JPH01294958A - Fuel injection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To perform injection of fuel in an arbitrary injection rate with excellent responsiveness by providing a means, which adjusts a pipe line for its releasing amount, and a means, communicating with a drain tank, in the pipe line connecting a fuel plunger pump to an injection nozzle. CONSTITUTION:When a cam 2 rotates following action of an engine, a plunger 4 in a pump 3 moves. While being based on a detection signal from a crank angle sensor 38, a controller 40 closes a selector valve 12 disconnecting the communication of a high pressure passage 11 with a drain tank. While because the controller 40 extends a piezoelectric element 17 through a driver 41, a throttle valve 20 advances in an adjusting chamber 14, disconnecting the high pressure passage 11 from an injection passage 30 by a seal part 24 of the throttle valve. Thereafter, being based on a detection signal from an engine speed sensor 39 or the like, the controller 40 contracts the piezoelectric element 17 retracting the throttle valve 20. As the result, fuel is supplied passing through the injection passage 30 to an injection nozzle 31 performing pilot injection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a fuel injection device during internal combustion.

[Prior Art] In a diesel engine fuel injection system, a plunger is moved by a cam plate that is rotated in synchronization with a crank installed in the engine, and the plunger is moved forward to pressurize the fuel in a pressurizing chamber. The amount of fuel injected at one time by an injection nozzle is adjusted by mechanically controlling the position of a spill ring that closes a passage that opens pressure fuel to a low-pressure side.

However, with this mechanical adjustment, although it is possible to adjust the injection amount, it is impossible to select the amount of injected fuel when the cam plate rotates by a certain angle, that is, to change the injection rate. For this reason, it is not possible to respond appropriately to the knocking phenomenon caused by the pressure increase due to the explosive combustion of the fuel injected during the ignition delay, and the increase in smoke that occurs during acceleration. I left some room.

In order to change the injection rate as described above, for example,
In No. 174561 and JP-A-62-3133,
A fuel injection device for a diesel engine as described below is disclosed.

That is, the fuel injection device disclosed in Japanese Patent Application Laid-Open No. 62-174561 has a control valve communicated with a high-pressure passage provided between a plunger pump and an injection nozzle. This control valve has a built-in piezo stack, and the control valve is opened and closed by operating voltage to expand and contract the piezo stack.

Then, as the cam rotates, the plunger in the plunger pump pressurizes the fuel in the pressurizing chamber, and this pressurized fuel is sent to the high pressure passage, and when the control valve is opened, the pressurized fuel passes through the control valve. By causing the fuel to flow into the drain passage, the injection nozzle is prevented from injecting fuel.

When the control valve is closed in the above state, the pressurized fuel flows into the inflow path of the injection nozzle, applies pressure to the needle valve, and opens the needle valve to cause the nozzle to inject fuel. after this,
A potential is applied to the piezo stack according to a predetermined duty ratio, the control valve is intermittently opened and closed, and the injection rate is adjusted.

Furthermore, in the fuel injection device disclosed in Japanese Patent Application Laid-open No. 62-3133, fuel in a pressurizing chamber is pressurized by a plunger driven by a cam action, and a pressure regulating chamber is provided in communication with the pressurizing chamber. The volume is variably set using a piezo element. Then, the plunger is moved forward to pressurize the fuel in the pressurizing chamber, and the pressurized fuel is injected from the injection nozzle to perform pilot injection. By short-circuiting the terminals of the piezo element during the forward movement of the plunger, the piezo element is rapidly contracted, the volume of the pressure adjustment chamber is rapidly increased, and the pressure inside the pressurization chamber is lowered at once. As a result, fuel injection from the injection nozzle is temporarily stopped, and when the plunger moves forward to a distance corresponding to the increased volume of the pressure adjustment chamber, the fuel in the pressure chamber is pressurized again, and the fuel injection by the nozzle The main injection is performed.

[Problems to be Solved by the Invention] Of the two fuel injection devices described above, the former has a configuration in which the control valve is opened and pressurized fuel is drained when not injecting, so there is no power loss when controlling the injection rate. It will be extremely large.

Additionally, during the intake stroke, the pressure in the high pressure passage drops to the fuel supply set pressure. This pressure drop extends not only to the high pressure passage but also to the injection nozzle. Therefore, when the fuel is pressurized with the next stroke of the plunger, the pressure rise characteristics are very poor because the pressure in the high pressure passage and the injection nozzle is reduced, and desired control cannot be performed due to a delay in pressure response.

In addition, the latter fuel injection device is configured with a focus on pilot injection, and the injection rate cannot be arbitrarily controlled over the entire fuel injection period, making it difficult to control smoke at high engine speeds, for example. It's impossible.

Furthermore, by arranging the pressure adjustment chamber upstream of the pressurizing chamber, the residual pressure between the delivery valve and the injection nozzle cannot be controlled. Therefore, the pressure within the injection pipe becomes a value that is influenced by the operating conditions, causing a surge phenomenon and the like, which deteriorates drivability and, depending on the residual pressure value, causes a delay in the response of the next injection.

In addition, fuel that remains between the pressurizing chamber and the injection nozzle after injection ends may continue to be injected or drip from the injection nozzle, worsening vibration and noise, and increasing harmful components in exhaust gas such as HC due to incomplete combustion. This may lead to empty fuel costs.

This invention was made to solve the above-mentioned problems, and its purpose is to avoid loss of power, and
Internal combustion that operates at any injection rate depending on the engine operating status, etc., and has excellent responsiveness, reduces vibration and noise, reduces harmful components in exhaust gas, and reduces fuel consumption. The purpose of the present invention is to provide a fuel injection device for an engine.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes a plunger pump that pressurizes fuel in a pressurizing chamber when a plunger moves forward, and a plunger pump that is connected to the pressurizing chamber of the plunger pump. ,
an injection nozzle that injects pressurized fuel sent from the pressurizing chamber; an adjustment means that is interposed in a pipe line connecting the plunger pump and the injection nozzle and adjusts the opening amount; a switching means for disconnectably communicating the high pressure fuel passage and the drain tank on the upstream side; a detection means for detecting at least one of the operating state of the engine and the pressure state in the pipe; The injection start time and injection end time are set according to the detection results, and at the start of injection, the switching means is switched to shut off the high-pressure fuel passage and the drain tank, and then the signal instructing the opening amount of the adjustment means is adjusted as described above. In addition to outputting to means,
The gist of the present invention is to provide a control means which outputs a signal supporting the closing of the adjustment means at the end of injection and then drives the switching means to communicate the high pressure fuel passage with the drain tank.

[Operation] At the time of injection start set by the control means based on the detection result of the detection means, the switching means is driven in accordance with the signal output by the control means, and communication between the high pressure fuel passage and the drain tank is cut off and the inside of the pipe is After the pressure is increased, the amount of opening of the regulating means is adjusted, and the injection rate is controlled over the entire injection time of the injection nozzle by changing the cross-sectional area of the fuel passage according to the amount of opening. Further, at the end of injection set by the control means based on the detection result of the detection means, the adjustment means is closed based on a signal output from the control means, and then the residual pressure between the adjustment means and the injection nozzle is adjusted to an appropriate value. The switching means is driven to establish communication between the equal pressure fuel passage and the drain tank, and the pressure in the pipe is lowered again.

[Example] Hereinafter, a first example of the present invention will be described in detail with reference to FIGS. 1 to 5.

In FIG. 1, in a fuel pressure booster 1, an outer end abutment plate 5 of a plunger 4 retracted within a plunger pump 3 is pressed against a cam 2 that rotates as the engine operates due to the biasing force of a compression spring 6. . A pressurized chamber 7 whose volume is variably changed by movement of the plunger 4 is configured within the plunger pump 3 .

The pressurizing chamber 7 is connected to a fuel pump 9 of a fuel supply device 8 via a check valve 10, and when the plunger 4 is moved to the suction position shown by the two-dot chain line according to the cam shape of the rotating cam 2. , the fuel (light oil) discharged from the pump 9 is adjusted to a pressure value set in advance by the relief valve 9a,
It passes through the check valve 10 and is sucked into the pressurizing chamber 7.

The pressurizing chamber 7 of the fuel pressure booster 1 is connected via a high-pressure passage 11 to an electromagnetic switching valve 12 and a high-speed response variable displacement mechanism 13, which are normally open. The variable capacity mechanism 13 includes a flow rate adjustment chamber 14 communicating with the high pressure passage 11, and a pressure applying chamber 16 communicating with the flow rate adjustment chamber 14 from the rear via a pressure transmission path 15. The volume of the pressure generating chamber 19 between the front side surface of the sliding member 18 attached to the front end of the piezo element 17 in the pressure applying chamber 16 and the front inner wall of the piezo element 17 is determined by the expansion and contraction of the piezo element 17. The transformed pressure generated by the change in the voltage is transmitted to the transmission path 15.

Further, a throttle valve 20 is disposed within the flow rate adjustment chamber 14, and a large diameter spring bearing part 21 is formed on the circumferential surface of the throttle valve 20. A pressure receiving part 22 having a shape is provided in a protruding manner.

