CN203770565U - Double-idler-wheel steering reducing type friction stepless speed change device - Google Patents

Abstract

The utility model provides a double-idler-wheel steering reducing type friction stepless speed change device. An input shaft gear is fixedly connected to an input shaft. The input shaft is installed on a machine frame. Input friction disks are fixedly connected to middle shafts. Each middle shaft is installed on the machine frame. First middle idler wheels are fixedly connected to first idler wheel shafts. First middle gears are fixedly connected to first gear shafts. The first middle gears and second middle gears are mutually meshed. Meanwhile, each first middle idler wheel and the corresponding input friction disk tightly press each other. An output friction disk is fixedly connected to an output shaft. The output shaft is installed on the machine frame, and motor shells are connected with machine frame movement pairs. Gearing-down is conducted between rotating rods and output shafts of the motors through first-stage gears. Each rotating rod is connected with the corresponding first idler wheel shaft or the corresponding second idler wheel shaft in a revolute pair mode. The double-idler-wheel steering reducing type friction stepless speed change device has the advantages of being simple in structure, free of lubrication, high in transmission efficiency, small in friction, and free of power output interrupt.

Description

Two roller steering diameter reducing type Friction Stepless devices

Technical field

The utility model belongs to mechanical transmission fields.Be specifically related to a kind of pair of roller steering diameter reducing type Friction Stepless device.

Background technique

Mechanical stepless speed changes mechanism is a kind of in the situation that input speed is constant, can realize output shaft rotating speed and change within the specific limits, to adapt to the usage requirement of various different operating modes.The Typical Representative of present stepless speed changing mechanism has the planetary variable transmission of middle rolling body type variable transmission (the stepless transmission of rolling cone flat plate type, the stepless transmission of steel ball tray type etc.) (the stepless transmission of pivoted arm output type, the stepless transmission of ball planet formula etc.) without middle rolling body type mechanical stepless speed changes transmission (the stepless transmission of orhtogonal axis, intersect the stepless transmission of axial cone disk ring bevel-type, the inclined disc type stepless transmission of optical axis etc.) dead axle as dead axle.Friction driving is the conventional mechanism form of mechanical stepless transmission, frictional force transmission campaign and power between the certain positive pressure lower transmission component of slip gear utilization, its ability of transmitting frictional force (torque) depends on friction factor and the positive pressure of driving component contact surface.Under certain positive pressure condition, the friction factor that increases friction drive wheel Surface Contact place is the important channel of improving frictional variable speed mechanism bearing capacity.But existing frictional variable speed mechanism, if the friction factor between its driving component is got higher value, in transmission process, change the effective rubbing contact radius of drive wheel and realize the required surface friction drag overcoming of stepless change, and the wearing and tearing of consequent driving component contact surface all will sharply increase.So, existing frictional variable speed mechanism in fact all can only select friction factor compared with metallic type friction driving parts little and that surface abrasion resistance is higher (metallic type drive wheel or driving belt), even also need, at driving component rubbing contact place filling traction lubricating oil, cause its bearing capacity to be very limited.

Therefore, the bearing capacity of raising friction type gear is to have very much realistic meaning.

The utility model proposes a class and there is the frictional variable speed device that two intermediate rollers turn to diameter changing mechanism, in the middle of it, adopted multiple variable speed mechanism, can in a big way, change velocity ratio.Owing to realizing coordinate synchronization between diameter changing device turning to of all cloth of many covers, can adopt synchronous mechanism to guarantee that the coordination of a plurality of rollers under a plurality of Electric Machine Control moves, only need adopt closed loop control just can realize the accurate control to whole device to wherein one or two motor.The drive wheel that can control high coefficient of friction by this class device and lazy-tongs thereof carries out level and smooth, continuous variation under lower resistance, low abrasive conditions.There is simple in structure, stepless change and handle the advantages such as light, multi-change speed, control be accurate.

Model utility content

Technical problem to be solved in the utility model, has been to propose to have frictional variable speed device and the synchronous mechanism thereof that two intermediate rollers turn to diameter changing mechanism.Its method for changing speed is to use the speed governing actuator of a set of similar wheel steering mechanism on intermediate roller, make intermediate roller produce lateral deviation, utilize the cornering behavior of intermediate roller, make intermediate roller under the effect of lateral force, change its radial position, realize the adjusting of speed ratio.Between two rollers, also introduced gear transmission, increased its speed adjustable range, overlapped on gear more and also can be convenient to realize accurate control with synchronous mechanism, because the existence of synchronous mechanism can also realize commutation function to a certain extent.Compare with general CVT mechanism, have simple in structurely, cost is low, and speed regulating mechanism operation is light, control the features such as accurate.

