JPS61190120A - Internal-combustion engine associated with supercharger - Google Patents

Abstract

PURPOSE:To improve the withstandability of controller for engine associated with a supercharger by quickening the speed of step motor for controlling the valve timing only under function of supercharger. CONSTITUTION:The intake/exhaust valves 20, 34 of engine associated with a supercharger 14 to be driven through a crank shaft 28 are opened/closed through the cam shafts 38, 40 which are controlled their open/close timing respectively through the actuators 41, 42. The controller 70 is provided with various engine parameters to control the open/close timing set in accordance with a memory 84 while to control the speed of step motor through the actuators 41, 42. Higher control speed of step motor will bring good controllability but low durability thereby it is controlled to increase the control speed only under operation of supercharger 14 thus to improve the durability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for controlling valve timing in a supercharged internal combustion engine according to operating conditions of a supercharger.

[Conventional technology]

A supercharger is used to increase the output of an internal combustion engine in its full-load operating range. However, as the pressure and temperature of the combustion chamber increase, non-king tends to occur. Therefore, the compression ratio is set lower than that of a normal internal combustion engine without a supercharger, thereby preventing non-king. However, by reducing the compression ratio, the pressure in the combustion chamber becomes insufficient in the partial load operating range, resulting in deterioration of combustion efficiency and reduction in fuel consumption rate. Therefore, in a supercharged internal combustion engine, there is a demand for a low compression ratio at full load, and a high compression ratio at partial load.However, due to the structure of the actual engine, it is difficult to make the compression ratio variable. Have difficulty.

Therefore, Japanese Utility Model Application Publication No. 59-49742 focuses on the fact that changing the actuation timing of the intake valve has the same effect as changing the compression ratio. That is, by delaying the valve timing of the intake valve, the angle from the bottom dead center in the rotational direction when the intake valve closes becomes larger. As a result, the period at which the piston begins to effectively compress is delayed, and the effective stroke of the piston becomes shorter, producing the same effect as lowering the compression ratio. Therefore, the valve timing of the intake valve is delayed from normal when the supercharger is operating under full load, and the valve timing is advanced to the normal value during partial load when the supercharger is not operating.

[Problem that the invention seeks to solve]

The supercharger starts operating when the clutch is engaged, but at that time the valve timing must be switched to the delayed side. The supercharger starts operating with relatively little delay when the clutch is engaged, but the step motor that changes the valve timing rotates one step at a time. Therefore, the rotational speed of the step motor is set to the maximum nopulse speed so that the supercharger can follow the operation. However, constantly rotating the pulse motor at a high rotational speed poses a problem in its durability.

[Means for solving problems]

In FIG. 1 illustrating the configuration of this invention, an internal combustion engine 1
A supercharger 3 is arranged in the intake pipe 2. According to this invention, there is a variable valve timing mechanism 4 that controls valve timing (3), a detection means 5 that detects the operating conditions of the supercharger 3, and a variable valve timing mechanism 4 that uses signals from the detection means 5. A supercharged internal combustion engine is provided, comprising means 6 for controlling the switching speed of valve timing.

[For production]

The supercharger operating condition detection means 5 detects the operating condition of the supercharger 3, and the control means 6 controls the valve timing switching speed by the variable valve timing mechanism 4 depending on the operating condition, that is, whether it is high load or low load. .

〔Example〕

In FIG. 2 showing an embodiment of the present invention, 1° is an air cleaner, 12 is a throttle valve, 14 is a supercharger such as a Roots pump, 16 is a surge tank, 18 is an intake boat, 2
0 is an intake valve, 22 is a cylinder block, 23 is a cylinder head, 24 is a piston, 26 is a connecting rod, 28 is a crankshaft, 30 is a combustion chamber, 32 is a spark plug, 3
4 is an exhaust valve, and 36 is an exhaust port. These are well-known components for internal combustion engines, and detailed explanations of their connection relationships will be omitted. This internal combustion engine is a so-called DOHC engine.
The engine is a type of internal combustion engine, and includes an intake camshaft 38 for driving the intake valve 20 and an exhaust camshaft 40 for driving the exhaust valve 34. Boo I at the shaft end of these camshafts 38 and 40
J41 and J42 are attached, and are wound around a timing pulley on the crankshaft 28 by a timing belt 43.

