JPH0362907B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fuel supply system for an internal combustion engine, and more particularly to a so-called unit injector in which a pump section and a fuel injection section are integrated into an injector body. Regarding.

[Prior Art] A pump portion comprising a cylinder having a discharge port and a suction port connectable to a fuel source, and a plunger slidably and precision fitted within the cylinder bore, and operatively engaged with the plunger. An input section that inputs power from a drive shaft that rotates in synchronization with a crankshaft of an internal combustion engine to drive the plunger back and forth, a fuel injection valve, and a fuel injection valve that connects a discharge port of the pump section. a fuel pressure-feeding passage connecting the fuel pressure-feeding passage; a fuel return passage that branches from the fuel pressure-feeding passage and returns the pressurized fuel pumped by the pump section to the fuel source; and an electronically controlled shutoff interposed in the fuel return passage. A unit injector in which a valve and a valve are integrally assembled into an injector body is known (for example, Utility Model Publication No. 56-31655 and U.S. Pat. No. 4,281,792).

[Problem to be solved by the invention]

This type of conventional unit injector is especially used in large direct injection diesel engines, and because it eliminates the need for an injection pipe, there is no so-called irregular injection, making it easy to obtain a high injection rate, and it is not affected by rotation too much. If you look only at the injection function, it is essentially high-performance, but on the other hand, since the pump part and fuel injection part are integrated compared to a model where they are separated, (1) the size is larger (2) The speed governor and injection timing control section are separated, making control difficult and difficult to simplify. (3) The injection system cannot be adjusted independently, making maintenance difficult. (4) A dedicated system for injection timing control is required. A drive camshaft is required. (5) In order to install it in an existing engine, the cylinder head and cylinder block must be significantly changed, which imposes many restrictions on installation, making it difficult to standardize it on engines with different displacements. Due to the inconvenience of
It has not yet become commonplace.

The present invention has been devised in view of the above-mentioned problems of the prior art.The problem to be solved is to miniaturize the pump section, the injection section, and the intake/exhaust valve by improving the arrangement relationship between the pump section, the injection section, and the intake/exhaust valve. In order to reduce the axial and vertical dimensions and limit installation constraints, we have eliminated the camshaft dedicated to driving the pump and made the camshaft for driving the pump common with the camshaft for driving the intake and exhaust valves.
By digitizing fuel metering and in particular using multiple electronically controlled shutoff valves and arranging them by function, adjustment, speed regulation, injection timing control, and injection amount metering can be simplified, and a wide range of engine rotation speeds can be achieved. To provide a unit injector which is compact and has excellent controllability, and is capable of surely metering over a range.

[Means to solve the problem]

As a means for solving the above-mentioned problems, the present invention provides a camshaft that is integrally equipped with a cam for driving a unit injector in addition to a cam for driving the opening and closing of an intake valve or an exhaust valve, and a camshaft that is integrated into an injector main body. a cylinder provided in the unit, a plunger slidably fitted into the cylinder to form a pressure chamber and reciprocally driven by the unit injector driving cam; and pressurizing the pressure chamber by the plunger. a fuel injection valve provided on another part of the injector body for receiving the fuel from the discharge port through the fuel pressure passage and injecting it into the combustion chamber of the internal combustion engine; and a suction port communicating the pressure chamber with a fuel source, and in addition, when viewed in the direction of the axis of the camshaft, the axis of the plunger is aligned with the axis of the fuel injection valve. The unit injector is substantially orthogonal to the intake valve or the exhaust valve, and intersects with the axis of the intake valve or the exhaust valve without overlapping.

