JP6242715B2 - Gas engine intake structure - Google Patents

Description

  The present invention relates to an intake structure for a gas engine using, for example, a gas suitable for a cogeneration system as a fuel.

  Conventionally, in the intake structure of a gas engine used in a cogeneration system, the area of the intake passage is set so that intake characteristics satisfying the operable condition from start to rated load operation can be obtained. The operable condition from the start to the rated load operation is an appropriate air-fuel ratio (A / F) that is fuel-rich to the extent that the start is possible at the start and that is fuel-lean to the extent that good fuel efficiency is obtained after the start. Therefore, it is necessary to supply the fuel amount and the air amount. In a gas engine in which air-fuel ratio control is not performed, the fuel efficiency deteriorates when the air-fuel ratio is set low so that it can be easily started, and the engine does not start easily when the air-fuel ratio is set high to improve fuel efficiency. It becomes.

  As an air-fuel ratio control device that can realize such a rich air-fuel ratio at start-up and lean at rated load operation, an inflow air amount adjustment valve is arranged at the outside air intake port of an air cleaner arranged in the intake passage of the gas engine. A valve that controls the degree of opening and closing of the amount adjusting valve with a valve opening amount control device is known (Patent Document 1). According to the air-fuel ratio control device of Patent Document 1, the valve opening amount control device discriminates the engine start state based on the engine speed detected by the sensor and the negative pressure in the air cleaner, and adjusts the inflow air amount at the start. When the valve is operated in the valve closing direction and the start-up state is released, the air-fuel ratio of the start-time rich and the operation-time lean air-fuel ratio can be realized by operating the inflow air amount adjusting valve to the fully-open state.

JP-A-6-264822

  However, in the air-fuel ratio control device of Patent Document 1, a plurality of sensors are required, and an inflow air amount adjustment valve and a control device for controlling the same are required. As a result, the cost of the gas engine as a whole increases. Here, it is conceivable to control the air-fuel ratio by increasing or decreasing the amount of fuel supplied to the gas engine. However, the pressure of the fuel supply source, which is the upper limit of the pressure adjustable by the fuel supply system of the gas engine, may be low. In some cases, it is difficult to ensure the air-fuel ratio required at the start-up simply by adjusting the fuel supply system. Further, an inflow gas amount adjusting valve similar to the inflow air amount control device and an inflow gas amount control device for controlling the same are required, and the cost of the gas engine as a whole is still increased. Furthermore, in the air-fuel ratio control device of Patent Document 1, since the inflow air amount adjustment valve is provided on the upstream side of the air cleaner, the entire gas engine is increased in size.

  In view of such a background, a first object of the present invention is to provide an intake structure for a gas engine that can realize a rich air-fuel ratio at start-up and lean during operation while suppressing an increase in size and cost of the device. To do.

  In order to improve fuel efficiency and reduce emissions, the blow-by gas in the crankcase may be recirculated to the air cleaner. The structure in which the blow-by gas passage is connected to the air cleaner is disclosed in Patent Document 1. When applied to, blow-by gas may adhere to the filter element and deteriorate intake characteristics. Accordingly, a second object is to provide an intake structure for a gas engine that can prevent deterioration of intake characteristics due to blow-by gas.

  In order to solve such problems, the present invention is provided with an air cleaner (12) provided in an intake passage (11) connected to a combustion chamber (2a), and on the downstream side of the air cleaner in the intake passage. An intake structure of a gas engine (1) comprising a gas mixer (13) for mixing the supplied fuel gas and intake air, wherein the air cleaner defines an intake chamber (41); A filter element (22) that is installed in the case and divides the intake chamber into an upstream chamber (42) and a downstream chamber (43), and an intake port (45a) are formed. Furthermore, a partition wall (45) partitioned into an upstream space (43U) and a downstream space (43L) and the intake port of the partition wall are provided so as to be openable and closable. While allowing the flow of fluid to the side space, a structure having a one-way valve (50) to prevent the flow of fluid to the upstream space from the downstream space.

