Abstract:
A viscometer capable of measuring a viscosity in high precision by increasing a transmission efficiency of a rotational torque while simplifying a structure and facilitating a down-sizing is provided. A viscometer comprises includes: a hollow shaft motor; a needle shaft piercing through a hollow driving shaft of the hollow shaft motor and having an upper end side and a lower end side supported to be rotatable; a spring configured to transmit a driving force of the hollow shaft motor to the needle shaft; a spindle attached to the lower end side of the needle shaft; and a phase difference detection unit configured to detect a rotational phase difference between the hollow driving shaft 4 and the needle shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of priority to Japanese Patent Application No. 2015-115727 filed on Jun. 8, 2015, the entire contents of which are incorporated by reference herein. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a viscometer for measuring a viscosity of a sample by rotating a spindle in the sample and measuring a reaction torque. 
         [0003]    BACKGROUND OF THE INVENTION Conventionally, there are various schemes that have been proposed as a viscometer for measuring a viscosity of a sample liquid. For example, as a viscometer of the scheme similar to a viscometer as described in Japanese Patent No. 3,475,019, as shown in  FIG. 3 , one in which a cylindrical spindle  102  is rotated in a sample liquid  101 , a reaction torque with respect to this rotation is measured, and a viscosity of the sample liquid is calculated has been proposed. 
         [0004]    This viscometer has a pulse motor  103 , and the spindle  102  that is immersed in the sample liquid  101  is rotated by a driving force of this pulse motor  103 . To a driving shaft  104  of the pulse motor  103 , a first metal shaft  106  is connected via a shaft coupler  105 . This first metal shaft  106  is supported to be rotatable by a first base  108  via a first through bearing  107 . This first base  108  is fixed to a chassis not shown in the figure. The first metal shaft  106  has a hollow lower end side. 
         [0005]    To the first metal shaft  106 , a first rotor plate  109  is attached. To the first rotor plate  109 , a coupling plate  111  is attached via a coupling pin  110 . This coupling plate  111  is connected to a second metal shaft  112 . This second metal shaft  112  is supported to be rotatable by a second base  114  via a second through bearing  113 . This second base  114  is fixed to the chassis not shown in the figure. The second metal shaft  112  is a hollow cylindrical shaft, which is made to be coaxial with the first Metal shaft  106 . 
         [0006]    In a vicinity of a lower end portion of the second metal shaft  112 , a first pivot crank  115  is attached. This first pivot crank  115  is a C-shaped member, and its upper end side is attached to a vicinity of the lower end portion of the second metal shaft  112 . A lower end side of the first pivot crank  115  is positioned on an axis of the second metal shaft  112 . On an upper face of the lower end side of the first pivot crank  115 , a jewel bearing  116  is attached. 
         [0007]    Then, between a hollow portion on the lower end side of the first metal shaft  106  and the jewel bearing  116 , a needle shaft  117  is disposed by piercing through the hollow portion of the second metal shaft  112 . An upper end portion of this needle shaft  117  is supported to be rotatable at a lower end side (a bottom part of the hollow portion) of the first metal shaft  106  via a bearing  122 . A lower end portion of the needle shaft  117  is made to be a conical protrusion, and supported to be ratatable at this protrusion by the jewel bearing  116 . This needle shaft  117  is made to be coaxial with the first metal shaft  106  and the second metal shaft  112 . 
         [0008]    In a vicinity of a lower end portion of the needle shaft  117 , a second pivot crank  118  is attached. This second pivot crank  118  is a C-shaped member, and its upper end side is attached to a vicinity of the lower end portion of the needle shaft  117 . A lower end side of the second pivot crank  118  is positioned on an axis of the needle shaft  117 . On a lower face of the lower end side of the second pivot crank  118 , a spindle holder  119  is attached. To this spindle holder  119 , the spindle  102  is attached coaxially to be detachable. 
         [0009]    A section between the first rotor plate  109  and the needle shaft  117  is coupled by a spiral shaped spiral spring  120 . An end portion on a center side of the spiral spring  102  is fixed to an upper end side portion of the needle shaft  117 . An end portion on an outer circumferential side of the spiral spring  120  is fixed to the first rotor plate  109 . Also, to an upper end side portion of the needle shaft  117 , a second rotor plate  121  that is parallel to the first rotor plate  109  is attached. 
         [0010]    In this viscometer, when the pulse motor  103  is driven and the driving shaft  104  is operated in rotation, the first metal shaft  106 , the first rotor plate  109 , the coupling plate  111 , the second metal shaft  112  and the first pivot crank  115  are operated in rotation with the identical speed as the driving shaft  104  by this driving force. At this point, a rotational force of the first rotor plate  109  is transmitted to the needle shaft  117  via the spiral spring  120 , and operates the needle shaft  117  in rotation. When the needle shaft  117  is operated in rotation, the second rotor plate  121 , the second pivot crank  118 , the spindle holder  119  and the spindle  102  are operated in rotation with the identical speed as the needle shaft  117 . 
