JPS609399Y2 - Fuel supply system for LP gas engine - Google Patents

Description

[Detailed description of the invention] The present invention relates to a fuel supply system for an LP gas engine, and in particular to an LPG engine equipped with a three-way type catalytic converter in the exhaust system.
The present invention relates to a fuel supply system for an LP gas engine that performs suitable air-fuel ratio control when applied to a P gas engine.

A so-called catalytic converter, which is installed in the middle of the exhaust system and converts harmful components in the exhaust gas into harmless gas by the action of a catalyst, has been known as one type of exhaust gas purification device.
Among them, there is a three-way type (CCRo type) catalytic converter that can oxidize CO and HC, reduce NOx, and simultaneously convert three types of CO, HC, and NOx into harmless gases.

When such a three-way type catalytic converter is installed in the exhaust system of an LP gas engine, the conversion rate of CO1HC1NOx to each harmless gas exhibits different characteristics depending on the air-fuel ratio used, as shown in Figure 1. HCXNO
In order to maintain the conversion ratio of each of required.

The present invention is different from the idea of performing air-fuel ratio control that always brings the air-fuel ratio used by an LP gas engine close to the stoichiometric air-fuel ratio.

By the way, the output of the 02 sensor, which is a type of air-fuel ratio sensor that detects the air-fuel ratio from engine exhaust gas components, changes with the operating air-fuel ratio as shown in Figure 2, and the rate of change becomes large after the stoichiometric air-fuel ratio. Therefore, by detecting the oxygen amount in the exhaust gas using the 02 sensor output, it is possible to relatively easily detect whether the air-fuel ratio used at that time is larger or smaller than the stoichiometric air-fuel ratio.

Therefore, as mentioned above, the main purpose of the present invention is to provide a fuel supply system for an LP gas engine that performs air-fuel ratio control that brings the air-fuel ratio used close to the stoichiometric air-fuel ratio at all times. In order to achieve the above-mentioned main purpose, the present invention detects the air-fuel ratio used at that time based on the output of the 02 sensor from the amount of oxygen in the exhaust gas, and supplies additional fuel to the intake passage downstream of the throttle valve based on the detected air-fuel ratio. Its detailed purpose is to control the flow rate of the fuel and control the air-fuel ratio.

According to the present invention, this purpose is achieved by supplying LP gas from a primary chamber containing LP gas whose pressure is regulated to a substantially constant pressure higher than atmospheric pressure and from the secondary chamber through a control valve. a secondary chamber containing LP gas whose pressure is regulated to be equal to atmospheric pressure; the control valve includes an LPG regulator configured to open in response to a decrease in pressure in the secondary chamber; and a throttle valve; one end opens into the venturi throttle section to define a fuel outlet, the other end opens into the secondary chamber of the LPG regulator, and an adjustment screw provided midway; A main fuel passage whose passage cross-sectional area is adjusted to provide an amount of fuel to generate an air-fuel mixture with an air-fuel ratio higher than the stoichiometric air-fuel ratio, and a secondary fuel passage of the LPG regulator located downstream of the throttle valve of the intake passage. A sub-fuel passage for supplying additional fuel from the chamber, a valve device provided in the middle of the sub-fuel passage for selectively communicating or blocking the passage, and an air-fuel ratio sensor for detecting an air-fuel ratio from exhaust gas components. , a calculation means for calculating an air-fuel ratio based on a detected value of the air-fuel ratio sensor, and when the air-fuel ratio calculated by the calculation means is larger than the stoichiometric air-fuel ratio, the valve device increases according to an increase in the difference. The present invention is closely related to the fuel supply system for an LP gas engine, which is configured to operate to connect the sub-fuel passages at a flow passage opening time of .

According to this configuration, when the air-fuel ratio is larger than the stoichiometric air-fuel ratio, in other words when the air-fuel mixture is lean, fuel is supplied into the intake passage from the sub-fuel passage in addition to the fuel supply from the main fuel passage, As a result, the air-fuel ratio is corrected to or brought closer to the stoichiometric air-fuel ratio.

