1. Field of the Invention
The invention relates to a transmission device, more particularly to a transmission device suitable for rotation speed control.
2. Description of the Related Art
Referring to
When the servo motor 12 drives rotation of the driving gear 111, power is transmitted to the driven gear 112 through the transmission gears 113 and is outputted through rotation of the driven gear 112. Angular displacement of the driven gear 112 alters the resistance of the potentiometer 14 and results in a change in the analog feedback voltage. The A/D converter 15 generates the digital feedback signal from the analog feedback voltage and provides the digital feedback signal to the controller 13. Based on the digital feedback signal, the controller 13 calculates the angular displacement and position of the driven gear 112, and is thus able to control the servo motor 12 for correcting the angular position of the driven gear 112 to meet requirements.
However, due to constant contact between a wiper and a resistance element, wear of the potentiometer 14 is inevitable. Moreover, ambient factors, such as temperature fluctuations, dust, etc., can affect the resistance change of the potentiometer 14. The potentiometer 14 is thus not suitable for precision servo control applications. In addition, the transmission device 1 requires the A/D converter 15 for feedback signal conversion, which results in higher costs
Therefore, the main object of the present invention is to provide a transmission device that is suitable for high precision applications.
Another object of the present invention is to provide a transmission device that has a relatively simple construction and that can be fabricated at a relatively low cost.
According to the present invention, a transmission device comprises a power output unit and a non-contact type sensing unit. The power output unit includes a power output member that is rotatable about an axis, and has at least one sensed portion that is co-rotatable with the power output member about the axis. The non-contact type sensing unit detects said at least one sensed portion and generates a sensor output from which angular displacement and position of the power output member can be calculated.
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:
Before the present invention is described in greater detail with reference to the accompanying preferred embodiments, it should be noted here in that like elements are denoted by the same reference numerals throughout the disclosure.
Referring to
The power output unit 2 includes a driving gear 21, a driven gear 22, and a plurality of transmission gears 23 meshing with the driving gear 21 and the driven gear 22 for power transmission. The driven gear 22 serves as a power output member in this embodiment, is rotatable about an axis, and is provided with a plurality of sensed portions 221 that are spaced apart radially from the axis and that are spaced apart angularly from each other, and a plurality of non-sensed portions 222, each of which is disposed between an adjacent pair of the sensed portions 221.
The servo motor 3 serves as a driving member in this embodiment, is coupled to the driving gear 21, and is used to drive rotation of the driving gear 21. The programmable controller 4 is connected to the servomotor 3 to control operation of the same.
The non-contact type sensing unit 5 is used to detect the sensed portions 221 and to generate a sensor output from which angular displacement and position of the driven gear 22 can be calculated. The non-contact type sensing unit 5 is connected to the programmable controller 4 and provides the sensor output to the programmable controller 4.
In this embodiment, the non-contact type sensing unit 5 includes an optical sensor 51 capable of transmitting and receiving light waves. The sensed portions 221 are parts of the driven gear 22 capable of reflecting the light waves transmitted by the optical sensor 51 back to the optical sensor 51, where as the non-sensed portions 222 are in the form of through holes having hole axes parallel to the axis.
When the servo motor 3 drives the driving gear 21 to rotate, power is transmitted to the driven gear 22 through the transmission gears 23, and is outputted through rotation of the driven gear 22. When the driven gear 22 rotates, light waves from the optical sensor 51 either pass through the non-sensed portions 222 or are reflected by the sensed portions 221 back to the optical sensor 51. The sensor output of the optical sensor 51 is thus in the form of a pulse train and is provided to the programmable controller 4. Based on the sensor output, the programmable controller 4 calculates the angular displacement and position of the driven gear 22, and is thus able to control the servo motor 3 for correcting the angular position of the driven gear 22 to meet requirements.
It is noted that, in other embodiments of this invention, the sensed and non-sensed portions 222, 221 may be provided on the driving gear 21 instead of the driven gear 22.
When the servo motor 3 drives the driving gear 21 to rotate, power is transmitted to the driven gear 24 through the transmission gears 23, and is outputted through rotation of the driven gear 24. When the driven gear 24 rotates, the magnetic field sensor 52 detects the sensed portions 242 intermittently. The sensor output of the optical sensor 51 is thus in the form of a pulse train and is provided to the programmable controller 4. Based on the sensor output, the programmable controller 4 calculates the angular displacement and position of the driven gear 24, and is thus able to control the servo motor 3 for correcting the angular position of the driven gear 24 to meet requirements.
When the servo motor 3 drives the driving gear 21 to rotate, power is transmitted to the driven gears 25 through the transmission gears 23, and is outputted through rotation of the driven gears 25. When the driven gears 25 rotate, the hall sensor 54 detects a parallel magnetic flux component of the sensed portion 26, and accordingly generates a sensor output that is provided to the programmable controller 4. Based on the sensor output, the programmable controller 4 calculates the angular displacement and position of the driven gears 25, and is thus able to control the servo motor 3 for correcting the angular position of the driven gears 25 to meet requirements.
In sum, since the transmission device of this invention uses the noncontact type sensing unit 5 instead of a potentiometer, service life and precision of the transmission device can be enhanced as compared to the aforementioned prior art. Moreover, since there is no need for feedback signal conversion when the optical sensor 51, the magnetic field sensor 52 or the hall sensor 54 is utilized, the A/D converter required in the conventional transmission device can be eliminated to result in a simpler construction and lower manufacturing costs.
While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.