JP3783706B2 - Stirling engine and hybrid system including the same - Google Patents

Description

  The present invention relates to a Stirling engine and a hybrid system including the same, and more particularly to a Stirling engine capable of reducing friction loss and a hybrid system including the same.

  The Stirling engine can be expected to have high thermal efficiency, and since it is an external combustion engine that heats the working fluid from the outside, it can utilize various low temperature difference alternative energy such as solar, geothermal, exhaust heat regardless of the heat source, It has the advantage of helping to save energy.

  Conventionally, a Stirling engine as shown in FIG. 18 is known. In the machine room 101, a high temperature side cylinder 102 and a low temperature side cylinder 103 are projected, a heater 104 is connected to the upper part of the high temperature side cylinder 102, and a cooler 105 is connected to the low temperature side cylinder 103. The heater 104 and the cooler 105 are connected to each other via the regenerator 106. An expansion piston 107 and a compression piston 108 are reciprocally disposed in the high temperature side cylinder 102 and the low temperature side cylinder 103, respectively, and both the pistons 107 and 108 are connected to the crankshaft 111 by connecting rods 109 and 110, respectively. The pistons 107 and 108 are configured to reciprocate with a predetermined phase difference, for example, 90 °.

A high temperature side cylinder 102, a low temperature side cylinder 103, a heater 104, a cooler 105, a regenerator 106, and a working fluid such as He, H ₂ , or N ₂ are enclosed in the piping, and the high temperature side cylinder The expansion space at the top of 102 and the compression space at the top of the low temperature side cylinder 103 are sealed by piston rings 112 and 113 mounted on the pistons 107 and 108, respectively.

  When the working fluid is heated by the heater 104 by a heat source (not shown), it expands and the expansion piston 107 is pressed down, and the crankshaft 111 is rotated. When the expansion piston 107 moves to the ascending stroke, the working fluid passes through the heater 104 and is transferred to the regenerator 106, where heat is applied to the heat storage material filled in the regenerator 106, and to the cooler 105. And is cooled, and compressed as the compression piston 108 moves upward. The working fluid compressed in this way flows to the heater 104 side, increases the temperature while taking heat away from the heat storage material in the regenerator 106, and flows into the heater 104, where the heat source again. Is heated and expanded.

  By the way, Japanese Patent Laid-Open No. 4-31656 (Patent Document 1) discloses a Stirling engine that guides a piston pin by a Watt Z-shaped approximate linear link mechanism.

  Japanese Patent Laid-Open No. 2002-89985 (Patent Document 2) discloses a technique using a gas bearing (gas bearing) between a piston and a cylinder. That is, in Patent Document 2, a floating force is generated in the piston by the gas supplied from the orifice formed in the gas bearing pad of the cylinder toward the piston, and the piston and the cylinder are in a non-contact state or light load. It is described that the frictional force disappears or becomes smaller by setting the state.

JP-A-4-31656 JP 2002-89985 A JP-A-5-256367

The Stirling engine has a problem that internal friction is large.
In order to ensure the output of the Stirling engine, it is necessary to increase the pressure of the working fluid in the cylinder. Therefore, it is necessary to reinforce the seal. In particular, the reinforcement of the seal by the piston ring causes a further increase in friction. Since the friction is large, it is necessary to increase the pressure of the high heat source and the working fluid in order to ensure a sufficient output. Further, there is a problem that the lubricating oil of the piston ring enters the heat exchanger and the heat exchanger deteriorates.

  There are many types of friction loss in Stirling engines, but the largest one is friction loss between the piston and the cylinder. The above Patent Document 1 does not disclose any friction loss between the piston and the cylinder, and the friction reduction for improving the efficiency of the Stirling engine is insufficient. In particular, when used in an environment where it is difficult to secure a sufficient amount of heat from the heat source, for example, when exhaust gas from an internal combustion engine of a vehicle is used as a heat source, friction is reduced as much as possible. There is a need.

  Further, the gas bearing has a low pressure resistance against side force. In particular, the gas bearing that is supported by the air pressure distribution of the minute clearance between the object to be supported without forcibly supplying the gas rather than the gas bearing forcibly supplying the gas employed in Patent Document 2 above. The pressure resistance against side force is lower. For this reason, when the piston is supported by the gas bearing, it is necessary to prevent the side force from being applied to the piston. However, Patent Document 2 does not take any measures against the side force of the piston. In particular, when using a gas bearing supported by the above air pressure distribution, it is necessary to take measures against the side force of the piston.

An object of the present invention is to provide a Stirling engine capable of reducing friction loss and a hybrid system including the same.
Another object of the present invention is to provide a Stirling engine and a hybrid system including the Stirling engine that can reduce friction loss and in which the heat exchanger does not deteriorate due to lubricating oil such as a piston ring.

A Stirling engine of the present invention is a Stirling engine that uses an exhaust system of an internal combustion engine as a heat source, and a piston that reciprocates in the cylinder while maintaining airtightness through a gas bearing between the cylinder, An approximate linear mechanism that is connected directly or indirectly to the piston and is configured to perform an approximate linear motion when the piston reciprocates in the cylinder, and the gas bearing is non-contact with pressure distribution The above-mentioned piston is supported .

  In the present invention, the piston mechanism of the Stirling engine is in a ringless (no piston ring) and oilless (non-lubricated) state to prevent deterioration of the heat exchanger due to lubricating oil while reducing friction loss. The structure of a gas bearing is adopted. The approximate linear mechanism causes an approximate linear motion when the piston reciprocates in the cylinder. Therefore, the side force of the piston is substantially eliminated. Therefore, the approximate linear mechanism has an organic meaning in combination with a gas bearing having a low side force pressure resistance.

