JP4241629B2 - Abnormality detection device for fuel supply pump - Google Patents

Description

  The present invention relates to an abnormality detection device for a fuel supply pump used in an accumulator fuel injection system.

Conventionally, a fuel supply pump used in an accumulator fuel injection system has been driven by an engine to rotate, a feed pump that is driven by the camshaft and pumps fuel from a fuel tank, and is pumped by the feed pump. A plunger that sucks and pressurizes fuel into the cylinder and a cam means that converts the rotational motion of the cam shaft into a linear motion and transmits the linear motion to the plunger are provided.
Part of the fuel pumped up by the feed pump is supplied to a cam chamber that houses the cam means, and is used as lubricating oil for lubricating the sliding portion of the cam means.
JP 2003-293835 A

By the way, the fuel supply pump described above is widely used not only in Japan but also overseas, and is used in various environments. For this reason, inferior fuel may be used, and in that case, the fuel supply pump may be adversely affected.
For example, if fuel with a high water content is sucked into the fuel supply pump, the lubricity of the fuel is inferior, leading to poor lubrication with respect to the cam means, and further causing malfunction of the plunger, making it impossible to discharge the fuel. There was a fear.
The present invention has been made based on the above circumstances, and an object thereof is to provide an abnormality detection device that can detect an abnormality of a fuel supply pump that occurs due to poor lubrication.

(Invention of Claim 1)
In an abnormality detection device for a fuel supply pump used in an accumulator fuel injection system , the fuel supply pump is driven by an engine and rotated by a cam shaft, and a feed pump that is driven by the cam shaft and pumps fuel from a fuel tank; A plunger for sucking and pressurizing the fuel pumped up by the feed pump into the cylinder and a cam means for converting the rotational motion of the cam shaft into a linear motion and transmitting it to the plunger is accommodated. A part of the fuel discharged from the feed pump is supplied to the cam chamber as lubricating oil, and the lubricating oil overflows from the cam chamber, and detects the temperature of the fuel sucked into the fuel supply pump. And a second fuel temperature sensor that detects the temperature of the fuel in the cam chamber or the temperature of the fuel that has overflowed from the cam chamber. The detection means for obtaining the temperature difference between the fuel temperature detected by the first fuel temperature sensor and the fuel temperature detected by the second fuel temperature sensor, and the temperature difference is equal to or greater than the threshold even when a predetermined time has elapsed. And an abnormality determining means for determining that the fuel supply pump is abnormal when it is equal to or greater than the threshold even when a predetermined time has elapsed .

(Invention of Claim 2)
The fuel supply pump abnormality detection device according to claim 1, further comprising a control device that controls to reduce the load of the fuel supply pump when it is determined that the fuel supply pump is abnormal .

  The best mode for carrying out the present invention will be described in detail with reference to the following examples.

FIG. 1 is a cross-sectional view of a fuel supply pump, and FIG. 2 is a configuration diagram of an accumulator fuel injection system including the fuel supply pump.
The accumulator fuel injection system of this embodiment is applied to, for example, a four-cylinder diesel engine. As shown in FIG. 2, a common rail 1 that accumulates fuel and a fuel supply that pumps fuel to the common rail 1 are used. A pump 2 and an injector 3 that injects high-pressure fuel supplied from the common rail 1 into the cylinder of the diesel engine are controlled by an electronic control unit (hereinafter referred to as ECU 4).

The common rail 1 accumulates the fuel pumped from the fuel supply pump 2 up to the target rail pressure. The target rail pressure is calculated by the ECU 4 according to the operating state of the diesel engine (for example, the accelerator opening and the rotational speed of the diesel engine).
As shown in FIG. 2, the fuel supply pump 2 includes a cam shaft 7 that is rotatably supported by a pump housing 6 via a bearing 5, a feed pump 8 that is driven by the cam shaft 7, and the feed pump 8. A regulating valve 9 that adjusts the discharge pressure of the cylinder, a cylinder block 10 that is liquid-tightly assembled to the pump housing 6, a plunger 12 that is inserted into a cylinder 11 formed in the cylinder block 10, and a camshaft 7 It comprises cam means (described later) that converts the rotational motion into linear motion and transmits it to the plunger 12.

  The feed pump 8 is configured by, for example, a well-known trochoid pump, and is driven by the camshaft 7 to rotate, thereby pumping up fuel from the fuel tank 13 and discharging it. The fuel discharged from the feed pump 8 branches and flows in two directions, one is supplied to the inside of the cylinder 11 (referred to as the pressurizing chamber 15) through the suction passage 14, and the other is passed through the overflow passage 16. It is supplied to a cam chamber 17 (described later). The fuel supplied from the feed pump 8 to the pressurizing chamber 15 of the cylinder 11 is metered by an electromagnetic metering valve 18 provided in the middle of the suction passage 14. The valve opening state of the electromagnetic metering valve 18 is controlled by the ECU 4 based on the operation state of the diesel engine.

The cylinder block 10 is assembled with a suction valve 19 that opens and closes the suction passage 14 and a discharge valve 21 that opens and closes the discharge passage 20.
The suction valve 19 is a check valve that opens when fuel is sucked into the pressurizing chamber 15 and prevents the fuel from flowing back from the pressurizing chamber 15 to the feed pump 8 side.
The discharge valve 21 is a check valve that opens when fuel is discharged from the pressurizing chamber 15 and prevents the discharged fuel from flowing back into the pressurizing chamber 15.

As shown in FIG. 1, the cam means includes an eccentric cam 22 having a circular cross section provided on the cam shaft 7, a cam ring 24 fitted to the outer periphery of the eccentric cam 22 via a metal bush 23 so as to be relatively rotatable, The tappet 25 abuts on the outer peripheral surface of the cam ring 24 and the like. The tappet 25 is integrally provided at the end of the plunger 12 and is pressed against the outer peripheral surface of the cam ring 24 by a spring 26.
The eccentric cam 22 is provided with a rotation center Ob at a position shifted from the rotation center Oa of the cam shaft 7 by a predetermined distance. When the cam shaft 7 rotates, the eccentric cam 22 rotates eccentrically with respect to the rotation center Oa of the cam shaft 7.

The cam ring 24 is provided with a flat outer peripheral surface with which the tappet 25 abuts. When the camshaft 7 rotates, the eccentric cam 22 rotates relative to the eccentric cam 22 with the tappet 25 constantly abutting against the flat surface. And eccentric rotation.
The tappet 25 moves up and down while sliding on the flat surface of the cam ring 24 according to the eccentric rotation of the cam ring 24. The plunger 12 reciprocates in the cylinder 11 by converting the eccentric rotation of the cam ring 24 into a linear motion via the tappet 25.

  The pump housing 6 is made of, for example, aluminum. A cam chamber 17 is formed by assembling the cylinder block 10, and the cam means is accommodated in the cam chamber 17. A part of the fuel discharged from the feed pump 8 is supplied to the cam chamber 17 as lubricating oil through the overflow passage 16. The fuel overflowing from the cam chamber 17 is returned to the fuel tank 13 through an overflow pipe 27 (see FIG. 2) connected to the downstream end of the overflow passage 16.

The operation of the fuel supply pump 2 will be described.
When the camshaft 7 is driven and rotated by the diesel engine, the feed pump 8 draws fuel from the fuel tank 13 and the fuel filtered by the fuel filter 28 (see FIG. 2) is supplied to the pressurizing chamber 15 in the cylinder 11 and the cam. Discharge into chamber 17. The fuel discharged from the feed pump 8 toward the pressurizing chamber 15 is regulated to a constant pressure by the regulating valve 9.

  On the other hand, when the plunger 12 moves in the cylinder 11 from the top dead center toward the bottom dead center due to the rotation of the camshaft 7, the pressure in the pressurizing chamber 15 decreases, so that the fuel discharged from the feed pump 8 is discharged. The suction valve 19 is pushed open to be sucked into the pressurizing chamber 15. Thereafter, when the plunger 12 that has reached the bottom dead center moves inside the cylinder 11 toward the top dead center, the fuel sucked into the pressurizing chamber 15 is pressurized, and the fuel pressure becomes the valve opening pressure of the discharge valve 21. When the pressure exceeds the value, the discharge valve 21 is opened, and the fuel in the pressurizing chamber 15 is pumped to the common rail 1.

The injector 3 is attached to each cylinder of the diesel engine, and is connected to the common rail 1 via a high-pressure pipe 29 as shown in FIG. The injector 3 has an electromagnetic valve 3a electronically controlled by the ECU 4, and a nozzle 3b whose fuel injection timing and injection amount are controlled via the electromagnetic valve 3a.
The solenoid valve 3a controls the fuel pressure in a control chamber (not shown) to which high-pressure fuel is supplied from the common rail 1, and opens a low-pressure passage (not shown) that leads to the control chamber. The pressure decreases, and the fuel pressure in the control chamber increases by closing the low pressure passage.