For achieving the above object, the technological scheme that the utility model adopts is:

Stepless speed changes devices without synchronous mechanism is mainly comprised of input shaft, input shaft gear, input friction disk, jack shaft, the first intermediate gear, the first gear shaft, the first transmission shaft, universal joint, the first intermediate roller, motor, gear dwang, bearing rod, the first roller shaft, the second intermediate roller, the second roller shaft, second driving shaft, the second intermediate gear, the second gear shaft, output shaft, output friction disk.

Increased on the basis of the above with the stepless speed changes devices system of synchronous mechanism than said system many synchronizing bar, synchronous mechanism.

Wherein, input shaft gear is fixed on input shaft, and input shaft is arranged in frame, and input friction disk is fixed on jack shaft, and jack shaft is arranged in frame, and input friction disk side is processed with tooth, meshes with input shaft gear; The first intermediate roller and input friction disk compress mutually, realize friction driving; The first intermediate roller is fixed on the first roller shaft, and the first transmission shaft is connected with the first roller shaft by universal joint, and the first gear shaft and the first drive shaft axis overlap, and the two is that sliding pair (spline or other) connects, and sliding pair direction is the two axial direction; The first intermediate gear is fixed on the first gear shaft, and the second intermediate gear is fixed on the second gear shaft, and the first intermediate gear and the second intermediate gear are gear engagement, and the first gear shaft and the second gear shaft are all arranged in frame; The second gear shaft and second driving shaft dead in line, both are sliding pair connection, sliding pair direction is both axial directions; The second intermediate roller is fixed on the second roller shaft, and the second roller shaft is connected with second driving shaft by universal joint; The second intermediate roller and output friction disk compress mutually, realize friction driving; Output friction disk is fixed on output shaft, and output shaft is arranged in frame.

Electric machine casing is that sliding pair is connected with frame, and sliding pair direction is identical with the sliding pair direction that gear shaft and transmission shaft form; The output shaft of motor connects firmly a gear, with the engagement of gear dwang gear, gear dwang is connected with roller shaft by revolute pair, the impacting force passing in order to bear roller shaft, bearing rod one end and electric machine casing connect firmly, and the other end is that revolute pair is connected with gear dwang; The housing of motor produces and reverses when preventing roller lateral deviation, and the Gear axis direction of gear dwang should be crossed its corresponding universal joint center.Electric machine casing, gear-driving rod, bearing rod in the layout of all the other positions with above-mentioned consistent.

Or this stepless speed changes devices is with synchronous mechanism, synchronous mechanism is connected with frame revolute pair; Synchronizing bar is connected with frame cylindric pair, and its one end is connected with transmission shaft by revolute pair, and the other end is embedded in the groove of disk on synchronous mechanism.

During gearing down, power is inputted by input shaft, via input friction disk, be passed to the first intermediate roller, by universal joint and spline, be passed to the first intermediate gear, by engagement pair, be delivered to the second intermediate gear, by spline and universal joint, be delivered to the second intermediate roller again, finally by output friction disk, output to output shaft.During stepless change, transmission shaft can move with synchronizing bar, and synchronizing bar driving device synchronizer rotates, thereby guarantees that left and right Liang Tao mechanism is synchronous, and during speedup transmission, power transfer path is contrary.