The gas bearing supports the support object in a non-contact manner by the pressure of the gas interposed in the minute clearance between the gas bearing and the support object. The gas bearing includes a so-called clearance seal. The gas intervening in the clearance can be a working fluid of the Stirling engine. The gas bearing includes an air bearing. From the viewpoint of simplification of the apparatus configuration, the gas bearing is preferably not a type in which gas is forcedly blown, but a type in which the gas bearing is supported in a non-contact manner with a gas pressure distribution. Gas bearings that support non-contact with gas pressure distribution instead of forcibly injecting gas are further reduced in the side pressure resistance capability, so the approximate linear mechanism that substantially eliminates the side force of the piston The combination with is optimal.

  In the Stirling engine of the present invention, a crankshaft that rotates about a drive shaft, an extension provided to extend downward from the piston, and a connecting rod that connects the extension and the crankshaft are further provided. The approximate linear mechanism is connected to a connecting portion between the extension portion and the connecting rod, and restricts the movement of the connecting portion so that the connecting portion performs an approximate linear motion along the axial center line of the cylinder. It is characterized by doing. The extension portion is provided so as to extend downward from the piston along the axial center line of the cylinder. The connecting rod is one element that connects the piston and the crankshaft. The approximate linear mechanism is connected to a connecting portion of a piston and a connecting rod having an extending portion provided to extend downward, and the connecting portion performs an approximate linear motion along the axial center line of the cylinder. The movement of the connecting part is restricted, and the connecting part is provided in the extension part.

  According to the present invention, since the approximate linear mechanism and the piston are connected by the extension portion, the possibility of interference between the approximate linear mechanism and the piston and the possibility of interference between the approximate linear mechanism and the cylinder are reduced. Can do. As a result, the approximate linear mechanism can be configured more compactly.

  In the Stirling engine of the present invention, the piston and the extension are connected to each other so as to be relatively rotatable. In this configuration, even when the locus of the lower end of the extension part is slightly deviated from the straight line, the deviation can be made to hardly affect the piston.

Hybrid system of the present invention is a hybrid system comprising a Stirling engine of the present invention, and the internal combustion engine of a vehicle, the Stirling engine is mounted on the vehicle, the heater of the Stirling engine is the internal combustion It is provided to receive heat from the exhaust system of the engine.

  The Stirling engine of the present invention has reduced friction loss due to the above-described configuration, so that it operates sufficiently even with a low-temperature heat source such as an exhaust system of an internal combustion engine, and is preferably used for energy recovery from the low-temperature heat source. It is suitable for building a hybrid system.

  The Stirling engine of the present invention connects a cylinder, a piston that reciprocates while maintaining airtightness in the cylinder via a gas bearing, a crankshaft that rotates about a drive shaft, and the piston and the crankshaft. A connecting rod and an approximate linear mechanism connected to a connecting portion between the piston and the connecting rod are provided. The movement of the connecting portion is regulated by the approximate linear mechanism so that the connecting portion performs an approximate linear motion along the axial center line of the cylinder.

  In the present invention, the piston has a piston head portion that constitutes a top portion of the piston, and a piston strut portion (extension member) that extends along the axial center line of the cylinder below the piston head portion. The connecting portion between the piston and the connecting rod is provided at the lower end of the piston strut portion. The piston head part and the piston column part are connected so as to be rotatable.

In the present invention, the approximate linear mechanism is configured such that the first displacement amount from the axial center line of the cylinder of the connecting portion at the top dead center of the piston is the cylinder of the connecting portion at the bottom dead center of the piston. This is characterized in that the value is smaller than the second shift amount from the axial center line. In this invention, the reason for setting the amount of deviation at the top dead center to be smaller than the amount of deviation at the bottom dead center is that, in the low temperature side power piston, the force by the compressed air is applied to the compression piston near the top dead center. This is because in the high temperature side power piston, a force by the expansion air is applied to the expansion piston in the vicinity of the top dead center. That is, if the amount of displacement at the top dead center is small, the thrust (lateral force) applied to the compression piston by the force of the compressed air or to the expansion piston by the force of the expansion air becomes small. Friction can be reduced. On the other hand, since the force due to the compressed air (or the force due to the expansion air) is not applied at the bottom dead center, the influence on the friction is small compared to the top dead center even if there is some deviation.

  In the present invention, the approximate linear mechanism is preferably a grasshopper mechanism. The grasshopper mechanism is particularly suitable for regulating the piston motion of a piston engine because the point of movement on the approximate straight line is biased to the vicinity of one end of the mechanism, and the compact mechanism provides good linearity. It is possible to obtain. From this, in particular, the grasshopper mechanism has an organic meaning in combination with a Stirling engine using a gas bearing.

  The grasshopper mechanism includes first and second lateral links and a longitudinal link, and a first end of the first lateral link is formed by the piston and the connecting rod. A second end portion of the first lateral link is pivotally connected to a first end portion of the longitudinal link, and the longitudinal direction is coupled to the coupling portion. The second end of the link is pivotally fixed at a predetermined position of the Stirling engine, and the first end of the second lateral link is intermediate the first lateral link. The second lateral link is pivotably connected to the first lateral link at a predetermined position, and the second end of the second lateral link is pivotable to the predetermined position of the Stirling engine. It is fixed.

  In the grasshopper mechanism, the first end of the second lateral link has a bifurcated structure, and the first end of the first lateral link is between the bifurcated structure. Can be configured to pass through. According to this configuration, even if the connecting rod is shortened, the first end of the first lateral link and the first end of the second lateral link do not interfere with each other. An increase in the longitudinal dimension of the piston engine can be suppressed.

  In the grasshopper mechanism, the first end portion of the first lateral link and the connecting portion between the piston and the connecting rod are connected by a single piston pin. it can. According to this configuration, since the first lateral link, the piston, and the connecting rod are connected by one piston pin, the structure of the connecting portion is simplified.

