JPH07279728A - Fuel pressure control device for injection fuel supplying type engine - Google Patents

Abstract

PURPOSE:To suppress excessive fuel consumption and improve engine performance by improving measuring accuracy of injection fuel by means of a fuel injection valve. CONSTITUTION:A fuel injection valve 4 is operated for receiving pressurized fuel 5 discharged from a fuel pump 8 through a fuel supply passage 11 and injecting the fuel 5 intermittently into a cylinder 2. An escape valve 17 is arranged for communicating the fuel supply passage 11 with its outside. Fuel pressure in the fuel supply passage 11 can be adjusted to be a specified value by intermittently opening the escape valve 17. The escape valve 17 is opened by at least once in each cycle of intermittent fuel injection by means of the fuel injection valve 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection fuel supply type engine in which pressurized fuel is appropriately intermittently injected by a fuel injection valve and supplied into a cylinder. The present invention relates to a fuel pressure control device that adjusts and controls the fuel pressure to a predetermined pressure.

[0002]

2. Description of the Related Art Generally, an injection fuel supply type engine is provided with a fuel pump for pressurizing and discharging fuel from a fuel tank, and receiving the pressurized fuel discharged from the fuel pump through a fuel supply passage. In addition, a fuel injection valve that intermittently injects this fuel into the cylinder is provided.

Further, in order to set the amount of fuel injected by the fuel injection valve to a predetermined amount, a fuel pressure control device for adjusting and controlling the fuel pressure so that the "pressure fluctuation width" of the fuel pressure in the fuel supply passage does not become too large. It is provided.

This fuel pressure control device is provided with a relief valve that allows the fuel supply passage to communicate with the fuel tank outside the fuel supply passage.

The pressurized fuel is supplied to the fuel supply passage from the fuel pump, so that the fuel pressure tends to increase regardless of the decrease in the fuel due to the fuel injection. The relief valve is intermittently opened by automatic control, whereby the fuel in the fuel supply passage is returned to the fuel tank, and the "pressure fluctuation width" of the fuel pressure is not so large.

[0006]

By the way, in the above-mentioned conventional structure, firstly, the opening cycle of the relief valve is made longer than the cycle of fuel injection by the fuel injection valve, and therefore the fuel pressure " It cannot be said to be sufficient to reduce the `` pressure fluctuation range '', and therefore, the amount of injected fuel that increases and decreases in accordance with the magnitude of this fuel pressure tends to vary. There is room for improvement in terms of.

Secondly, the relief valve is opened and the fuel pressure is adjusted regardless of the fuel injection timing of the fuel injection valve. Therefore, for example, "pressure fluctuation range" At the time when the fuel injection valve opens at the time when the fuel injection valve opens at the time when the fuel injection valve opens at the time when the fuel injection valve opens when the fuel injection valve opens at the time when the fuel injection valve opens at the time when the fuel injection valve opens when the fuel injection valve opens There is a very large variation in the amount, and there is room for improvement in terms of injection fuel metering accuracy.

If the accuracy of metering the injected fuel decreases as described above, the fuel is wasted and the engine performance deteriorates.

In view of the above problems, it is conceivable to shorten the relief valve opening time, increase the number of times the relief valve is opened, and reduce the "pressure fluctuation range" of the fuel pressure. .

However, if the opening time of the relief valve is simply shortened, due to the characteristics of the relief valve based on the inertial force of the valve body, etc., the "open / close valve operation" of the relief valve from the opening of the relief valve to the closing of the relief valve.
Becomes unstable, and in this case also, there is a problem that the weighing accuracy is impaired.

[0011]

SUMMARY OF THE INVENTION The present invention has been made paying attention to the above circumstances, and improves the accuracy of metering of the injected fuel in the fuel injection valve to suppress the wasteful consumption of the fuel and to improve the engine performance. The purpose is to improve.

