MX2013014987A - Multi-staged centric flat speed reducer with magnetic coupling and torque limit coupled to heliostat mirrors. - Google Patents

Abstract

The present invention is a device for reducing the speed of an electric engine for actuating a mechanism intended to follow the path of the sun to which a heliostat is subordinated. The device includes one or several reduction steps, depending on the needs. One stage of the mechanism contains an innerly toothed gear, also called crown, in which other outer toothed gear is orbiting as well as a crank for the exit movement. The crown is fixed to the carcass of the transmission and the coupling being eccentric with a mechanism formed by permanent magnets.

Description

PLANOCENTRIC SPEED REDUCER OF MULTIPLE STAGES WITH MAGNETIC COUPLING AND LIMIT OF TORQUE COUPLED TO HELIÓSTATOS MIRRORS BACKGROUND OF THE INVENTION Systems that take advantage of solar radiation use mirrors with flat or curved surfaces to capture solar energy. In order to capture the maximum amount of solar energy, the mirrors must move along the path that the sun describes on the surface of the earth. This movement is continuous throughout the day but its speed is very low. In order to achieve that the heliostats (systems that collect solar radiation) move at the speed of the sun, it requires automated systems that move the mirrors at very low speed. To achieve the automation of the movement of the heliostat mirrors, electric motors with speed control and a mechanism that connects them to the heliostat are used. Tracking the path of the sun from the surface of the earth is achieved by combining two rotations around two orthogonal axes that are called azimuth and elevation.

There are many alternatives to transform the rotary motion of an electric motor to move the heliostat mirrors and follow the path of the sun. However, to achieve the high speed reduction required by the heliostat, it is necessary to use high reduction transmissions. The high reduction transmissions that use the least number of components are the planocentric transmissions, which take advantage of the cycloidal movement of a gear with teeth on its outside that orbit inside a gear with internal teeth. The efficiency of these transmissions depends on the ability to convert the cycloidal movement, which by its nature is eccentric and requires special mechanisms to convert the movement of translation into a rotation movement. To achieve this, it has also developed various mechanisms that allow them.

Sang-Hyun Park (2005) in his doctoral thesis presents an analysis of the different alternatives for using the cycloidal movement in the transmission of movement. Jáuregui and López (1992) determine the design criteria for planocentric transmissions with high speed reduction. The record of this type of transmissions dates from the nineteenth century, Regan (1895) (US 546,249) presents the design of a transmission in which an external gear orbits inside an internal one, the characteristic of its design is the difference in diameters between The two gears are very small, achieving that the external gear orbits inside the internal gear and that the angular speed associated with the translation is very low compared to the rotation speed of the gear itself. In this design the inner gear remains fixed. Several designs emerged from this patent. Harrison (1910) (US 978,371) patented a transmission in which he used an Oldham type coupling to convert the movement of the inner gear orbit into a rotary movement concentric with the input shaft. Hatlee (1916) (US 1, 192,627) patented the form of gears including pure friction discs. Wildhaber (1926) (US 1, 601, 750) was the first to patent the circular profile in the teeth. Novikov in 1956 (U.S.S.R. No. 109750) reinvented the same concept. Fliesberg (1935) (US 2,049,696) explicitly describes the design of the teeth in the cycloidal movement and says that it is impossible to have small differences between the number of teeth of the internal gear and the external gear if the teeth are designed with standardized dimensions. Braren (1928) (US 1,694,031) patented a transmission using cycloidal gears. Perry (1939) (US 2,170,951) patented a stacking system of planocentric transmissions for further reduction. Jackson (1949) (US 2,475,504) protected in his invention the mechanism of coupling between the internal gear (orbit) and the output shaft. Sundt (1962) (US 3,037,400) patented the design of special teeth to achieve large reductions in speed from the principle of taking advantage of the orbit of an external gear coupled to an internal gear whose diameter difference is very small. Rouverol (1976) (US 3), 946,621) protects the design of a gear system with cycloidal movement. Osterwalder (1977) (US 4,023,441) protected in his patent the counterweight formed by two orbiting gears. Sfredda (1978) (US 4,112,788) protects a torque transmission with a mechanism that facilitates the transmission and reduces the force on the teeth of the gears. Shafter (1984) (US 4,452,102) patented a transmission based on a pair of internal gears that orbit, the gears are connected through an Oldham-type joint and an arrangement of ball bearings. Rennerfelt (1991) 's tooth design (US 5,030,184) protected in its patent the design of the gears of a planocentric transmission to avoid interference between the teeth of the internal gear and the external gear. Koriakov-Savoysky et al. (1996) (US 5,505,668) protected the design of a transmission whose teeth are not formed with involute curves. Schroeder (1999) (US 5,951,427) invents a planocentric transmission with hypocycloidal gears in which it proposes to eliminate the bearings and remove the bolt mechanism. Yao et al. they protected a method for the optimal design of a permanent magnetos transmission system so that conventional mechanical elements are not used. Smith (2001) (US 6,222,292) protected a magnetic copy for coupling rotary equipment. Gery (2002) (US 6,841,910) patented a magnetic copy consisting of two discs with permanent magnets with north and south poles in a configuration by opposite pairs so that torque is transmitted without there being mechanical contact between the parts in rotation. A similar development was protected by Wise (2007) (US 7,312,548) whose invention consists in the arrangement of two discs with radially distributed magnets that transmit the movement.

There is another group of inventions in which magnets are applied instead of mechanical gears to achieve speed reduction between two axes. Huber et al. (2010) patented a magnetic transmission in which there is a rotor with a set of magnets and a circular stator with electromagnets, when the electromagnets are switched the speed ratio is regulated. Bright et al. (2013) (US 8,546,988) protected the design of a transmission based on magnetic gears in which the mobile gear contains a series of radially organized magnets, a fixed gear containing another arrangement of magnets and an intermediate element (interpolo) between the two gears that regulate the speed ratio through a winding in which a controlled current is passed. Kuritani et al. (2013) (US 8,575,803) patented a magnetic clutch formed by an arrangement of three axially separated disks with radially distributed magnets, each disk having an equal number of magnets. Every third magnet has a different polarity from the adjacent magnets. Montgomery et al. (2013) (US 8,593,026) developed a transmission with variable speed ratio through the use of discs with radial arrangements of magnets, between the two discs of magnets an interpolo disk is placed that modifies the ratio of active magnets, in this way they can be configure different speed ratio modifying the ratio of magnets in the interpoles.

After reviewing the previous technique, the invention arises in order to achieve a mechanism that prevents damage to the azimuth transmission system of the heliostat by having a magnetic coupling between the gear and the crank, this in order that when, for some reason , the output shaft does not rotate the torque force will only separate the coupling magnetic without causing damage to the rest of the transmission system. This preventive system incorporated into the mechanism is what differentiates the invention from the rest of the existing technique.

OBJECT OF THE INVENTION The object of the present invention is a device that allows to reduce the speed of an electric motor (or other system that produces rotary movement) to drive the tracking mechanism to the movement of the sun of a heliostat. The transmission can have one or several stages of reduction. Each stage of reduction consists of a gear with internal teeth, or crown, in which another gear engages with external teeth. The crown is fixed to the casing of the transmission, which allows the gear to generate a cycloidal movement when rotating on its own axis. The cycloidal movement generates an eccentric trajectory whose speed is proportional to the difference of the radii of passage divided by the radius of the orbiting gear. To be able to convert the movement of translation of the orbit in a simple rotary movement requires an eccentric coupling, this eccentric coupling is made with a mechanism formed by permanent magnets.

DESCRIPTION OF THE INVENTION This invention relates to a planocentric transmission of one or several stages, each stage is formed by a fixed gear (2) with internal teeth and a gear with external teeth (7) that orbit inside. The relationship between the input speed (3) and the output speed is determined from the ratio of radii: gear pitch radius speed ratio radius of pitch of the crown - pitch radio The inner gear produces a cycloidal movement around the input shaft (1) the cycloidal movement of the center of the gear (3) is coupled through the magnet (1). In order to extract the power that enters the gear, the magnet (1) is magnetically linked with the output magnet (1) whose polarity is opposite to that of the magnet (1). The output movement is achieved by the magnetic coupling between the gear (7) and the crank (5) held together by the magnetic force that is formed between the magnets (1). To maintain the magnetic force, the exit handle has a groove (6), whose length is greater than the eccentricity of the gear (7), the magnet (1) has the freedom to slide along the groove and transmits the torque to the output shaft ( 3), to balance the movement the gear has a counterweight. The shape of the teeth of the gears can have various forms: involute profile, cycloidal profile or any other form that allows to generate the cycloidal trajectory of the gear inside the crown.