[Effect]

The cam that drives the unit injector of the present invention is provided on the same camshaft as the cam that drives the intake valve or the exhaust valve, so there is no need to provide a special camshaft for driving the unit injector. In that case, since a large number of cams will be provided on the same camshaft, their corresponding tappets will interfere with each other, so it is conceivable to make the camshaft longer.However, according to the present invention, the intake valve or exhaust valve Since the valve axis and the plunger are arranged so as to intersect so that they do not overlap, even if the spacing between the cams is relatively small, the tappets that drive the intake or exhaust valves and the tappets that drive the plunger of the unit injector can be easily connected. etc. can be arranged so that they do not interfere with each other. Moreover, by arranging the plunger and the fuel injector so that their axial lines are substantially perpendicular to each other, the height of the unit injector can be reduced. Miniaturization can be achieved by reducing the axial length and height of.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a partially sectional side view of an embodiment of the unit injector of the present invention, and the unit injector 10 has an injector body 12. As shown in FIG. The injector main body 12 is composed of a main portion, that is, a base portion 14 having an axis Nc, and a bent portion 16 having an axis Pc perpendicular to the axis Nc.

The bent portion 16 has a cylindrical bore 18 into which a tappet 20 constituting the input portion of the unit injector 10 is slidably fitted. A shim 22 is attached to the tappet 20, and this shim 22 corresponds to a dedicated cam 26 provided on a camshaft 24 for driving intake and exhaust valves provided in a cylinder head (not shown) of an internal combustion engine (not shown). are in contact with each other. As is well known, a cam 28 for driving intake and exhaust valves is formed on the camshaft 24, and this cam 28 for driving intake and exhaust valves drives the intake valve or exhaust valve 32 inserted through the valve guide 30 into the intake and exhaust valve tappet. 34 so that it can be pushed and moved.

In this case, the axial center line Pc of the bent portion 16 including the plunger 42 of the injector main body 12 intersects the axial center line Vc of the intake and exhaust valve 32 when viewed from the direction of the camshaft 24. The tappet 20 of the unit injector 10 and
Even if the distance between the intake and exhaust valves 32 and the tappets 34 is relatively small, there is no risk of them interfering with each other, making it possible to shorten the length of the camshaft 24 and, therefore, the overall length of the internal combustion engine. Become.

A cylinder 36 is formed in the bent portion 16 and constitutes a pump portion of the unit injector of the present invention. The cylinder 36 has a cylinder bore 40 defining a pressure chamber 38 of the pump section, into which a plunger 42 is slidably and precisely fitted. A spring retainer 46 is fixed to the outer end of the plunger 42 by a pusher 44, and a return spring 48 is interposed between the spring retainer 46 and the injector main body 14, and a return spring 48 is inserted between the tappet 20 and the cam 26. is biased towards. A suction port 50 and a discharge port 52 are open to the pressure chamber 38 of the cylinder 36.
The suction port 50 extends perpendicularly to the plane of the paper in FIG.

A fuel injection valve 56 is attached to the lower end of the main portion 14 of the injector body 12 with a nut 54 . The discharge port 52 of the pump part is the fuel pressure passage 5
8 to the fuel injection valve 56.

A first fuel return passage 62 is provided between the fuel return port 60 provided in the main portion 14 and the pressure chamber 38, and this first fuel return passage 62 is connected to the spool valve 66 of the first electromagnetic shutoff valve 64. It is designed to be cut off or conductive. This first shutoff valve 6
The solenoid 68 of No. 4 is connected to an electronic control unit (ECU), which will be described later, by wiring 70, and the spool valve 66 is connected to the first fuel return passage 62 when the solenoid 68 is energized, that is, when the illustrated cutoff valve 64 is inactive. The passage 62 is made conductive, and the passage 62 is cut off when the solenoid 68 is energized. Note that in the illustrated embodiment, this first
Although the fuel return passage 62 opens into the pressure chamber 38 of the pump section, it may alternatively be branched from the fuel pressure feeding passage 58.

A second fuel return passage 72 is provided between the fuel pressure passage 58 and the fuel return port 60. This second heat return passage 72 is connected to a second electromagnetic shutoff valve 74.
The spool valve 76 is opened and closed by a spool valve 76, and when a solenoid 80 connected to an electronic control unit (ECU) by wiring 78 is not energized, the spool valve 76 is in the second position as shown.
The fuel return passage 72 is cut off, and the passage 72 is made conductive when excited.
In FIG. 1, the second electromagnetic shutoff valve 74 is shown rotated by 90 degrees for convenience of illustration, but in reality, its axis is perpendicular to the plane of the paper.

