting the escape of the pin-like member is disposed in an end portion of the pin-like member.
The third aspect of the invention has a structure in which the pin-like member is designed to have length longer than a penetration zone to prevent stress from being concentrated at the escape-preventing portion. The pin-like member is arranged in the shaft member to be displaceable in the diametrical direction of the shaft member while retaining the escape-preventing portion. A releasing portion is formed in the escape-preventing portion and an end of the penetration zone, to and from which the escape-preventing portion is attached and separated, the releasing portion releasing the escape-preventing portion from the end of the penetration zone when load is applied to a portion between the escape-preventing portion and the end of the penetration zone. The farther the escape-preventing portion moves away from the end of the penetration zone, the more the pin-like member is displaced in an axial direction.
According to the fourth aspect of the invention, in order to achieve the escape prevention of the pin-like member with a simple structure, a swaging process is applied to the end portion of the pin-like member, and a large-diameter portion that is formed in the end portion of the pin-like member by the swaging process is used as the escape-preventing portion.
The fifth aspect of the invention has a structure in which the escape-preventing portion is arranged in the movable cam and restricts the pin-like member from escaping outside the movable cam along the axial direction.
According to the sixth aspect of the invention, in order that the escape prevention of the pin-like member may be easily achieved, the movable cam is provided with a cylindrical boss portion that is turnably fitted to the outer periphery of the outer camshaft. The pin-like member penetrates through a circumferential wall of the boss portion of the movable cam. The escape-preventing portion has a structure in which a stopper that is fitted to an outer periphery of the boss portion is used to prevent the escape of the pin-like member.
According to the seventh aspect of the invention, the stopper is formed into a ring so that the escape-preventing portion may be easily mounted on the boss portion with a simple structure.
According to the eighth aspect of the invention, the end portion of the pin-like member is formed into a spherical face to prevent stress from being applied from the pin-like member to the stopper in a concentrated manner.
According to the first aspect of the invention, it is possible to connect the movable cam located on the outer periphery of the outer camshaft and the inner camshaft located inside the outer camshaft without applying the press-fit load and axial force, which trigger a deformation and bending in components.
In result, the movable cam and the inner camshaft can be connected together while avoiding not only friction generation between components, attributable to the deformation and the bending, but also deformation in other components. Consequently, it is possible to secure stable variable performance and also to avoid an increase in engine friction, to thereby prevent abnormal wear of components. If the position at which the stress is applied to the pin-like member is changed, the pin-like member can be formed in a compact size.
According to the second aspect of the invention, the pin-like member is prevented from escaping with a simple structure by the escape-preventing portion that is formed in the end portion of the pin-like member.
According to the third aspect of the invention, it is possible, with a simpler structure, to avoid the stress concentration on the escape-preventing portion and prevent the escaping of the pin-like member, attributable to the stress concentration.
According to the fourth aspect of the invention, it is possible to retain the pin-like member with a simple structure in which the pin-like member is subjected to the swaging process.
According to the fifth aspect of the invention, the pin-like member is prevented from escaping with a simple structure by the escape-preventing portion that is formed in the movable cam.
According to the sixth aspect of the invention, it is possible to retain the pin-like member through an easy work that fits the stopper in the boss portion of the movable cam.
According to the seventh aspect of the invention, the ring-like stopper makes it possible to restrict the pin-like member from escaping in both axial directions with a simple structure and the easy work in which the stopper is fitted in the boss portion.
According to the eighth aspect of the invention, it is possible to avoid the stress concentration of the stopper, attributable to displacement of the pin-like member, to thereby assure highly reliable connection.
The invention will be described below with reference to a first embodiment shown in
In the cylinder block 1, three cylinders 3 (only partially shown) are formed along an anteroposterior direction of the engine as shown in
A combustion chamber 5 is formed under the cylinder head 2 correspondingly to each of the cylinders 3. A pair of intake ports 7 that intakes air and a pair of exhaust ports (not shown) that discharge air open in each of the combustion chambers 5. Each of the intake ports 7 is provided with a pair of intake valves 10 attached with tappets 9. The tappet 9 located on the top faces an upper portion of the cylinder head 2. Likewise, each of the exhaust ports (not shown) is provided with a pair of exhaust valves (not shown). The intake valves 10 and the exhaust valves (not shown) are used to open and close the intake ports 7 and the exhaust ports (not shown). An ignition plug, not shown, is disposed in each of the combustion chambers 5.