  In the grasshopper mechanism, the first end portion of the first lateral link, the end portion of the piston and the end portion of the connecting rod in the connecting portion between the piston and the connecting rod, Of the three end portions, two end portions each have a bifurcated structure, and the remaining one end portion is arranged at the center of the bifurcated structure of the two end portions. According to this structure, since the connection part of a 1st horizontal link, a piston, and a connecting rod becomes a symmetrical shape, it can prevent that the side force by making it an asymmetrical shape generate | occur | produces.

  According to the Stirling engine of the present invention, it is possible to reduce friction loss, operate with a low heat source and a low temperature difference, and increase the output.

  Hereinafter, an embodiment of the Stirling engine of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a front view showing a Stirling engine of the present embodiment. FIG. 3 is a side view of the same. As shown in FIGS. 1 and 3, the Stirling engine 10 of the present embodiment is an α-type (two-piston type) Stirling engine, and includes two power pistons 20 and 30. The piston 31 of the low temperature side power piston 30 has a phase difference so as to move with a delay of about 90 ° in crank angle with respect to the piston 21 of the high temperature side power piston 20.

  The working fluid heated by the heater 47 flows into the space (expansion space) above the cylinder (hereinafter referred to as the high temperature side cylinder) 22 of the high temperature side power piston 20. The working fluid cooled by the cooler 45 flows into the space (compression space) above the cylinder (hereinafter referred to as the low temperature side cylinder) 32 of the low temperature side power piston 30. The regenerator 46 stores heat when the working fluid reciprocates between the expansion space and the compression space. That is, when the working fluid flows from the expansion space to the compression space, the regenerator 46 receives heat from the working fluid, and when the working fluid flows from the compression space to the expansion space, passes the stored heat to the working fluid.

  As the two pistons 21 and 31 reciprocate, the reciprocating flow of the working gas occurs, and the ratio of the working fluid in the expansion space of the high temperature side cylinder 22 and the compression space of the low temperature side cylinder 32 changes. As it changes, pressure fluctuations occur. Comparing the pressures when the two pistons 21 and 31 are in the same position, the expansion piston 21 is considerably higher when it is lowered than when it is raised, and the compression piston 31 is lower. For this reason, the expansion piston 21 needs to perform a large positive work (expansion work) with respect to the outside, and the compression piston 31 needs to receive work (compression work) from the outside. Part of the expansion work is used for compression work, and the rest is taken out as an output via the drive shaft 40.

  Each of the high temperature side cylinder 22 and the low temperature side cylinder 32 is formed in a cylindrical shape, and is arranged upright on a crankcase 41 formed in a rectangular parallelepiped box shape. The high temperature side cylinder 22 and the low temperature side cylinder 32 are fixed to the upper surface portion 42 of the crankcase 41. The entire low temperature side cylinder 32 is housed inside the crankcase 41. A part of the high temperature side cylinder 22 is accommodated in the crankcase 41 and the remaining part is provided so as to extend to the outside of the crankcase 41.

  A cooler 45 is provided above the low temperature side cylinder 32, a regenerator 46 is provided on the cooler 45, and one end of a heater 47 is connected to the regenerator 46. Yes. The other end of the heater 47 is connected to the upper part of the high temperature side cylinder 22. Cooling water is used for the cooler 45.

  The higher the average pressure of the working fluid, the higher the pressure difference with respect to the same temperature difference caused by the cooler 45 and the heater 47, so that a higher output is obtained. Therefore, the working fluid in the high temperature side cylinder 22 and the low temperature side cylinder 32 is kept at a high pressure. In the present embodiment, the entire inside of the crankcase 41 is held at a high pressure. That is, the crankcase 41 functions as a high pressure container.

The pistons 21 and 31 are formed in a cylindrical shape. A small clearance of several tens of μm is provided between the outer peripheral surfaces of the pistons 21 and 31 and the inner peripheral surfaces of the cylinders 22 and 32. The working fluid (air) of the Stirling engine 10 is included in the clearances. Intervene. As will be described later, the pistons 21 and 31 are supported in a non-contact state by air bearings 48 with respect to the cylinders 22 and 32, respectively. Therefore, the piston ring is not provided around the pistons 21 and 31, and the lubricating oil generally used with the piston ring is not used. However, a fixed lubricant is attached to the inner peripheral surfaces of the cylinders 22 and 32. The sliding resistance of the working fluid of the air bearing 48 is originally extremely low, but a fixed lubricant is added to further reduce it. As described above, the air bearing 48 keeps the airtightness of the expansion space and the compression space with the working fluid (gas), and performs clearance sealing without ring and without oil.

  The Stirling engine 10 of this embodiment is used with a gasoline engine (internal combustion engine) in a vehicle to constitute a hybrid system. That is, the Stirling engine 10 uses the exhaust gas of the gasoline engine as a heat source. As shown in FIG. 2, the heater 47 of the Stirling engine 10 is disposed inside the exhaust pipe 100 of the gasoline engine of the vehicle, and the Stirling engine 10 is operated by heating the working fluid by the heat energy recovered from the exhaust gas. The attachment position of the heater 47 of the Stirling engine 10 is not limited to the exhaust pipe 100 as long as it is an exhaust system of the internal combustion engine of the vehicle.

  The Stirling engine 10 of the present embodiment is installed in a limited space in the vehicle such that the heater 47 is accommodated in the exhaust pipe 100, so that the installation of the Stirling engine 10 is more compact if the entire device is compact. The degree increases. For this purpose, the Stirling engine 10 employs a configuration in which the two cylinders 22 and 32 are arranged in series and not in a V shape.

