JPH0610772A - Hydrogen engine - Google Patents

Abstract

PURPOSE:To promote the release of hydrogen gas from hydrogen storage alloy during high load operation of a hydrogen engine during which the demand volume of fuel is large and the engine is operated at an air-fuel ratio such that NOx is like to be emitted, and to prevent earlier ignition so as to sufficiently restrain emission of NOx. CONSTITUTION:In a hydrogen engine fed with hydrogen from a hydrogen storage tank 16 having hydrogen storage alloy which releases hydrogen when it is heated, an EGR passage 30 incorporating an EGR valve 33 is formed, and a heat-exchange part 32 for supplying heat from EGR gas is connected in the EGR passage 30. Further, an ECU 40 controls the air-fuel ratio so as to set it as lambda=1 in a high load range, and controls the EGR valve 33 for supplying EGR gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen engine in which hydrogen is supplied from a hydrogen storage tank having a hydrogen storage alloy to an engine cylinder.

[0002]

2. Description of the Related Art Conventionally, hydrogen gas has been used as a fuel, and the hydrogen gas sent to a passage for supplying hydrogen gas is supplied to a cylinder of an engine through a valve for pressure adjustment and a timing valve that opens and closes at a predetermined timing. A hydrogen engine configured to do so is known (for example, Japanese Patent Publication No. 58-12458).

This type of hydrogen engine requires a hydrogen storage means capable of storing hydrogen gas and releasing the hydrogen gas into a passage for supplying hydrogen gas at any time. As the hydrogen storage means, the hydrogen gas is released by heating. A hydrogen storage tank having a built-in hydrogen storage alloy and having a heating means is conventionally known. For example, JP-A-60-248
In Japanese Patent No. 439, a plurality of fuel cylinders containing a hydrogen storage alloy are arranged in a casing of a tank, and a pipe for supplying engine exhaust gas is connected to the casing.
There is shown a structure in which the fuel cylinder is heated by exhaust gas introduced from this pipe to release hydrogen gas.

[0004]

By the way, since the hydrogen engine does not contain HC and CO in the exhaust gas, it is possible to improve the emission, but depending on the combustion conditions, etc., the reaction with the nitrogen in the air may occur. There is a possibility of NOx generation. As a countermeasure, the air-fuel ratio is made sufficiently leaner than the range where NOx is easily generated, that is, since the range of combustible air-fuel ratio of hydrogen gas is wide, for example, the excess air ratio λ
If the air-fuel ratio is adjusted so that is lean to λ = 2 or more, generation of NOx can be suppressed. However, at least in the high load region of the engine, it is necessary to increase the proportion of fuel to some extent, for example, λ = 1, in order to satisfy the output requirement. Since it is likely to occur, countermeasures are required. Further, in this high load region, since the required fuel amount is large, it is desired to promote the release of hydrogen gas from the hydrogen storage alloy of the hydrogen storage tank. In addition to this, since hydrogen gas has a high ignitability, it is necessary to take care not to cause premature ignition.

In view of the above circumstances, the present invention accelerates the release of hydrogen gas from the hydrogen storage alloy during high load operation in which the fuel demand is high and the air-fuel ratio is such that NOx is likely to be generated. An object of the present invention is to provide a hydrogen engine capable of sufficiently suppressing generation of NOx while preventing early ignition.

[0006]

In order to achieve the above object, the present invention comprises a hydrogen storage tank having a hydrogen storage alloy that releases hydrogen by heating, and heating means for the hydrogen storage tank. In a hydrogen engine in which hydrogen is supplied from a tank to an engine cylinder, an EGR passage for guiding EGR gas from an exhaust passage to an engine cylinder is formed, and an EGR valve for adjusting an EGR gas flow amount is provided in the EGR passage. In addition, a heat exchange part for supplying heat of the EGR gas to the hydrogen storage tank is provided in the middle of the EGR passage, and the air-fuel ratio is controlled according to the operating condition to increase the excess air ratio λ in the high load range. λ =
An air-fuel ratio control means for setting the value within the range of λ <2 at about 1 or more, and an EGR control means for controlling the EGR valve so as to supply the EGR gas to the cylinder of the engine at least in the high load range are provided. It is a thing.

In this structure, the air-fuel ratio control means controls the air-fuel ratio so that λ = 2 or more in the low load range, and the EGR control means controls the cylinder of the engine in the low load range. It is preferable to control the EGR valve so as to stop or reduce the supply of EGR gas.

[0008]

According to the above construction, during the high load operation in which the fuel supply amount is increased to secure the output and the air-fuel ratio becomes the air-fuel ratio in which NOx is easily generated, the temperature is lowered by the heat exchange in the heat exchange section. The above EGR gas is supplied to the cylinder of the engine to obtain the effect of suppressing NOx while preventing premature ignition, and the hydrogen released from the EGR gas to the hydrogen storage tank is promoted.

[0009]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the entire structure of a hydrogen engine according to an embodiment of the present invention. The engine of this embodiment is a rotary piston engine.

The rotary piston engine has a cylinder constituted by a rotor housing 1 and side housings located on both sides of the rotor housing 1, and a substantially triangular rotor 3 which divides three working chambers 2 therein. The rotor 3 is supported by the eccentric shaft 4 and rotates eccentrically,
The volume of each working chamber 2 changes, and an Otto cycle is performed. In a two-rotor rotary piston engine, cylinders are formed in front of and behind the side housing (intermediate housing) at an intermediate position, and a rotor 3 is arranged inside each of them. In FIG. 1, two cylinders are expanded and shown for convenience of drawing.

The side housing is provided with an intake port 6 for supplying air at a position facing the working chamber 2 in the intake stroke. Air is guided to the intake port 6 through an intake passage 7, and the intake passage 7 is provided with a throttle valve 8 operated by an actuator 9 such as a step motor and an air cleaner 10 and the like. There is. An exhaust port 11 is formed in the rotor housing 1 at a position facing the working chamber 2 in the exhaust stroke, and an exhaust passage 12 is connected to the exhaust port 11. A spark plug 13 is attached to the rotor housing 1 at a position facing the working chamber in the explosion stroke.

Further, in order to supply the pressurized hydrogen gas into the cylinder, there is provided a hydrogen port 15 which opens into the working chamber 2 separately from the intake port 6, and this hydrogen port 15
Is provided at a position that opens into the working chamber 2 from the middle of the intake stroke to the middle of the compression stroke. This hydrogen port 15
On the other hand, from the metal hydride tank (hereinafter referred to as MH tank) 16 which is a hydrogen storage tank to the fuel supply passage 17
Hydrogen gas is supplied via the.

The MH tank 16 has a hydrogen storage alloy capable of storing and releasing hydrogen therein. For this MH tank 16, MH is used as a heating means.
A heating pipe (not shown) inside the tank 16 and a heating water introducing passage 18 and a heating water outlet passage 1 connected to the heating pipe.
9 is provided. Then, the heating water introduction passage 1
The upstream end of 8 is connected to a cooling water passage 21 that communicates with the cooling water outflow side of the water jacket 20 of the engine, and the downstream end of the heating water outlet passage 19 is connected to the cooling water inflow side of the water jacket 20. Passage 22
The cooling water flowing out from the water jacket 20 is guided to the MH tank 16 as a heating medium by being connected to the water jacket 20, and is returned to the water jacket side after heating. The heating water introducing passage 18 is provided with an electromagnetic valve 23 for opening and closing the passage, and the heating water outlet passage 19 is provided with a pump 24.

A pressure regulator 2 is provided in the fuel supply passage 17.
6, a flow rate adjusting valve 27, a timing valve 28 and the like are provided. The pressure regulator 26 regulates the hydrogen gas supplied from the MH tank 16 to an appropriate pressure, for example, approximately 5
The pressure is adjusted to atmospheric pressure (3 to 7 atmospheric pressure). Further, the flow rate adjusting valve 27 controls the fuel flow rate by changing the passage area of the fuel supply passage 17 according to a control signal from the ECU 40 described later.

