Variable valve lift structure of motorcycle engine

Abstract

The utility model relates to the technical field of motorcycle engines, and discloses a variable valve lift structure of a motorcycle engine, which comprises a cam mandrel, a switching sleeve, an air inlet cam, an exhaust cam, an electromagnetic valve, a timing driven chain wheel, a spring and a steel ball, the spring and the steel ball are arranged in a blind hole of the cam mandrel, the electromagnetic valve is in contact with the switching sleeve, the switching sleeve, the low-lift air inlet cam and the high-lift air inlet cam are respectively fixed on the cam mandrel and rotate along with the cam mandrel, a first axial sliding rail is arranged on the cam mandrel, a cam sleeve is in clearance fit with the first axial sliding rail, and a second axial sliding rail is arranged on the second axial sliding rail. A timing driven chain wheel is fixedly connected to the cam sleeve, the cam mandrel moves in the axis direction relative to the axially static cam sleeve, and the cam mandrel is limited in a low-lift groove or a high-lift groove in the cam sleeve through a spring and a steel ball. The device is small in size, low in machining precision and high in reliability.

Description

Technical Field

[0001] The utility model relates to the technical field of motorcycle engines, in particular to a variable valve lift structure of a motorcycle engine. Background Art

[0002] Variable valve lift (VVL) is a technology that allows the valve opening degree to be automatically adjusted during the operation of the engine. The valve lift of a traditional gasoline engine is fixed, that is, the camshaft has only one cam profile, which makes the engine unable to obtain a good response in both high-speed and low-speed areas. Variable valve lift technology can enable the engine to obtain the best performance under different working conditions, thereby improving the efficiency and torque of the engine.

[0003] Chinese patent document CN103032121B discloses an internal combustion engine and a valve drive device for an internal combustion engine, including at least one rotatably supported camshaft for operating the gas exchange valves of multiple cylinders of a cylinder group, on which a sliding cam capable of axial sliding is arranged for each cylinder, wherein a common actuator is provided for these sliding cams so that these sliding cams axially slidably supported on the corresponding camshaft can slide axially; a valve drive device for an internal combustion engine is also proposed, the valve drive device having at least one rotatably supported camshaft for operating the gas exchange valves of multiple cylinders of a cylinder group, on which a sliding cam capable of axial sliding is arranged for each cylinder, wherein a common actuator is provided for these sliding cams so that these sliding cams axially slidably supported on the corresponding camshaft can slide axially.

[0004] Chinese patent document CN111335977A discloses a variable valve lift camshaft structure, including a core shaft and a plurality of cam sleeves sequentially sleeved on the core shaft, the cam sleeve including a journal and two cam groups arranged on both sides of the journal, the cam groups including a low-speed cam and a high-speed cam, the low-speed cams and the high-speed cams of the two cam groups are arranged in the same order, a low-speed cam and a high-speed cam away from the journal are provided with a stopper on the outer side, the cam sleeve makes a linear displacement on the core shaft and is limited by a limiter, and the cam sleeve makes a circular motion as the core shaft rotates. The conversion principle of high-speed cam and low-speed cam: a solenoid valve is provided on the cam sleeve. When the solenoid valve receives a signal of high-speed operation or low-speed operation, it will drive the cam sleeve to make a linear displacement in the left and right directions on the core shaft. The toothed groove cooperates with the toothed protrusion to ensure the straightness of the cam sleeve and the core shaft during the displacement process. When the engine is in a high-speed state, the steel ball is placed in the high-speed groove to make the valve contact with the high-speed cam. The valve produces a larger lift as the high-speed cam rotates. When the engine is in a low-speed state, the steel ball moves to the low-speed groove through the inclined guide surface. At this time, the valve contacts with the low-speed cam. The valve produces a lower lift as the low-speed cam rotates, realizing the mutual switching of the engine between high-speed working state and low-speed working state, reducing valve throttling loss, improving charging efficiency, improving the power output of the engine at high speed and high load, and reducing the fuel consumption of the engine.