[0012]

A fuel pressure control device for an injection fuel supply type engine of the present invention for achieving the above object receives a pressurized fuel 5 discharged from a fuel pump 8 through a fuel supply passage 11. A fuel injection valve 4 for intermittently injecting the fuel 5 into the cylinder 2 is provided, while a relief valve 17 for allowing the fuel supply passage 11 to communicate with the outside thereof is provided. The relief valve 17 is intermittently provided. When the fuel pressure in the fuel supply passage 11 can be adjusted to a predetermined pressure by opening the valve, the relief valve 17 is opened once or more in each cycle of intermittent fuel injection by the fuel injection valve 4. It is a thing.

In the above case, the number of times the relief valve 17 is opened in each cycle of intermittent fuel injection by the fuel injection valve 4 may be reduced as the engine 1 rotates from low speed to high speed.

Further, the fuel injection by the fuel injection valve 4 and the opening of the relief valve 17 may be synchronized with each other.

Further, the opening times of the relief valves 17 may be substantially the same.

[0016]

[Operation] The operation of the above configuration is as follows.

In FIGS. 1 and 2, the pressurized fuel 5 is supplied from the fuel pump 8 to the fuel supply passage 11 for supplying the fuel 5 to the fuel injection valve 4 to increase the fuel pressure, while the fuel pressure increases. The relief valve 17 is intermittently opened so that the fuel 5 in the fuel supply passage 11 is intermittently released to the outside.

By the way, conventionally, the number of times the relief valve 17 is opened is smaller than the number of times of fuel injection by the fuel injection valve 4, so that the “pressure fluctuation range” of the fuel pressure becomes large and the amount of injected fuel becomes According to the present invention, the number of times the relief valve 17 is opened in each cycle of intermittent fuel injection by the fuel injection valve 4 (N ₁ at a low speed, N at a high speed in FIG. 1) may occur. ₂ ) is set to one or more times, and therefore, the "pressure fluctuation width" of the fuel pressure in the fuel supply passage 11 (W _{1 at} low speed in FIG. ₁ , At high speeds, W ₂ ) becomes smaller than in the past. Therefore, variation in the amount of injected fuel that increases or decreases according to the magnitude of the fuel pressure is suppressed, and the accuracy of measuring the injected fuel in the fuel injection valve 4 is improved.

In the above case, the number of times the relief valve 17 is opened in each cycle of the intermittent fuel injection by the fuel injection valve 4 may be decreased as the engine 1 rotates from low speed to high speed.

That is, in FIG. 1, when the engine 1 rotates at a high speed, the time T ₈ of the fuel injection cycle by the fuel injection valve 4 becomes shorter accordingly. For this reason, if the number N ₂ of opening of the relief valve 17 in the above cycle is too large, the respective valve opening times T ₁₀ become extremely short. However, if the opening time T ₁₀ of the relief valve 17 is too short as described above, the characteristics of the relief valve 17 make the "open / close valve operation" of the relief valve 17 from the start of the opening to the end of the opening unstable. Become,
The measurement accuracy of the injected fuel in the fuel injection valve 4 is impaired.

Therefore, as described above, the number of times the relief valve 17 is opened in each cycle of intermittent fuel injection by the fuel injection valve 4 may be reduced as the engine 1 rotates from low speed to high speed. By doing so, even when the rotation speed is high, the opening time T ₁₀ can be lengthened and the time T ₁₀ is prevented from becoming too short because the number N ₂ of opening of the relief valve 17 in the above cycle is small. It Therefore, the “open / close valve operation” of the relief valve 17 is stable, and the accuracy of metering the injected fuel is improved.

Further, as shown in FIG. 9, the fuel injection by the fuel injection valve 4 and the opening of the relief valve 17 may be synchronized with each other.

In this way, the pressurized fuel 5 is supplied from the fuel pump 8 to the fuel supply passage 11, while the relief valve 1
The fuel pressure in the fuel supply passage 11 constantly fluctuates because the fuel 5 escapes from the fuel supply passage 11 to the outside by intermittent opening of the valve 7. However, the fuel pressure decreases due to the opening of the relief valve 17. The conditions over time become substantially the same at the time of each fuel injection.

