Patent Publication Number: US-2023158648-A1

Title: Impact rotary tool

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is based upon and claims the benefit of priority to Japanese Patent Application No. 2021-188797, filed on Nov. 19, 2011, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to impact rotary tools, and specifically, to an impact rotary tool including a hammer, an anvil, a sensor disposed in the vicinity of the anvil, and a circuit board to which an output of the sensor is given. 
     BACKGROUND ART 
     JP 2021-070108 A (Literature 1) discloses an electric tool including a motor, an impact mechanism (hammer), an output shaft (anvil), a torque measuring unit (sensor), a tightening torque computing unit, and a controller (circuit board). The impact mechanism receives rotational force from the motor and applies, to the output shaft, impact force obtained by converting part of the rotational force into pulsed rotational force. The torque measuring unit measures torque applied to the output shaft with reference to a strain of the output shaft caused by the impact force. The tightening torque computing unit computes tightening torque applied to a tightening member from the output shaft via a tip tool with reference to the torque thus measured. The controller controls the motor in accordance with the tightening torque thus computed. 
     In an impact rotary tool having a configuration as described above, striking force (an impact) produces abrasion powder generally at contact portions between the hammer and the anvil. Adhesion of conductive abrasion powder to the circuit board may make a non-conductive part conductive, which may destabilize operation of the impact rotary tool. 
     In the electric tool described in Literature 1, the tightening torque computing unit and other elements are housed in a case, thereby achieving a certain degree of suppression of the adhesive powder from adhering to the tightening torque computing unit and other elements, but further suppression is still required. 
     SUMMARY 
     An object of the present disclosure is to provide an impact rotary tool in which abrasion powder produced between a hammer and an anvil is suppressed from adhering to a circuit board. 
     An impact rotary tool according to an aspect of the present disclosure includes a motor, a hammer, an anvil, a sensor, a circuit board, and an isolator. The hammer is configured to receive rotational force around an axis from the motor and output striking rotational force. The striking rotational force is obtained by converting part of the rotational force into impact force around the axis. The anvil to which a tip tool is to be attached is configured to rotate, together with the tip tool, around the axis in response to the striking rotational force received from the hammer. The sensor is disposed in a vicinity of the anvil and is configured to sense a change in a state of the anvil, the change being according to the striking rotational force. The circuit board is configured to receive a sensing result by the sensor. The isolator is configured to isolate contact portions of the hammer and the anvil from at least the circuit board. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures depict one or more implementation in accordance with the present teaching, by way of example only, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements. 
         FIG.  1    is an external view of an impact rotary tool according to an embodiment of the present disclosure; 
         FIG.  2    is a sectional view of the impact rotary tool; 
         FIG.  3    is a side view of the impact rotary tool with a first housing being removed; 
         FIG.  4    is an exploded perspective view of the impact rotary tool with a second housing being removed; 
         FIG.  5    is a detailed view of the interior of a sensor of the impact rotary tool; 
         FIG.  6    is a side view of the impact rotary tool with a third housing being removed; and  FIG.  7 A  is a schematic diagram of the impact rotary tool,  FIG.  7 B  is a schematic diagram of a first variation of the impact rotary tool, and  FIG.  7 C  is a schematic diagram of a second variation of the impact rotary tool. 
     
    
    
     DETAILED DESCRIPTION 
     Figures described in the following embodiment are schematic views, and the ratio of sizes and the ratio of thicknesses of components do not necessarily reflect actual dimensional ratios. Note that a configuration described in the following embodiment is a mere example of the present disclosure. The present disclosure is not limited to the following embodiment, and various modifications may be made based on design and the like as long as the effect of the present disclosure is achieved. 
     (1) Overview 
     As shown in  FIGS.  1  to  4    and  FIG.  7 A , an impact rotary tool  1  according to the embodiment of the present disclosure includes a motor  11 , a hammer  12 , an anvil  13 , a sensor  14 , a circuit board  15 , and an isolator  10 . 
