WO2015198643A1 - Engine unit - Google Patents

Engine unit Download PDF

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Publication number
WO2015198643A1
WO2015198643A1 PCT/JP2015/056882 JP2015056882W WO2015198643A1 WO 2015198643 A1 WO2015198643 A1 WO 2015198643A1 JP 2015056882 W JP2015056882 W JP 2015056882W WO 2015198643 A1 WO2015198643 A1 WO 2015198643A1
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WO
WIPO (PCT)
Prior art keywords
oxygen sensor
sensor
oxygen
downstream
exhaust
Prior art date
Application number
PCT/JP2015/056882
Other languages
French (fr)
Japanese (ja)
Inventor
貴史 久保
幸博 谷川
恭弘 樋口
Original Assignee
ヤンマー株式会社
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Application filed by ヤンマー株式会社 filed Critical ヤンマー株式会社
Priority to JP2016529106A priority Critical patent/JPWO2015198643A1/en
Publication of WO2015198643A1 publication Critical patent/WO2015198643A1/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D45/00—Electrical control not provided for in groups F02D41/00 - F02D43/00
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • the present invention relates to an engine unit.
  • Patent Document 1 there is known a gas engine that operates by mixing a combustible gas such as natural gas or city gas with air and burning it (see Patent Document 1).
  • an engine unit that includes an oil tank so that it is not necessary to replace the lubricating oil over a long period of time (see Patent Document 2).
  • Such an engine employs an exhaust gas purification catalyst (for example, a three-way catalyst) for the purpose of reducing exhaust emissions (reducing CO, NOx, and THC in exhaust gas).
  • Patent Document 3 discloses an internal combustion engine having a three-way catalyst in an exhaust passage, an oxygen sensor provided in an exhaust passage upstream of the three-way catalyst, and an oxygen sensor provided in a downstream exhaust passage.
  • the upstream oxygen sensor is used for air-fuel ratio control, and the downstream oxygen sensor is upstream. This is used for correcting and controlling the deviation of the sensor output due to the deterioration of the oxygen sensor. Since the upstream oxygen sensor is arranged on the upstream side of the three-way catalyst, it is easily affected by the components of exhaust gas before purification and the heat, and is easily deteriorated.
  • the deviation control of the sensor output due to the deterioration of the upstream oxygen sensor is corrected by the downstream oxygen sensor.
  • the downstream oxygen sensor fails, the upstream oxygen sensor cannot be corrected and controlled.
  • the downstream oxygen sensor is disposed on the downstream side of the three-way catalyst, it is exposed to exhaust gas that has become hot due to passing through the three-way catalyst, so that the heat load becomes severe and the output deteriorates. There is a fear.
  • the output deterioration of the downstream oxygen sensor itself cannot be detected, it is necessary to maintain the detection accuracy of the downstream oxygen sensor. Therefore, in consideration of the output degradation of the upstream oxygen sensor and downstream oxygen sensor of the catalyst provided in the exhaust passage (exhaust path) in this way, the detection accuracy of the upstream and downstream oxygen sensors is long-term. It is hoped that it can be maintained.
  • the detection accuracy of the upstream and downstream oxygen sensors is maintained for a long time in consideration of output deterioration of the upstream oxygen sensor and downstream oxygen sensor of the catalyst provided in the exhaust path in the engine unit. It aims to provide a technology that can do.
  • the present invention Engine A catalyst provided in an exhaust path of the engine through which exhaust gas from the engine flows; A plurality of oxygen sensors arranged in the exhaust path for detecting the oxygen concentration of the exhaust gas; An engine unit comprising: control means for calculating an air-fuel ratio based on the oxygen concentration of the exhaust gas detected by the oxygen sensor;
  • the plurality of oxygen sensors includes: A first oxygen sensor disposed in an exhaust path upstream of the catalyst; A second oxygen sensor disposed in an exhaust path downstream of the catalyst;
  • the exhaust path on the downstream side of the catalyst includes a third oxygen sensor disposed on the downstream side of the second oxygen sensor.
  • the present invention provides the engine unit,
  • the control means acquires the sensor output of the second oxygen sensor and / or the third oxygen sensor, and corrects and controls the deviation of the sensor output of the first oxygen sensor compared with the sensor output of the first oxygen sensor. It is supposed to be.
  • the present invention provides the engine unit,
  • the exhaust path on the downstream side of the catalyst includes a heat exchanger that heats water with the exhaust gas,
  • the third oxygen sensor is provided in the vicinity of the heat exchanger.
  • the present invention provides the engine unit,
  • the control means acquires sensor output by periodically energizing the third oxygen sensor.
  • the present invention provides the engine unit,
  • the control means acquires the sensor output by periodically energizing the second oxygen sensor, and the interval for energizing the third oxygen sensor is longer than the interval for energizing the second oxygen sensor. It is a thing.
  • the present invention also provides: Engine, A catalyst provided in an exhaust path of the engine through which exhaust gas from the engine flows; A plurality of oxygen sensors arranged in the exhaust path for detecting the oxygen concentration of the exhaust gas; An engine unit comprising: control means for calculating an air-fuel ratio based on the oxygen concentration of the exhaust gas detected by the oxygen sensor;
  • the plurality of oxygen sensors includes: An upstream oxygen sensor disposed in an exhaust path upstream of the catalyst; A downstream oxygen sensor disposed in the exhaust path downstream of the catalyst, The exhaust path on the downstream side of the catalyst includes a heat exchanger that heats water with the exhaust gas, The downstream oxygen sensor is arranged in the heat exchanger, and the downstream oxygen sensor is cooled by water flowing in the heat exchanger.
  • the present invention provides the engine unit, A temperature sensor disposed near the downstream side of the catalyst and electrically connected to the control means for detecting the exhaust gas temperature;
  • the downstream oxygen sensor has a heater,
  • the control means includes The energization timing of the heater of the downstream oxygen sensor is controlled based on the temperature of the exhaust gas detected by the temperature sensor.
  • the first oxygen sensor is disposed in the exhaust path upstream of the catalyst, and the second oxygen sensor and the third oxygen sensor are sequentially disposed in the exhaust path downstream of the catalyst.
  • the first oxygen sensor is easily deteriorated by the influence of exhaust gas components and heat before the catalyst purification, but the second oxygen is sequentially arranged on the downstream side of the catalyst that is less affected by exhaust gas components and heat.
  • the sensor and the third oxygen sensor are unlikely to deteriorate. Therefore, even if output deterioration (sensor output deviation) occurs in the first oxygen sensor, the sensor output deviation of the first oxygen sensor can be corrected by the second oxygen sensor and the third oxygen sensor. That is, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
  • the third oxygen sensor is disposed downstream of the second oxygen sensor in the exhaust path and the most downstream of the plurality of oxygen sensors, the third oxygen sensor is least affected by the components contained in the exhaust gas and heat. Even if output degradation occurs in the first oxygen sensor or the second oxygen sensor, the third oxygen sensor can correct the deviation of the sensor output of the first oxygen sensor or the second oxygen sensor.
  • control means acquires the sensor output of the second oxygen sensor and / or the third oxygen sensor, and compares the sensor output of the first oxygen sensor with the sensor output of the first oxygen sensor. Control correction. Thereby, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
  • the third oxygen sensor is provided in the vicinity of the heat exchanger in the exhaust path downstream of the catalyst.
  • the third oxygen sensor is less susceptible to heat than the second oxygen sensor and can extend its life. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
  • the control means acquires the sensor output by periodically energizing the third oxygen sensor. Therefore, deterioration due to energization of the third oxygen sensor can be suppressed, and the life of the third oxygen sensor can be extended. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
  • the control means acquires the sensor output by periodically energizing the second oxygen sensor, and makes the interval for energizing the third oxygen sensor longer than the interval for energizing the second oxygen sensor. .
  • the 3rd oxygen sensor can suppress degradation by energization rather than the 2nd oxygen sensor, and can extend the lifetime of both the 2nd oxygen sensor and the 3rd oxygen sensor. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
  • the downstream oxygen sensor is disposed in the heat exchanger and is cooled by water flowing in the heat exchanger.
  • the thermal load with respect to a downstream oxygen sensor can be reduced, and the proof stress improvement of a downstream oxygen sensor can be aimed at. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
  • the energization timing of the heater of the downstream oxygen sensor is controlled by the temperature of the exhaust gas.
  • the exhaust temperature on the downstream side of the catalyst rises.
  • the heater of the downstream oxygen sensor is energized to start air-fuel ratio control. As a result, the time during which the air-fuel ratio control is not effective can be shortened.
  • the figure which shows an engine unit The figure which shows the structure of an engine.
  • the schematic diagram which shows the attachment position of the downstream oxygen sensor in the conventional heat exchanger The schematic diagram which shows the attachment position of the downstream oxygen sensor in the heat exchanger which concerns on embodiment of this invention.
  • FIG. 1 It is a figure which similarly shows the internal structure of the one end side of a heat exchanger, (a) is a side view of a conventional product, (b) is a perspective view of a conventional product, (c) is a side view of a second embodiment, (d ) Is a perspective view of the second embodiment.
  • Sectional drawing which similarly shows the one end side of a heat exchanger.
  • the figure which shows the electricity supply timing of the heater of the conventional downstream oxygen sensor.
  • the side view and rear view showing the state where the refrigeration container provided with the engine unit concerning the embodiment of the present invention was loaded on the truck.
  • the engine unit 100 according to the first embodiment of the present invention will be described.
  • FIG. 1 shows the engine unit 100.
  • the engine unit 100 is used as a power source for the gas heat pump.
  • the engine unit 100 includes an engine 1.
  • the engine unit 100 includes an oil tank 2.
  • FIG. 2 shows the structure of the engine 1.
  • the engine 1 is a so-called gas engine that operates by mixing a combustible gas such as natural gas or city gas with air to generate an air-fuel mixture and burning the air-fuel mixture.
  • the engine 1 mainly includes a main body 11, an intake passage 12, an exhaust passage 13, and a control means (controller) 40 (see FIG. 3).
  • the main body 11 converts the energy obtained by burning the fuel into a rotational motion.
  • the main body 11 mainly includes a cylinder block 111, a cylinder head 112, a piston 113, a crankshaft 114, a head cover 115, and an oil pan 116.
  • the main body 11 is combusted by a cylinder 111c provided in the cylinder block 111, a piston 113 slidably housed in the cylinder 111c, and a cylinder head 112 disposed so as to face the piston 113.
  • Chamber C is configured. That is, the combustion chamber C refers to an internal space whose volume changes due to the sliding motion of the piston 113.
  • the piston 113 is connected to the crankshaft 114 by a connecting rod, and the crankshaft 114 is rotated by the sliding motion of the piston 113.
  • a head cover 115 is provided above the cylinder head 112.
  • an oil pan 116 is provided below the cylinder block 111. Lubricating oil L is accumulated in the oil pan 116.
  • a water jacket 117 is provided around the cylinder block 111, and the cylinder block 111 is cooled by circulating cooling water inside the water jacket 117.
  • the water jacket 117 is provided with cooling water temperature detecting means 118 for detecting the temperature of the cooling water, and is connected to the control means 40 described later.
  • the control means 40 can acquire the temperature of the cooling water in the water jacket 117 detected by the cooling water temperature detection means 118.
  • the intake passage section 12 mixes combustible gas and air and guides them to the combustion chamber C.
  • the intake passage portion 12 is mainly composed of a mixer 121 (see FIG. 1), a fuel adjustment valve (also referred to as GVM) 123, and an intake manifold 122.
  • the mixer 121 and the fuel adjustment valve 123 constitute an air-fuel mixture supply device that supplies an air-fuel mixture composed of combustible gas and air to the combustion chamber C via the intake manifold 122.
  • the mixer 121 is a Venturi mixer.
  • the mixer 121 supplies a combustible gas to air sucked from the outside to generate an air-fuel mixture.
  • the mixer 121 is attached to one end of the intake manifold 122.
  • the fuel adjustment valve 123 adjusts the amount of flammable gas supplied to the mixer 121.
  • the air-fuel mixture supply apparatus including the mixer 121 and the fuel adjustment valve 123 performs fuel increase or fuel decrease within a predetermined range by changing the opening of the fuel adjustment valve 123.
  • the fuel adjustment valve 123 is electrically connected to the control means 40.
  • the control means 40 controls the opening degree of the fuel adjustment valve 123.
  • the intake manifold 122 guides the air-fuel mixture generated by the mixer 121 to each combustion chamber C.
  • the intake manifold 122 is formed to branch to each combustion chamber C so as to guide the air-fuel mixture to the four combustion chambers C.
  • the intake manifold 122 is connected to the head cover 115 by a pipe. This is to prevent the internal pressure of the cylinder block 111 and the head cover 115 from increasing.
  • the exhaust passage unit 13 guides the exhaust discharged from the combustion chamber C to the outside.
  • the exhaust passage section 13 mainly includes an exhaust manifold 131, an upstream side exhaust pipe 137, a three-way catalytic converter 132, a downstream side exhaust pipe 138, a first oxygen sensor 134, a second oxygen sensor 135, and a third And an oxygen sensor 136.
  • the exhaust manifold 131 guides the exhaust discharged from each combustion chamber C to the three-way catalytic converter 132 (hereinafter simply referred to as the catalytic converter 132) via the upstream side exhaust pipe 137.
  • the exhaust manifold 131 is formed so as to merge from each combustion chamber C so as to guide the exhaust from the four combustion chambers C.
  • the catalytic converter 132 removes off-flavors caused by aldehydes.
  • the catalytic converter 132 oxidizes aldehydes using a catalytic reaction with platinum or the like.
  • a heat exchanger 133 that heats water using exhaust gas is attached to the downstream exhaust pipe 138 on the downstream side of the catalytic converter 132 (see FIGS. 1 and 3).
  • a three-way catalyst is described as a catalyst for purifying exhaust gas, but is not particularly limited.
  • the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 detect the oxygen concentration in the exhaust gas discharged from the exhaust manifold 131 and output a detection signal corresponding to the oxygen concentration in the exhaust gas. It is a sensor. As shown in FIG. 3, the first oxygen sensor 134 is disposed in the exhaust manifold 131 upstream of the catalytic converter 132. Second oxygen sensor 135 is arranged in downstream exhaust pipe 138 on the downstream side of catalytic converter 132. The second oxygen sensor 135 is disposed on one end side of the downstream side exhaust pipe 138 and in the vicinity of the front end of the catalytic converter 132.
  • the third oxygen sensor 136 is disposed downstream of the second oxygen sensor 135 in the downstream exhaust pipe 138 downstream of the catalytic converter 132.
  • the third oxygen sensor 136 is disposed on the other end side (downstream end side) of the downstream side exhaust pipe 138 and in the vicinity of the heat exchanger 133.
  • the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 are electrically connected to the control means 40. Based on the measurement results of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136, and data and programs stored in advance, the control means 40 opens the throttle valve, the fuel adjustment valve 123, and the like.
  • a known oxygen sensor capable of detecting the oxygen concentration in the exhaust gas can be used, for example, a UEGO (Universal Exhaust Gas Oxygen) sensor. May be used.
  • the UEGO sensor can perform atmospheric calibration. When a UEGO sensor is used as the second oxygen sensor 135 and the third oxygen sensor 136, detection accuracy can be improved by periodically calibrating the air.
  • the control means 40 calculates the air-fuel ratio based on the oxygen concentration of the exhaust gas detected by the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136, and controls the opening of the fuel adjustment valve 123. To do.
  • the control means 40 has a storage unit.
  • the storage unit includes measurement results of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136, data stored in advance (for example, a map, etc.), and opening of a throttle valve, a fuel adjustment valve 123, and the like.
  • a program for controlling the degree via the actuator is stored.
  • control unit 40 constantly energizes the first oxygen sensor 134 and the second oxygen sensor 135 to acquire each sensor output in time series, and energizes the third oxygen sensor 136 every predetermined time to generate the third oxygen sensor 136.
  • the sensor output of the oxygen sensor 136 every predetermined time can be acquired.
  • the predetermined time for energizing the third oxygen sensor 136 can be arbitrarily set based on a predetermined program stored in the control means 40.
  • the control means 40 appropriately controls the energization state (always energization or energization every predetermined time) of each oxygen sensor independently of each of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136. can do.
  • control means 40 constantly energizes the first oxygen sensor 134 to acquire sensor outputs in time series, and independently energizes the second oxygen sensor 135 and the third oxygen sensor 136 at predetermined time intervals. Each sensor output for every predetermined time can be acquired.
  • the predetermined time for energizing each of the second oxygen sensor 135 and the third oxygen sensor 136 can be arbitrarily set based on a predetermined program stored in the control means 40.
