JP2898858B2 - Gas engine fuel control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel control system for a gas engine using natural gas as a fuel.

[0002]

2. Description of the Related Art A gas engine using natural gas as a fuel is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-259652.
And the mixture is mixed with the engine intake air at a predetermined ratio by a mixer, and this mixture is supplied to the engine.

The applicant of the present invention has filed applications for engines using natural gas as fuel, such as Japanese Utility Model Application No. 479972, Japanese Utility Model Application No. 4-79977, and Japanese Utility Model Application No. 4-79971.

[0004]

By the way, a vehicle driven by a gas engine using natural gas as a fuel is provided with ancillary equipment such as a garbage disposal device, and a part of the engine output is used as an auxiliary power take-out unit. When the auxiliary equipment is driven after being taken out of the engine, the engine speed changes depending on the load applied to the auxiliary equipment, even if the accelerator opening is constant. When the rotation speed fluctuates in this way, the stability and operability of the incidental equipment are deteriorated, and the engine may stall.

On the other hand, it is conceivable to control the rotation speed by changing the opening degree of an accelerator pedal or a lever interlocking with the accelerator pedal in accordance with a change in load.
In this case, control becomes complicated and operability is poor.

SUMMARY OF THE INVENTION It is an object of the present invention to keep the rotation speed of an engine constant at the time of taking out auxiliary power and to make it possible to drive auxiliary equipment stably.

[0007]

Accordingly, a first aspect of the present invention relates to a vehicle equipped with a gas engine using high-pressure natural gas as a fuel, as shown in FIG. 1, as a driving force for auxiliary equipment mounted on the vehicle. An auxiliary power take-out part (26) for taking out part of the engine output, a mixer (3) for mixing gas fuel and intake air at a predetermined ratio, and intake air bypassing the mixer (3) Opening / closing means for bypass passage (13)
Means for supplementarily supplying gaseous fuel (11), means for detecting exhaust air-fuel ratio (23) installed in the exhaust system, means for detecting engine speed (21), and detection when the auxiliary power is taken out. Means (A) for controlling the supply amount of the auxiliary fuel so that the air-fuel ratio is constant and controlling the bypass air amount so that the engine speed is constant.

According to a second aspect of the present invention, as shown in FIG. 2, in a vehicle equipped with a gas engine using high-pressure natural gas as a fuel, a part of the engine output is used as a driving force of auxiliary equipment mounted on the vehicle. Auxiliary power take-out part (26)
A mixer (3) for mixing gas fuel and intake air at a predetermined ratio; and a means (11) for supplementarily supplying gas fuel.
Means (21) for detecting the engine speed, and means (B) for controlling the supply amount of the auxiliary fuel so that the engine speed becomes constant when the auxiliary power is taken out.

[0009]

According to the first aspect of the present invention, when the auxiliary power is taken out, for example, when the rotation speed is lower than the target rotation speed due to a load fluctuation of the auxiliary equipment, the bypass air amount increases, and at the same time, the air-fuel ratio increases to the set air-fuel ratio. The supply amount of the auxiliary fuel is feedback-controlled so that the engine output increases, and the rotation speed increases to the target rotation speed. Conversely, when the rotation speed becomes higher than the target rotation speed, the amount of bypass air decreases while maintaining the air-fuel ratio at the set air-fuel ratio, the engine output decreases, and the rotation speed decreases to the target rotation speed.

In this manner, when the auxiliary power is taken out, the engine intake air amount and the fuel amount are increased, so that the rotational speed is maintained at the target constant rotational speed in response to a large load change of the incidental equipment. be able to.

In the second invention, when the auxiliary power is taken out, if the engine speed is lower than the target speed due to a change in the load of the auxiliary equipment, auxiliary fuel is supplied.
When the air-fuel ratio becomes richer than the lean air-fuel ratio set by the mixer, the engine output increases, the engine speed increases, and when the engine speed becomes higher than the target engine speed, the supply of auxiliary fuel is performed. The engine is stopped, the air-fuel ratio decreases, the engine output decreases, and the engine speed decreases.

In this way, even if the load on the incidental equipment fluctuates, the rotational speed can always be maintained at the target constant rotational speed.

[0013]

FIG. 3 shows a first embodiment of the present invention. In a gas engine 1 using natural gas as a fuel, an intake passage 2 mixes intake air and gas fuel at a fixed ratio, and performs lean mixing. A mixer 3 for generating air is provided.

As shown in FIG. 4, the mixer 3 guides the gas fuel depressurized by the gas regulator 6 to the venturi 5 provided upstream of the throttle valve 4 linked to the accelerator pedal (not shown), This fuel is sucked out according to the amount of intake air from a slit 7 opening to 5, and the intake air and fuel are mixed so as to have a constant lean air-fuel ratio. Reference numeral 8 denotes a shut-off valve for shutting off the fuel passage 9 when the engine is stopped, and reference numeral 14 denotes an adjusting screw for adjusting the initial opening of the fuel passage.

On the other hand, an auxiliary fuel passage 10 branching from the fuel passage 9 and communicating with the slit 7 is provided, and a fuel control valve 11 composed of an electromagnetic valve for opening and closing the auxiliary fuel passage 10 is provided. When the fuel control valve 11 opens,
The amount of gas fuel sucked from the venturi 5 is increased, and the air-fuel ratio generated by the mixer 3 is increased.

A bypass passage 12 is provided in the intake passage 2 for bypassing the mixer 3 to flow the intake air. The bypass passage 12 is provided with an intake control valve 13 for controlling the amount of air. When the intake control valve 13 opens, the engine intake air amount controlled corresponding to the opening of the throttle valve 4 relatively increases.

The intake control valve 13 is a diaphragm-driven valve, and the opening degree is controlled to be increased or decreased by controlling the supply air pressure by an electromagnetic valve 15. The shut-off valve 8 is also a diaphragm-driven valve similar to the above, and the solenoid valve 16
Controls the supply air pressure and opens and closes.

An idle adjustment valve 18 is provided in an idle adjustment passage 17 connecting the upstream and downstream of the throttle valve 4. The opening degree of the idle adjustment valve 18 bypasses the throttle valve 4 to flow the air-fuel mixture. The idle speed is adjusted.

A controller 20 for controlling the auxiliary fuel control valve 11, the solenoid valve 15 for controlling the amount of bypass air, the solenoid valve 16 for controlling fuel cutoff, and the idle regulating valve 18 in accordance with respective operating conditions is provided. Can be

For this reason, the controller 20 receives a rotational speed signal from a rotational speed sensor 21 for detecting the engine rotational speed, and measures the oxygen concentration in the exhaust gas installed in the engine exhaust passage 22 to obtain the exhaust air-fuel ratio. The switch 24 receives the air-fuel ratio signal from the exhaust sensor 23 for detecting the
, And controls the operation of each of the valves based on these signals as described later.

As shown in FIG. 5, an auxiliary output shaft 27 from an auxiliary power take-out portion 26 is provided from the gas engine 1 in addition to an output shaft 25 for driving the vehicle. , A hydraulic motor 29 driven by oil discharged from the hydraulic pump 28 drives ancillary equipment mounted on the vehicle, for example, refuse treatment equipment.

The controller 20 operates under the driving conditions of the auxiliary equipment regardless of the load fluctuation of the auxiliary equipment.
The amount of the bypass air is controlled so that the engine speed is constant, and the supply amount of the auxiliary fuel is controlled so that the air-fuel ratio at this time becomes the set air-fuel ratio.

Regarding the control operation of the controller 20,
This will be described in detail with reference to the flowchart of FIG.

First, in step 1, it is determined from the output of the switch 24 whether the auxiliary power is taken out or not in order to drive the auxiliary equipment. The engine speed Ne is detected based on a signal from the number sensor 21.

Then, at step 3, the engine speed Ne
Is determined to be higher or lower than a preset target rotational speed Nes. If the detected rotational speed Ne is low, the intake control valve 13 is opened in step 4. The intake control valve 13 is opened by driving the solenoid valve 15. On the contrary,
If the detected rotation speed Ne is not lower than Nes, the process goes to step 5 and the value is compared with Ne again. If Ne is higher than this, the intake control valve 13 is closed in step 6; Sometimes, the previous state is maintained.

When the bypass passage 12 is opened in this way, the bypass flow rate is added to the engine intake air amount controlled by the throttle valve opening, and the intake air amount relatively increases. When closed, the intake air volume decreases.

