JP2005061401A - Bi-fuel engine and mixture ratio estimation method of blended fuel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bi-fuel engine that can detect a mixture ratio between LPG and DME and can share fuel tank for storing both fuel of the LPG and DME. <P>SOLUTION: The bi-fuel engine includes an LPG/DME mixture tank 11 for mixing and storing the LPG and DME, and a mixture ratio sensor 15 for measuring a mixture ratio between the LPG and DME. The mixture ratio sensor 15 measures the mixture ratio, and an ECU 16 acquires property of the blended fuel from a measurement value of the mixture ratio, so as to reflect them in control of an engine 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a bi-fuel engine and a mixed fuel ratio estimation method, and more particularly, to a bi-fuel engine using a mixed fuel of liquefied petroleum gas (hereinafter referred to as LPG) and dimethyl ether (hereinafter referred to as DME) as fuel. And a method for estimating the mixture ratio of the mixed fuel.

  LPG and DME are fuels having similar characteristics that their boiling points are approximately the same, and they are gas at normal temperature and liquid when pressurized. LPG has already been used as an alternative fuel for light oil, and infrastructure such as an LPG stand has been established. DME has a high cetane number (LPG has a cetane number of about 12 whereas DME has a cetane number of about 55) and is an oxygen-containing fuel. ing.

  Since these LPG and DME can share the same infrastructure, there is a possibility that DME will be sold at the LPG stand. However, since it is considered that DME infrastructure development will not progress for the time being, if LPG and DME bi-fuel vehicles can be provided, it will be useful for the spread of DME vehicles and DME infrastructure development.

  In addition, as a related publicly known technology, when the DME cannot be replenished due to insufficient development of DME infrastructure, the fuel of the DME diesel engine that can be used for emergency travel using the diesel fuel stored in the mixing tank A supply system is disclosed (see, for example, Patent Document 1).

JP 2003-97307 A

  Bi-fuel vehicles often have their own fuel tanks, and two fuel tanks must be provided, which causes disadvantages such as increased vehicle weight and increased costs. The storage method of DME and LPG is almost the same, and since it is easy to mix DME and LPG, a method of solving the above disadvantages by using a common fuel tank is also conceivable.

  However, when DME and LPG are mixed, DME is a highly ignitable fuel, while LPG is a low ignitable fuel, and both fuels have significantly different ignitability and different calorific values. The amount will also vary. Therefore, there is a problem that it is necessary to detect the mixing ratio of the mixed fuel, calculate the fuel property, and perform engine control according to the fuel property.

  The present invention has been made in view of the above, and an object of the present invention is to provide a bi-fuel engine that can detect the mixing ratio of LPG and DME and can share a fuel tank that stores both fuels.

  It is another object of the present invention to provide a mixed fuel ratio estimation method that can easily detect the blend ratio of LPG and DME.

  In order to solve the above-described problems and achieve the object, a bi-fuel engine according to claim 1 of the present invention includes a fuel tank capable of mixing and storing LPG and DME, and a fuel supply line extending from the fuel tank to the engine. Or a mixing ratio sensor that is provided in the fuel tank and that measures the mixing ratio of the LPG and the DME, measures the mixing ratio of the LPG and the DME by the mixing ratio sensor, and determines the mixed fuel from the measured value. The characteristic is obtained and reflected in the engine control.

  A bi-fuel engine according to claim 2 of the present invention includes a fuel tank capable of mixing and storing LPG and DME, a compression chamber connected to the fuel tank and having a reciprocating piston inside, the fuel tank, and the compression An on-off valve provided between the chambers, and the piston is moved with the on-off valve opened to fill the compression chamber with the mixed fuel in the fuel tank, and the piston with the on-off valve closed And an actuator that compresses the mixed fuel filled in the compression chamber at a predetermined pressure, and a temperature sensor and a pressure sensor provided in the fuel tank, and the amount of movement of the piston during the mixed fuel compression or The volume loss in the compression chamber, the temperature and pressure detected by the temperature sensor and the pressure sensor, and an LPG unit stored in advance. The mixing ratio of the LPG and the DME is calculated using the data relating to the bulk modulus of the fuel and the data relating to the bulk modulus of the DME alone, and the property of the mixed fuel is obtained from the calculated value and reflected in the engine control. It is characterized by.

  A bi-fuel engine according to a third aspect of the present invention is the bi-fuel engine according to the second aspect, characterized in that the reciprocating motion of the piston is repeated a predetermined number of times when the mixed fuel is charged into the compression chamber. .

  According to a fourth aspect of the present invention, there is provided a bi-fuel engine comprising a fuel tank capable of mixing and storing LPG and DME, a sealed balance chamber connected to the fuel tank, and between the fuel tank and the sealed balance chamber. An open / close valve provided, an elastic container provided in the sealed balance chamber and filled with a predetermined amount of LPG, the open / close valve is opened to fill the closed balance chamber with fuel mixture, and the open / close valve is A piston and an actuator for compressing the LPG in the elastic container at a predetermined pressure in a closed state, and a movement amount of the piston at the time of compression of the mixed fuel or a volume reduction amount in the compression chamber is stored in advance. Calculate the mixing ratio of LPG and DME using the data related to the bulk modulus of a single substance and the data related to the bulk modulus of a single DME. Seeking properties of the mixed fuel is characterized in that is reflected in the engine control.

