JP4063603B2 - Fuel supply device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply device for an internal combustion engine that supplies fuel to an internal combustion engine using, for example, liquefied petroleum gas as a fuel.
[0002]
[Prior art]
As is well known, as an internal combustion engine (LPG engine) using liquefied petroleum gas (LPG) as a fuel, an LPG engine equipped with a fuel supply device that injects and supplies fuel in a liquid phase has been put into practical use. Here, such a fuel supply apparatus for an LPG engine is usually configured to employ a fuel circulation system called a fuel return system schematically shown in FIG.
[0003]
As shown in FIG. 24, in the fuel supply device 240 adopting the fuel return type fuel circulation system, the liquid phase fuel in the fuel tank 241 is pumped by the fuel pump 242, and the fuel supply path 243 is supplied. Then, the fuel is supplied into the delivery pipe 246 constituting the fuel injection mechanism 245 together with the injector 244. The fuel supplied into the delivery pipe 246 is injected and supplied to the internal combustion engine through the injector 244, while the fuel remaining in the delivery pipe 246 is returned to the fuel tank 241 through the return path 247. Further, in the fuel supply device 240, the fuel pressure state in the delivery pipe 246 (fuel injection mechanism 245) is maintained at a predetermined pressure through the pressure regulator 248 provided in the reflux path 247, thereby maintaining the liquid phase state of the fuel. However, fuel can be supplied to the internal combustion engine.
[0004]
[Problems to be solved by the invention]
By the way, even when the fuel in the delivery pipe 246 is maintained in a pressurized state through the pressure regulator 248 as described above, the temperature rise of the delivery pipe 246 caused by receiving heat from the combustion chamber of the internal combustion engine or the like. When the degree is large, it becomes difficult to maintain the injected fuel in a liquid phase state.
[0005]
That is, as shown in FIG. 25, for example, the fuel stored in a saturated state in the fuel tank 241 (point F: temperature THa / pressure Pf) is pressurized by the fuel pump 242 and regulated by the pressure regulator 248. It is assumed that the pressure according to the set value Pa is maintained (point Ga: temperature THa / pressure Pa). However, even in this case, when the temperature of the fuel in the delivery pipe 246 rises to the saturated vapor temperature THsv or more of the fuel by receiving heat from the internal combustion engine (point Gb: temperature THb / pressure Pa), Vaporized fuel (vapor) is generated. When fuel is supplied by the injector 244 on the assumption that the fuel in the delivery pipe 246 is in a liquid phase even though the fuel in the delivery pipe 246 contains vapor, There are concerns about such things. That is, since the fuel having a density lower than that of the liquid phase fuel is actually injected, the required amount of fuel cannot be secured, resulting in a deterioration in drivability.
[0006]
Therefore, as a countermeasure against such a situation, the pressure of the fuel in the delivery pipe is maintained in the liquid phase state even when the temperature of the fuel in the delivery pipe becomes equal to or higher than the normally assumed highest temperature THmx. It is conceivable that the pressure is maintained at a pressure Pb or higher. That is, in the fuel supply device 240, this corresponds to providing the recirculation path 247 with a pressure regulator in which the pressure adjustment set value is set to the pressure Pb or higher. However, in this case, although fuel vaporization can be suppressed, the load on the fuel pump 242 increases, so there is a new concern that it may lead to a decrease in the life of the fuel pump 242 and a deterioration in fuel consumption. The Even if it is not a fuel supply device for an LPG engine, the same problem as described above may occur if the fuel injection mechanism (delivery pipe) is a fuel supply device whose temperature rises due to heat received from the internal combustion engine.
[0007]
The present invention has been made in view of such circumstances, and an object of the present invention is to suitably maintain the liquid phase state of the fuel in the fuel injection mechanism while suppressing an increase in the load of the fuel pump. An object of the present invention is to provide a fuel supply device for an internal combustion engine.
[0008]
[Means for Solving the Problems]
  In the following, means for achieving the above object and its effects are described.
  (1) The invention described in claim 1A fuel injection mechanism for supplying fuel to the internal combustion engine, and a fuel in the fuel tank are pumped and supplied to the fuel injection mechanismFirstA fuel pump;thisA recirculation path for recirculating the fuel pumped by the fuel pump from the upstream or downstream of the fuel injection mechanism to the fuel tank;thisA fuel supply device for an internal combustion engine, comprising a pressure regulating mechanism provided in a return path and configured to maintain the pressure of the fuel in the fuel injection mechanism at a pressure according to a predetermined pressure regulation set value;By selectively introducing either the first pressure corresponding to the pressure of the fuel in the fuel tank or the second pressure higher than this pressure into the back pressure chamber of the pressure regulating mechanism, the predetermined pressure regulation is performed. Fuel for connecting a second fuel pump arranged in series with the first fuel pump, an outlet of the pressure regulating mechanism, and the fuel tank as pressure regulation value changing means for variably setting the pressure setting value A first back pressure introduction path branched from the path, a second back pressure introduction path branched from the fuel path connecting the first fuel pump and the second fuel pump, and the first back pressure. A third back pressure introduction path for connecting a joining portion between the introduction path and the second back pressure introduction path and a back pressure chamber of the pressure regulating mechanism; the first back pressure introduction path; and the second back pressure introduction path. The first back pressure guide is provided at a junction between the back pressure introduction path and the third back pressure introduction path. A first path state in which the path and the third back pressure introduction path are communicated and the second back pressure introduction path and the third back pressure introduction path are blocked; and the first back pressure Switching means for switching between a second path state in which the introduction path and the third back pressure introduction path are blocked and the second back pressure introduction path and the third back pressure introduction path are communicated; By selecting the first path state through the operation of the switching means, the first pressure is introduced into the back pressure chamber of the pressure regulating mechanism, and the second path state is selected through the operation of the switching means. And a control means for introducing the second pressure into the back pressure chamber of the pressure regulating mechanism.This is the gist.
[0009]
  According to the above configuration, either the first pressure corresponding to the fuel pressure in the fuel tank or the second pressure higher than the first pressure is selectively introduced into the back pressure chamber of the pressure regulating mechanism. As a result, the predetermined pressure setting value set in the pressure adjusting mechanism is variable. Incidentally, when the pressure of the fuel in the fuel injection mechanism is maintained at a higher pressure, that is, when a predetermined pressure adjustment setting set in the pressure adjustment mechanism is set to a higher value, generation of vaporized fuel is suppressed. Although the operation is enhanced, the load of the fuel pump tends to increase. In this regard, in the above configuration, the predetermined pressure adjustment set value can be made variable in the above manner, so that the second pressure is applied only when vaporized fuel is likely to be generated (or generated). The predetermined pressure adjustment set value is set to a high value by introducing it into the back pressure chamber. In other situations, the predetermined pressure adjustment set value is set to the above value by introducing the first pressure into the back pressure chamber. It becomes possible to set a value lower than the pressure adjustment set value set to a high value. As a result, generation of vaporized fuel can be suppressed, and when there is no fear of vaporized fuel, the load applied to the fuel pump can be reduced and the fuel pump can be driven. Thus, according to the above configuration, the liquid phase state of the fuel in the fuel injection mechanism can be suitably maintained while suppressing an increase in the load of the fuel pump.
Further, according to the above configuration, when the first back pressure introduction path is made active through the switching means, the first pressure is introduced into the back pressure chamber of the pressure regulating mechanism, and the second back pressure introduction path is made active. As a result, the second pressure is introduced into the back pressure chamber of the tuning pressure mechanism. In other words, when the first back pressure introduction path is activated, the back pressure chamber of the pressure regulating mechanism has a fuel having a pressure substantially equal to the pressure of the fuel downstream of the tuning pressure mechanism, that is, the fuel in the fuel tank. Will be introduced. On the other hand, when the second back pressure introduction path is activated, the fuel in the fuel path connecting the fuel pumps to the back pressure chamber of the pressure adjusting mechanism, that is, the fuel pump upstream of the fuel pumps Thus, the pressurized fuel is introduced. As a result, when the second back pressure introduction path is activated, the predetermined pressure setting value of the pressure regulating mechanism is higher than when the first back pressure introduction path is activated. As described above, the predetermined pressure setting value set in the pressure adjusting mechanism can be made variable by selectively making any of the back pressure introduction paths selectively active.
[0010]
  (2) The invention according to claim 2 is a fuel injection mechanism for supplying fuel to an internal combustion engine, a fuel pump for supplying fuel in a fuel tank to the fuel injection mechanism, and fuel pumped by the fuel pump A recirculation path for recirculating fuel from the upstream or downstream of the fuel injection mechanism to the fuel tank, and maintaining the pressure of the fuel in the fuel injection mechanism at a pressure corresponding to a predetermined pressure adjustment set value. In the fuel supply apparatus for an internal combustion engine, the first pressure corresponding to the pressure of the fuel in the fuel tank and the second pressure higher than the pressure are provided in the back pressure chamber of the pressure adjusting mechanism. As a pressure regulation value changing means for variably setting the predetermined pressure regulation setting value by selectively introducing any of the above, a single or a plurality of fuel pumps arranged in series with respect to the fuel pump, and Pressure regulation mechanism A first back pressure introduction path branched from a fuel path connecting the outlet and the fuel tank, and a second back pressure introduction path branched from any of the fuel paths connected to the respective outlets of the fuel pumps A third back pressure introduction path that connects a junction between the first back pressure introduction path and the second back pressure introduction path and a back pressure chamber of the pressure regulating mechanism, and the first back pressure introduction path. A pressure introduction path, the second back pressure introduction path, and the third back pressure introduction path, which are provided at a junction, and the first back pressure introduction path and the third back pressure introduction path communicate with each other; And a first path state in which the second back pressure introduction path and the third back pressure introduction path are blocked, and the first back pressure introduction path and the third back pressure introduction path. Switching between the second path state where the second back pressure introduction path is communicated with the third back pressure introduction path is cut off The first pressure is introduced into the back pressure chamber of the pressure regulating mechanism by selecting the first path state through an operation of the switching means and the switching means, and the second path through the operation of the switching means. The gist of the invention is that it comprises control means for introducing the second pressure into the back pressure chamber of the pressure regulating mechanism by selecting a state.
[0011]
  According to the above configuration, the liquid phase state of the fuel in the fuel injection mechanism can be suitably maintained while suppressing an increase in the load of the fuel pump.
