JPH03168309A - Valve opening and closing device for four cycle engine - Google Patents

Abstract

PURPOSE:To improve the durability of a valve and to prevent the deviation of valve opening and closing time by making the periphery of an eccentric plate serve as a bearing face, and rotatably supporting the eccentric plate on a collar member tightly held by a receiving part of a cam holder. CONSTITUTION:A receiving part 10 having an inner periphery concentric with a cam shaft 2 is protrusively provided on the peripheries of the end faces of cam holders 8a, 8b which rotatably support the end part of a valve system cam member and moreover support the cam shaft 2 through the valve system cam member. A collar member 11 having a inner hole 16 eccentric to its peripheral face is rotatably fitted in the inner periphery of the receiving part 10. An annulus ring-shaped eccentric plate 17 which encloses the cam shaft 2 with a clearance 18 kept between its periphery and the plate 17 is rotatably fitted in the inner hole 15. Thus, since the eccentric plate is rotatably supported on its periphery by the collar member 11, it is widened in its bearing area and improved in its durability. In addition to that, since the collar member 11 is tightly held by the receiving part 10 over its about whole periphery, valve opening and closing time does not deviate from its normal time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a valve opening/closing device for a four-stroke engine, and particularly to a valve opening/closing device for a four-stroke engine, and in particular, to a valve opening/closing device for a four-stroke engine. This invention relates to a valve opening/closing device.

In the 4-stroke engine, the valve opening timing is advanced at high speeds, and the valve closing timing is delayed, thereby lengthening the valve overlap period (the period in which the intake and exhaust valves are open at the same time), and reducing the inertia of the intake and exhaust. This effect is used to increase intake and exhaust efficiency to achieve high engine output.In addition, in low speed ranges, the valve opening timing is delayed and the valve closing timing is advanced, shortening the valve overlap period, exhaust rewiring, and intake air circulation. BACKGROUND ART A reduction in engine output has been attempted by preventing blow-through, and for this purpose, various variable valve timing valve operating systems have been proposed.

For example, in the valve opening/closing mechanism for a four-cycle engine described in Japanese Patent Laid-Open No. 63-1707 filed by the present applicant, a cam for opening and closing the valve is mounted eccentrically in the axial direction within a camshaft rotatably fitted. The shaft is inserted,
A plurality of rollers are movably disposed in contact with the outer peripheral surface of the eccentric shaft portion of the eccentric shaft, and these rollers pass through each roller holding window provided in the camshaft and protrude radially outward from the camshaft. ing. An eccentric collar is fitted onto the outer periphery of these rollers, and by rotating the eccentric shaft relative to the camshaft, the eccentric collar becomes eccentric with respect to the camshaft via the eccentric shaft portion and the roller. ing.

When the camshaft rotates, this rotation is transmitted to the eccentric collar through an engaging protrusion that is integral with the camshaft and slides into the radial groove of the eccentric collar, and the eccentric collar rotates around its eccentric central axis. The eccentric collar rotates, and the rotation of the eccentric collar is transmitted to the valve opening/closing cam via an engagement protrusion on the cam side that is in sliding contact with another radial groove that faces the radial groove on the same diameter, The cam rotates about the axis of the camshaft. As a result, a periodic phase difference occurs between the rotation of the camshaft and the rotation of the valve opening/closing cam, and the state of occurrence of this phase difference changes depending on the eccentricity state of the eccentric collar. By adjusting the amount of eccentricity of the eccentric collar depending on the state, a desired rotational phase difference can be generated between the camshaft and the valve opening/closing cam, and the valve opening/closing timing can be adjusted appropriately.

However, in this valve opening/closing mechanism, the eccentric collar uses its inner peripheral surface as a bearing surface and is supported by the eccentric shaft via the roller. Affects shaft durability.

In addition, since the eccentricity of the eccentric collar is adjusted by an eccentric shaft that passes through the center of the camshaft, it is possible to adjust the eccentricity of the eccentric collar by using the eccentric shaft that passes through the center of the camshaft. It is difficult to apply a suitable valve opening/closing mechanism.

Japanese Unexamined Patent Publication No. 59-131715 discloses an engine camshaft drive mechanism in which an eccentric coupling mechanism similar in principle to the above is inserted in the middle of a cam drive shaft.

