Patent Publication Number: US-2015073455-A1

Title: Liquid ejecting apparatus and medical device

Description:
PRIORITY INFORMATION 
     The present invention claims priority to Japanese Patent Application No. 2013-188257 filed Sep. 11, 2013, which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to ejection of a liquid. 
     2. Related Art 
     In a liquid ejecting apparatus used as a medical device, there is known a method of measuring an acceleration of an ejection port and selecting a mode of liquid ejection on the basis of the measured acceleration. One example of one such method is found in Japanese Patent Application JP-A-2012-143374. 
     Despite the advantages provided by this system, further improvements are required, including a reduction in the size of, a reduction in the cost of, the resource saving of, the manufacturing facilitation of, an improvement in the usability of a device, and the like. 
     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. 
     A first aspect of the invention provides a liquid ejecting apparatus. The liquid ejecting apparatus includes a liquid ejecting mechanism which is provided with a liquid chamber and a volume fluctuation portion that fluctuates a volume within the liquid chamber, a liquid supply portion that supplies a liquid to the liquid chamber, and a control portion that controls the volume fluctuation portion and the liquid supply portion, wherein the control portion changes at least one of a voltage applied to the volume fluctuation portion and a flow rate of a liquid supplied to the liquid chamber in accordance with a movement velocity of the liquid ejecting mechanism. According to this aspect, at least one of a voltage and a supplied flow rate (hereinafter, also referred to as a “supply flow rate”) which are associated with an excision depth is changed depending on the movement velocity of an ejection port, and thus it is possible to adjust excision ability in accordance with the movement velocity of the ejection port. 
     Another aspect of the invention provides a liquid ejecting apparatus including a liquid ejecting mechanism which is provided with a liquid chamber and a pressurization portion that pressurizes an inside of the liquid chamber and a control portion that changes a drive signal transmitted to the pressurization portion, in accordance with a movement velocity of the liquid ejecting mechanism. According to this aspect of the invention, it is possible to change the drive signal transmitted to the pressurization portion in accordance with the movement velocity of the liquid ejecting mechanism. 
     The invention can be implemented in the form other than the aspects stated above. For example, the invention can be implemented in forms such as a liquid ejecting method, a medical device, a surgery method, programs for realizing these methods, and a storage medium having these programs stored thereon. 
    
    
     
       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 configuration diagram illustrating a liquid ejecting apparatus. 
         FIG. 2  is an internal structure diagram illustrating the liquid ejecting mechanism. 
         FIG. 3  is a graph illustrating a drive waveform. 
         FIG. 4  is a flow diagram illustrating an ejection process according to a first embodiment of the invention. 
         FIGS. 5A and 5B  are graphs illustrating a relationship between each parameter and a movement velocity according to a first embodiment of the invention. 
         FIG. 6  is a graph illustrating a state where a drive waveform changes. 
         FIG. 7  is a graph illustrating a relationship between a supply flow rate and a required flow rate. 
         FIG. 8  is a graph illustrating a relationship between a required flow rate and a peak voltage. 
         FIG. 9  is a graph illustrating a relationship between a required flow rate and a drive frequency. 
         FIG. 10  is a graph illustrating a relationship between an ejection pressure and a peak voltage. 
         FIG. 11  is a graph illustrating a relationship between an excision depth and a peak voltage. 
         FIG. 12  is a flow diagram illustrating an ejection process according to a second embodiment of the invention. 
         FIGS. 13A and 13B  are graphs illustrating a relationship between each parameter and a movement velocity according to a third embodiment of the invention. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A first embodiment of the invention, or Embodiment 1, will be described below.  FIG. 1  shows a configuration of a liquid ejecting apparatus  10 . The liquid ejecting apparatus  10  is a medical device which is used in a medical institution, and has a function of incising or excising an affected part by ejecting a liquid onto the affected part. 
     The liquid ejecting apparatus  10  includes a liquid ejecting mechanism.  20 , a liquid supply mechanism  50 , a suction unit  60 , a control portion  70 , and a liquid container  80 . The liquid supply mechanism  50  and the liquid container  80  are connected to each other by a connection tube  51 . The liquid supply mechanism  50  and the liquid ejecting mechanism  20  are connected to each other by a liquid supply channel  52 . The connection tube  51  and the liquid supply channel  52  are formed of a resin. The connection tube  51  and the liquid supply channel  52  may be formed of materials other than a resin. For example, metals may be used. 