Therefore, since the fuel pressures of the fuel injection valves 4 at the time of each fuel injection can be made substantially the same as each other, the amounts of the injected fuel can be made substantially the same for each injection, thereby further improving the accuracy of measuring the injected fuel. To do.

Further, as shown in FIG. 12, the relief valve 17 may be opened for substantially the same time.

In this case, the opening time of the relief valve 17 (T ₉ and T _{10 in} FIG. 12) is set to the relief valve 1
If the shortest time immediately before the "open / close valve operation" of No. 7 becomes unstable is compared with setting the valve opening time to a certain long time every cycle of opening the valve, the relief valve 17 is opened. The number of valves can be increased.

Therefore, while avoiding the inconvenience that the measurement accuracy of the injected fuel is impaired due to the characteristic of the relief valve 17, the "pressure fluctuation width" of the fuel pressure (W ₁ , W in FIG. 12)
₂ ) can be made smaller so that the amount of injected fuel is almost the same for each injection, and as a result, the accuracy of metering the injected fuel is further improved.

[0028]

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

(Example 1)

1 to 5 show the first embodiment.

In FIG. 2 and FIG. 3, reference numeral 1 is an engine 1 which is an internal combustion engine, which has either two cycles or four cycles.

The engine 1 has a plurality of cylinders 2. A common crank shaft 3 driven by each of the cylinders 2 is provided, and a driven body is connected to the crank shaft 3 in an interlocking manner, that is, the crank shaft 3 serves as an output shaft. A fuel injection valve 4 is attached to each of the cylinders 2. Each of these fuel injection valves 4 has an electromagnetic valve 4a, and when the electromagnetic valve 4a is electrically turned on and off, the fuel injection valve 4 is opened or closed.

A fuel supply device 6 for supplying pressurized fuel 5 to each of the fuel injection valves 4 is provided. The fuel supply device 6 includes a fuel tank 7 for storing the fuel 5 and the fuel tank 7
A fuel pump 8 for receiving the fuel 5 from the above, pressurizing and discharging the fuel 5. The fuel pump 8 is of a trochoid type, and is connected to the crankshaft 3 to interlock with it. Therefore, the engine 1 is driven at a low speed and the crankshaft 3
When the engine rotates at a low speed, the amount of fuel 5 discharged from the fuel pump 8 is small, and when the engine 1 is driven at a high speed and the crankshaft 3 rotates at a high speed, the fuel 5 is discharged from the fuel pump 8 at the same time. The amount increases. Further, a low pressure pump 9 is provided between the fuel tank 7 and the fuel pump 8.
Is provided so that the discharge pressure of the fuel 5 from the fuel pump 8 is sufficiently high.

A fuel supply passage 11 is provided for connecting the discharge port of the fuel pump 8 to the receiving port of each of the fuel injection valves 4. The fuel supply passage 11 is provided in the vicinity of the fuel injection valves 4 and communicates with the fuel injection valves 4, and an introduction passage that communicates from the discharge port of the fuel pump 8 to the pressure accumulation chamber 12. 13 and 13.

In FIG. 2, reference numeral 14 is an electronic engine control device, and the engine control device 14 is provided with the fuel injection valve 4 described above.
Solenoid valve 4a is electrically connected.

A load detecting means 15 for detecting the load of the engine 1 is also provided. The load detecting means 15 is composed of, for example, an opening detection sensor for the throttle opening, and the detection signal of the load detecting means 15 is input to the engine control device 14. Based on this input, the engine control device 14 intermittently opens the fuel injection valve 4. In the two-cycle engine (or four-cycle engine), this valve opening is performed once per one rotation (or two rotations) of the crankshaft 3. With this valve opening, the fuel pump 8 causes the fuel injection valve 4 to operate as described above. The supplied fuel 5 is injected into each cylinder 2 for a predetermined time, and is used for combustion.

A fuel pressure control device 16 is provided for controlling and adjusting so that the "pressure fluctuation width" of the fuel pressure of the fuel 5 in the fuel supply passage 11, particularly in the pressure accumulating chamber 12, is small.

The fuel pressure control device 16 is provided with a relief valve 17 that allows the pressure accumulation chamber 12 to communicate with the outside thereof, and a return passage 18 that communicates the relief valve 17 with the fuel tank 7. The relief valve 17 has a solenoid valve 17a,
The solenoid valve 17a is electrically turned on and off to release the relief valve 1 described above.
7 is designed to open or close.

A rotation speed detecting means 20 which is a rotation speed sensor for detecting the rotation speed of the engine 1 (crankshaft 3) is provided. Further, a fuel pressure detecting means 21 which is a pressure sensor for detecting the fuel pressure of the fuel 5 in the pressure accumulating chamber 12 is provided.

The load detecting means 15 and the rotational speed detecting means 2
0 and each detection signal of the fuel pressure detection means 21 are input,
An electronic fuel pressure control device body 23 for intermittently opening the relief valve 17 is provided, and the fuel pressure control device body 23 constitutes a part of the engine control device 14. The fuel pressure control device main body 23 receives the detection signals and performs arithmetic processing, arithmetic processing means 25, target fuel pressure value deciding means 26 for deciding a target fuel pressure value, and opening / closing conditions of the relief valve 17. And a solenoid valve opening / closing control means 2 for controlling opening / closing of the relief valve 17 as above.
8 and.

1 to 5, FIG. 4 shows a flow chart of the fuel pressure control device main body 23, in which (P-1) to (P-1) in FIG.
(P-11) indicates each step of the program.

In particular, in FIG. 4, when the fuel pressure control device main body 23 is turned on (P-1), initialization is first performed (P-2). Next, when the engine 1 starts to drive (P-3), the load detection means 15 causes the engine 1 to operate.
Load is detected (P-4), and the rotation speed detection means 2
The number of revolutions of the engine 1 (crankshaft 3) is detected by 0 (P-5). The target fuel pressure value determining means 26 causes the calculation processing means 25 to which both of these detection signals are input to
The first map in FIG. 5 is searched (P-6).

The first map is programmed in the target fuel pressure value determining means 26. According to the first map, the target fuel pressure value increases substantially as the load on the engine 1 increases and as the engine 1 rotates at a higher speed.

Then, the target fuel pressure value is determined by the first map of the target fuel pressure value determining means 26 based on the detection signals of the load detecting means 15 and the rotation speed detecting means 20 (P-7). On the other hand, the fuel pressure in the pressure accumulating chamber 12 of the fuel supply passage 11 is detected by the fuel pressure detecting means 21 (P
-8).

Next, the target fuel pressure value determined in (P-7) and the detected fuel pressure value detected in (P-8) are compared by the arithmetic processing means 25 (P-9). In this comparison, if the detected fuel pressure value is larger than the target fuel pressure value, the solenoid valve opening / closing control means 28 opens the relief valve 17 (P-10). Then, the fuel 5 in the fuel supply passage 11 is released to the outside of the fuel supply passage 11 through the relief valve 17, and the fuel pressure in the fuel supply passage 11 starts to decrease. The fuel 5 released as described above is returned to the return passage 1
It is returned to the fuel tank 7 through 8.

Further, in the comparison of (P-9), if the detected fuel pressure value is smaller than the target fuel pressure value, the relief valve 17 is closed by the solenoid valve opening / closing control means 28 (P
-11). Then, the fuel 5 in the fuel supply passage 11 is prevented from being released to the outside of the fuel supply passage 11 through the relief valve 17, so that the pressurized fuel 5 supplied from the fuel pump 8 prevents the fuel supply passage 11 from flowing. Fuel pressure begins to rise.

Thereafter, the above (P-9) to (P-11) are repeated so that the fuel pressure in the fuel supply passage 11 is kept within a predetermined "pressure fluctuation range".

In FIG. 1, the engine speed reference signal, which is a pulse signal, is input to the arithmetic processing means 25 by the rotation speed detecting means 20 at every one rotation of the crankshaft 3 and at a certain crank angle. That is, the time of one cycle (T _{1 at} low speed, T _{2 at} high speed) of this engine rotation reference signal is the time of one rotation of the crankshaft 3 in a two-cycle engine (in a four-cycle engine, It corresponds to the time of two revolutions of the crankshaft 3). In this case, the time for one cycle at high speed is shorter than the time for one cycle at low speed T ₁ , for example, T
₁ = 5T ₂ etc.

Input of the engine rotation reference signal to the arithmetic processing means 25, the load detection means 15, the rotation speed detection means 2
0 and each detection signal of the fuel pressure detection means 21 and the like,
The engine control device 14 outputs a fuel injection signal to the fuel injection valve 4 after a certain time (T _{3 at} low speed, T _{4 at} high speed) from the input of the engine rotation reference signal to the arithmetic processing means 25, and At this time, the valve opening time of each fuel injection valve 4, that is, the fuel injection time (T at low speed)
_5, in the high-speed T ₆₎ is defined, during which the fuel 5 is injected into each cylinder 2.

Time of each cycle of intermittent fuel injection by the fuel injection valve 4 (T _{7 at} low speed, T _{8 at} high speed)
Substantially coincides with the cycle time of the engine rotation reference signal (T _{1 at} low speed, T _{2 at} high speed).

It is shown in FIG. 5 that the number of times the relief valve 17 is opened (N _{1 at} low speed, N _{2 at} high speed) is one or more in each cycle of intermittent fuel injection by the fuel injection valve 4. The map has been set. The valve opening time of the relief valve 17 at this time (T _{9 at} low speed, T _{10 at} high speed) is determined by the relief valve drive signal output from the electromagnetic valve opening / closing control means 28.

As described above, the number of times the relief valve 17 is opened in each cycle of intermittent fuel injection by the fuel injection valve 4 (N _{1 at} low speed, N _{2 at} high speed) is one or more times. The number of times the relief valve 17 has been opened has increased more than before,
"Pressure fluctuation range" of fuel pressure in the fuel supply passage 11
(W _{1 at} low speed, W _{2 at} high speed) becomes smaller than the conventional one. Therefore, the amount of injected fuel that increases or decreases according to the magnitude of the fuel pressure is suppressed accordingly, and the accuracy of metering the injected fuel in the fuel injection valve 4 is improved.

In the above case, the number of times of opening the relief valve 17 in each cycle of the intermittent fuel injection by the fuel injection valve 4 is reduced as the engine 1 rotates from low speed to high speed, that is, low speed rotation. The number of valve opening in N is N
₁ , the number of valve openings at high speed is N ₂ , and N ₁ > N ₂ .

That is, in FIG. 1, when the engine 1 is rotated at a high speed, the time T ₈ of the fuel injection cycle by the fuel injection valve 4 is shortened accordingly. For this reason, if the number N ₂ of opening of the relief valve 17 in the above cycle is too large, the respective valve opening times T ₁₀ become extremely short. However, if the opening time T ₁₀ of the relief valve 17 is too short as described above, the characteristics of the relief valve 17 make the "open / close valve operation" of the relief valve 17 from the start of the opening to the end of the opening unstable. Become,
The measurement accuracy of the fuel injected by the fuel injection valve 4 is impaired.

Therefore, as described above, the number of times the relief valve 17 is opened in each cycle of intermittent fuel injection by the fuel injection valve 4 is reduced as the engine 1 rotates from low speed to high speed. Even if the rotation speed is high, the number N ₂ of opening of the relief valve 17 in the above cycle is small, so that the valve opening time T ₁₀ is prevented from becoming too short. Valve operation "
To improve the accuracy of injection fuel metering.

The following figures show the second and third embodiments. Since these embodiments have many points in common with respect to the configuration and operation in the first embodiment, common reference numerals are given to the drawings and explanations thereof are omitted, and different points are mainly described. To do.

(Example 2)

6 to 9 show the second embodiment.

FIG. 6 shows a flow chart of the fuel pressure control device main body 23, and (P-1) to (P-18) show each step of the program. Note that (P-1) to (P-
8) is the same as the first embodiment.

The second map shown in FIG. 7 is searched based on the target fuel pressure value determined in (P-7) and the detection signal of the rotation speed detecting means 20 (P-12).

The second map is programmed in the arithmetic processing means 25. According to this second map, as the engine 1 rotates at high speed, and the above (P-7)
It is supposed that the opening time of the relief valve 17 becomes longer as the target fuel pressure value determined in step becomes larger.

On the other hand, the relief valve 1 is controlled by the electromagnetic valve opening / closing control means 28 according to the detected fuel pressure value detected in (P-8).
The valve opening time of 7 is corrected (P-13).

Then, the valve opening time of the relief valve 17 is determined by the retrieval of the second map in (P-12) and the correction in (P-13) (P-14).

The arithmetic processing means 25 which receives the detection signals of the load of the engine 1 detected in (P-4) and the rotational speed of the engine 1 (crankshaft 3) detected in (P-5) is inputted. Via the electromagnetic valve opening / closing control means 28, the third map of FIG. 8 is searched (P-15).

The third map is programmed in the solenoid valve opening / closing control means 28. According to the third map, the valve opening timing of the relief valve 17 is advanced as the load of the engine 1 is increased and the engine 1 is rotated at high speed.

On the other hand, the relief valve 1 is controlled by the electromagnetic valve opening / closing control means 28 according to the detected fuel pressure value detected in (P-8).
The valve opening timing of No. 7 is corrected (P-16).

Then, the valve opening timing of the relief valve 17 is determined by the retrieval of the third map in (P-15) and the correction in (P-16) (P-17).

Next, the solenoid valve opening / closing control means 28 sends a drive signal to the relief valve 17 according to the valve opening time determined in (P-14) and the valve opening timing determined in (P-17). It is output, and the relief valve 17 is repeatedly opened and closed (P-18).

In FIG. 9, reference numeral T ₁₁ is T in the first embodiment.
₁ corresponds to T ₂ , T ₁₂ corresponds to T ₃ and T ₄ in Example 1, T ₁₃ corresponds to T ₅ in Example 1, T ₁₄ corresponds to T ₇ in Example 1, T ₁₅ corresponds to T ₉ and T ₁₀ in the first embodiment. N ₃ corresponds to N ₁ and N ₂ in the _first embodiment, and W
₃ corresponds to W ₁ and W ₂ in the _first embodiment.

However, in this embodiment, the number of times the relief valve 17 is opened in one cycle of fuel injection is controlled by the fuel pressure control device main body 23 so as to be constant at both the low speed and the high speed of the engine 1. Then, it is said to be three times. The number of times the valve is opened may be once, twice, or four times or more.

The fuel injection by the fuel injection valve 4 and the opening of the relief valve 17 are controlled by the fuel pressure control device main body 23 in the same manner as described above. More specifically, the solenoid valve opening / closing control means 28 opens the relief valve 17 simultaneously with the input of the engine rotation reference signal, and opens the fuel injection valve 4 with a delay of a certain time T ₁₂ from this time. It has become.

According to this embodiment, the pressurized fuel 5 is supplied from the fuel pump 8 to the fuel supply passage 11, while the relief valve 17 is intermittently opened to allow the fuel 5 to flow from the fuel supply passage 11 to the outside thereof. As a result, the fuel pressure in the fuel supply passage 11 constantly fluctuates in height, but the time-dependent conditions of the decrease in fuel pressure due to the opening of the relief valve 17 become substantially the same at each fuel injection.

Therefore, since the fuel pressures of the fuel injection valve 4 at the time of each fuel injection are substantially the same, the amounts of injected fuel are made substantially the same for each injection, and therefore the accuracy of metering the injected fuel is improved. Has been improved.

(Example 3)

10 to 12 show the third embodiment.

FIG. 10 shows a flow chart of the fuel pressure control device main body 23, and (P-1) to (P-22) show respective steps of the program. Note that (P-1) to (P-
8) is the same as in the first embodiment.

The fourth map of FIG. 11 is searched by the target fuel pressure value determined in (P-7) and the detection signal of the rotation speed detecting means 20 (P-19).

The fourth map is programmed in the arithmetic processing means 25 on the condition that the respective valve opening times of the relief valve 17 are substantially the same. According to the fourth map, the cycle of opening the relief valve 17 becomes longer as the engine 1 rotates at a higher speed and the target fuel pressure value determined in (P-7) becomes larger. It is said that.

On the other hand, the relief valve 1 is controlled by the electromagnetic valve opening / closing control means 28 according to the detected fuel pressure value detected in (P-8).
The time of the valve opening cycle of 7 is corrected (P-20).

Then, the time of the opening cycle of the relief valve 17 is determined by the retrieval of the fourth map in (P-19) and the correction in (P-20) (P-2).
1). By this determination, a drive signal is output from the solenoid valve opening / closing control means 28 to the relief valve 17, and the relief valve 17 is repeatedly opened and closed (P-22).

In FIG. 12, the opening time (T ₁₆ , T ₁₇ ) of the relief valve 17 is constant at both low speed and high speed of the engine 1, and the cycle time of opening the relief valve 17 (T at low speed is T ₁₆ , at high speed, T ₁₇ ) is variable as described with reference to FIGS. 10 and 11.

According to this embodiment, the opening time (T ₉ , T ₁₀ ) of the relief valve 17 is set to the "open / close valve operation" of the relief valve 17.
Is set to the shortest time immediately before becoming unstable, and the valve opening time for each valve opening cycle is not simply lengthened, and the number of times the relief valve 17 is opened is increased accordingly.

Therefore, while avoiding the disadvantage that the measurement accuracy of the injected fuel is impaired due to the characteristics of the relief valve 17, the "pressure fluctuation width" (W ₁ , W ₂ ) of the fuel pressure is made smaller, The amount of injected fuel is made substantially the same for each injection, and the accuracy of metering the injected fuel in the fuel injection valve 4 is further improved.

[0084]

According to the present invention, there is provided a fuel injection valve for receiving the pressurized fuel discharged from the fuel pump through the fuel supply passage and intermittently injecting this fuel into the cylinder. In the fuel pressure control device in the injection fuel supply type engine, which is provided with a relief valve that allows the passage to communicate with the outside of the passage, and the fuel pressure of the fuel supply passage can be adjusted to a predetermined pressure by intermittently opening the relief valve, In each cycle of intermittent fuel injection by the fuel injection valve, the relief valve is opened once or more.

Therefore, the "pressure fluctuation width" of the fuel pressure in the fuel supply passage becomes smaller than in the conventional case because the number of times the relief valve is opened is increased as compared with the conventional case. Therefore, variation in the amount of injected fuel that increases or decreases according to the magnitude of the fuel pressure is suppressed, and the accuracy of metering the injected fuel in the fuel injection valve is improved.

As a result, wasteful consumption of fuel is suppressed,
Moreover, the engine performance is improved by supplying an appropriate amount of fuel into the cylinder.

In the above case, the number of times the relief valve is opened in each cycle of intermittent fuel injection by the fuel injection valve may be reduced as the engine speed changes from low speed to high speed.

That is, when the engine rotates at a high speed, the fuel injection cycle time is shortened accordingly. For this reason,
If the number of times the relief valve is opened in the above cycle is too large, each valve opening time becomes extremely short. However, if the opening time of the relief valve is too short as described above, the "open / close valve operation" of the relief valve from the opening of the relief valve to the end of its closure becomes unstable due to the characteristics of the relief valve, and the fuel injection The metering accuracy of the injected fuel in the valve is impaired.

Therefore, as described above, the number of times the relief valve is opened in each cycle of intermittent fuel injection by the fuel injection valve may be reduced as the engine speed changes from low speed to high speed. For example, even at high speed rotation, the number of times the relief valve is opened in the above cycle is small, so that the valve opening time can be lengthened and the time is prevented from becoming too short. Therefore, the “open / close valve operation” of the relief valve is stable, and the accuracy of metering the injected fuel is improved.

Further, the fuel injection by the fuel injection valve and the opening of the relief valve may be synchronized with each other.

In this way, while the pressurized fuel is supplied to the fuel supply passage from the fuel pump, the fuel is released from the fuel supply passage to the outside by intermittent opening of the relief valve. The fuel pressure in the fuel supply passage constantly fluctuates, but the conditions over time of the decrease in fuel pressure due to the opening of the relief valve are substantially the same at each fuel injection.

Therefore, since the fuel pressures of the fuel injection valves at the time of each fuel injection can be made substantially the same, the amount of injected fuel can be made substantially the same for each injection, thereby further improving the measurement accuracy of the injected fuel. .

Further, the opening times of the relief valves may be set to be substantially the same.

In such a case, if the valve opening time of the relief valve is set to the shortest time immediately before the "opening / closing valve operation" of the relief valve becomes unstable, the valve opening time for each valve opening cycle is set. The number of times the relief valve is opened can be increased more than when the time is set to a certain long time.

Therefore, while avoiding the inconvenience that the measurement accuracy of the injected fuel is impaired due to the characteristics of the relief valve, the "pressure fluctuation width" of the fuel pressure is made smaller, and the amount of injected fuel is changed to each injection amount. They can be made substantially the same as each other, and the measurement accuracy of the injected fuel in the fuel injection valve is further improved. Therefore,
By improving the above-mentioned measurement accuracy, wasteful consumption of fuel can be more reliably prevented, and engine performance can be more reliably improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a time chart in the first embodiment.

FIG. 2 is a general diagram of the first embodiment.

FIG. 3 is an electrical block diagram in the first embodiment.

FIG. 4 is a flowchart of the fuel pressure control device body in the first embodiment.

FIG. 5 is a first map diagram according to the first embodiment.

FIG. 6 is a diagram corresponding to FIG. 4 in the second embodiment.

FIG. 7 is a second map diagram according to the second embodiment.

FIG. 8 is a third map diagram according to the second embodiment.

FIG. 9 is a diagram corresponding to FIG. 1 in the second embodiment.

FIG. 10 is a diagram corresponding to FIG. 4 in the third embodiment.

FIG. 11 is a fourth map diagram according to the third embodiment.

FIG. 12 is a diagram corresponding to FIG. 1 in the third embodiment.

[Explanation of symbols]

 1 engine 2 cylinders 3 crankshaft 4 fuel injection valve 4a solenoid valve 5 fuel 6 fuel supply device 7 fuel tank 8 fuel pump 11 fuel supply passage 14 engine control device 15 load detection means 16 fuel pressure control device 17 relief valve 17a solenoid valve 18 return Passage 20 Rotation speed detection means 21 Fuel pressure detection means 23 Fuel pressure control device main body

Claims (4)

[Claims] 1. A fuel injection valve is provided which receives pressurized fuel discharged from a fuel pump through a fuel supply passage and intermittently injects this fuel into a cylinder, while the fuel supply passage is provided outside the fuel injection passage. In a fuel pressure control device for an injection fuel supply type engine, which is provided with a relief valve that enables communication, and by intermittently opening the relief valve, the fuel pressure in the fuel supply passage can be adjusted to a predetermined pressure. Pressure control device in an injection fuel supply type engine in which the number of times of opening of the relief valve in each cycle of general fuel injection is set to 1 or more. 2. The injection fuel supply type engine according to claim 1, wherein the number of times of opening the relief valve in each cycle of the intermittent fuel injection by the fuel injection valve is reduced as the engine speed changes from low speed to high speed. Fuel pressure control device. 3. The fuel pressure control device for an injection fuel supply type engine according to claim 1, wherein the fuel injection by the fuel injection valve and the opening of the relief valve are synchronized with each other. 4. The fuel pressure control device for an injection fuel supply type engine according to claim 1, wherein the relief valve opening times are substantially the same.