CN102242650B - Can be used for the continuous variable geometry camshaft of full Variable Valve Time - Google Patents

Abstract

The invention discloses a continuously variable geometry camshaft which can be used for fully variable valve timing. Three sub-cams are combined to form a cam; each sub-cam has a boss, and the boss is closely matched with its respective chute. ;The sleeve with chute is fixed in the hole of the central shaft by the fixed pin, and the coaxial twitch is realized by the drive of the central shaft; with the twitching of the central shaft, the axial movement of the sleeve is driven, and the three sub-cams are driven by the chute Movement along the angular direction enables the angle of the combined cam to be continuously adjusted, thereby realizing continuous and comprehensive adjustment of the valve timing.

Description

Continuously variable geometry camshafts available for fully variable valve timing

technical field

The invention relates to a continuously variable geometry camshaft which can be used for fully variable valve timing, which divides a common single cam into three combined cams, so that the cam angle can be continuously variable.

Background technique

The meaning of the existing variable valve timing mechanism is to change the overlapping angle of the intake valve and the exhaust valve, and the duration of the valve opening is fixed. However, when this valve timing mechanism increases the overlap angle, the exhaust valve opens late and the intake valve closes prematurely, which all cause additional exhaust loss of the engine and reduce the intake air volume. These all make the internal combustion engine The theoretically optimal output power and torque are lost. The method that can adjust the valve timing to the theoretical optimal value is called fully variable valve timing, which includes the timing of a single valve and the overlap angle of the intake and exhaust valves.

Publication No. CN101173618 describes a timing camshaft with continuously variable valve opening duration and valve opening advance angle. Although the cam is divided into a fixed part and a variable part, the opening duration of the valve can be changed, but its same The problem with the shaft rotation adjustment method is that only one variable sub-cam can be realized, so the result is the contradiction between the adjustable range and the basic shape angle of the sub-cam, that is, if the adjustable range of the cam angle is large, the basic shape of the sub-cam The angle must be very large, that is, as shown in the accompanying drawings, such a method has the advantage of increasing the power of the internal combustion engine at high speeds, but the disadvantage is that the internal combustion engine loses torque at low speeds. On the other hand, if the basic angle of the sub-cam is increased and the lift is to be maintained, the diameter of the central shaft must be increased, which will not only increase the weight of the mechanism, but also increase the linear velocity of the outer edge when the camshaft rotates, increasing the friction loss. In addition, the connection of the movable mechanism is relatively slender, and it is prone to failure or even complete failure in the heavy-duty working state of the cam.

Contents of the invention

This patent makes a new solution to the above-mentioned defects, and designs a new continuously variable geometry camshaft mechanism, which can be better compatible with the current design forms of internal combustion engines and provide better timing effects.

The invention provides a continuously variable geometry camshaft that can be used for fully variable valve timing. Three sub-cams are combined to form a cam, and each sub-cam has a flat top of the same height; each sub-cam has a boss , the bosses are closely matched with their respective chute; the casing with chute is fixed in the hole of the central shaft by the fixed pin, and the coaxial twitch is realized by the drive of the central shaft; with the twitching of the central shaft, the shaft of the casing is driven The chute drives the three sub-cams to move in the angular direction, so that the angle of the combined cams can be continuously adjusted to achieve continuous and comprehensive adjustment of the valve timing.

Description of drawings

Fig. 1 is an exploded view showing constituent parts of a camshaft.

Fig. 2 is an assembly diagram showing the assembly method of the sub-cam 1 and the bushing.

Fig. 3 is an assembly diagram, showing the assembly manner of the sub-cam 3 and the bushing.

Fig. 4 is an assembly diagram showing the assembly manner of the sub-cam 7 and the bushing.

Fig. 5 is a cross-sectional view and a combined view of the small-angle cam, showing the general assembly method of the camshaft, and at this moment, the adjustment state of the small-angle cam is formed.

Fig. 6 is a combination diagram of large-angle cams, showing the adjustment state where the camshaft forms a large-angle cam.

Figure 7 is a general assembly drawing showing an example of four cams per camshaft.

Detailed ways

An exemplary embodiment will be described below with reference to the drawings.

