JPH09287540A - Discharge quantity estimating device for fuel pump for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate the discharge quantity of a high pressure pump for an internal combustion engine. SOLUTION: Fuel temperature is estimated (S1), fuel properties (heavy and light qualities) are judged (S2), viscosity and density of fuel are estimated from the fuel temperature and the fuel properties (S3), the rotational speed Np of a fuel pump is calculated (S4), and an ejection quantity from the fuel pump is estimated with accuracy on the basis of the rotational speed NP while taking in consideration the viscosity and density of fuel (S5).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for estimating a discharge amount of a fuel pump for an internal combustion engine, and more particularly to a spark ignition direct injection type engine for directly injecting fuel discharged by a high pressure fuel pump into a combustion chamber. In order to correct the injection amount,
The present invention relates to a technique for accurately estimating the discharge amount of a high-pressure fuel pump.

[0002]

2. Description of the Related Art In recent years, in a spark ignition type engine such as a gasoline engine, research has been conducted on a system in which an injection hole of a fuel injection valve is installed facing a combustion chamber and fuel is directly injected into the combustion chamber by the fuel injection valve. According to the spark ignition type direct injection internal combustion engine, compared to a premixed spark ignition engine having a fuel injection valve at an intake port, the transient operation characteristics are deteriorated due to fuel transport delay and the exhaust gas composition is reduced. There is an advantage that the deterioration of can be suppressed.

In this type of engine, a high-pressure fuel pump is provided in the middle of a fuel supply passage as a method for increasing the fuel injection pressure in order to enhance the atomization effect of the fuel (Japanese Patent Laid-Open No. Hei 5 (1993)).
-321783 etc.).

[0004]

By the way, in the high-pressure fuel pump for the internal combustion engine, since the fuel pressure fluctuates sharply when the fuel pressure increases at the time of starting, the discharge amount of the fuel pump and the fuel from the fuel injection valve are increased. Attempts have been made to predict the boosting characteristic of the fuel pump based on the injection amount and correct the fuel injection amount.

In this case, the discharge amount of the fuel pump was estimated based on only the pump rotation speed, but the discharge amount could not be estimated with sufficient accuracy because it changes depending on the state of the fuel. The present invention has been made in view of such conventional problems, and an object thereof is to accurately estimate the discharge amount of a fuel pump for an internal combustion engine.

Further, particularly in an engine in which fuel is directly injected into a combustion chamber by a spark ignition engine such as a gasoline engine, a discharge amount at the time of starting the engine of a high-pressure pump used for promoting atomization of fuel is highly accurately estimated. The purpose is to Also,
As described above, it is an object to correct the fuel injection amount at the time of engine start and set it with high accuracy by estimating the discharge amount of the fuel pump with high accuracy and predicting the boosting characteristic.

[0007]

Therefore, the invention according to claim 1 is characterized in that the discharge amount of the fuel pump for supplying the fuel to the fuel injection valve is estimated in consideration of the physical characteristics of the fuel. . Further, the invention according to claim 2 is characterized in that the discharge amount of the fuel pump is estimated based on the rotation speed of the fuel pump, taking into consideration the physical characteristics of the fuel.

The invention according to claim 3 is characterized in that the physical properties of the fuel include the viscosity and density of the fuel. The invention according to claim 4 is characterized in that the viscosity and density of the fuel are estimated based on the fuel temperature and the property of the fuel.

Further, the invention according to claim 5 is characterized in that the fuel temperature is directly detected or is estimated based on the detected values of the engine temperature, the outside air temperature and the engine load. The invention according to claim 6 is characterized in that the discharge amount of the fuel pump is directly estimated based on the rotation speed of the fuel pump, the fuel temperature, and the property of the fuel.

The invention according to claim 7 is characterized in that the discharge amount of the fuel pump is estimated in order to correct the fuel injection amount from the fuel injection valve when the engine is started. The invention according to claim 8 is characterized in that the fuel injection valve directly injects fuel into a combustion chamber of a spark ignition type engine.

