Electrodynamic vibration generator

Abstract

[PROBLEM] To provide a vibration generator having a simplified configuration while maintaining accuracy.　[SOLUTION] A current application circuit 30 is a circuit for applying a drive current to a drive coil 20. An initial control means 32 controls the current application circuit 30 to apply a DC current to the drive coil 20. The initial control means 32 controls the current value of the DC current to keep a vibrating table 24 at a reference point (for example, the center point of the allowable range of vertical vibration) by means of the drive coil 20. When the initial setting is completed as described above, a drive control means 34 controls the voltage application circuit 30 so that a drive current obtained by superimposing a desired control current for vibration onto the DC current is output. As a result, the drive current in which the desired control current is superimposed on the DC current is applied to the drive coil 20, and the vibrating table 24 is vibrated.

Description

Electrodynamic vibration generator

[0001] The present invention relates to a vibration generator used for vibration testing and the like.

[0002] Generally, a vibration generator is configured by a vibrator and a power amplifier that supplies power to operate the vibrator (for example, Japanese Patent Application Laid-Open No. 2001-13033).

[0003] Fig. 15A shows a conventional vibrator used for vibration testing of products, etc. Magnetic path members 12 and 13 are provided. Excitation coils 14 and 16 are housed in magnetic path member 12. The excitation coils 14 and 16 form upper and lower magnetic circuits, as shown in Fig. 15B. This generates a magnetic flux in gap 18.

[0004] A drive coil 20 is provided in this gap 18. Therefore, when a drive current for generating a desired vibration is passed through the drive coil 20, the drive coil 20 can be moved up and down. A vibration table 24 is provided above the drive coil 20. Therefore, the vibration table 24, on which a sample, which is a product, is placed, can be vibrated up and down. The vibration table 24 is supported by an upper support mechanism and a lower support mechanism (not shown).

[0005] When using this vibrator, first, a sample is fixed to the vibration table 24. In this state, air is fed into the air suspension 22 provided below the vibration table 24, and the vibration table 24 is moved upward. When the vibration table 24 reaches the midpoint of the maximum vertical amplitude, air supply to the air suspension 22 is stopped and a valve (not shown) is closed. In this way, the initial setup is completed.

[0006] After the vibration table 24 is raised to the center point in this manner, the amplifier then applies drive power to the drive coil 20 to generate the desired vibration, vibrating the vibration table 24 and the sample.

[0007] The vibration generator described above has the following problems.

[0008] First, in the vibration generator described above, the vibration table 24 is raised to a predetermined reference position using the air suspension 22. Therefore, in order to match the vibration table 24 to the predetermined reference position, it is necessary to control the air suspension 22 using electricity and air pressure, which makes the configuration complicated.

[0009] Second, air intake and exhaust to the air suspension 22 are stopped during vibration, even for long periods of time. However, air leakage from the air suspension 22 (including air intake due to valve leakage) is essential. This necessitates difficult selection of air valves and piping components (according to the solenoid valve manufacturer, "minor air leakage is common sense"), and careful consideration is required for piping work. Generally, vibration generators can be used with both power amplifiers that do and do not allow DC current to flow. However, with the former, air leakage can cause the vibration center to shift, ultimately triggering over-displacement protection. With the latter, the center position held by air is held in place by DC current. This DC current can then be applied to activate protection, or when vibration is completed and the power amplifier is stopped, the DC current can be stopped, causing the specimen to plummet from its center position. In some cases, a collision with the bottom edge can result in unnecessary vibration loads on the specimen, potentially damaging it.

[0010] Thirdly, there is an upper limit to the excitation force that can be output by each vibration testing device, as specified in the device specifications. If the load weight including the jig is unknown, it is not possible to know the upper limit of the acceleration that can be output by loading it into the vibration testing device, and it is therefore necessary to know the load weight in advance.

[0011] SUMMARY OF THE INVENTION An object of the present invention is to solve any of the above problems and to provide a vibration generator having a simplified configuration while maintaining accuracy, or a vibration generator that can easily measure the payload.

[0012] The following are some independent features of the present invention. These features are independent of each other, and are not necessarily combined, but can be combined in any desired manner.