  A bi-fuel engine according to claim 5 of the present invention is a fuel tank capable of mixing and storing LPG and DME, and a fuel pressurization pump provided in the middle of a fuel supply line from the fuel tank to a fuel injection valve of the engine. A rotation speed / load detection means for detecting the rotation speed or load of the fuel pressurization pump, a pressure sensor for detecting fuel pressure at the fuel pressurization pump outlet, and a fuel temperature at the fuel pressurization pump outlet And the number of revolutions or load of the fuel pressurization pump for each reference fuel temperature stored in advance from the detected value of the number of revolutions or load of the fuel pressurization pump by the revolution number / load detection means. And calculating the mixing ratio of the LPG and the DME based on the characteristic diagram of the outlet pressure of the fuel pressurizing pump, and obtaining the property of the mixed fuel from the calculated value. It is characterized in that to reflect your on.

  According to a sixth aspect of the present invention, there is provided a method for estimating a mixture ratio of a mixed fuel, wherein a mixed fuel of LPG and DME is filled in a sealed container, and the filled mixed fuel is compressed at a predetermined pressure. The mixing ratio of the LPG and the DME is obtained based on a volume change.

  According to the bi-fuel engine according to the present invention (Claim 1), the fuel tank for storing LPG and DME is shared, and the vehicle weight can be reduced by using one fuel tank, and the manufacturing cost is reduced accordingly. can do. Also, by applying the present invention, a flexible bi-fuel engine vehicle that can use both LPG and DME fuels can be constructed, so that options for refueling are expanded. That is, when DME cannot be replenished due to infrastructure not yet developed, it is possible to travel with provisional LPG with infrastructure maintained, so it is possible to reduce the anxiety of running out of gas.

  Further, according to the bi-fuel engine according to the present invention (Claim 2), the fuel tank for storing LPG and DME can be shared, and the vehicle weight can be reduced by using one fuel tank. As well as a decrease in vehicle performance. Also, by applying the present invention, a flexible bi-fuel engine vehicle that can use both LPG and DME fuels can be constructed, so that options for refueling are expanded.

  Further, according to the bi-fuel engine according to the present invention (Claim 3), the fuel remaining in the compression chamber or the fuel remaining in the connection portion between the fuel tank and the compression chamber can be replaced, and the mixing ratio measurement can be performed. The accuracy can be further improved.

  Further, according to the bi-fuel engine according to the present invention (Claim 4), compared with the invention according to Claim 2, a temperature sensor and a pressure sensor are not required, and further cost reduction can be expected.

  In addition, according to the bi-fuel engine according to the present invention (Claim 5), since no special parts for calculating the mixing ratio are required, compared with the inventions according to Claims 2 and 4 above, Can be expected to reduce costs.

  Further, according to the mixed fuel mixture ratio estimation method according to the present invention (Claim 6), the mixture ratio can be calculated by utilizing the difference in volume modulus of elasticity between LPG and DME. That is, for example, if a volume change is detected using a closed container having a reciprocating piston inside, the mixing ratio can be calculated with a simple configuration.

  Embodiments of a bi-fuel engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  First, the basic concept for detecting the mixing ratio of LPG and DME will be described with reference to FIGS. 3 is a schematic diagram showing a state before compression of LPG, FIG. 4 is a schematic diagram showing a state after compression of LPG, FIG. 5 is a schematic diagram showing a state before compression of DME, and FIG. These are the schematic diagrams which show the state after compression of DME.

  It is known that the bulk modulus of DME varies with temperature and pressure, but is smaller than that of LPG. The detection of the mixing ratio according to the present invention utilizes the fact that the bulk modulus is different. As shown in FIGS. 3 to 6, a piston 18 is reciprocally arranged in a hermetically insulated compression chamber 17, and the piston 18 is configured to reciprocate by an actuator 19.

  As shown in FIG. 3, the compression chamber 17 before compression is filled with LPG having a volume V0 at a predetermined temperature, and from this state, as shown in FIG. The compression force F is applied to become volume V1. At this time, the volume change of the LPG is extremely small, the movement amount of the piston 18 is almost zero, and the volume V0 and the volume V1 are substantially equal.

  On the other hand, as shown in FIG. 5, the compression chamber 17 before compression is filled with DME having a volume V0 at a predetermined temperature (the same temperature as in the case of LPG shown in FIG. 3). As described above, when the piston 18 is driven by the actuator 19 and a predetermined compressive force F (the same pressure F as in the case of LPG shown in FIG. 4) is applied to the DME, the piston 18 is compressed to the volume V1. That is, the volume change of DME is larger than that of the LPG, the movement amount of the piston 18 is larger than zero, and the volume V1 is smaller than the volume V0.

  Thus, the volume change of LPG and DME at the same compressive force F under each temperature condition and pressure condition is measured in advance. Then, by measuring the volume change of the mixed fuel of LPG and DME actually contained in the fuel tank, the mixing ratio thereof can be estimated. If this mixing ratio is known, the fuel property can be calculated, and this can be reflected in the control of the bi-fuel engine (hereinafter referred to as the engine as appropriate). The above is the basic concept of mixing ratio measurement.

  Next, an engine according to Embodiment 1 of the present invention will be described with reference to FIG. Here, FIG. 1 is a block diagram showing a main part of the engine according to Embodiment 1 of the present invention. As shown in FIG. 1, the engine 10 is an internal combustion engine capable of spark ignition, for example, and is configured to be able to burn a mixed fuel of LPG and DME. Although not shown in the drawings, the engine 10 is provided with various basic devices necessary for the operation of the engine 10 such as a fuel pressurizing pump for pressurizing and supplying fuel to the engine 10.