     (1-1) Motor, Hammer, and Anvil 
     The motor  11  is supplied with electric power from a battery  16  (described later) and generates rotational force around an axis  200 . The hammer  12  receives the rotational force around the axis  200  from the motor  11  and outputs striking rotational force. The striking rotational force is force (impact rotational force) obtained by converting part of the rotational force from the motor  11  into striking force (pulse-like impact force) around the axis  200 . The anvil  13  to which a tip tool  2  is attached rotates, together with the tip tool  2 , around the axis  200  in response to the striking rotational force received from the hammer  12 . 
     (1-2) Sensor 
     The sensor  14  is disposed in the vicinity of the anvil  13  and senses a change in a state of the anvil  13 , the change being according to the striking rotational force generated by the hammer  12 . 
     In the present embodiment, the sensor  14  is a magnetostrictive sensor. The magnetostrictive sensor is a sensor configured to magnetically sense the strain of an object (in the present embodiment, the anvil  13 ), which will be described in detail later. 
     The sensor  14  may, however, be a strain sensor (e.g., a strain gauge configured to electrically sense a strain) other than the magnetostrictive sensor. The sensor  14  may be a sensor (e.g., an acceleration sensor) other than the strain sensor. 
     In the present embodiment, the change in the state to be sensed is a change in the strain of the anvil  13 . Alternatively, the change in the state may be a change (e.g., a change in angular velocity of the anvil  13  around the axis  200 ) other than the strain. 
     (1-3) Circuit Board 
     The circuit board  15  receives a sensing result by the sensor  14 . 
     In the embodiment, the sensor  14  and the circuit board  15  are electrically connected to each other via a lead line  14   c . Alternatively, the sensor  14  and the circuit board  15  may be connected to each other such that near field communication, for example, is possible therebetween. 
     The circuit board  15  in the present embodiment includes an amplifying circuit  15   a  and a processing circuit  15   b . The amplifying circuit  15   a  amplifies a signal (e.g., a voltage signal from a coil included in the magnetostrictive sensor) indicating the sensing result by the sensor  14 . The processing circuit  15   b  performs processing (e.g., conversion into a strain signal and computation to determine tightening torque with reference to the strain) of the voltage signal amplified by the amplifying circuit  15   a.    
     Note that amplification of the voltage signal and the conversion of the voltage signal thus amplified into the strain signal may be performed in the sensor  14 , and the circuit board  15  may perform only the computation to determine the tightening torque with reference to the strain. 
     (1-4) Isolator 
     The isolator  10  isolates contact portions of the hammer  12  and the anvil  13  from at least the circuit board  15 . 
     The contact portions of the hammer  12  and the anvil  13  are: a portion which is part of the anvil  13  and on which the striking rotational force from the hammer  12  acts; and a portion which is part of the hammer  12  and on which reaction force from the anvil  13  acts. 
     The portion, on which the striking rotational force from the hammer  12  acts, of the anvil  13  is an end (a rear end: e.g., an anvil claw  13   b ) on an opposite side from an end (a tip end  13   a ) to which the tip tool  2  is to be attached. The portion, on which the reaction force from the anvil  13  acts, of the hammer  12  is a portion in contact with the rear end of the anvil  13  (e.g., the hammer claw  12   a  to be fitted to the anvil claw  13   b ). 
     That is, the contact portions of the hammer  12  and the anvil  13  are, for example, the hammer claw  12   a  and the anvil claw  13   b  and are hereinafter referred to as contact portions ( 12   a  and  13   b ). 
     In this way, isolating the contact portions ( 12   a  and  13   b ), which are sources of abrasive powder, from the circuit board  15  by the isolator  10  enables the abrasive powder to be suppressed from adhering to the circuit board  15 . 
     (1-4-1) Housing 
     In the present embodiment, the isolator  10  is a housing  101 . As used herein, the housing  101  is a member which covers at least the contact portions ( 12   a  and  13   b ). The circuit board  15  is disposed outside the housing  101 . 
     In other words, the housing  101  encloses only a space (hereinafter referred to as a first space S 1 ) in which the contact portions ( 12   a  and  13   b ) are present, but the housing  101  does not enclose a space (hereinafter referred to as a second space S 2 ) in which the circuit board  15  is present. Thus, the contact portions ( 12   a  and  13   b ) are isolated from at least the circuit board  15 . 
