Material mixing method and mixing device

Abstract

To provide a material mixing method that can mix materials into a desired mixing state.SOLUTION: In a material mixing method, materials are put into a mixer (2) equipped with stirring blades (11) and are mixed. In the mixing, vibrations of the mixer (2) whose stirring blades (11) are being rotated are detected to monitor variation in vibrational acceleration. When the vibrational acceleration has a preset specific time pattern, the mixing is finished. For instance, the vibrational acceleration to be monitored is vibrational acceleration for any one or a plurality of frequency components which are 1, 2, 3 times rotational frequencies of the stirring blades (11), of vibrational frequency components.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mixing method for mixing materials using a mixer equipped with stirring blades, and to a mixing device equipped with a mixer and a control device. [Background technology]

[0002] Mixers equipped with impellers are well known and are described, for example, in Patent Document 1. The type of mixer described in Patent Document 1 includes a container into which materials are fed, a rotating shaft provided within the container, and multiple impellers attached to the rotating shaft. The rotating shaft is rotated by an electric motor and a reducer provided outside the container, allowing the impellers to rotate within the container. In other words, the materials can be mixed.

[0003] Some types of mixers, such as the mixer described in Patent Document 1, have a chopper installed inside the container. The chopper consists of a drive shaft that protrudes a predetermined length into the container and multiple metal plates attached to the drive shaft, and these metal plates rotate at high speed when the drive shaft rotates. When the material hits the chopper rotating at high speed, a strong dispersion force is applied, resulting in efficient mixing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-229461 Summary of the Invention [Problem to be solved by the invention]

[0005] The mixer described in Patent Document 1 excels in its ability to efficiently mix materials using multiple rotating mixing blades and a chopper. However, the optimal mixing state for materials depends on the purpose and type of material. Insufficient mixing may not be suitable for the intended purpose, while excessive mixing may alter the physical properties of the material. Therefore, mixers must be operated appropriately to achieve the appropriate mixing state. For example, a set operating time is used to operate the mixer. The set operating time is determined based on empirical evidence that the desired mixing state is achieved when the mixer is mixed with the type and weight of the target materials. However, the mixing state may change depending on environmental conditions such as room temperature and humidity, or the properties of the materials. In other words, setting an operating time does not guarantee that the desired mixing state will be achieved. Another method, instead of measuring operating time, involves detecting changes in the torque of the electric motor that rotates the mixing blades to estimate the mixing state of the materials and stopping mixing when the appropriate torque is reached. However, torque changes do not necessarily correlate highly with the mixing state, making it difficult to achieve the appropriate mixing state.

[0006] The present invention aims to solve these problems, specifically to provide a material mixing method that can mix materials into a desired mixed state, and further to provide a mixing device that is equipped with such a mixing method. [Means for solving the problem]

[0007] The present invention relates to a mixing method in which materials are fed into a mixer equipped with an agitating blade and mixed. During mixing, the vibration of the mixer is detected while the agitating blade is rotating, and changes in vibration acceleration are monitored. The time pattern is the pattern of change in the time direction, where the vibration acceleration takes on minimum and maximum values ​​over time depending on the mixing state of the material, and The mixing is completed when the vibration acceleration reaches a specific time pattern that is set in advance. According to another invention, the vibration acceleration to be monitored is 1, 2, 3, ... of the rotation frequency of the stirring blade among the frequency components of the vibration. 、6 The vibration acceleration is defined as one or more frequency components of the frequency range. [Effects of the Invention]

[0008] When mixing materials, the vibration acceleration changes over time, and the vibration acceleration correlates with changes in the mixed state of the materials. In other words, by monitoring changes in the vibration acceleration, the mixed state of the materials can be estimated. This invention is configured to complete mixing when the vibration acceleration conforms to a specific, pre-set time pattern. In other words, when the change in the vibration acceleration over time conforms to a specific pattern, mixing is stopped. This allows the desired mixed state to be obtained. Another invention monitors the vibration acceleration for one or more frequency components of the vibration that are 1, 2, 3, ... times the rotational frequency of the mixing blade. These frequency components exhibit characteristic patterns, as will be explained below. Therefore, the timing to stop mixing can be detected with high accuracy, allowing the desired mixed state to be obtained. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a front cross-sectional view showing a mixing device according to an embodiment of the present invention. [Figure 2] 2 is a side cross-sectional view of the mixing device according to the present embodiment, shown at cross section XX in FIG. 1. FIG. [Figure 3] 1 is a graph showing the relationship between mixing time and degree of mixing achieved when test materials are mixed. [Figure 4] 10 is a graph showing the change in vibration acceleration of the X-axis component over mixing time when the test material is mixed. [Figure 5] 10 is a frequency spectrum obtained by frequency analysis of vibration acceleration at a predetermined timing when the test material is mixed. [Figure 6] 1 is a graph showing the change over mixing time in vibration acceleration of the sixth harmonic frequency component with the mixer rotation frequency as the fundamental wave when the test material is mixed. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present embodiment will be described below. The material mixing method according to the present embodiment can be performed by various types of mixing devices and is not limited to a specific type of mixing device. However, the following description will be given focusing on a mixing device 1 according to the present embodiment, as shown in FIG. 1.