As shown in
Unlike the exhaust camshaft 13, the intake-side valve device 6a uses a camshaft formed by installing a separate member as shown in
The variable valve device 15 will be described below. A shaft member of the camshaft 14 is formed of double shaft 17 in which an inner camshaft 17b formed of a shaft member serving as a control member is turnably encased in an outer camshaft 17a formed of a hollow pipe member, for example, as shown in
A pair of intake cams 19 is provided to the outer camshaft 17a so as to corresponding to a pair of intake valves 10 with respect to each cylinder. The intake cams 19 are each formed by assembling a reference cam 20 deciding a reference phase and a cam lobe 22 (corresponding to the movable cam of the present application) serving as a movable cam.
The reference cam 20 is fastened in an outer periphery so as to coincide with one tappet of the outer camshaft 17a, for example, the left-side tappet 9. The reference cam 20 is made of a plate cam. The reference cam 20 is, for example, fastened to the outside of the outer camshaft 17a by press-fitting and is fastened above the left-side tappet 9. In this structure, a cam face of the reference cam 20 contacts the left-side tappet 9, and thus, the cam displacement of the reference cam 20 is transmitted to the left-side intake valve 10.
The cam lobe 22 has a cam nose 22a made of a plate cam. The cam nose 22a is combined with a portion for preventing misalignment, that is, a hollow boss portion 22b, thereby forming the entire cam lobe. The cam lobe 22 is fitted to the outside of the outer camshaft 17a to be turnable in a circumferential direction, and the cam nose 22a is located above the right-side tappet 9. In this structure, the cam face of the cam nose 22a comes into contact with the right-side tappet 9, and thus, the cam displacement of the cam nose 22a is transmitted to the right-side intake valve 10.
The boss portion 22b of the cam lobe 22 and the inner camshaft 17b are connected to each other with connecting means, for example, a connecting structure 21 that makes a pin member 24 (corresponding to the pin-like member of the present application) insert into the double shaft 17 along shaft-diametrical direction.
As shown in
A cam-phase changing mechanism 25 that makes relative displacement between the inner and outer shafts is mounted on one end portion of the double shaft 17, thereby forming the variable valve device 15 that is capable of changing the cam phase of the cam lobe 22 on the basis of the reference cam 20.
In other words, the cam-phase changing mechanism 25 uses a turning vane structure in which, for example, as shown in
The cam phase of the cam lobe 22 coincides with that of the reference cam 20 serving as a reference due to a biasing force of a return spring member 42 (shown only in
The shaft output from the crankshaft (not shown) is transmitted, for example, from a timing sprocket 39 provided to the housing 31 and a timing chain 40 hitched to a timing sprocket 13a provided to the end of the exhaust camshaft 13 through the housing 31 and the cam piece 37 to the outer camshaft 17a, thereby rotating-driving the reference cam 20 and thus opening/closing the left-side intake valve 10 through the tappet 9. Once hydraulic pressure is supplied from the OCV 44 into advance chambers located opposite the retard chambers 30, the cam lobe 22 rotates with the reference cam 20 while coinciding with the cam phase of the reference cam 20 as shown in a state A of
The connecting structure 21 that inserts the pin member 24, which enables the above-mentioned split variable, has a structure that connects the cam lobe 22 and the inner camshaft 17b while preventing friction between components. In such a structure, as shown in
As shown in
The cam lobe 22 and the inner camshaft 17b can therefore be connected to each other while unnecessary friction between components is prevented. This makes it possible to secure stable variability and prevent abnormal wear of components by avoiding an increase in engine friction. In particular, if the large diameter portions 54 formed by the swaging process are provided to the escape-preventing portions 50, the pin member 24 can be prevented from escaping with a simple structure.