[0005] The prior art has the following disadvantages: in the prior art, the cam sleeve is axially displaced on the core shaft, so that the cam sleeve, high-speed cam, low-speed cam and other structures move simultaneously, the motorcycle engine structure is not compact, the overall structure is complex and the volume is not easy to reduce. Summary of the invention

[0006] The utility model provides a variable valve lift structure of a motorcycle engine with a small size and a simple structure, comprising a cam core shaft, a switching sleeve, an intake cam, an exhaust cam, an electromagnetic valve, a timing driven sprocket, a spring and a steel ball, wherein the intake cam comprises a low-lift intake cam and a high-lift intake cam, the spring and the steel ball are arranged in a blind hole of the cam core shaft, the electromagnetic valve contacts the switching sleeve, and is characterized in that the switching sleeve, the low-lift intake cam and the high-lift intake cam are respectively fixed on the cam core shaft and rotate with the cam core shaft, the cam core shaft is provided with an axial slide rail 1, the axial slide rail 1 is gap-matched with a cam sleeve, the cam sleeve is fixedly connected with the timing driven sprocket, the cam core shaft moves in an axial direction relative to the axially stationary cam sleeve, the cam core shaft is limited in a low-lift groove or a high-lift groove on the cam sleeve by the spring and the steel ball, the electromagnetic valve causes the cam core shaft to move axially on the cam sleeve through the switching sleeve, and then drives the low-lift intake cam and the high-lift intake cam to move axially to realize the change of the valve.

[0007] In order to facilitate the reciprocating switching of the low-lift intake cam and the high-lift intake cam, the surfaces at both ends of the switching sleeve are provided with raised spiral profile one and spiral profile two which are symmetrical along the radial center line. The spiral line heights of the spiral profile one and the spiral profile two are equal, which is equal to the distance between the centers of the low-lift groove and the high-lift groove. The end points of the spiral lines of the spiral profile one and the spiral profile two are spiral line points, and the spiral line height determines the axial movement distance of the cam core shaft.

[0008] In order to facilitate the axial movement of the cam core shaft, the connecting shaft necks at both ends of the cam core shaft are used to support the cylinder head, and the inner ring of the cam sleeve is provided with an inner slide rail corresponding to the axial slide rail 1. The cross-sections of the axial slide rail 1 and the inner slide rail of the cam sleeve 4 are polygons with corresponding even numbers of sides, the even number ≥ 4, and the adjacent two sides are transitioned by circular arcs.

[0009] In order to facilitate the installation of the switching sleeve and achieve precise positioning of the switching sleeve, an axial slide rail 2 is also provided on the cam core shaft. The cross-section of the axial slide rail 1 is larger than the cross-section of the axial slide rail 2. A shoulder is formed on the axial slide rail 1. The switching sleeve is fixed on the axial slide rail 2, and one side of the switching sleeve is positioned by the shoulder.

[0010] Preferably, the inner ring of the switching sleeve is provided with an inner slide rail corresponding to the second axial slide rail, the cross-sections of the second axial slide rail and the inner slide rail are polygons with corresponding even numbers of sides, the even number ≥ 4, and the two adjacent sides are transitioned into circular arcs, the switching sleeve is clearance-matched with the second axial slide rail, the second axial slide rail is provided with a bushing and a bearing, the axial movement of the switching sleeve is limited by the shoulder, bushing and bearing, and there is no relative sliding between the switching sleeve and the cam core shaft.

[0011] In order to reduce the axial size of the variable valve lift structure as a whole, the exhaust cam is arranged at one end of the cam sleeve, and the cam sleeve journal 1 and cam sleeve journal 2 are arranged at the other end. The clearance on the cam sleeve journal 1 is matched with the signal wheel and the timing driven sprocket. The timing driven sprocket is a bowl-shaped tooth. The cam sleeve journal 2 is interference-fitted with a flange. The flange is accommodated in the concave cavity of the bowl-shaped tooth. The signal wheel and the bowl-shaped tooth are fixed on the flange. The cam sleeve, the timing driven sprocket, and the signal wheel rotate under the drive of the timing chain. The cam core shaft rotates synchronously under the drive of the cam sleeve. By setting the bowl-shaped tooth, the axial size of the camshaft assembly can be reduced, and the position of the engine timing chain can be closer to the center of the cylinder, the engine structure is more compact, and the engine volume is smaller. The crankcase, crankshaft, and cylinder block will not be developed again because the distance between the timing chain and the cylinder center becomes larger. Only the cylinder head needs to be developed to quickly upgrade the existing conventional engine products to variable valve products, thereby reducing the development cost.