  The LPG / DME mixing tank (fuel tank) 11 is configured so that LPG supplied from the LPG supply hole 13 and DME supplied from the DME supply hole 12 can be mixed and stored as mixed fuel. The fuel in the LPG / DME mixing tank 11 is configured to be supplied to the engine 10 through a fuel supply line 14.

  In the middle of the fuel supply line 14, for example, as described above, a mixing ratio sensor 15 configured to be able to measure the mixing ratio by using the difference in volume modulus between LPG and DME is provided. Further, a temperature sensor (not shown) for detecting the temperature of the mixed fuel and a pressure sensor (not shown) for measuring the pressure are provided in the vicinity of the mixture ratio sensor 15.

  An electronic control unit (hereinafter referred to as ECU) 16 calculates the fuel property based on the measurement value output from the mixing ratio sensor 15 so that the engine 10 can be controlled based on the engine control map stored in advance. It is configured.

  Next, the control operation will be described with reference to FIG. Here, FIG. 2 is a flowchart showing an engine control method based on the calculated fuel mixture ratio. First, the mixture ratio of LPG and DME of the mixed fuel in the fuel supply line 14 is measured by the mixture ratio sensor 15 (step S10).

  The measured value of the mixture ratio sensor 15 is output to the ECU 16 together with the temperature / pressure data of the temperature sensor and the pressure sensor, and the ECU 16 calculates the properties of the mixed fuel (step S11). Next, a predetermined engine control map is selected based on the calculated fuel properties (step S12), and the engine 10 is controlled based on the control information (step S13).

  As described above, according to the bi-fuel engine according to the first embodiment, the fuel tank for storing LPG and DME is shared, and the LPG / DME mixed tank 11 can be used to reduce the vehicle weight. As a result, the manufacturing cost can be reduced, and the deterioration of the vehicle performance can be suppressed.

  Also, by applying the present invention, a flexible bi-fuel engine vehicle that can use both LPG and DME fuels can be constructed, so that options for refueling are expanded. That is, when DME cannot be replenished due to infrastructure not yet developed, it is possible to travel with provisional LPG with infrastructure maintained, so it is possible to reduce the anxiety of running out of gas.

  In the first embodiment, the mixing ratio sensor 15 is described as being provided in the middle of the fuel supply line 14. However, the present invention is not limited to this, and the mixing ratio sensor 15 may be provided in the LPG / DME mixing tank 11 as described above. The effect can be expected.

  FIG. 7 is a schematic diagram showing the main part of the bi-fuel engine according to Embodiment 2 of the present invention, and FIG. 8 is a map showing the relationship between the piston movement amount, temperature, and pressure used when obtaining the mixing ratio. . In the following description, members that are the same as or correspond to those already described are denoted by the same reference numerals, and redundant description is omitted or simplified.

  The compression chamber 17 and the LPG / DME mixing tank 11 are connected by a detection line 22 and are configured such that mixed fuel can be introduced into the compression chamber 17 when necessary by opening and closing a valve (open / close valve) 23. The compression chamber 17 is provided with a temperature sensor 20 for detecting the temperature of the mixed fuel in the compression chamber 17 and a pressure sensor 21 for measuring the pressure. The fuel supply line 14 is provided with a fuel pressurizing pump 24 for pressurizing and supplying fuel to the engine 10.

  Next, a method for detecting the mixing ratio of LPG and DME will be described. First, the valve 23 is opened, and the piston 18 is driven by the actuator 19 so as to increase the volume in the compression chamber 17, whereby the mixed fuel in the LPG / DME mixed tank 11 is filled into the compression chamber 17.

  When the mixed fuel is filled, the reciprocating motion of the piston 18 is performed several times (for example, about three times), so that the fuel remaining in the compression chamber 17 and the detection line 22 between the compression chamber 17 and the valve 23 are detected. The remaining fuel can be replaced, and the accuracy of the mixture ratio measurement can be further improved.

  When the mixed fuel is filled to a preset amount, the valve 23 is closed, and the piston 18 is driven in the compression direction by the actuator 19 to compress the filled mixed fuel to a predetermined set pressure.

  The volume of the LPG alone stored in advance in the ECU (not shown) from the amount of movement of the piston 18 or the volume reduction in the compression chamber 17 and the temperature / pressure data from the temperature sensor 20 and the pressure sensor 21 at this time. The mixing ratio of LPG and DME is calculated using the data relating to the elastic modulus and the data relating to the bulk elastic modulus of the DME alone.

  That is, the mixing ratio of LPG and DME can be calculated as follows based on FIG. FIG. 8 shows the relationship between the movement amount X of the piston 18, the temperature T, and the pressure P. The piston movement amount map 26 according to the temperature and pressure when the DME is 100%, and the piston movement amount map according to the temperature and pressure when the LPG is 100%. 28 is shown.

In FIG. 8, X _DME is a point located on the map 26, and indicates the movement amount of the piston 18 at a certain temperature T ₁ and pressure P ₁ when _DME is 100%. X _LPG is a point located on the map 28, and indicates the amount of movement of the piston 18 by a certain temperature T ₁ and pressure P ₁ when _LPG is 100%. X _mix indicates the moving amount of the piston 18 of the mixed fuel obtained by actual measurement from the apparatus shown in FIG.

Thus piston movement amount X _DME and X _LPG is to measure the temperature T ₁ and pressure P ₁ by the temperature sensor 20 and pressure sensor 21 can be determined from the map 26, the piston moving distance X _mix is Since it can be obtained from actual measurement, the mixing ratio DME (%) of DME can be obtained by the following equation (1).

DME (%) = (X _DME -X _mix ) / (X _DME -X _LPG ) × 100 (1)

  The mixing ratio LPG (%) of LPG can be obtained by substituting the mixing ratio DME (%) of DME obtained by the equation (1) into the following equation (2).

  LPG (%) = 100−DME (%) (2)

  Based on the mixing ratio thus determined, the ECU calculates the properties of the mixed fuel. A predetermined engine control map is selected based on the calculated fuel property, and the engine 10 is controlled based on the control information.

  As described above, according to the bi-fuel engine according to the second embodiment, the fuel tank for storing LPG and DME is shared, and the LPG / DME mixed tank 11 is used to reduce the vehicle weight. As a result, the manufacturing cost can be reduced, and the deterioration of the vehicle performance can be suppressed. Further, by applying the present invention having a simple configuration, a flexible bi-fuel engine vehicle that can use both LPG and DME fuels can be constructed, so that options for refueling are expanded.

  FIG. 9 is a schematic diagram showing the main part of a bi-fuel engine according to Embodiment 3 of the present invention, and FIG. 10 is a map showing the relationship between the piston movement amount and the mixing ratio. The sealed balance chamber 30 that is hermetically insulated is connected to the LPG / DME mixing tank 11 through a fuel supply line 14, a valve (open / close valve) 31 and a detection line 22, as well as a fuel return line 32 and a valve 33. Connected through.

  The sealed balance chamber 30 includes a rubber sphere (elastic container) 34 containing LPG connected to the compression chamber 17 so as to expand and contract. That is, the rubber sphere 34 is filled with a predetermined amount of LPG, and the rubber sphere 34 can be expanded or contracted by driving the piston 18 with the actuator 19. .

  Next, a method for detecting the mixing ratio of LPG and DME will be described. First, the valve 31 and the valve 33 are opened, and the fuel pressurization pump 24 introduces the mixed fuel from the LPG / DME mixing tank 11 into the closed balance chamber 30, and surplus mixed fuel is mixed with the LPG / DME from the fuel return line 32. By overflowing into the tank 11, the entire system balance chamber 30 is filled with the mixed fuel. In this state, the valve 31 and the valve 33 are closed.

  At this time, the actuator 19 is operated so that the pressure of the LPG in the rubber sphere 34 and the pressure of the mixed fuel in the closed system balance chamber 30 are the same, and the rubber sphere 34 is inflated by the piston 18. At this time, the temperature of the LPG in the rubber sphere 34 and the temperature of the mixed fuel in the closed system balance chamber 30 are the same.

  Next, the actuator 19 is operated, and the compression of the LPG in the compression chamber 17 is started by the piston 18. If the fuel in the closed system balance chamber 30 is LPG itself, the volume modulus of elasticity is the same inside and outside the rubber sphere 34, so the piston 18 does not move, but the fuel in the closed system balance chamber 30 has a volume modulus of elasticity. If small DME is mixed or if the fuel in the closed balance chamber 30 is DME itself, the piston 18 is displaced to the compression side. Since the piston 18 is operated by the actuator 19, the movement amount of the piston 18 can be easily measured.

  If the amount of movement of the piston 18 or the amount of volume reduction in the compression chamber 17 is known, data relating to the bulk modulus of LPG alone and data relating to the bulk modulus of DME alone stored in advance in an ECU (not shown) (FIG. 10) can be used to calculate the mixing ratio of LPG and DME. For example, as shown in FIG. 10, if the movement amount of the piston 18 shown on the horizontal axis of the graph is determined, the mixing ratio shown on the vertical axis corresponding to this is obtained.

  Based on the mixing ratio thus determined, the ECU calculates the properties of the mixed fuel. A predetermined engine control map is selected based on the calculated fuel property, and the engine 10 is controlled based on the control information.

  As described above, according to the bi-fuel engine according to the third embodiment, the fuel tank for storing LPG and DME is shared, and the vehicle weight can be reduced by using one LPG / DME mixed tank 11. As a result, the manufacturing cost can be reduced, and the deterioration of the vehicle performance can be suppressed. Further, by applying the present invention having a simple configuration, a flexible bi-fuel engine vehicle that can use both LPG and DME fuels can be constructed, so that options for refueling are expanded.

  Further, since the mixed fuel in the closed balance chamber 30 to be measured and the LPG in the rubber sphere 34 are compared under the same temperature and pressure conditions, the temperature sensor for measuring the temperature and the pressure are measured. Therefore, a further cost reduction can be expected as compared with the system shown in the second embodiment.

  In the third embodiment, the fuel pressurizing pump 24 is used as a means for supplying fuel to the engine 10 and as a means for introducing fuel into the closed balance chamber 30 for measuring the mixing ratio. However, the present invention is not limited to this, and a fuel pressurizing pump may be provided individually. In the third embodiment, the system in which the rubber sphere 34 is filled with LPG has been described. However, the present invention is not limited to this. For example, the system may be configured as a system in which the rubber sphere 34 is filled with DME. The effect of can be expected.

  FIG. 11 is a schematic diagram showing the main part of a bi-fuel engine according to Embodiment 4 of the present invention, and FIG. 12 is a map showing the relationship between the rotational speed of the fuel pressurizing pump and the outlet pressure at a certain fuel temperature. In the fourth embodiment, the mixing ratio of LPG and DME is obtained from the pumping characteristics (see FIG. 12) of the fuel pressurizing pump 24 for supplying fuel to the engine 10 as shown in FIG.

  The fuel pressurizing pump 24 is provided in the middle of the fuel supply line 14. Further, a temperature sensor (not shown) for measuring the temperature of the fuel and a pressure sensor (not shown) for measuring the pressure are provided in the vicinity of the outlet of the fuel pressurizing pump 24. Further, the fuel pressurizing pump 24 is provided with a rotation speed / load detection means (not shown) for detecting the rotation speed or load thereof.

  As shown in FIG. 12, the pressure curves of LPG 100% and DME 100% are obtained in advance by experiments or the like according to the rotation speed or load of the fuel pressurizing pump 24, and are stored in advance in an ECU (not shown). Since these pressure curves differ for each fuel temperature, they are created and stored for each predetermined reference temperature.

  Therefore, based on the temperature actually measured by the temperature sensor, a pressure curve of the temperature is calculated by interpolation or extrapolation. Then, the mixing ratio of LPG and DME is calculated as follows from the actually measured pump conditions of the fuel pressurizing pump 24 and fuel pressure data.

That is, as shown in FIG. 12, it is assumed that the pump outlet pressure is P ₁ when the fuel pressurizing pump 24 has a certain operating condition, for example, the pump speed at a certain temperature is N ₁ . From the graph of FIG. 12, the outlet pressure P _LPG when _LPG is 100% at the pump rotation speed N ₁ and the outlet pressure P _DME when _DME is 100% are obtained. Therefore, the LPG mixing ratio LPG (%) can be obtained by substituting these values into the following equation (3).

LPG (%) = (P _LPG -P ₁ ) / (P _LPG -P _DME ) × 100 (3)

  Further, the DME mixing ratio DME (%) can be obtained by substituting the LPG mixing ratio LPG (%) obtained by the expression (3) into the following expression (4).

  DME (%) = 100-LPG (%) (4)

  As described above, according to the bi-fuel engine according to the fourth embodiment, the fuel tank for storing LPG and DME is shared, and the LPG / DME mixed tank 11 can be used to reduce the vehicle weight. As a result, the manufacturing cost can be reduced, and the deterioration of the vehicle performance can be suppressed. Further, by applying the present invention having a simple configuration, a flexible bi-fuel engine vehicle that can use both LPG and DME fuels can be constructed, so that options for refueling are expanded.

  Furthermore, since the mixing ratio of LPG and DME can be measured using the fuel pressurizing pump 24 that is essential for supplying fuel to the engine 10, no dedicated parts for measuring the mixing ratio are required, and the above-described second embodiment or A significant cost reduction can be achieved with respect to the third embodiment.

  FIG. 13 is a schematic view showing a main part of a bi-fuel engine according to Embodiment 5 of the present invention, FIG. 14 is a flowchart showing a control method of the bi-fuel engine, and FIG. 15 is a mixture ratio of LPG and a cetane number improver. FIG. 16 is a map showing the relationship between the DME mixing ratio and the fuel injection amount correction ratio.

  As shown in FIG. 13, in the fifth embodiment, a mixing ratio sensor 15 is provided in the LPG / DME mixing tank 11 and mixing from the mixing ratio sensor 15 is performed in order to improve the cetane number of LPG to a cetane number equivalent to DME. A cetane number improver addition device 40 for adding a predetermined amount of cetane number improver to the LPG / DME mixing tank 11 according to the ratio signal is provided.

  The cetane number improver addition device 40 can be configured by a known technique. Moreover, as a cetane number improver, nitrate ester, nitrite ester, an organic peroxide, and a nitro compound can be used, for example.

  A mixing ratio signal from the mixing ratio sensor 15 is input to the ECU 16. Further, in order to add the cetane number improver to the LPG / DME mixed tank 11, a cetane number improver addition signal is output from the ECU 16 to the cetane number improver addition device 40.

  In the fifth embodiment, a diesel engine is used as the engine 10. A fuel injection amount control signal is output from the ECU 16 to the fuel pump 24 and the injector 10a of the diesel engine 10. In addition, the code | symbol 10b has shown the intake pipe.

  Next, a method for controlling the diesel engine 10 will be described based on FIG. 14 with reference to FIGS. As shown in FIG. 14, first, when necessary, the mixing ratio sensor 15 measures the mixing ratio of LPG and DME in the LPG / DME mixing tank 11 (step S20), and inputs the mixing ratio signal to the ECU 16. For example, it is assumed that X (%) is measured as the mixing ratio of LPG. At this time, the mixing ratio of DME is (100-X) (%). In the following drawings, this mixing ratio is simply referred to as “ratio”.

  Next, the optimum cetane number for ignition is calculated by the ECU 16 from the measured mixing ratio, and the addition amount Yc of the cetane number improver to improve the cetane number of LPG to a cetane number equivalent to DME is shown in FIG. It calculates with the map shown and the following formula | equation (5) (step S21). The map shown in FIG. 15 is obtained in advance through experiments or the like.

Yc = α · X / 100 (5)
Here, α is the addition amount of the cetane number improver when the mixing ratio of LPG is 100%, and is obtained in advance by experiments or the like.

  By the way, since DME and LPG have different calorific values, it is necessary to change the fuel injection amount in accordance with their mixing ratio. That is, it is necessary to correct the basic fuel injection amount corresponding to the predetermined mixing ratio according to the actually measured mixing ratio.

  Therefore, the fuel injection amount correction ratio Z based on the DME mixing ratio (100-X) (%) is calculated using the map shown in FIG. 16 and the following equation (6) (step S22). The map shown in FIG. 16 calculates the calorific value of the mixed fuel from the DME mixing ratio (100-X) (%), and corrects the basic fuel injection amount so as to obtain optimum combustion from the calorific value. Therefore, it is obtained in advance by experiments or the like.

Z = β · (100−X) / 100 (6)
Here, β is a correction ratio of the fuel injection amount when the mixing ratio of DME is 100%, and is obtained in advance through experiments or the like.

  Next, the addition amount Yc of the cetane number improver calculated in step S21 is added to the LPG / DME mixed tank 11 by the cetane number improver addition device 40, and the correction ratio Z of the fuel injection amount calculated in step S22 is performed. The fuel injection amount is corrected based on (Step S23). Further, the fuel injection timing is also corrected as necessary.

  If the addition of the cetane number improver and the correction of the fuel injection amount are executed in step S23, the process returns to the start.

  As described above, according to the bi-fuel engine according to the fifth embodiment, the optimum addition amount of the cetane improver and the fuel injection amount (fuel injection timing) are determined based on the measured mixing ratio of LPG and DME. The optimum combustion of the diesel engine 10 can be realized regardless of the mixing ratio.

  As a result, it is possible to provide a vehicle that can use both DME, which is clean fuel but limited in availability, and LPG, which is relatively easy to obtain. A clean vehicle can be obtained.

  In the fifth embodiment, the mixing ratio sensor 15 and the cetane number improver adding device 40 are described as being provided in the LPG / DME mixing tank 11. However, the present invention is not limited to this and is provided in the middle of the fuel supply line 14. May be. In this case, the cetane number improver is added into the fuel supply line 14, and the same effect as described above can be expected.

  FIG. 17 is a schematic diagram showing a main part of a bi-fuel engine according to Embodiment 6 of the present invention, FIG. 18 is a flowchart showing a control method of the bi-fuel engine, and FIG. 19 shows an LPG mixing ratio and an ozone supply amount. It is a map which shows the relationship.

  In Example 5 described above, the ignitability of the mixed fuel was improved by adding a cetane number improver. However, in Example 6, the ignitability of the mixed fuel is improved by supplying ozone to the intake air. is there.

  That is, as shown in FIG. 17, in the sixth embodiment, the mixing ratio sensor 15 is provided in the LPG / DME mixing tank 11, while the mixing ratio signal from the mixing ratio sensor 15 is used to improve the ignitability of the mixed fuel. Accordingly, an ozone supply device 42 that generates a predetermined amount of ozone and supplies it to the intake air is provided in the intake pipe 10b.

  From the ECU 16, an ozone supply amount control signal is output toward the ozone supply device 42. The ozone supply device 42 can be configured by a known technique and can generate ozone, so that ozone replenishment work is unnecessary. Other configurations are the same as in the case of the fifth embodiment, and a duplicate description is omitted.

  Next, a control method of the diesel engine 10 will be described with reference to FIGS. 17 and 19 based on FIG. As shown in FIG. 18, first, when necessary, the mixing ratio sensor 15 measures the mixing ratio of LPG and DME in the LPG / DME mixing tank 11 (step S30), and inputs the mixing ratio signal to the ECU 16. For example, it is assumed that X (%) is measured as the mixing ratio of LPG.

  Next, the ECU 16 calculates the ozone supply amount Yo to the intake air that is optimal for ignition from the measured mixture ratio by the map shown in FIG. 19 and the following equation (7) (step S31). The map shown in FIG. 19 is obtained in advance through experiments or the like.

Yo = γ · X / 100 (7)
Here, γ is the ozone supply amount (ppm) when the mixing ratio of LPG is 100%, and is obtained in advance by experiments or the like.

  Next, the fuel injection amount correction ratio Z based on the DME mixing ratio (100-X) (%) is calculated using the map shown in FIG. 16 described in the fifth embodiment and the above equation (6) (step S32). .

  Next, the ozone supply amount Yo calculated in step S31 is supplied to the intake air by the ozone supply device 42, and the fuel injection amount is corrected based on the fuel injection amount correction ratio Z calculated in step S32. Step S33). Further, the fuel injection timing is also corrected as necessary.

  Note that if the supply of ozone and the correction of the fuel injection amount are executed in step S33, the process returns to the start.

  As described above, according to the bi-fuel engine according to the sixth embodiment, the optimum ozone supply amount and fuel injection amount (fuel injection timing) for improving the ignitability based on the measured mixing ratio of LPG and DME are determined. The optimum combustion of the diesel engine 10 can be realized regardless of the mixing ratio.

  As a result, it is possible to provide a vehicle that can use both DME, which is clean fuel but limited in availability, and LPG, which is relatively easy to obtain. A clean vehicle can be obtained.

  Further, since ozone is generated by the ozone supply device 42 and supplied to the intake air, it is not necessary to supply ozone at a stand or the like, and the burden on the user can be reduced.

  In the sixth embodiment, the mixing ratio sensor 15 is described as being provided in the LPG / DME mixing tank 11, but the present invention is not limited to this, and the mixing ratio sensor 15 may be provided in the middle of the fuel supply line 14. The effect can be expected.

  FIG. 20 is a schematic diagram showing a main part of a bi-fuel engine according to Embodiment 7 of the present invention, FIG. 21 is a flowchart showing a control method of the bi-fuel engine, and FIG. 22 is a relationship between in-cylinder pressure change and ignition delay. It is a map which shows.

  As shown in FIG. 20, the seventh embodiment adds a cylinder pressure sensor 10c that measures the cylinder pressure of the diesel engine 10 to the configuration shown in FIG. The change in ignitability due to addition is monitored, and the amount of cetane improver added can be corrected so as to achieve proper ignitability.

  Next, a method for controlling the diesel engine 10 will be described based on FIG. 21 with reference to FIGS. 20 and 22. Steps S30 to S33 shown in FIG. 21 are the same as the contents of steps S20 to S23 shown in FIG. 14 of the fifth embodiment, and therefore, redundant description will be omitted, and step S34 and subsequent steps will be described.

  When the addition of the cetane improver and the correction of the fuel injection amount in step S33 are executed, the ignition delay is measured by measuring the in-cylinder pressure change of the diesel engine 10 by the in-cylinder pressure sensor 10c (step S34).

  That is, the degree of ignition delay can be measured (determined) by using the measured in-cylinder pressure change and a map previously determined by experiment or the like as shown in FIG. When the ignition delay is within an appropriate range with respect to the appropriate value of the in-cylinder pressure change (broken line in FIG. 22) (Yes in Step S35), the cetane number improver is properly added in Step S33, and the combustion state is good. Since it can be judged that it is, it returns to the start.

  On the other hand, if the ignition delay is not within the appropriate range with respect to the adaptation value (indicated by the broken line in FIG. 22) of the in-cylinder pressure change (No at step S35), it is further determined whether the ignition delay is greater than the adaptation value. Judgment is made (step S36). This is because the addition amount of the cetane number improver is corrected according to the magnitude of the ignition delay.

  If the ignition delay is large with respect to the conforming value (Yes at Step S36), in order to improve the ignitability, a command to increase the addition amount of the cetane number improver is issued (Step S37). S33 is executed.

  Further, when the ignition delay is small with respect to the conforming value (No at Step S36), in order to suppress the ignitability, a command to decrease the addition amount of the cetane number improver is issued (Step S38). Step S33 is executed.

  The control of these steps S36, S37, and S38 is executed until the ignition delay is within an appropriate range, that is, until a good combustion state is obtained (Yes in step S35).

  As described above, according to the bi-fuel engine according to the seventh embodiment, the change in ignitability due to the addition of the cetane number improver is monitored by the in-cylinder pressure sensor 10c, and the cetane number improver so as to obtain proper ignitability. Since the addition amount is corrected, optimal combustion can be obtained, and further improvements in emission, fuel consumption and output can be achieved.

  In addition, in the said Example 7, although demonstrated as what adds the cylinder pressure sensor 10c which measures the cylinder pressure of the diesel engine 10 to the structure shown in FIG. 13 of the said Example 5, it is not limited to this, The in-cylinder pressure sensor 10c may be added to the configuration of the sixth embodiment shown in FIG. 17, and the same effect as described above can be expected.

  That is, in this case, the ozone supply amount may be calculated in step S31 of the flowchart shown in FIG. 21, and ozone may be supplied in step S33 based on the calculated supply amount. Moreover, what is necessary is just to control so that an ozone supply amount may be increased in step S37 and an ozone supply amount may be decreased in step S38.

  In the fifth embodiment, the sixth embodiment, and the seventh embodiment, when the engine 10 includes an exhaust gas recirculation device (EGR device) that recirculates part of the exhaust gas to the intake system, LPG and DME Therefore, the amount of oxygen in the adapted exhaust gas recirculation amount (EGR amount) can be calculated in consideration of the oxygen in DME. As a result, the EGR amount can be optimized, and NOx and the like in the exhaust gas can be reduced.

  Further, an odorant (sulfur compound) is added to the LPG. Therefore, in the fifth embodiment, the sixth embodiment, and the seventh embodiment, when the engine 10 includes an exhaust purification catalyst downstream of the exhaust passage, the sulfur content is obtained by integrating the mixing ratio of LPG and DME. Since it is possible to integrate the period in which DME that is not included is used, it is possible to reduce fuel consumption deterioration by changing the sulfur poisoning regeneration period of the catalyst. For example, it is preferable that the sulfur poisoning regeneration period is shortened when the mixing ratio of LPG is large, while the sulfur poisoning regeneration period is extended when the mixing ratio of DME is large.

  As described above, the bifuel engine and the mixed fuel mixing ratio estimation method according to the present invention are useful for a vehicle equipped with a bifuel engine using LPG and DME as a mixed fuel, and in particular, the mixing ratio of LPG and DME. This is suitable for a bi-fuel engine capable of detecting a fuel tank for storing both fuels and a method for estimating a mixture ratio of mixed fuel that can easily detect a mixture ratio of LPG and DME.

It is a block diagram which shows the principal part of the engine which concerns on Example 1 of this invention. It is a flowchart which shows the control method of the engine based on the calculated fuel mixture ratio. It is a schematic diagram which shows the state before compression of LPG. It is a schematic diagram which shows the state after compression of LPG. It is a schematic diagram which shows the state before compression of DME. It is a schematic diagram which shows the state after compression of DME. It is a schematic diagram which shows the principal part of the bi-fuel engine which concerns on Example 2 of this invention. It is a map which shows the relationship between the piston movement amount used when calculating | requiring a mixing ratio, temperature, and pressure. It is a schematic diagram which shows the principal part of the bi-fuel engine which concerns on Example 3 of this invention. It is a map which shows the relationship between piston movement amount and a mixture ratio. It is a schematic diagram which shows the principal part of the bi-fuel engine which concerns on Example 4 of this invention. It is a map which shows the relationship between the rotation speed of a fuel pressurization pump and outlet pressure in a certain fuel temperature. It is a schematic diagram which shows the principal part of the bi-fuel engine which concerns on Example 5 of this invention. It is a flowchart which shows the control method of a bi-fuel engine. It is a map which shows the relationship between the mixing ratio of LPG and the addition amount of a cetane improver. It is a map which shows the relationship between the mixing ratio of DME and the correction ratio of fuel injection amount. It is a schematic diagram which shows the principal part of the bi-fuel engine which concerns on Example 6 of this invention. It is a flowchart which shows the control method of a bi-fuel engine. It is a map which shows the relationship between the mixing ratio of LPG and ozone supply amount. It is a schematic diagram which shows the principal part of the bi-fuel engine which concerns on Example 7 of this invention. It is a flowchart which shows the control method of a bi-fuel engine. It is a map which shows the relationship between a cylinder pressure change and ignition delay.

Explanation of symbols

10 engine (bi-fuel engine)
10b Intake pipe 10c In-cylinder pressure sensor 11 LPG / DME mixed tank (fuel tank)
14 Fuel supply line 15 Mixing ratio sensor 16 ECU
17 Compression chamber 18 Piston 19 Actuator 20 Temperature sensor 21 Pressure sensor 22 Detection line 23 Valve (open / close valve)
24 Fuel pressurization pump 26 Piston movement map by temperature and pressure when DME is 100% (Data on bulk modulus of DME alone)
28 Piston movement map by temperature and pressure when LPG is 100% (Data on bulk modulus of LPG alone)
30 Sealed balance room 31 Valve (open / close valve)
34 Rubber sphere (elastic container)
40 Cetane improver addition device 42 Ozone supply device

Claims (6)

  A fuel tank capable of mixing and storing liquefied petroleum gas and dimethyl ether; a mixing ratio sensor for measuring a mixing ratio of the liquefied petroleum gas and the dimethyl ether provided in the fuel supply line from the fuel tank to the engine or in the fuel tank; The bifuel engine is characterized in that the mixture ratio of the liquefied petroleum gas and the dimethyl ether is measured by the mixture ratio sensor, and the property of the mixed fuel is obtained from the measured value and reflected in engine control.   A fuel tank capable of mixing and storing liquefied petroleum gas and dimethyl ether; a compression chamber having a piston connected to the fuel tank and reciprocating therein; an on-off valve provided between the fuel tank and the compression chamber; and the on-off valve The mixed fuel filled in the compression chamber by moving the piston in a state where the piston is moved to fill the compression chamber with the mixed fuel in the fuel tank and moving the piston in a state where the on-off valve is closed And a temperature sensor and a pressure sensor provided in the fuel tank, and a movement amount of the piston or a volume reduction amount in the compression chamber when the mixed fuel is compressed, and the temperature sensor and The temperature and pressure detected by the pressure sensor, and the data and dimensions related to the volume modulus of elasticity of liquefied petroleum gas stored in advance. A bi-fuel that calculates the mixing ratio of the liquefied petroleum gas and the dimethyl ether using data relating to the bulk modulus of a simple substance of ether and obtains the properties of the mixed fuel from the calculated values and reflects them in engine control engine.   The bi-fuel engine according to claim 2, wherein the reciprocating motion of the piston is repeated a predetermined number of times when the mixed fuel is filled in the compression chamber.   A fuel tank capable of mixing and storing liquefied petroleum gas and dimethyl ether; a sealed balance chamber connected to the fuel tank; an on-off valve provided between the fuel tank and the sealed balance chamber; and the sealed balance chamber An elastic container provided with a predetermined amount of liquefied petroleum gas, and the open / close valve is opened to fill the sealed balance chamber with fuel mixture, and the liquefied petroleum in the elastic container is closed with the open / close valve closed. A piston and an actuator for compressing gas at a predetermined pressure, and relating to a moving amount of the piston when the mixed fuel is compressed or a volume reduction amount in the compression chamber, and a volume elastic modulus of a liquefied petroleum gas alone stored in advance. Calculate the mixing ratio of liquefied petroleum gas and dimethyl ether using the data and data on the bulk modulus of dimethyl ether alone, and calculate From seeking properties of the mixed fuel bi-fuel engine, characterized in that is reflected in the engine control.   The fuel tank capable of mixing and storing liquefied petroleum gas and dimethyl ether, the fuel pressurization pump provided in the middle of the fuel supply line from the fuel tank to the fuel injection valve of the engine, and the rotation speed or load of the fuel pressurization pump Rotational speed / load detection means for detecting, a pressure sensor for detecting fuel pressure at the outlet of the fuel pressurizing pump, and a temperature sensor for detecting fuel temperature at the outlet of the fuel pressurizing pump; The characteristic diagram of the fuel pressure pump outlet pressure and the fuel pressure pump rotation speed or load stored for each reference fuel temperature stored in advance from the detected value of the fuel pressure pump rotation speed or load The mixing ratio of the liquefied petroleum gas and the dimethyl ether is calculated on the basis of the above, and the property of the mixed fuel is obtained from the calculated value and reflected in the engine control. Bi-fuel engine to be.   Filling a sealed container with a mixed fuel of liquefied petroleum gas and dimethyl ether, compressing the filled mixed fuel at a predetermined pressure, and obtaining a mixing ratio of the liquefied petroleum gas and the dimethyl ether based on a change in volume of the sealed container. A method for estimating a mixture ratio of a mixed fuel.

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