In this mechanism, an eccentric disk corresponding to the eccentric collar described above is rotatably fitted on the inner peripheral surface of an annular yoke, and by moving the yoke in a direction perpendicular to the cam drive shaft, the eccentric disk The amount of eccentricity is adjusted.

In this engine camshaft movement mechanism, since the outer peripheral surface of the eccentric disk is surrounded and supported by the annular yoke, the bearing area is increased, which is advantageous in terms of the durability of the eccentric disk. However, since the amount of eccentricity of the eccentric disk is adjusted by linearly displacing the yoke in the diametrical direction, a relatively large force is required to adjust the amount of eccentricity, and the amount of eccentricity must be adjusted subtly and continuously. Things are complicated. Furthermore, as the yoke is subject to forces in the radial and rotational directions as the cam drive shaft rotates, it is necessary to firmly fix the yoke against this force. goes completely crazy. Therefore, while setting the yoke position accurately,
A mechanism to securely fix this is essential, making the structure complicated and large.

Japanese Utility Model Application Publication No. 57-198306 also shows an intake/exhaust valve drive control device in which a similar eccentric coupling mechanism is inserted between a cam and a camshaft. A control ring is located between the flange and the cam and is eccentrically rotatable with respect to the axis of the camshaft, a disk is concentrically and rotatably housed in the control ring, and the disk is There are pins in different positions and grooves in the flange and cam to receive the pins. The control ring has a gear portion on its outer periphery, and is swingably supported by the engine body at a fulcrum provided at a position diametrically opposed to the gear portion, and the gear meshing with the gear portion rotates. This causes the disc to swing about the fulcrum, thereby making the disc eccentric with respect to the axis of the camshaft together with the control ring. However, since this control ring is fixed only by the gear portion and the fulcrum, its fixation is not sufficient, and the set position changes during operation, which tends to cause deviations in the valve opening and closing timing.

The present invention overcomes the problems of the conventional device as described above, and
The bearing area of the eccentric member is increased to improve durability, and the eccentric member is securely fixed in a set position so as to be rotatable, thereby preventing deviations in valve opening/closing timing. It is an object of the present invention to provide a valve opening/closing device for a four-stroke engine that allows the device to precisely and easily adjust the eccentric position of an eccentric member.

And for this reason, in the present invention, a valve cam member is rotatably fitted to a camshaft that is rotationally driven in synchronization with the crankshaft, and a cam is provided between the camshaft and the valve cam member. An eccentric member capable of eccentricity with respect to the shaft is interposed, and the cam shaft and the rotary valve cam member are respectively connected to the eccentric member via a coupling mechanism consisting of a radial groove and an engagement protrusion that engages with the groove. death,
In the valve opening/closing device for a four-stroke engine, the valve opening/closing timing of the valve can be adjusted by periodically changing the rotational phase of the valve cam member with respect to the camshaft by eccentricity of the eccentric member. A receiving portion having an inner circumferential surface concentric with the camshaft is protrudingly provided on the outer circumference of the end face of the cam holder which rotatably supports the end portion and supports the camshaft via the valve operating cam member, and the inner circumference A collar member having an outer circumferential surface having the same diameter as the surface and an inner hole eccentric to the outer circumferential surface is rotatably fitted onto the inner circumferential surface of the receiving portion, and the inner hole of the collar member is fitted with the collar member. An annular eccentric plate that surrounds the camshaft with a gap between it and its outer circumferential surface is rotatably fitted,
A drive member is provided which connects the eccentric plate to the camshaft and the valve drive cam via the connection mechanism, and rotates the collar member. Since the valve opening/closing device of the present invention is constructed in this way, the rotation of the camshaft is transmitted to the eccentric plate via the engaging protrusion and the groove, and the eccentric plate is connected to the shaft eccentric to the axis of the camshaft. The rotation of the eccentric plate is further transmitted to the valve operating cam member through similar grooves and retaining protrusions, and the valve operating cam member rotates about the axis of the camshaft. As a result, the rotational angular velocity of the valve operating cam member around the camshaft changes periodically, resulting in a fast-phase period in which the valve-operating cam member rotates at a faster phase than the camshaft, and a slow-phase period in which it rotates at a slower phase. However, the relationship between the advance and slow phases of the lever to the piston stroke changes depending on the eccentric direction of the eccentric plate with respect to the camshaft, so the eccentric direction is set to i[ to advance or retard the cam appropriately with respect to the camshaft. This allows the valve opening/closing timing to be adjusted as desired.