     In this way, covering the sources of the abrasive powder with the housing  101  to confine the abrasive powder in the housing  101  enables the abrasive powder to be suppressed from adhering to the circuit board  15  disposed outside the housing  101 . 
     In the impact rotary tool  1 , usually, the motor  11  is also disposed outside the housing  101 . The impact rotary tool  1  in the present embodiment further includes a battery  16 , a control circuit  17 , and a wireless communication circuit  18  (described later), and these elements are also disposed outside the housing  101 . 
     In other words, the housing  101  encloses only the first space S 1 , does not enclose the second space S 2 , and does not enclose a space (hereinafter referred to as a third space S 3 ) in which the motor  11  is present. In the third space S 3  in the present embodiment, the battery  16 , the control circuit  17 , and the wireless communication circuit  18  are further present. 
     Thus, the contact portions ( 12   a  and  13   b ) are isolated not only from the circuit board  15  but also from the motor  11 , the battery  16 , the control circuit  17 , the wireless communication circuit  18 , and other elements. 
     In the present embodiment, covering the contact portions ( 12   a ,  13   b ), which are the sources of the abrasive powder, with the housing  101  (e.g., a first housing  101 : described later), which is an aspect of the isolator  10 , confines the abrasive powder in the housing  101 , which consequently enables the abrasive powder to be suppressed from adhering to the circuit board  15  disposed outside the housing  101 . 
     In the electric tool of Patent Literature 1, the tightening torque computing unit corresponding to the circuit board  15 , and other elements are covered with a cover. In this case, however, the effect of suppressing adhesion of abrasive powder spreads only to the tightening torque computing unit and other elements. In contrast, when the sources of the abrasive powder are isolated by being covered with the housing  101  as in the present embodiment, the effect of suppressing adhesion of abrasive powder spreads also to circuits (e.g., the control circuit  17  and the wireless communication circuit  18 ) in addition to the circuit board  15 . 
     (1-4-2) Wall 
     The isolator  10  may be a wall  10   a . As used herein, the wall  10   a  is a member (see  FIG.  7 C ) which separates a space (hereinafter referred to as a fourth space S 4 ) in which the contact portions ( 12   a  and  13   b ) and the processing circuit  15   b  are present into the first space S 1  in which the contact portions ( 12   a  and  13   b ) are present and the second space S 2  in which the processing circuit  15   b  is present. Note that the wall  10   a  will be described in a second variation. 
     In this case, isolating the contact portions ( 12   a  and  13   b ) from the circuit board  15  by the wall  10   a , which is another aspect of the isolator  10 , enables the abrasive powder to be suppressed from adhering to the circuit board  15 . 
     (2) Details 
     The impact rotary tool  1  further includes the battery  16 , the control circuit  17 , and the wireless communication circuit  18  as shown in  FIGS.  2  and  6    in addition to the six elements ( 10  to  15 ) described above. 
     The battery  16  supplies electric power to the motor  11 . The control circuit  17  controls the motor  11  with reference to, for example, a processing result by the processing circuit  15   b . The wireless communication circuit  18  wirelessly communicates with an external device (not shown). 
     The isolator  10  in the present embodiment is the housing  101  and is specifically the first housing  101 . 
     (2-1) First Housing 
     The first housing  101  at least covers the contact portions ( 12   a  and  13   b ) between the hammer  12  and the anvil  13 . The circuit board  15  is disposed outside the first housing  101 . The circuit board  15  in the present embodiment is disposed inside a second housing  102  (described later) but is not limited to this example. 
     The first housing  101  encloses only the first space S 1  in which the contact portions ( 12   a  and  13   b ) are present and does not enclose the second space S 2  in which the circuit board  15  is present. 
     In the impact rotary tool  1  of the present embodiment, the hammer  12 , part of the anvil  13  except for the tip end  13   a  to which the tip tool  2  is to be attached, and the sensor  14  are present in the first space S 1  as shown in, for example,  FIGS.  2  and  7 A . Thus, the hammer  12 , most part of the anvil  13 , and the sensor  14  are covered with the first housing  101 . It is noted that, although the hammer  12  is entirely covered with the first housing  101  in  FIG.  2   , only a part thereof may be covered with the first housing  101 . 
