JPH0329984B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply system for an automobile, and more particularly to a fuel supply system for an automobile that is capable of supplying low-pressure fuel and supplying various types of fuel.

Conventionally, fuel supply systems for automobiles can be roughly divided into two types: carburetors and fuel injection systems, with the former employing a continuous fuel metering system and the latter employing an intermittent fuel metering system, and have been installed in multi-cylinder engines. Examples of each are described in JP-A-55-142950 and JP-A-54-108129. However, in these fuel supply systems, the diameter of the generated fuel droplets is not uniform and fine, making it impossible to achieve equal distribution to multiple cylinders, resulting in unstable fuel after fuel supply, and a reduction in fuel efficiency due to a decrease in combustion efficiency. Problems such as increased consumption and increased levels of harmful exhaust emissions occur. In addition, both of these types of fuel supply systems cannot cope with the diversification and lower quality of fuel, and a fuel supply system having a new atomization means is desired.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel supply device for an automobile that can atomize fuel and can generate a large amount of uniform fine droplets. In order to achieve the above object, the fuel supply device for an automobile according to the present invention includes an injection valve that measures and supplies fuel upstream of an intake pipe, an air amount sensor that measures the amount of air, and a device that determines the operating state of the engine. In a fuel supply device for an automobile that has a throttle valve that sprays fuel into an intake pipe by opening the injection valve, the injection valve is provided upstream of the throttle valve approximately on the central axis of the intake pipe, and A cylindrical vibrator supported by an ultrasonic vibrator is provided downstream of the injection valve approximately on the central axis, and the excitation frequency of the ultrasonic vibrator is changed at a predetermined period to atomize the fuel.

The gist of the present invention is as follows. That is, many researchers have already studied the ultrasonic vibration atomization technology, and ring vibration has been disclosed as a device to remove the limitation on the amount of liquid throughput, which is the biggest drawback. However, when fuel is supplied to the ring vibrating section, there is a phenomenon in which a part of the fuel does not become atomized, but coalesces, accumulates, and drips, which has been a problem for use in automobile fuel systems. The present invention has achieved its object by electrically controlling the vibration frequency of the ring vibration in order to prevent such fuel dripping.

Examples of the present invention will be described below.

FIG. 1 shows an overall configuration diagram of an engine system to which an embodiment of the present invention is applied.

In the figure, air and fuel are sucked in through an intake pipe 6 by opening and closing an intake valve 2 of an engine 1, and are ignited and combusted by a spark plug 3 to transmit output to wheels (not shown). The ignition timing of the ignition plug 3 is determined by transmitting a signal from the crank angle sensor 5 to the computer 20, and sending a signal to the ignition coil 4 at the required timing to cause ignition. A mixing cylinder 8 is installed in the intake pipe 6.
The air amount is controlled by the opening of the throttle valve 9, and the throttle valve opening status at that time is retrieved by the throttle valve opening sensor 10, and the computer 20 calculates and stores it. The mixing cylinder 8 has a slight bulge on the upstream side of the throttle valve 9, and an ultrasonic vibrator 11 is attached and fixed to the bulge from the outside. A ring vibrating section 1 is provided at the other end of the ultrasonic vibrator 11.
2 is fixed, and the center of the ring vibrating portion 12 and the central axis of the mixing cylinder 8 are configured to match. Further, the mixing cylinder 8 is bent into an L-shape at the upper part, and an injection valve 13 (both intermittent or continuous is possible) is inserted and fixed from the outside into the bent part. The axis of the injection valve 13 and the axis of the mixing cylinder 8 are aligned. The injection valve 13 and the fuel pressure regulator 14 are integrated, and the fuel sucked from the fuel tank 17 is guided to the regulator 14 via the pump 18 and filter 19, and is controlled to a predetermined pressure. It is returned to tank 17. An air amount sensor 15 (movable vane type, hot wire type, or Karman vortex type) is installed upstream of the mixing cylinder 8 to measure the amount of air, and its output is transmitted to the computer 20. On the other hand, exhaust gas produced by combustion passes through the exhaust pipe 7, is detected by the oxygen sensor 16, and is released into the atmosphere via a catalyst (not shown) and a muffler (not shown). The oxygen sensor 16 has a characteristic that changes depending on the excess oxygen concentration in the exhaust gas, and uses this characteristic to estimate the concentration of the mixture sucked into the engine 1 and control the opening time width of the injection valve 11. , fuel efficiency and exhaust purification properties.

