JPH0362906B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device that can arbitrarily control the injection timing of a fuel-injected internal combustion engine.

As a fuel injection device for a fuel injection type internal combustion engine, such as a diesel engine, there is a device called a unit injector as described in Japanese Patent Application Laid-Open No. 54-50726 or SAE Paper 750773.

Unlike normal injection devices, this device does not require the pump and injection valve to be connected via a long high-pressure pulse, so the injection rate can be easily increased.
For this reason, it is easier to control the injection timing,
This has the advantage of reducing the impact on exhaust emissions, fuel efficiency, etc.

That is, what was disclosed in the above-mentioned SAE paper is shown in FIGS. 1 and 2. A cam 1 that rotates in synchronization with the rotation of the engine and a rocker arm 2 are interlocked via a push rod 3, and a driven spring 4 is a mechanism that pressurizes the fuel in the pressure chamber 8 by pushing down the driven rod 5 with the rocker arm 2, thereby pushing down the plunger 7 in the pusher 6;
A mechanism for feeding fuel from the filter 9 to the pressure chamber through the vicinity of the spill deflector 10 via the upper port 11, the fuel relief hole 12 and the lower port 13, and the mechanism for feeding the fuel pressurized in the pressure chamber 8 through the fuel passage 14 to the pressure A mechanism for injecting fuel into the chamber 15, lifting the needle valve 17 against the spring 16 as the pressure in the pressure chamber 15 increases, and injecting the fuel from the nozzle 19 provided in the nozzle tip 18, A mechanism for rotating the gear 21 and rotating the plunger 7 is provided. Then, the upper edge 2 of the measuring groove 22
The plunger 7 is rotated by a control rack 20 via a gear 21 so that the injection amount and injection start and end timing are determined depending on the position and shape of the plunger 3 and the lower edge 24.

Therefore, in such a fuel injection device, the plunger rotation position is specified in response to the injection amount, thereby fixing the injection timing. Moreover, this method has the disadvantage that it is not possible to select the optimal injection timing under all engine operating conditions and thereby improve exhaust performance and fuel efficiency, and the device itself requires high-precision machining. It was hot.

In view of the above-mentioned disadvantages, it is an object of the present invention to arbitrarily control the injection amount and injection timing of an injection device, which is a unit injector, to eliminate the above-mentioned disadvantages of the conventional device.

To this end, the present invention provides two pressure chambers, a main pressure chamber and a sub-pressure chamber, whose volumes change by means of a plunger that reciprocates in synchronization with engine rotation, and a checker mounted in a direction that allows fuel suction to the main pressure chamber. A spool valve is interposed in a relief passage which is connected to the suction passage via a valve, is connected to the fuel injection passage, and further relieves the main pressure chamber to a low pressure fuel source, and is located at a predetermined position in the axial direction of the spool valve. The relief passage is configured to open, and the position of the spool valve is controlled by the pressure within the sub-pressure chamber. That is, the fuel pressure in the main pressure chamber and the sub-pressure chamber is always received, and when the pressure in the sub-pressure chamber exceeds a predetermined pressure difference with respect to the pressure in the main pressure chamber, the sub-pressure chamber is used as a low-pressure fuel source. a control valve which opens to A control device for controlling the opening/closing operation of the metering valve is provided to control the position of the spool valve, thereby controlling the timing of relief to the low pressure source of the main pressure chamber by simply controlling the opening/closing of one metering valve. The fuel injection timing and fuel injection amount can be controlled arbitrarily and with high precision, and the metering valve is opened and closed when the fuel pressure applied to the valve is low.
The driving electromagnetic force of the metering valve can be reduced, and the electromagnetic actuator can be downsized.

Embodiments of the present invention will be described below based on the drawings.

Unit injector 3 shown in Figures 3 to 7
The first plunger 32 is pushed down inside the cylinder portion 33 by a cam mechanism that rotates in synchronization with the crankshaft of the engine, as in the previous example of the conventional device, or directly by the cam mechanism, and It is moved upward by the elastic force of the driven spring 34. The lower end of the first plunger 32 is connected via a pawl 36 to the upper end of a second plunger 35 which is slidably inserted into the barrel portion 37 of the unit injector.
The plunger 32 and the second plunger 35 are configured to reciprocate together. The outer diameter of the lower end of the first plunger 32 is larger than the outer diameter of the second plunger 35.
The volume of the auxiliary pressure chamber 39 is changed by the reciprocation of the second plunger 35, and the volume of the main pressure chamber 40 formed below the second plunger 35 is changed by the reciprocation of the second plunger 35. It's getting old. Then, fuel (low-pressure fuel source) pre-pressurized by a pre-pressure pump 43 from a fuel tank 42 is introduced into the main pressure chamber 40 through an intake passage 44 and via a 45 installed in a direction that allows fuel intake. On the other hand, fuel is also introduced into the subpressure chamber 39 from the prepressure pump 43 via the passage 46 .

The needle valve 5 is connected to the injection port 49 of the nozzle tip portion 48 through the main pressure chamber 40 and the injection passage 47, and serves as a valve body that opens and closes the injection passage 47.
0 receives the fuel pressure in the pressure chamber 51 provided in the injection passage 47, and when the fuel pressure rises above a predetermined value, lifts against the needle spring 52 to open the injection passage 47 and release the fuel. is injected into the combustion chamber of an engine (not shown).

Fuel leaking from the pressure chamber 51 through the vicinity of the needle valve 50 passes through the spring chamber 53, the spill passage 54, and is recirculated into the fuel tank 42 via the return passage 55.
The fuel leaking from the main pressure chamber 40 through the periphery of the first plunger 32 and the second plunger 35 flows into the return passage 55 via an annular passage 56 on the outer periphery of the first plunger 32, which is also provided in the middle of the spill passage 54. It is starting to be refluxed.

The fuel pressure in the main pressure chamber 40 is transferred to the pre-pressure pump 43 through the spool valve 60 and the relief passage 61.
(positive pressure fuel source). That is, the spool valve 60 has an annular groove 62 on its outer periphery, and is a valve that opens a relief passage 61 at a predetermined position in the axial direction of the spool valve 60, and the position control of the spool valve 60 is performed by receiving pressure having an equal area at both ends in the axial direction. Control room 6 facing the surface
3 and the back pressure chamber 64, it is moved in one direction or stopped. The pressure in the control chamber 63 and the back pressure chamber 64 is controlled by the fuel pressure in the auxiliary pressure chamber 39 and the control valve 70. That is, the sub-pressure chamber 39 and the control chamber 63
are connected in communication by a control passage 65, and the control passage 65 is connected to a low pressure fuel source via a passage 46;
The opening and closing of the passage 46 is controlled by a control valve 70.

The control valve 70 receives the pressure in the auxiliary pressure chamber 39 even when the passage 46 is closed, but its pressure receiving area is smaller than the pressure receiving area when the valve is open. A spring 72 is interposed to bias the valve in the valve closing direction. The pressure inside the main pressure chamber 40 is connected to the control pressure chamber 71 through a passage 73.
The passage 73 is connected via a metering valve 80 to a low pressure fuel source. That is,
A metering valve 80 is interposed at a position that opens and closes communication of the passage 73 (a bypass passage that bypasses the fuel relief passage 61 and connects the main pressure chamber 40 and the low-pressure fuel source).
Further, the back pressure chamber 64 is always supplied with low pressure fuel sent from the prepressure pump 43.

The metering valve 80 includes a rotation sensor 91 for detecting engine rotational speed, such as a crank angle sensor for detecting the crank angle of the engine, a load sensor 92, such as an accelerator opening sensor for detecting the depression angle of an accelerator pedal, and the like. A control circuit 94 serving as a control device receives an engine operating state detection signal from an engine operating state detection device such as a water temperature sensor 93 that detects the engine cooling water temperature, and determines the optimal fuel injection amount and fuel injection according to the engine operating state. It calculates the start and end, and inputs the output signal to the electromagnetic actuator 95 to perform on/off control. In the figure, reference numeral 98 denotes a pressure regulator that controls the pressure of the fuel discharged from the pre-pressure pump 43 to be constant.

The operation of the fuel injection device having such a configuration will be explained next.

When the first plunger 32 and the second plunger 35 integrated therewith are pushed down in synchronization with engine rotation, the fuel in the main pressure chamber 40 is forced into the suction passage 44 and the injection passage 47, but the check valve 4
5 is closed, the fuel is guided to the pressure chamber 51 via the injection passage 47, the needle valve 50 is lifted against the elastic force of the needle spring 52, the nozzle 49 is opened, and fuel is injected and supplied to a combustion chamber (not shown). be done. On the other hand, the first and second plungers 32,
In the suction stroke in which the pressure chamber 51 moves upward, the pressure chamber 51
The internal pressure decreases and the needle valve 50 closes the nozzle 49 due to the elastic force of the needle spring 52. Then, the check valve 45 is opened, and the fuel in the fuel tank 42 is sucked into the main pressure chamber 40 through the prepressure pump 43 and the suction passage 44.

and the first and second plungers 32, 35
In the compression stroke, the spool valve 60 opens the relief passage 61 through the annular groove 62 depending on its control position, thereby relieving the compressed fuel in the main pressure chamber 40 to the low-pressure fuel source side, and injecting the fuel. The end date will be determined. On the other hand, the fuel injection start timing is determined by closing the metering valve 80. Also, the fuel injection period that determines the fuel injection amount is determined by the spool valve 6.
0 is the axial movement stroke of the spool valve 60 until the end of fuel injection when the relief passage 61 is opened, and it depends on the left end position of the spool valve 60. The left end position of the spool valve 60 is the first and second
During the suction stroke of the plungers 32 and 35, the control valve 70 closes and the fuel in the control chamber 63 is sucked into the auxiliary pressure chamber 39, which is controlled by moving the spool valve 60 to the left position in the figure. , the amount of movement thereof is controlled by the valve closing timing of the control valve 70. The closing timing of the control valve 70 is controlled by the opening of the metering valve 80.

The operation of such a fuel injection device will be explained in order of the operating stroke.

FIG. 3 shows the state in the compression stroke before fuel injection. That is, at this time, the metering valve 80 is open.
Therefore, the first plunger 32 and the second plunger 3
5 is pushed down and the fuel in the main pressure chamber 40 is pushed out, the check valve 45 is closed, but the metering valve 80 is open and the passage 73 is in communication with the low pressure fuel source, so the fuel in the main pressure chamber 40 is pushed out. The pushed out fuel is
It passes through the passage 73 and is relieved toward the suction passage 44 side. On the other hand, the fuel in the auxiliary pressure chamber 39 is
is opened against the relieved pressure in the main pressure chamber 40 and the elastic force of the spring 72, and is relieved into the suction passage 44 via the passage 46.
In other words, this means that even if the fuel pressure in the main pressure chamber 40 is transmitted to the pressure chamber 51 via the injection passage 47,
Since the pressure value is low, the needle valve 50 cannot be lifted against the elastic force of the needle spring 52, and the auxiliary pressure chamber 3
Even when the first plunger 32 is pushed down, the pressure of the fuel in the fuel in the auxiliary pressure chamber 39 does not increase, so that the pressure in the auxiliary pressure chamber 39 and the back pressure chamber 64 are introduced into the control chamber 63. The fuel pressure in the main pressure chamber 40 becomes equal to the fuel pressure in the main pressure chamber 40, and the spool valve 60 is not moved to any position.
The pressure inside is slightly higher than the pressure inside the main pressure chamber 40, which tends to move the spool valve 60 to the right in the figure, but due to the sliding resistance of the spool valve 60 and the viscous resistance of the fuel oil, There is almost no rightward movement of the valve 60).

In other words, even if the first and second plungers 32, 35 are pushed down, it cannot become an effective stroke for fuel injection.

Next, in order to start fuel injection, the control circuit 94 calculates the fuel injection start timing according to the engine operating conditions such as the rotation sensor 91, load sensor 92, water temperature sensor 93, etc., and sends the output signal to the electromagnetic actuator. 95 and closes the metering valve 80. Therefore, the relief of the passage 73 is closed by the metering valve 80 and the suction passage 44 is closed by the check valve 45, so that the fuel pressure in the pressure chamber 51 is reduced through the injection passage 47. It rises against the elastic force of the needle spring 52, opens the needle valve 50, and injects fuel from the nozzle 49 into a combustion chamber (not shown).

At the same time, due to the closing operation of the metering valve 80, the fuel pressure in the control pressure chamber 71 increases and the control valve 70
is moved to the left in the figure, and the passage 46 is closed. When the control valve 70 is in the closed state, the pressure receiving area on the side of the auxiliary pressure chamber 39 is small, so that the once closed state can be reliably maintained.

By closing the control valve 70, the fuel in the auxiliary pressure chamber 39 is introduced into the control chamber 63 via the control passage 65, and the fuel is introduced into the control chamber 63 through the control passage 65, and the fuel is introduced into the control chamber 63 through the pressure difference between the discharge pressure of the prepressure pump 43 and the back pressure chamber 64. Therefore, move the spool valve 60 to the right in the figure.

When the spool valve 60 continues to move to the right and the annular groove 62 opens the relief passage 61, the fuel in the main pressure chamber 40 is relieved to the low pressure side via the relief passage 61. As a result, the fuel pressure in the pressure chamber 51 decreases, and the needle valve 50 is closed by the elastic force of the needle spring 52, ending fuel injection.

Therefore, the fuel injection period is a period from the left end position of the spool valve 60 until the annular groove 62 opens to the relief passage 61 by moving to the right.

Next, the first and second plungers 32 and 35 complete the lift operation by the cam, and the driven spring 34
When the upward movement is started by the elastic urging force, fuel is sucked into the sub pressure chamber 39 and the main pressure chamber 40. At this time, in the main pressure chamber 40, the check valve 45 is opened due to the differential pressure between the prepressure pump 43 and the heating material discharge pressure, and fuel is introduced through the suction passage 44. In addition, in the case of the auxiliary pressure chamber 39, the intake fuel is transferred to the control passage 6.
5 to the fuel in the control chamber 63. Therefore, compared to the fuel pressure in the control passage 65,
Main pressure chamber 4 sufficient to open check valve 45
The pressure of the heating material in the control pressure chamber 71 decreases.
and resists the elastic force of the spring 72 due to the pressure receiving area difference when the control valve 70 is closed.
The control valve 70 moves to the right in the figure and is opened. For the time being,
Low-pressure discharge fuel from the pre-pressure pump 43 is introduced into the sub-pressure chamber 39 through the open passage 46 .

Note that the closing of the control valve 70 at the beginning of the suction stroke is actually instantaneous when the control valve 70 opens, so the fuel in the control chamber 63 is introduced into the subpressure chamber 39 and the spool valve 60 is closed. It can be considered that it is not enough to move leftward. FIG. 6 shows the state in the first half of the suction stroke.

Such a state in the first half of the suction stroke indicates that even if the first and second plungers 32 and 35 move upward, it will not be an effective stroke for moving the spool valve 60 to the left.

Next, in the latter half of the suction stroke, the metering valve 80 is opened. Therefore, the fuel discharged from the prepressure pump 43 can be sucked into the main pressure chamber 40 through the passage 73, so that the check valve 45 closes because there is no differential pressure before and after it. As a result, the fuel pressure within the control pressure chamber 71 of the control valve 70 increases, and the control valve 70 is closed. Therefore, from then on, fuel is sucked into the main pressure chamber 40 via the passage 73 or the check valve 45 which opens slightly, while fuel is sucked into the sub pressure chamber 39 through the first plunger 3.
2 rises, the fuel in the control chamber 63 of the spool valve 60 will flow into the increased auxiliary pressure chamber 39, and therefore the spool valve 60 will move to the left. The left movement of the spool valve 60 continues until the first plunger 32 reaches the top dead center position.
In other words, the left end position of the spool valve 60 is the metering valve 8
0 is determined by the effective stroke of the first plunger 32 that moves the spool valve 60 to the left from the open position, and the left end position of the spool valve 60 is determined by the position when the metering valve 80 is already open. It is determined by

In this state, when the first and second plungers 32 and 35 enter the downward stroke shown in FIG. 3 again, and the metering valve 80 is closed to block the passage 73 as shown in FIG. 4, fuel injection will start from that time. At the beginning, fuel injection is performed as the spool valve 60 moves to the right, and ends when the annular groove 62 opens the relief passage 61.

As is clear from the above, the fuel injection start point is when the metering valve 80 is closed, and the fuel injection end point is the point when the annular groove 62 communicates with the relief passage 61.
The fuel injection amount, that is, the fuel injection period corresponds to the rightward stroke (crank angle) of the spool valve 60. The rightward stroke is determined by the opening timing of the metering valve 80 during the suction stroke.

Therefore, by controlling the opening/closing timing of the metering valve 80 by the control circuit 94 operating the electromagnetic actuator 95 according to the engine operating conditions, it is possible to arbitrarily control the fuel injection start and end timing and the fuel injection amount of this device. It becomes.

The opening/closing operation of the plunger lift metering valve, spool valve operation, control valve operation, and pressure chamber pressure fluctuation in the above device are shown as a time chart in FIG.

Although the passage leading the fuel pressure in the main pressure chamber 40 to the control pressure chamber 71 of the control valve 70 is constructed via the annular groove 62 of the spool valve 60 in the case of this embodiment, it does not necessarily need to pass through the spool valve 60. Needless to say, it is okay.

As described above, according to the present invention, the fuel injection amount and the fuel injection timing can be controlled independently and arbitrarily by simply controlling the opening/closing timing of the metering valve according to the engine operating state. No matter how the conditions change, the optimal fuel injection rate can always be obtained, and the exhaust gas can be cleaned and fuel efficiency can be further improved.

Further, according to the present invention, the needle valve, the first and second plungers, the main pressure chamber, and the sub-pressure chamber are arranged on the same line, and the control system, that is, the control valve, spool valve, metering valve, etc. Since it can be constructed separately, it is possible to reduce the overall height of the injection valve, thereby reducing the height of the engine, lowering the bonnet of the vehicle, and improving visibility. Furthermore,
The metering valve only needs to operate when the pressure in the passage it opens and closes is low, and therefore it can be operated by a small electromagnetic actuator with relatively low output.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional fuel injection device, FIG. 2 is a partially enlarged sectional view of the same, and FIG. 3 is a longitudinal sectional view showing an embodiment of the fuel injection device of the present invention. 4 to 7, which show the downward stroke of the plunger before injection, are diagrams showing the operating state of the same embodiment as above. FIG. 4 shows the fuel injection state, FIG. 5 shows the fuel injection end state, and FIG. 7 shows the state in the first half of the fuel suction stroke, and FIG. 7 shows the state in the latter half of the fuel suction stroke. FIG. 8 is a time chart showing the operation timing of each component of the same embodiment. 31...unit injector, 32...first
Plunger, 35...Second plunger, 39...
Sub-pressure chamber, 40... Main pressure chamber, 42... Fuel tank, 43... Pre-pressure pump, 44... Suction passage, 4
5...Check valve, 46...Passage, 47...
Injection passage, 49... Spout, 50... Needle valve, 51... Pressure chamber, 52... Needle spring, 60... Spool valve, 61... Relief passage, 6
2... Annular groove, 63... Control chamber, 64... Back pressure chamber, 70... Control valve, 71... Control pressure chamber, 73
... Passage, 80 ... Metering valve, 91 ... Rotation sensor, 92 ... Negative pressure sensor, 93 ... Water temperature sensor,
94...control circuit, 95...electromagnetic actuator.

Claims (1)

[Claims] 1. A valve body 50 that opens the injection passage 47 upon receiving fuel pressure in the injection passage 47 of a predetermined value or higher, and a plunger 3 that reciprocates in synchronization with engine rotation.
2, 35; a main pressure chamber 40 whose volume changes as the plungers 32, 35 reciprocate and which is connected to the injection passage 47 upstream of the valve body 50; one end of which is connected to the main pressure chamber 40; A check valve 45 is installed in the suction passage 44 whose other end is connected to the low-pressure fuel source 42 and is installed in a direction that allows fuel suction; and a relief passage 61 that relieves the main pressure chamber 40 to the low-pressure fuel source 42. a spool valve 60 which is opened at a predetermined position in the axial direction, one side pressure receiving surface is connected to the low pressure fuel source 42, and both pressure receiving surfaces are formed to have the same area; a sub-pressure chamber 39 whose volume changes and which is connected to a pressure receiving surface of the spool valve 60 opposite to the low-pressure fuel source connection side; The sub pressure chamber 3 always receives the fuel pressure of
a control valve 70 that opens the auxiliary pressure chamber 39 to the low-pressure fuel source 42 when the pressure of the auxiliary pressure chamber 39 becomes a predetermined difference or more than the pressure of the main pressure chamber 40;
and an electromagnetically driven metering valve 80 that opens and closes communication between the bypass passage 73 connecting the low-pressure fuel source 42 and the low-pressure fuel source 42, and inputs detection signals from the engine operating state detection devices 91, 92, and 93 to calculate the fuel injection amount, Based on the fuel injection amount, the metering valve 80 is opened at a predetermined time while the plungers 32 and 35 are moving in a direction to expand the volume of the main pressure chamber 40, and the plungers 32 and 35 A fuel injection device for an internal combustion engine, comprising: a control device 94 that controls an opening/closing operation so as to close the valve at a predetermined time while the pressure chamber 40 is moving in a direction to reduce the volume thereof.