JP7255377B2 - Fuel reformer control method and fuel reformer - Google Patents

Description

The present invention relates to a fuel reformer for reforming fuel supplied to an internal combustion engine and a control method thereof.

2. Description of the Related Art As one of techniques for improving the thermal efficiency of internal combustion engines used in vehicles such as automobiles, there is a technique for increasing the ignitability of fuel by including hydrogen in the intake air supplied to the combustion chamber. As a method for making the intake air contain hydrogen, there is known a method of chemically reacting gasoline fuel and water with a reforming catalyst for generating hydrogen using the heat of the exhaust gas. In order to realize such means, the vehicle is provided with a water tank that stores water to be supplied to the reforming catalyst. There is a concern that the water in the water tank may freeze. Therefore, as a technique for coping with such problems, for example, Patent Document 1 (Japanese Patent Publication No. 2002-527660) discloses urea to prevent freezing of a urea solution and shorten the vaporization time. A technique of providing an electric heater for maintaining the temperature of the solution at an appropriate temperature has been disclosed.

Japanese translation of PCT publication No. 2002-527660

However, if an electric heater is used to prevent the water tank from freezing, there is a concern that the remaining battery level will decrease, which will adversely affect the operation of other electrical components. Therefore, it is conceivable to use the heat of the exhaust gas to thaw the frozen water. cannot be used unconditionally only for That is, from the viewpoint of improving the thermal efficiency, it is required to both warm up the hydrogen generation catalyst and defrost the water tank in the shortest time so that hydrogen generation by the reforming catalyst can be started early.

The present invention has been made in consideration of the above circumstances, and its object is to effectively utilize the heat of the exhaust gas, while simultaneously warming up the reforming catalyst and defrosting the water tank. An object of the present invention is to provide a fuel reformer capable of efficiently completing the process and starting hydrogen generation by a reforming catalyst at an early stage, and a method of controlling the same.

In order to achieve the above object, the present invention adopts the following solutions. That is, as described in claim 1, a reforming catalyst for promoting a steam reforming reaction of fuel supplied to an internal combustion engine, a water tank containing water to be supplied to the reforming catalyst, a reforming catalyst side exhaust gas passage for flowing exhaust gas from the internal combustion engine to the reforming catalyst side so that the heat of the exhaust gas from the internal combustion engine is given to the reforming catalyst; a water tank side exhaust gas passage for flowing exhaust gas from the internal combustion engine to the water tank side so that the heat of the internal combustion engine is given to the water tank; and the reforming catalyst side exhaust gas passage for the exhaust gas from the internal combustion engine. and an exhaust gas flow control valve for adjusting the flow rate to the water tank side exhaust gas passage, wherein the temperature of the reforming catalyst is adjusted to a reforming catalyst temperature obtaining step for obtaining a temperature of the water tank; a water tank temperature obtaining step for obtaining the temperature of the water tank; a catalyst temperature rise rate estimating step of estimating the target catalyst temperature attainment time required for the temperature of the reforming catalyst to reach the target catalyst temperature when the temperature is low; and the water tank temperature obtained in the water tank temperature obtaining step. is lower than a preset target water tank temperature, a water tank temperature rise rate estimating step of estimating the target water tank temperature attainment time required for the temperature of the water tank to reach the target water tank temperature; a temperature rise speed comparison step of comparing the target catalyst temperature attainment time and the target water tank temperature attainment time; and a valve control step of controlling the exhaust gas flow control valve so that the achievement times are close to each other.

According to the above solution method, the reforming catalyst side exhaust gas passage and the water tank side are arranged so that the target catalyst temperature achievement time and the target water tank temperature achievement time estimated from the temperatures of the reforming catalyst and the water tank become closer to each other. Since the flow rate of the exhaust gas flowing through the exhaust gas passage continues to be optimized according to the operating state of the internal combustion engine, the reforming catalyst and the water tank can reach the target temperature (optimal temperature) almost simultaneously. Therefore, the fuel reformer can start operating (hydrogen generation) in the shortest possible time without any delay caused by either the reforming catalyst or the water in the water tank reaching the target temperature. You can control it. In addition, since only the heat of the exhaust gas is used for this purpose, electric power is not consumed by the electric heater or the like, and it is possible to prevent a decrease in fuel consumption and an adverse effect on other electrical components.