Adjustment of the eccentric direction is performed by rotating the collar member by a driving member, and the eccentric plate is rotatably supported by the inner hole of the collar member over the entire outer peripheral surface thereof,
Is the outer peripheral surface the bearing surface? Since the bearing area is large, wear and seizure are less likely to occur and durability is improved. Moreover, since the collar member is fitted onto the inner circumferential surface of the receiving portion of the cam holder and is firmly held by the cam holder, the set eccentric state will not be disturbed during operation. Furthermore, since the collar member is fixed by the cam holder and no other special fixing member is required, the device becomes smaller and simpler. Further, since the eccentric state is adjusted by rotating the collar member, delicate adjustment is possible and adjustment can be easily performed with a relatively small force.

Sharp treatment group Hereinafter, the present invention will be described with reference to illustrated embodiments.

FIG. 1 is a plan view of a valve opening/closing device for a four-stroke engine according to the present invention, taken along a cross section passing through the center of the camshaft. Reference numeral 1 denotes a cylinder head, on the upper surface of which a camshaft 2 for an intake system and a camshaft 3 for an exhaust system are arranged parallel to each other. The engine of this embodiment is a four-cylinder engine with a double overhead cam, and cam members 41, 4, and 43 open and close each intake valve.
, 44 is the camshaft? The camshafts 2 are rotatably fitted into the camshaft 2 and arranged along the camshaft 2. Two cams 5 are formed on each cam member 4. Cam members 61, 6, 63, and 64 for opening and closing the exhaust valves of each cylinder are similarly mounted on the camshaft 3. Since the camshaft 2 side and the camshaft 3 side have substantially the same structure, the structure on the camshaft 2 side will be described in detail below.

The camshaft 2 is provided with a cam gear 7 at the center in its longitudinal direction, and is driven to rotate by the crankshaft at half the rotational speed of the crankshaft through a gear train meshing with the cam gear 7. That is, the gear train is arranged at the center of four cylinder rows arranged on the left and right, and this arrangement is most commonly used in four-stroke engines for motorcycles.

A cam member 4 and a cam member 4 are arranged adjacent to both sides of the cam gear 7, respectively.
Let's talk about. The end of the cam member 4 on the cam gear 7 side is rotatably supported by a cam holder 8. As shown in FIG. 2, the cam holder 8 has a lower half 8a and an upper half 8b.
It is divided into two parts, ? The cam member 43 is held by overlapping the upper half 8b on the lower half 8a fixed to the cylinder head 1 and fastening them with bolts. The cam holder 8 also supports the camshaft 2 via a cam member 43. An annular receiving portion 10 is formed on the outer circumference of the cam holder 8 and projects toward the cam gear 7. The inner circumferential surface 10a of the receiving portion 10 is shaped like a cylindrical surface concentric with the camshaft 2.

A collar member 11 is rotatably fitted into the receiving portion 10 with its outer peripheral surface in contact with the inner peripheral surface 10a.

A part of the outer peripheral surface of the collar member 11 is a gear part 12, and a collar drive gear 14 fixed to the end of a collar drive shaft 13 pivotally supported by the cam holder 8 meshes with this gear part 12. . The receiving portion 10 is partially cut out at the position of the collar drive gear 14, allowing the gear 14 and the gear portion 12 to mesh with each other. The collar member 11 is also provided with a connecting lever 15 that projects radially outward and then extends outside the cam gear 7 toward the cam member 4. This collar member 11 has an inner hole 16 eccentric to its outer peripheral surface.

Eccentric plate 1 having an outer diameter equal to the diameter of the second inner hole 16
7 is rotatably fitted. The eccentric plate 17 itself has a perfect circular ring shape, but as described above, the eccentric inner hole 1
As a result of being fitted into the camshaft 6, the camshaft 2 is eccentric to the camshaft 2. By rotating the collar member 11 by the collar drive gear 14, the eccentric direction with respect to the camshaft 2 is changed. Second
In the figure, P is the rotation center of the camshaft 2, and P2 is the eccentric plate 1.
7 indicates the center of rotation.