  When the heater 47 is disposed inside the exhaust pipe 100, the high-temperature side cylinder of the heater 47 is placed on the upstream side (the side close to the gasoline engine) 100a through which the relatively high-temperature exhaust gas flows in the exhaust pipe 100. 22 side is located, and it arrange | positions so that the low temperature side cylinder 32 side of the heater 47 may be located in the downstream (far side from a gasoline engine) 100b through which a relatively low temperature exhaust gas flows.

  The heat source of the Stirling engine 10 is exhaust gas of the gasoline engine of the vehicle as described above, and is not a heat source prepared exclusively for the Stirling engine 10. Therefore, the heat quantity is not so high, and the Stirling engine 10 needs to operate with the heat quantity of the exhaust gas, for example, about 800 ° C. Therefore, in this embodiment, the internal friction of the Stirling engine 10 is reduced as much as possible.

  In the present embodiment, in order to eliminate the friction loss due to the piston ring having the largest friction loss among the internal friction of the Stirling engine, as described above, instead of using the piston ring, instead of the cylinders 22 and 32 and the piston 21, Air bearings (air bearings) 48 are provided between each of them.

  Since the air bearing 48 has extremely small sliding resistance, the internal friction of the Stirling engine 10 can be greatly reduced. As described above, even if the air bearing 48 is used, the airtightness between the cylinders 22 and 32 and the pistons 21 and 31 is ensured, so that the high-pressure working fluid in the expansion space and the compression space is expanded and contracted. The problem of leakage does not occur.

  The air bearing 48 is a bearing in which the pistons 21 and 31 are floated in the air using the pressure (distribution) of air generated by a minute clearance between the cylinders 22 and 32 and the pistons 21 and 31. In the air bearing 48 of the present embodiment, the diameter clearance between the cylinders 22 and 32 and the pistons 21 and 31 is several tens of μm.

In order to realize an air bearing that floats an object in the air, in addition to forming a portion (pressure gradient) where the air pressure is mechanically increased, high-pressure air may be blown as described later. In the present embodiment, an air bearing having the same configuration as that of an air bearing used between a cylinder and a piston of a medical glass syringe is used instead of an air bearing that blows high-pressure air.

  Further, since the use of the air bearing 48 eliminates the need for lubricating oil used in the piston ring, there is a problem that the heat exchanger (regenerator 46, heater 47, etc.) 90 of the Stirling engine 10 is deteriorated by the lubricating oil. Does not occur. In the present embodiment, as described above, it is sufficient if the problem of sliding resistance and lubricating oil in the piston ring is solved. The present invention can be applied without being limited to the air bearing 48.

  It is also possible to use a static pressure air bearing between the pistons 21 and 31 and the cylinders 22 and 32 of the present embodiment. The static pressure air bearing is a device in which a pressurized fluid is ejected and an object (the pistons 21 and 31 in this embodiment) is levitated by the generated static pressure. Further, it is possible to use a dynamic pressure air bearing instead of the static pressure air bearing.

  When the pistons 21 and 31 are reciprocated in the cylinders 22 and 32 using the air bearing 48, the linear motion accuracy must be less than the diameter clearance of the air bearing 48. Further, since the load capacity of the air bearing 48 is small, the side forces of the pistons 21 and 31 must be substantially zero. That is, since the air bearing 48 has a low ability (pressure resistance ability) to withstand the force in the diameter direction (lateral direction, thrust direction) of the cylinders 22 and 32, the linear motion accuracy of the pistons 21 and 31 with respect to the axes of the cylinders 22 and 32 is low. Need to be expensive.

  In particular, the air bearing 48 of the type that is used in the present embodiment and is supported by levitating using a fine clearance air pressure has a low pressure resistance against the force in the thrust direction compared to the type that blows high-pressure air. Higher linear motion accuracy of the piston is required.

  For this reason, in the present embodiment, as shown in FIG. 3, a grasshopper mechanism (approximate linear link) 50 is employed in the piston / crank portion. The glass hopper mechanism 50 is smaller in size than the other linear approximation mechanism (for example, a watt mechanism), so that the size of the mechanism necessary for obtaining the same linear motion accuracy is small. It is done. In particular, the Stirling engine 10 of the present embodiment is installed in a limited space such that the heater 47 is accommodated in the exhaust pipe 100 of an automobile gasoline engine. However, the degree of freedom of installation increases.

  Further, the grasshopper mechanism 50 is advantageous in terms of fuel consumption because the weight of the mechanism necessary for obtaining the same linear motion accuracy is lighter than other mechanisms. Furthermore, the grasshopper mechanism 50 is easy to configure (manufacture / assemble) because the structure of the mechanism is relatively simple.

  Next, the approximate linear mechanism 50 of the grasshopper will be described with reference to FIGS.

A. Outline of piston / crank mechanism:
FIG. 4A is an explanatory view showing a piston / crank mechanism in a conventional Stirling engine, and FIG. 4B is an explanatory view showing a piston / crank mechanism in the Stirling engine 10 of the present embodiment. As shown in FIG. 4A, the conventional mechanism includes a cylinder 110, a piston 120, a connecting rod 130, and a crankshaft 140. The piston 120 and the connecting rod 130 are connected to each other by a piston pin 160 near the center of the piston 120. The connecting rod 130 and the crankshaft 140 are connected by a crank pin 162. When the piston 120 reciprocates up and down, the crankshaft 140 rotates about its axis 142 (also referred to as “drive shaft”).

  FIG. 4B shows a schematic configuration of the piston / crank mechanism of the Stirling engine 10. In the present embodiment, since the piston / crank mechanism adopts a common configuration for the high temperature side power piston 20 side and the low temperature side power piston 30 side, only the low temperature side power piston 30 side will be described below. Description of the high temperature side power piston 20 side is omitted.

  The piston / crank mechanism of the Stirling engine 10 includes a cylinder 32, a piston 31, a connecting rod 65, a crankshaft 61, and an approximate linear mechanism 50. The approximate linear mechanism 50 is an approximate linear mechanism of a grasshopper as described above.