The movable insertion of the pin member 24 differs from the conventional press-fit structure and screwing structure in which a reaction force driving valves constantly acts upon the same place of the pin member. In the movable insertion, load acts upon different places, so that if a pin diameter is made small, it is possible to achieve weight saving and a compact design. The compact design enables the decrease of weight, and makes it easier to improve variability response and apply the pin member to the engine. If lubricating oil is supplied to the clearance between the outer camshaft 17a and the inner camshaft 17b, the lubricating oil is also supplied to a gap between the camshafts 17 and the pin member 24. For that reason, an impact load that acts upon the pin member 24 is suppressed by an oil film, and the shifting of the pin member 24 becomes easy, making it possible to further improve the compact design of the pin member 24.
If lubricating oil is supplied to the clearance between the outer camshaft 17a and the inner camshaft 17b, the oil film makes the outer camshaft 17a and the inner camshaft 17b less likely to contact each other. Even if they are in contact, the increase of friction is prevented.
The second embodiment is a modification of the first. According to the second embodiment, when split variable is carried out, stress is prevented from being concentrated at the large diameter portions 54 (escape-preventing portion 50). When the displacement outputted from the inner camshaft 17b is transmitted to the pin member 24, the transmission is carried out by bringing the large diameter portions 54 of the pin member 24 and the through hole 52 (boss portion 22b) of the cam lobe 22 into contact. During the transmission, an outer periphery (shaft portion) of the pin member 24, except the large diameter portions 54, is away from the inner surface of the through hole of the cam lobe 22 because of the clearance 6, so that load is concentrated at the large diameter portions 54. This stress is concentrated at portions of the large diameter portions 54, which are noticeably different in diameter from the rest and is considered to be low in rigidity, namely, base portions of the large diameter portions 54. This raises the possibility that the large diameter portion 54 may be broken at the base portion thereof due to the stress concentration and may come off from the pin member 24. If the large diameter portion 54 comes off from the pin member 24, the large diameter portion 54 might bite into the engine, and the pin member 24 might fall off from the double shaft 17, leading to a damage on the engine.
According to the second embodiment, to solve the above problem, when load is applied between the large diameter portion 54 and the through hole 52, the large diameter portions 54 escape, and the load is received by the shaft portion of the pin member 24, which has stable strength, instead of bringing the outer periphery (shaft portion) of the pin member 24 and the inner surface of the through hole 52 into contact with each other.
More specifically, as shown in
With the above structure, when split variable is carried out, and load is applied to a portion between the large diameter portion 54 of the pin member 24 and the through hole 52 of the cam lobe 22, the oblique sides of the triangular portion 61 are displaced on the tapered faces 62 of the through hole 52 by the amount of the clearance δ as shown in
Stress is then prevented from being concentrated on the base portion of the large diameter portion 54 (escape-preventing portion 50). It is therefore possible to avoid the escape of the pin member 24 attributable to stress concentration.
In addition, the lubricating oil seeps through the long hole 26 of the outer camshaft 17a and enters the clearance δ between the pin member 24 and the through hole 52. The lubricating oil can supply lubrication for the axial displacement of the pin member 24 and can prevent wear between the pin member 24 and the through hole. Furthermore, it can be considered that wear occurs due to the turning motion of the pin member 24. However, such wear can be prevented by the lubrication.
A third embodiment of the invention will be described below with reference to
As shown in
As the stopper 65, for example, a ring-like band member 66 is utilized, which can be press-fitted to the outer periphery of the boss portion 22 as shown in
The band member 66 may be provided only to cylinders located at ends, in which the pin member 24 is easy to escape because torque fluctuation of all the cylinders is inputted thereto, instead of being provided to all the cylinders.
On the basis of the opening/closing timing of the multicylinder engine, the through hole 52 of the boss portion 22b and the through hole 53 of the inner camshaft 17b are formed at each predetermined phase angle, that is, for example, at each 120 degrees if the engine is a three-cylinder engine (shown in
With the above structure in which the pin member 24 that is movably inserted in the cam lobe 22 and the camshafts 17a and 17b is restricted from escaping outside the cam lobe 22 by the stopper 65 fitted to the cam lobe 22 (movable cam), the third embodiment, as with the first, is capable of connecting the cam lobe 22 located in the outer periphery of the outer camshaft 17a and the inner camshaft 17b located inside the outer camshaft 17a to each other without applying the large press-fit load and the large axial force to the cam lobe 22, the outer camshaft 17a and the inner camshaft 17b, which trigger a deformation and bending.