[0013] (1) A vibration generating device according to the present invention includes a magnetic flux generating source that generates magnetic flux, a drive coil that is disposed in the magnetic flux generated by the magnetic flux generating source and is driven by a current, a vibration table that is driven by the driving force of the drive coil and on which a test specimen is placed, a current application circuit that applies a drive current to the drive coil, initial control means that controls the current application circuit so that a direct current is applied to the drive coil as a drive current in an initial state to lift the vibration table to a reference position, and drive control means that controls the current application circuit so that a control current corresponding to a control signal is superimposed on the direct current and applied to the drive coil as a drive current in a driven state to vibrate the vibration table.

[0014] Since the vibration table is held at the reference position by a direct current, there is no need to use an air suspension or to control it, and the device can be simplified.

[0015] (2) The vibration generator according to the present invention is characterized by including a short-circuit switch that short-circuits both ends of the drive coil when an abnormal state is detected.

[0016] Therefore, it is possible to prevent the vibration table from suddenly falling due to the back electromotive force when an abnormality occurs.

[0017] (3) The vibration generator according to the present invention is characterized by including a fall prevention mechanism that is activated when an abnormal state is detected to prevent the vibration table from falling.

[0018] Therefore, it is possible to prevent the vibration table from suddenly falling due to the back electromotive force when an abnormality occurs.

[0019] (4) The vibration generating device according to the present invention is characterized by further comprising a calculation means for calculating a weight-related value of a test specimen placed on the vibration table based on the value of the DC current applied by the initial control means.

[0020] Since the weight-related value of the specimen is obtained from the DC current during initial control, there is no need to measure the weight of the specimen before loading it.

[0021] (5)(6) The vibration generating device according to the present invention comprises a magnetic flux generating source that generates magnetic flux, a drive coil that is disposed in the magnetic flux generated by the magnetic flux generating source and is driven by a current, a vibration table that is driven by the driving force of the drive coil and on which a test specimen is placed, a current application circuit that applies a drive current to the drive coil, initial control means that controls the current application circuit so that a direct current is applied to the drive coil as a drive current in an initial state in order to lift the vibration table to a reference position, and calculation means that calculates a weight-related value of the test specimen placed on the vibration table based on the value of the direct current applied by the initial control means.

[0022] Since the weight-related value of the specimen is obtained from the DC current during initial control, there is no need to measure the weight of the specimen before loading it.

[0023] In the embodiment, the "initial control means" corresponds to the difference calculator 84, the gain controller 86, and step S2.

[0024] In the embodiment, the "drive control means" corresponds to the adder 90 and step S6.

[0025] The concept of "device" includes not only a device consisting of one computer, but also a device consisting of multiple computers connected via a network, etc. Therefore, when the means of the present invention (or a part of the means) is distributed across multiple computers, these multiple computers correspond to the device.

[0026] The term "program" is a concept that includes not only programs that can be executed directly by a CPU, but also source-format programs, compressed programs, encrypted programs, programs that work in conjunction with an operating system to perform their functions, and the like.

[0027] 1 is a functional configuration of a vibration generator according to an embodiment of the present invention. FIG. 2 is a diagram showing the structure of a vibration exciter. FIG. 3 is a diagram showing the structure of a vibration table 24. FIG. 4 is a diagram showing a magnetic path member of a vibration exciter. FIG. 5 is a diagram showing a state in which the vibration table is incorporated into the magnetic path member. FIG. 6 is a diagram showing a state in which the vibration table is held at a reference position. FIG. 7 is a diagram showing the hardware configuration of a control circuit. FIG. 8 is a diagram for explaining the function of a switch 72. FIG. 9 is a flowchart of a hardware configuration control program when the control circuit is realized by a CPU. FIG. 10 is a flowchart of a control program. FIG. 11 is a diagram showing a mechanism for preventing falling using an air cylinder 80. FIG. 12 is a diagram showing a mechanism for preventing falling using an air cylinder 80. FIG. 13 is a functional configuration of a vibration generator according to a second embodiment. FIG. 14 is a flowchart of a control program. FIG. 15 is a diagram showing a conventional vibration generator.

