JP4555270B2 - Variable valve opening characteristics internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine with variable valve opening characteristics, and more particularly to a technique for improving support rigidity of a power transmission member and suppressing twisting of a control shaft.

  Many 4-cycle gasoline engines (hereinafter simply referred to as engines) are equipped with various valve opening characteristic variable mechanisms in order to improve output and fuel consumption, reduce harmful exhaust gas components, and the like. As a valve opening characteristic variable mechanism, there is a mechanism that switches between a low-speed cam and a high-speed cam according to the operating situation. However, in recent years, in order to realize further improvement of transient characteristics and reduction of throttle, etc. One that variably controls the phase and valve lift individually has become the mainstream.

As a variable valve lift device used for variable valve lift control, a control arm or control link for variable valve lift is installed between the cam and rocker arm to change the fulcrum of the control arm or the geometry of the control link. There has been proposed one in which the valve lift is changed by making it (see Patent Documents 1 and 2). When this type of variable valve lift device is mounted on a multi-cylinder engine, a power transmission member (for example, an outer periphery or an end of a control shaft (such as a turning shaft, a cam shaft, or a rotation shaft) that operates a variable valve lift mechanism of each cylinder. The sector gear) is formed separately or integrally, and this power transmission member is driven by an electric actuator installed at the center or end of the cylinder head.
JP 2004-521234 A JP 2005-248874 A

  As described below, the conventional variable valve lift device described above has various problems related to support of the power transmission member and the control shaft. That is, in the valve lift variable device of the above-mentioned patent document, since the power transmission member is disposed on the side of the support member (cam holder or the like), the power transmission member is cantilevered and its support rigidity is low. It is unavoidable that it becomes difficult to restrict the movement of the power transmission member in the thrust direction. Even if the electric actuator is installed near the center in the axial direction of the control shaft, the control shaft cannot be driven at an intermediate position in the axial direction due to the presence of the support member. In combination with this, there is a risk that the control shaft may be slightly tilted or twisted. On the other hand, in the variable valve lift device, it is necessary to regulate the movable range of the control shaft and the power transmission member for the purpose of preventing an excessive valve lift, etc. There was a problem that the assembly man-hours increased and the product price increased.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a variable valve opening characteristic internal combustion engine that realizes improvement in support rigidity of a power transmission member, suppression of twisting of a control shaft, and the like.

According to the first aspect of the present invention, there is provided a control shaft extending in the cylinder row direction , one end of which is swingably held by the control shaft, and a roller which holds the roller and the roller shaft between the camshaft and the rocker arm at the other end. a link, an actuator having a drive gear, while being rotatably supported in the cam holder, having a driven gear meshing with the drive gear, and a power transmission member for pivoting the control shaft by its rotation, the power An internal combustion engine in which valve opening characteristics of valves installed in a plurality of cylinders change simultaneously by turning the control shaft as the transmission member rotates, wherein the power transmission member is formed on the cam holder. It is arranged between a pair of support walls .

  According to a second aspect of the present invention, in the variable valve opening characteristic internal combustion engine according to the first aspect, a bearing for supporting the power transmission member is formed on each of the pair of support walls. Features.

According to a third aspect of the present invention, there is provided the variable valve opening characteristic internal combustion engine according to the first or second aspect, wherein the cam holder is provided with a stopper for restricting a turning range of the control shaft. Features.

  According to a fourth aspect of the present invention, in the variable valve opening characteristic type internal combustion engine according to any one of the first to third aspects, the power transmission member is a substantially central portion in the axial direction of the control shaft. It is located in.

According to the first aspect of the invention, the support rigidity of the power transmission member is improved, the control shaft is less likely to be inclined or twisted, and movement in the thrust direction is easily controlled. According to the second aspect of the invention, the length of the bearing can be made relatively large, and even when the operation is performed for a long period of time, the wear of the support pins and the like hardly occur. If the camshaft is held by a pair of support walls, the bearing length of the camshaft increases, and the camshaft is unlikely to fall down. According to the invention of claim 3, even if the power transmission member overruns for some reason, the valve overlift or the like does not occur, and the generation of noise, the deterioration of the engine performance, and the like are suppressed. According to the invention of claim 4, the control shaft is less likely to be inclined or twisted.

Hereinafter, an embodiment of the present invention and a partial modification thereof will be described in detail with reference to the drawings.
[Embodiment]
FIG. 1 is a perspective view showing a main part of an upper part of an engine according to the embodiment, FIG. 2 is a perspective view showing a main part of the VLC mechanism according to the embodiment, and FIG. 3 is a main part fracture III in FIG. 4 is a perspective view showing a connection state between the center cam holder and the gear link, FIG. 5 is a rotary sectional view showing a connection portion between the center cam holder and the gear link, and FIG. It is a figure which shows the operating range of a VLC mechanism. In the embodiment, for the convenience of explanation, the lower left in FIG.

<< Configuration of Embodiment >>
<Overall configuration>
An engine (variable valve opening characteristic internal combustion engine) E shown in FIG. 1 is a four-cycle in-line four-cylinder gasoline engine for automobiles. As shown in FIG. 2 and FIG. A DOHC 4-valve type valve operating mechanism is provided which includes an exhaust valve 2 and an intake valve 3, and drives the valves 2 and 3 by an exhaust camshaft 4 and an intake camshaft 5. An exhaust rocker arm 6 is interposed between the exhaust valve 2 and the exhaust camshaft 4, and an intake rocker arm 7 is interposed between the intake valve 3 and the intake camshaft 5. The exhaust valve 2 and the intake valve 3 are always urged in the closing direction by the valve springs 9 and 10.

  Five cam holders (support members) 11 to 15 are fastened to the upper surface of the cylinder head 1, and the cam shafts 4 and 5 and the rocker arms 6 and 7 are rotatably supported by the cam holders 11 to 15. In the present embodiment, among the cam holders 11 to 15, the right end one is the front cam holder 11, the center one is the center cam holder 13, the left end one is the rear cam holder 15, and the other two are the middle cam holder 12, And 14 respectively. As shown in FIG. 2, the center cam holder 13 has a pair of left and right support walls 16 and 17 on the exhaust side, and an axial center portion of the exhaust camshaft 4 is supported by the support walls 16 and 17. . A flat base plate 18 is installed on the upper surfaces of the cam holders 11 to 15, and the valve mechanism is covered with the base plate 18 and the head cover 19.

  The engine E of the present embodiment includes two variable valve timing control (VTC) mechanisms 41 and 42 that variably control the angle phases of the camshafts 4 and 5 as the valve opening characteristic variable mechanism, and the lift amount of the exhaust valve 2. And a VLC (Variable valve Lift Control) mechanism 20 that variably controls the engine.

<VLC mechanism>
As shown in FIGS. 2 and 3, the VLC mechanism 20 includes an electric motor (actuator) 21 installed in parallel with the camshafts 4 and 5 on the upper surface of a base plate 18 (not shown in FIG. 2), and an electric motor. A fan-shaped drive gear (spur gear) 22 attached to the shaft 21a of the gear 21, a gear link (power transmission member) 23 having an arc-shaped driven gear portion 23a and a shaft holder portion 23b, and a shaft holder portion of the gear link 23 A control shaft 24 rotatably supported by 23b, a roller link 25 in which the control shaft 24 is fitted and inserted at the base end thereof, and a roller link 26 rotatably supported by the tip of the roller link 25. The main components are a roller 27 and a spring unit 28 that constantly biases the roller 27 toward the exhaust camshaft 4. That. 1 is a sensor (rotary encoder) that detects the rotation angle of the drive gear 22, and an engine ECU (not shown) determines the position of the control shaft 24 based on the detection signal of the sensor 29. Then, the supply current to the electric motor 21 is feedback controlled.

  As shown in FIGS. 3 to 5, the gear link 23 is rotatably supported by the left and right support walls 16 and 17 of the center cam holder 13 via a support pin 31, and engages with the driven gear portion 23 a. 22 is driven to rotate. The left and right end surfaces of the support pin 31 are locked by thrust flanges 4 a and 4 b formed on the exhaust camshaft 4.

  As shown in FIGS. 4 and 5, an oil groove 31 a is formed along the axial direction on the outer peripheral surface of the support pin 31, while oil holes 16 a and 17 a are formed in the left and right support walls 16 and 17 of the center cam holder 13. The engine oil from the oil hole 4c formed in the exhaust camshaft 4 is supplied to the outer peripheral surface of the support pin 31 through these oil holes 16a and 17a and the oil groove 31a. The center cam holder 13 and the base plate 18 are provided with oil holes 16b, 17b, and 18a for jetting engine oil from the oil hole 4c of the exhaust camshaft 4 upward.

  The gear link 23 rotates steplessly between a position indicated by a solid line (minimum lift position) in FIG. 6 and a position indicated by a broken line (maximum lift position), whereby the control shaft 24 (that is, the shaft holder) is rotated. The part 23 b) turns around the support pin 31. On the end surfaces of the left and right support walls 16 and 17 in the center cam holder 13 are an upper stopper portion 13a that restricts the counterclockwise rotation of the gear link 23 and a lower portion that restricts the clockwise rotation of the gear link 23. A stopper portion 13b is formed. That is, in the present embodiment, the rotation range of the gear link 23 is regulated by forming the stopper portions 13 a and 13 b in the center cam holder 13 instead of installing an independent stopper member. Since the gear link 23 rotates only between the minimum lift position and the maximum lift position, wear or the like due to contact with the shaft holder portion 23b or the stopper portions 13a and 13b does not occur during normal operation. When the gear link 23 overruns from the minimum lift position or the maximum lift position for some reason, the shaft holder portion 23b is locked to the upper stopper portion 13a or the lower stopper portion 13b.

  The control shaft 24 is also rotatably supported by the cam holders 11, 12, 14, 15 other than the center cam holder 13 via a front link holder 33, a middle link holder 34, and a rear link holder 35. Although the front link holder 33 is pivotally supported on the end surface of the front cam holder 11, the middle link holder 34 has a middle cam formed by left and right arm portions 34b and 34c extending from the holding portion 34a as shown in FIG. The holders 12 and 14 are pivotally supported.

  The middle link holder 34 is connected to the middle cam holders 12 and 14 by pins 38, and the pins 38 are prevented from falling off by C-shaped retaining rings 39. Lubricating engine oil is supplied to the pin 38 from the middle cam holders 12 and 14 through an oil hole (not shown) communicating with the exhaust camshaft 4. Although not shown, the rear link holder 35 is also pivotally supported by the rear cam holder 15 in the same manner as the middle link holder 34. As with the center cam holder 13, the middle cam holders 11, 12 and the rear cam holder 15 also have an upper stopper portion for regulating the counterclockwise rotation of the middle link holder 34 and the rear link holder 35, and the middle link holder. 34 and a lower stopper portion for restricting the clockwise rotation of the rear link holder 35 is formed.

  As shown in FIG. 6, the roller link 25 swings around the minimum lift point P1 when the gear link 23 is at the minimum lift position, and the maximum lift point when the gear link 23 is at the maximum lift position. Swings around P2. The roller 27 is sandwiched between a pair of left and right link levers 25 a and 25 b formed on the roller link 25, and is in rolling contact with the cam lobe 4 d of the exhaust camshaft 4. The roller shaft 26 is in rolling contact with a circular arc surface 6 a formed on the exhaust rocker arm 6. In addition, the circular arc surface 6a has a center P3 obliquely above and below the minimum lift point P1.

<< Operation of Embodiment >>
When the engine E of the automobile is started, the engine ECU sets the target lift amount of the exhaust valve 2 based on various operation information such as the depression amount of the throttle pedal and the coolant temperature by the driver, and the electric motor of the VLC mechanism 20 The drive current is output to 21. Then, the drive gear 22 attached to the shaft 21a of the electric motor 21 rotates, and the gear link 23 meshed with the drive gear 22 by the driven gear portion 23a is rotationally driven in either the forward or reverse direction.

  When obtaining a combustion state that increases the amount of internal EGR that can be compressed and ignited, the engine ECU rotates the gear link 23 to the minimum lift position and moves the roller link 25 around the minimum lift point P1, as shown in FIG. Try to rock. As a result, even when the roller 27 is pushed down by the cam lobe 4d, the roller shaft 26 rolls along the arc surface 6a as shown by an arrow in FIG. 2 lift amount) is minimized. In the normal combustion state, the engine ECU rotates the gear link 23 to the maximum lift position and swings the roller link 25 around the maximum lift point P2 as shown in FIG. . Thereby, when the roller 27 is pushed down by the cam lobe 4d, the roller shaft 26 hardly rolls along the arc surface 6a, so that the lift amount of the exhaust valve 2 is maximized.

  When the gear link 23 is driven by the drive gear 22, a relatively large downward biasing force acts on the gear link 23 due to the engagement of the drive gear 22 and the driven gear portion 23a. However, in this embodiment, since the gear link 23 is supported by the left and right support walls 16 and 17 of the center cam holder 13, the gear link 23 is positioned in the center in the axial direction of the exhaust camshaft 4. The gear link 23 and the control shaft 24 are prevented from being slightly inclined or twisted. In addition, since the engine oil flows into the support pin 31 that supports the gear link 23 not only between the left and right support walls 16 and 17 but also between the gear link 23 through the oil groove 31a described above, a long period of time is required. Even if the operation over the range is performed, the wear of each sliding surface hardly occurs. The exhaust camshaft 4 has a support length at the center cam holder 13 that is significantly greater than the support lengths at the other cam holders 11, 12, 14, and 15, so that the support rigidity is increased and tilt and the like are effectively suppressed. Thus, the variation in valve lift among the cylinders was reduced.

  On the other hand, when the gear link 23 overruns from the minimum lift position or the maximum lift position for some reason, in this embodiment, the shaft holder portion 23b of the gear link 23 is the upper stopper portion 13a or the lower stopper portion of the left and right support walls 16 and 17. 13b. Similarly, the middle cam holders 11 and 12 and the rear cam holder 15 are also locked to the upper stopper portion or the lower stopper portion of the middle cam holders 11 and 12 and the rear cam holder 15. As a result, an overlift or the like of the exhaust valve 2 does not occur, and the generation of noise or the deterioration of engine performance is suppressed.

[Partial modification]
FIG. 9 is a perspective view showing a main part of an upper part of an engine according to a partial modification, and FIG. 10 is a cross-sectional view of a main part showing a VLC mechanism according to the partial modification.
As shown in FIGS. 9 and 10, some modified examples have substantially the same configuration as that of the above-described embodiment, but the power transmission method between the electric motor 21 and the gear link 23 is different. That is, in some modifications, the multistage gear train 50 is employed instead of the fan-shaped drive gear used in the embodiment.

  As shown in FIG. 10, the multistage gear train 50 includes four gears (first gear 51 to fourth gear 54). The first gear 51 is a relatively small diameter flat gear with a small number of teeth, and is attached to the shaft 21 a of the electric motor 21. The second gear 52 is a stepped gear having a large gear portion 52 a that meshes with the first gear 51 and a small gear portion 52 b that meshes with the third gear 53. The third gear 53 is an idler gear interposed between the second gear 52 and the fourth gear 54, and the sensor 29 is connected to the third gear 53. The fourth gear 54 is a stepped gear having a small gear portion 54 a that meshes with the third gear 53 and a large gear portion 54 b that meshes with the driven gear portion 23 a of the gear link 23.

  In some modified examples, by adopting such a configuration, the rotation of the electric motor 21 is transmitted to the gear link 23 with a relatively large reduction ratio, and the generated torque and the physique of the electric motor 21 are small. Could be adopted. Moreover, since the electric motor 21 and the sensor 29 can be installed at a relatively low position, the center of gravity and the overall height of the engine E are lower than those of the embodiment, and the motor performance of the automobile, the mountability of the engine E, and the like are improved. I was able to.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, in the above embodiment, the present invention is applied to an in-line four-cylinder DOHC gasoline engine that variably controls only the lift amount on the exhaust valve side, but the lift amount on the intake valve side is also variably controlled. Of course, the present invention can also be applied to SOHC engines and diesel engines. In the above embodiment, the spur gear mechanism is employed for driving the power transmission member by the actuator, but a worm reduction mechanism, a chain drive mechanism, a cam mechanism, or the like may be employed. Further, the specific configuration and the like of the variable valve opening characteristic mechanism can be changed as appropriate without departing from the gist of the present invention.

It is a principal part perspective view which shows the upper part of the engine which concerns on embodiment. It is a perspective view which shows the principal part of the VLC mechanism which concerns on embodiment. It is a principal part fracture III arrow directional view in FIG. It is a perspective view which shows the connection state of a center cam holder and a gear link. It is a rotation sectional view showing a connection part of a center cam holder and a gear link. It is a figure which shows the operating range of a VLC mechanism. It is operation | movement explanatory drawing of a VLC mechanism. It is operation | movement explanatory drawing of a VLC mechanism. It is a principal part perspective view which shows the upper part of the engine which concerns on a partial modification. It is principal part sectional drawing which shows the VLC mechanism which concerns on a partial modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Exhaust valve 4 Exhaust cam shaft 6 Exhaust rocker arm 13 Center cam holder (support member)
13a Upper stopper (stopper)
13b Lower stopper (stopper)
16 Support wall 17 Support wall 20 VLC mechanism 21 Electric motor (actuator)
22 drive gear 23 gear link (power transmission member)
24 Control shaft 31 Support pin 50 Multi-stage gear train E Engine

Claims (4)

A control shaft extending in the cylinder row direction ,
One end is swingably held on the control shaft, and the other end is a roller link that holds the roller and the roller shaft between the camshaft and the rocker arm.
An actuator having a drive gear ;
A power transmission member rotatably supported by the cam holder and having a driven gear meshing with the drive gear, and rotating the control shaft by rotation thereof ;
Have
An internal combustion engine in which valve opening characteristics of valves installed in a plurality of cylinders change simultaneously by turning the control shaft as the power transmission member rotates.
The variable valve opening characteristic internal combustion engine , wherein the power transmission member is disposed between a pair of support walls formed in the cam holder .   2. The variable valve opening characteristic internal combustion engine according to claim 1, wherein bearings for supporting the power transmission member are formed on the pair of support walls. The variable valve opening characteristic internal combustion engine according to claim 1 or 2, wherein the cam holder is formed with a stopper for restricting a turning range of the control shaft.   4. The variable valve opening characteristic internal combustion engine according to claim 1, wherein the power transmission member is positioned at a substantially central portion in an axial direction of the control shaft. 5.

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