  • FIG. 4 shows a flow of the correction control method of the first oxygen sensor in the engine 1.
  • the control means 40 first acquires the sensor outputs (output voltages) of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 (step S10). Next, the sensor outputs of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 are compared (step S20), and compared with the sensor output from the second oxygen sensor 135, the first oxygen sensor 134 is compared. If there is no deviation in the sensor output due to (when the deviation is within a predetermined allowable range) (YES in step S30), the sensor output from the first oxygen sensor 134 is adopted, and the air-fuel ratio is calculated from the sensor output. (Step S40).
  • step S30 If it is determined in step S30 that the sensor output of the first oxygen sensor 134 is deviated from the sensor output of the second oxygen sensor 135, that is, if it is determined that the output of the first oxygen sensor 134 has deteriorated ( In step S30, the control unit 40 compares the sensor outputs of the second oxygen sensor 135 and the third oxygen sensor 136 (step S50). When there is no deviation between the sensor outputs of the second oxygen sensor 135 and the third oxygen sensor 136 (when the deviation is within a predetermined allowable range) (YES in step S60), the sensor output from the second oxygen sensor 135 is adopted. Then, the air-fuel ratio is calculated from the sensor output (step S70).
  • step S60 If it is determined in step S60 that the sensor output of the second oxygen sensor 135 is different from the sensor output of the third oxygen sensor 136, that is, if it is determined that the output of the second oxygen sensor has deteriorated (step S60).
  • the control means 40 employs the sensor output from the third oxygen sensor 136 and calculates the air-fuel ratio based on the sensor output (step S80).
  • step S10 the sensor output from the third oxygen sensor 136 is acquired.
  • the third oxygen sensor 136 does not need to be always in the energized state (ON state).
  • the third oxygen sensor 136 is in an energized state (ON state) when correcting and controlling the first oxygen sensor 134 periodically (for example, about once every several tens of hours to several hundred hours) instead of always. Should be set. That is, the third oxygen sensor 136 only needs to be energized periodically when the control means 40 performs the correction control of the first oxygen sensor 134, and in this way, the third oxygen sensor 136 is energized. Deterioration can be suppressed.
  • step S10 the sensor output from the second oxygen sensor 135 is acquired.
  • the second oxygen sensor 135 does not have to be in a normally energized state (ON state).
  • the second oxygen sensor 135 can be set to be in an energized state (ON state) when correcting and controlling the first oxygen sensor 134 periodically instead of constantly. That is, the second oxygen sensor 135 may be energized only periodically when the control means 40 performs the correction control of the first oxygen sensor 134. In this way, the second oxygen sensor 135 is energized. Deterioration can be suppressed.
  • the third oxygen sensor 136 is less likely to be deteriorated by energization than the second oxygen sensor 135. May be.
  • FIG. 5 is a flowchart showing another embodiment of the correction control method for the first oxygen sensor.
  • step S10 first, after obtaining the sensor outputs of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 simultaneously (at the same time) (step S10), the first oxygen sensor 134 and The second oxygen sensor 135 is always energized and constantly acquires (acquires in time series) each sensor output.
  • the third oxygen sensor 136 is energized at a predetermined time interval to acquire the sensor output of the third oxygen sensor 136.
  • the sensor outputs of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 are acquired at the predetermined time interval (step S100).
  • step S200 the sensor outputs of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 are compared.
  • the sensor output from the first oxygen sensor 134 is adopted, and the air-fuel ratio is calculated from the sensor output (step S400).
  • the second oxygen sensor 135 is always energized, but is not particularly limited.
  • the second oxygen sensor 135 may be energized at a predetermined time interval.
  • the predetermined time interval at which the third oxygen sensor 136 is energized is set longer than the predetermined time interval at which the second oxygen sensor 135 is energized, and the second oxygen sensor 135 and the third oxygen sensor 136 are predetermined. It is preferable to set in advance in the control means 40 so as to acquire each sensor output in synchronization (synchronization) at time intervals. By doing in this way, the 2nd oxygen sensor 135 can suppress deterioration by electricity supply rather than the 3rd oxygen sensor 136, and can prolong a lifetime.
  • step S300 If it is determined in step S300 that the sensor output of the first oxygen sensor 134 is deviated from the sensor output of the second oxygen sensor 135, that is, if it is determined that the output of the first oxygen sensor 134 has deteriorated ( In step S300, the control unit 40 compares the sensor outputs of the second oxygen sensor 135 and the third oxygen sensor 136 (step S500). When there is no deviation between the sensor outputs of the second oxygen sensor 135 and the third oxygen sensor 136 (when the deviation is within a predetermined allowable range) (YES in step S600), the sensor output from the second oxygen sensor 135 is adopted. Then, the air-fuel ratio is calculated from the sensor output (step S700).
  • step S600 If it is determined in step S600 that the sensor output of the second oxygen sensor 135 is different from the sensor output of the third oxygen sensor 136, that is, if it is determined that the output of the second oxygen sensor has deteriorated (step S600).
  • the control means 40 employs the sensor output from the third oxygen sensor 136 and calculates the air-fuel ratio based on the sensor output (step S800).
  • the exhaust path of the engine 1 of the present embodiment includes three oxygen sensors (a first oxygen sensor 134, a second oxygen sensor 135, and a third oxygen sensor 136), but all three oxygen sensors are used. It does not have to be.
  • the control unit 40 alternately energizes the second oxygen sensor 135 and the third oxygen sensor 136 to acquire the sensor output, and compares the sensor output with the first oxygen sensor 134 with the first oxygen sensor 134.
  • the correction control may be performed. This is because deterioration due to energization in the second oxygen sensor 135 and the third oxygen sensor 136 can be suppressed by energizing the second oxygen sensor 135 and the third oxygen sensor 136 alternately.
  • a sensor output correction control method (deterioration detection method) of the first oxygen sensor 134 using the amount of change in the opening of the fuel adjustment valve 123 will be described.
  • the deterioration with time of the air-fuel ratio measured by one oxygen sensor (for example, the first oxygen sensor 134) after the initial and long-time operation is estimated, and the change amount of the sensor output of the oxygen sensor is controlled beforehand.
  • the change amount of the sensor output of the oxygen sensor is set in advance as a threshold value, and the control means 40 detects the deterioration of the sensor output of the first oxygen sensor 134.
  • FIG. 6 is at a predetermined engine speed
  • the vertical axis is the sensor output of the oxygen sensor
  • the horizontal axis is the oxygen concentration by the first oxygen sensor 134.
  • the sensor output at a predetermined engine speed is shifted above or below a reference value (for example, a sensor output value obtained from the second oxygen sensor 135 or the third oxygen sensor 136).
  • a reference value for example, a sensor output value obtained from the second oxygen sensor 135 or the third oxygen sensor 136.
  • the control means 40 determines that output degradation has occurred in the first oxygen sensor 134.
  • not only one oxygen sensor for example, the first oxygen sensor 134) but also three oxygen sensors (the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136) are not described above. In this way, the presence or absence of output deterioration can also be determined.
  • FIG. 7 is for a predetermined engine speed
  • the vertical axis is the sensor output (output voltage) of the downstream oxygen sensor
  • the horizontal axis is the opening of the fuel adjustment valve 123.
  • control means 40 monitors the change in the correction amount of the first oxygen sensor 134 by the downstream oxygen sensor from the reference value of the sensor output in real time, and when the predetermined value exceeds the normal value, the downstream side It is determined that output degradation has occurred in the oxygen sensors (for example, the second oxygen sensor 135 and the third oxygen sensor 136).
  • the first technical feature of the engine unit 100 is that, as a plurality of oxygen sensors, a first oxygen sensor 134 disposed in the exhaust path upstream of the catalytic converter 132 and an exhaust path downstream of the catalytic converter 132 are disposed. And the third oxygen sensor 136 disposed downstream of the second oxygen sensor 135 in the exhaust path downstream of the catalytic converter 132.
  • the first oxygen sensor 134 is easily deteriorated due to the influence of exhaust gas components and heat before the catalyst purification, but is sequentially arranged downstream of the catalytic converter 132 where the exhaust gas contents and heat are less affected.
  • the second oxygen sensor 135 and the third oxygen sensor 136 are not easily deteriorated.
  • the sensor output deviation of the first oxygen sensor 134 can be corrected by the second oxygen sensor 135 and the third oxygen sensor 136. That is, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time. Further, since the third oxygen sensor 136 is disposed downstream of the second oxygen sensor 135 in the exhaust path and the most downstream of the plurality of oxygen sensors, the third oxygen sensor 136 is least susceptible to the components contained in the exhaust gas and heat. Even if output degradation occurs in the first oxygen sensor 134 or the second oxygen sensor 135, the third oxygen sensor 136 can correct the deviation of the sensor output of the first oxygen sensor 134 or the second oxygen sensor 135.
  • the second technical feature of the engine unit 100 is that the control means 40 acquires the sensor output of the second oxygen sensor 135 and / or the third oxygen sensor 136 and compares it with the sensor output of the first oxygen sensor 134. This is a point of correcting and controlling the deviation of the sensor output of the first oxygen sensor 134. Thereby, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
  • the third technical feature of the engine unit 100 is that the third oxygen sensor 136 is provided in the vicinity of the heat exchanger 133 in the downstream side exhaust pipe 138. As described above, the third oxygen sensor 136 is disposed at a low heat load position on the heat exchanger 133 side (near the heat exchanger 133) in the downstream exhaust pipe 138, so that the heat load on the third oxygen sensor 136 is low. Thus, the third oxygen sensor 136 is less susceptible to heat than the second oxygen sensor 135 and can extend its life. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
  • the fourth technical feature of the engine unit 100 is that the control means 40 acquires the sensor output by periodically energizing the third oxygen sensor 136. Thereby, deterioration due to energization of the third oxygen sensor 136 can be suppressed, and the life of the third oxygen sensor 136 can be extended. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
  • the fifth technical feature of the engine unit 100 is that the control means 40 acquires the sensor output by periodically energizing the second oxygen sensor 135 and sets the interval of energizing the third oxygen sensor 136 to the second. This is a point that is longer than the interval at which the oxygen sensor 135 is energized. Thereby, the third oxygen sensor 136 can suppress deterioration due to energization more than the second oxygen sensor 135, and can extend the lifetime of both the second oxygen sensor 135 and the third oxygen sensor 136. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
  • the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time. Therefore, it is possible to suppress deterioration of exhaust emission during operation due to oxygen sensor failure. Furthermore, it is possible to lengthen the interval between periodic inspections of the oxygen sensor, and to save the labor of maintenance of the oxygen sensor. In addition, since the detection accuracy is maintained by the three oxygen sensors, the reliability of the detection accuracy by the fail-safe function can be ensured.
  • the engine unit 200 (engine 2) is a gas engine unit in which a part of the configuration of the oxygen sensor or the like of the engine unit 100 (engine 1) according to the first embodiment is changed, and the other configurations are related to the first embodiment. It is the same as engine unit 100 (engine 1).
  • the same components as those of the engine unit 100 according to the first embodiment are denoted by the same reference numerals, and the description of the components is omitted.
  • the engine unit 200 of the second embodiment includes an upstream oxygen sensor 134 (first oxygen of the first embodiment) arranged in the exhaust path upstream of the catalytic converter 132 as a plurality of oxygen sensors.
  • the downstream oxygen sensor 140 (see FIG. 12) disposed in the exhaust path downstream of the catalytic converter 132.
  • the exhaust path downstream of the catalytic converter 132 is provided with a heat exchanger 133 that heats water with the exhaust gas.
  • the downstream oxygen sensor 140 is disposed in the heat exchanger 133 and is cooled by water flowing in the heat exchanger 133.
  • a heat exchanger 133 shown in FIG. 12 is a shell-and-tube heat exchanger, and includes a number of gas pipes 139, 139 (see FIG. 15) through which exhaust gas passes and gas pipes 139, 139,. And a heat exchanger main body 145 for cooling the exhaust gas passing through the gas pipes 139, 139.
  • the heat exchanger main body 145 is provided with a cooling water inlet 145a and a cooling water outlet 145b, and the cooling water circulates in the heat exchanger main body 145. That is, the cooling water flows into the cooling water flow path 133b that is a space between the inner peripheral surface of the heat exchanger main body 145 and the outer peripheral surface of the gas pipes 139, 139.
  • the shape of the heat exchanger body 145 is cylindrical, and has an exhaust gas introduction part 146 and an exhaust gas exhaust part 147 which are two spaces partitioned by a partition plate 133c at the front end.
  • the downstream end 138a of the downstream side exhaust pipe 138 is communicated with the upper part of the front end portion of the heat exchanger body 145, and the exhaust gas is introduced into the exhaust gas introduction unit 146.
  • the introduced exhaust gas is cooled by cooling water that passes through the gas pipes 139, 139... And circulates in the heat exchanger body 145, and is provided at the lower part of the front end of the heat exchanger body 145.
  • Exhaust gas outlet 148 is exhausted.
  • the third oxygen sensor 136 is provided in the vicinity of the heat exchanger 133 in the downstream exhaust pipe 138.
  • the third oxygen sensor is provided.
  • the downstream oxygen sensor 140 is provided at one end of the heat exchanger 133 communicating with the downstream end 138 a of the downstream exhaust pipe 138.
  • the second oxygen sensor 135 is provided at the upstream end of the downstream exhaust pipe 138 of the catalytic converter 132 (immediately after the catalytic converter 132), as in the first embodiment.
  • the correction control of the first oxygen sensor 134 can be performed according to the flow of the correction control method of the first oxygen sensor 134 described as the first embodiment.
  • the second oxygen sensor 135 is not an essential configuration.
  • FIG. 11 is a schematic diagram showing the mounting position of the downstream oxygen sensor 140 in the heat exchanger 133 according to the second embodiment of the present invention, and the cooling water of the heat exchanger 133 is guided to the vicinity of the downstream oxygen sensor 140. The configuration is shown.
  • the heat exchanger 133 has a sensor cooling water flow path 133a (see FIGS. 13, 14, and 15) that is a substantially cylindrical space for cooling the downstream oxygen sensor 140 inside the heat exchanger main body 145, and A cooling water flow path 133b for exchanging heat with the exhaust gas and a partition plate 133c for partitioning the exhaust gas introduction part 146 and the exhaust gas exhaust part 147 are provided.
  • the sensor cooling water channel 133a communicates with the cooling water channel 133b.
  • the downstream oxygen sensor 140 is a sensor that detects the oxygen concentration in the exhaust gas discharged from the exhaust manifold 131 and outputs a detection signal corresponding to the oxygen concentration in the exhaust gas.
  • the downstream oxygen sensor 140 includes a heater 140 a that can be controlled by the control means 40.
  • the control means 40 can turn on or off the heater 140a with or without application of a predetermined voltage value (in the modified example of the second embodiment described later, rated voltage 11V).
  • the downstream oxygen sensor 140 is disposed on one end (front end) side of the heat exchanger 133.
  • the downstream oxygen sensor 140 is electrically connected to the control means 40.
  • the control means 40 controls the opening degree of the throttle valve, the fuel adjustment valve 123, and the like via an actuator based on the measurement results of the upstream oxygen sensor 134 and the downstream oxygen sensor 140 and data and programs stored in advance.
  • a known oxygen sensor capable of detecting the oxygen concentration in the exhaust gas can be used.
  • a UEGO Universal Exhaust Gas Oxygen
  • the UEGO sensor can perform atmospheric calibration. When a UEGO sensor is used as the upstream oxygen sensor 134 and the downstream oxygen sensor 140, detection accuracy can be improved by periodically performing atmospheric calibration.
  • a downstream side oxygen sensor from one end of the cooling water flow path 133b is used as the sensor cooling water flow path 133a. It extends to 140 attachment parts. 13 and 14 show the differences between the downstream oxygen sensor arranged in the conventional heat exchanger and the downstream oxygen sensor 140 arranged in the heat exchanger 133 according to the second embodiment.
  • the base A of the downstream oxygen sensor is not good if the temperature rises too much. It is not good if the temperature of the tip B serving as the detection part is lowered.
  • the cooling water flow path is extended forward from one end of the cooling water flow path 133b, A substantially cylindrical sensor cooling water flow path 133a (see FIG. 14) is provided so that the cooling water flows around the base A of the downstream oxygen sensor 140.
  • the cooling water flows around the base A of the downstream oxygen sensor 140, and the cooling water does not pass through the base A.