A sufficient gap 18 is secured between the inner periphery of the eccentric plate 17 and the outer periphery of the camshaft 2 so that the eccentric plate 17 and the camshaft 2 do not interfere with each other no matter which direction the eccentric plate 17 is eccentric.

The eccentric temporary 17 is provided with radial grooves 19 and 20 at opposite positions on the same diameter, and the groove 19 has a retaining protrusion 21 integral with the cam gear 7, and the groove 20 has a retaining protrusion 21 integral with the cam member 43. The engaging protrusions 22 are fitted and engaged with each other. The rotation of the engagement protrusion 21 is transmitted to the eccentric plate 17 via the groove 19, and the rotation of the eccentric plate 17 is transmitted to the engagement protrusion 2 via the groove 20.
2, the grooves 9 and 20 rotate around the rotation center P2 of the eccentric plate 17, and the engaging protrusions 21 and 22 rotate around the rotation center P of the camshaft 2, so the groove 19
, 20 and the engaging protrusions 21, 22 rotate while sliding relative to each other in the radial direction of the eccentric plate 17.

FIG. 2 shows the state when the eccentric plate 17 is eccentrically moved upward, and the eccentric plate rotation center P2 is the camshaft rotation center P2.
, is located directly above the . This state is a state adapted to high-speed rotation of the engine. In this embodiment, the angular position of the top of the cam 5 and the angular position of the retaining protrusion 22 match, and although the cam 5 is in a horizontal state in FIG. 2, the eccentric plate 17 When the cam 5 is pushed by the engaging protrusion 21 and rotates clockwise in the figure around the center P2, the cam 5 pushes up a rocker arm (not shown), and the rocker arm opens the intake valve. When the engaging protrusion 22 and the groove 20 reach the uppermost position as shown in FIG. 3, the opening degree of the intake valve becomes maximum. At this time, the diameter D of the camshaft 3 passing through the center of the retaining protrusion 21 and the engaging protrusion 2
The diameter d of the eccentric plate 17 passing through the center of the two overlaps with each other. From this state, when the engaging protrusion 21 further rotates together with the camshaft 3 and the diameter D rotates to the position indicated by D in the figure, the diameter d with P2 as the center of rotation occupies the position indicated by d+ in the figure. Since the engaging protrusion 22 is always on the diameter d, the cam 5 rotates in a phase that lags behind the rotation of the camshaft 2. on the other hand,
Before reaching the state shown in FIG. 3, when the diameter D is at the D2 position, the diameter d is at the d2 position, and the rotational phase of the cam 5 is ahead of the rotational phase of the camshaft 2. Therefore cam 5
, the intake valve opens earlier and closes later than when it is fixed to the camshaft 2. As mentioned above, this is a desirable valve opening/closing timing when the engine rotates at high speed.

When the engine rotates at low speed, the collar member 11 is rotated 180 degrees to eccentrically move the eccentric plate 17 to the lowermost position as shown in FIG. The relationship between the diameters D and d when the valve is open and closed is shown by D2, d2, and D, d, respectively in the figure, so the valve opens late and closes early, which is desirable during low-speed rotation. The valve opening/closing timing can be obtained. If the collar member 11 is set to an intermediate state between FIGS. 3 and 4, valve opening and closing timing suitable for medium speed rotation can be obtained.

The rotational position of the collar member 11 that determines the eccentric direction of the eccentric plate 17 is determined by the collar drive gear 14 that engages with the gear portion l2 and is fixed to the collar drive shaft l3. As shown in camshaft 2
A control gear 23 is fixed to the other end of the cam member 64 extending outwardly to the right in parallel with the cam shaft 2 and beyond the rightmost cam member 64 . And this control gear 23 is controlled? 1'll drive gear 24
The control drive gear 24 is rotated under the control of a control device, which will be described later, so that the control drive gear 23
, the collar drive shaft 13, and the collar drive gear 14, the collar member 1l is rotated and set to a rotational position according to the engine speed.