  As shown in FIGS. 3 and 4-2, a piston support 64 is connected to the piston 31. The piston 31 and the piston support | pillar part 64 are formed as a different body. The lower end portion of the piston 31 and the upper end portion of the piston support portion 64 are connected to each other by a pin 67 so as to be rotatable. The piston struts 64 are connected to each other by a piston pin 60 at the lower end of the piston struts 64. The connecting rod 65 and the crank shaft 61 are connected by a crank pin 62. When the piston 31 reciprocates up and down, the crankshaft 61 rotates around its axis 40 (also referred to as “drive shaft”).

  The approximate linear mechanism 50 has two lateral links 52 and 54 and one longitudinal link 56. One end of the first lateral link 52 is rotatably connected to the lower end of the piston support 64 at the position of the piston pin 60. One end of the second lateral link 54 is rotatably connected to the first lateral link 52 at a predetermined position in the middle of the first lateral link 52. The other end of the second lateral link 54 is rotatably fixed at a predetermined position of the piston / crank mechanism. One end of the longitudinal link 56 is rotatably connected to the first lateral link 52 at the end of the first lateral link 52 opposite to the piston pin 60. The other end of the longitudinal link 56 is rotatably fixed to a predetermined position of the piston / crank mechanism.

  In FIGS. 4A and 4B, a connecting portion (such as the drive shaft 40) represented by a black circle rotates or rotates about the axis, but does not change the relative position with the cylinder 32. (Hereinafter referred to as “fulcrum”). Further, a connecting portion (piston pin 60 or the like) represented by a white circle rotates or rotates around its axis and changes its relative position to the cylinder 32 (hereinafter referred to as “moving connecting point”). ). Here, “rotation” means turning in a range of 360 degrees or more, and “rotation” means turning in a range of less than 360 degrees.

  4A and 4B, the illustration of the Stirling engine 10 of the present embodiment is omitted except for the piston / crank mechanism and the cylinder 32.

  (A)-(C) of FIG. 5 is explanatory drawing which shows the link structure of the piston crank mechanism of this embodiment. FIG. 5A shows only the cylinder 32, the piston 31, the connecting rod 65, and the crankshaft 61. FIG. 5B shows only the approximate linear mechanism 50. (C) in FIG. 5 is the same as the mechanism shown in FIG. 4-2, and is a combination of the configurations of (A) and (B) in FIG.

In (A) to (C) of FIG. 5, various connection points are represented as follows.
(1) Moving connection point A: central axis of the piston pin 60 (FIG. 4-2).
(2) Moving connection point B: A connection point at the end of the first lateral link 52 opposite to the moving connection point A.
(3) Moving connecting point C: A connecting point at the end of the connecting rod 65 opposite to the moving connecting point A.
(4) Moving connection point M: A connection point at the midpoint of the first lateral link 52.
(5) Support point P: the central axis (drive shaft) of the crankshaft 61.
(6) Support point Q: A connection point at the end of the second lateral link 54 opposite to the moving connection point M.
(7) Support point R: A connection point at the end of the vertical link 56 opposite to the moving connection point B.

  The moving connection point A is the central axis of the piston pin 60 and moves along the up-down direction Z ((B) of FIG. 5) as the piston 31 reciprocates. In the present specification, the vertical direction Z means a direction along the axial center line (also referred to as “axial center”) of the cylinder 32. The moving connection points A and B are connection points at both ends of the first lateral link 52. The moving connection point B moves on an arcuate locus as the vertical link 56 rotates about the fulcrum R. The moving connection point B is set so as to have substantially the same vertical position as the vertical position X of the fulcrum Q of the second lateral link 54.

  If the length of the vertical link 56 is virtually set to infinity, and the moving connection point B moves linearly on the same vertical position X as the fulcrum Q, the movement connection point A Performs a movement close to a perfect straight line in the vertical direction Z. Actually, since the length of the longitudinal link 56 is finite, the moving connection point A moves on a locus slightly deviated from the linear motion (this will be described later). An almost complete linear motion mechanism can be realized by adopting a guide portion that linearly guides the moving connection point B instead of the longitudinal link 56. However, the friction between the guide portion and the moving connection point B is reduced. Increase. Therefore, from the viewpoint of reducing friction, the approximate linear mechanism 50 of the present embodiment is preferable to a complete linear motion mechanism.

The position of the moving connection point M in the middle of the first lateral link 52 is set so as to satisfy the following relationship.
AM × QM = BM ²

  Here, AM means the distance between the connection points A and M, QM means the distance between the connection points Q and M, and BM means the distance between the connection points B and M, respectively.

  6A to 6D show changes in the shape of the piston / crank mechanism accompanying the movement of the piston 31. Of the three moving connection points A, B, and M of the approximate linear mechanism 50, the moving connection points A and M move considerably with the movement of the piston 31. I understand that does not move much. FIG. 6A shows two angles θ and φ that can be used as indices indicating the degree of change in the shape of the approximate linear mechanism 50. The first angle θ is an angle ∠ MQX of the second lateral link 54 measured from the lateral direction X. The second angle φ is the inclination angle of the vertical link 56 from the vertical direction Z and is ∠BRZ. The ranges that the values of these angles θ and φ take depend on the setting of the moving range of the moving connection point A (that is, the stroke of the piston 31) and the length of each link of the approximate linear mechanism 50.