Also,According to the above configuration, the first back pressure introduction path is made active through the switching means, whereby the first pressure is introduced into the back pressure chamber of the pressure regulating mechanism, and the second back pressure introduction path is activated. As a result, the second pressure is introduced. In other words, when the first back pressure introduction path is activated, the back pressure chamber of the pressure regulating mechanism has a fuel having a pressure substantially equal to the pressure of the fuel downstream of the tuning pressure mechanism, that is, the fuel in the fuel tank. Will be introduced. On the other hand, when any of the second back pressure introduction paths is active, the back pressure chamber of the pressure regulating mechanism isIs smallThe fuel pressurized by at least one fuel pump is introduced. As a result, when any one of the second back pressure introduction paths is activated, the predetermined pressure setting value of the pressure regulating mechanism is higher than when the first back pressure introduction path is activated. . As described above, the predetermined pressure adjustment set value set in the pressure adjustment mechanism can be made variable by selectively making any one of the above-described back pressure introduction paths active.The
[0012]
  (3) The invention according to claim 3 is the fuel supply device for an internal combustion engine according to claim 1 or 2, wherein the switching means includes the first back pressure introduction path or the first in each of three ports. The gist is to provide a control valve to which the second back pressure introduction path or the third back pressure introduction path is connected.
[0014]
  (4) The invention according to claim 4 is a fuel injection mechanism for supplying fuel to an internal combustion engine, a fuel pump for supplying fuel in a fuel tank to the fuel injection mechanism, and fuel pumped by the fuel pump. A recirculation path for recirculating fuel from the upstream or downstream of the fuel injection mechanism to the fuel tank, and maintaining the pressure of the fuel in the fuel injection mechanism at a pressure corresponding to a predetermined pressure adjustment set value. In the fuel supply apparatus for an internal combustion engine, the first pressure corresponding to the pressure of the fuel in the fuel tank and the second pressure higher than the pressure are provided in the back pressure chamber of the pressure adjusting mechanism. As a pressure regulation value changing means for making the predetermined pressure regulation setting value variable by selectively introducing any one of the above, the fuel downstream of the pressure regulation mechanism is connected to the downstream side of the pressure regulation mechanism. In the back pressure chamber of the pressure regulating mechanism A first back pressure introduction path to be introduced, and a second discharge for introducing fuel discharged from an intermediate discharge port provided between the fuel suction port and the fuel discharge port of the fuel pump into the back pressure chamber of the pressure regulating mechanism. Back pressure introduction path, and switching means for selectively activating either the first back pressure introduction path or the second back pressure introduction path, and through the switching means, the first back pressure introduction path is provided. The first pressure is introduced into the back pressure chamber of the pressure regulating mechanism by making the introduction path active, and the second pressure is made by making the second back pressure introduction path active through the switching means. The gist is to introduce the pressure regulating mechanism into the back pressure chamber.
[0015]
  According to the above configuration, the liquid phase state of the fuel in the fuel injection mechanism can be suitably maintained while suppressing an increase in the load of the fuel pump.
Also,According to the above configuration, the first back pressure introduction path is activated through the switching means, whereby the first pressure is introduced into the back pressure chamber of the pressure regulating mechanism, and the second back pressure introduction path is activated. Thus, the second pressure is introduced into the back pressure chamber of the synchronized pressure mechanism. In other words, when the first back pressure introduction path is activated, the back pressure chamber of the pressure regulating mechanism has a fuel having a pressure substantially equal to the pressure of the fuel downstream of the tuning pressure mechanism, that is, the fuel in the fuel tank. Will be introduced. On the other hand, when the second back pressure introduction path is activated, the pressure of the fuel discharged from the intermediate discharge port of the fuel pump in the back pressure chamber of the pressure adjusting mechanism, that is, the fuel pressure at the fuel suction port of the fuel pump. Higher and lower than the fuel pressure at the fuel discharge port of the fuel pump. As a result, when the second back pressure introduction path is activated, the predetermined pressure regulation setting value of the pressure regulation mechanism is higher than when the first back pressure introduction path is activated. As described above, the predetermined pressure adjustment set value set in the pressure adjustment mechanism can be made variable by selectively making any one of the above-described back pressure introduction paths active.The
[0018]
  (5) The invention according to claim 5 is the fuel supply device for an internal combustion engine according to any one of claims 1 to 4, wherein the pressure regulation value changing means is a predetermined time from the start of the internal combustion engine. Until the time elapses, the gist is to introduce the second pressure into the back pressure chamber of the pressure regulating mechanism.
[0019]
According to the above configuration, the second pressure is introduced into the back pressure chamber of the pressure regulating mechanism until a predetermined time has elapsed since the start of the internal combustion engine. By the way, when the operation of the internal combustion engine is stopped and sufficient time has not elapsed and the operation of each part of the engine is restarted from a state where the temperature is high, the fuel injection mechanism is operated in the internal combustion engine. Of particular concern is the generation of vaporized fuel due to heat received from the engine. Therefore, in the above configuration, the second pressure is introduced into the back pressure chamber of the pressure regulating mechanism until the predetermined time has elapsed from the start of the internal combustion engine, that is, the predetermined pressure set in the synchronized pressure mechanism. By setting the pressure setting value to a higher value, the fuel pressure in the fuel injection mechanism is maintained at a higher pressure. Thereby, generation | occurrence | production of the vaporized fuel at the time of start-up of an internal combustion engine can be suppressed now suitably.
[0020]
  (6) The invention according to claim 6 is the fuel supply device for an internal combustion engine according to any one of claims 1 to 5, wherein the pressure regulation value changing means is configured to operate the fuel during operation of the internal combustion engine. The gist is to introduce the second pressure into the back pressure chamber of the pressure regulating mechanism when the pressure of the fuel in the injection mechanism is lower than the saturated vapor pressure of the fuel.
[0021]
According to the above configuration, during operation of the internal combustion engine, when the pressure of the fuel in the fuel injection mechanism becomes less than the saturated vapor pressure of the fuel, the second pressure is introduced into the back pressure chamber of the pressure regulating mechanism. As a result, the second pressure is introduced into the back pressure chamber only when vaporized fuel may be generated (or is generated), and the predetermined pressure adjustment set value is set to a high value. In the situation, the first pressure is introduced into the back pressure chamber, and the predetermined pressure adjustment set value is set to a value lower than the pressure adjustment set value set to the high value. As a result, the generation of vaporized fuel can be suitably suppressed, and the load on the fuel pump can be reduced and the fuel pump can be driven when there is no fear of the generation of vaporized fuel. .
[0022]
  (7) The invention according to claim 7 is the fuel supply apparatus for an internal combustion engine according to claim 6, wherein the pressure adjustment value changing means includes a saturated vapor characteristic of the fuel stored in the fuel tank, and the The gist is to estimate the saturated vapor pressure of the fuel in the fuel injection mechanism from the temperature of the fuel in the fuel injection mechanism.
[0023]
According to the above configuration, the saturated vapor pressure of the fuel in the fuel injection mechanism is estimated from the saturated vapor characteristic of the fuel stored in the fuel tank and the temperature of the fuel in the fuel injection mechanism. Incidentally, the saturated vapor pressure of the fuel tends to increase as the temperature of the fuel increases, and the relationship between the saturated vapor pressure and the temperature can be grasped through the saturated vapor characteristic (saturated vapor pressure curve) of the fuel. . Therefore, by estimating the saturated vapor pressure of the fuel in the fuel injection mechanism with the above-described aspect, it becomes possible to grasp an appropriate saturated vapor pressure corresponding to the temperature variation of the fuel.
[0024]
  (8) According to an eighth aspect of the present invention, in the fuel supply device for an internal combustion engine according to the seventh aspect, the pressure regulation value changing means is configured to control the temperature of the fuel stored in the fuel tank and the fuel. The gist is to estimate the composition of the fuel based on the pressure, and to estimate the saturated vapor characteristic of the fuel stored in the fuel tank based on the estimated composition of the fuel.
[0025]
According to the above configuration, the composition of the fuel is estimated based on the temperature of the fuel stored in the fuel tank and the pressure of the fuel, and is stored in the fuel tank based on the estimated fuel composition. The saturated vapor characteristics of the fuel that is present are determined. Incidentally, the saturated vapor characteristic of the fuel shows a different tendency depending on the composition of the fuel, and the composition of the fuel can basically be estimated through the temperature and pressure of the fuel. Therefore, by determining the saturated vapor characteristic of the fuel in the fuel tank with the above aspect, it becomes possible to grasp a more appropriate saturated vapor characteristic according to the composition of the fuel.
[0026]
  (9) The invention according to claim 9 is the fuel supply apparatus for an internal combustion engine according to claim 7 or 8, wherein the pressure adjustment value changing means expects a predetermined pressure to the estimated saturated steam pressure. The gist is that the obtained pressure is the saturated vapor pressure of the fuel in the fuel injection mechanism.
[0027]
According to the above configuration, the pressure obtained by taking a predetermined pressure into the estimated saturated vapor pressure is set as the saturated vapor pressure of the fuel in the fuel injection mechanism. As a result, when the pressure of the fuel in the fuel injection mechanism becomes lower than the saturated steam pressure set higher than the original saturated steam pressure of the fuel, the second pressure is introduced into the back pressure chamber of the pressure regulating mechanism. Become so. That is, a value higher than the saturated vapor pressure calculated by adding a predetermined pressure to the estimated saturated vapor pressure of the fuel in the fuel injection mechanism or multiplying a predetermined coefficient is set as the determination value. When the pressure of the fuel becomes less than this judgment value, the second pressure is introduced into the back pressure chamber of the pressure regulating mechanism. As described above, according to the above configuration, the second pressure is introduced into the back pressure chamber with a certain amount of margin and the action of suppressing the generation of vaporized fuel is enhanced. Will be able to.
[0028]
  (10) The invention according to claim 10 is the fuel supply device for an internal combustion engine according to any one of claims 1 to 9, wherein the internal combustion engine uses liquefied petroleum gas as fuel. It is said.
[0029]
ChiIncidentally, the situation in which vaporized fuel is generated in the fuel injection mechanism due to the heat received by the fuel injection mechanism is particularly a concern in vehicles equipped with a liquefied petroleum gas internal combustion engine. Therefore, the fuel supply device for an internal combustion engine using liquefied petroleum gas as fuel is the above claims 1 to 3.9By applying the invention described in any one of the above, the practicality of an internal combustion engine using liquefied petroleum gas as fuel can be made higher.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. The fuel supply device for a liquefied gas internal combustion engine according to this embodiment is a fuel supply device that supplies LPG to an internal combustion engine (LPG engine) that uses liquefied petroleum gas (LPG) as fuel.
[0031]
First, with reference to FIG. 1, the outline | summary is demonstrated about the fuel supply apparatus of the internal combustion engine concerning the embodiment. 1 shows an internal combustion engine 1 that is driven by using combustion energy of an air-fuel mixture as an output, a fuel supply device 3 that supplies fuel to the engine 1, and an electronic device that comprehensively controls the internal combustion engine 1 and the fuel supply device 3. The relationship of the control apparatus (ECU) 5 is typically shown.