The prevention of escape of the pin member 24 is easy since it is carried out by using the stopper 65 fitted to the outer periphery of the boss portion 22b of the cam lobe 22. In particular, if the ring-like stopper 65 is used, the pin member 24 is restricted from escaping in the axial direction simply by fitting the stopper 65 to the outer periphery of the boss portion 22b in which the pin member 24 is movably inserted (because the end portions of the pin member 24 are blocked by the stopper 65). This facilitates the work of connecting the cam lobe 22 and the inner camshaft 17b. Particularly, if a plurality of through holes 52 and 53 are formed, the cam lobe 22 can be connected to the inner camshaft 17b by using the same components in identical shape in all the cylinders.
The fourth embodiment is a modification of the third and is designed to prevent stress concentration on the band member 66 (stopper 65). If the common pin member 24 having flat end faces is used, a corner of the end of the pin member 24 repeatedly comes into contact with the inner surface of the band member 66 when the pin member 24 is displaced in the axial direction along with rotation of the double shaft 17. In result, stress is concentrated only on a part of the band member 66. The stress concentration induces a deformation and fracture in the band member 66. The deformation causes the escape of the band member 66, and the escape and fracture of the band member 66 lead to the escape of the pin member 24. Furthermore, there is the possibility that the pin member 24 that has escaped bites into the engine, leasing to a damage on the engine. For these reasons, stress concentration has to be avoided in order to secure the reliability of components.
To solve these problems, the present embodiment forms the end portions of the pin member 24 into spherical faces and thus eliminates the corner of the pin member 24, which triggers the stress concentration, by forming spherical faces 68. In this manner, the present embodiment prevents the stress from being concentrated on the inner surface of the band member 66. This eliminates the possibility that the band member 66 fractures due to stress concentration and prevents the escape of the pin member 24 attributable to the fracture, making it possible to retain high reliability.
The fifth embodiment is a modification of the third and the fourth. Instead of using the band member as a stopper, the fifth embodiment utilizes, for example, a snap member 67 formed by shaping a wire member into the shape of letter C. The snap member 67 is fitted to the outer periphery of the boss portion 22b so that the pin member 24 is restricted from escaping. Such a structure still provides the same advantages as in the third embodiment.
A sixth embodiment of the invention will be described below with reference to
As shown in
The second cam phase changing mechanism 71 is disposed in a rear end portion of the double shaft 17. More specifically, the outer camshaft 17a is fastened to a housing 71a of the second cam phase changing mechanism 71, and the inner camshaft 17b is fastened to a vane rotor 71b of the second cam phase changing mechanism 71.
The first cam phase changing mechanism 70 has a function of varying a rotation angle of the outer camshaft 17b relative to the timing sprocket 39, whereas the second cam phase changing mechanism 71 has a function of varying a rotation angle of the inner camshaft 17b relative to the outer camshaft 17a. In other words, the first cam phase changing mechanism 70 has a function of varying the opening/closing timing of the entire intake valve 10 in relation to the opening/closing timing of the exhaust valve, and the second cam phase changing mechanism 71 has a split variable function that varies difference of the opening/closing timing of a pair of intake valves 10 as with the cam phase changing mechanism 25 in the first embodiment.
A first oil control valve 72 that controls the suction and discharge of operating oil supplied to the first cam phase changing mechanism 70 and a first cam sensor 73 (detection means) that detects actual rotation angle of the outer camshaft 17b are fastened to the cylinder head 2. Fastened to a rear portion of the cylinder head 2 is a cover 74 that accommodates a lower half part of the second cam phase changing mechanism 71. A second oil control valve 75 that controls the suction and discharge of operating oil supplied to the second cam phase changing mechanism 71 and a second cam sensor 76 that detects rotation angle of the vane rotor 71b of the second cam changing phase mechanism 71 are fastened to the cover 74.