Further, as described in claim 2, a reforming catalyst for promoting a steam reforming reaction of fuel supplied to an internal combustion engine, a water tank containing water to be supplied to the reforming catalyst, and the a reforming catalyst side exhaust gas passage for flowing exhaust gas from the internal combustion engine to the reforming catalyst side so that the heat of the exhaust gas from the internal combustion engine is given to the reforming catalyst; a water tank side exhaust gas passage for flowing exhaust gas from the internal combustion engine to the water tank side so that the heat of the internal combustion engine is given to the water tank; and the reforming catalyst side exhaust gas passage for the exhaust gas from the internal combustion engine. an exhaust gas flow control valve that adjusts the flow rate to and the water tank side exhaust gas passage; a reforming catalyst temperature obtaining means that obtains the temperature of the reforming catalyst; and the temperature of the water tank is obtained. When the temperature of the reforming catalyst obtained by the water tank temperature obtaining means and the reforming catalyst temperature obtaining means is lower than a preset target catalyst temperature, the temperature of the reforming catalyst reaches the target catalyst temperature. a catalyst temperature rise rate estimating means for estimating a time required to reach a target catalyst temperature; Water tank temperature rise rate estimating means for estimating target water tank temperature attainment time required for water tank temperature to reach target water tank temperature; temperature rise rate comparison means, and based on the comparison result of the temperature rise rate comparison means, the exhaust gas flow rate control valve is controlled so that the target catalyst temperature attainment time and the target water tank temperature attainment time become closer to each other. and valve control means.

According to the above solution method, the reforming catalyst side exhaust gas passage and the water tank side are arranged so that the target catalyst temperature achievement time and the target water tank temperature achievement time estimated from the temperatures of the reforming catalyst and the water tank become closer to each other. Since the flow rate of the exhaust gas flowing through the exhaust gas passage continues to be optimized according to the operating state of the internal combustion engine, the reforming catalyst and the water tank can reach the target temperature (optimal temperature) almost simultaneously. Therefore, a fuel reformer is configured that starts operation (hydrogen generation) in the shortest time without causing a delay due to either the reforming catalyst or the water in the water tank reaching the target temperature with a delay. be able to. In addition, since only the heat of the exhaust gas is used for this purpose, electric power is not consumed by the electric heater or the like, and it is possible to prevent a decrease in fuel consumption and an adverse effect on other electrical components.

Preferred modes based on the above solution method are as described in claims 3 and subsequent claims in the scope of claims. That is, the reforming catalyst side exhaust gas passage and the water tank exhaust gas passage are provided in parallel so as to constitute a part of the exhaust gas passage of the internal combustion engine, and are located downstream of the reforming catalyst. The water tank exhaust gas passage branches off from the reforming catalyst side exhaust gas passage upstream of the reforming catalyst, and the It merges with the reforming catalyst side exhaust gas passage downstream of the reforming catalyst and upstream of the exhaust purification catalyst (corresponding to claim 3). In this case, since the reforming catalyst and the water tank are both provided upstream of the exhaust purification catalyst, the exhaust gas temperature is not lowered by the exhaust purification catalyst before it is supplied to the reforming catalyst and the water tank. Instead, the reforming catalyst and water tank are supplied with hot exhaust gas. Therefore, the temperatures of the reforming catalyst and the water tank can be raised early.

1 is a configuration diagram showing an example of the configuration of a fuel reformer of the present invention; FIG. 1 is a block configuration diagram showing an example of a control system of the present invention; FIG. 4 is a timing chart showing an example of control of the present invention; 4 is a timing chart showing an example of control of the present invention; 4 is a flow chart showing a control procedure of an example of control according to the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the configuration of part of a vehicle including a fuel reforming control device according to one embodiment of the present invention. Further, FIG. 2 shows the configuration of the control system in this embodiment.

As shown, the fuel reformer includes a reforming catalyst 1 (reformer) for generating hydrogen for fuel reforming, and a water tank storing water to be supplied to the reforming catalyst 1. 2. A reforming catalyst 1 is provided on a reformed gas supply passage 3 leading to an internal combustion engine E, and fuel from a fuel tank 4 and water from a water tank 2 are supplied to the reformed gas supply passage 3. As a result, hydrogen is generated by a chemical reaction between the reforming catalyst 1 and water, and fuel gas containing hydrogen is supplied to the internal combustion engine E.