Next, in step 7, the detected air-fuel ratio λ from the exhaust sensor 23 is read, and the detected air-fuel ratio λ is set to a preset air-fuel ratio λs (where λ is the reciprocal of the excess air ratio). Then, λs = 1 at the stoichiometric air-fuel ratio) is compared with the value at step 8, and if the air-fuel ratio is leaner than the set air-fuel ratio, the routine proceeds to step 9, where the auxiliary fuel control valve 11 is opened to increase the air-fuel ratio.

On the other hand, when the air-fuel ratio is not thinner than the set air-fuel ratio in step 8, the value is compared again with λs in step 10, and when the air-fuel ratio is rich, the fuel control valve 11 is closed in step 11; Keep it as it is.

In this way, the air-fuel ratio is maintained at the set air-fuel ratio which is the target air-fuel ratio.

Therefore, when taking out the auxiliary power,
Auxiliary fuel is supplied to the lean air-fuel mixture generated by the mixer 3, feedback control is performed so that the air-fuel ratio becomes the set air-fuel ratio, and when the engine speed falls below the target value, the bypass passage 12 is opened, and the intake air amount is relatively increased so as to maintain the same rotational speed.

Next, the overall operation will be described.

During normal operation, that is, when the auxiliary power is not taken out, the signal from the controller 20 closes the intake control valve 13 of the bypass passage 12 and also closes the auxiliary fuel control valve 11. Is supplied to the gas engine 1 to perform lean combustion, thereby maintaining good exhaust gas composition and fuel efficiency. In this state, the opening of the idle adjustment valve 18 is adjusted by the controller 20 during engine idling, and the supply amount of the air-fuel mixture is delicately increased / decreased even if the throttle valve opening is constant. Is controlled to maintain.

On the other hand, at the time of driving operation of the auxiliary equipment of the vehicle,
When the removal of the auxiliary power is detected, the bypass passage 12 is opened as described above, and the air-fuel ratio is also controlled to the set air-fuel ratio.
Therefore, the output of the engine is relatively increased, and a constant target rotational speed is always maintained with respect to the load fluctuation of the incidental equipment without adjusting the throttle valve opening.

In particular, since the bypass passage 12 is opened to relatively increase the intake air amount and the air-fuel mixture is switched to the set air-fuel ratio which is higher than the normal lean air-fuel ratio, the load on the incidental equipment greatly fluctuates. In addition, it is possible to swiftly absorb fluctuations in the rotational speed, that is, have a large fluctuation absorbing ability, and to stably maintain a constant rotational speed. Therefore, the auxiliary equipment can be driven stably and good operability can be exhibited.

Next, the embodiment of FIGS. 7 and 8 will be described.
This does not have the bypass passage 12 described above and does not perform feedback control of the air-fuel ratio, so that only the fuel is made rich at the time of taking out the auxiliary power so as to cope with the load fluctuation of the auxiliary equipment. .

For this reason, as shown in FIG. 7, although the auxiliary fuel control valve 11 is provided, the intake control valve 13 is not provided, and the controller 20 controls the opening degree of the auxiliary fuel control valve 11 when taking out the auxiliary power. As a result, the air-fuel ratio generated by the mixer 3 is increased, the engine output is increased, and the engine speed is maintained at the target constant speed.

Describing with reference to the flowchart of FIG. 8, steps 1 to 3 are the same as those of the flowchart of FIG.
If the engine speed is lower than the target engine speed, the fuel control valve 11 is opened in step 12. If the engine speed is not lower than the target engine speed, the fuel control valve 11 is compared with the set engine speed again in step 5. In step 13, the fuel control valve 1
1 is closed, otherwise, if it is the same as the target rotational speed, the previous state is maintained.

Therefore, when the engine speed is lower than the target engine speed at the time of taking out the auxiliary power, the auxiliary fuel control valve 11 is opened, and the air-fuel ratio of the air-fuel mixture generated in the mixer 3 becomes lean. It becomes relatively darker than the air-fuel ratio. Therefore, the output of the engine increases, and the engine speed increases. When the rotation speed becomes higher than the target rotation speed, the auxiliary fuel control valve 11 closes to make the air-fuel ratio lean, so that the rotation speed decreases. Thus, even if there is a load change when the auxiliary power is taken out. In addition, the engine speed can be maintained at a constant value.

In this embodiment, the load fluctuation is absorbed by adjusting the air-fuel ratio without changing the intake air amount, so that the load fluctuation absorbing ability is lower than that of the first embodiment. If it is adapted when the load of the auxiliary equipment is not so large, the practical use value is high because the configuration is simple and inexpensive.

[0040]

As described above, the first invention is directed to a vehicle equipped with a gas engine using high-pressure natural gas as fuel.
An auxiliary power take-out part for taking out a part of the engine output as a driving force of ancillary equipment mounted on the vehicle; a mixer for mixing gas fuel and intake air at a predetermined ratio; Opening and closing means for a bypass passage to be introduced;
Means for supplementarily supplying gaseous fuel, means for detecting exhaust air-fuel ratio provided in an exhaust system, means for detecting engine speed, and the auxiliary fuel so that the detected air-fuel ratio becomes constant when the auxiliary power is taken out. Means for controlling the amount of supply of air and controlling the amount of bypass air so that the engine speed is constant. When the auxiliary power is taken out, the amount of intake air to the engine is increased and the air-fuel ratio is increased. The rotational speed can be maintained at the target constant rotational speed with good response to a large load change of the equipment, and the driving stability and good operability of the auxiliary equipment can be exhibited.

According to a second aspect of the present invention, in a vehicle provided with a gas engine using high-pressure natural gas as a fuel, an auxiliary power take-out portion for taking out a part of the engine output as a driving force of ancillary equipment mounted on the vehicle. A mixer for mixing the gas fuel and the intake air at a predetermined ratio, a means for supplementarily supplying the gas fuel, a means for detecting the engine speed, and the engine speed being constant when the auxiliary power is taken out. Means for controlling the supply amount of the auxiliary fuel as described above, the rotational speed can always be maintained at the target constant rotational speed even when the load of the auxiliary equipment fluctuates, and the configuration is simple. Also, there is an effect that it can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first invention.

FIG. 2 is a configuration diagram of a second invention.

FIG. 3 is a cross-sectional view of the overall configuration showing the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of the main part.

FIG. 5 is a schematic configuration diagram of an auxiliary power take-out unit.

FIG. 6 is a flowchart showing the control operation.

FIG. 7 is a sectional view showing a main part of the second embodiment.

FIG. 8 is a flowchart showing the control operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas engine 2 Intake passage 3 Mixer 4 Throttle valve 11 Fuel control valve 12 Bypass passage 13 Intake control valve 20 Controller 21 Speed sensor 23 Exhaust sensor 24 Auxiliary power take-out detection switch 26 Auxiliary power take-out part

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ikuro Nozu Saitama Prefecture, Ooichi, Daiichi Ichibanchi, Nissan Diesel Kogyo Co., Ltd. (56) References JP-A-4-1468 (JP, A) JP-A-61-130731 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02M 23/04 301 F02M 21/02 301

Claims (2)

(57) [Claims] 1. A vehicle equipped with a gas engine using high-pressure natural gas as a fuel, an auxiliary power take-out unit for taking out a part of engine output as a driving force of ancillary equipment mounted on the vehicle, a gas fuel and intake air. , A bypass passage opening / closing means for bypassing the mixer and introducing intake air, a means for supplementarily supplying gaseous fuel, and an exhaust air-fuel ratio detection installed in the exhaust system. Means for detecting the engine speed, and controlling the supply amount of the auxiliary fuel so that the detected air-fuel ratio becomes constant when the auxiliary power is taken out, and the bypass air amount so that the engine speed is constant. And a control unit for controlling a fuel cell. 2. A vehicle equipped with a gas engine using high-pressure natural gas as a fuel, an auxiliary power take-out part for taking out a part of engine output as a driving force of ancillary equipment mounted on the vehicle, a gas fuel and intake air. And a means for supplementarily supplying gaseous fuel, a means for detecting the engine speed, and a method for mixing the auxiliary fuel so that the engine speed is constant when the auxiliary power is taken out. A fuel control device for a gas engine, comprising: means for controlling a supply amount.