The details of fixing the ultrasonic vibrator 11 to the mixing tube 8 will now be described with reference to FIG. 2.

The ultrasonic vibrator 11 is fixed to the vertical side surface of the mixing cylinder 8 with screws 33. The screws 33 simultaneously attach the cover 32 together. The cover 32 is made of metal to help reduce generated noise. In addition, when fixing the ultrasonic vibrator 11, an O-ring 3 is attached to the mixing cylinder 8.
0 and rubber pad 31 are inserted in advance and fixed. The O-ring 30 prevents air from leaking, and the rubber pad 31 prevents fuel from being drawn in.

Next, the structure of the ultrasonic transducer 11 will be explained with reference to FIG. FIG. 3a is a side sectional view of the vibrator, which is composed of a horn part 46, piezoelectric elements 42, 43, a fixing plate 44, and a piezoelectric element crimping screw 48, and is between two crimped piezoelectric elements 42, 43. Voltage applied to terminal 4
1 is provided, and when a pulse voltage of 300 to 500 V is applied between the applied voltage terminal 41 and the ground (for example, the flange portion 45), the piezoelectric elements 42 and 43 expand and contract, and the vibration causes the horn portion 46 formed at the tip of the flange 45 to expand and contract. and is transmitted to the ring vibrating section 12 at the tip. FIG. 3b shows a plan view of the ultrasonic vibrator 11.

FIG. 4a is a view of the ultrasonic transducer 11 shown in FIG.
5 is clearly shown. That is, although a screw 47 is provided at the tip of the horn portion 46 to fix the ring vibrator 12 as shown in FIG. It is sufficient to rotate the flange 45 and fix the aforementioned screw 33 when the axes coincide, and the flange 45 is provided with a gap 49 for fixing.

Next, the structure of the ring vibrating section 12 will be explained. Figure 5 shows an example of a ring vibrating part, and Figure 5a is a plan view showing an arm 51 on the ring part and a fixing screw part 5.
2, the arm 51 and the ring part 12 are made by welding or integral casting, and the fixing screw part 52
corresponds to the ring vibrator fixing screw 47. The arm 51 is installed as shown in FIG. 5b, and is located at the center of the ring cross section. The state of fuel atomization at this time is as shown in FIG. 5c, when the fuel is spread into a thin film according to the arrow and supplied to the ring vibrator 12, the behavior is shown by the dotted line. That is, even though the supplied fuel is directed downward rather than upward, the atomized fuel is mixed upstream and downstream.

Next, cases of other shapes of the ring vibrator 12 will be explained. FIG. 6a is a plan view at that time, and a vertical rim 53 is inserted between the ring vibrator 12 and the arm 51 and fixed thereto. In this case, as shown in FIG. 6b, the vibration mode of the ring vibrator 12 changes due to the vertical rim 53, and the fuel is scattered and atomized only downward, as shown in FIG. 6c. Next, a case where a horizontal rim 54 is inserted into the ring portion of the ring vibrator 12 as shown in FIGS. 7a and 7b will be described. In this case, the vibration mode is more vibration in the vertical direction of the ring than in the circumferential direction, causing fuel to splatter. See Figure 7c.

Next, as a method of promoting multiple vibrations with one ring, the methods shown in FIGS. 8 and 9 can be considered.

In other words, in FIG.
A tapered portion 55 as shown in FIG. b is provided to increase the vibration amplitude toward the lower end and to promote atomization.

