CN108180049B - Double-shaft multi-roller rocker arm type variable valve lift mechanism - Google Patents

Abstract

The invention relates to a double-shaft multi-roller rocker arm type variable valve lift mechanism, and belongs to the technical field of engine parts. The cam shaft assembly is characterized by comprising a driving cam shaft assembly, an eccentric cam shaft assembly, a multi-roller rocker arm, a valve spring and a valve, wherein a driving cam of the driving cam shaft assembly is in contact connection with a first connecting end of the multi-roller rocker arm, an eccentric cam of the eccentric cam shaft assembly is in contact connection with a second connecting end of the multi-roller rocker arm, a third connecting end of the multi-roller rocker arm is in contact connection with a cup-shaped tappet, and the valve spring and the valve are connected below the multi-roller rocker arm. When the valve lift and the duration are required to be changed, the eccentric cam angle can be controlled according to requirements to change the position of the multi-roller rocker arm, and different valve lift curves are output. And the mechanism can realize independent control of a single valve after proper structural optimization.

Description

Double-shaft multi-roller rocker arm type variable valve lift mechanism

Technical Field

The invention relates to the technical field of engine parts, in particular to a double-shaft multi-roller rocker arm type variable valve lift mechanism.

Background

The pumping loss generated in the air exchange process of the engine accounts for 10-20% of the total mechanical loss, and is an important influence factor for restricting the improvement of the fuel economy performance of the modern engine.

In order to further develop the potential of reducing the oil consumption, the over-expansion cycle technology is generally applied to the engine. The technology needs that the engine changes the load by controlling the closing time of the intake valve under the premise that the opening time of the intake valve is not changed, so that the expansion ratio and the compression ratio of the engine are not equal any more. This requires that the valve train has the capability of changing the lift and wrap angle of the valve lift curve at the same time, which cannot be realized smoothly only by the conventional adjustment of the valve timing.

Typical variable valve lift mechanisms currently exist as two-step decoupled variable rocker arm structures under grant CN 203547817U. The structure uses a switch type electromagnetic valve to control the coupling and decoupling of the inner rocker arm body and the outer rocker arm body, when the inner rocker arm body and the outer rocker arm body are coupled, the mechanism uses a large rocker arm ratio to output a high-lift molded line, and when the inner rocker arm body and the outer rocker arm body are decoupled, the mechanism uses a small rocker arm ratio to output a low-lift molded line. The mechanism is compact in structure and easy to control. The main drawbacks present are: 1. the continuous variable of the output lift and duration can not be realized; 2. when the mechanism is in a low lift state, the friction pairs are in sliding contact, and the friction loss is large.

Typical variable valve lift mechanisms currently exist such as a continuous variable valve lift structure with authority number CN 200910143843.6. According to the structure, a stepping motor is used for rotating a connecting arm in a multi-link mechanism, so that the swing amplitude of a swing arm in the mechanism is changed, and when the swing amplitude of the swing arm is increased, the lift range and the duration of a mechanism valve are synchronously increased. The mechanism can realize continuous variable of lift and duration. The main drawbacks present are: 1. the minimum swing amplitude of a swing arm of the mechanism cannot be zero due to structural characteristics, and cylinder deactivation of an engine cannot be realized; 2. the independent control of different-cylinder and same-cylinder valves cannot be realized; 3. the connecting arm needs to be driven by a stepping motor, the structure is complex, and the implementation cost of hardware and software is high.

As described above, the conventional variable valve lift apparatus has problems of basic functions, embodiments, and the like to different degrees, and it is difficult to achieve development goals of high performance, low cost, and easy realization at the same time.

Disclosure of Invention

The invention aims to provide a double-shaft multi-roller rocker arm type variable valve lift mechanism aiming at the defects of the prior art.

The technical scheme adopted by the invention is as follows: the cam shaft assembly is characterized by comprising a driving cam shaft assembly, an eccentric cam shaft assembly, a multi-roller rocker arm, a valve spring and a valve, wherein a driving cam of the driving cam shaft assembly is in contact connection with a first connecting end of the multi-roller rocker arm, an eccentric cam of the eccentric cam shaft assembly is in contact connection with a second connecting end of the multi-roller rocker arm, a third connecting end of the multi-roller rocker arm is in contact connection with a cup-shaped tappet, and the valve spring and the valve are connected below the multi-roller rocker arm.

