JPH04187806A - Controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To exhibit an excellent engine brake by providing a means for selecting a cam of a relative small generation output in an operating region where an engine brake is required. CONSTITUTION:There are provided a plurality of cams 10 each having a cam profile of a different output characteristic, and a cam switching mechanism 11 for selectively switching the cams 10 according to an operating condition and transmitting movement of the cam to at least either one of an intake or an exhaust valve. Furthermore, there are provided a means 12 for detecting an operating condition where an engine brake is required, and a means 13 for selecting the cam of relatively small generating output in the operating region when the engine brake is required. When the engine brake is required, the cam of a relatively small output is selected in the operating region. Therefore, it is possible to exhibit an excellent engine brake.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an output control device for an internal combustion engine for automobiles, etc., which is equipped with a variable valve mechanism that switches cams depending on operating conditions.

(Prior Art) A valve train that drives intake and exhaust valves between internal combustion engines is set so as to obtain optimal valve timing in accordance with the output characteristics required by the engine.

However, this required valve timing differs depending on the operating conditions of the engine. For example, in a low load range, both the valve lift and valve opening period are small, whereas in a high load range, a large valve lift and valve opening period are required. Engines that operate under a wide range of conditions, such as automobile internal combustion engines,
It is quite difficult to set the valve timing for which operating range, and in any case, it is not possible to achieve optimal matching under all operating conditions.

Therefore, as described in Japanese Patent Application Laid-Open No. 63-167016, by providing multiple cams with different cam characteristics (cam profiles) and switching the cams depending on the operating conditions, each cam is operated at the optimal valve timing. A variable valve device that makes it possible to do this has been proposed.

This is achieved by switching between a low-speed output cam with high torque characteristics in the low-speed range and a high-speed output cam with high torque characteristics in the high-speed range, depending on the operating conditions, to achieve high output from low speeds to high speeds. It is something that we are trying to bring out. In addition to this, it has also been proposed to provide a fuel efficiency cam with excellent fuel efficiency characteristics in a partial load range to improve fuel efficiency in the partial load range.

(Problem to be Solved by the Invention) By the way, the above-mentioned cam switching is a control that targets the cam that provides the best output and fuel efficiency depending on the driving condition, so the cam selection may vary depending on the driving condition of the vehicle. may not always be appropriate.

For example, when driving downhill, there are times when it is desirable to apply engine braking, but if the cam selection is made by adjusting the output, engine braking becomes less effective.

Engine braking is sometimes required not only when driving downhill but also when driving on curved roads, and in vehicles with automatic transmissions, when the first or second range (no automatic transmission) is selected by the driver's will. In some cases, it may be easier to drive if engine braking is effective.

Therefore, an object of the present invention is to control cam switching in a driving state where engine braking is required so that the engine braking is most effective in that driving state.

(Means for Solving the Problems) Therefore, as shown in FIG. 1(A), the present invention provides a plurality of cams 10 having cam profiles with different output characteristics, and selectively controlling these cams 10 depending on the operating state. Means 12 for detecting an operating state requiring engine braking in an internal combustion engine equipped with a cam switching mechanism 11 that switches the cam and transmits the movement of the cam to at least one of the intake and exhaust valves.
and means 13 for switching to a cam that generates a relatively small output in that operating range when engine braking is required.
Equipped with

Further, as shown in FIG. 1(B), a plurality of cams 10 having cam profiles with different output characteristics, and these cams 1
In an internal combustion engine, the internal combustion engine is equipped with a cam switching mechanism 11 that selectively switches 0 depending on the operating state and transmits the movement of the cam to at least one of the intake and exhaust valves, and means 12 for detecting an operating state that requires engine braking. , means 14 for determining a crooked road running state 2, and means 15 for switching to a cam in which the amount of change in output with respect to a change in accelerator opening is maximized when engine braking is required and the vehicle is in the crooked road running state.

