JP3518417B2 - Common rail fuel injector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a common rail fuel injection device.

[0002]

2. Description of the Related Art A common rail type fuel injection device is known as a fuel injection device for a diesel engine. The common rail fuel injection device is provided with a common rail that holds high-pressure fuel supplied to the injector. The common rail is common to all the cylinders, and a necessary amount of high-pressure fuel is pressure-fed and supplied by a fuel pump to maintain the common rail pressure at a predetermined value. The fuel injection of the injector and the fuel pressure feeding of the fuel pump are controlled by an electronic control unit (ECU) which constitutes a control means.

In a fuel pump, normally, a pump drive shaft that rotates at half the engine speed when engine power is transmitted rotates the fuel injection of each cylinder, and the same number of fuels as the number of cylinders per rotation of the pump drive shaft. It is configured to perform pressure feeding (1 injection 1 pressure feeding) (for example, JP-A-62-258).
No. 160). The device disclosed in the above-mentioned JP-A-62-258160 is provided with a plurality of plunger barrels, and the cams provided on the pump drive shafts corresponding to the respective plungers drive the plungers respectively to add fuel in the plunger barrels. A fuel pump configured to press and feed is used. The fuel pressure feed amount is set according to the opening / closing timing of the PCV valve that allows the fuel in the plunger barrel to escape.

[0004]

However, the common rail type fuel injection device has a high maximum rotation speed (5000r).
When applied to a small diesel engine (pm or more), there are the following problems. That is, generally, the higher the engine speed is, the higher the operating speed of the fuel pump is, and it is difficult to perform stable fuel pressure feeding with high metering accuracy without causing suction failure even in a high rotation range. Therefore, the required specifications for the fuel pump are high, such as the PCV valve having high responsiveness is required, and it is necessary to newly develop a high-performance fuel pump. Further, in order to increase the engine crank angle information in the ECU in order to improve the fuel pressure feeding accuracy and the fuel injection timing accuracy, the angle interrupt calculation load of the ECU becomes large.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a common rail type fuel injection device capable of reducing the specifications required for the fuel pump and reducing the calculation load.

[0006]

According to a first aspect of the present invention, the fuel introduced into the pressure chamber whose volume is expanded and contracted by the fuel injection control of the injector provided for each cylinder of the engine and the power of the engine is supplied to the PCV valve. the fuel in the pressure chamber with reduction of the volume of the pressure chamber confined by closing a fuel pump for pumping the common rail 1 injection 1 pumping
In the control means for controlling the fuel pressure feed of the fuel pump in which the pressure chamber expands and contracts so as to enable the fuel pressure feed to be thinned by prohibiting the closing of the PCV valve and making the fuel in the pressure chamber non-pressurized. A means for setting the number of times of pressure feed by the fuel pump during one cycle of the fuel injection of each cylinder is set to a number smaller than the number of cylinders. The above pressure feed
The engine speed setting means sets the engine speed to
Up to the number of revolutions, fuel pressure feeding is performed in synchronization with fuel injection,
When the gin rotation speed exceeds the predetermined rotation speed, the PCV voltage
Perform valve closing prohibition control.

By thinning the fuel pressure feeding, the interval until the next pressure feeding can be made longer than that of the above-mentioned one-injection one-pressure feeding device, and a margin can be given to the pump operation to relax the required specifications of the fuel pump. Further , since the fuel pressure feeding control is thinned out, the calculation load can be reduced.

[0008]

[0009]

According to the second aspect of the present invention, a common rail pressure detecting means for detecting the fuel pressure of the common rail is provided, and the control means reads the fuel pressure of the common rail for each fuel injection control of each cylinder, and based on the fuel pressure. Set to calculate the fuel injection amount.

When fuel pumping is performed asynchronously with fuel injection
In this case, the fuel injection time will be the fuel pressure of the common rail at that time.
Since it is decided immediately, it is necessary to obtain sufficient fuel injection amount accuracy.
You can

[0012]

[0013]

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A shows the configuration of a common rail fuel injection device according to an embodiment of the present invention. The engine 1 is provided with a plurality of injectors 2 corresponding to the combustion chambers of each cylinder, and these injectors 2 are connected to a common rail 3 common to all the cylinders. The injector 2 opens or closes according to a control signal, and can switch between injection and stop of fuel supplied from the common rail 3. The control signal turns on and off the injection control electromagnetic valve 21 built in the injector 2, and for example, while the electromagnetic valve 21 is open, the fuel in the common rail 3 is injected from the injector 2 to the corresponding cylinder.

A fuel pump 4 is connected to the common rail 3 for continuously accumulating the common rail 3 with fuel having a high predetermined pressure corresponding to the fuel injection pressure. Fuel pump 4
Comprises a feed pump section 4a for sucking fuel from the fuel tank 5 and a high-pressure pump section 4b for pressurizing the sucked low-pressure fuel and pumping it to the common rail 3.
The fuel in the common rail 3 is controlled to a predetermined high pressure.

The ECU 6 executes fuel injection control of the injector 2 and fuel pressure feed control of the fuel pump 4. The ECU 6 has a general hardware configuration including a CPU and the like, calculates the valve opening timing and valve opening time of the injector 2 based on input signal information from various sensors for detecting the engine state, and sends a control signal to the injector 2. In addition to the output, the fuel pumping amount of the fuel pump 4 is calculated and a control signal is output to the fuel pump 4.

A pressure sensor 71, which is a common rail pressure detecting means for detecting the pressure of fuel held on the common rail 3 (hereinafter, simply referred to as common rail pressure), is provided as the above-mentioned various sensors, and a common rail pressure signal is input to the ECU 6 from this. is doing. The ECU 6 has a pressure sensor 7
1, the engine speed sensor 7 as various sensors described above.
2. An engine status signal from the throttle sensor 73 or the like is input.

FIG. 1B shows an engine 1 provided with the above fuel pump 4. Engine 1 is engine block 1
1, an oil pan 12 is provided below the head cover 13, and a head cover 13 is covered above the oil pan 12, and the head cover 13 is mounted in the engine room. Six cylinders 101, 102, 103, 104, 105, 106 formed in the engine block 11
The power generated at is transmitted to the crankshaft 100. The fuel injection from the injector 2 into each of the cylinders 101 to 106 is performed by the # 1 cylinder 101, # 5 cylinder 105, # 3 cylinder 103, # 6 cylinder 106, # 2 cylinder 102, # 4 cylinder 104 at every 120 ° CA. The crankshaft 100 rotates once (engine rotation) twice to complete one cycle. The present invention can be applied not only to the in-line 6-cylinder engine but also to the in-line 4-cylinder engine and the like, but in the following description, the engine 1 will be described as a 6-cylinder engine.

A fuel pump 4 is attached to a side surface of the engine block 11, and a crankshaft 100 is provided from a housing of the fuel pump 4.
Has projecting parallel to the pump drive shaft 400 is a rotation of the crank shaft 100 is transmitted at a reduced speed to the pump drive shaft 400 via a reduction gear mechanism 8. The reduction gear mechanism 8 includes a crank gear 81 fitted around the crankshaft 100.
, A reduction gear 82, and a pump drive gear 83 fitted around the pump drive shaft 400.
The pump drive shaft 400 can be rotated 3/4 rotation while 00 rotates twice. This allows the crankshaft 1
The pump operation can be performed more slowly than in the conventional device in which the pump drive shaft 400 makes one revolution while 00 makes two revolutions. The configuration of the fuel pump 4 includes a rotary supply pump,
Various types of proposed pumps may be used. In the following description, a rotary supply pump will be described.

FIG. 2 shows the overall functional structure of the high-pressure pump section 4b of the fuel pump 4. The low-pressure fuel delivered from the feed pump 4a passes through the PCV valve 41 and flows into the fuel pumping section 42. The fuel compressed and pressurized in the fuel pumping unit 42 is supplied to the common rail 3 through the check valve 43. Here, the PCV valve 41 is an electromagnetic valve in which the valve body 411 is attracted and closed by energization of the solenoid 412, and energization of the solenoid 412 is given as a control signal from the ECU 6. The check valve 43 has a forward direction from the fuel pumping section 42 toward the common rail 3.