Further, according to a ninth aspect of the present invention, as shown in FIG. 1, a first fuel pump for discharging fuel at a relatively low pressure and a fuel discharged from the first fuel pump are relatively A second fuel pump that discharges at a high pressure to the internal combustion engine of the spark ignition direct injection type, in which the fuel discharged from the second fuel pump is injected into the combustion chamber of the engine by a fuel injection valve. Pump rotation speed detection means for detecting the rotation speed of the fuel pump, fuel temperature detection means for detecting the fuel temperature of the engine directly or by estimation, fuel property determination means for determining the property of the engine, and the detected fuel temperature The fuel characteristic estimation means for estimating the viscosity and density of the fuel based on the property of the fuel determined to be, and the detected second for correcting the fuel injection amount from the fuel injection valve when the engine is started. Fuel A discharge amount estimating means for estimating a discharge amount of the second fuel pump in consideration of the viscosity and density of the rotational speed and the estimated fuel pump, characterized by being configured to include.

[0012]

According to the first aspect of the present invention, by estimating the discharge amount of the fuel pump in consideration of the physical characteristics of the fuel, it is possible to increase the amount of fuel in consideration of the change in the discharge amount due to the physical characteristics. Accurate estimation can be performed. Further, according to the invention of claim 2, since the discharge amount of the fuel pump is basically proportional to the rotation speed of the fuel pump, the discharge speed is based on the rotation speed and changes due to the physical characteristics of the fuel. Can be taken into consideration to perform highly accurate estimation.

According to the third aspect of the present invention, the physical quantity of the fuel includes the viscosity and density of the fuel, which has a great influence on the discharge quantity, so that the discharge quantity can be estimated with sufficiently high accuracy. It can be carried out. Further, according to the invention of claim 4, it is difficult to directly detect the viscosity and the density of the fuel, but it is possible to estimate them based on the fuel temperature and the property of the fuel.

According to the invention of claim 5, the fuel temperature can be detected with high accuracy when directly detected, and
If the estimation is performed based on the detected values of the engine temperature, the outside air temperature, and the engine load, the cost can be reduced without using a dedicated fuel temperature sensor. According to the invention of claim 6, the discharge amount of the fuel pump is directly estimated based on the rotation speed of the fuel pump, the fuel temperature, and the property of the fuel, so that the calculation process can be simplified. it can.

Further, according to the invention of claim 7, the boosting characteristic of the fuel pump is predicted by the discharge amount of the fuel pump estimated at the time of starting the engine, and the fuel injection amount is corrected and set with high accuracy. Therefore, the engine performance at the time of starting can be improved. Further, according to the invention of claim 8 and the invention of claim 9, in the spark ignition type direct injection engine, it is necessary to atomize the fuel in order to promote leaning of the air-fuel ratio, so that the high pressure fuel pump is Although it is used, the fuel pressure for the high pressure has a large fluctuation in fuel pressure at the start,
There is a great need to predict the boosting characteristic and correct the fuel injection amount. Therefore, by estimating the discharge amount of the fuel pump in this type of engine with high accuracy, the boosting characteristic can be predicted with high accuracy, and the effect of improving engine performance at the time of starting is great.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows the overall system configuration of an embodiment of the present invention. In FIG. 2, the engine 1 has an electromagnetic fuel injection valve 2 arranged so that its injection hole faces the combustion chamber 3 and sucked into the combustion chamber 3 via an intake port 4 and an intake valve 5. This is a spark ignition type direct injection engine that injects fuel from the fuel injection valve 2 to form air-fuel mixture and ignites the air-fuel mixture by spark ignition by a spark plug 6.

The exhaust gas of the engine 1 is discharged from the fuel chamber 3 through an exhaust valve 7 and an exhaust port 8, and is discharged into the atmosphere through an exhaust purification catalyst and a muffler (not shown). The fuel in the fuel tank 9 is discharged at a relatively low pressure by the first fuel pump 10 and is filtered by the filter 12 interposed in the low-pressure side fuel passage 11A, and then the low-pressure side on the downstream side of the filter 12 The fuel adjusted to a constant low pressure by the low pressure regulator 13 provided bypassing the fuel passage 11B is sent to the second fuel pump 14 for high pressure.