[0028] 1 shows the functional configuration of a vibration generator according to one embodiment of the present invention. A current application circuit 30 is a circuit for applying a drive current to the drive coil 20. An initial control means 32 controls the current application circuit 30 to apply a direct current to the drive coil 20. The initial control means 32 controls the value of the direct current to cause the drive coil 20 to raise the vibration table 24 to a reference point (for example, the center point of the range in which up and down vibration is possible).

[0029] When the initial setting is completed as described above, the drive control means 34 controls the voltage application circuit 30 so that a drive current in which a desired control current for vibration is superimposed on the DC current is output. As a result, a drive current in which the desired control current is superimposed on the DC current is applied to the drive coil 20, causing the vibration coil 24 to vibrate.

[0030] In this embodiment, the vibration table 24 is raised to a reference point by a direct current, so that an air suspension and its control are not required, and the configuration of the device can be simplified.

[0031] 1.2 Structure of the vibration generator Figure 2 shows a cross-sectional view of the structure of the vibration generator. Magnetic path members 12 and 13 are provided. Excitation coils 14 and 16 are housed in the magnetic path member 12. The excitation coils 14 and 16 generate magnetic flux in the gap 18.

[0032] A drive coil 20 is provided in this gap 18. Therefore, when a drive current for generating a desired vibration is passed through the drive coil 20, the drive coil 20 can be moved up and down. A vibration table 24 is provided above the drive coil 20. Therefore, the vibration table 24, on which a sample, which is a product, is placed, can be vibrated up and down. The vibration table 24 is provided with a shaft 25 for stabilizing the up and down movement. The vibration table 24 is also supported by an upper support mechanism 17 and a lower support mechanism 29.

[0033] In this embodiment, the structure does not include the air suspension 22. Therefore, there is no need for a cavity to provide the air suspension 22, and the cavity can be filled with a magnetic material. In other words, magnetic efficiency is good.

[0034] 3 shows the configuration of the vibration table 24. The vibration table 24 has a housing 28 that is generally cylindrical overall, and has a table 26 on top for fixing a specimen.

[0035] A support plate 27 extending radially from the shaft 25 is provided below the table 26. The support plate 27 is fixed to the shaft 25 and a housing 28. An opening 29 is provided in the housing 28, leaving an area for fixing the support plate 27.

[0036] Furthermore, the lower part remains cylindrical, with a drive coil 20 wound around the outer periphery.

[0037] Figure 4 shows the configuration of the magnetic bodies 12 and 13. The magnetic body 12 is formed in a cylindrical shape with a bottom, and the magnetic body 13 is provided in its central portion. The magnetic body 13 is made up of eight triangular prisms, which are arranged with a predetermined gap 11 between them. A gap 18 is provided between the outer magnetic body 12 and the inner magnetic body 13. The cylindrical portion of the vibration table 24 in Figure 3 is inserted into this gap 18.

[0038] 5 shows the state in which the vibration table 24 is inserted into the gap 18 between the magnetic bodies 12 and 13. The cylindrical portion of the housing 28 of the vibration table 24 is inserted into the gap 18, and the support plate 27 of the vibration table 24 is inserted into the interval 11. After the insertion, the auxiliary magnetic body 15 is inserted between the magnetic bodies 12 and 13.

[0039] A metal protrusion 42 is provided on the side of the table 26. A proximity sensor 40 is provided facing this protrusion 42. The protrusion 42 is formed so that the height of the part facing the proximity sensor 40 changes in accordance with the vertical movement of the vibration table 24. This allows the proximity sensor 40 to detect the height position of the vibration table 24.

[0040] 1.3 Configuration and Operation of the Control Circuit 80 Figure 6 shows the configuration of the control circuit 80. The center position indicator 82 has an operation unit for determining the center position (initial position when no excitation signal is present) of the vibration table 24. The operator can determine the desired center position by operating this operation unit.

[0041] A difference calculator 84, which is configured by an operational amplifier or the like, calculates the difference between the output of the proximity sensor 40 (i.e., the position of the vibration table 24) and the center position determined by the center position indicator 82. This difference is provided to a gain controller 86.