[0012] In order to facilitate the support of the cam sleeve, two limiting plates are provided in the middle of the cam sleeve, and the cam sleeve journal three is located between the limiting plates. The cam sleeve journal three is used to install the bearing to connect the cylinder head or is directly connected to the cylinder head.

[0013] Preferably, the switching sleeve is split into two switching sleeves, each switching sleeve is provided with only one raised spiral profile, the split switching sleeves are arranged at different positions and driven by different solenoid valves, one switching sleeve is used for switching from low lift to high lift, and the other switching sleeve is used for switching from high lift to low lift.

[0014] Preferably, the intake cam abuts against the intake rocker arm, and the exhaust cam abuts against the exhaust rocker arm. When the engine is not started and is operating at a low speed, the intake rocker arm abuts against the low-lift intake cam, and the opening of the intake valve lift is controlled by the low-lift intake cam. When the engine speed increases from a low speed to a critical switching speed, the solenoid valve extends a pin head, and the pin head contacts the spiral contour of the rotating switching sleeve. The switching sleeve and the cam core shaft are displaced in the axial direction relative to the cam sleeve that is axially stationary, so that the high-lift intake cam on the cam core shaft moves toward the low-lift intake cam, and the displacement distance is the spiral height of a preset spiral line. When the displacement action is terminated, the cam core shaft is positioned in the high-lift groove of the cam sleeve by a spring and a steel ball, the pin head of the solenoid valve is retracted, the high-lift intake cam contacts the intake rocker arm, and the intake valve lift is controlled by the high-lift intake cam.

[0015] In order to be suitable for multi-cylinder engines, the cam core shaft is provided with a plurality of cam sleeves, switching sleeves, intake cams and exhaust cams, any of which is provided with a low-lift groove or a high-lift groove, and limiting springs and steel balls are provided at corresponding positions on the cam core shaft.

[0016] The utility model has the following beneficial effects:

[0017] 1. This structure is arranged on the engine cylinder head. The valve lift switching action: the two end journals on the cam core shaft and the shaft diameter on the cam sleeve are supported in the cylinder head mounting hole. The cam sleeve limit plate on the cam sleeve cooperates with the cylinder head to limit the axial movement of the cam sleeve. The cam sleeve and the timing driven sprocket and signal wheel installed on the cam sleeve can rotate under the drive of the timing chain. The cam core shaft rotates synchronously under the drive of the cam sleeve. At low speed, the low-lift intake cam on the cam core shaft contacts the intake rocker arm to meet the low-lift requirement of the engine. When the engine speed reaches the preset valve lift switching speed range, the solenoid valve will extend the pin head. The solenoid valve is fixed on the cylinder head. The rotating switching sleeve contacts a pin head of the solenoid valve. Under the guidance of the preset spiral profile contact line of the switching sleeve, the switching sleeve and the cam core shaft make axial displacement together, and the high-lift intake cam moves toward the low-lift intake cam and contacts the intake rocker arm to complete the switching from low lift to high lift. On the contrary, when the engine speed is lower than the switching speed, the other pin of the solenoid valve contacts the spiral profile on the switching sleeve, completing the switch from high lift to low lift. The cam shaft of the utility model is not only short in axial dimension, but also because the cam sleeve, bowl-shaped teeth and signal wheel do not need to move, only the cam shaft and the intake cam need to move axially, eliminating the space required for the movement of the cam sleeve, bowl-shaped teeth and signal wheel in the cylinder head, making the engine structure more compact and smaller in size, and requiring fewer parts to move, and correspondingly requiring lower precision requirements for the cylinder head, gears and cam shaft, the overall reliability is also improved, and the parts are easy to process.