     Thus, covering most parts of the hammer  12  and the anvil  13  which are the sources of the abrasive powder, and the sensor  14  in the vicinity of the anvil  13  with the first housing  101  enables the abrasive powder to be suppressed from adhering to the circuit board  15  disposed outside the housing  101  while protecting the hammer  12 , the anvil  13 , and the sensor  14 . 
     (2-2) Second Housing 
     The impact rotary tool  1  further includes the second housing  102  as shown in, for example,  FIGS.  1  and  4   . The second housing  102  is disposed outside the first housing  101  and covers the circuit board  15 . 
     The second housing  102  encloses the second space S 2  in which the circuit board  15  is present. In the present embodiment, in the second space S 2 , only the circuit board  15  is present, but other members may be present in addition to the circuit board  15 . 
     As shown in, for example,  FIGS.  4  and  7 A , the second housing  102  in the present embodiment has one main surface  102   c  which is open. The second housing  102  is, at the side of the one main surface  102   c  which is open, fixed to an outer surface  101   b  of the first housing  101  with the circuit board  15  being housed therein. 
     Specifically, the impact rotary tool  1  further includes four screws  102   b  as shown in  FIG.  4   , the outer surface  101   b  of the first housing  101  has four screw holes  101   a  formed therein, and the second housing  102  has four through holes  102   a  formed therein. 
     As shown in, for example,  FIG.  2   , the circuit board  15  is disposed on the outer surface  101   b  of the first housing  101  and is connected to the sensor  14  in the first housing  101  via the lead line  14   c.    
     The four screws  102   b  are inserted through the four through holes  102   a  of the second housing  102  and are tightened into the four screw holes  101   a  formed in the outer surface  101   b  of the first housing  101 . In this way, the second housing  102  is, at the side of the one main surface  102   c  which is open, fixed to the outer surface  101   b  of the first housing  101 . 
     In the present embodiment, the four screws  102   b  enables the second housing  102  to be attached to and detached from the outer surface  101   b  of the first housing  101 . Alternatively, the second housing  102  may be fixed to the outer surface  101   b  of the first housing  101  with an adhesive or the like. 
     In the present embodiment, in addition to covering the most parts of the hammer  12  and the anvil  13 , and the sensor  14  in the vicinity of the anvil  13  with the first housing  101 , covering the circuit board  15  with the second housing  102  as described above enables the abrasive powder to be more effectively suppressed from adhering to the circuit board  15 . 
     Note that the one main surface  102   c  of the second housing  102  does not have to be open (see first variation). Moreover, the second housing  102  may further cover the first housing  101  in addition to the circuit board  15  (see other variations). 
     (2-3) Circuit Board 
     (2-3-1) Disposition of Circuit Board 
     The circuit board  15  is fixed to the outer surface  101   b  of the first housing  101 . 
     The circuit board  15  is fixed to the outer surface  101   b  of the first housing  101  by, for example, the second housing  102 . 
     As described above, the one main surface  102   c  of the second housing  102  in the present embodiment is open, and the circuit board  15  is directly fixed to the outer surface  101   b  of the first housing  101  while the circuit board  15  is housed in the second housing  102  as shown in, for example,  FIGS.  4  and  7 A . 
     Specifically, the circuit board  15  is disposed on the outer surface  101   b  of the first housing  101 , and the second housing  102  is fixed, at the one main surface  102   c  which is open, to the outer surface  101   b  of the first housing  101  such that the second housing  102  covers the circuit board  15 . That is, the circuit board  15  is sandwiched between the outer surface  101   b  of the first housing  101  and an inner surface  102   d  of the second housing  102 , thereby being fixed to the outer surface  101   b  of the first housing  101 . 
     Therefore, the second housing  102  of the present embodiment enables the circuit board  15  to be directly fixed to the first housing  101  and the abrasive powder to be suppressed from adhering to the circuit board  15 . 
