JP4836975B2 - Cooker - Google Patents

Description

  The present invention relates to a heating cooker that can suppress heating efficiency and the gradient of the internal temperature of an object to be heated, so-called heating unevenness.

  In a conventional cooking device, for example, there is a structure in which a radial slot antenna or a dipole antenna is provided as means for irradiating microwaves to an object to be heated accommodated in a heating chamber. Each of these antennas feeds a high frequency from one point of the antenna shaft provided at the center of the disk, and generates a strong high frequency locally in a slot or dipole installed on the surface of the antenna. Heating is realized (for example, see Patent Documents 1 and 2).

JP 2004-327273 A (FIGS. 1 and 2) JP 2001-250672 A (FIGS. 3 and 4)

  In the conventional antenna shape described above, high-frequency power is fed from the shaft portion of the antenna, one end of which is installed in the waveguide, and a high-frequency current is generated on the disk. In this case, a portion where a high electric field is locally generated and a portion where the high electric field is not generated are generated. Specifically, there is a portion that strongly heats the object to be heated by strongly transmitting high frequency to the slot portion in the antenna provided with the slot and to the tip portion of the dipole in the antenna provided with the dipole. Paradoxically and relatively, this phenomenon means that there is a portion that is not strongly heated on the antenna. That is, it indicates that there are a strong part and a weak part where the object to be heated is irradiated with a high frequency, and the heated object has a problem that there is a part that is well heated and a part that is weakly heated, that is, uneven heating.

  In addition, there is an example in which heating is performed by rotating the antenna with a motor for the purpose of alleviating heating unevenness, but eventually the strong electric field part moves concentrically, and the intensity of heating occurs concentrically. There is a problem.

  Furthermore, the dimensions of the slot antenna and dipole antenna are determined by the wavelength of the oscillating high frequency. For example, when trying to radiate radio waves efficiently, for example, the slot antenna is ½ wavelength, and the dipole antenna is from the shaft that is the power feeding unit. A total length of ½ wavelength is required, with ¼ wavelength on each side. For example, referring to 2.45 GHz, which is a high-frequency wavelength used in home microwave ovens, the wavelength is 122.4 mm and the half wavelength is 61.2 mm. The size of the bottom of a microwave oven for home use is about 400 × 300, even if it is large, and the dimensions of the flat plate of the antenna are at most about 200 mm in diameter, considering the arrangement of peripheral components.

  In such an antenna, it is impossible to arrange a large number of slot antennas in a radial shape with a slot size of approximately ½ wavelength that efficiently generates a high frequency. There is a problem that the antenna becomes very inefficient in heating. In other words, in order to promote efficient incidence and absorption of high-frequency waves to the object to be heated to promote heating and to correct heating unevenness in the object to be heated, uniform high-frequency waves are applied from as wide a part as possible on the antenna. It is important to generate or obtain a high-frequency generation distribution according to the type and amount of the object to be heated, but in conventional cooking devices, it becomes an antenna shape that must generate a strong electric field locally, There is a problem that sufficient heating efficiency and heating unevenness correction have not been performed.

  The present invention has been made to solve the above-described problems, and can obtain a heating cooker that can efficiently heat an object to be heated without heating unevenness and can be heated according to the type and amount of the object to be heated. For the purpose.

A heating cooker according to the present invention includes a heating chamber for storing an object to be heated, a high-frequency oscillator for oscillating a high frequency for heating the object to be heated, a waveguide for guiding the high frequency oscillated from the high-frequency oscillator, An antenna for propagating the high frequency guided into the wave tube toward the heating chamber, and the antenna includes a shaft for propagating the high frequency guided into the waveguide, and a branched conductive path formed extending in a plurality of directions from the shaft. When, is composed of a plurality of radio-frequency radiation portion consisting of a flat plate and loop conductive path is formed coupled to coupled respectively branched conductive paths in two locations of the flat plate, a plurality of radio-frequency radiation unit, such as around the shaft The two coupling positions of the loop conductive path with respect to the flat plate are substantially perpendicular to each other when viewed from the central axis direction of the flat plate, and the loop conductive path extends from the coupling portion with the branch conductive path to the flat plate. Against one side of the length of, the length to the other flat plate is characterized in that a quarter wavelength of the high frequency long.