Further, the valve device that cuts off the communication of the sub-fuel passage is constituted by a valve device having a flow adjustment function, and the valve of the valve device is opened in accordance with the difference between the air-fuel ratio calculated by the calculation means and the stoichiometric air-fuel ratio. By controlling the air-fuel ratio or the valve opening time, the air-fuel ratio can always be more closely matched to the stoichiometric air-fuel ratio.

In such a case, it is preferable that the fuel flow rate of the main fuel passage when fuel is not being supplied from the sub-fuel passage is set so that the air-fuel mixture is slightly lean.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 3 is a somewhat exploded cross-sectional view of one embodiment of the fuel supply system for an LP gas engine according to the present invention.

In the figure, reference numeral 1 denotes a casing of a capretor, and a venturi throttle section 3 is disposed in an intake passage 2 passing through the interior thereof, and a throttle valve 4 is located downstream of the venturi throttle section 3 on the throttle shaft. It is provided in such a manner that it can rotate about 5 as a fulcrum.

The casing 1 includes a main fuel passage 9 connected at one end to a main fuel outlet port 7 of the LPG regulator 6 and opening into the venturi throttle section 3 at the other end to define a main fuel outlet. , the fuel supplied from the LPG regulator 6 to this main fuel passage 9 is:
The fuel is sent to the main fuel outlet 8 while its flow rate is adjusted by an adjustment screw 10 provided in the middle.

Further, the casing 1 is connected at one end to a sub-fuel take-out port 11 of the LPG regulator 6, and opens downstream of the throttle valve 4 in the intake passage 2 at the other end to define a sub-fuel outlet 12. The fuel supplied from the LPG regulator 6 to this sub-fuel passage 13 passes through a valve device 14 provided in the middle, and its flow rate is adjusted by a sub-fuel jet 15. The fuel is sent to the fuel outlet 12.

The LPG regulator 6 includes a diaphragm-operated first valve device 17 that reduces and vaporizes high-pressure LP gas stored in a liquid state in a fuel tank 16 to a predetermined pressure (approximately 0.33 to 9/c1 ft), and the LPG regulator 6 includes a diaphragm-operated first valve device 17 that reduces and vaporizes high-pressure LP gas stored in a liquid state in a fuel tank 16 to a predetermined pressure (approximately 0.33 to 9/c1ft). a second valve device 19 operated by a diaphragm that reduces the pressure of the LP gas at a predetermined pressure stored in the converter 18 to substantially atmospheric pressure; The main fuel extraction port 7 and the sub fuel extraction port 11 are formed in the secondary chamber 20 to temporarily store the LP gas whose pressure has been reduced to 100%.

21 is a 0° sensor (lambda sensor) provided in the exhaust pipe 22, and the 0° sensor 21 detects the amount of oxygen contained in the exhaust gas flowing through the exhaust pipe 22 and converts it into an electrical signal. and sends the electrical signal to the computer 23.

This 02 sensor 21 is provided facing into the exhaust pipe 22 on the upstream side of the catalytic converter and the like.

The computer 23 includes calculation means for calculating an air-fuel ratio based on the electric signal output by the 02 sensor 23, and is configured to output an electric signal to the valve device 14 according to the result calculated by the calculation means. ing.

In this case, the computer 23 outputs an electric signal to the valve device 14 to open the valve device when the calculated air-fuel ratio is greater than the stoichiometric air-fuel ratio.

Therefore, the sub-fuel passage 13 is blocked and the sub-fuel passage 13
When fuel is not being supplied from the main fuel passage 9, the amount of fuel flowing through the main fuel passage 9 is adjusted in advance by the adjustment screw 10 so that the air-fuel ratio is slightly larger than the stoichiometric air-fuel ratio, in other words, the air-fuel mixture is slightly lean. If set, the computer 23 outputs an electric signal to the valve device 14 according to the difference between the air-fuel ratio calculated based on the amount of oxygen in the exhaust gas detected by the 02 sensor 15 and the stoichiometric air-fuel ratio, and thereby The valve device 14 opens in response to the electrical signal.