As described above, the lower end portion of the piston 31 and the upper end portion of the piston support 64 are connected to each other by the pin 67 so as to be rotatable. In this configuration, even when the locus of the lower end of the piston column 64 slightly deviates from the straight line, the displacement does not work as a force for tilting the piston 31 (that is, the displacement of the lower end of the piston column 64 is not applied to the piston 31). Has the advantage of having little effect). That is, in order to absorb the deviation from the linear motion that occurs during the reciprocating motion of the grasshopper mechanism 50, the piston 31 and the piston support 64 are connected in a relatively movable state (free state), not rigidly. To do. In this embodiment, it connects using the pin 67 as an example. Moreover, compared with the case where a piston and a piston support | pillar part are integrally formed, there also exists an advantage that the operation | work which assembles a piston with an approximate linear mechanism and a connecting rod becomes easy. On the other hand, although not shown in the figure, when the piston column part 64 and the piston 31 are integrally formed, even if the piston 31 is inclined with respect to the cylinder 32 for some reason, the piston column part 64 is an approximate straight line. There is an advantage that the inclination is corrected when exercise is performed.

7-1 is explanatory drawing which shows an example of the specific dimension of the piston crank mechanism in this embodiment. FIG. 7B is an explanatory diagram of the locus of the moving connection point A. It can be seen that the dimensions shown in FIG. 7-1 satisfy the relationship (AM × QM = BM ² ) described above. As shown in FIG. 7B, the trajectory of the moving connection point A includes an approximate straight line portion, and this approximate straight line portion is used as the stroke range of the piston 31. At this time, the stroke range of the piston 31 is set so that the amount of deviation from the straight line at the top dead center is smaller than the amount of deviation from the straight line at the bottom dead center. Here, the “straight line” of the “deviation amount from the straight line” means the axial center line of the cylinder 32. In the example of FIG. 7-2, the amount of deviation at the top dead center is about 5 μm, and the amount of deviation at the bottom dead center is about 20 μm. This numerical value is measured at room temperature.

  The reason why the amount of deviation from the straight line of the moving connection point A at the top dead center is set to be smaller than the amount of deviation at the bottom dead center is that the force by the compressed air is applied to the piston 31 near the top dead center. (Similarly, in the high temperature side power piston 20, the force by the expanded air is applied to the piston 21 in the vicinity of the top dead center). That is, if the displacement amount at the top dead center is small, the thrust (lateral force) applied to the piston 31 (or to the piston 21 by the force of the expanded air) due to the force of the compressed air becomes small. Alternatively, friction between the piston 21 and the cylinder 22) can be reduced. On the other hand, since the force due to the compressed air (or the force due to the expansion air) is not applied at the bottom dead center, the influence on the friction is small compared to the top dead center even if there is some deviation.

  The approximate straight line portion in the locus of the moving connection point A can be increased by increasing the length of each link 52, 54, 56. However, if the link is lengthened, the size of the approximate straight line mechanism 50 is increased. There is a problem of growing. In other words, the amount of deviation from the straight line at the top dead center or the bottom dead center and the size of the approximate linear mechanism 50 are in a trade-off relationship. Considering these points, it is preferable to configure the approximate linear mechanism 50 so that the deviation from the straight line of the moving connection point A at the top dead center of the piston 31 is about 10 μm or less when measured at room temperature. Further, it is preferable that the amount of deviation at the bottom dead center is about 20 μm or less.

  As shown in FIG. 7-2, when the range of the stroke of the piston 31 is set, the angle θ of the second lateral link 54 takes a value in the range of 8.8 ° to −17.9 °. (FIG. 7-1). The maximum value (8.8 °) of the angle θ corresponds to the case where the piston 31 is at the top dead center (FIG. 6-1), and the minimum value (−17.9 °) is at the bottom dead center. This corresponds to the case (FIG. 6-3). The angle φ of the longitudinal link 56 takes a value in the range of 0 ° to 2.2 °. The minimum value (0 °) of the angle φ corresponds to the case where the connection points Q, A, M, and B are arranged substantially in a straight line, and the maximum value (2.2 °) is the largest absolute value of the angle θ. Corresponds to the case (bottom dead center in this example). Note that the range of the values of these angles θ and φ depends on the dimensions of the links of the approximate linear mechanism 50 and the setting of the stroke range of the piston 31.

B. Specific shape examples:
8 and 9 show an example of a specific shape of the piston / crank mechanism in the present embodiment. As described above, the piston 31 is formed in a columnar shape. A piston ring groove and a piston ring are not provided on the outer peripheral surface of the piston 31. The plan view (transverse section) shape of the piston 31 is formed into a highly accurate perfect circle. The cylinder 32 is formed in a cylindrical shape, and the shape of the inner peripheral portion of the cylinder 32 in plan view is formed in a highly accurate perfect circle. As described above, the air bearing 48 is provided between the outer peripheral surface of the piston 31 and the inner peripheral portion of the cylinder 32. The air bearing 48 with good sealing performance is realized by forming the shape of each of the inner peripheral portions of the piston 31 and the cylinder 32 in a planar shape with high accuracy.

  A piston support 64 is provided between the piston pin 60 and the piston 31 in order to ensure a predetermined distance or more between the piston pin 60 and the piston 31. By opening a predetermined distance or more between the piston pin 60 and the piston 31 by the piston support 64, the piston 31 and the approximate linear mechanism 50 can be prevented from contacting when the piston 31 reciprocates.

  The length of the piston support 64 is set so that the length from the upper end of the piston 31 to the piston pin 60 is a value in a range of about 1/2 times or more and less than 1 time of the stroke of the piston 31. It is preferable. The reason is that if the length of the piston support 64 is excessively short, the approximate linear mechanism 50 may collide with the cylinder 32 or the piston 31 at the top dead center. Moreover, if the length of the piston support | pillar part 64 is too long, it is because the energy loss will increase by the part which the weight increases.