         [0011]    At this point, if the viscosity of the sample liquid  101  is zero, the spindle  102  receives no resistance against rotating, so that the spiral spring  120  is not displaced, and the needle shaft  117  and the second rotor plate  121  are rotated with the identical speed and the identical phase as the first metal shaft  106  and the first rotor plate  109 . When the viscosity of the sample liquid  101  is non-zero, the spindle  102  receives a resistance against rotating, so that the spiral spring  120  is displaced by this reaction torque, and the needle shaft  117  and the second rotor plate  121  are rotated with a phase delayed with respect to the first metal shaft  106  and the first rotor plate  109 . In a state where the reaction torque due to a resistance of the sample liquid  101  and a torque due to a recovering force of the displaced spiral spring  120  are balanced, the rotational speed of the needle shaft  117  and the second rotor plate  121  becomes the identical speed as the rotational speed of the first metal shaft  106  and the first rotor plate  109 , and a phase delay corresponding to a displacement amount of the spiral spring  120  is maintained to be constant. In this state, when a phase difference between the first rotor plate  109  and the second rotor plate  121  is detected, it is possible to calculate the viscosity of the sample liquid  101  from this phase difference. 
         [0012]    In the conventional viscometer as described above, from the first metal shaft  106  up to the second metal shaft  112  and the first pivot crank  115  are coupled to the driving shaft  104 , and their inertial mass is large, so that a large driving force is required., and it is difficult to make the pulse motor  103  compact. Also, it is difficult to use one with a variable adjustable speed as the pulse motor  103 , in order to avoid a larger size of the pulse motor  103 . 
         [0013]    Also, with respect to these members that are coupled to the driving shaft  104 , the pulse motor  103  is in a state of cantilever support, so that it is difficult to make the device configuration compact. Moreover, as the pulse motor  103  is cantilever supporting these members, an inclination of the axis is prone to occur, and in order to prevent an inclination, it is inevitable to make the members such as bearing and the like in a large size. Also, a transmission loss of the rotational torque is prone to occur, so that the viscosity measurement in high precision is difficult. 
       SUMMARY OF THE INVENTION 
       [0014]    The present invention has been achieved in view of the above described problems, and has an object of providing a viscometer capable of measuring a viscosity in high precision by increasing a transmission efficiency of a rotational torque, while simplifying a structure and facilitating a down-sizing. 
         [0015]    In order to resolve the above described problems and achieve the above noted object, the viscometer according to the present invention has the following configuration. 
       Configuration I 
       [0016]    A viscometer, comprising: a hollow shaft motor to be a driving source fixed to a chassis; a needle shaft, provided to be piercing through a hollow driving shaft of the hollow shaft motor, having an upper end side supported to be rotatable by the chassis and a lower end side supported to be rotatable by a lower end side of the hollow driving shaft; a spring configured to transmit a driving power of the hollow shaft motor to the needle shaft; a spindle holder, provided on the lower end side of the needle shaft, to which a spindle is attached to be detachable; and a phase difference detection unit configured to detect a rotational phase difference between the hollow driving shaft and the needle shaft; wherein when the spindle attached to the spindle holder is immersed into a sample liquid and the hollow shaft motor is driven, the spring is displaced due to a reaction torque caused by a resistance due to a viscosity of the sample liquid with respect to the spindle, the rotational phase difference between the hollow driving shaft and the needle shaft is detected in a state where a torque caused by a recovering force of the displaced spring and the reaction torque are balanced, and a viscosity of the sample liquid is determined according to the detected rotational phase difference. 
       Configuration II 
       [0017]    In the viscometer having the configuration I, an upper end side of the needle shaft is supported to be rotatable by the chassis via bearings; the lower end side of the needle shaft is supported to be rotatable by a C-shaped first pivot crank attached to the lower end side of the hollow driving shaft; the spindle holder is attached to a C-shaped second pivot crank attached to the lower end side of the needle shaft; and the rotational phase difference between the hollow driving shaft and the needle shaft is detected by detecting a rotational phase difference between the first pivot crank and the second pivot crank. 
         [0018]    In the viscometer according to the present invention having the configuration I, the hollow shaft motor to be a driving source and the needle shaft provided to be piercing through a hollow driving shaft of this hollow shaft motor are provided, and a viscosity of the sample liquid is determined by detecting the rotational phase difference between the hollow driving shaft and the needle shaft, so that a structure is simple and a down-sizing is facilitated, while a transmission efficiency of the rotational torque is increased so that a viscosity measurement in high precision is possible. 
