JP2012021461A - Free-piston engine-driven linear power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a more efficient free-piston engine-driven linear power generator.SOLUTION: This free-piston engine-driven linear generator 10 includes at least one linear generator 12 provided with an engine unit 14 and a power generation unit. The engine unit 14 is provided with a piston 32 reciprocatingly disposed in a cylinder 30, and a combustion chamber 36 and an air chamber 34 provided on both sides of the piston 32 and having volume changed in association with the reciprocating motion of the piston 32. The power generation unit is the linear generator provided with the piston 32 and a coil 22 fixed on the outer periphery of the piston 32, and generating power in association with the reciprocating motion of the piston 32. The piston 32 reciprocates in the cylinder 30 by combustion pressure generated when burning an air-fuel mixture in the combustion chamber 36, and repulsive power of gas in the air chamber, compressed by the combustion pressure.

Description

  The present invention relates to a free piston engine-driven linear power generator that generates electric power by using a motion of a free piston engine that reciprocates a piston in a cylinder without using a crank mechanism.

  Conventionally, a free piston engine that reciprocates a piston in a cylinder without using a crank mechanism is widely known. In some cases, a power generation device including the free piston engine is also known.

  For example, Patent Document 1 discloses a free piston engine-driven linear power generation device that generates power using the motion of a free piston engine. This power generation device is disposed in the same straight line and is operated by shifting the stroke, and a pair of left and right free piston engines, and a shaft portion including a magnet portion that reciprocates by connecting pistons of the engines. And a mechanism for generating a magnetic field around the magnet portion, and generates electric power by reciprocating motion of the shaft portion.

  Patent Document 2 discloses a free piston engine in which a combustion chamber is provided between two pistons arranged to face each other in a cylinder, and an air chamber is provided on the opposite side of each piston from the combustion chamber. In this free piston engine, the piston is reciprocated by the combustion pressure when the fuel is burned in the combustion chamber and the compression reaction force of the air chamber compressed by the piston that moves under the combustion pressure. .

JP 2001-241302 A Japanese Utility Model Publication No. 58-139532

  Such a free piston engine is expected as an internal combustion engine advantageous for downsizing. However, the conventional free piston engine has a problem that excessive vibration is easily generated or efficiency is low. For example, in the free piston engine described in Patent Document 1, since two pistons move asymmetrically, large vibrations are likely to occur during driving. In order to avoid this problem, it is conceivable to arrange two or four free piston engines so as to be symmetrical. However, in this case, since there are four or eight combustion chambers (corresponding to cylinders), new problems such as an increase in the number of cylinders and an increase in size arise.

  Moreover, although the free piston engine described in Patent Document 2 can suppress and reduce the occurrence of vibration because the two pistons move symmetrically, the air chamber pushed by the combustion pressure becomes high temperature and high pressure, There was a problem that heat loss was caused and efficiency was lowered. Moreover, in this patent document 2, the electric power generation which directly utilized the movement of the piston was not performed, and it was not necessarily efficient.

  Accordingly, an object of the present invention is to provide a more efficient free piston engine drive linear power generator.

  A free-piston engine-driven linear power generator according to the present invention is a free-piston equipped with one or more linear generators composed of an engine unit that reciprocates a piston in a cylinder and a power-generating unit that generates power in accordance with the reciprocating motion of the piston. A drive linear power generator, wherein the engine unit includes a piston disposed in a reciprocating manner in a cylinder, a combustion chamber and an air chamber that are provided on both sides of the piston and change in volume as the piston reciprocates. The power generation unit is a linear generator that includes the piston and a coil fixed to the outer periphery of the piston, and generates electric power as the piston reciprocates, and the piston includes the combustion chamber Combustion pressure generated at the time of combustion of a fuel / air mixture in the air and an air chamber compressed by the combustion pressure It reciprocates in the cylinder by the repulsive force of the gas, characterized in that.

  In a preferred aspect, a permanent magnet is embedded in the piston, and the power generation unit generates power by changing a relative positional relationship between the permanent magnet and the coil as the piston reciprocates.

  In another preferred embodiment, the apparatus includes two linear generators arranged on the same line so as to be symmetrical, and the pistons of the two engine units provided in the two linear generators reciprocate symmetrically. In order to move, the two engine units operate synchronously. In this case, it is desirable that the two engine units provided in the two linear generators share one air chamber.

  In another preferred aspect, the engine unit further includes an internal pressure adjusting means for adjusting the internal pressure of the air chamber so as to keep the internal pressure within a certain range. In another preferred embodiment, a ceramic coating is applied to at least a part of a contact portion of the inner surface of the cylinder with the reciprocating piston. In another preferred aspect, the combustion chamber is provided with a scavenging hole whose opening area changes according to the position of the piston in the cylinder, and an exhaust valve for controlling the discharge of burned gas from the combustion chamber. It has been.

  In another preferred aspect, the piston has a hollow structure with a hollow inside, and the piston and the cylinder have a communication hole that allows air to flow into and out of the piston. Is provided. In another preferred aspect, the engine unit further includes position detection means for detecting the position of the piston. In another preferred aspect, at least a part of the cylinder is made of a magnetic steel sheet.

  In another preferred aspect, the air chamber has a heat shield structure that inhibits heat exchange between the air chamber gas and the outside. In this case, the heat shield structure is a heat shield film that is formed on at least a part of the inner wall of the air chamber and has a lower thermal conductivity and a heat capacity per unit volume than the base material forming the air chamber.

  According to the present invention, since the power is generated by directly using the movement of the piston, the efficiency can be further improved.

It is a schematic block diagram of the linear electric power generating apparatus which is embodiment of this invention. It is a figure which shows another example of a linear electric power generating apparatus. It is a figure which shows another example of a linear electric power generating apparatus. It is a graph which shows the displacement of the piston in an engine unit. It is a graph which shows the speed change of the piston in an engine unit. It is a graph which shows the pressure change of a combustion chamber and an air chamber. It is a figure which shows each parameter used by simulation. It is a power generation efficiency map used in the simulation. It is a schematic block diagram of the linear electric power generating apparatus which is other embodiment of this invention. It is a schematic block diagram of the linear electric power generating apparatus which is other embodiment of this invention. It is a schematic block diagram of the conventional free piston engine. It is a schematic block diagram of the other conventional free piston engine.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a free piston engine drive linear power generator (hereinafter abbreviated as “linear power generator”) 10 according to a first embodiment of the present invention.

  The linear power generator 10 includes a single linear generator 12. The linear generator 12 includes an engine unit 14 (free piston engine) that reciprocates the piston 32 in the cylinder 30 by combustion pressure, and a power generation unit that generates power using the movement of the piston 32. Yes. The power generation unit includes a cylinder 30 that functions as a stator and a piston 32 that functions as a mover. A permanent magnet 20 is embedded in the outer surface of the piston 32, and a power generation coil 22 is fixedly installed on the inner wall of the cylinder 30 (the outer periphery of the permanent magnet 20). When the piston 32 reciprocates in the cylinder 30 by driving the engine unit 14, the relative positional relationship between the permanent magnet 20 and the power generation coil 22 changes, and thereby the magnetic field around the permanent magnet 20 changes. An induced electromotive force is generated in the power generation coil 22 in accordance with the change in the magnetic field. Electric power is generated by the induced electromotive force, and the electric power obtained by the power generation is transmitted to a battery or the like via a control device (not shown).

  The engine unit 14 is a unit that reciprocates the piston 32 in the cylinder 30. The engine unit 14 includes a cylinder 30 that also functions as a stator of the power generation unit, a piston 32 that also functions as a mover of the power generation unit, combustion chambers 36 provided on both sides of the piston 32 in the cylinder 30, and air. And a chamber 34. That is, the piston 32 is sandwiched between the combustion chamber 36 and the air chamber 34. As the piston 32 reciprocates, the volumes of the combustion chamber 36 and the air chamber 34 change.