In Fig. 9, the vibrating ring part is doubled, the ring vibrator 12 and the middle ring 56 are fixed with one arm 51 as shown in Fig. 9b, and the ring vibrator is fixed as shown in Fig. 9C. 12 and the annular gap of the middle ring 56 to promote atomization by supplying thin film fuel.

Next, the vibration mode of the ring vibrator will be described. 10A, B, C, and D are vibration modes for the ring vibrator shape shown in FIG. 5, and the vibration modes differ depending on the outer and inner diameters and wall thicknesses of the ring. The larger the diameter of the ring and the thinner the wall thickness of the ring, the more nodes of vibration there will be, and the finer particles of fuel will be promoted. Figure 10A shows vibration order n = 2, vibration frequency = 23kHz, outer diameter 19φ (mm), inner diameter 15φ
(mm), height 20 (mm) ring oscillator, Fig. 10B
is vibration order n = 3, vibration frequency = 25kHz, outer diameter
A ring vibrator with a diameter of 17φ (mm), an inner diameter of 15φ (mm), and a height of 20 (mm), shown in Figure 10C, has a vibration order of n=4, a vibration frequency of 27kHz, 29kHz, an outer diameter of 22φ (mm), an inner diameter of 20φ.
(mm), height 15 (mm) ring oscillator, Fig. 10D
is vibration order n = 7, vibration frequency = 29kHz, outer diameter
It is a ring vibrator with a diameter of 42φ (mm), an inner diameter of 40φ (mm), and a height of 20 (mm). 12 in Figure 10 is the position of zero vibration, 6
0 indicates the amplitude during vibration. That is, the fuel that has arrived at the location where the amplitude is largest is repelled and atomization is promoted, and the fuel that is at the location where the amplitude is zero is not atomized. According to the observation results, it was found that the fuel at the zero amplitude position gradually moves toward the maximum amplitude position, and atomization can be achieved. Therefore, the method of dropping fuel is as much as possible above the ring oscillator, using a thin film in the circumferential direction. Therefore, after the fuel is injected by the injection valve 13 shown in FIG. 1, a device is added to swirl the fuel and discharge it so that the spray becomes as thin as possible. good. In addition to the vibration (circumferential direction) shown in FIG. 10, the ring vibrator shown in FIG.
As shown in Figure 1, the vibration in the axial direction of the ring vibrator is added, and the ring vibrates in such a way that the upper and lower ends become antinodes. Therefore, as shown in FIG. 5c, the finely divided fuel is scattered upward and downward in the axial direction of the ring vibrator 12. In this way, by appropriately selecting the shape of the ring oscillator, the direction of dispersion of the atomized fuel can be adapted to a preset fuel supply system at any time.

Next, we will examine the ring vibrator's diameter, excitation frequency, ring wall thickness, liquid throughput, fatigue limit, etc.

Figure 12 shows the relationship between vibration frequency and average droplet diameter.
The diameter of the ring is shown as a parameter. As can be seen from FIG. 12, the larger the vibration frequency and the larger the ring diameter, the smaller the average diameter of the fuel tends to be. FIG. 13 shows the relationship between the ring diameter and the liquid throughput using the ring wall thickness as a parameter. As can be seen from the figure, the larger the ring diameter and the thinner the ring wall thickness, the larger the liquid throughput.

Figure 14 shows the relationship between ring thickness and durability time.
There are differences in the arm mounting methods shown in each figure. Furthermore, if the ring wall thickness is 1 mm or more, a service life of 5 years or more can be ensured.