[0042] The gain controller 86 increases or decreases the DC output so that the difference between the two approaches 0. The DC output of the gain controller 86 is provided to the power module 20 via an adder 90. The power module 35 amplifies the provided signal and supplies power to the drive coil 20.

[0043] The position of the vibration table 24 changes depending on the magnitude of the power supplied to the drive coil 20, and this position change is detected by the proximity sensor 40. Therefore, the vibration table 24 is maintained at the center position (see FIG. 5b) set by the center position indicator 82 by a feedback circuit consisting of the proximity sensor 40, difference calculator 84, gain controller 86, and drive coil 20. In this manner, initial control is completed.

[0044] In this way, when the vibration table 24 is held at the initial position in the initial control, the vibration signal input circuit 88 then receives a vibration signal (a waveform signal representing a desired vibration) from the vibration control circuit.

[0045] The vibration signal input circuit 88 receives an analog vibration signal. Alternatively, the vibration signal may be digital data and converted into an analog signal. The analog vibration signal is provided to an adder 90, which is composed of an operational amplifier and the like. In the initial control, the adder 90 is controlled to output a direct current that holds the vibration table 24 in the initial position. Therefore, the adder 90 outputs a vibration signal whose center value is the direct current.

[0046] The power module 35 amplifies this signal and supplies it to the drive coil 20. Therefore, the vibration table 24 is vibrated in accordance with the vibration signal, centered on the set initial position. Drive control is performed in this manner.

[0047] If control stops when a system abnormality occurs or when the vibration test is completed, the vibration table 24 may fall, causing unnecessary vibrations to the test piece.

[0048] Therefore, in this embodiment, a switch 72 is provided. The short circuit indication signal output circuit 92 outputs a short circuit indication signal when it receives a stop signal from the vibration control circuit, when a drive current exceeding a limit value is output, when the vibration table 24 vibrates beyond a predetermined limit, when it receives a signal indicating an abnormal state from the vibrator in an abnormal situation such as when a power supply malfunctions, or when it receives an emergency stop signal from the thermostatic bath or the like due to an operator's operation.

[0049] When the short circuit instruction signal is given to the switch 72, the switch 72 turns on. If there is a static magnetic field from the excitation coils 14, 16, this generates a current that generates a driving force in the direction that prevents the fall of the drive coil 20, which is falling together with the vibration table 24, as shown in Figure 7. This brakes the fall of the vibration table 24, allowing it to be lowered gently.

[0050] In the event of a power outage, power is also cut off to the excitation coils 14 and 16, which generate the static magnetic field. However, due to the nature of the excitation coils 14 and 16, the magnetic flux does not change suddenly even when the power supply is cut off, and the static magnetic field remains for approximately the time required for the brake. Therefore, even if the excitation current is not supplied due to a power outage, the brake can be applied in the same way.

[0051] Furthermore, it is preferable that the switch 72 be structured so that it turns on when the power supply to the control circuit 80 is lost and the control circuit 80 stops. For example, a switch whose reference position is off and which turns off only while a signal is being sent from the control circuit 80 is used. In this case, the switch turns to its reference on position when the control circuit 80 stops.

[0052] 1.4 Control Circuit 80 Configured by a CPU FIG. 8 shows a hardware configuration when the control circuit 80 is configured using a CPU. In this embodiment, the control circuit 80 has a CPU 50, a memory 52, an SSD 54, and an I / O port 56. An operating system (such as TRON) 58 and a control program 60 are recorded on the SSD 54. The control program 60 performs its functions in cooperation with the operating system 58. Note that the control program 60 may be operated independently.

[0053] The I / O port 56 is connected to the proximity sensor 40, a vibration control circuit 70, and an amplifier 30, which is a current application circuit. The vibration control circuit 70 performs control and outputs a control signal so that the desired vibration can be applied to the specimen fixed to the table 26. The power module 35 is a circuit for outputting a drive current to the drive coil 20. In this embodiment, a switch 72 is provided for shorting the output of the power module 35. This switch 72 can be controlled from the CPU 50 via the I / O port 56.