While the camshafts 38 and 40 are rotating, the intake valve 20 and the exhaust valve 34 are moved by the valve spring 4 at respective timings.
It is well known that the valve opens against the pressure of 4. A distributor 46 supplies a drive signal to the spark plug 32 at a predetermined timing based on a signal from an igniter (not shown).

As is well known, the Roots pump 14 as a supercharger has a pair of rotors (not shown) that are driven to rotate in opposite directions, and a pump 1J48 is mounted on the rotating shaft 14a of one of the rotors.
is fixed, and this pulley 48 has a built-in clutch (not shown) in this embodiment, which is engaged or released depending on the supercharging conditions. Boo IJ 4 B is connected to a pulley 52 on the crankshaft 28 via a belt 50, and when the clutch is engaged, the rotation of the crankshaft 28 is transmitted to the Roots pump 14 to perform a supercharging operation. Note that the clutch is an optional element and does not necessarily need to be provided.

In this case, the Roots pump will be driven all the time.

Further, the present invention is not limited to roots pump type superchargers, but can also be applied to turbo type superchargers.

A bypass passage 54 that bypasses the roots pump 14 is connected at one end between the roots pump 14 and the surge tank 16, and the other end of the bypass passage 54 is connected between the throttle valve 12 and the roots pump 14. A bypass control valve 56 is arranged on the bypass passage 54. This control valve 56 is operated to be closed in the operating region of the supercharger and opened to the non-supercharged region.

The intake camshaft 38 for driving the intake valve 20 has a variable valve timing mechanism 5 of a type that controls valve timing by twisting the camshaft relative to the crankshaft 28.
8 are connected. This variable valve timing mechanism is the third
The structure is shown in FIGS. 5 to 5. Intake camshaft 38
An inner sleeve 59 is fixed to one end with a bolt 60, and an outer sleeve 62 is mounted on the inner sleeve 59.
However, it is rotatable by a roller bearing 63. The outer sleeve 62 is formed integrally with the boolean IJ41 for driving the intake camshaft 38. Inner sleeve 59
The outer sleeve 62 is provided with protrusions 59a and 62a that extend alternately in the axial direction and have a circumferential width of approximately 90 degrees.

A roller 63 between each adjacent protrusion 59a and 62a
and 64 are arranged coaxially, and the projections 59a and 62 respectively
It is in contact with edges 59b and 62b opposite to a. In this embodiment, four pairs of rollers 63 and 64 are installed,
It is provided on the slider 65. The slider 65 is rotatable on a nut 66 having an internal thread through a roller bearing 65°. 67 is a step motor whose output shaft 67a has a thread formed on its outer surface and engages with the inner thread of the NAND 66. The motor 67 has a guide part 67b in its housing, which guide part 67b is located in an axial guide groove 66a formed in the nut 66. With this structure, the rotational operation of the output shaft 67a of the step motor 67 is converted into linear motion of the NAND 66. Projections 59a and 62a of the inner sleeve 59 and outer sleeve 62
The opposing edges 59b and 62b are one (5) as shown in FIG.
9b) is parallel to the axial direction, while the other (62b) is inclined. As a result, when the rollers 63 and 64 move in the axial direction as indicated by the arrows due to the rotation of the step motor 67, the inner sleeve 59 and the outer sleeve 62 rotate relative to each other. Therefore, the intake camshaft 38 connected to the inner sleeve 59 is rotated relative to the pulley 41 connected to the outer sleeve 62, in other words, relative to the crankshaft 52, and the valve timing of the intake valve 20 is changed. . FIG. 6(A) shows a valve timing diagram when the rotating shaft 67a of the step motor 67 is at the reference position.
The intake valve 20 begins to open at an angle α before top dead center TDC (
1, 0), it closes at an angle of β after bottom dead center BDC (1.
C). On the other hand, FIG. 6(b) is a valve timing diagram when the rotating shaft 67a of the step motor 67 is rotated from the reference position, and the intake valve 20 starts to open at α゛ (<α) before TDC, and after BDC. It ends at β゛(〉β). In this embodiment, the exhaust valve 34 has the same valve timing in (a) and (b), and starts opening at the BDC angle and finishes closing at an angle after TDC.