FIG. 15 shows another embodiment. This embodiment relates to a continuous injection type fuel supply system, whereas the embodiment shown in Fig. 1 is an intermittent injection type.
Air taken in through the air cleaner 81 is moved up and down by a fuel metering piston 83 in proportion to the movement of a cantilever type air metering valve 82, and the amount of fuel is absorbed by the gap between the air and the slit 84 cut in the cylinder. The fuel is metered and sent to the injection valve 13 (continuous flow). The injection valve 13 is placed midway through the air passage of the intake pipe 6, and an ultrasonic vibrator 11 and a ring vibrator 12 are installed downstream of the nozzle of the injection valve 13 to promote atomization of the fuel. All of these controls are performed by the computer 20, and each sensor, engine water temperature sensor 8
Based on the signals such as No. 6, the opening time width of the injection valve, the control of the ignition timing, the opening time width of the EGR valve 85, and the application time and period of application of the ultrasonic vibrator 11 are determined.

Next, the circuit configuration and operation of the method for driving the ultrasonic transducer 11 described above will be explained.

As mentioned above, when the ultrasonic vibrator 11 is excited at a constant frequency, the spray injected from the fuel injection valve collides with the ring vibrator 12, instantly atomizes and is sucked into the engine, but microscopically Considering this, the moment the fuel adheres to the ring vibrator 12, the weight of the ring vibrator changes, and the resonance point of the ring vibrator 12 shifts by the amount of weight change. If the resonance point shifts in this way, the vibration amplitude for atomization cannot be ensured, atomization is delayed, and the accumulation of a liquid film is promoted, creating a vicious cycle. To overcome this phenomenon, the vibration frequency of the ultrasonic vibrator 11 that excites the ring vibrator 12 may be slightly changed by the amount of the micro liquid film. Due to this frequency change, the deposited liquid film is instantaneously atomized, and no liquid film is formed.

Therefore, as shown in Figure 16a, a steady applied voltage waveform causes the above-mentioned problem, so as shown in Figure 16b, the applied voltage cycle is changed at intervals of a certain period (0.1ms to 10ms). When the fuel is changed, the fuel supply system (15th
(see figure), uniform and fine droplet groups can be obtained.

The same thing can be said about the case of intermittent fuel supply as shown in FIG. 17 (see FIG. 1). That is, FIG. 17a shows the injection valve 1
This is the drive pulse waveform of No. 3. Therefore, fuel is injected from the injection valve 13 during this pulse-on time.
In the case of conventional ultrasonic vibration, as shown in FIG. 17b, the ultrasonic vibrator 11 is excited only during the time when the injection valve 13 is open to make the fuel spray finer. As mentioned above, if the device is excited at a certain frequency, an adverse phenomenon of liquid film formation will occur. In the case of intermittent injection, since the amount of fuel injected per unit time is always equal to the maximum flow rate, it has the disadvantage that liquid film formation is more likely to occur than in continuous injection (see FIG. 15). Therefore, as shown in FIG. 17c, if the frequency at which the ultrasonic vibrator 11 is excited by the injection valve opening time width is slightly changed as described above, the formation of a liquid film is eliminated and uniform and fine droplets are formed. A group is obtained.

Next, a specific configuration of the drive circuit will be disclosed. First, the circuit configuration in the case where the frequency of the voltage applied to the ultrasonic vibrator 11 is periodically changed in the case of continuously supplying fuel (see Fig. 15) is shown in Fig. 18.
Shown in the figure. Everything in this circuit is computer 20
Built-in. For example, 12M in the clock circuit 101.
A signal is emitted at a certain frequency by a Hz crystal oscillator 101. This clock circuit 1
01 is also used as a clock circuit for the computer 20 shown in FIG. clock circuit 10
1 signal into three frequency dividing circuits 104, 105, 10
6, the signals are converted into signals having frequencies of, for example, 21.5kHz, 20.5kHz, and 2kHz. Here 21.5kHz, 20.5k
The frequency of Hz is a frequency for exciting the ultrasonic transducer 11, and the frequency of 2kHz is a signal for switching between the excitation frequencies of 21.5kHz and 20.5kHz. Therefore, when exciting an ultrasonic transducer continuously,
This means that the excitation frequency is switched every 0.5ms. Frequency divider circuit 104 that generates 21.5kHz and 20.5k
The frequency divider circuit 105 that generates Hz separately generates signals of two types of frequencies shown in FIG. 16b,
A signal from a frequency divider circuit 106 that generates 2kHz switches between the two. AND circuit 107 and AND circuit 1
08 and the OR circuit 110 are the two types of frequency divider circuits 104 and 105 (for example, the frequency divider circuit 104 that generates 21.5kHz and the frequency divider circuit 1 that generates 20.5kHz).
05) are switched and synthesized. AND circuit 1
09 connects the signal from the OR circuit 110, which is synthesized as described above, in response to the on/off signal of the engine control I/OLSI 103 connected to the microcomputer 102. 2 power transistors 11
3 and 114 intermittent the primary side current applied to the primary side of the high voltage generating coil 115 based on the on/off signal amplified by the two knot circuits 111 and 112. The secondary side of the high voltage generating coil 115 is connected to the ultrasonic transducer 11, and alternating high frequency generated voltage is applied thereto.