     Further, fixing the circuit board  15  to the outer surface  101   b  of the housing  101  enables the distance between the sensor  14  and the circuit board  15  to be shortened. In the present embodiment, the sensor  14  and the circuit board  15  are connected to each other via the lead line  14   c , and the length of the lead line  14   c  is thus shortened. 
     Furthermore, fixing the circuit board  15  to the outer surface  101   b  of the first housing  101  results in that the sensor  14  in the first housing  101  and the circuit board  15  on the outer surface  101   b  of the first housing  101  vibrate together with the first housing  101  in response to the striking rotational force from the hammer  12 , which enables tension to be suppressed from being caused at the lead line  14   c.    
     The connection between the sensor  14  and the circuit board  15  is not limited to a wired connection via the lead line  14   c  but may be a wireless connection. In this case, the wireless communication distance is shortened. 
     (2-3-2) Configuration of Circuit Board 
     The circuit board  15  includes a processing circuit  15   b . The processing circuit  15   b  processes the sensing result by the sensor  14 . 
     The sensor  14  in the present embodiment is a magnetostrictive sensor as described above, and the processing circuit  15   b  processes a voltage signal from a coil  14   b  (described later) included in the magnetostrictive sensor. 
     The circuit board  15  in the present embodiment further includes an amplifying circuit  15   a . The amplifying circuit  15   a  amplifies the voltage signal from the coil  14   b  and gives the voltage signal thus amplified to the processing circuit  15   b . The processing circuit  15   b  processes the voltage signal thus amplified by the amplifying circuit  15   a.    
     Specifically, the processing circuit  15   b  converts the voltage signal thus amplified into a strain signal that varies in accordance with the strain. 
     In this way, amplifying the voltage signal from the coil  14   b  included in the magnetostrictive sensor  14  by the circuit board  15  and then converting the voltage signal into the strain signal enable the strain of the anvil  13  to be magnetically sensed. 
     Furthermore, the processing circuit  15   b  performs computation to determine the tightening torque with reference to the strain indicated by the strain signal. The tightening torque is torque which is produced around the axis  200  and which is applied to the tightening member such as a screw via the tip tool  2  from the anvil  13 . 
     The processing result by the processing circuit  15   b  is given to the control circuit  17 . A connection between the processing circuit  15   b  and the control circuit  17  is also usually a wired connection but may be a wireless connection. 
     (2-4) Third Housing 
     The impact rotary tool  1  further includes a third housing  103 . 
     The third housing  103  is disposed outside the first housing  101  and outside the second housing  102  and covers at least the motor  11 . 
     The third housing  103  in the present embodiment encloses the third space S 3  in which the motor  11  and other elements are present. In the impact rotary tool  1 , the battery  16 , the control circuit  17 , the wireless communication circuit  18 , and other elements are also present in the third space S 3  as shown in  FIG.  2   . 
     Thus, the third housing  103  also covers the battery  16 , the control circuit  17 , the wireless communication circuit  18 , and other elements present in the third space S 3 . 
     In this way, covering the motor  11  and other elements with the third housing  103  enables abrasion powder produced at the contact portions ( 12   a  and  13   b ) of the hammer  12  and the anvil  13  to be suppressed from adhering to the motor  11  and other elements. 
     Note that depending on the type of the motor  11 , friction, for example, between a brush and the a commutator may produce abrasive powder, but covering the motor  11  with the third housing  103  enables such abrasive powder to be suppressed from adhering to the circuit board  15 . 
     The control circuit  17  and the wireless communication circuit  18  are disposed in the third space S 3  (in the third housing  103 ) in the present embodiment, but at least one of the control circuit  17  or the wireless communication circuit  18  may be disposed in the second space S 2  (in the second housing  102 ). That is, both or one of the control circuit  17  and the wireless communication circuit  18  may be an element(s) included in the circuit board  15 . 
     (2-5) Sensor 
     The sensor  14  in the present embodiment is a magnetostrictive sensor and is hereinafter referred to as a “magnetostrictive sensor  14 ”. The magnetostrictive sensor  14  magnetically senses the strain of the anvil  13  and outputs a signal corresponding to the sensing result. 
