JP2009041474A - Internal combustion engine, internal combustion engine system, and control method for internal combustion engine - Google Patents

Abstract

Disclosed is a diesel engine that can improve fuel consumption and noise while preventing deterioration of exhaust gas properties using kerosene as fuel oil.
The ratio of the pilot injection amount to the total injection amount of fuel oil is 5% to 25%, preferably 5% to 20%. The fuel oil injection timing is from the time when the center line of the sprayed fuel oil does not contact the cylinder cylinder inner wall to 20 ° before top dead center, preferably from 40 ° before top dead center to 25 ° before top dead center. The time at which 5% of the fuel oil obtained from the heat generation rate in the cylinder burns is defined as the crank angle from 5 ° before top dead center to 5 ° after top dead center.
[Selection] Figure 1

Description

  The present invention relates to an internal combustion engine that uses kerosene as fuel oil, an internal combustion engine system, and a control method for the internal combustion engine.

Since kerosene heat pumps are installed in residential areas, it is necessary to improve fuel consumption (fuel consumption) and reduce noise.
However, since the current kerosene heat pump performs a single-stage injection of fuel oil, the rapid increase in pressure due to the rapid combustion of light components in kerosene, which in turn increases noise.
It is necessary to improve this combustion and suppress noise by suppressing pressure rise.

Diesel engines, on the other hand, have good combustion efficiency and are installed in automobiles, ships, construction machinery, generators, etc., and are widely used in society.
However, exhaust gas from diesel engines contains many environmental pollutants such as nitrogen oxides (NO _x ), particulate matter (Particulate Matter: PM), and total hydrocarbons (Total Hydro Carbon: THC). .
Therefore, various measures have been taken for the purpose of reducing environmental pollutants (for example, see Patent Document 1 to Patent Document 3).

The one described in Patent Document 1 is a diesel engine with a multi-stage injection mechanism, particularly using a diesel engine fuel oil having a cetane number or cetane index of 45 or less and a 90 vol% distillation temperature of 270 ° C to 360 ° C. It is shown that when the pilot injection amount ratio is 30% or less, fuel consumption and exhaust gas are purified.
However, Patent Document 1 does not show an optimum operation method corresponding to light fuel oil such as kerosene.

Patent Document 2 discloses that a combustion chamber having a cylindrical or conical protrusion is provided in the center of the combustion chamber, and the fuel oil is diffused into the annular groove by spraying the main fuel oil without spraying the main fuel oil. The purpose is that. The purpose of this pilot injection, the fuel oil is sprayed on the projections of the combustion chamber, it is set to be realized low noise and low NO _x by the ignition delay of the main injection by the liquid dispersion.
However, since the example is not described in Patent Document 2, it is unclear, but it is generally said that when the fuel oil comes into contact with the combustion wall, the combustion temperature is lowered and combustion failure occurs.

In the device described in Patent Document 3, the pilot injection timing is preferably 80 ° before top dead center (80 ° BTDC) to 40 ° after top dead center (40 ° ATDC). Although the conventional pilot injection timing is performed from 10 ° before top dead center (10 ° BTDC) to after top dead center (10 ° ATDC), this method suppresses ignition of main injection and causes rapid in-cylinder pressure. The rise is suppressed and vibration noise is suppressed. However, this method has a drawback that smoke is increased due to lack of oxygen because main injection is performed at the time when combustion by pilot injection occurs. Therefore, Patent Document 3 proposes a preferable injection condition.
However, when fuel oil is injected with a single injection nozzle in the injection timing range as claimed, the fuel oil hits the inner wall of the cylinder, causing scuffing and lacquering.
In addition, although it is possible to distinguish between pilot injection and main injection using two injection nozzles, there is a disadvantage that the equipment becomes complicated.

JP 2005-290041 A Japanese Patent Laid-Open No. 10-252476 JP 2004-176593 A

  As described above, in the conventional methods as described in Patent Documents 1 to 3, when using kerosene which is a light fuel oil, fuel consumption improvement and noise reduction are sufficiently improved without deteriorating exhaust gas properties. The current situation is not.

  In view of such circumstances, the present invention provides an internal combustion engine, an internal combustion engine system, and a control method for an internal combustion engine that can improve fuel efficiency and reduce noise by using kerosene as fuel oil to prevent deterioration of exhaust gas properties. With the goal.

The internal combustion engine according to the present invention is an internal combustion engine that uses kerosene as fuel oil, and is a direct injection type in which multistage fuel oil injection is performed before main injection, and the fuel oil injection includes one multi-injection nozzle. It is characterized by having a common rail system that uses multistage injection.
In the present invention, the direct injection type in which kerosene is used as fuel oil and multistage fuel oil injection is performed before main injection, and multistage injection is performed as fuel oil injection using a single multi-injection nozzle in a common rail system.
As a result, even if kerosene, which is a light fuel oil, is used as a fuel oil for an internal combustion engine, it is possible to prevent deterioration of exhaust gas properties and improve fuel consumption and noise.

And in this invention, it is preferable that it is the internal combustion engine of Claim 1, Comprising: It is set as the structure which is a diesel engine in which the said multi-injection nozzle has four or more injection nozzles.
In the present invention, the present invention is applied to a diesel engine having four or more nozzles, preferably 6 or more and 13 nozzles or less as a multi-hole nozzle.
As a result, the combustion efficiency as a diesel engine is good and widely spread to society, maintaining the beneficial point that the manufacturing technology can be easily transferred, and improving the fuel efficiency and noise reduction while preventing the deterioration of exhaust gas properties. can get.
Here, if the number of nozzle holes is less than four, the number of nozzle holes may be small and it may be difficult to obtain uniform spray. If there are more than 13 nozzles, the cost may increase due to the complexity of the configuration. For this reason, it is preferable to apply to the diesel engine which has 4 or more, preferably 6 or more and 13 or less injection holes as a multi-injection nozzle.

According to the present invention, the internal combustion engine according to claim 1 or 2 is provided with a pilot injection mechanism, and a pilot injection amount ratio in a total injection amount of the fuel oil is 5% or more and 25% or less. The fuel oil injection timing is preferably set from the time when the center line of the fuel oil to be sprayed does not contact the inner wall of the cylinder cylinder to 20 ° before top dead center.
In the present invention, the ratio of the pilot injection amount in the total injection amount of the fuel oil in the pilot injection mechanism is 5% or more and 25% or less, preferably 5% or more and 20% or less. The time from the time when the center line does not contact the inner wall of the cylinder to 20 ° before the top dead center.
As a result, even if kerosene, which is a light fuel oil, is used as the fuel oil, deterioration of exhaust gas properties can be prevented, and fuel efficiency can be improved and noise can be reduced.
Here, when the ratio of the pilot injection amount to the total injection amount of the fuel oil is less than 5%, the effect of the pilot injection is reduced, and there is a possibility that the disadvantage of only the effect of the main one-stage injection may occur. On the other hand, if the pilot injection amount ratio is more than 25%, there is a possibility that the premixed gas suddenly burns during high load operation, resulting in inconvenience that noise increases. For this reason, the pilot injection amount ratio is set to 5% to 25%, preferably 5% to 20%.
In addition, the fuel oil injection timing is advanced from the time when the center line of the fuel oil to be sprayed does not contact the inner wall of the cylinder cylinder, that is, earlier, that is, the fuel oil protrudes from the combustion chamber of the diesel engine. If this is done, the fuel oil may hit the inner wall of the cylinder, causing scuffing and lacquering, which may damage the cylinder. On the other hand, if the spray timing of the fuel oil is retarded, that is, delayed from 20 ° before top dead center, premixing by pilot injection may not be sufficiently performed. For this reason, it is preferable that the spraying timing of the fuel oil is from the time when the center line of the fuel oil to be sprayed does not contact the inner wall of the cylinder to 20 ° before the top dead center.

Furthermore, in the present invention, the internal combustion engine according to claim 3, wherein the fuel oil injection timing is preferably set from 40 ° before top dead center to 25 ° before top dead center. .
In the present invention, the fuel oil injection timing is from 40 ° before top dead center to 25 ° before top dead center.
As a result, even if kerosene, which is a light fuel oil, is used as the fuel oil, deterioration of the exhaust gas properties can be prevented, and fuel consumption can be improved and noise can be reduced.
Here, if the fuel oil injection timing is advanced, that is, advanced from 40 ° before top dead center, the fuel oil may hit the inner wall of the cylinder, and scuffing or lacquering may occur, damaging the cylinder. On the other hand, if the spray timing of the fuel oil is retarded from 25 ° before the top dead center, premixing by pilot injection may not be sufficiently performed. For this reason, it is preferable to set the fuel oil injection timing from 40 ° before top dead center to 25 ° before top dead center.

Still further, in the present invention, the internal combustion engine according to claim 3 or claim 4, wherein the time at which 5% of the fuel oil obtained from the heat generation rate in the cylinder cylinder burns is increased by a crank angle. It is preferable to set it as the range set to 5 degrees before a dead center to 5 degrees after a top dead center.
In the present invention, the time at which 5% of the fuel oil obtained from the heat generation rate in the cylinder is burned is in the range from 5 ° before top dead center to 5 ° after top dead center at the crank angle.
As a result, even if kerosene, which is a light fuel oil, is used as the fuel oil, deterioration of the exhaust gas properties can be prevented, and fuel consumption can be improved and noise can be reduced.
Here, when 5% of the fuel oil obtained from the heat generation rate burns, the crank angle is advanced from 5 ° before top dead center and retarded from 5 ° after top dead center. May get worse. For this reason, it is preferable that the time at which 5% of the fuel oil obtained from the heat generation rate burns is from 5 ° before top dead center to 5 ° after top dead center at the crank angle.

According to the present invention, there is provided the internal combustion engine according to any one of claims 3 to 5, wherein the pilot injection mechanism has a condition that the pilot injection amount ratio is calculated by the following expression (1). It is preferable to have a set configuration.
Pilot injection amount ratio = (Pilot injection opening time) /
((All nozzle opening times for pilot injection and main injection) x 100) …… (1)
In the present invention, the pilot injection amount ratio is set to the condition calculated by the above equation (1).
As a result, even if kerosene, which is a light fuel oil, is used as the fuel oil, deterioration of the exhaust gas properties can be prevented, and fuel consumption can be improved and noise can be reduced.

And in this invention, it is an internal combustion engine in any one of Claim 1 thru | or 6, Comprising: It is preferable that the said kerosene is set as the structure based on JISK2203.
In the present invention, kerosene conforming to JIS K 2203 is used as fuel oil.
As a result, even with kerosene, which is a light fuel oil, the above configuration can prevent deterioration of exhaust gas properties and improve fuel consumption and noise.

An internal combustion engine system according to the present invention includes an internal combustion engine according to any one of claims 3 to 7, a rotational speed detection means for detecting a rotational speed of an output shaft of the internal combustion engine, and rotation of the output shaft. The rotational load detection means for detecting the load, the injection timing data relating to the injection timings of the main injection and the pilot injection of the internal combustion engine, and the injection amount data relating to the injection amounts of the main injection and the pilot injection are associated as one control data. A plurality of storage means, and a control means for setting the injection timing and the injection amount in accordance with the rotational speed and rotational load of the output shaft are provided.
In the present invention, the storage means stores the injection timing data relating to the main injection and pilot injection timings of the internal combustion engine according to any one of claims 3 to 7 and the injection quantity relating to the main injection and pilot injection amounts. A plurality of data are stored in association with each other as one control data. The rotational speed detecting means detects the rotational speed of the output shaft of the internal combustion engine, and the rotational load detecting means detects the rotational load of the output shaft of the internal combustion engine. Then, the control means sets the injection timing and the injection amount of the internal combustion engine according to the detected rotational speed and rotational load based on the control data stored in the storage means, and controls the operation of the internal combustion engine.
As a result, even with kerosene, which is a light fuel oil, it is possible to prevent deterioration of exhaust gas properties and to improve fuel efficiency and reduce noise more efficiently according to the operating state of the internal combustion engine.

An internal combustion engine control method according to the present invention is a control method for an internal combustion engine having a common rail system in which kerosene is used as fuel oil and multistage injection is performed by a single multi-injection nozzle, and occupies the total injection amount of the fuel oil. The pilot injection ratio is 5% to 25%, and the fuel oil injection timing is from the time when the center line of the fuel oil to be sprayed does not contact the inner wall of the cylinder to 20 ° before top dead center. To do.
In the present invention, the ratio of the pilot injection amount to the total injection amount of the fuel oil is set to 5% to 25%, and the fuel oil injection timing is dead from the time when the center line of the fuel oil sprayed does not contact the inner wall of the cylinder cylinder. Up to 20 ° before the point.
For this reason, even with kerosene, which is a light fuel oil, it is possible to prevent deterioration of exhaust gas properties and to improve fuel efficiency and reduce noise more efficiently according to the operating state of the internal combustion engine.

In the present invention, it is controlled by at least one integrated circuit selected from a programmable logic device (PLD), a programmable logic array (PLA), and a dedicated control device. The fuel oil is preferably supplied.
As a result, since the supply of the fuel oil composition in the internal combustion engine is controlled by the above-described method, even if the load on the internal combustion engine fluctuates suddenly, the combustion in the internal combustion engine is always optimal. It becomes possible to drive while maintaining the state. Therefore, the fuel consumption rate is improved, noise, etc. NO _x and PM in the exhaust gas can be further suppressed adverse effects by reducing the environment.

Hereinafter, the best mode for carrying out the present invention will be described in detail.
In this embodiment, as an internal combustion engine using kerosene as fuel oil, a diesel engine having a multi-stage injection mechanism, that is, a diesel engine equipped with a common rail fuel injection system is exemplified, but the present invention is not limited to this configuration. Absent. Further, the present invention is not limited to two stages and can be applied to a plurality of stages.

[Diesel engine system]
The diesel engine system as the internal combustion engine system in the present embodiment is used for, for example, a heat pump air conditioner using kerosene, a generator, an automobile (when using so-called city light oil like Sweden), an off-road vehicle such as a construction machine, and the like. It is
The diesel engine system includes a diesel engine as an internal combustion engine and an operation control unit as a control means constituting the fuel injection system.

A diesel engine has a multistage injection mechanism, for example, an engine with a pilot injection mechanism. This diesel engine uses kerosene as fuel oil. As the kerosene, for example, one conforming to JIS K 2203 is used. In addition, as fuel oil, not only kerosene but various additives can be appropriately blended as necessary within a range that does not hinder the object and effect of the present invention.
The diesel engine is provided with a plurality of fuel injectors, a common rail, and a fuel pump that constitute a fuel injection system.

The fuel injector is connected to a cylinder cylinder of a diesel engine main body (not shown) and supplies fuel into the cylinder cylinder.
The common rail is connected to the fuel pump and holds the fuel oil supplied from the fuel pump at a predetermined pressure. The common rail is connected to a plurality of fuel injectors and supplies fuel oil at a prescribed high pressure to the fuel injectors.

The operation control unit includes at least one integrated circuit selected from a programmable logic device (PLD), a programmable logic array (PLA), and a dedicated control device. .
This operation control unit controls the supply of fuel oil to the diesel engine.
Specifically, the pilot injection amount ratio in the total fuel oil injection amount is 5% to 25%, preferably 5% to 20%. That is, the pilot injection amount ratio is set to a condition calculated by the following equation (1).
Pilot injection amount ratio = (Pilot injection opening time) /
((All nozzle opening times for pilot injection and main injection) x 100) …… (1)
Here, when the ratio of the pilot injection amount to the total injection amount of the fuel oil is less than 5%, the effect of the pilot injection is reduced, and there is a possibility that the disadvantage of only the effect of the main one-stage injection may occur. On the other hand, if the pilot injection amount ratio is more than 25%, there is a possibility that the premixed gas suddenly burns during high load operation, resulting in inconvenience that noise increases. For this reason, the pilot injection amount ratio is set to 5% to 25%, preferably 5% to 20%.

In addition, the operation control unit may be configured such that the center line of the fuel oil sprayed at the fuel oil injection timing does not contact the inner wall of the cylinder cylinder to 20 ° before the top dead center, preferably 40 ° before the top dead center. Up to 25 ° front.
Here, the injection timing of the fuel oil is advanced from the time when the center line of the fuel oil to be sprayed does not contact the inner wall of the cylinder cylinder, that is, the fuel oil protrudes beyond the combustion chamber partitioned in the cylinder of the diesel engine. If early injection is performed, fuel oil may hit the inner cylinder wall, causing scuffing and lacquering, which may damage the cylinder. On the other hand, if the spray timing of the fuel oil is retarded, that is, delayed from 20 ° before top dead center, premixing by pilot injection may not be sufficiently performed. For this reason, the fuel oil spraying time is changed from the time when the center line of the fuel oil to be sprayed does not contact the cylinder inner wall to 20 ° before the top dead center, preferably from 40 ° before the top dead center to 25 ° before the top dead center. Up to.

Furthermore, the operation control unit sets the time when 5% of the fuel oil obtained from the heat generation rate in the cylinder burns to a range of 5 ° before top dead center and 5 ° after top dead center at the crank angle. is doing.
The fuel consumption rate deteriorates when 5% of the fuel oil obtained from the heat release rate burns when the crank angle is advanced from 5 ° before top dead center and from 5 ° after top dead center There is a fear. For this reason, it is preferable that the time at which 5% of the fuel oil obtained from the heat generation rate burns is from 5 ° before top dead center to 5 ° after top dead center at the crank angle.

The operation control unit controls the supply of fuel oil according to the operation status of the diesel engine, that is, the rotational speed and rotational load of an output shaft (not shown) of the diesel engine.
Specifically, the operation control unit includes, for example, a rotation speed sensor as a rotation speed detection unit that detects the rotation speed of the output shaft of the diesel engine, and a rotation load detection unit as a rotation load detection unit that detects the rotation load of the output shaft. Based on the detection signals output from the sensors, the rotational speed and rotational load of the output shaft are recognized.
The operation control unit also stores a plurality of injection timing data relating to the injection timings of the main injection and pilot injection of the diesel engine and injection amount data relating to the injection amounts of the main injection and pilot injection as a single piece of control data. Storage means (not shown) of the structure is provided.
Then, the operation control unit sets the injection timing and the injection amount according to the rotation speed and the rotation load of the output shaft recognized from the detection signal based on the plurality of control data stored in the storage means.

[Diesel engine operation control]
Next, a setting operation of a control program for carrying out operation control of the diesel engine in the operation control unit will be described with reference to the drawings.
FIG. 1 is a flowchart showing an operation control program setting operation.

First, fuel oil is designated (step S1). That is, JIS No. 1 kerosene, which is kerosene based on JIS K 2203, is set.
And the estimation program which determines the injection quantity from the nozzle outlet of the common rail which is an injection nozzle is created (step S2). For example, an arithmetic program for calculating the injection amount is set based on the injection pressure, the injection time, and the like according to the use application and the characteristics of the diesel engine.

Thereafter, a map of the diesel engine operation method is created (step S3). That is, the process of setting the optimum operation condition by appropriately changing the rotation speed and the rotation load of the output shaft of the diesel engine for which the operation control content is set is performed.
Specifically, the rotational speed and rotational load of the output shaft of the diesel engine are set to a specific operation state (step S31). Then, the injection amount and the injection time, which are the main injection conditions suitable for the one-stage injection, are set (step S32).
Thereafter, a suitable pilot injection condition is set based on the suitable main injection condition set in step S32 (step S33). When setting the pilot injection conditions, if the measured values of the main injection amount and the pilot injection amount do not match the estimated values, the injection amount ratio is substituted with the injection time ratio.
And the suitable main injection condition vicinity is searched from the suitable pilot injection conditions set by step S33 (step S34).
By repeating these steps S32 to S34, optimum main injection conditions and pilot injection conditions at a specific rotational speed and rotational load are set (step S35). In this way, by setting the rotation speed and the rotation load as appropriate and similarly setting the optimum main injection conditions and pilot injection conditions, the optimum fuel oil injection conditions corresponding to the operating conditions of the diesel engine are displayed in a map form. Set to This set map is stored in the storage means of the operation control unit.

[Effects of the embodiment]
According to the above-described embodiment, as described above, kerosene is used as fuel oil, a direct injection type in which multistage fuel oil injection is performed before main injection, and a single rail injection nozzle is used as fuel oil injection in a common rail system. The multi-stage injection is used.
For this reason, even if kerosene, which is light fuel oil, is used as fuel oil, it is possible to prevent deterioration of exhaust gas properties and improve fuel consumption and noise.
In particular, it is suitable to apply to a diesel engine having 4 or more, preferably 6 or more and 13 or less injection holes as a multi-injection nozzle.
By setting the above-described predetermined pilot injection conditions, even if kerosene is used as fuel oil, it is possible to improve fuel efficiency and reduce noise while reliably preventing deterioration of exhaust gas properties.
In particular, an operation control unit including at least one integrated circuit selected from a programmable logic device (PLD), a programmable logic array (PLA), and a dedicated control device. The fuel oil injection conditions are controlled.

[Modification of Embodiment]
The aspect described above shows one aspect of the present invention, and the present invention is not limited to the above-described embodiment, and within the scope of achieving the objects and effects of the present invention. Needless to say, the modifications and improvements are included in the contents of the present invention. In addition, the specific structure and shape in carrying out the present invention may be used as other structures and shapes within the scope of achieving the object and effect of the present invention.

Next, the present invention will be described in more detail with reference to examples and comparative examples.
In addition, this invention is not restrict | limited at all to description content, such as these Examples.

[Examples 1-7, Comparative Examples 1-7]
Hereinafter, an experiment for confirming the fuel injection condition of the diesel engine 200 using kerosene as fuel oil will be described with reference to the drawings.

(diesel engine)
As an experimental engine, an AVL single-cylinder engine equipped with a common rail multistage injection mechanism was used. As fuel oil, JIS No. 1 kerosene was used.
(Engine specifications)
Cylinder diameter x piston process: 105mm x 115mm
Exhaust volume: 996 cm ³
Compression ratio: 18.6
Maximum fuel injection pressure: 135 MPa
And the injection nozzle of the common rail type fuel injection device of this engine is provided with six injection holes with a hole diameter of 0.12 mm. Further, as shown in FIG. 2, the fuel chamber has a substantially conical protrusion 201 at the center. FIG. 2 also shows the fuel injection direction from the injection nozzle at 40 ° before top dead center. Up to 40 ° before the top dead center indicates that the center line L of the fuel oil sprayed from the nozzle hole is within the combustion chamber.

(Experiment)
The cylinder pressure was measured with a pressure sensor (Product: QC33C, manufactured by AVL LIST GMBH), and combustion pressure analysis was performed.
The fuel oil flow rate was measured with a flow meter (trade name: DF-2410, manufactured by Ono Sokki Co., Ltd.), and the supplied weight was confirmed with a weight scale (trade name, GP-12KR, manufactured by AND).
The exhaust gas was measured with an analyzer (trade name: MEXA-9100DEGR manufactured by Horiba Seisakusho).
Noise was measured with a sound level meter (manufactured by Nippon Kagaku Kogyo Co., Ltd., 1988, normal sound level type approval No. S-15-1).

And according to the operation | movement which sets the operating condition of the diesel engine in embodiment mentioned above, the injection condition of fuel oil was set. The pilot injection amount ratio was set from the time ratio of the injection nozzle.
Here, when performing electronic control, a table in which the injection timing of pilot injection and main injection determined according to the rotational speed and rotational load of the engine using the method as described above, and each injection amount is determined. From the program incorporating, a suitable injection timing and injection amount corresponding to a desired rotational speed and rotational load are determined by interpolation or extrapolation. The program itself was controlled by using a general-purpose INCA software.

The following two conditions were set as operating conditions.
Operating condition 1
・ Rotation speed: 1500rpm
・ Injection pressure: 600bar
・ IMEP (average effective pressure shown): 8bar
Operating condition 2
・ Rotation speed: 2000rpm
・ Injection pressure: 600bar
・ IMEP (shown mean effective pressure): 6bar

(Result: Operating condition 1)
The results under operating condition 1 are shown in Tables 1 and 2.

In Tables 1 and 2, the fuel consumption rate ratio was defined by the following equation (2) based on the fuel consumption rate of Comparative Example 1.
Combustion consumption rate ratio = (fuel consumption rate obtained by experiment-fuel consumption rate obtained in Comparative Example 1) x 100
/ (Fuel consumption rate obtained in Comparative Example 1) …… (2)
Thus, the smaller the fuel consumption rate ratio, the smaller the fuel consumption and the better.
The converted NO _x concentration is the NO _x concentration obtained by correcting so that the oxygen in the exhaust gas becomes 13%.

Furthermore, in order to clarify the improvement effect, the improvement rate is shown by the following formula based on the evaluation items of Comparative Example 1. The relationship between the pilot injection timing and the improvement rate is shown in FIG.
Improvement rate = (Evaluation item value obtained in experiment−Evaluation item value obtained in Comparative Example 1) × 100
/ (Evaluation item value obtained in Comparative Example 1) …… (3)

And as shown in Table 1, with respect to the comparative example 1, the comparative examples 2 and 3 are cases where the main injection timing is delayed and advanced respectively. From the test results, Comparative Example 1 has the lowest illustrated combustion consumption rate, and NO _x and noise are also low.
Therefore, based on the main injection timing, the pilot injection amount ratio is set to 20%, and the pilot injection timing is changed from −36 ° ATDC to −20 ° ATDC (−36 ° to −20 ° before top dead center). It shows to Examples 1-3 (refer Table 1).
As a result, other than the converted NO _x concentration is generally in the direction of improvement as compared with Comparative Example 1. In particular, as shown in FIG. 3, an improvement effect was observed when the pilot injection timing was in the range of −36 ° ATDC to −29 ° ATDC.

Examples 2 and 4 to 6 show the results of changing the pilot injection amount ratio by 5 to 30% with the pilot injection timing set to -30 ° ATDC.
As a result, although the improvement effect is generally seen as compared with Comparative Example 1, it is found that all the evaluation items are improved as compared with Comparative Example 1 particularly when the pilot injection amount ratio is in the range of 5 to 16%. It was.
The relationship between the pilot injection amount ratio and the improvement rate is shown in FIG.

FIG. 5 shows the relationship between the heat generation rate and the crank angle at a rotational speed of 1500 rpm.
As shown in FIG. 5, the comparative example 1 is a single-stage injection, and a rapid pressure increase is caused by the premixed combustion of light components.
On the other hand, in Example 5, since the pilot injection amount is small, the fuel concentration is lean, the ignition delay time is long, and rapid heat generation is suppressed. Therefore, as shown also in Table 2, it turns out that the maximum pressure increase rate and noise are suppressed.
In Comparative Example 4, since the pilot injection amount is large, the ignition delay time is short, and a rapid heat generation rate is generated without performing lean combustion by premixing. Therefore, as shown in Table 2, the maximum pressure increase rate and noise are increased. Further, in Comparative Example 4, the fuel consumption rate and the converted NO _x concentration are higher than those in Examples 4 and 5. As described above, when the heat generation rate is measured together with the pilot injection amount ratio, it is understood that at least the heat generation rate peak value accompanying the pilot injection needs to be kept lower than the heat generation rate peak value of the main injection. .

(Result: Operating condition 2)
Table 3 shows the results under operating condition 2. FIG. 6 shows the relationship between the heat generation rate and the crank angle at a rotational speed of 2000 rpm.

As shown in Table 3, even under the condition of a rotational speed of 2000 rpm, fuel efficiency improvement, exhaust gas purification, noise are achieved under the conditions where the pilot injection timing is −30 ° ATDC and the pilot injection amount ratio is 10 to 20%, compared to the single-stage injection. Reduction is expected.
In Example 7, the maximum in-cylinder pressure increase rate caused by combustion was larger than that of Comparative Example 5, but the noise of the entire engine was low.
Furthermore, when the engine cylinder pressure is being measured, it is a preferable pilot operation condition that the heat generation time by pilot injection is in the vicinity of the top dead center.

  5 and 6, which are preferable conditions in FIGS. 5 and 6, the crank angles at the time of 5% combustion of the fuel oil obtained from the heat generation rate are −2.89 ° ATDC and +0. It turns out that it is 54 degrees ATDC.

  The present invention can be applied to any internal combustion engine using kerosene as fuel oil, such as a heat pump air conditioner using kerosene, an off-road vehicle such as a generator, an automobile, and a construction machine.

It is a flowchart which shows the operation | movement which sets the fuel-injection conditions in the diesel engine system which concerns on this invention. It is explanatory drawing which shows the relationship between the cylinder cylinder inner wall and fuel injection direction in the experiment which confirms the fuel-injection conditions based on this invention. It is a graph which shows the relationship between the pilot injection timing and the improvement rate in the experiment which confirms the fuel-injection conditions which concern on this invention. It is a graph which shows the relationship between the pilot injection quantity ratio and the improvement rate in the experiment which confirms the fuel-injection conditions based on this invention. It is a graph which shows the relationship between the heat release rate and crank angle in the rotational speed 1500rpm in the experiment which confirms the fuel-injection conditions based on this invention. It is a graph which shows the relationship between the heat release rate and the crank angle in the rotational speed 2000rpm in the experiment which confirms the fuel-injection conditions based on this invention.

Claims (10)

An internal combustion engine using kerosene as fuel oil,
It is a direct injection type that performs multi-stage fuel oil injection before main injection,
The internal combustion engine characterized in that the fuel oil injection has a common rail system that performs multi-stage injection using one multi-injection nozzle. The internal combustion engine according to claim 1,
The internal combustion engine, wherein the multi-injection nozzle is a diesel engine having four or more injection holes. The internal combustion engine according to claim 1 or 2,
Equipped with a pilot injection mechanism,
The ratio of pilot injection to the total injection amount of the fuel oil is 5% or more and 25% or less,
The internal combustion engine characterized in that the fuel oil injection timing is set from the time when the center line of the fuel oil to be sprayed does not contact the inner wall of the cylinder cylinder to 20 ° before top dead center. An internal combustion engine according to claim 3,
The fuel oil injection timing is set from 40 ° before top dead center to 25 ° before top dead center. An internal combustion engine according to claim 3 or claim 4,
The time when 5% of the fuel oil obtained from the heat generation rate in the cylinder burns is set in the range from 5 ° before top dead center to 5 ° after top dead center at the crank angle. Internal combustion engine. An internal combustion engine according to any one of claims 3 to 5,
The pilot injection mechanism is set such that the pilot injection amount ratio is calculated by the following equation (1): Pilot injection amount ratio = (Pilot injection opening time) /
((All nozzle opening times for pilot injection and main injection) x 100) …… (1)
An internal combustion engine characterized by that. An internal combustion engine according to any one of claims 1 to 6,
The internal combustion engine, wherein the kerosene conforms to JIS K 2203. An internal combustion engine according to any one of claims 3 to 7,
Rotation speed detection means for detecting the rotation speed of the output shaft of the internal combustion engine;
Rotational load detecting means for detecting the rotational load of the output shaft;
Storage means for storing a plurality of injection timing data relating to each injection timing of main injection and pilot injection of the internal combustion engine and injection amount data relating to each injection amount of main injection and pilot injection as one control data;
Control means for setting the injection timing and the injection amount according to the rotational speed and rotational load of the output shaft;
An internal combustion engine system comprising: A control method for an internal combustion engine having a common rail system in which kerosene is used as fuel oil and multistage injection is performed by one multi-injection nozzle,
The ratio of pilot injection to the total injection amount of the fuel oil is 5% or more and 25% or less,
The method for controlling an internal combustion engine, characterized in that the fuel oil injection timing is from the time when the center line of the fuel oil to be sprayed does not contact the inner wall of the cylinder cylinder to 20 ° before top dead center. A control method for an internal combustion engine according to claim 9,
The fuel oil is supplied under the control of at least one integrated circuit selected from a programmable logic device (PLD), a programmable logic array (PLA), and a dedicated control device. A control method for an internal combustion engine.

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