  According to the present invention, the high-frequency radiation portion including the flat conductive plate and the loop conductive path formed by joining the flat plate to the flat plate is configured in the antenna that radiates high frequency. Therefore, strong electric field radiation can be realized in a wide area on the flat plate of the antenna, and the object to be heated can be efficiently heated without uneven heating.

  1 is an external perspective view of a heating cooker showing an embodiment of the present invention, FIG. 2 is a sectional view of the heating cooker showing the embodiment, and FIG. 3 is a perspective view of an antenna used in the heating cooker of the embodiment. 4 and 4 are plan views showing the antenna in an enlarged manner.

  1 and 2, a heating chamber 2 is provided inside the cooker body 1, and a door 3 and an operation panel 4 are provided on the front surface of the cooker body 1. The heating chamber 2 is composed of a casing formed in a substantially rectangular parallelepiped shape with an open front, and a high-frequency transmission plate 5 serving as a bottom surface of the heating chamber 2 is detachably installed above the bottom of the casing. The high-frequency transmission plate 5 is made of, for example, ceramic, on which an object to be heated 6 is installed and transmits high frequency. The door 3 is attached to the cooker body 1 so as to be openable and closable, and is provided with a viewing window 3a configured by sandwiching a punching metal with glass. The cooking state of the object 6 to be heated stored in the heating chamber 2 can be confirmed by the visual window 3a. The temperature detection device 7 installed on the upper side surface of the heating chamber 2 is, for example, an infrared sensor that detects the temperature of the object to be heated 6 based on infrared rays emitted from the object to be heated 6.

  A waveguide 9 made of a conductor is attached to the bottom of the casing forming the heating chamber 2, and a high frequency oscillator 8 is installed in the waveguide 9 to rotate the antenna 11. 10 is attached. Although not shown, a space between the cooker body 1 and the heating chamber 2 is provided with a control unit that controls the high-frequency oscillator 8, the motor 10, and the like according to the operation of the operation panel 4. This control unit controls the output of the high-frequency oscillator 8 based on the temperature detected by the temperature detecting device 7, and temporarily stops the rotation of the motor 10 at a predetermined timing and rotates it again, depending on the cooking time. I have. Because the motor 10 is temporarily stopped, the high-frequency irradiation state to the object 6 to be heated changes, so that uniform and high-speed heating can be achieved.

  As will be described later, the antenna 11 is disposed in a space (antenna housing portion) between the bottom of the housing and the high-frequency transmission plate 5 and is connected to the motor 10 through a conductive shaft 12 provided at the center. . The bottom of the housing in which the shaft 12 of the antenna 11 is inserted and each hole of the waveguide 9 are formed in a circular shape. The shaft of the motor 10 is D-cut in the axial direction, and the shaft 12 of the antenna 11 is provided with a hole that is D-cut in the axial direction. Thereby, the idling of the antenna 11 is prevented. The above-described high-frequency oscillator 8 is a magnetron that oscillates a high frequency of about 1 kW and 2.45 GHz for home use, for example.

Here, the configuration and operation of the antenna 11 in the embodiment will be described with reference to FIGS.
As shown in FIG. 3, the antenna 11 includes a shaft 12, a branch conductive path 13 that extends, for example, in three directions around the shaft 12, and three high-frequency radiations respectively coupled to the tip of the branch conductive path 13. Part 16. The high-frequency radiating portion 16 is formed in a loop shape by being coupled to the flat plate 14 formed in a disc shape and two outer peripheral portions of the flat plate 14, and the loop conductive path 15 coupled to the distal end portion of the branch conductive path 13. It is made up of. The shaft 12 is detachably connected to the motor 10 as described above, and the diameter of the flat plate 14 is approximately ½ wavelength of the oscillated high frequency.

  The loop conductive path 15 is composed of a first conductive part 15a and a second conductive part 15b with a joint portion with the tip of the branch conductive path 13 as a boundary. Among them, the first conductive portion 15a is bent at a substantially right angle in a direction orthogonal to the central axis of the flat plate 14, and is coupled to the outer peripheral portion of the flat plate 14, and the second conductive portion 15b is a first conductive portion. The plate 15 is bent at a substantially right angle so as to be parallel to a portion extending from the corner of the plate 15 to the flat plate 14, and is further bent at a substantially right angle in a direction perpendicular to the central axis of the flat plate 14 to be formed on the outer peripheral portion of the flat plate 14. Are combined. The coupling positions of the first and second conductive portions 15 a and 15 b with respect to the flat plate 14 are substantially perpendicular when viewed from the central axis direction of the flat plate 14.