  • the engine unit 200 of the second embodiment includes an upstream oxygen sensor 134 (first oxygen of the first embodiment) arranged in the exhaust path upstream of the catalytic converter 132 as a plurality of oxygen sensors. And the downstream oxygen sensor 140 disposed in the vicinity of the downstream side of the catalytic converter 132. Further, a temperature sensor 141 that is electrically connected to the control means 40 and detects the exhaust gas temperature is provided in the vicinity of the downstream side of the catalytic converter 132. In the modification of the second embodiment, the control means 40 is configured to control the energization timing of the heater 140a of the downstream oxygen sensor 140 based on the temperature of the exhaust gas detected by the temperature sensor 141.
  • the temperature sensor 141 is electrically connected to the control means 40, and can detect the temperature of the exhaust gas flowing through the exhaust path downstream of the catalytic converter 132.
  • the control means 40 can detect the exhaust temperature by the temperature sensor 141 and can control the energization timing of the heater 140a of the downstream oxygen sensor 140 based on the exhaust temperature.
  • downstream oxygen sensor 140 and the like described above include those using a solid electrolyte that generates an electromotive force according to the principle of an oxygen concentration cell, such as ceramics such as zirconia.
  • a downstream oxygen sensor 140 has a temperature range in which the oxygen concentration in the exhaust gas can be accurately detected due to its nature.
  • the heater 140a inside the downstream oxygen sensor 140 ( The temperature is adjusted to increase the accuracy of detecting the oxygen concentration by performing rated energization with respect to (see FIG. 8).
  • control means 40 stores data such as a predetermined time during which the heater 140a in the downstream oxygen sensor 140 is energized, and the exhaust gas based on the oxygen concentration of the exhaust gas detected by the downstream oxygen sensor 140.
  • the air-fuel ratio of the mixed gas that is the source of the above is calculated.
  • control method is achieved by a program and data stored in the control means 40.
  • step S11 when the operation of the engine 2 is started, the process proceeds to step S11.
  • step S11 the control means 40 detects the exhaust gas temperature by the temperature sensor 141.
  • step S12 the control means 40 determines whether or not the exhaust gas temperature detected by the temperature sensor 141 is equal to or higher than a preset exhaust gas temperature threshold. If the exhaust gas temperature is equal to or higher than the exhaust gas temperature threshold, the process proceeds to step S13. If the exhaust gas temperature is lower than the exhaust gas temperature threshold, the process of S11 is continued.
  • step S13 rated energization (11V in FIG. 17) is started in the heater 140a included in the downstream oxygen sensor 140.
  • step S14 the oxygen concentration is detected by the downstream oxygen sensor 140, the oxygen concentration (sensor output) is adopted, the air-fuel ratio is calculated by the control means 40 as described above, and the air-fuel ratio control is performed.
  • oxygen sensors are assembled on the upstream side and the downstream side of the exhaust manifold.
  • An exhaust temperature sensor is attached to the three-way catalyst outlet.
  • Some conventional downstream oxygen sensors have a built-in heater to increase the temperature inside the sensor.
  • the energization timing to the heater of the downstream oxygen sensor is controlled by the engine cooling water temperature (for example, when the engine cooling water temperature becomes 40 ° C. or higher in warm-up operation). Therefore, air-fuel ratio control cannot be executed during warm-up.
  • the exhaust gas temperature at which the temperature sensor 141 detects the energization timing of the heater 140a of the downstream oxygen sensor 140 by the control means 40 based on the control flow of the heater 140a of the downstream oxygen sensor 140 described above.
  • the downstream exhaust temperature of the catalytic converter 132 increases.
  • the heater of the downstream oxygen sensor 140 is energized at the time when the exhaust gas temperature rises (threshold value reaching the predetermined exhaust gas temperature), and the air-fuel ratio control is started. As a result, as indicated by the dotted arrow in FIG. 17, the time during which the air-fuel ratio is not effective is reduced.
  • the configuration of the modification of the second embodiment suppresses the deterioration of exhaust characteristics. Moreover, the engine performance in warm air can be maintained.
  • the present invention is not limited to an engine device such as a diesel engine mounted on a stationary generator or a refrigerator, but can be applied to a device or a moving body including various internal combustion engines.
  • FIG. 19 shows the refrigeration container 10 loaded on the truck 2, but such a refrigeration container 10 includes a container 3 and a refrigeration unit 4.
  • the engine unit according to the present invention can be applied as an engine unit that drives a generator constituting the refrigeration unit 4.

Abstract

An engine unit according to the present invention is capable of maintaining, over the long-term, the detection accuracy of oxygen sensors on the upstream side and the downstream side of a three-way catalyst, taking into account the output deterioration of the oxygen sensor on the upstream side and the oxygen sensor on the downstream side. An engine unit (100) comprises: an engine (1); a catalytic converter (132) provided in the exhaust passage; a plurality of oxygen sensors disposed in the exhaust path of the catalytic converter (132); and a control means (40) that calculates the air-fuel ratio based on the concentration of oxygen in the exhaust gas detected by the oxygen sensors. The plurality of oxygen sensors of the engine unit (100) comprise: a first oxygen sensor (134) disposed on the upstream side of the catalytic converter (132), a second oxygen sensor (135) disposed on the downstream side of the catalytic converter (132), and a third oxygen sensor (136) disposed on the downstream side of the second oxygen sensor (135) in the exhaust path on the downstream side of the catalytic converter (132).

Description

エンジンユニットEngine unit
　本発明は、エンジンユニットに関する。 The present invention relates to an engine unit.
　従来より、天然ガスや都市ガス等の可燃性ガスを空気と混合し、燃焼させることによって稼働するガスエンジンが知られている（特許文献１参照）。また、オイルタンクを備えることにより、長期にわたって潤滑油の交換を不要としたエンジンユニットが存在している（特許文献２参照）。このようなエンジンには、排気エミッション低減（排気ガス中のＣＯ、ＮＯｘ、ＴＨＣ低減）を目的として排ガス浄化用の触媒（例えば、３元触媒）が採用されている。また、このようなエンジンでは、ストイキ状態（理想空燃比である空気過剰率λ＝１）の混合気で燃焼させる、いわゆるストイキ燃焼が採用されている。ストイキ燃焼が採用されるエンジンでは、ストイキ状態を維持するために、排気経路における高精度な空燃比の制御が必要となる。空燃比は排気ガス中の酸素濃度に基づいて算出されるため３元触媒の上流側及び下流側の排気経路に２個の酸素センサを設置する構成のものが知られている（特許文献３参照）。 Conventionally, there is known a gas engine that operates by mixing a combustible gas such as natural gas or city gas with air and burning it (see Patent Document 1). In addition, there is an engine unit that includes an oil tank so that it is not necessary to replace the lubricating oil over a long period of time (see Patent Document 2). Such an engine employs an exhaust gas purification catalyst (for example, a three-way catalyst) for the purpose of reducing exhaust emissions (reducing CO, NOx, and THC in exhaust gas). In such an engine, so-called stoichiometric combustion is employed in which combustion is performed with an air-fuel mixture in a stoichiometric state (the air excess ratio λ = 1 which is an ideal air-fuel ratio). In an engine that employs stoichiometric combustion, in order to maintain the stoichiometric state, it is necessary to control the air-fuel ratio with high accuracy in the exhaust path. Since the air-fuel ratio is calculated based on the oxygen concentration in the exhaust gas, there is known a configuration in which two oxygen sensors are installed in the exhaust path upstream and downstream of the three-way catalyst (see Patent Document 3). ).
　特許文献３には、排気通路に三元触媒を備え、該三元触媒の上流側の排気通路内に酸素センサを設けるとともに、下流側の排気通路内にも酸素センサを設けた内燃機関が開示されている。このような三元触媒の上流側及び下流側の排気通路にそれぞれひとつずつ酸素センサを備えるエンジンの場合、上流側の酸素センサが空燃比制御のために用いられ、下流側の酸素センサは上流側の酸素センサの劣化によるセンサ出力のズレを補正制御するために用いられる。上流側の酸素センサは、三元触媒の上流側に配置されることから浄化前の排気ガスの含有成分や熱の影響を受けやすく、劣化がすすみやすい。そのため、上流側の酸素センサの劣化によるセンサ出力のズレを下流側の酸素センサで補正制御を行うが、下流側の酸素センサが故障した場合は上流側の酸素センサを補正制御することができない。また、下流側の酸素センサは、三元触媒の下流側に配置されることから当該三元触媒を通過することで高熱となった排気ガスにさらされるため、熱負荷が過酷となり、出力劣化するおそれがある。加えて、下流側の酸素センサ自身の出力劣化を検知することができないため、下流側の酸素センサの検知精度を維持する必要がある。そのため、このように排気通路（排気経路）に設けられる触媒の上流側の酸素センサや下流側の酸素センサの出力劣化を考慮して、上流側及び下流側の酸素センサの検知精度を長期的に維持できることが望まれている。 Patent Document 3 discloses an internal combustion engine having a three-way catalyst in an exhaust passage, an oxygen sensor provided in an exhaust passage upstream of the three-way catalyst, and an oxygen sensor provided in a downstream exhaust passage. Has been. In the case of an engine having one oxygen sensor in each of the upstream and downstream exhaust passages of such a three-way catalyst, the upstream oxygen sensor is used for air-fuel ratio control, and the downstream oxygen sensor is upstream. This is used for correcting and controlling the deviation of the sensor output due to the deterioration of the oxygen sensor. Since the upstream oxygen sensor is arranged on the upstream side of the three-way catalyst, it is easily affected by the components of exhaust gas before purification and the heat, and is easily deteriorated. For this reason, the deviation control of the sensor output due to the deterioration of the upstream oxygen sensor is corrected by the downstream oxygen sensor. However, if the downstream oxygen sensor fails, the upstream oxygen sensor cannot be corrected and controlled. Further, since the downstream oxygen sensor is disposed on the downstream side of the three-way catalyst, it is exposed to exhaust gas that has become hot due to passing through the three-way catalyst, so that the heat load becomes severe and the output deteriorates. There is a fear. In addition, since the output deterioration of the downstream oxygen sensor itself cannot be detected, it is necessary to maintain the detection accuracy of the downstream oxygen sensor. Therefore, in consideration of the output degradation of the upstream oxygen sensor and downstream oxygen sensor of the catalyst provided in the exhaust passage (exhaust path) in this way, the detection accuracy of the upstream and downstream oxygen sensors is long-term. It is hoped that it can be maintained.
特開２００７－１３２２８１号公報JP 2007-132281 A 特開２００８－３８７８１号公報JP 2008-38781 A 特開２００９－２６４３８９号公報JP 2009-264389 A
　本発明は、エンジンユニットにおいて、排気経路に設けられる触媒の上流側の酸素センサや下流側の酸素センサの出力劣化を考慮して、上流側及び下流側の酸素センサの検知精度を長期的に維持することができる技術を提供することを目的としている。 In the engine unit, the detection accuracy of the upstream and downstream oxygen sensors is maintained for a long time in consideration of output deterioration of the upstream oxygen sensor and downstream oxygen sensor of the catalyst provided in the exhaust path in the engine unit. It aims to provide a technology that can do.
　本発明の解決しようとする課題は以上の如くであり、次にこの課題を解決するための手段を説明する。 The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.
　即ち、本発明は、
　エンジンと、
　前記エンジンからの排気ガスが流れる前記エンジンの排気経路に設けられる触媒と、
　前記排気経路に配置され、前記排気ガスの酸素濃度を検出する複数の酸素センサと、
　前記酸素センサにより検出された排気ガスの酸素濃度に基づいて空燃比を算出する制御手段と、を備えたエンジンユニットにおいて、
　前記複数の酸素センサは、
　前記触媒の上流側の排気経路に配置される第１酸素センサと、
　前記触媒の下流側の排気経路に配置される第２酸素センサと、
　前記触媒の下流側の排気経路において、前記第２酸素センサの下流側に配置される第３酸素センサと、から構成される、としたものである。 That is, the present invention
Engine,
A catalyst provided in an exhaust path of the engine through which exhaust gas from the engine flows;
A plurality of oxygen sensors arranged in the exhaust path for detecting the oxygen concentration of the exhaust gas;
An engine unit comprising: control means for calculating an air-fuel ratio based on the oxygen concentration of the exhaust gas detected by the oxygen sensor;
The plurality of oxygen sensors includes:
A first oxygen sensor disposed in an exhaust path upstream of the catalyst;
A second oxygen sensor disposed in an exhaust path downstream of the catalyst;
The exhaust path on the downstream side of the catalyst includes a third oxygen sensor disposed on the downstream side of the second oxygen sensor.
　本発明は、前記エンジンユニットにおいて、
　前記制御手段は、前記第２酸素センサ及び／又は前記第３酸素センサのセンサ出力を取得し、前記第１酸素センサのセンサ出力と比較して該第１酸素センサのセンサ出力のズレを補正制御する、としたものである。 The present invention provides the engine unit,
The control means acquires the sensor output of the second oxygen sensor and / or the third oxygen sensor, and corrects and controls the deviation of the sensor output of the first oxygen sensor compared with the sensor output of the first oxygen sensor. It is supposed to be.
　本発明は、前記エンジンユニットにおいて、
　前記触媒の下流側の排気経路には、前記排気ガスにより水を熱する熱交換器を備え、
　前記第３酸素センサは、前記熱交換器近傍に設けられる、としたものである。 The present invention provides the engine unit,
The exhaust path on the downstream side of the catalyst includes a heat exchanger that heats water with the exhaust gas,
The third oxygen sensor is provided in the vicinity of the heat exchanger.
　本発明は、前記エンジンユニットにおいて、
　前記制御手段は、前記第３酸素センサに定期的に通電することでセンサ出力を取得する、としたものである。 The present invention provides the engine unit,
The control means acquires sensor output by periodically energizing the third oxygen sensor.
　本発明は、前記エンジンユニットにおいて、
　前記制御手段は、前記第２酸素センサに定期的に通電することでセンサ出力を取得するとともに、前記第３酸素センサに通電する間隔を前記第２酸素センサに通電する間隔よりも長くした、としたものである。 The present invention provides the engine unit,
The control means acquires the sensor output by periodically energizing the second oxygen sensor, and the interval for energizing the third oxygen sensor is longer than the interval for energizing the second oxygen sensor. It is a thing.
　また、本発明は、
　エンジンと、
　前記エンジンからの排気ガスが流れる前記エンジンの排気経路に設けられる触媒と、
　前記排気経路に配置され、前記排気ガスの酸素濃度を検出する複数の酸素センサと、
　前記酸素センサにより検出された排気ガスの酸素濃度に基づいて空燃比を算出する制御手段と、を備えたエンジンユニットにおいて、
　前記複数の酸素センサは、
　前記触媒の上流側の排気経路に配置される上流側酸素センサと、
　前記触媒の下流側の排気経路に配置される下流側酸素センサと、から構成され、
　前記触媒の下流側の排気経路には、前記排気ガスにより水を熱する熱交換器を備え、
　前記下流側酸素センサは、前記熱交換器に配置されるとともに、該熱交換器内を流れる水により前記下流側酸素センサが冷却される、としたものである。 The present invention also provides:
Engine,
A catalyst provided in an exhaust path of the engine through which exhaust gas from the engine flows;
A plurality of oxygen sensors arranged in the exhaust path for detecting the oxygen concentration of the exhaust gas;
An engine unit comprising: control means for calculating an air-fuel ratio based on the oxygen concentration of the exhaust gas detected by the oxygen sensor;
The plurality of oxygen sensors includes:
An upstream oxygen sensor disposed in an exhaust path upstream of the catalyst;
A downstream oxygen sensor disposed in the exhaust path downstream of the catalyst,
The exhaust path on the downstream side of the catalyst includes a heat exchanger that heats water with the exhaust gas,
The downstream oxygen sensor is arranged in the heat exchanger, and the downstream oxygen sensor is cooled by water flowing in the heat exchanger.
　本発明は、前記エンジンユニットにおいて、
　前記触媒の下流側近傍に配置されるとともに前記制御手段に電気的に接続され、前記排気ガス温度を検出する温度センサをさらに備え、
　前記下流側酸素センサは、ヒータを有し、
　前記制御手段は、
　前記温度センサにより検出される排気ガスの温度に基づいて前記下流側酸素センサのヒータの通電タイミングを制御する、としたものである。 The present invention provides the engine unit,
A temperature sensor disposed near the downstream side of the catalyst and electrically connected to the control means for detecting the exhaust gas temperature;
The downstream oxygen sensor has a heater,
The control means includes
The energization timing of the heater of the downstream oxygen sensor is controlled based on the temperature of the exhaust gas detected by the temperature sensor.
　本発明の効果として、以下に示すような効果を奏する。 As the effects of the present invention, the following effects are obtained.
