JPS59108855A - Feeding method of lpg for engine - Google Patents

Abstract

PURPOSE:To permit the feeding of a proper amount of LPG by controlling the driving electric current for an injection valve on the basis of LPG pressure, the manifold negative-pressure and the revolution speed of an engine, and eliminating the influence of the pressure variation of LPG. CONSTITUTION:An injection valve 6 for jetting LPG through an LPG-cylinder 9, opening and closing valve 10, heat exchanger 11, and a passage 12 is installed downstream from a throttle valve 2 in the intake pipe 3 for an engine 5. Each detected value of a pressure detector 13 for detecting the LPG pressure in the passage 12, pressure detector 14 for detecting the manifold negative-pressure in the intake pipe 3, and an engine speed detector 15 is input into an electronic control circuit 16, and the optimum driving current is read-out from the memory data on the basis of these input values and output into the injection valve 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an LPG supply method for an engine that injects LPG at its own pressure into an intake passage.

In the method in which LPG flowing out of the cylinder is vaporized and gasified in a heat exchanger using mainly engine cooling water and injected into the intake passage, the fuel itself has pressure, so it needs to be pressurized like in the gasoline injection method. It has the advantage of simplifying the system. In such an LPG injection system, a feedback control method is adopted in which an electronic control device is used to send the engine operating status as an input signal and output a drive current to control the injection amount based on pre-stored data. In this case, it is the LPG pressure change that is most difficult to control. That is, vaporized and gasified LP
G shows a significantly large pressure change due to temperature changes, so even if the injection amount is controlled using a control signal from the electronic control device, pressure fluctuations will occur due to the influence of temperature before it is injected into the intake passage. However, not only was it not possible to secure the optimum supply amount required by the engine, but the actual supply amount was significantly different from the engine request amount, making it impossible to keep the harmful components of engine exhaust gas within specified values. .

The present invention solves these problems and eliminates temperature changes or LPG
This was invented for the purpose of providing a method that can supply an appropriate amount of LPG to an engine even if the pressure of LPG entering an injection valve fluctuates due to changes in its composition.

The present invention aims to achieve this objective.

When the LPG flowing out of the cylinder is vaporized and gasified and injected into the intake passage by the injection valve, l'! L on the entrance side of the shooting machine
PG pressure, manifold negative pressure, and engine speed are detected and input to an electronic control device, and based on these input signals, a drive current is output from the electronic control device to a prime mover that operates the injection valve. It is characterized in that the injection amount of LG is controlled according to the above three factors.

Hereinafter, a specific example of the present invention will be explained with reference to the drawings.The intake passage 1 is composed of an air supply passage 3 having a throttle box 2 and a manifold 4 under the influence of the air supply passage 3, and an injection valve opened in the manifold 4. The vaporized LPG is injected from the nozzle 7 of 6 at its own pressure, mixed with air, and supplied to the engine 5.

LPG is opened and closed 9Pto from cylinder 9, heat exchanged.

The on-off valve 10 opens in conjunction with the turning on of the starting switch of the engine 5, leaving the valve at the low level only while the engine 5 is running.
PG flows out from the cylinder 9, and a heat exchanger 11 heats liquid LPG with engine cooling water to vaporize it.

A pressure detector 13 is provided in the passage 12 to detect the LPG pressure close to the inlet of the injection valve 6, and a pressure detector 14 is provided in the manifold 4 to detect the broken manifold negative pressure.
Furthermore, a speed detector 15 is provided to detect the engine rotation speed, and the voltage signal or current signal generated by detecting these three elements is sent as an input/signal to the electronic control bag [16 and is stored in advance. Outputs drive current according to input signal based on data.

It drives the prime mover 8 of the injection valve 6. still.

At least one of the factors for determining the engine operating condition, such as battery voltage, engine temperature, engine ignition timing, engine intake air fft, M valve opening, and exhaust gas composition, is sent as an input signal to the electronic control device 16, The optimum air-fuel ratio is obtained and feedback control is performed in a timely manner.

The electronic control device 16 controls the optimum supply amount of LPG required by the engine depending on the engine load, that is, the manifold 0 pressure, the engine rotation speed, and the pressure of LPG entering the injection valve 6.
This is to store preset data to ensure that
;b The input signal is processed by arithmetic processing, or the differential pressure between the LPG pressure and the manifold negative pressure is detected by one pressure detector, and the signal generated by this is input to the electronic control device 16 and processed by arithmetic processing.

When a solenoid is used as the prime mover 8 of the injection valve 6 and the injection bone is controlled by repeatedly opening and closing the injection valve 6 every exposure time using a drive current consisting of a pulse current with a constant cycle, the opening of the injection valve 6 per unit time is The square time ratio or duty ratio is.

For example, as shown in FIG. 2, the value of the curved surface A corresponds to the engine rotational speed and the differential pressure.

When using a step motor as the driving force f1.88 of the injection valve 6 and controlling the injection amount by changing the opening of the injection valve 6 almost steplessly depending on the number of pulses of the drive current consisting of pulse current, the opening is as shown in Fig. 2. shows the same tendency as the duty ratio.

When the manifold negative pressure is high and the LPG pressure at the inlet of the small injection valve is high, a large amount of LPG is sent to the intake passage 1, and the actual supply amount becomes larger than the engine demand. In this case, if the injection valve 6 is operated to reduce the injection amount by decreasing the duty ratio in accordance with the increase in differential pressure, the actual supply amount can be made to match the engine required amount. However, when the differential pressure is constant and the engine speed increases, the injection valve 6 is operated to increase the injection amount in response to the increase in the engine demand.

As described above, according to the present invention, when the LPG injected from the injection valve into the intake passage causes a pressure change due to temperature change, this pressure change is correlated with the manifold negative pressure and the engine rotation speed. Since the injection amount is controlled by an electronic control device through arithmetic processing, the influence of LPG pressure fluctuations is eliminated compared to conventional methods that control the injection amount based on, for example, manifold negative pressure and engine rotation speed. Therefore, it is possible to always supply an appropriate amount of LPG to the engine's required supply amount. Therefore, not only can the harmful components of the engine exhaust gas be kept within the specified value, but also the correction width of the LPG injection amount by normal feedback control can be significantly reduced to improve control performance.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram of injection valve control. 1...Intake path, 5...Engine, 6.
... Injection valve, 8 ... Prime mover, 9 ...
...Cylinder, 11...Heat exchanger, 13.14
......Pressure detector, 15... Speed detector, 16... Electronic control device. Figure 1 Figure 2

Claims (1)

[Claims] When LPG flowing out of a cylinder is vaporized and gasified and injected into the intake passage by an injection valve, the LPG pressure at the inlet of the injection valve, manifold negative pressure, and engine speed are detected and input to an electronic control device. A method for supplying LPG to an engine, comprising: outputting a driving current from the electronic control device to a prime mover operating the injection valve based on an input signal, and controlling an LPG injection amount according to the three factors.