  The length of the first and second conductive portions 15a and 15b is such that when the length of the first conductive portion 15a is L, the length of the other second conductive portion 15b is (L + 1/4 wavelength). ). This is because a current whose phase is shifted by 90 ° flows into the flat plate 14. Further, rounds 17 are formed at the corners of the first and second conductive portions 15a and 15b (see FIG. 4), in order to reduce sparks caused by concentration of electric field at high output. is there.

In the antenna 11 configured as described above, the high frequency oscillated from the high frequency oscillator 8 propagates into the waveguide 9 and is converted into a high frequency current by the shaft 12 of the antenna 11 . Then, the converted high-frequency current is shunted by the branch conductive path 13 extending in three directions, and each high-frequency current is shunted by the first and second conductive portions 15a and 15b as shown in FIG. It flows in almost right angles from two directions. In this case, the high-frequency current flowing into the flat plate 14 via the first conductive portion 15a and the high-frequency current flowing into the flat plate 14 via the second conductive portion 15b are combined in a vector manner, so that each flat plate 14 Various currents flow on the top. At this time, since the length of the second conductive portion 15b is (L + 1/4 wavelength) with respect to the length L of the first conductive portion 15a, the high-frequency current whose phase is shifted by 90 ° is generated by the flat plate 14. Flow into. As a result, a magnetic field is excited by the high-frequency current along with the time change of the high-frequency current due to the high frequency, an electric field is generated by this magnetic field, and the time change of the magnetic field and the electric field increases or decreases with the phase of the high frequency. Is generated and transmitted through the high-frequency transmission plate 5 and radiated into the heating chamber 2.

  When the first and second conductive portions 15a and 15b are viewed as current sources in the flat plate 14, in addition to the geometrical current source arrangement being shifted by 90 °, a current whose phase is also shifted by 90 ° is synthesized. It will be. By utilizing the difference between the two, circularly polarized waves in which a strong electric field is radiated in an annular shape are generated on the flat plate 14 of the antenna 11.

  Next, the principle of generation of circularly polarized waves will be described with reference to FIG. FIG. 5 is a schematic diagram showing a high-frequency current flowing on the flat plate of the antenna. In the figure, the solid line indicates the high-frequency current flowing on the flat plate 14, the broken line indicates the high-frequency current on the loop conductive path whose direction and magnitude change according to the phase, and the length indicates the magnitude of the current. .

  The high frequency current excited by the high frequency has an amplitude such that the direction is reversed every 90 °. For example, the high-frequency current on the first conductive portion 15a flowing in from the lower side of the page at the phase 0 ° flows greatly downward, but the current decreases as the phase changes from phase 22.5 ° to 45 °. After that, the direction in which the high-frequency current flows begins to reverse, and at the phase 90 °, the current flows in the opposite direction with the same magnitude as the phase 0 °. This is the same phenomenon in the second conductive portion 15b that flows from the right side of the page. However, since the inflow distance from the shaft 12 of the antenna 11 that is a current source to the flat plate 14 is different, the direction of flowing into the flat plate 13 is different. Will change.

In the synthesis of the high-frequency currents flowing from the lower side and the right side of the page, the flowing direction is sequentially changed for each phase as a synthesized current as indicated by a solid line on the flat plate 14 . As a result, the direction of the high-frequency current flowing on the flat plate 14 is rotated once while the phase changes by 180 °. That is, an electromagnetic wave (high frequency) generated in the vertical direction on the paper surface (in the direction of the central axis of the flat plate 14) generated along with the movement of the high frequency current moves in the strong electric field portion in an annular shape with the phase. Further, since a current change for each phase also occurs on the loop conductive path 15, the strong electric field portion moves and electromagnetic waves are radiated.

  This phenomenon is an event that is performed at a frequency of 2.45 GHz in a home microwave oven. In other words, the time for the strong electric field portion to make one rotation on the flat plate 14 is 1/450 million times a second. When heating the object 6 to be heated, this time order is much smaller than the heating time which is usually several tens of seconds to several tens of minutes and the rotational speed of the antenna 11 which normally rotates at about 5-6 rpm. For this reason, the high frequency applied to the article 6 to be heated is practically the same as giving a strong electric field in an annular shape on the flat plate 14.