FIG. 2 is a diagram showing how the fuel passages and electrical wiring of the unit injector of the embodiment shown in FIG. 1 are connected.
The four solenoids 68 and 80 are connected to an electronic control unit (ECU) 82 by wires 70 and 78, respectively. This electronic control unit 82 calculates fuel injection timing and fuel injection amount according to signals from an engine speed sensor 84 and a load sensor 86, and sends corresponding electric signals to the solenoids 68 and 8.
It is designed so that it can be output to 0.

The suction port 50 of the unit injector 10 is connected to a low-pressure fuel pump 92 by a low-pressure fuel pipe 90 equipped with a check valve 88, and the latter sucks up fuel in a fuel tank 94 through a strainer 96 and supplies it to the low-pressure fuel pipe. 90. The low-pressure fuel pump 92 is provided with a bypass 100 with a restriction 98 to adjust the fuel supply pressure in the low-pressure fuel line.

Fuel return port 6 of unit injector 10
0 is connected to the fuel tank 94 by a fuel return pipe 102. This fuel return pipe 102 has a branch pipe 10
4 to the fuel return ports of the unit injectors of other cylinders. Further, the low pressure fuel pump 92 is connected to the suction port 50 of the unit injector of another cylinder through a branch pipe 106.

A compression spring 1 is provided in the back pressure chamber 108 of the fuel injection valve 56.
10 is provided to bias the needle valve 112 to a normally closed position. A drain pipe 114 is connected to the back pressure chamber 108.

Next, the operation of this unit injector will be explained with reference to FIGS. 2 and 3.

As the cam 26 for driving the unit injector rotates, the plunger 42 moves to the right in FIG. 2, and pressure feeding of fuel is started. The pumped fuel is
Although it is branched into a fuel pressure feeding passage 58 and a first fuel return passage 62, the spool valve 66 of the first cutoff valve 64 is in the illustrated rest position and makes the first fuel return passage 62 conductive. Fuel return pipe 102
It escapes to the fuel tank 94 through the fuel pressure passage 58.
Injection does not start because the fuel pressure within the tank does not rise. As the pressure feeding process further progresses, the electronic control unit 82 outputs an electronic signal to the solenoid 68 of the first shutoff valve 64 in response to the signals from the engine speed sensor 84 and the load sensor 86, and the spool valve 66 moves downward. It moves and blocks the first fuel return passage 62. At this time, the spool valve 76 of the second shutoff valve 74 is in the illustrated rest position, blocking the second fuel return passage 72. For this reason, the fuel pressure passage 5
The fuel pressure within the injection valve 56 increases, and this pressure increases the fuel pressure within the injection valve 56.
When the valve opening pressure exceeds , fuel injection starts. Therefore, by controlling the cutoff timing of the first cutoff valve 64 by the electronic control unit 82, the fuel injection timing is controlled.

Next, the electronic control unit 82 outputs an electric signal to the solenoid 80 of the second shutoff valve 74 after a predetermined period of time has elapsed from the activation timing of the first shutoff valve 64 according to the engine speed and load, and the spool valve 7
6 upward in the figure. As a result, the fuel pressure passage 58 is communicated with the fuel return pipe 102, and the fuel pressure in the fuel pressure passage 58 drops to a sudden drop, and fuel injection ends.

As the stroke progresses further and the plunger 42 enters the suction stroke, the output of electrical signals to the first and second shutoff valves 64 and 74 is stopped, and these shutoff valves return to their initial rest positions, causing the pressure inside the pressure chamber 38 to stop. Fuel flows into the pressure chamber 38 from the low pressure fuel pipe 90 and the suction port 50 due to the negative pressure generated. At this time, the fuel flows into the pressure chamber 38 with the fuel supply pressure determined by the throttle 98 of the bypass 100, so that no bubbles are generated in the fuel due to the negative pressure in the pressure chamber.

When the stroke progresses further and the plunger 42 reaches the leftmost position in FIG. 2, the program of the electronic control unit 85 is reset and the next cycle is repeated.

FIG. 3 is a timing chart showing the relationship between the operating timing of the first and second shutoff valves 64 and 74 and the fuel injection amount. Curve A shows the control pulse of the shutoff valve 64, and curve B shows the control pulse of the second shutoff valve 74. The control pulse is represented by the curve C, the injection flow rate of the fuel injection valve 56 is represented by the curve C, and the horizontal axis represents the time. The first shutoff valve 64 operates from a reference time _T0 corresponding to a predetermined angular position of the crankshaft of the internal combustion engine to a time _T1.
The second shutoff valve 74 is activated after the time T ₂ has elapsed, and the second shutoff valve 74 is activated after the time T ₂ has elapsed. Therefore, as described above, the fuel injection timing can be controlled by increasing or decreasing the time _T1 . On the other hand, the fuel injection amount is determined by the operating time difference ΔT=T ₂ −T ₁ between the first and second shutoff valves. This means that the heating material injection time T ₃ can be set substantially without being influenced by the response performance of the first and second cutoff valves 64 and 74. Therefore, as can occur when the engine is running at a high speed, the fuel injection time T ₃ is limited to the cutoff valves 64 and 7.
Even if the response time is very close to or less than the response time of No. 4, it is possible to reliably control the fuel injection amount. This allows reliable metering over a wide range of rotational speeds. Third
As shown by the dotted line in the figure, when the activation timing of the second cutoff valve 74 is delayed, the injection amount increases.

As shown in FIG. 2, a bypass 116 may be provided in the first shutoff valve 64, and a variable flow rate restrictor 118 whose flow rate is variably controlled by the electronic control unit 82 may be provided in the bypass 116. In this way, when the fuel injection valve 56 is actuated, a portion of the pressurized fuel in the fuel pressure passage 58 is returned to the fuel tank, thereby making it possible to adjust the oil feeding rate of the fuel pressure passage 58. As a result, fuel can be supplied from the injection valve at a flow rate that matches the engine speed. Also, instead of the bypass 116 and the variable flow rate restrictor 118, a cutoff valve 6 is provided with a throttle passage 120 as shown in FIG. 4 as a first cutoff valve.
4' may also be used.

FIG. 5 shows another embodiment of the fuel metering section, in which components common to those in FIG. 2 are designated by the same reference numerals. The main difference from the configuration in Figure 2 is:
A second shutoff valve 74 for controlling the final stage of fuel injection, that is, the fuel injection amount, is provided in the third passage 300 that connects the needle back pressure chamber 108 of the injection valve 56 and the fuel pressure passage 58. In this embodiment, the variable flow rate restrictor 118 is provided in the fuel pressure passage 58.

Control of injection timing in the embodiment of FIG. 5 is similar to that described above with respect to FIGS. 2 and 3. That is, at the beginning of the pressure feeding stroke of the plunger 42, the spool valve 66 of the first cutoff valve 64 is closed to the first fuel return passage 6.
The spool valve 76 of the second cutoff valve 74 cuts off the third passage 300. With the start of the pumping stroke of the plunger 42, the fuel pumping passage 5
At first, the fuel pressure-fed to the injector 8 escapes to the fuel tank 94 via the fuel source passage 62, so the injection valve 56 does not open. Next, at a predetermined time, a signal is output from the electronic control unit (ECU) 82 to the first cutoff valve 64, and the first fuel return passage is cut off, thereby starting fuel injection.

Next, after a predetermined period of time has elapsed since the activation timing of the first shutoff valve 64, an electric signal is output from the electronic control unit 82 to the second shutoff valve 74. As a result, the spool valve 76 of the second shutoff valve 74 moves downward in FIG. 5, thereby opening the third passage 300. Therefore, the pressurized fuel in the fuel pressure passage 58 is guided to the needle back pressure chamber 108 of the injection valve 56 and is forced into the needle valve 108.
12 to end the injection. At that time, the fuel pressure becomes needle back pressure, so the needle valve 112
The time required for closing is shorter than in the embodiments of FIGS. 1 and 2. In this way, also in this embodiment, the end of fuel injection, that is, the fuel injection amount, is controlled by the electronic control unit, and the fuel is metered by increasing or decreasing the difference in operating time of the first and second shutoff valves. Ru. Moreover, since the fuel pressure is applied to the needle back pressure chamber to terminate the injection, it is possible to control the injection amount more accurately.

〔Effect of the invention〕

Since the present invention has the configuration described in the section of the solution section, it is possible to obtain a unit injector that is compact and has a small vertical dimension. In addition, the camshaft for driving the unit injector is shared with the camshaft for driving the intake and exhaust valves of the engine, eliminating the need for a dedicated camshaft, resulting in a simpler structure and easier installation into existing engines. It became possible. In particular, if the present invention is implemented, the axial center line of the plunger will not overlap the axial center line of the intake and exhaust valves when viewed in the camshaft direction, and their tappets will not interfere with each other. The degree of freedom in the assembly positional relationship between the intake and exhaust valves and the unit injector can be improved.

[Brief explanation of drawings]

FIG. 1 is a partially sectional side view of an embodiment of the unit injector of the present invention, FIG. 2 is a connection diagram of the fuel passage and electrical wiring of the embodiment of FIG.
Figure 3 is a timing chart showing the relationship between the operating timing of the shutoff valve and the fuel injection amount, and Figure 4 is a timing chart showing the relationship between the operating timing of the shutoff valve and the fuel injection amount.
FIG. 5 is a diagram showing a modification of the cutoff valve, and is a diagram showing another embodiment of the fuel metering section. 10... Unit injector, 12... Injector body, 14... Main part, 16... Bent part, 18... Bore of bent part, 20... Tappet,
22...Shim, 24...Camshaft for driving intake and exhaust valves,
26... Injector drive cam, 28... Intake/exhaust valve drive cam, 30... Valve guide, 32...
...Intake and exhaust valve, 36...Cylinder, 38...Pressure chamber, 40...Cylinder bore, 42...Plunger, 50...Suction port, 52...Discharge port,
56...Fuel injection valve, 58...Fuel pressure feeding passage, 6
0... Fuel return port, 62... First fuel return passage, 64... First electromagnetic shutoff valve, 66... Spool valve, 68... Solenoid, 70... Wiring, 72
...Second fuel return passage, 74...Second electromagnetic shutoff valve, 76...Spool valve, 78...Wiring, 80...
... Solenoid, 82 ... Electronic control unit (ECU), 84 ... Engine speed sensor, 86
... Engine load sensor, 88 ... Check valve, 90 ... Low pressure fuel pipe, 92 ... Low pressure fuel pump, 94 ... Fuel tank, 98 ... Bypass throttle, 100 ... Bypass, 102 ... Fuel return pipe , 104, 106...branch pipe, 108...back pressure chamber of fuel injection valve, 112...needle valve, 114
...Drain pipe, 116...Bypass, 118...
... Variable flow rate restriction, 120 ... Throttle passage of the first shutoff valve, 300 ... Third passage.

Claims (1)

[Claims] 1. A camshaft which is integrally equipped with a cam for driving a unit injector in addition to a cam for driving the opening and closing of an intake valve or an exhaust valve, a cylinder provided in a part of the injector body, and a cylinder that slides on the cylinder. a plunger that is reciprocally driven by the unit injector driving cam and that is fitted together to form a pressure chamber; a plunger that receives fuel pressurized by the plunger in the pressure chamber from a discharge port through a fuel pressure passage; a fuel injection valve provided in another part of the injector body for injecting fuel into a combustion chamber of an internal combustion engine; and a suction port communicating the pressure chamber to a fuel source when the plunger is in a predetermined position. In addition, when viewed in the direction of the axial center line of the camshaft, the axial center line of the plunger is substantially perpendicular to the axial center line of the fuel injection valve, and Alternatively, a unit injector is characterized in that it intersects the axis of the exhaust valve without overlapping it.