The crown (2), the gear (7), the crank (5) and the output shaft (3) are made of non-magnetic materials (plastic, aluminum, zinc-aluminum, non-magnetic steels, etc.). The magnets 1 are constructed of ferromagnetic materials, neodymium or any material that has the property of maintaining magnetism permanently.

To increase the reduction ratio, more than one reduction stage can be coupled. Each stage can have a different speed ratio by individually adjusting the radii of the crown (2) and the gear (7). Another eccentric gear (8) is mounted on the output shaft that orbits the crown of the next stage (9). The second gear engages a second crank (10) through two magnets (11) similar to those of the first stage. The length of the slot of the exit crank depends on the speed reduction of each stage.

The magnetic coupling between the gear (7) and the output handle (5) serves as a torque control. If for some reason the torque applied to the transmission exceeds the magnetic force that exists between the magnets (1) the gear of the crank is decoupled, in this way the torque is limited protecting the transmission elements or the elements that are connected to it.

The input shaft of the transmission (3) (with all its stages) is coupled with an electric motor, or other movement system, and the output shaft (crank) (5) is connected to the mechanism that moves the mirrors of the heliostat. The mechanism (12) is placed in the middle part of the base of the heliostat.

DESCRIPTION OF THE FIGURES The invention is illustrated in the following figures: Figure 1 is a schematic representation of the gear arrangement and the crown.

Figure 2 is a schematic representation of the general arrangement of the transmission stage formed by the fixed crown, the gear with cycloidal movement, the magnetic coupling and the output handle Figure 3 is a schematic representation of the arrangement of various stages in tandem to have a greater reduction ratio.

Figure 4 is a perspective representation of the assembly arrangement of the transmission in a heliostat.

Claims (8)

CLAIMS Having sufficiently described the invention, I consider it a novelty and therefore claim as my exclusive property contained in the following clauses:

1. A transmission to move mirrors that follow the movement of the sun, which is characterized by having: a fixed gear (called crown and with teeth inside), a moving eccentric gear (with teeth on the outside) that orbits inside the crown describing a cycloidal movement, a magnetic coupling that transmits the movement of the gear's orbit, a crank that connects the gear's orbit with the output shaft and the mechanical elements that connect the axes to the housing.

2. A transmission to move mirrors that follow the movement of the sun described in clause 1 characterized by the crank that has one or more magnets placed in radial grooves that make the magnetic coupling with the gear.

3. A transmission to move mirrors that follow the movement of the sun described in clause 1, characterized by an eccentric gear with external teeth that orbit inside the crown and that has one or more fixed magnets, placed at a distance greater than the eccentricity of the gear, which are coupled magnetically with their pairs located on the crank.

4. A transmission to move mirrors that follow the movement of the sun described in clause 1 characterized by a fixed gear, or crown, whose internal teeth have a geometry that allows cycloidal movement of the eccentric gear, whose profile is built with an involute curve, cycloidal or circular.

5. A transmission to move mirrors that follow the movement of the sun described in clause 1 characterized by an eccentric gear with teeth on the outside constructed with a complementary to the teeth curve of the fixed gear in such a way that a conjugate movement between the two curves

6. The eccentric gear described in clause 5 that is characterized by being mounted on an eccentric arm through a bearing or bearing and having a counterweight that balances the centrifugal forces produced by the eccentricity.

7. The transmission described in clauses 1, characterized in that it can be mounted in tandem with other similar transmissions to increase the speed reduction ratio

8. The transmission described in clauses 1, characterized in that it is coupled to the mechanism that hold the mirrors of a heliostat and that allows to follow the movement of the sun.