  According to this configuration, since the engine speed is low at the time of starting, the intake negative pressure is small, the one-way valve opens relatively small according to its elastic modulus and becomes fuel rich (low air-fuel ratio). The one-way valve is greatly opened by a relatively large intake negative pressure, resulting in a lean fuel (high air-fuel ratio). In addition, since the air-fuel ratio can be made rich at start-up and lean during operation by the partition wall and the one-way valve, it is possible to suppress an increase in the cost of the entire gas engine.

  In the invention described above, the one-way valve may be a reed valve (50) attached to the downstream space side of the partition wall.

  According to this configuration, a one-way valve can be realized by a reed valve having a simple configuration, and an increase in cost can be suppressed. Moreover, since it is easy to set the opening degree with respect to the negative pressure, a desired air-fuel ratio can be set according to the state of the gas engine.

  In the above invention, the crank chamber (5b) may be further connected to the downstream space of the air cleaner, and further provided with a blow-by gas passage (15) for guiding blow-by gas in the crank chamber to the downstream space. .

  According to this configuration, the downstream end of the blow-by gas passage communicates with the downstream space downstream of the partition wall, and the intake port is closed by the one-way valve except when the downstream space is negative pressure. Adhesion to the filter element is suppressed, and deterioration of the intake characteristics can be prevented.

  As described above, according to the present invention, an intake structure for a gas engine capable of realizing a rich air-fuel ratio at start-up and lean during operation while suppressing an increase in size and cost of the apparatus is provided, and an intake characteristic is deteriorated by blow-by gas. It is possible to provide an intake structure for a gas engine that can prevent the above.

Schematic configuration diagram of a gas engine according to an embodiment Cross section of the air cleaner shown in FIG. The graph which shows the sound insulation characteristic by the intake structure shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the gas engine 1 is a four-cycle single-cylinder spark ignition engine that uses city gas (or LP gas or LB gas, hereinafter simply referred to as “gas”) as fuel. The gas engine 1 can be used, for example, as an electric motor for a cogeneration apparatus. When the gas engine 1 is used as an electric motor of a cogeneration apparatus, the cogeneration apparatus is not only the gas engine 1 but also a power generation unit (not shown) that generates power by being driven by the gas engine 1, and a heat exchanger that uses residual heat of the gas engine 1 as a heat source. Etc. and is housed in a cogeneration case.

  The gas engine 1 includes an engine body 2, an intake system 3 that supplies a mixture of fuel gas and air to the engine body 2, and an exhaust system 4 that guides exhaust gas discharged from the engine body 2. . The engine body 2 defines a cylinder 5a and a crank chamber 5b, an engine block 5 arranged with the cylinder axis line horizontal, a cylinder head 6 joined to one end of the engine block 5 on the cylinder 5a side, and a cylinder head And a cylinder head cover 7 joined to an end of the engine block 5 opposite to the engine block 5. In the illustrated example, the engine block 5 is arranged in a direction in which the crankshaft 8 extends in the horizontal direction, but may be arranged in a direction in which the crankshaft 8 extends in the vertical direction.

  The intake system 3 includes an intake passage 11 having an upstream end 11a opened to the atmosphere and a downstream end 11b connected to the combustion chamber 2a of the engine body 2, an air cleaner 12 provided in the intake passage 11, and an intake passage 11 A gas mixer 13 provided on the downstream side of the air cleaner 12 and a fuel supply path 14 having an upstream end connected to a fuel supply source (not shown) and a downstream end 14b connected to the gas mixer 13 are provided. The gas mixer 13 mixes fresh air supplied from the intake passage 11 and fuel gas supplied from the fuel supply passage 14. The intake system 3 includes an upstream end 15 a that communicates with the crank chamber 5 b and a downstream end 15 b that communicates with the intake passage 11, and includes a blow-by gas passage 15 that recirculates the blow-by gas in the crank chamber 5 b to the intake passage 11. It is out.

