Patent Application
20240234070
The present disclosure is directed to a filament for an X-ray generator. More particularly, the present inventive concept is directed to a method for manufacturing a filament which is capable of concentrating X-ray beam energy to obtain high-efficiency dose and good resolution, a filament manufactured by said method, and an X-ray tube having said filament.
An X-ray system which is capable of imaging the inside of the human body in a non-invasive way is commonly used for diagnosis and treatment in medical institutions, and has been developed to enable more convenient and precise use owing to the development of advanced technology. In addition, the X-ray system is used to observe the internal shape of a subject not only in the medical field but also in the non-destructive examination field. An X-ray system uses the principle that X-rays irradiated to a subject are absorbed differently according to a difference in density of substances inside the subject. Since a tissue with a high density absorbs more X-rays than a tissue with a low density, when the transmitted X-rays are observed in an X-ray photosensitive film or a detector after X-rays are transmitted through a living tissue, tissues with high density appear darker than tissues with low density. Accordingly, the structure of internal tissues of the subject can be clearly distinguished by the density difference.
In general, such an X-ray system may include an X-ray tube that generates X-rays, a voltage generator that generates and supplies a high voltage required for the X-ray tube, an X-ray detector that detects X-rays passing through a subject, and a controller that controls the operation of the X-ray tube and the voltage generator. Here, the X-ray tube and the voltage generator constitute an X-ray generator.
The X-ray generator generates X-rays by providing a predetermined signal to the X-ray tube according to tube voltage, tube current, irradiation time, etc. calculated appropriately from the voltage generator, and colliding thermal electrons emitted from a filament (cathode) of the X-ray tube according to said signal provided from the voltage generator on a target (anode) at high speed. That is, X-rays are generated in a way that a current flows from the voltage generator to the filament of the X-ray tube to heat the filament, electron emission is induced in the heated filament to emit electrons around the filament, and the emitted electrons move toward the target and collide with the target due to a strong electric field caused by a high voltage difference.
A filament of an X-ray generator for inducing electron emission is shown in
However, there is a problem that a filament having an emitter with a conventional shape, such as coil or spiral shape as shown in
Korean Application Publication No. 10-2022-0007379
To solve the above-mentioned problems, the present inventive concept provides a method for manufacturing a filament which is capable of concentrating X-ray beam energy to obtain high-efficiency dose and good resolution.
Also, the present inventive concept provides a method of manufacturing a filament which is capable of concentrating X-ray beam energy by changing a shape of an emitter.
Further, the present inventive concept provides a filament, a method for manufacturing the same, and an X-ray tube including the same.
According to an embodiment of the present inventive concept, a method for manufacturing a filament includes the steps of inserting and bonding an electrode having a desired length into a through-hole of a plate-shaped base to form a first part: bonding a wire having a desired length to one surface of a plate-shaped disc to form a second part: and bonding the electrode of the first part and the wire of the second part to form a filament.
The step of forming a first part and the step of forming a second part are performed simultaneously or sequentially.
The base is larger and thicker than the disc, and the electrode has a larger line width than the wire.
The step of forming a first part includes the steps of providing a plate-shaped base with a through-hole and an electrode having a desired length: inserting the electrode into the through-hole of the base and providing a brazing filler in a bonding portion: and carrying out brazing at a desired temperature to bond the base and the electrode.
The brazing process is carried out by increasing a temperature to a melting point of the brazing filler in a step-wise manner.
The brazing process includes the steps of introducing a coupled entity of the base and the electrode into a furnace: increasing a temperature of the furnace from room temperature to a first temperature at a desired ramp-up rate (a first heat-up step): heating the resulting product to the first temperature for a desired time to remove residual organic matters (a burn-out step); increasing the furnace temperature from the first temperature to a second temperature at a desired ramp-up rate (a second heat-up step); maintaining the second temperature for a desired time (a preheating step): increasing the furnace temperature from the second temperature to a third temperature at a desired ramp-up rate (a third heat-up step): carrying out brazing at the third temperature for a desired time to bond the base and the electrode (a brazing step); lowering the furnace temperature from the third temperature at a desired ramp-down rate (a furnace cooling step): and withdrawing a first part that the base and the electrode are bonded and cooling the first part in air (an air cooling step).
