JP2012202387A - Free piston type generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a free piston type generator capable of adjusting a motion period of a piston or a compression ratio in combustion while keeping system efficiency (engine heat efficiency×power generation efficiency) at a sufficiently preferable value.SOLUTION: The free piston type generator 10 for generating electricity accompanied by the linear reciprocating motion of the piston 20 is provided with a combustion chamber 26 and a spring 28 at both sides sandwiching the piston 20, and includes: an engine unit 16 in which the piston 20 reciprocates at combustion pressure when the fuel is combusted in the combustion chamber 26, and a restoring force of the spring compressed by the piston 20; a power generation unit 14 for generating electricity accompanied by the reciprocation of the piston 20; and a control means 50 for controlling the drive of the engine unit 16 and the power generation unit 14. The control means adjusts the motion frequency of the piston 20 or the compression ratio in combustion by adjusting balance between the fuel jetting volume for jetting to the combustion chamber and the power generation load, the reaction force of the spring part 28, and an intake air volume into the combustion chamber 26.

Description

  The present invention relates to a free piston generator that generates electric power with linear reciprocation of a piston.

  Conventionally, a free piston generator that incorporates a power generation unit into a free piston engine that reciprocates the piston in the cylinder by the combustion pressure obtained when the fuel is burned in the combustion chamber, and generates power with the reciprocating motion of the piston. Is widely known.

JP 2008-223628 A Japanese Utility Model Publication No. 58-139532 JP 2006-170071 A

“University Lecture Internal Combustion Engine”, Ichiro Kimura, Tadami Sakai, P269, Maruzen Co., Ltd. “Design and Thinking of Free Piston Gas Generator”, Fujio Nagao, Proceedings of the Japan Society of Mechanical Engineers, April 1951

  The free piston engine has a problem that it is difficult to adjust the piston movement cycle and the compression ratio during combustion to a desired value because the piston is not mechanically constrained. As a result, the thermal efficiency of the engine part decreases, the power generation efficiency decreases, and the movement frequency fluctuates (and thus the power generation amount fluctuates), which makes it impossible to synchronize the movement cycles of the plurality of cylinders and generates vibration. Such a problem sometimes occurred.

  Here, Patent Document 1 discloses a technique for stopping power generation by a generator when the speed of a piston becomes a predetermined speed or less as a technique for setting a compression ratio to a desired value. According to such a technique, the compression ratio can be adjusted to a desired value to some extent. However, since the adjustment range of the power generation load cannot be set widely, the thermal efficiency of the engine may be lowered or the power generation efficiency may be lowered.

  In addition, a technique has been proposed in which two pistons are coaxially arranged symmetrically to reduce vibration. In order to reduce vibration by this method, it is required that the motions of the two pistons be completely symmetrical (the motion cycles are synchronized). Patent Document 2 and Non-Patent Documents 1 and 2 disclose techniques using a mechanical link mechanism and gears to synchronize two pistons. According to such a technique, the two pistons can be synchronized, and as a result, vibration can be reduced. However, these techniques cause problems such as increased friction and inertial mass, and significantly reduce the efficiency of free piston engines.

  In Patent Document 3, a linear motor that generates electric power according to the reciprocating motion of the piston and drives the piston as necessary, and synchronizes the two pistons by changing the operating frequency of the linear motor. Is disclosed. However, this Patent Document 3 does not disclose how to actually change the operating frequency of the linear motor.

  In other words, conventionally, the piston movement cycle and the compression ratio during combustion can be adjusted while maintaining the efficiency of the free piston linear generator (that is, the thermal efficiency of the engine section x the power generation efficiency of the linear generator section) at a substantially suitable value. There was no free piston generator to get. Therefore, an object of the present invention is to provide a free piston generator that can adjust the piston motion cycle and the compression ratio during combustion without reducing the efficiency of the free piston linear generator.

  The free-piston generator of the present invention is a free-piston generator that generates electric power as the piston reciprocates linearly, and is provided with combustion chambers and spring portions on both sides of the piston, and burns fuel in the combustion chamber. An engine unit in which the piston reciprocates due to the combustion pressure when the piston is compressed and a restoring force of the spring portion compressed by the piston, a power generation unit that generates power in accordance with the reciprocation of the piston, and driving of the engine unit and power generation unit Control means for controlling, the control means, the balance between the fuel injection amount injected into the combustion chamber and the power generation load, the repulsive force of the spring portion, the intake air amount into the combustion chamber, the spark ignition timing, the fuel By adjusting at least one of the injection timing and the fuel injection rate, the motion frequency of the piston or the compression ratio at the time of combustion is adjusted.

  In a preferred aspect, the control means adjusts the movement frequency of the piston so that the engine units are arranged coaxially and symmetrically, and the drive phases of the two engine units are matched.

  In another preferred embodiment, the combustion in the combustion chamber is performed by a premixed compression self-ignition method in which an air-fuel mixture in which fuel and air are mixed is compressed to a high temperature and self-ignited. The compression ratio at the time of combustion is adjusted so that the combustion timing of the fuel becomes a predetermined timing.

  In another preferred aspect, the combustion in the combustion chamber is performed by a spark ignition system that ignites an air-fuel mixture in which fuel and air are mixed using spark as a spark, and the control means is configured to detect knocking. First, the compression ratio is decreased.

  In another preferred aspect, the spring portion is an air chamber that is provided on the opposite side of the combustion chamber with the piston interposed therebetween, and whose volume changes with the reciprocating motion of the piston. The control means is configured to increase or decrease the repulsive force of the spring portion by increasing or decreasing the amount of air in the air chamber.

  In another preferred aspect, the control unit uses, as an adjustment index, a power generation load constant that is a value obtained by dividing the power generation load by the piston speed when adjusting the power generation load. In this case, it is preferable that the control unit increases or decreases the power generation amount by increasing or decreasing the values of the power generation load coefficient and the fuel injection amount while maintaining the ratio between the power generation load coefficient and the fuel injection amount substantially constant. . It is also desirable that the control unit increases the value of the motion frequency and the compression ratio by increasing the ratio of the fuel injection amount to the power generation load coefficient. It is also preferable that the control unit adjusts the power generation load so that the integrated value of the power generation load in the compression stroke is larger than the integrated value of the power generation load in the expansion stroke.

  According to the present invention, by adjusting at least one of the balance between the fuel injection amount and the power generation load, the repulsive force of the spring portion, the intake air amount into the combustion chamber, the spark ignition timing, the fuel injection timing, and the fuel injection rate. Because the piston's motion frequency or the compression ratio at the time of combustion is adjusted, the piston's motion cycle and the compression ratio at the time of combustion are not accompanied by an increase in mechanical friction loss by providing a link mechanism. Can be adjusted.

