JP2014062510A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine using temperature sensors for easily detecting a deteriorating condition of a catalyst.SOLUTION: A gas engine 1 includes: a three-way catalyst 2, wherein an upstream temperature sensor 21 and a downstream temperature sensor 22 are provided upstream and downstream of the three-way catalyst 2, respectively. The gas engine 1 further includes: a control part 10 for detecting the deterioration of the three-way catalyst 2 on the basis of whether a temperature difference ΔT between the upstream temperature sensor 21 and the downstream temperature sensor 22 is a predetermined value or smaller, or not. The control part 10 detects the deterioration of the catalyst while applying a control map showing relationships between each of the speed, load, excess air ratio and ignition timing of the gas engine 1 and the predetermined value for determining whether an actually measured temperature difference is the predetermined value or smaller, or not.

Description

  The present invention relates to an internal combustion engine that can detect a deterioration state of a catalyst in an internal combustion engine provided with an exhaust purification catalyst having oxidation ability.

  In general, for example, an oxygen storage catalyst or a three-way catalyst is known as an exhaust purification catalyst having oxidation ability. Such a catalyst releases oxygen stored in the gas phase when the air-fuel ratio deviates from stoichiometric to the rich side, and takes in oxygen in the gas phase when it deviates to the lean side. Exhaust gas purification capacity is demonstrated by occlusion.

  Therefore, when the catalyst deteriorates, oxygen is not stored or released, and the exhaust gas purification ability is lost.

  Therefore, conventionally, in order to determine the deterioration state of the catalyst, an oxygen sensor is provided before and after the catalyst, and the catalyst deterioration state is calculated by applying information obtained from these oxygen sensors to the calculation formula. There is known a method for determining the deterioration state (see, for example, Patent Document 1).

Japanese Patent No. 3564064

  However, in the above conventional technique, in order to determine catalyst deterioration using an oxygen sensor, it is necessary to determine catalyst deterioration by calculating with a complicated calculation formula.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an internal combustion engine that can easily detect a deterioration state of a catalyst by a temperature sensor.

  In order to solve the above problems, an internal combustion engine according to the present invention is an internal combustion engine provided with an exhaust purification catalyst having oxidation ability, and temperature sensors are provided upstream and downstream of the catalyst, and the temperature is measured by these upstream temperature sensors. A controller for detecting deterioration of the catalyst based on whether or not the temperature difference between the upstream temperature and the downstream temperature measured by the downstream temperature sensor is equal to or less than a predetermined value is provided.

  In the internal combustion engine, the control unit measures the above-described measurement on a control map indicating a correlation between the temperature difference between the upstream temperature and the downstream temperature at the initial use of the catalyst and the rotational speed, load, excess air ratio, and ignition timing in the internal combustion engine. It is also possible to detect whether or not a predetermined value or less by applying a temperature difference.

  In the internal combustion engine, the control unit may include the temperature on the control map in at least one of a situation where the internal combustion engine is at a high speed, a high load, or an excess air ratio is richer than the stoichiometric. You may apply a difference.

  In the internal combustion engine, the control unit may include a reporting unit that reports the catalyst degradation when the catalyst degradation is detected.

  According to the present invention, since the deterioration state of the catalyst can be detected, the exhaust purification performance can be maintained.

1 is a schematic diagram showing an outline of the overall configuration of an internal combustion engine according to the present invention. It is the schematic which shows the structure of the three-way catalyst vicinity of the internal combustion engine shown in FIG. It is a graph which shows the relationship between the torque of the internal combustion engine in a certain driving | running condition, and the temperature measured by a temperature sensor. 4 is a graph showing the relationship between the torque of the internal combustion engine and the exhaust gas concentration in the situation shown in FIG. 3. It is a graph which shows the relationship between the torque of the internal combustion engine in the situation shown in FIG. 3, and the temperature difference of the temperature measured by an upstream temperature sensor and a downstream temperature sensor.

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

  FIG. 1 shows an outline of the overall configuration of a gas engine 1 according to the present invention, FIG. 2 shows a configuration in the vicinity of the three-way catalyst 2 of the gas engine 1, and FIG. 3 shows torque and upstream temperature sensor 21 in a certain operating situation. 4 shows the relationship between upstream temperature T1 and downstream temperature T2 measured by downstream temperature sensor 22, FIG. 4 shows the relationship between torque and exhaust gas concentration in the situation shown in FIG. 3, and FIG. 5 shows FIG. The relationship between the torque in the situation and the temperature difference ΔT between the upstream temperature T1 and the downstream temperature T2 is shown.

  In this gas engine 1, temperature sensors 21 and 22 are respectively provided upstream and downstream of the three-way catalyst 2, and an upstream temperature T 1 measured by the upstream temperature sensor 21 and a downstream temperature measured by the downstream temperature sensor 22. A control unit 10 is provided that detects catalyst deterioration based on a temperature difference ΔT with respect to the temperature T2.