The step of forming a second part includes the steps of providing a wire having a desired length and a plate-shaped disc: and placing the wire on one surface of the disc and bonding the disc and the wire using a micro-spot welding process.
The electrode of the first part is bonded to the wire of the second part using a micro-spot welding process.
The electrode is bonded to the wire by aligning the center of the base with the center of the disc.
According to another embodiment of the present inventive concept, a filament includes a plate-shaped base having a desired thickness: an electrode provided through at least two regions of the base: a wire connected to one end of the electrode: and a plate-shaped disc connected to the other end of the wire that is opposite to one end connected to the electrode.
The base, the electrode, the wire and the disc are made of different materials.
The base is larger and thicker than the disc, and the electrode has a larger line width than the wire.
The center of the base is aligned and bonded with the center of the disc.
According to another embodiment of the present inventive concept, an X-ray tube includes a filament configured to emit electrons by the supply of power: a target configured to receive the electrons from the filament and emit X-rays: a body configured to seal the filament and the target while facing each other: and a cap configured to emit heat in close contact with the target, wherein the filament includes a plate-shaped base having a desired thickness: an electrode provided through at least two regions of the base: a wire connected to one end of the electrode: and a plate-shaped disc connected to the other end of the wire that is opposite to one end connected to the electrode.
The target has a shape inclined in a direction that X-rays are emitted.
The centers of the base, the electrode and the target are together aligned.
A filament according to the embodiments of the present inventive concept is characterized by passing an electrode through a plate-shaped base having a desired thickness, connecting a wire to one region of the electrode, and connecting a plate-shaped disc to an end of the wire. At this time, the centers of the plate-shaped base and the plate-shaped disc are aligned with each other and the center of a target. In addition, the filament according to the embodiments of the present inventive concept is manufactured by bonding the base and the electrode by high-temperature brazing, and bonding the wire and the disc, and the electrode and the wire by micro-spot welding.
A plate disc-shaped filament according to the present inventive concept can concentrate X-ray beam energy in a narrow region of a target compared to the prior art, and thus high-efficiency dose and good resolution can be obtained. That is, when a conventional spring-shaped filament is used, X-ray beam energy is not concentrated in a narrow region of a target and spreads widely. In contrast, the plate disc-shaped filament according to the present inventive concept can concentrate X-ray beam energy in a narrow region of a target compared to the conventional filament, and thus high-efficiency dose and good resolution over the prior art can be obtained.
Hereinafter, the embodiments of the present inventive concept will be described in detail with reference to the accompanying drawings. However, the present inventive concept is not limited to the embodiments disclosed below and may be implemented in many different forms. It should be understood that these embodiments are provided only to complete the disclosure of the present inventive concept, and to fully inform those skilled in the art the scope of the present inventive concept. In order to clearly express various layers and each region in the drawings, a thickness is enlarged. In the drawings, the same reference numerals refer to the same elements.
Now, referring to
Hereinafter, the filament according to an embodiment of the present inventive concept will be described in more detail for each element.
The base 110 is configured to fix the disc 140 facing a target and fix the filament within an X-ray tube. That is, in order for electrons generated from the filament to move toward the target due to a high voltage, the filament must be securely fixed inside the X-ray tube, and a side opposite to the target must be blocked. To this end, the base 110 of the filament is provided within the X-ray tube spaced apart from the target. Also, the base 110 has through-holes through which the electrode 120 passes in two or more regions. Preferably, the base 110 has two through-holes formed to be spaced apart from each other by a desired distance based on its central point, and the electrode 120 is inserted and fixed through the through-holes. That is, since the electrode 120 is inserted and fixed through the through-holes of the base 110, the power may be supplied to the filament from the outside while the filament is present inside the X-ray tube. The base 110 may be made of a ceramic material and may have a circular plate shape having a desired thickness. The base 110 may have a double plate shape including a first plate and a second plate as shown in
The electrode 120 is inserted into and fixed to the base 110 through the through-hole. The electrode 120 is connected to an external voltage generator to apply a current to the disc 140 connected to the electrode 120, so that thermal electrons may be generated from the disc 140. The electrode 120 may be made of a metallic material which is different from the base 110. For example, the electrode 120 may be made of a material that conducts electricity well such as copper, or may be made of Kovar. According to an embodiment of the present inventive concept, the electrode 120 may be made of Kovar, an alloy of iron, nickel, and cobalt, which has properties similar to ceramic as the material of the base 110, and has a coefficient of thermal expansion similar to that of glass at a low temperature. Also, the electrode 120 may have a shape in which an upper portion of the base 110 is bent. That is, as shown in
The wire 130 may be provided to connect the electrodes 120 and the disc 140. Also, the electrodes 120 may be directly connected to the disc 140 without the wire 130 by bending two electrodes 120 inward. It is preferable to connect the electrodes 120 to the disc 140 through the wire 130 in consideration of a distance between two electrodes 120, a size of the disc 140, etc. The wire 130 is thinner than the electrodes 120, and may be formed of the same or a different material as the electrodes 120. For example, the wire 130 may be formed of tungsten or tungsten alloys. As the tungsten alloy, an alloy of tungsten and rhenium such as Tungsten 97% Rhenium 3% alloy may be used. The wire 130 may be made of two separate parts, or as a single elongate part. That is, two wires 130 may be respectively extended from the distal ends of two electrodes 120 and may be connected to a lower surface of the disc 140. Alternatively, both distal ends of one wire 130 may be connected to the distal ends of two electrodes 120 with its central portion bent and may be connected to a lower surface of the disc 140. According to an embodiment of the present inventive concept, one wire 130 may be bent to be connected to the electrodes 120 and the disc 140. In this case, the wire 130 may be bonded to the electrodes 20 and the disc 140 by micro-spot welding.
The disc 140 may be provided in the form of a plate having a desired thickness. The disc 140 may be provided in a circular plate shape having a size and a thickness smaller than that of the base 110. One surface (lower surface) of the disc 140 is bonded to the wire 130, and the other surface (upper surface) opposite to this surface faces the target. The disc 140 may be made of a metallic material such as Ta. Here, the center of the disc 140 may be aligned with the center of the base 110. That is, an X-ray beam must be focused on the target for high-efficiency dose and good resolution. To this end, the center of the disc 140 and the center of the target must be aligned. According to the present inventive concept, the centers of the base 110, the disc 140 and the target are aligned to concentrate the X-ray beam. The size of the disc 140 and the length of the wire 130 are major factors that may determine the characteristics (specification) of the product. Here, the length of the wire 130 may be a length between the electrode 120 and the disc 140. For example, if an X-ray dose should be 3 mA, the disc 140 may have a diameter of 1.22 mm and a thickness of 0.1 mm, and the wire 130 may have a line width of 0.1 mm and a length of 2.8 mm.
Referring to
The target 200 is provided on the other side of the body 300 to face the filament 100, and is configured to receive the electrons emitted from the filament 100 and emit X-rays. The target 200 is preferably made of a metallic material such as copper. The electrons move at a high speed due to a high voltage and collide with a surface of metal, thereby generating X-rays. Also, the target 200 has a shape inclined in a direction in which X-rays are emitted, and is configured to emit X-rays in said direction when the electrons emitted from the filament 100 collide with the target 200. Since different X-ray emission patterns may be produced in the same electrons according to the structure, slope, material, etc. of the target 200, the target 200 may have various structures for the applications of X-rays.
The body 300 has one side connected to the filament 100 and the other side connected to the target 200 and is configured to form a sealing between the filament 100 and the target 200. That is, the filament 100 and the target 200 are sealed inside the body 300 while facing each other. The inside of the X-ray tube should be in a vacuum state so that electrons can move without being disturbed. To this end, the body 300 is required to enclose the entire X-ray tube including the filament 100 and the target 200. The body 300 is preferably made of a ceramic material which is capable of insulating a high voltage and does not affect the movement of electrons. Also, it is preferable that a metal part in contact with the body 300 made of a ceramic material be manufactured using a material having a coefficient of thermal expansion similar to that of the ceramic material such as Kovar, to resist a high temperature.