In a further preferred structure, the eccentric camshaft assembly comprises an inner eccentric camshaft shaft, an outer eccentric camshaft shaft outside the inner eccentric camshaft shaft, and an eccentric cam, the eccentric cam and the inner eccentric camshaft shaft are connected through a positioning pin in interference fit, the outer eccentric camshaft shaft is provided with a key-shaped hole in the movement direction of the positioning pin, and the width of the key-shaped hole is larger than the outer diameter of the positioning pin.

In a further preferred embodiment, the eccentric camshaft inner shaft is connected to an output of an eccentric cam inner shaft drive.

In a further preferred configuration, the eccentric camshaft outer shaft is fixedly connected to the cylinder head by a fixing bolt.

In a further preferable structure, the multi-roller rocker arm comprises a rocker arm body, and the two ends and the bottom of the upper part of the rocker arm body form a first connecting end, a second connecting end and a third connecting end of the multi-roller rocker arm respectively through a first rocker arm upper roller, a second rocker arm upper roller and a rocker arm lower roller which are arranged on a roller shaft, wherein the first rocker arm upper roller is in contact connection with the eccentric cam, the second rocker arm upper roller is in contact connection with the driving cam, and the rocker arm lower roller is used for being in contact connection with the cup-shaped tappet.

In a further preferable structure, one side of the rocker arm body, which is provided with the roller on the second rocker arm, is also connected with the return device through a support arm shaft.

In a further preferred structure, a hook spring is arranged between the multi-roller rocker arm and the eccentric camshaft assembly.

In a further preferable structure, a first spring groove is formed in an outer shaft of the eccentric camshaft, a second spring groove is formed in a roller shaft of the roller on the first rocker arm, one end of the hook spring is fixed to the first spring groove, and the other end of the hook spring is fixed to the second spring groove.

In a further preferred structure, the eccentric cam inner shaft driver comprises a driver rotor, a driver stator, a driver return spring arranged between the driver rotor and the driver stator, and an eccentric cam inner shaft signal disc for representing the position of the eccentric cam inner shaft, wherein the driver rotor is connected with the eccentric cam inner shaft.

In a further preferred structure, the cup-shaped tappet comprises a tappet shell and a tappet upper cover arranged on the tappet shell, wherein an annular groove is formed in the upper end of the tappet shell, a flanging is arranged at the bottom of the tappet upper cover, the tappet shell and the tappet upper cover are connected in a matched mode through the annular groove and the flanging, a gap is formed between the flanging and the annular groove, and a tappet return spring is arranged in the gap.

Compared with the prior variable valve lift mechanism, the invention has the following remarkable beneficial effects:

1. the function is comprehensive: the valve timing mechanism can continuously change the lift and wrap angle parameters of a valve lift curve, is matched with a variable valve timing mechanism for use, and can meet the requirement of over-expansion cycle use that the expansion ratio and the compression ratio of an engine are unequal by controlling the closing time of an intake valve to change load on the premise that the opening time of the intake valve is unchanged. Meanwhile, when the idle stroke of the cup-shaped tappet is larger than or equal to the maximum valve lift generated when the eccentric cam keeps the minimum eccentric amount to work, the driving cam rotates to not open the intake valve, so that cylinder deactivation is realized, the load rate of each cylinder of the engine is further improved, and greater oil consumption and emission benefits are brought.

2. The structure is simple: the driving of the eccentric cam in the mechanism is completed by a simple oil pressure vane phaser, complex motors, worm gears and worms, space three-dimensional cams and multi-connecting-rod driven parts are not arranged in system parts, the system control only needs to increase one angular displacement parameter of the eccentric cam shaft, the hardware and software implementation cost is low, and the practicability is high.

3. The friction loss is small: when the mechanism is in each working state, the cam and the driven piece are in rolling contact, and the friction loss is small.

4. Can be independently controlled: the eccentric cam and the three-roller rocker arm are arranged at the position where the lift and duration change is needed, the eccentric cam is cancelled at the position where the lift and duration change is not needed, the double-roller rocker arm and the hydraulic tappet are arranged, and independent control of a single valve can be achieved according to requirements.

Drawings

FIG. 1 is a schematic structural diagram of the present invention, wherein 1 is a driving camshaft assembly, 2 is an eccentric camshaft assembly, 3 is a fixing bolt, 4 is a cylinder cover, 5 is an eccentric cam inner shaft driver, 6 is a hook spring, 7 is a multi-roller rocker arm, 8 is a return device, 9 is a cup tappet, 10 is a valve spring, and 11 is a valve.

FIG. 2 is a schematic view showing the detailed structure of the drive camshaft assembly and the eccentric camshaft assembly, wherein 1-a-drive camshaft, 1-b-drive camshaft signal plate, 2-a-positioning pin, 2-b-eccentric cam, 2-c-eccentric camshaft outer shaft, 2-d-eccentric camshaft inner shaft, 2-e-fixing bolt hole, 2-f-first spring groove, and 2-g-actuator oil hole.