　本発明によれば、触媒の上流側の排気経路に第１酸素センサ、触媒の下流側の排気経路に第２酸素センサ及び第３酸素センサを順に配置している。触媒浄化前の排気ガスの含有成分や熱の影響を受けて第１酸素センサは劣化しやすいが、排気ガスの含有成分や熱の影響が少ない触媒の下流側に順に配置された、第２酸素センサ及び第３酸素センサは劣化しにくい。そのため、第１酸素センサに出力劣化（センサ出力のズレ）が生じても、第２酸素センサ及び第３酸素センサにより第１酸素センサのセンサ出力のズレを補正することができる。すなわち、排気経路における酸素センサの検知精度を長期的に維持することができる。また、第３酸素センサは、排気経路において第２酸素センサよりも下流側であって複数の酸素センサのうち最も下流に配置されるため排気ガスの含有成分や熱の影響を最も受けにくく、第１酸素センサや第２酸素センサに出力劣化が生じても、第３酸素センサにより第１酸素センサや第２酸素センサのセンサ出力のズレを補正することができる。 According to the present invention, the first oxygen sensor is disposed in the exhaust path upstream of the catalyst, and the second oxygen sensor and the third oxygen sensor are sequentially disposed in the exhaust path downstream of the catalyst. The first oxygen sensor is easily deteriorated by the influence of exhaust gas components and heat before the catalyst purification, but the second oxygen is sequentially arranged on the downstream side of the catalyst that is less affected by exhaust gas components and heat. The sensor and the third oxygen sensor are unlikely to deteriorate. Therefore, even if output deterioration (sensor output deviation) occurs in the first oxygen sensor, the sensor output deviation of the first oxygen sensor can be corrected by the second oxygen sensor and the third oxygen sensor. That is, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time. Further, since the third oxygen sensor is disposed downstream of the second oxygen sensor in the exhaust path and the most downstream of the plurality of oxygen sensors, the third oxygen sensor is least affected by the components contained in the exhaust gas and heat. Even if output degradation occurs in the first oxygen sensor or the second oxygen sensor, the third oxygen sensor can correct the deviation of the sensor output of the first oxygen sensor or the second oxygen sensor.
　本発明によれば、制御手段は、第２酸素センサ及び／又は第３酸素センサのセンサ出力を取得し、第１酸素センサのセンサ出力と比較して該第１酸素センサのセンサ出力のズレを補正制御する。これにより、排気経路における酸素センサの検知精度を長期的に維持することができる。 According to the present invention, the control means acquires the sensor output of the second oxygen sensor and / or the third oxygen sensor, and compares the sensor output of the first oxygen sensor with the sensor output of the first oxygen sensor. Control correction. Thereby, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
　本発明によれば、第３酸素センサは、触媒の下流側の排気経路において、熱交換器近傍に設けられる。このように第３酸素センサを熱交換器近傍に配置することで、第３酸素センサは、第２酸素センサに比べて熱の影響をより受けにくく、寿命を延ばすことができる。従って、排気経路における酸素センサの検知精度を長期的に維持することができる。 According to the present invention, the third oxygen sensor is provided in the vicinity of the heat exchanger in the exhaust path downstream of the catalyst. By disposing the third oxygen sensor in the vicinity of the heat exchanger in this manner, the third oxygen sensor is less susceptible to heat than the second oxygen sensor and can extend its life. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
　本発明によれば、制御手段は、第３酸素センサに定期的に通電することでセンサ出力を取得する。これにより、第３酸素センサの通電による劣化を抑えることができ、第３酸素センサの寿命を延ばすことができる。従って、排気経路における酸素センサの検知精度を長期的に維持することができる。 According to the present invention, the control means acquires the sensor output by periodically energizing the third oxygen sensor. Thereby, deterioration due to energization of the third oxygen sensor can be suppressed, and the life of the third oxygen sensor can be extended. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
　本発明によれば、制御手段は、第２酸素センサに定期的に通電することでセンサ出力を取得するとともに、第３酸素センサに通電する間隔を第２酸素センサに通電する間隔よりも長くした。これにより、第３酸素センサは、第２酸素センサよりも通電による劣化を抑えることができ、第２酸素センサ及び第３酸素センサの両方の寿命を延ばすことができる。従って、排気経路における酸素センサの検知精度を長期的に維持することができる。 According to the present invention, the control means acquires the sensor output by periodically energizing the second oxygen sensor, and makes the interval for energizing the third oxygen sensor longer than the interval for energizing the second oxygen sensor. . Thereby, the 3rd oxygen sensor can suppress degradation by energization rather than the 2nd oxygen sensor, and can extend the lifetime of both the 2nd oxygen sensor and the 3rd oxygen sensor. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
　本発明によれば、下流側酸素センサは、熱交換器に配置されるとともに、熱交換器内を流れる水により冷却される。これにより、下流側酸素センサに対する熱負荷を低減し、下流側酸素センサの耐力向上を図ることができる。従って、排気経路における酸素センサの検知精度を長期的に維持することができる。 According to the present invention, the downstream oxygen sensor is disposed in the heat exchanger and is cooled by water flowing in the heat exchanger. Thereby, the thermal load with respect to a downstream oxygen sensor can be reduced, and the proof stress improvement of a downstream oxygen sensor can be aimed at. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
　本発明によれば、下流側酸素センサは、排気ガスの温度により前記下流側酸素センサのヒータの通電タイミングが制御される。排気ガス中にＣＯ、ＴＨＣ等が多い場合、触媒下流側の排気温度は上昇する。この特性を利用し、排気温度が上昇した時点で下流側酸素センサのヒータに通電し、空燃比制御をスタートする。これにより、空燃比制御が効かない時間の短縮を図ることができる。 According to the present invention, in the downstream oxygen sensor, the energization timing of the heater of the downstream oxygen sensor is controlled by the temperature of the exhaust gas. When there are a lot of CO, THC, etc. in the exhaust gas, the exhaust temperature on the downstream side of the catalyst rises. Using this characteristic, when the exhaust gas temperature rises, the heater of the downstream oxygen sensor is energized to start air-fuel ratio control. As a result, the time during which the air-fuel ratio control is not effective can be shortened.
エンジンユニットを示す図。The figure which shows an engine unit. エンジンの構造を示す図。The figure which shows the structure of an engine. 排気経路における触媒コンバータ及び酸素センサの配置を示す図。The figure which shows arrangement | positioning of the catalytic converter and oxygen sensor in an exhaust path. エンジンにおける第１酸素センサの補正制御方法のフローを示す図。The figure which shows the flow of the correction | amendment control method of the 1st oxygen sensor in an engine. エンジンにおける第１酸素センサの補正制御方法の別実施形態を示す図。The figure which shows another embodiment of the correction | amendment control method of the 1st oxygen sensor in an engine. センサ出力と酸素濃度との関係を示す図。The figure which shows the relationship between a sensor output and oxygen concentration. センサ出力と燃料調整弁の開度の関係を示す図。The figure which shows the relationship between a sensor output and the opening degree of a fuel adjustment valve. 排気経路における触媒コンバータ、酸素センサ及び温度センサの配置を示す図。The figure which shows arrangement | positioning of the catalytic converter, oxygen sensor, and temperature sensor in an exhaust path. 排気経路に配置されるセンサ及び該排気経路に対応する排気温度変化を示す図。The figure which shows the exhaust temperature change corresponding to the sensor arrange | positioned in an exhaust path, and this exhaust path. 従来の熱交換器における下流側酸素センサの取付位置を示す模式図。The schematic diagram which shows the attachment position of the downstream oxygen sensor in the conventional heat exchanger. 本発明の実施形態に係る熱交換器における下流側酸素センサの取付位置を示す模式図。The schematic diagram which shows the attachment position of the downstream oxygen sensor in the heat exchanger which concerns on embodiment of this invention. 熱交換器の内部構造を示す図。The figure which shows the internal structure of a heat exchanger. 従来品と第２実施形態の各々における下流側酸素センサ周辺部を示す説明図であり、（ａ）は従来品の下流側酸素センサ周辺部を示す図、（ｂ）は（ａ）における拡大図、（ｃ）は第２実施形態の下流側酸素センサ周辺部を示す図、（ｄ）は（ｃ）における拡大図。It is explanatory drawing which shows the downstream oxygen sensor periphery part in each of a conventional product and 2nd Embodiment, (a) is a figure which shows the downstream oxygen sensor periphery part of a conventional product, (b) is an enlarged view in (a). (C) is a figure which shows the downstream oxygen sensor periphery part of 2nd Embodiment, (d) is an enlarged view in (c). 同じく熱交換器の一端側の内部構造を示す図であり、（ａ）は従来品の側面図、（ｂ）は従来品の斜視図、（ｃ）は第２実施形態の側面図、（ｄ）は第２実施形態の斜視図。It is a figure which similarly shows the internal structure of the one end side of a heat exchanger, (a) is a side view of a conventional product, (b) is a perspective view of a conventional product, (c) is a side view of a second embodiment, (d ) Is a perspective view of the second embodiment. 同じく熱交換器の一端側を示す断面図。Sectional drawing which similarly shows the one end side of a heat exchanger. 従来の下流側酸素センサのヒータの通電タイミングを示す図。The figure which shows the electricity supply timing of the heater of the conventional downstream oxygen sensor. 第２実施形態の変形例に係る下流側酸素センサのヒータの通電タイミングを示す図。The figure which shows the energization timing of the heater of the downstream oxygen sensor which concerns on the modification of 2nd Embodiment. 第２実施形態の変形例に係る下流側酸素センサの制御フローを示す図。The figure which shows the control flow of the downstream oxygen sensor which concerns on the modification of 2nd Embodiment. 本発明の実施形態に係るエンジンユニットを備えた冷凍コンテナがトラックに積載された状態を示す側面図及び背面図。The side view and rear view showing the state where the refrigeration container provided with the engine unit concerning the embodiment of the present invention was loaded on the truck.
　本願の発明に係る第１実施形態であるエンジンユニット１００について説明する。 The engine unit 100 according to the first embodiment of the present invention will be described.
　図１は、エンジンユニット１００を示している。 FIG. 1 shows the engine unit 100.
　本エンジンユニット１００は、ガスヒートポンプの動力源として使用される。エンジンユニット１００は、エンジン１を備えている。また、エンジンユニット１００は、オイルタンク２を備えている。 The engine unit 100 is used as a power source for the gas heat pump. The engine unit 100 includes an engine 1. The engine unit 100 includes an oil tank 2.
　まず、エンジン１の構造について簡単に説明する。 First, the structure of the engine 1 will be briefly described.
　図２は、エンジン１の構造を示している。 FIG. 2 shows the structure of the engine 1.
　エンジン１は、天然ガスや都市ガス等の可燃性ガスを空気と混合して混合気を生成し、この混合気を燃焼させることによって稼働するエンジン、いわゆるガスエンジンである。エンジン１は、主に主体部１１と、吸気経路部１２と、排気経路部１３と、制御手段（コントローラ）４０（図３参照）で構成されている。 The engine 1 is a so-called gas engine that operates by mixing a combustible gas such as natural gas or city gas with air to generate an air-fuel mixture and burning the air-fuel mixture. The engine 1 mainly includes a main body 11, an intake passage 12, an exhaust passage 13, and a control means (controller) 40 (see FIG. 3).
　主体部１１は、燃料を燃焼させて得たエネルギーを回転運動に変換する。主体部１１は、主にシリンダブロック１１１と、シリンダヘッド１１２と、ピストン１１３と、クランクシャフト１１４と、ヘッドカバー１１５と、オイルパン１１６と、で構成されている。 The main body 11 converts the energy obtained by burning the fuel into a rotational motion. The main body 11 mainly includes a cylinder block 111, a cylinder head 112, a piston 113, a crankshaft 114, a head cover 115, and an oil pan 116.
　主体部１１には、シリンダブロック１１１に設けられたシリンダ１１１ｃと、該シリンダ１１１ｃに摺動自在に収納されたピストン１１３と、該ピストン１１３に対向するように配置されたシリンダヘッド１１２と、で燃焼室Ｃが構成されている。つまり、燃焼室Ｃは、ピストン１１３の摺動運動によって容積が変化する内部空間を指す。ピストン１１３は、コネクティングロッドによってクランクシャフト１１４と連結されており、該ピストン１１３の摺動運動によってクランクシャフト１１４を回転させる。なお、シリンダヘッド１１２の上部には、ヘッドカバー１１５が設けられている。また、シリンダブロック１１１の下部には、オイルパン１１６が設けられている。オイルパン１１６には、潤滑油Ｌが溜まっている。 The main body 11 is combusted by a cylinder 111c provided in the cylinder block 111, a piston 113 slidably housed in the cylinder 111c, and a cylinder head 112 disposed so as to face the piston 113. Chamber C is configured. That is, the combustion chamber C refers to an internal space whose volume changes due to the sliding motion of the piston 113. The piston 113 is connected to the crankshaft 114 by a connecting rod, and the crankshaft 114 is rotated by the sliding motion of the piston 113. A head cover 115 is provided above the cylinder head 112. In addition, an oil pan 116 is provided below the cylinder block 111. Lubricating oil L is accumulated in the oil pan 116.
　シリンダブロック１１１の周囲にはウォータージャケット１１７が設けられ、このウォータージャケット１１７の内部に冷却水を循環させることでシリンダブロック１１１を冷却している。このウォータージャケット１１７には、冷却水の水温を検出する冷却水温度検知手段１１８が配設され、後述する制御手段４０に接続される。制御手段４０は、冷却水温度検知手段１１８により検出されるウォータージャケット１１７における冷却水の温度を取得することが可能である。 A water jacket 117 is provided around the cylinder block 111, and the cylinder block 111 is cooled by circulating cooling water inside the water jacket 117. The water jacket 117 is provided with cooling water temperature detecting means 118 for detecting the temperature of the cooling water, and is connected to the control means 40 described later. The control means 40 can acquire the temperature of the cooling water in the water jacket 117 detected by the cooling water temperature detection means 118.
　吸気経路部１２は、可燃性ガスと空気を混合して燃焼室Ｃへ導く。吸気経路部１２は、主にミキサ１２１と（図１参照）、燃料調整弁（ＧＶＭとも呼ばれる）１２３と、吸気マニホールド１２２と、で構成されている。ミキサ１２１及び燃料調整弁１２３は、吸気マニホールド１２２を介して燃焼室Ｃに可燃性ガスと空気からなる混合気を供給する混合気供給装置を構成する。 The intake passage section 12 mixes combustible gas and air and guides them to the combustion chamber C. The intake passage portion 12 is mainly composed of a mixer 121 (see FIG. 1), a fuel adjustment valve (also referred to as GVM) 123, and an intake manifold 122. The mixer 121 and the fuel adjustment valve 123 constitute an air-fuel mixture supply device that supplies an air-fuel mixture composed of combustible gas and air to the combustion chamber C via the intake manifold 122.
　ミキサ１２１は、ベンチュリー式のミキサである。ミキサ１２１は、外部から吸入された空気に可燃性ガスを供給して混合気を生成する。ミキサ１２１は、吸気マニホールド１２２の一端に取り付けられている。燃料調整弁１２３は、ミキサ１２１に供給する可燃性ガス供給量を調整する。ミキサ１２１及び燃料調整弁１２３から構成される混合気供給装置は、燃料調整弁１２３の開度を変更することにより、所定の範囲内で燃料増加又は燃料減少を実行する。燃料調整弁１２３は、制御手段４０に電気的に接続されている。制御手段４０は、燃料調整弁１２３の開度を制御する。 The mixer 121 is a Venturi mixer. The mixer 121 supplies a combustible gas to air sucked from the outside to generate an air-fuel mixture. The mixer 121 is attached to one end of the intake manifold 122. The fuel adjustment valve 123 adjusts the amount of flammable gas supplied to the mixer 121. The air-fuel mixture supply apparatus including the mixer 121 and the fuel adjustment valve 123 performs fuel increase or fuel decrease within a predetermined range by changing the opening of the fuel adjustment valve 123. The fuel adjustment valve 123 is electrically connected to the control means 40. The control means 40 controls the opening degree of the fuel adjustment valve 123.
　吸気マニホールド１２２は、ミキサ１２１によって生成された混合気を各燃焼室Ｃへ案内する。吸気マニホールド１２２は、４つの燃焼室Ｃへ混合気を案内すべく、各燃焼室Ｃへ分岐するように形成されている。なお、吸気マニホールド１２２は、パイプによってヘッドカバー１１５と接続されている。シリンダブロック１１１やヘッドカバー１１５の内部圧力が高まるのを防ぐためである。 The intake manifold 122 guides the air-fuel mixture generated by the mixer 121 to each combustion chamber C. The intake manifold 122 is formed to branch to each combustion chamber C so as to guide the air-fuel mixture to the four combustion chambers C. The intake manifold 122 is connected to the head cover 115 by a pipe. This is to prevent the internal pressure of the cylinder block 111 and the head cover 115 from increasing.