It is a lineblock diagram of the free piston type generator which is an embodiment of the present invention. It is a figure which shows an analysis model. It is a power generation efficiency map used for analysis. It is a table | surface which shows the precondition of an analysis. It is the graph which showed typically the movement mode of the free piston type generator. It is a figure which shows a simulation result. It is an enlarged view of Drawing 6 (d) and (e). It is a table | surface which shows the relationship between the initial pressure of an air chamber and the initial pressure of a combustion chamber, and a motion frequency obtained by simulation. It is a figure which shows the movement aspect of a piston. It is a figure which shows the movement aspect of a piston. It is a block diagram of another free piston type generator. It is a block diagram of another free piston type generator.

  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 generator 10 according to an embodiment of the present invention.

  This free piston generator 10 is a device that converts the piston movement caused by the combustion pressure into electrical energy and takes it out. Two generators 12a and 12b arranged symmetrically (hereinafter, subscript alphabet is used if they are not distinguished from each other). And a control unit 50 that controls the drive of the two power generation devices 12a and 12b.

  One power generation device 12 is roughly divided into an engine unit 16 that reciprocates the piston 20 in the cylinder 18 by combustion pressure, and a power generation unit 14 that generates power using the movement of the piston 20. In the present embodiment, two such power generation devices 12 are arranged so as to be bilaterally symmetrical on the coaxial line.

  The power generation unit 14 includes a cylinder 18 that functions as a stator and a piston 20 that functions as a mover. A permanent magnet 24 is embedded in the outer surface of the piston 20, and a power generation coil 22 is fixedly installed on the inner wall of the cylinder 18 (the outer periphery of the permanent magnet 24). When the piston 20 reciprocates in the cylinder 18 by driving the engine unit 16, the relative positional relationship between the permanent magnet 24 and the power generation coil 22 changes, and thereby the magnetic field around the permanent magnet 24 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 (not shown).

  The engine unit 16 is a unit that reciprocates the piston 20 within the cylinder 18. The engine unit 16 includes a cylinder 18 that also functions as a stator of the power generation unit 14, a piston 20 that also functions as a mover of the power generation unit 14, and combustion chambers 26 provided on both sides of the piston 20 in the cylinder 18. And an air chamber 28. That is, the piston 20 is sandwiched between the combustion chamber 26 and the air chamber 28. The volumes of the combustion chamber 26 and the air chamber 28 change as the piston 20 reciprocates. In the present embodiment, the two engine units 16a and 16b are arranged on the same axis so that the air chamber 28 is located at the center and the combustion chamber 26 is located at both the left and right ends.

  As described above, the cylinder 18 functions as a stator, and a power generation coil 22 is embedded therein. A combustion chamber 26 is formed on one end side of the cylinder 18 and an air chamber 28 is formed on the other end side, and the piston 20 is slidably disposed between the chambers 26 and 28. Here, in this embodiment, a step is formed inside the cylinder 18, and a small diameter portion where the combustion chamber 26 is formed and a large diameter portion where the inner diameter is larger than the small diameter portion and the air chamber 28 is formed are provided. ing. The already described power generation coil 22 is disposed on the inner surface of the large diameter portion. The reason why the step is formed inside the cylinder 18 and the small diameter portion and the large diameter portion are provided will be described in detail later.

  The piston 20 functions as a mover and is slidably disposed inside the cylinder 18. The piston 20 is also formed with a step similar to the cylinder 18 and includes a small diameter portion positioned on the combustion chamber 26 side and a large diameter portion positioned on the air chamber 28 side with a larger diameter than the small diameter portion. Yes. And the permanent magnet 24 is arrange | positioned on the outer surface of a large diameter part among this piston 20. FIG.

  The combustion chamber 26 is a chamber that burns an air-fuel mixture of fuel and fresh air (air). The combustion chamber 26 is provided with a fuel injection valve 30, an ignition plug 32, an exhaust valve 34, a scavenging hole 36, and the like. The fuel injection valve 30 is a valve body attached to the end surface of the combustion chamber 26 (the closed end surface of the cylinder 18), and supplies fuel into the combustion chamber 26. The spark plug 32 ignites an air-fuel mixture in which fuel and fresh air are mixed to cause combustion (explosion). The exhaust valve 34 is attached to the end face of the combustion chamber 26 (closed end face of the cylinder 18), and discharges burnt gas generated after combustion to the outside. The scavenging hole 36 is a hole provided at a position near the air chamber 28 of the combustion chamber 26 in order to take in fresh air into the combustion chamber 26. The opening amount of the scavenging hole 36 changes according to the displacement of the piston 20. That is, when the piston 20 is positioned near the end portion on the combustion chamber 26 side and the combustion chamber 26 is compressed, the scavenging holes 36 are shielded by the piston 20. In this case, introduction of fresh air into the combustion chamber 26 is inhibited. On the other hand, when the piston 20 moves to the air chamber 28 side (the right side of the drawing) due to the combustion pressure, the scavenging holes 36 are gradually opened, and the introduction of new air is promoted. Instead of the scavenging hole 36 opened and closed by the piston 20, a scavenging valve that is opened and closed by electrical or hydraulic pressure may be provided.

  The air chamber 28 is a chamber provided on the opposite side of the combustion chamber 26 and surrounded by the end surfaces of the cylinder 18 and the piston 20. The gas in the air chamber 28 (air or the like) existing inside the air chamber 28 serves as a spring portion (air spring) that pushes the piston 20 that has moved to the air chamber 28 side by combustion of the air-fuel mixture back to the combustion chamber 26 side. Function. That is, when the piston 20 moves to the air chamber 28 side by the combustion pressure in the combustion chamber 26, the air chamber 28 is compressed. The compressed air chamber 28 pushes the piston 20 back to the combustion chamber 26 side to expand again by the compressed reaction.

  The air chamber 28 is provided with a pressure regulating valve 38 that adjusts the pressure of the air chamber 28. The pressure regulating valve 38 causes the inside air of the air chamber 28 to flow out to the outside when the pressure in the air chamber 28 is excessive, and allows the outside air to flow into the air chamber 28 when the pressure in the air chamber 28 is too small. The pressure regulating valve 38 may be, for example, a combination of a pressure sensor and an electromagnetic valve that opens and closes according to a detection value of the pressure sensor, or a mechanical valve that mechanically opens and closes at a constant pressure. It may be a duckbill valve.