FIG. 3 is a schematic diagram showing an internal cross-sectional structure of an eccentric camshaft assembly, in which 2-a-dowel pins, 2-b-eccentric cams, 2-c-eccentric camshaft outer shaft, 2-d-eccentric camshaft inner shaft, and 2-f-key type bores.

Fig. 4 is a detailed structural schematic diagram of an eccentric cam inner shaft driver, wherein 5-a-driver rotor, 5-b-driver oil gallery, 5-c-driver wiper, 5-d-driver stator, 5-e-eccentric cam inner shaft signal disc, and 5-f-driver return spring.

FIG. 5 is a schematic diagram of a detailed construction of a multi-roller rocker arm and return, wherein 7-a-first rocker arm upper roller (in contact with eccentric cam), 7-b-roller shaft, 7-c-rocker arm body, 7-d-rocker arm lower roller, 7-e-second rocker arm upper roller (in contact with drive cam), 7-f-support arm shaft, 7-g-second spring groove, 8-a-U-shaped groove, 8-b-return spring.

FIG. 6 is a schematic view of a detailed structure of a cup-shaped tappet, wherein 9-a-tappet upper cover, 9-b-tappet return spring, 9-c-oil-gas passing small hole, 9-d-tappet shell, 9-f-annular groove, 9-g-flanging and 9-h-gap.

FIG. 7 is a schematic structural diagram of the mechanism for performing the cylinder deactivation function, wherein 1-the drive camshaft assembly, 2-the eccentric camshaft assembly, 3-the fixing bolt, 4-the cylinder head, 5-the eccentric cam inner shaft driver, 6-the hook spring, 7-the multi-roller rocker arm, 8-the return device, 9-the cup tappet, 10-the valve spring, 11-the valve, 12-the non-cylinder deactivation rocker arm, 13-the hydraulic tappet, 14-the non-cylinder deactivation cup tappet.

FIG. 8 is a schematic diagram of valve lift output characteristics for different eccentricity angles for an eccentric cam internal shaft actuator adjustment range of 0-100.

FIG. 9 is a schematic diagram of valve lift output characteristics for different eccentricity angles for an eccentric cam internal shaft actuator adjustment range of 0-120.

Detailed Description

The invention will be further described in detail with reference to the following drawings and specific examples, which are not intended to limit the invention, but are for clear understanding.

As shown in fig. 1, the camshaft timing mechanism comprises a driving camshaft assembly 1, and further comprises an eccentric camshaft assembly 2, a multi-roller rocker arm 7, a valve spring 10 and a valve 11, wherein a driving cam of the driving camshaft assembly 1 is in contact connection with a first connecting end of the multi-roller rocker arm 7, an eccentric cam 2-b of the eccentric camshaft assembly 2 is in contact connection with a second connecting end of the multi-roller rocker arm 7, a third connecting end of the multi-roller rocker arm 7 is in contact connection with a cup-shaped tappet 9, and the valve spring 10 and the valve 11 are connected below the multi-roller rocker arm 7.

As shown in fig. 2 and 3, the eccentric camshaft assembly 2 includes an eccentric camshaft inner shaft 2-d, an eccentric camshaft outer shaft 2-c, and an eccentric cam 2-b, the eccentric cam 2-b and the eccentric camshaft inner shaft 2-d are connected by a dowel pin 2-a with interference fit, the eccentric camshaft outer shaft 2-c is provided with a key hole 2-f in the moving direction of the dowel pin 2-a, and the width of the key hole 2-f is larger than the outer diameter of the dowel pin 2-a.

The eccentric camshaft inner shaft 2-d is connected with the output end of the eccentric cam inner shaft driver 5.

The eccentric camshaft outer shaft 2-c is fixedly connected with a cylinder head 4 through a fixing bolt 3.

As shown in fig. 5, the multi-roller rocker arm 7 comprises a rocker arm body 7-c, a first rocker arm upper roller 7-a, a second rocker arm upper roller 7-e and a rocker arm lower roller 7-d are respectively sleeved at two ends and the bottom of the upper part of the rocker arm body 7-c through a roller shaft 7-b to form a first connecting end, a second connecting end and a third connecting end of the multi-roller rocker arm 7, wherein the first rocker arm upper roller 7-a is in contact connection with the eccentric cam 2-b, the second rocker arm upper roller 7-e is in contact connection with the driving cam, and the rocker arm lower roller 7-d is used for being in contact connection with the cup-shaped tappet 9.

