Patent Publication Number: US-2015073452-A1

Title: Liquid ejecting apparatus, liquid ejecting method, and medical instrument

Description:
This application claims the benefit of Japanese Patent Application No. 2013-188270, filed on Sep. 11, 2013. The content of aforementioned application is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to ejection of a liquid. 
     2. Related Art 
     In a liquid ejecting apparatus which is used as a medical instrument, a technique for controlling energy of a liquid ejected from an ejection port is known (for example, JP-A-2010-51896). The ejection of the liquid from the ejection port includes a continuous type which continuously performs ejection and an intermittent type which intermittently performs ejection. In all cases, parameters, such as an ejection speed and a flow rate, are controlled, thereby adjusting capacity, such as resection capacity of the medical instrument. 
     In recent years, in the liquid ejecting apparatus which is used as the medical instrument, a method which measures an acceleration of the ejection port and selects a mode of liquid ejection based on the acceleration has been suggested (for example, JP-A-2012-143374). 
     This liquid ejecting apparatus is excellent in that a predetermined action can be affected to a target using a medium, such as a liquid, and widespread use is possible. In a liquid ejecting apparatus of a type which is switched to a specific ejection mode according to the moving speed of the ejection port, high safety of the medical instrument is secured. The inventors have studied the aspects of use of the apparatus and have found an easy-to-use configuration. In addition, reduction in size of the apparatus, low cost, resources saving, ease of manufacturing, improvement of usability, and the like are required. The inventors have attempted to solve these problems. 
     SUMMARY 
     An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples. 
     Application Example 1 
     A first aspect of the invention provides a liquid ejecting apparatus which ejects a liquid. The liquid ejecting apparatus includes a liquid ejecting mechanism which receives a drive signal as input and makes the pressure of the liquid in an internal liquid chamber fluctuate according to the drive signal to make the liquid be ejected from an ejection port. The liquid ejecting apparatus may be configured such that the drive signal is changed according to the moving speed of the liquid ejecting mechanism and the relationship between the amount of variation of the moving speed and the amount of change of the drive signal is able to be set. 
     According to the liquid ejecting apparatus, it is possible to set the relationship between the amount of variation of the moving speed and the amount of change of the drive signal. In the liquid ejecting apparatus, the drive signal is changed according to the moving speed of the liquid ejecting mechanism using the set relationship. As a result, it is possible to easily perform the ejection of the liquid with a predetermined relationship. 
     Application Example 2 
     The liquid ejecting apparatus according to the aspect of the invention described above may further include a user interface which receives an instruction of a set value, and a setting unit which sets the relationship between the amount of variation of the moving speed and the amount of change of the drive signal according to the set value instructed by the user interface. 
     According to the liquid ejecting apparatus, it is possible to set the relationship between the amount of variation of the moving speed and the amount of change of the drive signal by the set value instructed through the user interface, and to allow the user to easily establish a desired relationship. 
     Application Example 3 
     The liquid ejecting apparatus according to the aspect of the invention described above may further include a storage unit which stores a plurality of relationships between the amount of variation of the moving speed and the amount of change of the drive signal, and a setting unit which sets the relationship between the amount of variation of the moving speed and the amount of change of the drive signal to one relationship selected from the storage unit. 
     According to the liquid ejecting apparatus, since a plurality of relationships are stored in advance and one relationship selected among the plurality of relationships is set, it is possible to easily establish a desired relationship. 
     Application Example 4 
     In the liquid ejecting apparatus according to the aspect of the invention described above, the drive signal may include at least one of the frequency of the drive signal and the voltage of the drive signal. 
     In the liquid ejecting apparatus, since an easy-to-control element, such as the frequency of the drive signal or the voltage of the drive signal, is used, it is possible to easily control the ejection state of the liquid. The drive signal is changed to change the state of the liquid ejected from the ejection port, and if the relationship with the amount of change of a parameter capable of establishing the change can be set, a parameter other than the drive frequency of the drive signal or the voltage of the drive signal may be used. For example, the amount of supply of the liquid to the liquid chamber, the representative volume of the liquid chamber, or the like may be used to change the ejection state of the liquid from the ejection port. 
     Application Example 5 
     In the liquid ejecting apparatus according to the aspect of the invention described above, when the moving speed is a first speed, the drive signal may be determined to be a first value, and when the moving speed is a second speed faster than the first speed, the drive signal may be determined to be a second value at which power by the ejected liquid is higher than power of the first value. 
     According to the liquid ejecting apparatus, since power increases with an increase in the moving speed, a difference in power per unit distance (or unit time) is suppressed. 
     Application Example 6 
     In the liquid ejecting apparatus according to the aspect of the invention described above, the setting unit may set the relationship between the increase of the second speed with respect to the first speed of the moving speed and the increase of the second value with respect to the first value of the drive signal. 
     According to the liquid ejecting apparatus, since the relationship between the increase of the moving speed and the increase of the drive signal is set, the relationship between both the increase of the moving speed and the increase of the drive signal can be easily understood. 
     Application Example 7 
     In the liquid ejecting apparatus according to the aspect of the invention described above, the setting unit may set one of a first mode, in which the increase ratio of the increase of the value and the increase of the moving speed is set to be less than 1, a second mode, in which the increase ratio is set to 1, and a third mode, in which the increase ratio is set to be greater than 1, according to information input by the user interface. 
     According to the liquid ejecting apparatus, since one of the three modes can be easily selected by the user interface, it is possible to easily select a desired relationship. 
     Application Example 8 
     The liquid ejecting apparatus according to the aspect of the invention described above may further include a liquid supply unit which supplies the liquid to the liquid chamber, and the supply flow rate of the liquid to the liquid chamber by the liquid supply unit may be adjusted according to change of the drive signal. 
     In the liquid ejecting apparatus, if the drive signal is changed, the amount of the liquid to be supplied to the liquid chamber may vary. For this reason, the supply flow rate of the liquid to the liquid chamber is adjusted according to change of the drive signal, making it possible to supply neither too much nor too little of the liquid. 