  Here, in the present embodiment, the inner diameter of the cylinder 18 in the air chamber 28 is made larger than the inner diameter of the cylinder 18 in the combustion chamber 26, and the pressure receiving area of the air chamber 28 (the area in contact with the end face of the piston 20) is set as the combustion chamber. 26 is larger than the pressure receiving area. With such a configuration, even if the degree of compression of the air chamber 28 is low, a sufficient repulsive force can be obtained. That is, the force pushing the piston 20 of the air chamber 28 is a value obtained by multiplying the internal pressure of the air chamber 28 by the pressure receiving area of the piston 20. Therefore, a larger pressing force (repulsive force) can be obtained as the pressure receiving area is larger. In other words, if the pressure receiving area is large, a sufficient repulsive force can be obtained even if the internal pressure is low. As a result, the temperature rise accompanying the compression of the air chamber 28 can be reduced, and consequently heat loss can be reduced.

  Moreover, when it is set as this structure, the surface area of the piston 20 with respect to the bore diameter of the combustion chamber 26 can be enlarged. By increasing the area of the outer surface of the piston 20 where the permanent magnet 24 is installed, the area of the permanent magnet 24 that can be installed can be increased, and as a result, the power generation output can be increased.

  Such an engine unit 16 is provided with knocking detection means for detecting the occurrence of knocking, piston position detection means 40 for detecting the position of each piston 20, and the like. A known knocking sensor or the like can be used as the knocking detection means.

  The piston position detection means 40 is not particularly limited as long as it can detect at least that the piston 20 has reached a specific position. Therefore, for example, the position of the piston 20 may be detected over the entire stroke, such as an optical linear encoder or a magnetostrictive linear displacement sensor. As another form, one or more position sensors (such as an optical sensor or a gap sensor) detect the sensor passage timing of the piston 20, and based on the passage timing and the sensor installation position (known), the piston 20 The motion frequency may be calculated. Further, the obtained arrival timing and sensor installation position may be collated in advance with a map of easy motion characteristics, a motion equation may be solved, or a simple model may be applied. With such a configuration, the arrival timing at the top dead center / bottom dead center, the position of the top dead center / bottom dead center (the position changes in a free piston engine), the compression ratio, and the position of the piston 20 in the entire stroke range. Can also be obtained. Further, in order to enable more accurate position estimation, friction loss may be taken into consideration from the lubricating oil temperature and the water temperature.

  Furthermore, as another form, the arrival timing to the top dead center / bottom dead center may be detected based on the pressure of the combustion chamber 26 or the air chamber 28. That is, a pressure sensor is provided in the combustion chamber 26 or the air chamber 28, and the timing when the pressure in the combustion chamber 26 reaches the maximum is set to the timing when the top dead center is reached, and the timing when the pressure in the air chamber 28 is maximized. You may detect as arrival timing to a dead point. When detecting the arrival timing at the top dead center based on the pressure in the combustion chamber 26, a pressure sensor used for detection of the combustion state / combustion timing and the intake / exhaust state / timing is used as a pressure sensor used for the detection. It can be used as it is, and the arrival timing to the top dead center can be detected while preventing an increase in the number of parts. Further, when the arrival timing to the bottom dead center is detected based on the pressure of the air chamber 28, the piston position can be calculated with high accuracy by removing the influence of leakage from the air chamber 28, and the operating frequency is adjusted by adjusting the pressure of the air spring chamber. It can also be used as information for adjusting.

  The control unit 50 controls driving of the two engine units 16 and the power generation unit 14. In particular, the control unit 50 of this embodiment adjusts at least the power generation load, the fuel injection amount, the air amount in the air chamber 28, and the intake air amount to the combustion chamber 26 in order to adjust the motion frequency and the compression ratio during combustion. Adjust one. The reason for adjusting these parameters will be described in detail later.

  Next, the operation of the free piston generator 10 will be described. The two engine units 16 perform the same stroke at the same timing. The operation flow of each engine unit 16 is as follows. First, in a state where there is a fuel-air mixture inside the combustion chamber 26, when the piston 20 moves to the combustion chamber 26 side and the combustion chamber 26 is sufficiently compressed, the ignition plug 32 ignites the mixture. Is made. By this ignition, the air-fuel mixture is combusted (explosion), and the combustion pressure (gas expansion force) causes the piston 20 to move toward the air chamber 28, whereby the combustion chamber 26 is expanded and the air chamber 28 is compressed. At this time, in the combustion chamber 26, the exhaust valve 34 is opened, and the burned gas is exhausted in the combustion chamber 26. Further, when the piston 20 moves to the air chamber 28 side, the scavenging holes 36 closed by the piston 20 are gradually opened, and fresh air is taken into the combustion chamber 26.

  On the other hand, the air chamber 28 is compressed by the piston 20 that moves due to the combustion pressure. When the piston 20 sufficiently compresses the air chamber 28, this time, the piston 20 is pushed back to the combustion chamber 26 side by the force (repulsive force) of the compressed air in the air chamber 28 expanding. Thereby, the expansion of the air chamber 28 and the compression of the combustion chamber 26 are started. In the present embodiment, the pressure receiving area of the air chamber 28 is larger than the pressure receiving area of the combustion chamber 26. Therefore, even if the internal pressure of the air chamber 28 is relatively small, the repulsive force (internal pressure × pressure receiving area) received by the entire piston 20 can be increased. As a result, the temperature rise of the air chamber 28 accompanying compression can be reduced, heat loss is reduced, and the system efficiency of the free piston generator 10 is improved.

  As the piston 20 moves to the combustion chamber 26 side, the scavenging hole 36 is closed. Further, the exhaust valve 34 is also closed, and the combustion chamber 26 is sealed. In this state, fuel is injected, and the combustion chamber 26 is filled with a mixture of fresh air and fuel. When the piston 20 sufficiently compresses the combustion chamber 26, the air-fuel mixture is ignited by the spark plug 32. Then, the piston 20 again moves to the air chamber 28 side, and the air chamber 28 is compressed. Thereafter, the same cycle, that is, the cycle of compression / compression of the combustion chamber 26 and the expansion (compression stroke) of the air chamber 28, the mixture combustion, and the expansion of the combustion chamber 26 and the compression of the air chamber 28 (expansion stroke) are repeated. Then, in the process of this cycle, the magnetic field around the permanent magnet 24 embedded in the piston 20 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 present embodiment, spark ignition is exemplified, but compression ignition combustion (diesel combustion) may be used, or premixed compression self-ignition combustion may be used. In the above description, the power generation unit 14 using the permanent magnet 24 is shown. However, the power generation unit 14 may be configured not to use the permanent magnet 24 by applying a reluctance synchronous motor that does not use the permanent magnet 24.

  Here, in the present embodiment, as described above, the two engine units 16 are arranged on the same straight line and symmetrically so that the air chamber 28 is located at the center. In driving, the two pistons 20 are driven in synchronism with each other so as to move symmetrically. That is, at the timing when the piston 20 on the right side of the drawing moves to the right and starts to compress the combustion chamber 26, the piston 20 on the left side of the drawing also moves to the left and starts to compress the combustion chamber 26. At the timing when the mixture is ignited at 26, the mixture is also ignited in the combustion chamber 26 on the left side of the drawing.

  In this way, by executing the same stroke at the same timing in the two engine units 16, the two pistons 20 move symmetrically. Thus, the vibration force generated in one engine unit 16 can be canceled by the vibration force generated in the other engine unit 16, and vibration of the entire power generation unit can be canceled.

  Here, in order to fully exhibit the vibration canceling effect, the two pistons 20 are required to be accurately synchronized. In order to perform efficient power generation, it is required to set the compression ratio to a suitable value according to the situation and the fuel type.

  In the present embodiment, in view of this problem, the drive status of the drive of the free piston generator 10 is monitored, and according to this drive status, the balance between the fuel injection amount and the power generation load, the air amount of the air chamber 28, the combustion chamber At least one of the intake air amount to 26, ignition timing, fuel injection timing, and fuel injection rate is adjusted, and the motion frequency of the piston 20 and the compression ratio during combustion are adjusted.

  More specifically, in this embodiment, the motion cycle of the piston 20 and the compression ratio at the time of combustion are adjusted. The movement period of the piston 20 is mainly adjusted in order to synchronize the two engine units 16 accurately. That is, the control unit 50 monitors whether or not the phases of the two pistons 20 are in agreement based on the piston position detected by the piston position detection means 40. When the phases of the two pistons 20 are deviated, the movement cycle of one of the pistons 20 is changed and adjusted so as to have the same phase as the other piston 20.

  Moreover, the control part 50 acquires a compression ratio based on the piston position etc. which were detected by the piston position detection means 40, and compares the obtained compression ratio with the target compression ratio range. Then, the compression ratio is increased or decreased so that the compression ratio falls within the target compression ratio range. Further, not only the increase / decrease according to the comparison with the target compression ratio range as described above, but also the compression ratio may be increased / decreased according to the driving situation. For example, when knocking is detected in the case of the spark ignition method, the control unit 50 may reduce the compression ratio so as to eliminate the knocking. In the case of the premixed compression self-ignition system, the combustion timing in which the combustion noise and the thermal efficiency fall within a desirable range varies depending on the type of fuel used. Therefore, the compression ratio may be adjusted according to the type of fuel used so that a suitable combustion timing can be obtained.

  Thus, in this embodiment, the movement cycle of the piston 20 and the compression ratio during combustion are variably adjusted as necessary. These variable adjustments are realized by adjusting at least one of the balance between the fuel injection amount and the power generation load, the air amount in the air chamber 28, and the intake air amount into the combustion chamber 26. Hereinafter, the reason why the motion period and the compression ratio can be adjusted by adjusting these parameters will be described.

  First, the relationship between the fuel injection amount and the power generation load balance, the motion cycle, and the compression ratio will be described. As a result of analyzing the motion of the free piston generator 10 by numerical simulation, the applicant of the present application has obtained that the motion cycle and the compression ratio can be varied according to the balance between the fuel injection amount and the power generation load. Hereinafter, the result of the numerical simulation will be described in detail.

  FIG. 2 is a diagram showing an analysis model used in this numerical simulation. Moreover, FIG. 3 is a figure which shows the power generation efficiency of the linear generator used for the said analysis, and FIG. 4 is a table | surface which shows calculation conditions.

  As shown in FIG. 2, in this embodiment, the free piston generator 10 having only one power generation device 12 is used as an analysis model. In this analysis model, the pressure receiving area of the air chamber 28 is Aair, and the pressure receiving area of the combustion chamber 26 is Acomb (Aair> Acomb).

  In order to model the ignition / combustion process, a multi-step Shell model was used in the ignition process. In this simulation, premixed compression self-ignition capable of realizing low NOx characteristics is premised. The heat release from the combustion chamber 26 and the air chamber to the wall is modeled using the Woschni equation. The power generation efficiency of the linear power generation unit 14 is based on the map shown in FIG.

In this analysis model, the power generation load is controlled to be proportional to the piston speed. That is, when the displacement of the piston 20 is x, the time is t, and the power generation load (braking force by power generation) is F, control is performed so as to satisfy Formula 1. In the present embodiment, the coefficient c in Equation 1 is referred to as a “power generation load coefficient” and is used as an index for adjusting the power generation load.

Next, consider the movement of the piston 20. The motion of the piston 20 can be obtained by solving the equation of motion of Equation 2. In Equation 2, m is the mass of the piston 20, Pcomb is the pressure in the combustion chamber 26, Pair is the pressure in the air chamber 28, and fric is the frictional force.

  FIG. 5 is a graph schematically showing the motion mode of the free piston generator 10 solved as described above. The horizontal axis represents the fuel injection amount, and indicates the amount of fuel energy input to the free piston generator 10. The vertical axis represents the power generation load coefficient c described above, which is an index for determining the amount of energy extracted from the free piston generator 10.

  The region above the boundary line A in FIG. 5 means that the power generation load is larger than the input energy, and is a “motion stop” region in which the motion of the piston 20 cannot be continued. The region on the upper right side of the boundary line B in FIG. 5 exceeds the energy that can be absorbed by the free piston generator 10, and is a region that cannot be operated due to the limitation of the power generation amount of the free piston generator 10. Therefore, the “operable region” in which the free piston generator 10 can actually operate is a region below both the boundary line A and the boundary line B (the hatched region in FIG. 5).

  FIG. 6 and FIG. 7 show the results of calculating various characteristic values in this operable region by combining the combustion cycle simulation and the motion simulation. In FIG. 6, (a) is the indicated thermal efficiency, (b) is the amount of power generation, (c) is the motion frequency, and (d) is a contour map of the compression ratio during operation. FIGS. 7A and 7B are enlarged views of FIGS. 6C and 6D, respectively.

  In the present embodiment, basically, the fuel injection amount and the power generation load coefficient are adjusted along the reference line L in FIGS. 7A and 7B, and the free piston generator 10 is driven. The reference line L is a line that substantially coincides with the boundary line between the operable range and the motion stop range. At this time, when it is desired to increase the power generation amount, the fuel injection amount and the power generation load coefficient are increased along the reference line L, and when it is desired to decrease the power generation amount, the fuel injection amount and the power generation load coefficient are increased along the reference line L. Lower. In other words, when only the power generation amount is desired to be changed, the values of both the power generation load coefficient and the fuel injection amount are changed while keeping the ratio between the power generation load coefficient and the fuel injection amount substantially constant.