The first oil control valve 72 and the second oil control valve 75 are supplied with operating oil from a hydraulic pressure supply portion 45 (for example, an oil pump that is fastened to the cylinder block of the engine 1).
The operating oil is supplied from the first oil control valve 72 to the first cam phase changing mechanism 70 through an oil passage 81 formed in the cylinder head 2 and an oil passage 83 formed in a cam piece 82. The cam piece 82 is a portion of a front end portion of the outer camshaft 17a supported by the bearing 18a and is formed to have a column-like shape. Oil grooves 84 are formed in an inner circumferential surface of the bearing 18a in a ring-like configuration. The oil passage 83 opens an outer circumferential surface of the cam piece 82 so as to face the oil grooves 84. This produces a structure in which the oil passages 81 and 83 are constantly connected together between the bearing 18a and the cam piece 82, which make relative rotation. The oil drained from the first oil control valve 72 is discharged into a cam chamber of the cylinder head 2 and a chain case. The oil supplied from the hydraulic pressure supply portion 45 is discharged into a space 87 between the outer camshaft 17a and the inner camshaft 17b through an oil passage 89 formed in the cylinder head 2, an oil passage 85 formed in the inner circumferential surface of the bearing 18a, and an oil passage 86 formed in the cam piece 82. The oil drained into the space 87 is supplied as lubricating oil to sliding portions of inner circumferential surfaces of the bearing 18b and the cam lobe 22 through an oil passage 88 and the long hole 26.
The operating oil is supplied from the second oil control valve 75 to the second cam phase changing mechanism 71 through an oil passage 90 formed in the cylinder head 2 and an oil passage 92 formed in a cam piece 91. The cam piece 91 is a portion of a rear end portion of the outer camshaft 17b supported by a bearing 18c and is formed to have a cylindrical shape. Oil grooves 93 are formed in an inner circumferential surface of the bearing 18c in a ring-like configuration. The oil passage 92 opens in an outer circumferential surface of the cam piece 91. This produces a structure in which the oil passages 90 and 92 are constantly connected to each other between the bearing 18c and the cam piece 91, which make relative rotation.
The first cam sensor 73 is situated adjacent to and in front of the bearing 18c located at the backmost position. A front end of the cam piece 91 is projecting from the bearing 18c in a forward direction. The front end portion extends in a radial outward direction and is provided with a sensor target 100 (material to be detected) of the first cam sensor 73. The first cam sensor 73 detects the actual rotation angle of the outer camshaft 17a by detecting the passing timing of the sensor target 100 along with the rotation of the outer camshaft 17a.
The second cam sensor 76 is situated so that a sensor target 101 fastened to the vane rotor 71b of the second cam phase changing mechanism 71 passes in front of a detection face. The second cam sensor 76 detects the passing timing of the sensor target 101 along with the rotation of the inner camshaft 17b and thus detects the actual rotation angle of the inner camshaft 17b. The sensor target 101 is a disc-like member that covers a rear face of the second cam phase changing mechanism 71 and is formed so that a part of an edge portion thereof is projecting to face the detection face of the second cam sensor 76.
An engine control unit 110 inputs not only driving conditions (torque, revolution, etc.) of the engine 1 but also a detection value of the first and second cam sensors 73 and 76, thereby controlling the first oil control valve 72 and the second oil control valve 75. On the basis of the driving conditions of the engine 1, the engine control unit 110 calculates a target value of the rotation angle of the outer camshaft 17a, which corresponds to the phase of the entire intake valves 10 and a target value of actual rotation angle difference between the outer camshaft 17a and the inner camshaft 17b, which corresponds to phase difference of the opening/closing timing of the intake valves 10. Moreover, the engine control unit 110 obtains the actual rotation angle difference between the outer camshaft 17a and the inner camshaft 17b on the basis of difference between the actual rotation angle of the outer camshaft 17a, which is inputted by the first cam sensor 73, and the actual rotation angle of the inner camshaft 17b, which is inputted by the second sensor 76. The engine control unit 110 controls the operation of the first cam phase changing mechanism 70 by controlling the first oil control valve 72 so that the actual rotation angle of the outer camshaft 17a, which is inputted by the first cam sensor 73, is equal to the target value. At the same time, the engine control unit 110 controls the operation of the second cam phase changing mechanism 71 by controlling the second oil control valve 75 so that the actual rotation angle difference between the outer camshaft 17a and the inner camshaft 17b is equal to the target value.