     The magnetostrictive sensor  14  includes, for example, a magnetostrictive film  14   a  and the coil  14   b  as shown in  FIG.  5   . The magnetostrictive film  14   a  is disposed on at least part of an outer peripheral surface  13   c  of the anvil  13 , and the coil  14   b  surrounds the magnetostrictive film  14   a.    
     In the present embodiment, the magnetostrictive film  14   a  is formed, for example, slightly rearward on the outer peripheral surface  13   c  of the anvil  13  (at the side of the anvil claw  13   b ) over a range of approximately ⅓ to ¼ of the length of the anvil  13  as shown in  FIG.  2   . 
     The magnetostrictive film  14   a  is formed by, for example, heat spraying of a magnetostrictive material such as ferrite onto the anvil  13 . Note that the type of the magnetic material and the method of forming the magnetostrictive film  14   a  are not particularly limited. 
     When the anvil  13  receives the striking rotational force from the hammer  12  and thus strains, the anvil  13  applies its stress to the magnetostrictive film  14   a , thereby changing the magnetic permeability of the magnetostrictive film  14   a . When the magnetic permeability of the magnetostrictive film  14   a  is changed, the inverse magnetostriction effect changes the impedance of the coil  14   b . The coil  14   b  outputs a voltage signal according to such an impedance change. 
     The voltage signal from the coil  14   b  is given to the circuit board  15  as described above, is amplified by the amplifying circuit  15   a , and is then converted into a strain signal by the processing circuit  15   b.    
     In this way, the voltage signal from the coil  14   b  included in the magnetostrictive sensor  14  is amplified and is then converted into the strain signal by the circuit board  15 , which enables the strain of the anvil  13  to be magnetically sensed. 
     Further, the processing circuit  15   b  also performs computation processing to determine the tightening torque with reference to the strain. The tightening torque is torque which is produced around the axis  200  and which is applied to the tightening member such as a screw via the tip tool  2  from the anvil  13 . 
     In this way, performing computation by the circuit board  15  enables the tightening torque exerted by the tip tool  2  attached to the anvil  13  to be calculated based on the strain of the anvil  13 . 
     (3) First Variation 
     In the impact rotary tool  1  in the embodiment described above, the one main surface  102   c  of the second housing  102  is open as shown in  FIG.  7 A , and the circuit board  15  is directly fixed to the outer surface  101   b  of the first housing  101  by the inner surface  102   d  of the second housing  102 . That is, the circuit board  15  in the embodiment is covered with part of the first housing  101  and the second housing  102 . 
     In contrast, in an impact rotary tool  1  of a first variation, none of surfaces of the second housing  102  is open as shown in  FIG.  7 B , and the circuit board  15  entirely covered with the second housing is fixed to the outer surface  101   b  of the first housing  101 . 
     In a similar manner to the embodiment, the first variation also provides the effect of preventing abrasion powder from adhering to the circuit board  15 . 
     (4) Second Variation 
     In an impact rotary tool  1  in a second variation, the isolator  10  is the wall  10   a  as shown in  FIG.  7 C . 
     The wall  10   a  separates a space (hereinafter referred to as a fourth space S 4 ) in a fourth housing  104  into the first space S 1  and the second space S 2 . The fourth housing  104  covers the hammer  12 , part of the anvil  13  except for its one end (tip end  13   a ) to which the tip tool  2  is to be attached, and the circuit board  15 . 
     In this way, separating the fourth space S 4  into the first space S 1  and the second space S 2  by the wall  10   a  also isolates the contact portions ( 12   a  and  13   b ) from the circuit board  15  and enables abrasive powder to be suppressed from adhering to the circuit board  15 . 
     (5) Other Variations 
     In an impact rotary tool  1  in other variations, the second housing  102  further covers the first housing  101  in addition to the circuit board  15 . 
     That is, the most parts of the hammer  12  and the anvil  13 , and the sensor  14  in the vicinity of the anvil  13  are covered with the first housing  101 , and further, the first housing  101  is, together with the circuit board  15 , covered with the second housing  102 . 