  Next, with the antenna 11 described above as one type, another antenna configuration that can be selectively used according to the type and amount of the object to be heated 6 and the desired heating distribution will be described with reference to FIGS. . FIG. 6 is a plan and perspective view showing a second type antenna used in the cooking device of the embodiment, and FIG. 7 is a plan and perspective view showing a third type antenna used in the cooking device of the embodiment. FIG. 8 is a perspective view showing a fourth type antenna used in the cooking device of the embodiment. Note that the same or corresponding parts as those in FIGS. 3 and 4 are denoted by the same reference numerals and description thereof is omitted.

  In the antenna 111 shown in FIG. 6, the lengths L1, L2, and L3 of the branch conductive paths 131 extending in three directions around the shaft 16 are different, and the other portions have the same structure as the antenna 11 described above. . When the antenna 111 is rotated by the motor 10, the high-frequency radiation portion 16 coupled to the branch conductive path 131 having the length L1 rotates at a position farthest from the shaft 12 and coupled to the branch conductive path 131 having the length L3. The high-frequency radiating unit 16 rotates in the vicinity of the shaft 12, and the high-frequency radiating unit 16 coupled to the branch conductive path 131 having the length L2 rotates approximately in the middle of the two high-frequency radiating units 16 described above. Become. With this configuration, the movement range of the strong electric field portion when the antenna 111 is rotated is wider than that of the antenna 11, and therefore, a wide area of the heating chamber 2 can be heated.

  The antenna 112 shown in FIG. 7 includes two high-frequency radiating portions 161 that share the loop conductive path 151, and the high-frequency radiating portion 161 has an auxiliary radiating portion that protrudes from the outer peripheral portion of the flat plate 14. 20 is provided. The loop conductive path 151 is configured such that a central shared portion is directly coupled to the shaft 12. This type of antenna 112 is characterized in that the electric field strength is slightly increased and decreased in the circumferential direction on the high-frequency rotation orbit, and therefore heats the object 6 to be heated, which can be expected to conduct heat and convection. Suitable for Further, in addition to the strong electric field on the flat plate 14, the auxiliary radiating unit 20 can further enhance the heating to the outer periphery.

  The antenna 113 shown in FIG. 8 is configured by arranging the high-frequency radiating portion 162 on the shaft 12 while changing the height up and down, and the flat plate 14 of the high-frequency radiating portion 162 is respectively connected via the loop conductive path 152. Directly coupled to the shaft 12. With this configuration, it is possible to keep the operating range during rotation of the antenna 113 small while maintaining the field emission effect of each high-frequency radiation part 162 itself, and a small object to be heated placed in the center of the heating chamber 2 6 can be efficiently heated.

Next, the combined electric field strength distribution during antenna rotation will be described with reference to FIGS. 9 and 10.
FIG. 9 is a schematic diagram showing a comparison of the combined electric field intensity distribution of the embodiment and the conventional antenna. Among them, the shaded portions shown in (b) and (d) are obtained when the antenna rotates 360 degrees once. It is a synthetic electric field strength distribution.

  In the conventional antenna, the electric field intensity distribution is as shown in (c), and when it is rotated once, it becomes an annular combined electric field intensity distribution as shown in (d). On the other hand, in the antenna 112 described with reference to FIG. 7, as shown in FIG. 7A, a strong circular electric field is emitted on the flat plate 14 and an electric field is emitted from the loop conductive path 151 installed inside the flat plate 14. When the antenna 112 makes one rotation, a circular combined electric field strength distribution is obtained as shown in FIG.

  FIG. 10 is a schematic diagram showing a combined electric field strength distribution during antenna rotation for each of the antennas shown in FIGS.

  In the antenna 11, as shown in (a), the difference in the combined electric field strength distribution from the flat plate 14 and the loop conductive path 15 is small, and the heating area is medium. Become. As shown in (b), the antenna 111 can heat a wide area and is suitable for heating an object to be heated 6 having a large heating area such as a large pizza.