     The liquid container  80  reserves a physiological saline solution. Pure water or a drug solution may be reserved instead of the physiological saline solution. The liquid supply mechanism  50  supplies a liquid suctioned from the liquid container  80  through the connection tube  51  by the driving of a built-in pump to the liquid ejecting mechanism  20  through the liquid supply channel  52 . 
     The liquid ejecting mechanism  20  is an appliance which is manipulated by a user of the liquid ejecting apparatus  10  with the mechanism held in his/her hand. A user incises or excises an affected part by applying a liquid, intermittently ejected from an ejection port  58 , to the affected part. 
     The control portion  70  transmits a drive signal to a pulsation generation portion  30  built into the liquid ejecting mechanism  20  through a signal cable  72 . The control portion  70  controls a flow rate of a liquid which is supplied to the pulsation generation portion  30  by controlling the liquid supply mechanism.  50  through a control cable  71 . A foot switch  75  is connected to the control portion  70 . When a user turns on the foot switch  75 , the control portion  70  controls the liquid supply mechanism  50  to supply a liquid to the pulsation generation portion  30 , and transmits a drive signal to the pulsation generation portion  30  to generate pulsation in the pressure of the liquid supplied to the pulsation generation portion  30 . The details of the mechanism of pulsation generation and the ejection control of a liquid from the liquid ejecting mechanism  20  will be described more fully below. 
     The suction unit  60  is used for suctioning a liquid or an excised substance in the vicinity of the ejection port  58 . The suction unit  60  and the liquid ejecting mechanism  20  are connected to each other by a suction channel  62 . While a switch for bringing the suction unit  60  into operation is turned on, the suction unit  60  suctions the inside of the suction channel  62  at all times. The suction channel  62  passes through the inside of the liquid ejecting mechanism  20 , and opens in the vicinity of the apical end of an ejection tube  55 . 
     The suction channel  62  is covered with the ejection tube  55  extending from the apical end of the liquid ejecting mechanism  20 . For this reason, as shown in a view taken in the direction of arrow A of  FIG. 1 , the wall of the ejection tube  55  and the wall of the suction channel  62  form a substantially concentric cylinder. A channel into which a suctioned substance suctioned from a suction port  64 , which is the apical end of the suction channel  62  flows, is formed between the outer wall of the ejection tube  55  and the inner wall of the suction channel  62 . The suctioned substance is suctioned to the suction unit  60  through the suction channel  62 . Meanwhile, this suction is adjusted by a suction adjustment mechanism  65  described later with reference to  FIG. 2 . 
       FIG. 2  shows an internal structure of the liquid ejecting mechanism  20 . The liquid ejecting mechanism  20  has the pulsation generation portion  30 , an inlet channel  40 , an outlet channel  41 , a connection tube  54 , a built in acceleration sensor  69 , and includes the suction force adjustment mechanism  65 . 
     The pulsation generation portion  30  generates pulsation in the pressure of a liquid which is supplied from the liquid supply mechanism  50  through the liquid supply channel  52  to the liquid ejecting mechanism  20 . The pressurized and pulsed liquid is supplied to the ejection tube  55 . The liquid supplied to the ejection tube  55  is intermittently ejected from the ejection port  58 . The ejection tube  55  is formed of stainless steel. The ejection tube  55  may be formed of other metals such as brass, or other materials, such as reinforced plastic, which have a predetermined rigidity or higher. 
     As shown in the enlarged view of the lower portion of  FIG. 2 , the pulsation generation portion  30  includes a first case  31 , a second case  32 , a third case  33 , a bolt  34 , a piezoelectric element  35 , a reinforcement plate  36 , a diaphragm  37 , a packing  38 , an inlet channel  40  and an outlet channel  41 . The first case  31  is a cylindrical member. The entirety of the first case  31  is hermetically sealed by the second case  32  being bonded to one end thereof, and the third case  33  being fixed to the other end thereof using the bolt  34 . The piezoelectric element  35  is disposed in a space which is formed inside the first case  31 . 
