COOLING FEATURE”

FIELD OF THE INVENTION

The present invention relates to a stepper motor based linear actuator with cooling feature. More particularly, the present invention is directed towards a stepper motor based linear actuator that is equipped with a liquid submerged sealing jacket for providing coolant to the motor during operation that prevents overheated and have application in thermal expansion valves.

BACKGROUND OF THE INVENTION

Stepper motors cause a predictable amount of motion, usually rotating, in response to a number of pulses introduced into the drive circuit that affect the motion by causing appropriate current changes in the motor windings. Such motors are used in large number of applications including intake systems, idle air control valve, thermal expansion valves, exhaust systems, suspension control and meter display drive and alike. Can stack stepper motor based linear actuator is one of the type of stepper actuator that is responsible for developing a force with precise motion through a straight line. These motors are extensively used at high volume in various industries due to its high performance and produce high torque at a given motor winding current. The higher motor winding current causes higher heating of the motor.

However, in the past, many problems have been encountered when trying to implement a stepper motor in the drive means. One such problem is the tendency of the stepper motor rotor to vibrate or hunt around the final step position when stopped. This vibration is mainly the result of rotor and load inertia. Such undesirable vibrations in the motor are often unacceptable since the attenuation of these vibrations requires a lot of time. The uneven vibration and oscillation cause heating problem in stepper motor, therefore it is required to prevent the motor from getting overheated during its operation.

US6756705B2 discloses a linear stepper motor, comprising; an annular stator structure; an axially extending, cylindrical, permanent magnet shaft extending coaxially through said annular stator structure; and the axially extending, cylindrical, permanent magnet shaft having a smooth external surface along a portion thereof with axially alternating N and S poles defined circumferentially in an outer periphery of the portion of the axially extending, cylindrical, permanent magnet shaft. This invention also provides a method of magnetizing the shaft of such a motor and a fixture and method of manufacturing the fixture thereof. Although this invention provides the linear motion for various industrial application, but does not provide any means for preventing the stepper motor from getting overheated.

US20150249377A1 discloses a linear stepping motor having anti-rotating screw, comprising a stator, a rotor, a front-end cover, a rear-end cover and a screw, characterized in that the screw is an anti-rotating screw. This invention aims on efficiency and working service life but does not provide any means for preventing the stepper motor from getting overheated.

Therefore, in order to overcome the aforementioned drawback, there exists a need to develop highly reliable stepper motor based linear actuator incorporated with liquid submerged sealing jacket to avoid the motor from getting overheated during its operation.

OBJECT OF THE INVENTION

The main object of the present invention is to provide a stepper motor based linear actuator that is used for precise motion.

Another object of the present invention is to provide a sealing jacket in the stepper motor to separate the rotor assembly and stator assembly.

Yet another object of the present invention is to circulate the coolant liquid inside the rotor assembly of motor to prevent the motor form getting overheated during its operation.

Still another object of the present invention is to develop a stepper motor based linear actuator with cooling feature that is highly reliable, cost effective and user friendly.

SUMMARY OF THE INVENTION The present invention is envisioned to a stepper motor based linear actuator incorporated with a sealing jacket for separating stator assembly from rotor assembly and providing circulation of a coolant liquid into the motor when the operating temperature of motor exceeds threshold value thereby preventing the motor from the getting overheated.

In an embodiment, the present invention relates to a stepper motor based linear actuator with cooling feature, comprising of a housing, a stator assembly, a rotor assembly, a sealing jacket for separating stator assembly from rotor assembly, wherein the liquid upon exceeding threshold temperature, circulates inside the sealing jacket and thus preventing the motor from any damages caused by excessive amount of generated heat, wherein, the housing accommodates plurality of motor components such as stator assembly, rotor assembly and sealing jacket; the sealing jacket is submerged with a coolant liquid and the coolant liquid used herein is selected from but not limited to R134a and R1234yfa that flows inside the rotor assembly without affecting stator assembly for cooling the motor.

BRIEF DESCRIPTION OF THE DRAWINGS

The object of the invention may be understood in more details and more particularly description of the invention briefly summarized above by reference to certain embodiments thereof which are illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the appended drawings illustrate preferred embodiments of the invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective equivalent embodiments.

Fig. 1 represents an exploded view of stepper motor based linear actuator with cooling feature in accordance with an embodiment of the present invention.