[0018] 2. In the utility model, there is no need to develop the crankcase, crankshaft, cylinder block, etc. again because the distance between the timing chain and the cylinder center becomes larger. Only the cylinder head needs to be developed to quickly upgrade the existing conventional engine products to variable valve products, thereby reducing the development cost.

[0019] 3. The utility model occupies less internal space in the cylinder head, and a spark plug installation position is reserved. The spark plug on the engine cylinder head is arranged on the outside of the journal of the cam core shaft. The outside refers to the side opposite to the switching sleeve with the timing driven sprocket as the boundary. This makes the spark plug position closer to the center of the cylinder head, which can burn more quickly to generate thrust, thereby improving the power performance of the engine; it can also improve the fuel economy of the engine and reduce fuel consumption; reduce unburned fuel and exhaust emissions, and be more environmentally friendly.

[0020] 4. It is applicable to single-cylinder motorcycle engines and multi-cylinder motorcycle engines. In a multi-cylinder engine, only one cam sleeve needs to be limited, and the overall structure is simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of an embodiment of a variable valve lift structure of a motorcycle engine;

[0022] Figure 2 It is a schematic diagram of the cam shaft structure;

[0023] Figure 3 It is a side view of the cam spindle;

[0024] Figure 4 is a schematic diagram of a cam sleeve;

[0025] Figure 5 is a cross-sectional view of the cam sleeve;

[0026] Figure 6 is a schematic diagram of a switching set;

[0027] Figure 7 It is a front view of the switching sleeve;

[0028] Figure 8 is a schematic diagram of a bowl-shaped tooth;

[0029] Fig. 9 It is a cross-sectional view of the variable valve lift structure of a motorcycle engine. DETAILED DESCRIPTION

[0030] The following is further described in detail through specific implementation methods:

[0031] 1. The reference numerals in the drawings of the specification include: cam core shaft 1, low lift intake cam 1-1, high lift intake cam 1-2, intake rocker arm 2, exhaust rocker arm 3, cam sleeve 4, exhaust cam 4-1, cam sleeve journal three 4-2, right limit plate 4-3, left limit plate 4-4, high lift groove 4-5, low lift groove 4-6, cam sleeve journal two 4-7, cam sleeve journal one 4-8, timing driven sprocket 5, signal wheel 6, switching sleeve 7, spiral profile one 7-1, spiral profile two 7-2, spiral line point 7-3, groove 7-4, radial center line 7-5, bearing one 8, bushing 9, flange 10, bolt 11, spring 12, steel ball 13, VVL solenoid valve 14, connecting journal one a, axial slide rail two b, axial slide rail one c, blind hole d, connecting journal two e, shoulder f. Example

[0032] like Figures 1 to 9As shown, a variable valve lift structure of a motorcycle engine comprises a cam core shaft 1, an intake rocker arm 2, an exhaust rocker arm 3, a switching sleeve 7, an intake cam, a VVL solenoid valve 14, a timing driven sprocket 5, a signal wheel 6, a bearing 8, a spring 12 and a steel ball 13, wherein the intake cam comprises a low-lift intake cam 1-1 and a high-lift intake cam 1-2, the spring 12 and the steel ball 13 are arranged in a blind hole d of the cam core shaft 1, the axis of the blind hole d is perpendicular to the axis of the cam core shaft 1, the VVL solenoid valve 14 is fixed on the cylinder head, the VVL solenoid valve 14 is in contact with the switching sleeve 7, the switching sleeve 7, the low-lift intake cam 1-1 and the high-lift intake cam 1-2 are respectively fixed on the cam core shaft 1 and rotated with the cam core The shaft 1 rotates, and an axial slide rail c is provided on the cam shaft 1. A cam sleeve 4 is gap-fitted on the axial slide rail c. The cam sleeve 4 is provided with an exhaust cam 4-1, a flange 10, a timing driven sprocket 5 and a signal wheel 6. The cam shaft 1 moves in the axial direction relative to the axially stationary cam sleeve 4. The cam shaft 1 is limited in the low-lift groove 4-6 or the high-lift groove 4-5 on the cam sleeve 4 by the spring 12 and the steel ball 13. The center distance in the low-lift groove 4-6 or the high-lift groove 4-5 is the axial sliding distance of the cam shaft 1. The steel ball 13 cooperates with the low-lift groove 4-6 or the high-lift groove 4-5 on the inner side of the cam sleeve 4 to axially position the relative position of the cam shaft 1 and the cam sleeve 4.