  On the other hand, when it is desired to increase the motion frequency or the compression ratio, the fuel injection amount is increased and the power generation load coefficient is decreased, so that the injection amount and the power generation load coefficient are separated from the reference line L. In other words, the motion frequency and the compression ratio can be increased by increasing the ratio of the fuel injection amount to the power generation load coefficient. The reason for this control will be described.

  The free piston generator 10 is naturally required to be able to change the efficiency of the entire system (thermal efficiency of the engine portion × power generation efficiency of the generator portion) as necessary.

  Based on such a viewpoint, referring to the contour map of the indicated thermal efficiency in FIG. 6A, in order to obtain high efficiency, the fuel injection amount and the power generation load coefficient are stored in the regions E1 and E2 in FIG. 6A. It turns out that is desirable. For this reason, it is understood that the fuel injection amount and the power generation load coefficient are desirably adjusted along the reference line L shown in FIGS. 6B, it can be seen that by adjusting the fuel injection amount and the power generation load coefficient along the line L, the power generation amount can be appropriately increased or decreased.

  Further, as long as the motion frequency and compression ratio contour maps in FIGS. 6C and 6D (FIGS. 7A and 7B) are referred to, the fuel injection amount and the power generation load coefficient along the reference line L are determined. It can be seen that even if the adjustment is made, the motion frequency and the compression ratio hardly change. That is, as long as the fuel injection amount and the power generation load coefficient are adjusted along the reference line L, the power generation amount can be adjusted without changing the motion frequency and the compression ratio.

  On the other hand, if it is necessary to change the motion frequency or compression ratio due to a phase shift between the two pistons 20 or misfire, the fuel injection amount is increased, the power generation load coefficient is decreased, or both It can be seen that the motion frequency increases and the compression ratio increases by executing.

  Therefore, in this embodiment, while adjusting the fuel injection amount and the power generation load coefficient along the reference line L defined in advance, the fuel injection amount of the fuel injection amount must be changed when it is necessary to change the motion frequency or the compression ratio. At least one of an increase and a decrease in the power generation load coefficient is executed.

  In this embodiment, considering the efficiency and in-cylinder pressure, the reference line is a boundary line between the operable range and the motion stop range, but by setting the more operable range side line as the reference line, Adjustment in the direction of lowering the motion frequency and the compression ratio is also possible. In any case, it can be seen from these simulation results that the motion frequency and the compression ratio can be adjusted by adjusting the power generation load coefficient and the fuel injection amount. Note that the engine output changes by changing the ignition timing in a spark ignition engine and the fuel injection timing and fuel injection rate in a compression ignition engine. Therefore, changing these has the same effect as changing the fuel injection amount. That is, bringing the ignition timing closer to the most efficient timing (in general, earlier) corresponds to increasing the fuel injection amount. Similarly, changing the fuel injection rate so as to increase the thermal efficiency (in general, increasing the injection rate) corresponds to increasing the fuel injection amount. In addition to increasing or decreasing the fuel injection rate on average, there is an adjustment method in which the shape of the fuel injection rate is changed (for example, the first half is lowered).

  Next, the relationship between the air amount in the air chamber 28 and the intake air amount in the combustion chamber 26, the motion frequency, and the compression ratio will be described. FIG. 8 is a table showing the relationship between the initial pressure of the air chamber 28 and the initial pressure of the combustion chamber 26 and the motion frequency obtained as a result of analyzing the motion of the free piston generator 10 by numerical simulation.

  The preconditions for this numerical simulation are the same as those described above, and are performed using the analysis model shown in FIG. 2, the power generation efficiency shown in FIG. 3, and the calculation conditions shown in FIG. The power generation load coefficient is a constant value.

  Here, the initial pressure of the air chamber 28 is a pressure when the volume of the air chamber 28 is maximized at the top dead center of the piston 20 and the pressure of the air chamber 28 is minimized. The initial pressure of the combustion chamber 26 is a pressure when the volume of the combustion chamber 26 is maximized and the pressure of the combustion chamber 26 is minimized at the bottom dead center of the piston 20. In the case of a 4-cycle engine, the initial pressure in the combustion chamber 26 substantially corresponds to the pressure obtained by subtracting the pressure drop due to the flow resistance at the intake valve during intake from the intake pipe pressure, and in the case of a 2-cycle period, scavenging is performed. This substantially corresponds to the pressure obtained by subtracting the pressure drop due to the suction resistance at the scavenging hole 36 from the pressure. Changing the initial pressure in the air chamber 28 and the initial pressure in the combustion chamber 26 corresponds to changing the amount of gas trapped in those chambers.

  As is apparent from the table of FIG. 8, it can be seen that when the initial pressure of the air chamber 28 is increased (column B in the table), the motion frequency increases compared to the reference state (column A in the table). This is considered to be caused by an increase in the spring constant of the air chamber 28 that functions as a spring portion. In the present embodiment, by taking advantage of this characteristic, the motion frequency is increased or decreased by increasing or decreasing the initial pressure of the air chamber 28. Further, the compression ratio is adjusted to a desired value by increasing or decreasing the motion frequency. The initial pressure in the air chamber 28 can be adjusted by a pressure adjusting valve provided in the air chamber 28.

  Next, the relationship between the initial pressure of the combustion chamber 26 and the motion frequency will be examined. As is apparent from the table of FIG. 8, it can be seen that when the initial pressure of the combustion chamber 26 is increased (C column in the table), the motion frequency changes compared to the reference state (A column of the table). However, unlike the initial pressure of the air chamber 28, when the initial pressure of the combustion chamber 26 is increased, the motion frequency does not always increase. This is due to the following reason.

  Even in the combustion chamber 26, if the initial pressure is increased, the repulsive force of the air spring is increased, and an action to increase the motion frequency occurs. On the other hand, in the case of the premixed compression auto-ignition method as in this simulation, the change in the combustion timing and the heat generation rate pattern due to the change in the equivalence ratio also affects the motion frequency. As described above, when the initial pressure in the combustion chamber 26 is changed, a change in the combustion state also occurs. Therefore, the increase in the combustion chamber initial pressure does not necessarily increase the motion frequency.