  As shown in FIG. 9, the piston strut 64, the connecting rod 65, and the first and second lateral links 52 and 54 are configured not to interfere with each other even when the piston 31 moves up and down. Yes. Specifically, in the example of FIG. 9, the piston strut portion 64 is provided in the center of the cylinder 32 in the axial direction, and both sides of the piston strut portion 64 are sandwiched between two plate-like members of the connecting rod 65. ing. Two plate-like members of the first lateral link 52 are arranged outside the connecting rod 65. These three types of members 24, 30, 52 are connected by a piston pin 60. Further, two plate-like members of the second lateral link 54 are installed on the outer side of the first lateral link 52. In other words, in this example, the connecting rod 65 and the two lateral links 52 and 54 each have a bifurcated structure in which the end portion is divided into two plate-like members, and the central piston column 64 is provided from both sides. It is arranged at each position to sandwich.

  10 is a longitudinal sectional view of a main part at a position where the crank is rotated from FIG. 8 and the horizontal links 52 and 54 are horizontal, and FIG. 11 is a sectional view taken along the line CC in FIG. In FIG. 11, for convenience of illustration, the connecting rod 65 and the piston support 64 are hatched.

  FIGS. 12 to 16 show various shapes and positional relationships (connected states) that can be taken by the piston strut 64, the connecting rod 65, and the first lateral link 52. FIG. The arrangement of FIG. 12 is obtained by reversing the positional relationship between the connecting rod 65 and the piston support 64 from the arrangement of FIG. That is, in FIG. 12, the connecting rod 65 is disposed at the center, the bifurcated structure portion of the piston support 64 is disposed on the outer side, and the bifurcated structure portion of the first lateral link 52 is disposed on the outer side. ing. The bifurcated portion of the second lateral link 54 is disposed on the outermost side.

The arrangement of FIG. 13 is obtained by reversing the positional relationship between the connecting rod 65 and the first lateral link 52 from the arrangement of FIG. That is, in FIG. 13, the piston support 64 is disposed at the center, the bifurcated structure portion of the first lateral link 52 is disposed on the outer side, and the bifurcated structure portion of the connecting rod 65 is disposed on the outer side. ing.

  The arrangement of FIG. 14 is obtained by reversing the positional relationship between the piston support 64 and the first lateral link 52 from the arrangement of FIG. That is, in FIG. 14, the connecting rod 65 is disposed at the center, the bifurcated structure portion of the first lateral link 52 is disposed on the outer side, and the bifurcated structure portion of the piston support 64 is disposed on the outer side. ing.

  The arrangement of FIG. 15 is obtained by reversing the positional relationship between the piston support 64 and the first lateral link 52 from the arrangement of FIG. That is, in FIG. 15, the first lateral link 52 is disposed at the center, the bifurcated structure portion of the piston support 64 is disposed on the outer side, and the bifurcated structure portion of the connecting rod 65 is disposed on the outer side. ing.

  The arrangement in FIG. 16 is obtained by reversing the positional relationship between the piston support 64 and the connecting rod 65 from the arrangement in FIG. That is, in FIG. 16, the first lateral link 52 is disposed at the center, the bifurcated structure portion of the connecting rod 65 is disposed on the outer side, and the bifurcated structure portion of the piston support 64 is disposed on the outer side. ing.

  11 to 16, the end of the second lateral link 54 has a bifurcated structure and is disposed outside the other members 64, 65, 52, 60. When the approximate linear mechanism operates, the end portion of the first lateral link 52 passes between the bifurcated structures between the bifurcated structures of the second lateral link 54. According to such a configuration, even if the connecting rod 65 is shortened, the end of the first lateral link 52 and the end of the second lateral link 54 do not interfere with each other. An increase in the vertical dimension of the mechanism can be suppressed.

  In the configuration shown in FIGS. 11 to 16, the end of the first lateral link, the lower end of the piston support 64 (the lower end of the piston), and the upper end of the connecting rod 65 are combined with one piston pin 60. It is connected. According to such a configuration, the first lateral link 52, the piston strut portion 64, and the connecting rod 65 are connected by the single piston pin 60. Therefore, the structure of this connecting portion is simplified and can be made compact. There is an advantage.

  Furthermore, in the configuration shown in FIGS. 11 to 16, two of the three end portions, that is, the end portion of the first lateral link 52, the lower end of the piston column 64, and the upper end of the connecting rod 65 are used. Each has a bifurcated structure, and the remaining one end is disposed at the center of the bifurcated structure of the two ends. According to such a configuration, the connecting portion of the first lateral link 52, the piston strut portion 64, and the connecting rod 65 has a symmetric shape, so that side forces due to the asymmetric shape are generated. There is an advantage that it can be prevented.

  The positional relationship between these members 64, 65, 52, and 54 can be other than the positional relationships shown in FIGS.

  FIGS. 17-1 to 17-3 are explanatory views showing modifications of the piston / crank mechanism. The mechanism of FIG. 17-1 is the same as that of the present embodiment shown in FIGS. The longitudinal link 56 of the mechanism is arranged above the connection point B, and the other configurations are the same as those in the above embodiment. The same effect as that of the above embodiment can be obtained by the mechanism of FIG.

The mechanism of FIG. 17-2 moves the fulcrum Q of the mechanism of the present embodiment shown in FIGS. 5A to 5C to the movement coupling point B side, and moves to the movement coupling point A (piston pin) and the fulcrum. It is arranged on a straight line connecting P (crankshaft), and the other configurations are the same as in the above embodiment. The mechanism shown in FIG. 17C has the fulcrum Q further disposed on the right side. In the mechanism of FIGS. 17-2 and 17-3, the length of the second lateral link 54 is shorter than that of the above embodiment, and there is an advantage that it is more compact than the mechanism of the above embodiment. The mechanism of FIG. 17-2 has an advantage that the linearity is better than the mechanisms of FIGS. 17-1 and 17-3.