The second high-pressure fuel pump 14 is driven directly by the crankshaft or camshaft of the engine 1 or indirectly via a gear or a belt, and pressurizes the low-pressure fuel to a high pressure and discharges it. . The fuel discharged from the second pump 14 is
The fuel pressure is adjusted to a constant high pressure by a high pressure regulator 16 provided in the high pressure side fuel passage 15 in a bypass manner. And
Control unit with built-in microcomputer
The fuel injection valve 2 is controlled to open according to a pulse signal having a predetermined width corresponding to the engine operating state sent from the fuel injection chamber 17 at a predetermined injection timing.
Inject into and supply.

The control unit 17 is for detecting the engine speed for the fuel injection control, and
A crank angle sensor 18, which is also used for detecting the rotational speed of the second fuel pump 14, an air flow meter 19, which is used for detecting the intake air flow rate, and a water temperature which has a function of detecting the engine cooling water temperature and estimating the fuel temperature by the water temperature. Detection signals from various sensors such as the sensor 20 are input.

Here, the control unit 9 controls the pulse width of the injection pulse signal and outputs the injection pulse signal at the start timing, that is, the fuel injection valve 2.
Controls the fuel injection period. Further, an evaporated fuel processing device is provided for sucking the evaporated fuel from the fuel tank into the intake system for combustion processing.

That is, as shown in FIG. 3, one end of an evaporated fuel passage 21 is connected to the fuel tank 9, and the other end of the evaporated fuel passage 21 is connected to a canister 22. The canister 22 temporarily adsorbs and collects the evaporated fuel generated in the fuel tank 9. The fuel vapor passage 21
Is formed so as to join into the canister 22 after branching into two in the middle, and one of the branch pipe portions 21a is formed.
A mechanical check valve 23 is mounted on the other side, and an electromagnetic check valve bypass valve 24 is mounted on the other side 21b.
The check valve 23 is opened under a pressure higher than a predetermined value.

A pressure sensor for detecting the pressure in the fuel vapor passage 21, that is, the pressure in the fuel tank 9, is provided in the fuel vapor passage 21 between the check valve 23, the check valve bypass valve 24, and the canister 22. 25 are provided. An atmosphere introduction path 27 for introducing fresh air is connected to the canister 22.
An electromagnetic drain cut valve 28 for selectively shutting off the introduction of fresh air is installed in the.

On the other hand, a purge passage 30 for supplying the evaporated fuel temporarily adsorbed and collected by the canister 22 to the intake collector portion 29 of the intake manifold extends between the canister 22 and the intake collector portion 29. An electromagnetic purge cut valve 31 and a purge control valve 32 are provided in series in the middle of the purge passage 30. The purge cut valve 31 is an electromagnetic valve that opens and closes the purge passage 30 in an ON / OFF manner, and the purge control unit valve 32 is a flow rate adjustment valve whose opening is adjusted.

When the purge cut valve 31, the purge control valve 32, and the drain cut valve 28 are opened, the canister is opened via the purge passage 30.
Withdraw from the canister 22 with the fresh air introduced in 22
The (purged) evaporated fuel is sucked into the intake collector portion 29 and is used for combustion in the engine 1. The check valve bypass valve 24, the drain cut valve 28, the purge cut valve 31, and the purge control valve 32 are controlled to be opened and closed by the control unit 17.

A routine for estimating the discharge amount in order to predict the boosting characteristic of the second high-pressure fuel pump at the time of engine startup in such a system configuration will be described with reference to FIG. In step 1, the fuel temperature is estimated from the engine cooling water temperature detected by the water temperature sensor 20. Note that a fuel temperature sensor may be provided in the fuel passage to detect the fuel temperature directly, and the fuel temperature can be detected with high accuracy. However, according to the estimation as in the present embodiment, since the fuel temperature sensor is not used, Cost is enough.

In step 2, the properties of fuel (heavy and light) are determined. This is because a heavy and light sensor may be provided in the fuel passage to directly detect the heavy and light fuel, but in the present embodiment,
As will be described later, it is estimated based on the pressure of the evaporated fuel. In step 3, based on the estimated fuel temperature and fuel properties, the viscosity and density of the fuel are estimated by calculation or by retrieval from a map.

In step 4, the rotation speed Np of the second fuel pump 14 is calculated. Since the second fuel pump 14 is driven by the engine as described above, the rotational speed Np of the pump 14 is the same as or proportional to the engine rotational speed Ne detected by the crank angle sensor 18. You can In step 5, the discharge amount obtained on the basis of the pump rotation speed Np is corrected by the estimated viscosity and density of the fuel to calculate the discharge amount.

In this way, the discharge amount of the second fuel pump 14 which is calculated with high accuracy by correcting the viscosity and the density which are the physical characteristics of the fuel and has a great influence on the discharge amount, and the fuel injection valve 6 The second fuel pump according to the model based on the fuel injection amount from the fuel and the capacity of the accumulator that stores the fuel.
The boosting characteristic at the time of starting of 14 is predicted, and the fuel injection amount is corrected based on the boosting characteristic.

In this way, since the discharge amount of the second fuel pump 14 is estimated with high accuracy, the boosting characteristic can also be predicted with high accuracy, and the fuel injection amount is finally corrected with high accuracy. The starting performance of the engine can be improved. Next, while controlling the canister purge by controlling the opening and closing of the various valves, the property of the fuel is judged based on the pressure of the evaporated fuel in the fuel tank as shown in the flowchart of FIG.

In step 21, the purge cut valve is
13 closed, purge control valve 14 fully closed, drain cut valve 9 closed, check valve bypass valve 6
Set each to open. In step 22, in the initial state, the pressure EV detected by the pressure sensor 7, that is, the detected value EVPRESS of the evaporated fuel pressure in the fuel tank 2 is set to the initial value EVPIN.
Read as T.

Next, in step 23, the purge process is performed by controlling each of the valves to the state at the time of the purge process. During this time, the engine is warmed up, and the fuel temperature rises accordingly. The specific state of each valve during the purging process is that the purge cut valve 13 is opened and the purge control valve 14 is set to the purge ratio (purge mixture flow rate / intake air flow rate) set based on the engine operating state. The drain cut valve 9 is opened and the check valve bypass valve 36 is closed.

In step 24, it is determined whether or not a predetermined time has elapsed after the start. After that, go to step 25,
The purging process is stopped and each valve is set to the same state as in step 22. Immediately after the purging process is stopped, the fuel vapor pressure in the fuel tank 2 is negative. In step 26, a timer for measuring the elapsed time from the reset state of each valve is started.

In step 27, the pressure in the fuel tank 2 detected by the pressure sensor 7 is the same as in step 23.
It is determined whether or not it is larger than the predetermined value C by the predetermined value C or more detected before the purging process, and the process proceeds to step 28 after waiting for the predetermined value C or more. Here, the difference between the initial pressure and the saturated pressure after warm-up increases as the fuel temperature at start-up is lower even when using fuel of the same nature, so as shown in FIG.
The predetermined value C is variably set so that the lower the fuel temperature at the time of starting, the greater the value.

Then, in step 28, the fuel tank
The pressure EVPRES in 31 is the initial value EVP before purging
Elapsed time TMVP from INT until the value exceeds the predetermined value C
Is greater than or equal to the predetermined time D, and if it is greater than or equal to the predetermined time D, proceed to step 29 to determine that the fuel is heavy, and if the elapsed time is less than the predetermined value, proceed to step 30. Determines that the fuel is light. Here, when the fuel temperature increase rate ΔT is large even when the fuel having the same properties is used,
Since the pressure rise rate also increases, the fuel temperature increase rate ΔT
Then, as shown in FIG. 7, the increasing rate Δ of the fuel temperature is calculated.
The predetermined time D is variably set to increase as T decreases.

That is, when the fuel property is heavy, the volatility is low, the saturation pressure of the evaporated fuel after warm-up is low, and the pressure rising rate is low, so that the difference from the initial value becomes a predetermined value C or more. However, if the fuel property is light, the volatility is high, so the saturation pressure and the rate of pressure increase after evaporative fuel warm-up are low, and the difference from the initial value becomes a predetermined value C or more in a short time. Therefore, it is possible to distinguish between heavy and light.

Further, in the above embodiment, the fuel property is discriminated into two types, that is, heavy and light, but the level of heavy and light is detected linearly, and the empty state is determined according to the degree of heavy and light. The initial value of the air-fuel ratio of the fuel ratio lean control may be set, and more detailed control can be performed. FIG. 8 shows a flow chart of the discharge amount estimation according to the second embodiment of the present invention. What is different from the discharge amount estimation according to the first embodiment shown in the flow chart of FIG. 4 is the fuel temperature and the property of the fuel. Therefore, the discharge amount is estimated by direct search or calculation from the map in step 11, together with the rotation speed Np of the second fuel pump, without using the estimation of the fuel viscosity and the density. By doing so, the calculation process is shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing an overall system configuration according to an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of an evaporated fuel processing device.

FIG. 4 is a flowchart of a routine for similarly estimating the discharge amount of the fuel pump.

FIG. 5 is a flowchart showing a fuel property estimation routine.

FIG. 6 is a diagram showing a relationship between a predetermined value and a fuel temperature at the time of starting.

FIG. 7 is a diagram showing a relationship between a fuel temperature increase rate and a predetermined time.

FIG. 8 is a flowchart of a routine for estimating the discharge amount of the fuel pump according to the second embodiment of the present invention.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Fuel Injection Valve 3 Combustion Chamber 9 Fuel Tank 10 First Fuel Pump 14 Second Fuel Pump 17 Control Unit 21 Evaporative Fuel Passage 22 Canister 23 Check Valve 24 Check Bypass Valve 25 Pressure Sensor 27 Atmospheric Pressure Inlet 28 Drain cut valve 30 Purge passage 31 Purge cut valve 32 Purge control valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayuki Yasuoka 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd.

Claims (9)

[Claims] 1. A discharge amount estimating device for a fuel pump for an internal combustion engine, wherein a discharge amount of a fuel pump for supplying fuel to a fuel injection valve is estimated in consideration of physical characteristics of the fuel. 2. The fuel pump for an internal combustion engine according to claim 1, wherein the discharge amount of the fuel pump is estimated based on the rotational speed of the fuel pump and the physical characteristics of the fuel are added. Discharge rate estimation device. 3. The discharge estimation device for an internal combustion engine fuel pump according to claim 1, wherein the physical characteristics of the fuel include the viscosity and density of the fuel. 4. The discharge amount estimating apparatus for an internal combustion engine fuel pump according to claim 3, wherein the viscosity and density of the fuel are estimated based on the fuel temperature and the property of the fuel. 5. The discharge of an internal combustion engine fuel pump according to claim 2, wherein the discharge amount of the fuel pump is directly estimated based on the rotation speed of the fuel pump, the fuel temperature and the properties of the fuel. Quantity estimation device. 6. The fuel for an internal combustion engine according to claim 4 or 5, wherein the fuel temperature is directly detected or is estimated based on detected values of engine temperature, outside air temperature and engine load. Pump discharge rate estimation device. 7. The discharge amount of a fuel pump is estimated in order to correct the fuel injection amount from a fuel injection valve when the engine is started. For estimating the discharge rate of a fuel pump for an internal combustion engine. 8. The fuel pump for an internal combustion engine according to claim 1, wherein the fuel injection valve directly injects fuel into a combustion chamber of a spark ignition type engine. Discharge rate estimation device. 9. A first fuel pump that discharges fuel at a relatively low pressure, and a second fuel pump that discharges fuel at a relatively high pressure from the first fuel pump, In a spark ignition direct injection internal combustion engine in which fuel discharged from the second fuel pump is injected into a combustion chamber of the engine by a fuel injection valve, pump rotation speed detecting means for detecting a rotation speed of the second fuel pump, Based on the fuel temperature detection means for detecting the fuel temperature of the engine directly or by estimation, the fuel property determination means for determining the property of the engine, and the detected fuel temperature and the property of the determined fuel, the viscosity of the fuel And fuel density estimating means for estimating the density, and the detected rotational speed of the second fuel pump and the estimated fuel viscosity and density in order to correct the fuel injection amount from the fuel injection valve when the engine is started. Preparative consideration the discharge quantity estimation apparatus of the second internal combustion engine fuel pump to the discharge amount estimating means for estimating a discharge amount of the fuel pump, characterized in that it is configured to include.