     The piezoelectric element  35  is a laminated piezoelectric element. One end of the piezoelectric element  35  is fastened to the diaphragm  37  with the reinforcement plate interposed therebetween. The other end of the piezoelectric element  35  is fastened to the third case  33 . The diaphragm  37  is created by a metal thin film. The peripheral edge of the diaphragm  37  is fastened to the first case  31 , and is interposed 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 . 
     A drive signal is input from the control portion  70  through the signal cable  72  to the piezoelectric element  35 . The signal cable  72  is inserted from a rear end  22  of the liquid ejecting mechanism  20 . The signal cable  72  accommodates two electrode wires  74  and one signal wire  76  for an acceleration sensor. The electrode wire  74  is connected to the piezoelectric element  35  within the pulsation generation portion  30 . The piezoelectric element  35  is expanded and contracted on the basis of the drive signal transmitted from the control portion  70 . The volume of the liquid chamber  39  is fluctuated by the expansion and contraction of the piezoelectric element  35 . 
     The inlet channel  40  into which a liquid flows is connected to the second case  32 . The inlet channel  40  is bent into a U shape, and extends toward the rear end  22  of the liquid ejecting mechanism  20 . The liquid supply channel  52  is connected to the inlet channel  40 . The liquid supplied from the liquid supply mechanism  50  is supplied to the liquid chamber  39  through the liquid supply channel  52 . 
     When the piezoelectric element  35  is expanded and contracted at a predetermined frequency the diaphragm  37  vibrates. When the diaphragm  37  vibrates, the volume of the liquid chamber  39  is fluctuated, and the pressure of the liquid within the liquid chamber pulsates. A pressurized liquid flows out from the outlet channel  41  which is connected to the liquid chamber  39 . 
     The ejection tube  55  is connected to the outlet channel  41  through the metal-made connection tube  54 . The liquid flowing out to the outlet channel  41  is ejected from the ejection port  58  through the connection tube  54  and the ejection tube  55 . 
     The suction force adjustment mechanism  65  is used for adjusting a force in order for the suction channel  62  to suction a liquid or the like from the suction port  64 . The suction force adjustment mechanism  65  includes an operating portion  66  and a hole  67 . The hole  67  is a through-hole for connecting the suction channel  62  and the operating portion  66 . When a user opens and closes the hole  67  with a finger of a hand grasping the liquid ejecting mechanism  20 , the amount of air flowing into the suction channel  62  through the hole  67  is adjusted depending on the degree of the opening and closing, and thus the suction force of the suction port  64  is adjusted. The adjustment of the suction force may be realized by control using the suction unit  60 . 
     The liquid ejecting mechanism  20  includes the acceleration sensor  69 . The acceleration sensor  69  is a piezo-resistive 3-axis acceleration sensor. The 3 axes are respective axes of XYZ shown in  FIG. 2 . The X axis is in parallel with the passing-through direction of the hole  67 , and an upward direction is a positive direction. The Z axis is in parallel with the long-axis direction of the ejection tube  55 , and a direction in which a liquid is ejected is set to a negative direction. The Y axis is defined by a right-handed system with reference to the X axis and the Z axis. 
     As shown in  FIG. 2 , the acceleration sensor  69  is disposed in the vicinity of an apical end  24  of the liquid ejecting mechanism  20 . A measurement result is input to the control portion  70  through the signal wire  76  for an acceleration sensor. 
       FIG. 3  is a graph illustrating a waveform of a drive signal (hereinafter, referred to as a “drive waveform”) which is input to the piezoelectric element  35 . The vertical axis represents a voltage and the horizontal axis represents a time. The drive waveform is described by a combination of sine curves. The peak voltage and frequency of the drive waveform is changed by an ejection process (described more fully with respect to  FIG. 4 ). 
     The piezoelectric element  35  is deformed so that the volume of the liquid chamber  39  is contracted when the voltage value of a drive signal increases. This contraction is repeatedly generated by the drive signal being repeatedly input. As a result, a liquid is intermittently ejected. 
       FIG. 4  is a flow diagram illustrating an ejection process. The ejection process is repeatedly executed by the control portion  70  while the foot switch  75  is stepped on. Initially, a velocity S of the ejection port  58  is calculated (step S 100 ). The term “velocity S” as used herein refers to an absolute value of velocity in the XY plane. That is, it is an absolute value of a velocity ignoring a velocity in a Z-axis direction. The velocity S is calculated on the basis of the 3-axis acceleration which is measured by the acceleration sensor  69 . 
     The velocity S is calculated as a parameter influencing the excision depth of the affected part. This is because the excision ability acting on each local region of the affected part per unit time is influenced by a movement velocity between the ejection port  58  and the affected part. In the present embodiment, on the assumption that the affected part remains stationary, the velocity S is handled as the movement velocity between the affected part and the ejection port  58 . Meanwhile, considering that the affected part moves due to respiration or the like, the velocity S may be handled as a relative velocity between the ejection port  58  and the affected part. 
     Subsequently, a peak voltage and a drive frequency are determined on the basis of the calculated velocity S (step S 200 ).  FIGS. 5A and 5B  are graphs illustrating a relationship between a peak voltage and a drive frequency and the velocity S, respectively.  FIG. 5A  shows a peak voltage in the vertical axis, while  FIG. 5B  shows a drive frequency in the vertical axis. The horizontal axis is common with respect to the velocity S, and scales are coincident with each other in  FIGS. 5A and 5B . 
     As shown in  FIGS. 5A and 5B , in each velocity range of Sa≦velocity S≦S3 and S3≦velocity S≦Sb, parameters having changing values are different from each other. That is, Sa, S3 and Sb are velocities which are previously determined as thresholds for switching changing parameters. 
     When the relation of velocity S≦Sa is satisfied, the peak voltage is fixed to Vmin which is a minimum value, and the drive frequency is fixed to Fmin which is a minimum value. When the parameters are set in this manner, the excision ability becomes lowest. 
     When the relation of Sa≦velocity S≦S3 is satisfied, the drive frequency is fixed to Fmin, whereas the peak voltage linearly increases with an increase in the velocity S. when the relation of velocity S=S3 is satisfied, the peak voltage is set to Vmax which is a maximum value. Vmin is set so that the excision ability does not decrease excessively. Vmax is set so that the load of the piezoelectric element  35  does not increase excessively. 
     When the relation of S3≦velocity S≦Sb is satisfied, the peak voltage is fixed to Vmax, whereas the drive frequency linearly increases with an increase in the velocity S. When the relation of velocity S=Sb is satisfied, the drive frequency is set to Fmax which is a maximum value. Fmin is set to so that the excision ability does not decrease excessively and the intermittent ejection is realized. Fmax is set so that the load of the piezoelectric element  35  does not increase excessively. When the peak voltage and the drive frequency are changed in this manner, the drive waveform is changed. 
       FIG. 6  is a graph illustrating a state where the drive waveform is changed. The vertical axis represents a voltage and the horizontal axis represents a time.  FIG. 6  illustrates three drive waveforms. A curve J represents a drive waveform when the peak voltage is set to Vmin and the drive frequency is set to Fmin. That is, the curve J represents a drive waveform when the above-mentioned relation of velocity S≦Sa is satisfied. A curve B represents a drive waveform when the peak voltage is set to Vmax and the drive frequency is set to Fmin. That is, the curve B represents a drive waveform when the above-mentioned relation of velocity S=S3 is satisfied. A curve C represents a drive waveform when the peak voltage is set to Vmax and the drive frequency is set to Fmax. That is, the curve C represents a drive waveform when the above-mentioned relation of velocity S≧Sb is satisfied. 
     When the peak voltage becomes higher, the amount of expansion and contraction of the piezoelectric element  35  increases. Therefore, a fluctuation ratio between volume fluctuations of the liquid chamber  39  becomes higher. The term “fluctuation ratio” as used herein refers to a value obtained by dividing a maximum volume in the volume fluctuations by a minimum volume. When a ratio between volume fluctuations becomes higher, pressure fluctuation within the liquid chamber  39  increases. When the pressure fluctuation within the liquid chamber  39  increases, the liquid is ejected with great force. Further, when the peak voltage becomes higher, the amount of the liquid ejected increases. When the peak voltage becomes higher due to these actions, the excision ability increase. As a result, even when the excision ability acting per unit area by the velocity S becoming faster decreases, the decrease is offset, and the excision depth is stabilized. Meanwhile, the term “offset” as used herein is not limited to a case where the excision depth does not change entirely even when the velocity S changes, and includes a case where at least a portion of an influence due to the velocity S changing is diminished. 
