The present invention relates to the field of mechanical transmission, in particular, to a line gear mechanism meshing on a basis of space conjugate curve meshing theory and able to provide periodically variable transmission ratio.
In gearing-up or gearing-down between two axes, a gear able to realize a variable transmission velocity ratio is called the variable-ratio gear. The variable-ratio gear is mainly used in transmission occasions with special requirements, for example, in aspects of stepless speed regulation in automobile, oval gear flowmeter, and manipulator with variable transmission ratio.
A gear often used for transmission with variable transmission ratio is mainly a non-circular gear, since a non-circular gear mechanism may realize a special movement and function operation, such as swing, indexing, and varying speed, and in the meantime, the non-circular gear may be designed according to transmission ratio function. At present, the non-circular gear used for transmission with variable speed ratio refers to a non-cylindrical gear, and a non-bevel gear. Elliptic bevel gear is a typical non-bevel gear, in named for its large end node being a spherical ellipse. Orthogonal non-circular surface gear pair is a new-style variable-ratio gear transmission, and it has advantages of the non-circular gear, non-bevel gear and face gear, with its design and processing being more simple than the non-circular gear with variable transmission ratio. In addition, variable transmission ratio may be realized by a planetary gear set. Continuous variable magnetic gear comprises a three-phase winding stator and three concentric rotors. By controlling the speed of a central rotor, the transmission ratio between an input rotor and an output rotor can vary.
Line gear is a new-type gear utilizing a space curve meshing theory in the place of a traditional space curve surface meshing theory, which is mainly applied to micro transmission field, and has advantages such as small dimension, large transmission ratio, and easy manufacturing. At present, the line gear pair can be applied to transmissions on two vertical axes, two intersecting axes and two skewed axes, and its researches such as design equation, contact ratio, strength criterion, micro transmission and manufacturing field have tended to be perfect.
In a micro mechanical device with limited dimension, sometimes there is complicated transmission requirement of periodically variable transmission ratio, which is hard to realize by controlling, while traditional non-circular gear is not suitable for micro dimension.
Based on the theory of a line gear, the present invention provides a solution for designing a variable-ratio line gear mechanism. A line gear pair mechanism designed by this solution may provide a transmission with periodically variable transmission ratio.
The technical solution adopted in the present invention is as follows.
A variable-ratio line gear mechanism forms a transmission pair consisting of a driving line gear and a driven line gear, of which axes intersect at an arbitrary angle. The driving line gear consists of a wheel body and line teeth, and the driven line gear consists of a wheel body and line teeth. Contact curves of the line tooth of the driving line gear and the line tooth of the driven line gear mesh in accordance with a pair of spatial conjugate curves. The driving line gear is connected with an actuator to provide an input. There are one or more line teeth on the driving line gear. The line tooth of the driving line gear meshes with the line tooth of the driven line gear by point contact. The driven line gear is connected with an output end to provide a movement or an output of force. The line tooth on the driven line gear is the one with property of variable transmission ratio. In one movement period, a plurality of transmission ratios exist, and a smooth transition among different transmission ratios can be made, resulting in a transmission with periodically variable transmission ratio.
In the above-described variable-ratio line gear mechanism, the contact curve on the line tooth of the driving line gear for meshing is a circular helix. The line tooth of the driven line gear is divided into an equal transmission ratio part and a variable transmission ratio part. There are two equations for the contact curves on the line tooth for meshing: one is an equal transmission ratio equation for realizing equal transmission ratio, and the other one is a variable transmission ratio equation for realizing variable transmission ratio.
During the transmission of the above-described variable-ratio line gear mechanism, the variable transmission ratio equation can make the transmission ratio of the line gear smoothly change from one value to another, i.e. a derivative value of transmission ratio function increases or decreases from 0 to a certain value, and then smoothly back to 0.
During the transmission of the above-described variable-ratio line gear mechanism, in order to reduce the rotation and jumpiness of the operation of said mechanism, derivatives of both the variable transmission ratio equation and the variable transmission ratio equation can transit smoothly, i.e. derivative and second derivative of the variable transmission ratio equation both increase or decrease from 0 to a certain value, and then smoothly back to 0.
Accordingly, in the above-described variable-ratio line gear mechanism, O−xyz is a Cartesian coordinate system that is arbitrarily fixed in space, wherein O is an origin of the coordinate system O−xyz, and x, y, z are three coordinate axes of the coordinate system O−xyz. A Cartesian coordinate system Op−xpypzp is determined in accordance with a position of the coordinate system O−xyz, wherein a plane xpOpzp is in a same plane as a plane xOz, a distance from a coordinate origin Op to the axis z is a, a distance from Op to the axis x is b, and an angle between the axis z and an axis zp is (π−θ). θ is an angle between angular velocity vectors of the driving and driven line gears, with 0°≤θ≤180°. Coordinate systems O1−x1y1zi and O2−x2y2z2 are respectively the coordinate systems fixed on the driving line gear and the driven line gear. During transmission, the driving line gear and driven line gear rotate around the axis z and the axis zp, respectively, and an initial meshing place of the driving line gear and the driven line gear is an initial position. At the initial position, coordinate systems O−x1y1z1 and O2−x2y2z2 coincide with the coordinate systems O−xyz and Op−xpypzp respectively. At any time, the origin O1 coincides with O, an axis z1 coincides with the axis z, the origin O2 coincides with Op, an axis z2 coincides with the axis zp, the driving line gear rotates around the axis z at a uniform angular velocity ω1, angular velocity direction of the driving line gear is a negative direction of the axis z, and an angle that the driving line gear rotates through around the axis z is φ1; the driven line gear rotates around the axis zp at a uniform angular velocity ω2, angular velocity direction of the driven line gear is a negative direction of the axis zp, an angle that the driven line gear rotates through around the axis zp is φ2, then an equation of the contact curve for the driving line gear is as follows in the coordinate system O−x1y1z1:
and then said variable transmission ratio equation is determined by the following two methods:
1) The variable transmission ratio equation smoothly transits, with an equation for its variable transmission ratio contact curve being as follows:
wherein, A and C are determined by equations
m is a helical radius of the contact curve of the driving line gear, n is a parameter of the contact curve of the driving line gear related to a pitch, with
being defined if the pitch is p, and t is a parameter, with
representing that the contact curve of one line tooth of the driving line gear is a helix of ¼ circumference. When t=−π, the line teeth of the driving line gear and driven line gear begin to mesh. When
the driving line gear rotates through ¼ circumference, and the line teeth of the driving line gear and driven line gear mesh to an end and begin to demesh. ia and ib are respectively the transmission ratio before and after some period of change process; φa and φb are respectively a start angle and an end angle of some line tooth of the driving line gear during transmission in a variable transmission ratio process, for example, when
2) Derivatives of the variable transmission ratio equation and variable transmission equation both can smoothly transit, i.e. equation for the variable transmission ratio contact curve is as follows:
Wherein, E, F and G are determined by equations
m is a helical radius of the contact curve of the driving line gear, n is a parameter of the contact curve of the driving line gear related to a pitch, with
being defined if the pitch is p, and t is a parameter, with
representing that the contact curve of one line tooth of the driving line gear is a helix of ¼ circumference. When t=−π, the line teeth of the driving line gear and driven line gear begin to mesh. When
the driving line gear rotates through ¼ circumference, and the line teeth of the driving line gear and driven line gear mesh to an end and begin to demesh. ia and ib are respectively the transmission ratio before and after some period of change process; φa and φb are respectively a start angle and an end angle of some line tooth of the driving line gear during transmission in a variable transmission ratio process, for example, when
The variable transmission ratio equations created in accordance with claims 5 and 6 may be used in the variable-ratio line gear mechanism.
The line tooth on the driving line gear obtained in the present mechanism is designed on the basis of a circular helix, and there may be one or more line teeth. The line tooth of the driving line gear meshes with the line tooth of the driven line gear by point contact. The driven line gear is connected with an output end to provide a movement or an output of force. Line tooth on the driven line gear includes multiple designs, and may be designed as the line tooth with property of variable transmission ratio according to different equations for the contact curve on the line gear. In one movement period, a plurality of transmission ratios may exist, and a smooth transition among different transmission ratios can be made.
Principle of the present invention is that: in accordance with space conjugate curve meshing theory of the line gear, contact curve equation of the line tooth of the driven line gear required by transmission with equal transmission ratio can be designed; the contact curve equation of the line tooth of the driven line gear is improved, so that the transmission ratio is a certain value when it begins to enter into meshing, and the transmission ratio becomes another value when demeshing, with the transmission ratio smoothly changing in this period, i.e. a derivative value of transmission ratio function increases or decreases from 0 to a certain value, and then smoothly back to 0, or the derivative value of the variable transmission ratio function and second derivative of the variable transmission ratio function both increase or decrease from 0 to a certain value, and then smoothly back to 0, thereby the contact curve equation of the line tooth of the driven line gear required by the transmission with variable transmission ratio being obtained.
Compared with the prior arts, the present invention has the following advantages:
1. It is able to provide a plurality of transmission ratios during a movement period of the driven line gear, and to enable smooth transitions between respective transmission ratios in accordance with movement rules.
2. The transmission only depends on the point contact between the line tooth of the driving line gear and the line tooth of the driven line gear, so as long as the accuracy of the contact curve is guaranteed, with the design being simple, the processing being convenient and the weight and bulk being smaller than that of a traditional gear with variable transmission ratio, which is more suitable for microminiature mechanical and electrical products.
3. Line tooth number of the driving line gear is at least 1, being able to provide a transmission with greater transmission ratio, and able to design the line gear pair under a condition of axes intersecting at an arbitrary angle.
The present invention is further described below in combination with the drawings, but the implementations of the present invention are not limited hereto.
1. A variable-ratio line gear mechanism described in the present invention comprises a driving line gear and a driven line gear. Coordinate systems of the driving line gear and driven line gear, which are shown in
As shown in
O1−x1y1z1 and O2−x2y2z2 are respectively the coordinate systems fixed on the driving line gear and the driven line gear. During transmission, the driving line gear and driven line gear rotate around the axis z and the axis zp, respectively.
2. The variable-ratio line gear mechanism is shown in
As shown in
An equation designing the above-described line teeth with equal transmission ratio and variable transmission ratio is determined by the following equations.
The line tooth of the driving line gear is determined by its contact curve equation. The equation of the contact curve in O1−x1y1z1 is:
The line tooth of the driven line gear is determined by its contact curve equation. The driven contact curve is calculated by the contact curve of the line tooth of the driving line gear and a space curve meshing theory, and its equation in O2−x2y2z2 is as follows:
When the transmission ratio is i, the contact curve equation on the line tooth with equal transmission ratio is:
When the transmission ratio is ia to ib, there may be two forms of the contact curve equation on the variable-ratio line gear mechanism, one is:
wherein, A and C is determined by:
The other one is:
wherein, E, F and G are determined by:
The physical meaning of each parameter in the equations is as follows:
m is a helical radius of the contact curve of the driving line gear;
n is a parameter of the contact curve of the driving line gear related to a pitch, with
being defined if the pitch is p;
t is a parameter, with
representing that the contact curve of one line tooth of the driving line gear is a helix of ¼ circumference. When t=−π, the line teeth of the driving line gear and driven line gear begin to mesh; when
the driving line gear rotates through ¼ circumference, and the line teeth of the driving line gear and driven line gear mesh to an end and begin to demesh;
a and b are position parameters of the driving line gear and driven line gear, as shown in
θ is an angle parameter of the driving line gear and driven line gear, as shown in FIG. 1;
ia and ib are two transmission ratios which are required;
φ1 is a rotation angle of the driving line gear;
φ2 is a rotation angle of the driven line gear;
φa and φb are respectively a start angle and an end angle of some line tooth of the driving line gear during transmission in a variable transmission ratio process, for example, when
3. In accordance with equations (1) to (3), it is possible to establish a line tooth entity. The line tooth entity only needs to meet the strength requirement, and line tooth entity itself does not have any specific shape requirement. As shown in
Number | Date | Country | Kind |
---|---|---|---|
2015 1 0497584 | Aug 2015 | CN | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/CN2015/100289 | 12/31/2015 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2017/024749 | 2/16/2017 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
2585971 | Sloane | Feb 1952 | A |
3178959 | Schwesinger | Apr 1965 | A |
4326431 | Stephenson | Apr 1982 | A |
5170677 | Yonekura | Dec 1992 | A |
5222405 | Reynolds | Jun 1993 | A |
5251507 | Takahara et al. | Oct 1993 | A |
20110132117 | Yaeger | Jun 2011 | A1 |
Number | Date | Country | |
---|---|---|---|
20170343095 A1 | Nov 2017 | US |