  Therefore, in the case of the combustion chamber initial pressure (the amount of intake air in the combustion chamber 26), the motion frequency cannot be increased or decreased simply by increasing or decreasing the pressure. However, as shown in FIG. 8, it is clear that changing the initial pressure in the combustion chamber also changes the motion frequency. Therefore, when adjusting the motion frequency with the combustion chamber initial pressure, it is desirable to obtain data indicating the correlation between the combustion chamber initial pressure and the motion frequency in advance or to perform model-based control. . Then, if necessary, the compression ratio is adjusted to a desired value by increasing or decreasing the motion frequency. The initial pressure in the combustion chamber is adjusted by adjusting the pressure in the intake pipe (in the case of a 4-cycle engine) and the scavenging chamber (in the case of a 2-cycle engine) with a supercharger, a scavenging pump, and an intake throttle valve. The

  As is clear from the above description, in this embodiment, the balance between the fuel injection amount and the power generation load (power generation load coefficient), the air amount of the air chamber 28 (initial pressure), and the intake air amount of the combustion chamber 26 (initial pressure). At least one of these is adjusted to adjust the motion frequency or the compression ratio. Thereby, also in the free piston type generator 10 without mechanical restraint, a desired motion frequency and compression ratio can be obtained, and as a result, improvement in efficiency and reduction in vibration can be achieved. In the premixed compression auto-ignition method, the optimal combustion timing varies depending on the type of fuel used, but in this embodiment, the compression ratio and thus the combustion timing are changed by changing the balance between the fuel injection amount and the power generation addition. Therefore, it is possible to cope with various fuel types without changing the configuration of the free piston generator 10.

  As is apparent from the above description, in the present embodiment, a power generation load coefficient that is a value obtained by dividing the power generation load by the piston speed is used as an adjustment index of the power generation load. Therefore, when the free piston generator 10 is controlled, it is necessary to change the power generation load according to the piston speed so that the power generation load coefficient becomes a desired value. The change of the power generation load in accordance with the piston speed can be performed by, for example, PWM control using an inverter. As another form, after rectifying with a diode bridge, the power generation load can be changed by adjusting the boosting amount with a DC / DC converter or changing the value of the load resistance.

  Further, the power generation load coefficient may be changed for purposes other than the change of the motion frequency and the compression ratio. For example, in order to reduce the moving speed of the piston 20 in the vicinity of the top dead center and lengthen the residence time of the piston 20 in the vicinity of the top dead center, the integrated value of the power generation load in the compression stroke is integrated with the integration of the power generation load in the expansion stroke. You may adjust electric power generation load so that it may become larger than a value. Specifically, for example, the power generation load coefficient in the compression stroke may be made larger than the power generation load coefficient in the expansion stroke. FIG. 9 is a diagram showing a movement mode of the piston 20 at this time. In FIG. 9, the thick solid line indicates the movement of the piston 20 during the expansion stroke, and the thick broken line indicates the movement of the piston 20 during the compression stroke. In this case, the piston 20 moves from the top dead center (speed zero point) to the air chamber 28 side, and finally reaches the bottom dead center (speed zero point) at the point O (speed zero point) −. It passes through point A1-point O. Subsequently, in the compression stroke that moves from the bottom dead center (zero speed point) to the combustion chamber 26 side and finally reaches the top dead center (zero speed point), the piston 20 is point O-point A2-point O. Will be passed sequentially. At this time, in the compression stroke, the power generation load coefficient is higher than in the expansion stroke, and the braking force acting on the piston 20 is large. As a result, the speed approaching the top dead center becomes slow, and as a result, the piston 20 residence time near the top dead center can be kept long.

  As another form, the power generation load may be constant (the power generation load coefficient is inversely proportional to the speed) in the compression stroke as shown in FIG. By setting it as this structure, the motion of piston 20 near a top dead center is controlled, and an equal volume can be raised. Thus, it is possible to improve the thermal efficiency and reduce the size of the free piston generator 10. Also in this configuration, the braking force acting on the piston 20 can be increased in the compression stroke, and as a result, the piston 20 residence time near the top dead center can be kept long. When the power generation load coefficient is changed according to the stroke or the like as described above, when it is desired to avoid the change of the motion frequency or the compression ratio, the relationship between the fuel injection amount and the power generation load coefficient is represented by the reference line L in FIG. Thus, the fuel injection amount may be changed in accordance with the change in the power generation load coefficient.

  Further, in a region where the piston speed is low, the power generation load may be zero and power generation may be stopped. That is, as is clear from the power generation efficiency line map of FIG. 3 and the like, the power generation efficiency is low when the piston speed is low. Therefore, it is also desirable to stop power generation when the piston speed is equal to or lower than a specific threshold. Thereby, efficiency can be improved.

  Further, in the present embodiment, as shown in FIG. 1, the free piston generator 10 in which the two power generation devices 12 are coaxially arranged symmetrically so that the air chamber 28 is located at the center is illustrated. If it is a type generator, the composition may be changed suitably.

  For example, as shown in FIG. 11, the free piston generator 10 in which the two power generation devices 12 are arranged symmetrically so that the combustion chamber 26 is positioned in the center instead of the air chamber 28 may be targeted. With this configuration, there is an advantage that a part of the valve mechanism for gas exchange can be shared by the two power generation devices 12. Moreover, it is good also considering the free piston type generator 10 which consists of the single electric power generating apparatus 12 as another form. That is, as shown in FIG. 12, the present invention may be applied to the case where only the single power generation device 12 is used, instead of arranging the two power generation devices 12 symmetrically. In this case, since only one piston 20 exists, it is naturally not necessary to match the phases of the two pistons 20. However, even in this case, it is necessary to adjust the compression ratio and the compression timing, so the present invention is sufficiently effective. Further, in the above-described embodiment, the form in which the pressure receiving area of the air chamber 28 is larger than the pressure receiving area of the combustion chamber 26 is exemplified, but as shown in FIG. Naturally, 10 may be the target. Furthermore, in this embodiment, the air spring constituted by the air chamber 28 is used as a spring portion that pushes back the piston 20, but a free piston type power generation using a mechanical spring instead of the air chamber 28 (air spring). The machine 10 may be targeted. In this case, the motion frequency and the compression ratio may be adjusted by adjusting at least one of the balance between the power generation load and the combustion injection amount and the intake air amount of the combustion chamber 26.

  DESCRIPTION OF SYMBOLS 10 Free piston type generator, 12 Power generator, 14 Power generation unit, 16 Engine unit, 18 Cylinder, 20 Piston, 22 Power generation coil, 24 Permanent magnet, 26 Combustion chamber, 28 Air chamber, 30 Fuel injection valve, 32 Spark plug, 34 exhaust valve, 36 scavenging hole, 38 pressure regulating valve, 40 piston position detecting means, 50 control unit.

