JP2006329166A - Fuel supply control device of liquefied petroleum gas engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively clean and remove a deposit deposited in a combustion chamber, particularly, on a top surface of a piston. <P>SOLUTION: This fuel supply control device of an LPG engine is constituted so that LPG can be supplied to an intake port as liquid fuel; and supplies a liquid spray of the LPG in the combustion chamber by temporarily switching to intake synchronous injection (S20 and S30) when determining as being any operation area (S10 of YES, and S60 of YES) by determining whether or not an operation area of present time exists in an operation area (Step S10) of easily depositing the deposit by a predetermined quantity in the combustion chamber or an operation area (S60) having the large cleaning effect of the deposit by the liquid LPG; and afterwards, operates for a specific time T2 (S50) by returning to ordinary exhaust stroke injection (S40); and performs the ordinary exhaust stroke injection (S70) when determining as being not any operation area (S10 of NO, and S60 of NO). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel supply control device for an LPG engine that supplies liquefied petroleum gas (hereinafter referred to as LPG) as liquid fuel to an intake port or the like, and more specifically, is deposited on a combustion chamber, particularly on the top surface of a piston. The present invention relates to a fuel supply control device for an LPG engine that can effectively clean and remove deposits.

  In recent years, liquid fuel such as LPG has attracted attention as an alternative fuel to liquid fuel such as gasoline from the viewpoint of energy countermeasures and environmental countermeasures, and an LPG engine configured to be able to supply this liquid fuel to an intake port or a cylinder. Have been developed.

  As related prior art, for example, the following are known. That is, in a bi-fuel engine that normally performs gas fuel injection, when the operating range in which deposit accumulation is estimated has elapsed for a predetermined time and the operating range (high load, low temperature operation) where the deposit cleaning effect can be expected is reached. A technique for cleaning and removing the deposit by performing gasoline injection has been proposed (see, for example, Patent Document 1).

  In addition, in an LPG engine that injects vaporized fuel, a technique has been proposed in which exhaust stroke injection is performed at a low load and intake stroke injection is performed at a high load (see, for example, Patent Document 2).

  Also, the fuel vapor pressure, liquid specific gravity and fuel composition are obtained, and based on this, the valve opening time of the fuel injection valve is controlled, and the fuel flow rate is controlled so as to achieve a constant excess air ratio. An apparatus has been proposed (see, for example, Patent Document 3).

JP 2004-239213 A JP 2003-301746 A Japanese Utility Model Publication No.59-43659

  As is well known, LPG is often applied to an engine as a gaseous fuel, but the vaporization characteristics are very good even when applied as a liquid fuel. For this reason, there is no effect of washing away deposits caused by oil in the cylinder by the non-volatile fuel.

  Therefore, such deposits are likely to accumulate in the combustion chamber, particularly on the top surface of the piston, and there is a risk that problems such as pre-ignition due to this deposit are likely to occur.

  In particular, a fuel supply control device that effectively cleans and removes deposited deposits by liquid spraying LPG, which cannot be expected to have a deposit cleaning effect as much as gasoline, into a combustion chamber, is specifically disclosed in any of the above patent documents. However, it has been desired to provide a fuel supply control device for such an LPG engine.

  The present invention has been made in view of the above, and provides a fuel supply control device for an LPG engine that can effectively clean and remove deposits accumulated in a combustion chamber, particularly on the top surface of a piston. With the goal.

  In order to solve the above-described problems and achieve the object, a fuel supply control apparatus for an LPG engine according to claim 1 of the present invention provides a fuel supply for an LPG engine configured to supply LPG as liquid fuel to an intake port. An operation region determination means for determining whether or not the current operation region is in an operation region in which a predetermined amount of deposit is easily accumulated in the combustion chamber or an operation region in which the deposit cleaning effect by the liquid fuel is large. When the current operation region is determined to be any one of the operation regions by the operation region determination means, the LPG liquid spray is supplied into the combustion chamber by temporarily switching to intake synchronous injection. Intake-synchronized injection switching means.

  Therefore, according to the present invention, the LPG in the liquid spray is temporarily inhaled synchronously, so that deposits deposited on the combustion chamber, particularly on the top surface of the piston, are effectively washed away.