[0033] The surfaces at both ends of the switching sleeve 7 are provided with a raised spiral profile 1 7-1 and a spiral profile 2 7-2 symmetrically along the radial center line 7-5. The spiral line heights of the spiral profile 1 7-1 and the spiral profile 2 7-2 are equal, and the spiral line height is equal to the distance between the centers of the low lift groove 4-6 and the high lift groove 4-5. The spiral profile 1 7-1 corresponds to the position of the low lift intake cam 1-1 and the low lift groove 4-6, and the spiral profile 2 7-2 corresponds to the position of the high lift intake cam 1-2 and the high lift groove 4-5. The spiral line height determines the axial movement distance of the cam core shaft 1. The spiral line end points of the spiral profile 1 7-1 and the spiral profile 2 7-2 are spiral line points 7-3. When the pin head of the VVL solenoid valve 14 moves to the spiral line point 7-3, it is retracted to avoid interfering with the rotation of the switching sleeve 7. A weight-reducing groove 7-4 is also provided between the spiral profile 1 7-1 and the spiral profile 2 7-2.

[0034] Of course, the switching sleeve 7 can be split into two switching sleeves along the radial center line 7-5, and only one raised spiral profile is set on each switching sleeve. The spiral profiles on the two switching sleeves are spiral profile one 7-1 and spiral profile two 7-2 respectively. The split switching sleeves are set at different positions and driven by different VVL solenoid valves 14. One switching sleeve is used to switch from low lift to high lift, and the other switching sleeve is used to switch from high lift to low lift.

[0035] The cam sleeve 4 is an active rotating mechanism, and the cam core shaft 1 is driven to rotate by the cam sleeve 4. When the speed is in the preset valve lift switching speed range, the VVL solenoid valve 14 is controlled by the electronic control system to extend the pin head in time according to the cam angle position signal provided by the signal wheel 6. The signal wheel 6 is the signal given by the signal wheel 6. Since the switching action of the valve lift must be completed in the base circle part of the low-lift intake cam 1-1 and the high-lift intake cam 1-2, otherwise the switching cannot be achieved; then the vehicle electronic control system must know the real-time position of the cam, so the signal wheel 6 installed on the cam sleeve 4 can provide the signal of the cam base circle position. The specific signal calculation involves the VVL electric Magnetic valve, VVL solenoid valve is an existing mature technology and will not be elaborated here. When the cam core shaft 1 drives the switching sleeve 7 to rotate, the spiral profile 1 7-1 or the spiral profile 2 7-2 on the switching sleeve 7 contacts with a pin head of the VVL solenoid valve 14. Since the VVL solenoid valve 14 is fixed on the cylinder head and will not move at all, the cam core shaft 1 and the switching sleeve 7 produce axial displacement under the interaction force between the switching sleeve 7 and the pin head, and then the high or low lift intake cam 1-1, 1-2 can be completed. Contact with the intake rocker arm 2 to achieve different valve lift requirements. The structure of the VVL solenoid valve 14 is an existing mature technology and the principle will not be elaborated here.

[0036] The two ends of the cam core shaft 1 are provided with a connecting journal a and a connecting journal e. The connecting journal a is close to one end of the switching sleeve 7, and the connecting journal e is close to one end of the intake cam. The connecting journal a and the connecting journal e can be installed with a bearing 8 at the same time or one of them can be installed with a bearing 8 and supported on the cylinder head. The inner ring of the cam sleeve 4 is provided with an inner slide rail corresponding to the axial slide rail c. The cam core shaft 1 is also provided with an axial slide rail b. The cross-section of the axial slide rail c is larger than the cross-section of the axial slide rail b. A shoulder f is formed on the axial slide rail c. The switching sleeve 7 is fixed on the axial slide rail b, and one side of the switching sleeve 7 is positioned by the shoulder f.