The cap 400 is configured to emit heat in close contact with the target 200 opposite to the body 300. That is, when the electrons are emitted from the filament 100 and collide with the target 200 to generate X-rays, heat is generated in the collision process. In particular, when high-energy X-rays are emitted from a small X-ray apparatus rather than a large X-ray apparatus, a lot of heat is generated in a narrow target area, so that this may cause the deformation of the device or affect its performance. Accordingly, the cap 400 is connected to the target 200 that generates a lot of heat to serve to rapidly dissipate heat from the target 200. To this end, the cap 400 is preferably made of a metallic material having high electrical conductivity. Also, the outer surface of the cap 400 may be formed in a corrugated shape to maximize its heat dissipation area, thereby increasing heat dissipation efficiency. Also, the cap 400 may preferably be made of the same material as the target 200 to rapidly dissipate heat from the target 200. As a material for the cap 400, a metal such as copper that facilitates X-ray emission may be used.
The X-ray tube according to the present inventive concept may have the center of the filament 100 aligned with the center of the target 200. That is, as shown in
Referring to
The X-ray tube 1000 has a configuration as shown in
The voltage generator 2000 may generate a desired voltage and supplies it to the X-ray tube 1000. That is, the voltage generator 2000 may generate a desired voltage for generating X-rays in the X-ray tube 1000. In the embodiments of the present inventive concept, the voltage generator 2000 may generate a voltage by using a pulse width modulation (PWM) method. The voltage generator 2000 using the pulse width modulation method according to the embodiments of the present inventive concept may include the console 2100 which receives an X-ray irradiation signal from an X-ray irradiation switch 10, generates control signals for on/off, tube voltage, tube current, and irradiation time of the X-ray generator and detects an X-ray irradiation signal: the pulse controller 2200 which generates pulse signals having a desired width to be modulated for said tube voltage, tube current, and irradiation time according to the control signals from the console 2100: and the high voltage generation unit 2300 which generates a DC high voltage according to the pulse signals from the pulse controller 2200 and applies it to the X-ray tube 1000. In the voltage generator 2000 according to the present inventive concept, the console 2100 detects the X-ray irradiation signal to generate a desired detection signal, and the pulse controller 2200 detects the detection signal from the console 2100 to control the pulse signals.
Referring to
Hereinafter, the filament manufacturing method according to an embodiment of the present inventive concept will be described in more detail for each step.
To form a first part, the step of bonding a base and an electrode (S100) may be carried out using the high temperature brazing according to the process conditions as illustrated in
The base serves to fix the disc to face the target and to fix the filament within the X-ray tube. Therefore, the base may have a diameter corresponding to an inner diameter of the X-ray tube to tightly enclose the X-ray tube. Also, the base may have the same shape as a cross-sectional shape of the X-ray tube, for example, a circular base may be provided. That is, the base may have a circular plate shape with a desired thickness. The base has through-holes in two or more regions through which the electrodes pass. Preferably, the base has two through-holes formed to be spaced apart from each other by a desired distance based on the central point. The base may be made of a ceramic material.
The electrode receives power from an external voltage generator and transmits it to the disc to generate electrons from the disc. The electrode has a desired length and may be prepared in a shape corresponding to the through-holes of the base. For example, if the through-holes are circular, the electrodes may have a cylindrical shape, and if the through-holes are rectangular, the electrodes may have a hexahedral shape. Also, the electrode may have a desired length, i.e., an appropriate length depending on a length inserted into the X-ray tube through an upper side of the base and a length extending below the base and connected to the voltage generator. In this case, since a distance between the disc and the target may be adjusted according to a length of the electrode inserted into the X-ray tube, the length of the electrode inserted into the X-ray tube may also be determined in consideration of the distance between the disc and the target. The electrode may be made of a material different from that of the base, for example, a metallic material such as Kovar may be used.
The electrodes are inserted into the through-holes of the base to fix the electrodes to the base. Then, a brazing filler (filler metal) is provided at a bonding portion between the base and the electrodes. That is, the brazing filler is formed around the through-holes of the base into which the electrodes are inserted. The brazing filler may be selected from materials having a desired melting point without changing the shapes and properties of the base and the electrodes.