Further, as shown in FIG. 1(C), a plurality of cams 10 having cam profiles with different output characteristics and these cams 1
Cam switching that selectively switches 0 depending on the operating condition and transmits the movement of this cam to at least one of the intake and exhaust valves! ! Means 12 for detecting an operating state requiring engine braking in an internal combustion engine equipped with Al1If11
a means 16 for determining whether to cut off the fuel supply which is carried out in a predetermined deceleration state; and a means 17 for switching to the cam that maximizes the pumping loss in that operating range when engine braking is required and the fuel is cut off. Equipped with

<Operations> According to the first invention, when engine braking is required, a cam with a relatively small output in that operating range is selected, so that good engine braking can be performed.

According to the second invention, when driving on a curved road that requires engine braking, by selecting the cam that has the largest variation in output torque with respect to the accelerator opening, smooth acceleration can be achieved as needed along with engine braking. This also ensures good drivability.

According to the third invention, when the fuel is cut off, the output generated by the engine is zero and engine braking is effective due to pumping loss, but the effectiveness of engine braking is maximized by selecting the cam with the largest pumping loss.

(Example) Embodiments of the present invention will be described below based on the drawings.

First, FIGS. 2 and 3 show the basic configuration of a variable valve system, which was originally published in Japanese Patent Application No. 2-117 by the present applicant.
No. 261 has already been proposed, and includes two output type cams that emphasize output in the low rotation range and high rotation range, and a fuel efficiency cam that emphasizes fuel efficiency in the partial load range. The system is designed to switch between two cams depending on driving conditions.

21 is set to a cam profile that emphasizes fuel efficiency, and has a small cam lift and a small first cam (fuel efficiency cam) that has a slow lift start and early lift end, and 22 is a cam profile that generates high torque in the low rotation range. is set to
The second cam (low-speed output cam) 23, which has a relatively larger cam lift than the first cam 21, is set to a cam profile that generates high torque in a high rotation range, and has a higher cam lift and lift section than the second cam 22. The third cam (high-speed output cam) has a large output cam, and these are installed in parallel on the same camshaft.

24 is an intake/exhaust valve (intake valve or exhaust valve); 25 is a main rocker arm that is in constant contact with the first cam 21 via a roller 26; 24 is opened and closed.

Two sub-rocker arms 28 and 29 that swing around the shaft 30 are supported on the main rocker arm 25 in parallel with the roller 26, and one sub-rocker arm 28 is supported by the second cam 22 and the other. The sub-rocker arm 29 contacts the third cam 23.

When these sub rocker arms 28 and 29 are not engaged with the main rocker arm 25, they are always urged by the lost motion spring 31 so as to contact the second and third cams 22 and 23, so that they are not engaged with the main rocker arm 25. moves (oscillates) independently.

In order to selectively engage these sub-rocker arms 28 and 29 with the main rocker arm 25, a cylindrical pin 3 is attached to the swinging portion of one of the sub-rocker arms 28.
2, this bin 32 is also attached to the main rocker arm 25.
Bins 34 are disposed coaxially with each other so as to be able to slide freely in one direction, and these bins 32 and 34 are normally held in the state shown in Fig. 2 by a return spring 36. Although the rocker arm 25 is disengaged, a passage 40 is inserted into the hydraulic chamber 38 in which the bin 34 is housed.
When pressure oil is introduced through the cylinder, the bottles 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 at the base circle of the first cam 21, and after integration, the valve timing follows the second cam 22, which has a larger lift than the first cam 21. Switch.

In other words, due to the characteristics of the first cam 21 emphasizing fuel efficiency, the second cam 21
The cam 22 switches to a characteristic that emphasizes output in the low rotation range.

The other sub-rocker arm 29 is constructed in the same manner, and when pressure oil is introduced into the hydraulic chamber 39 through the passage 41, the bottles 35 and 33 are pushed out against the return spring 37, and the sub-port, By the engagement of the seventh car arm 29 with the main rocker arm 25, the valve timing is switched to depend on the third cam 23, which has a larger lift amount and lift section than the first cam 21, as described above, and the valve timing is switched to depend on the third cam 23, which has a larger lift amount and lift section than the first cam 21, as described above. This results in output-oriented characteristics.

In addition, FIG. 4 shows the valve lift characteristics from the first cam 21 to the third cam 23, and the full-open output characteristics when using each cam are shown in FIG. According to this, although the generated torque is low, the fuel efficiency is good, the second cam 22 has the highest maximum torque in the low rotation range, and the third cam 23 generates less torque in the low rotation range than the second cam 22, but The maximum torque is greatest in the high rotation range.