  The combustion chamber 36 is a chamber in which an air-fuel mixture of fuel and fresh air (air) is combusted. The combustion chamber 36 is provided with a fuel injection valve 40, an ignition plug (not shown), an exhaust valve 38, a scavenging hole 42, and the like. The fuel injection valve 40 is a valve body attached to the end surface of the combustion chamber 36 (closed end surface of the cylinder 30), and supplies fuel into the combustion chamber 36. The spark plug ignites an air-fuel mixture in which fuel and fresh air are mixed to cause combustion (explosion). The exhaust valve 38 is attached to the end face of the combustion chamber 36 (closed end face of the cylinder 30), and discharges burnt gas generated after combustion to the outside.

  The scavenging hole 42 is a hole provided in an intermediate portion of the cylinder 30 for taking in fresh air into the combustion chamber 36. The amount of opening of the scavenging hole 42 changes according to the displacement of the piston 32. That is, when the piston 32 is located near the end portion on the combustion chamber 36 side (left side in the drawing) and the combustion chamber 36 is compressed, the scavenging holes 42 are shielded by the piston 32. In this case, introduction of fresh air into the combustion chamber 36 is hindered. On the other hand, when the piston 32 moves to the air chamber 34 side (the right side of the drawing) due to the combustion pressure, the scavenging holes are gradually opened, and the introduction of new air is promoted. In this way, by providing the scavenging hole 42 whose opening amount is variable according to the displacement of the piston 32 at the position near the air chamber 34 and providing the exhaust valve 38 at the opposite end, The fuel gas can be discharged in one direction. Thus, burned gas can be discharged and fresh air can be sucked more efficiently.

  The air chamber 34 is a chamber provided on the opposite side of the combustion chamber 36 and surrounded by the end faces of the cylinder 30 and the piston 32. The air chamber gas (air or the like) existing inside the air chamber 34 functions as an air spring that pushes the piston 32 that has moved to the air chamber 34 side by combustion of the air-fuel mixture back to the combustion chamber 36 side. That is, when the piston 32 moves toward the air chamber 34 due to the combustion pressure in the combustion chamber, the air chamber 34 is compressed. The compressed air chamber 34 pushes the piston 32 back toward the combustion chamber 36 so as to expand again by the compressed reaction.

  Here, in order to appropriately prevent the engine unit 14 from being damaged by appropriately reciprocating the piston 32 by the compression / expansion of the air chamber 34 (expansion / compression of the combustion chamber 36), the air chamber 34 is used. It is necessary that the pressure is within a certain range. Therefore, in the present embodiment, a pressure regulating valve 46 for adjusting the pressure is provided in the air chamber 34 so that the pressure of the air chamber 34 falls within a certain range. The pressure regulating valve 46 causes the inside air of the air chamber 34 to flow out to the outside when the pressure in the air chamber 34 exceeds the upper limit value, and causes the outside air to flow into the air chamber when the pressure in the air chamber 34 falls below the lower limit value. The pressure is kept within a certain range. The pressure regulating valve 46 may be, for example, a combination of a pressure sensor (not shown) and an electromagnetic valve that opens and closes according to a detection value of the pressure sensor, or a machine that mechanically opens and closes at a constant pressure. It may be a type valve, such as a duckbill valve.

  Here, there is a problem that the inside of the air chamber 34 compressed by the combustion pressure becomes high pressure and high temperature due to compression of the air chamber gas (air), heat loss increases, and efficiency decreases. In the present embodiment, in order to reduce heat loss in the air chamber 34 and improve power generation efficiency, the air chamber 34 is provided with a heat shield structure that inhibits heat exchange between the air chamber gas and the outside.

  Although various forms are conceivable as the heat shield structure, for example, the heat shield structure may be realized by configuring at least a part of the inner wall of the air chamber 34 with a material having low thermal conductivity. An example of the material having a low thermal conductivity is ceramic. By forming the inner wall surface of the cylinder 30 constituting the air chamber 34 and the end portion of the piston 32 with such a material, heat exchange with the outside is prevented, and heat loss can be reduced.

  As another form, a thermal barrier film may be formed on at least a part of the inner wall of the air chamber 34. The thermal barrier film is a film body having a sufficiently small thermal conductivity and heat capacity. As such a thermal barrier film, for example, the heat capacity per unit volume and the inside of the film-like first heat insulating material having a lower thermal conductivity than the base material (cylinder 30 and piston 32) forming the air chamber 34, and It is desirable to use a film body in which a second heat insulating material having a lower thermal conductivity than both the base material and the first heat insulating material is mixed. Here, as the first heat insulating material, ceramics such as zirconia, silicon, titanium, and zirconium can be used. In addition, as the second heat insulating material, a hollow ceramic bead, a hollow glass bead, a heat insulating material having a fine porous structure mainly composed of silica, and the like can be used. Further, for example, a heat shielding film as disclosed in JP 2009-243352 A or WO 09/020206 pamphlet may be used.

  Since such a heat shield film has a sufficiently small heat capacity and thermal conductivity, it is easy to follow the temperature change of the air chamber gas and easily reduce heat loss. That is, normally, the heat loss Q is expressed as follows: h is the heat transfer coefficient resulting from the pressure and gas flow in the air chamber 34, A is the surface area in the air chamber 34, Tg is the gas temperature in the air chamber 34, When the wall surface temperature to be contacted is Twall, it is expressed by the equation Q = A · h · (Tg−Twall). As is clear from this equation, the heat loss Q decreases as the difference between the temperature Tg of the air chamber gas and the wall surface temperature Twall of the air chamber 34 decreases. Therefore, in order to reduce heat loss, it is desirable to make the wall surface temperature Twall of the air chamber 34 follow the temperature Tg of the air chamber gas. Such high temperature followability is realized by using a material having sufficiently low thermal conductivity and heat capacity per unit volume. Moreover, it is not sufficient that the thermal conductivity and the heat capacity per unit volume are low, and it is also desirable that the mechanical and thermal strength be sufficient. The thermal barrier film is sufficiently low while maintaining the mechanical strength by mixing the second heat insulating material with sufficiently low thermal conductivity and heat capacity per unit volume into the first heat insulating material with high mechanical strength. It can have thermal conductivity and heat capacity per unit volume. Then, by providing such a heat shield film on the inner wall of the air chamber 34, heat loss can be effectively reduced.

  Further, when this thermal barrier film is used, the inner surface temperature of the air chamber 34 increases only when the air chamber 34 is compressed (when the temperature of the air chamber gas rises), and rises constantly. It becomes difficult to do. Therefore, compared with the case where the wall surface is made of a material having a low thermal conductivity, the temperature rise of the magnet can be mitigated when the thermal barrier film is used. In order to improve efficiency, it is also desirable to reduce heat loss in the combustion chamber 36. Therefore, it is desirable to provide the above-described heat shielding film also on the inner surface of the combustion chamber 36.

  The cylinder 30 is provided with one or more, more preferably a plurality of sensors 44 for detecting the position of the piston 32. The sensor 44 detects that the tip of the piston 32 has crossed, and for example, an optical or eddy current sensor can be used. A control unit (not shown) estimates the position and speed of the piston 32 for each time from the detection signal of the sensor 44. Then, the control unit controls the opening / closing timing of various valves, the plug ignition timing, the fuel supply amount, the supply timing, and the like based on the estimation result.

  As described above, the piston 32 is a member that reciprocates in the cylinder 30 according to the combustion pressure and the compression repulsion force of the air chamber 34. A permanent magnet 20 is embedded in the outer peripheral surface of the piston 32, and also functions as a mover of the power generation unit.

  In the present embodiment, in order to improve the cooling efficiency of the piston 32, the piston 32 has a hollow structure, and communication holes 48 and 50 are formed in the piston 32 and the cylinder 30. That is, as shown in FIG. 1, in this embodiment, a hollow body having a hollow inside is used as the piston 32. Communication holes 48 and 50 are formed in the piston 32 and the cylinder 30, respectively. If the communication hole 48 of the piston 32 and the communication hole 50 of the cylinder 30 overlap with the displacement of the piston 32, the air inflow into the piston 32 and the air outflow from the piston 32 to the outside are allowed. The piston 32 is cooled from the inside by the air flowing in and out. Further, a part of the air also goes around the outer periphery of the piston 32, and the piston 32 can be cooled from the outer periphery. The number of the communication holes 48 and 50 is not particularly limited, and may be two as shown in FIG. 1 or may be more as shown in FIG. As shown in FIG. 2, by providing a large number of communication holes 48 in the piston 32, the positions through which air passes change one after another, and the piston 32 can be cooled more efficiently.

  The piston 32 reciprocates in the cylinder 30 as described repeatedly. In the present embodiment, at least a part of the sliding portion (contact portion) between the cylinder 30 and the piston 32 is provided with a coating for sliding without lubrication. The coating is not particularly limited as long as it can reciprocate the piston 32 without lubrication. For example, a ceramic coating can be employed. By applying such coating, the piston 32 can be reciprocated without supplying the lubricant, and the configuration of the engine unit 14 can be further simplified. In addition, in order to improve electric power generation efficiency, this cylinder 30 may be comprised from an electromagnetic steel plate as shown in FIG. And you may provide the above-mentioned scavenging hole 42 and the cooling water path 52 for flowing cooling water in this electromagnetic steel plate.

  Next, the operation of the engine unit 14 will be described. First, when there is a fuel-air mixture in the combustion chamber 36, the piston 32 moves to the combustion chamber 36 side (the left side in the drawing) and the combustion chamber 36 is sufficiently compressed. Is ignited. By this ignition, the air-fuel mixture is combusted (exploded), and the combustion pressure (gas expansion force) causes the piston 32 to move toward the air chamber 34 so that the combustion chamber 36 is expanded and the air chamber 34 is compressed. At this time, in the combustion chamber 36, the exhaust valve is opened, and the burned gas is exhausted in the combustion chamber 36. Further, as the piston 32 moves toward the air chamber 34, the scavenging holes 42 closed by the piston 32 are gradually opened, and fresh air is taken into the combustion chamber 36.

  On the other hand, the air chamber 34 is compressed by the piston 32 that moves due to the combustion pressure. By this compression, the gas in the air changes to high temperature and high pressure. However, since the air chamber 34 is provided with a heat shield structure, heat loss due to the high temperature is greatly suppressed. In particular, when a thermal barrier film is used as the thermal barrier structure, the inner surface of the air chamber 34 (the surface of the thermal barrier film) also increases in temperature following the increase in the temperature of the air chamber gas. Effectively suppressed. Further, when the internal pressure of the air chamber 34 becomes excessive as the air chamber gas is compressed, the internal pressure is adjusted to be equal to or lower than the upper limit value by the pressure regulating valve 46. Thereby, damage to the engine unit 14 and the like are effectively prevented.

  When the piston 32 sufficiently compresses the air chamber 34, this time, the piston 32 is pushed back toward the combustion chamber 36 by the expansion force (repulsive force) of the compressed air in the air chamber 34. Thereby, the expansion of the air chamber 34 and the compression of the combustion chamber 36 are started. As the piston 32 moves toward the combustion chamber 36, the scavenging holes 42 are closed. Further, the exhaust valve 38 is also closed, and the combustion chamber 36 is sealed. In this state, fuel is injected and the combustion chamber 36 is filled with a mixture of fresh air and fuel.

  At this time, the air chamber 34 is rapidly expanding, and the temperature of the air chamber gas is lowered. When a thermal barrier film is employed as the thermal barrier structure, the inner surface temperature of the air chamber 34 also decreases following the temperature decrease of the air chamber gas. As a result, the temperature rise of the magnet can be effectively mitigated. Further, when the pressure in the air chamber 34 is excessively reduced as the air chamber 34 expands, the pressure is adjusted by the pressure regulating valve 46 so that the internal pressure becomes equal to or higher than the lower limit value.

  When the piston 32 sufficiently compresses the combustion chamber 36, the air-fuel mixture is ignited by the spark plug. Then, the piston 32 again moves to the air chamber 34 side, and the air chamber 34 is compressed. Thereafter, the same cycle, that is, the compression / compression of the combustion chamber 36, the expansion of the air chamber 34, the mixture combustion, and the expansion of the combustion chamber 36 / the compression of the air chamber 34 is repeated. In the course of this cycle, the magnetic field around the permanent magnet 20 embedded in the piston 32 changes, and an induced electromotive force is generated in the power generation coil 22 according to the change in the magnetic field, thereby generating power. In the above description, spark ignition is exemplified, but compression ignition combustion (diesel combustion) may be used, or premixed compression auto ignition combustion may be used as described later. In the above description, a power generation unit using a permanent magnet is shown. However, a reluctance synchronous motor that does not use a permanent magnet may be applied, and the power generation unit may be configured not to use a permanent magnet.

  Next, the characteristics of the engine unit 14 will be described with reference to FIGS. FIG. 4 is a graph showing the displacement of the piston 32 when the engine unit 14 is driven. In FIG. 4, the horizontal axis indicates time, and the vertical axis indicates the displacement of the piston 32. FIG. 5 is a graph showing the speed of the piston 32. The horizontal axis represents time, and the vertical axis represents the speed of the piston 32. Further, FIG. 6 is a graph showing the pressure history of the combustion chamber 36 and the air chamber 34. In FIG. 6, the horizontal axis indicates time, the vertical axis indicates pressure, the solid line indicates the pressure in the combustion chamber 36, and the broken line indicates the pressure in the air chamber 34.

  As apparent from FIG. 4, according to the engine unit 14, the time during which the piston 32 stays at the top dead center and the bottom dead center is short as compared with the engine having the crank mechanism. Further, in an engine having a normal crank mechanism, when premixed compression auto-ignition combustion is used, ignition occurs at a timing when the piston 32 is separated from the top dead center of the piston (that is, a deviation in ignition timing), and the equal volume There is a possibility that the reduction of the combustion efficiency and the reduction of the combustion efficiency may occur. On the other hand, since the free piston engine does not have a crank mechanism, the position of the top dead center of the piston is not determined mechanically, and if premixed compression self-ignition occurs, it is generated due to the inertial force of the piston thereafter. After the lag time, it immediately turns from compression to expansion. As a result, the isovolume can be kept high, and as a result, the efficiency can be improved.

  Next, the results of verifying the efficiency of the linear power generator 10 by simulation will be described. First, the preconditions for simulation will be described. In order to model the ignition / combustion process that changes according to the temperature, pressure, and concentration of the mixture of fuel and fresh air, a multi-step Shell model was used in the ignition process, and a Kong model was used in the combustion process. In this simulation, premixed compression self-ignition capable of realizing low NOx characteristics is premised.

  Regarding gas exchange, as in a general two-stroke engine, the scavenging hole height D is assumed to be about 1/3 of the piston stroke L (D = L / 3) (see FIG. 7). When the combustion chamber 36 and the scavenging hole 42 communicate with each other, it is assumed that all the burned gas in the combustion chamber 36 is replaced with 0.2 Mpa and 330 K air. Regarding the heat radiation to the cooling water, the heat radiation from the combustion chamber 36 to the cooling water and the heat radiation from the air chamber 34 to the cooling water are modeled using the Woschni equation.

For the power generation efficiency of the power generation unit, the map of FIG. 8 was used. This is a map created based on the power generation efficiency of a commercial generator (25 kW) determined by the rotational speed and the load torque. The rotor rotational speed of the commercial generator is determined by the permanent magnet 20 in the linear power generator. The load torque is converted into a load at a speed crossing. The power generation load F was calculated based on the following Equation 1, and the power generation amount in the linear power generation apparatus 10 was calculated by multiplying the power generation load F by the above-described power generation efficiency. In Equation 1, c represents an electromagnetic force coefficient, and x represents a displacement of the piston 32.
F = c · (dx / dt) Equation 1

And the operation | movement of the linear electric power generating apparatus 10 is calculated combining the above model and the equation of motion of following formula 2. In Equation 2, m represents the mass of the piston 32, ΔP represents the pressure difference between the combustion chamber 36 and the air chamber 34, and K represents the cross-sectional area of the piston 32.
m · (d2x / dt2) = ΔP · K−F Equation 2

  Here, the three types of linear power generators A to C shown in Table 1 are to be simulated. As shown in Table 1, all of the linear power generators A to C have a bore (cylinder 30 inner diameter) of 56 mm, a scavenging hole height of 50 mm, a piston mass of 1700 g, and a fuel injection amount of 10.0 mg / st. On the other hand, these three linear power generators A to C are different from each other in heat insulation rate of the air chamber. That is, the linear power generator A does not have a heat shield structure, the linear power generator B has a heat shield rate of 20% for the air chamber, and the linear power generator C has a heat shield rate of 50% for the air chamber.

  Table 2 shows the results of simulation under the above conditions. As shown in Table 2, it can be seen that the higher the heat shielding rate, the lower the cooling loss, and the improved indicated thermal efficiency, power generation efficiency, overall efficiency, and specific output.

  Next, the linear power generator 10 of 2nd embodiment is demonstrated with reference to FIG. In this linear power generator 10, two linear generators 12 described in the first embodiment are arranged on the same straight line and symmetrically so that the air chamber 34 is located at the center. That is, the linear power generation apparatus 10 includes two engine units 14 arranged to be symmetrical on the same straight line, and two power generation units arranged to be symmetrical on the same straight line. Yes. In this linear power generator 10, the first linear generator 12a and the second linear generator 12b are driven in synchronism so that the pistons 32 move left and right symmetrically. That is, at the timing when the piston 32 of the first linear generator 12a moves to the right and starts to compress the combustion chamber 36, the piston 32 of the second linear generator 12b also moves to the left and compresses the combustion chamber 36. At the timing when the mixture is ignited in the combustion chamber 36 of the first linear generator 12a, the mixture is also ignited in the combustion chamber 36 of the second linear generator 12b.

  Thus, by performing the same stroke at the same timing in both the first linear generator 12a and the second linear generator 12b, the two pistons 32 move symmetrically. As a result, the excitation force generated in the first linear generator 12a and the second linear generator 12b can be offset, and the vibration of the engine can be reduced.

  Here, as is apparent from the above description, the engine unit 14 of the present embodiment is a free piston engine having an air chamber 34 and a combustion chamber 36, so that vibration is reduced as compared with the conventional case. However, the number of cylinders can be reduced and the size can be reduced.

  This will be described in comparison with the prior art. FIG. 11 is a schematic configuration diagram of a conventional free piston engine 100 described in Patent Document 1 and the like. As shown in FIG. 11, the conventional free piston engine 100 is provided with combustion chambers 136 on both sides of one piston 132. The piston 132 is reciprocated by repeating the operation of pushing back the piston 132 pushed by the combustion pressure generated in the combustion chamber 136 on one side with the combustion pressure generated in the combustion chamber 136 on the opposite side. That is, the conventional free piston engine 100 corresponds to a two-cylinder configuration having two combustion chambers 136. In the case of such a configuration, in order to cancel the vibration generating force, two free piston engines 100 are arranged in series as shown in FIG. 11, or the four free piston engines 100 are moved up and down as shown in FIG. Must be placed in parallel. According to the configuration shown in FIG. 11, the movement of the piston 132 is bilaterally symmetric, and the vibration can be canceled out. However, the configuration of FIG. 11 corresponds to a four-cylinder having four combustion chambers 136, and causes an increase in the number of cylinders and an increase in size as compared with the present embodiment. In the configuration shown in FIG. 12, the movement of the piston 132 is bilaterally and vertically symmetrical, so that it is possible to cancel the reciprocating vibration force and rotational moment. However, this corresponds to an eight cylinder having eight combustion chambers 136. Therefore, the number of cylinders and the size increase more than the configuration of FIG.

  On the other hand, in the present embodiment, the piston 32 is pushed back by the reaction of compressing the air chamber 34, and one corresponding piston 32 exists for each combustion chamber 36. Therefore, it is easy to drive the two pistons 32 corresponding to the two combustion chambers 36 symmetrically, and as a result, in a two-cylinder configuration in which only two combustion chambers 36 exist (that is, the configuration shown in FIG. 9). Even in such a case, the vibration force in the reciprocating direction (cylinder axis direction) can be canceled out. Furthermore, no rotational moment is generated due to the arrangement on the same straight line. As a result, the linear power generator 10 with fewer cylinders and a smaller size and reduced vibration can be obtained.

  In FIG. 9, the air chamber 34 interposed between the two pistons 32 is separated into two. In other words, the two engine units 14 use separate air chambers 34. However, as shown in FIG. 10, the wall interposed between the two pistons 32 may be removed so that the two engine units 14 share one air chamber 34. Even in such a configuration, the piston 32 can move symmetrically, can cancel the reciprocating vibration force, and no rotational moment is generated.

  DESCRIPTION OF SYMBOLS 10 Linear generator, 12 Linear generator, 14 Engine unit, 20 Permanent magnet, 22 Generator coil, 30 Cylinder, 32 Piston, 34 Air chamber, 36 Combustion chamber, 38 Exhaust valve, 40 Fuel injection valve, 42 Scavenging hole, 44 Sensor, 46 pressure regulating valve, 48, 50 communication hole, 52 cooling water channel.

Claims (12)

A free piston drive linear power generator comprising one or more linear generators comprising an engine unit that reciprocates a piston in a cylinder, and a power generation unit that generates power in response to the reciprocation of the piston,
The engine unit is
A piston disposed in a reciprocating manner in a cylinder;
A combustion chamber and an air chamber that are provided on both sides of the piston and change in volume as the piston reciprocates;
With
The power generation unit is a linear generator that includes the piston and a coil that is fixed to the outer periphery of the piston, and that generates electric power as the piston reciprocates,
The piston reciprocates in the cylinder by the combustion pressure generated when the fuel / air mixture is burned in the combustion chamber and the repulsive force of the air chamber gas compressed by the combustion pressure.
The free piston engine drive linear power generator characterized by the above-mentioned. It is a free piston engine drive linear power generator of Claim 1,
A permanent magnet is embedded in the piston,
The power generation unit generates power by changing the relative positional relationship between the permanent magnet and the coil with the reciprocation of the piston.
The free piston engine drive linear power generator characterized by the above-mentioned. The free piston engine drive linear power generator according to claim 1 or 2,
It has two linear generators arranged to be symmetrical on the same line,
The two engine units operate synchronously so that the pistons of the two engine units provided in the two linear generators reciprocate symmetrically,
The free piston engine drive linear power generator characterized by the above-mentioned. It is a free piston engine drive linear power generator according to claim 3,
The two engine units share a single air chamber, and a free piston engine drive linear power generator. A free-piston engine-driven linear power generator according to any one of claims 1 to 4,
The free-piston engine-driven linear power generator, wherein the engine unit further comprises an internal pressure adjusting means for adjusting the internal pressure of the air chamber so as to keep the internal pressure within a certain range. It is a free piston engine drive linear power generator according to any one of claims 1 to 5,
A free-piston engine-driven linear power generator, wherein a ceramic coating is applied to at least a part of a contact portion with a reciprocating piston on an inner surface of the cylinder. It is a free piston engine drive linear power generator according to any one of claims 1 to 6,
The combustion chamber is provided with scavenging holes whose opening area changes according to the position of the piston in the cylinder, and an exhaust valve that controls the discharge of burned gas from the combustion chamber. Free piston engine driven linear generator. A free piston engine-driven linear power generator according to any one of claims 1 to 7,
The piston has a hollow structure with a hollow inside,
The piston and the cylinder are provided with communication holes that allow air inflow into the piston and air out from the piston inside.
The free piston engine drive linear power generator characterized by the above-mentioned. A free piston engine drive linear power generator according to any one of claims 1 to 8,
The free-piston engine-driven linear power generator, wherein the engine unit further comprises position detection means for detecting the position of the piston. A free-piston engine-driven linear power generator according to any one of claims 1 to 9,
At least a part of the cylinder is made of an electromagnetic steel plate, and a free piston engine drive linear power generator. It is a free piston engine drive linear power generator according to any one of claims 1 to 10,
The free-piston engine-driven linear power generator, wherein the air chamber has a heat shield structure that inhibits heat exchange between the air chamber gas and the outside. It is a free piston engine drive linear power generator of Claim 11,
The heat shield structure is a heat shield film formed on at least a part of the inner wall of the air chamber and having a lower thermal conductivity and a heat capacity per unit volume than a base material forming the air chamber. Free piston engine driven linear generator.

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