Note that the variable valve timing device is not limited to the structure shown in the drawings, and may be any device that can provide continuously changing valve timing.

In FIG. 2, 70 is a control circuit that controls the valve timing, ignition timing, and supercharger of the present invention based on signals from each operating condition sensor.

Among these sensors, the air flow meter 72 is, for example, a potentiometer type, is provided upstream of the throttle valve 12, and generates a signal corresponding to the intake air amount Q. For example, a semiconductor pressure sensor 74 is installed in the surge tank 1'6.
is installed to obtain a signal according to the boost pressure P. Further, the distributor 46 has a rotation speed sensor 7 as a Hall element facing the permanent magnet piece 46b on the distribution shaft 46a.
8 is provided to generate a signal corresponding to the engine rotational speed Ne.

The control circuit 70 is configured as a microcomputer in this embodiment, and includes a microprocessing unit (MPU).
) 82, a memory 84, an input port 86, an output port 88, and a bus 90 that connects these units and transfers instructions and data. The input boat 86 is connected to each of the above-mentioned sensors, that is, the air flow meter 72, the pressure sensor 74, and the rotation speed sensor 78. The input boat 86 includes a sensor that generates an analog signal among the sensors, that is, an air flow meter 72, a converter that converts the analog signal from the pressure sensor 74 into a digital signal, and a sensor 78 that generates a pulse signal for each crank angle. It is equipped with a circuit that calculates the rotation speed Ne of the engine. on the other hand,
The output port 88 is connected to the (lO) actuation solenoid (not shown) of the clutch portion of the pulley 14a of the Roots pump 14, the bypass control valve 56, and the step motor 67 of the variable valve timing mechanism 58.

Nonvolatile portions of memory 84, such as read-only memory
A program for executing valve timing control according to the present invention is stored in the (ROM). Other programs that are not directly related to the present invention but are used to perform various engine controls (for example, fuel injection control, etc.) are stored. The program of the present invention will be described below, but first an outline of the control will be explained. In an internal combustion engine with a supercharger, the compression ratio of the piston 24 is set smaller than in an internal combustion engine without a supercharger, as described at the beginning.

However, if left as is, there is a problem in that the combustion efficiency deteriorates during operations other than high loads when the supercharger 14 does not work. Therefore, as in Utility Model Application Publication No. 59-49742, the valve timing is basically set on the advance side, thereby obtaining the same effect as increasing the compression ratio when not supercharging. Sometimes the valve timing is delayed and the compression ratio is lowered to achieve the same effect. That is, in FIG. 6, the effective compression of the piston occurs at point 1 when the intake valve closes. Starting from C, al,! ! 2 is the stroke of the piston that performs effective compression. Since pl>β2, the intake valve closes quickly, setting (a) provides the same effect as increasing the compression ratio. In other words, setting the valve timing to (a) when not supercharging improves the combustion efficiency at times other than high loads, and setting the valve timing to (b) when supercharging prevents knocking and is effective. Can be supercharged. However, although the turbocharger has a fast response and starts supercharging immediately after the clutch is engaged, the valve timing control requires time for the step motor to complete the switching from (a) to (b) in Figure 6. During this period, even though the turbocharger is working, the valve timing advances, causing transient non-king. To prevent this, the pulse speed of the step motor is set to the maximum, which affects the durability of the step motor. In this invention, attention is paid to the fact that the valve timing must be changed quickly only when the engine speed is high, and the valve timing is changed slowly when the engine speed is low.