In addition, a technique has been proposed in which two pistons are coaxially arranged symmetrically to reduce vibration. In order to reduce vibration by this method, it is required that the movements of the two pistons be completely symmetrical (the movement period is synchronized ) . Patent Document 2 and Non-Patent Documents 1 and 2 disclose techniques using a mechanical link mechanism and gears to synchronize two pistons. According to such a technique, the two pistons can be synchronized, and as a result, vibration can be reduced. However, these techniques cause problems such as increased friction and inertial mass, and significantly reduce the efficiency of free piston engines.

In a preferred embodiment, prior SL engine unit is arranged symmetrically coaxially, said control means adjusts the movement frequency of the piston to match the driving phases of the two engine units.

In another preferred embodiment, the control means, when adjusting the power generation load, using a generator load as an adjustment index generation load coefficient is divided by the piston speed. In this case, it is preferable that the control unit increases or decreases the power generation amount by increasing or decreasing the values of the power generation load coefficient and the fuel injection amount while maintaining the ratio between the power generation load coefficient and the fuel injection amount substantially constant. . It is also desirable that the control unit increases the value of the motion frequency and the compression ratio by increasing the ratio of the fuel injection amount to the power generation load coefficient. It is also preferable that the control unit adjusts the power generation load so that the integrated value of the power generation load in the compression stroke is larger than the integrated value of the power generation load in the expansion stroke.

It is a lineblock diagram of the free piston type generator which is an embodiment of the present invention. It is a figure which shows an analysis model. It is a power generation efficiency map used for analysis. It is a table | surface which shows the precondition of an analysis. It is the graph which showed typically the movement mode of the free piston type generator. It is a figure which shows a simulation result. FIG. 7 is an enlarged view of ( c ) and ( d ). It is a table | surface which shows the relationship between the initial pressure of an air chamber and the initial pressure of a combustion chamber, and a motion frequency obtained by simulation. It is a figure which shows the movement aspect of a piston. It is a figure which shows the movement aspect of a piston. It is a block diagram of another free piston type generator. It is a block diagram of another free piston type generator.

Here, in the present embodiment, the inner diameter of the cylinder 18 in the air chamber 28 is made larger than the inner diameter of the cylinder 18 in the combustion chamber 26, and the pressure receiving area of the air chamber 28 (the area in contact with the end face of the piston 20) is set as the combustion chamber. 26 is larger than the pressure receiving area. With such a configuration, even if the degree of compression of the air chamber 28 is low, a sufficient repulsive force can be obtained. That is, the force pushing the piston 20 of the air chamber 28 is a value obtained by multiplying the internal pressure of the air chamber 28 by the pressure receiving area of the piston 20. Therefore, a larger pressing force (repulsive force) can be obtained as the pressure receiving area is larger. In other words, if the pressure receiving area is large, a sufficient repulsive force can be obtained even if the internal pressure is low. As a result, it is possible to reduce the temperature rise associated with the compression of the air chamber 28, thereby reducing heat loss and preventing oil ignition .

Moreover, when it is set as this structure, the surface area of the outer periphery of piston 20 with respect to the bore diameter of the combustion chamber 26 can be enlarged. By increasing the area of the outer surface of the piston 20 where the permanent magnet 24 is installed, the area of the permanent magnet 24 that can be installed can be increased, and as a result, the power generation output can be increased.

The piston position detection means 40 is not particularly limited as long as it can detect at least that the piston 20 has reached a specific position. Therefore, for example, the position of the piston 20 may be detected over the entire stroke, such as an optical linear encoder or a magnetostrictive linear displacement sensor. As another form, one or more position sensors (such as an optical sensor or a gap sensor) detect the sensor passage timing of the piston 20, and based on the passage timing and the sensor installation position (known), the piston 20 The motion frequency may be calculated. Further, the obtained arrival timing and sensor installation position may be collated with a map of motion characteristics prepared in advance, a motion equation may be solved, or applied to a simple model. With such a configuration, the arrival timing at the top dead center / bottom dead center, the position of the top dead center / bottom dead center (the position changes in a free piston engine), the compression ratio, and the position of the piston 20 in the entire stroke range. Can also be obtained. Further, in order to enable more accurate position estimation, friction loss may be taken into consideration from the lubricating oil temperature and the water temperature.

The control unit 50 controls driving of the two engine units 16 and the power generation unit 14 . The control unit 50 of the present embodiment adjusts at least one of the power generation load, the fuel injection amount, the air amount in the air chamber 28, and the intake air amount to the combustion chamber 26 in order to adjust the motion frequency and the compression ratio during combustion. Adjust. The reason for adjusting these parameters will be described in detail later.

On the other hand, the air chamber 28 is compressed by the piston 20 that moves due to the combustion pressure. When the piston 20 sufficiently compresses the air chamber 28, this time, the piston 20 is pushed back to the combustion chamber 26 side by the force (repulsive force) of the compressed air in the air chamber 28 expanding. Thereby, the expansion of the air chamber 28 and the compression of the combustion chamber 26 are started. In the present embodiment, the pressure receiving area of the air chamber 28 is larger than the pressure receiving area of the combustion chamber 26. Therefore, even if the internal pressure of the air chamber 28 is relatively small, the repulsive force (internal pressure × pressure receiving area) received by the entire piston 20 can be increased. As a result, the temperature rise of the air chamber 28 accompanying compression can be reduced, heat loss is reduced, and the system efficiency of the free piston generator 10 is improved. In addition, ignition of oil mixed in the air chamber 28 can be prevented.

Thus, in this embodiment, the movement cycle of the piston 20 and the compression ratio during combustion are variably adjusted as necessary. These variable adjustments are realized by adjusting at least one of the balance between the fuel injection amount and the power generation load, the air amount in the air chamber 28, the intake air amount into the combustion chamber 26, and the ignition timing . Hereinafter, the reason why the motion period and the compression ratio can be adjusted by adjusting these parameters will be described.

The region above the boundary line A in FIG. 5 means that the power generation load is larger than the kinetic energy of the piston driven by the input energy , and the “motion stop” region in which the motion of the piston 20 cannot be continued. Become. The area on the upper right side of the boundary line B in FIG. 5 is an area in which the kinetic energy of the piston exceeds the energy that can be absorbed by the free piston generator 10 and cannot be operated due to the power generation limit of the free piston generator 10. Become. Therefore, the “operable region” in which the free piston generator 10 can actually operate is a region below both the boundary line A and the boundary line B (the hatched region in FIG. 5).

Naturally, the free piston generator 10 is required to be able to change the power generation output of the entire system (the output of the engine unit x the power generation efficiency of the generator unit) as necessary.