  The gas engine 1 is provided with a compressor 12a of a turbocharger 12 in an intake passage 11a, and fuel gas mixed with air by a mixer 14 via an A / F valve 13 is supercharged by the compressor 12a and is supplied to an intercooler. 15. It is introduced into the intake port 17a of the cylinder head 17 through the throttle valve 16. The exhaust gas discharged from the exhaust port 17b of the cylinder head 17 to the exhaust path 11b passes through the three-way catalyst 2 through the turbine 12b of the turbocharger 12 and is exhausted.

  As shown in FIG. 2, the three-way catalyst 2 is provided so as to be carried in a purification device 20 provided in the exhaust passage 11b. A temperature sensor 21 is provided on the upstream side of the three-way catalyst 2, and a temperature sensor 22 is provided on the downstream side. From the upstream temperature T1 and the downstream temperature T2 of the exhaust gas before and after passing through the three-way catalyst 2, The temperature difference ΔT can be measured.

  This temperature difference ΔT is input to the control unit 10, and the control unit 10 determines whether the three-way catalyst 2 is functioning effectively based on the information on the temperature difference ΔT, or is not functioning due to deterioration. Thus, the deterioration of the three-way catalyst 2 can be detected.

  That is, the exhaust gas passing through the three-way catalyst 2 from the exhaust port 17b through the exhaust passage 11b is decomposed by releasing the oxygen stored in the three-way catalyst 2. When the exhaust gas is decomposed by this oxidation reaction, heat is generated. Therefore, if the three-way catalyst 2 functions effectively, the temperature measured by the temperature sensor 21 provided on the upstream side of the three-way catalyst 2. The temperature T2 measured by the temperature sensor 22 provided on the downstream side is higher than T1, and a temperature difference ΔT is generated. Further, since this temperature difference ΔT is caused by the oxidation reaction of the exhaust gas, there is a correlation with the exhaust gas in each operation situation.

  Therefore, at the beginning of using the new three-way catalyst 2, as shown in FIG. 5, the operating state changes, for example, the total amount of exhaust gas (CO, NOx, THC) at the time of torque fluctuation as shown in FIG. In addition, the temperature difference ΔTr has a proportional relationship. Therefore, the control unit 10 measures the upstream temperature T1 and the downstream temperature T2 at the current torque, and determines whether or not the temperature difference ΔT is the temperature difference ΔTr at the beginning of use assumed from the exhaust gas amount. The deterioration of the three-way catalyst 2 can be detected by applying it to a control map as shown in FIG. That is, when the torque actually measured at the time of determination is applied to the torque of the control map as shown in FIG. 5, the temperature difference ΔT actually measured at the torque is more predetermined than the temperature difference ΔTr of the control map. When the value is smaller than the value, the oxidation reaction is not sufficiently performed, and the three-way catalyst 2 is deteriorated.

  The detection of the deterioration of the three-way catalyst 2 by the control unit 10 is notified via the notification means 3. This notification may be performed by blinking a lamp, may be performed by generation of an alarm sound, or may be performed by using these in combination.

  Further, even if the deterioration of the three-way catalyst 2 is detected, the three-way catalyst 2 does not immediately become unusable. The life of the three-way catalyst 2 is determined when the exhaust gas cannot be sufficiently purified, that is, from the temperature difference ΔTr in the control map. Is also determined when the measured temperature difference ΔT becomes small to some extent. Therefore, the control unit 10 determines that the three-way catalyst 2 has reached the end of its life when the actually measured temperature difference ΔT is smaller than the temperature difference ΔTr of the control map by a predetermined value or more. Will be reported again. This notification may be performed by blinking a lamp, may be performed by generation of an alarm sound, may be performed by stopping the gas engine 1, or of these Some may be used in combination for notification.

  Note that the setting of the predetermined value, that is, how much the actually measured temperature difference ΔT is smaller than the temperature difference ΔTr in the control map, the life of the three-way catalyst 2 is determined. Since it varies depending on the environment and driving conditions, determine these factors. This predetermined value can be set to be degraded if it is detected several degrees lower than the temperature difference ΔTr of the control map input to the control unit 10, or can be detected several percent lower than the temperature difference ΔTr of the control map. If so, it can also be set as deterioration. This setting can be easily performed by simply setting a numerical value.

  Further, since the temperature difference ΔT actually measured when the three-way catalyst 2 deteriorates becomes smaller than the temperature difference ΔTr in the control map, the actually measured temperature difference ΔT does not become larger than the temperature difference ΔTr in the control map. If something grows, it will be another problem. Therefore, it may be set so that an abnormality is detected even when the actually measured temperature difference ΔT is larger than the temperature difference ΔTr of the control map by a certain predetermined value or more.

  In the above, the control map of the temperature difference ΔTr in the torque fluctuation is shown, but this control map may be a control map of the temperature difference ΔTr in the rotation speed fluctuation.

  However, in detecting the deterioration of the three-way catalyst 2 by comparing the actual temperature difference ΔT with the temperature difference ΔTr of the control map, in the case of torque fluctuation, as shown in FIG. It is more preferable to judge in the low torque range or the high torque range where the difference ΔTr is likely to occur. In the case of the air-fuel ratio, the air-fuel ratio where the exhaust gas concentration becomes deep and the temperature difference ΔTr is likely to occur, that is, the richer side than the stoichiometry. It is more preferable to make a determination based on the air-fuel ratio deviated to, and in the case of a rotational speed fluctuation, it is more preferable to make a determination in a high rotation range where the absolute amount of exhaust gas increases and the temperature difference ΔTr tends to occur.

  Further, the three-way catalyst 2 cannot cause an exhaust gas oxidation reaction when the oxygen stored in the three-way catalyst 2 is depleted. Therefore, the gas engine 1 needs to be in a state where the three-way catalyst 2 has sufficiently occluded oxygen by lean operation or perturbation operation. The determination of the deterioration of the three-way catalyst 2 is preferably carried out in time after the oxygen is sufficiently occluded.

  The gas engine 1 of the present invention configured as described above is simple enough to measure the upstream temperature T1 and the downstream temperature T2 of the exhaust gas before and after passing through the three-way catalyst 2 by the upstream temperature sensor 21 and the downstream temperature sensor 22. With this configuration, the control unit 10 can detect whether or not the three-way catalyst 2 has deteriorated.

  In addition, if a predetermined value indicating how much the actually measured temperature difference ΔT is smaller than the temperature difference ΔTr in the control map is set, it is possible to know the replacement time of the three-way catalyst 2 due to deterioration.

  Furthermore, since the deterioration of the three-way catalyst 2 can be known, it is possible to prevent the exhaust gas purification function from being deteriorated due to the deterioration of the three-way catalyst 2 without knowing it.

  As an application of the gas engine 1, it can be suitably used as a drive source of a gas heat pump device (not shown). At this time, the gas heat pump device is required to have a high load in winter and summer, but it can sufficiently cope with a medium and low load in the spring and autumn seasons. Moreover, the gas engine 1 drives a plurality of compressors when a high load is required, and conversely, when the load is low, it is normal to drive a single compressor. Therefore, when this gas engine 1 is used to configure a gas heat pump device, a lean operation should be performed when the load is medium and low, and a stoichiometric operation should be switched when a high load is required. It is more preferable that it is made to be able to. In this case, the thermal efficiency is reduced because the stoichiometric operation is performed at a high load, but the mechanical efficiency is increased by driving a plurality of compressors, so that the thermal efficiency is equivalent to the lean operation at a medium / low load. Naturally, the thermal efficiency at the time of medium and low loads is excellent because the lean operation is performed. Therefore, it is possible to increase the efficiency of year-round energy consumption efficiency (APF).

  Moreover, this gas engine 1 can be used suitably also as a drive source of a cogeneration apparatus (illustration omitted). That is, the cogeneration apparatus can achieve energy saving by performing a stoichiometric operation when performing a lean operation during normal operation and switching to a heat main operation with a high load.

  In the present embodiment, the specific configuration of the gas engine 1 is not particularly limited to that shown in FIG. 1, for example, the gas engine 1 without the turbocharger 12 or the intercooler 15. Also good. The configuration of the A / F valve 13 may also be the gas engine 1 having a plurality of valves for lean operation and stoichiometric operation.

  Further, in the present embodiment, the gas engine 1 is described. As for the type of the internal combustion engine, if an exhaust purification catalyst having an oxidation capability (for example, an oxygen storage catalyst, a three-way catalyst) is used, The engine is not limited to the gas engine 1, and may be, for example, a diesel engine or other various engines.

DESCRIPTION OF SYMBOLS 1 Gas engine 10 Control part 2 Three-way catalyst 21 Upstream temperature sensor 22 Downstream temperature sensor 3 Notification means T1 Upstream temperature T2 Downstream temperature (DELTA) T Actually measured temperature difference (DELTA) Tr Control map temperature difference

Claims (4)

In an internal combustion engine equipped with an exhaust purification catalyst having oxidation ability,
Temperature sensors are provided upstream and downstream of the catalyst,
A controller that detects deterioration of the catalyst based on whether or not a temperature difference between the upstream temperature measured by the upstream temperature sensor and the downstream temperature measured by the downstream temperature sensor is equal to or less than a predetermined value; An internal combustion engine.   The control unit applies the measured temperature difference to a control map indicating the correlation between the temperature difference between the upstream temperature and the downstream temperature at the beginning of catalyst use and the rotational speed, load, excess air ratio, and ignition timing in the internal combustion engine. The internal combustion engine according to claim 1, wherein the internal combustion engine detects whether or not a predetermined value or less. The control unit applies the temperature difference to the control map in at least any one of a case where the internal combustion engine is at a high rotation speed, a high load, or an excess air ratio is on a richer side than the stoichiometry. 3. The internal combustion engine according to 2.
Internal combustion engine.   The internal combustion engine according to any one of claims 1 to 3, wherein the control unit includes notification means for reporting the catalyst deterioration when the catalyst deterioration is detected.

Images