[0037] The inner ring of the switching sleeve 7 is provided with an inner slide rail corresponding to the axial slide rail 2b. The cross-sections of the axial slide rail 1c, the axial slide rail 2b, the inner slide rail of the cam sleeve 4 and the inner slide rail of the switching sleeve 7 are polygons with corresponding even-numbered sides, where the even number is 4, and the adjacent two sides are transitioned into circular arcs. The cam sleeve 4 is clearance-matched with the axial slide rail 1c, and the switching sleeve 7 is clearance-matched with the axial slide rail 2b. The axial slide rail 2b is provided with a bushing 9 and a bearing 18. The axial movement of the switching sleeve 7 is limited by the shoulder f, bushing 9 and bearing 18. On the one hand, the cam core shaft 1 is clearance-matched with the cam sleeve 4, and the cam core shaft 1 can move in the axial direction relative to the axially stationary cam sleeve 4, playing a guiding role; on the other hand, due to the shape factors of the cross-sections of the two slide rails, the axial slide rail 1c on the surface of the cam core shaft 1 is meshed with the inner slide rail of the cam sleeve 4, so that the cam core shaft 1 rotates with the cam sleeve 4, playing a transmission role.

[0038] The exhaust cam 4-1 is arranged at one end of the cam sleeve 4, and the exhaust cam 4-1 is integrated with the cam sleeve 4. The other end of the cam sleeve 4 is provided with a cam sleeve journal 1 4-8 and a cam sleeve journal 2 4-7. The cam sleeve journal 1 4-8 is clearance-matched with a signal wheel 6 and a timing driven sprocket 5. The timing driven sprocket 5 is a bowl-shaped tooth, and the bowl-shaped tooth has two through holes. The cam sleeve journal 2 4-7 is interference-fitted with a flange 10, and the flange 10 is accommodated in the concave cavity of the bowl-shaped tooth. The signal wheel 6 and the bowl-shaped tooth are connected by bolts 11. Fixed on the flange 10, the cam sleeve 4, the timing driven sprocket 5 and the signal wheel 6 rotate under the drive of the timing chain, and the cam core shaft 1 rotates synchronously under the drive of the cam sleeve 4, reducing the axial dimension of the camshaft assembly, so that the engine timing chain position can be closer to the cylinder center, the engine structure is more compact, and the engine volume is smaller. There is no need to develop the crankcase, crankshaft, cylinder block, etc. again due to the increase in the distance between the timing chain and the cylinder center. Only the cylinder head needs to be developed to quickly upgrade the existing conventional engine products to variable valve products.

[0039] like Fig. 9 As shown, the spark plug position on the engine cylinder head can be arranged on the outside of the connecting journal 2e of the cam core shaft 1, and the outside refers to the side opposite to the switching sleeve 7 with the timing driven sprocket 5 as the boundary. The switching sleeve 7 and the bearing 1-8 are installed on the left side of the bowl-shaped tooth. The left side of the switching sleeve 7 is axially positioned by the bushing 9 and the bearing 1-8, and the bearing 1-8 is limited by the step or retaining ring set on the cylinder head.

[0040] The cam sleeve journal 4-8 is provided for assembling the bowl-shaped teeth and the signal wheel 6. The center hole of the bowl-shaped teeth and the signal wheel 6 is clearance-matched with the journal, so that the bowl-shaped teeth and the signal wheel 6 can be assembled onto the cam sleeve journal 4-8, which makes it more convenient to hang the timing chain onto the bowl-shaped teeth. The bowl-shaped teeth and the signal wheel 6 are fixed to the flange 10 by bolts 11, and the engine timing chain will drive the bowl-shaped teeth and the signal wheel 6 to rotate around the axis of the cam sleeve 4.