One side of the rocker arm body 7-c, which is provided with the roller 7-e on the second rocker arm, is also connected with a return device 8 through a support arm shaft 7-f.

And a hook spring 6 is arranged between the multi-roller rocker arm 7 and the eccentric camshaft assembly 2. A first spring groove 2-f is formed in the outer shaft 2-c of the eccentric camshaft, a second spring groove 7-g is formed in a roller shaft of a roller 7-a on the first rocker arm, one end of the hook spring 6 is fixed to the first spring groove 2-f, and the other end of the hook spring is fixed to the second spring groove 7-g.

As shown in fig. 4, the eccentric cam inner shaft driver 5 comprises a driver rotor 5-a, a driver stator 5-d, an eccentric cam inner shaft signal disc 5-e and a driver return spring 5-f, and the driver rotor 5-a is connected with the eccentric camshaft inner shaft 2-d.

As shown in fig. 6, the cup-shaped tappet 9 includes a tappet housing 9-d and a tappet upper cover 9-a disposed on the tappet housing 9-d, wherein an annular groove 9-f is disposed at an upper end of the tappet housing 9-d, a flange 9-g is disposed at a bottom of the tappet upper cover 9-a, the tappet housing 9-d and the tappet upper cover 9-a are cooperatively connected through the annular groove 9-f and the flange 9-g, a gap 9-h is disposed between the flange 9-g and the annular groove 9-f, and a tappet return spring 9-b is disposed in the gap 9-h.

The mechanism is arranged on the air inlet side of the top of the cylinder cover of the engine and mainly comprises the following structures.

The driving camshaft assembly 1 is used for receiving torque transmitted by a crankshaft, driving a driven part to move and overcoming spring moment and friction moment, and structures such as a driving camshaft signal disc 1-b, a thrust plate, a high-pressure oil pump cam and the like can be selectively integrated on the driving camshaft 1-a according to development requirement difference.

An eccentric camshaft assembly 2 for adjusting the position of the rocker arm and ultimately changing the rocker ratio of the mechanism.

An eccentric cam inner shaft driver 5 for rotating the eccentric camshaft inner shaft 2-d, controlling the amount of eccentricity, and capable of holding the eccentric cam 2-b in a fixed phase.

And a fixing bolt 3 for locking the position of the eccentric camshaft outer shaft 2-c from relative rotation with the structural member.

The multi-roller rocker arm 7 is used for receiving cam and eccentric cam lift signals and converting the signals into a follower to move along the direction of a valve axis.

And a special cup tappet 9 which can provide a section of idle stroke and ensure that the valve cannot be automatically opened when the mechanism is at the initial position of the rocker arm with different cam base circle sections.

To achieve the stated object, these parts need to have the following structural features that are distinguished from existing mechanisms.

The eccentric camshaft is of a shaft sleeve type structure, the eccentric cam 2-b and the eccentric camshaft inner shaft 2-d are connected through a positioning pin 2-a in interference fit, in order to enable the eccentric camshaft inner shaft 2-d to rotate relative to the eccentric camshaft outer shaft 2-c, the eccentric camshaft outer shaft 2-c is provided with a key type hole 2-f which is determined in angle and slightly larger than the outer diameter of the positioning pin 2-a in the moving direction of the positioning pin 2-a in a digging mode. The inner shaft of the eccentric cam is fixedly connected with the inner shaft driver rotor of the eccentric cam, the driver is driven by oil pressure on two sides of the rotor and can drive the eccentric cam to rotate around the axis of the eccentric cam, and when the oil pressure moments on two sides of the rotor are balanced, the eccentric cam 2-b keeps static and outputs constant cam lift to the multi-roller rocker arm 7. The eccentric cam outer shaft is reserved with fixing bolt holes 2-e, and the camshaft is rotated to be screwed into the fixing bolts during installation, so that the position of the outer shaft can be fixed, and a determined initial phase is provided for the mechanism.

In order to ensure that the roller and the eccentric cam keep contact in the operation process, a first spring groove 2-f needs to be processed at the outer shaft rod part of the eccentric cam, 2 hook springs 6 are arranged between a multi-roller rocker arm 7 and the eccentric shaft to generate pulling force, and the eccentric cam and the roller surface of the rocker arm roller are ensured to be contacted constantly in the operation process. The eccentric camshaft or the parts fixedly connected with the eccentric camshaft are also provided with a signal panel for representing the relative position of the eccentric camshaft to provide real-time angular position information of the eccentric camshaft for the phase sensor, and the eccentric camshaft inner shaft signal panel 5-e and the driver rotor 5-a are fixedly connected and integrated in the eccentric camshaft driver.