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

The selection of this cam in the control unit 51 is
Based on the characteristics shown in the figure, when the required torque and rotational speed are in the range of the first cam 21, which is the fuel efficiency cam, this fuel economy cam is used, and from this state, the accelerator opening degree increases and the required torque is adjusted to the fuel efficiency cam. When the second cam 22, which is a low-speed output cam, moves out of the range, for example, the fuel efficiency cam is switched to the low-speed output cam, and the rotation speed increases from the low rotation range to the high rotation range. Then, the output cam is switched to the third cam 23, which is a high-speed output cam.

For this reason, the control unit 51 has the engine speed,
Signals are input from a crank angle sensor 52 that detects the crank angle position, an accelerator operation amount sensor 53 that detects the operation amount (depression amount) of the accelerator pedal, and a cam position sensor 58 that detects the actually selected cam position. When the cam switching timing is determined based on these as described above, the operation of the electromagnetic 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, pressure oil from the oil pump is introduced into the hydraulic chamber 38 in order to operate the second cam 22, and when the other solenoid valve 46 is opened, the third solenoid valve 46 is opened.
Pressure oil is introduced into the hydraulic chamber 39 in order to operate the cam 23.

By the way, in the control unit 51, the output characteristics of the cams are different for the same throttle opening, and if left as is, a large torque step will occur when the cam is switched, and the discontinuous output fluctuations will deteriorate driveability and cause vehicle body vibration. However, in order to avoid these phenomena, the opening degree of the throttle valve 57 provided in the intake passage and the ignition timing of the ignition device 59 are corrected and controlled in response to the switching.

The opening degree of the throttle valve 57 is increased or decreased independently of an accelerator pedal (not shown) via a servo drive circuit 55 that receives a signal from the control unit 51 and a servo motor 56 that operates based on this drive signal. The actual opening of the valve 57 is fed back to the control unit 51 via the throttle opening sensor 54. Note that the throttle valves 57 may be provided in independent intake passages for each cylinder.

The control unit 51 basically determines the required torque from the signal of the accelerator operation amount sensor 53, and uses the cam position at that time determined from the output of the cam position sensor 58.
The throttle opening position required to generate the required torque is calculated, and the throttle valve 5 is operated via the servo motor 57.
7. Determine the opening degree.

When cam switching is determined, when switching from the first cam 21 to the second or third cam 22, 23 having a larger output torque, the servo drive circuit 55, the servo motor 56
The opening degree of the throttle valve 57 is corrected to decrease in accordance with the torque level difference from the switching target to absorb the increased torque. Also, the second or third cam 22.2
3 to the first cam 21 with a smaller output torque, conversely, the opening degree of the throttle valve 57 is increased to perform output correction control so as to absorb the torque difference.

Although not shown, it is also possible to simultaneously correct and control the ignition timing of the ignition device to suppress fluctuations in output.

On the other hand, in the present invention, the control unit 51 under operating conditions where engine braking is required,
The cam is also selected to provide the best engine braking under the driving conditions.

As mentioned above, each cam is selected on the basis of the best fuel efficiency and maximum generated output depending on the driving condition at that time, but the smaller the engine output at the same accelerator opening, the more Under favorable operating conditions where engine braking is required, such cam selection does not necessarily correspond to the requirements. Therefore, under operating conditions that require engine braking, the cam is selected so that the engine output is relatively small (including negative work).

Driving conditions that require engine braking include, for example, when driving on a descending road, when a vehicle with an automatic transmission operates the shift lever to the first or second range that does not automatically shift, or when the engine brake is actively applied. For example, as a means 60 for detecting such conditions, an inclinometer that detects the front and rear inclination of the vehicle, or an inclinometer that detects the amount of change in acceleration with respect to the throttle opening, is used to estimate downhill road running. At least one of a shift position sensor for detecting the shift position of the transmission, an engine brake request switch operable by the driver, etc. is provided.

In addition, since deceleration and acceleration are often repeated alternately when driving on a curved road with continuous curves without engine braking, it is recommended to select a cam that can easily increase or decrease the generated torque in response to accelerator operation. Preferably, furthermore, in a state where the engine output is zero such as during deceleration fuel cutoff,
The effectiveness of engine braking changes depending on the amount of pumping loss in the engine, and in such cases, it is best to select a cam that provides the maximum pumping loss during engine motoring.