[0032]
As shown in FIG. 1, an internal combustion engine 1 is provided on a cylinder block 11, a plurality of cylinders 12 that are provided in the cylinder block 11 and burns an air-fuel mixture therein, and are disposed above the plurality of cylinders 12. The cylinder head 13 is provided.
[0033]
Here, a piston 16 connected to a crankshaft 14, which is an output shaft of the internal combustion engine 1, via a connecting rod 15 is accommodated in the cylinder 12 so as to be able to reciprocate. Combustion of the air-fuel mixture is carried out in the combustion chamber 17 formed in opposition to each other. The combustion chamber 17 is connected to an intake passage 24 including an air cleaner 21, a throttle valve 22, a surge tank 23, and the like, and an exhaust passage 26 including a catalyst device 25. The intake air is supplied through the injector INJ included in the fuel supply device 3. Fuel is supplied to the passage 24 by injection.
[0034]
Next, the configuration of the fuel supply device 3 will be described with reference to FIGS. 2 and 3. 2 shows the detailed configuration of the fuel supply device 3 shown in FIG. 1 and the relationship between the fuel supply device 3 and the ECU 5. FIG. 3 shows the inside of the broken line of the fuel supply device 3 shown in FIG. The detailed configuration of each is schematically shown.
[0035]
As shown in FIG. 2, in the fuel supply device 3, the liquid phase fuel stored in the fuel tank 31 is connected via the inter-pump fuel path Rdp and has the same discharge capacity. The fuel pump 32a and the second fuel pump 32b are pressurized and fed to the fuel supply path Rd1 provided with the fuel filter 33. The pumped liquid-phase fuel is supplied together with the injector INJ to a delivery pipe 35 constituting the fuel injection mechanism 34, and the injector INJ is opened in response to a signal from the ECU 5 to be injected and supplied to the intake passage 24. Is done. Then, the fuel remaining in the delivery pipe 35 is returned to the fuel tank 31 via the return path Rd2 including the upstream side return path Rd2U and the downstream side return path Rd2L.
[0036]
In addition, the recirculation path Rd2 is provided with a pressure regulator 36 (pressure regulating mechanism) including a fuel chamber 36Rf and a back pressure chamber 36Rp, and the fuel pressure in the delivery pipe 35 (fuel injection mechanism 34) is the same. The pressure is maintained according to a predetermined pressure adjustment set value (pressure adjustment set value P) set for the pressure regulator 36. The detailed configuration of the pressure regulator 36 will be described later. In addition, a first back pressure introduction path Rd3 connected to the back pressure introduction path Rd5 via a three-port valve 37 (switching means) is connected to the downstream recirculation path Rd2L. Can flow into the back pressure chamber 36Rp via the first back pressure introduction path Rd3 and the back pressure introduction path Rd5. The inter-pump fuel path Rdp is connected to a second back pressure introduction path Rd4 that is also connected to the back pressure introduction path Rd5 via the 3-port valve 37, and flows through the inter-pump fuel path Rdp. The fuel can be caused to flow into the back pressure chamber 36Rp through the second back pressure introduction path Rd4 and the back pressure introduction path Rd5. Then, through the switching operation of the three-port valve 37, communication between one of the first back pressure introduction path Rd3 and the second back pressure introduction path Rd4 and the back pressure introduction path Rd5 is selectively enabled. . The pressure regulation value changing means (back pressure changing means) includes the above-described 3-port valve 37 and the like, and the 3-port valve 37 is controlled in accordance with a signal from the ECU 5.
[0037]
Further, the fuel supply device 3 detects the state of the fuel in the tank temperature sensor 71, the tank pressure sensor 72 and the delivery pipe 35 (fuel injection mechanism 34) for detecting the state of the fuel in the fuel tank 31. The detection system 7 includes an injection mechanism temperature sensor 73 and an injection mechanism pressure sensor 74. Incidentally, the tank temperature sensor 71 detects the temperature of the fuel in the fuel tank 31 (fuel tank temperature THtk), and the tank pressure sensor 72 detects the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk). The injection mechanism temperature sensor 73 is the temperature of fuel in the delivery pipe 35 (fuel injection mechanism 34) (injection mechanism temperature THdv), and the injection mechanism pressure sensor 74 is the pressure of fuel in the delivery pipe 35 (fuel injection mechanism 34). (Injection mechanism pressure Pdv) is detected. Data detected by these sensors 71 to 74 is input to the ECU 5, and the ECU 5 performs the switching operation of the three-port valve 37 based on the input detection data.
[0038]
Next, a detailed configuration of the pressure regulator 36 will be described with reference to FIG.
As shown in FIG. 3, the pressure regulator 36 includes a metal housing 36Hg, and is divided into the fuel chamber 36Rf and the back pressure chamber 36Rp through a diaphragm 36Df provided therein. Here, in the fuel chamber 36Rf, the upstream recirculation path Rd2U for allowing the fuel remaining in the delivery pipe 35 to flow into the fuel chamber 36Rf, and the fuel in the fuel chamber 36Rf are recirculated to the fuel tank 31. The downstream reflux path Rd2L is connected. The diaphragm 36Df is pressed toward the fuel chamber 36Rf through the spring 36Sg provided in the back pressure chamber 36Rp, so that the fuel flow from the upstream recirculation path Rd2U to the downstream recirculation path Rd2L is basically the above diaphragm. It is in a state of being blocked by 36Df. The back pressure chamber 36Rp is connected to a back pressure introduction path Rd5 for flowing either the fuel flowing through the downstream recirculation path Rd2L or the fuel flowing through the inter-pump fuel path Rdp into the back pressure chamber 36Rp. ing. When the pressure of the fuel in the fuel chamber 36Rf becomes equal to or higher than the pressure of the spring 36Sg (pressure regulator set pressure Psg) with respect to the pressure of the fuel flowing into the back pressure chamber 36Rp, the diaphragm 36Df The fuel in the fuel chamber 36Rf is pushed down to the chamber 36Rp side and is returned to the fuel tank 31 via the downstream reflux path Rd2L. The pressure obtained by adding the pressure regulator set pressure Psg to the pressure of the fuel flowing into the back pressure chamber 36Rp becomes a value corresponding to the pressure adjustment set value P of the pressure regulator 36.
[0039]
Next, each fuel path switched through the three-port valve 37 will be described with reference to FIGS. In the following, the fuel path when the first back pressure introduction path Rd3 and the back pressure introduction path Rd5 are in communication with each other will be referred to as the first fuel path, and the second back pressure introduction path Rd4 and the back pressure introduction path will be described. The fuel path when Rd5 is in communication is defined as the second fuel path.
[0040]
First, a fuel circulation mode when the first fuel path is activated will be described with reference to FIGS. 4 and 5. 4 schematically shows the fuel supply device 3 when the first fuel path is active, and FIG. 5 schematically shows the fuel circulation mode within the broken line in FIG. 4 and 5, the fuel path indicated by a broken line indicates a state where the fuel flow is blocked.
[0041]
As shown in FIG. 4, when the first back pressure introduction path Rd3 and the back pressure introduction path Rd5 are communicated with each other, the back pressure chamber 36Rp has a downstream recirculation path Rd2L having a mode shown by a broken line in FIG. The fuel that circulates will be introduced. Accordingly, the diaphragm 36Df of the pressure regulator 36 is caused by the pressure of the fuel flowing through the downstream recirculation path Rd2L, that is, the pressure obtained by adding the pressure regulator set pressure Psg to the fuel pressure in the fuel tank 31 (fuel tank pressure Ptk). It will be pushed to the fuel chamber 36Rf side. Thereby, the pressure regulation set value P of the pressure regulator 36 is expressed by the following equation:
Ptk + Psg [1]
It becomes a value corresponding to the value calculated through. In the following, the pressure adjustment set value P corresponding to the value calculated through the above calculation formula will be referred to as a first pressure adjustment set value Pst.
[0042]
Then, when the first pressure adjustment set value Pst is validated as the pressure adjustment set value P of the pressure regulator 36, the fuel pressure in the delivery pipe 35 (fuel injection mechanism 34) is changed to the first pressure adjustment set value. The pressure corresponding to the value Pst is maintained.
[0043]
Next, the fuel circulation mode when the second fuel path is activated will be described with reference to FIGS. FIG. 6 schematically shows the fuel supply device 3 when the second fuel path is active, and FIG. 7 schematically shows the fuel circulation mode within the broken line in FIG. Moreover, the fuel path shown with a broken line in FIG.6 and FIG.7 has shown the state by which the distribution | circulation of the fuel was interrupted | blocked.
[0044]
As shown in FIG. 6, when the second back pressure introduction path Rd4 and the back pressure introduction path Rd5 are communicated with each other, the back pressure chamber 36Rp has an inter-pump fuel path Rdp having a mode shown by a broken line in FIG. The fuel that circulates will be introduced. Accordingly, the diaphragm 36Df of the pressure regulator 36 has a pressure (fuel) by the first fuel pump 32a that is higher than the pressure of the fuel flowing through the inter-pump fuel path Rdp, that is, the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk). The pressure is set to the fuel chamber 36Rf side by a pressure obtained by adding the pressure regulator set pressure Psg to the pressure higher by the pump pressurizing pressure Ppm). Thereby, the pressure regulation set value P of the pressure regulator 36 is expressed by the following equation:
Ptk + Ppm + Psg [2]
It becomes a value corresponding to the value calculated through. In the following, the pressure adjustment set value P corresponding to the value calculated through the above calculation formula will be referred to as a second pressure adjustment set value Pnd.
[0045]
Then, when the second pressure adjustment set value Pnd is validated as the pressure adjustment set value P of the pressure regulator 36, the fuel pressure in the delivery pipe 35 (fuel injection mechanism 34) is set to the second pressure adjustment set value. The pressure corresponding to the value Pnd is maintained.
[0046]
Next, with reference to FIG. 8, a description will be given of a switching process of the three-port valve for selectively enabling any one of the pressure regulation set values Pst and Pnd. Incidentally, this process is repeatedly performed with a predetermined time as a cycle.
[0047]
As shown in FIG. 8, in this process, first, data (fuel tank temperature THtk, fuel tank pressure Ptk, injection mechanism temperature THdv, injection mechanism pressure Pdv) detected by the sensors 71 to 74 are read (step S101). . Next, the propane ratio R in the fuel (LPG) stored in the fuel tank 31 is estimated by applying the fuel tank temperature THtk and the fuel tank pressure Ptk to a predetermined map (step S102). Then, the estimated propane ratio R is expressed by the following saturated vapor pressure calculation formula
Psv = (4 × 10^-6R + 5 × 10^-6) T^Three
+ (0.001R + 0.007) T²
+ (0.102R + 0.0447) T
+ (3.6098R + 1.2419) ... [3]
Is applied to determine the saturated vapor pressure curve of LPG corresponding to the propane ratio R (step S103). In the saturated vapor pressure calculation formula [3], “Psv” is the saturated vapor pressure of LPG (kg / cm²), “T” indicates the temperature of LPG, and “R” indicates the ratio of propane in LPG. Incidentally, the saturated vapor pressure is a threshold pressure of a fluid pressure indicating whether a fluid at an arbitrary pressure is in a liquid phase or a gas phase (including a mixed state of a gas phase and a liquid phase). That is, when the fluid pressure is equal to or higher than the saturated vapor pressure of the fluid, the fluid is in a liquid phase state, and when the fluid pressure is less than the saturated vapor pressure of the fluid, the fluid is in a gas phase state. .