The timing valve 28 has, for example, a valve body 28a located in a communication portion between the hydrogen port 15 and the fuel supply passage 17, and the timing valve drive camshaft rotates in conjunction with the eccentric shaft 4. The valve 28a is opened and closed by a cam 28b. And, so that the intake port 6 is opened near the top dead center and closed near the bottom dead center,
While the timing of opening and closing the intake port due to the rotation of the rotor 3 is set, the opening and closing timing of the timing valve 28 is set so that the timing valve 28 is opened during a predetermined period in the first half of the compression stroke after the intake port 6 is closed. . The reason why the timing valve 28 is opened and the supply of hydrogen gas is started from the time when the intake port 6 is closed and the intake of air is completed is that hydrogen having a large volume ratio is supplied during the air intake process. This is because if the gas is inhaled, the inflow of air is likely to be obstructed and backfire may occur due to the outflow of hydrogen gas to the intake passage 7 side.

Further, as shown in FIG. 1 and in an enlarged view of the essential part of FIG. 2, an EGR passage 30 is provided for guiding a part of the exhaust gas to the cylinder of the engine as EGR gas. The EGR passage 30 has an exhaust passage 12 at one end.
And the other end is connected to the cylinder,
It communicates with the intake port 6 through an EGR port 31 formed in the side housing. A heat exchange portion 32 that passes through the MH tank 16 is provided in the middle of the EGR passage 30. In the heat exchange portion 32, the heat of the EGR gas is M
It is designed to be applied to the hydrogen storage alloy of the H tank 16.

In the vicinity of the cylinder-side end of the EGR passage 30, E which controls the flow of EGR gas is provided.
A GR valve 33 is provided. This EGR valve 3
3 has an actuating portion 34 consisting of a diaphragm device,
It operates according to negative pressure, and its operating portion 34 is connected to a negative pressure introducing passage 35 that communicates with the intake passage 7 downstream of the throttle valve 8. A duty solenoid valve 36 for adjusting the negative pressure applied to the operating portion 34 of the EGR valve 33 is provided in the negative pressure introduction passage 35, and the duty solenoid valve 36 is controlled by a duty signal to open the EGR valve 33. The degree is controlled.

Reference numeral 40 denotes a control unit (ECU) that controls hydrogen supply and EGR. The ECU 40 includes a rotation speed sensor 41 for detecting an engine rotation speed, an accelerator opening degree sensor 42 for detecting an accelerator opening degree (depression amount of the accelerator pedal), and a pressure regulator 2.
Detection signals from a pressure sensor 43 that detects the pressure in the fuel supply passage downstream of 6, an air-fuel ratio sensor 44 that detects the air-fuel ratio by detecting the oxygen concentration in the exhaust passage 12, and the like are input. From the ECU 40, the flow rate adjusting valve 2
7. Signals for controlling the duty solenoid valve 36 in the negative pressure introducing passage 35 for the EGR valve 33, the solenoid valve 23 and the pump 24, the actuator 9 of the throttle valve 8 and the like are output.

The ECU 40 includes an air-fuel ratio control means for controlling the air-fuel ratio according to the operating condition and an EGR control means. As the air-fuel ratio control means, the ECU 40 controls the throttle valve 8 on the basis of the operating state detected by the rotation speed sensor 41, the accelerator opening sensor 42, etc. and the air-fuel ratio detected by the air-fuel ratio sensor 44. The air-fuel ratio is controlled by controlling the flow rate adjusting valve 27. In this case, if the air-fuel ratio is represented by the excess air ratio λ,
In order to secure output performance in the operating region on the high load side, the air-fuel ratio should be within the range of λ <2 when λ = 1 or more, and in the operating region on the low load side, λ should be advantageous to improve fuel efficiency and emissions.
Control to a lean air-fuel ratio of 2 or more. For example, as shown in FIG. 3, in the operating region A on the high load side, λ =
The air-fuel ratio becomes leaner toward the lower load side, such as λ = 2 in the medium load operating range B and λ = 3 in the low load operating range C. Then, an air-fuel ratio map corresponding to such an operating state is stored in advance, and the air-fuel ratio is controlled based on this map.

