JP4196849B2 - Fuel fractionator for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel fractionator for an internal combustion engine.

There is known an exhaust emission control device that heats a part of a path for circulating a fuel to fractionate the fuel into a low-boiling component and a high-boiling component, and supplies the low-boiling component obtained by the fractionation from the upstream of the catalyst. (See Patent Document 1). Other techniques related to the present invention include Patent Documents 2 and 3.
Japanese Patent No. 2850547 Japanese Patent No. 3402505 JP-A-8-246850

  The conventional apparatus is not provided with means for detecting an abnormality of the fuel fractionation apparatus. Therefore, the internal combustion engine may be operated as it is even if a pump or the like that supplies fuel to the fuel fractionation unit is out of order. In this case, since the low boiling point component cannot be recovered, the exhaust gas purification using the catalyst is not performed normally, and the exhaust emission may be deteriorated.

  Therefore, an object of the present invention is to provide a fuel fractionation device for an internal combustion engine that can detect an abnormality in equipment used for fractionation of fuel.

  The fuel fractionating device for an internal combustion engine of the present invention is connected to a fuel supply system of the internal combustion engine, and fractionates a fractionation passage for fractionating fuel into a gas phase and a liquid phase, and a gas fractionated in the fractionation passage. An internal combustion engine comprising: a branching portion for branching the phase fuel and the liquid phase fuel; a temperature detecting means for detecting the temperature of the branching portion; and a flow rate adjusting means for adjusting the flow rate of the fuel supplied to the fractionation passage In this fuel fractionation device, the flow rate of the fuel supplied to the fractionation passage is set so that the liquid phase fuel is applied to the temperature detection means, and based on the change in the temperature detected by the temperature detection means when the fuel flow rate is set. Thus, the above-described problem is solved by providing abnormality determination means for determining whether or not the fuel fractionation device is abnormal.

  When the liquid phase fuel is applied to the temperature detection means that has detected the temperature of the branch portion, the detection value of the temperature detection means changes. When the fuel fractionation device is normal, the fuel flow rate at which the liquid phase fuel is applied to the temperature detection means by the abnormality judgment means is supplied to the fractionation passage, so that the detection value of the temperature detection means changes. On the other hand, when there is an abnormality in the fuel fractionation device, the detected value changes differently from the case where the device is normal. For example, if there is an abnormality in the flow rate adjusting means and the fuel is not supplied to the fractionation passage, the fuel is not supplied to the fractionation passage even if the fuel flow rate at which the liquid phase fuel is applied to the temperature detection means by the abnormality determination means. The detection value of the temperature detection means hardly changes. In this way, by setting the fuel flow rate so that the liquid phase fuel is applied to the temperature detection means, and observing the change in the temperature detected by the temperature detection means at this time, it is possible to diagnose whether there is an abnormality in the fuel fractionation device. Therefore, it is possible to prevent the internal combustion engine from operating without ensuring the vapor phase fuel. Thereby, for example, when the gas phase fuel is supplied to the catalyst and the exhaust gas is purified, the deterioration of the exhaust emission can be suppressed.

  When the amount of liquid phase fuel applied to the temperature detection means is small, there is a possibility that the detection value of the temperature detection means hardly changes. Therefore, in order to change the detection value of the temperature detecting means with certainty, it is desirable that the amount of liquid phase fuel flowing into the branch portion is large. Therefore, in the fuel fractionating device for an internal combustion engine according to the present invention, the abnormality determination means may set a fuel flow rate that is higher than a fuel flow rate range set at the time of fuel fractionation when the abnormality is determined. .

  The fuel fractionating device for an internal combustion engine of the present invention includes a liquid phase passage branched downward from the branch portion, and a gas phase passage branched from the branch portion above the liquid phase passage, The abnormality determination means may adjust the flow rate of the fuel supplied to the fractionation passage so that the fractionated liquid phase fuel does not flow into the gas phase passage. In this case, mixing of the liquid phase fuel into the vapor phase fuel can be suppressed. Therefore, the properties of the gas phase fuel can be stabilized.