[0048]
Next, the saturated vapor pressure Psv of the fuel in the delivery pipe 35 (fuel injection mechanism 34) is calculated from the determined saturated vapor pressure curve and the injection mechanism temperature THdv (step S104). Then, it is determined whether or not the first pressure adjustment set value Pst of the pressure regulator 36 is equal to or higher than the calculated saturated steam pressure Psv (step S105). When the first pressure adjustment set value Pst is equal to or higher than the saturated steam pressure Psv (step S105: Yes), the switching operation of the three-port valve 37 in the direction in which the first back pressure introduction path Rd3 and the back pressure introduction path Rd5 communicate with each other. Is performed (step S106). On the other hand, when the first pressure adjustment set value Pst is less than the saturated steam pressure Psv (step S105: No), the 3 port valve 37 is set in the direction in which the second back pressure introduction path Rd4 and the back pressure introduction path Rd5 communicate with each other. A switching operation is performed (step S107).
[0049]
As described above, according to the above processing, when the first pressure adjustment set value Pst is less than the saturated steam pressure Psv, the second pressure adjustment set value Pnd of the pressure regulator 36 is validated, and otherwise, the first pressure adjustment set value Pst is effective. The pressure regulation setting value Pst of 1 is validated.
[0050]
Next, the operational effects achieved through the above configuration will be described with reference to FIG. FIG. 9 shows the relationship between the pressure adjustment set values Pst and Pnd together with the saturated vapor pressure curve (saturated vapor characteristic) of the fuel. Further, the saturated steam temperature of the fuel corresponding to the first pressure regulation set value Pst is the first saturated steam temperature THst, and the saturated steam temperature of the fuel corresponding to the second pressure regulation set value Pnd is the second saturated steam temperature. THnd. Incidentally, the saturated vapor temperature is a threshold temperature of the temperature of the fluid indicating whether the fluid at an arbitrary temperature is in a liquid phase or a gas phase (including a mixed state of a gas phase and a liquid phase). That is, when the temperature of the fluid is equal to or higher than the saturated vapor temperature of the fluid, the fluid is in a gas phase, and when the temperature of the fluid is lower than the saturated vapor temperature of the fluid, the fluid is in a liquid phase.
[0051]
Therefore, for example, when the delivery pipe 35 is maintained at the first pressure regulation set value Pst (point Xa: temperature THdva / pressure Pst), it is assumed that the temperature of the delivery pipe 35 has increased due to heat received from the internal combustion engine 1. (Point Xb: temperature THdvb / pressure Pst), vaporized fuel is generated in the delivery pipe 35. On the other hand, when the delivery pipe 35 is maintained at the second pressure regulation setting value Pnd (point Ya: temperature THdva / pressure Pnd), even if the delivery pipe 35 rises in temperature as described above (point Xb: temperature THdvb / pressure Pnd) and the liquid phase state of the fuel is maintained. As described above, when the delivery pipe 35 is maintained at the second pressure adjustment set value Pnd, the fuel vapor suppression effect is enhanced, but the load of each fuel pump 32a, 32b increases, so that the service life is increased. There is concern about a decrease in fuel consumption and fuel consumption.
[0052]
Therefore, in this embodiment,
[A] When the first pressure adjustment set value Pst is less than the saturated steam pressure Psv, that is, when the temperature of the fuel in the delivery pipe 35 (injection mechanism temperature THdv) is equal to or higher than the saturated steam temperature of the fuel, The pressure setting value Pnd is validated.
[B] When the first pressure adjustment set value Pst is equal to or higher than the saturated steam pressure Psv, that is, when the temperature of the fuel in the delivery pipe 35 (injection mechanism temperature THdv) is lower than the saturated steam temperature of the fuel, The pressure set value Pst is made valid.
Thus, the pressure adjustment set value P is made variable. As a result, the second pressure regulation set value Pnd that increases the load of the fuel pump is made effective only when the fuel is likely to vaporize, and the first pressure regulation set value Pst is set during other normal operations. Therefore, generation of vaporized fuel can be suitably suppressed while suppressing an increase in the load of the fuel pump.
[0053]
Next, with reference to FIG. 10, an example of how the pressure adjustment set value is changed by the switching process of the three-port valve (FIG. 8) will be described.
For example, if it is detected that the first pressure adjustment set value Pst is less than the saturated steam pressure Psv at time t101, the ECU 5 performs the switching operation of the three-port valve 37, and the second back pressure introduction path Rd4. And the back pressure introduction path Rd5 are communicated (FIGS. 10C and 10A). As a result, the second pressure adjustment set value Pnd is validated as the pressure adjustment set value P of the pressure regulator 36, and the pressure of the fuel in the delivery pipe 35 is a pressure corresponding to the second pressure adjustment set value Pnd. (FIG. 10B). If it is detected at time t102 that the first pressure adjustment set value Pst has become equal to or higher than the saturated steam pressure Psv, the ECU 5 performs the switching operation of the three-port valve 37, and the first back pressure introduction path Rd3. And the back pressure introduction path Rd5 are communicated (FIGS. 10C and 10A). As a result, the first pressure adjustment set value Pst is validated as the pressure adjustment set value P of the pressure regulator 36, and the pressure of the fuel in the delivery pipe 35 is a pressure corresponding to the first pressure adjustment set value Pst. (FIG. 10B). If it is detected again at time t103 that the first pressure adjustment set value Pst is less than the second pressure adjustment set value Pnd, the pressure adjustment set value P is changed in the same manner as described above. Thereafter, the processing according to the above processing mode is continued.
[0054]
As described above in detail, according to the fuel supply apparatus for an internal combustion engine according to the first embodiment, the excellent effects listed below can be obtained.
(1) In the present embodiment, the pressure adjustment set value P of the pressure regulator 36 is made variable by switching the fuel introduced into the back pressure chamber 36Rp of the pressure regulator 36. As a result, the second pressure regulation set value Pnd is validated only when vaporized fuel may be generated, and in other situations, the first pressure regulation set value Pst is validated. Therefore, it becomes possible to suitably maintain the liquid phase state of the fuel in the fuel injection mechanism while suppressing an increase in the load of the fuel pump.
[0055]
(2) In the present embodiment, when the first pressure regulation set value Pst is less than the saturated steam pressure Psv, the second pressure regulation set value Pnd is made valid as the pressure regulation set value P of the pressure regulator 36. I have to. As a result, the second pressure regulation set value Pnd is valid only when vaporized fuel may be generated, and the first pressure regulation set value Pst is valid in other situations. Thus, it is possible to suppress the generation of vaporized fuel while suitably suppressing the decrease in the life of the fuel pump and the deterioration in fuel consumption.
[0056]
(3) In this embodiment, the saturated vapor pressure Psv of the fuel in the delivery pipe 35 is estimated from the saturated vapor characteristic curve of the fuel in the fuel tank 31 and the temperature of the fuel in the delivery pipe 35 (injection mechanism temperature THdv). Like to do. As a result, it is possible to estimate an appropriate saturated vapor pressure corresponding to the temperature fluctuation of the fuel in the delivery pipe 35.
[0057]
(4) In the present embodiment, the composition of the fuel is estimated based on the temperature of the fuel in the fuel tank 31 (fuel tank temperature THtk) and the pressure of the fuel (fuel tank pressure Ptk). Based on this, the saturated vapor pressure curve of the fuel in the fuel tank 31 is determined. This makes it possible to grasp a more appropriate saturated vapor pressure curve according to the fuel composition.
[0058]
(5) In the present embodiment, the fuel is pressurized through the fuel pumps (the first fuel pump 32a and the second fuel pump 32b) having the same performance. As a result, parts can be shared, so that an increase in cost of the entire apparatus can be suitably suppressed.
[0059]
(6) In this embodiment, the fuel is pressurized through two fuel pumps (the first fuel pump 32a and the second fuel pump 32b). As a result, the load applied to each fuel pump is reduced as compared with the case where the fuel is pressurized through one fuel pump, so that the life of each fuel pump can be suitably maintained.
[0060]
(7) Since two fuel pumps are provided, a high discharge capacity can be obtained even when a small fuel pump is employed. As a result, it is not necessary to develop a large fuel pump to satisfy the required discharge capacity, and the fuel supply device 3 can be easily realized.
[0061]
Note that the first embodiment can be implemented as, for example, the following form, which is appropriately changed.
In the first embodiment, the fuel pumps having the same discharge capacity are employed as the first fuel pump 32a and the second fuel pump 32b. However, fuel pumps having different discharge capacities may be used.
[0062]
In the first embodiment, the fuel flowing through the first back pressure introduction path Rd3 and the second back pressure introduction path Rd4 is supplied to the pressure regulator 36 via the 3-port valve 37 and the back pressure introduction path Rd5, respectively. Although it was set as the structure introduce | transduced into the back pressure chamber 36Rp, it can also be changed as follows, for example. That is, the 3-port valve 37 and the back pressure introduction path Rd5 are excluded from the fuel supply device 3, and the first back pressure introduction path Rd3 and the second back pressure introduction path Rd4 are independently connected to the back pressure chamber 36Rp. To do. A control valve that selectively opens and closes each of the back pressure introduction paths Rd3 and Rd4 is provided in each of the back pressure introduction paths Rd3 and Rd4, and the pressure adjustment set value is variable through the opening and closing operation of the control valve. You can also
[0063]
In the first embodiment, the configuration includes two fuel pumps (the first back pressure introduction path Rd3 and the second back pressure introduction path Rd4) for pumping the fuel. It is also possible to change to. That is, the back pressure for introducing the fuel discharged by the fuel pump excluding the most downstream fuel pump into the back pressure chamber 36Rp of the pressure regulator 36 from the downstream of the fuel pump, including three or more fuel pumps. It can also be set as the structure which provides an introduction path | route. When a plurality of back pressure introduction paths are provided, any one of the plurality of back pressure introduction paths can be selectively activated. Will be able to.
[0064]
(Second Embodiment)
A second embodiment embodying the present invention will be described with reference to FIGS.
[0065]
In the present embodiment, the basic configuration of the entire apparatus is the same as that of the first embodiment (FIG. 1), but the configuration of the fuel supply device 3 shown in FIG. 2 is changed to the configuration shown in FIG. Has been.
[0066]
Here, prior to the description of the fuel supply device of the present embodiment, an outline thereof will be described.
As in the first embodiment, the present embodiment also has a function of changing the pressure adjustment set value P of the pressure regulator 36 by switching the fuel introduced into the back pressure chamber 36Rp of the pressure regulator 36. It has to be prepared. In the first embodiment, the above function is realized by introducing the fuel of either the downstream reflux path Rd2L or the inter-pump fuel path Rdp into the back pressure chamber 36Rp. In the present embodiment, the above functions are realized in the following manner. Hereinafter, the fuel supply apparatus of the present embodiment will be described with reference to FIG.
[0067]
As shown in FIG. 11, the fuel supply device 3 of the present embodiment is obtained by adding the following changes to the fuel supply device 3 (FIG. 2) of the first embodiment. ing. That is, as shown in the broken line, one fuel pump for pumping the fuel stored in the fuel tank 31 (fuel pump 32) is provided, and accordingly, the inter-pump fuel paths Rdp and 3 The port valve 37 is excluded. In addition, a first back pressure introduction path Rd6 provided with a first throttle mechanism 38a and connected to the back pressure introduction path Rd8 is connected to the downstream recirculation path Rd2L. The circulating fuel can be caused to flow into the back pressure chamber 36Rp via the first throttle mechanism 38a and the back pressure introduction path Rd8. On the other hand, a second back pressure introduction path Rd7 connected to the back pressure introduction path Rd8 is connected to the upstream recirculation path Rd2U and connected to the back pressure introduction path Rd8. Can flow into the back pressure chamber 36Rp via the second throttle mechanism 38b and the back pressure introduction path Rd8. The second back pressure introduction path Rd7 is selectively opened and closed through a control valve 39 (switching means) controlled by the ECU 5. In the present embodiment, it is assumed that fixed diaphragm mechanisms having the same diaphragm diameter are employed as the first diaphragm mechanism 38a and the second diaphragm mechanism 38b.
[0068]
Next, each fuel path switched through the control valve 39 will be described with reference to FIGS. In the following, the fuel path when the second back pressure introduction path Rd7 is inactive is referred to as the first fuel path, and the fuel path when the second back pressure introduction path Rd7 is active. Is the second fuel path.
[0069]
First, the fuel circulation mode when the first fuel path is activated will be described with reference to FIGS. 12 and 13. 12 schematically shows the fuel supply device 3 when the first fuel path is active, and FIG. 13 schematically shows the fuel circulation mode within the broken line in FIG. Moreover, the fuel path shown with a broken line in FIG.12 and FIG.13 has shown the state by which the distribution | circulation of the fuel was interrupted | blocked.
[0070]
As shown in FIG. 12, when the second back pressure introduction path Rd7 is made inactive, the fuel flowing through the downstream return path Rd2L in the back pressure chamber 36Rp in the manner shown by the broken line in FIG. Will be introduced. Accordingly, the diaphragm 36Df of the pressure regulator 36 is caused by the pressure of the fuel flowing through the downstream recirculation path Rd2L, that is, the pressure obtained by adding the pressure regulator set pressure Psg to the fuel pressure in the fuel tank 31 (fuel tank pressure Ptk). It will be pushed to the fuel chamber 36Rf side. Thereby, the pressure regulation set value P of the pressure regulator 36 is expressed by the following equation:
Ptk + Psg [1]
It becomes a value corresponding to the value calculated through. In the following, the pressure adjustment set value P corresponding to the value calculated through the above calculation formula will be referred to as a first pressure adjustment set value Pst.
[0071]
Then, when the first pressure adjustment set value Pst is validated as the pressure adjustment set value P of the pressure regulator 36, the fuel pressure in the delivery pipe 35 (fuel injection mechanism 34) is changed to the first pressure adjustment set value. The pressure corresponding to the value Pst is maintained.
[0072]
Next, a fuel circulation mode when the second fuel path is activated will be described with reference to FIGS. 14 and 15. 14 schematically shows the fuel supply device 3 when the second fuel path is active, and FIG. 15 schematically shows the fuel circulation mode within the broken line in FIG. 14 and 15, the fuel path indicated by a broken line indicates a state where the fuel flow is blocked.
[0073]
As shown in FIG. 14, when the second back pressure introduction path Rd7 is activated, the fuel flowing through the upstream recirculation path Rd2U is introduced into the back pressure chamber 36Rp in the manner shown by the broken line in FIG. Will come to be. That is, a part of the fuel flowing through the second throttle mechanism 38b flows into the back pressure chamber 36Rp, and other fuel is returned to the fuel tank 31 via the first throttle mechanism 38a. Become. Therefore, the diaphragm 36Df of the pressure regulator 36 has a pressure regulator that is higher than the fuel pressure in the fuel tank 31 (fuel tank pressure Ptk) by a pressure loss (throttle loss pressure Pls) by the first throttle mechanism 38a. The pressure is applied to the fuel chamber 36Rf side by the pressure applied with the set pressure Psg. Thereby, the pressure regulation set value P of the pressure regulator 36 is expressed by the following equation:
Ptk + Pls + Psg [4]
It becomes a value corresponding to the value calculated through. In the following, the pressure adjustment set value P corresponding to the value calculated through the above calculation formula will be referred to as a second pressure adjustment set value Pnd.
[0074]
Then, the pressure adjustment set value P of the pressure regulator 36 is set to the second pressure adjustment set value Pnd, so that the fuel pressure in the delivery pipe 35 (fuel injection mechanism 34) becomes the second pressure adjustment set value. The pressure according to Pnd is maintained.
[0075]
Next, with reference to FIG. 16, a control valve opening / closing process for selectively enabling any one of the pressure regulation setting values Pst and Pnd will be described. Incidentally, this process is repeatedly performed with a predetermined time as a cycle.
[0076]
As shown in FIG. 16, in this processing, the processing up to step S105 is performed in a manner according to the switching processing of the three-port valve in the first embodiment. When the first pressure adjustment set value Pst is equal to or higher than the saturated steam pressure Psv (step S105: Yes), the control valve 39 is closed (step S106a), and the first pressure adjustment set value Pst becomes the saturated steam pressure Psv. When it is less than (step S105: No), the control valve 39 is opened (step S107a).
[0077]
As described above, according to the above processing, when the first pressure adjustment set value Pst is less than the saturated steam pressure Psv, the second pressure adjustment set value Pnd of the pressure regulator 36 is validated, and otherwise, the first pressure adjustment set value Pst is effective. The pressure regulation setting value Pst of 1 is validated. Thereby, generation | occurrence | production of vaporized fuel can be suppressed suitably, suppressing the increase in the load of a fuel pump.
[0078]
Next, with reference to FIG. 17, an example of how the pressure adjustment set value is changed by the control valve switching process (FIGS. 8 and 16) will be described.
For example, when it is detected that the first pressure adjustment set value Pst is less than the saturated steam pressure Psv at time t171, the control valve 39 is opened through the ECU 5, and the second back pressure introduction path Rd7 is activated. (FIGS. 17C and 17A). As a result, the second pressure adjustment set value Pnd is validated as the pressure adjustment set value P of the pressure regulator 36, and the pressure of the fuel in the delivery pipe 35 is a pressure corresponding to the second pressure adjustment set value Pnd. (FIG. 17B). If it is detected at time t172 that the first pressure adjustment set value Pst has become equal to or higher than the saturated steam pressure Psv, the control valve 39 is closed through the ECU 5, and the second back pressure introduction path Rd7 is inactive. (FIGS. 17C and 17A). As a result, the first pressure adjustment set value Pst is validated as the pressure adjustment set value P of the pressure regulator 36, and the pressure of the fuel in the delivery pipe 35 is a pressure corresponding to the first pressure adjustment set value Pst. (FIG. 17B). If it is detected again at time t173 that the first pressure adjustment set value Pst is less than the second pressure adjustment set value Pnd, the pressure adjustment set value P is changed in the same manner as described above. Thereafter, the processing according to the above processing mode is continued.
[0079]
As described above in detail, according to the fuel supply device for an internal combustion engine according to the second embodiment, the effects according to the effects (1) to (4) according to the first embodiment are achieved. In addition, the following effects can be obtained.
[0080]
(5) In the present embodiment, the pressure regulation set value P is obtained through the first back pressure introduction path Rd6 where the first throttling mechanism 38a is provided and the second back pressure introduction path Rd7 where the second throttling mechanism 38b is provided. To be able to make changes. As described above, the pressure regulation set value P can be changed without the configuration in the first embodiment, that is, the configuration in which two fuel pumps for pumping fuel are provided. An increase in the cost of the entire apparatus is more preferably suppressed.
[0081]
In addition, the said 2nd Embodiment can also be implemented as the following forms which changed this suitably, for example.
In the second embodiment, the control valve 39 is provided upstream of the second throttle mechanism 38b in the second back pressure introduction path Rd7. However, the control valve 39 is provided with the second back pressure introduction. It can also be set as the structure provided downstream from the 2nd aperture mechanism 38b of path | route Rd7.
[0082]
In the second embodiment, by connecting the second back pressure introduction path Rd7 to the upstream recirculation path Rd2U, the fuel flowing through the upstream recirculation path Rd2U is transferred to the back pressure chamber 36Rp of the pressure regulator 36. Although it is configured to be introduced, it can be changed as follows, for example. In other words, the end of the second back pressure introduction path Rd7 on the upstream recirculation path Rd2U side may be connected to the fuel supply path Rd1.
[0083]
In the second embodiment, one throttle mechanism (the first throttle mechanism 38a and the second throttle mechanism 38b) is provided in each of the first back pressure introduction path Rd6 and the second back pressure introduction path Rd7. Although it is configured, it is also possible to provide another throttle mechanism in each back pressure introduction path. In short, as long as at least one throttle mechanism is provided in each of the first back pressure introduction path Rd6 and the second back pressure introduction path Rd7, the configuration is not limited to the configuration exemplified in the above embodiment, and any configuration is possible. Can be adopted.
[0084]
In the second embodiment, the first diaphragm mechanism 38a and the second diaphragm mechanism 38b employ the same diaphragm diameter. However, it is also possible to employ diaphragm mechanisms having different diaphragm diameters. . Incidentally, the second pressure regulation setting value Pnd is set in the fuel tank 31 by setting the throttle diameter of the first throttle mechanism 38a to be larger than that of the second throttle mechanism 38b (increasing the cross-sectional area of the fuel path). It becomes possible to set the value close to the fuel pressure. On the other hand, the second pressure regulating set value Pnd of the pressure regulator 36 is set by setting the throttle diameter of the second throttle mechanism 38b larger than that of the first throttle mechanism 38a (increasing the cross-sectional area of the fuel path). It is possible to set a value close to the upstream fuel pressure.
[0085]
In the second embodiment, the fixed diaphragm mechanism is adopted as the first diaphragm mechanism 38a and the second diaphragm mechanism 38b. However, at least one of them can be a variable diaphragm mechanism. When such a configuration is employed, the second pressure regulation set value Pnd can be made variable in the manner described above by adjusting the throttle diameter of the variable throttle mechanism during operation of the internal combustion engine 1. Become.
[0086]
(Third embodiment)
A third embodiment of the present invention will be described with reference to FIGS.
[0087]
In the present embodiment, the basic configuration of the entire apparatus is the same as that of the first embodiment (FIG. 1), but the configuration of the fuel supply device 3 shown in FIG. 2 is changed to the configuration shown in FIG. Has been.
[0088]
Here, prior to the description of the fuel supply device of the present embodiment, an outline thereof will be described.
As in the first embodiment, the present embodiment also has a function of changing the pressure adjustment set value P of the pressure regulator 36 by switching the fuel introduced into the back pressure chamber 36Rp of the pressure regulator 36. It has to be prepared. In the first embodiment, the above function is realized by introducing the fuel of either the downstream reflux path Rd2L or the inter-pump fuel path Rdp into the back pressure chamber 36Rp. In the present embodiment, the above functions are realized in the following manner. Hereinafter, the fuel supply apparatus of the present embodiment will be described with reference to FIG.
[0089]
As shown in FIG. 18, the fuel supply device 3 of the present embodiment is obtained by adding the following changes to the fuel supply device 3 (FIG. 2) of the first embodiment. ing. That is, as shown in the broken line, one fuel pump for pumping the fuel stored in the fuel tank 31 (fuel pump 32) is used, and the second back pressure introduction path Rd4 is connected to the same fuel. The configuration is connected to the pump 32.
[0090]
Here, with reference to FIG. 19, the detailed structure about the connection aspect of 2nd back pressure introduction path | route Rd4 with respect to the said fuel pump 32 is demonstrated. FIG. 19 schematically shows the configuration of the fuel pump 32.
[0091]
As shown in FIG. 19, the fuel pump 32 sucks the fuel in the fuel tank 31 from the fuel inlet 32Ip through rotation of the rotor 32Rt provided in the housing 32Hg (rotation in the direction of the arrow), The pressure is applied and discharged from the fuel discharge port 32Ep to the fuel supply path Rd1. In the present embodiment, the second back pressure introduction path Rd4 is connected to the intermediate discharge port 32Mp provided between the fuel intake port 32Ip and the fuel discharge port 32Ep, and the rotation of the rotor 32Rt. The pressurized fuel is discharged to the corresponding fuel path through the intermediate discharge port 32Mp and the fuel discharge port 32Ep.
[0092]
Next, each fuel path switched through the three-port valve 37 will be described with reference to FIGS. In the following, the fuel path when the first back pressure introduction path Rd3 and the back pressure introduction path Rd5 are in communication with each other will be referred to as the first fuel path, and the second back pressure introduction path Rd4 and the back pressure introduction path will be described. The fuel path when Rd5 is in communication is defined as the second fuel path.
[0093]
First, the fuel circulation mode when the first fuel path is activated will be described with reference to FIGS. 20 and 21. FIG. 20 schematically shows the fuel supply device 3 when the first fuel path is active, and FIG. 21 schematically shows the fuel circulation mode within the broken line in FIG. 20 and 21, the fuel path indicated by a broken line indicates a state where the fuel flow is blocked.
[0094]
As shown in FIG. 20, when the first back pressure introduction path Rd3 and the back pressure introduction path Rd5 are communicated with each other, the back pressure chamber 36Rp has a downstream recirculation path Rd2L having a mode shown by a broken line in FIG. The fuel that circulates will be introduced. Accordingly, the diaphragm 36Df of the pressure regulator 36 is caused by the pressure of the fuel flowing through the downstream recirculation path Rd2L, that is, the pressure obtained by adding the pressure regulator set pressure Psg to the fuel pressure in the fuel tank 31 (fuel tank pressure Ptk). It will be pushed to the fuel chamber 36Rf side. As a result, the pressure adjustment set value P of the pressure regulator 36 is expressed by the following equation:
Ptk + Psg [1]
It becomes a value corresponding to the value calculated through. In the following, the pressure adjustment set value P corresponding to the value calculated through the above calculation formula will be referred to as a first pressure adjustment set value Pst.
[0095]
Then, when the first pressure adjustment set value Pst is validated as the pressure adjustment set value P of the pressure regulator 36, the fuel pressure in the delivery pipe 35 (fuel injection mechanism 34) is changed to the first pressure adjustment set value. The pressure corresponding to the value Pst is maintained.
[0096]
Next, the fuel circulation mode when the second fuel path is activated will be described with reference to FIGS. 22 schematically shows the fuel supply device 3 when the second fuel path is active, and FIG. 23 schematically shows the fuel circulation mode within the broken line in FIG. In addition, the fuel path indicated by the broken line in FIGS. 22 and 23 indicates a state where the fuel flow is blocked.
[0097]
As shown in FIG. 22, when the second back pressure introduction path Rd4 and the back pressure introduction path Rd5 are communicated with each other, the back pressure chamber 36Rp has a mode shown by a broken line in FIG. The fuel discharged from the discharge port 32Mp is introduced. Accordingly, the diaphragm 36Df of the pressure regulator 36 is higher than the pressure of the fuel discharged from the intermediate discharge port 32Mp, that is, the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk), and the fuel discharge port of the fuel pump 32. The pressure is set to the fuel chamber 36Rf side by the pressure obtained by adding the pressure regulator set pressure Psg to the pressure lower than the fuel pressure at 32 Ep (fuel pump intermediate pressure Pmd). As a result, the pressure adjustment set value P of the pressure regulator 36 is expressed by the following equation:
Pmd + Psg [5]
It becomes a value corresponding to the value calculated through. In the following, the pressure adjustment set value P corresponding to the value calculated through the above calculation formula will be referred to as a second pressure adjustment set value Pnd.
[0098]
Then, when the second pressure adjustment set value Pnd is validated as the pressure adjustment set value P of the pressure regulator 36, the fuel pressure in the delivery pipe 35 (fuel injection mechanism 34) is set to the second pressure adjustment set value. The pressure corresponding to the value Pnd is maintained.
[0099]
In the present embodiment, the same process as the three-port valve switching process (FIG. 8) in the first embodiment is repeatedly performed with a predetermined time as a cycle. Thereby, generation | occurrence | production of vaporized fuel can be suppressed suitably, suppressing the increase in the load of a fuel pump.
[0100]
As described above in detail, according to the fuel supply device for an internal combustion engine according to the third embodiment, the effects according to the effects (1) to (4) according to the first embodiment are achieved. In addition, the following effects can be obtained.
[0101]
(5) In the present embodiment, the pressure regulation set value P can be changed through the first back pressure introduction path Rd3 and the second back pressure introduction path Rd4 connected to the intermediate discharge port 32Mp of the fuel pump 32. I can do it. As described above, the pressure adjustment set value P can be changed without the configuration in the first embodiment, that is, the configuration in which two fuel pumps for pumping fuel are provided. An increase in the cost of the entire apparatus is more preferably suppressed.
[0102]
Note that the third embodiment can be implemented as an appropriate modification of the above, for example, as follows.
In the third embodiment, the intermediate discharge port 32Mp of the fuel pump 32 is provided at the position shown in FIG. 19, but any position between the fuel suction port 32Ip and the fuel discharge port 32Ep is provided. Can be provided.
[0103]
In the third embodiment, the fuel pump 32 is provided with one fuel discharge port (intermediate discharge port 32Mp) different from the fuel discharge port 32Ep. However, for example, the following modifications can be made. It is. That is, another fuel discharge port is provided, and a fuel path for introducing fuel discharged from the newly provided fuel discharge port into the back pressure chamber 36Rp of the pressure regulator 36 and the fuel path are selectively opened and closed. It can also be set as the structure provided with the control valve which performs.
[0104]
(Other embodiments)
Other elements that can be changed in common with the above-described embodiments include the following.
[0105]
In each of the above-described embodiments, the pressure regulation set value P of the pressure regulator 36 can be varied through the three-port valve switching process (FIG. 8) or the control valve opening / closing process (FIGS. 8 and 16) while the internal combustion engine 1 is in operation. For example, the following modifications are possible. That is, the second pressure regulation setting value Pnd is made valid as the pressure regulation setting value P until a predetermined time has elapsed from the start of operation of the internal combustion engine 1, and after the predetermined time has elapsed, the switching of the three-port valve is performed. The pressure adjustment set value P can be made variable through the process (FIG. 8) or the control valve opening / closing process (FIGS. 8 and 16). In the case of adopting such a configuration, the second pressure regulation set value Pnd is surely made effective when the internal combustion engine 1 is started. Therefore, generation of vaporized fuel at the time of starting the internal combustion engine 1 is more suitably suppressed. Will be able to.
[0106]
In the above embodiments, the pressure adjustment set value P is changed in the following manner:
[A] When the first pressure regulation set value Pst is less than the saturated steam pressure Psv, the second pressure regulation set value Pnd is validated.
[B] When the first pressure regulation set value Pst is less than the saturated steam pressure Psv, the first pressure regulation set value Pst is validated.
However, it can be changed as follows, for example. That is,
[A] When the first pressure regulation set value Pst is less than the saturated steam pressure Psv, the second pressure regulation set value Pnd is validated.
[B] When the second pressure adjustment set value Pnd is valid, when the pressure set lower than the first pressure adjustment set value Pst by a predetermined pressure is equal to or higher than the saturated steam pressure Psv The first pressure adjustment set value Pst is made valid.
The pressure adjustment set value P can be changed in such a manner.
[0107]
In each of the above embodiments, the three-port valve 37 (control valve 39) is operated based on the comparison between the first pressure adjustment set value Pst and the saturated vapor pressure Psv of the fuel in the delivery pipe 35. However (FIG. 8, FIG. 16: Step S105), for example, it is possible to change as follows. That is, a pressure that allows a predetermined pressure to be calculated as the saturated steam pressure Psv calculated in the manner illustrated in the above embodiments, that is, a pressure higher than the saturated steam pressure Psv and the first pressure adjustment set value Pst. It is also possible to adopt a configuration in which the three-port valve 37 (control valve 39) is operated based on the comparison.
[0108]
In the above embodiments,
[A] The saturated vapor pressure Psv of the fuel is estimated from the saturated vapor pressure curve and the temperature of the fuel in the delivery pipe 35 (injection mechanism temperature THdv) (FIG. 8: Step S104).
[B] The three-port valve 37 (control valve 39) is operated based on the comparison between the first pressure adjustment set value Pst and the saturated steam pressure Psv (FIGS. 8 and 16: Step S105).
For example, the following modifications can be made. That is, instead of the above processes,
[A] The saturated vapor temperature THsv of the fuel in the delivery pipe 35 is estimated from the saturated vapor pressure curve and the first pressure adjustment set value Pst.
[B] The three-port valve 37 (control valve 39) is operated based on a comparison between the temperature of the fuel in the delivery pipe 35 (injection mechanism temperature THdv) and the saturated steam temperature THsv.
It is also possible to adopt a configuration for performing such processing.
[0109]
In each of the above embodiments, the saturated vapor pressure curve of the fuel is determined based on the saturated vapor pressure calculation formula [1]. However, the saturated vapor pressure calculation formula [1] is included in each of the above embodiments. However, the present invention is not limited to the calculation formulas exemplified above, and any appropriate calculation formula can be adopted.
[0110]
In each of the above embodiments, the saturated vapor pressure curve of the fuel is determined based on the propane ratio R estimated from the temperature and pressure of the fuel in the fuel tank 31. For example, the following modifications are made. Is also possible. In other words, it is possible to set a saturated vapor pressure curve of the fuel in advance and not to estimate the propane ratio R.
[0111]
In each of the above embodiments, the first back pressure introduction path Rd3 is connected to the downstream recirculation path Rd2L. However, the first back pressure introduction path Rd3 may be connected to the fuel tank 31. it can.
[0112]
In each of the above embodiments, the fuel supply device 3 adopts a so-called fuel return type fuel circulation system in which the fuel remaining in the delivery pipe 35 is returned to the fuel tank 31 from the downstream of the delivery pipe 35. Although the present invention is applied to the present invention, the present invention can also be applied to the following fuel supply apparatus. In other words, the present invention can also be applied to a fuel supply apparatus that employs a so-called fuel returnless fuel circulation system that recirculates fuel pumped by the fuel pump from the upstream of the delivery pipe 35 to the fuel tank 31. Is possible.
[0113]
In the above embodiments,
[A] In the first embodiment, either the fuel in the downstream recirculation path Rd2L or the fuel pressurized by the first fuel pump 32a is introduced into the back pressure chamber 36Rp of the pressure regulator 36.
[B] In the second embodiment, the back pressure chamber of the pressure regulator 36 uses either the fuel in the downstream recirculation path Rd2L or the fuel flowing from the upstream recirculation path Rd2U through the second throttle mechanism 38b. Introduced into 36Rp.
[C] In the third embodiment, either the fuel in the downstream recirculation path Rd2L or the fuel discharged from the intermediate discharge port 32Mp of the fuel pump 32 is introduced into the back pressure chamber 36Rp of the pressure regulator 36.
In this manner, the pressure regulation set value P of the pressure regulator 36 can be made variable. However, the configuration for making the tuning pressure set value P variable is not limited to the configuration exemplified in each of the above embodiments. It can be changed as appropriate. In short, either the fuel having a pressure corresponding to the pressure of the fuel in the fuel tank 31 or the fuel having a pressure higher than the pressure can be selectively introduced into the back pressure chamber 36Rp of the pressure regulator 36. Any configuration can be employed as long as it exists.
[0114]
In each of the above embodiments, the present invention is applied to the fuel supply device for an internal combustion engine that uses liquefied petroleum gas (LPG) as fuel. However, the fuel supply device to which the present invention is applied is a fuel for the internal combustion engine. The present invention is not limited to the supply device, and can be applied to, for example, a fuel supply device for an internal combustion engine that uses gasoline or the like as fuel. Further, the configuration as the internal combustion engine is not limited to the configuration exemplified in each of the above embodiments, and any configuration can be adopted. In short, the present invention can be applied to any internal combustion engine that obtains an output by combusting an air-fuel mixture, and even in such a case, it is possible to achieve operational effects in accordance with the operational effects of the above embodiments.
[0115]
Including the above matters, it is finally added that the fuel supply device for an internal combustion engine according to the present invention includes the following technical idea.
(1) In the fuel supply apparatus for an internal combustion engine according to claim 2, the switching means is provided in the first back pressure introduction path and selectively opens and closes the first back pressure introduction path. A control valve, and a second control valve that is provided in each of the second back pressure introduction paths and selectively opens and closes the back pressure introduction path. A fuel supply device for an internal combustion engine, wherein one of the second control valves is opened and the second back pressure introduction path is activated by closing the first control valve. .
[0116]
  (2) Claim1Or the fuel supply device for an internal combustion engine according to claim 4, wherein the switching means is provided in the first back pressure introduction path and selectively opens and closes the first back pressure introduction path; And a second control valve that is provided in the second back pressure introduction path and selectively opens and closes the second back pressure introduction path. A fuel supply apparatus for an internal combustion engine, wherein the second back pressure introduction path is activated by opening a control valve and closing the first control valve.
[0117]
  (3) Claim15. The fuel supply device for an internal combustion engine according to claim 4, wherein the switching means includes an end portion on the back pressure chamber side of the first back pressure introduction path and a back pressure chamber side end of the second back pressure introduction path. Each of the end portions is connected, and a three-way switching valve is provided for introducing any of the fuel flowing through the first and second back pressure introduction paths into the back pressure chamber of the pressure regulating mechanism. The fuel pressure supply device for an internal combustion engine, wherein the pressure regulation value changing means activates the second back pressure introduction path through a switching operation of the three-way switching valve.
[0119]
(5) A fuel injection mechanism for injecting and supplying fuel to the internal combustion engine, a fuel pump for supplying fuel in the fuel tank into the fuel injection mechanism, and a fuel pumped by the fuel pump upstream of the fuel injection mechanism Alternatively, a return path for returning from the downstream to the fuel tank, a variable pressure mechanism provided in the return path to vary the pressure of the fuel in the fuel injection mechanism, and a downstream side of the variable pressure mechanism A first back pressure introduction path for introducing fuel into the back pressure chamber of the adjustable pressure mechanism, a fuel pump provided in series with the fuel pump, and a fuel path connecting the fuel pumps. A second back pressure introduction path for introducing fuel into the back pressure chamber of the adjustable pressure mechanism, and a back pressure changing means that selectively activates one of the first and second back pressure introduction paths. An internal combustion machine comprising: Fuel supply system.
[0120]
(6) A fuel injection mechanism for injecting and supplying fuel to the internal combustion engine, a fuel pump for supplying fuel in the fuel tank to the fuel injection mechanism, and fuel pumped by the fuel pump upstream of the fuel injection mechanism or A recirculation path for recirculation from the downstream to the fuel tank, a modulatable pressure mechanism provided in the recirculation path to vary the pressure of the fuel in the fuel injection mechanism, and a fuel downstream of the modulatable pressure mechanism The fuel discharged from the first back pressure introduction path for introducing the fuel into the back pressure chamber of the variable pressure mechanism and the intermediate discharge port provided between the fuel suction port and the fuel discharge port of the fuel pump. A second back pressure introduction path for introducing into the back pressure chamber of the modulatable pressure mechanism, and a back pressure changing means for selectively making one of the first and second back pressure introduction paths active. Fuel supply for an internal combustion engine characterized by comprising Location.
[0121]
(7) A fuel injection mechanism that injects fuel into the internal combustion engine, a fuel pump that supplies fuel in a fuel tank to the variable pressure mechanism, and fuel that is pumped by the fuel pump upstream of the fuel injection mechanism. Alternatively, a return path for returning from the downstream to the fuel tank, a variable pressure mechanism provided in the return path to vary the pressure of the fuel in the fuel injection mechanism, and a fuel on the downstream side of the variable pressure mechanism A first back pressure introduction path for introducing the fuel into the back pressure chamber of the variable modulation pressure mechanism, and fuel provided in the first back pressure introduction path and flowing through the first back pressure introduction path A first throttle mechanism for regulating a flow rate; a second back pressure introduction path for introducing fuel upstream of the modulatable pressure mechanism into a back pressure chamber of the modulatable pressure mechanism; and the second back pressure The flow rate of the fuel that is provided in the introduction path and circulates in the second back pressure introduction path An internal combustion engine comprising: a second throttle mechanism for controlling; and back pressure changing means that is provided in the second back pressure introduction path and selectively activates the second back pressure introduction path. Fuel supply system.
[0122]
(8) In the fuel supply apparatus for an internal combustion engine according to (5) or (6), the back pressure changing means is provided in the first back pressure introduction path and selects the first back pressure introduction path. A first control valve that opens and closes automatically, and a second control valve that is provided in the second back pressure introduction path and selectively opens and closes the second back pressure introduction path. A fuel supply device for an internal combustion engine.
[0123]
(9) In the fuel supply device for an internal combustion engine according to (5) or (6), the back pressure changing means includes an end of the first back pressure introduction path on the back pressure chamber side and the second back pressure chamber. A back pressure introduction path is connected to each end of the back pressure chamber on the back pressure chamber side and introduces fuel flowing through each back pressure introduction path into the back pressure chamber of the variable pressure mechanism. A fuel supply device for an internal combustion engine, comprising a three-way switching valve connected thereto.
[0124]
(10) In the fuel supply apparatus for an internal combustion engine according to (7), the back pressure changing means is provided in the second back pressure introduction path and selectively opens and closes the second back pressure introduction path. A fuel supply device for an internal combustion engine, comprising a control valve.
[Brief description of the drawings]
FIG. 1 is a schematic view schematically showing the overall configuration of a fuel supply device for an internal combustion engine according to a first embodiment of the present invention.
FIG. 2 is a schematic view schematically showing the overall configuration of the fuel supply apparatus of the embodiment.
FIG. 3 is a cross-sectional view schematically showing a configuration of a pressure regulator provided in the fuel supply device of the embodiment.
FIG. 4 is a diagram schematically showing one switching state of a fuel path in the fuel supply device according to the embodiment.
FIG. 5 is a diagram schematically showing a fuel circulation mode in the fuel supply apparatus according to the embodiment;
FIG. 6 is a diagram schematically showing one switching state of a fuel path in the fuel supply device of the embodiment.
FIG. 7 is a view schematically showing a fuel circulation mode in the fuel supply apparatus according to the embodiment;
FIG. 8 is a flowchart showing switching processing of a three-port valve performed in the same embodiment.
FIG. 9 is a graph showing a saturated vapor pressure curve of liquefied petroleum gas.
FIG. 10 is a timing chart showing an example of a change mode of the pressure adjustment set value by the switching process of the 3-port valve performed in the embodiment.
FIG. 11 is a schematic diagram schematically showing the overall configuration of a fuel supply device for an internal combustion engine according to a second embodiment of the present invention.
FIG. 12 is a diagram schematically showing one switching state of a fuel path in the fuel supply device according to the embodiment.
FIG. 13 is a view schematically showing a fuel circulation mode in the fuel supply apparatus according to the embodiment;
FIG. 14 is a diagram schematically showing one switching state of the fuel path in the fuel supply device according to the embodiment;
FIG. 15 is a view schematically showing a fuel circulation mode in the fuel supply apparatus according to the embodiment;
FIG. 16 is a flowchart showing a part of a control valve opening / closing process performed in the embodiment;
FIG. 17 is a timing chart showing an example of how the pressure regulation set value is changed by the control valve opening / closing process performed in the embodiment;
FIG. 18 is a schematic view schematically showing the overall configuration of a fuel supply device for an internal combustion engine according to a third embodiment of the present invention.
FIG. 19 is a cross-sectional view schematically showing a configuration of a fuel pump provided in the fuel supply device of the embodiment.
FIG. 20 is a view schematically showing one switching state of the fuel path in the fuel supply device of the embodiment.
FIG. 21 is a view schematically showing a fuel circulation mode in the fuel supply apparatus according to the embodiment;
FIG. 22 is a diagram schematically showing one switching state of the fuel path in the fuel supply device according to the embodiment;
FIG. 23 is a view schematically showing a fuel circulation mode in the fuel supply apparatus according to the embodiment;
FIG. 24 is a schematic view schematically showing the overall configuration of a conventional fuel supply apparatus.
FIG. 25 is a graph showing a saturated vapor pressure curve of liquefied petroleum gas.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 3 ... Fuel supply apparatus, 5 ... Electronic control unit (ECU), 7 ... Detection system, INJ ... Injector, 11 ... Cylinder block, 12 ... Cylinder, 13 ... Cylinder head, 14 ... Crankshaft, 15 ... Connecting rod, 16 ... piston, 17 ... combustion chamber, 21 ... air cleaner, 22 ... throttle valve, 23 ... surge tank, 24 ... intake passage, 25 ... catalyst device, 26 ... exhaust passage, 31 ... fuel tank, 32 ... fuel pump 32a ... first fuel pump, 32b ... second fuel pump, 32Hg ... housing, 32Rt ... rotor, 32Ip ... fuel inlet, 32Ep ... fuel outlet, 32Mp ... intermediate outlet, 33 ... fuel filter, 34 ... Fuel injection mechanism, 35 ... delivery pipe, 36 ... pressure regulator, 36Rf ... fuel chamber, 36Rp ... back Chamber, 36Hg ... Housing, 36Df ... Diaphragm, 36Sg ... Spring, 37 ... Three-port valve, 38a ... First throttle mechanism, 38b ... Second throttle mechanism, 39 ... Control valve, 71 ... Fuel tank temperature sensor, 72 ... Fuel tank pressure sensor, 73 ... injection mechanism temperature sensor, 74 ... injection mechanism pressure sensor, Rdp ... fuel path between pumps, Rd1 ... fuel supply path, Rd2 ... recirculation path, Rd2U ... upstream recirculation path, Rd2L ... downstream recirculation path , Rd3 ... first back pressure introduction path, Rd4 ... second back pressure introduction path, Rd5 ... back pressure introduction path, Rd6 ... first back pressure introduction path, Rd7 ... second back pressure introduction path, Rd8 ... Back pressure introduction route.

Claims (10)

A fuel injection mechanism for supplying fuel to an internal combustion engine, a first fuel pump pumping supplied to the fuel injection mechanism fuel in the fuel tank, upstream or downstream of the fuel pumped by the fuel pump the fuel injection mechanism internal combustion engine having a circulation path for refluxing to the fuel tank, and this provided a reflux path pressure a predetermined regulating pressure regulating mechanism for maintaining the pressure corresponding to pressure value of the fuel in the fuel injection mechanism from In the fuel supply device of
By selectively introducing either the first pressure corresponding to the fuel pressure in the fuel tank or the second pressure higher than the pressure into the back pressure chamber of the pressure regulating mechanism, the predetermined pressure regulation is performed. As a pressure adjustment value changing means for variably setting the pressure setting value,
A second fuel pump arranged in series with the first fuel pump;
A first back pressure introduction path branched from a fuel path connecting the outlet of the pressure regulating mechanism and the fuel tank;
A second back pressure introduction path branched from a fuel path connecting the first fuel pump and the second fuel pump;
A third back pressure introduction path that connects a joining portion of the first back pressure introduction path and the second back pressure introduction path and a back pressure chamber of the pressure regulating mechanism;
The first back pressure introduction path and the third back pressure introduction path are provided at a junction of the first back pressure introduction path, the second back pressure introduction path, and the third back pressure introduction path. A first path state in which the introduction path is communicated and the second back pressure introduction path and the third back pressure introduction path are blocked; the first back pressure introduction path and the third back pressure introduction path; A switching means for switching between a second path state in which the pressure introduction path is blocked and the second back pressure introduction path and the third back pressure introduction path are communicated with each other;
By selecting the first path state through the operation of the switching means, the first pressure is introduced into the back pressure chamber of the pressure regulating mechanism, and the second path state is selected through the operation of the switching means. And a control means for introducing the second pressure into the back pressure chamber of the pressure regulating mechanism . A fuel injection mechanism for supplying fuel to the internal combustion engine, a fuel pump for supplying fuel in the fuel tank by pressure to the fuel injection mechanism, and a fuel tank for supplying fuel pumped by the fuel pump from upstream or downstream of the fuel injection mechanism A fuel supply for an internal combustion engine comprising a recirculation path for recirculating to the fuel and a pressure regulating mechanism provided in the recirculation path for maintaining the pressure of the fuel in the fuel injection mechanism at a pressure according to a predetermined pressure regulation set value In the device
  By selectively introducing either the first pressure corresponding to the pressure of the fuel in the fuel tank or the second pressure higher than this pressure into the back pressure chamber of the pressure regulating mechanism, the predetermined pressure regulation is performed. As a pressure adjustment value changing means for variably setting the pressure setting value,
  Single or multiple fuel pumps arranged in series with the fuel pump;
  A first back pressure introduction path branched from a fuel path connecting the outlet of the pressure regulating mechanism and the fuel tank;
  A second back pressure introduction path branched from any of the fuel paths connected to the respective outlets of the fuel pumps;
  A third back pressure introduction path that connects a joining portion of the first back pressure introduction path and the second back pressure introduction path and a back pressure chamber of the pressure regulating mechanism;
  The first back pressure introduction path and the third back pressure introduction path are provided at a junction of the first back pressure introduction path, the second back pressure introduction path, and the third back pressure introduction path. A first path state in which the introduction path is communicated and the second back pressure introduction path and the third back pressure introduction path are interrupted; the first back pressure introduction path and the third back pressure introduction path; A switching means for switching between a second path state in which the pressure introduction path is blocked and the second back pressure introduction path and the third back pressure introduction path are communicated with each other;
  By selecting the first path state through the operation of the switching means, the first pressure is introduced into the back pressure chamber of the pressure regulating mechanism, and the second path state is selected through the operation of the switching means. And a control means for introducing the second pressure into the back pressure chamber of the pressure regulating mechanism.
  A fuel supply device for an internal combustion engine. The fuel supply device for an internal combustion engine according to claim 1 or 2,
  The switching means includes a control valve to which the first back pressure introduction path, the second back pressure introduction path, or the third back pressure introduction path is connected to each of three ports.
  A fuel supply device for an internal combustion engine. A fuel injection mechanism for supplying fuel to the internal combustion engine, a fuel pump for supplying fuel in the fuel tank by pressure to the fuel injection mechanism, and a fuel tank for supplying fuel pumped by the fuel pump from upstream or downstream of the fuel injection mechanism A fuel supply for an internal combustion engine comprising a recirculation path for recirculating to the fuel and a pressure regulating mechanism provided in the recirculation path for maintaining the pressure of the fuel in the fuel injection mechanism at a pressure according to a predetermined pressure regulation set value In the device
  By selectively introducing either the first pressure corresponding to the pressure of the fuel in the fuel tank or the second pressure higher than this pressure into the back pressure chamber of the pressure regulating mechanism, the predetermined pressure regulation is performed. As a pressure regulation value changing means for making the pressure set value variable, a first back connected to the downstream side of the pressure regulation mechanism and introduces fuel downstream of the pressure regulation mechanism into a back pressure chamber of the pressure regulation mechanism. A pressure introduction path, and a second back pressure introduction path for introducing fuel discharged from an intermediate discharge port provided between the fuel suction port and the fuel discharge port of the fuel pump into the back pressure chamber of the pressure regulating mechanism; Switching means for selectively activating either the first back pressure introduction path or the second back pressure introduction path,
  By activating the first back pressure introduction path through the switching means, the first pressure is introduced into the back pressure chamber of the pressure regulating mechanism, and the second back pressure introduction path is activated through the switching means. Thus, the second pressure is introduced into the back pressure chamber of the pressure regulating mechanism.
  A fuel supply device for an internal combustion engine. The fuel supply device for an internal combustion engine according to any one of claims 1 to 4,
  The pressure regulation value changing means introduces the second pressure into the back pressure chamber of the pressure regulation mechanism until a predetermined time has elapsed since the start of the internal combustion engine.
  A fuel supply device for an internal combustion engine. In the fuel supply device for an internal combustion engine according to any one of claims 1 to 5,
  The pressure regulation value changing means is configured to apply the second pressure to the back pressure chamber of the pressure regulation mechanism when the pressure of the fuel in the fuel injection mechanism is lower than the saturated vapor pressure of the fuel during operation of the internal combustion engine. A fuel supply apparatus for an internal combustion engine. The fuel supply device for an internal combustion engine according to claim 6,
  The pressure regulation value changing means estimates the saturated vapor pressure of the fuel in the fuel injection mechanism from the saturated vapor characteristic of the fuel stored in the fuel tank and the temperature of the fuel in the fuel injection mechanism. A fuel supply device for an internal combustion engine. The fuel supply device for an internal combustion engine according to claim 7,
  The pressure regulation value changing means estimates the composition of the fuel based on the temperature of the fuel stored in the fuel tank and the pressure of the fuel, and based on the estimated composition of the fuel The saturated vapor characteristics of fuel stored in
  A fuel supply device for an internal combustion engine. The fuel supply device for an internal combustion engine according to claim 7 or 8,
  The pressure regulation value changing means sets a pressure obtained by taking a predetermined pressure into the estimated saturated steam pressure as a saturated steam pressure of the fuel in the fuel injection mechanism.
  A fuel supply device for an internal combustion engine. The fuel supply apparatus for an internal combustion engine according to any one of claims 1 to 9,
  The internal combustion engine uses liquefied petroleum gas as fuel.
  A fuel supply device for an internal combustion engine.

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