The eccentric camshaft driver 5 is a core part for changing the system valve lift, the adjusting range of the eccentric camshaft driver determines the available range of the eccentric cam lift, and compared with the conventional design, the driver rotor 5-a in the patent has 1-2 less blades and aims to increase the adjustable range to be more than 100 degrees of cam rotation angle. It is worth to be noted that, different from a conventional phaser which needs to overcome a camshaft resistance moment generated by a periodic compression valve spring, an eccentric cam only plays a role of a fulcrum during operation, a driver only needs to overcome an unbalanced moment brought to the eccentric cam by contact of a rocker roller during operation, and the moment is far smaller than the camshaft resistance moment, so that the requirement on the driving capacity of a shaft driver 5 in the eccentric cam is not high, the axial radial length of the shaft driver can be smaller than that of the conventional phaser, and a driver return spring 5-f needs to be additionally arranged at the front end to ensure that a rotor returns to an initial position after the phaser stops.

3 rollers are arranged on the multi-roller rocker arm 7 and are respectively in rolling contact with the surface of the driving cam, the surface of the eccentric cam and the upper end surface of the cup-shaped tappet, and in order to ensure that the rocker arm does not float after assembly is finished, 3 motion degrees of freedom of the rocker arm are limited in design, and the rocker arm is only allowed to translate and rotate in a cam plane.

The return device 8 is used for supporting the multi-roller rocker arm 7, so that the driving cam is constantly contacted with the roller surface of the rocker arm in the operation process, and the transverse displacement of the rocker arm is limited. The plunger head of the return device is provided with a U-shaped groove 8-a matched with the shape of the supporting arm of the rocker arm, the supporting arm shaft 7-f is placed in the groove during installation, and the return device can push the rocker arm upwards under the action of a return device spring 8-b to achieve the function. On the engine cylinder cover of this mechanism of installation, need draw corresponding mounting hole for the return ware, the mounting hole degree of depth must be greater than the lowest position that can reach when the return ware descends to guarantee the realization of return function.

The cup-shaped tappet 9 needs to provide a section of idle stroke with spring force pre-tightening for a mechanism, in order to realize the function, the cup-shaped tappet 9 needs to be provided with a tappet upper cover 9-a and a tappet housing 9-d which can generate relative motion in the height direction, a compression spring is arranged between the tappet housing 9-d and the tappet housing 9-d for providing pre-tightening, and in addition, in order to avoid the damage of the cup-shaped tappet caused by the impact force generated when the lower surface of the upper tappet cover is contacted with the upper surface of the housing, a non-metal buffer layer is also arranged between the upper cover and the housing.

In addition to the structural features, the components included in the mechanism have the following installation, coordination and movement relationships.

The driving camshaft and the eccentric camshaft are arranged in a cylinder cover camshaft support, a journal is in clearance fit with a support hole, the driving camshaft rotates around a shaft during working, an outer shaft of the eccentric camshaft is fixedly connected with the cylinder cover through a fixing bolt, and an inner shaft swings around the shaft according to the requirements of angular positions. The upper end of the rocker arm is in rolling contact with the two cams, wherein the contact between the rocker arm roller and the driving cam is ensured by the upward jacking of the return device, the supporting arm shaft is hinged with the head of the return device through a U-shaped groove, the contact between the rocker arm roller and the eccentric cam is ensured by the pulling force in the direction of the line of continuity generated between the two shafts by the hook spring, the roller is connected with the rocker arm roller shaft through a roller bearing, the inner ring of the bearing is in interference joint with the rocker arm roller shaft, the outer ring is in interference joint with the inner ring of the roller, and the.

The operation principle of the mechanism to realize the variable valve lift will be described with reference to fig. 1.

When the mechanism in fig. 1 works normally, the driving camshaft assembly 1 is driven by the crankshaft to rotate, the multi-roller rocker arm 7 is driven to periodically overcome the resistance of the valve spring 10, and the engine valve 11 is opened and closed after the idle stroke arranged at the top of the cup-shaped tappet 9 is eliminated. When the phase of the eccentric cam inner shaft driver 5 is kept fixed and the drive camshaft assembly 1 is in the base circle position, the top surface of the cup tappet 9 is at its upper limit position at the eccentricity. Only when the displacement of the top surface of the cup tappet 9 exceeds the size of the idle stroke, the valve 11 will gradually open, bringing fresh charge to the combustion chamber.