[0054] 9 and 10 show flowcharts of the control program 60. Fig. 9 is a flowchart of the initial setting, and Fig. 10 is a flowchart of the drive process.

[0055] In the initial setting of FIG. 9, the CPU 50 turns off the switch 72 (step S1).

[0056] Next, the CPU 50 controls the power module 35 to output a direct current, acquires the output of the proximity sensor 40, and controls the vibration table 24 to maintain its position at a reference position (for example, the center point of the vertical range of movement) (step S2). As a result, the vibration table 24 rises from its lowest position (FIG. 5a) and is maintained at the reference position as shown in FIG. 5b.

[0057] Once the initial settings are completed as described above, the CPU 50 provides a control signal from the vibration control circuit 70 to the power module 35 (step S6). The vibration control circuit 70 outputs a control signal (waveform signal) for applying a desired vibration to the test piece fixed to the vibration table 24. In response to this control signal, the amplifier 30 outputs a control current corresponding to the control signal, which is superimposed on a DC current, as a drive current and is provided to the drive coil 20. Therefore, the vibration table 24 vibrates up and down based on the control signal, centered on the reference position shown in FIG. 5b.

[0058] In this manner, the specimen fixed to the vibration table 24 can be vibrated.

[0059] Furthermore, if an abnormality occurs in the vibrator, for example, if a drive current exceeding a limit value is output, if the vibration table 24 vibrates beyond a specified limit, or if an abnormality occurs in the power supply, the vibration table 24 may fall, causing unnecessary vibrations to the test specimen.

[0060] Therefore, in this embodiment, a switch 72 is provided. In the event of an abnormality such as the one described above, a stop signal is sent. Upon receiving this signal, the CPU 50 turns on the switch 72 (step S8). If a static magnetic field is generated by the excitation coils 14, 16, this generates a current that generates a driving force in the direction that prevents the drive coil 20 from falling along with the vibration table 24, as shown in FIG. 7. This brakes the fall of the vibration table 24, allowing it to be lowered gently.

[0061] 1.5 Modifications (Other) (1) In the above embodiment, the switch 72, which is a short-circuiting switch, shorts both ends of the drive coil 20, generating reverse power during a fall, thereby acting as a brake. However, instead of or in addition to this, an air cylinder 82 may be provided as a fall prevention mechanism, as shown in FIG. 11. When the control circuit 80 receives a stop signal, it extends the rod 84 of the air cylinder 82 to prevent the vibration table 24 from falling. In FIG. 11, the rod 84 is shown in the extended state by the dashed line. It is preferable to provide multiple air cylinders 82.

[0062] 12, when an auxiliary table 27 is provided on the vibration table 24, an air cylinder 82 may be provided below the auxiliary table 27 as a fall prevention mechanism. The rod 84 of the air cylinder 82 is normally retracted so as not to interfere with the vibration. When a stop signal is received, the CPU 50 extends the rod 84 of the air cylinder 82. This makes it possible to prevent the vibration table 24 from suddenly falling.

[0063] (2) In the above embodiment, the center point of the vertical movement range of the vibration table is set as the reference position. However, a position below (above) the center point may also be set as the reference position.

[0064] (3) In the above embodiment, the static magnetic field is formed by the excitation coils 14 and 16, but the static magnetic field may be formed by a permanent magnet.

[0065] (4) In the above embodiment, the proximity sensor 40 is used to detect the position of the vibration table 24. However, other sensors such as a laser distance finder may also be used.

[0066] (5) In the above embodiment, an air suspension is not provided. However, an air suspension may be provided as in the past. Under normal circumstances, the air suspension may be opened and not function, but in an emergency (such as when a stop signal is received), the air suspension may be activated (by closing the release valve) to send in air and be used to prevent falls. In this case, the air suspension is only used to prevent falls, so precise adjustment and control are not required.

[0067] (6) In the above embodiment, the excitation coil is used as the magnetic flux generation source. However, a permanent magnet may be used as the magnetic flux generation source.

[0068] (7) The above embodiment and its modifications can also be applied to other embodiments.