[0011] <Mixing device> A mixing device 1 according to this embodiment is generally composed of a horizontal mixer 2 and a control device 3 that controls the mixer 2. The mixer 2 is provided with a cylindrical container 5 into which materials are introduced and mixed, and this container 5 is oriented horizontally and fixed to a housing 6. The container 5 is provided with a material inlet 5a at its top and a material outlet 5b at its bottom.

[0012] A rotating shaft 8 is installed in the center of the cylinder within the container 5. The rotating shaft 8 is horizontal and has three arms 10, 10, 10 attached to it, with impellers 11, 11, 11 fixed to the tips of each arm. As shown in Figure 2, the three impellers 11, 11, 11 are spaced 120 degrees apart from one another when viewed from the side. One end 8a of the rotating shaft 8 protrudes outward from the container 5. A drive mechanism 13 consisting of an electric motor, a reducer, etc. is installed in the housing 6, and the protruding end 8a of the rotating shaft 8 is connected to the drive mechanism 13. Therefore, when the drive mechanism 13 is driven, the rotating shaft 8 rotates, causing the impellers 11, 11, 11 to rotate. In other words, the materials in the container 5 are mixed. The drive mechanism 13 is connected to and controlled by the control device 3.

[0013] Two choppers 14, 14 are also provided inside the vessel 5. The choppers 14, 14 consist of drive shafts 16, 16 protruding a predetermined length into the vessel 5 and multiple metal plates 17, 17, ... attached to the drive shafts 16, 16. Although a drive device is not shown in FIGS. 1 and 2, when the drive device rotates the drive shafts 16, 16, the metal plates 17, 17 rotate at high speed. This applies a strong dispersing force to the materials inside the vessel 5. These choppers 14, 14 can be driven or stopped when mixing the materials. The choppers 14, 14 are controlled by the control device 3.

[0014] <Acceleration sensor> To implement the material mixing method of this embodiment, at least one acceleration sensor is required to detect vibrations of the mixer 2. The mixing device 1 of this embodiment is provided with first and second acceleration sensors 19 and 20, as shown in FIGS. 1 and 2. The first acceleration sensor 19 is provided in the upper portion of the housing 6, and the second acceleration sensor 20 is provided in the lower portion of the housing 6. The acceleration sensors 19 and 20 may be of any type as long as they can detect vibrations of the mixer 2. In this embodiment, however, a capacitive triaxial acceleration sensor (BMX055 manufactured by Bosch) is used. The first and second acceleration sensors 19 and 20 are capable of detecting vibration accelerations in three orthogonal directions, i.e., the x-, y-, and z-directions. The first and second acceleration sensors 19 and 20 are connected to the control device 3, and the measured vibration accelerations are monitored by the control device 3.

[0015] Incidentally, indicators for grasping the vibration state include not only vibration acceleration but also vibration amplitude, vibration energy, etc. However, evaluating the vibration state using vibration amplitude or vibration energy is essentially equivalent to evaluating it using vibration acceleration. This is because vibration acceleration is closely related to vibration energy, vibration amplitude, etc. In the material mixing method according to the present embodiment, which will be described next, the mixing state is estimated by monitoring the vibration acceleration, but even if the mixing state is estimated by monitoring the vibration amplitude and vibration energy, this essentially amounts to monitoring the vibration acceleration.

[0016] <Material Mixing Method According to the Present Embodiment> The material mixing method according to this embodiment is performed by the control device 3. In short, the method estimates the mixing state of the materials by monitoring the vibration acceleration detected by the acceleration sensors 19 and 20 when the mixer 2 is operated to mix the materials, and determines whether mixing is complete based on this information. The vibration acceleration changes over time when the materials are mixed. The pattern of change in this vibration acceleration over time, i.e., the time pattern, has a strong correlation with the mixed state of the materials. The material mixing method according to this embodiment utilizes this correlation. In other words, when the vibration acceleration forms a specific time pattern while mixing the materials, it is determined that the desired mixed state has been achieved, and mixing is complete.