When the mechanism in the figure 1 needs to change the valve lift, hydraulic oil is controlled by an engine oil control valve and flows into the eccentric cam inner shaft driver 5, the driver rotor 5-a moves to drive the eccentric cam 2-b fixedly connected with the driver rotor to rotate, the output eccentric amount is changed, and therefore the upper limit position of the top surface of the cup tappet 9 is changed when the base circle position is changed. The lower the upper limit position, the greater the precompression of the cup tappet 9 by the mechanism, the smaller the idle stroke to be overcome, and the variation that results from this is that the drive cam rotation can output a greater valve lift and duration. The higher the upper limit position is, the smaller the precompression of the mechanism on the cup tappet 9 is, and the larger the idle stroke to be overcome is, so that the change is that the driving cam can output smaller valve lift and duration outwards.

How the mechanism performs the cylinder deactivation function without changing the arrangement will be described with reference to fig. 7.

In the drawings, reference numerals 1 to 11 denote parts common to the cylinders and parts of the valve train provided for the cylinders requiring cylinder deactivation, which are described in the description of the drawings and will not be described again. In the figures, 12-14 show the valve train components of a normal cylinder without cylinder deactivation, wherein 12 is a non-deactivated rocker arm, 13 is a hydraulic tappet, and 14 is a non-deactivated cup tappet.

The valve system parts of the cylinder without cylinder deactivation have the following characteristics: the maximum cam lift is smaller than that of a cylinder deactivation cylinder cam, because in the cylinder deactivation cylinder, a valve is positioned between two shafts, and the mechanism rocker ratio is about 0.5, while in a cylinder non-cylinder deactivation cylinder, the valve is positioned on the other side of a driving cam and a fulcrum, and the mechanism rocker ratio is about 2, and a relatively small cam lift can be selected to obtain a corresponding valve lift curve. The tappet top surface has sunken gyro wheel groove structure for the axial of gyro wheel is spacing, and the tappet lateral wall is equipped with prevents changeing the round pin structure, ensures that the very cylinder does not take place to rotate in the course of the work, and the gyro wheel trench position does not change.

As can be seen from fig. 7, the mechanism can realize independent control of the valve lift of each cylinder by replacing the parts 6, 7, 8, and 9 with the parts 10, 11, and 12 without changing the position of the driving camshaft and the height and angle of the valve, so that partial cylinders can be deactivated in some working conditions, and the utilization rate of the load in the cylinders can be improved.

The 4 curves plotted in fig. 8 are motion lift curves corresponding to vertical displacement of the lower roller of the rocker arm when the eccentric cam in the mechanism is at different phase angles. The first characteristic of the output curve is: the displacement of the output roller is increased along with the increase of the eccentric angle of the mechanism, but the wrap angle of the working section of the driving cam is not changed from beginning to end, and the wrap angle of the working section of the output curve is equal to the eccentric angle when the wrap angle is 0 degrees; the second characteristic of the output curve is: the mechanism has the advantages that the output curve is integrally lifted in a state of being more than 0-degree eccentric angle along with the increase of the eccentric angle, the change of the eccentric cam lift results in the change of the initial position of the lower roller of the rocker arm, and if the idle stroke with a certain size is not set, the phenomenon that the valve cannot be closed tightly can occur in the phase position of the eccentric cam in the adjusting process.

In fig. 8, a valve non-opening area is below the hollow stroke line, and the physical meaning is as follows: in the area, the vertical displacement of the lower roller of the rocker arm caused by the rotation of the driving cam does not bring the change of the valve lift; an actual valve lift curve is arranged above a hollow stroke line in fig. 6, and at the moment, after the influence of the idle stroke of the tappet is completely eliminated, the tappet shell can be driven by the vertical displacement of the lower roller of the rocker arm caused by the rotation of the driving cam, so that the valve is driven to move downwards to be opened.

In order to meet the use requirement, the idle stroke is larger than the vertical displacement of the minimum rocker arm lower roller when the eccentric angle is maximum, namely the lower limit position of the hole stroke marked in fig. 6, and if the cylinder closing function is required to be met, the idle stroke is larger than or equal to the vertical displacement of the maximum rocker arm lower roller when the eccentric angle is minimum, namely the cylinder closing position is realized by the idle stroke marked in fig. 6.

In one embodiment of the invention, the base radius of the drive cam is 15mm and the maximum cam lift is 10 mm. The eccentric cam inner shaft driver is of a 3-blade structure and has an adjustment range of 100 degrees, so that the cam lift of the eccentric cam can be changed within a range of 10-15.04 mm. The vertical distance between the axis of the plunger of the return device and the axis of the driving cam shaft is 19.87mm, and the idle stroke of the tappet is equal to the vertical displacement of the roller under the largest rocker arm when the eccentric angle is the smallest, and the vertical displacement is 3.15 mm.