Further, the front inner wall of the adjustment chamber 14 and the spring receiver are formed with a pointed tip formed at the front end of the throttle valve 20 because the throttle valve 20 is always biased rearward by a compression spring 23 installed between the front inner wall of the adjustment chamber 14 and the spring receiver part 20. The shaped seal portion 24 opens the valve seat 25 and closes it as shown by the two-dot chain line by the negative pressure generated in the high pressure passage 11 during the suction stroke.

Further, the variable capacity mechanism 13 is provided with a pressure balance passage 26 that bypasses the flow rate adjustment chamber 14 and communicates the high pressure passage 11 and the transmission passage 15, and the pressure of the high pressure passage 11 is guided to the balance chamber 46 by this balance passage 26. As a result, the axial force due to the fuel pressure applied to the throttle valve 20 is canceled out. Therefore, the throttle valve 20 is held at an appropriate position by the pressure of the compression spring 23 and the transmission path 14. Further, pressure sensors 28 and 29 are attached to the high pressure passage 11 and the adjustment chamber 14, respectively, to detect the internal pressures thereof.

Further, the flow rate adjustment chamber 14 is connected to an injection nozzle 31 via an injection passage 30, and its needle valve 32 is connected to a compression spring 3.
3, it is always biased in the closing direction. Then, when pressurized fuel is supplied from the adjustment chamber 14 of the variable displacement mechanism 13 to the injection nozzle 31, this pressure moves the needle valve 32 in the opening direction against the force of the compression spring 33, and the injection Fuel injection is performed from the hole 34. Then, this injected fuel is drawn in at a separate stage, mixed with compressed air in the combustion chamber, and combusted.

The controller 40 also includes the pressure sensors 28 and 29.
In addition, there is a temperature sensor 35 that monitors the temperature of the intake air, an ignition timing sensor 36 that detects the time during which the injected fuel burns in the combustion chamber by monitoring temperature, etc., an accelerator position sensor 37 that detects the amount of accelerator operation, and an accelerator position sensor 37 that detects the amount of accelerator operation. A crank angle sensor 38 that detects the crank angle and an engine rotation speed sensor 39 are respectively connected. Furthermore, the controller 40 is connected to the terminal of the piezo element 17 of the variable capacity mechanism 13 via the switching valve 12 and the driver 41.

The controller 40 has control means and various sensors 2.
8, 29, and 35 to 39 constitute a detection means, and various operating characteristic signals are transmitted to these pressure sensors 28, 29 and sensors 35 to 39 during pressure in the pipe and engine movement.
is output to the controller 40. Then, the controller 40 reads data from a pre-stored program according to these operating characteristic signals, calculates the injection rate, injection timing, injection time, and injection amount that match the operating state of the engine, and outputs a signal based on the calculation results. The signal is output to the switching valve 12 to close it. Thereafter, the controller 40 sends a signal to the driver 41, and the driver 41 outputs a voltage signal to the piezo element 17 of the variable capacitance mechanism 13 based on this signal to cause the element 17 to expand or contract.

The volume of the pressure generation chamber 19 is changed by the expansion and contraction of the piezo element 17, and the resulting pressure change generated by the compression of the fuel in the generation chamber 19 is applied to the throttle valve 20 in the transmission path 15.
The pressure is transmitted to the end face of the pressure receiving part 22, and the throttle valve 20 is connected to the adjustment chamber 14.
The high pressure passage 11 is opened and closed by being displaced inside.

Now, the crank of the engine is rotated by a predetermined angle, and due to the rotation of the cam 2, the plunger 4 in the plunger pump 3 starts to move toward the solid line position. The rotation of the crank described above is detected by the crank angle sensor 38, and based on the detection signal from the crank angle sensor 38, the controller 40 outputs a voltage signal to the switching valve 12 to close it (Fig. 2 (■)). , the communication between the high pressure passage 11 and the drain tank is cut off. Prior to this, the piezo element 17 is expanded by a predetermined amount via the driver 41 in response to a signal output from the controller 40, and the throttle valve 20 is displaced in the adjustment chamber 14, and the seal portion 24 connects the high pressure passage 11 and the injection passage. 30 is cut off.

After this, when the cam 2 further rotates, the fuel in the pressurizing chamber 7 is compressed and pressurized, and the pressure in the high pressure passage 11 is increased. When the crank angle sensor 38 detects a predetermined angle before injection, it outputs a detection signal to the controller 40. Then, the controller 40 calculates the injection timing according to the signal from the rotation speed sensor 39, etc., and lowers the voltage applied to the piezo element 17 at a timing based on the calculation result (Fig. 3 ■) to contract it. Throttle valve 20 in the adjustment chamber 14
to retreat. As a result, the seal portion 2 of the throttle valve 20
4 is pushed backward to open the valve seat 25 and open the high pressure passage 1.
Pressurized fluid flows into the injection passage 30 from adjustment chamber 1 through adjustment chamber 4, and the pressure within the injection passage 30 increases (Fig.
). Then, this pressure is applied to the injection nozzle 31, the needle valve 32 is opened against the force of the compression spring 33, and pilot injection of fuel is started at an appropriate timing (
Figure 5 ■).

After this, the fuel supply to the injection nozzle 31 is cut off in order to suppress diesel knock. That is, controller 4
0 outputs a signal to the driver 41 according to the program and applies a voltage to the piezo element 17 (Fig.
Cut off communication with. At this time, the pressure inside the injection passage 30 and the injection nozzle 31 is still rising (Fig. 4 ■),
Viloft injection! l! However, due to the above-mentioned interruption between both passages 11 and 30, the pressure in the high pressure passage 11 rises again with a slight delay, and the pressure in the injection passage 30 and injection nozzle 31 decreases to the level of the needle valve. 32 descends until it closes.

After the pilot injection ends with a slight delay from the expansion of the piezo element 17, the controller 40 outputs a signal to the driver 41 to perform the main injection, and reduces the voltage value applied to the piezo element 17 (the first Figure 3 ■). As a result, pressurized fuel passes through the injection passage 30 to the injection nozzle 3.
1 and flows into the needle valve 3 in the injection nozzle 31.
The injection passage 3 whose spring pressure was lower than the spring pressure of the compression spring 33 of No. 2
The pressure inside 0 gradually increases and exceeds the same spring pressure (4th
Figure ■), the needle valve 32 is opened and main injection is started (Figure 5 ■).

At the time of main injection, the controller 40 accurately grasps the operating condition of the engine in advance based on signals from various sensors 28, 29, 35-39, and calculates an injection rate suitable for this. Then, a signal according to this calculation result is sent to the driver 41.
The voltage applied to the piezo element 17 is lowered while changing the voltage value as appropriate (Fig. 3 -). Accordingly,
With the displacement of the throttle valve 20 in the adjustment chamber 14, the amount of communication between the high pressure passage 11 and the injection passage 30 continuously shows minute changes, leading to changes in the pressure inside the injection passage 30 and the injection nozzle 31. (Figure 4 ■). Then, main injection is performed while changing the injection rate in accordance with a change in the opening amount of the needle valve 32 in the injection nozzle 31 due to a change in the pressure in the injection nozzle 31 (FIG. 5).

Then, when the controller 40 recognizes that the injection end time is near based on the signal from the crank angle sensor 38,
Outputs a signal to the switching valve 12 and opens it (Fig. 2
). At the same time, the controller 40 outputs a signal to the driver 41 and applies a predetermined voltage to the piezo element 17 to cause it to expand (Fig. 3 ■).
0 by moving the high pressure passage 11 and the injection passage 30.
Cut off communication with. At this time, the pressure in the injection passage 30 and the injection nozzle 31 is decreasing (Fig. 4 (■)), and the main injection is also continued while weakening the injection pressure. Then, the main injection was terminated at a timing slightly later than this (Fig. 5 ■).

Thereafter, the controller 40 reduces the voltage applied to the piezo element 17 via the driver 41 (FIG. 2), and causes the throttle valve 20 in the adjustment chamber 14 to move back slightly. Thereby, the residual pressure in the injection passage 30 and the injection nozzle 31 is maintained at an appropriate value, and the compression stroke of the next stroke of the plunger 4 is waited for.

Furthermore, when the engine is operating at high speed, control is performed to achieve appropriate timing, duration, and amount using a Δ-shaped injection rate waveform, as shown in FIG. This overcomes the conventional drawback of smoke generation during acceleration.

In the above embodiment, control of the injection rate depends only on adjusting the flow rate of the pressurized fuel by displacement of the throttle valve 20 in the flow rate adjustment chamber 14, and when controlling the injection rate, the control of the injection rate from the pressurization chamber 7 is performed. Since the pressurized fuel flowing to 31 is not drained in the middle of the flow path, power loss is avoided.

Furthermore, by opening the switching valve 12 at the end of injection and draining the pressurized fuel in the high pressure passage 11, it is possible to avoid pressurized fuel from flowing into the adjustment chamber 14 and the injection passage 30 after the injection ends. .

Therefore, the amount of pressurized fuel that reaches the injection nozzle 31 after injection is completed is extremely small, and surplus fuel is less likely to be injected or dripped from the injection nozzle 31.

Next, a second embodiment of the present invention will be described with reference to FIGS. 7 and 8. In this embodiment, an accumulator 42 is provided in the high-pressure passage 11, and when the high-pressure passage 11 and the injection passage 30 are cut off by the throttle valve 20 in the adjustment chamber 14 and the pressure inside the high-pressure passage 11 is increased, the accumulator 42 remains there. The structure is such that pressurized fuel is absorbed into the accumulator 42 and pressure is accumulated.

With this configuration, the injection rate will draw a curve as shown by the solid line in FIG. ), it is now possible to widen the injection time range, which was almost determined by the cam shape when not in use, and the overpressure bone can be effectively utilized for injection rate control (
Figure 8 (shaded area).

Next, a third embodiment of the present invention will be described with reference to FIG. This embodiment shows a modification of the fuel pressure booster 1, in which the first
A hydraulic mechanism is used in place of the cam 2 in the embodiments to the third embodiment.

That is, the controller 40 recognizes the injection timing from the signals from the crank angle sensor 38 and the engine speed sensor 39, outputs a signal to the three-way valve 43, and maintains it in the communication position shown. Then, the accumulator 44 is communicated with the low pressure chamber 45 of the plunger pump 3 via the three-way valve 43, and by increasing the volume of the low pressure chamber 45,
The fuel in the pressurizing chamber 7 is pressurized and sent to a high pressure passage to perform fuel injection.

Further, when fuel injection is not performed, the plunger 4 is held in the upper position by the biasing force of the compression spring 6, and the pressurizing chamber 7
The fuel discharged by the pump 9 is sucked by the negative pressure generated inside.

With this configuration, the fuel pressure booster 1 does not need to include the cams of the above embodiments, and the manufacturing process can be simplified without designing and manufacturing complicated cams.

[Effects] As detailed above, according to the present invention, power loss can be avoided, the engine can be operated at any injection rate depending on the operating condition of the engine, etc., and furthermore, it has excellent responsiveness. It is effective in reducing fuel vibration and noise, reducing harmful components in exhaust gas, and reducing fuel waste.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of the hydraulic system and electrical system showing the first embodiment of the present invention, Fig. 2 is a diagram showing changes in voltage applied to the switching valve, and Fig. 3 is related to Fig. 2. Fig. 4 is a diagram showing the pressure in the injection passage and the injection nozzle in relation to Fig. 2.3, and Fig. 5 is a diagram showing the pressure in the injection passage and the injection nozzle in relation to Fig. 2.3. FIG. 6 is a diagram showing the injection rate during high-speed operation, and FIG. 7 is a hydraulic and electrical circuit showing a second embodiment of the present invention. Similarly, FIG. 8 is a diagram showing changes in the injection rate in the second embodiment, and FIG. 9 is a circuit diagram of the hydraulic system and electric system showing the third embodiment. Plunger pump 3, plunger 4, pressurizing chamber 7, high-speed response variable displacement mechanism 13 as adjustment means, switching valve 12 as switching means, pressure sensors 28, 29, temperature sensor 35, ignition timing sensor 36 and accelerator as detection means Position sensor 37, crank angle sensor 38, engine speed sensor 39, injection nozzle 31, controller 40° as a control means Patent applicant Toyota Industries Corporation Agent
Patent Attorney On 1) Hiroshi Nobunobu Figure 6 Figure 8 Injection v1 ■ Kabuto injection time □ Injection time -chi

Claims (1)

[Claims] 1. a plunger pump that pressurizes fuel in a pressurizing chamber when the plunger moves forward; an injection nozzle that communicates with the pressurizing chamber of the plunger pump and injects pressurized fuel sent from the pressurizing chamber; and the plunger pump. an adjusting means that is interposed in a pipe connecting the injection nozzle and the injection nozzle and adjusts the amount of opening; and a switching means that connects the high-pressure fuel passage upstream of the adjusting means and the drain tank in a disconnectable manner in the pipe. , a detection means for detecting at least one of the operating state of the engine and the pressure state in the pipe, and setting the injection start time and injection end time according to the detection result of the detection means, and switching the switching means at the time of starting injection. After driving to shut off the high pressure fuel passage and the drain tank, outputting a signal instructing the opening amount of the adjusting means to the adjusting means,
A fuel injection device for an internal combustion engine, comprising: a control means that outputs a signal supporting closing of the adjustment means at the end of injection, and then drives the switching means to communicate the high pressure fuel passage with a drain tank.