When needs regulate velocity ratio, by micro-machine is synchronous, drive all gear dwangs to turn over reposefully in the same direction equal angular, can drive accordingly first, second intermediate roller to produce lateral deviation, because side drift angle is very little, micro-machine need not consume too many power, and resistance is also little.Suppose that now the first intermediate roller is p1 with the point of contact of input friction disk, the speed that p1 is ordered is vp1, is pure rolling between the first intermediate roller and input friction disk, and the speed that on the first intermediate roller, p1 is ordered is so also vp1, the speed that on the first intermediate roller, p1 is ordered can be understood as a resultant velocity, two-part, consists of: the one, the p1 o'clock rotational velocity with respect to the rotation axis of the first intermediate roller vr1, its direction is perpendicular to the rotation axis of the first intermediate roller; Two is that the first intermediate roller integral body is along the translational velocity Vs1 of spline.Existence due to spline vthe direction of s1 is also determined, and is had vp1= vr1+ vs1, the first intermediate roller can be towards input friction disk inner side with speed vs1 moves, and similarly, between the second intermediate roller and output friction disk, also exists a point of contact p2, and by moving direction and vector compositive relation, can obtain the second intermediate roller also can be towards the inner side of exporting friction disk with speed vs2 moves, consistent with the moving direction of the second intermediate roller by known the first intermediate roller of direction of analysis Vs2.When the first intermediate roller and the second intermediate roller return motor just separately when the direction of guide mechanism moves to a rational position, now vs1= vs2=0, arrives a new transmission position, realizes the variation of velocity ratio.After steer motor is just returned, intermediate roller arrives new transmission contact radius position, and now motor is by locking (lockable mechanism can be taked the modes such as electromagnetic braking mode, not shown in FIG.), to guarantee that velocity ratio is in steady state.

In the utility model, in order to guarantee there are enough positive pressures on the friction pair between the first intermediate roller and input friction disk, the second intermediate roller and output friction disk, whole mechanism needs to compress up and down simultaneously, impacting force is comprised of two-part, a part acts on output friction disk, upwards, another part acts on the input assembly being comprised of input shaft, input shaft gear, input friction disk, jack shaft direction, and direction is downward.For making device still can apply impacting force after producing wearing and tearing, can apply impacting force with the spring of compression.Impacting force is delivered to roller by friction disk, by roller shaft, gear dwang, bearing rod, is delivered to electric machine casing, by electric machine casing, is born.

In the utility model, in order to make transmission, stablize and uniform stressed, intermediate transmission turns to diameter changing mechanism assembly, comprise the first intermediate gear, the first gear shaft, the first roller shaft, the first transmission shaft, the first intermediate roller, the second intermediate roller, the second roller shaft, the second gear shaft, second driving shaft, the second intermediate gear, have 2 covers (universal joint, motor, gear dwang, bearing rod has 4), be symmetrically distributed in the both sides of exporting friction disk.As long as above-mentioned centre turns to diameter changing mechanism assembly can be symmetrically distributed in output friction disk around, can have in theory many covers, but many covers turn to diameter changing mechanism when carrying out speed governing, symmetric part must be Complete Synchronization.

Its solution

(1) each motor is carried out to closed loop control and revise how cover turns to the kinematic error of moving between diameter changing mechanism, guarantee synchronous and accurately control.

(2) use part synchronous mechanism, by synchronous mechanism, guarantee that symmetric part is synchronized with the movement, only need carry out closed loop control to upper and lower two motors accurately controls package unit

(3) use integrated synchronous mechanism.Its working principle is: the disk shown in A and B view (hereinafter referred to as deep bid and shallow bid) is fixed together by axle, is referred to as synchronous mechanism.Synchronous mechanism can rotate around frame, and rotation axis is the circle center line connecting direction of deep bid and shallow bid.The centrosymmetric groove that has on deep bid and shallow bid, synchronizing bar is embedded in respectively in the groove of deep bid and shallow bid, in order to guarantee left and right Liang Tao mechanism synchronizing moving.The radius ratio of deep bid and shallow bid (the two is similar fitgures) is to be determined with the ratio of output friction disk point of contact speed by the first intermediate roller and speed and second intermediate roller of input friction disk point of contact.In order to guarantee that the first intermediate roller and the second intermediate roller are definite values along the ratio of the distance of the movement of axis all the time.Synchronous mechanism effectively prevented foozle and use in the mechanism left and right that causes of wearing and tearing and upper and lower asynchronous.Under the effect of synchronous mechanism, can only to one of them motor, carry out closed loop control and accurately control package unit.Whole synchronizer has simple in structure, and reliability is strong, has very strong usability.