In other words, the phase of the entire intake valves 10 is varied by the first cam phase changing mechanism 70, and the actual phase is recognized from the rotation angle of the outer camshaft 17a, which is detected by the first cam sensor 73. The phase difference of the opening/closing timing of the intake valves 10 is varied by the second cam phase changing mechanism 71, and the actual phase difference is recognized from the rotation angle difference between the outer camshaft 17a and the inner camshaft 17b, which is detected by the first cam sensor 73 and the second cam sensor 76.
Particularly in the present embodiment, the boss portion 22b of the cam lobe 22 extends rearwards, and pin members 24 (24a to 24c) are positioned absolutely behind tappets 9 of intake valves 10 driven by respective cam lobes 22.
Among the cam lobes 22, the backmost cam lobe 22 has a rear end projecting rearwards up to the vicinity of the cam piece 91. A projecting portion 120 is projecting forwards so as to cover at least a part of each end face of the pin member 24c. To be more specific, the projecting portion 120 is projecting forward in a ring-like shape and has an internal diameter that is slightly larger than an external diameter of a boss portion 22a. A depression formed by the projecting portion 120 is covered with a rear end portion of the boss portion 22a including at least a part of the pin member 24.
As described above, since the projecting portion 120 is provided to the cam piece 91 so as to face both the ends of the pin member 24, for example, even if the pin member 24c intends to shift outwards, the end face of the pin member 24c interferes with the projecting portion 120. The outward shifting of the pin member 24c is thus restricted. For example, if the pin member 24c escapes due to alternate load at the time of the valve lift, the projecting portion 120 inhibits the escape of the pin member 24c. The pin member 24 is thus prevented from interfering with and damaging the cylinder head 2 and the tappet 9 by escaping and projecting. In particular, the pin member 24 that has escaped and projected is prevented from damaging components of the tappet 9 of the intake valve 10 and the like and thus making the intake valve 10 incapable of shifting in an open state. Peripheral components, such as a con rod, a crank, and the cylinder block, are reliably prevented from being damaged. Even if the pin member 24c is fractured by a cam driving force, the fractured part of the pin member 24 does not fall off due to the projecting portion 120, and is thus prevented from falling off and biting into the intake valve 10 and the tappet 9 to make the intake valve 10 and the tappet 9 incapable of shifting in the open state.
Since the sixth embodiment provides the projecting portion 120 to the cam piece 91, the escape of the pin member 24 can be achieved with a simple structure by using the cam piece 91 that is a separate functional component disposed adjacent to the pin member 24c.
According to the sixth embodiment, the escape prevention is provided to the pin member 24c connecting the backmost cam lobe 22 among the three cam lobes 22. This is because the sixth embodiment has a structure in which the second cam phase changing mechanism 71 is rotated at the rear end of the inner cam shaft 17b, and the number of times the inner camshaft 17b receives torsion is higher in the rear portion since the torsion is accumulated in the rear portion due to the alternate load at the time of valve lift. Another reason is that, even if torsion resonance is generated in the inner camshaft 17b, torsion stress is applied to a side that is close to the second cam changing mechanism 71, so that there occurs a large deformation, and it is highly likely that the backmost pin member 24c among the pin members 24a to 24c escapes or fractures. It is then possible to effectively apply the invention only to the pin member 24c that is highly likely to escape among the pin members 24a to 24c, and successfully obtain the advantage of escape prevention with a simpler structure.
Since the sensor target 100, in addition to the projecting portion 120, is integrally formed in the front end portion of the cam piece 71, when the pin member 24 escapes and collides with the projecting portion 120, the projecting portion 120 of the cam piece 91 is deformed together with the sensor target 100, and there causes output abnormality in the first cam sensor 73. It is therefore possible to detect the escape of the pin member 24 from the output abnormality of the first cam sensor 73.
