Patent Application
20150361973
1. Technical Field
The present invention relates to a liquid transport device and a liquid transport method.
2. Related Art
As a liquid transport device for transporting a liquid, there has been known a micropump described in JP-A-2013-24185 (Document 1). In the micropump, there is disposed a plurality of fingers along a tube, and by a cam sequentially pushing the fingers, the tube is squeezed and thus the liquid is transported. Further, there is disposed an encoder for measuring the rotational angle of the cam or a rotor for rotationally driving the cam.
In such a liquid transport device as described in Document 1, a transport operation and a halt operation of the liquid are performed repeatedly in some cases. For example, in the case of using the liquid transport device as an insulin injection device, there is repeated an operation of sending an insulin solution for three seconds per minute, and stopping the liquid transport for the remaining 57 seconds. In such an insulin injection device as described above, since there is a high requirement for precisely controlling the transport amount of the insulin, it is arranged that the rotational angle of the cam or the rotor can be detected with high accuracy using an optical encoder. However, if the power of the light emitting section and the light receiving section of the optical encoder is always kept in the ON state, the power consumption in stopping the liquid transport operation is wasted.
Further, in such a liquid transport device as described in Document 1, in order to perform the liquid transport with accuracy, it is necessary to detect the rotational angle of the cam with high accuracy using the encoder. In other words, it is necessary to, for example, transport a correct amount of insulin within the period of three seconds in which the liquid transport operation is performed out of the period of one minute. However, when repeatedly performing the liquid transport operation and the halt operation, the position of the cam is shifted due to the factor that an external force is applied in stopping the liquid transport operation, or the detection position is varied due to the influence of a backlash of a rotation mechanism of the cam, and thus, the detection value by the encoder fluctuates to make it easy to cause an error. Further, there is also a possibility that the detection value of the encoder fluctuates due to the influence of noise and so on. If such a fluctuation occurs, the actual rotational angle of the cam or the rotor becomes uncertain, and therefore, it becomes difficult to transport an accurate amount of liquid when resuming the liquid transport operation in the halt state.
An advantage of some aspects of the invention is to reduce the power consumption of the encoder in a liquid transport device driven by rotation of a rotor.
Another advantage of some aspects of the invention is to reduce the fluctuation of a detection value of an encoder in a liquid transport device driven by rotation of a rotor.
A principal aspect of the invention is directed to a liquid transport device including a drive mechanism having a rotor rotating when transporting a liquid, and a detection section adapted to detect a rotational angle of the rotor, wherein power of the detection section is switched between an ON state and an OFF state in sync with switching between drive and halt of the drive mechanism.
Other features of the invention will be apparent from the present specification and the accompanying drawings.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
The description of the present specification and the accompanying drawings will make at least following items apparent.
A liquid transport device includes a drive mechanism having a rotor rotating when transporting a liquid, and a detection section adapted to detect a rotational angle of the rotor, and power of the detection section is switched between an ON state and an OFF state in sync with switching between drive and halt of the drive mechanism.
According to such a liquid transport device, since the detection section is powered OFF during the period in which the drive mechanism does not operate, the power consumption of the detection section in performing the liquid transport operation can be reduced. Further, by reducing the power consumption of the detection section, the power consumption of the whole of the liquid transport device can be reduced.
In such a liquid transport device as described above, it is preferable that the detection section includes a light emitting section adapted to emit light, and a light receiving section adapted to receive the light emitted, and power of the light emitting section is switched between the ON state and the OFF state in sync with switching between the ON state and the OFF state of power of the drive mechanism.
According to such a liquid transport device, the power consumption can be reduced in the light emitting section having high energy consumption among the detection section in performing the liquid transport operation. By reducing the power consumption of the light emitting section, the power consumption of the whole of the liquid transport device can more significantly be reduced.
In such a liquid transport device as described above, it is preferable that the detection section has an encoder circuit adapted to output an output signal having a predetermined level based on a detection value of a rotational angle of the rotor, and power of the encoder circuit is switched between the ON state and the OFF state in sync with switching between the ON state and the OFF state of power of the drive mechanism.
According to such a liquid transport device, the power consumption in the encoder circuit among the constituents of the detection section can be reduced. Thus, in performing the liquid transport operation with the liquid transport device, the power consumption of the operation of detecting the rotational angle of the rotor can be reduced.
In such a liquid transport device as described above, it is preferable that in starting drive of the drive mechanism, the power of the light emitting section is set to the ON state, and then the power of the encoder circuit is set to the ON state, and in stopping drive of the drive mechanism, the power of the encoder circuit is set to the OFF state, and then the power of the light emitting section is set to the OFF state.
According to such a liquid transport device, even in the case of performing intermittent drive of repeating drive and halt of the drive mechanism, the power consumption in the detection section can be reduced while accurately controlling the liquid transport operation. In other words, it is possible to achieve both of the accurate liquid transport operation and the reduction of the power consumption in the liquid transport device.
In such a liquid transport device as described above, it is preferable that the detection section includes an encoder adapted to detect a rotational angle of the rotor, a comparator circuit adapted to compare the detection value detected by the encoder and a predetermined reference value with each other to output a signal having one of an H level and an L level, and a reference value setting section adapted to detect the signal output to vary the reference value.
According to such a liquid transport device as described above, in performing the liquid transport operation, it becomes possible to suppress the fluctuation of the detection value of the encoder, and it becomes possible to more accurately control the drive/halt operation of the drive mechanism. Therefore, it becomes possible to accurately control the timing of setting the power to the ON state in sync with drive of the drive mechanism and the timing of setting the power to the OFF state in sync with the halt of the drive mechanism, and thus, it is possible to reduce the power consumption in performing the liquid transport operation (the intermittent drive) of repeating drive and halt in the liquid transport device.
In such a liquid transport device as described above, it is preferable to include a resetting section adapted to store a level of the signal output at a time point when the drive mechanism has stopped in a case of performing intermittent drive of repeating drive and halt of the drive mechanism, and apply a resetting voltage having a level corresponding to a level of the signal stored to the comparator circuit in driving the drive mechanism again.
According to such a liquid transport device as described above, even in the case in which the position of the cam or the rotor has been shifted due to the influence of an external force while the drive mechanism is at rest, the rotation of the cam and so on can be controlled in the same state as at the time of stopping drive in resuming drive of the drive mechanism. Therefore, it becomes possible to more accurately control the drive/halt operation of the drive mechanism. Thus, it becomes possible to more accurately control the timing of switching the power of the detection section between the ON state and the OFF state, and it becomes easy to further reduce the power consumption in the intermittent drive in the liquid transport device.
In such a liquid transport device as described above, it is preferable that the comparator circuit includes a comparator adapted to compare a level of an input voltage and a reference voltage with each other to output the signal having one of the H level and the L level, and the resetting section applies the resetting voltage to a terminal of the comparator to which the input voltage is input.
According to such a liquid transport device as described above, by applying the resetting voltage to the input voltage side of the comparator, it becomes easy to reproduce the level of the output signal, which has been output when the drive mechanism has stopped, at the time of resuming drive of the drive mechanism. Thus, it becomes possible to more accurately control the drive/halt operation of the drive mechanism, and therefore, it becomes possible to accurately control the liquid transport operation in the intermittent drive in the liquid transport device.
In such a liquid transport device as described above, it is preferable that the comparator circuit includes a comparator adapted to compare a level of an input voltage and a level of a reference voltage with each other to output the signal having one of the H level and the L level, and the resetting section applies the resetting voltage to a terminal of the comparator to which the reference voltage is input.
According to such a liquid transport device as described above, by applying the resetting voltage to the reference voltage input side of the comparator, it becomes easy to reproduce the level of the output signal, which has been output when the drive mechanism has stopped, at the time of resuming drive of the drive mechanism. Thus, it becomes possible to more accurately control the drive/halt operation of the drive mechanism, and therefore, it becomes possible to accurately control the liquid transport operation in the intermittent drive in the liquid transport device. Further, since it is possible to apply the resetting voltage to an arbitrary position between the output side and the reference voltage input side of the comparator, the degree of freedom of circuit design increases, and it becomes possible to compactly configure the liquid transport device.
In such a liquid transport device as described above, it is preferable that the detection section includes a first encoder adapted to detect the rotational angle of the rotor, a second encoder adapted to detect the rotational angle of the rotor at a different position from a position of the first encoder, and a control section adapted to determine a rotational direction of the rotor based on whether the level of the signal, which is output by the second encoder when the level of the signal output by the first encoder varies, is the H level or the L level.
According to such a liquid transport device, even in the case in which the rotational position of the rotor has been shifted due to the influence of the external force while the drive mechanism has been at rest, the direction in which the shift has occurred can be identified, and therefore, it becomes easy to correct the shift. Thus, in resuming drive of the drive mechanism in the halt state, it becomes easy to perform the more accurate liquid transport operation.
In such a liquid transport device as described above, it is preferable to include a cam driven by the rotation of the rotor to thereby transport the liquid, a rotation detection encoder adapted to detect a rotation reference position of at least one of the cam and the rotor, a rotational angle detection encoder adapted to detect the rotational angle of the rotor, and a control section adapted to detect a shift amount between the rotation reference position of at least one of the cam and the rotor detected by the rotation detection encoder, and the rotational angle of the rotor detected by the rotational angle detection encoder, and correct the rotation reference position as much as the shift amount detected.
According to such a liquid transport device as described above, even in the case in which the rotation reference position to be a reference in detecting the rotational angle of the rotor and so on has been shifted, the shift amount can periodically be detected, and therefore, by correcting the rotation reference position as much as an amount corresponding to the shift amount, the detection accuracy of the rotational angle can be enhanced. Thus, even in the case of repeating drive and halt in the liquid transport device, the accurate liquid transport operation can be performed.
Further, there will become apparent a liquid transport method including detecting a rotational angle of a rotor rotating when transporting a liquid, and switching a power of a detection section adapted to detect the rotational angle of the rotor between an ON state and an OFF state in sync with switching between drive and halt of a drive mechanism having the rotor.
A liquid transport device includes a drive mechanism having a rotor rotating when transporting a liquid, and an encoder adapted to detect a rotational angle of the rotor, a comparator circuit adapted to compare the detection value detected by the encoder and a predetermined reference value with each other to output a signal having one of an H level and an L level, and a reference value setting section adapted to detect the signal output to vary the reference value.
According to such a liquid transport device as described above, the fluctuation of the detection value of the encoder can be reduced due to the hysteresis characteristic in detecting the rotational angle of the rotor. By reducing the fluctuation of the detection value, it becomes easy to correctly detect the rotational angle of the rotor, and therefore, it becomes possible to accurately control the operation of the drive mechanism. Thus, the accurate liquid transport operation can be realized in the liquid transport device.
In such a liquid transport device as described above, it is preferable that the drive mechanism includes a piezoelectric actuator adapted to make a vibrator element, which vibrates in accordance with a drive signal applied to the vibrator element, have contact with the rotor to rotate the rotor, and the piezoelectric actuator is biased so that an end portion of the vibrator element and an outer circumferential portion of the rotor have contact with each other in a state in which a vibration orbit of the vibrator element and a rotational plane of the rotor are in parallel to each other.
According to such a liquid transport device as described above, the rotor is biased against the vibrator element in the drive section to thereby generate a force in a direction perpendicular to the rotational plane of the rotor, and even in the case in which the optical path length of the rotary encoder is fluctuated, chattering in the detection value can be suppressed. Therefore, in the liquid transport device for transporting a liquid by rotating the rotor with a piezoelectric actuator, the liquid transport operation can accurately be performed.
In such a liquid transport device as described above, it is preferable that there is included a cam rotationally driven by the rotation of the rotor to thereby transport the liquid, the drive mechanism includes a reduction section adapted to reduce revolution of the rotor and then transmit the rotation of the rotor to the cam, and the detection section detects a rotational angle of the reduction section.
According to such a liquid transport device as described above, the rotational angle of the cam can correctly be detected. Specifically, by detecting the rotational angle of the cam via a reduction mechanism disposed at the position, at which the distance from the cam is short, and the influence of the backlash is small, it becomes easy to detect the rotation operation of the cam in the period of transporting the liquid. Further, since the rotation amount of the reduction section with respect to the rotation amount of the cam becomes large if the reduction ratio in the reduction section is large, by detecting the rotational angle of the reduction section, the resolution of the rotational angle of the cam increases, and the rotational angle of the cam can be detected with high accuracy. Therefore, it becomes easy to accurately detect the liquid transport amount in performing the liquid transport operation with the liquid transport device.
In such a liquid transport device as described above, it is preferable that there is included a cam rotationally driven by the rotation of the rotor to transport the liquid, the drive mechanism includes a reduction section adapted to reduce revolution of the rotor and then transmit the rotation of the rotor to the cam, and the detection section detects a rotational angle of the cam.
According to such a liquid transport device as described above, the rotational angle of the cam can correctly be detected. Specifically, by directly detecting the rotational angle of the cam using the detection section provided to the cam, it becomes easy to correctly detect the actual operation of the cam in the period of transporting the liquid. Further, by directly detecting the rotational angle of the cam, it becomes easy to obtain the data, in which the influence of the backlash is hardly included, namely the data with little noise. Therefore, it becomes easy to accurately detect the liquid transport amount in performing the liquid transport operation with the liquid transport device.
In such a liquid transport device as described above, it is preferable to include a resetting section adapted to store a level of the signal output at a time point when the drive mechanism has stopped in a case of performing intermittent drive of repeating drive and halt of the drive mechanism, and apply a resetting voltage having a level corresponding to a level of the signal stored to a predetermined terminal of the comparator circuit in driving the drive mechanism again.
According to such a liquid transport device as described above, even in the case in which the position of the cam or the rotor has been shifted due to the influence of an external force while the drive mechanism is at rest, the rotation of the cam and the rotor can be controlled in the same state as at the time of stopping drive in resuming drive of the drive mechanism. Thus, even in the case of performing the intermittent drive of repeating drive and halt in the liquid transport device, the liquid transport amount can accurately be controlled.
Further, there will become apparent a liquid transport method including detecting a rotational angle of a rotor rotating when transporting a liquid, comparing a detection value detected and a predetermined reference value with each other to output a signal having one of an H level and an L level, and detecting the signal output to vary the reference value.
According to such a liquid transport method as described above, the fluctuation of the detection value of the rotational angle of the rotor detected by the encoder can be reduced due to the hysteresis characteristic in detecting the rotational angle of the rotor. By reducing the fluctuation of the detection value, it becomes easy to correctly detect the rotational angle of the rotor, and therefore, it becomes possible to accurately control the operation of the drive mechanism. Therefore, the accurate liquid transportation can be realized.
The liquid transport device 1 is a device for transporting a liquid. The liquid transport device 1 is provided with a main body 10, a cartridge 20, and a patch 30. The main body 10, the cartridge 20, and the patch 30 can be separated as shown in
The pump section 5 has a function as a pump for transporting the liquid stored in the cartridge 20, and is provided with a tube 21, a plurality of fingers 22, a cam 11, and a drive mechanism 12.
The tube 21 is a pipe for transporting a liquid. The upstream side (the upstream side with reference to the transportation direction of the liquid) of the tube 21 communicates with a storage section 26 for the liquid in the cartridge 20. The tube 21 has such elasticity that the tube 21 is choked when being pressed by the fingers 22, and is restored when the force from the fingers 22 is released. The tube 21 is disposed along the inner surface of a tube guide wall 25 of the cartridge 20 so as to partially have a circular arc shape. The part of the tube 21 having a circular arc shape is disposed between the inner surface of the tube guide wall 25 and the plurality of fingers 22. The center of the circular arc of the tube 21 coincides with the rotational center of the cam 11.
Fingers 22 are members for choking the tube 21. The fingers 22 act in a following manner with a force applied from the cam 11. The fingers 22 each have a shaft section having a rod-like shape and a pressing section having a flange shape, and forms a T shape. The shaft section having a rod-like shape has contact with the cam 11, and the pressing section having a flange shape has contact with the tube 21. The fingers 22 are each supported so as to be movable along the shaft direction.
The plurality of fingers 22 is disposed radially from the rotational center of the cam 11 at regular intervals. The plurality of fingers 22 is disposed between the cam 11 and the tube 21. Here, the seven fingers 22 are disposed.
The cam 11 has projection sections 11A at a plurality of places (four places in
The drive mechanism 12 is a mechanism for rotationally driving the cam 11, and has a piezoelectric actuator 121, a rotor 122, and a reduction transmission mechanism 123 as shown in
The piezoelectric actuator 121 is an actuator for rotating the rotor 122 using the vibration of piezoelectric elements. By applying a drive signal to the piezoelectric elements bonded to the both sides of the vibrator element having a rectangular shape, the piezoelectric actuator 121 vibrates the vibrator element. The end portion of the vibrator element is disposed at the position at which the end portion can have contact with the rotor 122. When the vibrator element vibrates, the end portion of the vibrator element vibrates so as to draw a predetermined orbit such as an elliptical orbit or a figure-eight orbit, and by intermittently having contact with the rotor 122 in a part of the vibration orbit, the rotor 122 is driven rotationally. The piezoelectric actuator 121 is biased toward the rotor 122 with a pair of springs (spring members) so that the end portion of the vibrator element has contact with the rotor 122. In other words, the piezoelectric actuator 121 is biased so that the end portion of the vibrator element and the outer circumferential portion of the rotor 122 have contact with each other in the state in which the vibration orbit of the vibrator element and the rotational plane of the rotor 122 are parallel to each other.
The rotor 122 is a driven body rotated by the piezoelectric actuator 121. The rotor 122 is provided with a rotor pinion constituting a part of the reduction transmission mechanism 123.
The reduction transmission mechanism 123 is a mechanism for transmitting the rotation of the rotor 122 to the cam 11 at a predetermined reduction ratio. The reduction transmission mechanism 123 is formed of a rotor pinion, a transmission wheel 123A, and a cam wheel (see
It should be noted that among the tube 21, the plurality of fingers 22, the cam 11, and the drive mechanism 12 constituting the pump section 5, the cam 11 and the drive mechanism 12 are provided to the main body 10, and the tube 21 and the plurality of fingers 22 are provided to the cartridge 20. The main body 10 is also provided with detection sections 40 for measuring the rotational angle of the cam 11 or the like, a control section 50 for performing control of the piezoelectric actuator 121 and so on, and a battery 19 for supplying the piezoelectric actuator 121 and so on with electrical power.
The detection sections 40 include a cam rotation detection section 41 for detecting the rotational state of the cam 11, and a first rotor rotation angle detection section 43, a second rotor rotation angle detection section 44, and a rotor rotation detection section 45 for detecting the rotational state of the rotor 22. Here, the “rotational state” of the cam 11 or the rotor 22 denotes the rotation amount from each of rotation reference positions set respectively, and is detected as the rotational angle of the cam 11 or the rotor 22.
The cam rotation detection section 41 is a rotary encoder provided with a photo reflector formed of a light emitting section 41A and a light receiving section 41B. The light emitting section 41A is a light source, which emits light for detecting the rotational angle of the detection object (here, the cam 11), and a light emitting diode, for example, is used. The light receiving section 41B is a light receiving section for receiving the light, which has been emitted from the light emitting section 41A, and then reflected by the detection object, and a photodiode, for example, is used. In the present embodiment, the cam 11 is provided with a cam-side reflecting section 111, the cam-side reflecting section 111 reflects the light from the light emitting section 41A, and the light receiving section 41B receives the light thus reflected.
The first rotor rotation angle detection section 43 is a rotary encoder provided with a light emitting section 43A and a light receiving section 43B, and the second rotor rotation angle detection section 44 is a rotary encoder provided with a light emitting section 44A and a light receiving section 44B. These sections each have substantially the same structure as that of the cam rotation detection section 41. Further, the rotor rotation detection section 45 is also a similar rotary encoder, and is provided with a light emitting section 45A and a light receiving section 45B. The first rotor rotation angle detection section 43 and the second rotor rotation angle detection section 44 are disposed at positions shifted by a predetermined rotational angle from each other with respect to the rotational direction of the rotor 122 (see
The rotor 122 is provided with first rotor-side reflecting sections 124 and a second rotor-side reflecting section 125.
It should be noted that the cam rotation detection section 41, the first rotor rotation angle detection section 43, the second rotor rotation angle detection section 44, and the rotor rotation detection section 45 are each not limited to a reflective optical sensor (so-called photo reflector), but can also be a transmissive optical sensor.
The control section 50 has a counter 51, a storage section 52, an arithmetic section 53, and a driver 54 as shown in
Further, the rotor rotation detection section 45 outputs the output signal ROT_Z in accordance with the amount of the reflected light received in the light receiving section 45B. Since the single second rotor-side reflecting section 125 is formed along the circumferential direction of the rotor 122 as shown in
The cam rotation detection section 41 outputs the output signal CAM_Z in accordance with the amount of the reflected light received in the light receiving section 41B. Since the single cam-side reflecting section 111 is formed along the circumferential direction of the cam 11 as shown in
As described above, since the rotor 122 rotates 40 revolutions while the cam 11 rotates one revolution, the number of pulses included in the output signal ROT_A of the first rotor rotation angle detection section 43 corresponding to the rotor 122 in one cycle of the output signal CAM_Z of the cam rotation detection section 41 is obtained as 40×12=480. Therefore, defining each of the rising edge and the falling edge of the pulse in the signal ROT_A as one count, it results that 960 counts numbered as 0 through 959 are measured in every revolution of the cam 11 as shown in
Further, by using the relationship between the output signals CAM_Z, ROT_Z, and the output signal ROT_A, the control section 50 can identify the rotation reference position of the cam 11 (the rotor 122). Here, the rotation reference position denotes a position used as a reference when detecting the rotational angle of the cam 11 or the rotor 122. By detecting the moving distance from the rotation reference position, the control section 50 can calculate the rotational angle (rotation amount) of the cam 11 or the rotor 122.
Although the details will be described later, since the drive state and the halt state are repeated (intermittent drive) in the drive mechanism 12 according to the present embodiment, the rotation reference position of the cam 11 (the rotor 122) is shifted from the rotation reference position at the time of stoppage as much as roughly one or two pulses of the output signal ROT_A (the output signal ROT_B) in some cases due to the influence of a backlash of the reduction transmission mechanism 123, outside forces or the like when restarting drive of the cam 11 (the rotor 122) in the halt state. In such a case, by correcting the rotation reference position of the cam 11 (the rotor 122) as much as the shifted pulses, it becomes possible to correctly perform the subsequent rotation control of the cam 11 (the rotor 122). For example, in the case of restarting drive of the drive mechanism 12 in the halt state, the control section 50 counts the number of pulses of the output signal ROT_A (the output signal ROT_B) included in one cycle of the output signal CAM_Z or the output signal ROT_Z. Then, if the number of the pulses of the output signal ROT_A included in one revolution of the cam 11 is one pulse smaller than 960 pulses, the correction is performed so as to set the position, at which the number of pulses is one pulse smaller than that at the original rotation reference position, as an updated rotation reference position. In contrast, if the number of pulses is one pulse larger, the position at which the number of pulses is one pulse larger than that at the original rotation reference position is set as the updated rotation reference position.
Further, the control section 50 can detect whether the rotational direction of the rotor 122 or the like is shifted in the normal rotation direction or the reverse rotation direction based on the relationship between the output signals ROT_A and ROT_B. Specifically, the control section 50 determines the direction in which the drive mechanism 12 has rotated based on whether the level of the output signal ROT_B, which is detected when the level of the output signal ROT_A is changed, is the H level or the L level.
For example, at certain timing T1 shown in
The liquid transport operation by the liquid transport device 1 is performed by sequentially pressing the plurality of fingers 22 to cause a peristaltic motion in the tube 21 while rotating the cam 11 as described above to thereby move the liquid filling the inside of the tube 21. Therefore, in order to realize an accurate liquid transport operation, it is required to accurately control the rotation amount of the cam 11. In particular, in the case of using the liquid transport 1 as an insulin injection device and so on, accurate control is required for the insulin injection amount and the injection timing. For example, in the insulin injection device, there is performed the intermittent drive of performing the insulin injection operation for 3 seconds, and then halting the injection operation for 57 seconds. Here, the maximum injection amount of each injection is about 30 U (unit; 1 unit is equal to about 10 microliter).
In the case of performing such intermittent drive, noise is included in the output signals ROT_A, ROT_B representing the rotational condition of the rotor 122 detected by the detection sections 40 in some cases. It is conceivable that, for example, due to the backlash of the rotor 122 and the reduction transmission mechanism 123, the noise is generated when restarting the rotor 122 once stopped, or the electrical noise is included in the drive signal of the piezoelectric actuator 121 (the S/N ratio is decreased). Further, an influence of the noise generated due to the structure of the drive mechanism 12 according to the present embodiment is conceivable.
In such a configuration, when rotating the rotor 122, there acts the force of lifting the rotor 122 upward centered on the contact part between the rotor 122 and the vibrator element. In the present specification, the influence of such force is referred to as “pitch.” In contrast, when the rotor 122 is stopped, since the force acting on the rotor 122 becomes difficult to act, the “pitch” is difficult to occur. In the case in which the “pitch” has occurred, since the vertical position of the rotor 122 is displaced as much as several through several tens of micrometers compared to the case in which the “pitch” has not occurred, the optical path length of the first rotor rotation angle detection section 43 varies. As a result, the level of the voltage detected by the light receiving section 43B varies, and there is a possibility that the potential, which is opposite to the potential to be normally output, is output. For example, although the first rotor rotation angle detection section 43 should normally output the output signal ROT_A having the H level, the output signal ROT_A having the L level is output in some cases. In other words, the influence of the “pitch” acts as the noise to inhibit the information related to the accurate rotational position and so on of the rotor 122 from being obtained, and there is a possibility that it becomes unachievable for the control section 50 to perform the accurate liquid transportation. Further, there is a possibility that there occurs so-called chattering in which the output signal ROT_A violently vibrates between the H level and the L level due to the influence of the noise to make it difficult to detect the actual rotational angle of the rotor 122.
In order to realize the accurate liquid transport operation using the liquid transport device 1, it is important to reduce the influence of the noise and so on generated when rotating or stopping the rotor 122. In the present embodiment, whether the output signal (e.g., the output signal ROT_A described above) at the time point when stopping the rotor 122 is in the H level or in the L level is previously stored in the storage section 52. Further, when rotationally driving the rotor 122 again, the state of the output signal at the time of the stoppage is set to a circuit for outputting the output signal with reference to the state of the output signal having been stored at the time of stoppage to thereby make it difficult to generate a difference in position between the halt period of the rotor 122 and the time when resuming the operation. Further, on this occasion, by providing a hysteresis characteristic to the circuit for outputting the output signal, it is arranged that the rotational angle of the rotor 122 in performing the intermittent drive of the drive mechanism 12 can accurately be detected.
The encoder circuit 400 has the first rotor rotation angle detection section 43, a voltage follower 401, voltage follower resistors 402A, 402B, a comparator circuit 410, a resetting circuit 420, an ALL POW SW, and a ROT_A SW.
Firstly, the ROT_A SW for setting the light emitting section 43A of the first rotor rotation angle detection section 43 to the light emission state is set to the ON state, and subsequently, the ALL POW SW for setting the light receiving section 43B to a light receivable state is set to the ON state. It should be noted that by setting the ALL POW SW to the ON state, a reference voltage Vb described later is set to be supplied to a comparator 411. The light having been emitted from the light emitting section 43A and then reflected by the first rotor-side reflecting sections 124 of the rotor 122 is received by the light receiving section 43B. The light receiving section 43B outputs the voltage having the level corresponding to the light intensity of the reflected light thus received, and then the voltage is input to a plus-terminal side of the voltage follower 401. The minus-terminal side of the voltage follower 401 constitutes a feedback loop, and thus, the voltage input to the voltage follower 401 is subject to impedance conversion, and is then output. The voltage output from the voltage follower 401 is input to a minus-terminal side of the comparator 411 of the comparator circuit 410 via a resistor 421 of the resetting circuit 420.
The comparator circuit 410 is a circuit for outputting a voltage signal having the H level or the L level in accordance with the level of the voltage input thereto. The comparator circuit 410 according to the present embodiment has the comparator 411, reference voltage resistors 412A, 412B, voltage divider resistors 413A, 413B, and hysteresis resistors 414A, 414B.
To the plus-side input terminal of the comparator 411, there is input the reference voltage Vb as a reference value, and an input voltage Vin is input to the minus-side input terminal. Further, the comparator 411 outputs the voltage signal having the L level in the case in which the input voltage Vin is equal to or higher than the reference voltage Vb (Vin≧Vb), and outputs the voltage signal having the H level in the case in which the input voltage Vin is lower than the reference voltage Vb (Vin<Vb). The voltage signal thus output is used as the signal ROT_A. In the present embodiment, the voltage having been supplied from the power supply (3.3V) and then adjusted in the level via the reference voltage resistors 412A, 412B is input to the plus-side input terminal of the comparator 411 as the reference voltage Vb. Meanwhile, the voltage detected by the first rotor rotation angle detection section 43 is input to the minus-side input terminal of the comparator 411 via the voltage follower 401 and the resistor 421 as the input voltage Vin. For example, in the case in which the reference voltage Vb is equal to 2.5 V, if the input voltage Vin is equal to or higher than 2.5 V, the output signal ROT_A having the L level (e.g., 0 V) is output, and if the input voltage Vin is lower than 2.5 V, the output signal ROT_A having the H level (e.g., 3.3 V) is output.
Here, in the case in which noise is included in the output voltage of the first rotor rotation angle detection section 43, there is a possibility that the level of the input voltage Vin vibrates in a predetermined range. For example, in the example described above, when the input voltage Vin vibrates up and down in the vicinity of the reference voltage Vb equal to 2.5V, the output signal ROT_A violently fluctuates (causes chattering) between the H level and the L level, and it becomes unachievable to figure out the accurate rotational condition of the rotor 122. To deal with such a problem, in the comparator circuit 410 according to the present embodiment, the hysteresis resistors 414A, 414B are disposed to thereby provide a hysteresis characteristic to the circuit to suppress the chattering in the output signal ROT_A.
The hysteresis resistors 414A, 414B are disposed between the output-side terminal and the input-side terminal (the plus-side terminal) of the comparator 411. In the case in which the voltage (the output signal ROT_A) in the output-side terminal of the comparator 411 is in the H level, the reference voltage Vb is changed to have a value Vbh higher than the original value, and then input to the plus-side input terminal of the comparator 411 (Vbh>Vb) due to the relationship between the hysteresis resistors 414A, 414B and the reference voltage resistors 412A, 412B, and the voltage divider resistors 413A, 413B. In contrast, in the case in which the output signal ROT_A is in the L level, the reference voltage Vb is changed to have a value Vbl lower than the original value, and then input to the plus-side input terminal of the comparator 411 (Vb>Vbl) due to the relationship between the reference voltage resistors 412A, 412B, and the hysteresis resistors 414A, 414B and the voltage divider resistors 413A, 413B. Therefore, the reference voltage resistors 412A, 412B, the voltage divider resistors 413A, 413B, and the hysteresis resistors 414A, 414B constitute a reference value setting section, and due to the operation of the reference value setting section, the reference voltage Vb of the comparator 411 varies between Vbl through Vbh.
In other words, in the encoder circuit 400 according to the present embodiment, since the chattering in the output signal ROT_A can be suppressed by outputting the output signal ROT_A based on the hysteresis characteristic, the fluctuation of the output value of the encoder is reduced, and it becomes easy to obtain an accurate output value with a small influence of the noise and so on.
As described above, in the case in which drive and stoppage of the drive mechanism 12 are repeated, due to the fact that the rotor 122 slightly moves during the period from when the rotor 122 is stopped to when the rotation is resumed, the detection value to be detected by the first rotor rotation angle detection section 43 fluctuates in some cases. In the encoder circuit of the related art, since the rotation of the rotor 122 is controlled based on the detection value at the time of resuming drive, if the state in the period of stopping drive and the state at the time of resuming drive are different from each other, it is difficult to accurately control the liquid transport amount. In particular, in the case of using the liquid transport device as an insulin injector, since it is required to inject an optimum amount of insulin to a patient, it is necessary to perform more accurate liquid transport control. Therefore, in the encoder circuit 400 according to the present embodiment, the reference voltage value of the comparator 411 at the time of resuming drive is reset by the resetting circuit 420 to thereby suppress the fluctuation of the detection value, and thus, it is arranged that the accurate output signal ROT_A can be output even in the case in which the liquid transport device 1 is driven intermittently.
As shown in
For example, it is assumed that the output signal ROT_A having the H level has been output at the time point when the rotation of the rotor 122 has stopped. In this case, the resetting section 423 inputs the resetting voltage corresponding to the L level to the minus-side input terminal of the comparator 411 as the input voltage Vin. Then, since the input voltage Vin becomes lower than the reference voltage Vb, the comparator 411 outputs the output signal ROT_A having the H level. It should be noted that when the output signal ROT_A having the H level is output, the reference voltage Vb of the comparator 411 rises to the value Vbh, and in the subsequent operation of the rotor 122, the output signal ROT_A is output with reference to the value Vbh. Further, in the case in which the output signal ROT_A having the L level has been output at the time point when the rotation of the rotor 122 has stopped, the resetting section 423 inputs the resetting voltage corresponding to the H level to the comparator 411. Thus, the comparator 411 outputs the output signal ROT_A having the L level. As described above, by providing the resetting circuit 420, the difference in the output signal between the time point when drive of the drive mechanism 12 has been stopped and the time point of resuming drive can be suppressed.
It should be noted that it is also possible to modify the configuration of the resetting circuit 420.
In the present embodiment, in order to accurately realize the liquid transport operation, the rotational angles of the rotor 122 and the cam 11 are detected using the optical sensors such as the first rotor rotation angle detection section 43 included in the detection sections 40. In such optical sensors, it is necessary to continuously supply the light emitting sections and the light receiving sections with the electrical power when performing the detection. On the other hand, the intermittent drive of driving the device for 3 seconds and then halting drive for 57 seconds is assumed in the liquid transport device 1 according to the present embodiment as described above, and it is not necessary to keep the detection sections 40 operating when halting drive. This is because it becomes possible to inhibit the state of the output signal from changing between the period of halting drive and the time point of resuming drive due to the comparator circuit 410, and therefore, it is not necessary to monitor the shift of the rotational angle of the rotor 122 and so on during the stoppage.
Therefore, the control section 50 performs the control so that the detection sections 40 are supplied with the electrical power only in the predetermined period of driving the drive mechanism 12, and are prevented from being supplied with the electrical power during the period in which the drive mechanism 12 is at rest to thereby reduce the energy as much as an amount consumed by the detection sections 40 during the halt period.
In starting (resuming) drive of the drive mechanism 12 in the halt state, a drive start signal as a logic signal for defining the start of drive is generated. It is also possible for the drive start signal to periodically be generated under the management using a timer or the like, or to be generated in response to an instruction (operation) for commencement of injection performed by the user of the liquid transport device 1. In
Thus, it becomes possible to perform accurate drive control even in the case of intermittently driving the drive mechanism 12. When the waiting time has elapsed after the setting of the reference voltage is complete, the control section 50 sets (S105) the power switches of the encoder circuits to the ON state. The power switch of the encoder circuit denotes a main power switch of the overall circuit for starting up the piezoelectric actuator 121 and supplying the light receiving section of the optical sensor (rotary encoder) with the electrical power, and corresponds to, for example, the ALL POW SW shown in
In
In the present embodiment, by performing such control of the power supply in starting drive of the drive mechanism 12 and in halting drive of the drive mechanism 12, the power consumption in the detection sections 40 can be reduced. For example, as shown in
The embodiment described above is for facilitating understanding of the invention, but not for providing limited interpretations of the invention. It is obvious that the invention can be modified or improved within the scope and the spirit thereof, and includes equivalents thereof.
Although in the embodiment described above, the rotor 122 of the drive mechanism 12 is provided with the rotary encoders (the first rotor rotation angle detection section 43, the second rotor rotation angle detection section 44, and the rotor rotation detection section 45), and the rotational angle of the rotor 122 is detected using these encoders, it is also possible to dispose the rotary encoders at other positions. For example, it is also possible to arrange that the transmission wheel 123A of the reduction transmission mechanism 123 is provided with a rotary encoder similar to the first rotor rotation angle detection section 43 to detect the rotational angle of the transmission wheel 123A. Similarly, it is also possible to arrange that the cam 11 is provided with a rotary encoder similar to the first rotor rotation angle detection section 43 to directly detect the rotational angle of the cam 11. By detecting the rotational angle at the position near to the cam 11, it becomes difficult for the influence of the backlash and so on to be included, and further, it becomes easy to detect the actual operation performed when the projection sections 11A of the cam 11 press the fingers. It should be noted that since the revolution of the cam 11 is reduced at a predetermined reduction ratio with respect to the revolution of the rotor 122, by detecting the rotational angle of the rotor 122, the data with higher resolution can be detected.
Although in the above description of the embodiments, there is explained the example of using a so-called tube pump, which transports the liquid in the tube by compressing the tube with a plurality of fingers, as the pump section of the liquid transport device, the configuration of the pump section is not limited to this example. It is also possible to use other pumps capable of transporting a liquid with an action of a cam such as a screw pump for transporting a liquid in an axial direction by rotating a screw, or a plunger pump, which converts rotation of a cam into a motion of a plunger, and transporting a liquid using a reciprocal motion of the plunger.
The entire disclosure of Japanese Patent Application Nos. 2014-122132, filed Jun. 13, 2014 and 2014-122133, filed Jun. 13, 2014 are expressly incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-122132 | Jun 2014 | JP | national |
| 2014-122133 | Jun 2014 | JP | national |