     When the drive frequency becomes higher, the number of times at which the liquid is ejected per unit time increases. Further, in a case of the present embodiment, as shown in  FIG. 6 , when the drive frequency becomes higher, a rise time is shortened. The term “rise time” as used herein refers to a time taken for the voltage value of the drive signal to reach a peak from zero. When the rise time is shortened, the contraction of the liquid chamber  39  is executed in a short time. As a result, the liquid is ejected with great force. When the drive frequency becomes higher due to these actions, the excision ability increases, and the excision depth is stabilized even when the velocity S becomes faster. 
     After the peak voltage and the drive frequency are determined as described above, a supply flow rate is determined (step S 300 ), and control is executed on the basis of the peak voltage, the drive frequency, and the supply flow rate which are determined (step S 400 ). The term “supply flow rate” as used herein refers to a volumetric flow rate of the liquid which is supplied by the liquid supply mechanism  50 . 
       FIG. 7  is a graph conceptually illustrating a method of determining a supply flow rate. The vertical axis represents a supply flow rate and a required flow rate, and the horizontal axis represents a time. The required flow rate refers to a required flow rate in order for the liquid chamber  39  to be filled with a liquid, and the calculation method thereof will be described later along with  FIGS. 8 and 9 . 
     The supply flow rate is set to a value which slightly exceeds the required flow rate in principle. When the supply flow rate falls below the required flow rate, ejection may not possibly be executed even in a case where the volume of the liquid chamber  39  is contracted. When the ejection is not normally executed in this manner, the excision ability may decrease. On the other hand, when the supply flow rate drastically exceeds the required flow rate, a liquid is ejected even at a time when the ejection is interrupted in order to realize the intermittent ejection, and the intermittent ejection may not be able to be normally executed. Further, when the supply flow rate drastically exceeds the required flow rate, the affected part is filled with a liquid, which may cause interference with a surgical operation. Thus, as described above, it is preferable that the supply flow rate be a value which slightly exceeds the required flow rate. 
     In the present embodiment, when the required flow rate changes, the supply flow rate is temporarily increased. When the required flow rate is Fd, and the required flow rate becomes 2×Fd from a state where the supply flow rate is Fs (&gt;Fd), the supply flow rate is temporarily set to 3×Fs, and then is made to gradually converge on 2×Fs. Portions of the graph designed as points A in a curve showing the supply flow rate of  FIG. 7  conceptually shows this flow rate control. 
     Alternatively, when the required flow rate is Fd, and the required flow rate becomes 0.5×Fd from a state where the supply flow rate is Fs, the supply flow rate is temporarily set to 0.75×Fs, and then is made to gradually converge on 0.5×Fs. A portion of the graph designed as point B in the curve showing the supply flow rate of  FIG. 7  conceptually shows this flow rate control. 
     In this manner, when the required flow rate changes, the supply flow rate is made to be larger than a target value temporarily, and thus the ejection of the liquid is prevented from not being able to be normally executed with the lack of the supply flow rate due to control delay or undershoot. 
       FIG. 8  is a graph illustrating experimental results regarding a relationship between the required flow rate and the peak voltage. Each point on the graph represents experimental results, and the straight line represents an approximation straight line of each point. As shown in  FIG. 8 , when the peak voltage is increased two times, the required flow rate is increased approximately 1.5 times. 
       FIG. 9  is a graph illustrating experimental results regarding a relationship between the required flow rate and the drive frequency. Each point on the graph represents experimental results, and the straight line represents an approximation straight line of each point. As shown in  FIG. 9 , when the drive frequency is increased two times, the required flow rate is increased approximately two times. 
     The determination of the supply flow rate in step S 300  shown in  FIG. 4  is realized by calculating the required flow rate on the basis of the relationships shown in FIGS.  8  and  9  illustrate the process of calculating the supply flow rate on the basis of the calculated required flow rate. 
     As described above, the supply flow rate is determined on the basis of the relationship with the required flow rate and also influences the excision ability.  FIG. 10  is a graph illustrating a relationship between the ejection pressure and the peak voltage when the supply flow rate is classified into two cases. The drive frequency is set to the same value in any case. Even when the supply flow rate is set to any case of 3 ml/min and 6 ml/min, the ejection pressure increases with an increase in the peak voltage. This shows an improvement in the excision ability with an increase in the peak voltage described above. 
     As shown in  FIG. 10 , in each peak voltage, the case of 6 ml/min has the ejection pressure higher than the case of 3 ml/min. 
       FIG. 11  is a graph illustrating a relationship between the excision depth and the peak voltage when the supply flow rate is classified into two cases. This excision depth is shown by a value which is made non-dimensional by setting a case where the peak voltage is 5V and the supply flow rate is 3 ml/min to 1. The drive frequency is set to the same value in any case. 
     Similarly to a case of the ejection pressure ( FIG. 10 ), even when the supply flow rate is set to any case of 3 ml/min and 6 ml/min, the excision depth increases with an increase in the peak voltage, the case of 6 ml/min has the excision depth larger than the case of 3 ml/min in each peak voltage. 
     In any of the graphs shown in  FIGS. 10 and 11 , an increase in the supply flow rate shows contribution to an improvement in the excision ability. The relationship between velocity S and the peak voltage and the relationship between the velocity S and the drive frequency described above is determined with the addition of a change in the excision ability by the supply flow rate which is determined on the basis of the relationship with the required flow rate. 
     As described above, as the velocity S increases, the peak voltage is changed so that the excision ability is improved, thereby allowing the excision depth to be stabilized. Further, when the peak voltage reaches a maximum value, the drive frequency and the peak voltage are changed, thereby allowing the excision depth to be stabilized. 
     According to the present embodiment, the range of the velocity S which changes the peak voltage and the drive frequency is separated, and it is easy to determine values of the peak voltage and the drive frequency in each velocity range. Meanwhile, since the range of the velocity S which changes the drive frequency and the peak voltage is separated, the peak point of the drive waveform draws a locus having such a shape that a Γ shape is clockwise rotated by 90 degrees, as shown in  FIG. 6 , during a change in the drive waveform. 
     As an example, S1 to S4 shown in  FIGS. 5A and 5B  are first to fourth velocities in the accompanying claims, V1 and V2 are first and second voltages, and F1 and F2 are first and second frequencies. The piezoelectric element  35  and the diaphragm  37  in the embodiment are an example of a volume fluctuation portion in the accompanying claims. 
     A second embodiment of the invention, or Embodiment 2, will be described below. In Embodiment 2, an ejection process shown in  FIG. 12  is executed instead of the ejection process shown in  FIG. 4 . A hardware configuration is the same as in Embodiment 1, and thus the description thereof will be omitted. Step S 100 , step S 300  and step S 400  in the ejection process of Embodiment 2 are the same as in Embodiment 1, and thus the description thereof will be omitted. In Embodiment 2, step S 210  to step S 240  are executed instead of step S 200  in Embodiment 1. 
     After the velocity S is calculated (step S 100 ), the peak voltage is determined on the basis of the calculated velocity S (step S 210 ). A method of determining the peak voltage is the same as in Embodiment 1. That is, a case of velocity S≦Sa is fixed to Vmin, a case of Sa velocity S≦Sb linearly increases, and a case of Sb velocity S is fixed to Vmax. 
     Next, it is determined whether the peak voltage is set to a maximum value (Vmax) (step S 220 ). When the peak voltage is set to a value less than the maximum value (step S 220 , NO), the drive frequency is set to a minimum value (Fmin) (step S 240 ). Setting of the peak voltage to a value less than the maximum value means ability to improve the excision ability due to a change in the peak voltage. Thus, since it is not necessary to improve the excision ability by changing the value of the drive frequency, the drive frequency is set to the minimum value. 
     On the other hand, when the peak voltage is set to the maximum value (step S 220 , YES), the drive frequency is determined on the basis of the velocity S (step S 230 ). Setting of the peak voltage to the maximum value means inability to improve the excision ability due to a change in the peak voltage. Consequently, step S 230  is executed in order to improve the excision ability by changing the value of the drive frequency. In Embodiment 2, it is also possible to obtain the same control result as in Embodiment 1. 