Superiority of the present utility model is:

1. crucial transmission part is the intermediate roller with certain viscous-elastic behaviour, and the friction factor of itself and friction disk is high, and cost is low, simple in structure, and without lubricated, transmission efficiency is high, and intermediate roller is replaceable;

2. in the time need carrying out speed governing, it is little that the effective rubbing contact radius of change drive wheel is realized the required surface friction drag overcoming of stepless change, turn to diameter changing mechanism operation light, and it is little to wear and tear;

3. do not need to disconnect power transmission during speed governing;

4. by pair of engaged gears, realize the power power transmission between upper bottom roller, widened the range of choice of velocity ratio, mechanism's adaptability is stronger;

5. mechanism can be with synchronous mechanism, and the asynchrony phenomenon that effectively solves foozle from mechanical mechanism aspect and use wearing and tearing to bring, can accurately control package unit easily.

Accompanying drawing explanation

Fig. 1 is structural representation of the present utility model;

Fig. 2 is that the utility model is with the structural representation of lazy-tongs;

Fig. 3 is another structural representation with lazy-tongs of the utility model;

Fig. 4 (1) (2) is the utility model speed control principle figure

Attached number in the figure explanation:

0 frame, 1 input shaft, 2 input shaft gears, 3 input friction disks, 4 jack shafts, 5 first intermediate gears, 6 first gear shafts, 7 first transmission shafts, 8 universal joints, 9 first intermediate rollers, 10 gear dwangs, 11 bearing rods, 12 motors, 13 first roller shafts, 14 second intermediate rollers, 15 second roller shafts, 16 second driving shafts, 17 second intermediate gears, 18 second gear shafts, 19 output shafts, 20 output friction disks;

Fig. 2 and Fig. 3 are the device with synchronous mechanism, and numbering is described as follows:

21 synchronizing bars, 22 synchronous mechanisms (all the other labels are identical with accompanying drawing 1).

Embodiment

Refer to shown in Fig. 1, Fig. 2, Fig. 3 and Fig. 4 (1) (2), the utility model will be further described.

Fig. 1 is comprised of input shaft 1, input shaft gear 2, input friction disk 3, jack shaft 4, the first intermediate gear 5, the first gear shaft 6, the first transmission shaft 7, universal joint 8, the first intermediate roller 9, gear dwang 10, bearing rod 11, motor 12, the first roller shaft 13, the second intermediate roller 14, the second roller shaft 15, second driving shaft 16, the second intermediate gear 17, the second gear shaft 18, output shaft 19, output friction disk 20.

Fig. 2 and Fig. 3 have increased synchronizing bar 21, synchronous mechanism 22 on the basis of the above than Fig. 1.

Input shaft gear 2 is fixed on input shaft 1, and input shaft 1 is arranged in frame 0, and input friction disk 3 is fixed on jack shaft 4, and jack shaft 4 is arranged in frame, and input friction disk 3 sides are processed with tooth, with input shaft gear 2 engagements; The first intermediate roller 9 and input friction disk 3 compress mutually, can realize friction driving; The first intermediate roller 9 is fixed on the first roller shaft 13, and the first transmission shaft 7 is connected with the first roller shaft 13 by universal joint 8, the first gear shaft 6 and the first transmission shaft 7 deads in line, and the two is sliding pair connection, sliding pair direction is the two axial direction; The first intermediate gear 5 is fixed on the first gear shaft 6, and the second intermediate gear 17 is fixed on the second gear shaft 18, and the first intermediate gear 5 and the second intermediate gear 17 are gear engagement, and the first gear shaft 6 and the second gear shaft 18 are all arranged in frame 0; The second gear shaft 18 and second driving shaft 16 deads in line, both are sliding pair connection, sliding pair direction is both axial directions; The second intermediate roller 14 is fixed on the second roller shaft 15, and the second roller shaft 15 is connected with second driving shaft 16 by universal joint; The second intermediate roller 14 and output friction disk 20 compress mutually, realize friction driving; Output friction disk 20 is fixed on output shaft 19, and output shaft 19 is arranged in frame 0.

Motor 12 housings are with frame 0 for sliding pair is connected, and sliding pair direction is identical with the sliding pair direction that gear shaft and transmission shaft form; The output shaft gear of motor 12, with the 10 gear engagements of gear dwang, gear dwang 10 is connected with roller shaft by revolute pair, the impacting force passing in order to bear roller shaft, bearing rod 11 one end and motor 12 housings connect firmly, and the other end and gear dwang 10 are connected for revolute pair; The housing of motor 12 produces and reverses when preventing roller lateral deviation, and the Gear axis direction of gear dwang 10 should be crossed its corresponding universal joint center.Gear dwang 10, bearing rod 11, motor 12 is consistent with above-mentioned method for arranging in the layout of all the other positions.