     Application Example 9 
     Another aspect of the invention provides a medical instrument. The medical instrument may include a liquid supply unit which supplies the liquid to the liquid chamber, and the liquid supply unit may supply a liquid for medical use to the liquid chamber. The medical instrument can appropriately set the relationship between the moving speed of the ejection port of the liquid ejecting apparatus and the drive signal and can use the relationship in medicine. 
     Application Example 10 
     In the medical instrument according to the aspect of the invention described above, the liquid ejecting apparatus may apply pulsation to the liquid to perform the ejection of the liquid. When pulsation is applied to the liquid, it becomes possible to perform incision or resection more appropriately. 
     Application Example 11 
     Still another aspect of the invention provides a liquid ejecting apparatus including a liquid ejecting mechanism and a change unit. The liquid ejecting mechanism may receive a drive signal as input and may make the pressure of a liquid in an internal liquid chamber fluctuate according to the drive signal to make the liquid be ejected from an ejection port. The change unit may change a parameter involved in fluctuation of the state of the liquid ejected from the ejection port according to the moving speed of the liquid ejecting mechanism. In the liquid ejecting apparatus, the relationship between the moving speed and the parameter corresponding to the moving speed is able to be set. 
     According to the liquid ejecting apparatus, it is possible to set the relationship between the amount of variation of the moving speed and the amount of change of the parameter. In the liquid ejecting apparatus, the parameter is changed according to the moving speed of the liquid ejecting mechanism using the set relationship. As a result, it is possible to easily perform the ejection of the liquid with a relationship set in advance. 
     Application Example 12 
     Yet another aspect of the invention provides a liquid ejecting method. The liquid ejecting method makes a liquid be supplied to a liquid chamber, makes a pressure in the liquid chamber fluctuate according to a drive signal, and makes the liquid of the liquid chamber be ejected from an ejection port at the tip of an ejection pipe by fluctuation of the pressure in the liquid chamber. The liquid ejecting method may include setting the relationship between the amount of variation of the moving speed of the ejection port and the amount of change of a parameter involved in fluctuation of the state of the liquid ejected from the ejection port, and changing the parameter according to the moving speed using the set relationship. 
     According to the liquid ejecting method, the relationship between the amount of variation of the moving speed and the amount of change of the parameter involved in fluctuation of the state of the liquid can be set by the setting unit. The liquid ejecting apparatus uses the set relationship to change the state of the liquid ejected from the ejection port according to the moving speed of the ejection port. As a result, it is possible to easily perform the ejection of the liquid with a relationship set in advance. 
     Other Application Examples 
     The liquid ejecting apparatus according to the aspect of the invention described above may further include a housing which accommodates hardware configured to output a signal to the liquid ejecting mechanism, and an operating unit which is provided in the housing and instructs to change the relationship. In the liquid ejecting apparatus, since the operating unit and the housing which accommodates hardware configured to output a signal to the liquid ejecting mechanism can be united as a single body, it is possible to achieve ease of handling of the apparatus. 
     Alternatively, the liquid ejecting apparatus according to the aspect of the invention described above may further include a pedal which receives an instruction to eject the liquid and outputs the instruction to the liquid ejecting mechanism, and an operating unit which is provided near the pedal and selects the setting of the relationship. In the liquid ejecting apparatus, since it is possible to perform an instruction of ejection by the pedal and to perform the selection of the setting near the pedal, convenience is excellent. 
     A plurality of components provided to each of the aspects of the invention described above are not necessarily essential, and in order to solve all or a part of the problems described above or in order to achieve all or a part of the advantages described in the specification, it is possible to arbitrarily perform modification, elimination, replacement with another new component, and partial deletion of restriction content on some of the plurality of components. Furthermore, in order to solve all or a part of the problems described above or in order to achieve all or apart of the advantages described in the specification, it is also possible to combine some or all of the technical features included in one of the aspects of the invention with some or all of the technical features included in another aspect of the invention to thereby form an independent aspect of the invention. 
     The invention can be implemented in various forms other than the apparatus. The invention can be implemented in the forms of, for example, a manufacturing method of a liquid ejecting apparatus, a control method of a liquid ejecting apparatus, a computer program for implementing the control method, and a non-temporary recording medium on which the computer program is recorded. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a schematic configuration diagram of a liquid ejecting apparatus (medical instrument). 
         FIG. 2  is an internal configuration diagram of a liquid ejecting mechanism. 
         FIG. 3  is an explanatory view illustrating the appearance of a control unit. 
         FIG. 4  is a block diagram showing the internal configuration of a control unit. 
         FIG. 5  is a graph showing a drive waveform. 
         FIG. 6  is a flowchart (first embodiment) showing ejection processing. 
         FIG. 7  is a graph showing the relationship between an ejection port speed S and a drive frequency F with a set value a as a parameter. 
         FIG. 8  is a flowchart showing a 20 msec interrupt routine for setting a set value a. 
         FIG. 9  is a flowchart showing a memory switch interrupt routine which changes a set value of a preset switch. 
         FIG. 10  is a perspective view showing the appearance of a foot switch in a second embodiment. 
         FIG. 11  is an explanatory view illustrating the relationship between a speed S in a right-left (up-down) direction and a drive frequency F. 
         FIG. 12  is an explanatory view illustrating another relationship between a speed S and a drive frequency F (or peak voltage E). 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A. First Embodiment 
     A1. Overall Configuration 
     A first embodiment will be described.  FIG. 1  shows the configuration of a liquid ejecting apparatus  10 . The liquid ejecting apparatus  10  is a medical instrument which is used in a medical institution and has a function of ejecting a liquid to an affected part to incise or resect the affected part. 