     A third embodiment, or Embodiment 3, will be described below. In Embodiment 3, step S 200  of the ejection process is executed on the basis of the relationships shown in  FIGS. 13A and 13B  instead of the relationship between the peak voltage and the drive frequency, and the velocity S in Embodiment 1 shown in  FIGS. 5A and 5B .  FIG. 13A  shows a drive frequency in the vertical axis, while  FIG. 13B  shows a peak voltage in the vertical axis. The horizontal axis is common with the velocity S in both  FIGS. 13A and 13B , and scales are coincident with each other in  FIGS. 13A and 13B . 
     As shown in  FIGS. 13A and 13B , the drive frequency increases in the velocity range of Sa≦velocity S≦S3′, and the peak voltage increases in the velocity range of S3′≦velocity S≦Sb. That is, unlike Embodiment 1, the excision ability is first improved by a change in the drive frequency, and the excision ability is improved by a change in the peak voltage when the drive frequency reaches the maximum value. 
     In Sa and Sb of Embodiment 3, the same values as the values adopted in Embodiment 1 are adopted. Sa is a velocity in which an improvement in the excision ability is preferably started, and which is because it is common with Embodiment 1 in this viewpoint. Sb is the slowest velocity of velocities in which the drive frequency and the peak voltage are set to the maximum value, and thus is set to the same value as in Embodiment 1 even when a change order is countercharged. S3′ is a value which is set as a velocity when the drive frequency reaches the maximum value, and thus a value different from S3 in Embodiment 1 is adopted. Sa and Sb may be, of course, values different from those in Embodiment 1, and S3′ may be the same value as S3. 
     In Embodiment 3, it is also possible to stabilize the excision depth in a similar manner as in Embodiment 1. Regarding whether any of the peak voltage and the drive frequency is preferentially changed, it is considered that one of the peak voltage and the drive frequency in which the excision depth is further stabilized is selected on the basis of the characteristics of the piezoelectric element  35 . 
     Embodiment 4 will be described below. In a liquid ejection method, a laser light may be used. In the ejection method using laser light, for example, pressure fluctuation occurring by intermittently irradiating a liquid with laser light and vaporizing the liquid may be used. 
     A liquid ejecting apparatus in Embodiment 4 includes an output portion that outputs laser light into a liquid chamber in accordance with a drive signal, and an ejection port that ejects a liquid from the liquid chamber, and a control portion that outputs laser light to the output portion by a first output when a movement velocity of the ejection port is a first velocity and outputs laser light to the output portion by a second output higher than the first output when the movement velocity is a second velocity faster than the first velocity. According to such an aspect, energy of laser light in one-time emission increases, and pressure fluctuation within the liquid chamber increases. As a result, a liquid is ejected with great force to thereby increase the excision ability and the excision depth is stabilized even when the movement velocity becomes faster. 
     In addition, the control portion may set a maximum voltage of the drive signal to a first voltage when the movement velocity is the first velocity, and may set the maximum voltage of the drive signal to a second voltage higher than the first voltage when the movement velocity is the second velocity. In such an aspect, it is possible to easily control an output of laser light. Energy of laser light per one-time output easily rises by adjusting a voltage, and the excision depth is stabilized even when the movement velocity becomes faster. 
     In Embodiment 4, the control portion may change a frequency of the drive signal in accordance with the movement velocity. In such an aspect, the output of laser light can be adjusted by methods other than a change in the maximum voltage, and the excision depth is stabilized even when the movement velocity becomes faster through an easy operation. 
     Further, the control portion may set a frequency of the drive signal to a first frequency when the maximum voltage is the first and second voltages, and may set the frequency of the drive signal to a second frequency higher than the first frequency when the maximum voltage is a third voltage higher which is than the second voltage. In such an aspect, when the maximum voltage is the first and second voltages, the output is controlled by a change in the maximum voltage without changing the frequency of the drive signal, and thus the values of the first and second voltages are easily determined. 
     In a fourth embodiment of the invention, Embodiment 4, the control portion may set the maximum voltage to a third voltage and set a frequency of the drive signal to the second frequency when the movement velocity is the third velocity faster than the second velocity, and may set the maximum voltage to the third voltage and set the frequency of the drive signal to a third frequency higher than the second frequency when the movement velocity is a fourth velocity faster than the third velocity. In such an aspect, when the movement velocity is the third and fourth velocities, the output is controlled by a change in the frequency without changing the maximum voltage of the drive signal, and thus the values of the second and third frequency are easily determined. 