  The air cleaner 12 has a case 21 formed in a box shape and a filter element 22 installed inside the case 21. The case 21 includes a case main body 23 that holds the filter element 22 and a cover member 24 that is detachably attached to the case main body 23. Since the cover member 24 is detachably attached, the filter element 22 can be maintained.

  The upper surface of the cover member 24 is integrally formed with an intake pipe 25 that extends upward and then curves and extends substantially horizontally. An intake inlet that opens at the tip of the intake pipe 25 is an upstream end of the intake passage 11. 11a. The case body 23 includes two case members 26 and 27 that are divided into two in the intake air flow direction. Hereinafter, the two case members 26 and 27 are referred to as a first case member 26 and a second case member 27 in order from the upstream side. The air cleaner 12 purifies the air taken from the intake inlet and sends the purified air to the gas mixer 13. Details of the air cleaner 12 will be described later.

  A proportional valve unit 31 is provided in the fuel supply path 14. The proportional valve unit 31 includes an electromagnetic valve 32 and a proportional valve 33 provided on the downstream side of the electromagnetic valve 32. The electromagnetic valve 32 is a normally closed on-off valve, and is opened by electric power supplied from a power source (not shown). The electromagnetic valve 32 is closed when the gas engine 1 is stopped and prohibits the fuel gas from being supplied to the engine body 2, and is opened when the gas engine 1 is driven to supply the fuel gas to the engine body 2. The proportional valve 33 is an electromagnetic that controls the flow rate of the fuel gas passing through the fuel supply path 14 by controlling the supply pressure of the fuel gas according to the magnitude of the energization current without depending on the pressure of the supplied fuel gas. It is a proportional valve. Since the proportional valve 33 can keep the supply pressure of the fuel gas substantially constant, a conventional pressure regulator can be omitted, and the apparatus can be made compact. Note that such a proportional valve 33 may have a known configuration as described in, for example, Japanese Patent Laid-Open No. 8-42400, and a detailed description thereof will be omitted here.

  The gas mixer 13 has a gas nozzle (not shown) provided at the downstream end 14b of the fuel supply passage 14, a throttle valve (not shown), and a throttle motor 34 that opens and closes the throttle valve, and intake negative pressure from the gas nozzle. In response to this, the amount of fuel gas ejected is mixed with the intake air to generate a mixed gas. The generated mixed gas is sent to the combustion chamber 2 a of the engine body 2 through the intake passage 11.

  The cylinder head 6 is provided with a spark plug (not shown) so that the electrode faces the combustion chamber 2a. The spark plug is supplied with electric power from a power source (not shown) via an ignition device including an ignition coil, thereby generating a spark discharge at a predetermined timing and igniting the air-fuel mixture to burn the fuel gas.

  Further, at the time of combustion of the fuel gas, the gas having a high pressure in the combustion chamber 2a leaks into the crank chamber 5b through a gap between the piston and the peripheral wall surface of the cylinder 5a. The blow-by gas leaked into the crank chamber 5b contains unburned air-fuel mixture and oil. If it is released into the atmosphere as it is, it causes air pollution. It is returned to the intake passage 11 through the passage 15.

  The exhaust system 4 has an exhaust passage 36 that guides the already burned gas generated in the combustion chamber 2a to the atmosphere. A muffler 37 is provided in the exhaust passage 36.

  As shown in FIG. 2, the case 21 of the air cleaner 12 defines an intake chamber 41 therein. The filter element 22 is detachably attached to the end opening on the cover member 24 side of the case body 23. Thus, the intake chamber 41 is partitioned into an upstream chamber 42 that becomes a dust chamber by the filter element 22 and a downstream chamber 43 through which the purified intake air flows.