         [0019]    In the viscometer according to the present invention having the configuration II, the upper end side of the needle shaft is supported to be rotatable by the chassis via bearings, and the lower end side of the needle shaft is supported to be rotatable by a C-shaped first pivot crank attached to the lower end side of the hollow driving shaft, so that the inclination of the needle shaft can be prevented, and the rotational resistance of the needle shaft can be made extremely low, so that a viscosity measurement in high precision is possible. 
         [0020]    Namely, the present invention is capable of providing a viscometer capable of measuring a viscosity in high precision by increasing a transmission efficiency of a rotational torque, while simplifying a structure and facilitating a down-sizing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a longitudinal cross sectional view showing a configuration of a viscometer according to one embodiment of the present invention. 
           [0022]      FIG. 2  is a block diagram showing a configuration of a viscometer according to one embodiment of the present invention. 
           [0023]      FIG. 3  is a longitudinal cross sectional view showing a configuration of a prior art viscometer. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    In the following, the embodiment of the present invention will be described with references to the drawings. 
         [0025]      FIG. 1  is a longitudinal cross sectional view showing a configuration of a viscometer according to one embodiment of the present invention. 
         [0026]    As shown in  FIG. 1 , the viscometer according to the present invention is a device in which a cylindrical spindle  102  is rotated in a sample liquid  101 , a reaction torque with respect to this rotation is measured, and a viscosity of the sample liquid is calculated. 
         [0027]    This viscometer has a hollow shaft motor  3  to be a driving source, and the spindle  102  that is immersed in the sample liquid  101  is rotated by a driving force of this hollow shaft motor  3 . A hollow driving shaft  4  of the hollow shaft motor  3  is formed in a hollow cylindrical shape. The hollow shaft motor  3  is fixed at an upper end side and a lower end side by a first base  6  and a second base  7  that constitute a chassis  5 . On an upper end portion of the hollow driving shaft  4  of the hollow shaft motor  3 , a rotor plate  8  is attached. 
         [0028]    Note that the hollow shaft motor  3  is a pulse motor, and it is possible to use a dry cell as its driving power source. Also, the hollow shaft motor  3  is capable of making a rotational speed adjustment. 
         [0029]    In a vicinity of a lower end portion of the hollow driving shaft  4  of the hollow shaft motor  3 , a first pivot crank  9  is attached. This first pivot crank  9  is a C-shaped member, and its upper end side is attached to a vicinity of the lower end portion of the hollow driving shaft  4 . A lower end side of the first pivot crank  9  is positioned on an axis of the hollow driving shaft  4 . On an upper face of the lower end side of the first pivot crank  9 , a jewel bearing  10  is attached. 
         [0030]    Then, a needle shaft  11  is disposed by piercing through the hollow driving shaft  4  of the hollow shaft motor  3 . An upper end portion of this needle shaft  11  is supported to be rotatable by a third base  13  that constitutes the chassis  5  via a bearing  12 . A lower end portion of the needle shaft  11  is made to be a conical protrusion, and supported to be rotatable at this protrusion by the jewel bearing  10  on the lower end side of the hollow driving shaft  4 . This needle shaft  11  is made to be coaxial with the hollow driving shaft  4 . 
         [0031]    In a vicinity of a lower end portion of the needle shaft  11 , a second pivot crank  14  is attached. This second pivot crank  14  is a C-shaped member, and its upper end side is attached to a vicinity of the lower end portion of the needle shaft  11 . A lower end side of the second pivot crank  14  is positioned on an axis of the needle shaft  11 . On a lower face of the lower end side of the second pivot crank  14 , a spindle holder  15  is attached. To this spindle holder  15 , the spindle  102  is attached coaxially to be detachable. 
         [0032]    The spindle  102  can be exchanged with that of a different material, size and shape, depending on a type and a viscosity of the sample liquid for which the viscosity is to be measured. The sample liquid in which this spindle  102  is to be immersed is preferably contained in a container that is as large as possible, and preferably at least 500 ml of the sample liquid is contained in the container. 
         [0033]    A section between the rotor plate  8  and the needle shaft  11  is coupled by a spiral shaped spiral spring  16 . This spiral spring  16  is a spring for transmitting a driving force of the hollow shaft motor  3  to the needle shaft  11 . An end portion on a center side of the spiral spring  16  is fixed to an upper end side portion of the needle shaft  11 . An end portion on an outer circumferential side of the spiral spring  16  is fixed to the rotor plate  8 . 
