JPH051576A - Controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the extent of fuel consumption in keeping off a wasteful use of unnecessary engine power by prohibiting any changeover to a high-power cam at the time of accelerator racing or the like and driving an engine with a low-power cam. CONSTITUTION:This controller is provided with at least two cams 1 with cam profiles for both low and high outputs and a cam selector mechanism 2 which selectively selects these cams according to a driving state while transmitting these cam motions to at least either of inlet and exhaust valves. In addition, there are provided a means 3 for detecting a fact that any transmission of power to a driving wheel from an engine is interrupted, and another means 4 which prohibits any changeover to a high-power cam at a time when this power cut off state is detected, and maintains an engine drive by a low-power cam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine for an automobile or the like, which has a variable valve mechanism for selectively switching cams according to operating conditions.

[0002]

2. Description of the Related Art A valve train for driving intake and exhaust valves of an internal combustion engine is set so as to obtain optimum valve timing in accordance with output characteristics required by the engine.

However, the required valve timing differs depending on the operating conditions of the engine. For example, both the valve lift and the valve opening period are small in the low load region, whereas the large valve lift and the valve opening period are required in the high load region. To be done. For an internal combustion engine for automobiles, which has a wide range of operating conditions, it is difficult to set which operating region the valve timing is set to, and in any case, optimal matching cannot be achieved under all operating conditions.

Therefore, as disclosed in Japanese Patent Laid-Open No. 63-167016, a plurality of cams having different cam characteristics (cam profiles) are provided, and the cams are selectively switched according to the operating conditions. There has been proposed a variable valve operating device that can be operated at an optimum valve timing.

This is because a low speed type high output cam having a high torque characteristic in a low rotation range and a high speed type high output cam having a high torque characteristic in a high rotation range are switched according to operating conditions. It is intended to exert high output from to high speed range. In addition to this, it has also been proposed to provide a low-output cam (fuel consumption cam) having excellent fuel consumption characteristics in the low and medium speeds and the partial load range to improve the fuel consumption in the partial load range.

[0006]

The switching of the cam is automatically performed according to the engine speed and the load. Therefore, the switching of the cam is performed not only when the vehicle is running, but also when the vehicle is running.
Even when the transmission is in neutral or when the vehicle is stopped with the clutch disengaged, when the accelerator is depressed and so-called idling is performed, the load is increased and the low output cam is switched to the high output cam. Was being done.

If the high output cam is switched to when the power is not transmitted to the drive wheels in this way, engine output that is not actually needed is wasted, and if the accelerator is frequently blown off, fuel consumption will be reduced. There was a problem that was worse.

In view of this, the present invention prevents unnecessary waste of engine output and improves fuel efficiency by prohibiting switching to a high output cam and operating with a low output cam when the accelerator is idle. With the goal.

[0009]

The present invention, as shown in FIG. 1, includes at least two cams 1 having low and high output cam profiles, and selectively switching between these cams depending on operating conditions. In an internal combustion engine equipped with a cam switching mechanism 2 that absorbs the movement of the cam and transmits it to at least one of the exhaust valves, means 3 for detecting that the transmission of power from the engine to the drive wheels is cut off, and this power When the cutoff state of the transmission is detected, the switching to the high output cam is prohibited to maintain the operation with the low output cam.

[0010]

Therefore, even when the power of the engine is not transmitted, for example, when the transmission is in neutral, or when the clutch is disengaged, even if the accelerator is depressed to idle the engine, the low output cam remains. Since the vehicle is driven, deterioration of fuel consumption is prevented accordingly.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

First, FIGS. 2 and 3 show the basic structure of a variable valve mechanism.
-117261 has already been proposed, two high output cams that emphasize output in the low speed range and high speed range respectively, and low output (fuel efficiency) that emphasizes fuel efficiency in the partial load range separately from this. The three cams, the cam and the cam, are switched according to the driving situation.

Reference numeral 21 is a fuel profile-oriented cam profile, and the first cam (low output cam) having a small cam lift, a small lift section in which the lift start is slow and the lift end is early, and 22 is a high torque in a low rotation range. The second cam (low speed type high output cam) 23, which is set to a cam profile that generates a relatively large cam lift compared to the first cam 21, is set to a cam profile that generates a high torque in a high rotation range. A third cam (high speed type high output cam) having a larger cam lift and lift section than the second cam 22, and these are provided in parallel on the same cam shaft.

24 is an intake / exhaust valve (intake valve or exhaust valve),
Reference numeral 25 denotes a main rocker arm that is in constant contact with the first cam 21 via a roller 26, and swings around a rocker shaft 27 as a fulcrum to open and close the intake / exhaust valve 24.

The main rocker arm 25 has a shaft 3
Two sub-rocker arms that swing about 0 as a fulcrum
8, 29 are supported in parallel with the roller 26, one sub rocker arm 28 contacts the second cam 22, and the other sub rocker arm 29 contacts the third cam 23.