FIG. 3 shows a sectional structure of a surface of the fuel pumping section 42 of the high-pressure pump section 4b which is perpendicular to the pump rotation shaft 400. The head 401 is a cylinder in a direction crossing the center line of the pump rotation shaft 400. A pair of plungers 403 facing each other are slidably inserted into the cylinder 402. 4 plungers 40
The space surrounded by the tip surface of 3 is a pressure chamber 404.
At the base end of each plunger 403, a shoe 406 that is in sliding contact with a shoe guide 405 that surrounds the outer periphery of the head 401 and a roller 407 are linearly moved in the cylinder 402 integrally. On the outer periphery of the shoe guide 405, a cam 408 that is coaxially connected to the pump drive shaft 400 and rotates is disposed. A cam ridge is formed on the inner peripheral portion of the cam 408 facing the roller 407, and the plunger 403 is pressed via the roller 407. Then, the plunger 403 is displaced according to the change in the cam lift of the cam 408, and the volume of the pressure chamber 404 is expanded or contracted.

The fuel is pressure-fed as follows. Figure 4
As shown in, the cam lift changes back and forth at a constant cycle,
The target PCV when the plunger 403 moves in the direction of the center of the circle
At the closing timing of the valve 41, a control signal is output from the ECU 6 to the PCV valve 41 to close the PCV valve 41, and the pressure chamber 404 is shut off from the low pressure feed pump 4a side. After this, the plunger 403 in the direction of the center of the circle
The fuel in the pressure chamber 404 is compressed in accordance with the linear movement of the above, and when the pressure exceeds the common rail pressure, the check valve 43 opens and pressure feeding of the fuel from the pressure chamber 404 to the common rail 3 is started.

The closing timing of the PCV valve 41 is given by the elapsed angle TF (° CA) from a predetermined reference position. The smaller the TF is, the more the PCV valve 41 is closed in the stage where the cam lift is small, that is, the stage where the pressure chamber volume is large, so that the fuel pressure feed amount increases. On the contrary, the larger the TF, the smaller the pumping amount.

In the fuel pump 4 of the illustrated example, four cam lobes are formed on the cam 408, and fuel can be fed four times during one rotation of the pump drive shaft 400. Therefore, from the speed reduction ratio of the speed reduction gear mechanism 8, the fuel injection into each cylinder 101 to 106 makes one round, and the crankshaft 100 rotates twice (720 ° CA) three times (= 4 × 3/4), that is, 24
Pumping is performed every 0 ° CA. Therefore, as shown in FIG. 5, the fuel is fed once for every two fuel injections. In the illustrated example, the # 1 cylinder 101, the # 2 cylinder 102, and the # 3 cylinder 103 are the cylinders for which pressure feeding is performed.

In general, the following method is used to perform one pressure feed for two injections. Number of cylinders of the engine m, number of times of pumping n per revolution of the pump drive shaft, engine speed re
, And the rotational speed rp of the pump drive shaft decelerated by the reduction gear mechanism, n × rp = (m / 2) × (re / 2)
Therefore, the reduction ratio (rp / re) = m / 4n. Further, more preferably, the reduction ratio (rp / re) is set to 1/2 or less, which is the reduction ratio of the conventional device. Therefore, n ≧ m / 2.

Next, the fuel injection control of the injector 2 and the fuel pressure feed control of the fuel pump 4 executed in the ECU 6 will be described. 6 shows the fuel injection control of the injector 2, and FIG. 7 and FIG. 8 show the fuel pressure feed control of the fuel pump 4. Both are executed every 120 ° CA.

The fuel injection control will be described. In step S101, the target injection amount QFIN is calculated based on the operating condition parameters such as the accelerator opening ACCP and the vehicle speed,
The actual common rail pressure NPC is read in step S102, and the cylinder number is read in step S103. In step S104, the injection pulse TQ is calculated from the target injection amount QFIN and the actual common rail pressure NPC. The injection pulse TQ is the length of the valve opening control signal to the injector 2. In step S105, the injection timing TFIN is calculated from the target injection amount QFIN and the engine speed NE.