  The nozzle 3b incorporates a needle (not shown) for opening and closing a nozzle hole (not shown), and the fuel pressure in the control chamber is used as the back pressure of the needle (force that urges the needle in the valve closing direction). It is working. Therefore, when the solenoid valve 3a opens the low pressure passage, the fuel pressure in the control chamber decreases, and the valve opening force that urges the needle in the valve opening direction exceeds the fuel pressure in the control chamber, the needle opens and the common rail 1 is injected from a nozzle hole (not shown). On the other hand, when the solenoid valve 3a closes the low pressure passage and the fuel pressure in the control chamber rises, and the fuel pressure in the control chamber becomes larger than the valve opening force that biases the needle in the valve opening direction, the needle is closed. Injection ends.

The ECU 4 includes various sensors for detecting the operating state of the diesel engine (for example, the NE sensor 30 for detecting the rotational speed of the diesel engine, the accelerator opening sensor 31 for detecting the accelerator opening, and the fuel pressure accumulated in the common rail 1). The sensor information detected by the pressure sensor 32 to be detected) is input, and based on these sensor information, the fuel pressure accumulated in the common rail 1, the injection amount injected from the injector 3, the injection timing, and the like are controlled.
Further, the ECU 4 has a function of abnormality determination means for determining whether or not there is an abnormality in the fuel supply pump 2 based on the temperature change of the fuel passing through the cam chamber 17 of the fuel supply pump 2.

Next, the processing procedure of the ECU 4 related to the abnormality detection processing of the fuel supply pump 2 will be described based on the flowchart shown in FIG.
Step 10: Input temperature information from the fuel temperature sensor. The ECU 4 includes a first fuel temperature sensor (not shown) that detects the temperature of the fuel drawn into the fuel supply pump 2 and a second fuel temperature that detects the fuel temperature in the cam chamber 17 of the fuel supply pump 2. Temperature information is input from each sensor 33 (see FIG. 2).

The first fuel temperature sensor is attached to, for example, a fuel pipe 35 connected to the fuel suction port 34 (see FIG. 2) of the fuel supply pump 2 and detects the temperature of the fuel sucked into the fuel supply pump 2. Alternatively, it is attached to the pump housing 6 of the fuel supply pump 2 to detect the temperature of the fuel sucked by the feed pump 8.
On the other hand, for example, as shown in FIG. 2, the second fuel temperature sensor 33 is attached to the pump housing 6 of the fuel supply pump 2 to detect the fuel temperature in the cam chamber 17. Alternatively, the temperature of the fuel overflowing from the cam chamber 17 may be detected by being attached to the overflow pipe 27.

Step 20: A temperature difference ΔT between the fuel temperature detected by the first fuel temperature sensor and the fuel temperature detected by the second fuel temperature sensor 33 is obtained, and it is determined whether or not the ΔT is equal to or greater than a threshold value ΔTk. To do.
Step 30 ... When ΔT is smaller than ΔTk, it is determined as “normal operation”. In this case, nothing is displayed, and control command values (for example, engine speed, rail pressure, injection amount, etc.) relating to the operating state of the diesel engine are not changed.
Step 40 ... When ΔT is equal to or greater than ΔTk, a display or history is given that some abnormality has occurred in the fuel supply pump 2.

  Step 50: It is determined whether or not a predetermined time t (for example, 5 seconds) has elapsed. This determination process is performed in order to prevent erroneous determination due to a temporary variation in ΔT. For example, when the engine speed and the rail pressure suddenly drop due to idling soak or the like due to high-speed and high-load operation, the amount of latent heat of the pump is higher than that during steady operation, so the fuel temperature detected by the second fuel temperature sensor 33 Will rise temporarily. As a result, ΔT may be equal to or greater than ΔTk and may be erroneously determined as “abnormal”. Therefore, the fuel temperature detected by the fuel temperature sensor is read again until the predetermined time t elapses, and the determination process of step 20 is repeatedly executed.

  Step 60 ... When ΔT is equal to or greater than ΔTk at the time when the predetermined time t has elapsed, it is not a misjudgment due to a temporary fluctuation of ΔT, but some abnormality (for example, seizure of the tappet 25) has occurred in the fuel supply pump 2. As a result, since it can be determined that the fuel temperature detected by the second fuel temperature sensor 33 is continuously rising, the direction in which the load (discharge amount) of the fuel supply pump 2 is reduced (engine speed, rail pressure, Control is made to a retreat mode for suppressing the injection amount and the like.

(Effect of Example 1)
For example, if the lubricity of the fuel supplied to the cam chamber 17 of the fuel supply pump 2 is deteriorated, a sliding failure (such as a sliding failure of the tappet 25) occurs in the cam means, and the amount of heat generated increases. That is, the temperature of the fuel suddenly rises. Therefore, by monitoring the temperature change of the fuel supplied to the cam chamber 17, it can be detected at an early stage whether or not an abnormality has occurred in the fuel supply pump 2. That is, before the failure of the fuel supply pump 2 becomes large (for example, before the operation is stopped), an abnormality occurring in the fuel supply pump 2 (not a serious failure but a relatively mild abnormality) can be detected. And a highly safe fuel injection system.

Further, since maintenance and inspection can be performed before the abnormal state of the fuel supply pump 2 progresses and causes a serious failure, there is also an effect that maintenance costs in the market can be reduced.
Further, when an abnormality is detected in the fuel supply pump 2, the vehicle is controlled in the save mode, so that, for example, it is possible to travel on its own to the nearby service area in the save mode without stopping the engine.

In Example 1, ΔT is compared with ΔTk to determine whether there is an abnormality. For example, high-speed high-load (high rail pressure and high pump discharge amount) with a high PV value and insufficient lubrication. Since the risk of seizure of the tappet 25 occurs at low speed and high load (high rail pressure and large pump discharge amount), ΔTk is determined in consideration of changes in operating conditions as shown in the following example. It is desirable.
At Ne ≧ 2500 rpm, it is determined as “abnormal” when ΔT ≧ ΔTk continues for 5 seconds or more.
At Ne <2500 rpm, it is determined as “abnormal” when rail pressure ≧ 80 MPa and ΔT ≧ ΔTk continues for 5 seconds or more.

(Modification)
In Example 1, ΔT is obtained by using two fuel temperature sensors (first fuel temperature sensor and second fuel temperature sensor 33), and ΔT is compared with ΔTk to determine whether there is an abnormality. However, it is also possible to use only the second fuel temperature sensor 33 to determine whether there is an abnormality. That is, it can be determined as “abnormal” when the fuel temperature detected by the second fuel temperature sensor 33 is equal to or higher than a predetermined temperature that cannot occur during normal operation.

In the first embodiment, an example of detecting an increase in fuel temperature due to seizure of the tappet 25 is described. However, even when seizure occurs in the feed pump 8, it is possible to detect an abnormality by the same method. is there.
Further, in the first embodiment, the method for detecting an abnormality based on the temperature change of the fuel is described. However, it is also possible to detect the abnormality based on the temperature change of the pump housing 6 or the cylinder block 10 having a high thermal conductivity. is there.

It is sectional drawing of a fuel supply pump. It is a block diagram of the pressure accumulation type fuel injection system containing a fuel supply pump. It is a flowchart which shows the process sequence of ECU regarding an abnormality detection process.

Explanation of symbols

2 Fuel supply pump 4 ECU (abnormality detection device / abnormality determination means)
6 Pump housing 7 Cam shaft 8 Feed pump 11 Cylinder 12 Plunger 13 Fuel tank 17 Cam chamber 22 Eccentric cam (cam means)
24 Cam ring (cam means)
25 Tappet (cam means)
33 Second fuel temperature sensor (temperature detection means)

Claims (2)

In the abnormality detecting device of a fuel supply pump used in the accumulator fuel injection system,
The fuel supply pump is driven by an engine and rotated by a camshaft, a feed pump that is driven by the camshaft and pumps fuel from a fuel tank, and fuel pumped by the feed pump is sucked into a cylinder and added. And a cam means for converting the rotational motion of the cam shaft into a linear motion and transmitting the linear motion to the plunger. One of the fuel discharged from the feed pump is contained in a cam chamber in which the cam means is accommodated. The portion is supplied as lubricating oil, and the lubricating oil overflows from the cam chamber,
A first fuel temperature sensor for detecting a temperature of fuel sucked into the fuel supply pump; and a second fuel temperature sensor for detecting a fuel temperature in the cam chamber or a temperature of fuel overflowed from the cam chamber. ,
Detection means for obtaining a temperature difference between the fuel temperature detected by the first fuel temperature sensor and the fuel temperature detected by the second fuel temperature sensor; and even when the temperature difference has exceeded a predetermined time An abnormality detection device for a fuel supply pump, comprising: an abnormality determination means for determining whether or not the fuel supply pump is abnormal when the predetermined time elapses or more. . In the fuel supply pump abnormality detection device according to claim 1,
An abnormality detection device for a fuel supply pump , comprising: a control device that controls to reduce the load on the fuel supply pump when it is determined that the fuel supply pump is abnormal.

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