Therefore, in order to perform optimal control of engine braking under these driving conditions, when the amount of change in output per unit time of the steering angle sensor that detects the steering angle of the vehicle exceeds a set value, it is determined that the vehicle is traveling on a curved road. and means 62 for determining a deceleration fuel cutoff state that is performed when the accelerator opening is below a predetermined low opening and the engine speed is above a predetermined rotation.

Based on these outputs, the control unit 51 controls cam switching so that the engine brake is most effective when the engine brake is requested, as shown in the flowchart of FIG.

In step 1.2, engine brake request detection means 60;
When a judgment input requesting engine braking is read from the curved road running judgment means 61, deceleration fuel cutoff judgment cutoff 62, etc., it is first judged whether or not there is a request for engine braking, and if there is no request, normal cam switching is performed in step 10. The process moves to control, and if there is a request, it is determined in step 3.4 whether or not the vehicle is traveling on a curved road and whether or not the fuel is being cut off.

If neither is available, read the operating conditions such as engine speed and accelerator opening in step 5, select the cam with the lowest output in that operating range from the preset map, and switch the cam. (step 6.7).

Figure 8 shows the maximum throttle opening output characteristics of each cam and the equal output characteristics between cam regions.According to this characteristic region, as shown in Figure 9, a cam with a relatively small output is selected. be.

In other words, the third cam has the maximum output in area A in Figure 8, the second cam in area B, and the first cam in area C.
Therefore, if different cams are selected for each region, the generated torque will be reduced, and by reducing the accelerator opening degree, the driving force will be immediately reduced, and a high engine braking effect will be obtained.

Note that depending on the operating range at that time, it may be possible to select two cams, but in this case, selecting the cam that generates smaller torque will increase the effectiveness of engine braking accordingly.

Next, when it is determined in step 3 that the vehicle is traveling on a curved road, the process proceeds to step 9, and the cam with the largest output change amount in response to the change in accelerator opening degree is selected.

Figure 10 shows the maximum output characteristics of each cam with respect to accelerator opening and rotation speed. Therefore, at a constant rotation speed, the range of change in output torque is large relative to the change in accelerator opening in each region. In this case, it is the cam that produces the maximum output.

FIG. 11 shows this, and either the second cam or the third cam is selected. When driving on a winding road with a series of curves, engine braking is often applied when entering each curve and acceleration is applied when exiting each curve. Therefore, the larger the variation in the generated torque in response to the driver's accelerator operation, the easier it is to drive. becomes good.

If it is determined in step 4 that deceleration fuel is cut off, the process moves to step 8 and the cam that provides the maximum pumping loss during fuel cutoff is selected.

FIG. 12 shows the magnitude of pumping loss when no fuel is supplied, and the pumping loss of the first cam is maximum in the low rotation range, followed by the second and third cams.

Therefore, by selecting the cam with the maximum pumping loss in each region as shown in FIG. 13, the effectiveness of engine braking can be enhanced.

Note that the first cam generates the same torque, so the pumping loss is minimal, but when the fuel is cut off (motoring)
When compared with the generated torque at zero, the work loss (negative work) in the suction stroke is large due to the smaller cam lift and lift period compared to other cams, increasing the pumping loss. .

In this way, when engine braking is required, the cam that provides the highest engine braking effect and is easiest to operate is selected depending on the operating conditions at that time, ensuring good drivability.

It should be noted that when switching the cams, a torque step difference as described above occurs, so the control unit 51 performs correction control of the throttle opening degree to prevent this. Therefore, as a general rule, there is no change in the generated torque immediately after switching the cam, but if the driver reduces the accelerator opening in order to apply more engine braking, the selected cam will produce a greater engine braking effect. It is.

(Effects of the Invention) As described above, according to the first invention, there is provided a means for detecting an operating state that requires engine braking, and a cam that generates a relatively small output in the operating range when engine braking is required. Since a means for switching is provided, when engine braking is required, a cam with a relatively small output in that operating range is selected, so that engine braking can be effectively applied.