[0069] 2. Second Embodiment 2.1 Functional Configuration Figure 13 shows the functional configuration of a vibration generator according to another embodiment. The current application circuit 30 is a circuit for applying a drive current to the drive coil 20. The initial control means 32 controls the current application circuit 30 to apply a direct current to the drive coil 20. The initial control means 32 controls the current value of the direct current to cause the drive coil 20 to raise the vibration table 24 to a reference point (for example, the center point of the range in which up and down vibration is possible).

[0070] The calculation means 35 calculates a weight-related value of the test piece placed on the vibration table 24 based on the current value for raising the vibration table 24 to the reference point by the initial control means 32 .

[0071] In this embodiment, the weight-related value of the specimen is calculated based on the value of the DC current during initial control, so that the weight-related value of the specimen can be obtained without using a weighing scale or the like.

[0072] 2.2 Structure of the Vibration Generator The structure of the vibration generator is the same as that of the first embodiment shown in FIGS.

[0073] 2.3 Configuration and Operation of Control Circuit 80 The configuration of the control circuit 80 is the same as that shown in FIGS. 6 and 8 in the first embodiment.

[0074] When the control circuit 80 is configured as shown in Figure 6, the center position indicator 82 is set to a position (for example, the center of the movable range) that is predetermined for calculation purposes. The test specimen is fixed to the vibration table 24, and the drive current value required to maintain the vibration table 24 at the predetermined position is obtained. This can be done by measuring the DC current of the power module 80.

[0075] Next, the weight of the specimen is calculated based on the measured DC current. This calculation process can be performed by a computer or the like. The total weight of the vibration table 24 and the weight of the specimen is proportional to the value of the DC current (the DC current for holding the specimen at the reference position). Therefore, the weight of the specimen can be calculated as follows:

[0076] The weight of the vibration table 24 is m kg, the force coefficient of the vibrator is BLN / A, a driving current IA (peak value) is applied, and the acceleration is am / s 2 When excitation is performed at this value, if the excitation force of the vibrator at that time is FN, then the following holds: F=m*a=BL*I... (1) where F, a, and I are the rated values ​​of the vibrator and are known values.

[0077] When a specimen of M kg is fixed to the vibration table 24 and held at the reference position by passing a DC current Idc through it, the gravitational acceleration is 9.8 m / s 2 Then, as above, it can be expressed as Fdc=(m+M)*9.8=BL*Idc...(2).

[0078] From equations (1) and (2), the weight M of the specimen can be calculated as follows: M=(Idc / I*a / 9.8-1)*m

[0079] Once the initial setup is complete as described above, the required maximum excitation force is calculated based on the weight of the specimen and the maximum acceleration of the vibration to be applied in the test. In other words, the required maximum excitation force is calculated as follows: required maximum excitation force = specimen weight x maximum acceleration.

[0080] If the calculated required maximum excitation force is less than the rated excitation force of the vibration generator, the vibration test is started. However, if the calculated required maximum excitation force exceeds the rated excitation force of the vibration generator, the vibration test is not started.

[0081] The driving process is the same as that shown in FIG. 10 in the first embodiment.

[0082] 2.4 Control Circuit 80 Configured by a CPU When the control circuit 80 is configured by a CPU, the hardware configuration is the same as that shown in FIG.

[0083] 14 and 10 show flowcharts of the control program 60. Fig. 14 is a flowchart of the initial setting, and Fig. 10 is a flowchart of the drive process.

[0084] In the initial setting of FIG. 14, the CPU 50 turns off the switch 72 (step S1).

[0085] Next, the CPU 50 controls the power module 35 to output a direct current, acquires the output of the proximity sensor 40, and controls the vibration table 24 to maintain its position at a reference position (for example, the center point of the vertical range of movement) (step S2). As a result, the vibration table 24 rises from its lowest position (FIG. 5a) and is maintained at the reference position as shown in FIG. 5b.

[0086] Next, the CPU 50 calculates the weight of the specimen based on the determined DC current (step S55). The total weight of the vibration table 24 and the weight of the specimen is proportional to the value of the DC current (DC current for holding the specimen at the reference position). Therefore, the weight of the specimen can be calculated as follows:

[0087] The weight of the vibration table 24 is m kg, the force coefficient of the vibrator is BLN / A, a driving current IA (peak value) is applied, and the acceleration is am / s 2 When excitation is performed at this value, if the excitation force of the vibrator at that time is FN, then the following holds: F=m*a=BL*I... (1) where F, a, and I are the rated values ​​of the vibrator and are known values.

[0088] When a specimen of M kg is fixed to the vibration table 24 and held at the reference position by passing a DC current Idc through it, the gravitational acceleration is 9.8 m / s 2 Then, as above, it can be expressed as Fdc=(m+M)*9.8=BL*Idc...(2).

[0089] From equations (1) and (2), the weight M of the specimen can be calculated as follows: M=(Idc / I*a / 9.8-1)*m

[0090] Once the initial setup is complete as described above, the required maximum excitation force is calculated based on the weight of the specimen and the maximum acceleration of the vibration to be applied in the test. In other words, the required maximum excitation force is calculated as follows: required maximum excitation force = specimen weight x maximum acceleration.

[0091] If the calculated required maximum excitation force is less than the rated excitation force of the vibration generator, the CPU 50 starts the vibration test. However, if the calculated required maximum excitation force exceeds the rated excitation force of the vibration generator, the CPU 50 displays a message to that effect and does not start the vibration test.

[0092] The driving process is the same as that shown in FIG. 10 in the first embodiment.

[0093] 2.5 Modifications (Other) (1) In the above embodiment, the weight of the specimen is calculated using a formula. However, the relationship between the weight of the specimen and the DC current may be measured in advance, and the weight may be calculated based on this relationship.

[0094] (2) In the above embodiment, the weight of the test specimen is calculated. However, the weight ratio of multiple test specimens may be calculated. In this case, the weight ratio of the test specimens can be calculated based on the ratio of the DC currents required to lift each test specimen to the reference position, without calculating the weight of each test specimen based on the DC current.

[0095] (3) The above embodiment and its modifications can also be applied to other embodiments.

Claims

1. A vibration generating device comprising: a magnetic flux generating source that generates magnetic flux; a drive coil that is disposed in the magnetic flux generated by the magnetic flux generating source and is driven by current; a vibration table that is driven by the driving force of the drive coil and on which a test specimen is placed; a current application circuit that applies a drive current to the drive coil; initial control means that, in an initial state, controls the current application circuit so that a direct current is applied as a drive current to the drive coil in order to lift the vibration table to a reference position; and drive control means that, in a driven state, controls the current application circuit so that a control current corresponding to a control signal is superimposed on the direct current and applied as a drive current to the drive coil in order to vibrate the vibration table.

2. The device according to claim 1, further comprising a short-circuit switch that short-circuits both ends of the drive coil when an abnormal state is detected.

3. The device according to claim 1, further comprising a fall prevention mechanism that is activated when an abnormal state is detected to prevent the vibration table from falling.

4. The apparatus according to claim 1, further comprising a calculation means for calculating a weight-related value of a specimen placed on said vibration table based on the value of said DC current applied by said initial control means.

5. A vibration generating device comprising: a magnetic flux generating source that generates magnetic flux; a drive coil that is disposed in the magnetic flux generated by the magnetic flux generating source and is driven by an electric current; a vibration table that is driven by the driving force of the drive coil and on which a test specimen is placed; a current application circuit that applies a drive current to the drive coil; initial control means that controls the current application circuit so that a direct current is applied to the drive coil as a drive current in an initial state in order to lift the vibration table to a reference position; and calculation means that calculates a weight-related value of the test specimen placed on the vibration table based on the value of the direct current applied by the initial control means.

6. A control program for realizing a controller for a vibration generating device by a computer, which causes the computer to function as: initial control means for controlling a current application circuit to apply a direct current as a drive current to a drive coil in order to lift the vibration table to a reference position in the initial state; and calculation means for calculating a weight-related value of a specimen placed on the vibration table based on the value of the direct current applied by the initial control means.

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