     The liquid ejecting apparatus  10  has a liquid ejecting mechanism (handpiece)  20 , a liquid supply mechanism  50 , a suction device  60 , a control unit  70 , and a liquid container  80 . The liquid supply mechanism  50  and the liquid container  80  are connected together by a connection tube  51 . The liquid supply mechanism  50  and the liquid ejecting mechanism  20  are connected together by a liquid supply flow channel  52 . The connection tube  51  and the liquid supply flow channel  52  are formed of resin. The connection tube  51  and the liquid supply flow channel  52  may be formed of a material (for example, metal) other than resin. 
     The liquid container  80  stores physiological saline. Instead of physiological saline, pure water or a chemical may be used. The liquid supply mechanism  50  supplies the liquid sucked from the liquid container  80  through the connection tube  51  to the liquid ejecting mechanism  20  through the liquid supply flow channel  52  by driving of an internal pump. 
     The liquid ejecting mechanism  20  is a tool which is operated in a hand of a user of the liquid ejecting apparatus  10 . The liquid ejecting mechanism  20  can intermittently eject the liquid by an internal pulsation generation unit  30 . The user hits an affected part with the liquid intermittently ejected, thereby incising or resecting the affected part. The details of a pulsation generation mechanism and control for ejecting the liquid from the liquid ejecting mechanism  20  will be described below. 
     The control unit  70  includes an operating unit  77  and a display unit  78 . The control unit  70  is connected to the liquid supply mechanism  50  through a control cable  71 , is connected to the liquid ejecting mechanism  20  through a signal cable  72 , and is further connected to a foot switch  75 . The control unit  70  can control the liquid supply mechanism  50  through the control cable  71  and controls the flow rate of the liquid supplied to the pulsation generation unit  30 . The control unit  70  can transmit a drive signal to the pulsation generation unit  30  embedded in the liquid ejecting mechanism  20  through the signal cable  72 . If the user turns on the foot switch  75 , the control unit  70  performs control such that the liquid supply mechanism  50  executes the supply of the liquid to the pulsation generation unit  30 , and transmits the drive signal to the pulsation generation unit  30  to generate pulsation in the pressure of the liquid supplied to the pulsation generation unit  30 . The internal configuration of the control unit  70  or processing using the operating unit  77  or the like will be described in detail. 
     The suction device  60  is provided to suck the liquid around an ejection port  58  or a resected substance. The suction device  60  and the liquid ejecting mechanism  20  are connected together by a suction flow channel  62 . The suction device  60  constantly sucks the inside of the suction flow channel  62  while the switch for operating the suction device  60  is turned on. The suction flow channel  62  passes through the liquid ejecting mechanism  20  and is opened near the tip of an ejection pipe  55 . 
     The suction flow channel  62  covers the ejection pipe  55  extending from the tip of the liquid ejecting mechanism  20 . For this reason, as shown in an A-arrow diagram of  FIG. 1 , the wall of the ejection pipe  55  and the wall of the suction flow channel  62  form a substantially concentric cylinder. A flow channel through which a sucked substance sucked from a suction port  64  at the tip of the suction flow channel  62  is formed between the outer wall of the ejection pipe  55  and the inner wall of the suction flow channel  62 . The sucked substance is sucked to the suction device  60  through the suction flow channel  62 . The suction is adjusted by a suction adjustment mechanism  65  described below referring to  FIG. 2 . 
     A2. Internal Configuration of Liquid Ejecting Mechanism 
       FIG. 2  shows the internal structure of the liquid ejecting mechanism  20 . The liquid ejecting mechanism  20  includes a pulsation generation unit  30 , an entrance flow channel  40 , an exit flow channel  41 , a connection tube  54 , an acceleration sensor  69 , and a suction force adjustment mechanism  65 . 
     The pulsation generation unit  30  generates pulsation in the pressure of the liquid supplied from the liquid supply mechanism  50  to the liquid ejecting mechanism  20  through the liquid supply flow channel  52 . The liquid in which pulsation of the pressure is generated is supplied to the ejection pipe  55 . The liquid supplied to the ejection pipe  55  is intermittently ejected from the ejection port  58 . The ejection pipe  55  is formed of stainless steel. The ejection pipe  55  may be formed of other materials having predetermined rigidity or more, for example, other metals, such as brass, or reinforced plastics. 
     As shown in an enlarged view on the lower side of  FIG. 2 , the pulsation generation unit  30  includes a first case  31 , a second case  32 , a third case  33 , bolts  34 , a piezoelectric element  35 , a reinforcing plate  36 , a diaphragm  37 , a packing  38 , an entrance flow channel  40 , and an exit flow channel  41 . The first case  31  is a tubular member. The first case  31  is closed as a whole in a state where the second case  32  is bonded to one end portion of the first case  31  and the third case  33  is fixed to the other end portion by the bolts  34 . The piezoelectric element  35  is disposed in a space formed inside the first case  31 . 
     The piezoelectric element  35  is a laminated piezoelectric element. One end of the piezoelectric element  35  is fixed to the diaphragm  37  through the reinforcing plate  36 . The other end of the piezoelectric element  35  is fixed to the third case  33 . The diaphragm  37  is produced by a metal thin film. The peripheral portion of the diaphragm  37  is fixed to the first case  31  and is sandwiched between the first case  31  and the second case  32 . A liquid chamber  39  is formed between the diaphragm  37  and the second case  32 . 
     The piezoelectric element  35  receives the drive signal from the control unit  70  through the signal cable  72  as input. The signal cable  72  is inserted from a rear end portion  22  of the liquid ejecting mechanism  20 . The signal cable  72  accommodates two electrode lines  74  and one signal line  76  for an acceleration sensor. The electrode lines  74  are connected to the piezoelectric element  35  in the pulsation generation unit  30 . The piezoelectric element  35  expands and contracts based on the drive signal transmitted from the control unit  70 . The volume of the liquid chamber  39  fluctuates by the expansion and contraction of the piezoelectric element  35 . 
     The entrance flow channel  40  into which the liquid flows is connected to the second case  32 . The entrance flow channel  40  is bent in a U shape and extends toward the rear end portion  22  of the liquid ejecting mechanism  20 . The liquid supply flow channel  52  is connected to the entrance flow channel  40 . The liquid supplied from the liquid supply mechanism  50  is supplied to the liquid chamber  39  through the liquid supply flow channel  52 . 
