JPH037573Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a fuel pressure control device for a fuel supply system of an engine equipped with an electronically controlled fuel injection device, and particularly to a pressure regulator for controlling a negative pressure signal source of a throttle valve. The present invention relates to a fuel pressure control device that can improve the idling durability of an engine at high temperatures by acting on a fuel pressure regulator.

[Background Art of the Invention] An electronically controlled fuel injection device is a device that, in place of a carburetor, electrically controls the amount of fuel supplied and injects it into the engine. In this device, it is necessary to keep the fuel pressure from the fuel pump to the fuel injection valve constant, especially in order to improve the accuracy of fuel flow control. In order to improve the accuracy of fuel flow control in the fuel injection valve, in the case of a low-pressure fuel injection system that has a pressure regulator that maintains the differential pressure between the intake pipe internal pressure and the fuel pressure at a constant value, the absolute pressure of the fuel pressure is determined by the engine load. It varies depending on the conditions, with the lowest at idle and highest at full load.

By the way, the properties of gasoline used as fuel vary depending on the region,
Varies depending on season and manufacturer. In particular, if components with low boiling points are mixed in, the fuel flow rate will be low during idle when the engine cooling water temperature is high.
Since the replacement with new fuel is slow, in other words, the movement of fuel within the fuel pipe near the fuel injection valve is slow, so the fuel is also overheated. Due to this fuel overheating, when the vapor pressure of the low boiling point component of the fuel exceeds its boiling point in response to the low fuel pressure at idle, steam bubbles are generated (particularly steam bubbles are generated near the fuel injection valve). A so-called vapor lock occurs, which impedes fuel flow, resulting in an air-fuel ratio that is too lean and poor idling durability.

Therefore, in order to correct this, a device has been announced in the past that opens the pipe line that leads the intake pipe negative pressure to the pressure regulator to atmospheric pressure when the cooling water temperature becomes high (Utility Model Publication No. 57-193965). Publication No.). By opening the pipe line to atmospheric pressure at high temperatures, the absolute pressure of the fuel increases to the same level as under full load, making it difficult to generate steam bubbles, resulting in poor idle durability caused by steam bubbles. On the other hand, a closed-loop air-fuel ratio control device using an O ₂ sensor compensates for the tendency of the injection amount to increase due to an increase in fuel pressure.

[Problems with background technology]

However, the reason why the fuel pressure is originally changed according to the intake pipe negative pressure is to ensure that the opening time of the fuel injection valve and the injection amount correspond correctly, and this function can be achieved by using the closed-loop air-fuel ratio correction as described above. If replaced, the correction will be effective during steady operation such as idling, but when the load suddenly changes due to sudden accelerator operation (sudden change in intake pipe negative pressure), the closed-loop air-fuel ratio correction device using the O ₂ sensor will not be able to keep up. The correction becomes invalid. For this reason, there have been problems such as deterioration of exhaust gas, excessive consumption of fuel, and complexity due to additional correction control.
Incidentally, as a related technique, "Fuel supply device for fuel injection type engine" (Japanese Utility Model Publication No. 11266/1983) has been proposed.

[Purpose of the invention] The present invention was made in view of the above circumstances, and its purpose is to effectively prevent vapor lock when the engine is at high temperature, improve idling sustainability, and reduce the load caused by sudden accelerator operation. To provide a fuel pressure control device that can effectively prevent deterioration of exhaust gas and wasteful fuel consumption even if there is a sudden change.

[Summary of the invention] According to the invention, the above object is achieved as follows. In other words, there is a sub-path installed near the throttle valve that guides the negative pressure generated in the gap between the throttle valve and the throttle bore to the pressure regulator, and a main path that guides the intake negative pressure to the pressure regulator. The system is connected to the pressure regulator via a control valve, and the control valve closes the main system when the engine cooling water temperature reaches a predetermined temperature upper limit, and switches and connects the width system to the pressure regulator. It is characterized by being configured to do so. As a result, the fuel pressure is normally changed by the intake pipe negative pressure according to the engine temperature, and when the engine temperature is high, the fuel pressure is changed by the negative pressure signal transmitted from the throttle valve.
This is designed to improve as much as possible the idling durability when the engine is at high temperature.

[Embodiment of the invention] Hereinafter, a preferred embodiment of a fuel pressure control device for a fuel supply system of a fuel injection engine according to the invention will be described with reference to the accompanying drawings.

FIG. 1 is a system diagram of a fuel pressure control device for an electronically controlled fuel injection engine showing one embodiment of the present invention.

As shown in the figure, 1 is a fuel tank, 2 is a fuel pump, and 3 is a fuel injection valve.
The fuel is sucked into the fuel pump 2 and fed under pressure. After dust and moisture are filtered by the fuel filter 4, the fuel flows to the fuel injection valve 3, and is simultaneously injected from the tip of the fuel injection valve 3 into the intake pipe 5 of each cylinder. Further, the remaining fuel that has not been injected passes through the pressure regulator 6 and returns into the fuel tank 1. The pressure regulator 6 is used to adjust the fuel pressure applied to the fuel injection valve 3, and a diaphragm 7 divides the interior into a damper chamber 8 and a fuel chamber 9. The damper chamber 8 includes a spring 10 that pushes down the diaphragm 7 and closes the outlet of the fuel chamber 9.
A control port 11 is provided to receive a negative pressure signal to adjust the force of the spring 10. Fuel enters the fuel chamber 9 from the inlet of the pressure regulator 6, and if the fuel pressure is high, it overcomes the force of the spring 10 and pushes up the diaphragm 7, opens the outlet and returns to the fuel tank 1, but if the pressure is low, the fuel enters the fuel chamber 9. The outlet remains blocked and does not return to the fuel tank 1, and this action keeps the fuel pressure from the fuel pump 2 to the fuel injection valve 3 constant.

A main line 12 branched from the intake pipe 5 is connected to the control port 11, and a negative pressure signal sent to the damper chamber 8 is formed by the intake pipe negative pressure transmitted from the main line 12. The force of the spring 10 is adjusted in accordance with the intake pipe negative pressure to change the fuel pressure. Further, a sub-system path 14 is connected to the control port 11, which is formed by branching from the intake pipe 5 in the vicinity of the throttle valve 24 that controls the intake flow rate and at a position upstream of the throttle valve 24. Throttle valve 2 through
The damper chamber 8 is configured to transmit a negative pressure signal generated in the gap between the damper chamber 4 and the throttle bore 25 to the inside of the damper chamber 8. The negative pressure signal of the throttle valve 24 has a characteristic that during idling, it is closer to atmospheric pressure than the intake pipe negative pressure, and rapidly approaches the intake pipe internal pressure as the throttle valve opens. The sub-system path 14 and the main system path 12 are both branched from the intake pipe 5, but the width path 14 is located upstream of the throttle valve 24 as described above, and the main system path 12 is The difference is that it is located downstream of the throttle valve 24.

At the connection point between the main line 12 that guides the intake pipe negative pressure to the pressure regulator 6 and the auxiliary line 14 that guides the negative pressure signal generated in the gap between the throttle valve 24 and the throttle bore 25, A control valve 13 is interposed to close the main line 12 upon its operation and to guide a negative pressure signal from the sub line 14, which is different from the intake pipe negative pressure, to the pressure regulator 66. . This control valve 13 is configured, for example, by an electromagnetic three-way valve that is activated by a switching signal a and selectively connects the control port 11 of the pressure regulator 6 to the main line 12 or the sub-line 14. . The switching signal a is generated by a temperature sensor provided to indirectly detect the engine temperature, such as the intake pipe 5.
Alternatively, it is formed based on a detection signal from a temperature sensor 17 provided in the water cooling jacket 16 of the engine body 15. That is, the detection signal obtained from the temperature sensor 17 is transmitted to various other sensors such as the air flow sensor 18 and the throttle valve switch 1.
9, the signals from the O ₂ sensor 20, the ignition switch 21, the vehicle speed sensor 22, etc. are sent to the control unit 23, which processes these signals. This control unit 23 controls, when the engine temperature detected by the temperature sensor 17 exceeds a predetermined upper limit temperature,
That is, when the cooling water is at a high temperature, the control port 11 of the pressure regulator 6 is connected to the sub-system path 14.
The control valve 13 is operated to output an ON switching signal and, conversely, to output an OFF switching signal that connects the control port 11 of the pressure regulator 6 to the main line 12 when the cooling water temperature is low. let

The O ₂ sensor 20 is used for closed-loop air-fuel ratio control, and the control unit 23 controls the fuel injection valve 3 based on the detection signal from the O ₂ sensor 20 to detect the tendency of the injection amount to increase as the fuel pressure increases. This can be corrected by issuing a pulse that controls the valve opening time.

The operation of this device having the above configuration will now be described. .

When the engine cooling water temperature is low, that is, when the engine temperature detected by the temperature sensor 17 is below a predetermined temperature upper limit, the control section 23 detects the low water temperature and sends an OFF switching signal to the control valve 13,
The control port 11 of the pressure regulator 6 is connected to the main line 12. Control port 11 is main path 1
2, a negative pressure signal based on the intake pipe negative pressure is applied to the pressure regulator 6, and the fuel pressure is changed in accordance with the intake pipe negative pressure. Therefore,
At such normal water temperature, the differential pressure between the fuel pressure and the intake pipe negative pressure is constant, so the opening time of the fuel injection valve and the injection amount can be made to correspond correctly. Conventionally, when the engine cooling water temperature is high, that is, when the engine temperature detected by the temperature sensor 17 exceeds a predetermined upper temperature limit, the control port 11 of the pressure regulator 6 is opened to the atmosphere, and the second As shown in the figure, as a result of keeping the absolute value of the fuel pressure constant regardless of the engine load condition, the differential pressure between the fuel pressure and the intake pipe negative pressure increases as the engine load increases, as shown in Figure 3. Therefore, if there is a sudden change in load due to a particularly rapid accelerator operation, the closed-loop air-fuel ratio correction by the O ₂ sensor 20 will not be able to follow up, resulting in worsening of exhaust gas and excessive fuel consumption. It was bringing. In contrast, in the present invention, since the control port 11 of the pressure regulator 6 is connected to the width line 14, the pressure regulator 6
A negative pressure signal from the throttle valve 24 is applied instead of the intake pipe negative pressure that had been applied until then. As mentioned above, the negative pressure signal of the throttle valve 24 has a characteristic that it is atmospheric pressure at idle and approaches the intake pipe negative pressure as the throttle opening increases, so it is adjusted by the pressure regulator 6. As shown in FIG. 2, the fuel pressure applied changes from the characteristic at normal water temperature to the characteristic at high water temperature according to the present invention. That is, during idling, the absolute value of fuel pressure is increased to prevent vapor lock and improve idling durability. In this case, the flow rate characteristic of the fuel injection valve 3 increases due to the increase in fuel pressure, but the flow rate is automatically corrected by the action of the closed loop system using the O ₂ sensor 20. On the other hand, in a transient state caused by a sudden change in the accelerator pedal, due to the characteristics of the negative pressure signal of the throttle valve 24, the fuel pressure rapidly approaches the normal operating normal fuel pressure as soon as the throttle opens. Injection amounts can be matched correctly, and deterioration of exhaust gas and wasteful fuel consumption can be effectively and easily prevented. In this case, in the partial load region, there is also a region where the fuel pressure is lower than that at idle, but since the fuel consumption is higher than at idle, the flow in the fuel pipe near the fuel injection valve 3 is fast, and the amount of heating per unit flow rate is By reducing the engine speed and cooling the engine room by increasing the airflow rate of the fan or cooling the engine room by the running wind, vapor lock becomes less likely to occur than when the engine is idling, so it is not a problem.

In this way, a signal applied to the control port 11 of the pressure regulator 6 is sent via the control valve 13 to the intake pipe negative pressure source, depending on the engine cooling water temperature.
When the coolant temperature is high, the load signal source is switched to the throttle valve 24, so during steady idling when the water temperature is high, the fuel pressure can be increased to effectively prevent vapor lock and improve idling sustainability. At the same time, even in an excessive state due to a sudden change in the accelerator pedal, deterioration of exhaust gas and wasteful fuel consumption can be effectively prevented.

In the above embodiment, a closed-loop correction device using the O ₂ sensor 20 is used to correct the flow rate of the fuel injection valve 3 due to an increase in fuel pressure at high water temperature. It is also possible to store different data in advance in the control unit 23 for normal times and for rising times, and to correct the flow rate of the fuel injection valve 3 based on this stored data. Further, in the above embodiment, in order to limit the increase in fuel pressure only to the idle time, the switching signal of the control signal is formed from the AND of the idle contact signal of the throttle valve switch 19 and the detection signal of the temperature sensor 17. Good too.

FIG. 4 shows a modification of the embodiment shown in FIG. 1, in which the control port 11 of the pressure regulator 6
, depending on the engine cooling water temperature, instead of selectively connecting it to the main line 12 which leads the intake pipe negative pressure via the control valve 13 or the sub-line 14 which leads the negative pressure signal of the throttle valve 24. The auxiliary line 14 is directly connected to the main line 12 leading to the port 11, and by employing a water temperature detection type negative pressure valve 31, a negative pressure signal from the throttle valve 24 is sent to the pressure regulator 6 only when the cooling water temperature is high. It is designed to be poured. In this case, the air flowing from the intake pipe negative pressure source through the main system path 12 acts in a direction to cancel the tendency of the air-fuel ratio to become enriched due to an increase in fuel pressure. By appropriately selecting the diameter of the orifice 30, the air-fuel ratio can be maintained appropriately without relying on a closed-loop air-fuel ratio correction device. At the same time, the overall intake air-fuel mixture volume increases due to the increase in injection volume due to the increase in fuel pressure and the air flowing in from the intake pipe negative pressure source, so the idle speed increases and the rotation speed of the cooling fan increases proportionally. Therefore, there is an advantage that the fan air volume increases and the cooling capacity improves. In addition, the above orifice 3
0 can be omitted by appropriately selecting the diameter and length of each pipe.

In addition, in both of the above embodiments, the cooling water was selected as the engine temperature detection site, but this is not necessarily the case.As is clear from FIG. 5, the intake air temperature is also cooled depending on the engine load condition. Since it shows the same tendency as the water temperature, the intake air temperature may be detected instead of the cooling water temperature. Of course, the ambient temperature of the engine may also be detected.

[Effects of the invention] In summary, the present invention provides the following excellent effects.

(1) During normal idling when the engine is at high temperature, the fuel pressure can be increased to prevent vapor lock, so it is possible to improve the idling sustainability when the engine is at high temperature as much as possible.
In a transient state caused by a sudden change in the accelerator pedal, the throttle valve can be opened and the fuel pressure can be quickly brought close to the normal fuel pressure for normal operation, so deterioration of exhaust gas and wasteful fuel consumption can be effectively prevented.

(2) Correction of the increase in injection amount due to a rapid rise in fuel pressure can be made simply by guiding the negative pressure signal generated near the throttle valve to the pressure regulator, without performing complex correction control. This can be done by configuration alone.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing a preferred embodiment of the fuel pressure control device for the fuel supply system of a fuel injection engine according to the present invention, and Fig. 2 compares the fuel pressure of the conventional and the present invention with respect to engine load. Figure 3 is a fuel absolute pressure characteristic diagram, and Figure 4 is a differential pressure characteristic diagram comparing the differential pressure between fuel pressure and intake pipe negative pressure between the conventional and the present invention.
The figure is a system diagram showing another embodiment of the fuel pressure control device according to the present invention, and FIG. 5 is a diagram showing temperature characteristics of various parts with respect to engine load. In the figure, 1 is the fuel tank, 2 is the fuel pump, and 3 is the fuel tank.
1 is a fuel injection valve, 5 is an intake pipe, 6 is a pressure regulator, 11 is a control port, 12 is a main system path, 1
3 is a control valve, 14 is a sub-system, 15 is an engine body, 16 is a water cooling jacket, 17 is a temperature sensor,
20 is an O ₂ sensor, 23 is a control section, 24 is a throttle valve, and 25 is a throttle bore.

Claims (1)

[Scope of utility model registration request] A sub-path is provided near the throttle valve and leads the negative pressure generated in the gap between the throttle valve and the throttle bore to the pressure regulator, and a main path leads the intake negative pressure to the pressure regulator. The control valve is connected through a control valve, and the control valve is configured to close the main path and switch the sub-system path to the pressure regulator when the engine cooling water temperature reaches a predetermined temperature upper limit value. A fuel pressure control device for a fuel supply system of a fuel injection engine, characterized in that: