JP2013256886A - Free piston generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a displacement of a piston while suppressing a degradation of sealing performance between the piston and a cylinder.SOLUTION: A free piston generator 10 includes a cylinder 12 formed in a cylindrical shape, a piston 14 disposed inside the cylinder 12, and a combustion chamber 16 and an air chamber 18 formed to oppose to each other with the piston 14 interposed therebetween, and for reciprocating the piston 14 therein. The generator 10 also includes a seal member 20 slidably contacting an outer circumferential face of the piston 14, a groove portion 22 formed in the outer circumferential face of the piston 14, a displacement detector 26 for detecting a displacement of the groove portion 22, and a fill member 24 filled in a part of the groove portion 22 which slidably contacts the seal member 20, and made of a constituent material having a different property from a constituent material of the piston 14 that is detected by the displacement detector 26.

Description

  The present invention relates to a free piston generator.

  Conventionally, a generator using a piston (free piston) that reciprocates in a cylinder without being mechanically restricted is known. For example, Patent Documents 1 and 2 disclose a two-stroke engine driven free piston generator including a cylindrical cylinder and a piston disposed inside the cylinder.

  A combustion chamber and an air chamber are formed inside the cylinder so as to face each other with the piston interposed therebetween. A scavenging hole is provided in the combustion chamber. Fresh air is introduced into the combustion chamber from the scavenging holes. Further, the combustion chamber is provided with an injector for injecting fuel. The combustion chamber is provided with ignition means, and the ignition means burns the fuel-air mixture produced in the combustion chamber. The piston is moved to the air chamber side by the combustion pressure generated at that time. The air chamber has a function as a so-called air spring. As the piston moves, the air chamber is compressed to generate a repulsive force, and the repulsive force pushes the piston back toward the combustion chamber.

  A coil is provided on the inner peripheral surface of the cylinder. A permanent magnet is provided on the outer peripheral surface of the piston. As the piston reciprocates, the positions of the permanent magnet and the coil change relatively. At this time, an induced electromotive force is generated in the coil. The generated electric power is supplied to power storage means such as a battery.

  Further, Patent Document 3 discloses that in order to detect the displacement of an object that moves linearly, a movement amount measurement slit is formed on the surface of the object, and a detection unit that detects the displacement of the slit is provided. .

JP 2012-21461 A JP 2012-31746 A JP-A-3-267719

  By the way, even when it is not the scavenging period during which fresh air is introduced into the fuel chamber, pressure is applied to the scavenging holes, and there is a possibility that fresh air will blow through the air chamber through the gap between the piston and the cylinder. This leads to a loss of the scavenging pump that sends fresh air into the scavenging holes, so it is preferable to seal the gap between the piston and the cylinder. Specifically, it is conceivable to provide a lining seal ring in sliding contact with the piston outer peripheral surface on the cylinder inner peripheral surface. In this case, a permanent magnet is provided on the outer peripheral surface of the piston, and the permanent magnet may be made of a brittle material. Therefore, it is preferable to provide a seal ring so that the permanent magnet does not slide. It is.

  In addition, when a slit is cut in the outer peripheral surface of the piston in order to detect the displacement of the piston, if the slit is cut in the permanent magnet, the magnetic force fluctuates due to the uneven shape and the induced electromotive force may become unstable. There is. Therefore, it is preferable to provide a slit avoiding the permanent magnet.

  If the slit and the seal ring are provided so as to avoid the permanent magnet, the seal ring 110 and the slit 112 may come into sliding contact as shown in FIG. For example, when the length of the piston in the moving direction is shortened to reduce the size of the free piston generator (when a space other than the permanent magnet is removed from the outer peripheral surface of the piston), the above case may occur. . If irregularities due to slits are formed on the sliding contact surface with the seal ring, the sealing performance may be deteriorated. Then, an object of this invention is to provide the free piston type generator which can measure the displacement of a piston, maintaining the sealing performance of a piston and a cylinder.

  The present invention relates to a free piston generator. The generator includes a cylinder formed in a cylindrical shape, a piston disposed in the cylinder, a combustion chamber and an air chamber that are provided so as to face each other with the piston interposed therebetween and reciprocate the piston. . Further, a seal member provided on the inner peripheral surface of the cylinder and in sliding contact with the outer peripheral surface of the piston, a groove formed on the outer peripheral surface of the piston, a displacement detector for detecting displacement of the groove, Is provided. Furthermore, a portion of the groove that is in sliding contact with the seal member is filled, and a filling member having a detection characteristic of the displacement detector different from that of the constituent material of the piston is provided.

  Moreover, in the said invention, it is suitable that the friction coefficient of the said filling material is below the friction coefficient of the constituent material of the said piston.

  In the above invention, the groove portion includes a groove pattern in which a plurality of grooves are formed along the moving direction of the piston, and a plurality of the displacement detectors are provided, and each of the displacement detectors extends in the moving direction. It is preferable that the detection range of the groove pattern is offset along.

  Further, in the above invention, the groove portion includes a groove pattern in which a plurality of grooves are formed along a moving direction of the piston, and the groove pattern is formed in a plurality around the periphery of the piston. Is preferably offset along the moving direction of the piston within a range less than the width of the groove along the moving direction of the piston with respect to the other groove pattern.

  Further, in the above invention, the groove portion includes a groove pattern in which a plurality of grooves are formed along a moving direction of the piston, and the groove pattern is formed in a plurality around the piston, and the groove pattern is It is preferable that they are formed so as to oppose each other along the radial direction of the piston. Further, the displacement detector preferably outputs a signal corresponding to the displacement of the groove pattern, and adds the signals corresponding to the opposed groove patterns when obtaining the displacement of the groove pattern. It is.

  In the above invention, it is preferable that the groove is formed so that an interval between adjacent grooves along the moving direction of the piston becomes narrower toward the end side.

  In the above invention, it is preferable that the groove portion includes a portion formed so that an interval between adjacent grooves is a first interval and a portion formed so as to be a second interval. It is.

  In the above invention, it is preferable that the filling member includes a first filling member and a second filling member that have different detection characteristics of the displacement detector.

  In the above invention, it is preferable that the groove portion includes a groove formed so that the groove depth is the first depth and a groove formed so as to be the second depth.

  In the above invention, it is preferable that a pressure sensor is provided in at least one of the air chamber and the combustion chamber, and the position of the piston is detected according to the value of the pressure sensor.

  In the above invention, a coil is provided on the inner peripheral surface of the cylinder, and a magnet is provided on the outer peripheral surface of the piston. The piston is moved by supplying a current to the coil to generate a magnetic field. In this case, it is preferable that the position of the piston is detected according to a current value supplied to the coil.

  Further, in the above invention, an arithmetic unit that calculates the position of the piston according to a signal from the displacement detector is provided, and the arithmetic unit calculates the speed and acceleration of the piston from the already received signal, and It is preferable to calculate the current position of the piston according to the speed and acceleration.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to measure the displacement of a piston, suppressing the fall of the sealing performance of a piston and a cylinder.

It is side surface sectional drawing which illustrates the free piston type generator which concerns on this Embodiment. It is a figure explaining the output signal of a displacement detector. It is side surface sectional drawing which illustrates a groove part. It is the front view and side view which illustrate a groove part. It is side surface sectional drawing which illustrates the free piston type generator which concerns on this Embodiment. It is side surface sectional drawing which illustrates a groove part. It is side surface sectional drawing explaining the displacement detection of a piston. It is a figure explaining the arithmetic processing of a displacement signal. It is side surface sectional drawing which illustrates the free piston type generator which concerns on this Embodiment. It is side surface sectional drawing which illustrates the conventional free piston type generator.

  FIG. 1 illustrates a free piston generator 10 according to the present embodiment. The free piston generator 10 includes a cylinder 12, a piston 14, a combustion chamber 16, an air chamber 18, a seal member 20, a groove 22, a filling member 24, and a displacement detector 26.

  The cylinder 12 is a cylindrical member, and can include a piston 14, a combustion chamber 16, an air chamber 18 and the like inside. The cylinder 12 is preferably made of a member that can withstand a high temperature environment caused by combustion in the combustion chamber 16. For example, it may be made of a material such as aluminum. A coil 27 is provided on the inner peripheral surface of the cylinder 12. The coil 27 is connected to power storage means such as a battery (not shown).

  A combustion chamber 16 and an air chamber 18 are provided in the cylinder 12 so as to face each other with the piston 14 interposed therebetween. The combustion chamber 16 generates combustion pressure and moves the piston 14. For example, the combustion chamber 16 may be provided on the end side inside the cylinder 12.

  In the combustion chamber 16, a scavenging hole 28, an exhaust port 30, an exhaust valve 32, an injector 34, and an ignition means 36 are provided. The scavenging holes 28 introduce new air into the combustion chamber 16. When introducing fresh air, the scavenging pump (not shown) may be driven to introduce fresh air into the scavenging holes 28 from the outside. The scavenging hole 28 may be opened, for example, on the inner wall surface of the cylinder 12. When the piston 14 is located at the top dead center, the scavenging hole 28 is blocked by the piston 14 and the piston 14 is located at the bottom dead center. It may be formed in a position that is sometimes released. The top dead center refers to the time when the piston 14 is located closest to the combustion chamber 16, and the bottom dead center refers to the time when the piston 14 is located closest to the air chamber 18. The exhaust port 30 discharges the exhaust after the mixture of fresh air and fuel is burned in the combustion chamber. Further, there may be a loop flow type that does not have the exhaust port 30 and performs scavenging and exhausting only by the scavenging holes 28. The injector 34 is an injection unit that injects fuel. The fuel may be supplied at a port before the scavenging holes 28. The ignition means 36 ignites the air-fuel mixture to generate combustion pressure. For example, the opening timing of the exhaust valve 32, the injection timing of the injector 34, and the ignition timing of the ignition means 36 may be determined according to the position of the piston 14. Further, the combustion pressure may be generated by a compression self-ignition method without the ignition means 36.

  The air chamber 18 has a so-called air spring function that pushes the piston 14 back to the combustion chamber 16 side. When the piston 14 moves from the combustion chamber 16 side to the air chamber 18 side, the air chamber 18 is compressed. A repulsive force is generated by this compression, and the piston 14 is pushed back to the combustion chamber 16 side by the repulsive force. Here, the air chamber 18 may be provided with a pressure regulating valve 38 for keeping the internal pressure within a certain range.

  In order to increase the repulsive force applied to the piston 14, the piston 14, the combustion chamber 16, and the air chamber 18 are configured so that the area of the end surface on the air chamber 18 side is larger than the end surface on the combustion chamber 16 side of the piston 14. May be.

  The seal member 20 seals a gap with the outer peripheral surface of the piston 14 by sliding contact with the outer peripheral surface of the piston 14. By sealing the outer peripheral surface of the piston 14, gas leakage from the combustion chamber 16 can be suppressed. The seal member 20 may be, for example, a seal ring formed in an annular shape along the shape of the outer peripheral surface of the piston 14. The seal member 20 may be fixed to the inner peripheral surface of the cylinder 12. For example, a seal groove may be cut in the inner peripheral surface of the cylinder 12 and the seal member 20 may be fitted in the seal groove. Further, it is preferable that the seal member 20 is provided at a position where it does not slide into contact with the permanent magnet 40 provided on the piston 14. For example, the seal member 20 may be provided closer to the combustion chamber 16 than the position of the permanent magnet 40 when the piston 14 is at top dead center.

  The displacement detector 26 detects the displacement of the groove portion 22 of the piston 14 described later. By detecting the displacement of the groove portion 22, the displacement of the piston 14 can be obtained. The displacement detector 26 may be provided in the cylinder 12 and may be provided in the vicinity of the groove 22. For example, the detection surface may be exposed on the inner peripheral surface of the cylinder 12.

  Further, the displacement detector 26 may be capable of outputting a detection signal and a displacement signal as shown in FIG. The detection signal S1 output from the displacement detector 26 may take two values according to the unevenness of the groove 22. For example, when the displacement detector 26 is opposed to the portion filled with the filling member 24, the displacement detector 26 outputs the detection signal S1H. Further, the displacement detector 26 outputs a detection signal S1L when it is opposed to the constituent member of the piston 14 that is not filled in the filling member 24.

  A counter that counts the value of the detection signal S1 may be provided in the displacement detector 26. For example, the counter may be configured by a hardware circuit in the displacement detector 26. Each time the value of the detection signal S1 changes, the displacement signal value C1 is increased or decreased by 1. The position of the piston 14 can be calculated by increasing or decreasing the displacement signal value C1. The counter may count the displacement signal value C1 in real time.

  The displacement detector 26 may be any means that can detect the displacement of the groove 22, and may be a non-contact sensor such as an eddy current sensor, an optical sensor, or a capacitance sensor. In the cylinder 12, lubricating oil or the like adheres to the inner surface of the cylinder 12 or the outer surface of the piston 14, and it may be difficult to ensure an optically good detection environment. From such a viewpoint, it is preferable to use an eddy current sensor or a capacitance sensor as the displacement detector 26.

  The A / D converter 25 converts the displacement signal value C1 output from the displacement detector into a digital signal. Further, the computing unit 23 obtains the displacement of the piston 14 based on the taken displacement signal while taking the digitally converted displacement signal. For example, as exemplified by the filled black circle plot in FIG. 2, the displacement signal value C1 is captured at every sampling timing corresponding to the clock signal.

  Returning to FIG. 1, the piston 14 is reciprocated in the cylinder 12 by the action of the combustion chamber 16 and the air chamber 18. The piston 14 may have a shape along the inner peripheral surface of the cylinder 12. For example, it may be cylindrical. In order to enable reciprocal movement within the cylinder 12, there is a clearance (clearance) between the inner peripheral surface of the cylinder 12 and the outer peripheral surface of the piston 14 except for the sliding contact portion with the seal member 20. It is suitable that it is provided. For example, the gap may be 0.2 mm or greater and 50 mm or less.

  A permanent magnet 40 is provided on the outer peripheral surface of the piston 14. As the piston 14 reciprocates in the cylinder 12, the positions of the permanent magnet 40 provided in the piston 14 and the coil 27 provided in the cylinder 12 change relatively. At this time, an induced electromotive force is generated in the coil 27. The generated electric power is supplied to power storage means such as a battery (not shown).

  The piston 14 is preferably made of a material that can withstand the temperature rise due to the combustion chamber 16 and the pressure rise in the air chamber 18. For example, the piston 14 may be made of a metal material such as aluminum.

  A groove 22 is formed on the outer peripheral surface of the piston 14. Here, when the groove 22 is formed in the permanent magnet 40, the thickness of the permanent magnet 40 changes, and the induced electromotive force may vary accordingly. Therefore, the groove portion 22 is preferably provided at a position on the outer peripheral surface of the piston 14 away from the permanent magnet 40. For example, the groove 22 may be provided closer to the combustion chamber 16 than the permanent magnet 40 in the outer peripheral surface of the piston 14.

  The groove part 22 may include a groove pattern in which a plurality of grooves are formed along the moving direction of the piston 14. Further, it is preferable that the groove portion 22 is formed so as to be included in the detection range of the displacement detector 26 when the piston 14 is located at the top dead center and the bottom dead center. By doing so, it is possible to detect the total displacement of the piston 14. For example, the length of the groove portion 22 along the moving direction of the piston 14 may be provided to be equal to or longer than the stroke length (reciprocating length) of the piston 14.

  Further, the groove 22 may be formed so as to adapt to the reciprocating motion of the piston 14. For example, the piston 14 has a small displacement per unit time near the top dead center and the bottom dead center, and a large displacement per unit time between the top dead center and the bottom dead center. In order to adapt to such reciprocating movement of the piston 14, as illustrated in FIG. 3A, the interval (pitch) between adjacent grooves along the moving direction of the piston 14 is set to the end side. You may form the groove part 22 so that it may become narrow as it goes. By doing so, it is possible to accurately detect the displacement of the piston 14 near the top dead center and the bottom dead center.

  Further, a reference pattern that serves as a reference value for obtaining the absolute value of the displacement of the piston 14 may be formed in the groove 22. For example, you may make it form the peculiar pattern from which the space | interval of an adjacent groove | channel differs from other things. For example, as illustrated in FIG. 3B, a groove pattern 22A having a groove interval d1 and a reference pattern 22B having a groove interval d2 may be formed. Alternatively, as illustrated in FIG. 3C, a groove 22C having a groove width W3 and a reference groove 22D having a groove width W4 may be formed.

  For example, when the displacement detector 26 detects the reference pattern 22B or the reference groove 22D, in other words, when the reference pattern 22B or the reference groove 22D crosses the displacement detector 26, the displacement detector 26 determines the position of the piston 14 as the reference coordinates. It may be reset to (for example, 0). As another method for forming the reference pattern 22B, as illustrated in FIG. 3D, a reference groove 22E having a depth different from the depth of the other grooves may be formed.

  In order to improve the accuracy of displacement detection of the piston 14, a plurality of groove portions 22 may be formed. For example, as illustrated in FIG. 4, a plurality of groove portions 22 may be formed around the circumference of the piston 14. Here, it is preferable that the groove patterns of the respective groove portions 22 are offset from the groove patterns of the other groove portions 22 along the moving direction of the piston 14. At this time, the offset width W <b> 1 may be in a range less than the groove width W <b> 2 along the moving direction of the piston 14.

  A displacement detector 26 is provided in each of the plurality of grooves 22. In FIG. 4, displacement detectors 26F to 26I are provided for the four groove portions 22F to 22I. The switching points of the detection signal pulses detected by the displacement detectors 26F to 26I are shifted by the offset width W1. The displacement detection resolution is improved by shifting the pulse switching point.

  The plurality of groove portions 22 may be provided so as to face each other along the radial direction of the piston 14. By doing in this way, it becomes possible to compensate for the fluctuation of the detection signal accompanying the vibration of the piston 14. The piston 14 may vibrate in a direction orthogonal to the reciprocating movement in addition to the reciprocating movement indicated by the arrows in FIG. As a result, the distance between the displacement detector 26 and the groove 22 changes. Due to this change, the waveform of the detection signal output from the displacement detector 26 may fluctuate. For example, when the displacement detector 26 is an eddy current sensor, the amplitude of the detection signal decreases as the distance between the displacement detector 26 and the groove 22 increases, and the amplitude increases as it approaches. In order to compensate for such variations, the detection signals of the grooves 22 arranged opposite to each other may be added. In this case, it is preferable to form the opposing groove portions 22 without being offset along the moving direction of the piston 14.

  When the piston 14 vibrates, one of the opposed groove portions 22 is separated from the displacement detector 26, and the other approaches the displacement detector 26. Therefore, the amplitude of one detection signal is reduced and the amplitude of the other detection signal is increased. When one of the opposed displacement detectors 26 adds the other detection signal, the influence of the fluctuation is cancelled.

  Instead of providing a plurality of grooves 22 and offsetting each of them, as shown in FIG. 5, a plurality of displacement detectors 26 are provided for a single groove pattern, and the detection ranges of these displacement detectors 26 are provided. May be offset along the direction of movement of the piston 14.

  The groove portion 22 is filled with a filling member 24. The filling member 24 is filled at least in a portion where the groove 22 is in sliding contact with the seal member 20. When filling, it is preferable to fill the groove member 22 with the filling member 24 so that the sliding surface with the seal member 20 becomes smooth. Since the filled portion becomes smooth, the sealing performance with the seal member 20 is kept good. For example, the filling amount of the filling member 24 may be the same as the volume of the groove. Further, the filling member 24 may be filled so that the outer peripheral surface of the piston 14 and the outer surface of the filling member 24 are flush with each other.

  The filling member 24 preferably includes a material whose detection characteristic of the displacement detector 26 is different from that of the constituent material of the piston 14. For example, when the displacement detector 26 is an eddy current sensor, the filling member 24 may be made of a material having a different impedance from that of the constituent material of the piston 14. For example, the filling member 24 may be a resin material such as epoxy or PEEK, or a metal material such as iron or copper.

  In consideration of sliding with the seal member 20, the friction coefficient of the filling member 24 is preferably equal to or less than the friction coefficient of the constituent material of the piston 14. By doing so, friction loss during power generation can be suppressed.

  Note that the reference position of the groove 22 may be determined by changing the material of the filling member 24. For example, as shown in FIG. 6, a groove pattern having a uniform groove width and groove interval is formed in the groove portion 22. Furthermore, the predetermined groove 44 is filled with the filling member 24A, and the other groove 46 is filled with a filling member 24B having a detection characteristic of the displacement detector 26 different from that of the filling member 24A. For example, the filling member 24A may be made of a material having a different impedance from that of the filling member 24B.

  Next, detection of the position of the piston 14 when the free piston generator 10 is started will be described with reference to FIG. When starting the free piston generator 10, a current is supplied to the coil 27 to generate a magnetic field in the coil 27. The piston 14 is moved by the generated magnetic field. For example, the piston 14 is moved to the air chamber 18 side. When the piston 14 moves to a predetermined starting position, the air-fuel mixture is combusted in the combustion chamber 16.

  If the displacement detector 26 detects the reference pattern of the groove 22 while the piston 14 is moved by the magnetic field of the coil 27, the absolute value of the position of the piston 14 can be obtained. On the other hand, the displacement detector 26 cannot detect the reference pattern of the groove portion 22 while the piston 14 is moved by the magnetic field of the coil 27 such that the reference position is located closer to the air chamber 18 than the displacement detector 26. There is a case. In such a case, means for estimating the position of the piston 14 other than the displacement detector 26 may be used.

  For example, the position of the piston 14 may be estimated based on a change in the current supplied to the coil 27. Since the air chamber 18 is compressed as the piston 14 moves to the air chamber 18 side, more current is required to move the piston 14 further to the air chamber 18 side. That is, the current value increases as the piston 14 moves to the air chamber 18 side. Therefore, a threshold value is provided for the supply current value to the coil 27, and the supply current to the coil 27 is switched so that the piston 14 is moved to the combustion chamber 16 side when the supply current value exceeds the threshold value. By doing so, the displacement detector 26 can reliably detect the reference pattern of the groove 22.

  Further, instead of monitoring the current supplied to the coil 27, a pressure sensor 48 may be provided in the air chamber 18, and the position of the piston 14 may be estimated based on the pressure change of the pressure sensor 48. For example, a threshold value may be provided for the pressure value, and the supply current to the coil 27 may be switched so that the piston 14 is moved to the combustion chamber 16 side when the pressure value of the air chamber 18 exceeds the threshold value. .

  In the above description, the case where the piston 14 is first moved toward the air chamber 18 is illustrated, but the piston 14 may be moved toward the combustion chamber 16 first. In that case, it is preferable to provide the pressure sensor 48 in the combustion chamber 16.

  Next, calculation of the predicted value of displacement of the piston 14 will be described. When the movement of the piston 14 is slow, such as when the piston 14 is moving near the top dead center or the bottom dead center, as shown in FIG. 8, the displacement signal value C1 over two sampling timings t1 and t2. May not change. If so, the calculator 23 erroneously determines that the piston 14 has not moved, and there is a risk of executing abnormal control such as stopping fuel injection.

  Therefore, it is preferable to predict the current position of the piston 14 by processing the displacement signal. Specifically, the calculator 23 calculates the speed and acceleration of the piston 14 from the already received displacement signal value C1. Further, the locus of the piston 14 as shown by a broken line is calculated based on the obtained speed and acceleration. In addition, as shown by the solid triangle plot, when the displacement signal value C1 has not changed from the previous sampling timing, a predicted value of the position of the piston 14 in the locus is calculated.

  In the above-described embodiment, the groove 22 is provided on the combustion chamber 16 side of the piston 14 with respect to the permanent magnet 40, and the seal member 20 and the displacement detector 26 are provided on the combustion chamber 16 side of the cylinder 12 with respect to the coil 27. Although provided, it is not limited to this form. For example, the groove 22 may be provided closer to the air chamber 18 of the piston 14 than the permanent magnet 40, and the seal member 20 and the displacement detector 26 may be provided closer to the air chamber 18 of the cylinder 12 than the coil 27. Further, as shown in FIG. 9, a piston ring 50 provided on the piston 14 may be used as the seal member 20. In the form shown in FIG. 9, the length of the piston 14 along the moving direction is extended as compared with the above-described embodiment. It is possible to measure the displacement of the piston 14 while suppressing the deterioration of the sealing performance.