Therefore, in the present embodiment, the fuel injection amount and the power generation load coefficient are adjusted along the predetermined reference line L. On the other hand, if it is necessary to change the motion frequency or the compression ratio, the fuel injection amount is adjusted . even without least the standby power generation load factor to perform one of the increase and decrease.

In this embodiment, considering the efficiency and in-cylinder pressure, the reference line is a boundary line between the operable range and the motion stop range, but by setting the more operable range side line as the reference line, Adjustment in the direction of lowering the motion frequency and the compression ratio is also possible. In any case, it can be seen from these simulation results that the motion frequency and the compression ratio can be adjusted by adjusting the power generation load coefficient and the fuel injection amount. Note that the engine output changes by changing the ignition timing in a spark ignition engine and the fuel injection timing and fuel injection rate in a compression ignition engine. Therefore, changing these has the same effect as changing the fuel injection amount. In other words, bringing the ignition timing to the most efficient time (generally be accelerated to) has the same effect as that increasing the amount of fuel injection. Similarly, changing the fuel injection rate so as to increase the thermal efficiency (in general, increasing the injection rate) corresponds to increasing the fuel injection amount. In addition to increasing or decreasing the fuel injection rate on average, there is an adjustment method in which the shape of the fuel injection rate is changed (for example, the first half is lowered).

Here, the initial pressure of the air chamber 28 is a pressure when the volume of the air chamber 28 is maximized at the top dead center of the piston 20 and the pressure of the air chamber 28 is minimized . The initial pressure of the combustion chamber 26 is a pressure when the volume of the combustion chamber 26 is maximized and the pressure of the combustion chamber 26 is minimized at the bottom dead center of the piston 20. In the case of a 4-cycle engine, the initial pressure in the combustion chamber 26 substantially corresponds to the pressure obtained by subtracting the pressure drop due to the flow resistance at the intake valve during intake from the intake pipe pressure, and in the case of a 2-cycle period, scavenging is performed. This substantially corresponds to the pressure obtained by subtracting the pressure drop due to the suction resistance at the scavenging hole 36 from the pressure. Changing the initial pressure in the air chamber 28 and the initial pressure in the combustion chamber 26 corresponds to changing the amount of gas trapped in those chambers.

As is clear from the above description, in this embodiment, the balance between the fuel injection amount and the power generation load (power generation load coefficient), the air amount of the air chamber 28 (initial pressure), and the intake air amount of the combustion chamber 26 (initial pressure). At least one of these is adjusted to adjust the motion frequency or the compression ratio. Thereby, also in the free piston type generator 10 without mechanical restraint, a desired motion frequency and compression ratio can be obtained, and as a result, improvement in efficiency and reduction in vibration can be achieved. In the premixed compression auto-ignition method, the optimal combustion timing differs depending on the type of fuel used, but in this embodiment, the compression ratio and thus the combustion timing are changed by changing the balance between the fuel injection amount and the power generation load. Therefore, it is possible to cope with various fuel types without changing the configuration of the free piston generator 10.

As another form, the power generation load may be constant (the power generation load coefficient is inversely proportional to the speed) in the compression stroke as shown in FIG. By setting it as this structure, the motion of piston 20 near a top dead center is suppressed , and an equal volume can be raised. Thus, it is possible to improve the thermal efficiency and reduce the size of the free piston generator 10. Also in this configuration, the braking force acting on the piston 20 can be increased in the compression stroke, and as a result, the piston 20 residence time near the top dead center can be kept long. When the power generation load coefficient is changed according to the stroke or the like as described above, when it is desired to avoid the change of the motion frequency or the compression ratio, the relationship between the fuel injection amount and the power generation load coefficient is represented by the reference line L in FIG. Thus, the fuel injection amount may be changed in accordance with the change in the power generation load coefficient.

Claims (9)

A free-piston generator that generates power as the piston reciprocates,
An engine unit in which a combustion chamber and a spring part are provided on both sides of the piston, and the piston reciprocates by a combustion pressure when the fuel is burned in the combustion chamber and a restoring force of the spring part compressed by the piston;
A power generation unit that generates power with the reciprocating motion of the piston;
Control means for controlling driving of the engine unit and the power generation unit;
With
The control means includes at least one of a balance between a fuel injection amount injected into the combustion chamber and a power generation load, a repulsive force of a spring portion, an intake air amount into the combustion chamber, a spark ignition timing, a fuel injection timing, and a fuel injection rate. To adjust the piston motion frequency or compression ratio during combustion.
A free piston generator. The free piston generator according to claim 1,
The control means includes a free-piston generator in which the engine units are arranged symmetrically on the same axis, and the motion frequency of the piston is adjusted so that the drive phases of the two engine units coincide with each other. . The free piston generator according to claim 1,
Combustion in the combustion chamber is performed by a premixed compression self-ignition method in which a mixture of fuel and air is compressed to a high temperature and self-ignited.
The free piston generator, wherein the control means adjusts the compression ratio at the time of combustion so that the combustion timing of the fuel becomes a predetermined time. The free piston generator according to claim 1,
Combustion in the combustion chamber is performed by spark ignition of a mixture of fuel and air,
The free-piston generator, wherein the control means reduces the compression ratio when knocking is detected. A free piston generator according to any one of claims 1 to 4,
The spring portion is an air chamber that is provided on the opposite side of the combustion chamber across the piston and changes in volume as the piston reciprocates, and the piston is combusted by the repulsive force of the indoor gas when compressed. It consists of an air chamber that pushes to the room side,
The free piston generator, wherein the control means increases or decreases the repulsive force of the spring portion by increasing or decreasing the amount of air in the air chamber. A free piston generator according to any one of claims 1 to 5,
In the adjustment of the power generation load, the control unit uses a power generation load constant that is a value obtained by dividing the power generation load by the piston speed as an adjustment index. A free piston generator according to claim 6,
The controller is configured to increase or decrease the power generation amount by increasing or decreasing the values of the power generation load coefficient and the fuel injection amount while maintaining the ratio between the power generation load coefficient and the fuel injection amount substantially constant. Piston generator. A free piston generator according to claim 6 or 7,
The said control part raises the value of a movement frequency and a compression ratio by raising the ratio of the fuel injection quantity with respect to the said electric power generation load coefficient, The free piston type generator characterized by the above-mentioned. A free piston generator according to any one of claims 1 to 9,
The said control part is a free piston type generator which adjusts the said electric power generation load so that the integrated value of the electric power generation load in a compression stroke may become larger than the integrated value of the electric power generation load in an expansion stroke.

Images