When the sub rocker arms 28 and 29 are not engaged with the main rocker arm 25, they are constantly urged by the lost motion spring 31 so as to come into contact with the second and third cams 22 and 23, and the main rocker arms 28 and 29 are urged. It moves (swings) independently of the arm 25.

In order to selectively engage the sub rocker arms 28 and 29 with the main rocker arm 25, first, a columnar pin 32 is provided at the swinging portion of one of the sub rocker arms 28, and then the main rocker arm 24. Also, a pin 34 is provided coaxially with the pin 32 so as to be slidable in the cam shaft direction, and the pins 32 and 34 are normally urged by a return spring 36 to be held in the state of FIG. , The main rocker arm 25 is disengaged from the main rocker arm 25.
When the pressure oil is introduced through 0, the pins 32 and 34 are pushed out by a predetermined amount, and the sub rocker arm 28 engages with the main rocker arm 25.

The sub rocker arm 28 is integrated with the main rocker arm 25 when it is in the base circle of the first cam 21 and the second cam 22, and after the integration, the second rocker having a larger lift than the first cam 21. The valve timing is switched according to the cam 22. That is, the characteristic of the first cam 21 that emphasizes fuel consumption is switched to the characteristic of the second cam 22 that emphasizes output in the low rotation range.

The other sub-rocker arm 29 is also constructed similarly to this, and when pressure oil is introduced into the hydraulic chamber 39 through the passage 41, the pins 35 and 33 are pushed out against the return spring 37, Sub rocker arm 2
By engaging 9 with the main rocker arm 25,
The valve timing is switched so as to depend on the third cam 23 in which both the lift amount and the lift section are larger than those of the first cam 21 as described above, and output-oriented characteristics in the high rotation range can be obtained.

In FIG. 4, the first cam 21 to the third cam 2
The valve lift characteristics up to 3 are shown. The full-open output characteristic when each cam is used is as shown in FIG. 5. According to the first cam 21, although the generated torque is low, the fuel consumption is good,
The second cam 22 has the highest maximum torque in the low rotation range,
The torque generated by the third cam 23 in the low rotation range is the second cam 22.
However, the maximum torque in the high speed range is the largest.

By the way, switching from the first cam 21 to the second and third cams 22 and 23 and vice versa.
A control unit 51 as shown in FIG. 6 is provided to control the switching from the 2,23 to the first cam 21.
The optimum cam is selected according to the driving condition.

The selection of this cam in the control unit 51 is based on the characteristics shown in FIG. 5, and when the required torque and rotation speed are within the range of the first cam 21, which is a low output fuel consumption cam, this fuel consumption cam is used. From this state, when the accelerator opening increases and the required torque deviates from the fuel consumption cam region to the region of the second cam 22, which is a low speed type output cam, for example, the fuel consumption cam is switched to the low speed type output cam, and , When the rotation speed rises from the low speed range to the high speed range,
It is switched to the third cam 23 which is a high speed type output cam.

Therefore, the control unit 51 has a crank angle sensor 52 for detecting the engine speed and crank angle position, and an accelerator operation amount sensor for detecting the operation amount (depression amount) of the accelerator pedal as parameters representative of the operating state. 53. When the respective signals from the cam position sensor 58 for detecting the actually selected cam position are input and the cam switching timing is determined based on these signals,
The operation of the solenoid valves 45 and 46 for switching the hydraulic pressure to the two hydraulic chambers 38 and 39 is controlled.

That is, when one solenoid valve 45 is opened, the pressure oil from the oil pump is introduced into the hydraulic chamber 38 in order to operate the second cam 22, and the other solenoid valve 46 is opened. The pressure oil is introduced into the hydraulic chamber 39 in order to activate the hydraulic oil 23.

By the way, at the time of switching the cam, the control unit 51 causes a large torque step due to the output characteristic of the cam if the throttle opening remains the same, which deteriorates drivability due to discontinuous output fluctuation, and causes vehicle vibration. In order to prevent this, the opening degree of the throttle valve 57 provided in the intake passage corresponding to the cam switching is corrected and controlled to prevent this.

The throttle valve 57 is opened and closed independently of an accelerator pedal (not shown) via a servo drive circuit 55 which receives a signal from the control unit 51 and a servo motor 56 which operates based on this drive signal. At the same time, the actual opening of the throttle valve 57 is fed back to the control unit 51 via the throttle opening sensor 54. It should be noted that the throttle valve 57 may be provided in each intake passage independently for each cylinder.

The control unit 51 basically determines the required torque from the signal of the accelerator operation amount sensor 53, and is required to generate the required torque at the cam position at that time obtained from the output of the cam pojosin sensor 58. The throttle opening position is calculated, and the opening of the throttle valve 57 is determined via the servo motor 56.

Then, the cam switching is judged and, for example, the first
The second or third cam 2 having a large output torque from the cam 21
At the time of switching to 2, 23, the opening degree of the throttle valve 57 is corrected through the servo drive circuit 55 and the servo motor 56 so as to absorb the increased torque in accordance with the torque step difference with the switching target cam. Further, when switching from the second or third cam 22 or 23 to the first cam 21 having a small output torque, on the contrary, the output correction control is performed so that the opening degree of the throttle valve 57 is increased to absorb the torque step. I do.