[0041] like Figure 5 As shown, when the cam sleeve 4 does not need to be provided with a bearing: two limit plates are provided in the middle of the cam sleeve 4, namely a left limit plate 4-4 and a right limit plate 4-3, and a cam sleeve journal three 4-2 is located between the left limit plate 4-4 and the right limit plate 4-3. The cam sleeve journal three 4-2 is supported in the cylinder head mounting hole, and the left limit plate 4-4 limits the flange 10.

[0042] When a bearing is required on the cam sleeve 4: only a right limit plate 4-3 is provided in the middle of the cam sleeve 4 for positioning the right side of the bearing, the flange 10 is pressed onto the cam sleeve journal 4-7 and axially limited by the bearing, the bearing is axially positioned by the step hole and the pressure plate on the cylinder head, and the flange 10 is interference fit with the cam sleeve 4.

[0043] The intake cam abuts against the intake rocker arm 2, and the exhaust cam 4-1 abuts against the exhaust rocker arm 3. When the engine is not started and working at a low speed, the intake rocker arm 2 abuts against the low-lift intake cam 1-1, and the opening of the intake valve lift is controlled by the low-lift intake cam 1-1. When the engine speed increases from a low speed to a critical switching speed, the VVL solenoid valve extends a pin head, and the pin head contacts the spiral profile of the rotating switching sleeve 7. The switching sleeve 7 and the cam core shaft 1 are relative to each other in the axial direction. The stationary cam sleeve 4 is displaced in the axial direction, so that the high-lift intake cam 1-2 on the cam core shaft 1 moves toward the low-lift intake cam 1-1, and the displacement distance is the spiral height of the preset spiral line. When the displacement action is terminated, the cam core shaft 1 is positioned in the high-lift groove 4-5 of the cam sleeve 4 by the spring 12 and the steel ball 13, the pin head of the VVL solenoid valve is retracted, the high-lift intake cam 1-2 contacts with the intake rocker arm 2, and the intake valve lift is controlled by the high-lift intake cam 1-2.

[0044] According to the type of single-cylinder or multi-cylinder engine, a corresponding number of cam sleeves 4, switching sleeves 7, intake cams, and exhaust cams 4-1 are arranged on the cam core shaft 1, wherein any one of the cam sleeves 4 is provided with a low-lift groove 4-6 or a high-lift groove 4-5, and limiting springs 12 and steel balls 13 are arranged at corresponding positions on the cam core shaft 1. The cam sleeve 4 may not use a flange 10 to fix the bowl-shaped teeth, and may also be directly press-fitted with a conventional timing driven sprocket 5.

[0045] The above is only an embodiment of the utility model. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the utility model before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for the technicians in this field, without departing from the structure of the utility model, several deformations and improvements can be made, which should also be regarded as the protection scope of the utility model, which will not affect the effect of the implementation of the utility model and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to explain the content of the claims.

Claims

1. A variable valve lift structure for a motorcycle engine, comprising a cam core shaft, a switching sleeve, an intake cam, an exhaust cam, a solenoid valve, a timing driven sprocket, a spring and a steel ball, wherein the intake cam comprises a low-lift intake cam and a high-lift intake cam, the spring and the steel ball are arranged in a blind hole of the cam core shaft, the solenoid valve is in contact with the switching sleeve, and is characterized in that: The switching sleeve, low-lift intake cam and high-lift intake cam are respectively fixed on the cam core shaft and rotate with the cam core shaft. The cam core shaft is provided with an axial slide rail 1, and a cam sleeve is clearance-matched on the axial slide rail 1. The cam sleeve is fixedly connected to a timing driven sprocket. The cam core shaft moves in the axial direction relative to the axially stationary cam sleeve. The cam core shaft is limited in the low-lift groove or the high-lift groove on the cam sleeve by the spring and the steel ball.

2. The variable valve lift structure of a motorcycle engine according to claim 1, characterized in that: The surfaces at both ends of the switching sleeve are provided with raised spiral profile 1 and spiral profile 2 symmetrically along the radial center line, the spiral line heights of spiral profile 1 and spiral profile 2 are equal, and the spiral line height is equal to the distance between the centers of the low lift groove and the high lift groove.