The process will be explained below using flowcharts shown in FIGS. 7 and 8. FIG. 7 shows a control routine for the supercharger. This routine is configured as a time interrupt routine that is executed every predetermined time, for example every 25 msec. 100 indicates its start. In step 102, it is determined whether the old flag GH, which is set or reset in response to high load operation of the engine, is 1 or not. If the load is high, the flag is HIGH = 1, and Yes
The process branches to step 104, and in step 104, MPt
182, a signal is applied from the output boat 88 to the clutch portion of the drive pulley 48 of the Roots pump 14, and the clutch portion is engaged. At 106, a signal is sent to the bypass control valve 56, which closes the bypass control valve 56. Therefore, the rotation of the clutch 28 of the engine is transmitted to the Roots pump 14 via the pulley 52, belt 50, and pulley 48, and since the bypass control valve 56 is closed, the intake air from the Roots pump 14 is The entire amount is sent in a compressed state to the combustion chamber 30 via the surge tank 16 to perform supercharging.

If it is not a high load operation in step 102, the flag old GII=0, it is determined as No, and the process proceeds to 110, where M
A command to release the clutch is output from the output boat 88 to the PU 82 . Therefore, the crankshaft 28 is separated from the Roots pump 14, and supercharging is not performed. 112
Then, a command to open the bypass control valve 56 is output, and as a result, the bypass passage 54 that bypasses the Roots pump 14 is opened, and a portion of the intake air passes through the bypass passage 54.

FIG. 8 shows a flowchart of the valve timing control routine. This routine is a time interrupt routine that is executed at predetermined time intervals, which is longer than required to execute the step rotation of the output shaft 67a of the step motor 67, but can provide a predetermined control accuracy. In step 201, it is determined whether the engine is operating under high load. This judgment is based on the intake air amount Q
The determination can be made based on whether the ratio of the rotational speed Ne (detected by the rotational speed sensor 78) to the air flow no. detected by the Tough 2 is larger than a predetermined value. If no, proceed to 202 and flag old G
It is determined whether ll is O or not. This flag becomes 1 when the load is high and becomes 0 when the load is low. In switching from high load to low load, old GH=1, and the determination is No.

Next, the process proceeds to 203, where the flag II IGH is set to O, and in 204, the number of rotation waiting routines M of the step motor is set.
Set to May. At 206, the target value of the step motor is set to 0 (initial). Here 5 TEP =
0 corresponds to the position of the output shaft of the step motor when taking the most advanced valve timing shown in FIG. 6(a). Next, the process goes to 207 and the flag F is set to O. This flag is 0 during valve timing switching and 1 after switching is complete.
This is the flag.

When the low load condition continues and this routine is entered next time 2
At 02, since 1lIGH=o, the branch is YES, and the process proceeds to 20B, where it is determined whether F=1 or not. During valve timing switching, the determination is No, and the process proceeds to 209, where the counter m is incremented. This (15).

The counter m is for measuring the number of times the rotation routine of the step motor is thinned out.

If 201 is Yes, the load is high, and in 210 it is determined whether the flag II I G 11 is 1 or not. No in switching from low load to high load, proceed to 211,! r,
1IIGll is set to 1. Next, the process advances to 212, where calculations corresponding to the number of rotations of the waiting number M are performed. In the memory 84, as shown in FIG. 9, there is a map of M that becomes smaller as the number of revolutions increases. The MPU 82 calculates the value of M according to the existing rotational speed Ne from the same map. Next, the process proceeds to step 213, where the target value of the valve timing of the intake valve 20, that is, the target position 5T of the output shaft 67a of the step motor 67 is determined.
EP is set to a value necessary to obtain the delayed valve timing shown in (b) of FIG.

This amount of delay can be set by the pressure and the number of rotations. After setting 5TEI', execute step 207 described above and set F to 0.

When the high load condition continues and this routine is entered next time 21
If the value is 0, the result is Yes, and unless the valve timing switching is completed at 208 (F=O), the process proceeds to 209 where the counter m is incremented.

In step 214, it is determined whether the value of counter m has reached the number of waiting times M set in 204 or 212. If the counter m has not reached the set value, the process branches to No and exits from this routine.

Therefore, the rotational operation of the step motor is reduced by M times in accordance with the rotational speed Ne. When m has reached the set value M, it is determined as Yes in 214, and the process proceeds to 215, where the counter m is reset, and then proceeds to 216.In step 216, the target value 5TEP of the position of the output shaft 67a of the step motor 67 is set. It is determined whether or not the current position REAL is equal to the current position REAL. If they do not match, the determination is NO, and the process proceeds to 217, where it is determined whether the target value is larger than the current value. Target value 5
When TEP is larger than the current value REAL, it is recognized that it is necessary to correct the valve timing in the direction of delay, and
18, the step motor 67a is connected from the output boat 88.
Proceed to step 1 and rotate the motor one step forward. (Forward rotation here means the direction of rotation of the step motor that retards the valve timing in the direction from (a) to (b) in Figure 6.)
At step 219, since one step forward rotation has been executed, the current value REAL of the step motor is incremented by one.

21 when the target value 5TEP is smaller than the current value REAL
7 is determined as No, the process proceeds to 220 and the step motor is set to 1.
A step reversal instruction is output. What is reversal here?
It means the rotation in the direction of advancing the valve timing from (b) to (a) in FIG.

At step 221, since one step reversal has been executed, the current value REAL of the step motor is decremented by one.

5 TEP when step motor target value and current value match
= REAL, 216 is Yes, 22
2, the flag F is set to 1. Therefore, in 208, Y
es, and the step motor is not rotated.

Through the feedbank control as described above, the shaft position of the step motor can be controlled in accordance with the operation of the supercharger. At this time, the valve timing on the delayed side is switched to 203.
The following processing executes thinning of the number of times M=f(Ne), which decreases as the rotation speed increases, and the valve timing switching speed increases according to the rotation speed. Further, switching of the valve timing to the advance side is executed every maximum number of thinnings (May), and the switching speed is a constant slow value.

〔Effect of the invention〕

According to this invention, the step motor drive routine is thinned out depending on the engine speed. The higher the rotation, the less the number of thinning operations. Therefore, the rotational speed of the step motor, that is, the variable speed of the valve timing, increases as the rotational speed increases, and when the rotational speed is low, the rotational speed of the step motor decreases. Therefore, the rotation of the step motor is usually slow, and the durability of the step motor can be improved.

Although the drive of the step motor is thinned out according to the rotation speed, it can be thinned out depending on other operating conditions such as supercharging pressure or a combination thereof.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of this invention. FIG. 2 is a diagram showing an embodiment. FIG. 3 is a cross-sectional view of the variable valve timing mechanism in the camshaft direction. FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. FIG. 5 is a view taken from the ■ direction arrow in FIG. Figure 6 is a valve timing diagram. FIGS. 7 and 8 are flowcharts. FIG. 9 is a diagram showing the setting of the number of thinnings in the step motor drive routine with respect to the rotation speed. 14...Supercharger, 58...Variable valve timing mechanism, 67...Step motor, 70...Control circuit, 72...Air flow meter, 78...Rotational speed sensor. Fig. 3 I:18: f8---Camshaft 41-m-Timing pulley 59-m-Inner sleeve 62-m-Aftersleeve 63.64-m-Roller 67-m-Step motor Fig. 4■ 5 Figure 6 (a) (b) Figure 7

Claims (1)

[Claims] In an internal combustion engine equipped with a supercharger, there is provided a variable valve timing mechanism for controlling valve timing, a means for detecting supercharger operating conditions, and a switching speed of the valve timing of the variable valve timing mechanism based on a signal from the detecting means. A supercharged internal combustion engine comprising means for controlling.