The temperature of the reforming catalyst 1 and the temperature of water in the water tank 2 are detected by a catalyst temperature sensor 5 and a water tank temperature sensor 6, respectively, and these detected values are input to the controller U. A controller U controls the amount of fuel supplied from the fuel tank 4 and the amount of water supplied from the water tank 2 . The reformed gas supply passage 3 is connected to an intake port 7 of the internal combustion engine E so that fuel reformed by the reforming catalyst 1, that is, a reformed gas containing hydrogen gas and CO, flows. Fuel supply (supply of reformed gas) to the intake port 7 is controlled by a reformed gas supply amount control valve 8 .

A reforming catalyst 1 and a water tank 2 are arranged on an exhaust gas passage 10 of an internal combustion engine E. As shown in FIG. More specifically, the exhaust gas passage 10 branches upstream of the reforming catalyst 1 into a reforming catalyst side exhaust gas passage 10A, a water tank side exhaust gas passage 10B, and a pre-reforming fuel supply passage 13. The quality catalyst 1 is arranged in the reforming catalyst side exhaust gas passage 10A, and the water tank 2 is arranged in the water tank side exhaust gas passage 10B. The reforming catalyst 1 is provided with a heat exchange mechanism for receiving the heat of the exhaust gas, and the water tank 2 is provided with a temperature raising mechanism 2A utilizing the heat of the exhaust gas. Thereby, the heat of the exhaust gas on the exhaust gas passage 10 can be applied to the reforming catalyst 1 and the water tank 2 by heat exchange. The pre-reforming fuel supply passage 13 is a passage for supplying part of the exhaust gas flowing through the exhaust gas passage 10 to the reforming catalyst 1, and is also connected to a gasoline tank to supply gasoline fuel into the passage. Gasoline fuel can be supplied to the reforming catalyst along with the exhaust gas flowing in the passage.

The reforming catalyst side exhaust gas passage 10A and the water tank side exhaust gas passage 10B join again on the downstream side of the reforming catalyst 1 to form one exhaust gas passage 10 again. An exhaust purification catalyst 11 for purifying the exhaust gas is provided in the exhaust gas passage 10 so as to be located downstream of the confluence point of the reforming catalyst side exhaust gas passage 10A and the water tank side exhaust gas passage 10B. . In this way, the reforming catalyst 1 and the water tank 2 are provided upstream of the exhaust purification catalyst 11, so that the exhaust gas temperature is relatively low as immediately after the internal combustion engine E is started, and the exhaust gas passes through the exhaust purification catalyst 11. Even in a situation where it is difficult to obtain the effect of increasing the temperature of the exhaust gas, the reforming catalyst 1 and the water tank 2 are supplied with the exhaust gas having the highest possible temperature immediately after leaving the internal combustion engine E. Therefore, the catalyst temperature and the tank water temperature can be quickly increased by the heat of the exhaust gas.

An exhaust gas flow rate adjustment valve 12 is provided at a branching portion from the exhaust gas passage 10 to the water tank side exhaust gas passage 10B. The inflow amount (flow ratio) of the exhaust gas from the exhaust gas passage 10 to the reforming catalyst side exhaust gas passage 10A and the water tank side exhaust gas passage 10B is changed. For example, in the present embodiment, when the valve opening of the exhaust gas flow control valve 12 is fully open, the exhaust gas flowing through the exhaust gas passage 10 flows through the reforming catalyst side exhaust gas passage 10A and the water tank side exhaust gas passage 10B. On the other hand, as the valve opening becomes smaller, the amount of exhaust gas flowing into the water tank side exhaust gas passage 10B decreases. A controller U controls the opening degree of the exhaust gas flow rate control valve 12 .

Here, in this embodiment, the exhaust gas flow control valve 12 is provided only on the water tank side exhaust gas passage 10B. Since the reforming catalyst 1 also acts as a resistance to the exhaust gas, the water tank side exhaust gas passage 10B is configured so that the pipe line resistance is smaller than that of the reforming catalyst 1, thereby reducing the water tank side exhaust gas passage 10B. The exhaust gas flow rate of the reforming catalyst side exhaust gas passage 10A and the water tank side exhaust gas passage 10B can be controlled only by adjusting the opening degree of the exhaust gas flow rate adjusting valve 12 provided only on the upper side, but the water tank side exhaust gas passage 10B can be controlled. in the case where it is difficult to make a passage with a lower pipe resistance than the reforming catalyst 1, the water tank side exhaust gas passage 10B, which is upstream of the reforming catalyst side exhaust gas passage 10A and the water tank side exhaust gas passage 10B is branched. An additional exhaust gas flow control valve (not shown) may be provided downstream of the portion.

The controller U is a control device (electronic control unit: ECU) configured using a microcomputer, and includes catalyst temperature rise rate estimation means 21 and water tank temperature rise rate estimation means 22 as processing means (programs). , temperature rise rate comparison means 23 and valve control means 24 .

The catalyst temperature rise rate estimating means 21 calculates the temperature θc of the reforming catalyst 1 detected by the catalyst temperature sensor 5 and the period from when the internal combustion engine E is instructed until the temperature of the reforming catalyst 1 is measured, or immediately before. Based on the difference (predetermined adjustment interval t described below) between the time when the temperature of the reforming catalyst 1 was measured and the time when the temperature of the reforming catalyst 1 was measured this time, the reforming catalyst 1 reduces the exhaust gas A time (target catalyst temperature reaching achievement time Tc) required to reach a predetermined target temperature (target catalyst temperature) by being warmed by the heat is calculated (estimated). As the target catalyst temperature, a temperature (activation temperature) appropriate for the chemical reaction between the reforming catalyst 1 and water is set. (Specifically, for example, 600° C. is set). Further, the calculation of the target catalyst temperature reaching achievement time Tc is repeated at each predetermined adjustment interval t (a constant time interval in which continuous operation is performed while the exhaust gas flow rate adjustment bubble 12 maintains a constant throttle opening), It is supposed to be updated.

The water tank temperature rise rate estimating means 22 measures the temperature θw of the water in the water tank 2 detected by the water tank temperature sensor 6, the period from when the internal combustion engine E is instructed until the temperature of the water tank 2 is measured, Alternatively, based on the difference between the time when the temperature of the water tank 2 was measured immediately before and the time when the temperature of the water tank 2 was measured this time (adjustment interval t described below), the water tank 2 detects the heat of the exhaust gas. A time (target water tank temperature attainment time Tw) required to reach a predetermined target temperature (target water tank temperature) by being warmed by is calculated (estimated). As the target water tank temperature, a temperature (for example, 0° C.) is set at which at least part of the water in the water tank 2 is thawed and available. Further, the calculation of the target water tank temperature attainment time Tc is repeated and updated at each adjustment interval t, similarly to the calculation of the target catalyst temperature attainment time Tc.

The temperature rise speed comparing means 23 compares the target catalyst temperature reaching time Tc estimated by the catalyst temperature rising speed estimating means 21 with the target water tank temperature reaching time Tw estimated by the water tank temperature rising speed estimating means 22. Then, it is determined whether the target catalyst temperature attainment time Tc and the target water tank temperature attainment time Tw are equal or whichever is greater.

The valve control means 24 adjusts the target catalyst temperature reaching time Tc and the target water tank temperature reaching time Tw to be equal (that is, the reforming catalyst 1 and the water tank 2 reach the target temperature at the same time), or the difference between the target catalyst temperature attainment time Tc and the target water tank temperature attainment time Tw is equal to or less than a predetermined target time Tt. The valve opening degree of the valve 12 is adjusted.

Specifically, when the target catalyst temperature reaching achievement time Tc and the target water tank temperature reaching achievement time Tw are equal, if the state (the operating state of the vehicle and the opening degree of the exhaust gas flow control valve 12) continues, Since the reforming catalyst 1 and the water tank 2 are expected to reach their target temperatures almost at the same time, the valve opening of the exhaust gas flow control valve 12 is kept at the opening at that time, and the rate of increase of the catalyst temperature and the water tank temperature is controlled. keep as is.

On the other hand, when the target catalyst temperature reaching achievement time Tc is longer than the target water tank temperature reaching achievement time Tw, if this state continues, the timing at which the reforming catalyst 1 reaches the target temperature Since it is predicted that the timing of reaching the target temperature will be delayed, the amount of exhaust gas flowing through the reforming catalyst side exhaust gas passage 10A is increased by decreasing the opening degree of the exhaust gas flow rate control valve 12. To reduce the amount of exhaust gas flowing through the water tank side exhaust gas passage 10B. As a result, the rate of increase of the catalyst temperature of the reforming catalyst 1 is accelerated, and the rate of increase of the tank water temperature of the water tank 2 is decreased. The achievement time Tw becomes longer. As a result, the target catalyst temperature attainment time Tc and the target water tank temperature attainment time Tw are controlled so as to approach each other.

Conversely, when the target catalyst temperature attainment time Tc is longer than the target water tank temperature attainment attainment time Tw, if this state continues, the timing at which the water tank 2 reaches the target temperature is expected to reach the target temperature later than the timing of reaching the target temperature. , to increase the amount of exhaust gas flowing through the water tank side exhaust gas passage 10B. As a result, the rate of increase in the catalyst temperature of the reforming catalyst 1 is slowed down, and the rate of increase in the tank water temperature of the water tank 2 is increased. The time Tw becomes shorter. As a result, the target catalyst temperature attainment time Tc and the target water tank temperature attainment time Tw are controlled so as to approach each other.

As described above, according to the fuel reformer of the present embodiment, at each predetermined adjustment interval t, the target catalyst temperature The time Tc to reach the target water tank temperature and the time Tw to reach the target water tank temperature are calculated. degree is adjusted. That is, the flow rate ratio of the exhaust gas to the reforming catalyst side exhaust gas passage 10A and the water tank side exhaust gas passage 10B is repeatedly optimized in accordance with the operating state of the internal combustion engine E, which constantly changes according to the driver's accelerator operation. This is continued until the reforming catalyst 1 and the water tank reach the target temperature. As a result, the reforming catalyst 1 and the water tank 2 are finally controlled so as to reach the target temperatures almost without time difference.

In this way, the reforming catalyst 1 and the water in the water tank 2 reach the proper temperature for the chemical reaction (hydrogen generation) with a minimum time difference (warming up the reforming catalyst 1 and the water in the water tank 2). Since the thawing is completed almost at the same time), it is possible to suppress the timing of starting the operation of the fuel reformer due to a delay in reaching the appropriate temperature in either one of them. Thus, the fuel reformer can begin proper operation (hydrogen production) in the shortest achievable time.

Next, according to the timing charts of FIGS. 3 and 4, the target catalyst temperature reaching time Tc and the target water tank temperature reaching time Tw are calculated, and the opening degree of the exhaust gas flow control valve 12 is controlled based on these calculations. will be described in more detail.

FIG. 3 shows the temperature change of the reforming catalyst 1 and the water tank 2 in the first adjustment interval t (from engine start) and the calculation of the target temperature reaching achievement time. At this first adjustment interval t, the opening degree (throttle opening degree) of the exhaust gas flow control valve 12 is set to the initial opening degree Φ0, which is a predetermined value corresponding to the temperature at that time. As a result, the reforming catalyst 1 and the water tank 2 are warmed according to the flow ratio of the exhaust gas to the reforming catalyst side exhaust gas passage 10A and the water tank side exhaust gas passage 10B, which is determined by the initial opening degree Φ0. is rising.

In this way, when the first adjustment interval t elapses, the temperature of the reforming catalyst 1 rises to θc1, and the water temperature of the water tank 2 rises to θw1. It is detected by the temperature sensor 6 .

The reforming catalyst temperature rise rate estimating means 21 detects this state (vehicle driving state and the degree of opening of the exhaust gas flow rate control valve 12) continues, and the catalyst temperature rises at the same pace (slope), the catalyst temperature reaches the target temperature (for example, 600° C.) The required time is calculated, and this estimated time is set as the target catalyst temperature attainment time Tc1 at this point.

Similarly, the water tank temperature rise rate estimating means 22 detects that the tank water temperature of the water tank 2 has risen from the initial temperature (for example, -20°C) to the temperature θw1 at the adjustment interval t. Then, when the tank water temperature rises at the same pace (slope), the time required for the catalyst temperature to reach the target temperature (for example, 0°C) is calculated, and this estimated time is used as the target water temperature at this point. The temperature rise speed comparison means 23 compares the calculated target catalyst temperature attainment time Tc1 with the target water tank temperature attainment time Tw1 to determine the magnitude relationship between them. In the example shown in FIG. 3, the target catalyst temperature attainment time Tc1 is longer than the target water tank temperature attainment time Tw1. It is determined that the target temperature is reached first and that the reforming catalyst 1 reaches the target temperature later.

The valve control means 24 changes the throttle opening degree of the exhaust gas flow control valve 12 based on the comparison result by the temperature increase speed comparison means 23 . In the example shown in FIG. 3, the target catalyst temperature reaching achievement time Tc1 is longer than the target water tank temperature reaching achievement time Tw1, and the temperature rise of the reforming catalyst 1 is delayed. The throttle opening is changed to an opening Φ1 smaller than the initial opening Φ0 so as to increase the amount of exhaust gas flowing through the water tank side exhaust gas passage 10B and decrease the amount of exhaust gas flowing through the water tank side exhaust gas passage 10B.

FIG. 4 shows how the next adjustment interval t has elapsed with the changed throttle opening Φ1. As shown, the reforming catalyst 1 and the water tank 2 are warmed at a rate different from the previous adjustment interval, and after the second adjustment interval t (after a total time of 2t), the reforming catalyst 1 rises to .theta.c2 and the water temperature of the water tank 2 rises to .theta.w2, and these temperatures are detected by the catalyst temperature sensor 5 and the water tank temperature sensor 6, respectively.

The reforming catalyst temperature rise rate estimating means 21 calculates the target catalyst temperature reaching achievement time Tc2 when this state continues based on the catalyst temperature rise (from θc1 to θc2) during the current adjustment interval t. calculate. Further, the water tank temperature rise rate estimating means 22 calculates the target water tank temperature reaching achievement time Tw2 when this state continues, based on the increase in tank water temperature (increase from θw1 to θw2).

In this manner, by updating the target catalyst temperature attainment time Tc and the target water tank temperature attainment time Tw at each adjustment interval t, the target catalyst temperature attainment time Tc and the target water tank temperature attainment time Tw are updated. values approach each other. For example, the current throttle opening Φ1 increases the amount of exhaust gas flowing through the reforming catalyst side exhaust gas passage 10A and reduces the amount of exhaust gas flowing through the water tank side exhaust gas passage 10B compared to the previous throttle opening Φ0. , the current target catalyst temperature reaching time Tc2 is shorter than the previous target catalyst temperature reaching time Tc1, and the current target water tank temperature reaching time Tw2 is shorter than the previous target water tank temperature reaching time Tw2. As a result, the target catalyst temperature attainment time Tc and the target water tank temperature attainment time Tw become closer to each other (the time lag in reaching the target temperature becomes smaller).

As described above, the target catalyst temperature attainment time Tc2 and the target water tank temperature attainment time Tw2 have become closer to each other due to the update at the time when the first adjustment interval t has elapsed, but as shown in FIG. The catalyst temperature attainment time Tc2 is still longer than the target water tank temperature attainment time Tw2. Therefore, the temperature rise speed comparison means 23 and the valve control means 24 are updated when the second adjustment interval t elapses so that the temperature rise of the reforming catalyst 1 is further accelerated and the temperature information of the water tank 2 is delayed. Control is performed to further increase the throttle opening of the exhaust gas flow control valve 12 .

Next, an example of the control procedure of the fuel reformer of the present invention will be described according to the flowchart of FIG. In the control, first, in step S1, the exhaust gas flow control valve 12 is set to an initial opening degree Φ0, which is a predetermined value corresponding to the temperature at that time.

In step S2, the target catalyst temperature attainment time Tc is calculated based on the change in the catalyst temperature when the predetermined adjustment interval t has elapsed. Further, in step S3, the target water tank temperature attainment time Tw is calculated based on the change in the water tank temperature when the predetermined adjustment interval t has elapsed.

In step S4, it is determined whether or not the temperature of the reforming catalyst 1 (catalyst temperature) is equal to or higher than the target catalyst temperature, and if the catalyst temperature is equal to or higher than the target catalyst temperature, the process proceeds to step S5. In step S5, it is determined whether or not the temperature of the water tank 2 (water tank temperature) is equal to or higher than the target water tank temperature. Since both tanks 2 have already been warmed up to the target temperature, the process proceeds to step S6, and the exhaust gas flow rate adjustment valve 12 is fully closed (the entire flow rate in the exhaust gas passage 10 is reduced to the reforming catalyst side exhaust gas passage). 10A) to end the processing cycle.

On the other hand, if it is determined in step S4 that the catalyst temperature is not equal to or higher than the target catalyst temperature, and if it is determined in step S5 that the water tank temperature is not equal to or higher than the target water tank temperature, the reforming catalyst 1 and the water tank 2 Since at least one of them has not reached the target temperature, the process proceeds to step S7 and subsequent steps.

In step S7, it is determined whether or not the target catalyst temperature attainment time Tc and the target water tank temperature attainment time Tw are equal. If this state is maintained, it is estimated that the reforming catalyst 1 and the water tank 2 will reach the target temperature almost at the same time. Returning, the processing from step S2 onward is repeated.

On the other hand, if it is determined in step S7 that the target catalyst temperature attainment time Tc and the target water tank temperature attainment time Tw are not equal, the process proceeds to step S9, in which the target catalyst temperature attainment time Tc is set longer than the target water tank temperature attainment time Tw. is also greater. In this determination, if the target catalyst temperature attainment time Tc is longer than the target water tank temperature attainment time Tw, the time at which the reforming catalyst 1 reaches the target catalyst temperature is earlier than the time at which the water tank 2 reaches the target water tank temperature. Therefore, the flow advances to step S10 to set the valve opening of the exhaust gas flow control valve 12 to be smaller than the current valve opening. As a result, the exhaust gas flow rate in the reforming catalyst side exhaust gas passage 10A is increased, and the exhaust gas flow rate in the water tank side exhaust gas passage 10B is decreased (that is, the catalyst temperature rise speed is increased and the tank water temperature rise speed is slowed down). ) and returns to step S2.

When it is determined in step S9 that the target catalyst temperature attainment time Tc is not longer than the target water tank temperature attainment time Tw, the time when the water tank 2 reaches the target water tank temperature is the time when the reforming catalyst 1 reaches the target catalyst temperature. Therefore, the process proceeds to step S11 to set the valve opening of the exhaust gas flow control valve 12 larger than the current valve opening. As a result, the exhaust gas flow rate in the water tank side exhaust gas passage 10B is increased, and the exhaust gas flow rate in the reforming catalyst side exhaust gas passage 10A is decreased (that is, the water tank temperature rise speed is increased (catalyst temperature rise speed is slowed down) and the process returns to step S2.

In this manner, the process from step S5 to step S7 is repeated until the catalyst temperature and the water tank temperature reach the target temperatures, so that the valve opening of the exhaust bus flow control valve 12 changes to the current situation (vehicle operating conditions), and finally control is executed such that the reforming catalyst 1 and the water tank 2 reach the target temperatures almost simultaneously.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and appropriate modifications can be made within the scope of the claims. For example, in the above embodiment, the target water tank temperature is set to 0° C. where the water in the water tank is thawed. The temperature may be controlled to keep it higher.

INDUSTRIAL APPLICABILITY The present invention can be used for a fuel reformer installed in a vehicle such as an automobile.

E Internal combustion engine U Controller 1 Reforming catalyst 2 Water tank 2A Temperature raising mechanism 3 Reformed gas supply passage 4 Fuel tank 5 Catalyst temperature sensor 6 Water tank temperature sensor 7 Intake port 8 Reformed gas supply amount adjustment valve 10 Exhaust gas passage 10A Reforming catalyst side exhaust gas passage 10B Water tank side exhaust gas passage 11 Exhaust purification catalyst 12 Exhaust gas flow rate adjustment valve 13 Pre-reforming fuel supply passage 21 Catalyst temperature rise speed estimation means 22 Water tank temperature rise speed estimation means 23 Temperature rise speed Comparison means 24 Valve control means

Claims (3)

a reforming catalyst for promoting the steam reforming reaction of the fuel supplied to the internal combustion engine;
a water tank containing water to be supplied to the reforming catalyst;
a reforming catalyst side exhaust gas passage through which the exhaust gas from the internal combustion engine flows to the reforming catalyst side so that the heat of the exhaust gas from the internal combustion engine is given to the reforming catalyst;
a water tank side exhaust gas passage for flowing the exhaust gas from the internal combustion engine to the water tank side so that the heat of the exhaust gas from the internal combustion engine is given to the water tank;
controlling a fuel reforming device provided with an exhaust gas flow control valve for adjusting the flow rate of exhaust gas from the internal combustion engine to the reforming catalyst side exhaust gas passage and the flow rate to the water tank side exhaust gas passage; In a method for controlling a fuel reformer,
a reforming catalyst temperature acquiring step of acquiring the temperature of the reforming catalyst;
a water tank temperature obtaining step of obtaining the temperature of the water tank;
When the temperature of the reforming catalyst obtained in the reforming catalyst temperature obtaining step is lower than a preset target catalyst temperature, the target catalyst temperature required for the temperature of the reforming catalyst to reach the target catalyst temperature is achieved. a catalyst temperature rise rate estimation step for estimating time;
When the temperature of the water tank obtained in the water tank temperature obtaining step is lower than a preset target water tank temperature, the target water tank temperature required for the temperature of the water tank to reach the target water tank temperature is achieved. a water tank temperature rise rate estimation step of estimating time;
a temperature rise speed comparison step of comparing the target catalyst temperature attainment time and the target water tank temperature attainment time;
a valve control step of controlling the exhaust gas flow control valve so that the target catalyst temperature attainment time and the target water tank temperature attainment time approach each other based on the comparison result of the temperature rise speed comparison step; A control method for a fuel reformer. a reforming catalyst for promoting the steam reforming reaction of the fuel supplied to the internal combustion engine;
a water tank containing water to be supplied to the reforming catalyst;
a reforming catalyst side exhaust gas passage through which the exhaust gas from the internal combustion engine flows to the reforming catalyst side so that the heat of the exhaust gas from the internal combustion engine is given to the reforming catalyst;
a water tank side exhaust gas passage for flowing the exhaust gas from the internal combustion engine to the water tank side so that the heat of the exhaust gas from the internal combustion engine is given to the water tank;
an exhaust gas flow rate control valve for adjusting a flow rate of exhaust gas from the internal combustion engine to the reforming catalyst side exhaust gas passage and a flow rate to the water tank side exhaust gas passage;
a reforming catalyst temperature acquiring means for acquiring the temperature of the reforming catalyst;
a water tank temperature acquiring means for acquiring the temperature of the water tank;
A target catalyst temperature required for the temperature of the reforming catalyst to reach the target catalyst temperature when the temperature of the reforming catalyst obtained by the reforming catalyst temperature obtaining means is lower than a preset target catalyst temperature. a catalyst temperature rise rate estimating means for estimating the achievement time;
A target water tank temperature required for the temperature of the water tank to reach the target water tank temperature when the temperature of the water tank obtained by the water tank temperature obtaining means is lower than a preset target water tank temperature. a water tank temperature rise rate estimating means for estimating the achievement time;
a temperature rise rate comparing means for comparing the target catalyst temperature attainment time and the target water tank temperature attainment time;
valve control means for controlling the exhaust gas flow control valve so that the target catalyst temperature attainment time and the target water tank temperature attainment time approach each other based on the comparison result by the temperature rise rate comparison means. reformer. In the fuel reformer of claim 2,
The reforming catalyst side exhaust gas passage and the water tank exhaust gas passage are provided in parallel so as to constitute a part of the exhaust gas passage of the internal combustion engine,
an exhaust purification catalyst disposed on the exhaust gas passage so as to be located downstream of the reforming catalyst;
The water tank exhaust gas passage branches off from the reforming catalyst side exhaust gas passage upstream of the reforming catalyst, and the reforming catalyst side exhaust gas is downstream of the reforming catalyst and upstream of the exhaust purification catalyst. A fuel reformer adapted to merge with the gas passages.

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