Two electrodes passing through the base are bonded to the base by high-temperature brazing. The high-temperature brazing process for bonding the base and the electrodes may be carried out by introducing the base having two electrodes inserted into the through-holes into a desired furnace. As illustrated in
Hereinafter, the high-temperature brazing process will be described in more detail for each step with reference to the recipe graph illustrated in
The first heat-up step (S131) is a process of increasing the temperature of the furnace from room temperature (RT) to a first predetermined temperature at a desired ramp-up rate. For example, the first heat-up step (S131) increases the temperature of the furnace at a ramp-up rate of 10° C./min for 60 minutes to maintain the furnace at a temperature of 600° C. In this case, the ramp-up rate, ramp-up time, and first temperature used for the first heat-up step (S131) may be adjusted, for example within ±10˜20% of the exemplified temperature. That is, according to a size and material of the product having two electrodes inserted into the through-holes of the base, and the melting point of the brazing filler, the ramp-up rate, the ramp-up time, and the first temperature may be adjusted to 10±2° C./min, 60±12 mins, and 600±120° C., respectively. The first heat-up step (S131) may be performed to prevent the damage of the product due to rapid temperature increase by gradually increasing the temperature of the furnace. That is, the first heat-up step (S131) allows to prevent the damage of the product due to thermal expansion between a ceramic base and a metal electrode and the brazing filler formed in the bonding portion between the base and the electrodes. Although the ceramic base may undergo a slight dimensional change due to thermal expansion during the first heat-up step (S131), since the coefficient of thermal expansion thereof is smaller than that of other metallic materials, the product is not subjected to a physical impact. However, if the furnace temperature is increased to the brazing temperature with rapid ramp-up rate and time, cracks or damages may occur at the bonding portion between the base and the electrodes. Therefore, it is preferable to perform the first heat-up step (S131) under the foregoing conditions. Also, since there is a problem that the entire process is delayed when the ramp-up rate and time are slower than the foregoing conditions, it is preferable to perform the first heat-up step (S131) while controlling the ramp-up rate and time, and the first temperature depending on the size and material of the base and electrode, and the melting point of the brazing filler.
The burn-out step (S132) is a process of heating the product to the first temperature raised through the first heat-up step (S131) for a desired time to remove residual organic matters. For example, the burn-out step (S132) may be performed at a temperature of 600° C. for 60 minutes. The ceramic base and the metal electrode may be kept in a clean state by chemical pretreatment (i.e., washing), but such chemical pretreatment leaves residual organic matters. Also, cutting oil used in the processing of the ceramic base and the metal electrode may remain in the product. Such residual organic matters may be removed by heat treatment at a desired temperature for a desired time, which may be referred to as a burn-out process. Although the ceramic base may undergo a slight dimensional change due to thermal expansion during the burn-out step at a desired temperature, since the coefficient of thermal expansion thereof is smaller than that of other metallic materials, the product is not subjected to a physical impact.
The second heat-up step (S133) is a process of increasing the temperature of the furnace from the first temperature to a second predetermined temperature at a desired ramp-up rate. For example, the second heat-up step (S133) increases the temperature of the furnace at a ramp-up rate of 10° C./min for 40 minutes to maintain the furnace at a temperature of 1000° C. In this case, the ramp-up rate, ramp-up time, and second temperature used for the second heat-up step (S133) may be adjusted within ±10˜20% of the exemplified temperature. That is, according to a size and material of the product having two electrodes inserted into the through-holes of the base, the melting point of the brazing filler, and the first temperature, the ramp-up rate, the ramp-up time, and the second temperature may be adjusted to 10±2° C./min, 40±8 mins, and 1000±200° C., respectively. The second heat-up step (S133) may be performed to increase the temperature of the furnace prior to the pre-heating step (S134).
Next, the pre-heating step (S134) is a process of maintaining the product at the second temperature raised through the second heat-up step (S133) for a desired time. For example, the pre-heating step (S134) may be performed at a temperature of 1000° C. for 30 minutes. Since the brazing filler used in the present inventive concept has a melting point of, for example 1060° C., to reach this temperature, the temperature is uniformly maintained across the product and other elements during the pre-heating.
The third heat-up step (S135) is a process of increasing the temperature of the furnace from the second temperature to a third predetermined temperature at a desired ramp-up rate. For example, the third heat-up step (S135) increases the temperature of the furnace at a ramp-up rate of 12° C./min for 5 minutes to maintain the furnace at a temperature of 1060° C. That is, the temperature is raised to 1060° C. which is the melting point of the brazing filler. The ramp-up rate and the third temperature may be adjusted according to the melting point of the brazing filler.
The brazing step (S136) is a process of performing brazing at the third temperature for a desired time to bond the ceramic base and the metal electrodes. For example, the brazing filler is melted at a temperature of 1060° C., thereby bonding the ceramic base and the metal electrodes and fixing the metal electrodes to the ceramic base. That is, the separate ceramic base and metal electrodes are bonded using the brazing filler. Since the brazing step is performed at a high temperature, the temperature and time may be adjusted in consideration of the respective thermal expansions of the metal and ceramic.
Next, the furnace cooling step (S137) is a process of decreasing the temperature of the furnace used in the brazing step from 1060° C. at a desired rate. For example, the temperature of the furnace may be decreased to 600° C. That is, the temperature of the furnace is lowered from the brazing temperature to a predetermined temperature to remove the brazed product from the furnace.
The air cooling step (S138) is a process of decreasing the temperature of the product removed from the furnace in air.
The wire and the disc are provided (S210), and the wire is bonded to a lower surface of the disc to form a second part (S220). The bonding of the wire and the disc may be performed using a micro-spot welding process.
The wire may be provided to connect the electrodes to the disc. The electrodes may be connected to the disc through the wire in consideration of a distance between the electrodes, a size of the disc, etc. The wire is thinner than the electrode. The wire may be formed of the same or a different material as the electrode. For example, the wire may be formed of tungsten or tungsten alloys. The wire may be made of two separate parts, or as a single elongate part. That is, two wires may be respectively connected to a lower surface of the disc. Alternatively, one wire may be connected to a lower surface of the disc with its central portion bent.
The disc may be provided in the form of a plate having a desired thickness. The disc may be provided in a circular plate shape having a size and a thickness smaller than that of the base. One surface (lower surface) of the disc is bonded to the wire, and the other surface (upper surface) opposite to this surface faces the target. The disc may be made of a metallic material such as Ta. The size of the disc and the length of the wire are major factors that may determine the characteristics (specification) of the product. For example, if an X-ray dose should be 3 mA, the disc may have a diameter of 1.22 mm and a thickness of 0.1 mm, and the wire may have a line width of 0.1 mm and a length of 2.8 mm.
The wire may be bonded to the disc to form the second part. The step of bonding the wire and the disc (S220) may be performed by a micro-spot welding process. The wire and the disc may be bonded and secured to each other using a jig. That is, the wire and the disc may be secured to the jig, and then they may be bonded using micro-spot welding. The micro-spot welding process is done within about 0.3 seconds according to the conditions as illustrated in
The first part with the base and the electrode bonded and the second part with the wire and the disc bonded are bonded to form the filament (S300). The electrode of the first part is bonded to the wire of the second part wherein an upper end of the electrode may be bonded to a lower end of the wire. A micro-spot welding process may be used as a bonding method to form the filament. The wire and the electrode may be bonded and secured to each other using a jig. That is, the base is secured to the jig to expose a distal end of the electrode and the disc is secured to the jig to expose the wire at a position opposite thereto. Then, the wire may be bonded to the electrode by the micro-spot welding. For example, the micro-spot welding process may be performed in a state in which the first part is secured to a lower side and the second part is secured to an upper side. The micro-spot welding process may be done within about 0.3 seconds as illustrated in
Although the technical idea of the present inventive concept has been specifically described with reference to the foregoing embodiments, it should be noted that these embodiments are merely illustrative of the present inventive concept and do not serve to limit the present inventive concept. In addition, those skilled in the art will understand that various embodiments may be implemented within the scope of the present inventive concept.
In the drawings of the present inventive concept, the following reference numbers refer to the following elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0108486 | Aug 2022 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2022/017148 | 11/3/2022 | WO |