Fig. 2 represents a side view of stepper motor based linear actuator with cooling feature in accordance with an embodiment of the present invention.

Fig. 3 represents a cross-sectional view of stepper motor based linear actuator with cooling feature in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

Many aspects of the invention can be better understood with references made to the drawings below. The components in the drawings are not necessarily drawn to scale. Instead, emphasis is placed upon clearly illustrating the components of the present invention. Moreover, like reference numerals designate corresponding parts through the several views in the drawings. Before explaining at least one embodiment of the invention, it is to be understood that the embodiments of the invention are not limited in their application to the details of construction and to the arrangement of the components set forth in the following description or illustrated in the drawings. The embodiments of the invention are capable of being practiced and carried out in various ways. In addition, the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

The present invention is directed towards a stepper motor based linear actuator that develops a force with precise linear motion through a straight line and prevents the motor from getting overheated by allowing circulation of coolant liquid in the rotor assembly whenever needed. Moreover, the present invention is having applications in thermal expansion valves where precise motion with force is required.

In main embodiment, the present intention relates to a stepper motor 10 based linear actuator with cooling features comprises of a housing 1, a stator assembly 2, a rotor assembly 3, and a sealing jacket 4. The sealing jacket 4 is provided between the stator assembly 2 and the rotor assembly 3. The sealing jacket 4 is having a hollow cylinder shape. The sealing jacket 4 is having a uniform and fine thickness lying in the range of 0.1 mm to 1 mm and the coolant continuously flows inside the sealing jacket 4. The sealing jacket 4 is made of a solid sheet of a waterproof material including but not limited to steel or thermoplastic. The stepper motor 10 based linear actuator develops a force with precise motion through a straight line and having applications with the thermal expansion valve. The sealing jacket 4 is assembled to a mating product through a welding process. A coolant liquid passes through the rotor assembly 3 of the motor without causing any harm to the stator assembly 2 as the sealing jacket 4 separate the stator assembly 2 from the rotor assembly 3. The coolant liquid comprises a R134a and R1234yfa. Further, the stepper motor 10 based linear actuator incorporated with liquid submerged sealing jacket 4 to prevent the stepper motor 10 from getting overheated during its operation.

Fig. 1 and Fig. 2, shows the exploded and side view of the stepper motor 10 based linear actuator is illustrated. The present invention provides a stepper motor 10 based linear actuator with cooling feature, comprising of a housing 1; a stator assembly 2; a rotor assembly 3; and a sealing jacket 4 for separating stator assembly 2 from rotor assembly 3; wherein the sealing jacket 4 is a hollow cylinder and made of a solid sheet of a waterproof material of uniform and fine thickness and the housing 1 accommodates the components such as stator assembly 2, rotor assembly 3 and sealing jacket 4 is depicted in Fig. 2.

Now referring to Fig. 3, a cross-sectional view of the stepper motor 10 based linear actuator is illustrated. Said stepper motor 10 based linear actuator comprises of a housing 1 for providing accommodation to plurality of components such as a stator assembly 2; a rotor assembly 3; a sealing jacket 4 for separating stator assembly 2 from rotor assembly 3. The sealing jacket is submerged in the coolant liquid and prevents the motor from getting overheated. So, depending upon coolant temperature, motor temperature is controlled. Upon exceeding a threshold temperature, when the coolant liquid circulates inside the sealing jacket 4 it prevents the stepper motor 10 from any damages caused by excessive amount of generated heat.

The present invention provides a highly reliable stepper motor based linear actuator that develops a force with precise motion through a straight line and having applications with the thermal expansion valve where precise motion is required with force. During the operation of linear actuator, the stepper motors emit losses in the form of heat. The production of excessive heat in the motor damages the rotor and stator winding and as a result of which the motor stop working. Therefore, in order to mitigate such conditions, the present invention provides a circulating path for coolant liquid to flow in the rotor assembly and keeps the motor temperature under rated value. The coolant liquid including but not limited to R134a and R1234yfa passes through the rotor assembly of the motor without causing any harm to the stator assembly as the sealing jacket separate the stator assembly from the rotor assembly. The sealing jacket is completely submerged in the liquid and consists of a hollow cylinder with a fine thickness and is assembled to mating product through welding. The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principals of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.