  The first case member 26 of the air cleaner 12 includes a rectangular cylindrical peripheral wall 44 that holds the filter element 22, and a partition wall 45 that is provided on the side opposite to the filter element 22 of the peripheral wall 44 so as to close the opening of the peripheral wall 44. Have. On the other hand, the second case member 27 is integrally formed with an intake connection pipe 46 that extends laterally from the lower portion of the left side surface and forms the downstream end of the air cleaner 12. Thereby, the downstream chamber 43 is further divided into the upstream space 43U and the downstream space 43L by the partition wall 45. An intake port 45 a is formed in the approximate center of the partition wall 45.

  The second case member 27 is integrally formed with a blow-by gas connection pipe 47 that extends downward from the lower surface and forms the downstream end 15 b of the blow-by gas passage 15. Thereby, the downstream end 15 b of the blow-by gas passage 15 communicates with the downstream space 43 </ b> L downstream of the partition wall 45 in the air cleaner 12.

  A reed valve 50 is provided on the surface of the partition wall 45 on the downstream space 43L side so as to open and close the intake port 45a. The reed valve 50 is made of a flat plate having elasticity, and one end side is fixed to the partition wall 45 by a bolt / nut 51. When the pressure in the downstream space 43L and the pressure in the upstream space 43U are balanced, the reed valve 50 abuts against the partition wall 45 to close the intake port 45a, and intake negative pressure is generated in the intake passage 11. When the pressure in the downstream space 43L becomes lower than the pressure in the upstream space 43U, the inlet 45a is opened by elastic deformation in a direction away from the partition wall 45 as indicated by an imaginary line. Thereby, the flow of fluid from the upstream space 43U to the downstream space 43L is allowed, while the flow of fluid from the downstream space 43L to the upstream space 43U is blocked. The reed valve 50 is more elastically deformed as the intake negative pressure (pressure difference) is larger, and the intake flow rate passing through the intake port 45a is increased. On the side opposite to the partition wall 45 of the reed valve 50, a stopper 52 is provided that is fixed to the partition wall 45 together with the reed valve 50 by bolts and nuts 51 and restricts movement of the reed valve 50 in the opening direction. Thereby, the deformation amount of the reed valve 50 is limited.

  The gas engine 1 having such an intake structure operates as follows. First, when the gas engine 1 is started, since the engine speed (speed) is low, a relatively small intake negative pressure is generated in the intake passage 11 via the gas mixer 13, so that the reed valve 50 is elastically deformed to a small extent, A relatively small amount of intake air is supplied to the gas mixer 13. On the other hand, the fuel gas is supplied to the gas mixer 13 at a predetermined pressure by the proportional valve 33. Therefore, a fuel-rich mixed gas is generated by the gas mixer 13 and supplied to the combustion chamber 2a. Thereby, the startability of the gas engine 1 becomes favorable.

  On the other hand, when the gas engine 1 is performing the rated load operation, the engine speed is higher than that at the time of start-up, so the intake negative pressure generated in the intake passage 11 via the gas mixer 13 is relatively large. Therefore, the reed valve 50 is greatly elastically deformed, and a relatively large amount of intake air is supplied to the gas mixer 13. On the other hand, the fuel gas is supplied to the gas mixer 13 at a predetermined pressure by the proportional valve 33. Therefore, a fuel-lean mixed gas is generated by the gas mixer 13 and supplied to the combustion chamber 2a. Thereby, the fuel consumption performance of the gas engine 1 is improved.

  In addition, there is a pulsation in the intake air, and the sound pressure in the blowback direction from the engine body 2 is transmitted through the intake passage 11 and leaks from the tip of the intake pipe 25. However, in the gas engine 1 according to the embodiment, the intake passage When pressure in the blowback direction is applied to 11, the reed valve 50 closes the intake port 45a and blocks the pulsating pressure. FIG. 3 shows the noise (sound pressure level) generated by the gas engine 1 (provided with the reed valve 50) according to the present invention with a solid line, and the gas engine according to the comparative example (without the reed valve 50) generates. Noise is indicated by broken lines. As shown in the figure, in the gas engine 1 according to the present invention, the sound pressure level of generated noise is compared when the reed valve 50 closes the intake port 45a when the sound pressure in the blowback direction is transmitted through the intake passage 11. Compared to the example.

