JP2010007595A - Fuel supply system for lpg engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a good vaporization state of injection fuel without using an electric heater in a fuel supply system of an LPG engine, in the situation that the temperature of engine cooling water is low and vaporization performance in a vaporizer is not sufficient. <P>SOLUTION: The fuel supply system 1A is equipped with a fuel supply passage 5 extending from a fuel tank 3, a vaporizer 60 for vaporizing the LPG in a heat exchanger, into which cooling water has been introduced, to regulate the vaporized LPG into a gas fuel with a given pressure in a regulating unit, an injector 8, and an electronic control unit 10A for performing opening and closing operations of the injector 8, and controls the driving of the injector 8 by means of the electronic control unit 10A to supply the fuel to the LPG engine 2. The fuel supply system 1A is provided with a temperature sensor 10d for detecting the engine cooling water temperature and a fuel discharge pressure setting means for changing the fuel discharge pressure of the vaporizer 60. Then, the electronic control unit 10A operates the fuel discharge pressure setting means depending on the engine cooling water temperature, thus regulating the fuel discharge pressure into the fuel injection pressure for enabling all the LPG to be vaporized. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel supply device for an LPG (liquefied petroleum gas) engine, and in particular, it uses the heat of engine cooling water as a means for heating and vaporizing LPG, and is good even in a situation where the temperature of the engine cooling water is not sufficiently high. The present invention relates to a fuel supply device for an LPG engine having a function for ensuring a proper vaporization state.

  A fuel supply system that uses LPG in a predetermined positive pressure state and injects it into the intake pipe of the engine is well known. In this system, the heat of engine cooling water that has been warmed up is used as a means for heating and vaporizing LPG. The LPG engine fuel supply device 1C as shown in the layout diagram of FIG. 9 is widely used.

  In this fuel supply device 1C, LPG is taken out from the fuel tank 3 in a liquid state, passes through the shutoff valve 5a in the vicinity of the fuel tank 3 and the shutoff valve 5b in the engine room while being sent through the fuel supply passage 5, and the vaporizer 6 LPG is vaporized by exchanging heat with engine cooling water in the internal heat exchanging section, and adjusted to a gas having a predetermined pressure by the pressure regulating section. In this way, LPG is discharged from the vaporizer 6 with the pressure difference from the atmospheric pressure adjusted to be substantially constant, and sent to the injector 8 that is controlled to be opened and closed by the electronic control unit 10C to be supplied to each cylinder of the engine 2. Be injected.

  However, in the fuel supply apparatus 1C of such a system, the pressure of the gas fuel regulated by the vaporizer 6 is substantially constant without depending on the engine water temperature. Therefore, after the engine 2 is warmed up, the vaporizer 6 is vaporized. While there is a surplus capacity, the vaporizer 6 may have insufficient vaporization capacity because the engine water temperature is low during engine startup or during warm-up. Therefore, LPG is supplied to the engine 2 in a liquid state, and the air-fuel ratio becomes excessive, and problems such as deterioration of the engine operating state and engine stall are likely to occur. Further, when the unburned gas reaches the catalyst 9, it will be damaged and cause fatal damage.

In order to solve this problem, for example, as described in JP-A-6-239150, a means for electrically heating and vaporizing the LPG by arranging an electric heater in the path of the LPG fuel of the vaporizer is known. . However, disposing an electric heater leads to an increase in manufacturing cost and results in an excessive burden on a battery whose function is likely to deteriorate at low temperatures.
JP-A-6-239150

  The present invention is intended to solve the above-described problems, and an LPG engine fuel supply device is used without using an electric heater in a situation where the engine coolant temperature is low and the vaporizer vaporization capability is insufficient. It is an object to ensure a good vaporized state of the injected fuel.

  Accordingly, the present invention provides a fuel supply passage that extends from a fuel tank that stores LPG, and an LPG that is disposed in the middle of the fuel supply passage and vaporizes in a heat exchange section that introduces engine coolant, and a pressure adjustment section. A vaporizer that adjusts the gas fuel to a predetermined pressure, an injector that is disposed at the end of the fuel supply passage and injects the gas fuel, and an electronic control unit that opens and closes the injector, the electronic control unit comprising: In the fuel supply device that supplies fuel to the LPG engine while controlling the injector according to the detected engine operating state, the cooling water temperature detecting means for detecting the engine cooling water temperature and the fuel discharge pressure of the vaporizer are changed. Fuel discharge pressure setting means is provided, and the electronic control unit detects the cooling water temperature. By operating the fuel discharge pressure setting means in accordance with the engine coolant temperature detected by the stage, LPG is characterized by adjusting all vaporizable fuel injection pressure.

