Internal combustion engine system

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an internal combustion engine system switchable between a spark ignition operation and a homogeneous charge compression ignition operation.

2. Description of the Related Art

In recent years, in order to improve fuel efficiency and reduce emission matters in internal combustion engines, compression ignition internal combustion engines represented by homogeneous charge compression ignition internal combustion engines have been under review. In a homogeneous charge compression ignition internal combustion engine, oxygen containing gas and a compression ignition fuel are introduced into a cylinder and compressed to ignite spontaneously.

However, as distinct from spark ignition internal combustion engines, homogeneous charge compression ignition internal combustion engines have problems that it is difficult to control ignition timing and the engines can be operated safely only in a narrow operating range. More specifically, the problems mean that use of a fuel with high ignitability tends to cause knocking when required load of the engine is high, and that use of a fuel with low ignitability tends to cause misfire when required load of the engine is low. In order to overcome the problems, there is known an internal combustion engine system switchable between a spark ignition operation and a homogeneous charge compression ignition operation depending on operation conditions or the like (for example, see Japanese Patent Laid-Open No. 2001-152919, and No. 2002-130006.)

Furthermore, in order to overcome the problems, it is conceivable that two or more types of fuels having different ignition characteristics are prepared, and the mixture ratio of the fuels is controlled when the fuels are provided to the homogeneous charge compression ignition internal combustion engine, thereby controlling the ignition timing. Examples of the two or more types of fuels having different ignition characteristics may include a combination of liquid hydrocarbon such as gasoline or GTL naphtha and ethanol.

Use of ethanol allows the so-called “carbon neutral effect”, thereby contributing to carbon dioxide emission reductions. The carbon neutral effect means that combustion of ethanol derived from plants emits carbon dioxide but the net carbon emissions are zero because the material plants absorb carbon dioxide by carrying out photosynthesis in their growth processes.

The liquid hydrocarbon and the ethanol may be contained in separate tanks. Alternatively, the liquid hydrocarbon and the ethanol may be contained as a mixed fuel in a single tank and separated into the liquid hydrocarbon and the ethanol as necessary. It is known that addition of water to the mixed fuel of liquid hydrocarbon and ethanol easily separates the fuel into the liquid hydrocarbon and an ethanol-water mixture (for example, see Japanese Patent Laid-Open No. 58-96155).

When the liquid hydrocarbon is compared to ethanol, ethanol is less self ignitable than the liquid hydrocarbon. Therefore, a mixture ratio of the ethanol and the liquid hydrocarbon is adjusted, thereby changing ignition characteristics, for example, represented by the octane number. As a result, the ignition timing of a homogeneous charge compression ignition can be controlled.

However, there is demanded development of an internal combustion engine system in which the ignition timing of a homogeneous charge compression ignition can be controlled more effectively.

SUMMARY OF THE INVENTION

In order to overcome the problems, an object of the present invention is to provide an internal combustion engine system switchable between a spark ignition operation and a homogeneous charge compression ignition operation in which the ignition timing of a homogeneous charge compression ignition can be controlled precisely during the homogeneous charge compression ignition operation.

In order to achieve the object, a first aspect of the internal combustion engine system according to the present invention is an internal combustion engine system switchable between a spark ignition operation and a homogeneous charge compression ignition operation, comprising: a first fuel tank containing ethanol; a second fuel tank containing at least one of gasoline and GTL naphtha; a reforming means for reforming a portion of ethanol provided from the first fuel tank to an internal combustion engine by heating and bringing the ethanol into contact with a catalyst to obtain diethyl ether; a heat exchange means for exchanging heat between exhaust heat of the internal combustion engine and a heating medium to heat the heating medium; an ethanol heating means for heating ethanol provided to the reforming means with the heating medium heated by the heat exchange means; and a fuel supply controlling means for controlling a mixture ratio of ethanol provided from the first fuel tank to the internal combustion engine, at least one of gasoline and GTL naphtha provided from the second fuel tank to the internal combustion engine, and diethyl ether provided from the reforming means to the internal combustion engine.

According to the first aspect of the internal combustion engine system, a portion of ethanol contained in the first fuel tank can be reformed to diethyl ether with the reforming means. The ethanol has a lower self ignitability than the gasoline and GTL naphtha whereas the diethyl ether has a higher self ignitability than the gasoline and GTL naphtha.

Therefore, by controlling a mixture ratio of the ethanol, at least one of gasoline and GTL naphtha, and the diethyl ether provided to the internal combustion engine with the fuel supply controlling means, the ignition timing of a homogeneous charge compression ignition can be controlled precisely.

By the way, when the ethanol is reformed to the diethyl ether by using a catalyst, it is necessary to keep the temperature of ethanol brought into contact with the catalyst to be a constant temperature of about 200° C. For this purpose, it is conceivable that exhaust heat of the internal combustion engine can be used as a heat source for heating the ethanol up to the temperature. However, it is difficult to maintain desired reforming properties by direct use of exhaust heat of the internal combustion engine, because large heat radiation causes ununiform temperatures of the reforming means and ethanol has a large latent heat.

Therefore, in the first aspect of the internal combustion engine system, heat is exchanged between exhaust heat of the internal combustion engine and a heating medium by using the heat exchange means to heat the heating medium, and the heating medium is used to heat the ethanol with the ethanol heating means. As a result, the temperature of the ethanol can be easily kept at a constant temperature of about 200° C. The ethanol is brought into contact with the catalyst in the reforming means, thereby easily maintaining desired reforming properties.

Next, a second aspect of the internal combustion engine system according to the present invention is an internal combustion engine system switchable between a spark ignition operation and a homogeneous charge compression ignition operation, comprising: a first fuel tank containing ethanol; a second fuel tank containing at least one of gasoline and GTL naphtha; a reforming means for reforming a portion of ethanol provided from the first fuel tank to an internal combustion engine by heating and bringing the ethanol into contact with a catalyst to obtain diethyl ether; a heat exchange means for exchanging heat between exhaust heat of the internal combustion engine and a heating medium to heat the heating medium; an intake air heating means for heating intake air of the internal combustion engine with the heating medium heated by the heat exchange means; and a fuel supply controlling means for controlling a mixture ratio of ethanol provided from the first fuel tank to the internal combustion engine, at least one of gasoline and GTL naphtha provided from the second fuel tank to the internal combustion engine, and diethyl ether provided from the reforming means to the internal combustion engine.

According to the second aspect of the internal combustion engine system, as with the first aspect, by controlling a mixture ratio of the ethanol, at least one of gasoline and GTL naphtha, and the diethyl ether provided to the internal combustion engine with the fuel supply controlling means, the ignition timing of a homogeneous charge compression ignition can be controlled precisely.

In this case, the ignition timing can also be controlled by heating intake air of the internal combustion engine. Therefore, in the second aspect of the internal combustion engine system, heat is exchanged between exhaust heat of the internal combustion engine and a heating medium by using the heat exchange means to heat the heating medium, and the heating medium is used to heat intake air of the internal combustion engine with the intake air heating means.

As a result, the control of the ignition timing by the function of the fuel supply controlling means can be complemented by the heating of intake air with the intake air heating means, thereby controlling the ignition timing precisely and effectively.

The second aspect of the internal combustion engine system may further comprise an ethanol heating means for heating ethanol provided to the reforming means with the heating medium heated by the heat exchange means. As a result, the control of the ignition timing by the function of the fuel supply controlling means can be complemented by the heating of intake air in the intake air heating means, and also desired reforming properties can be maintained easily with the reforming means.

Note that equipping of the ethanol heating means in the second aspect of the internal combustion engine system has the same meaning as equipping of the intake air heating means in the first aspect of the internal combustion engine system.

In addition, both of the first and second aspects may comprise a fuel tank containing a mixed fuel comprising ethanol and at least one of gasoline and GTL naphtha; and a separating means for separating the mixed fuel provided from the fuel tank into at least one of gasoline and GTL naphtha and an ethanol-water mixture by adding water to the mixed fuel; instead of a first fuel tank containing ethanol and a second fuel tank containing at least one of gasoline and GTL naphtha.

In this case, as with the first and second aspects, a portion of the ethanol-water mixture obtained in the separating means is reformed to a diethyl ether-water mixture with the reforming means. After that, a mixture ratio of the ethanol-water mixture, at least one of gasoline and GTL naphtha, and the diethyl ether-water mixture to be provided to the internal combustion engine is controlled with the fuel supply controlling means. In the case that the internal combustion engine system comprises the ethanol heating means, heat is exchanged between exhaust heat of the internal combustion engine and a heating medium by using the heat exchange means to heat the heating medium, and the heating medium is used to heat the ethanol-water mixture with the ethanol heating means.

In each aspect of the internal combustion engine system, the spark ignition operation is carried out during high engine load conditions, while the homogeneous charge compression ignition operation is carried out during low engine load conditions.

In each aspect of the internal combustion engine system, when the internal combustion engine halts, the heating medium is cooled. As a result, when the internal combustion engine resumes, the heating medium is heated again from the cooled state. Therefore, it takes time until the ethanol, the ethanol-water mixture, or intake air of the internal combustion engine can be heated.

For this reason, each aspect of the internal combustion engine system preferably comprises an adiabatic storage container for containing the heating medium heated by the heat exchange means and storing the heating medium under adiabatic conditions during a halt of the internal combustion engine. In this each aspect of the internal combustion engine system, the heating medium is housed in the adiabatic storage container on the halt of the internal combustion engine and the heating medium is stored therein during the halt of the internal combustion engine, thereby preventing the heating medium from cooling. As a result, when the internal combustion engine resumes, the ethanol, the ethanol-water mixture, or intake air of the internal combustion engine can be heated at once.

Examples of the adiabatic storage container may include a heat storage container for storing cooling water heated by a water cooled internal combustion engine for the purpose of rapid warming up (see Japanese Patent Laid-Open No. 2001-207845).

When each aspect of the internal combustion engine system comprises the adiabatic storage container, the system preferably further comprises a first thermal detecting means for detecting a temperature of the adiabatic storage container; a second thermal detecting means for detecting a temperature of the heating medium heated by the heat exchange means; and a flow controlling means for flowing the heating medium to the adiabatic storage container only when the temperature detected by the first thermal detecting means is higher than the temperature detected by the second thermal detecting means during an operation of the internal combustion engine.

The flow controlling means flows the heating medium to the adiabatic storage container only when the temperature detected by the first thermal detecting means is higher than the temperature detected by the second thermal detecting means during an operation of the internal combustion engine. As a result, the heating medium is heated by the heat exchange means and also by the adiabatic storage container, thereby extending the range of temperature control during an operation of the internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIG. 1</figref> is a system configuration diagram showing a configuration example of the internal combustion engine system according to the present invention;

<figref idref="DRAWINGS">FIG. 2</figref> is a system configuration diagram showing a configuration of an engine room in the internal combustion engine system of <figref idref="DRAWINGS">FIG. 1</figref>;

<figref idref="DRAWINGS">FIG. 3</figref> is a function explanatory view of an embodiment of functions of a heating medium in the system of <figref idref="DRAWINGS">FIG. 2</figref>;

<figref idref="DRAWINGS">FIG. 4</figref> is a function explanatory view of another embodiment of functions of a heating medium in the system of <figref idref="DRAWINGS">FIG. 2</figref>; and

<figref idref="DRAWINGS">FIG. 5</figref> is a system configuration diagram showing another configuration example of the internal combustion engine system according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in further detail with reference to the attached drawings. <figref idref="DRAWINGS">FIG. 1</figref> is a system configuration diagram showing a configuration example of the internal combustion engine system according to the present invention. <figref idref="DRAWINGS">FIG. 2</figref> is a system configuration diagram showing a configuration of an engine room in the internal combustion engine system of <figref idref="DRAWINGS">FIG. 1</figref>. <figref idref="DRAWINGS">FIGS. 3 and 4</figref> are function explanatory views of functions of a heating medium in the system of <figref idref="DRAWINGS">FIG. 2</figref>. <figref idref="DRAWINGS">FIG. 5</figref> is a system configuration diagram showing another configuration example of the internal combustion engine system according to the present invention.

As shown in <figref idref="DRAWINGS">FIG. 1</figref>, an internal combustion engine system <b>1</b> according to the present embodiment comprises an internal combustion engine <b>3</b> installed in an engine room <b>2</b>, a first fuel tank <b>4</b><i>a </i>and a second fuel tank <b>4</b><i>b </i>that provide fuels to the internal combustion engine <b>3</b>. The internal combustion engine <b>3</b> is a hybrid combustion engine switchable between a spark ignition operation and a homogeneous charge compression ignition operation. The engine <b>3</b> is a flexible fuel vehicle that can be operated with fuels of ethanol and at least one of gasoline and GTL naphtha in an arbitrary mixture ratio. The first fuel tank <b>4</b><i>a </i>contains ethanol as a fuel to be provided to the internal combustion engine <b>3</b>. The second fuel tank <b>4</b><i>b </i>contains gasoline or GTL naphtha as a fuel to be provided to the internal combustion engine <b>3</b>. The second fuel tank <b>4</b><i>b </i>may contain a mixed fuel of gasoline and GTL naphtha.

The first fuel tank <b>4</b><i>a </i>is connected to a first injector <b>6</b><i>a </i>of the internal combustion engine <b>3</b> via a first duct <b>5</b><i>a. </i>A pump <b>7</b><i>a </i>is installed at some midpoint of the first duct <b>5</b><i>a. </i>Ethanol contained in the first fuel tank <b>4</b><i>a </i>is provided to the first injector <b>6</b><i>a </i>by the pump <b>7</b><i>a. </i>

In this case, a distributor <b>8</b> is installed at a downstream position of the pump <b>7</b><i>a. </i>A second duct <b>5</b><i>b </i>branches from the distributor <b>8</b>. A reforming device <b>9</b> is installed at some midpoint of the second duct <b>5</b><i>b </i>so that the reforming device <b>9</b> reforms ethanol provided therein from the distributor <b>8</b> via the second duct <b>5</b><i>b </i>by bringing the ethanol being heated into contact with a catalyst, thereby providing diethyl ether. The second duct <b>5</b><i>b </i>is connected to a second injector <b>6</b><i>b </i>of the internal combustion engine <b>3</b> so that the diethyl ether obtained in the reforming device <b>9</b> is provided to the second injector <b>6</b><i>b </i>via the second duct <b>5</b><i>b. </i>

On the other hand, the second fuel tank <b>4</b><i>b </i>is connected to a third injector <b>6</b><i>c </i>of the internal combustion engine <b>3</b> via a third duct <b>5</b><i>c. </i>A pump <b>7</b><i>b </i>is installed at some midpoint of the third duct <b>5</b><i>c. </i>Liquid hydrocarbon such as gasoline, GTL naphtha or a mixed fuel of gasoline and GTL naphtha is provided to the third injector <b>6</b><i>c </i>by the pump <b>7</b><i>b. </i>

In the internal combustion engine system <b>1</b>, the first to third injectors <b>6</b><i>a, </i><b>6</b><i>b </i>and <b>6</b><i>c </i>are electrically connected to a fuel supply controlling device <b>10</b>. The fuel supply controlling device <b>10</b> controls a mixture ratio of ethanol, diethyl ether and the liquid hydrocarbon provided to the internal combustion engine <b>3</b>.

As shown in <figref idref="DRAWINGS">FIG. 2</figref>, the engine room <b>2</b> comprises the internal combustion engine <b>3</b>; an exhaust device <b>11</b> for letting out exhaust from the internal combustion engine <b>3</b>; and an intake device <b>12</b> for providing intake air to the internal combustion engine <b>3</b>.

The exhaust device <b>11</b> comprises an exhaust pipe <b>13</b> connected to the internal combustion engine <b>3</b>; and a first heat exchange device <b>14</b> located at some midpoint of the exhaust pipe <b>13</b> for exchanging heat between exhaust heat provided to the exhaust pipe <b>13</b> and a heating medium, thereby heating the heating medium.

On the other hand, the intake device <b>12</b> is connected to the internal combustion engine <b>3</b>. The intake device <b>12</b> comprises a direct line <b>15</b> for providing intake air to the internal combustion engine <b>3</b>; and a heating line <b>16</b> branching from the direct line <b>15</b> at an upstream position of the direct line <b>15</b> and merging again with the direct line <b>15</b> at a downstream position. A first flow control valve <b>17</b><i>a </i>is provided to the direct line <b>15</b> at a downstream position of the branch point between the direct line <b>15</b> and the heating line <b>16</b>. A second flow control valve <b>17</b><i>b </i>is provided to the heating line <b>16</b> at an upstream position of the merging point of the direct line <b>15</b> and the heating line <b>16</b>. The openings of the flow control valves <b>17</b><i>a </i>and <b>17</b><i>b </i>are adjusted by an electromagnetic control throttle device (not shown). A second heat exchange device <b>18</b> is provided at some midpoint of the heating line <b>16</b> as an intake air heating means for exchanging heat between the heating medium heated by the first heat exchange device <b>14</b> and intake air, thereby heating the intake air.

The heating medium is circulated via a heating medium circulating system <b>19</b> installed in the engine room <b>2</b>. The circulating system <b>19</b> comprises from its upstream to its downstream a low pressure pump <b>20</b>, a flow control valve <b>21</b>, a first heat exchange device <b>14</b>, a reforming device <b>9</b> and a second heat exchange device <b>18</b>. The heating medium is heat-exchanged with the intake air in the second heat exchange device <b>18</b>, then heat-exchanged with engine cooling water provided by an engine cooling water circulating system <b>23</b> in a third heat exchange device <b>22</b> provided at a downstream position of the second heat exchange device <b>18</b> to cool the heating medium, and then returned to the low pressure pump <b>20</b>. The heating medium circulating system <b>19</b> comprises a bypass <b>19</b><i>a </i>branching from the circulating system <b>19</b> at the flow control valve <b>21</b> and merging with the circulating system <b>19</b> at a position between the first heat exchange device <b>14</b> and the reforming device <b>9</b>. The reforming device <b>9</b> also functions as an ethanol heating means by exchanging heat between the heating medium heated by the first heat exchange device <b>14</b> and ethanol provided to the reforming device <b>9</b> via the second duct <b>5</b><i>b, </i>thereby heating the ethanol.

The engine cooling water circulating system <b>23</b> is composed of a first cooling water pipe <b>23</b><i>a, </i>a second cooling water pipe <b>23</b><i>b, </i>a third cooling water pipe <b>23</b><i>c, </i>and a fourth cooling water pipe <b>23</b><i>d. </i>The first cooling water pipe <b>23</b><i>a </i>connects the internal combustion engine <b>3</b> to an ethanol preheating device <b>24</b> installed in the second duct <b>5</b><i>b </i>at an upstream position of the reforming device <b>9</b>, thereby providing engine cooling water heated in the internal combustion engine <b>3</b> to the ethanol preheating device <b>24</b>. The second cooling water pipe <b>23</b><i>b </i>connects the ethanol preheating device <b>24</b> to the internal combustion engine <b>3</b>, thereby providing engine cooling water cooled in the ethanol preheating device <b>24</b> to the internal combustion engine <b>3</b>. The third cooling water pipe <b>23</b><i>c </i>connects the internal combustion engine <b>3</b> to the second heat exchange device <b>18</b> via the third heat exchange device <b>22</b>, thereby exchanging heat between engine cooling water and the heating medium in the third heat exchange device <b>22</b>, and further providing the heated engine cooling water to the second heat exchange device <b>18</b>. The fourth cooling water pipe <b>23</b><i>d </i>connects the second heat exchange device <b>18</b> to the internal combustion engine <b>3</b>, thereby providing engine cooling water cooled by heat-exchanging with the intake air in the second heat exchange device <b>18</b> to the internal combustion engine <b>3</b>. The fourth cooling water pipe <b>23</b><i>d </i>is connected to the first cooling water pipe <b>23</b><i>a. </i>

Referring now to <figref idref="DRAWINGS">FIG. 3</figref>, there is described an aspect of functions of a heating medium in the internal combustion engine system <b>1</b> according to the present embodiment.

Examples of the heating medium may include mineral oils, silicone oils and the like having boiling points of 200° C. or higher. The heating medium can be well known heating mediums generally used in plants and the like, and no special heating medium is necessary.

In the heating medium circulating system <b>19</b>, the heating medium is circulated by the low pressure pump <b>20</b>, thereby first providing a required amount of the heating medium to the first heat exchange device <b>14</b> via the flow control valve <b>21</b> while allowing an excess of the heating medium to circumvent the first heat exchange device <b>14</b> via the bypass <b>19</b><i>a. </i>In the first heat exchange device <b>14</b>, heat is exchanged between exhaust and the provided heating medium to heat the heating medium, and the heating medium heated is provided to the reforming device <b>9</b>.

At an upstream position of the reforming device <b>9</b>, a temperature sensor <b>25</b> is provided. The flow control valve <b>21</b> is feedback-controlled in response to the temperature of the heating medium detected by the temperature sensor <b>25</b> so that the temperature becomes suitable (in general, 200° C.) for reforming ethanol to diethyl ether in the reforming device <b>9</b>. Thus the flow control valve <b>21</b> controls the amount of the heating medium to be provided to the first heat exchange device <b>14</b>.

The reforming device <b>9</b> also functions as an ethanol heating means for heating ethanol provided via the second duct <b>5</b><i>b, </i>and configured so that the ethanol and the heating medium form a counter current. The heating medium provided to the reforming device <b>9</b> first heats the reforming device main body <b>9</b><i>a, </i>and then heats ethanol in the fourth heat exchange device <b>9</b><i>b. </i>

The reforming device <b>9</b> has a heat capacity roughly proportional to its weight. Therefore, when ethanol is directly heated with exhaust, the heat capacity causes temperature variation in the beginning of reforming. However, in the present embodiment, the reforming can be conducted with stability from the beginning of the reforming by first heating the reforming device <b>9</b> with the heating medium up to about a reforming temperature, and then providing ethanol to the reforming device <b>9</b>. In this case, when the catalyst is configured to be surrounded by the heating medium, the temperature of the catalyst is stabilized and spatial temperature unevenness is prevented, thereby providing excellent reforming properties.

In the present embodiment, an ethanol preheating device <b>24</b> is provided on the second duct <b>5</b><i>b </i>at an upstream position of the reforming device <b>9</b>, thereby preheating ethanol provided to the reforming device <b>9</b>. As a result, the required heat capacity of the heating medium can be prevented from becoming excessive. The ethanol preheating device <b>24</b> can preheat ethanol to be provided to the reforming device <b>9</b> up to about 80° C. by providing engine cooling water heated in the internal combustion engine <b>3</b> via the first cooling water pipe <b>23</b><i>a. </i>

The heating medium drained from the reforming device <b>9</b> is subsequently provided to the second heat exchange device <b>18</b>, and heat-exchanged with intake air, thereby heating the intake air. The heating medium having a considerable quantity of heat even after heating the intake air is subsequently provided to the third heat exchange device <b>22</b>, thereby heat-exchanging with engine cooling water provided to the third heat exchange device <b>22</b> via the third cooling water pipe <b>23</b><i>c. </i>As a result, the heating medium is cooled to about 80° C. Thus cooled heating medium is returned to the low pressure pump <b>20</b>.

The intake air provided to the second heat exchange device <b>18</b> may be preheated by heat-exchanging with engine cooling water provided via the third cooling water pipe <b>23</b><i>c </i>before the intake air is heated by heat exchanging with the heating medium. In this case, the engine cooling water provided via the third cooling water pipe <b>23</b><i>c </i>is heated in the internal combustion engine <b>3</b> and provided to the third heat exchange device <b>22</b> as shown in <figref idref="DRAWINGS">FIG. 2</figref>.

The engine cooling water provided via the third cooling water pipe <b>23</b><i>c </i>is provided to the third heat exchange device <b>22</b>, heated by heat-exchanging with the heating medium, and drained to the fourth cooling water pipe <b>23</b><i>d. </i>In this case, by providing a heater core <b>26</b> at some midpoint of the fourth cooling water pipe <b>23</b><i>d, </i>the heater core <b>26</b> can be heated with the engine cooling water, whereby a heater can be used at an early stage. Alternatively, warming up can be conducted with the engine cooling water heated in the third heat exchange device <b>22</b>.

The heating medium circulating system <b>19</b> is composed of only control systems and heat exchanging systems, and thus pressure loss is small and the system <b>19</b> does not require high pressure. Therefore, the low pressure pump <b>20</b> can be used for circulating the heating medium.

The heating medium is required to have a flow rate so that temperature control stability can be maintained for reforming ethanol to diethyl ether in the reforming device <b>9</b>. However, the amount of the ethanol is small, and thus the flow rate of the heating medium is not necessarily very high. For example, a flow rate of several liters per minute meets the requirement. Therefore, a small pump is sufficient as the low pressure pump <b>20</b>, and thus its electrical power consumption is as small as several tens of watts at the largest.

The heating medium passing through the low pressure pump <b>20</b> has a temperature of about 80° C. by being cooled in the third heat exchange device <b>22</b> as described above. Therefore, the low pressure pump <b>20</b> requires some heat resistance but does not require a special heat resisting means.

Use of the heating medium provides high control stability when compared with heating ethanol directly with exhaust because the heating medium has a higher flow rate than the ethanol, has a higher heat capacity and brings about less influence by heat radiation, and the heating medium does not boil during heating.

In the present embodiment, the flow control valve <b>21</b> is used for distributing the heating medium to the first heat exchange device <b>14</b> and the bypass <b>19</b><i>a. </i>

Alternatively, instead of the flow control valve <b>21</b>, a thermo valve such as a bimetal type may be used. Use of such a thermo valve simplifies the device configuration because of not requiring power supply or a control circuit.

According to the internal combustion engine system <b>1</b> of the present embodiment, ethanol is heated by using a heating medium heated by heat-exchanging with exhaust as mentioned above, thereby easily assuring desired reforming properties in the reforming device <b>9</b>. As a result, by controlling a mixture ratio of ethanol, diethyl ether and the liquid hydrocarbon, ignition properties of a fuel can be changed continuously, thereby controlling the ignition timing precisely during a homogeneous charge compression ignition operation.

In addition, according to the internal combustion engine system <b>1</b> of the present embodiment, intake air is heated by using a heating medium heated by heat-exchanging with exhaust as mentioned above, thereby controlling the ignition timing precisely and effectively during a homogeneous charge compression ignition operation.

The internal combustion engine system <b>1</b> of the present embodiment comprises both an ethanol heating means (the reforming device <b>9</b> (the fourth heat exchange device <b>9</b><i>b</i>)) and an intake air heating means (the second heat exchange device <b>18</b>) that use a heating medium heated by heat-exchanging with exhaust as mentioned above. However, the internal combustion engine system <b>1</b> may comprise only the ethanol heating means or only the intake air heating means. It should be noted that in the case of comprising only the intake air heating means, the internal combustion engine system <b>1</b> requires a means for heating ethanol provided to the reforming device <b>9</b> with a heat source other than the heating medium.

Referring now to <figref idref="DRAWINGS">FIG. 4</figref>, there is described another aspect of functions of a heating medium in the internal combustion engine system <b>1</b> according to the present embodiment.

As for the configuration shown in <figref idref="DRAWINGS">FIG. 4</figref>, a heating medium circulating system <b>19</b> comprises a control valve <b>27</b> at an upstream position of the reforming device <b>9</b>; and an adiabatic storage container <b>29</b> connected to a duct <b>28</b><i>a </i>branched at the control valve <b>27</b> in which the adiabatic storage container <b>29</b> is connected to the heating medium circulating system <b>19</b> at a downstream position of the control valve <b>27</b> via a duct <b>28</b><i>b. </i>The heating medium circulating system <b>19</b> further comprises a temperature sensor <b>30</b><i>a </i>for detecting the temperature of a heating medium at an upstream position of the control valve <b>27</b>; and a temperature sensor <b>30</b><i>b </i>in the adiabatic storage container <b>29</b> for detecting a temperature of the adiabatic storage container <b>29</b>. Both of the temperature sensors <b>30</b><i>a </i>and <b>30</b><i>b </i>are electrically connected to the control valve <b>27</b> and output the detected temperatures to the control valve <b>27</b>.

The heating medium circulating system <b>19</b> further comprises an absorption air conditioning system regenerator <b>31</b> at a downstream position of the reforming device <b>9</b>. Connected ducts to the absorption air conditioning system regenerator <b>31</b> are a water-lithium bromide duct <b>32</b><i>a </i>for providing lithium bromide which has absorbed water from an absorption air conditioning system not shown to the regenerator <b>31</b>; a drainage duct <b>32</b><i>b </i>for draining water obtained by evaporating the lithium bromide which has absorbed water in the absorption air conditioning system regenerator <b>31</b>; and a lithium bromide duct <b>32</b><i>c </i>for providing again lithium bromide regenerated by the evaporation to the absorption air conditioning system.

Except the above configuration, the configuration shown in <figref idref="DRAWINGS">FIG. 4</figref> is the same as that of <figref idref="DRAWINGS">FIG. 3</figref>. Therefore, the same reference numerals are assigned to the same configuration and explanations thereof are omitted. In <figref idref="DRAWINGS">FIG. 4</figref>, the ethanol preheating device <b>24</b>, the temperature sensor <b>25</b> and the heater core <b>26</b> are omitted.

In the configuration shown in <figref idref="DRAWINGS">FIG. 4</figref>, the same heating medium as with <figref idref="DRAWINGS">FIG. 3</figref> is circulated in the heating medium circulating system <b>19</b> with the low pressure pump <b>20</b>, and heated with the first heat exchange device <b>14</b> as with <figref idref="DRAWINGS">FIG. 3</figref>. The heating medium heated in the first heat exchange device <b>14</b> heats ethanol in the reforming device <b>9</b> as with <figref idref="DRAWINGS">FIG. 3</figref>. Subsequently, the heating medium heats intake air of the internal combustion engine <b>3</b> in the second heat exchange device <b>18</b> and then heat-exchanges with engine cooling water in the third heat exchange device <b>22</b>, whereby the heating medium is cooled to about 80° C. Thus cooled heating medium is returned to the low pressure pump <b>20</b> as mentioned above.

By the way, when the internal combustion engine <b>3</b> is halted, the heating medium is not heated anymore in the first heat exchange device <b>14</b> and is cooled. Once the heating medium is cooled, it takes time to heat again the heating medium. Therefore, when the internal combustion engine <b>3</b> is operated again, it takes time until the ethanol and the intake air can be heated.

Then in configuration shown in <figref idref="DRAWINGS">FIG. 4</figref>, when the internal combustion engine <b>3</b> is halted, a control valve <b>27</b> detects the halt of the internal combustion engine <b>3</b>, and introduces the heating medium to an adiabatic storage container <b>29</b> via a duct <b>28</b><i>a, </i>whereby the heating medium is contained in the adiabatic storage container <b>29</b>. Thus the heating medium is stored at the temperature heated in the first heat exchange device <b>14</b>. On the other hand, on detecting the operation of the internal combustion engine <b>3</b>, the adiabatic storage container <b>29</b> provides the stored heating medium to the heating medium circulating system <b>19</b> via the duct <b>28</b><i>b, </i>thereby circulating the heating medium. As a result, a heating medium with high temperature can be circulated in the heat circulating system from the start of the operation, whereby the ethanol or the intake air can be heated in an extremely short period.

In this case, the control valve <b>27</b> generally closes the duct <b>28</b><i>a, </i>and thus the heating medium is not introduced to the adiabatic storage container <b>29</b>. The duct <b>28</b><i>b </i>comprises a check valve not shown so that the heating medium circulating in the heating medium circulating system <b>19</b> does not flow from the duct <b>28</b><i>b </i>into the adiabatic storage container <b>29</b>.

By the way, during an operation of the internal combustion engine <b>3</b> and the heating medium circulating in the heating medium circulating system <b>19</b>, the temperature T<b>1</b> of the heating medium may become lower than the temperature T<b>2</b> in the adiabatic storage container <b>29</b> depending on the condition. Therefore, in the configuration shown in <figref idref="DRAWINGS">FIG. 4</figref>, the temperature T<b>1</b> of the heating medium is detected by a temperature sensor <b>30</b><i>a </i>provided in the heating medium circulating system <b>19</b> at an upstream position of the control valve <b>27</b>, and also the temperature T<b>2</b> in the adiabatic storage container <b>29</b> is detected by a temperature sensor <b>30</b><i>b </i>provided in the adiabatic storage container <b>29</b>. Then the control valve <b>27</b> compares the temperatures detected by the temperature sensors <b>30</b><i>a </i>and <b>30</b><i>b. </i>Only when the temperature T<b>2</b> in the adiabatic storage container <b>29</b> is higher than the temperature T<b>1</b> of the heating medium (T<b>2</b>&gt;T<b>1</b>), the heating medium is flowed into the adiabatic storage container <b>29</b>.

In this case, the heating medium is heated by being introduced to the adiabatic storage container <b>29</b> from the control valve <b>27</b> via the duct <b>28</b><i>a, </i>subsequently being passed through the adiabatic storage container <b>29</b> and being returned to the heating medium circulating system <b>19</b> from the duct <b>28</b><i>b. </i>Therefore, the heating medium is heated by the first heat exchange device <b>14</b> and also by the adiabatic storage container <b>29</b>. As a result, temperature control range during an operation of the internal combustion engine <b>3</b> can be increased.

In the configuration of <figref idref="DRAWINGS">FIG. 4</figref>, an absorption air conditioning system regenerator <b>31</b> may be provided at some midpoint of the heating medium circulating system <b>19</b>, for example, at a position between the reforming device <b>9</b> and the second heat exchange device <b>18</b>. For example, an absorption air conditioning system (not shown) uses water as a coolant and lithium bromide as an absorbing solution. Water absorbed by the lithium bromide is provided to the absorption air conditioning system regenerator <b>31</b> via a water-lithium bromide duct <b>32</b><i>a. </i>The absorption air conditioning system regenerator <b>31</b> heats and evaporates lithium bromide which has absorbed water by using the heating medium, thereby separating the lithium bromide which has absorbed water into water and lithium bromide. The separated water is drained from a drainage duct <b>32</b><i>b. </i>The lithium bromide separated by the evaporation and regenerated is provided again to the absorption air conditioning system via a lithium bromide duct <b>32</b><i>c. </i>

In <figref idref="DRAWINGS">FIG. 5</figref>, there is shown another internal combustion engine system <b>41</b> according to the present embodiment. The internal combustion engine system <b>41</b> has an identical configuration with the internal combustion engine system <b>1</b> shown in <figref idref="DRAWINGS">FIG. 1</figref> except that the system <b>41</b> comprises a fuel tank <b>42</b> containing a mixed fuel comprising ethanol and at least one of gasoline and GTL naphtha; and a separator <b>43</b> that separates the mixed fuel provided from the fuel tank <b>42</b> into an ethanol-water mixture and liquid hydrocarbon such as gasoline, GTL naphtha or a mixed fuel of gasoline and GTL naphtha by adding water to the mixed fuel, and the first duct <b>5</b><i>a </i>and the third duct <b>5</b><i>c </i>are connected to the separator <b>43</b>.

In the internal combustion engine system <b>41</b>, the ethanol-water mixture obtained in the separator <b>43</b> is provided to the first injector <b>6</b><i>a </i>of the internal combustion engine <b>3</b> via the first duct <b>5</b><i>a. </i>The reforming device <b>9</b> brings the ethanol-water mixture provided from the distributor <b>8</b> via the second duct <b>5</b><i>b </i>into contact with a catalyst while heating the ethanol-water mixture, thereby reforming the mixture to a diethyl ether-water mixture. The diethyl ether-water mixture obtained in the reforming device <b>9</b> is provided to the second injector <b>6</b><i>b </i>via the second duct <b>5</b><i>b. </i>

Subsequently, the fuel supply controlling device <b>10</b> controls a mixture ratio of the ethanol-water mixture, the diethyl ether-water mixture and the liquid hydrocarbon to be provided to the internal combustion engine <b>3</b>.

The functions of a heating medium in the internal combustion engine system <b>41</b> are identical with those in the internal combustion engine system <b>1</b> except that the ethanol is replaced with the ethanol-water mixture and the diethyl ether is replaced with the diethyl ether-water mixture.