[0017] The time pattern of vibration acceleration required to determine the completion of mixing varies depending on the type of material. In other words, the time pattern of vibration acceleration when mixing one material cannot be used for a different type of material. Therefore, it is necessary to obtain in advance the relationship between the time pattern of vibration acceleration and the mixed state according to the type of material being mixed. This can be obtained through a preparation process in which the target material is mixed on a trial basis. Next, the preparation process will be explained using experimental materials as an example.

[0018] <Preparation process> The materials used in the experiment were calcium carbonate (SUPER1500, manufactured by Maruo Calcium) and ferric oxide (Todacolor 140ED, manufactured by Toda Kogyo). These materials become darker in brightness as mixing progresses and the ferric oxide particles become smaller in diameter, making them suitable for evaluating the degree of mixing. Note that the degree of mixing does not necessarily have to be evaluated by particle size; it can also be evaluated by other indicators, such as viscosity.

[0019] As the first step in the preparation process, the relationship between mixing time and the degree of mixing achieved is first determined. 24.0 kg of calcium carbonate and 1.263 kg of ferric oxide are added to container 5 of mixer 2 and mixed. Mixing is stopped at an appropriate time, the brightness is measured with a brightness meter, and the mixed state is obtained. Mixing is started again, stopped at an appropriate time, the brightness is measured, and the mixed state is obtained. This process is repeated. The results obtained are shown in Figure 3. Graph 31 shows the changes when mixing is performed by driving not only mixing blades 11, 11, 11 but also choppers 14, 14, while graph 32 shows the changes when mixing is performed by driving only mixing blades 11, 11, 11 with choppers 14, 11, 14 stopped.

[0020] In the second stage of the preparation process, the relationship between mixing time and changes in vibration acceleration is obtained. The same amount of material as that added in the first stage is added to the container 5 of the mixer 2 and mixed. During mixing, the vibration acceleration detected by the acceleration sensors 19 and 20 is recorded. Figure 4 shows the relationship between mixing time and the vibration acceleration of the x-direction component of the first acceleration sensor 19. In this embodiment, the x-direction is the direction parallel to the rotation axis 8. Graph 35 shows the changes when mixing is performed by driving not only the mixing blades 11, 11, 11 but also the choppers 14, 14, while graph 36 shows the changes when mixing is performed by stopping the choppers 14, 14 and driving only the mixing blades 11, 11, 11.

[0021] Figure 5 shows a frequency spectrum obtained by frequency analysis of vibration acceleration measured at a certain timing. In the frequency spectrum, reference numeral 41 represents the frequency component corresponding to the rotational frequency of the agitator blades 11. Similarly, reference numerals 42, 43, 44, 45, and 46 represent the second, third, fourth, fifth, and sixth harmonics of the fundamental frequency of the agitator blades 11. The vibration acceleration of this nth harmonic frequency component also exhibits a characteristic change over time. Figure 6 shows a graph illustrating the relationship between mixing time and vibration acceleration for the sixth harmonic frequency component during the second stage of the preparation process. Graph 51 shows the change when both the agitator blades 11 and the chopper 14 are driven during mixing, while graph 52 shows the change when the chopper 14 is stopped and only the agitator blades 11 are driven.

[0022] <Operation> As shown in graphs 35 and 36 in Figure 4 and graphs 51 and 52 in Figure 6, the vibration acceleration changes over time. In other words, the time pattern of the vibration acceleration changes as the mixed state of the materials changes. When mixing materials, if the vibration acceleration is monitored and a specific time pattern is detected and mixing is stopped, the materials can be mixed in the desired state. An example of this operation will be described.

[0023] The mixing of materials by driving both the mixing blades 11, 11, 11 and the choppers 14, 14 is performed as follows. For example, suppose mixing is to be completed when the mixing degree reaches 90%. Graph 31 in Figure 3 (with the mixing blades 11, 11, 11 and the choppers 14, 14 driven) indicates that the mixing time required to reach 90% mixing is approximately 1200 seconds. Graph 35 in Figure 4 (with the mixing blades 11, 11, 11 and the choppers 14, 14 driven) indicates that the mixing time reaches a minimum value, as indicated by reference numeral 61, just before approximately 1200 seconds, and then begins to increase. In other words, the time pattern indicates a minimum value followed by an increase. The time pattern indicated by reference numeral 61 is stored in the control device 3. When the mixing blades 11, 11, 11 and the choppers 14, 14 are driven in the mixer 2 to perform mixing, the control device 3 monitors the x-direction component of the vibration acceleration. The mixing is stopped when the time pattern indicated by reference numeral 61 is detected. This allows the mixing to be completed at a mixing rate of 90%.

[0024] The following procedure is used to stop the choppers 14 and drive only the agitating blades 11 to mix the materials. For example, suppose that mixing is to be completed when the mixing level reaches 60%. Graph 33 in Figure 3 (only the agitating blades 11 are driven) indicates that the mixing time required to achieve 60% mixing is approximately 200 seconds. Graph 51 in Figure 6 (only the agitating blades 11 are driven) shows that the mixing time reaches a maximum value at approximately 200 seconds, as indicated by reference numeral 62, and then begins to decrease. In other words, this is a time pattern in which the mixing level reaches a maximum value and then begins to decrease. The time pattern indicated by reference numeral 62 is stored in the control device 3. When the mixer 2 drives only the agitating blades 11 to mix the materials, the control device 3 monitors the frequency component of the sixth harmonic of the vibration acceleration. The control device 3 then stops mixing when it detects the time pattern indicated by reference numeral 62. This allows the mixing of the materials to be completed when the mixing level reaches 60%.

[0025] Only two examples of actual operation have been explained, but the time pattern to be monitored can be freely selected according to the desired degree of mixing. In the above explanation, the x-direction component of vibration acceleration and the frequency component of the sixth harmonic wave were explained, but it is also possible to monitor the y-direction and z-direction components of vibration acceleration, or the frequency component of an nth harmonic wave other than the sixth harmonic wave. Alternatively, the x-direction component of vibration acceleration and the frequency component of the nth harmonic wave can be monitored simultaneously, and mixing can be completed by detecting that a specific time pattern has been reached for each. [Explanation of symbols]

[0026] 1 Mixing device 2 Mixer 3 Control device 5 Container 6 Housing 8 Rotation axis 10 Arm 11 Mixing blade 13 drive mechanism 14 chopper 16 Drive shaft 17 Metal plate 19, 20 Acceleration sensor

Claims

1. A mixing method in which materials are mixed by being introduced into a mixer equipped with stirring blades, The vibration of the mixer during rotation of the stirring blade is detected as vibration acceleration, A time pattern is a pattern of change in the time direction in which the vibration acceleration takes on a minimum value or a maximum value over time depending on the mixing state of the material, A material mixing method in which mixing is completed when it is detected that the vibration acceleration has formed a predetermined specific time pattern.

2. 2. The material mixing method according to claim 1, wherein the vibration acceleration to be monitored is the vibration acceleration for one or more frequency components of the vibration that are 1, 2, 3, ..., 6 times the rotation frequency of the stirring blade among the frequency components of the vibration.

3. The mixing method includes a preparation step of setting the specific time pattern, 3. The material mixing method according to claim 1, wherein the preparation step comprises: feeding equivalent materials into the mixer, mixing the materials, observing changes in the mixed state of the materials, detecting a time pattern of the vibration acceleration when a desired mixed state is reached, and determining the specific time pattern.

4. 3. The material mixing method according to claim 1, wherein the vibration acceleration monitored is the vibration acceleration in each of three components of the vibration in the x-direction, y-direction, and z-direction, which are orthogonal to each other.

5. 3. The method for mixing materials according to claim 1, wherein the mixer is provided with a chopper for dispersing the materials, and the chopper is driven in parallel with the rotation of the stirring blades.

6. a mixer into which the material is fed; a rotating stirring blade provided in the mixer; a vibration detection means provided in the mixer; a control device; The control device, when rotating the stirring blades, obtains vibration acceleration from the vibration of the mixer detected by the vibration detection means and monitors changes in the vibration acceleration, and determines a time pattern as a change in the time direction in which the vibration acceleration takes on minimum and maximum values ​​over time depending on the mixing state of the materials, and stops the stirring blades when it detects that the vibration acceleration has become a specific time pattern that is preset in the control device.

7. 7. The mixing device according to claim 6, wherein the vibration acceleration monitored by the control device is a vibration acceleration for one or more frequency components of the vibration that are 1, 2, 3, ..., 6 times the rotational frequency of the stirring blade among the frequency components of the vibration.

8. 8. The mixing device according to claim 6, wherein the vibration acceleration monitored by the control device is vibration acceleration in each of three components of the vibration in the x-direction, y-direction, and z-direction, which are orthogonal to each other.

9. 8. The mixing device according to claim 6, wherein the mixer is provided with a chopper for dispersing the material, and the chopper is driven by the control device in parallel with the rotation of the stirring blade.

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