  In addition, the fuel supply control device for an LPG engine according to claim 2 of the present invention is configured to be able to directly supply LPG as liquid fuel into the combustion chamber, and to be able to switch between stratified combustion and homogeneous combustion according to the operating conditions. The present fuel supply control apparatus for an LPG engine, wherein the current operation region is an operation region in which a predetermined amount of deposit is likely to accumulate in the combustion chamber or an operation region in which the deposit cleaning effect by the liquid fuel is large When the operation region determination means determines that the current operation region is any one of the operation regions, the injection is performed near the intake top dead center in the homogeneous combustion state. Intake top dead center vicinity injection switching means for temporarily switching and supplying the LPG liquid spray into the combustion chamber. .

  Therefore, according to the present invention, the LPG in the liquid spray is directly injected into the combustion chamber, particularly the top surface of the piston, in the vicinity of the intake top dead center, thereby effectively cleaning and removing the deposits accumulated in the portion. .

  According to a third aspect of the present invention, in the fuel supply control apparatus for an LPG engine according to the first or second aspect of the present invention, the operating region in which the deposit is likely to accumulate by a predetermined amount is a low load / low rotation region. It is characterized by this.

  Therefore, according to the present invention, in the low load / low rotation region, the in-cylinder temperature is not as high as in the high load / high rotation region, and deposits due to combustion residues are easily formed. be able to. Also, in the low load / low rotation region, the exhaust flow is not as high as in the high load / high rotation region, and the combustion residue is not easily discharged by the exhaust gas and easily accumulates in the cylinder. it can. Further, in the low load / low rotation region, the pressure change in the cylinder is large and so-called oil rise and oil fall are likely to occur, so that the oil that causes this combustion residue can be effectively washed away.

  According to a fourth aspect of the present invention, there is provided the fuel supply control device for an LPG engine according to any one of the first to third aspects, wherein the operating region where the deposit cleaning effect is large is a high load region or This is an operating region when the engine coolant temperature or the lubricating oil temperature is lower than a predetermined value.

  Therefore, according to the present invention, in the high load (high fuel) region, the amount of fuel to be supplied is large, and the time and number of times that the non-volatile components exist are large. Further, since there are many non-volatile components of the fuel even when the engine coolant temperature or the lubricating oil is at a low temperature, the deposit can be easily removed by washing.

  According to the fuel supply control device for an LPG engine according to the present invention (Claim 1), deposits accumulated on the combustion chamber, particularly on the top surface of the piston, are generated by temporarily injecting LPG in a liquid spray synchronously with intake air. It can be effectively washed away.

  Further, according to the fuel supply control apparatus for an LPG engine according to the present invention (Claim 2), the LPG in the liquid spray is directly injected into the combustion chamber, particularly the top surface of the piston, near the intake top dead center. It is possible to effectively clean and remove deposits deposited on the substrate.

  Further, according to the fuel supply control device for an LPG engine according to the present invention (Claim 3), the deposit can be effectively washed and removed in the operation region where the deposit due to the combustion residue is easily formed.

  Further, according to the fuel supply control device for an LPG engine according to the present invention (Claim 4), it is possible to effectively wash and remove the deposit in an operation region in which the non-volatile components of the supplied fuel are large.

  Embodiments of a fuel supply control device for an LPG engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 2 is a schematic diagram showing a schematic configuration of the engine. As shown in FIG. 2, the LPG engine (hereinafter abbreviated as “engine” as appropriate) 10 is configured to inject LPG into the intake port 15 by an injector (LPG injection valve) 24. In FIG. 2, reference numeral 10a denotes a combustion chamber, 11 denotes a cylinder bore, and 14a denotes an intake manifold.

  The injection timing and the injection time by the injector 24 are controlled by an electronic control unit (hereinafter referred to as ECU) (not shown). Data regarding the injection timing and the injection time is stored in advance in the ECU in the form of a map as a function of the operating state (for example, load) of the engine 10 and the engine speed. Further, the cumulative value of the injection time, which will be described later, is measured by a predetermined counter.

  LPG is supplied from the LPG tank 37 to the injector 24 by a feed pump 40 through a fuel supply pipe 38 and a delivery pipe 39 at a predetermined pressure. Excess fuel from the delivery pipe 39 is returned to the LPG tank 37 by the return pipe 41.

  The intake passage 14 is provided with an air cleaner 16, an electronic throttle (not shown), an air flow meter (not shown) for detecting the intake air amount, an intake air temperature sensor (not shown) for detecting the intake air temperature, and the like. ing. In addition, a catalyst 42 for purifying exhaust gas is provided in the exhaust passage 19 through the exhaust manifold 18.

  The basic control of the engine 10 configured as described above is based on the output values of an engine speed sensor, a throttle opening sensor, an accelerator opening sensor, an engine cooling water temperature sensor, an engine lubricating oil temperature sensor, etc. (not shown). It is executed by the ECU.

  Next, the control method according to the first embodiment will be described with reference to FIGS. Since the basic control of the engine 10 is the same as the conventional basic control, detailed description thereof is omitted, and the characteristic control method according to the first embodiment will be described in detail.

  Here, FIG. 1 is a flowchart showing a control operation according to the first embodiment of the present invention, FIG. 3 is an explanatory diagram showing an example of a low load / low rotation region where deposits are likely to be deposited, and FIG. 4 is a deposit cleaning effect. FIG. 6 is an explanatory view showing a high load region where expectation is large. The following control is executed by the ECU.

  First, it is determined whether or not the load / rotation region is likely to deposit deposits on the piston top surface or the like in the combustion chamber 10a (step S10), or whether or not the deposit cleaning effect is an expected region (step S60). Among these, if it is any region (Yes at Step S10, Yes at Step S60), switching to intake synchronous injection (Step S20). At this time, the ECU functions as an operation region determination unit and also functions as an intake synchronous injection switching unit.

  In the determination in step S10, whether or not the deposit is likely to accumulate in the load / rotation region is determined based on whether or not the current operation region is in the low load / low rotation partial load region on the map as shown in FIG. You just have to judge. This map is stored in advance in the ECU.

  This is because in the low load / low rotation region, the in-cylinder temperature is not as high as in the high load / high rotation region, and deposits due to combustion residues are easily formed. Further, since the exhaust flow is not as high in the low load / low rotation region as in the high load / high rotation region, the combustion residue is difficult to be discharged by the exhaust gas and easily accumulates in the cylinder. Further, in the low load / low rotation region, the pressure change in the cylinder is large, so that so-called oil rise and oil fall are likely to occur, and this oil causes combustion residues.

  Further, in the determination in step S60, whether or not the deposit cleaning effect is an expected high region is determined based on whether or not the current operation region is a high load (high fuel) region in the map as shown in FIG. You just have to judge.

  This is because, in the high load (high fuel) region, the amount of fuel to be supplied is large, and the time and number of times that the non-volatile components exist are large, so that the deposit can be easily removed by washing. This map is stored in advance in the ECU.

  In the determination in step S60, it has been described that whether or not the deposit cleaning effect is a region where the expected cleaning effect is large is determined as whether or not the current operation region is a high load (high fuel) region. For example, it may be determined whether the engine coolant temperature or the lubricating oil temperature is lower than a predetermined value. This is also because in these cases, since there are many non-volatile components of the fuel, the deposit can be easily removed by washing.

  On the other hand, if it is not in any of the above regions (No at Step S10, No at Step S60), since there is little need for deposit cleaning, normal exhaust stroke injection is performed (Step S70), and this control is terminated.

  The intake-synchronized injection in step S20 can be injected into the cylinder as a liquid spray even with LPG because the intake valve (not shown) is open. Therefore, although not as much as gasoline, this intake synchronous injection cleans deposits accumulated in the combustion chamber 10a, particularly on the top surface of the piston.

  On the other hand, the intake-synchronized injection is not normally performed because it is disadvantageous in comparison with the exhaust stroke injection in terms of mixing and emission (smoke generation, etc.), but LPG is easily vaporized, so there are few such disadvantages.

  In this way, LPG intake-synchronized injection has fewer advantages and disadvantages than gasoline, so the frequent use of this switch to intake-synchronized injection increases the above-mentioned advantages (cleaning effect), and demerits (mixing and emission) It is possible to cope with reducing disadvantages.

  After a predetermined period T1 has elapsed after switching to the intake-synchronous injection (Yes at Step S30), the routine returns to normal exhaust stroke injection (Step S40). This fixed period T1 is a cumulative time worth washing, which is counted by a counter (not shown) after switching to the intake synchronous injection, and can be about 1 to 2 minutes, for example, as an empirical value obtained by experiments or the like.

  And this exhaust stroke injection will complete | finish this control, if the continuous driving | operation of predetermined fixed period T2 passes (step S50 affirmation).

  The predetermined period T2 is an accumulated time counted by a counter (not shown) after returning to the exhaust stroke injection, and can be set to, for example, about 30 to 60 minutes as an empirical value obtained by experiments or the like.

  The above control logic can be repeatedly executed as necessary. In addition, when there is a user's accelerator operation (for example, when an accelerator pedal is depressed for acceleration) and the change in the accelerator opening is more than a certain value, an interrupt request is always issued, and the elapsed periods T1, T2 Is reset, and the process returns to the start of this control (immediately before step S10).

  As described above, according to the fuel supply control device for the LPG engine 10 according to the first embodiment, the LPG in liquid spray is injected synchronously and injected into the combustion chamber 10a, particularly on the top surface of the piston, for a certain period T1. The deposited deposit can be effectively washed away.

  FIG. 5 is a schematic diagram showing a schematic configuration of an engine according to Embodiment 2 of the present invention, and FIG. 6 is a flowchart showing a control operation. In the following description, the same or corresponding parts as those already described or the step numbers are denoted by the same reference numerals, and redundant description is omitted or simplified.

  In the first embodiment, the injector 24 is configured to inject the fuel into the intake port 15, whereas the second embodiment is configured such that the injector 24 performs direct in-cylinder injection into the combustion chamber 10a. Different. The engine 10 is configured to be able to switch between stratified combustion and homogeneous combustion in accordance with operating conditions.

  As described above, in the second embodiment, in order to realize the direct injection, the high pressure pump 38a is further provided, and the injector 24 and the piston are adapted to be compatible with the direct injection. Other configurations are the same as in the case of the first embodiment, and a duplicate description is omitted.

Next, a control method according to the second embodiment will be described with reference to FIG. 5 based on FIG.
First, it is determined whether or not the load / rotation region is likely to deposit deposits on the piston top surface or the like in the combustion chamber 10a (step S10), or whether the deposit cleaning effect is a region that is expected to be high (step S60).

  These determinations may be made with reference to the map shown in FIG. 3 or 4 as in the case of the first embodiment. At this time, the ECU functions as an operation region determination unit.

  If it is one of the above regions (Yes at Step S10, Yes at Step S60), it is determined whether or not the current combustion state is stratified combustion (Step S22). When the present invention is applied to a direct injection engine that performs stoichiometric combustion and does not perform stratified combustion, this determination step S22 is omitted.

  When the current combustion state is stratified combustion (Yes at Step S22), the combustion mode is switched to homogeneous combustion (Step S24). This is because stratified charge combustion cannot be performed near the top dead center. If it switches to homogeneous combustion, it will switch to injection top dead center vicinity injection (for example, 340-360 degree BTDC) (step S26). At this time, the ECU functions as an intake top dead center vicinity injection switching means.

  If the combustion is homogeneous from the beginning (No at Step S22), only the injection timing is switched to the vicinity of the intake top dead center (Step S26). In this intake top dead center injection, since the LPG liquid spray directly collides with the piston, the deposit accumulated in the combustion chamber 10a, particularly on the top surface of the piston, is washed, although not as much as gasoline.

  On the other hand, injection near the top dead center of intake is not normally performed because it is disadvantageous compared to injection at normal injection timing in terms of mixing, emission (smoke generation, etc.) and oil dilution, but LPG is easy to vaporize There are few such disadvantages.

  On the other hand, if it is not in any of the above regions (No at Step S10, No at Step S60), there is little need for deposit cleaning, so normal combustion control is performed (Step S72), and this control is terminated.

  After a predetermined fixed period T1 has elapsed after switching to the intake top dead center injection (Yes in step S30), the normal injection timing and the combustion state before switching to the intake top dead center injection are restored (step S42). For example, in step S24, when the stratified combustion is switched to the homogeneous combustion, the stratified combustion before switching is restored.

  Further, this fixed period T1 is an accumulated time worth washing, which is counted by a counter (not shown) after switching to near-intake-top dead center injection. For example, it is about 1 to 2 minutes as an experimental value obtained by experiments or the like. can do.

  Then, after returning to the normal injection timing and combustion state before switching (step S42), when the continuous operation for a predetermined period T2 has elapsed (Yes in step S50), this control is terminated.

  This fixed period T2 is the cumulative injection time counted by a counter (not shown) after returning to the normal injection timing and combustion state before switching, and is, for example, about 30 to 60 minutes as an experimental value obtained by experiments or the like. can do.

  The above control logic can be repeatedly executed as necessary. When the accelerator operation is performed by the user and the change in the accelerator opening is greater than a certain value, an interrupt request is always issued, the counter values of the elapsed periods T1 and T2 are reset, and the start of this control (immediately before step S10). Return to).

  As described above, according to the fuel supply control device of the LPG engine 10 according to the second embodiment, the LPG of the liquid spray is directly applied to the combustion chamber 10a, particularly to the top surface of the piston, near the intake top dead center for a certain period T1. By spraying, deposits deposited at the location can be effectively washed away.

  In Embodiment 1 and Embodiment 2 described above, LPG is used as the liquid fuel. However, for example, this is used for hydrocarbons such as butane, propane, or methanol that can be stored in a liquid state. The invention can also be applied, and the same effect as described above can be expected.

  As described above, the fuel supply control device for an LPG engine according to the present invention is useful for an LPG engine configured to be able to supply LPG as liquid fuel to a combustion chamber, and in particular, in the combustion chamber, particularly on the top surface of a piston. It is suitable for LPG engines aiming at effective cleaning and removal of accumulated deposits.

It is a flowchart which shows the control action which concerns on Example 1 of this invention. It is a schematic diagram which shows schematic structure of an engine. It is explanatory drawing which shows an example of the low load and low rotation area | region where deposits are easy to accumulate. It is explanatory drawing which shows the high load area | region where the deposit cleaning effect is large expectation. It is a schematic diagram which shows schematic structure of the engine which concerns on Example 2 of this invention. It is a flowchart which shows control operation.

Explanation of symbols

10 Engine (LPG engine)
10a Combustion chamber 14 Intake passage 15 Intake port 24 Injector 37 LPG tank 38 Fuel supply pipe 38a High pressure pump 39 Delivery pipe 40 Feed pump

Claims (4)

A fuel supply control device for a liquefied petroleum gas engine configured to be able to supply liquefied petroleum gas as liquid fuel to an intake port,
An operation region determination means for determining whether or not the current operation region is in an operation region where deposits are likely to be deposited in a predetermined amount in the combustion chamber or an operation region where the cleaning effect of the deposit by the liquid fuel is great;
When the current operation region is determined to be any one of the operation regions by the operation region determination means, the liquid spray of the liquefied petroleum gas is supplied into the combustion chamber by temporarily switching to intake synchronous injection. Intake synchronous injection switching means;
A fuel supply control device for a liquefied petroleum gas engine. A fuel supply control device for a liquefied petroleum gas engine configured to be able to directly supply liquefied petroleum gas as liquid fuel into a combustion chamber, and configured to be able to switch between stratified combustion and homogeneous combustion according to operating conditions,
An operation region determination means for determining whether or not the current operation region is in an operation region where deposits are likely to accumulate in a predetermined amount in the combustion chamber or an operation region in which the deposit cleaning effect by the liquid fuel is large;
When the operation region determination means determines that the current operation region is any one of the operation regions, the liquefied petroleum gas is temporarily switched to near the intake top dead center injection in the homogeneous combustion state. An intake top dead center vicinity injection switching means for supplying a liquid spray into the combustion chamber;
A fuel supply control device for a liquefied petroleum gas engine.   3. The fuel supply control device for a liquefied petroleum gas engine according to claim 1, wherein the operation region in which the deposit is likely to be deposited is a low load / low rotation region.   4. The operation region where the deposit cleaning effect is large is a high load region or an operation region when the engine cooling water temperature or the lubricating oil temperature is lower than a predetermined value. The fuel supply control device of the liquefied petroleum gas engine as described.

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