With the above structural parameters, the mechanism can output the following characteristic point valve lift characteristics. When the phase of the eccentric cam is 0 degree, the lift of the eccentric cam is 10mm, the maximum lift of a corresponding valve lift curve is 0mm, and the wrap angle of the valve lift curve is 0 degree CrA; when the phase of the eccentric cam is 62.2 degrees, the lift of the eccentric cam is 12mm, the maximum lift of a corresponding valve lift curve is 1.64mm, and the wrap angle of the valve lift curve is 71.4 degrees CrA; when the phase of the eccentric cam is 88.4 degrees, the lift of the eccentric cam is 14mm, the maximum lift of a corresponding valve lift curve is 3.10mm, and the wrap angle of the valve lift curve is 102.2 degrees CrA; when the phase of the eccentric cam is 100 degrees, the lift of the eccentric cam is 15.04mm, the maximum lift of a corresponding valve lift curve is 3.81mm, and the wrap angle of the valve lift curve is 118.7 degrees CrA, namely shown in FIG. 8.

In another embodiment of the invention, the base radius of the drive cam is 15mm and the maximum cam lift is 12 mm. The eccentric cam inner shaft driver is of a 2-blade structure and has a 120-degree adjusting range, so that the cam lift of the eccentric cam can be changed within a range of 10-16.86 mm.

The vertical distance between the axis of the plunger of the return device and the axis of the driving cam shaft is 19.87mm, and the vertical displacement of the roller under the largest rocker arm when the idle stroke of the tappet is larger than the minimum eccentric angle is 3.58 mm. With the above structural parameters, the mechanism can output the following characteristic point valve lift characteristics. When the phase of the eccentric cam is 0 degree, the lift of the eccentric cam is 10mm, the maximum lift of a corresponding valve lift curve is 0mm, and the wrap angle of the valve lift curve is 0 degree CrA; when the phase of the eccentric cam is 62.2 degrees, the lift of the eccentric cam is 12mm, the maximum lift of a corresponding valve lift curve is 1.63mm, and the wrap angle of the valve lift curve is 60 degrees CrA; when the phase of the eccentric cam is 88.4 degrees, the lift of the eccentric cam is 14mm, the maximum lift of a corresponding valve lift curve is 3.24mm, and the wrap angle of the valve lift curve is 97.0 degrees CrA; when the phase of the eccentric cam is 120 degrees, the lift of the eccentric cam is 16.86mm, the maximum lift of a corresponding valve lift curve is 5.55mm, and the wrap angle of the valve lift curve is 140 degrees CrA, namely shown in FIG. 9.

In the embodiment, it can be seen that the valve lift curve can be continuously changed within a certain maximum lift and working section wrap angle range by appropriately changing the geometrical parameters of the mechanism. The variable valve lift mechanism fixedly connected with the driving camshaft is matched for use, the opening and closing time of the intake valve can be changed simultaneously, and the requirement of overexpansion cycle control is met.

The following implementation main points of should also be noted for guaranteeing mechanism reliability in this patent implementation: determining the width lower limit of the roller through finite element analysis to ensure that the contact stress is smaller than the allowable stress value of the cam and roller materials after heat treatment and leaving a proper safety coefficient; the upper limit of the width of the roller needs to be determined through tolerance dimension chain analysis, and the side face of the roller does not exceed the cam surface and the roller does not press the sharp edge of the cam when the mechanism is in maximum axial deviation. In the embodiment, the width of the driving cam and the eccentric cam is 10mm, and the width of the roller is 8 mm. The driving cam and the eccentric cam are required to be ensured to be positioned at each position, the moment generated by the return device spring at the supporting point is smaller than the moment generated by the cup tappet spring at the supporting point, the aim is to ensure that the vertical displacement of the lower roller of the rocker arm is controlled by a cam profile, and the valve can be completely closed when the driving cam is positioned at a base circle position, namely a lower limit position of idle stroke, at the maximum eccentric amount of the eccentric cam.

And under different valve lifts, the system has different safe rotating speeds. The compression amount of the spring in the low lift state is small, the rotating speed of the system in disorder is low, the compression amount of the spring in the high lift state is large, and the rotating speed of the system in disorder is high. Attention needs to be paid to system calibration, and the excessively small valve lift is avoided to the greatest extent under the working condition of high rotating speed, so that the phenomenon of valve system maladjustment is avoided.

Details not described in this specification are within the skill of the art that are well known to those skilled in the art.

Claims (9)

1. A double-shaft multi-roller rocker arm type variable valve lift mechanism comprises a driving camshaft assembly (1) and is characterized by further comprising an eccentric camshaft assembly (2), a multi-roller rocker arm (7), a valve spring (10) and a valve (11), wherein a driving cam of the driving camshaft assembly (1) is in contact connection with a first connecting end of the multi-roller rocker arm (7), an eccentric cam (2-b) of the eccentric camshaft assembly (2) is in contact connection with a second connecting end of the multi-roller rocker arm (7), a third connecting end of the multi-roller rocker arm (7) is in contact connection with a cup-shaped tappet (9), and the valve spring (10) and the valve (11) are connected below the multi-roller rocker arm (7);

the eccentric camshaft assembly (2) comprises an eccentric camshaft inner shaft (2-d), an eccentric camshaft outer shaft (2-c) outside the eccentric camshaft inner shaft (2-d) and an eccentric cam (2-b), the eccentric cam (2-b) and the eccentric camshaft inner shaft (2-d) are connected through a positioning pin (2-a) in interference fit, a key type hole (2-f) is formed in the eccentric camshaft outer shaft (2-c) in the movement direction of the positioning pin (2-a), and the width of the key type hole (2-f) is larger than the outer diameter of the positioning pin (2-a).

2. The dual-shaft multi-roller rocker arm variable valve lift mechanism of claim 1, wherein the eccentric camshaft inner shaft (2-d) is connected to an output of an eccentric camshaft inner shaft driver (5).

3. The dual-shaft multi-roller rocker arm type variable valve lift mechanism of claim 1, wherein the eccentric camshaft outer shaft (2-c) is fixedly connected with the cylinder head (4) by means of fixing bolts (3).

4. The dual-spool multi-roller rocker arm variable valve lift mechanism of claim 1, the multi-roller rocker arm (7) comprises a rocker arm body (7-c), the two ends and the bottom of the upper part of the rocker arm body (7-c) form a first connecting end, a second connecting end and a third connecting end of the multi-roller rocker arm (7) through a first rocker arm upper roller (7-a), a second rocker arm upper roller (7-e) and a rocker arm lower roller (7-d) which are arranged on a roller shaft (7-b), wherein the roller (7-a) on the first rocker arm is in contact connection with the eccentric cam (2-b), the second rocker arm upper roller (7-e) is in contact connection with the driving cam, and the rocker arm lower roller (7-d) is used for being in contact connection with the cup-shaped tappet (9).

5. The dual-shaft multi-roller rocker arm type variable valve lift mechanism of claim 4, wherein the side of the rocker arm body (7-c) on which the roller (7-e) on the second rocker arm is provided is further connected to a return means (8) via a support arm shaft (7-f).

6. The dual-shaft multi-roller rocker arm type variable valve lift mechanism of claim 4, wherein a hook spring (6) is provided between the multi-roller rocker arm (7) and the eccentric camshaft assembly (2).

7. The dual-shaft multi-roller rocker arm type variable valve lift mechanism of claim 6, wherein a first spring groove (2-f) is formed in the eccentric camshaft outer shaft (2-c), a second spring groove (7-g) is formed in the roller shaft of the roller (7-a) on the first rocker arm, one end of the hook spring (6) is fixed at the first spring groove (2-f), and the other end of the hook spring is fixed at the second spring groove (7-g).

8. The dual-shaft multi-roller rocker arm type variable valve lift mechanism of claim 2, wherein the eccentric cam inner shaft driver (5) comprises a driver rotor (5-a), a driver stator (5-d), a driver return spring (5-f) arranged between the driver rotor (5-a) and the driver stator (5-d), and an eccentric cam inner shaft signal disc (5-e) for representing the position of the eccentric cam inner shaft (2-d), wherein the driver rotor (5-a) is connected with the eccentric cam inner shaft (2-d)

And (6) connecting.

9. The dual-spool multi-roller rocker arm variable valve lift mechanism of claim 1, the cup-shaped tappet (9) comprises a tappet housing (9-d) and a tappet upper cover (9-a) arranged on the tappet housing (9-d), wherein, the upper end of the tappet shell (9-d) is provided with an annular groove (9-f), the bottom of the tappet upper cover (9-a) is provided with a flanging (9-g), the tappet shell (9-d) is matched and connected with the tappet upper cover (9-a) through an annular groove (9-f) and a flanging (9-g), a gap (9-h) is arranged between the flanging (9-g) and the annular groove (9-f), and a tappet return spring (9-b) is arranged in the gap (9-h).

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