Therefore, the sub-fuel passage 13 is communicated with the passage opening time or passage cross-sectional area according to the electrical signal outputted from the computer 23, and a predetermined amount of additional fuel is supplied to the sub-fuel port 12, which causes the intake pipe negative pressure. By being sucked into the intake pipe, the amount of fuel sent to the intake passage 2 is increased in accordance with the fuel sucked out from the main fuel outlet 8, and as a result, the air-fuel ratio is corrected to the stoichiometric air-fuel ratio or brought close to it. Become.

FIG. 4 is a somewhat exploded sectional view showing another embodiment of the fuel supply system for an LP gas engine according to the present invention. Pressurized LPG gas is supplied from a sub-fuel take-out port 11' opened to the fuel tank 18.

This sub-fuel passage 13' has a fuel outlet portion open to the intake passage 2 so as to supply sub-fuel to the downstream side of the throttle valve 4 of the intake passage 2.

In this embodiment as well, additional fuel is supplied from the sub-fuel passage 13' into the intake passage 2 according to the difference between the air-fuel ratio calculated by the computer 23 and the stoichiometric air-fuel ratio, so that the air-fuel ratio becomes the same as in the previous embodiment. Correction control is performed to the stoichiometric air-fuel ratio.

In any of the above embodiments, the valve device 14 is preferably provided as close as possible to the sub-fuel outlet side of the sub-fuel passage, and the space between the valve device 13 and the sub-fuel outlet is minimized. By reducing this, responsiveness can be improved.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the conversion rate of HClC01NOx to each harmless gas and the air-fuel ratio in a three-way type catalytic converter, and Figure 2 is a graph showing the relationship between the 0□ sensor output and the air-fuel ratio. , Figure 3 shows the LP according to the present invention.
FIG. 4 is a sectional view showing in a somewhat exploded view one embodiment of a fuel supply system for a gas engine; FIG. 4 is a somewhat exploded view showing another embodiment of the fuel supply system for an LP gas engine according to the present invention FIG. 1 - Capretor casing, 2 - Intake passage, 3 - Henchuri throttle section, 4 - Throttle valve, 5 - Throttle shaft, 6 - LPG regulator, 7 - Main fuel extraction port, 8 - Main fuel outlet, 9 - Main fuel ? 4 aisles, 1
0~Adjustment screw, 11.11'~Sub fuel extraction port, 12~Sub fuel outlet, 13.13'~Sub fuel passage, 14~Valve device, 15~Sub fuel jet, 1
6~Fuel tank, 17~First valve device, 18~
- Conversion, 19~Second valve device, 20~Secondary chamber, 2
1-02 sensor, 22-exhaust pipe, 23-computer.

Claims (1)

[Scope of utility model registration request] A primary chamber containing LP gas whose pressure is regulated to a substantially constant pressure higher than atmospheric pressure, and LP gas from the above-mentioned and secondary chambers via a control valve.
and a secondary chamber containing LP gas supplied with gas and regulated to a pressure substantially equal to atmospheric pressure, and the control valve is configured to open in response to a decrease in pressure within the secondary chamber. an LPG regulator, an intake passage having a venturi throttle and a throttle valve; one end opening into the venturi throttle to define a fuel outlet; the other end opening into the venturi throttle;
a main fuel passage which opens into the secondary chamber of the regulator and whose passage cross-sectional area is adjusted by an adjustment screw provided in the middle so as to supply an amount of fuel that generates an air-fuel mixture with an air-fuel ratio higher than the stoichiometric air-fuel ratio; , a sub-fuel passage for supplying additional fuel from the secondary chamber of the LPG regulator to the downstream side of the throttle valve of the intake passage; and a sub-fuel passage provided in the middle of the sub-fuel passage to selectively communicate or block the passage. The valve device includes a valve device, an air-fuel ratio sensor that detects an air-fuel ratio from exhaust gas components, and a calculation means that calculates an air-fuel ratio based on a detected value of the air-fuel ratio sensor, and the valve device is calculated by the calculation device. A fuel supply for an LP gas engine, characterized in that when the air-fuel ratio is larger than the stoichiometric air-fuel ratio, the sub-fuel passage is operated to communicate with the sub-fuel passage at a flow passage opening time that increases as the difference increases. system.