     If the piezoelectric element  35  expands and contracts at a predetermined drive frequency, the diaphragm  37  vibrates. If the diaphragm  37  vibrates, the volume of the liquid chamber  39  fluctuates and the pressure of the liquid in the liquid chamber is pulsed. The pressurized liquid flows out of the exit flow channel  41  connected to the liquid chamber  39 . 
     The ejection pipe  55  is connected to the exit flow channel  41  through the metallic connection tube  54 . The liquid flowing out of the exit flow channel  41  is ejected from the ejection port  58  through the connection tube  54  and the ejection pipe  55 . 
     The suction force adjustment mechanism  65  adjusts a force when the suction flow channel  62  sucks the liquid or the like from the suction port  64 . The suction force adjustment mechanism  65  includes an operating unit  66  and a hole  67 . The hole  67  is a through hole which connects the suction flow channel  62  and the operating unit  66 . If the user opens and closes the hole  67  with the finger of the hand holding the liquid ejecting mechanism  20 , the amount of air flowing into the suction flow channel  62  through the hole  67  is adjusted by the degree of opening and closing, and accordingly, the suction force of the suction port  64  is adjusted. The adjustment of the suction force may be implemented by control of the suction device  60 . 
     The liquid ejecting mechanism  20  includes an acceleration sensor  69 . The acceleration sensor  69  is a piezoresistive three-axis acceleration sensor. The three axes are the respective axes of XYZ shown in  FIG. 2 . The X axis is parallel to the through direction of the hole  67 , and an upward direction is a positive direction. The Z axis is parallel to the major axis direction of the ejection pipe  55 , and a direction in which the liquid is ejected is a negative direction. The Y axis is defined by a right handed system based on the X axis and the Z axis. 
     As shown in  FIG. 2 , the acceleration sensor  69  is disposed near a tip portion  24  of the liquid ejecting mechanism  20 . A measurement result is input to the control unit  70  through the signal line  76  for an acceleration sensor. Accordingly, the control unit  70  analyzes a signal from the acceleration sensor  69 , thereby detecting the moving direction and speed of the liquid ejecting mechanism  20  in the right-left direction (y-axis direction) or the moving direction and speed of the liquid ejecting mechanism  20  in the up-down direction (x-axis direction). In this embodiment, although the motion of the ejection port  58  is found by a signal from one acceleration sensor  69 , if a plurality of acceleration sensors are provided, and calculation is performed using the outputs of the plurality of acceleration sensors, the motion of the ejection port  58  can be detected with higher precision. 
     A3. Configuration and Action of Control Unit 
     As described above, the control unit  70  performs various settings in addition to the moving speed of the ejection port  58  using the acceleration sensor  69 . The appearance and the internal configuration of the control unit  70  will be described.  FIG. 3  is an explanatory view showing the appearance of a full panel of the control unit  70  in this embodiment. As shown in the drawing, the control unit  70  includes a power switch  79  in addition to an operating unit  77  and a display unit  78 . The operating unit  77  is provided with a rotary setter  91  which directly designates a set value a described below, a selection switch  92 , three preset switches  95 ,  96 , and  97 , a memory switch  94  which causes the preset switches to store the set value, and the like. The preset switches  95  to  97  include a mechanism which is selectively turned on, and one of the switches is constantly turned on. In  FIG. 3 , the preset switch  96  is turned on (blackened state). The display unit  78  is a liquid crystal display panel and can display various kinds of text and images (primarily, graphs). 
       FIG. 4  shows the internal configuration of the control unit  70 . The control unit  70  includes a CPU  101  which controls overall control, a flash ROM (F•ROM)  102 , a RAM  103 , a switch interface (switch I/F)  107 , a display control unit  108 , and a control interface (control I/F)  110 . The F•ROM  102  is a rewriteable memory which stores a processing program of the CPU  101 , a preset value of the set value a, and the like in a nonvolatile manner. The RAM  103  provides a work area when the CPU  101  executes the program. The switch I/F  107  is an interface to which a signal from the operating unit  77  is input. The display control unit  108  is a dedicated controller which is connected to the display unit  78  and controls the display of the display unit  78 . The control I/F  110  is connected to the liquid ejecting mechanism  20 , the liquid supply mechanism  50 , and the foot switch  75 , and provides an interface for exchanging signals with the respective units. These units are connected together by a bus. 
     The control unit  70  controls the liquid supply mechanism  50 , the pulsation generation unit  30  of the liquid ejecting mechanism  20 , or the like under the control of the CPU  101 , and controls the ejection of the liquid from the ejection port  58 . The control for the ejection of the liquid includes the size of the liquid ejected from the ejection port  58 , the intensity (energy per unit time) of the liquid, and the like. The size or ejection intensity of the liquid to be ejected is changed by adjusting the drive signal output from the control unit  70  to the piezoelectric element  35  through the electrode lines  74 .  FIG. 5  is a graph showing the waveform (hereinafter, referred to as “drive waveform”) of the drive signal input to the piezoelectric element  35 . The vertical axis represents voltage and the horizontal axis represents time. The drive waveform is described by a combination of sinusoidal curves. The frequency (alternatively, peak voltage or the like) of the drive signal in the drive waveform varies with ejection processing described below. The liquid ejected from the ejection port  58  of the liquid ejecting mechanism  20  is pulsed according to the drive waveform. In the following description, the behavior (pulsation) of the liquid corresponding to one period of the drive waveform shown in  FIG. 5  is referred to as one pulse. In one pulse, although the liquid ejected from the ejection port  58  becomes a perfect droplet and is independent, the liquid may be ejected dragging along a satellite, or the flow of the liquid from the ejection port  58  may be substantially continuous. The ejection of the liquid includes a concept of liquid discharge, liquid droplet emission, or the like. 