  In the fuel fractionating device for an internal combustion engine according to the present invention, the abnormality determining means may determine whether or not the fuel fractionating device is abnormal when it is determined that fuel fractionation is not required (claim). Item 4). Thus, by performing the abnormality determination while avoiding the fuel fractionation request time, it is possible to determine the abnormality of the fuel fractionation apparatus while securing vapor phase fuel by fractionation. Note that when fractional distillation is not required, for example, gas phase fuel may be sufficiently secured in a tank that stores gas phase fuel.

  In the fuel fractionating device for an internal combustion engine according to the present invention, the abnormality judging means determines that the fuel fractionation is performed when it is determined that the temperature of the branch portion is lower than the target temperature at the time of fuel fractionation. You may determine the presence or absence of abnormality of an apparatus (Claim 5). When the temperature of the branch portion is lower than the target temperature, the gas fuel having a desired property cannot be recovered, so that no fuel is supplied to the fractionation passage. Furthermore, when such a state continues, it is considered that there is almost no gas-phase fuel in the fractionation passage, and the temperature of the gas-phase fuel is not detected by the temperature detecting means. If there is a gas phase fuel and a liquid phase fuel in the fractionation passage, the temperatures of both fuels are almost the same, so even if the liquid phase fuel is applied to the temperature detection means (that is, even if the fuel fractionation device is normal) The value may hardly change. When the temperature of the vapor phase fuel is not detected by the temperature detection means, the detected value can be changed by applying liquid phase fuel to the temperature detection means. Therefore, abnormality diagnosis is performed when the branching portion is in such a state.

  The fuel fractionating device for an internal combustion engine according to the present invention includes a fuel tank for storing the fuel of the internal combustion engine, fuel temperature acquisition means for acquiring the temperature of the fuel stored in the fuel tank, and the fuel tank from the fuel tank. A fuel supply pump that supplies fuel to the distilling passage, and when the abnormality determination means determines that there is an abnormality, the rate of increase in the temperature of the fuel stored in the fuel tank is greater than or equal to an allowable range. If it is determined that there is an abnormality in the flow rate adjusting means, and if it is determined that the temperature increase rate of the fuel stored in the fuel tank is smaller than an allowable range, the fuel supply pump is abnormal. (6). When there is an abnormality in the flow rate adjusting means and fuel is not supplied to the fractionation passage, the entire amount of fuel sucked up by the fuel supply pump is returned to the fuel tank. Since the temperature of the returned fuel is increased by the energy consumed by the fuel supply pump, the temperature of the fuel in the fuel tank rapidly increases. Therefore, when the rate of temperature increase is greater than or equal to the allowable range, it can be determined that the flow rate adjusting means is abnormal. On the other hand, when there is an abnormality in the fuel supply pump, the fuel is not sucked up from the fuel tank, so that the fuel is not returned from the fuel supply pump to the fuel tank. Therefore, it is considered that the temperature of the fuel tank is difficult to rise. Therefore, when the temperature increase rate increase is smaller than the allowable range, it can be determined that the fuel supply pump is abnormal.

  In the fuel fractionating device for an internal combustion engine according to the present invention, the abnormality determination means may decrease the amount of fuel set at the time of abnormality determination as the temperature of the branch portion increases. The viscosity of the fuel decreases as the temperature of the fuel increases. The higher the temperature of the branch portion, the higher the temperature of the liquid phase fuel, so the fuel viscosity decreases. As described above, when the viscosity of the liquid phase fuel is low, if the amount of the liquid phase fuel flowing into the branch portion is large, the liquid phase fuel may flow into the gas phase passage. Therefore, as the temperature of the branch is higher, the amount of fuel to be set is decreased and the inflow of liquid phase fuel into the gas phase passage is suppressed. Thereby, the property of the gas phase fuel can be further stabilized.

  According to the present invention, since abnormality diagnosis of the fuel fractionation device is performed by the abnormality determination means, it is possible to avoid long-term operation of the internal combustion engine in a state where gas phase fuel is not secured. Therefore, for example, when exhaust gas is purified by supplying gas-phase fuel to the catalyst, deterioration of exhaust emission can be suppressed.

  FIG. 1 shows an internal combustion engine to which a fuel fractionation apparatus according to an embodiment of the present invention is applied. The internal combustion engine 1 in FIG. 1 is configured as a diesel engine having a plurality (four in FIG. 1) of cylinders 2. As is well known, an intake passage 3 and an exhaust passage 4 are connected to the internal combustion engine 1, and a compressor 5 a of a turbocharger 5, an intercooler 6 that cools intake air, and a throttle valve 7 for adjusting the intake air amount are connected to the intake passage 3. Is provided. In the exhaust passage 4, an exhaust turbine 5 b of the turbocharger 5 and an exhaust purification catalyst 8 are provided. The exhaust passage 4 is connected to the intake passage 3 by an EGR passage 10 via an EGR cooler 9 in order to return a part of the exhaust gas to the intake passage 3.

  The internal combustion engine 1 is provided with a fuel supply device 11. The fuel supply device 11 includes a fuel injection valve 12 for injecting fuel into each cylinder 2, a common rail 13 for storing high-pressure fuel injected from the fuel injection valve 12, a fuel tank 14 for storing fuel, and a fuel tank 14 A remaining amount sensor 15 that outputs a signal corresponding to the remaining amount of fuel and a fuel pump 16 that supplies fuel from the fuel tank 14 to the common rail 13 are provided. The fuel tank 14 outputs an air communication pipe 14a for adjusting the pressure in the fuel tank 14 and a signal corresponding to the temperature of the fuel in the fuel tank 14 (hereinafter also referred to as raw material fuel). A raw material fuel temperature sensor 17 is provided.

  In addition, the internal combustion engine 1 includes a light gas phase fuel (hereinafter sometimes referred to as a light fuel) that contains many low-boiling components and a heavy liquid-phase fuel that contains many high-boiling components (hereinafter also referred to as light fuel). Hereinafter, the fuel fractionation device 18 for fractional distillation is also described, and the fractionated light fuel and raw material fuel are subjected to exhaust purification by the exhaust purification catalyst 8 and the exhaust purification catalyst during function regeneration. 8 is provided with a fuel addition device 19 for adding to the exhaust passage 4 upstream. As the exhaust purification catalyst 8, a NOx storage reduction catalyst that absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean and reduces NOx when the air-fuel ratio of the inflowing exhaust gas is rich and a reducing agent is present, or an oxidation catalyst is used. A supported particulate filter or the like is used. The NOx storage reduction catalyst is supplied with raw material fuel or light fuel during NOx reduction for reducing NOx stored in the NOx storage material or during SOx reduction for reducing SOx stored in the storage material. The particulate filter is supplied with raw material fuel and light fuel during PM oxidation removal for burning particulate (PM) collected by the filter. In addition, a light fuel or a raw material fuel may be supplied to a selective reduction type NOx catalyst which is composed of a noble metal and zeolite, selectively traps hydrocarbons and selectively reduces NOx under a lean atmosphere of the exhaust gas.

  The fuel fractionator 18 includes a fractionation passage 20 as fractionation means, a raw material fuel pump 21 for supplying raw material fuel from the fuel tank 14 to the fractionation passage 20, and a raw material fuel supplied to the fractionation passage 20. A flow rate adjusting valve 22 for adjusting the flow rate of the gas, a gas phase passage 23 and a liquid phase passage 24 branched from the fractionation passage 20, a light fuel tank 25 for storing light fuel fractionated in the fractionation passage 20, A storage amount sensor 26 that outputs a signal corresponding to the amount of light fuel stored in the fuel tank 25 is provided. The fractionation passage 20 is provided with a fractionation temperature sensor 27 that outputs a signal corresponding to the temperature in the fractionation passage 20. The light fuel tank 25 is provided with an air communication pipe 25a for adjusting the pressure in the light fuel tank 25, and a light fuel temperature sensor 28 for outputting a signal corresponding to the temperature of the light fuel in the light fuel tank 25. It has been. The fuel fractionator 18 also includes a first heat exchanger 29 that exchanges heat between the raw material fuel and the light fuel, and a second heat exchanger 30 that exchanges heat between the raw material fuel and the heavy fuel. It has been. Of the raw material fuel sucked by the raw material fuel pump 21, the raw material fuel that has not been supplied to the fractionation passage 20 is returned to the fuel tank 14 via the raw material fuel return passage 21a. As the flow rate adjusting valve 22, a valve that is closed by a biasing means such as a spring at the time of failure or non-energization is used.

  The fractionation passage 20 is disposed in the exhaust manifold 4a of the exhaust passage 4 and vaporizes the fractionation section 20a for raising the temperature of the fuel to a target temperature (for example, 200 to 250 degrees) and the light fuel vaporized in the fractionation section 20a. The phase passage 23 is provided with branching portions 20b that guide the heavy fuel that has not been vaporized to the liquid phase passage 24, respectively. FIG. 2 shows an example of the structure of the branch part 20b. As shown in FIG. 2A, the gas phase passage 23 is connected so as to extend in the horizontal direction from the fractionation section 20a at the branching portion 20b. On the other hand, the liquid phase passage 24 is connected to the fractionation section 20a so as to extend vertically downward at the branch portion 20b. In this way, the liquid phase passage 24 is connected, and only heavy fuel is guided to the liquid phase passage 24 by gravity. The gas phase passage 23 is connected to the light fuel tank 25, and the liquid phase passage 24 is connected to the fuel tank 14.

  The fuel addition device 19 includes a light fuel addition injector 31 that adds light fuel to the exhaust passage 4, a light fuel supply pump 32 that supplies light fuel from the light fuel tank 25 to the light fuel addition injector 31, and raw material fuel to the exhaust passage. 4 is provided with a raw material fuel addition injector 33 to be added to 4, and an additional raw material fuel supply pump 34 for supplying the raw material fuel from the fuel tank 14 to the raw fuel addition injector 33. Of the light fuel sucked up by the light fuel pump 32, the amount not added to the exhaust passage 4 is returned to the light fuel tank 25 via the light fuel return passage 32a.

  The operating state of the internal combustion engine 1 is controlled by an engine control unit (ECU) 35. The ECU 35 is configured as a computer in which a microprocessor and peripheral devices such as ROM and RAM necessary for its operation are combined. The ECU 35 operates the light fuel addition injector 31 and the raw fuel addition injector 33, for example, at a predetermined cycle to add the raw fuel and the light fuel to the exhaust purification catalyst 8. Further, the ECU 35 controls the operation of the flow rate adjusting valve 22 to adjust the amount of fuel supplied to the fractionation passage 20 so that the raw material fuel is fractionated at the target temperature. In order to appropriately control the operation of each device according to the operating state of the internal combustion engine 1, the ECU 35 has signals from the remaining amount sensor 15, the storage amount sensor 26, the fractionation temperature sensor 27, the light fuel temperature sensor 28, and the like. Is entered.

  If an abnormality occurs in the fuel fractionator 18 and gas phase fuel cannot be secured, the exhaust gas is not properly purified by the catalyst 8, and the exhaust emission may deteriorate. Therefore, the ECU 35 executes the abnormality diagnosis control routine of FIG. 3 to determine whether or not the raw material fuel pump 21, the flow rate adjustment valve 22, and the fractionation temperature sensor 27 are abnormal. In addition, the ECU 35 identifies an abnormal device by executing the abnormality location determination routine of FIG. The routines of FIGS. 3 and 4 are executed when the internal combustion engine 1 is started, and are repeatedly executed at a predetermined cycle during the operation of the internal combustion engine 1. The ECU 35 functions as an abnormality determining unit by executing the routine of FIG. 3, and functions as an abnormal point determining unit by executing the routine of FIG.

  In the control routine of FIG. 3, the ECU 35 first determines in step S11 whether or not the internal combustion engine 1 is in an operating state. Whether or not the internal combustion engine 1 is in an operating state is determined with reference to, for example, the operation of an engine rotation angle sensor (not shown). If it is determined that the internal combustion engine 1 is not in an operating state, the current control routine is terminated. On the other hand, when it is determined that the internal combustion engine 1 is in the operating state, the process proceeds to step S12, and the ECU 35 determines whether or not the internal combustion engine 1 is in the cold state. Whether or not the internal combustion engine 1 is in the cold state is determined with reference to an output signal of the fractional distillation temperature sensor 27, for example. If it is determined that the internal combustion engine 1 is not cold, the current control routine is terminated. On the other hand, when it is determined that the internal combustion engine 1 is in the cold state, the process proceeds to step S13, and the ECU 35 determines whether or not a diagnosis condition for diagnosing the abnormality of the fuel fractionation device 18 is satisfied. As a case where the diagnosis condition is not satisfied, for example, there is a case where an abnormality has already been detected. If it is determined that the diagnosis condition is not satisfied, the current control routine is terminated.

  On the other hand, if it is determined that the diagnosis condition is satisfied, the process proceeds to step S14, and the ECU 35 performs diagnosis. The diagnosis is performed by periodically supplying fuel to the fractionation passage 20 and referring to the output signal of the fractionation temperature sensor 27 at the time of periodic fuel supply. The amount of fuel supplied to the fractionation passage 20 at the time of diagnosis is set so that the liquid phase fuel that has flowed into the branching portion 20b is applied to the fractionation temperature sensor 27. In order to apply liquid phase fuel to the fractionation temperature sensor 27 in this way, the fuel flow rate supplied to the fractionation passage 20 is increased from that during fuel fractionation to increase the amount of liquid phase fuel flowing into the branch portion 20b. . At this time, the fuel flow rate is also adjusted so that the liquid phase fuel does not flow into the gas phase passage 23. FIG. 2B shows an example of the state of the liquid phase fuel in the branch portion 20b at the time of diagnosis. Note that the liquid phase fuel at the time of fuel fractionation flows into the liquid phase passage 24 in a state as shown in FIG. 2A, for example. Note that the fuel flow rate set at the time of diagnosis may be changed according to the temperature of the raw material fuel and the temperature of the branching portion 20b. The viscosity of the fuel decreases as the temperature of the fuel increases. Therefore, the flow rate of the fuel supplied to the fractionation passage 20 may be adjusted according to the temperature of the raw material fuel and the temperature of the branch portion 20b with reference to a map as shown in FIG. Thus, by adjusting the fuel flow rate according to the temperature, it is possible to more reliably suppress the inflow of the liquid phase fuel into the gas phase passage 23.

  In the next step S15, the ECU 35 determines whether or not the raw material fuel pump 21, the flow rate adjustment valve 22 and the fractional distillation temperature sensor 27 are normal. Whether or not these devices are normal is determined from, for example, a change in the output signal of the fractionation temperature sensor 27 with respect to periodic fuel supply to the fractionation passage 20. FIGS. 6A to 6C show examples of changes in the output signal of the fractional temperature sensor 27 at the time of diagnosis. FIG. 6D shows an example of the change over time in the flow rate of the fuel supplied to the fractionation passage 20 at the time of diagnosis.

  FIG. 6A shows the change over time in the output signal of the fractional distillation temperature sensor 27 when these devices are normal. The temperature of the branch portion 20b rises as the internal combustion engine 1 is warmed up. Further, when there is no abnormality in the fuel fractionation device 18 and fuel is periodically supplied to the fractionation passage 20, the output signal is periodically changed by the liquid phase fuel periodically applied to the fractionation temperature sensor 27. . Therefore, when the fuel fractionation device 18 is normal, the output signal of the fractionation temperature sensor 27 shows a waveform in which these temperature changes are synthesized.

  FIGS. 6B and 6C show temporal changes in the output signal of the fractionation temperature sensor 27 when the raw material fuel pump 21, the flow rate adjustment valve 22 and the fractionation temperature sensor 27 are abnormal. When there is an abnormality in the raw material fuel pump 21 and the flow rate adjustment valve 22, the fuel is not supplied to the fractionation passage 20, so that the liquid phase fuel is not periodically applied to the fractionation temperature sensor 27. In this case, only the temperature rise of the branch portion 20 b due to warming up of the internal combustion engine 1 is detected by the fractionation temperature sensor 27. Therefore, the time change as shown in FIG. On the other hand, when the fractionation temperature sensor 27 is abnormal, the fractionation temperature sensor 27 outputs only a constant value signal. Therefore, an output signal having a constant value is detected as shown in FIG.

  Returning to the description of FIG. If it is determined that the raw material fuel pump 21, the flow rate adjustment valve 22 and the fractionation temperature sensor 27 are normal, the process proceeds to step S16, and the ECU 35 has no abnormality in the abnormality flag Fsp indicating that these devices are abnormal. Substitute 0 indicating that Thereafter, the current control routine is terminated. On the other hand, if it is determined that it is not normal, the process proceeds to step S17 to determine whether or not there is an abnormality in the fractional distillation temperature sensor 27. If it is determined that the fractionation temperature sensor 27 is abnormal, the process proceeds to step S18, and the ECU 35 turns on a sensor abnormality flag indicating that the fractionation temperature sensor 27 is abnormal. On the other hand, if it is determined that there is no abnormality, step S18 is skipped. In the next step S19, the ECU 35 substitutes 1 indicating that there is an abnormality in the abnormality flag Fsp. In the following step S20, the ECU 35 turns on an abnormal lamp in the instrument panel, warns the driver of the abnormality, and then ends the current control routine. The abnormality flag Fsp is stored in the RAM of the ECU 35 so that it can be referred to from other control routines, and is not reset even after the control routine of FIG.

  In the abnormality diagnosis control routine in FIG. 3, it is not determined which of the raw material fuel pump 21 and the flow rate adjustment valve 22 has an abnormality. Therefore, the ECU 35 determines a device having an abnormality by the abnormality location determination routine of FIG.

  In the abnormal part determination routine of FIG. 4, the ECU 35 determines in step S21 whether or not the value of the abnormality flag Fsp is 1 (the fuel fractionator 18 is abnormal). If it is determined that the value of the abnormality flag Fsp is not 1, the current control routine is terminated. When it is determined that the value of the abnormality flag Fsp is 1, the process proceeds to step S22, and the ECU 35 determines whether or not the temperature of the raw material fuel is equal to or lower than the standard raw material fuel temperature range during operation of the internal combustion engine 1. To do. After the warm-up operation is completed, the temperature of the raw material fuel in the fuel tank 14 becomes a temperature within a certain range due to the fuel returned from the fuel pump 16 and the like. Thus, when the temperature of the raw material fuel has risen to a certain range, the detection accuracy of the temperature rise rate of the raw material fuel acquired in the next step S23 is deteriorated. Therefore, this fixed range is set as the standard temperature range. If it is determined that the temperature of the raw material is not below the standard temperature range, the current control routine is terminated.

  On the other hand, when it is determined that the raw material fuel temperature is equal to or lower than the standard temperature range, the process proceeds to step S23 where the ECU 35 calculates the raw fuel temperature rising speed dVT in the fuel tank 14. The rising speed dVT is calculated with reference to the time change of the output signal of the raw material fuel temperature sensor 17. In the next step S24, the ECU 35 determines whether or not the rising speed dVT exceeds the abnormality determination rising speed threshold value dVTcr. For example, the rate of increase in the raw material fuel temperature when the flow rate adjustment valve 22 is normal and only part of the raw material fuel is returned to the fuel tank 14 is set in dVTcr. When there is an abnormality in the flow rate adjustment valve 22 and no fuel is supplied from the flow rate adjustment valve 22 to the fractionation passage 20, all the fuel sucked up by the raw material fuel pump 21 is returned to the fuel tank 14. Therefore, the rate of increase in the temperature of the fuel in the fuel tank 14 is faster than when part of the raw material fuel is returned to the fuel tank 14. On the other hand, when there is an abnormality in the raw material fuel pump 21, the raw material fuel is not sucked up, so that the fuel is not returned from the raw material fuel pump 21. Therefore, dVT is equal to or less than dVTcr. Thus, by comparing dVT with dVTcr, it is possible to determine an abnormal device.

  If it is determined that dVT exceeds dVTcr, the process proceeds to step S25, and ECU 35 substitutes 1 indicating that the flow rate adjustment valve 22 is abnormal into a valve abnormality flag Flg indicating that the flow rate adjustment valve 22 is abnormal. To do. On the other hand, if it is determined that the dVT does not exceed the dVTcr, the process proceeds to step S26, and the ECU 35 sets the valve abnormality flag Flg to 0 indicating that the flow rate adjustment valve 22 is not abnormal (that is, the raw material fuel pump 21 is abnormal). substitute. After the process of step S25 or S26 ends, the process proceeds to step S27, and the ECU 35 performs a process according to the failure location. Thereafter, the current control routine is terminated. For example, when the flow rate adjustment valve 22 is abnormal (Flg value is 1), the raw material fuel pump 21 is stopped to suppress an excessive temperature rise in the fuel tank 14 as a process corresponding to the failure location. . On the other hand, when there is an abnormality in the raw material fuel pump 21 (Flg value is 0), for example, power supply to the raw material fuel pump 21 is stopped in order to suppress useless power consumption. Further, when 1 or 0 is assigned to the valve abnormality flag Flg, the control signal is not sent to the flow rate adjusting valve 22.

  As described above, by executing the control routine of FIGS. 3 and 4, it is possible to determine which of the raw fuel pump 21, the flow rate adjustment valve 22, and the fractionation temperature sensor 27 is abnormal.

  Next, another example of a diagnostic control routine for causing the ECU 35 to function as diagnostic means will be described with reference to FIG. The control routine of FIG. 7 is also executed when the internal combustion engine 1 is started, and is repeatedly executed at a predetermined cycle while the internal combustion engine 1 is in operation. In the control routine of FIG. 7, the same processes as those of the control routine of FIG. 3 are denoted by the same reference numerals and description thereof is omitted.

  In the control routine of FIG. 7, the ECU 35 performs the same processing as in FIG. 3 until step S12. If it is determined in step S12 that the internal combustion engine 1 is not in the cold state, the process proceeds to step S31, and the ECU 35 determines whether fuel fractionation is required. Whether or not fuel fractionation is required is determined with reference to, for example, the storage amount sensor 26. If light fuel is sufficiently stored in the light fuel tank 25, fuel fractionation is not required. Judge. If it is determined that fractional distillation is requested, the current control routine is terminated. On the other hand, if it is determined that fractional distillation is not requested, the process proceeds to step S32, and the ECU 35 determines whether or not the fuel fractionator 18 is in an operating condition that allows fuel fractionation. Whether or not the operating conditions allow fuel fractionation is determined with reference to, for example, an output signal from the fractionation temperature sensor 27. Even if fuel is supplied to the fractionation passage 20, the fuel temperature rises to the target temperature. If it is determined that it is not, it is determined that the operating condition is such that fuel fractionation is impossible. If it is determined that the operating conditions do not allow fractional distillation of fuel, the current control routine is terminated.

  On the other hand, if it is determined that the operating conditions allow fuel fractionation, the process proceeds to step S33, and the ECU 35 calculates a temperature difference dTds between the temperature of the branch portion 20b and the standard fractionation temperature at the time of fuel fractionation. For example, a target temperature at the time of fuel fractionation is set as the standard fractionation temperature. In subsequent step S34, the ECU 35 determines whether or not a state in which dTds is larger than a determination value dTcr has continued for a predetermined time. As the determination value dTcr, for example, a temperature difference between the temperature of the branching portion 20b when the fuel is not raised to the target temperature even when the fuel is supplied to the fractionation passage 20 and the target temperature at the time of fuel fractionation is set. . Further, as the predetermined time, for example, a time until the vapor phase fuel is discharged from the fractionation passage 20 is set to such an extent that the temperature of the vapor phase fuel is not detected by the fractionation temperature sensor 27. When there is almost no vapor phase fuel in the fractionation passage 20, the fractionation temperature sensor 27 does not detect the temperature of the vapor phase fuel. Therefore, the output signal of the fractionation temperature sensor 27 can be changed by the liquid phase fuel. Therefore, it can be diagnosed whether the fuel fractionator 18 is abnormal. When it is determined that the state where dTds is greater than the determination value dTcr is not continuous for a predetermined time, the current control routine is terminated. On the other hand, if it is determined that it has been continuous for a predetermined time, the process proceeds to step S14, and the same processing as in the control routine of FIG. Thereafter, the current control routine is terminated.

  In the diagnostic control routine of FIG. 7, abnormality diagnosis of the fuel fractionation device 18 is also performed when it is determined that the temperature of the vapor phase fuel is not detected by the fractionation temperature sensor 27. As a result, abnormality diagnosis can be performed even during operation of the internal combustion engine 1, so that an abnormality of the fuel fractionation device 18 can be found at an early stage.

  The present invention is not limited to the above embodiment, and may be implemented in various forms within the scope of the technical idea of the present invention. For example, the internal combustion engine is not limited to a diesel engine, and the present invention can also be applied to a gasoline engine. The use of light fuel is not limited to the functional regeneration of the exhaust purification catalyst. For example, it may be supplied to the intake passage when the internal combustion engine is started. By supplying light fuel in this way, it is possible to improve the startability of the internal combustion engine and improve the exhaust emission at the start.

1 is a view showing an internal combustion engine to which a fuel fractionating apparatus according to an embodiment of the present invention is applied. The figure which expands and shows a part of fractionation channel | path of FIG. The flowchart which shows the abnormality diagnosis control routine which ECU of FIG. 1 performs. The flowchart which shows the abnormal location determination routine which ECU of FIG. 1 performs. The figure which shows an example of the relationship between the raw material fuel temperature and the temperature of a branch part, and the fuel quantity supplied to a fractionation channel. The figure which shows an example of the change of the output signal of a fractional distillation temperature sensor at the time of diagnostic control routine execution. The flowchart which shows the other Example of the abnormality diagnosis control routine which ECU of FIG. 1 performs.

Explanation of symbols

1 Internal combustion engine 11 Fuel supply device (fuel supply system)
14 Fuel tank 17 Raw material fuel temperature sensor (Fuel temperature acquisition means)
18 Fuel Fractionation Device 20 Fractionation Passage 20b Branch 21 Raw Material Fuel Pump (Fuel Supply Pump)
22 Flow rate adjusting valve (Flow rate adjusting means)
23 Gas phase passage 24 Liquid phase passage 27 Fractionation temperature sensor (temperature detection means)
35 Engine control unit (abnormality determination means, abnormal location determination means)

Claims (7)

A fractionation passage that is connected to a fuel supply system of an internal combustion engine and fractionates the fuel into a gas phase and a liquid phase, and a branching portion that branches the gas phase fuel and the liquid phase fuel that are fractionated in the fractionation passage And a fuel fractionation device for an internal combustion engine, comprising: temperature detection means for detecting the temperature of the branch portion; and flow rate adjustment means for adjusting a flow rate of fuel supplied to the fractionation passage.
The flow rate of the fuel supplied to the fractionation passage is set so that liquid temperature fuel is applied to the temperature detection means, and the fuel fractionation device is configured based on the change in the temperature detected by the temperature detection means when the fuel flow rate is set. A fuel fractionation device for an internal combustion engine, comprising an abnormality determination means for determining whether or not there is an abnormality.   2. The fuel fractionation device for an internal combustion engine according to claim 1, wherein the abnormality determination unit sets a fuel flow rate larger than a fuel flow rate range set at the time of fuel fractionation when the abnormality is judged. A liquid phase passage branched downward from the branch portion, and a gas phase passage branched upward from the branch portion to the liquid phase passage,
3. The internal combustion engine according to claim 1, wherein the abnormality determination unit adjusts a flow rate of fuel supplied to the fractionation passage so that the fractionated liquid phase fuel does not flow into the gas phase passage. Fuel fractionator.   The said abnormality determination means determines the presence or absence of the abnormality of the said fuel fractionation apparatus, when it is judged that the fuel fractionation is not requested | required. Fuel fractionation device for internal combustion engine.   The abnormality determination means determines whether or not there is an abnormality in the fuel fractionation device when it is judged that the state where the temperature of the branch portion is lower than the target temperature at the time of fuel fractionation continues. The fuel fractionation device for an internal combustion engine according to any one of claims 1 to 4. A fuel tank for storing fuel of the internal combustion engine, fuel temperature acquisition means for acquiring the temperature of the fuel stored in the fuel tank, a fuel supply pump for supplying fuel from the fuel tank to the fractionation passage, With
If it is determined by the abnormality determination means that there is an abnormality, it is determined that the flow rate adjustment means is abnormal if it is determined that the rate of increase in the temperature of the fuel stored in the fuel tank is above an allowable range. And an abnormality location determination means for determining that the fuel supply pump is abnormal when it is determined that the rate of temperature rise of the fuel stored in the fuel tank is smaller than an allowable range. The fuel fractionation device for an internal combustion engine according to any one of claims 1 to 5.   The fuel fractionation device for an internal combustion engine according to any one of claims 1 to 6, wherein the abnormality determination unit decreases the fuel amount set at the time of abnormality determination as the temperature of the branch portion is higher.

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