  In this way, the fuel discharge pressure setting means adjusts the fuel discharge pressure from the vaporizer according to the level of the vaporizer's vaporization capacity that depends on the engine coolant temperature so as to obtain a fuel injection pressure at which all liquid fuel can be vaporized. As a result, even in a situation where the vaporization capability of the vaporizer is insufficient, such as when starting at a low temperature, it is possible to avoid the fuel being supplied to the LPG engine as a liquid without using an electric heater.

  Further, in the fuel supply device for the LPG engine described above, a fuel pressure detecting means for detecting the pressure of the gas fuel discharged from the vaporizer is disposed in the fuel supply passage between the vaporizer and the injector, and is electronically controlled. If the unit is characterized in that the fuel discharge pressure of the vaporizer is adjusted while detecting the output signal of the fuel pressure detection means, the fuel injection pressure can be controlled more accurately by feedback control. In this case, if the fuel pressure detecting means detects the fuel pressure as an absolute pressure, the control can be performed with higher accuracy.

  Further, in the above-described fuel supply device for the LPG engine, the electronic control unit includes a fuel flow rate detecting means for detecting the fuel flow rate supplied to the LPG engine, and an adjustment amount based on the detected fuel flow rate is provided. If the fuel injection pressure is adjusted to take into account, it is possible to perform control that can avoid a situation in which liquid fuel is mixed into the injected fuel.

  Furthermore, in the above-described fuel supply apparatus for an LPG engine, the electronic control unit includes LPG composition estimation means for detecting the composition of LPG stored in the fuel tank, and takes into account adjustments based on the detected LPG composition. If the fuel injection pressure is adjusted, control that makes it easier to avoid liquid fuel injection can be realized.

  In this case, the electronic control unit detects the pressure and temperature in the fuel tank via a predetermined sensor. Based on the detected pressure and temperature data in the fuel tank, the electronic control unit uses a predetermined calculation method to determine the LPG to be used. If the ratio of propane and butane is estimated, the composition of LPG can be detected easily and accurately.

  In addition, in the fuel supply apparatus for the LPG engine described above, if the fuel discharge pressure setting means is an electronic control type equipped with a step motor or solenoid, the fuel injection pressure can be controlled by operating the electronic control unit. It will be more reliable.

  According to the present invention, the electronic control unit operates the fuel discharge pressure setting means according to the engine coolant temperature to adjust the fuel injection pressure so that all the liquid fuel can be vaporized. Even in a situation where the capacity is insufficient, a good vaporized state of the injected fuel can be ensured without using an electric heater.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a layout view of a fuel supply device 1A for supplying gas fuel to an LPG engine 2, which is a first embodiment of the present invention. The basic hardware configuration is the same as that of the conventional fuel supply apparatus 1C shown in FIG. 9, but this electronic control unit 10A detects the engine coolant temperature with the temperature sensor 10d, and in addition, the vaporizer The fuel discharge pressure (fuel injection pressure) is detected by a pressure sensor 10c disposed in the fuel supply passage 5 between the fuel injector 60 and the injector 8.

  The electronic control unit 10A is similar to the conventional example in that it detects the output signals from the air flow sensor 10e and the O2 sensor 10f and also detects the engine operating state such as the engine speed. In addition, the vaporizer 60 is provided with a fuel discharge pressure setting means for changing the discharge pressure so that the electronic control unit 10A can adjust the fuel injection pressure appropriately by operating the fuel discharge pressure setting means. It is characterized by that.

  In addition, the software configuration (control method) of the electronic control unit 10A is different from the electronic control unit 10C of the conventional fuel supply device 1C. That is, the electronic control unit 10A according to the present embodiment performs fuel injection so that all the LPG is vaporized (at least liquid is not injected from the injector) according to the detected engine coolant temperature data. It has the function of adjusting the pressure.

  In a fuel supply system that injects gaseous fuel, the fuel injection pressure is made higher than the atmospheric pressure to ensure an optimal air-fuel ratio. Accordingly, when the engine cooling water temperature is low at the time of starting the engine or immediately after the starting, it is difficult to vaporize all the fuel, and it becomes easy to cause malfunction of the engine with the injection of liquid fuel.

  That is, LPG is a mixed gas mainly composed of propane and butane, but as shown in the LPG vapor pressure diagram of FIG. 5, the vapor pressure tends to increase as the temperature increases and the propane ratio increases. Have. Therefore, LPG exists in a liquid state when the pressure is higher than the pressure on the basis of the vapor pressure at each temperature and in a gaseous state when the pressure is lower. Therefore, it can be seen from the vapor pressure characteristics of LPG that the fuel vaporizes more easily as the fuel injection pressure is lowered under the same temperature condition.

  Therefore, in the present invention, a map and a relational expression based on a graph showing the relationship of the vaporizer discharge pressure (= fuel injection pressure) according to the engine coolant temperature as shown in FIG. 6 is stored in advance in the memory of the electronic control unit 10A. In other words, the fuel discharge pressure setting means of the vaporizer 60 is operated so that the fuel injection pressure at which all LPG can be vaporized is obtained from the detected engine coolant temperature and fuel injection pressure.

  In this embodiment, the feedback control is performed while detecting the fuel discharge pressure of the vaporizer 60 by the pressure sensor 10c as the fuel pressure detecting means. However, the fuel injection pressure can be controlled even if the fuel discharge pressure is not detected. It is. However, it goes without saying that more accurate control can be realized by performing feedback control based on pressure data detected by the pressure sensor 10c.

  On the other hand, as an example of the fuel discharge pressure setting means of the vaporizer, as shown in FIG. 3, the vaporizer 61 is configured such that the bypass path 61b of the fuel introduction path to the pressure regulating chamber 61a is opened and closed by a valve body by driving a solenoid 61c. Alternatively, as shown in FIG. 4, a vaporizer 62 is assumed in which the stepping motor 62 adjusts the spring pressure of the pressure regulating spring of the diaphragm. Since the solenoid 61c and the step motor 62b are precisely electronically controlled by the electronic control unit 10A, a desired fuel injection pressure can be easily realized accurately.

  By the way, the normal vaporizer usually introduces air into the back pressure chamber of the diaphragm, and the discharge pressure is usually determined based on the atmospheric pressure. Therefore, in a place with a low atmospheric pressure such as a high altitude, even if the gauge pressure is the same as that in the low altitude, the discharge pressure of the vaporizer also decreases as the absolute pressure decreases. Accordingly, it is recommended that the pressure sensor 10c for detecting the fuel injection pressure is detected by an absolute pressure.

  In addition, the fuel vaporization state is greatly affected by the cooling due to the latent heat of vaporization of the evaporating fuel, and it is well known that this is governed by the fuel flow rate. However, the fuel is not easily vaporized. Therefore, based on the graph showing the relationship between the fuel flow rate and the vaporizer discharge pressure shown in FIG. 7, it is more accurate to determine the fuel discharge pressure of the vaporizer 60 in consideration of the adjustment amount by the fuel flow rate in addition to the engine cooling water temperature. Control is possible.

  As described above, in the present embodiment, the fuel injection pressure is controlled by taking into account various factors that affect the vaporization state of the LPG while using the engine coolant temperature as an axis. Even in situations where it is difficult to sufficiently vaporize LPG, such as during cold start, without using an electric heater that consumes battery power, The catalyst can be effectively prevented from being damaged.

  FIG. 2 shows a layout of a fuel supply device 1B for supplying gas fuel to the LPG engine 2, which is a second embodiment of the present invention. In this embodiment, the hardware configuration is substantially the same as that of the fuel supply device 1A of the first embodiment, but the pressure sensor 10a and the temperature sensor 10b are arranged in the fuel tank 3, and the pressure in the fuel tank 3 is The temperature data is input to the electronic control unit 10B.

  That is, as shown in the vapor pressure diagram of LPG in FIG. 5, the vapor pressure of LPG increases as the proportion of propane increases. Generally, propane vaporizes more easily than butane. It is well known that the state of vaporization changes. Therefore, as described above, the fuel injection pressure for vaporizing LPG can be determined more precisely by considering the ratio of propane in LPG in addition to the factors of engine water temperature and fuel flow rate.

  Therefore, in the present embodiment, an LPG composition estimation means is provided in the software configuration of the electronic control unit 10B, and a predetermined map, calculation formula, etc. are based on the detected pressure and temperature of the LPG in the fuel tank 3. The LPG composition is estimated using the fuel, and the fuel based on the estimated LPG composition and the adjustment based on the map and calculation formula based on the graph showing the relationship between the LPG propane ratio and the vaporizer discharge pressure as shown in FIG. It is characterized in that the injection pressure is obtained and the fuel discharge pressure setting means of the vaporizer 60 is operated so as to realize this.

  As described above, the LPG fuel supply apparatus 1B according to the present embodiment adjusts the fuel injection pressure to a more precise fuel injection pressure based on the estimated LPG composition in addition to the functions of the fuel supply apparatus 1A according to the first embodiment. Therefore, even more accurate fuel injection control can be realized, and even if it is difficult to vaporize liquefied gas fuel at the time of cold start, the LPG remains liquid without using an electric heater. Can be more effectively avoided.

  As described above, with regard to the fuel supply device for the LPG engine, even if the engine cooling water temperature is such that sufficient LPG vaporization cannot be expected by the present invention, the LPG remains liquid without using an electric heater. The supply can be effectively avoided, and a good vaporization state of the injected fuel can be secured.

1 is a layout view showing a first embodiment of the present invention. 1 is a layout view showing a first embodiment of the present invention. The longitudinal cross-sectional view which shows an example of the fuel discharge pressure setting means of a vaporizer. The longitudinal cross-sectional view which shows an example of the fuel discharge pressure setting means of a vaporizer. LPG vapor pressure diagram. The graph which shows the relationship between engine cooling water temperature and vaporizer discharge pressure. The graph which shows the relationship between a fuel flow volume and a vaporizer discharge pressure. The graph which shows the relationship between a LPG propane ratio and a vaporizer discharge pressure. The layout which shows a prior art example.

Explanation of symbols

  1A, 1B Fuel supply device, 2 engine, 3 fuel tank, 5 fuel supply passage, 8 injector, 10A, 10B electronic control unit, 10a, 10c pressure sensor, 10b, 10d temperature sensor, 60, 61, 62 vaporizer

Claims (7)

  A fuel supply passage extending from a fuel tank that stores LPG, and a gas fuel that is disposed in the middle of the fuel supply passage and vaporizes the LPG in a heat exchange section into which engine cooling water has been introduced and at a pressure adjustment section. An engine that is arranged at the end of the fuel supply passage, injects gaseous fuel, and an electronic control unit that opens and closes the injector, and is detected by the electronic control unit In a fuel supply device that supplies fuel to the LPG engine while controlling the injector according to the state, a cooling water temperature detecting means for detecting the engine cooling water temperature and a fuel discharge pressure setting for changing the fuel discharge pressure of the vaporizer Means, and the electronic control unit detects the engine detected by the cooling water temperature detecting means. By operating the fuel discharge pressure setting means in accordance with the emission coolant temperature, fuel supply system for LPG engine, characterized in that LPG is adjusted to all vaporizable fuel injection pressure.   Fuel pressure detection means for detecting the pressure of the gaseous fuel discharged from the vaporizer is disposed in the fuel supply passage between the vaporizer and the injector, and the electronic control unit outputs the fuel pressure detection means. The fuel supply apparatus for an LPG engine according to claim 1, wherein the fuel injection pressure is adjusted while detecting a signal.   3. The fuel supply apparatus for an LPG engine according to claim 2, wherein the fuel pressure detecting means detects the fuel pressure as an absolute pressure.   The electronic control unit includes a fuel flow rate detecting means for detecting a fuel flow rate supplied to the LPG engine, and adjusts the fuel injection pressure to take into account an adjustment based on the detected fuel flow rate. The fuel supply device for an LPG engine according to claim 1, 2 or 3.   The electronic control unit includes an LPG composition estimation means for detecting the composition of LPG stored in the fuel tank, and adjusts the fuel injection pressure in consideration of the adjustment by the detected LPG composition. The fuel supply apparatus for an LPG engine according to claim 1, 2, 3, or 4.   The electronic control unit estimates the ratio of propane and butane in the LPG used by a predetermined calculation method based on the pressure and temperature data detected through a predetermined sensor in the fuel tank. 6. The fuel supply device for an LPG engine according to claim 1, 2, 3, 4 or 5. The fuel supply apparatus for an LPG engine according to claim 1, 2, 3, 4, 5 or 6, wherein the fuel discharge pressure setting means is an electronic control type equipped with a step motor or a solenoid.

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