　排気経路部１３は、燃焼室Ｃから排出された排気を外部へ導く。排気経路部１３は、主に排気マニホールド１３１と、上流側排気管１３７と、三元触媒コンバータ１３２と、下流側排気管１３８と、第１酸素センサ１３４と、第２酸素センサ１３５と、第３酸素センサ１３６と、で構成されている。 The exhaust passage unit 13 guides the exhaust discharged from the combustion chamber C to the outside. The exhaust passage section 13 mainly includes an exhaust manifold 131, an upstream side exhaust pipe 137, a three-way catalytic converter 132, a downstream side exhaust pipe 138, a first oxygen sensor 134, a second oxygen sensor 135, and a third And an oxygen sensor 136.
　排気マニホールド１３１は、各燃焼室Ｃから排出された排気を、上流側排気管１３７を介して三元触媒コンバータ１３２（以下、単に触媒コンバータ１３２と呼ぶ）へ案内する。排気マニホールド１３１は、４つの燃焼室Ｃから排気を案内すべく、各燃焼室Ｃから合流するように形成されている。触媒コンバータ１３２は、アルデヒド類に起因する異臭を除去する。触媒コンバータ１３２は、白金等による触媒反応を利用してアルデヒド類を酸化させる。なお、触媒コンバータ１３２の下流側の下流側排気管１３８には、排気ガスを利用して水を熱する熱交換器１３３が取り付けられている（図１、図３参照）。
　また、本実施形態では排気ガスを浄化するための触媒として三元触媒を挙げて説明しているが、特に限定するものではない。 The exhaust manifold 131 guides the exhaust discharged from each combustion chamber C to the three-way catalytic converter 132 (hereinafter simply referred to as the catalytic converter 132) via the upstream side exhaust pipe 137. The exhaust manifold 131 is formed so as to merge from each combustion chamber C so as to guide the exhaust from the four combustion chambers C. The catalytic converter 132 removes off-flavors caused by aldehydes. The catalytic converter 132 oxidizes aldehydes using a catalytic reaction with platinum or the like. A heat exchanger 133 that heats water using exhaust gas is attached to the downstream exhaust pipe 138 on the downstream side of the catalytic converter 132 (see FIGS. 1 and 3).
In the present embodiment, a three-way catalyst is described as a catalyst for purifying exhaust gas, but is not particularly limited.
　第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６は、排気マニホールド１３１から排出された排気ガス中の酸素濃度を検出して排気ガス中の酸素濃度に応じた検出信号を出力するセンサである。図３に示すように、第１酸素センサ１３４は、触媒コンバータ１３２の上流側の排気マニホールド１３１に配置される。第２酸素センサ１３５は、触媒コンバータ１３２の下流側の下流側排気管１３８に配置される。第２酸素センサ１３５は、下流側排気管１３８の一端側であって触媒コンバータ１３２の前端近傍に配置される。第３酸素センサ１３６は、触媒コンバータ１３２の下流側の下流側排気管１３８において、第２酸素センサ１３５の下流側に配置される。第３酸素センサ１３６は、下流側排気管１３８の他端側（下流端側）であって熱交換器１３３近傍に配置される。第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６は、制御手段４０に電気的に接続されている。制御手段４０は、第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６の計測結果と、予め記憶されるデータやプログラムとに基づいて、スロットル弁や燃料調整弁１２３等の開度をアクチュエータを介して制御することによって、混合気の空燃比を適切な値(例えば、理想空燃比である空気過剰率λ＝１)となるように制御している。
　なお、第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６は、排気ガス中の酸素濃度を検出可能な公知の酸素センサを用いることができ、例えばＵＥＧＯ（Ｕｎｉｖｅｒｓａｌ　Ｅｘｈａｕｓｔ　Ｇａｓ　Ｏｘｙｇｅｎ）センサを用いてもよい。ＵＥＧＯセンサは、大気校正を実施することができる。第２酸素センサ１３５及び第３酸素センサ１３６として、ＵＥＧＯセンサを用いた場合は、定期的に大気校正することにより検知精度を向上させることができる。 The first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 detect the oxygen concentration in the exhaust gas discharged from the exhaust manifold 131 and output a detection signal corresponding to the oxygen concentration in the exhaust gas. It is a sensor. As shown in FIG. 3, the first oxygen sensor 134 is disposed in the exhaust manifold 131 upstream of the catalytic converter 132. Second oxygen sensor 135 is arranged in downstream exhaust pipe 138 on the downstream side of catalytic converter 132. The second oxygen sensor 135 is disposed on one end side of the downstream side exhaust pipe 138 and in the vicinity of the front end of the catalytic converter 132. The third oxygen sensor 136 is disposed downstream of the second oxygen sensor 135 in the downstream exhaust pipe 138 downstream of the catalytic converter 132. The third oxygen sensor 136 is disposed on the other end side (downstream end side) of the downstream side exhaust pipe 138 and in the vicinity of the heat exchanger 133. The first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 are electrically connected to the control means 40. Based on the measurement results of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136, and data and programs stored in advance, the control means 40 opens the throttle valve, the fuel adjustment valve 123, and the like. Is controlled via an actuator so that the air-fuel ratio of the air-fuel mixture becomes an appropriate value (for example, the excess air ratio λ = 1 which is an ideal air-fuel ratio).
As the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136, a known oxygen sensor capable of detecting the oxygen concentration in the exhaust gas can be used, for example, a UEGO (Universal Exhaust Gas Oxygen) sensor. May be used. The UEGO sensor can perform atmospheric calibration. When a UEGO sensor is used as the second oxygen sensor 135 and the third oxygen sensor 136, detection accuracy can be improved by periodically calibrating the air.
　制御手段４０は、第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６により検出された排気ガスの酸素濃度に基づいて空燃比を算出するとともに、燃料調整弁１２３の開度を制御する。制御手段４０は、記憶部を有する。該記憶部には、第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６の計測結果と、予め記憶されるデータ（例えばマップ等）と、スロットル弁や燃料調整弁１２３等の開度をアクチュエータを介して制御するためのプログラム等が記憶されている。 The control means 40 calculates the air-fuel ratio based on the oxygen concentration of the exhaust gas detected by the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136, and controls the opening of the fuel adjustment valve 123. To do. The control means 40 has a storage unit. The storage unit includes measurement results of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136, data stored in advance (for example, a map, etc.), and opening of a throttle valve, a fuel adjustment valve 123, and the like. A program for controlling the degree via the actuator is stored.
　制御手段４０は、例えば、第１酸素センサ１３４及び第２酸素センサ１３５に常時通電して各センサ出力を時系列で取得するとともに、所定の時間毎に第３酸素センサ１３６に通電して第３酸素センサ１３６の所定の時間毎のセンサ出力を取得することができる。第３酸素センサ１３６に通電する前記所定の時間は、制御手段４０に格納される所定のプログラムに基づいて任意に設定することができる。
　なお、制御手段４０は、第１酸素センサ１３４、第２酸素センサ１３５、及び第３酸素センサ１３６をそれぞれ独立して各酸素センサの通電状態（常時通電や所定の時間毎の通電）を適宜制御することができる。 For example, the control unit 40 constantly energizes the first oxygen sensor 134 and the second oxygen sensor 135 to acquire each sensor output in time series, and energizes the third oxygen sensor 136 every predetermined time to generate the third oxygen sensor 136. The sensor output of the oxygen sensor 136 every predetermined time can be acquired. The predetermined time for energizing the third oxygen sensor 136 can be arbitrarily set based on a predetermined program stored in the control means 40.
The control means 40 appropriately controls the energization state (always energization or energization every predetermined time) of each oxygen sensor independently of each of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136. can do.
　さらに、制御手段４０は、第１酸素センサ１３４に常時通電してセンサ出力を時系列で取得し、所定の時間毎に第２酸素センサ１３５、第３酸素センサ１３６にそれぞれ独立して通電して所定の時間毎の各センサ出力を取得することができる。第２酸素センサ１３５、第３酸素センサ１３６のそれぞれに通電する前記所定の時間は、制御手段４０に格納される所定のプログラムに基づいて任意に設定することができる。 Further, the control means 40 constantly energizes the first oxygen sensor 134 to acquire sensor outputs in time series, and independently energizes the second oxygen sensor 135 and the third oxygen sensor 136 at predetermined time intervals. Each sensor output for every predetermined time can be acquired. The predetermined time for energizing each of the second oxygen sensor 135 and the third oxygen sensor 136 can be arbitrarily set based on a predetermined program stored in the control means 40.
　以下に、エンジン１における第１酸素センサの補正制御方法について説明する。 Hereinafter, a correction control method of the first oxygen sensor in the engine 1 will be described.
　図４は、エンジン１における第１酸素センサの補正制御方法のフローを示している。 FIG. 4 shows a flow of the correction control method of the first oxygen sensor in the engine 1.
　制御手段４０は、先ず、第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６の各センサ出力（出力電圧）を取得する（ステップＳ１０）。次に、第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６の各センサ出力を比較して（ステップＳ２０）、第２酸素センサ１３５によるセンサ出力と比較して第１酸素センサ１３４によるセンサ出力のズレが無い場合（ズレが所定の許容範囲以内である場合）は（ステップＳ３０のＹＥＳ）、第１酸素センサ１３４によるセンサ出力を採用して、該センサ出力により空燃比を算出する（ステップＳ４０）。 The control means 40 first acquires the sensor outputs (output voltages) of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 (step S10). Next, the sensor outputs of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 are compared (step S20), and compared with the sensor output from the second oxygen sensor 135, the first oxygen sensor 134 is compared. If there is no deviation in the sensor output due to (when the deviation is within a predetermined allowable range) (YES in step S30), the sensor output from the first oxygen sensor 134 is adopted, and the air-fuel ratio is calculated from the sensor output. (Step S40).
　ステップＳ３０において、第２酸素センサ１３５によるセンサ出力と比較して、第１酸素センサ１３４のセンサ出力にズレが有る場合、すなわち第１酸素センサ１３４が出力劣化していると判定された場合は（ステップＳ３０のＮＯ）、制御手段４０は、第２酸素センサ１３５及び第３酸素センサ１３６の各センサ出力を比較する（ステップＳ５０）。第２酸素センサ１３５及び第３酸素センサ１３６の各センサ出力のズレが無い場合（ズレが所定の許容範囲以内である場合）は（ステップＳ６０のＹＥＳ）、第２酸素センサ１３５によるセンサ出力を採用して、該センサ出力により空燃比を算出する（ステップＳ７０）。 If it is determined in step S30 that the sensor output of the first oxygen sensor 134 is deviated from the sensor output of the second oxygen sensor 135, that is, if it is determined that the output of the first oxygen sensor 134 has deteriorated ( In step S30, the control unit 40 compares the sensor outputs of the second oxygen sensor 135 and the third oxygen sensor 136 (step S50). When there is no deviation between the sensor outputs of the second oxygen sensor 135 and the third oxygen sensor 136 (when the deviation is within a predetermined allowable range) (YES in step S60), the sensor output from the second oxygen sensor 135 is adopted. Then, the air-fuel ratio is calculated from the sensor output (step S70).
　ステップＳ６０において、第３酸素センサ１３６によるセンサ出力と比較して、第２酸素センサ１３５のセンサ出力にズレが有る場合、すなわち第２酸素センサが出力劣化していると判定された場合は（ステップＳ６０のＮＯ）、制御手段４０は、第３酸素センサ１３６によるセンサ出力を採用して、該センサ出力により空燃比を算出する（ステップＳ８０）。 If it is determined in step S60 that the sensor output of the second oxygen sensor 135 is different from the sensor output of the third oxygen sensor 136, that is, if it is determined that the output of the second oxygen sensor has deteriorated (step S60). The control means 40 employs the sensor output from the third oxygen sensor 136 and calculates the air-fuel ratio based on the sensor output (step S80).
　なお、ステップＳ１０において、第３酸素センサ１３６によるセンサ出力を取得するが、第３酸素センサ１３６は常時通電状態（ＯＮ状態）である必要はない。例えば、第３酸素センサ１３６は、常時ではなく定期的（例えば、数十時間～数百時間に１回程度）に第１酸素センサ１３４を補正制御する際に通電状態（ＯＮ状態）となるように設定すればよい。すなわち、第３酸素センサ１３６は、制御手段４０により第１酸素センサ１３４の補正制御を実施する際に、定期的に通電するだけでよく、このようにすることで第３酸素センサ１３６の通電による劣化を抑制することができる。 In step S10, the sensor output from the third oxygen sensor 136 is acquired. However, the third oxygen sensor 136 does not need to be always in the energized state (ON state). For example, the third oxygen sensor 136 is in an energized state (ON state) when correcting and controlling the first oxygen sensor 134 periodically (for example, about once every several tens of hours to several hundred hours) instead of always. Should be set. That is, the third oxygen sensor 136 only needs to be energized periodically when the control means 40 performs the correction control of the first oxygen sensor 134, and in this way, the third oxygen sensor 136 is energized. Deterioration can be suppressed.
　また、ステップＳ１０において、第２酸素センサ１３５によるセンサ出力を取得するが、第２酸素センサ１３５は常時通電状態（ＯＮ状態）である必要はない。例えば、第２酸素センサ１３５は、常時ではなく定期的に第１酸素センサ１３４を補正制御する際に通電状態（ＯＮ状態）となるように設定することもできる。すなわち、第２酸素センサ１３５は、制御手段４０により第１酸素センサ１３４の補正制御を実施する際に、定期的に通電するだけでもよく、このようにすることで第２酸素センサ１３５の通電による劣化を抑制することができる。さらに、第３酸素センサ１３６に通電する間隔を第２酸素センサ１３５に通電する間隔よりも長くすることで、第３酸素センサ１３６が第２酸素センサ１３５よりも通電による劣化をしにくくなるようにしてもよい。 In step S10, the sensor output from the second oxygen sensor 135 is acquired. However, the second oxygen sensor 135 does not have to be in a normally energized state (ON state). For example, the second oxygen sensor 135 can be set to be in an energized state (ON state) when correcting and controlling the first oxygen sensor 134 periodically instead of constantly. That is, the second oxygen sensor 135 may be energized only periodically when the control means 40 performs the correction control of the first oxygen sensor 134. In this way, the second oxygen sensor 135 is energized. Deterioration can be suppressed. Further, by making the interval for energizing the third oxygen sensor 136 longer than the interval for energizing the second oxygen sensor 135, the third oxygen sensor 136 is less likely to be deteriorated by energization than the second oxygen sensor 135. May be.
　また、図５は、第１酸素センサの補正制御方法の別実施形態を示すフローである。図５に示すように、先ず、第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６の各センサ出力を同時（同時刻）に取得後（ステップＳ１０）、第１酸素センサ１３４及び第２酸素センサ１３５においては常時通電してそれぞれのセンサ出力を常時取得（時系列で取得）する。これに対して、第３酸素センサ１３６においては、所定の時間間隔で通電して第３酸素センサ１３６のセンサ出力を取得する。こうして、前記所定の時間間隔で第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６の各センサ出力を取得する（ステップＳ１００）。次に、所定の時間間隔が経過する毎に第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６の各センサ出力を比較する（ステップＳ２００）。第２酸素センサ１３５によるセンサ出力と比較して第１酸素センサ１３４によるセンサ出力にズレが無い場合は、すなわち第１酸素センサ１３４が出力劣化していないと判定された場合（ズレが所定の許容範囲以内である場合）は（ステップＳ３００のＹＥＳ）、第１酸素センサ１３４によるセンサ出力を採用して、該センサ出力により空燃比を算出する（ステップＳ４００）。
　なお、図５で示す第１酸素センサの補正制御方法では、第２酸素センサ１３５に常時通電しているが、特に限定するものではない。例えば、第２酸素センサ１３５に所定の時間間隔で通電しても構わない。この場合、第３酸素センサ１３６が通電する所定の時間間隔は、第２酸素センサ１３５が通電する所定の時間間隔よりも長く設定されるとともに第２酸素センサ１３５及び第３酸素センサ１３６が所定の時間間隔で同期（シンクロ）して各センサ出力を取得するように、制御手段４０には予め設定することが好ましい。このようにすることで、第２酸素センサ１３５は、第３酸素センサ１３６よりも通電による劣化が抑えられ、長寿命化することができる。 FIG. 5 is a flowchart showing another embodiment of the correction control method for the first oxygen sensor. As shown in FIG. 5, first, after obtaining the sensor outputs of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 simultaneously (at the same time) (step S10), the first oxygen sensor 134 and The second oxygen sensor 135 is always energized and constantly acquires (acquires in time series) each sensor output. On the other hand, the third oxygen sensor 136 is energized at a predetermined time interval to acquire the sensor output of the third oxygen sensor 136. Thus, the sensor outputs of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 are acquired at the predetermined time interval (step S100). Next, each time the predetermined time interval elapses, the sensor outputs of the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136 are compared (step S200). When there is no deviation in the sensor output from the first oxygen sensor 134 compared to the sensor output from the second oxygen sensor 135, that is, when it is determined that the first oxygen sensor 134 has not deteriorated in output (the deviation is a predetermined tolerance). If it is within the range (YES in step S300), the sensor output from the first oxygen sensor 134 is adopted, and the air-fuel ratio is calculated from the sensor output (step S400).