Further, the circuit having the configuration shown in FIG. 18 is also used for operations including stopping of ultrasonic vibration as shown in FIGS. 17b and 17c. The generation and stop of the signal from the OR circuit 110 is controlled by the signal from the microcomputer 102, and by the control signal from the engine control I/OLSI 103 to the injector drive circuit or the on/off output provided for the vibrator drive circuit. Let's do it. The two power transistors 113 and 114 are 2
The primary side current applied to the primary side of the high voltage generating coil 115 is intermittent based on the on/off signal amplified by the two knot circuits. High voltage generation coil 1
The secondary side of 15 is connected to the ultrasonic transducer 11, and a high voltage whose frequency changes as shown in FIG. 17c is applied.

As described above, as a method of applying voltage to the ultrasonic transducer 11, the applied voltage control method as shown in FIGS. 16b and 17c has been disclosed for the above-mentioned fuel supply system, that is, continuous flow and intermittent flow. Here, when the fuel supply system is continuous injection (a vaporizer system can also be applied), a method of intermittently applying high voltage to the ultrasonic vibrator 11 can be considered, but in this method, the fuel is continuously supplied. Since the fuel is intermittently excited, the fuel spray forms a mass of spray and flies inside the intake pipe, as shown in FIG. Therefore, the ultrasonic transducer 11
If the timing of excitation is synchronized with the intake of the engine, a mass of spray will gather near the spark plug, so that stratified air supply can be achieved only by controlling the ultrasonic vibrator 11. Further, by slightly shifting the excitation time period of the ultrasonic vibrator 11 with respect to the opening time period of the injection valve, it is possible to form a spray at an arbitrary timing of intake air and to cause the spray to be sucked into the engine. At this time, a ring vibrator shape as shown in FIG. 20 is suitable. That is, the ring vibrator 12
The above-mentioned stratified air supply can be achieved by providing a step and providing a fuel retention section 91, and atomizing the fuel during the time it takes to excite the ultrasonic vibrator 11. Also, ring vibrator 1
The fuel can also be temporarily retained on the wall surface of the ring vibrator by changing the axial length and diameter of the ring vibrator.

A case may be considered in which the ultrasonic vibrator is continuously excited in the next intermittent injection. This case is effective when the amount of fuel is increased, such as when starting the engine or during excessive operation. Furthermore, by arranging the injection valve and the ultrasonic vibrator upstream of the throttle valve so that their central axes almost coincide with each other, under heavy-load operating conditions,
Since the throttle valve is nearly fully open, the atomized fuel floats in the airflow and is sucked into the intake pipe. Some of the fuel adheres to the intake pipe 6, but since it is atomized, it evaporates quickly and forms a homogeneous mixture of air and fuel. Further, under operating conditions with a small load, the opening degree of the throttle valve is small, so some fuel adheres to the upper surface of the throttle valve, but due to improved atomization, the fuel adheres uniformly to the upper surface of the throttle valve. The uniformly deposited fuel is re-atomized at the end of the throttle valve by the air flow rate depending on the pressure difference across the throttle valve. In other words, the more uniformly the fuel adheres to the upper surface of the throttle valve, the smaller the particle size downstream of the throttle valve is, and the more the mixing of air and fuel is promoted.