  As described above, in the above-described embodiments and modifications, the piston / crank mechanism is provided with the approximate linear mechanism 50 so that the lower end of the piston 31 moves along the approximate linear trajectory along the axial center of the cylinder 32. As a result, the linear motion accuracy of the piston 31 is high, the side force of the piston 31 can be made substantially zero, and the air bearing 48 having a low pressure resistance in the thrust direction between the piston 31 and the cylinder 32. Even if it is provided, no problem occurs.

  The approximate linear mechanism of the grasshopper is particularly suitable for restricting the movement of the piston of the Stirling engine 10 because the point (moving connection point A) moving on the approximate straight line is biased near one end of the mechanism. Moreover, it is possible to obtain good linearity with a compact mechanism.

FIG. 1 is a front view showing a first embodiment of the Stirling engine of the present invention. FIG. 2 is a front view showing a state of being attached to an exhaust pipe in the first embodiment of the Stirling engine of the present invention. FIG. 3 is a side view showing the first embodiment of the Stirling engine of the present invention. FIG. 4A is an explanatory diagram of a conventional piston / crank mechanism. FIGS. 4-2 is explanatory drawing which shows the piston crank mechanism applied to 1st Embodiment of the Stirling engine of this invention. FIG. 5 is an explanatory view showing a link configuration of the piston / crank mechanism in the first embodiment of the Stirling engine of the present invention. 6-1 is explanatory drawing which shows the shape change of the piston crank mechanism accompanying the movement of a piston in 1st Embodiment of the Stirling engine of this invention. FIG. 6-2 is another explanatory view showing a shape change of the piston / crank mechanism accompanying the movement of the piston in the first embodiment of the Stirling engine of the present invention. FIG. 6-3 is still another explanatory view showing the shape change of the piston / crank mechanism accompanying the movement of the piston in the first embodiment of the Stirling engine of the present invention. FIG. 6-4 is still another explanatory view showing the shape change of the piston / crank mechanism accompanying the movement of the piston in the first embodiment of the Stirling engine of the present invention. FIGS. 7-1 is explanatory drawing which shows an example of the specific dimension of a piston crank mechanism in 1st Embodiment of the Stirling engine of this invention. 7-2 is explanatory drawing which shows the locus | trajectory of the movement connection point A in 1st Embodiment of the Stirling engine of this invention. FIG. 8 is a longitudinal sectional view of an essential part showing an example of a specific shape of a piston / crank mechanism in the first embodiment of the Stirling engine of the present invention. FIG. 9 is a cross-sectional view of the main part of the piston / crank mechanism in the state of FIG. FIG. 10 is a longitudinal sectional view of a main part of the piston / crank mechanism at a position where the crank is rotated from the state of FIG. FIG. 11 is a cross-sectional view of the main part of the piston / crank mechanism in the state of FIG. FIG. 12 is a cross-sectional view of an essential part showing a modification of the connecting part of the piston / crank mechanism in the first embodiment of the Stirling engine of the present invention. FIG. 13 is a cross-sectional view of an essential part showing a modification of the connecting part of the piston / crank mechanism in the first embodiment of the Stirling engine of the present invention. FIG. 14 is a cross-sectional view of an essential part showing a modification of the connecting part of the piston / crank mechanism in the first embodiment of the Stirling engine of the present invention. FIG. 15 is a cross-sectional view of an essential part showing a modification of the connecting part of the piston / crank mechanism in the first embodiment of the Stirling engine of the present invention. FIG. 16 is a cross-sectional view of an essential part showing a modification of the connecting part of the piston / crank mechanism in the first embodiment of the Stirling engine of the present invention. FIG. 17A is an explanatory view of another modification of the piston / crank mechanism in the first embodiment of the Stirling engine of the present invention. FIG. 17-2 is an explanatory diagram showing still another modified example of the piston / crank mechanism in the first embodiment of the Stirling engine of the present invention. FIGS. 17-3 is explanatory drawing which shows the further modification of a piston crank mechanism in 1st Embodiment of the Stirling engine of this invention. FIG. 18 is a partial cross-sectional side view showing a configuration example of a conventional Stirling engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Stirling engine 20 High temperature side power piston 21 Expansion piston 22 High temperature side cylinder 30 Low temperature side power piston 31 Compression piston 32 Low temperature side cylinder 45 Cooler 46 Regenerator 47 Heater 48 Air bearing 50 Approximate linear mechanism 60 Piston pin 62 Crank pin 64 Piston strut 65 Connecting rod 67 Pin 90 Heat exchanger 100 Exhaust pipe

Claims (4)

A Stirling engine that uses an exhaust system of an internal combustion engine as a heat source,
A cylinder,
A piston that reciprocates in the cylinder while maintaining airtightness between the cylinder and a gas bearing;
An approximate linear mechanism connected to the piston directly or indirectly, and provided to perform an approximate linear motion when the piston reciprocates in the cylinder, and
The Stirling engine , wherein the gas bearing supports the piston in a non-contact manner with a pressure distribution . The Stirling engine according to claim 1,
Furthermore,
A crankshaft that rotates around a drive shaft;
An extension provided to extend downward from the piston;
A connecting rod connecting the extension and the crankshaft;
The approximate linear mechanism is connected to a connecting portion between the extension portion and the connecting rod, and restricts the movement of the connecting portion so that the connecting portion performs an approximate linear motion along the axial center line of the cylinder. Stirling engine characterized by The Stirling engine according to claim 2,
The Stirling engine, wherein the piston and the extension portion are connected so as to be relatively rotatable. A Stirling engine according to any one of claims 1 to 3,
A hybrid system comprising the internal combustion engine of a vehicle,
The Stirling engine is mounted on the vehicle,
The hybrid system, wherein a heater of the Stirling engine is provided to receive heat from an exhaust system of the internal combustion engine.

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