     Considering per pulse, simplistically, if the peak voltage (also referred to as intensity) of the drive signal increases, the maximum deformation of the piezoelectric element  35  increases and the contraction of the volume of the liquid chamber  39 , that is, the amount of ejection per pulse increases. If the rising time of the drive signal is shortened, the deformation of the piezoelectric element  35  occurs quickly and the speed of the liquid ejected for each pulse increases. As a result, energy per pulse of the liquid to be intermittently ejected increases. Meanwhile, if the frequency (hereinafter, referred to as a drive frequency) of the drive signal increases, the number of pulses (the number of pulsations) to be ejected per unit time increases. As a result, the total amount of energy of the liquid to be ejected per unit time increases. 
     Next, processing of the control unit  70  will be described in detail. First, processing for controlling the intensity (energy per unit time) of the liquid to be ejected from the liquid ejecting mechanism  20  will be first described, and then, processing for setting the set value a will be described. 
       FIG. 6  is a flowchart showing ejection processing which is executed by the control unit  70 . The ejection processing is repeatedly executed by the control unit  70  while the foot switch  75  is pushed down. Initially, the speed S of the ejection port  58  is calculated (Step S 200 ). The speed S used herein is the absolute value of a speed on the XY plane. That is, the speed S is the absolute value of a speed without regard to a speed in the Z-axis direction. The speed S is calculated based on the acceleration along the three axes measured by the acceleration sensor  69 . 
     The speed S is calculated as a parameter which affects the resection depth of the affected part. This is because a resection capacity acting on each local region of the affected part per unit time is affected by the relative speed of the ejection port  58  and the affected part. In this embodiment, on an assumption that the affected part is stationary, the speed S is handled as the moving speed of the affected part and the ejection port  58 . Considering that the affected part is moved by breathing or the like, the speed S may be handled as the relative speed of the ejection port  58  and the affected part. 
     Subsequently, processing for reading the set value a is performed (Step S 210 ). The set value a is a value which is set by operating the operating unit  77 , and in this embodiment, is set in a range of 0.5 to 2.0. Although a method of setting the set value a will be described below in detail, here, it is assumed that the set value is set based on the states of the preset switches  95  to  97  of the operating unit  77 . In a state shown in  FIG. 3 , that is, a state in which the preset switch  96  is pressed, the set value a is set to a value of 1.0. If the preset switch  95  is pressed, a value of 0.5 is set, and if the preset switch  97  is pressed, a value of 2.0 is set. 
     If the speed S and the set value a are determined, next, the drive frequency of the piezoelectric element  35  is determined based on the speed S (Step S 220 ). The drive frequency F is determined by Expression (1). 
         F=a·N·S   (1)
 
     Here, a is the above-described set value, and N is a constant determined in advance. Expression (1) shows that, if the speed S increases, the drive frequency F increases in proportion to a·N. The set value a is set to one of 0.5, 1.0, and 2.0 by the states of the preset switches  95  to  97 . The relationship between the speed S of the ejection port  58  and the drive frequency F is shown in  FIG. 7  with the set value a as a parameter. In the drawing, a solid line J indicates the relationship when the set value a is the value of 1.0, a two-dot-chain line C indicates the relationship when the set value a is the value of 0.5, and a broken line B indicates the relationship when the set value a is the value of 2.0. 
     As shown in the drawing, if the speed S increases, the drive frequency F is determined to be a large value without depending on the set value a. However, if the set value a is the value of 0.5, an increase ΔF of the drive frequency F with respect to an increase ΔS of the speed S is less than when the set value a is the value of 1.0 (½), and if the set value a is the value of 2.0, the increase ΔF of the drive frequency F with respect to the increase ΔS of the speed S is greater than when the set value a is the value of 1.0 (two times). As a result, in the use range SL to SH of the speed of the ejection port  58  during treatment, when determining the drive frequency F by the speed S of the ejection port  58 , the increase ratio (ΔF/ΔS) is set by the states of the preset switches  95  to  97 . 
     Since the drive frequency F corresponds to the number of pulses of the liquid to be ejected per unit time, when the speed S increases, if the drive frequency F remains unchanged, the energy of the liquid to be applied to a unit length of a treatment part is lowered. In a sense, resection or incision capacity by the liquid ejecting mechanism  20  is degraded. In contrast, as in Expression (1), if the drive frequency F increases in proportion to the speed S, the energy of the liquid to be applied to the unit length of the treatment part increases by that much. In this embodiment, when the set value a is the value of 1.0, the energy per unit length of the treatment part is kept constant. When the set value a is the value of 0.5, the increase of the frequency necessary for making the energy per unit length of the treatment part constant is suppressed to ½ with an increase of the speed S of the ejection port  58 . When the set value a is the value of 2.0, the increase of the frequency necessary for making the energy per unit length of the treatment part constant is increased to two times with an increase of the speed S of the ejection port  58 . 
     For this reason, when the set value a is the value of 1.0, the resection or incision capacity is substantially kept constant regardless of the speed S of the ejection port  58 . When the set value a is the value of 2.0, when moving the liquid ejecting mechanism  20  rapidly, the energy per unit length increases, and thus, resection or incision can be performed at higher speed. When moving the liquid ejecting mechanism  20  slowly, the energy per unit length decreases, and thus resection or incision capacity becomes insensitive and more careful treatment is possible. When the set value a is the value of 0.5, when moving the liquid ejecting mechanism  20  rapidly, the energy per unit length decreases, and thus, it is possible to avoid a possibility that resection or incision is performed to an unexpected depth with high-speed movement. When moving the liquid ejecting mechanism  20  slowly, the energy per unit length increases, and thus, resection or incision capacity increases and treatment in a wide range (to a deep place) with reliable motion is possible. These have the relationship of resection or incision capacity to motion of the liquid ejecting mechanism  20 , a preferable relationship is different depending on the preference of the user, the characteristic of a use target, or the like rather than saying that any is correct. In this embodiment, this can be freely set by the states of the preset switches  95  to  97 . 
     After the drive frequency F is determined by the speed S, next, the supply flow rate is determined based on the drive frequency F (Step S 230 ), and control is executed such that the determined drive frequency and supply flow rate are implemented (Step S 240 ). The supply flow rate is the volume flow rate of the liquid supplied by the liquid supply mechanism  50 . If the drive frequency increases, the amount of the liquid ejected per unit time varies, and the liquid of an amount slightly exceeding a necessary flow rate is supplied from the liquid supply mechanism  50  to the liquid ejecting mechanism  20  conforming to this. 
     In the above-described embodiment, the increase of the drive frequency F to the speed S is set to one of the three states by the value of the set value a set by the states of the preset switches  95  to  97 . A method of setting the set value a will be described below. 
     A4. Setting of Set Value a 
       FIG. 8  is a flowchart showing an interrupt processing routine which is executed by the control unit  70  for every 20 msec. This processing is executed for every 20 msec using a timer embedded in the CPU  101  after the power switch  79  of the control unit  70  is turned on and a program of initial setting or initial inspection is executed. If the processing shown in  FIG. 8  starts, first, determination is performed about the side to which the selection switch  92  of the operating unit  77  is switched (Step S 100 ). If it is determined that the selection switch  92  is switched to the preset switch side, the CPU  101  performs processing for setting the set value a according to the states of the preset switches  95  to  97  (Step S 110 ). Specifically, determination is performed about which of the three preset switches  95  to  97  is pressed, and if the preset switch  95  is pressed, the value set in the switch in advance is set to the set value a. Since the value of 0.5 is set by default, the set value a is set to the value of 0.5 by default. In the example shown in  FIG. 3 , since the preset switch  96  is pressed, in this case, the value set in the preset switch  96  in advance is set to the set value a. The value allocated to the preset switch  96  by default is 1.0. Similarly, if the preset switch  97  is pressed, the value set in the preset switch  97  in advance is set to the set value a. The value allocated to the preset switch  97  by default is 2.0. 
     In Step S 100 , if it is determined that the selection switch  92  is switched to the setter  91  side, subsequently, the CPU  101  reads a value VR of the setter  91  (Step S 120 ). Then, processing for setting the set value a according to the read value VR is performed (Step S 130 ). The value VR of the setter  91  is changed in a range of 0 to 100 by the position of a knob. A way to set the set value a with respect to the value VR of the setter  91  is arbitrary, and the set value a may be set by a function or a table may be prepared in advance and the set value a may be set referring to the table. As the function, for example, the following expression is established. 
         a= 0.5 +VR× 0.015 
     Then, if VR varies from 0 to 100, the set value a is set within the same range as the range (0.5 to 2.0) of setting by the preset switches  95  to  97 . Of course, if the following expression is established, when VR varies from 0 to 100, the set value a is set between 0.1 and 5.1 and can be set within a wider range than the range of setting by the preset switches  95  to  97 . 
         a= 0.1 +VR× 0.05 
     A way to set the set value a by the setter  91  may be determined assuming variation in the range of preference of each user or the like. 
     In Step S 130 , after the set value a is set according to the value VR of the setter  91  or in Step S 110 , after the set value a is set according to the state of the preset switch, a characteristic according to the set value a is displayed on the display unit  78  (Step S 140 ), the process exits to “RTN”, and the interrupt routine ends. In regards to the display on the display unit  78 , the relationship between the moving speed S of the ejection port  58  and the intensity of the liquid ejected from the ejection port  58  is displayed by the set value a. The relationship of  FIG. 7  described above is displayed on the display unit  78 . 
     As described above, although the preset switches  95  to  97  are respectively set to the values of 0.1, 1.0, and 2.0 by default, in this embodiment, the preset values may be changed. This processing is shown in  FIG. 9 .  FIG. 9  shows an interrupt routine which starts when the memory switch  94  provided in the operating unit  77  is operated. If this processing starts, first, the CPU  101  performs determination about whether or not the liquid ejecting apparatus  10  of this embodiment is during operation (Step S 160 ). The term “during operation” means that the foot switch  75  is operated and the ejection of the liquid from the liquid ejecting mechanism  20  is performed. If it is determined to be during operation, next, processing for reading the current set value a is performed (Step S 170 ). The set value a is a default value set in each of the preset switches  95  to  97  or a value set by the value VR of the setter  91 . 
     Accordingly, the read set value a is set in the preset switches  95  to  97  currently being turned on (Step S 180 ). With this processing, if the current set value a is the default value of each of the preset switches  95  to  97 , the value is set in the preset switches  95  to  97  as it is, and if the current set value a is the value set by the setter  91 , the value is set in the preset switches  95  to  97  currently being turned on. For example, when the selection switch  92  is switched to the setter side and the user operates the setter  91  to perform treatment with the set value a preferred by the user, if the memory switch  94  is operated, the set value a at this time is set in the preset switches  95  to  97  currently being turned on. 
     When the memory switch  94  is turned on and the interrupt routine of  FIG. 9  is activated, if the liquid ejecting apparatus  10  is not during operation (Step S 160 : “NO”), processing for returning the set value of each of the preset switches  95  to  97  to an initial value is performed (Step S 190 ). The set values are set to the values of 0.5, 1.0, and 2.0 already described. With this, it is possible to easily return the setting of each of the preset switches  95  to  97  to a default state. After the above-described processing, the process exits to “RTN”, and this interrupt routine ends. 
     A5. Functional Effect of First Embodiment 
     According to the first embodiment described above, the following functional effects are obtained. 
     (1) Since the drive frequency F increases and decreases with a proportional relationship with respect to the speed S of the ejection port  58  of the liquid ejecting mechanism  20 , even if the speed S varies, in any cases, variation of the energy per unit length is suppressed, and stable treatment is possible. 
     (2) The increase ΔF of the drive frequency F with respect to the increase ΔS of the speed S can be selected out of the three kinds set in the preset switches  95  to  97 , and it is possible to flexibly cope with the preference of the user, a difference of a treatment target, or the like. 
     (3) The set value a can be freely set by the setter  91 , and the relationship between the increase ΔS of the speed S and the increase ΔF of the drive frequency F by the set value a according to the preference of the user can be set. 
     (4) The set value a can be easily set in each of the preset switches  95  to  97  and can be simply called. 
     (5) The set value set in each of the preset switches  95  to  97  can be simply returned to the default value. 
     (6) As shown in  FIG. 7 , control can be performed such that the relationship between the increase ΔS of the speed S and the increase ΔF of the drive frequency F can be established in the treatment range SL to SH, and the pulsed ejection of the liquid is not performed outside the range. 
     B. Second Embodiment 
     Next, a second embodiment will be described. A liquid ejecting apparatus  10  of the second embodiment has the same hardware configuration as in the first embodiment excluding the configuration of a foot switch  75 . In the second embodiment, the foot switch  75  is provided with a selection switch  315  of a set value in addition to a pedal  310  configured to instruct ON and OFF of normal ejection. The selection switch  315  is a momentary on type switch, and each time the user presses the selection switch  315 , an interrupt request is output to the control unit  70 . If the interrupt request is received, the control unit  70  sets the set value a to one of the three values set in the preset switches  95  to  97  in regular order each time the selection switch  315  is operated. That is, each time the selection switch  315  is operated, the set value a is switched in the following order. 
     [1] the value set in the preset switch  95  (0.5 by default)
 
[2] the value set in the preset switch  96  (1.0 by default)
 
[3] the value set in the preset switch  97  (2.0 by default)
 
     If the selection switch  315  is further operated, the set value a is switched in order from [1]. The switched set value a is displayed on the display unit  78  of the control unit  70  every time, and this is the same as the first embodiment. 
     According to the liquid ejecting apparatus  10  of the second embodiment configured as above, the set value a is switched by a simple operation to push down the selection switch  315  provided in the foot switch  75  familiar to the user, and the liquid ejecting mechanism  20  can be used in a desired mode. Accordingly, in addition to the same effects as the effects of the first embodiment, since the user does not necessarily operate the preset switches  95  to  97  of the control unit  70 , there is a merit that user operation is simple. 
     C. Modification Examples 
     The invention is not limited to the above-described embodiments, and can be of course carried out in various aspects. 
     Hereinafter, some of the modification examples are illustrated. 
     C1. Modification Example 1 
     In the above-described embodiments, the drive frequency F is changed with respect to the speed S. The intensity of resection or incision by the liquid ejecting apparatus  10  may be controlled by the peak voltage of the drive signal, the rising time, the supply amount of the liquid to the liquid chamber, or the like, as well as the drive frequency. Accordingly, while the drive frequency F is kept constant, the relationship shown in  FIG. 7  may be applied to the peak voltage E, the peak voltage E may be changed with respect to the speed S, and the relationship may be determined according to the set value a. 
     Alternatively, while the drive frequency F or the peak voltage E is kept constant, the relationship shown in  FIG. 7  may be applied to the rising time of the drive signal, the rising time may be changed with respect to the speed S, and the relationship may be determined according to the set value a. The shorter the rising time, the stronger the resection or incision force. 
     Of course, instead of changing one of the parameters, such as the drive frequency, the peak voltage, the rising time of the drive signal, and the supply amount of the liquid to the liquid chamber, according to the speed S, a configuration in which a plurality of parameters are changed simultaneously or continuously in the range of the speed S may be introduced. At this time, the relationship of  FIG. 7  may be applied to a plurality of parameters simultaneously and adjusted. For example, first, the drive frequency F may be changed according to the speed S, and then, after the drive frequency F exceeds the upper and lower limit values, another parameter, for example, the peak voltage may be changed. If a plurality of parameters are used, it is possible to further expand the variable range (dynamic range) of the intensity of resection or incision with respect to the speed S. 
     C2. Modification Example 2 
     In the above-described embodiments, although the speed S is handled as the absolute value of the moving speed in the X and Y directions, since the acceleration sensor  69  can discriminate the direction, different set values may be used depending on the directions. For example, as shown in  FIG. 11 , the drive frequency F, the peak voltage E, or the like may be controlled while distinguishing between motion in the right direction (or upward direction) of the ejection port  58  of the liquid ejecting mechanism  20  and motion in the left direction (or downward direction). In the example shown in  FIG. 11 , the magnitude of the increase ΔF of the drive frequency F with respect to the increase ΔS of the speed S differs between motion in the right direction and motion in the left direction. In summary, the amount of change of the intensity of resection or incision with respect to the speed S differs between motion in the right direction and motion in the left direction. 
     The user is normally right-handed or left-handed, and a difference in characteristic according to handedness may be implemented. In  FIG. 11 , if a characteristic of a solid line Jy is preferred to a right-handed operator, it is assumed that a characteristic of a broken line By is preferred for a left-handed operator. 
     Alternatively, if a tissue of an internal organ as a treatment target has directivity, it is effective to change the characteristic accordingly. For example, when resection or incision of a muscle is performed, ease of resection or incision in a fibrous tissue direction of the muscle is different from ease of resection or incision in a direction intersecting the fibrous tissue. For example, if the characteristic differs in the X direction and the Y direction, resection or incision is facilitated. 
     C3. Modification Example 3 
     As shown in  FIG. 7 , the setting of the set value a illustrated in the first embodiment is substantially linear in the use range SL to SH. The relationship between the speed S and the drive frequency (alternatively, the peak voltage or the like) is not necessarily linear, if a configuration in which a table is prepared, the relationship is stored in the table, and the table is looked up from the speed S is made, any relationships can be established. 
