Fuel supply device for gaseous fuel

Abstract

To efficiently reduce a difference between an actual temperature and a target temperature of gaseous fuel.SOLUTION: A fuel supply device 200 for an internal combustion engine 10 includes fuel piping 40 for supplying gaseous fuel from a tank 20 to a fuel injection valve 15. A first heat exchanger 80 and a second heat exchanger 90 in which a temperature of a heating medium is lower than that of the first heat exchanger 80 are connected to the fuel piping 40. When an actual temperature of the gaseous fuel is lower than a target temperature of the gaseous fuel and a temperature difference between the actual temperature of the gaseous fuel and the target temperature of the gaseous fuel is large, a control device 100 executes processing for increasing a ratio of the amount of the gaseous fuel to be subjected to heat exchange in the first heat exchanger 80 out of the gaseous fuel to be subjected to heat exchange in the heat exchangers, compared to when the temperature difference is small.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fuel supply device for gaseous fuel. [Background technology]

[0002] For example, Patent Document 1 describes a fuel supply device for gaseous fuel that includes a tank for storing gaseous fuel, a fuel injection valve for supplying the gaseous fuel to a cylinder of an internal combustion engine, and a fuel passage for supplying the gaseous fuel from the tank to the fuel injection valve. This fuel supply device includes a heat exchanger for exchanging heat with the gaseous fuel flowing through the fuel passage, thereby suppressing a temperature drop associated with the expansion of the gaseous fuel and a temperature rise associated with the compression of the gaseous fuel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-166424 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the temperature of the gaseous fuel changes, the density of the gaseous fuel changes, which affects the injection amount accuracy of the fuel injection valve. Therefore, a target temperature is set for the gaseous fuel. Then, it is considered to control the actual temperature of the gaseous fuel so as to reduce the deviation from the target temperature. In this case, it is desired to efficiently reduce the deviation between the actual temperature of the gaseous fuel and the target temperature. [Means for solving the problem]

[0005] A fuel supply device for gaseous fuel that solves the above problem includes a tank for storing gaseous fuel, a fuel injection valve for supplying the gaseous fuel to a cylinder of an internal combustion engine, and a fuel passage for supplying the gaseous fuel from the tank to the fuel injection valve. A heat exchanger that exchanges heat with the gaseous fuel is connected to the fuel passage. The heat exchanger includes a first heat exchanger and a second heat exchanger having a lower temperature of a heat medium than the first heat exchanger. The fuel supply device includes a control device that executes a process to increase the proportion of the amount of the gaseous fuel that is heat exchanged in the first heat exchanger among the amount of the gaseous fuel that is heat exchanged in the heat exchanger when the actual temperature of the gaseous fuel is lower than the target temperature of the gaseous fuel and the temperature difference between the actual temperature of the gaseous fuel and the target temperature of the gaseous fuel is large, compared to when the temperature difference is small. Effect of the Invention

[0006] This fuel supply device for gaseous fuel can efficiently reduce the deviation between the actual temperature of the gaseous fuel and the target temperature. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing a fuel system and a control device of an internal combustion engine in one embodiment. [Diagram 2] 4 is a flowchart showing a procedure of a process executed by the control device of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, a specific embodiment of a fuel supply device for gaseous fuel will be described with reference to FIGS. <About the fuel system and control device of the internal combustion engine> An internal combustion engine 10 shown in FIG. 1 is an internal combustion engine that uses hydrogen gas, which is a gaseous fuel, as fuel.

[0009] The fuel supply device 200 provided in the internal combustion engine 10 includes a fuel injection valve 15, a tank 20, a fuel pipe 40 forming a fuel passage, a first shutoff valve 21, a second shutoff valve 22, a pressure reducing valve 30, and a delivery pipe 60.

[0010] The fuel injector 15 supplies fuel to the cylinders of the internal combustion engine 10 . The tank 20 stores hydrogen gas, which is a gaseous fuel, in a compressed state. The fuel pipe 40 is connected to the tank 20 and a delivery pipe 60 .

[0011] The fuel injection valve 15 is connected to the delivery pipe 60 . The gaseous fuel stored in the tank 20 is supplied to the fuel injection valve 15 via a fuel pipe 40 and a delivery pipe 60 .

[0012] In the fuel pipe 40, a first shutoff valve 21, a pressure reducing valve 30, and a second shutoff valve 22 are arranged in this order in the direction of fuel flow. The first shutoff valve 21 is an electromagnetic valve and is disposed near the outlet of the tank 20. When the first shutoff valve 21 is open, fuel is supplied from the tank 20 to the fuel pipe 40. When the first shutoff valve 21 is closed, fuel supply from the tank 20 to the fuel pipe 40 is stopped.

[0013] The pressure reducing valve 30 is an electromagnetic valve that adjusts the fuel pressure, which is the pressure of the hydrogen gas supplied to the fuel injection valve 15, to a pressure that corresponds to the engine operating state. The second shutoff valve 22 is an electromagnetic valve, and is disposed near the delivery pipe 60. When the second shutoff valve 22 is open, fuel is supplied to the delivery pipe 60. When the second shutoff valve 22 is closed, fuel supply to the delivery pipe 60 is stopped.

[0014] The first shutoff valve 21 and the second shutoff valve 22 are maintained in a closed state while the internal combustion engine 10 is stopped. On the other hand, the first shutoff valve 21 and the second shutoff valve 22 are maintained in an open state while the internal combustion engine 10 is operating.

[0015] A heat exchanger that exchanges heat with the gaseous fuel is connected to the fuel pipe 40. The heat exchanger has a first heat exchanger 80 and a second heat exchanger 90 that has a lower temperature of the heat medium than the first heat exchanger 80.

[0016] A first circulation path 42 for circulating the gaseous fuel within the first heat exchanger 80 is connected to the first heat exchanger 80 . The first circulation path 42 is composed of a pair of flow paths branching off from a portion of the fuel pipe 40 between the pressure reducing valve 30 and the second shutoff valve 22 .

[0017] The amount of gaseous fuel flowing through the first circulation path 42 is adjusted by controlling the aperture of a first valve 44, which is a solenoid valve provided in the first circulation path 42. When the aperture of the first valve 44 is "0" and in a fully closed state, the amount of gaseous fuel flowing through the first circulation path 42 is "0". As the aperture of the first valve 44 increases, the amount of gaseous fuel flowing through the first circulation path 42 increases. The basic value of the aperture of the first valve 44 is "0".

[0018] The first heat exchanger 80 is provided in the exhaust passage 18 of the internal combustion engine 10, and the heat medium is exhaust gas. In the first heat exchanger 80, heat is exchanged between the exhaust gas and the gaseous fuel. Note that, when the delivery pipe 60 becomes hot due to heat received from the internal combustion engine 10, such as during high load operation, the temperature of the gaseous fuel may greatly exceed the outside air temperature, but basically the temperature of the gaseous fuel in the delivery pipe 60 is equal to or lower than the outside air temperature. Also, the temperature of the exhaust gas exceeds the outside air temperature during engine operation. Therefore, the gaseous fuel is heated in the first heat exchanger 80.

[0019] A second circulation path 46 for circulating the gaseous fuel within the second heat exchanger 90 is connected to the second heat exchanger 90 . The second circulation path 46 is composed of a pair of flow paths branching off from the fuel pipe 40 at a location between the pressure reducing valve 30 and the second shutoff valve 22. In addition, the second circulation path 46 branches off from the fuel pipe 40 downstream of the first circulation path 42 in terms of the fuel flow direction.

[0020] The amount of gaseous fuel flowing through the second circulation path 46 is adjusted by controlling the aperture of a second valve 48, which is a solenoid valve provided in the second circulation path 46. When the aperture of the second valve 48 is "0" and in a fully closed state, the amount of gaseous fuel flowing through the second circulation path 46 is "0". As the aperture of the second valve 48 increases, the amount of gaseous fuel flowing through the second circulation path 46 increases. The basic value of the aperture of the second valve 48 is "0".

[0021] The second heat exchanger 90 is a water-cooled oil catch tank that collects oil in the blow-by gas discharged from the internal combustion engine 10, and a water passage 91 for circulating the cooling water of the internal combustion engine 10 is connected to the second heat exchanger 90. The heat medium of the second heat exchanger 90 is the cooling water of the internal combustion engine 10. In the second heat exchanger 90, heat exchange is performed between the cooling water and the gaseous fuel, and between the cooling water and the blow-by gas. The temperature of the cooling water is basically equal to or higher than the outside air temperature. Therefore, the gaseous fuel is also heated in the second heat exchanger 90. However, the temperature of the cooling water is lower than the temperature of the exhaust gas. Therefore, when the gaseous fuel is heated in the first heat exchanger 80, the heating speed of the gaseous fuel is faster than when the gaseous fuel is heated in the second heat exchanger 90. In addition, as described above, when the temperature of the gaseous fuel is significantly higher than the outside air temperature, or when the internal combustion engine 10 is in the middle of warming up and the temperature of the cooling water has not yet increased, the temperature of the cooling water may be lower than the temperature of the gaseous fuel. In this case, the gaseous fuel is cooled in the second heat exchanger 90 .

[0022] The control device 100 performs various controls of the internal combustion engine 10 by controlling various control objects such as the fuel injector 15, the first shutoff valve 21, the pressure reducing valve 30, the second shutoff valve 22, the first valve 44, and the second valve 48. The control device 100 includes a CPU 110 and a memory 120 configured from a ROM, a RAM, and the like, and the CPU 110 executes programs stored in the memory 120 to perform various controls.

[0023] The control device 100 refers to various values ​​necessary for controlling the internal combustion engine 10. For example, the control device 100 refers to a detection signal of an accelerator position sensor 71 that detects an accelerator operation amount ACCP, which is an operation amount of an accelerator pedal operated by a driver of a vehicle equipped with the internal combustion engine 10. The control device 100 also refers to a detection signal of a water temperature sensor 72 that detects a water temperature THW, which is a temperature of the cooling water of the internal combustion engine 10. The control device 100 also refers to a detection signal of a temperature sensor 73 that detects a fuel temperature THf, which is an actual temperature of the gaseous fuel in the delivery pipe 60. In addition, the control device 100 refers to a detection signal for calculating the engine speed of the internal combustion engine 10, a detection signal of an intake air amount, etc.

[0024] <Regarding temperature control of gas fuel> The control device 100 executes the following process during engine operation to efficiently reduce the deviation between the actual temperature of the gaseous fuel and the target temperature.

[0025] The procedure of the above process is shown in Fig. 2. The process shown in Fig. 2 is implemented by the CPU 110 repeatedly executing a program stored in the memory 120 of the control device 100 at predetermined intervals. In the following, step numbers are represented by numbers preceded by "S."

[0026] When this process starts, the control device 100 acquires the fuel temperature THf (S100). Next, the control device 100 calculates a temperature difference Δt between the target temperature THft and the fuel temperature THf (S110). The target temperature THft is a target temperature of the gaseous fuel in the delivery pipe 60, and is set in advance. As an example, in this embodiment, a temperature of about 25 degrees, which is the temperature of the outside air in a standard state, is set as the target temperature THft. The set value of the target temperature THft may be changed as appropriate in consideration of controllability, cost, and the like. The temperature difference Δt is a value obtained by subtracting the fuel temperature THf from the target temperature THft.

[0027] Next, the control device 100 judges whether the fuel temperature THf is lower than the target temperature THft (S120). If it is judged that the fuel temperature THf is lower than the target temperature THft (S120: YES), the control device 100 judges whether the temperature difference Δt is equal to or greater than a threshold value Δtref (S130). The threshold value Δtref is set to a value large enough to accurately judge that the current fuel temperature THf needs to be increased quickly based on the temperature difference Δt being equal to or greater than the threshold value Δtref.

[0028] When it is determined in the process of S130 that the temperature difference Δt is equal to or greater than the threshold value Δtref (S130: YES), the control device 100 sets the opening of the first valve 44 based on the temperature difference Δt (S160). In the process of S160, the control device 100 sets the opening of the first valve 44 so that the opening increases as the temperature difference Δt increases. As a result, the amount of gaseous fuel that exchanges heat with the first heat exchanger 80 is adjusted to increase as the temperature difference Δt increases. In the process of S160, the control device 100 maintains the opening of the second valve 48 at a basic value of "0".

[0029] On the other hand, when it is determined in the process of S130 that the temperature difference Δt is less than the threshold value Δtref (S130: NO), the control device 100 sets the opening of the second valve 48 based on the temperature difference Δt (S170). In the process of S170, the control device 100 sets the opening of the second valve 48 so that the opening increases as the temperature difference Δt increases. As a result, the amount of gaseous fuel that exchanges heat with the second heat exchanger 90 is adjusted to increase as the temperature difference Δt increases. In the process of S170, the control device 100 maintains the opening of the first valve 44 at the basic value of "0".

[0030] In the process of S120 described above, when it is determined that the fuel temperature THf is equal to or higher than the target temperature THft (S120: NO), the control device 100 determines whether the fuel temperature THf is higher than the target temperature THft (S140).

[0031] If it is determined that the fuel temperature THf is higher than the target temperature THft (S140: YES), the control device 100 acquires the current water temperature THW and determines whether or not the water temperature THW is lower than the fuel temperature THf (S150).

[0032] If it is determined in the process of S150 that the water temperature THW is lower than the fuel temperature THf (S150: YES), the control device 100 sets the opening of the second valve 48 based on the temperature difference Δt (S180). In the process of S180, the control device 100 sets the opening of the second valve 48 so that the opening increases as the temperature difference Δt increases. As a result, the amount of gaseous fuel that exchanges heat with the second heat exchanger 90 is adjusted to increase as the temperature difference Δt increases. In the process of S180, the control device 100 maintains the opening of the first valve 44 at a basic value of "0".

[0033] Then, after executing any one of the processes of S160, S170, and S180, or if a negative determination is made in any one of the processes of S140 and S150, the control device 100 ends this process in the current execution cycle.

[0034] <effect> The operation of this embodiment will be described. As the gaseous fuel in the tank 20 is consumed, the temperature of the gaseous fuel in the tank 20 decreases with a decrease in the pressure in the tank 20. Therefore, the temperature of the gaseous fuel supplied to the fuel injection valve 15 via the delivery pipe 60 also decreases with the consumption of the fuel.

[0035] Here, as shown in Fig. 2, when the fuel temperature THf is lower than the target temperature THft (S120: YES) and the temperature difference Δt between the fuel temperature THf and the target temperature THft is greater than or equal to the threshold value Δtref (S130: YES), the process of S160 is executed. In the process of S160, a process is executed to increase the ratio of the amount of gaseous fuel that is heat exchanged in the first heat exchanger 80 to the amount of gaseous fuel that is heat exchanged in the heat exchanger. More specifically, the aperture of the second valve 48 is maintained at "0" to be in a closed state, while the aperture of the first valve 44 is set based on the temperature difference Δt. As a result, the temperature of the gaseous fuel is raised using only the first heat exchanger 80.

[0036] <Effects> The effects of this embodiment will be described. (1) When the fuel temperature THf is lower than the target temperature THft (S120: YES in FIG. 2), the gaseous fuel is heated in the heat exchanger, so that the difference between the fuel temperature THf and the target temperature THft is reduced. Here, when the temperature difference Δt between the fuel temperature THf and the target temperature THft is large (S130: YES in FIG. 2), the ratio of the amount of gaseous fuel heat-exchanged in the first heat exchanger 80 among the amount of gaseous fuel heat-exchanged in the heat exchanger is increased. Therefore, the heating speed of the gaseous fuel is faster than when the ratio of the amount of gaseous fuel heat-exchanged in the second heat exchanger 90, which has a lower temperature of the heat medium than the first heat exchanger 80, is increased. Therefore, the difference between the fuel temperature THf and the target temperature THft can be efficiently reduced.

[0037] (2) When the fuel temperature THf is lower than the target temperature THft (S120: YES in FIG. 2), the gaseous fuel is heated in the heat exchanger, so that the difference between the fuel temperature THf and the target temperature THft becomes small. Here, when the temperature difference Δt between the fuel temperature THf and the target temperature THft is small (S130: NO in FIG. 2), the ratio of the amount of gaseous fuel heat-exchanged in the second heat exchanger 90 among the amount of gaseous fuel heat-exchanged in the heat exchanger is increased. More specifically, the opening degree of the first valve 44 is maintained at "0" to be in a closed state, while the opening degree of the second valve 48 is set based on the temperature difference Δt. As a result, the temperature of the gaseous fuel is raised using only the second heat exchanger 90. Therefore, the heating speed of the gaseous fuel becomes slower than when the ratio of the amount of gaseous fuel heat-exchanged in the first heat exchanger 80, which has a higher temperature of the heat medium than the second heat exchanger 90, is increased. Therefore, the controllability of the temperature of the gaseous fuel when the amount of the gaseous fuel undergoing heat exchange is improved.

[0038] (3) When the fuel temperature THf is higher than the target temperature THft (S140 in FIG. 2: YES) and the water temperature THW, which is the temperature of the heat medium of the second heat exchanger 90, is lower than the fuel temperature THf (S150 in FIG. 2: YES), the control device 100 executes the process of S180. That is, the opening degree of the first valve 44 is maintained at "0" to be in a closed state, while the opening degree of the second valve 48 is set based on the temperature difference Δt. As a result, the heat exchange of the gaseous fuel is performed only in the second heat exchanger 90, and the gaseous fuel is cooled in the second heat exchanger 90. Therefore, even in a situation where the gaseous fuel is likely to be in a high temperature state, the deviation between the fuel temperature THf and the target temperature THft can be reduced.

[0039] (4) Since the difference between the fuel temperature THf and the target temperature THft can be reduced, the temperature of the gaseous fuel is stabilized, and therefore the accuracy of the injection amount of the fuel injection valve 15 is stabilized. <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0040] In the process of S160, the opening degree of the second valve 48 is maintained at the basic value of "0". Alternatively, the opening degree of the second valve 48 may be set to a value other than "0", for example, based on the temperature difference Δt. Even in this modified example, the opening degrees of the first valve 44 and the second valve 48 are adjusted so that the proportion of the amount of gaseous fuel heat-exchanged in the first heat exchanger 80 is increased among the total amount of gaseous fuel heat-exchanged in the first heat exchanger 80 and the second heat exchanger 90. This makes it possible to obtain the same effect as in (1) above.

[0041] In the process of S170, the opening degree of the first valve 44 is maintained at the basic value of "0". Alternatively, the opening degree of the first valve 44 may be set to a value other than "0" based on, for example, the temperature difference Δt. Even in this modified example, the opening degrees of the first valve 44 and the second valve 48 are adjusted so that the ratio of the amount of gaseous fuel heat-exchanged in the second heat exchanger 90 to the total amount of gaseous fuel heat-exchanged in the first heat exchanger 80 and the second heat exchanger 90 becomes large. This makes it possible to obtain the same effect as in (2) above.

[0042] The second heat exchanger 90 may use cooling water as a heat medium, and the target for heat exchange by the heat medium is not limited to blow-by gas. For example, a water-cooled intercooler may be used. The heat medium of the second heat exchanger 90 may be, for example, a lubricating oil for the internal combustion engine 10 other than water.

[0043] The branching position of the first circulation path 42 in the fuel pipe 40 may be changed as appropriate. In addition, the branching position of the second circulation path 46 in the fuel pipe 40 may also be changed as appropriate. The positions of the first circulation path 42 and the second circulation path 46 may be interchanged. In other words, the second circulation path 46 may branch off from the fuel pipe 40 upstream of the first circulation path 42 in the fuel flow direction.

[0044] The gaseous fuel is hydrogen gas, but other gaseous fuels, such as compressed natural gas, may be used. The control device 100 includes a CPU 110 and a memory 120, and executes software processing. However, this is merely an example. The control device 100 may include, for example, a dedicated hardware circuit (e.g., ASIC, etc.) that processes at least a part of the software processing executed in the above embodiment. That is, the control device 100 may have any of the following configurations (a) to (c). (a) A processing device that executes all of the above processing according to a program, and a program storage device such as a memory that stores the program. (b) A processing device and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) A dedicated hardware circuit that executes all of the above processing. Here, the software circuit including the processing device and the program storage device, and the dedicated hardware circuit may be multiple. That is, the above processing may be executed by a processing circuit that includes at least one of one or more software circuits and one or more dedicated hardware circuits. The program storage device, i.e., the computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. [Explanation of symbols]

[0045] 10. Internal combustion engine 15...Fuel injection valve 18...Exhaust passage 20. Tank 21…First shutoff valve 22...Second shutoff valve 30…Reducing valve 40…Fuel piping 42…1st circulation route 44…First valve 46…Second circulation route 48…Second valve 60…Delivery pipe 71...Accelerator position sensor 72...Water temperature sensor 73...Temperature sensor 80...1st heat exchanger 90…Second heat exchanger 91…Water passage 100...Control device 110…CPU 120…Memory 200…Fuel supply device

Claims

1. A fuel supply device for gaseous fuel, comprising: a tank for storing gaseous fuel; a fuel injection valve for supplying the gaseous fuel to a cylinder of an internal combustion engine; and a fuel passage for supplying the gaseous fuel from the tank to the fuel injection valve, a heat exchanger that exchanges heat with the gas fuel is connected to the fuel passage; The heat exchanger includes a first heat exchanger and a second heat exchanger in which a temperature of a heat medium is lower than that of the first heat exchanger, When the actual temperature of the gas fuel is lower than the target temperature of the gas fuel and the temperature difference between the actual temperature of the gas fuel and the target temperature of the gas fuel is large, a ratio of the amount of the gas fuel that is heat exchanged in the first heat exchanger to the amount of the gas fuel that is heat exchanged in the heat exchanger is increased compared to when the temperature difference is small. A fuel supply system for gaseous fuel.

2. The control device executes a process of performing heat exchange between the gas fuel and only the second heat exchanger when the actual temperature of the gas fuel is higher than the target temperature of the gas fuel and the temperature of the heat medium of the second heat exchanger is lower than the actual temperature of the gas fuel.

2. A fuel supply system for gaseous fuel according to claim 1.

3. The control device executes a process of adjusting the amount of the gaseous fuel that exchanges heat with the heat exchanger based on the temperature difference.

2. A fuel supply system for gaseous fuel according to claim 1.

4. The heat medium of the first heat exchanger is exhaust gas from the internal combustion engine.

2. A fuel supply system for gaseous fuel according to claim 1.

5. The heat medium of the second heat exchanger is the cooling water of the internal combustion engine.

2. A fuel supply system for gaseous fuel according to claim 1.

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