  As described above, in the present embodiment, the air cleaner 12 includes the partition wall 45 in which the intake port 45a is formed and the reed valve 50 that opens and closes the intake port 45a. Accordingly, it opens relatively small and becomes rich in fuel (low air-fuel ratio), and in rated load operation, the reed valve 50 is largely opened by a relatively large intake negative pressure to become fuel lean (high air-fuel ratio). In addition, since the air-fuel ratio of the start time rich and the lean time of operation can be realized by the partition wall 45 and the reed valve 50, the cost increase of the entire gas engine 1 is suppressed.

  Further, in the present embodiment, a one-way valve that allows the flow of fluid from the upstream space 43U to the downstream space 43L while blocking the flow of fluid from the downstream space 43L to the upstream space 43U is a downstream space. Since the reed valve 50 is disposed at 43L and attached to the partition wall 45, a one-way valve can be realized with a simple configuration, and an increase in cost is suppressed. In addition, since the reed valve 50 can easily set the opening degree with respect to the negative pressure, it is easy to set a desired air-fuel ratio according to the state of the gas engine 1. Furthermore, since the reed valve 50 is attached to the partition wall 45 having a larger area than the cross-sectional area of the intake pipe member that defines the intake passage 11, the reed valve 50 is easily attached and has good workability.

  In the present embodiment, the downstream end 15b of the blow-by gas passage 15 communicates with the downstream space 43L. Therefore, except when the downstream space 43L is under negative pressure, the intake port 45a is closed by the reed valve 50, and blow-by gas does not adhere to the filter element 22. Thereby, the deterioration of the intake characteristics is prevented.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, in the above-described embodiment, the gas engine 1 has been described as an example for a cogeneration apparatus, but the gas engine 1 may be used as a generator or a vehicle drive source. In addition, the specific configuration, arrangement, quantity, angle, material, and the like of each member and part can be changed as appropriate without departing from the spirit of the present invention. On the other hand, all the components shown in the above embodiment are not necessarily essential, and may be appropriately selected.

DESCRIPTION OF SYMBOLS 1 Gas engine 2a Combustion chamber 5b Crank chamber 11 Intake passage 12 Air cleaner 13 Gas mixer 15 Blow-by gas passage 21 Case 22 Filter element 41 Intake chamber 42 Upstream chamber 43 Downstream chamber 43L Downstream space 43U Upstream space 45 Partition 45a Inlet port 50 Reed valve (one-way valve)

Claims (2)

An air cleaner provided in the intake passage to be connected to the combustion chamber, wherein provided on the downstream side of the air cleaner of the intake passage, a gas mixer for mixing the intake fuel gas that will be supplied, and a fuel supply source and the gas mixer A gas engine provided with a connected fuel supply path, and an electromagnetic proportional valve that controls a flow rate of the fuel gas passing through the fuel supply path by controlling a supply pressure of the fuel gas according to a magnitude of an energization current . An intake structure,
The air cleaner includes a case that defines an intake chamber, a filter element that is installed in the case and divides the intake chamber into an upstream chamber and a downstream chamber, an intake port is formed, and the downstream chamber is Further, a partition wall that is divided into an upstream space and a downstream space, and the intake port is openably and closably attached to the downstream space side of the partition wall , allowing fluid flow from the upstream space to the downstream space. to one, it has a lead valve for preventing the flow of fluid to the upstream space from the downstream space,
The reed valve is more elastically deformed as the intake negative pressure is larger, and the fuel supply source is configured such that the opening degree of the reed valve with respect to the intake negative pressure becomes fuel rich at engine start and fuel lean at rated load operation. An intake structure for a gas engine, which is set according to the pressure of the engine. The intake structure for a gas engine according to claim 1 , further comprising a blow-by gas passage that connects the crank chamber and the downstream space of the air cleaner and guides the blow-by gas in the crank chamber to the downstream space. .

Images