Figure 1 is an exploded schematic view of the camshaft. Any cam on the camshaft is composed of three sub-cams, and the value of the crankshaft angle corresponding to the sub-cams satisfies the angle requirement for early opening of the valve at the lowest speed of the internal combustion engine. Sub-cam 1, 3, 7 shown in the figure, wherein 1, 7 are the sub-cams on both sides, there are extensions, and 3 is the sub-cam in the middle, there is no extension. Each sub-cam has a flat top of equal height, and the flat tops of sub-cams 1, 3, and 7 are combined to form a smooth whole. The sub-cam 1 cooperates with the sleeve pipe 2, the sub-cam 3 cooperates with the sleeve pipe 4, and the sub-cam 7 cooperates with the sleeve pipe 6. Fixed pins 10, 9, 8 are used to fix sleeve pipes 2, 4, 6 on three corresponding holes of the central shaft respectively, so that sleeve pipes become a part completely fixed together with the central shaft. Both the rotation of the central shaft and the twitching along the axis of the central shaft will drive the sleeves 2, 4, 6 to move together. The angle of the equal-height flat top of each sub-cam is the upper limit of the cam angle adjustment, and determines the maximum range of the continuously adjustable variation of the cam.

Figure 2 is a schematic diagram of the assembly and cooperation of the No. 1 sub-cam of the camshaft and its corresponding sleeve. The shape of the boss 11 of the sub-cam 1 is the same as that of the chute 12 of the sleeve 2, which can be closely matched. The sub-cam 1 It is installed coaxially with the casing 2, and the boss 11 corresponds to the sliding groove 12, so the sub-cam can be driven by the casing 2 to rotate axially. The chute 12 of the sleeve 2 is twisted in the axial direction, and when the sleeve 2 is twitched in the axial direction, the sub-cam 1 will rotate along the chute 12 relative to the sleeve in the direction of rotation angle.

Figure 3 is a schematic diagram of the assembly of the second sub-cam of the camshaft and its corresponding sleeve. The shape of the boss 14 of the sub-cam 3 is the same as the chute 13 of the sleeve 4, which can be closely matched. The sub-cam 3 Installed coaxially with the sleeve 4, the boss 14 corresponds to the slide groove 13, so the sub-cam can be driven by the sleeve 4 to rotate axially. The chute 13 of the sleeve 4 is twisted in the axial direction, and when the sleeve 4 twitches in the axial direction, the sub-cam 3 will rotate along the chute 13 relative to the sleeve in the direction of rotation angle.

Figure 4 is a schematic diagram of the assembly of the third sub-cam of the camshaft and its corresponding sleeve. The shape of the boss 16 of the sub-cam 7 is the same as the chute 15 of the sleeve 6, which can be closely matched. The sub-cam 7 It is installed coaxially with the sleeve 6, and the boss 16 corresponds to the sliding groove 15, so the sub-cam can be driven by the sleeve 6 to rotate axially. The chute 15 of the sleeve 6 is twisted in the axial direction. When the sleeve 6 twitches in the axial direction, the sub-cam 7 will rotate along the chute 15 relative to the sleeve in the direction of rotation angle.

Fig. 5 is a sectional view and a combined view of the small-angle cam. The angle of the cam on the camshaft at this moment is a relatively small angle, that is, the angle of each sub-cam 1,3,7. The B-B cross-sectional view in the figure shows the assembly relationship of its various components. The fixing pin 10 fixes the sleeve 2 on the central shaft 5 , the fixing pin 9 fixes the sleeve 4 on the central shaft 5 , and the fixing pin 8 fixes the sleeve 6 on the central shaft 5 . The length dimension of fixed pin 8,9,10 is less than the internal diameter of sub-cam 1,3,7, so sub-cam 1,3,7 can slide along chute 12,13,15.

Fig. 6 is a large-angle camshaft combination diagram, it can be seen that the camshaft moves axially with the central shaft 5 relative to the sub-cams 1, 3, 7, and the direction is to move from the sub-cam 7 to the sub-cam 1. This movement drives the axial movement of the bushing, and the sub-cams 1, 3, 7 are driven by the chute of the bushing, and the sub-cams move in the angular direction relative to the central axis, so that a differential motion is generated between the sub-cams, and the combination The angle of the cam can be adjusted continuously, and the shape of the equivalent cam can be changed significantly, forming a so-called large-angle cam. Therefore, with the twitching of the central shaft 5, the camshaft realizes the continuous and comprehensive adjustment of the valve timing. The adjustment direction of the cam angle increases from the sub-cam 7 to the sub-cam 1, and vice versa, the cam angle decreases.

Fig. 7 is a general assembly drawing, which is an example of 4 cams per camshaft, showing that the sub-cams 1, 3, 7 rely on the extension sleeves 17, 18, 19 of the same inner and outer radii as the extensions of the sub-cams. Squeeze close together, and the two ends are fixed whole camshaft system by camshaft holder 20 and fixed cover 22 and bolt 23. The central shaft 5 shown in the figure also has spline teeth 21, so that the rotational moment of the central shaft can still be provided when the central shaft moves in the axial direction; the hydraulic thrust plate 24 is the hydraulic system to push the central shaft 5 to make axial reciprocating adjustment movements source of power. As shown in the figure, the camshaft is in the low-speed and small-angle adjustment state. The camshaft holder 20 and the fixed cover 22 are fixed on the cylinder head, and there is a suitable cavity inside to accommodate the reciprocating twitch of the central shaft 5. exercise space.