In the sixth embodiment, there is created a small space between the end face of the pin member 24c and an internal surface of the projecting portion 120. This way, the advantage of escape prevention of the pin member 24c can be retained, and at the same time, error in an internal diameter of the projecting portion 120 is allowed, which improves productivity. In the event if the pin member 24c is fractured, a fractured piece is prevented from falling off.
In addition, since the pin members 24a to 24c are positioned absolutely behind the tappet 9 of the intake valve 10, even if the pin members 24a to 24c fall off, they are prevented from colliding directly with the tappet 9. The pin members 24a and 24b are also prevented from at least damaging the intake valve 10.
As shown in
To be specific, the timing sprocket 39 is fastened to a housing 125a of the cam phase changing mechanism 125, and the outer camshaft 17a is fastened to a vane rotor 125b of the first cam phase changing mechanism 125. As in the first embodiment, the opening/closing timing of one of the intake valves 10 is fixed, whereas that of the other intake valve 10 is varied by the cam phase variable mechanism 125.
The rear end of the inner camshaft 17b is projecting in a rearward direction slightly further than the rear end of the outer camshaft 17a. A sensor target 126 (material to be detected) of the inner camshaft 17b is fastened to the rear end of the inner camshaft 17b with a bolt 127. The sensor target 126 is a disc-like member. A detection face of a cam sensor 128 (detection means) that detects the actual rotation angle of the inner camshaft 17b is disposed in an outer circumferential surface of the sensor target 126. The actual rotation angle of the inner camshaft 17b, which is detected by the cam sensor 128, is used to control the operation of the cam phase variable mechanism 125. In an outer circumferential portion of the sensor target 126, there is provided projections 129 projecting like a flange in a forward direction. The projections 129 cover at least a part of end faces of the pin member 24c connecting the backmost cam lobe 22, and are arranged to restrict the outward shifting of the pin member 24c.
According to the seventh embodiment, therefore, the sensor target 126 disposed to the rear end of the double shaft 17 is also used to prevent the escape of the pin member 24c. In the above-described manner, the present embodiment uses the sensor target 126 that is another functional component disposed adjacent to the pin member 24c to achieve the escape prevention of the pin member 24c with a simple structure.
According to the seventh embodiment, the escape prevention is provided to the pin member 24c connecting the backmost cam lobe 22 as in the sixth embodiment. However, the rear end of the inner camshaft 17b is formed into a free end, so that a front end portion is rotated by the cam phase changing mechanism 125. In this case, the outer camshaft 17a and the inner camshaft 17b have substantially the same length. The rear end of the inner camshaft 17b that is positioned farthest from the cam phase changing mechanism 125 oscillates most. Depending upon the scale of this oscillation, the possibility of escape of the pin member 24c is increased. Among the pin members 24a to 24c, therefore, the escape prevention is effectively carried out with respect to the pin member 24c only, which is most likely to escape.
As shown in
The sensor target 130 of the eighth embodiment is fastened not to the inner camshaft 17b but to the cam lobe 22. The sensor target 130 is formed to have a shape of a lid covering the rear end of the double shaft 17. In an outer circumferential portion thereof, projections 131 are formed like a flange. If the rear end portion of the cam lobe 22 is tightly fitted into the projections 131, the sensor target 130 is fastened. In this case, if the projections 131 are designed to cover at least a part of the ends of the pin member 24c, the sensor target 130 functions as an escape stopper for the pin member 24c. In particular, the eighth embodiment offers easy assembly because a sensor target 90 can be fastened without bolt.
As shown in
The rear end of the outer camshaft 17a is closed with a disc-like plug 136. This prevents an outflow of the lubricating oil supplied between the inner camshaft 17a and the outer camshaft 17b.
According to the present embodiment, in each cylinder, the cam lobe 22 driven by the inner camshaft 17a is located in front, and the reference cam 20 fastened to the outer camshaft 17b is located at the rear. The pin member to be provided with escape prevention is the pin member 24a connecting the front cam lobe 22. In the front cam lobe 22, the front end of the boss portion 22b extends forwards as far as a point close to the cam piece 37 of the front end portion of the outer camshaft 17a. In the rear end portion of the cam piece 37, there is provided a projection 120 projecting rearwards to cover the front end portion of the boss portion 22b of the cam lobe 22. As in the sixth embodiment, the projection 120 is designed to cover at least a part of the end faces of the pin member 24a. The present embodiment is thus capable of preventing the escape of the pin member 24a by using the cam piece 37. According to the present embodiment, the inner camshaft 17b is shorter than the outer camshaft 17a, and the cam phase changing mechanism 125 is used to rotate the front end of the inner camshaft 17b. The number of times the inner camshaft 17b receives torsion due to alternate load at the time of valve lift is higher in the front portion since the torsion is accumulated in the front portion of the inner camshaft 17b located closer to the cam phase changing mechanism 125. This raises the possibility of escape of the pin member 24a. The pin member 24a is provided with escape prevention, which is located closest of the pin members 24a to 24c to the front end of the inner camshaft 17b.
The invention is not limited to the above-described embodiments and may be modified in various ways without deviating from the gist of the invention. For example, the first and second embodiments use the pin member that can be subjected to the swaging process and the large diameter portion that is formed by the swaging process. It is also possible, instead, to utilize a rivet member as the pin member and apply the swaging process to the rivet, to thereby form an escape-preventing portion. The point is that a pin-like member that is movably inserted and an escape-preventing portion are combined together.
Although the sixth to ninth embodiments provide the projections 120, 129 and 131 for the escape prevention of the pin member 24 to the cam pieces 37 and 91 or the sensor targets 126 and 130, the invention is not limited to this. For example, the projection 120 or the like may be provided to another functional component that is disposed adjacent to the pin member to be provided with escape prevention, such as an assembly hexagon nut fixed to the outer periphery of the outer camshaft 17b.
In the sixth to ninth embodiments, the escape prevention is provided to the pin member 24a connecting the frontmost cam lobe 22 among all the cam lobes 22 or the pin member 24c connecting the backmost cam lobe 22. The escape prevention, however, may be provided to both the front and backmost pin members 24a and 24c. The pin member 24b connecting the cam lobe 22 other than both the outermost cam lobes may be provided with the projection 120 or the like covering both the ends of the pin member 24 for escape prevention if another functional component such as the hexagon nut is adjacently located.
In the above-described embodiments, the invention is applied to the intake-side variable valve device. Instead, the invention may be applied to an exhaust-side variable valve device as long as the engine is equipped with a variable valve device on the exhaust side. Moreover, the invention may be applied not only in a three-cylinder engine but also in an engine with any number of cylinders.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-013108 | Jan 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/072886 | 12/20/2010 | WO | 00 | 2/28/2012 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/089809 | 7/28/2011 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6186102 | Kosuge et al. | Feb 2001 | B1 |
| 8186319 | Pluta et al. | May 2012 | B2 |
| 8225762 | Lancefield et al. | Jul 2012 | B2 |
| 20100132640 | Methley et al. | Jun 2010 | A1 |
| 20100282193 | Timothy et al. | Nov 2010 | A1 |
| Number | Date | Country |
|---|---|---|
| 4419557 | Oct 1995 | DE |
| 2 424 257 | Sep 2006 | GB |
| 52-32647 | Mar 1977 | JP |
| 10-325309 | Dec 1998 | JP |
| 2000-240412 | Sep 2000 | JP |
| 2009-144521 | Jul 2009 | JP |
| 2009-144522 | Jul 2009 | JP |
| 10-1998-071049 | Oct 1998 | KP |
| 10-2009-0064806 | Jun 2009 | KP |
| WO 2009005999 | Jan 2009 | WO |
| Entry |
|---|
| Extended European Search Report dated Apr. 16, 2013 for European Application No. 10843973.8. |
| Japanese Office Action issued in Japanese Patent Application No. 2011-550814 on May 9, 2012. |
| Korean Office Action issued in Korean Patent Application No. 10-2012-7005390 on Dec. 13, 2012. |
| Number | Date | Country | |
|---|---|---|---|
| 20120160197 A1 | Jun 2012 | US |