3. The variable valve lift structure of a motorcycle engine according to claim 2, characterized in that: The connecting journals at both ends of the cam core shaft 1 are used to support the cylinder head. The inner ring of the cam sleeve 4 is provided with an inner slide rail corresponding to the axial slide rail c. The cross-sections of the axial slide rail c and the inner slide rail of the cam sleeve 4 are polygons with corresponding even numbers of sides, the even number ≥ 4, and the adjacent two sides are transitioned into circular arcs.

4. The variable valve lift structure of a motorcycle engine according to any one of claims 1 to 3, characterized in that: The cam shaft is also provided with an axial slide rail 2, the cross section of the axial slide rail 1 is larger than the cross section of the axial slide rail 2, a shoulder is formed on the axial slide rail 1, the switching sleeve is fixed on the axial slide rail 2, and one side of the switching sleeve is positioned by the shoulder.

5. The variable valve lift structure of a motorcycle engine according to claim 4, characterized in that: The inner ring of the switching sleeve is provided with an inner slide rail corresponding to the second axial slide rail. The cross-sections of the second axial slide rail and the inner slide rail are polygons with corresponding even-numbered sides, the even number ≥ 4, and the two adjacent sides are transitioned into circular arcs. The switching sleeve is clearance-matched with the second axial slide rail. The second axial slide rail is provided with a bushing and a bearing. The axial movement of the switching sleeve is limited by the shoulder, bushing and bearing.

6. The variable valve lift structure of a motorcycle engine according to claim 5, characterized in that: The exhaust cam is arranged at one end of the cam sleeve, and cam sleeve journal 1 and cam sleeve journal 2 are arranged at the other end. The cam sleeve journal 1 is clearance-fitted with the signal wheel and the timing driven sprocket. The timing driven sprocket is a bowl-shaped tooth. The cam sleeve journal 2 is interference-fitted with a flange. The flange is accommodated in the concave cavity of the bowl-shaped tooth. The signal wheel and the bowl-shaped tooth are fixed on the flange. The cam sleeve, the timing driven sprocket and the signal wheel rotate under the drive of the timing chain, and the cam core shaft rotates synchronously under the drive of the cam sleeve.

7. The variable valve lift structure of a motorcycle engine according to claim 6, characterized in that: Two limiting plates are arranged in the middle of the cam sleeve, and a cam sleeve journal 3 is arranged between the limiting plates.

8. The variable valve lift structure of a motorcycle engine according to claim 1, characterized in that: The switching sleeve is split into two switching sleeves, each of which is provided with only one raised spiral profile. The split switching sleeves are arranged at different positions and driven by different solenoid valves. One switching sleeve is used for switching from low lift to high lift, and the other switching sleeve is used for switching from high lift to low lift.

9. The variable valve lift structure of a motorcycle engine according to claim 6 or 7, characterized in that: The intake cam abuts against the intake rocker arm, and the exhaust cam abuts against the exhaust rocker arm. When the engine is not started and working at a low speed, the intake rocker arm abuts against the low-lift intake cam, and the opening of the intake valve lift is controlled by the low-lift intake cam. When the engine speed increases from a low speed to a critical switching speed, the solenoid valve extends a pin head, and the pin head contacts the spiral profile of the rotating switching sleeve. The switching sleeve and the cam core shaft are displaced in the axial direction relative to the cam sleeve that is axially stationary, so that the high-lift intake cam on the cam core shaft moves toward the low-lift intake cam. The displacement distance is the spiral height of the preset spiral line. When the displacement action is terminated, the cam core shaft is positioned in the high-lift groove of the cam sleeve by the spring and the steel ball, the pin head of the solenoid valve is retracted, the high-lift intake cam contacts the intake rocker arm, and the intake valve lift is controlled by the high-lift intake cam.

10. The variable valve lift structure of a motorcycle engine according to claim 9, characterized in that: The cam shaft is provided with a plurality of cam sleeves, switching sleeves, intake cams and exhaust cams, wherein any of the switching sleeves is provided with a low lift groove or a high lift groove, and limiting springs and steel balls are provided at corresponding positions on the cam shaft.

Images