Assume that the angle of each sub-cam is 240 degrees, and the angle corresponding to the flat top of the sub-cam is 26 degrees. On the condition that the flat tops of the sub-cams are continuous with each other, the adjustment angle of the chute is set to 24 degrees, that is, the crankshaft angle is 48 degrees. degree, the angle of the three sub-cams as a whole can reach 96 degrees, that is, the cam can be continuously adjusted from 240 degrees to 336 degrees, which can fully meet the valve positive in the extremely large speed range from ordinary commercial internal combustion engines to competition internal combustion engines. time requirements. For common civilian internal combustion engines, the maximum angle of the cam can be reduced in exchange for a smaller minimum angle of the cam, so as to fully meet the valve timing at low speeds of the internal combustion engine. The twisted angle of the chute of the bushing and the inner boss of the sub-cam can be adjusted as required, so that the timing of the valve can be changed asymmetrically.

The edge of the bushing with chute is smooth in the above example, and it can also be made into a toothed pattern, which meshes with each other to transmit torque and increase the maximum torque that the overall camshaft can transmit. The angle of the sub-cam 3 in the middle position can also be selected to be slightly smaller than that of the sub-cams 1, 7 in order to reduce the profile and be borne by the stronger sub-cams 1, 7 during the high stress state when the valve is opened and closed. Reliability can be further improved.

The above exemplary embodiment is only an illustration of a more general configuration, which, as a highly simplified version, can be assigned to the slotted sleeves 2, 4 of the three sub-cams 1, 3, 7 , 6 are merged into one casing, and the angles on the cross section of the inner bosses of different sub-cams 1, 3, 7 and the corresponding slide grooves on the original casing 2, 4, 6 are adjusted to different directions And redefine on the sleeve pipe that merges, thus, sub-cam 1, 3, 7 just do not need an extension section, all as simple as sub-cam 3.

In a word, the present invention adopts the method of dividing a cam into three sub-cams, and makes the three sub-cams perform angular differential, so that the angle of the cam as a whole relative to the crankshaft can be continuously adjusted. By adjusting the angle of each sub-cam The angle and the angle of the chute can make the cam meet any requirements for valve opening time, duration and closing time, but only one opening of the valve in one working cycle of the cylinder, rather than multiple openings. But the present invention is not limited to changing the angle of the cam. When the sub-cam is independent and becomes a separate cam for driving a valve, it can also be applied to common single overhead camshaft engines to adjust the valve overlap angle.

The above description is merely for explaining the exemplary embodiments of the present invention, and it is not intended to be exclusive or to limit the present invention to the specific form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the spirit of the invention without departing from the essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the invention. The present invention may be practiced otherwise than as specifically explained and illustrated without departing from the spirit and scope of the invention.

Claims (1)

1. A continuously variable geometry camshaft that can be used for fully variable valve timing. Each cam on the camshaft is composed of several sub-cams; each sub-cam has a corresponding sleeve inside, and all sub-cams and The sleeves are all sleeved on a central shaft, which has two degrees of freedom of rotation and axial movement, and each sleeve and the central shaft are fixed together with a fixed pin; The sub-cam is also characterized in that the value of the crankshaft angle corresponding to the sub-cam satisfies the angle requirement for early opening of the valve at the lowest speed of the internal combustion engine, and each sub-cam has a flat top of equal height; The sub-cams are also characterized in that there is a boss in each of the sub-cams, and the bosses are closely matched with the chute of the corresponding sleeve. The chute of the sleeve is twisted in the axial direction, and the shape of the boss is Compatible with the chute, the torsion direction and angle of the chute and boss on different sleeves and sub-cams are different, and the sub-cam and sleeve can slide along the direction of the boss or chute; The central shaft is also characterized by spline teeth and a hydraulic thrust plate at one end, and the other end is subject to a camshaft retainer and restraint and can slide axially, and is pushed by a hydraulic system to drive the central shaft and the bushing Do axial translation movement; The assembly method of the camshaft is that the sub-cams of each cam of the camshaft rely on the sub-cams and the extension sleeves to squeeze each other tightly together, and the two ends of the camshaft are fixed by the camshaft holder, the fixed cover and the bolts. shaft system.