The stepless speed changes devices with synchronous mechanism, synchronous mechanism 22 is connected with frame 0 revolute pair; Synchronizing bar 21 is connected with frame 0 cylindric pair, and its one end is connected with transmission shaft by revolute pair, and the other end is embedded in the groove of disk on synchronous mechanism 22.

Two roller steering diameter reducing type Friction Stepless devices, adopted two breast wheels that have viscous-elastic behaviour, the friction factor between itself and friction disk is higher, has promoted the bearing capacity of friction type stepless speed changer, and introduced gear transmission between two rollers, expanded the scope of velocity ratio.

While needing to regulate velocity ratio, the gear dwangs all by driven by motor turn over equal angular in the same direction reposefully along axis, can drive accordingly upper and lower intermediate roller to produce lateral deviation effect, utilize the lateral force that the cornering behavior of intermediate roller produces can be so that high coefficient of friction drive wheel contact radius carries out level and smooth, continuous variation under lower resistance, low abrasive conditions, realize the adjusting of speed ratio, and use load-carrying member that the impacting force of friction driving is delivered on electric machine casing.

On the basis of the above, turn to diameter changing mechanism can arrange many covers, guarantee many covers turn to synchronized movement between diameter changing mechanism method have: (1) is carried out closed loop control to each motor and is revised many covers and turn to the kinematic error between diameter changing mechanism, guarantee synchronous and accurately control.(2) synchronous mechanism, guarantee symmetric part coordinate synchronization, upper and lower two motors carry out closed loop control and accurately control package unit (3) and use accompanying drawing 3 synchronous mechanisms to guarantee that two rollers in Duo Tao mechanism and Mei Tao mechanism are synchronized with the movement, and carry out closed loop control to one of them motor and accurately control package unit.

On the basis of the above: on disk, have groove, become certain track, synchronizing bar is embedded in groove, the rotation that moves radially drive disk of synchronizing bar, symmetrical groove can guarantee that many covers turn to synchronous between diameter changing mechanism, and upper low groove becomes the proportional synchronized movement that can guarantee between bottom roller of size.

Fig. 3 is because synchronous mechanism exists, and the motion of device is easily definite, and during gearing down, power is inputted by input shaft 1, supposes that the rotating speed of input shaft 1 is , the number of teeth of input shaft gear 2 is , on input friction disk 3, the number of teeth of the tooth of processing is , input so friction disk 3 and around the rotating speed of the axis of jack shaft 4 be , i.e. velocity ratio .

The point of contact of supposing the first intermediate roller 9 and input friction disk 3 apart from the distance of jack shaft 4 axis is , the point of contact of the second intermediate roller 14 and output friction disk 20 apart from the distance of output shaft 19 axis is , the radius of the first intermediate roller 9 is , the radius of the second intermediate roller 14 is , the number of teeth of the first intermediate gear 5 is , the number of teeth of the second intermediate gear 17 is , jack shaft 4 to the velocity ratio between output shaft 19 is so

The resultant gear ratio of mechanism is:

。

If we suppose that the radius of inputting friction disk 3 is , the radius of output friction disk 20 is , and , because the rotating ratio of breast wheel 9 and 14 is definite value, and there is synchronous mechanism 12.Both are also a definite value along the distance of the variation of spline so, if order

, so , and have

； ；

X can change continuously, and the velocity ratio excursion of system is

Can find, this mechanism can realize commutation function within the specific limits.Easily find, when the first intermediate roller 9 process input shaft roller 3 central position, produce commutation.But now, because the first intermediate roller 9 is in input friction disk 3 central positions, there is no lateral deviation effect, in dead center position.Need to rely on the lateral deviation effect of the second intermediate roller 14, by synchronous mechanism 22, drive the first intermediate roller 9 to move, realize commutation function.

For the velocity ratio excursion of accompanying drawing 1 and accompanying drawing 2 devices, because first, second intermediate roller can be controlled respectively by motor 12, its velocity ratio excursion is wider by the device that makes a farfetched comparison Fig. 3.

When power is inputted from output terminal, this mechanism can realize stepless speedup;

Below in conjunction with accompanying drawing 4, elaborate speed control principle:

In the time will changing velocity ratio, suppose along axis, to turn over reposefully counterclockwise one by 4 micro-machines, 12 Timing Belt moving gear dwangs 10 angle, can drive accordingly so intermediate roller 9,14 to rotate (for roller is more easily rotated, universal joint is that roller shaft should be as far as possible short to the distance of roller), the plan view of result is as shown in Fig. 3 (1), the first intermediate roller 9 is below input friction disk 3, therefore be represented by dotted lines: the point of contact of supposing the first intermediate roller 9 and input friction disk 3 is p1, and input friction disk 3 rotates according to direction as shown, and the speed that p1 is ordered is vp1, supposes that between the first intermediate roller 9 and input friction disk 3 be pure rolling, and the speed that on the first intermediate roller 9, p1 is ordered is so also vp1, the speed that on the first intermediate roller 9, p1 is ordered can be understood as a resultant velocity, is dimeric, the one, the p1 o'clock rotational velocity with respect to the rotation axis of the first intermediate roller 9 vr1, direction is perpendicular to the rotation axis of the first intermediate roller 9, and two is that the first intermediate roller 9 is along the translational velocity of spline integral body vs1, due to the existence of spline vthe direction of s1 is also determined, and is had vp1= vr1+ v1the vector correlation formula that s is such, is not difficult to find out that in Fig. 2 (1) the first intermediate roller 9 can be interior with one towards input friction disk 3 vthe speed of s1 moves, similarly, between the second intermediate roller 14 and output friction disk 20, also exist a point of contact p2, in Fig. 2 (2), according to illustrated moving direction and vector compositive relation, be not difficult to find out that the second intermediate roller 14 also can be towards exporting in friction disk 20 with one vthe speed of s2 moves, and upper and lower motion is consistent.When upper and lower intermediate roller returns motor just when the direction of guide mechanism moves to a rational position, make be zero, so now vs1= vs2=0, arrives a new transmission position, realizes the variation of velocity ratio.After steer motor is just returned, intermediate roller arrives new transmission contact radius position, and now motor is by locking (lockable mechanism can be taked the modes such as electromagnetic braking mode, not shown in FIG.), to guarantee that velocity ratio is in steady state.

Claims (3)

1. a two roller steering diameter reducing type Friction Stepless device, comprise input shaft, input shaft gear, input friction disk, jack shaft, the first intermediate gear, the first gear shaft, the first transmission shaft, universal joint, the first intermediate roller, motor, gear dwang, bearing rod, the first roller shaft, the second intermediate roller, the second roller shaft, second driving shaft, the second intermediate gear, the second gear shaft, output shaft, output friction disk, with the device of synchronous mechanism, also have synchronous mechanism, synchronizing bar; It is characterized in that: input shaft gear is fixed on input shaft, input shaft is arranged in frame, and input friction disk is fixed on jack shaft, and jack shaft is arranged in frame, and input friction disk side is processed with tooth, meshes with input shaft gear; The first intermediate roller is fixed on the first roller shaft, and the first intermediate gear is fixed on the first gear shaft, the first gear shaft and the first roller shaft dead in line, and both are sliding pair connection; The second intermediate roller is fixed on the second roller shaft, and the second intermediate gear is fixed on the second gear shaft, the second gear shaft and the second roller shaft dead in line, and both are sliding pair connection; The first intermediate gear and the second intermediate gear are intermeshing, simultaneously, the first intermediate roller and input friction disk compress mutually, the second intermediate roller and output friction disk compress mutually, output friction disk is fixed on output shaft, and output shaft is arranged in frame, and electric machine casing is connected with machine frame movement is secondary, the output shaft of dwang and motor is by primary gear speed reducing transmission, and dwang and the first roller shaft or the second roller shaft are revolute pair and are connected.

2. according to claim 1 pair of roller steering diameter reducing type Friction Stepless device, two breast wheels that have viscous-elastic behaviour have been it is characterized in that adopting, friction factor between itself and friction disk is higher, promoted the bearing capacity of friction type stepless speed changer, and introduced gear transmission between two rollers, expanded the scope of velocity ratio.

3. according to claim 1 pair of roller steering diameter reducing type Friction Stepless device, it is characterized in that: on the basis of the above, synchronizing bar and upper lower disc have been increased, on disk, have groove, become certain track, synchronizing bar is embedded in groove, synchronizing bar move radially the rotation that drives disk, symmetrical groove can guarantee that many covers turn to synchronous between diameter changing mechanism.