Further, according to the second invention, there is provided a means for detecting a driving state requiring engine braking, a means for determining a winding road driving state, and an accelerator when engine braking is required and the winding road driving state is present. Since it is equipped with a means to switch to the cam that maximizes the amount of change in output with respect to changes in opening,
When driving on curved roads that require engine braking, by selecting the cam that has the largest variation in output torque with respect to accelerator opening, smooth acceleration is achieved as needed along with engine braking, resulting in good drivability. Secured.

Further, according to a third aspect of the present invention, there is provided a means for detecting an operating state that requires engine braking, a means for determining whether fuel supply is cut off in a predetermined deceleration state, and a means for detecting a driving state in which engine braking is required, a means for determining whether fuel supply is cut off in a predetermined deceleration state, and a fuel supply cutoff when engine braking is requested and fuel cutoff. When the fuel is cut off, the cam with the largest pumping loss is selected, and the cam with the largest pumping loss is selected. The effectiveness of engine braking is the best.

[Brief explanation of drawings]

FIGS. 1(A) to (C) are block diagrams of the present invention, and FIG.
The figure is a plan view of a variable valve mechanism showing an embodiment of the present invention.
The figure is also a sectional view taken along the line X-X, Figure 4 is an explanatory diagram showing the lift characteristics of each cam, Figure 5 is an explanatory diagram showing the output characteristics of each cam based on torque and rotational speed, and Figure 6 is an explanatory diagram showing the lift characteristics of each cam. A block diagram of the control unit, FIG. 7 is a flowchart showing the control operations executed in the control unit, and FIG. 8 shows the cam region based on the maximum output characteristic and equal output characteristic of each cam based on the output and rotation speed. Explanatory diagram,
Figure 9 is an explanatory diagram showing the selection range of each cam when engine braking is required, Figure 10 is an explanatory diagram showing the output characteristics of each cam based on accelerator opening and rotation speed, and Figure 11 is when driving on a curved road. FIG. 12 is an explanatory diagram showing the selection area of each cam based on the rotation speed, and FIG. 13 is an explanatory diagram showing the selection area of each cam at the time of fuel cutoff. . 21...first cam, 22...second cam, 23...
Third cam, 24... Intake/exhaust valve, 25... Main rocker arm, 28.29... Sub rocker arm, 51
... Control unit, 52... Crank angle sensor, 53... Accelerator operation amount sensor, 60... Engine brake detection means, 61... Curved road running determination means, 62... Fuel cutoff determination means. Fig. 1 (A) Fig. 1 (C) 25-, In-rocker arm 28.29--Blocker arm Fig. 3 21-23- Cam Fig. 4 Fig. 5 Engine armrest height rpm Fig. 8 (Small) Engine speed (Large) Figure 9 Figure 10 Figure 11

Claims (1)

[Scope of Claims] 1. A plurality of cams having cam profiles with different output characteristics, and a cam switching mechanism that selectively switches these cams depending on operating conditions and transmits the motion of the cams to at least one of the intake and exhaust valves. In an internal combustion engine, means for detecting an operating condition requiring engine braking;
1. A control device for an internal combustion engine, comprising means for switching, when engine braking is required, to a cam that generates a relatively small output in that operating range. 2. An internal combustion engine equipped with a plurality of cams having cam profiles with different output characteristics, and a cam switching mechanism that selectively switches these cams depending on operating conditions and transmits the motion of the cams to at least one of the intake and exhaust valves. means for detecting an operating condition requiring engine braking;
The vehicle is characterized by comprising means for determining whether the vehicle is traveling on a curved road, and means for switching to a cam that maximizes the amount of change in output in response to a change in accelerator opening when engine braking is required and the vehicle is traveling on a curved road. Internal combustion engine control device. 3. An internal combustion engine equipped with a plurality of cams having cam profiles with different output characteristics, and a cam switching mechanism that selectively switches these cams depending on the operating state and transmits the motion of the cams to at least one of the intake and exhaust valves. means for detecting an operating condition requiring engine braking;
A means for determining whether fuel supply is cut off in a predetermined deceleration state, and a means for switching to a cam that maximizes pumping loss in that operating range when engine braking is required and fuel is cut off. An internal combustion engine control device characterized by: