JP2021032144A - Fuel supply device of natural gas engine - Google Patents

Abstract

To avoid an abnormal rise of pressure in a tank.SOLUTION: A fuel supply device of a natural gas engine comprises: a first tank T1 and a second tank T2 for liquefying and storing fuel being a natural gas; a first valve V1 and a second valve V2 arranged at the first tank and the second tank, respectively; a detection unit for detecting a quantity of a liquid component of the fuel stored in the first tank and the second tank; and a control unit 100 for controlling the opening/closing of the first valve and the second valve on the basis of the quantity of the liquid component of the fuel which is detected by the detection unit. When a prescribed closing-prohibition condition for prohibiting the valve-closing of one valve is established even if a prescribed closing condition for valve-closing either of the first valve and the second valve is established, the control unit prohibits the valve-closing of one valve.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a fuel supply device for a natural gas engine that uses natural gas as fuel.

Some fuel supply devices for such natural gas engines are provided with a plurality of tanks for liquefying and storing fuel.

Japanese Unexamined Patent Publication No. 2014-152869

In such a case, it is preferable that the liquid fuel in each tank is consumed as evenly as possible. Therefore, a valve is provided in each tank, and the valve of each tank is opened and closed as appropriate to equalize the consumption of liquid fuel in each tank as much as possible.

However, when a valve is closed, it becomes very difficult to reduce the pressure in the tank corresponding to the valve. Therefore, there is a risk that the pressure inside the tank will rise abnormally, and it is necessary to take some measures.

Therefore, the present disclosure was devised in view of such circumstances, and an object thereof is to provide a fuel supply device for a natural gas engine capable of avoiding an abnormal increase in pressure in a tank.

According to one aspect of the present disclosure
The first and second tanks that liquefy and store fuel, which is natural gas,
The first valve and the second valve provided for the first tank and the second tank, respectively,
A detection unit for detecting the amount of the liquid component of the fuel stored in the first tank and the second tank, respectively.
A control unit that controls the opening and closing of the first valve and the second valve based on the amount of the liquid component of the fuel detected by the detection unit.
With
The control unit has a predetermined closing prohibition condition for prohibiting the closing of one of the first valve and the second valve even when a predetermined closing condition for closing one of the first valve and the second valve is satisfied. When is satisfied, a fuel supply device for a natural gas engine is provided, which is characterized by prohibiting the closing of one of the valves.

Preferably, the closing prohibition condition is when the pressure in the tank corresponding to the one is equal to or higher than a predetermined abnormality determination value, or when the pressure sensor provided for the tank corresponding to the one is abnormal. To establish.

According to the present disclosure, it is possible to avoid an abnormal increase in pressure in the tank.

It is the schematic which shows the fuel supply apparatus of the natural gas engine which concerns on this embodiment. It is a figure which shows the method of opening / closing control of a 1st valve and a 2nd valve. It is a flowchart of the control routine of this embodiment. It is a time chart which shows an example of the control of this embodiment. It is a time chart which shows an example of control of a modification example. It is a flowchart of the control routine of the modification.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the following embodiments.

FIG. 1 is a schematic view showing a fuel supply device for a natural gas engine according to the present embodiment. An engine as an internal combustion engine (not shown) is a natural gas engine that uses natural gas as fuel, and is used as a power source for vehicles, particularly large vehicles such as trucks. However, the use of the engine is arbitrary, and it may be applied to a moving body other than a vehicle, for example, a ship, a construction machine, or an industrial machine. Further, the engine does not have to be mounted on a moving body, and may be a stationary engine.

The engine is provided with an injector 1 for each cylinder. The fuel supply device is for supplying fuel to the injector 1. The supplied fuel is injected from the injector 1 when the injector 1 is opened.

The fuel supply device includes a first tank T1 and a second tank T2 for liquefying and storing fuel, and a first valve V1 and a second valve V2 provided for the first tank T1 and the second tank T2, respectively. A detection unit for detecting (including estimation) the amount of the liquid component of the fuel stored in the first tank T2 and the second tank T2, respectively, and a first unit based on the amount of the liquid component of the fuel detected by the detection unit. It includes a control unit that controls opening and closing of the valve V1 and the second valve V2.

Since the first tank T1 and the second tank T2 are similar, only the first tank T1 will be described as a representative. The first tank T1 stores compressed and liquefied natural gas (LNG (Liquefied Natural Gas)) inside. The liquid component of the fuel is accumulated in the lower layer in the first tank T1. The liquid component of this fuel is referred to as a liquid fuel and is represented by the symbol L. The gas component of the fuel is accumulated in the upper layer in the first tank T1. The gas component of this fuel is referred to as a gaseous fuel and is represented by the reference numeral G. When liquid fuel and gaseous fuel are not distinguished, they are collectively referred to as fuel and are represented by reference numeral F.

As is well known, the fuel F contains a carbon compound such as methane, ethane, propane and butane as a composition. Each composition has a different boiling point and a different octane number. Methane has the highest octane number, and then ethane, propane, and butane have the lowest octane numbers.

The upstream ends of the first tank outlet pipe B1 and the second tank outlet pipe B2 are individually connected to the upper ends of the first tank T1 and the second tank T2. The downstream ends of the first tank outlet pipe B1 and the second tank outlet pipe B2 are merged and connected to the upstream ends of the common fuel supply pipe 2. The downstream end of the fuel supply pipe 2 is branched and connected to the injector 1 of each cylinder (only one cylinder is shown). A pressure reducing valve 3 for reducing the fuel pressure to an appropriate pressure is provided in the middle of the fuel supply pipe 2.

Since the first valve V1 and the second valve V2 are similar, only the first valve V1 will be described as a representative. The first valve V1 is formed by a solenoid valve and is installed in the first tank outlet pipe B1. When the first valve V1 is opened, it is allowed that the gaseous fuel of the first tank T1 is supplied to the injector 1 through the first tank outlet pipe B1 and the fuel supply pipe 2. On the other hand, when the first valve V1 is closed, the supply of such gaseous fuel is prohibited.

On the upstream side of the first valve V1 in the first tank outlet pipe B1, a first pressure sensor Sp1 for detecting the pressure in the first tank T1 and a first for detecting the temperature in the first tank T1. A temperature sensor St1 is provided. The first pressure sensor Sp1 and the first temperature sensor St1 substantially detect the pressure and temperature of the gaseous fuel G in the first tank T1. The second tank outlet pipe B2 is also provided with a similar second pressure sensor Sp2 and a second temperature sensor St2. The pressure sensor and the temperature sensor may be provided in the tank.

The control unit is formed by an electronic control unit (referred to as an ECU (Electronic Control Unit)) 100. The ECU 100 also controls the entire engine including the injector 1. The ECU 100 includes a CPU (Central Processing Unit) having a calculation function, a storage medium such as a ROM (Read Only Memory) and a RAM (Random Access Memory), an input / output port, and a storage device other than the ROM and the RAM. The ECU 100 receives the output signals of the above-mentioned sensors and the like via wirings and wireless communication devices (not shown), and outputs the instruction signals to the above-mentioned valves and the injector 1 and the like.

The ECU 100 detects the amount M1 of the liquid fuel L in the first tank T1 based on the pressure P1 detected by the first pressure sensor Sp1 and the temperature T1 detected by the first temperature sensor St1 (specifically, presume.

Specifically, the ECU 100 applies the pressure P1 and the temperature T1 to the gas state equation (PV = nRT) to calculate the volume Vg of the gas fuel G. Next, the ECU 100 calculates the amount (remaining amount) M1 of the liquid fuel L by subtracting the volume Vg of the gas fuel G from the total volume of the first tank T1 and the first tank outlet pipe B1 stored in advance.

Similarly, the ECU 100 detects the amount M2 of the liquid fuel L in the second tank T2 based on the pressure P2 detected by the second pressure sensor Sp2 and the temperature T2 detected by the second temperature sensor St2.

As described above, the above-mentioned detection unit is composed of the first pressure sensor Sp1, the first temperature sensor St1, the second pressure sensor Sp2, the second temperature sensor St2, and the ECU 100.

Generally, in order to detect the amount of liquid fuel in the tank, a method of installing a fuel level sensor in the tank is adopted. However, fuel level sensors are generally expensive. On the other hand, pressure sensors and temperature sensors are generally inexpensive because they are general-purpose products that are also used in other applications. In the present embodiment, since the detection unit is composed of the pressure sensor and the temperature sensor, there is an advantage that the detection unit can be manufactured at low cost. However, a fuel level sensor may be used as long as there is no problem in terms of cost.

The pressure in each tank is highly dependent on the ambient temperature of each tank, but in a vehicle, the ambient temperature of each tank is not always equal due to the layout of engine cooling water and fuel piping. Therefore, the vaporization rate from the liquid fuel L to the gas fuel G is higher in the tank having the higher atmospheric temperature than in the tank having the lower atmosphere temperature, and the pressure of the gas fuel G is higher. Therefore, if both the first valve V1 and the second valve V2 are opened, the gas fuel G in the tank having the higher pressure continues to be consumed preferentially or unilaterally, and the liquid fuel L in the tank is unilaterally consumed. Continues to decrease. In other words, the amount of fuel consumed may be biased, and a situation may occur in which fuel continues to be consumed in one tank while fuel is not consumed in the other tank.

In this case, in the tank with no fuel consumption, the composition ratio of the composition having a large number of carbon atoms (for example, propane) is increased in the composition of the gaseous fuel G, and the composition ratio of the composition having a small number of carbon atoms (for example, methane) is increased. The phenomenon of becoming heavier, that is, becomes lower, progresses. Then, since the octane number of the gas fuel G decreases, there arises a problem that the engine is knocked when the gas fuel G in the tank is started to be used.

Therefore, it is preferable that the fuel consumption of each tank is not biased and equalized. Therefore, in the present embodiment, the first valve V1 and the second valve V2 are controlled to open and close so that the amount of liquid fuel in each tank is equalized as much as possible.

Specifically, as will be described later, the ECU 100 calculates the difference in the amount of liquid fuel in each tank, and controls the opening and closing of the first valve V1 and the second valve V2 so that the difference is equal to or less than a certain value. As a result, the amount of liquid fuel in each tank can be equalized, and it is possible to suppress the occurrence of knocking and the decrease in output due to the heaviness of the fuel.

By the way, when one of the first valve V1 and the second valve V2 is closed, it becomes very difficult to reduce the pressure in the tank corresponding to the one valve. Therefore, there is a risk that the pressure inside the tank will rise abnormally, and it is necessary to take some measures.

Therefore, in the present embodiment, the following control is performed to avoid an abnormal increase in the pressure in the tank.

FIG. 2 shows a method of opening / closing control of the first valve V1 and the second valve V2 executed by the ECU 100. The vertical axis shows the remaining amount difference ΔM (= M1-M2), which is the difference between the amounts of the liquid fuel L in the first tank T1 and the second tank T2, and this is calculated by the ECU 100.

The ECU 100 compares the remaining amount difference ΔM with a predetermined threshold value β, α, −α, −β (α, β> 0, β> α), and each time the remaining amount difference ΔM exceeds or falls below the threshold value, the number is changed. The open / closed state of one of the 1st valve V1 and the 2nd valve V2 is switched. Such switching has a hysteresis characteristic to prevent hunting. Specifically, it is as follows.

(1) The ECU 100 switches the second valve V2 from opening to closing when a predetermined second valve closing condition (referred to as V2 closing condition) is satisfied. The V2 closing conditions are (i) the first valve V1 is open, (ii) the second valve V2 is open, and (iii) the remaining amount difference ΔM exceeds the second valve closing threshold (referred to as V2 closing threshold) β. It is established when This corresponds to the transition from state I to state II in FIG.

When the V2 closing condition is satisfied, the remaining amount difference ΔM is large, and the amount of liquid fuel M2 in the second tank T2 is considerably smaller than the amount of liquid fuel M1 in the first tank T1. Therefore, in this case, the second valve V2 is closed in order to eliminate the fuel consumption of the second tank T2. As a result, the amount of liquid fuel can be equalized.

(2) The ECU 100 switches the second valve V2 from closed to open when a predetermined second valve opening condition (referred to as V2 opening condition) is satisfied. The V2 opening conditions are (i) the first valve V1 is open, (ii) the second valve V2 is closed, and (iii) the remaining amount difference ΔM is lower than the second valve opening threshold (referred to as V2 opening threshold) α. It is established when This corresponds to the transition from state II to state III in FIG.

When the V2 opening condition is satisfied, the remaining amount difference ΔM is smaller than before, and the liquid fuel amount M1 in the first tank T1 is reduced due to consumption and approaches the liquid fuel amount M2 in the second tank T2. Therefore, in this case, the second valve V2 is opened to allow the fuel consumption of the second tank T2.

(3) The ECU 100 switches the first valve V1 from opening to closing when a predetermined first valve closing condition (referred to as V1 closing condition) is satisfied. The V1 closing conditions are (i) the first valve V1 is open, (ii) the second valve V2 is open, and (iii) the remaining amount difference ΔM is the first valve closing threshold (referred to as V1 closing threshold) -β. It is established when it falls below. This corresponds to the transition from state III to state IV in FIG.

When the V1 closing condition is satisfied, the absolute value of the remaining amount difference ΔM is large, and the amount of liquid fuel M1 in the first tank T1 is considerably smaller than the amount of liquid fuel M2 in the second tank T2. Therefore, in this case, the first valve V1 is closed in order to eliminate the fuel consumption of the first tank T1. As a result, the amount of liquid fuel can be equalized.

In the present embodiment, the absolute value of the V1 closed threshold value −β is made equal to the absolute value of the V2 closed threshold value β, but may be different.

(4) The ECU 100 switches the first valve V1 from closed to open when a predetermined first valve opening condition (referred to as V1 opening condition) is satisfied. The V1 open conditions are (i) the first valve V1 is closed, (ii) the second valve V2 is open, and (iii) the remaining amount difference ΔM is the first valve open threshold (referred to as V1 open threshold) −α. It is established when it exceeds. This corresponds to the transition from state IV to state V in FIG.

When the V1 opening condition is satisfied, the absolute value of the remaining amount difference ΔM is smaller than before, and the liquid fuel amount M2 of the second tank T2 becomes smaller due to consumption and approaches the liquid fuel amount M1 of the first tank T1. There is. Therefore, in this case, the first valve V2 is opened to allow the fuel consumption of the first tank T1.

In the present embodiment, the absolute value of the V1 open threshold value −α is made equal to the absolute value of the V2 open threshold value α, but may be different.

In the state where the first valve V1 is open and the second valve V2 is open (I, III, V), only the gas fuel G having the higher pressure among the gas fuels G in both tanks is directed toward the injector 1. Be supplied.

By the way, for example, even if the V2 closing condition is satisfied as described in (1), if the second valve V2 is closed as it is according to this, the pressure in the second tank T2 may rise abnormally and cause a problem. ..

This case is, for example, a case where boil-off gas is generated in the second tank T2. When boil-off gas is generated, the pressure in the second tank T2 may rise abnormally. In that case, the second tank T2 may be damaged.

Therefore, in the present embodiment, the second valve closing prohibition condition (referred to as V2 closing prohibition condition) for prohibiting the closing of the second valve V2 is set in advance, and even when the V2 closing condition is satisfied, V2 is closed. When the prohibition condition is satisfied, the closing of the second valve V2 is prohibited. As a result, the second valve V2 is opened, and it is possible to prevent the pressure in the second tank T2 from rising abnormally.

Specifically, the V2 closing prohibition condition is satisfied when the pressure P2 detected by the second pressure sensor Sp2 is equal to or higher than the predetermined abnormality determination value P2s, or when the second pressure sensor Sp2 is abnormal. When the pressure P2 becomes the abnormality determination value P2s or more, it can be considered that the pressure in the second tank T2 has risen abnormally due to the generation of boil-off gas. To avoid. When the second valve V2 is opened, the generated boil-off gas can be consumed and the pressure in the tank can be lowered to less than the abnormality determination value P2s. On the other hand, when the second pressure sensor Sp2 is abnormal, the detection value itself of the second pressure sensor Sp2, which is the comparison target with the abnormality determination value P2s, is unreliable. Therefore, for safety, the second valve V2 is closed. To avoid an abnormal rise in pressure inside the tank. Whether or not the second pressure sensor Sp2 is abnormal can be determined by the diagnostic function of the ECU 100 or the self-diagnosis function of the second pressure sensor Sp2 itself.

The valve closing prohibition based on such a closing prohibition condition is similarly applied even when the V1 closing condition is satisfied as described in (3) above. Briefly, the first valve closing prohibition condition (referred to as V1 closing prohibition condition) is set in advance, and even when the V1 closing prohibition condition is satisfied, when the V1 closing prohibition condition is satisfied, the first valve is satisfied. V1 valve closing is prohibited. Specifically, the V1 closing prohibition condition is satisfied when the pressure P1 detected by the first pressure sensor Sp1 is equal to or higher than a predetermined abnormality determination value P1s, or when the first pressure sensor Sp1 is abnormal.

Next, the control routine in this embodiment will be described with reference to FIG. The illustrated routine is repeatedly executed by the ECU 100 every predetermined calculation cycle τ (for example, 10 msec).

First, in step S101, it is determined whether or not the V1 opening condition is satisfied. If it is not established, the process proceeds to step S103, and if it is established, the first valve V1 is opened in step S102, and then the process proceeds to step S103.

In step S103, it is determined whether or not the V2 opening condition is satisfied. If it is not established, the process proceeds to step S105, and if it is established, the second valve V2 is opened in step S104, and then the process proceeds to step S105.

In step S105, it is determined whether or not the V1 closing condition is satisfied. If not, the process proceeds to step S108.

If it is satisfied, it is determined in step S106 whether or not the V1 closing prohibition condition is satisfied. If it is not satisfied, the process proceeds to step S107, the first valve V1 is closed, and then the process proceeds to step S108.

On the other hand, if it is established, step S107 is skipped and the process proceeds to step S108. As a result, the closing of the first valve V1 is substantially prohibited, and the first valve V1 is opened.

Similarly, in step S108, it is determined whether or not the V2 closing condition is satisfied. If not, the routine ends.

If it is satisfied, it is determined in step S109 whether or not the V2 closing prohibition condition is satisfied. If it is not satisfied, the process proceeds to step S110 to close the second valve V2, and then the routine ends.

On the other hand, if it is established, step S110 is skipped and the routine is terminated. As a result, the closing of the second valve V2 is substantially prohibited, and the second valve V2 is opened.

FIG. 4 shows an example of the control of the present embodiment. The horizontal axis is time t. Before time t1, the first valve V1 is open and the second valve V2 is open, and only the gas fuel G of the second tank T2 having the higher pressure is unilaterally consumed, and the liquid of the second tank T2 is consumed. Only the amount of fuel M2 is reduced.

At time t1, the second valve V2 is closed because the remaining amount difference ΔM exceeds the V2 closing threshold β and the V2 closing condition is satisfied and the V2 closing prohibition condition is not satisfied. As a result, the consumption of the gas fuel G in the second tank T2 is stopped, and only the gas fuel G in the first tank T1 is consumed, so that the amount of liquid fuel can be equalized.

After that, at time t2, the remaining amount difference ΔM fell below the V2 opening threshold value α, so that the second valve V2 was opened.

After that, at time t3, the remaining amount difference ΔM falls below the V1 closing threshold value −β, and the V1 closing condition is satisfied. However, at this time, since the V1 closing prohibition condition is satisfied, the closing of the first valve V1 is prohibited, and the first valve V1 is still in the open state.

Although not shown, the first valve V1 will be closed when the V1 closing prohibition condition is not satisfied.

Next, a modified example will be described. As shown in FIG. 5, in this modified example, basically, the open / closed state of the first valve V1 and the second valve V2 is alternately switched every time the operating time tk of the engine elapses for a predetermined time γ. As a result, the fuel in the first tank T1 and the fuel in the second tank T2 are consumed alternately at equal intervals, so that the amount of liquid fuel in each tank can be equalized.

On the other hand, when the V1 closing prohibition condition is satisfied even after the lapse of the predetermined time γ, the switching to close the first valve V1 is not performed. Similarly, when the V2 closing prohibition condition is satisfied even after the lapse of the predetermined time γ, the switching to close the second valve V2 is not performed.

The ECU 100 counts the operation time tk by its own timer, and resets the operation time tk to zero when the open / closed state of both valves is switched.

The basic control of this modification is as follows.

(1) When a predetermined V2 closing condition is satisfied, the ECU 100 switches the second valve V2 from opening to closing and switches the first valve V1 from closing to opening. The V2 closing condition is satisfied when (i) the first valve V1 is closed, (ii) the second valve V2 is open, and (iii) the operating time tk exceeds the predetermined time γ. This corresponds to switching at time t1 in FIG.

(2) When the predetermined V1 closing condition is satisfied, the ECU 100 switches the first valve V1 from the valve opening to the valve closing and the second valve V2 from the valve closing to the valve opening. The V1 closing condition is satisfied when (i) the first valve V1 is open, (ii) the second valve V2 is closed, and (iii) the operating time tk exceeds the predetermined time γ. This corresponds to switching at time t2 in FIG.

On the other hand, the V1 closing prohibition condition and the V2 closing prohibition condition in this modification are the same as those in the above-mentioned basic embodiment.

Even when the V2 closing condition is satisfied, when the V2 closing prohibition condition is satisfied, the second valve V2 is not switched to the closed valve and the first valve V1 is not switched to the open valve. .. This corresponds to the state at time t3 in FIG.

Similarly, although not shown, even when the V1 closing condition is satisfied, when the V1 closing prohibition condition is satisfied, the first valve V1 is switched to the closed valve and the second valve V2 is opened. Is not switched.

FIG. 6 shows a control routine of this modified example. In this modification, steps S101 to S104 of the basic embodiment (FIG. 3) are omitted, and only steps S205 to S210 similar to steps S105 to S110 of the basic embodiment are executed. As a result, the control of this modified example can be smoothly executed.

Although the embodiments of the present disclosure have been described in detail above, various other embodiments and modifications of the present disclosure can be considered.

(1) For example, the number of tanks for storing fuel and the corresponding valves may be three or more. In this case, the present disclosure is applicable to any two.

(2) Similarly, the number of tank outlet pipes, pressure sensors, and temperature sensors corresponding to the tank may be three or more.

The embodiments of the present disclosure are not limited to the above-described embodiments, and all modifications, applications, and equivalents included in the ideas of the present disclosure defined by the claims are included in the present disclosure. Therefore, the present disclosure should not be construed in a limited manner and may be applied to any other technique belonging within the scope of the ideas of the present disclosure.

T1 1st tank T2 2nd tank V1 1st valve V2 2nd valve Sp1 1st pressure sensor Sp2 2nd pressure sensor 100 Electronic control unit (ECU)

Claims (2)

The first and second tanks that liquefy and store fuel, which is natural gas,
The first valve and the second valve provided for the first tank and the second tank, respectively,
A detection unit for detecting the amount of the liquid component of the fuel stored in the first tank and the second tank, respectively.
A control unit that controls the opening and closing of the first valve and the second valve based on the amount of the liquid component of the fuel detected by the detection unit.
With
The control unit has a predetermined closing prohibition condition for prohibiting the closing of one of the first valve and the second valve even when a predetermined closing condition for closing one of the first valve and the second valve is satisfied. A fuel supply device for a natural gas engine, characterized in that the closing of one of the valves is prohibited when the above is satisfied. The closing prohibition condition is satisfied when the pressure in the tank corresponding to the one is equal to or higher than a predetermined abnormality determination value, or when the pressure sensor provided for the tank corresponding to the one is abnormal. The fuel supply device for a natural gas engine according to claim 1.

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