  DESCRIPTION OF SYMBOLS 10 Free piston type generator, 12 cylinder, 14 piston, 16 Combustion chamber, 18 Air chamber, 20 Seal member, 22 Groove part, 23 Calculator, 24 Filling member, 25 A / D converter, 26 Displacement detector, 27 Coil 28, scavenging holes, 30 exhaust ports, 32 exhaust valves, 34 injectors, 36 ignition means, 38 pressure regulating valves, 40 permanent magnets, 44 predetermined grooves, 46 grooves other than predetermined grooves, 48 pressure sensors, 50 piston rings.

Claims (12)

A cylinder formed in a cylindrical shape;
A piston disposed in the cylinder;
A combustion chamber and an air chamber, which are provided so as to face each other with the piston interposed therebetween, and which reciprocates the piston;
A seal member provided on the inner peripheral surface of the cylinder and in sliding contact with the outer peripheral surface of the piston;
A groove formed on the outer peripheral surface of the piston;
A displacement detector for detecting the displacement of the groove,
Of the groove portion, the filling member is slidably contacted with the seal member, and the filling member is different in detection characteristics of the displacement detector from the constituent material of the piston,
A free-piston generator characterized by comprising: The free piston generator according to claim 1,
The free piston generator according to claim 1, wherein a friction coefficient of the filling material is equal to or less than a friction coefficient of a constituent material of the piston. The free piston generator according to claim 1 or 2,
The groove part includes a groove pattern in which a plurality of grooves are formed along the moving direction of the piston,
A free piston generator, wherein a plurality of the displacement detectors are provided, and each of the displacement detectors has a detection range of the groove pattern offset along the moving direction. The free piston generator according to claim 1 or 2,
The groove portion includes a groove pattern in which a plurality of grooves are formed along the moving direction of the piston, and the groove pattern is formed in a plurality around the piston,
Each of the groove patterns is offset along the moving direction of the piston within a range less than the width of the groove along the moving direction of the piston with respect to the other groove patterns. A free piston generator. The free piston generator according to claim 1 or 2,
The groove portion includes a groove pattern in which a plurality of grooves are formed along the moving direction of the piston, and the groove pattern is formed in a plurality around the piston,
The groove pattern is formed to face along the radial direction of the piston,
The displacement detector outputs a signal corresponding to the displacement of the groove pattern, and adds the signals corresponding to the opposed groove patterns when obtaining the displacement of the groove pattern. A free piston generator. A free piston generator according to any one of claims 1 to 5,
The free piston generator according to claim 1, wherein the groove is formed such that an interval between adjacent grooves along the moving direction of the piston becomes narrower toward an end side. A free piston generator according to any one of claims 1 to 5,
The groove portion includes a portion formed such that an interval between adjacent grooves is a first interval and a portion formed so as to be a second interval, a free piston type Generator. A free piston generator according to any one of claims 1 to 7,
The free-piston generator, wherein the filling member includes a first filling member and a second filling member having different detection characteristics of the displacement detector. A free piston generator according to any one of claims 1 to 8,
The groove part includes a groove formed to have a groove depth of a first depth and a groove formed to have a second depth of the free piston generator. A free piston generator according to any one of claims 1 to 9,
At least one of the air chamber and the combustion chamber is provided with a pressure sensor, and the position of the piston is detected according to the value of the pressure sensor. A free piston generator according to any one of claims 1 to 10,
A coil is provided on the inner peripheral surface of the cylinder,
A magnet is provided on the outer peripheral surface of the piston,
When the piston is moved by supplying a current to the coil to generate a magnetic field, the position of the piston is detected according to the current value supplied to the coil. Generator. A free piston generator according to any one of claims 1 to 11,
An arithmetic unit that calculates the position of the piston in response to a signal from the displacement detector;
The arithmetic unit calculates a speed and acceleration of the piston from a signal already received, and calculates a current position of the piston according to the speed and acceleration.

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