  Further, in the antenna 112, as shown in (c), the heating area is medium when viewed from above, and the strong electric field portion has an annular shape, so that the heating stirring effect by the convection and heat conduction of the object to be heated itself can be obtained. It has a heating distribution suitable for soups and stewed dishes that can be expected. Contrary to the antenna 111, the antenna 113 can concentrate the electric field on the central portion of the heating chamber 2, so that milk, liquor, etc. in a container with a tall and small bottom area can be heated well. Can be done.

  As described above, according to the embodiment, since the high-frequency radiation part including the loop conductive path formed by coupling the flat plate and the flat plate to the high-frequency antenna is configured, It is possible to move the strong electric field portion for each phase of the high frequency. For this reason, it is possible to realize emission of a strong electric field in a wide area on the flat plate of the antenna, and efficiently heat the object to be heated without uneven heating. be able to.

In addition, since the high-frequency power fed from the branch conductive path is incident on the flat plate at almost right angles from two places via the loop conductive path, the moving effect of the strong electric field portion can be increased.
Furthermore, the loop conduction path that conducts in two branches with respect to the flat plate has a path length so that the phase of the high-frequency current flowing into the flat plate is shifted by a quarter wavelength with respect to the other path. By periodically changing the combined vector of the current flowing through the flat plate, a so-called circularly polarized wave is emitted that spirally emits strong radio waves from the flat plate into the heating chamber. As a result, there is an effect of giving an efficient and uniform temperature rise effect to the object to be heated.

  Further, since the plurality of high-frequency radiation portions of the antenna are formed of a circular conductive plate and a circular flat plate having a diameter of about ½ of the wavelength, there is an effect that a wide area in the heating chamber can be heated uniformly. Furthermore, since an efficient heating zone can be formed in a certain area immediately above the flat plate, the installation position of the object to be heated and the temperature rise area of the object to be heated are specified, and there is an effect of increasing the heating effect in any specific area.

  Furthermore, since the antenna can be attached and detached, the antenna can be changed according to the object to be heated. For this reason, an antenna exhibiting a heating distribution suitable for each object to be heated can be used. It is possible to improve the quality of finished products.

  The antenna according to the present embodiment includes the antennas 111 and 112 having the center of gravity greatly deviated from the shaft 12 as shown in FIGS. 6 and 7, and the antennas 11, 111, 112, and 113 by the user. The antenna itself is heated due to high temperature caused by another heat source in the heating chamber 2 and high-frequency current propagating to the antennas 11, 111, 112, 113. Therefore, it is necessary to ensure rigidity that the plate thickness is 0.3 mm or more, preferably 0.5 to 1.0 mm.

  Further, although the flat plate 14 has a circular shape, as shown in FIG. 11, the object to be heated may be heated by the antenna 114 including the high-frequency radiation portion 163 having the rectangular flat plate 141. Although not shown in FIG. 11, the antenna 114 is coupled to the shaft 12, the branch conductive path 13 formed extending in three directions around the shaft 12, and 3 connected to the tip of the branch conductive path 13. It is comprised with the two high frequency radiation | emission parts 163. The high-frequency radiation portion 163 includes a flat plate 141 formed in a square shape, a loop conductive path 15 that protrudes from two outer peripheral portions of the flat plate 141, is formed in a loop shape, and is coupled to the distal end portion of the branch conductive path 13. It is made up of. The shaft 12 is detachably connected to the motor 10 as described above, and the thickness of the flat plate 14 is in the range of 0.5 to 1.0 mm.

  The loop conductive path 15 includes a first conductive part 15 a and a second conductive part 15 b with the center line of the branch conductive path 13 as a boundary. Among them, the first conductive portion 15a is bent at a substantially right angle in a direction orthogonal to the central axis of the flat plate 14, and is coupled to the outer peripheral portion of the flat plate 141, and the second conductive portion 15b is a first conductive portion 15b. It is bent and extended substantially at a right angle so as to be parallel to a portion extending from the corner of the portion 15a to the flat plate 141, and further bent at a substantially right angle in a direction perpendicular to the central axis of the flat plate 141 to be formed on the outer periphery of the flat plate 141. Are combined. The coupling positions of the first and second conductive portions 15 a and 15 b with respect to the flat plate 141 are substantially perpendicular when viewed from the central axis direction of the flat plate 141. The length of the first and second conductive portions 15a and 15b is such that when the length of the first conductive portion 15a is L, the length of the other second conductive portion 15b is (L + 1/4 wavelength). ). This is because the current whose phase is shifted by 90 ° flows into the flat plate 141 as described above. In addition, rounds 17 are formed at the corners of the first and second conductive portions 15a and 15b in order to reduce sparks caused by concentration of the electric field at high output. The antenna 141 configured in this way can also synthesize high-frequency currents on the surface and generate various electric fields.

  In the above embodiment, the cooking device having a high frequency oscillator has been described. However, a radiant heater as a heating source is provided on the top surface of the heating chamber 2, a hot air heater is provided on the back surface, Needless to say, it can be combined with the high-frequency heating of the present invention after the generation device is provided.

It is an external appearance perspective view of the heating cooker which shows embodiment of this invention. It is sectional drawing of the heating cooker which shows embodiment. It is a perspective view of the antenna used for the heating cooker of embodiment. It is a top view which expands and shows an antenna. It is a schematic diagram which shows the high frequency current which flows on the flat plate of an antenna. It is the top view and perspective view which show the 2nd type antenna used for the heating cooker of embodiment. It is the top view and perspective view which show the antenna of the 3rd type used for the heating cooker of embodiment. It is a perspective view which shows the 4th type antenna used for the heating cooker of embodiment. It is a schematic diagram which compares embodiment and the synthetic electric field strength distribution of the conventional antenna in comparison. It is a schematic diagram which shows the synthetic | combination electric field strength distribution at the time of antenna rotation for every antenna quoted in FIGS. It is a top view which shows the square antenna of the heating cooker which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cooker main body, 2 Heating chamber, 3 Door, 3a Viewing window, 4 Operation panel, 5 High frequency transmission board, 6 Heated object, 7 Temperature detection apparatus, 8 High frequency oscillator, 9 Waveguide, 10 Motor, 11 Antenna, 12 shaft, 13 branch conductive path, 14 flat plate, 15 loop conductive path, 15a first conductive part, 15b second conductive part, 16 high frequency radiation part,
17 are, 111 antenna, 131 branch conductive path, 112 antenna,
151 loop conduction path, 161 high frequency radiation section, 113 antenna, 152 loop conduction path, 162 high frequency radiation section, 114 antenna, 141 flat plate, 163 high frequency radiation section, 20 auxiliary radiation section.

Claims (8)

A heating chamber for storing an object to be heated;
A high frequency oscillator that oscillates a high frequency for heating an object to be heated;
A waveguide for guiding a high frequency oscillated from the high frequency oscillator;
An antenna for propagating the high frequency guided into the waveguide toward the heating chamber,
The antenna is formed by coupling a shaft that propagates a high frequency guided into the waveguide, a branched conductive path formed extending in a plurality of directions from the shaft, and a flat plate and two portions of the flat plate. It is composed of a plurality of high-frequency radiating sections each consisting of a branched conductive path and a loop conductive path coupled to each other,
The plurality of high-frequency radiating portions are arranged at equal intervals around the shaft, and the two coupling positions of the loop conductive path with respect to the flat plate are substantially perpendicular when viewed from the central axis direction of the flat plate. The loop conductive path is characterized in that the length from one side to the flat plate to the other flat plate is longer by a quarter wavelength of the high frequency than the length from one side to the flat plate. To cook. The cooking device according to claim 1 , wherein the flat plate is formed in a circular shape having a diameter of approximately ½ wavelength of a high frequency. The cooking device according to claim 1 , wherein the flat plate is formed in a rectangular shape in which at least one side is approximately ½ wavelength of high frequency. The heating cooker according to any one of claims 1 to 3 , further comprising a motor that is installed in the waveguide and rotates the antenna via the shaft. The cooking device according to any one of claims 1 to 4 , wherein an antenna housing portion is provided in the heating chamber, and a high-frequency transmission plate that divides the antenna housing portion and the heating chamber is detachably installed. . The cooking device according to any one of claims 4 to 5 , wherein the shaft of the antenna is detachably connected to the motor. The cooking device according to any one of claims 1 to 6 , wherein the loop conductive path has a right-angled bent portion. The cooking device according to any one of claims 1 to 7 , wherein the flat plate has a thickness of 0.3 mm or more.

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