Further, the ECU 40 serves as EGR control means.
Is the rotation speed sensor 41 and the accelerator opening sensor 4
At least λ = 1 based on the operating state detected by 2 etc.
It is assumed that the EGR is performed in the specific operating region A on the high load side, and for example, the EGR is performed in this operating region A,
The EGR is stopped in the medium load operating range B where λ = 2 and the low load operating range C where λ = 3. It should be noted that the EGR rate does not necessarily have to be completely stopped in the medium and low load operating regions B and C, and the EGR rate is reduced in the medium load operating region B as compared to the case in the high load operating region A. In the low load operating range C, E
The GR rate may be controlled to be reduced or stopped.

Further, the ECU 40 uses the pressure sensor 43.
The solenoid valve 23 and the pump 24 according to the signal from the
Control the heating action of the MH tank 16 by the engine cooling water, thereby controlling the amount of hydrogen gas released. When EGR is performed, heating by the EGR gas and heating by the engine cooling water are performed. The hydrogen gas is released so as to meet the required amount.

According to the hydrogen engine of this embodiment as described above, the hydrogen storage alloy of the MH tank 16 releases hydrogen gas in response to heating, and this hydrogen gas passes through the fuel supply passage 17, the pressure regulator 26 and the flow rate. It is supplied to the cylinder of the engine through the adjusting valve 27 and the timing valve 28.

By controlling the air-fuel ratio according to the operating state, in the high load operating region A, the hydrogen gas supply amount is increased in accordance with the increase of the intake air amount while being adjusted to λ = 1. In this case, the EGR valve 33 is opened by EGR control according to the operating state, and the EGR gas led to the EGR passage 30 from the exhaust passage 12 is supplied to the cylinder of the engine after passing through the heat exchange portion 32. Due to
Premature ignition is prevented, NOx is suppressed, and MH
Hydrogen gas release in the tank 16 is promoted.

That is, the relationship between the air-fuel ratio and the NOx generation amount when EGR is not performed is as shown in FIG. 4, and the NOx generation amount increases in the vicinity of λ = 1 (maximum slightly on the lean side from λ = 1. Therefore, in the high load operation region A, the amount of NOx originally generated tends to increase. On the other hand, when EGR is performed, NOx is suppressed by suppressing an increase in combustion temperature due to the inactive component. In this case, if the temperature of the EGR gas flowing into the working chamber 2 is high, premature ignition is likely to be caused, but the EGR gas passes through the heat exchange portion 32 and the heat is taken away here, and the temperature becomes sufficiently low. By supplying the EGR gas to the cylinder, premature ignition is prevented, and the effect of lowering the combustion temperature and suppressing NOx is significantly enhanced.

Further, the heat taken from the EGR gas in the heat exchange portion 32 is given to the MH tank 16, so that the heating of the hydrogen storage alloy is assisted and the release of hydrogen is promoted. Therefore, the required hydrogen supply amount is secured in the high load region.

On the other hand, in the operating regions B and C on the low load side (medium load or low load), the air-fuel ratio is made lean to λ = 2 or more, and when it becomes lean to this extent, NOx is essentially emitted. Significantly reduced (see Figure 4). Therefore, in these operating regions B and C, EGR is stopped or reduced, and thereby combustion stability is enhanced.

FIG. 5 shows another embodiment of the present invention. In this embodiment, the heat of the EGR gas is supplied to the MH tank 16 indirectly via the heat exchanger 50. That is, the heat exchanger 50 as a heat exchange portion is provided outside the MH tank 16, and the EGR passage 3 is provided so that the EGR gas is sent to the cylinder side through the heat exchanger 50.
0 is formed and the auxiliary heating water is supplied to the water tank 52.
The auxiliary heating water passage 51 is formed so as to circulate between the heat exchanger 50 and the pipe 51a inside the MH tank 16. The auxiliary heating water passage 51 is provided with a pump 53 whose flow rate can be adjusted. When the supply of EGR gas is stopped, the pump 5 is activated by a signal from the ECU 40.
3 is to be stopped.

Even in the case of this embodiment, when the load is high, λ
The air-fuel ratio is controlled to about = 1 and EGR is performed. In this case, in the heat exchanger 50, EG
By exchanging heat between the R gas and the auxiliary heating water, the temperature of the EGR gas lowers and the temperature of the auxiliary heating water rises, and the high-temperature water becomes MH tank 16
And is heated. Other configurations and operations are similar to those of the embodiment shown in FIGS.

The present invention can be applied not only to the rotary piston engine but also to a reciprocating engine.

[0030]

The present invention provides an EG equipped with an EGR valve in a hydrogen engine in which hydrogen is supplied from a hydrogen storage tank having a hydrogen storage alloy that releases hydrogen when heated.
R passage is formed and EGR is performed for the hydrogen storage tank.
A heat exchange part for supplying heat of gas is provided in the middle of the EGR passage, and EGR gas is supplied in a high load region where the air-fuel ratio is controlled within a range of λ <2 when λ = 1 or more. Therefore, fuel supply and NOx in the high load range
Can be effectively suppressed. In particular, the heat exchanging portion makes it possible to utilize the heat of the EGR gas to accelerate the release of hydrogen, cool the EGR gas, and prevent premature ignition while enhancing the NOx suppressing action.

In the above structure, in the low load range,
When the air-fuel ratio is controlled so as to be lean to λ = 2 or more, and the supply of EGR gas is stopped or reduced (claim 2), NOx in the low load range is obtained.
It is possible to secure combustion stability while suppressing the above.

[Brief description of drawings]

FIG. 1 is a schematic view of the entire structure of a hydrogen engine according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a part of the engine.

FIG. 3 is a diagram showing an example of operating region divisions for air-fuel ratio control and EGR control according to operating conditions.

FIG. 4 is a diagram showing a relationship between an air-fuel ratio and a NOx generation amount.

FIG. 5 is a schematic view of the entire structure of a hydrogen engine according to another embodiment of the present invention.

[Explanation of symbols]

 12 exhaust passage 16 MH tank (hydrogen storage tank) 17 fuel supply passage 30 EGR passage 32 heat exchange part 33 EGR valve 40 ECU 50 heat exchanger

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI technical display location F02D 43/00 N 7536-3G (72) Inventor Tsutomu Fukuma 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture No. Mazda Co., Ltd.

Claims (2)

[Claims] 1. A hydrogen storage tank having a hydrogen storage alloy that releases hydrogen by heating, and a heating means for the hydrogen storage tank, wherein hydrogen is supplied from the hydrogen storage tank to a cylinder of an engine. In the engine, an EGR passage for guiding EGR gas from the exhaust passage to the cylinder of the engine is formed, and the EGR passage is formed in this EGR passage.
An EGR valve that adjusts the gas flow rate is provided, and a heat exchange part that supplies heat of the EGR gas to the hydrogen storage tank is provided in the middle of the EGR passage, and the air-fuel ratio is controlled according to the operating state. The excess air ratio λ in the high load area
= 1 or more and an air-fuel ratio control means for setting within a range of λ <2, and an EGR control means for controlling the EGR valve so as to supply the EGR gas to the cylinder of the engine at least in the high load range. A hydrogen engine characterized by that. 2. The air-fuel ratio control means has a λ in a low load range.
The air-fuel ratio is controlled to be leaner than or equal to 2 or more, and the EGR control means controls the EGR valve so as to stop or reduce the supply of EGR gas to the cylinder of the engine in the low load region. Claim 1
The described hydrogen engine.