         [0034]    Then, this viscometer has a phase difference detection unit for detecting a rotational phase difference between the hollow driving shaft  4  and the needle shaft  11 . Namely, on a side face portion of the first pivot crank  9 , a first segment to be detected  17  is attached. This first segment to be detected  17  is detected by a first interrupter  18  attached to the chassis  5 . The first interrupter  18  detects a passage of the first segment to be detected  17  once during one rotation of the first pivot crank  9 . 
         [0035]    Also, on a side face portion of the second pivot crank  14 , a second segment to be detected  19  is attached. This second segment to be detected  19  is detected by a second interrupter  20  attached to the chassis  5 . The second interrupter  20  detects a passage of the second segment to be detected  19  once during one rotation of the second pivot crank  14 . 
         [0036]    Note that, on the chassis  5 , a display unit  21  comprising a liquid crystal display panel or an organic EL display panel is provided. 
         [0037]    In this viscometer, by detecting a rotational phase difference between the hollow driving shaft  4  and the needle shaft  11 , the viscosity (mPa·S) of the sample liquid  101  is obtained according to the detected rotational phase difference. Namely, in this viscometer, when the hollow shaft motor  3  is driven and the hollow driving shaft  4  is operated in rotation, the rotor plate  8  is operated in rotation with the identical speed as the hollow driving shaft  4  by this driving force. At this point, a rotational force of the rotor plate  8  is transmitted to the needle shaft  11  via the spiral spring  16 , and operates the needle shaft  11  in rotation. When the needle shaft  11  is operated in rotation, the second pivot crank  14 , the spindle holder  15  and the spindle  102  are operated in rotation with the identical speed as the needle shaft  11 . 
         [0038]    At this point, if the viscosity of the sample liquid  101  is zero, the spindle  102  receives no resistance against rotating, so that the spiral spring  16  is not displaced, and the needle shaft  11  is rotated with the identical speed and the identical phase as the rotor plate  8 . 
         [0039]    When the viscosity of the sample liquid  101  is non-zero, the spindle  102  receives a resistance against rotating, so that the spiral spring  16  is displaced by this reaction torque, and the needle shaft  11  is rotated with a phase delayed with respect to the rotor plate  8 . In a state where the reaction torque due to a resistance of the sample liquid  101  and a torque due to a recovering force of the displaced spiral spring  16  are balanced, the rotational speed of the needle shaft  11  becomes the identical speed as the rotational speed of the rotor plate  8 , and a phase delay corresponding to a displacement amount of the spiral spring  16  is maintained to be constant. In this state, when a phase difference between the hollow driving shaft  4  and the needle shaft  11 , that is a phase difference between the first pivot crank  9  and the second pivot crank  14 , is detected, it is possible to calculate the viscosity of the sample liquid  101  from this phase difference. 
         [0040]      FIG. 2  is a block diagram showing a configuration of the viscometer according to one embodiment of the present invention. 
         [0041]    As shown in  FIG. 2 , in this viscometer, the hollow shaft motor  3  is controlled by a motor control circuit  22 , as to its activation, stopping, and rotational speed. The motor control circuit  22  is controlled by a control circuit  23  for controlling this device as a whole. The control circuit  23  operates as a power is supplied from a power source unit  24 . Also, the power source unit  24  supplies a driving power to the hollow shaft motor  3  and other units. This power source unit  24  supplies the driving power to respective units of this device by being supplied with a power from a commercial AC power source, or a dry cell or a battery. 
         [0042]    Also, to the control circuit  23 , various control signals can be inputted from an input unit  25 . These control signals are signals for activating or stopping the operation of this device, and instructing the rotational speed of the hollow shaft motor  3  (the rotational speed adjustment) and the like. 
         [0043]    The detection signals indicating the detections of the first and second segments to be detected  17  and  19  by the first and second interrupters  18  and  20  are sent to the control circuit  23 . The control circuit  23  calculates the viscosity of the sample liquid  101  according to the detection signals sent from the first and second interrupters  18  and  20 . 
         [0044]    Also, the control circuit  23  carries out a prescribed display on the display unit  21 . The contents to be displayed on the display unit  21  may include at least one of the viscosity (mPa·S) of the sample liquid  101  that is measured (calculated), the rotational speed of the hollow shaft motor  3 , the rotational phase difference between the first pivot crank  9  and the second pivot crank  14 , the power on/off state, and the like. 
         [0045]    The present invention is applicable to a viscometer for measuring a viscosity of a sample by rotating a spindle in the sample and measuring a reaction torque. 
         [0046]    Although the present invention has been fully described in connection with the preferred embodiment thereof with reference to the accompanying drawings, it is apparent to those skilled in the art that changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims.