JP2019132159A - Cam device of internal combustion engine - Google Patents

Abstract

To provide a variable cam device which is excellent in a control function of intake air and exhaust air.SOLUTION: A cam 2 corresponding to each valve 1 is constituted of a fixed unit cam body 3 fixed to a camshaft 8, and a movable unit cam body 4 rotating with respect to the camshaft 8. The fixed unit cam body 3 and the movable unit cam body 4 are aligned in parallel with each other in an axial direction, and tightly adhere to each other. The movable unit cam body 4 rotates in an advance angle direction by an amount of a clearance between a stopper 17 and an engagement groove 18. The movable unit cam body 4 is energized to a reference attitude such that the movable unit cam body is tightly superimposed on the fixed unit cam body 3 by a spring 19. By sending oil to a front part of the engagement groove 18 via a longitudinal hydraulic hole 22 and a branched hydraulic hole 23, the movable unit cam body 4 rotates in the advance angle direction. Since the cam 2 corresponding to each valve 1 is a profile variable type, an intake air amount and an exhaust air amount are increased and decreased with good responsiveness linked with an opening of a throttle valve and an engine speed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a cam device for an internal combustion engine.

  In an internal combustion engine, an intake valve and an exhaust valve are each opened and closed by cams provided on a cam shaft. However, in order to ensure intake and exhaust, it is beneficial to variably control the opening and closing of the valves.

  With regard to this point, there is a conventional VVT device that advances or retards the rotational phase of the camshaft, but the VVT device can only change the valve opening timing and adjust the valve opening range. Since it is not possible, it is difficult to say that fine control over the intake air amount and the exhaust air amount can be performed.

  On the other hand, in Patent Document 1, in an internal combustion engine in which a pair (two each) of intake valves and exhaust valves are arranged corresponding to one cylinder, a pair of cams are rotated relative to each other, whereby a pair of It is disclosed to change the combined opening and closing range of the valve. More specifically, in Patent Document 1, the swirl flow generation function is improved by changing the opening start timing of the pair of intake valves.

JP 2010-138859 A

  In Patent Literature 1, the opening range of a valve can be changed by changing the opening / closing timing of a pair of valves as a whole of one cylinder. However, one pair of valves is closed while the other is opened and the other is opened. Since one side closes in the open state, the adjustment function of the intake air amount and the exhaust air amount is not necessarily high, and therefore, the change responsiveness of the intake air amount and the exhaust air amount at high speed rotation is not necessarily high. Guessed.

  Specifically, regarding intake air, even if the opening range of the two valves as a whole is widened, the intake amount of intake air does not increase so much, so it is not possible to increase the charging efficiency during high-speed rotation. May not be obtained. Similarly, regarding exhaust gas, exhaust performance cannot be improved during high-speed rotation, and in this case as well, there is a concern that the exhaust gas may remain in the cylinder and thus improvement in charging efficiency cannot be expected.

  In addition, since the opening and closing timings of the pair of valves are shifted, there is a concern that turbulent flow is likely to occur in the cylinder and the stable combustion may be hindered when taking intake air.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a variable cam device capable of finely controlling intake / exhaust according to various conditions such as the rotational speed.

The present invention is a configuration in which a cam for opening and closing an intake valve or an exhaust valve is provided on a camshaft,
“The cam corresponding to one valve is composed of a plurality of unit cam bodies that are divided in the axial direction of the cam shaft and are in close contact with each other, and the plurality of unit cam bodies are arranged around the axis of the cam shaft. The composite cam profile composed of the plurality of unit cam bodies is variable by being rotated relative to each other. ''
The feature is that.

  There can be various patterns for the relative rotation of the plurality of unit cam bodies. For example, there is an aspect in which the cam is composed of a fixed unit cam body fixed to the cam shaft and a movable unit cam body rotating on the cam shaft. As another aspect, there is an aspect in which the plurality of unit cam bodies rotate independently on the cam shaft.

  From the viewpoint of control of the advance angle and the retard angle, there are a mode in which the composite cam profile spreads to the advance side, a mode to spread to the retard side, and a mode to spread to both the advance side and the retard side. . Further, the change of the composite cam profile can be a stepless change or a step change. By adopting a hydraulic change structure as in the embodiment and controlling the hydraulic pressure feed with the oil control valve used in the VVT device, stepless control can be easily realized.

  A feature of the present invention is that the profile of individual cams can be changed. Therefore, in the case of an internal combustion engine in which a pair of intake valves and exhaust valves exist corresponding to one cylinder, the composite cam profile of the two intake valves and the composite cam profile of the two exhaust valves are respectively changed, Control of intake air amount and exhaust amount, intake air timing and exhaust gas timing can be performed.

  For this reason, even at high speed rotation, it is possible to easily increase the intake air amount and the exhaust air amount with high responsiveness according to the rotational speed. As a result, it is possible to secure a high filling efficiency and obtain a desired output even at high speed rotation.

  When the hydraulic change device is employed as in the embodiment, the movable unit cam body can be rotated relative to the load even when a load is applied, and therefore, the combined cam profile of each intake valve or exhaust valve in one hydraulic system Can be changed all at once. For this reason, cost can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows 1st Embodiment, (A) is a longitudinal front view, (B) IIA-IIA sectional view, (B) (BB) view of (A), (C) Oil supply means FIG. FIGS. 1A and 1B are cross-sectional views taken along the line AA in FIG. 1B, in which FIG. 1A is a view in a reference posture, and FIG. (A) is a principal longitudinal section front view in a standard posture of a 2nd embodiment, and (B) is a principal part longitudinal front view in a standard posture of a 3rd embodiment. (A) is a principal part longitudinal front view of 4th Embodiment, (B) is a principal part longitudinal front view of 5th Embodiment.

(1). Basic Structure of First Embodiment Next, an embodiment of the present invention will be described based on the drawings. First, the first embodiment shown in FIGS. In this embodiment, one cam 2 corresponding to one valve (intake valve or exhaust valve) 1 is sandwiched between two fixed unit cam bodies 3 and both fixed unit cam bodies 3, respectively. It is composed of two movable unit cam bodies 4. Accordingly, one valve 1 is driven by one cam 2 in which three unit cam bodies 3 and 4 are combined.

  In this embodiment, the movable unit cam body 4 is thicker than the fixed unit cam body 3, and the total thickness of the two fixed unit cam bodies 3 is one movable unit cam body 4. It is about the same as the thickness. The valve 1 has the same structure as that of the prior art, and includes a valve shaft 5 and a valve lifter 6 fixed to the valve shaft 5, and is urged in a forward direction by a spring 7.

  Each unit cam body 3, 4 is fitted on a cam shaft 8, and the cam shaft 8 is rotatably held by a bearing portion 10 of the cylinder head 9 and a cam cap 11. As shown in FIG. 1A, the fixed unit cam body 3 is fixed to the camshaft 8 by a key 12, for example. The keyway 13 of the fixed unit cam body 3 is open to the front and rear side surfaces of the fixed unit cam body 3 (otherwise, the fixed unit cam body 3 cannot be fitted. The cam body 3 is held so as not to be displaced by a snap ring 14 fitted on the cam shaft 8.

  As shown by a one-dot chain line in FIG. 1A, the camshaft 8 is fixed to the camshaft 8 by a screw 16 inserted in the countersink hole 15 with a countersink hole 15 formed in the camshaft 8 so as to cross the camshaft 8. The cam body 3 may be fixed. In this case, the opening of the counterbore hole 15 may be closed with a plug.

  As shown in FIG. 2, the movable unit cam body 4 is rotatably fitted to the cam shaft 8, but is directed to the cam shaft 8 toward the protruding portion (cam portion) of the movable unit cam body 4. While the protruding stopper 17 is fixed, the movable unit cam body 4 is formed with an engagement groove 18 into which the protruding portion of the stopper 17 is fitted in a certain range along the circumferential direction. Therefore, the movable unit cam body 4 rotates relative to the camshaft 8 by the clearance between the thickness of the stopper 17 (thickness in the circumferential direction) and the circumferential width of the engagement groove 18.

  In this embodiment, the movable unit cam body 4 has a reference posture in which the movable unit cam body 4 is exactly overlapped with the fixed unit cam body 3 when viewed from the axial direction of the cam shaft 8. In this reference posture, the stopper 17 is engaged. Of the end face of the groove 18, it abuts on one end face (front end face) 18 a located forward in the rotational direction of the camshaft 8.

  Further, in the movable unit cam body 4, a spring (compression coil spring) 19 is disposed between the other end surface (rear end surface) 18 b of the engagement groove 18 and the stopper 17. Therefore, the movable unit cam body 4 is biased to the reference state. One end of the spring 19 is fitted in a spring receiving recess 20 formed in the stopper 17, and the spring 19 is set to be accommodated in the spring receiving recess 20 when contracted. In the present embodiment, the movable unit cam body 4 is also urged so as to be stable in the reference posture by the rotation of the cam shaft 8. ).

(2) Control structure In the movable unit cam body 4, an auxiliary groove 21 communicating with the engagement groove 18 is formed on the front side in the rotation direction of the camshaft 8 with the stopper 17 interposed therebetween. The camshaft 8 is formed with a longitudinal hydraulic hole 22 that passes through the axial center thereof, and a branch hydraulic hole 23 that branches from the longitudinal hydraulic hole 22 and communicates with the auxiliary groove 21 and the engaging groove 18. Needless to say, the branch hydraulic hole 23 is formed at each movable unit cam body 4.

  The engaging groove 18 and the auxiliary groove 21 are opened (cut open) on both front and rear side surfaces of the movable unit cam body 4. Therefore, it is preferable to interpose a sealing material between the movable unit cam body 4 and the fixed unit cam body 3 to prevent oil leakage.

  As shown in FIG. 1C, one transverse passage 24 communicating with the longitudinal hydraulic hole 22 and extending in the radial direction at a portion of the cam shaft 8 located at one cam cap 11, and a transverse passage An annular groove 25 communicated with 24 is formed, and the annular groove 25 communicates with a semicircular passage 26 formed on the inner periphery of the cam cap 11. The semicircular passage 26 communicates with an oil passage (not shown) formed on the mating surface between the cam cap 11 and the bearing portion 10, and the oil passage is filled with oil pumped by an oil pump. doing.

  Although not shown in the drawing, an oil control valve (OCV) for controlling the oil feed through the longitudinal hydraulic hole 22 is disposed at an appropriate portion of the passage for sending the pressure oil to the longitudinal hydraulic hole 22. The oil control valve may be attached to one cam cap 11 or to the cylinder head 9.

  As described above, the movable unit cam body 4 is biased to the reference posture by the spring 19. When the pressure oil is sent to the longitudinal hydraulic hole 22, as shown in FIG. 2B, the oil flows into the auxiliary groove 21, thereby moving the movable unit cam body 4 in the rotation direction of the cam shaft 8. Rotate. That is, the movable unit cam body 4 rotates in the advance direction. Thereby, the composite cam profile formed by the fixed unit cam body 3 and the movable unit cam body 4 has a form in which the width of the apex portion (width in the circumferential direction) that contacts the valve lifter 6 is widened.

  Accordingly, the opening range of the valve 1 is increased. Precisely, the closing timing of the valve 1 is the same as that in the reference posture, but the opening timing is earlier. Therefore, when the valve 1 is an intake valve, the intake amount can be increased. Since the composite cam profile spreads at each valve 1, the intake amount can be greatly increased when applied to the intake valve, and the exhaust amount can be greatly increased when applied to the exhaust valve. Therefore, even in the high speed rotation region, the intake air amount and the exhaust air amount can be made to follow in a state in which the opening degree of the throttle valve is quickly responsive, which can contribute to the improvement of the output.

  By adjusting the amount of oil sent to the longitudinal hydraulic hole 22 with the oil control valve, the rotation angle of the movable unit cam body 4 can be adjusted steplessly. Therefore, the opening and closing of the valve 1 can be finely controlled according to various conditions such as the rotation speed and load. In the embodiment, the movable unit cam body 4 is rotated from the reference posture to the advance side, but can also be rotated from the reference posture to the retard side. As an urging means for the movable unit cam body 4, a torsion torsion spring wound around the cam shaft 8 can be used.

  The oil amount adjustment by the oil control valve can be performed in stages. In the case of stepwise control, two-step control of the reference posture and the fully rotated state and three-step control including an intermediate step can be arbitrarily selected.

  Adopting a system in which the movable unit cam body 4 is sandwiched between the front and rear fixed unit cam bodies 3 as in this embodiment has an advantage that the stability of the movable unit cam body 4 can be improved. Further, when the thickness of the movable unit cam body 4 and the total thickness of the two fixed unit cam bodies 3 are set to the same level, the valve lifter 6 can be Since the hit state can be made uniform, there is an advantage that wear can be suppressed. Further, since the pressing force acts on the shaft center of the valve shaft 5, the valve shaft 5 is not twisted and the durability can be improved.

  Moreover, in this embodiment, since the movable unit cam body 4 is corrected to the reference posture by the spring 19, the structure can be simplified. Since the oil control valve can use what is marketed for VVT, while being excellent in reliability, it can also contribute to cost reduction.

(3). Other Embodiments Next, other embodiments shown in FIGS. 3 and 4 will be described. In each of the following embodiments, the cam 2 is composed of two fixed unit cam bodies 3 and one movable unit cam body 4.

  The second embodiment shown in FIG. 3A is basically the same as the first embodiment, except that the first longitudinal hydraulic hole 28 and the second longitudinal hydraulic hole 29 are formed in the camshaft 8. The first longitudinal hydraulic hole 28 communicates with the auxiliary groove 21, and the second longitudinal hydraulic hole 29 passes through the branch hydraulic hole 23 at a position on the rear side in the rotation direction across the stopper 17 in the engagement groove 18. It communicates via the auxiliary groove 21.

  In this embodiment, hydraulic pressure is used to hold the movable unit cam body 4 in the reference posture, and the function (movement) of the cam 2 is the same as in the first embodiment. The oil feed to the second longitudinal hydraulic hole 29 may be controlled by an oil control valve, or may be only pressurized with a constant pressure lower than the pressure to the first longitudinal hydraulic hole 28.

  In the third embodiment shown in FIG. 3B, the stopper 17 is set to be positioned at the intermediate portion of the engagement groove 18 in the reference posture, and the first longitudinal hydraulic hole 28 and the first Two longitudinal hydraulic holes 29 are formed, and the engagement groove 18 can be hydraulically applied from both sides of the stopper 17 via the branch hydraulic hole 23 and the auxiliary groove 21. Therefore, in this embodiment, the movable unit cam body 4 can be rotated in both the advance direction and the retard direction with the reference posture interposed therebetween. For this reason, intake and exhaust can be controlled more finely.

  The fourth embodiment shown in FIG. 4 is a modification of the third embodiment. The difference from the third embodiment is that the longitudinal hydraulic holes 28 and 29 have a large cross-sectional area. It is only a very short point.

  In the fifth embodiment shown in FIG. 4B, the stopper 17 protrudes inward from the movable unit cam body 4, and therefore the engagement groove 18 is formed in the cam shaft 8. A plate spring 30 is used as a means for biasing to the reference posture, and the branch hydraulic hole 23 is L-shaped. Reference numeral 31 denotes a plug.

  The stopper 17 is fixed to the movable unit cam body 4 by a pin 32 (a screw may be used). Therefore, a through hole 33 for driving the pin 32 is formed through the shaft center in the cam shaft 8, and the through hole 33 is closed with a plug 34.

  The embodiment of the present invention has been described above, but the present invention can be embodied in various ways. For example, the cam body can be composed of one fixed unit cam body and one movable unit cam body. Or it is also possible to comprise only a plurality of movable unit cam bodies 4. The present invention may be applied to both the cam device for the intake valve and the cam device for the exhaust valve, or only one of them. It can also be used in combination with VVT.

  The present invention can be embodied in a cam device for an internal combustion engine. Therefore, it can be used industrially.

1 Valve 2 Cam 3 Fixed Unit Cam Body 4 Movable Unit Cam Body 6 Valve Lifter 8 Cam Shaft 17 Stopper 18 Engaging Groove 19, 30 Spring for Energizing the Movable Unit Cam Body to the Reference Position 21 Auxiliary Groove 22, 28 , 29 Longitudinal hydraulic hole 23 Branch hydraulic hole

Claims (1)

The camshaft is provided with a cam that opens and closes an intake valve or an exhaust valve,
The cam corresponding to one valve is composed of a plurality of unit cam bodies that are divided in the axial direction of the cam shaft and are in close contact with each other, and the plurality of unit cam bodies are arranged around the axis of the cam shaft. By making the relative rotation, the composite cam profile composed of the plurality of unit cam bodies is variable.
A cam device for an internal combustion engine.

Images