In the first oxygen sensor correction control method shown in FIG. 5, the second oxygen sensor 135 is always energized, but is not particularly limited. For example, the second oxygen sensor 135 may be energized at a predetermined time interval. In this case, the predetermined time interval at which the third oxygen sensor 136 is energized is set longer than the predetermined time interval at which the second oxygen sensor 135 is energized, and the second oxygen sensor 135 and the third oxygen sensor 136 are predetermined. It is preferable to set in advance in the control means 40 so as to acquire each sensor output in synchronization (synchronization) at time intervals. By doing in this way, the 2nd oxygen sensor 135 can suppress deterioration by electricity supply rather than the 3rd oxygen sensor 136, and can prolong a lifetime.
　ステップＳ３００において、第２酸素センサ１３５によるセンサ出力と比較して、第１酸素センサ１３４のセンサ出力にズレが有る場合、すなわち第１酸素センサ１３４が出力劣化していると判定された場合は（ステップＳ３００のＮＯ）、制御手段４０は、第２酸素センサ１３５及び第３酸素センサ１３６の各センサ出力を比較する（ステップＳ５００）。第２酸素センサ１３５及び第３酸素センサ１３６の各センサ出力のズレが無い場合（ズレが所定の許容範囲以内である場合）は（ステップＳ６００のＹＥＳ）、第２酸素センサ１３５によるセンサ出力を採用して、該センサ出力により空燃比を算出する（ステップＳ７００）。 If it is determined in step S300 that the sensor output of the first oxygen sensor 134 is deviated from the sensor output of the second oxygen sensor 135, that is, if it is determined that the output of the first oxygen sensor 134 has deteriorated ( In step S300, the control unit 40 compares the sensor outputs of the second oxygen sensor 135 and the third oxygen sensor 136 (step S500). When there is no deviation between the sensor outputs of the second oxygen sensor 135 and the third oxygen sensor 136 (when the deviation is within a predetermined allowable range) (YES in step S600), the sensor output from the second oxygen sensor 135 is adopted. Then, the air-fuel ratio is calculated from the sensor output (step S700).
　ステップＳ６００において、第３酸素センサ１３６によるセンサ出力と比較して、第２酸素センサ１３５のセンサ出力にズレが有る場合、すなわち第２酸素センサが出力劣化していると判定された場合は（ステップＳ６００のＮＯ）、制御手段４０は、第３酸素センサ１３６によるセンサ出力を採用して、該センサ出力により空燃比を算出する（ステップＳ８００）。 If it is determined in step S600 that the sensor output of the second oxygen sensor 135 is different from the sensor output of the third oxygen sensor 136, that is, if it is determined that the output of the second oxygen sensor has deteriorated (step S600). The control means 40 employs the sensor output from the third oxygen sensor 136 and calculates the air-fuel ratio based on the sensor output (step S800).
　また、本実施形態のエンジン１の排気経路は、３つの酸素センサ（第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６）備えているが、当該３つの酸素センサをすべて使用しなくてもよい。例えば、第１酸素センサ１３４と第２酸素センサ１３５の２箇所の酸素センサを使用する場合や、第１酸素センサ１３４と第３酸素センサ１３６の２箇所の酸素センサを使用する場合や、第２酸素センサ１３５と第３酸素センサ１３６の２箇所を使用する場合であってよい。さらに、例えば、制御手段４０が第２酸素センサ１３５と第３酸素センサ１３６とに交互に通電してセンサ出力を取得し、第１酸素センサ１３４によるセンサ出力と比較して該第１酸素センサ１３４の補正制御を行ってもよい。このように第２酸素センサ１３５と第３酸素センサ１３６の交互に通電することで、第２酸素センサ１３５と第３酸素センサ１３６における通電による劣化を抑制することができるからである。 Further, the exhaust path of the engine 1 of the present embodiment includes three oxygen sensors (a first oxygen sensor 134, a second oxygen sensor 135, and a third oxygen sensor 136), but all three oxygen sensors are used. It does not have to be. For example, when two oxygen sensors of the first oxygen sensor 134 and the second oxygen sensor 135 are used, when two oxygen sensors of the first oxygen sensor 134 and the third oxygen sensor 136 are used, There may be a case where two locations of the oxygen sensor 135 and the third oxygen sensor 136 are used. Further, for example, the control unit 40 alternately energizes the second oxygen sensor 135 and the third oxygen sensor 136 to acquire the sensor output, and compares the sensor output with the first oxygen sensor 134 with the first oxygen sensor 134. The correction control may be performed. This is because deterioration due to energization in the second oxygen sensor 135 and the third oxygen sensor 136 can be suppressed by energizing the second oxygen sensor 135 and the third oxygen sensor 136 alternately.
　次に、エンジン１における第１酸素センサ１３４のセンサ出力の補正制御方法（劣化検知方法）について説明する。 Next, a sensor output correction control method (deterioration detection method) of the first oxygen sensor 134 in the engine 1 will be described.
　燃料調整弁１２３の開度の変化量を用いた第１酸素センサ１３４のセンサ出力の補正制御方法（劣化検知方法）について説明する。 A sensor output correction control method (deterioration detection method) of the first oxygen sensor 134 using the amount of change in the opening of the fuel adjustment valve 123 will be described.
　先ず、１つの酸素センサ（例えば、第１酸素センサ１３４）により計測される、初期と長時間運転後の空燃比の経時劣化を推定し、酸素センサのセンサ出力の変化量を事前に制御手段４０に設定しておく。当該酸素センサのセンサ出力の変化量を予めしきい値として設定し、制御手段４０は第１酸素センサ１３４のセンサ出力の劣化を検知する。ここで、図６は、所定のエンジン回転数におけるものであり、縦軸が酸素センサのセンサ出力であり、横軸が第１酸素センサ１３４による酸素濃度である。図６に示すように、所定のエンジン回転数におけるセンサ出力が基準値（例えば、第２酸素センサ１３５または第３酸素センサ１３６から得られるセンサ出力値）よりも上方もしく下方にズレてしきい値を越えた場合に（図６の点線よりも上側の領域や下側の領域に至る場合に）、制御手段４０は第１酸素センサ１３４において出力劣化が生じていると判定する。
　なお、上記のように一つの酸素センサ（例えば、第１酸素センサ１３４）だけでなく、３つの酸素センサ（第１酸素センサ１３４、第２酸素センサ１３５及び第３酸素センサ１３６）について、上記のようにして出力劣化の有無を判定することもできる。 First, the deterioration with time of the air-fuel ratio measured by one oxygen sensor (for example, the first oxygen sensor 134) after the initial and long-time operation is estimated, and the change amount of the sensor output of the oxygen sensor is controlled beforehand. Set to. The change amount of the sensor output of the oxygen sensor is set in advance as a threshold value, and the control means 40 detects the deterioration of the sensor output of the first oxygen sensor 134. Here, FIG. 6 is at a predetermined engine speed, the vertical axis is the sensor output of the oxygen sensor, and the horizontal axis is the oxygen concentration by the first oxygen sensor 134. As shown in FIG. 6, the sensor output at a predetermined engine speed is shifted above or below a reference value (for example, a sensor output value obtained from the second oxygen sensor 135 or the third oxygen sensor 136). When the value is exceeded (when reaching the area above or below the dotted line in FIG. 6), the control means 40 determines that output degradation has occurred in the first oxygen sensor 134.
As described above, not only one oxygen sensor (for example, the first oxygen sensor 134) but also three oxygen sensors (the first oxygen sensor 134, the second oxygen sensor 135, and the third oxygen sensor 136) are not described above. In this way, the presence or absence of output deterioration can also be determined.
　次に、燃料調整弁１２３の開度と触媒コンバータ１３２の下流側の酸素センサの出力特性による、第１酸素センサ１３４のセンサ出力の補正制御方法（劣化検知方法）について説明する。 Next, a correction control method (deterioration detection method) of the sensor output of the first oxygen sensor 134 based on the opening degree of the fuel adjustment valve 123 and the output characteristics of the oxygen sensor downstream of the catalytic converter 132 will be described.
　先ず、予め燃料調整弁１２３の開度と触媒コンバータ１３２の下流側の酸素センサ（例えば、第２酸素センサ１３５や第３酸素センサ１３６）の出力特性の関係を図７に示すように、マップ化して制御手段４０の記憶部に記憶させておく。ここで、図７は、所定のエンジン回転数におけるものであり、縦軸が下流側の酸素センサのセンサ出力（出力電圧）であり、横軸が燃料調整弁１２３の開度である。そして、制御手段４０は、リアルタイムでセンサ出力の基準値からの下流側の酸素センサによる第１酸素センサ１３４の補正量の変化をモニターし、正常値に対して所定範囲を超えた場合に下流側の酸素センサ（例えば、第２酸素センサ１３５や第３酸素センサ１３６）に出力劣化が生じていると判定する。 First, the relationship between the opening degree of the fuel adjustment valve 123 and the output characteristics of the oxygen sensors (for example, the second oxygen sensor 135 and the third oxygen sensor 136) on the downstream side of the catalytic converter 132 is previously mapped as shown in FIG. And stored in the storage unit of the control means 40. Here, FIG. 7 is for a predetermined engine speed, the vertical axis is the sensor output (output voltage) of the downstream oxygen sensor, and the horizontal axis is the opening of the fuel adjustment valve 123. Then, the control means 40 monitors the change in the correction amount of the first oxygen sensor 134 by the downstream oxygen sensor from the reference value of the sensor output in real time, and when the predetermined value exceeds the normal value, the downstream side It is determined that output degradation has occurred in the oxygen sensors (for example, the second oxygen sensor 135 and the third oxygen sensor 136).
　以下に、本エンジンユニット１００の技術的特徴について説明する。 The technical features of the engine unit 100 will be described below.
　本エンジンユニット１００における第一の技術的特徴は、複数の酸素センサとして、触媒コンバータ１３２の上流側の排気経路に配置される第１酸素センサ１３４と、触媒コンバータ１３２の下流側の排気経路に配置される第２酸素センサ１３５と、触媒コンバータ１３２の下流側の排気経路において、第２酸素センサ１３５の下流側に配置される第３酸素センサ１３６と、から構成される点である。触媒浄化前の排気ガスの含有成分や熱の影響を受けて第１酸素センサ１３４は劣化しやすいが、排気ガスの含有成分や熱の影響が少ない触媒コンバータ１３２の下流側に順に配置された、第２酸素センサ１３５及び第３酸素センサ１３６は劣化しにくい。そのため、第１酸素センサ１３４に出力劣化（センサ出力のズレ）が生じても、第２酸素センサ１３５及び第３酸素センサ１３６により第１酸素センサ１３４のセンサ出力のズレを補正することができる。すなわち、排気経路における酸素センサの検知精度を長期的に維持することができる。また、第３酸素センサ１３６は、排気経路において第２酸素センサ１３５よりも下流側であって複数の酸素センサのうち最も下流に配置されるため排気ガスの含有成分や熱の影響を最も受けにくく、第１酸素センサ１３４や第２酸素センサ１３５に出力劣化が生じても、第３酸素センサ１３６により第１酸素センサ１３４や第２酸素センサ１３５のセンサ出力のズレを補正することができる。 The first technical feature of the engine unit 100 is that, as a plurality of oxygen sensors, a first oxygen sensor 134 disposed in the exhaust path upstream of the catalytic converter 132 and an exhaust path downstream of the catalytic converter 132 are disposed. And the third oxygen sensor 136 disposed downstream of the second oxygen sensor 135 in the exhaust path downstream of the catalytic converter 132. The first oxygen sensor 134 is easily deteriorated due to the influence of exhaust gas components and heat before the catalyst purification, but is sequentially arranged downstream of the catalytic converter 132 where the exhaust gas contents and heat are less affected. The second oxygen sensor 135 and the third oxygen sensor 136 are not easily deteriorated. Therefore, even if output deterioration (sensor output deviation) occurs in the first oxygen sensor 134, the sensor output deviation of the first oxygen sensor 134 can be corrected by the second oxygen sensor 135 and the third oxygen sensor 136. That is, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time. Further, since the third oxygen sensor 136 is disposed downstream of the second oxygen sensor 135 in the exhaust path and the most downstream of the plurality of oxygen sensors, the third oxygen sensor 136 is least susceptible to the components contained in the exhaust gas and heat. Even if output degradation occurs in the first oxygen sensor 134 or the second oxygen sensor 135, the third oxygen sensor 136 can correct the deviation of the sensor output of the first oxygen sensor 134 or the second oxygen sensor 135.
　本エンジンユニット１００における第二の技術的特徴は、制御手段４０が、第２酸素センサ１３５及び／又は第３酸素センサ１３６のセンサ出力を取得し、第１酸素センサ１３４のセンサ出力と比較して該第１酸素センサ１３４のセンサ出力のズレを補正制御する点である。これにより、排気経路における酸素センサの検知精度を長期的に維持することができる。 The second technical feature of the engine unit 100 is that the control means 40 acquires the sensor output of the second oxygen sensor 135 and / or the third oxygen sensor 136 and compares it with the sensor output of the first oxygen sensor 134. This is a point of correcting and controlling the deviation of the sensor output of the first oxygen sensor 134. Thereby, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
　本エンジンユニット１００における第三の技術的特徴は、第３酸素センサ１３６が、下流側排気管１３８における熱交換器１３３近傍に設けられる点である。このように第３酸素センサ１３６を下流側排気管１３８における熱交換器１３３側（熱交換器１３３の近傍）の熱負荷の低い位置に配置することで、第３酸素センサ１３６に対する熱負荷が低くなり、第３酸素センサ１３６は、第２酸素センサ１３５に比べて熱の影響をより受けにくく、寿命を延ばすことができる。従って、排気経路における酸素センサの検知精度を長期的に維持することができる。 The third technical feature of the engine unit 100 is that the third oxygen sensor 136 is provided in the vicinity of the heat exchanger 133 in the downstream side exhaust pipe 138. As described above, the third oxygen sensor 136 is disposed at a low heat load position on the heat exchanger 133 side (near the heat exchanger 133) in the downstream exhaust pipe 138, so that the heat load on the third oxygen sensor 136 is low. Thus, the third oxygen sensor 136 is less susceptible to heat than the second oxygen sensor 135 and can extend its life. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
　本エンジンユニット１００における第四の技術的特徴は、制御手段４０は、第３酸素センサ１３６に定期的に通電することで、センサ出力を取得する点である。これにより、第３酸素センサ１３６の通電による劣化を抑えることができ、第３酸素センサ１３６の寿命を延ばすことができる。従って、排気経路における酸素センサの検知精度を長期的に維持することができる。 The fourth technical feature of the engine unit 100 is that the control means 40 acquires the sensor output by periodically energizing the third oxygen sensor 136. Thereby, deterioration due to energization of the third oxygen sensor 136 can be suppressed, and the life of the third oxygen sensor 136 can be extended. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
　本エンジンユニット１００における第五の技術的特徴は、制御手段４０は、第２酸素センサ１３５に定期的に通電することでセンサ出力を取得するとともに、第３酸素センサ１３６に通電する間隔を第２酸素センサ１３５に通電する間隔よりも長くした点である。これにより、第３酸素センサ１３６は、第２酸素センサ１３５よりも通電による劣化を抑えることができ、第２酸素センサ１３５及び第３酸素センサ１３６の両方の寿命を延ばすことができる。従って、排気経路における酸素センサの検知精度を長期的に維持することができる。 The fifth technical feature of the engine unit 100 is that the control means 40 acquires the sensor output by periodically energizing the second oxygen sensor 135 and sets the interval of energizing the third oxygen sensor 136 to the second. This is a point that is longer than the interval at which the oxygen sensor 135 is energized. Thereby, the third oxygen sensor 136 can suppress deterioration due to energization more than the second oxygen sensor 135, and can extend the lifetime of both the second oxygen sensor 135 and the third oxygen sensor 136. Therefore, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time.