     In addition, a liquid supply portion is included that supplies a liquid to the liquid chamber at a flow rate which is set by the control portion. The control portion may set the flow rate to a first flow rate when the movement velocity is the first velocity and may set the flow rate to a second flow rate higher than the first flow rate when the movement velocity is the second velocity. In such an aspect, the supplied flow rate can be appropriately set. 
     Further, the control portion may change the maximum voltage and the frequency of the drive signal in accordance with the movement velocity. Consequently, the output of laser light can be changed by the maximum voltage and the frequency of the drive signal. 
     The invention is not limited to the aforementioned embodiments, examples, and modification examples of this specification, and can be implemented by various configurations without the gist of the invention. For example, technical features in the embodiments, examples, and modification examples which correspond to the technical features in the respective aspects described in the summary of the invention can be appropriately replaced or combined in order to solve some or all of the aforementioned problems, or to achieve some or all of the aforementioned effects. The technical features can be appropriately deleted as long as they are not described as essential features in this specification. For example, the following is exemplified. 
     In an alternative embodiment, the drive frequency may not be changed. That is, the adjustment of the excision ability may be realized by changing the peak voltage and the supply flow rate. 
     The adjustment of the excision ability may be realized by only changing the peak voltage without changing the drive frequency and the supply flow rate. 
     Alternatively, the adjustment of the excision ability may be realized by only changing the supply flow rate without changing the peak voltage and the drive frequency. When a configuration is adopted in which the peak voltage and the drive frequency are not changed, it is possible to simplify the configuration of the control portion. 
     The peak voltage, the drive frequency and the supply flow rate may be determined using a function. 
     A velocity range in which the peak voltage is fluctuated and the velocity range in which the drive frequency is fluctuated may overlap each other. 
     The drive waveform may not be a combination of sine curves, and may be increased or decreased, for example, in a stepwise manner. 
     A relationship between each of the peak voltage and the drive frequency and the velocity of the ejection port may be specified in a curve manner, and may alternately be specified in a stepwise manner. 
     The drive frequency may be changed in a state where a rise time is fixed. That is, the drive frequency may be changed by changing a time until the voltage of the drive signal reaches zero from a peak. In this manner, when the drive frequency is determined with respect to the movement velocity, the influence of a change in the rise time can be excluded, and thus the determination of the drive frequency is facilitated. 
     The velocity of the ejection port may be calculated, for example, by the acceleration sensor which is installed on the apical end of the ejection port. In this case, calculation results are considered to be more accurate. 
     Alternatively, the velocity of the ejection port may be calculated using image processing. For example, the velocity of the ejection port may be calculated by installing a marker on the apical end of the ejection port, and grasping the movement of the marker using a camera. 
     When a robot operates the liquid ejecting apparatus, the velocity of the ejection port can be grasped by the robot, and thus the grasped value may be used without requiring calculation. 
     The movement velocity of the ejection port may be calculated with the addition of the movement velocity of the affected part. The measurement of the movement velocity of the affected part may be realized by predicting or measuring movement due to respiration or pulsation. Meanwhile, the detection of the movement velocity may be performed at a place moving in association with the movement of the ejection port without being limited to that of the ejection port, and the movement velocity of the liquid ejecting mechanism may be detected. 
     In addition, control for ejecting a liquid may be performed so that at least one of a predetermined liquid amount, energy of a predetermined liquid, a predetermined pressure of a liquid, and the like is given to an object to which a liquid is ejected regardless of a change in the movement velocity of the ejection port, and control may be performed in which two or more physical quantities of a predetermined liquid amount, energy of a predetermined liquid, and a predetermined pressure of a liquid may be combined. 
     The type of the acceleration sensor may be a capacitance type and may be a heat detection type. In addition, a sensor may be used which is capable of detecting the movement velocity of the ejection port indirectly or directly without being limited to acceleration. 
     The liquid ejecting apparatus may be used in other than the medical device. 
     For example, the liquid ejecting apparatus may be used in a cleaning apparatus that removes contaminants using an ejected liquid. 
     The liquid ejecting apparatus may be used in a drawing apparatus that draws a line or the like using an ejected liquid. 
     In a liquid ejection method, laser light may be used. In the ejection method using laser light, for example, pressure fluctuation occurring by intermittently irradiating a liquid with laser light and vaporizing the liquid may be used.