The injection pulse TQ and injection timing TFIN calculated in steps S104 and S105 are set, and the injector 2 is controlled based on the set injection pulse TQ and injection timing TFIN.

The fuel pressure feeding control will be described. In step S201, the cylinder number is read, and then in step S20.
At 2, it is determined whether or not the cylinder is a cylinder (# 1, # 2, # 3) that performs fuel pressure feed in synchronization with fuel injection. When the cylinder numbers are # 1, # 2, and # 3, the process proceeds to step S203.

In step S203, the target injection amount QFIN
And engine speed NE to target common rail pressure PF
IN is calculated, and in step S204, the actual common rail pressure NPC is read.

In step S205, the target injection amount QFIN
And target common rail pressure PFIN to PCV valve 4
The basic valve closing timing TFBASE of 1 is calculated.

In step S206, the valve closing timing proportional correction term TFP is calculated from the deviation between the actual common rail pressure NPC and the target common rail pressure PFIN. In step S207, the valve closing timing integral correction term TFI is calculated.
It is calculated from the integrated value of the deviation between the PC and the target common rail pressure PFIN.

In step S208, steps S205 to S205.
The basic valve closing timing TFBASE calculated in S207,
Valve closing timing proportional correction term TFP, valve closing timing integral correction term TFI
From this, the final valve closing timing TF is calculated by the equation (1). By performing such proportional correction and integral correction, the common rail pressure can be controlled to the target common rail pressure better. TF = TFBASE + TFP + TFI (1)

In step S209, the final valve closing timing T
F is set, and the fuel pump 4 is driven based on the set final valve closing timing TF.

In step S202, when the read cylinder number is not the number of the pressure-fed cylinder (# 2, # 4, # 6), this control routine is terminated without executing the procedure from step S203.

Thus, the # 2, # 4 and # 6 cylinders 10
In the fuel injection of Nos. 2, 104, and 106, the fuel pump 4 does not perform fuel pressure feeding, but the actual common rail pressure NPC is detected and the actual common rail pressure NP is detected for each fuel injection of each cylinder.
Since the injection pulse TQ is set according to C, the fuel injection can be performed with high accuracy in the fuel injection of any cylinder.

In the common rail type fuel injection device, the reduction gear mechanism 8 allows two injections and one pumping with a smaller number of times of fuel pumping than the conventional one injection and one pumping. The number of times fuel is fed per revolution, that is, the number of cam peaks of the cam 408 (4) is the number of cylinders (6)
Lesser configurations can be used. Therefore, even when it is applied to an engine with a high maximum engine speed, there is a margin in pump operation, the required specifications of the fuel pump can be relaxed, and the cost can be reduced. For example, the responsiveness of the PCV valve 41 that determines the adjustment accuracy of the fuel pressure feed amount does not need to be particularly high. Further, since the fuel pump 4 can be configured so that the cam crests and the number of plunger barrels are smaller than the number of cylinders as described above, the fuel pump can be downsized.

Fuel pressure feeding by the fuel pump 4 is carried out by # 1, #
It is performed only in synchronism with the fuel injection of the # 2, # 3 cylinders 101, 102 and 103, and the number of times of pressure feeding control may be smaller than that of a conventional device for one injection and one pressure feeding, so that the calculation load on the ECU 6 can be reduced. it can.

Further, in the present embodiment, the reduction gear mechanism 8 is set to perform the pressure feeding once for the two injections, but the number of the pressure feedings can be reduced by controlling the opening / closing of the PCV valve. Good. That is, the fuel pressure feeding is normally performed corresponding to the cam crest, and in the case of FIG. 3, the pressure feeding can be performed four times for one rotation of the pump drive shaft, but the pressure feeding is thinned by the opening / closing control of the PCV valve. That is, if the fuel should be pumped, the PCV valve is closed at the timing when the pressure chamber volume is reduced normally, and if the pressure is not sent, the PCV valve is closed at the timing when the pressure chamber volume is reduced. Prohibit closing the valve. Since the fuel in the pressure chamber is not pressurized when the closing of the PCV valve is prohibited, the fuel is not pumped. As a result, the number of times of pressure feeding can be reduced, and a sufficient interval between fuel pressure feeding and the next pressure feeding can be secured. Therefore, even if the responsiveness of the PCV valve is not sufficient to perform fuel pumping in synchronization with each fuel injection, high metering accuracy can be obtained in fuel pumping.