　また、上述したように本発明によれば、排気経路における酸素センサの検知精度を長期的に維持することができる。これにより、酸素センサ不良による運転中の排気エミッションの悪化を抑制することができる。さらに、酸素センサの定期検査の間隔を長くして、酸素センサのメンテナンスの手間を省くことができる。また、３つの酸素センサにより検知精度を保持するため、フェールセーフ機能による検知精度の信頼性を確保することができる。 Further, as described above, according to the present invention, the detection accuracy of the oxygen sensor in the exhaust path can be maintained for a long time. Thereby, it is possible to suppress deterioration of exhaust emission during operation due to oxygen sensor failure. Furthermore, it is possible to lengthen the interval between periodic inspections of the oxygen sensor, and to save the labor of maintenance of the oxygen sensor. In addition, since the detection accuracy is maintained by the three oxygen sensors, the reliability of the detection accuracy by the fail-safe function can be ensured.
　次に、本願の発明に係る第２実施形態であるエンジンユニット２００（エンジン２）について説明する。エンジンユニット２００（エンジン２）は、第１実施形態に係るエンジンユニット１００（エンジン１）の酸素センサ等の一部の構成を変更したガスエンジンユニットであり、その他の構成は第１実施形態に係るエンジンユニット１００（エンジン１）と同じである。
　なお、以下の説明において、第１実施形態に係るエンジンユニット１００と同一の構成については符号を同一とし、その構成の説明は省略する。 Next, an engine unit 200 (engine 2) according to a second embodiment of the present invention will be described. The engine unit 200 (engine 2) is a gas engine unit in which a part of the configuration of the oxygen sensor or the like of the engine unit 100 (engine 1) according to the first embodiment is changed, and the other configurations are related to the first embodiment. It is the same as engine unit 100 (engine 1).
In the following description, the same components as those of the engine unit 100 according to the first embodiment are denoted by the same reference numerals, and the description of the components is omitted.
　図８に示すように、第２実施形態のエンジンユニット２００は、複数の酸素センサとして、触媒コンバータ１３２の上流側の排気経路に配置される上流側酸素センサ１３４（第１実施形態の第１酸素センサ１３４と同じ）と、触媒コンバータ１３２の下流側の排気経路に配置される下流側酸素センサ１４０（図１２参照）とを主に有している。また、触媒コンバータ１３２の下流側の排気経路には、排気ガスにより水を熱する熱交換器１３３を備える。下流側酸素センサ１４０は、熱交換器１３３に配置されるとともに、該熱交換器１３３内を流れる水により冷却される構成となっている。 As shown in FIG. 8, the engine unit 200 of the second embodiment includes an upstream oxygen sensor 134 (first oxygen of the first embodiment) arranged in the exhaust path upstream of the catalytic converter 132 as a plurality of oxygen sensors. And the downstream oxygen sensor 140 (see FIG. 12) disposed in the exhaust path downstream of the catalytic converter 132. Further, the exhaust path downstream of the catalytic converter 132 is provided with a heat exchanger 133 that heats water with the exhaust gas. The downstream oxygen sensor 140 is disposed in the heat exchanger 133 and is cooled by water flowing in the heat exchanger 133.
　図１２に示す熱交換器１３３は、シェルアンドチューブ型熱交換器であり、排気ガスが通る多数のガス管１３９・１３９・・・（図１５参照）と、ガス管１３９・１３９・・・を内装しガス管１３９・１３９・・・内を通る排気ガスを冷却する熱交換器本体１４５と、を有する。 A heat exchanger 133 shown in FIG. 12 is a shell-and-tube heat exchanger, and includes a number of gas pipes 139, 139 (see FIG. 15) through which exhaust gas passes and gas pipes 139, 139,. And a heat exchanger main body 145 for cooling the exhaust gas passing through the gas pipes 139, 139.
　熱交換器本体１４５には、冷却水入口１４５ａおよび冷却水出口１４５ｂが設けられ、冷却水が熱交換器本体１４５内を循環する。すなわち、熱交換器本体１４５の内周面とガス管１３９・１３９・・・の外周面との間の空間となる冷却水流路１３３ｂに、冷却水が流れる。熱交換器本体１４５の形状は円筒状であり、前端部には仕切板１３３ｃによって区画された二つ空間である排気ガス導入部１４６及び排気ガス排気部１４７を有している。 The heat exchanger main body 145 is provided with a cooling water inlet 145a and a cooling water outlet 145b, and the cooling water circulates in the heat exchanger main body 145. That is, the cooling water flows into the cooling water flow path 133b that is a space between the inner peripheral surface of the heat exchanger main body 145 and the outer peripheral surface of the gas pipes 139, 139. The shape of the heat exchanger body 145 is cylindrical, and has an exhaust gas introduction part 146 and an exhaust gas exhaust part 147 which are two spaces partitioned by a partition plate 133c at the front end.
　熱交換器本体１４５の前端部の上部には、下流側排気管１３８の下流端１３８ａが連通され、排気ガスが排気ガス導入部１４６に導入される。導入された排気ガスは多数のガス管１３９・１３９・・・内を通過して熱交換器本体１４５内を循環する冷却水により冷却され、熱交換器本体１４５の前端部の下部に設けられた排気ガス出口１４８から排出される。 The downstream end 138a of the downstream side exhaust pipe 138 is communicated with the upper part of the front end portion of the heat exchanger body 145, and the exhaust gas is introduced into the exhaust gas introduction unit 146. The introduced exhaust gas is cooled by cooling water that passes through the gas pipes 139, 139... And circulates in the heat exchanger body 145, and is provided at the lower part of the front end of the heat exchanger body 145. Exhaust gas outlet 148 is exhausted.
　上述した第１実施形態のエンジンユニット１００では、第３酸素センサ１３６を下流側排気管１３８における熱交換器１３３近傍に設ける構成としているが、第２実施形態のエンジンユニット２００では、第３酸素センサ１３６を下流側排気管１３８に設ける代わりに該下流側排気管１３８の下流端１３８ａに連通される熱交換器１３３の一端に下流側酸素センサ１４０を設ける構成となっている。
　なお、第２実施形態においては、図８に示すように、第１実施形態と同様に第２酸素センサ１３５を触媒コンバータ１３２の下流側排気管１３８の上流端（触媒コンバータ１３２の直後）に設けて、第１実施形態として説明した第１酸素センサ１３４の補正制御方法のフローに従って第１酸素センサ１３４の補正制御をすることもできる。また、第２実施形態においては、第２酸素センサ１３５は必須の構成ではない。 In the engine unit 100 of the first embodiment described above, the third oxygen sensor 136 is provided in the vicinity of the heat exchanger 133 in the downstream exhaust pipe 138. However, in the engine unit 200 of the second embodiment, the third oxygen sensor is provided. Instead of providing 136 in the downstream exhaust pipe 138, the downstream oxygen sensor 140 is provided at one end of the heat exchanger 133 communicating with the downstream end 138 a of the downstream exhaust pipe 138.
In the second embodiment, as shown in FIG. 8, the second oxygen sensor 135 is provided at the upstream end of the downstream exhaust pipe 138 of the catalytic converter 132 (immediately after the catalytic converter 132), as in the first embodiment. Thus, the correction control of the first oxygen sensor 134 can be performed according to the flow of the correction control method of the first oxygen sensor 134 described as the first embodiment. In the second embodiment, the second oxygen sensor 135 is not an essential configuration.
　上述した特許文献３に開示される内燃機関においては、排気マニホールドの上流側と下流側に酸素センサが組み付けられている。また、三元触媒出口に排気温度センサが取り付けられている。また、従来の下流側酸素センサとしては、図９に示すように、排気ガスの熱交換器に取り付けられる場合があり、この場合の下流側酸素センサの取付位置としては、図１０に示すように、熱交換器における排気ガスの導入部となる、熱交換器の一端側となっている。このような下流側酸素センサの取付位置においては、熱交換を行うための冷却水が満たされていないため、下流側酸素センサは熱負荷の厳しい環境で使用されることになる。このように、熱交換器に下流側酸素センサを設ける構成においても本発明の効果を奏する形態について以下に説明する。図１１は、本発明の第２実施形態に係る熱交換器１３３における下流側酸素センサ１４０の取付位置を示す模式図であり、該下流側酸素センサ１４０近傍に熱交換器１３３の冷却水を導く構成を示している。 In the internal combustion engine disclosed in Patent Document 3 described above, oxygen sensors are assembled on the upstream side and the downstream side of the exhaust manifold. An exhaust temperature sensor is attached to the three-way catalyst outlet. Further, as shown in FIG. 9, a conventional downstream oxygen sensor may be attached to an exhaust gas heat exchanger. In this case, as shown in FIG. It is one end side of the heat exchanger that serves as an exhaust gas introduction part in the heat exchanger. At the mounting position of such a downstream oxygen sensor, the cooling water for performing heat exchange is not filled, so the downstream oxygen sensor is used in an environment with severe heat load. Thus, the form which has an effect of the present invention also in the composition which provides a downstream oxygen sensor in a heat exchanger is explained below. FIG. 11 is a schematic diagram showing the mounting position of the downstream oxygen sensor 140 in the heat exchanger 133 according to the second embodiment of the present invention, and the cooling water of the heat exchanger 133 is guided to the vicinity of the downstream oxygen sensor 140. The configuration is shown.
　熱交換器１３３は、熱交換器本体１４５の内部に、下流側酸素センサ１４０を冷却するための略円筒状の空間であるセンサ冷却水流路１３３ａ（図１３、図１４及び図１５参照）と、排気ガスと熱交換を行うための冷却水流路１３３ｂと、排気ガス導入部１４６及び排気ガス排気部１４７とを仕切るための仕切板１３３ｃとを有している。センサ冷却水流路１３３ａは、冷却水流路１３３ｂに連通している。 The heat exchanger 133 has a sensor cooling water flow path 133a (see FIGS. 13, 14, and 15) that is a substantially cylindrical space for cooling the downstream oxygen sensor 140 inside the heat exchanger main body 145, and A cooling water flow path 133b for exchanging heat with the exhaust gas and a partition plate 133c for partitioning the exhaust gas introduction part 146 and the exhaust gas exhaust part 147 are provided. The sensor cooling water channel 133a communicates with the cooling water channel 133b.
　下流側酸素センサ１４０は、排気マニホールド１３１から排出された排気ガス中の酸素濃度を検出して排気ガス中の酸素濃度に応じた検出信号を出力するセンサである。下流側酸素センサ１４０は、制御手段４０で制御可能なヒータ１４０ａを備える。制御手段４０は、該ヒータ１４０ａを所定の電圧値（後述する第２実施形態の変形例では、定格電圧１１Ｖ）の印加の有無でヒータ１４０ａのオンもしくはオフすることができる。下流側酸素センサ１４０は、熱交換器１３３の一端（前端）側に配置される。下流側酸素センサ１４０は、制御手段４０に電気的に接続されている。制御手段４０は、例えば、上流側酸素センサ１３４、下流側酸素センサ１４０の計測結果と、予め記憶されるデータやプログラムとに基づいて、スロットル弁や燃料調整弁１２３等の開度をアクチュエータを介して制御することによって、混合気の空燃比を適切な値(例えば、理想空燃比である空気過剰率λ＝１)となるように空燃比制御している。
　なお、上流側酸素センサ１３４及び下流側酸素センサ１４０は、排気ガス中の酸素濃度を検出可能な公知の酸素センサを用いることができ、例えばＵＥＧＯ（Ｕｎｉｖｅｒｓａｌ　Ｅｘｈａｕｓｔ　Ｇａｓ　Ｏｘｙｇｅｎ）センサを用いてもよい。ＵＥＧＯセンサは、大気校正を実施することができる。上流側酸素センサ１３４及び下流側酸素センサ１４０として、ＵＥＧＯセンサを用いた場合は、定期的に大気校正することにより検知精度を向上させることができる。 The downstream oxygen sensor 140 is a sensor that detects the oxygen concentration in the exhaust gas discharged from the exhaust manifold 131 and outputs a detection signal corresponding to the oxygen concentration in the exhaust gas. The downstream oxygen sensor 140 includes a heater 140 a that can be controlled by the control means 40. The control means 40 can turn on or off the heater 140a with or without application of a predetermined voltage value (in the modified example of the second embodiment described later, rated voltage 11V). The downstream oxygen sensor 140 is disposed on one end (front end) side of the heat exchanger 133. The downstream oxygen sensor 140 is electrically connected to the control means 40. For example, the control means 40 controls the opening degree of the throttle valve, the fuel adjustment valve 123, and the like via an actuator based on the measurement results of the upstream oxygen sensor 134 and the downstream oxygen sensor 140 and data and programs stored in advance. By controlling the air-fuel ratio, the air-fuel ratio is controlled so that the air-fuel ratio of the air-fuel mixture becomes an appropriate value (for example, the excess air ratio λ = 1 which is an ideal air-fuel ratio).
As the upstream oxygen sensor 134 and the downstream oxygen sensor 140, a known oxygen sensor capable of detecting the oxygen concentration in the exhaust gas can be used. For example, a UEGO (Universal Exhaust Gas Oxygen) sensor may be used. The UEGO sensor can perform atmospheric calibration. When a UEGO sensor is used as the upstream oxygen sensor 134 and the downstream oxygen sensor 140, detection accuracy can be improved by periodically performing atmospheric calibration.
　図１３（ｃ）（ｄ）、図１４（ｃ）（ｄ）、図１５に示すように、熱交換器１３３においては、センサ冷却水流路１３３ａとして、冷却水流路１３３ｂの一端から下流側酸素センサ１４０の取付部まで延設されている。図１３、図１４においては、従来の熱交換器に配置された下流側酸素センサと第２実施形態に係る熱交換器１３３に配置された下流側酸素センサ１４０との相違点を示している。図１３（ｂ）に示すように、熱交換器に取り付けられた下流側酸素センサの機能を発揮する使用条件として、下流側酸素センサの基部Ａは温度が上がり過ぎると良くなく、下流側酸素センサの検知部となる先端部Ｂは温度が下がると良くない。そのため、基部Ａのみを冷却する構成が望まれる。そこで、第２実施形態では、図１３（ｃ）（ｄ）、図１４（ｃ）（ｄ）、図１５に示すように、冷却水流路として冷却水流路１３３ｂの一端から前方に延設され、下流側酸素センサ１４０の基部Ａの周囲に冷却水が回り込むように略円筒状のセンサ冷却水流路１３３ａ（図１４参照）が設けられている。これにより、下流側酸素センサ１４０は熱交換器１３３の冷却水により冷却されるので、下流側酸素センサ１４０に対する熱負荷を低減し、下流側酸素センサ１４０の耐力向上を図ることができる。すなわち、触媒コンバータ１３２を通過することで高温となった排気ガスによる下流側酸素センサ１４０の出力劣化を防ぐことができる。ひいては、エンジン性能を維持することができる。
　なお、第２実施形態では、下流側酸素センサ１４０の基部Ａの周囲に冷却水が流れるものであって、冷却水が該基部Ａ内を通過する構成ではない。 As shown in FIGS. 13 (c) (d), 14 (c) (d), and 15, in the heat exchanger 133, a downstream side oxygen sensor from one end of the cooling water flow path 133b is used as the sensor cooling water flow path 133a. It extends to 140 attachment parts. 13 and 14 show the differences between the downstream oxygen sensor arranged in the conventional heat exchanger and the downstream oxygen sensor 140 arranged in the heat exchanger 133 according to the second embodiment. As shown in FIG. 13 (b), as a use condition for exhibiting the function of the downstream oxygen sensor attached to the heat exchanger, the base A of the downstream oxygen sensor is not good if the temperature rises too much. It is not good if the temperature of the tip B serving as the detection part is lowered. Therefore, a configuration in which only the base A is cooled is desired. Therefore, in the second embodiment, as shown in FIGS. 13 (c) (d), 14 (c) (d), and FIG. 15, the cooling water flow path is extended forward from one end of the cooling water flow path 133b, A substantially cylindrical sensor cooling water flow path 133a (see FIG. 14) is provided so that the cooling water flows around the base A of the downstream oxygen sensor 140. Thereby, since the downstream oxygen sensor 140 is cooled by the cooling water of the heat exchanger 133, the thermal load on the downstream oxygen sensor 140 can be reduced and the proof stress of the downstream oxygen sensor 140 can be improved. That is, it is possible to prevent the output deterioration of the downstream oxygen sensor 140 due to the exhaust gas having a high temperature by passing through the catalytic converter 132. As a result, engine performance can be maintained.
In the second embodiment, the cooling water flows around the base A of the downstream oxygen sensor 140, and the cooling water does not pass through the base A.
　次に、本願の発明に係る第２実施形態の変形例について説明する。なお、以下の説明において、第１実施形態に係るエンジンユニット１００及び第２実施形態に係るエンジンユニット２００と同一の構成については符号を同一とし、その構成の説明は省略する。 Next, a modification of the second embodiment according to the invention of the present application will be described. In the following description, the same components as those of the engine unit 100 according to the first embodiment and the engine unit 200 according to the second embodiment are denoted by the same reference numerals, and the description of the configurations is omitted.
　図８に示すように、第２実施形態のエンジンユニット２００は、複数の酸素センサとして、触媒コンバータ１３２の上流側の排気経路に配置される上流側酸素センサ１３４（第１実施形態の第１酸素センサ１３４と同じ）と、触媒コンバータ１３２の下流側近傍に配置される下流側酸素センサ１４０とを有している。また、触媒コンバータ１３２の下流側近傍には、制御手段４０に電気的に接続され、排気ガス温度を検出する温度センサ１４１を備える。第２実施形態の変形例では、制御手段４０が、温度センサ１４１により検出される排気ガスの温度に基づいて下流側酸素センサ１４０のヒータ１４０ａの通電タイミングを制御する構成としている。 As shown in FIG. 8, the engine unit 200 of the second embodiment includes an upstream oxygen sensor 134 (first oxygen of the first embodiment) arranged in the exhaust path upstream of the catalytic converter 132 as a plurality of oxygen sensors. And the downstream oxygen sensor 140 disposed in the vicinity of the downstream side of the catalytic converter 132. Further, a temperature sensor 141 that is electrically connected to the control means 40 and detects the exhaust gas temperature is provided in the vicinity of the downstream side of the catalytic converter 132. In the modification of the second embodiment, the control means 40 is configured to control the energization timing of the heater 140a of the downstream oxygen sensor 140 based on the temperature of the exhaust gas detected by the temperature sensor 141.
　温度センサ１４１は、制御手段４０に電気的に接続され、触媒コンバータ１３２の下流側の排気経路を流れる排気ガス温度を検出することができる。制御手段４０は、温度センサ１４１により排気温度を検出し、該排気温度に基づいて下流側酸素センサ１４０のヒータ１４０ａの通電タイミングを制御することができる。 The temperature sensor 141 is electrically connected to the control means 40, and can detect the temperature of the exhaust gas flowing through the exhaust path downstream of the catalytic converter 132. The control means 40 can detect the exhaust temperature by the temperature sensor 141 and can control the energization timing of the heater 140a of the downstream oxygen sensor 140 based on the exhaust temperature.
　上述した下流側酸素センサ１４０等の具体例としては、ジルコニア等のセラミックスのように、酸素濃淡電池の原理により起電力を発生する固体電解質を用いたものが挙げられる。このような下流側酸素センサ１４０には、その性質上排気ガス中の酸素濃度を精度良く検出可能な温度域が存在し、本実施形態では下流側酸素センサ１４０の内部に備えられたヒータ１４０ａ（図８参照）に対して定格通電を行うことで、酸素濃度の検出精度を高めるための温度調節を行っている。 Specific examples of the downstream oxygen sensor 140 and the like described above include those using a solid electrolyte that generates an electromotive force according to the principle of an oxygen concentration cell, such as ceramics such as zirconia. Such a downstream oxygen sensor 140 has a temperature range in which the oxygen concentration in the exhaust gas can be accurately detected due to its nature. In this embodiment, the heater 140a (inside the downstream oxygen sensor 140 ( The temperature is adjusted to increase the accuracy of detecting the oxygen concentration by performing rated energization with respect to (see FIG. 8).
　また、制御手段４０には、下流側酸素センサ１４０におけるヒータ１４０ａに通電を行う所定時間等のデータが格納され、下流側酸素センサ１４０により検出される排気ガスの酸素濃度に基づいて、当該排気ガスの元となる混合ガスの空燃比を算出する。 Further, the control means 40 stores data such as a predetermined time during which the heater 140a in the downstream oxygen sensor 140 is energized, and the exhaust gas based on the oxygen concentration of the exhaust gas detected by the downstream oxygen sensor 140. The air-fuel ratio of the mixed gas that is the source of the above is calculated.
　次に、図１８を用いて、第２実施形態の変形例に係る下流側酸素センサ１４０のヒータ１４０ａの制御方法について説明する。当該制御方法は、制御手段４０に格納されたプログラム及びデータ等により達成されるものである。 Next, a method for controlling the heater 140a of the downstream oxygen sensor 140 according to a modification of the second embodiment will be described with reference to FIG. The control method is achieved by a program and data stored in the control means 40.
　まず、エンジン２の運転を開始すると、ステップＳ１１に移行する。 First, when the operation of the engine 2 is started, the process proceeds to step S11.
　ステップＳ１１において、制御手段４０は、温度センサ１４１により排気ガス温度を検出する。 In step S11, the control means 40 detects the exhaust gas temperature by the temperature sensor 141.
　ステップＳ１２において、制御手段４０は、温度センサ１４１により検出した排気ガス温度が予め設定された排気ガス温度の閾値以上か否かを判断する。排気ガス温度が排気ガス温度の閾値以上であればステップＳ１３に移行し、排気ガス温度の閾値未満であればＳ１１の処理を継続して行う。 In step S12, the control means 40 determines whether or not the exhaust gas temperature detected by the temperature sensor 141 is equal to or higher than a preset exhaust gas temperature threshold. If the exhaust gas temperature is equal to or higher than the exhaust gas temperature threshold, the process proceeds to step S13. If the exhaust gas temperature is lower than the exhaust gas temperature threshold, the process of S11 is continued.
　ステップＳ１３において、下流側酸素センサ１４０が有するヒータ１４０ａに定格通電（図１７では、１１Ｖ）が開始される。 In step S13, rated energization (11V in FIG. 17) is started in the heater 140a included in the downstream oxygen sensor 140.
　ステップＳ１４において、下流側酸素センサ１４０によって酸素濃度が検出され、該酸素濃度（センサ出力）を採用して、上述したように制御手段４０により空燃比が算出され、空燃比制御が行われる。 In step S14, the oxygen concentration is detected by the downstream oxygen sensor 140, the oxygen concentration (sensor output) is adopted, the air-fuel ratio is calculated by the control means 40 as described above, and the air-fuel ratio control is performed.
　上述した特許文献３に開示される内燃機関においては、排気マニホールドの上流側と下流側に酸素センサが組み付けられている。また、三元触媒出口に排気温度センサが取り付けられている。また、従来の下流側酸素センサとして、センサ内部の温度を上昇させるため、ヒータを内蔵しているものがある。しかしながら、図１６に示すように、従来の場合は下流側酸素センサのヒータへの通電タイミングはエンジン冷却水温度による制御（例えば、暖気運転としてエンジンの冷却水温度が４０℃以上になったときに、ヒータがＯＮ状態となる制御）が行われているため、暖気中は空燃比制御を実行することができない。 In the internal combustion engine disclosed in Patent Document 3 described above, oxygen sensors are assembled on the upstream side and the downstream side of the exhaust manifold. An exhaust temperature sensor is attached to the three-way catalyst outlet. Some conventional downstream oxygen sensors have a built-in heater to increase the temperature inside the sensor. However, as shown in FIG. 16, in the conventional case, the energization timing to the heater of the downstream oxygen sensor is controlled by the engine cooling water temperature (for example, when the engine cooling water temperature becomes 40 ° C. or higher in warm-up operation). Therefore, air-fuel ratio control cannot be executed during warm-up.
　第２実施形態の変形例では、上述した下流側酸素センサ１４０のヒータ１４０ａの制御フローに基づいて制御手段４０により下流側酸素センサ１４０のヒータ１４０ａの通電タイミングを温度センサ１４１で検出される排気温度で制御する。例えば、ＣＯ、ＴＨＣが多い場合、触媒コンバータ１３２の下流排気温度は上昇する。この特性を利用し、排気温度が上昇した時点（所定の排気温度に達した閾値）で下流側酸素センサ１４０のヒータに通電し、空燃比制御をスタートする。これにより、図１７の点線矢印で示すように、空燃比が効かない時間の短縮を図る。 In the modification of the second embodiment, the exhaust gas temperature at which the temperature sensor 141 detects the energization timing of the heater 140a of the downstream oxygen sensor 140 by the control means 40 based on the control flow of the heater 140a of the downstream oxygen sensor 140 described above. To control. For example, when CO and THC are large, the downstream exhaust temperature of the catalytic converter 132 increases. Using this characteristic, the heater of the downstream oxygen sensor 140 is energized at the time when the exhaust gas temperature rises (threshold value reaching the predetermined exhaust gas temperature), and the air-fuel ratio control is started. As a result, as indicated by the dotted arrow in FIG. 17, the time during which the air-fuel ratio is not effective is reduced.
　第２実施形態の変形例のように構成することで、排気特性の悪化を抑制する。また、暖気中のエンジン性能を維持することができる。 The configuration of the modification of the second embodiment suppresses the deterioration of exhaust characteristics. Moreover, the engine performance in warm air can be maintained.
　本発明は、定置型の発電機または冷凍機などに搭載するディーゼルエンジン等のエンジン装置に限定するものではなく、種々の内燃機関を備えた装置や移動体に適用することができる。 The present invention is not limited to an engine device such as a diesel engine mounted on a stationary generator or a refrigerator, but can be applied to a device or a moving body including various internal combustion engines.
　例えば、図１９は、トラック２に積載された冷凍コンテナ１０を示しているが、このような冷凍コンテナ１０は、コンテナ３と冷凍ユニット４から構成されている。当該冷凍ユニット４を構成する発電機を駆動するエンジンユニットとして本発明に係るエンジンユニットを適用することが可能である。 For example, FIG. 19 shows the refrigeration container 10 loaded on the truck 2, but such a refrigeration container 10 includes a container 3 and a refrigeration unit 4. The engine unit according to the present invention can be applied as an engine unit that drives a generator constituting the refrigeration unit 4.
　１００　　エンジンユニット
　１　　　　エンジン
　４０　　　制御手段
　１２１　　ミキサ
　１２３　　燃料調整弁
　１３１　　排気マニホールド（排気経路）
　１３２　　触媒コンバータ（三元触媒）
　１３３　　熱交換器
　１３４　　第１酸素センサ
　１３５　　第２酸素センサ
　１３６　　第３酸素センサ
　１３７　　上流側排気管（排気経路）
　１３８　　下流側排気管（排気経路）
　１４０　　下流側酸素センサ
　１４１　　温度センサ DESCRIPTION OF SYMBOLS 100 Engine unit 1 Engine 40 Control means 121 Mixer 123 Fuel adjustment valve 131 Exhaust manifold (exhaust path)
132 Catalytic converter (three-way catalyst)
133 Heat exchanger 134 First oxygen sensor 135 Second oxygen sensor 136 Third oxygen sensor 137 Upstream exhaust pipe (exhaust path)
138 Downstream exhaust pipe (exhaust path)
140 Downstream oxygen sensor 141 Temperature sensor

Claims (7)

  1. 　エンジンと、
    　前記エンジンからの排気ガスが流れる前記エンジンの排気経路に設けられる触媒と、
    　前記排気経路に配置され、前記排気ガスの酸素濃度を検出する複数の酸素センサと、
    　前記酸素センサにより検出された排気ガスの酸素濃度に基づいて空燃比を算出する制御手段と、を備えたエンジンユニットにおいて、
    　前記複数の酸素センサは、
    　前記触媒の上流側の排気経路に配置される第１酸素センサと、
    　前記触媒の下流側の排気経路に配置される第２酸素センサと、
    　前記触媒の下流側の排気経路において、前記第２酸素センサの下流側に配置される第３酸素センサと、から構成される、ことを特徴とするエンジンユニット。     Engine,
    A catalyst provided in an exhaust path of the engine through which exhaust gas from the engine flows;
    A plurality of oxygen sensors arranged in the exhaust path for detecting the oxygen concentration of the exhaust gas;
    An engine unit comprising: control means for calculating an air-fuel ratio based on the oxygen concentration of the exhaust gas detected by the oxygen sensor;
    The plurality of oxygen sensors includes:
    A first oxygen sensor disposed in an exhaust path upstream of the catalyst;
    A second oxygen sensor disposed in an exhaust path downstream of the catalyst;
    An engine unit comprising: a third oxygen sensor disposed downstream of the second oxygen sensor in an exhaust path downstream of the catalyst.
  2. 　前記制御手段は、前記第２酸素センサ及び／又は前記第３酸素センサのセンサ出力を取得し、前記第１酸素センサのセンサ出力と比較して該第１酸素センサのセンサ出力のズレを補正制御する、ことを特徴とする請求項１に記載のエンジンユニット。 The control means acquires the sensor output of the second oxygen sensor and / or the third oxygen sensor, and corrects and controls the deviation of the sensor output of the first oxygen sensor compared with the sensor output of the first oxygen sensor. The engine unit according to claim 1, wherein:
  3. 　前記触媒の下流側の排気経路には、前記排気ガスにより水を熱する熱交換器を備え、
    　前記第３酸素センサは、前記熱交換器近傍に設けられる、ことを特徴とする請求項１又は請求項２に記載のエンジンユニット。     The exhaust path on the downstream side of the catalyst includes a heat exchanger that heats water with the exhaust gas,
    The engine unit according to claim 1 or 2, wherein the third oxygen sensor is provided in the vicinity of the heat exchanger.
  4. 　前記制御手段は、前記第３酸素センサに定期的に通電することでセンサ出力を取得する、ことを特徴とする請求項１から請求項３のいずれか一項に記載のエンジンユニット。 The engine unit according to any one of claims 1 to 3, wherein the control means acquires sensor output by periodically energizing the third oxygen sensor.
  5. 　前記制御手段は、前記第２酸素センサに定期的に通電することでセンサ出力を取得するとともに、前記第３酸素センサに通電する間隔を前記第２酸素センサに通電する間隔よりも長くした、ことを特徴とする請求項４に記載のエンジンユニット。 The control means acquires the sensor output by periodically energizing the second oxygen sensor, and makes the interval of energizing the third oxygen sensor longer than the interval of energizing the second oxygen sensor. The engine unit according to claim 4.
  6. 　エンジンと、
    　前記エンジンからの排気ガスが流れる前記エンジンの排気経路に設けられる触媒と、
    　前記排気経路に配置され、前記排気ガスの酸素濃度を検出する複数の酸素センサと、
    　前記酸素センサにより検出された排気ガスの酸素濃度に基づいて空燃比を算出する制御手段と、を備えたエンジンユニットにおいて、
    　前記複数の酸素センサは、
    　前記触媒の上流側の排気経路に配置される上流側酸素センサと、
    　前記触媒の下流側の排気経路に配置される下流側酸素センサと、から構成され、
    　前記触媒の下流側の排気経路には、前記排気ガスにより水を熱する熱交換器を備え、
    　前記下流側酸素センサは、前記熱交換器に配置されるとともに、該熱交換器内を流れる水により前記下流側酸素センサが冷却される、ことを特徴とするエンジンユニット。     Engine,
    A catalyst provided in an exhaust path of the engine through which exhaust gas from the engine flows;
    A plurality of oxygen sensors arranged in the exhaust path for detecting the oxygen concentration of the exhaust gas;
    An engine unit comprising: control means for calculating an air-fuel ratio based on the oxygen concentration of the exhaust gas detected by the oxygen sensor;
    The plurality of oxygen sensors includes:
    An upstream oxygen sensor disposed in an exhaust path upstream of the catalyst;
    A downstream oxygen sensor disposed in the exhaust path downstream of the catalyst,
    The exhaust path on the downstream side of the catalyst includes a heat exchanger that heats water with the exhaust gas,
    The downstream oxygen sensor is disposed in the heat exchanger, and the downstream oxygen sensor is cooled by water flowing through the heat exchanger.
  7. 　前記触媒の下流側近傍に配置されるとともに前記制御手段に電気的に接続され、前記排気ガス温度を検出する温度センサをさらに備え、
    　前記下流側酸素センサは、ヒータを有し、
    　前記制御手段は、
    　前記温度センサにより検出される排気ガスの温度に基づいて前記下流側酸素センサのヒータの通電タイミングを制御する、ことを特徴とする請求項６に記載のエンジンユニット。     A temperature sensor disposed near the downstream side of the catalyst and electrically connected to the control means for detecting the exhaust gas temperature;
    The downstream oxygen sensor has a heater,
    The control means includes
    The engine unit according to claim 6, wherein energization timing of a heater of the downstream oxygen sensor is controlled based on a temperature of exhaust gas detected by the temperature sensor.
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