Another embodiment of the present invention is shown in FIG.
5 was used. With this method as well, the fuel can be made sufficiently fine, and it is also easy to manufacture.

As explained above, according to the automotive fuel supply device of the present invention, the injection valve and the ultrasonic vibrator are provided upstream of the throttle valve so that their respective central axes are substantially aligned, so that even under low load, the upper surface of the throttle valve remains The adhering fuel is re-atomized, promoting the mixing of air and fuel,
A large amount of uniform and fine droplets can be generated.

[Brief explanation of drawings]

1 and 15 show an embodiment according to the present invention, FIG. 2 shows an example of how the ultrasonic transducer is mounted, and FIGS. 3 and 4 show the structure of the ultrasonic transducer. Figure 5, Figure 6,
FIG. 7, FIG. 8, FIG. 9, FIG. 20, and FIG. 21 each show the structure of a ring vibrator. 10th
11 shows the vibration mode of the ring vibrator. Figures 12, 13 and 14 show the characteristics of the ring vibrator. FIGS. 16 and 17 are explanatory diagrams of applied pulses to the ultrasonic transducer, FIG. 18 is an explanatory diagram of the driving circuit of the ultrasonic transducer, and FIG. 19 is an explanatory diagram of the transportation situation of the spray. 30... O-ring, 31... Rubber pad, 32
...cover, 41...applied voltage terminal, 42, 43...piezoelectric element, 44...fixing plate, 45...flange, 46...
Horn part, 47...Ring vibrator fixing screw, 48...
Piezoelectric element crimping screw, 49...Fixing gap, 5
1...Arm, 52...Fixing screw, 53...Vertical rim,
54...Horizontal rim, 55...Taper, 56...Medium ring, 60...Vibration mode, 81...Air cleaner, 8
2...Air amount metering valve, 83...Fuel metering piston,
84...Slit, 85...EGR control valve, 86...Cooling water temperature sensor, 91...Fuel retention section, 101...Clock circuit, 102...Microcomputer, 10
3... Engine control I/OLSI, 104, 105,
106... Frequency dividing circuit, 107, 108, 109... AND circuit, 110... OR circuit, 111, 112...
Knot circuit, 113, 114... power transistor, 115... high voltage generation coil, 11... ultrasonic vibrator.

Claims (1)

[Scope of Claims] 1. The fuel injection valve includes an injection valve that measures and supplies fuel upstream of the intake pipe, an air amount sensor that measures the amount of air, and a throttle valve that determines the operating state of the engine. In the automobile fuel supply device that sprays the fuel into the intake pipe by opening the valve, the injection valve is provided upstream of the throttle valve substantially on the central axis of the intake pipe, and the injection valve is provided downstream of the injection valve. A fuel for an automobile, characterized in that a cylindrical vibrator supported by a sonic vibrator is provided substantially on the central axis, and the excitation frequency of the ultrasonic vibrator is changed at a predetermined period to atomize the fuel. Feeding device. 2. The fuel supply device for an automobile according to claim 1, wherein the cylindrical vibrator is formed in a cylindrical shape. 3. The fuel supply device for an automobile according to claim 1, wherein the cylindrical vibrator is formed into a rectangular tube shape. 4. The fuel supply device for an automobile according to claim 1, wherein the cylindrical vibrator is formed into a cylinder, and the inside of the cylinder is formed in a tapered shape. Device. 5. An automobile fuel supply device according to any one of claims 1 to 4, characterized in that a rim is provided between the ultrasonic vibrator and the cylindrical vibrator. fuel supply device. 6. In the automobile fuel supply system according to any one of claims 1 to 5, the excitation frequency of the ultrasonic vibrator is synthesized by combining a clock frequency transmitted from a computer for controlling an internal combustion engine. An automobile fuel supply device characterized by frequency division.