In this case, it is also possible to set the ECU so as to perform the control in synchronization with the injection in the low rotation speed region where the operating speed of the pump is slow, and to perform the PCV valve closing prohibition control when the engine speed exceeds a predetermined value. Good.

The parts of the common rail fuel injection device are not limited to those described in the present embodiment, and may be arbitrary as long as they do not violate the spirit of the present invention. For example, the fuel pump is not a rotary supply pump but the above-mentioned Japanese Patent Laid-Open No. 62-
The fuel pump of the system described in Japanese Patent No. 258160 may be used. Further, the pump drive shaft does not have to be configured to perform pressure feeding four times with one rotation.

[Brief description of drawings]

FIG. 1A is an overall configuration diagram of a common rail fuel injection device according to an embodiment of the present invention, and FIG. 1B is a perspective view of an engine equipped with a fuel pump that constitutes the common rail fuel injection device. is there.

FIG. 2 is a functional configuration diagram of a fuel pump of the common rail fuel injection device according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view of essential parts of a fuel pump of the common rail fuel injection device according to the embodiment of the present invention.

FIG. 4 is a first time chart showing the operation of the common rail fuel injection device according to the embodiment of the present invention.

FIG. 5 is a second time chart showing the operation of the common rail fuel injection device according to the embodiment of the present invention.

FIG. 6 is a first flowchart showing control executed in an electronic control unit of the common rail fuel injection device according to the embodiment of the present invention.

FIG. 7 is a second flowchart showing control executed in the electronic control unit of the common rail fuel injection device according to the embodiment of the present invention.

FIG. 8 is a third flowchart showing control executed in the electronic control unit of the common rail fuel injection device according to the embodiment of the present invention.

[Explanation of symbols]

1 engine 100 crankshaft 2 injector 21 solenoid valve 3 common rail 4 fuel pump 400 pump drive shaft 41 PCV valve (solenoid valve) 4a feed pump section 4b high pressure pump section 6 electronic control unit (control means , pressure feed number setting means ) 71 pressure sensor (Common rail pressure detection means )

Continuation of front page (56) References JP-A-9-287536 (JP, A) JP-A-11-62779 (JP, A) JP-A-8-144826 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) F02D 41/38 F02D 41/20 395 F02M 47/00

Claims (2)

(57) [Claims] 1. An injector which is provided for each cylinder of an engine and injects fuel into the cylinder, and a common rail which holds fuel accumulated at a predetermined pressure and supplies it to the injector.
The fuel in the pressure chamber with reduction of the volume of the pressure chamber confining the fuel volume introduced into the pressure chamber to scaled by the power of the engine by closing the PCV valve to a fuel pump for pumping the common rail 1 injection 1 pumping Can be above the pressure
In a common rail fuel injection device comprising a fuel pump whose chamber expands and contracts, and control means for performing fuel injection control of an injector and fuel pressure feeding control of a fuel pump, the control means prohibits closing of the PCV valve. By setting the fuel in the pressure chamber to a non-pressurized state, the fuel pressure feeding is thinned, and the number of times of pressure feeding of the fuel by the fuel pump during one cycle of the fuel injection of each cylinder is set to a number smaller than the number of cylinders. It allowed comprising a, and the pumping number setting
The fixing means is designed so that the engine speed is in the low speed range to a predetermined speed.
Until the fuel is pumped in synchronism with fuel injection,
When the rotation speed exceeds the predetermined rotation speed, the PCV valve
A common rail type fuel injection device characterized by performing a valve closing prohibition control of the . 2. The common rail fuel injection device according to claim 1, wherein a common rail fuel pressure is detected.
A rail pressure detecting means is provided, and the control means is provided for each cylinder.
Read the fuel pressure of the common rail for each fuel injection control
Set to calculate the fuel injection amount based on the fuel pressure
Common rail fuel injection device.