The other end of the cam member 43 is also supported by a cam holder 8a similar to the cam holder 8, and this cam holder 8a
An eccentric mechanism having a collar member 11a and an eccentric plate 17a similar to those described above is held in the receiving portion 10a, thereby connecting the cam shaft 2 and the cam member 44. Since its structure and operation are exactly the same as those described above, detailed explanation will be omitted. However, the collar member 11a does not include the connecting lever 15. A retaining protrusion 21a that is different from the collar member 11 and corresponds to the engaging protrusion 21
is provided protruding from a flange member 25 screwed onto the camshaft 2. A collar drive gear 14a that meshes with the gear portion 12a of the collar member 11a is fixed to the collar drive shaft 13, and the collar member 11 and the collar member 11a are adjusted simultaneously by the collar drive shaft l3.

The cam member 4 is rotatably supported at both ends by cam holders 8b and 8c similar to the cam holder 8, and a similar eccentric comprising a collar member 1lb and an eccentric plate 17b is mounted on the receiving portion 10b of the cam holder 8b adjacent to the cam gear 7. A mechanism is held through which the cam member 4 is held. is connected to the camshaft 2. Connecting lever 26 from collar member 1lb
protrudes outward in the radial direction, and the tip of the connecting lever 26 is sandwiched between two forks provided at the tip of the connecting lever 15 of the collar member 11 (see FIG. 5). Therefore, the collar member 1lb rotates together with the collar member 11, and the collar member 1lb is adjusted simultaneously with the adjustment of the collar member 11.

The gear portion 12b of the collar member 1lb includes a cam holder 8b,
? It meshes with a driven gear 28 fixed to the right end of a connecting shaft 27 pivotally supported by c.

Cam member 4. is the drive coupling device 1 for the cam member 44;
It is drivingly connected to the camshaft 2 through a mechanism completely similar to 111a, 17a, and 25, and the collar member 1
A driving gear 29 fixed to the connecting shaft 27 meshes with the driving gear 1c, and rotation of the collar member 1lb is transmitted to the collar member 11C via the driven gear 28, the connecting shaft 27, and the driving gear 29. As a result, the rotation of the control drive gear 24 causes the four collar members 1l, lla, Llb, and llc to simultaneously rotate by the same amount, and the intake valve opening/closing timings for the four cylinders are adjusted at the same time according to the engine speed. . The cam members 6l, 6■, 63, 64 on the exhaust valve side are also the cam members 4, 64 on the intake valve side.
, 4■, 43, and 44, and the control drive gear 24 meshes with the control gear 23 and also meshes with a similar control gear 30 on the exhaust valve side (see FIGS. 1 and 6). ).

The control drive gear 24 is rotationally driven under the control of a control device as schematically shown in FIG. 7, for example. 31 is a step motor provided outside the engine 32, and the output shaft 33 of the step motor 31 and the input shaft 34 of the control flit drive gear 24 are connected by a timing belt 35. A current controlled by an electronic control unit (ECU) 37 is supplied to the step motor 31 from a power source 36 . The electronic control unit 37 measures the engine rotation speed based on the signal from the engine rotation sensor 38, turns on and off the current to the step motor 31 according to the rotation speed, and controls its direction. 31 rotates forward or reverse by a required number of rotations when necessary, and rotates the control drive gear 24 by a predetermined angle via a timing belt 35. As described above, the valve opening/closing timing is adjusted in accordance with the rotation of the control drive gear 24.

In this embodiment, the eccentric plate l7 is rotatably fitted into the inner hole {6 of the collar member 11, and the outer peripheral surface of the eccentric plate 17 serves as a bearing surface for the rotation of the eccentric plate 17, so that the bearing area is reduced. It is large and therefore less likely to wear or seize, improving durability.

Moreover, the collar member ll itself is firmly held over almost the entire outer peripheral surface by the inner peripheral surface of the receiving part 0 of the cam holder 8, and the collar drive gear 1
4 acts as a stopper and reliably prevents the rotation of the collar member 11, so that the collar member 11 does not move during operation and the eccentric state of the eccentric plate 17 changes and the valve opening/closing timing is not deviated.

The fixing of the collar member 1 as described above is performed using the cam holder 8, and no other special fixing member is required to firmly fix the collar member 11, so the device is small and
In addition to simplifying the structure, since the bulging portion of the multiple cylinder is limited to only a part of the connecting lever 15, 26, the engine as a whole can be made compact.