       FIG. 12  shows an example of this relationship. In the first embodiment, the relationship between both is determined by a proportional coefficient, which is the set value a, and the drive frequency when the set value a is the value of 0.5, 1.0, and 2.0 is set to become the same value at the substantially center of the use range SL to SH of the ejection port speed S. For this reason, for example, when the set value a is the value of 2.0, and when the speed S is fast, the drive frequency F is greater than when the set value a is the value of 1.0. Meanwhile, when the speed S is slow, the drive frequency F is less than when the set value a is the value of 1.0. In contrast, in the setting example shown in  FIG. 12 , three setting examples are shown, and while the drive frequency F with respect to the speed S becomes equal at a substantially center speed SO as in the first embodiment ( FIG. 7 ), the following points are different. That is, in the setting example shown in  FIG. 12 , if the relationship indicated by a broken line Bx is selected, the drive frequency F constantly falls below the relationship (the relationship of the set value a=1.0) indicated by a solid line Jx. If the relationship indicated by a two-dot-chain line Cx is selected, the drive frequency F constantly exceeds the relationship (the relationship of the set value a=1.0) indicated by the solid line Jx. With the relationship shown in  FIG. 7 , even if the relationships (solid line J, broken line B, and two-dot-chain line C) when the set value a=0.5, 1.0, and 2.0 intersect at the lower limit value SL of the speed range, the same relationship can be established. 
     If this setting is used, the intensity of resection or incision of the liquid ejected from the liquid ejecting mechanism  20  of the liquid ejecting apparatus  10  does not depend on speed, a setting Cx is constantly strongest, and a setting Bx is constantly weakest. For this reason, for example, when a treatment target is a comparatively soft tissue, such as a brain tissue, the setting Bx in which the intensity of resection or incision is lowest is selected, and when a treatment target is a comparatively touch tissue, such as a muscle, the setting Cx is selected. With this, it is possible to provide the same cutting quality with respect to the same speed S without depending on a treatment target. 
     C4. Other Modification Examples 
     A parameter involved in the state of the liquid to be ejected is not limited to the ejection intensity, various parameters, such as the ejection amount of the liquid, the size of a liquid droplet to be intermittently ejected, and the duration of single ejection, may be used. 
     The intensity of ejection may be controlled by adjusting the representative volume of the liquid chamber  39  as well as the drive frequency or the peak voltage. The representative volume of the liquid chamber may be the volume of the liquid chamber  39  when no voltage is applied to the piezoelectric element  35  or may be the volume when a predetermined voltage is applied to the piezoelectric element  35 . Alternatively, an average value may be used. The representative volume of the liquid chamber  39  can be easily changed by, for example, providing another piezoelectric element between the piezoelectric element  35  and the third case  33  and applying a voltage to the piezoelectric element to expand at a predetermined length. Of course, any configuration, for example, a configuration in which the volume of the liquid chamber  39  is variable may be introduced insofar as a configuration in which the volume of the liquid chamber  39  can be changed. 
     The drive waveform may be a combination of sinusoidal curves, and for example, may be increased or decreased in a stepwise manner. 
     The relationship between each of the peak voltage and the drive frequency and the speed of the ejection port may be defined in a curved manner or may be defined in a stepwise manner. 
     While the rising time is fixed, the drive frequency may be varied. That is, the time when the voltage of the drive signal falls down the peak and reaches zero may be changed, thereby varying the drive frequency. With this, when determining the drive frequency with respect to the moving speed, it is possible to exclude the influence of variation in the rising time, whereby the determination of the drive frequency is facilitated. 
     Although a case where the relationship between the amount of variation of the moving speed of the ejection port and the amount of change of the parameter involved in fluctuation of the state of the liquid can be set by the setting unit, the relationship between the moving speed of the ejection port and the parameter involved in fluctuation of the state of the liquid with respect to the moving speed of the ejection port may be stored. With this, even if ejection starts when the ejection port is moving, it is possible to perform desired liquid ejection. 
     The speed of the ejection port may be calculated by, for example, an acceleration sensor provided at the tip of the ejection port. In this case, it is considered that the calculation result is more correct. 
     Alternatively, the speed of the ejection port may be calculated using image processing. For example, a marker may be provided at the tip of the ejection port, and the movement of the marker may be captured by a camera, thereby calculating the speed of the ejection port. 
     When a robot operates the liquid ejecting apparatus, since the speed of the ejection port can be recognized by the robot, it is not necessary to calculate the speed of the ejection port, and the recognized value may be used. In addition to the moving speed of the affected part, the relative speed of the ejection port may be calculated. The measurement of the moving speed of the affected part may be attained by predicting or measuring motion by breathing or pulse. 
     The detection of the moving speed it not limited to the ejection port, and detection may be performed at a place which moves with the movement of the ejection port, or the moving speed of the liquid ejecting mechanism may be detected. 
     In this embodiment, although a case where the liquid ejecting mechanism  20  is a tool which is operated in the hand of the user has been described, the liquid ejecting mechanism  20  may be a tool which is operated into a living body as a liquid ejecting mechanism for use in an endoscope, such as a laparoscope. 
     The type of the acceleration sensor may be an electrostatic capacitance type or a heat detection type. The invention is not limited to the acceleration sensor, and a sensor which can detect the moving speed of the ejection port indirectly or directly may be used. 
     The liquid ejecting apparatus may be used other than a medical instrument. 
     For example, the liquid ejecting apparatus may be used in a cleaning apparatus which removes dirt by an ejected liquid. 
     The liquid ejecting apparatus may be used in a drawing apparatus which draws a line or the like by an ejected liquid. 
     A system for liquid ejection may be a system using laser light. An ejection system using laser light may be an ejection system which uses fluctuation in pressure by intermittently irradiating laser light onto a liquid and vaporizing the liquid. 
     It should be noted that the invention is not limited to the embodiments, the specific examples, and the modification examples described above, but can be implemented with a variety of configurations within the scope or the spirit of the invention. For example, the technical features in the embodiments, the specific examples, and the modification examples corresponding to the technical features in the aspects described in SUMMARY section can appropriately be replaced or combined in order to solve all or a part of the problems described above or in order to achieve all or a part of the advantages. Furthermore, the technical feature can appropriately be eliminated unless described in the specification as an essential component.