Although not shown, it is possible to further suppress the output fluctuation at the time of switching by correcting and controlling the ignition timing of the ignition device at the same time.

On the other hand, in the present invention, when the control unit 51 determines that the accelerator is idle while the vehicle is stopped, even if the load or the rotational speed is increased, the first cam 21 on the low output side to the first cam 21 on the high output side is controlled. The changeover to the second and third cams 22 and 23 is prohibited to prevent unnecessary waste of engine output and to improve fuel efficiency.

Therefore, in the control unit 51,
As means 60 for detecting the cut-off state of the power transmission from the engine to the drive wheels, for example, in the case of an automatic transmission, the inhibitor switch detects the N and P ranges, and in the case of a manual transmission, the neutral switch or a clutch pedal. When a signal from the clutch on / off switch is input, even if the conditions for switching from the engine speed or load to the second and third cams 22 and 23 that are high output cams are satisfied,
The first cam 21, which is a low output cam, is held as it is without switching the cam.

However, in this embodiment, when a power transmission interruption state occurs (for example, when the clutch is temporarily disengaged due to a gear shift operation) during traveling, the above control is stopped and the vehicle is traveling. The driveability is not adversely affected, and the control is similarly stopped to ensure a sufficient starting torque while traveling on an uphill road.

Therefore, when the vehicle is traveling at a vehicle speed above a certain level by the signal from the vehicle speed sensor 62 and when the output of the tilt angle sensor 61 for detecting the tilt angle of the front and rear of the vehicle body is equal to or more than a predetermined value, the power transmission is performed. Even if the cutoff state of is determined,
If the cam switching condition is satisfied, it is possible to switch to the second and third cams 22 and 23 which are high output cams.

These controls executed by the control unit 51 will be described with reference to the flowchart of FIG.

In steps 1 to 3, the power transmission state from the detecting means 60, the vehicle speed from the vehicle speed sensor 62, and the uphill road signal from the inclination angle sensor 61 are read. First, in step 4, it is determined whether or not the vehicle is stopped. To be judged.

When the vehicle is not stopped, the routine proceeds to step 8 and the normal cam switching control is maintained as it is. When the vehicle is stopped, it is determined in step 5 whether or not the vehicle is traveling uphill on the basis of the inclination angle of the vehicle body. To do. When traveling on an uphill road, the process also proceeds to step 8 and the normal cam switching control is maintained.

On the other hand, when the vehicle is not traveling uphill,
In step 6, it is determined whether or not the power is not transmitted to the drive wheels, and when it is determined that the transmission is in the cutoff state, the process proceeds to step 7 and the high output cam is transmitted regardless of the operating conditions. Prohibit switching and operate with low output cam.

By maintaining the low output cam in the state where the power is cut off in this way, even if the driver makes the accelerator idle, unnecessary waste of the engine output is caused as the minimum engine intake air amount. Prevents and improves fuel efficiency. At the same time, as a result of preventing such unnecessary cam switching, it is possible to eliminate the torque shock that accompanies the cam switching.

However, such control is performed only when the vehicle is stopped, and is prohibited while the vehicle is running. Therefore, even if the power transmission is interrupted temporarily, the low output cam is not forcibly switched. The drivability during running is kept good.

Further, when starting on an uphill road, since switching to the high output cam is permitted according to the engine speed and the load, a sufficient starting torque can be obtained if necessary.

[0041]

As described above, according to the present invention, when the accelerator is idle while the vehicle is stopped, switching to the high output cam is prohibited and the low output cam is operated. It is possible to prevent unnecessary engine output from being wasted and improve fuel efficiency, while eliminating the torque shock generated due to unnecessary cam switching.

[Brief description of drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is a plan view of a variable valve mechanism showing an embodiment of the present invention.

3 is a sectional view taken along line XX of FIG.

FIG. 4 is an explanatory diagram showing lift characteristics of each cam.

FIG. 5 is an explanatory diagram showing output characteristics of each cam based on torque and rotation speed.

FIG. 6 is a block diagram of a control unit.

FIG. 7 is a flowchart showing a control operation executed in a control unit.

[Explanation of symbols]

 21 1st cam 22 2nd cam 23 3rd cam 24 Intake / exhaust valve 25 Main rocker arm 28 Sub rocker arm 29 Sub rocker arm 51 Control unit 60 Power transmission cutoff detection means 61 Tilt angle sensor 62 Vehicle speed sensor

Claims (1)

Claim: What is claimed is: 1. At least two cams having a low-power and a high-power cam profile, and selectively switching these cams according to operating conditions and sucking the movements of the cams and exhaust valves. In an internal combustion engine having a cam switching mechanism that transmits to at least one side, a means for detecting that the transmission of power from the engine to the drive wheels is cut off, and a high output cam is detected when this cutoff state of power transmission is detected. And a means for maintaining the operation at a low output cam by prohibiting the switching of the internal combustion engine.