     Also in this case, the contact portions ( 12   a  and  13   b ), which are the sources of abrasive powder, are covered with the first housing  101  and are thus isolated from the circuit board  15 , which therefore enables the abrasive powder to be suppressed from adhering to the circuit board  15 . Further, the processing circuit  15   b  is doubly covered with the first housing  101  and the second housing  102 , which therefore enables the processing circuit  15   b  to be more effectively protected. 
     (6) Summary 
     An impact rotary tool ( 1 ) of a first aspect includes a motor ( 11 ), a hammer ( 12 ), an anvil ( 13 ), a sensor ( 14 ), a circuit board ( 15 ), and an isolator ( 10 ). The hammer ( 12 ) is configured to receive rotational force around an axis ( 200 ) from the motor ( 11 ) and output striking rotational force. The striking rotational force is obtained by converting part of the rotational force into striking force around the axis ( 200 ). The anvil ( 13 ) to which a tip tool ( 2 ) is to be attached is configured to rotate, together with the tip tool ( 2 ), around the axis ( 200 ) in response to the striking rotational force received from the hammer ( 12 ). The sensor ( 14 ) is disposed in a vicinity of the anvil ( 13 ) and is configured to sense a change in a state of the anvil ( 13 ), the change being according to the striking rotational force. The circuit board ( 15 ) is configured to receive a sensing result by the sensor ( 14 ). The isolator ( 10 ) isolates contact portions ( 12   a  and  13   b ) of the hammer ( 12 ) and the anvil ( 13 ) from at least the circuit board ( 15 ). 
     According to this aspect, the contact portions ( 12   a  and  13   b ), which are sources of abrasive powder, of the hammer ( 12 ) and the anvil ( 13 ) are isolated from at least the circuit board ( 15 ). This enables the abrasive powder to be suppressed from adhering to the circuit board ( 15 ). 
     In an impact rotary tool ( 1 ) of a second aspect referring to the first aspect, the isolator ( 10 ) includes a housing ( 101 ) covering at least the contact portions ( 12   a  and  13   b ), and the circuit board ( 15 ) is disposed outside the housing ( 101 ). 
     According to this aspect, the sources of the abrasive powder are covered with the housing ( 101 ) to confine the abrasive powder in the housing ( 101 ). This enables the abrasive powder to be suppressed from adhering to the circuit board ( 15 ) disposed outside the housing ( 101 ). 
     In an impact rotary tool ( 1 ) of a third aspect referring to the second aspect, the circuit board ( 15 ) is fixed to an outer surface ( 101   b ) of the housing ( 101 ). 
     This aspect enables the distance between the sensor ( 14 ) and the circuit board ( 15 ) to be shortened. For example, when the sensor ( 14 ) and the circuit board ( 15 ) are connected to each other via a lead line ( 14   c ), the length of the lead line ( 14   c ) is shortened. Further, the circuit board ( 15 ) on the outer surface ( 101   b ) of the housing ( 101 ) and the sensor ( 14 ) in the housing ( 101 ) vibrate together in response to the striking rotational force from the hammer ( 12 ). This enables tension to be suppressed from being caused at the lead line ( 14   c ). 
     In an impact rotary tool ( 1 ) of a fourth aspect referring to the third aspect, the housing ( 101 ) covers the hammer ( 12 ), part of the anvil ( 13 ) except for a tip end ( 13   a ) to which the tip tool ( 2 ) is to be attached, and the sensor ( 14 ). 
     According to this aspect, most parts of the hammer ( 12 ) and the anvil ( 13 ) which are the sources of the abrasive powder, and the sensor ( 14 ) in the vicinity of the anvil ( 13 ) are covered with the housing ( 101 ). This enables the abrasive powder to be suppressed from adhering to the circuit board ( 15 ) disposed outside the housing ( 101 ) while protecting the most parts of the hammer ( 12 ) and the anvil ( 13 ), and the sensor ( 14 ). 
     Note that when the circuit board ( 15 ) is covered with a cover or the like, the effect of suppressing adhesion of abrasive powder spreads only to the circuit board ( 15 ). However, when the sources of the abrasive powder are covered with the housing ( 101 ) to be isolated from the circuit board ( 15 ) as in this aspect, the effect of suppressing adhesion of abrasive powder usually also spreads to elements (e.g., the control circuit  17 ) in addition to the circuit board ( 15 ). This enables the abrasive powder to be suppressed from adhering to the elements other than the circuit board ( 15 ). 
     In an impact rotary tool ( 1 ) of a fifth aspect referring to the fourth aspect, the housing ( 101 ) is a first housing ( 101 ). The impact rotary tool ( 1 ) further includes a second housing ( 102 ). The second housing ( 102 ) is disposed outside the first housing ( 101 ) and covers the circuit board ( 15 ). 
     According to this aspect, the contact portions ( 12   a  and  13   b ), which are the sources of the abrasive powder, are covered with the first housing ( 101 ), and the circuit board ( 15 ) is covered with the second housing ( 102 ). This enables the abrasive powder to be further effectively suppressed from adhering to the circuit board ( 15 ). 
     In an impact rotary tool ( 1 ) of a sixth aspect referring to the fifth aspect, the second housing ( 102 ) has one main surface ( 102   c ) which is open. The second housing ( 102 ) is, at a side of the one main surface ( 102   c ) which is open, fixed to an outer surface ( 101   b ) of the first housing ( 101 ) with the circuit board ( 15 ) being housed in the second housing ( 102 ). The circuit board ( 15 ) is fixed to the first housing ( 101 ) by the outer surface ( 101   b ) of the first housing ( 101 ) and an inner surface ( 102   d ) of the second housing ( 102 ). 
     This aspect enables the second housing ( 102 ) to fix the circuit board ( 15 ) to the first housing ( 101 ) and the abrasive powder to be suppressed from adhering to the circuit board ( 15 ). 
     An impact rotary tool ( 1 ) of a seventh aspect referring to the sixth aspect further includes a third housing ( 103 ). The third housing ( 103 ) is disposed outside the first housing ( 101 ) and outside the second housing ( 102 ) and covers at least the motor ( 11 ). 
     According to this aspect, the motor ( 11 ) and other elements are covered with the third housing ( 103 ). This enables abrasion powder produced at the contact portions ( 12   a  and  13   b ) of the hammer ( 12 ) and the anvil ( 13 ) to be suppressed from adhering to the motor ( 11 ) and other elements. Further, even when abrasive powder is produced, for example, due to friction between a brush and a commutator in the motor ( 11 ), this aspect enables the abrasive powder to be suppressed from adhering to the circuit board ( 15 ). 
     In an impact rotary tool ( 1 ) of an eighth aspect referring to any one of the first to seventh aspects, the sensor ( 14 ) is configured to sense a strain of the anvil ( 13 ) and output a signal corresponding to a sensing result. The circuit board ( 15 ) includes a processing circuit ( 15   b ). The processing circuit ( 15   b ) is configured to perform computation processing to determine tightening torque with reference to the signal output from the sensor ( 14 ). The tightening torque is torque which is produced around the axis ( 200 ) and which is applied from the anvil ( 13 ) to a tightening member via the tip tool ( 2 ). 
     This aspect enables the tightening torques to be calculated based on the strain of the anvils  13 . 
     In an impact rotary tool ( 1 ) of a ninth aspect referring to the eighth aspect, the sensor ( 14 ) includes a magnetostrictive film ( 14   a ) and a coil ( 14   b ). The magnetostrictive film ( 14   a ) is disposed on at least part of an outer peripheral surface ( 13   c ) of the anvil ( 13 ). The coil ( 14   b ) surrounds the magnetostrictive film ( 14   a ). The circuit board ( 15 ) further includes an amplifying circuit ( 15   a ). The amplifying circuit ( 15   a ) is configured to amplify a voltage signal from the coil ( 14   b ) and give the voltage signal thus amplified to the processing circuit ( 15   b ). 
     This aspect enables the strain of the anvil ( 13 ) to be magnetically sensed. 
     While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that they may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all modifications and variations that fall within the true scope of the present teachings.