Further, since the eccentric state of the eccentric plate 17 is adjusted by rotating the collar member 11 through engagement between the gear portion l2 and the collar drive gear 14, delicate adjustment is possible and requires a relatively small force. Adjustments can be made easily.

Furthermore, since the opening and closing timings of the intake valves and exhaust valves of the four cylinders are controlled simultaneously by the rotation of the only control drive gear 24,
Adjustment of valve opening/closing timing is extremely easy.

According to the present invention, since the eccentric plate is rotatably supported by the collar member with its outer peripheral surface serving as a bearing surface, the bearing area is large and the durability is therefore improved.

Moreover, since the collar member is firmly held by the receiving part of the cam holder over almost the entire outer circumferential surface of the collar member,
There is no possibility that the collar member moves during operation and the eccentric state of the eccentric plate changes, causing deviations in the valve opening/closing timing. Furthermore, the collar member is fixed using a cam holder, and no other special fixing member is required to firmly fix the collar member, so the device becomes smaller and simpler. In addition, since the eccentric state of the eccentric plate is adjusted by rotating the collar member, it is possible to make subtle adjustments, and it also has many excellent effects, such as being able to easily make adjustments with a relatively small force. is obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a valve opening/closing device for a four-cycle engine according to the present invention taken along a cross section passing through the center of the camshaft, FIG. 2 is a sectional view taken along line II-H in FIG. 1, and FIGS.
The figures are diagrams for explaining the rotational phase relationship between the camshaft and the cam during high-speed rotation and low-speed rotation of the engine, respectively, and are a schematic diagram showing the relative positions of each member in the same cross section as Figure 2, and Figure 5. The figure is an external view of a connecting lever that connects adjacent collar members to each other, and Figure 6 is Vl-V in Figure 1.
FIG. 7, which is a sectional view taken along line I, is a schematic diagram showing a control device for a control drive gear. DESCRIPTION OF SYMBOLS 1... Cylinder head, 2... Camshaft, 3... Camshaft, 4... Cam member, 5... Cam, 6... Cam member, 7... Cam gear, 8...・Cam holder, 9...
・Bolt, 10... Receiving part, l1... Collar member,
12... Gear part, l3... Collar drive shaft, 14...
・Collar drive gear, 15...Connection lever, 16...
Inner hole, 17... Eccentric plate, 18... Gap, 19... One groove, 20... Groove, 21... Engaging protrusion, 22... Engaging protrusion, 23... Control gear , 24... Control drive gear, 25... Flange member, 26... Connection lever, 2
7... Connection shaft, 28... Driven gear, 29... Drive gear, 30... Control gear, 31... Step motor, 32... Engine, 33... Output shaft, 34・・・
- Input shaft, 35... Tying belt, 36... Power supply, 37... Electronic control unit, 38... Engine rotation sensor.

Claims (1)

[Claims] A valve-driving cam member is rotatably fitted to a camshaft that is rotatably driven in synchronization with the crankshaft, and an eccentric member that can be eccentric with respect to the camshaft is interposed between the camshaft and the valve-driving cam member. ,
The camshaft and the valve drive cam member are each connected to the eccentric member through a connection mechanism consisting of a radial groove and an engagement protrusion that engages with the groove, and the eccentricity of the eccentric member causes the camshaft to be connected to the camshaft. In a valve opening/closing device for a four-stroke engine, which is capable of adjusting the valve opening/closing timing by periodically changing the rotational phase of a valve cam member, the end portion of the valve cam member is rotatably supported and A receiving portion having an inner circumferential surface concentric with the camshaft is protrudingly provided on an outer circumferential portion of an end face of a cam holder that supports the camshaft via a valve cam member, and a receiving portion having an outer circumferential surface having the same diameter as the inner circumferential surface. A collar member having an inner hole eccentric with respect to the outer circumferential surface is rotatably fitted onto the inner circumferential surface of the receiving portion, and the camshaft is inserted into the inner hole of the collar member with a gap between it and the outer circumferential surface. rotatably fit an annular eccentric plate surrounding the camshaft and the valve drive cam member via the connecting mechanism,
A valve opening/closing mechanism for a four-cycle engine, further comprising a driving member for rotating the collar member.