JPS59208113A - Exhaust valve control device in engine - Google Patents

Abstract

PURPOSE:To reduce the amount of released nitrogen oxide without recirculation of exhaust gas by controlling the exhaust valve closing time, according to the engine operating conditions. CONSTITUTION:Engine operating conditions are detected by a crank angle sensor 21, a negative pressure sensor 13, and an idle switch 22, and the detected data are input in a control device 14. The control unit 14 is provided with a memory means which memorizes the exhaust valve closing time data that minimize the amount of released nitrogen oxide in accordance with each number of revolutions of and each load to an engine. It selects the exhaust valve closing time which gives the minimum release of nitrogen oxide based on the detected engine operating conditions and controls an actuator 12 in order to control the closing time of an exhaust valve 2. With this contrivance, the amount of burnt fuel gas remaining in a cylinder can be controlled to restrict release of nitrogen oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to reduce nitrogen oxides (
The present invention relates to an engine exhaust valve control device that reduces NOx) by controlling the closing timing of the engine's exhaust valve without using exhaust gas recirculation (EGR).

Conventionally, in four-stroke engines, N in exhaust gas
In order to reduce Ox, so-called EGR, in which part of the exhaust gas is recirculated to the intake pipe, is generally performed.

The basic configuration of this EGR system is shown in Figure 1. 1 is an intake valve for sucking air-fuel mixture or air into the cylinder 9, and 2 is an intake valve for discharging the burned gas in the cylinder 9 to the outside. 3 and 4 are cams driven by the crankshaft 6 to operate the intake valve 1 and exhaust valve 2, respectively; 5 is a piston that reciprocates within the cylinder 9; 7 is an intake pipe; 8 is an exhaust pipe , 9 is a cylinder, lo is a throttle valve that adjusts the amount of air-fuel mixture supplied to the engine, 11 is an air-fuel mixture generating means, such as a carburetor or a fuel injection device, that mixes fuel with intake air, 100 is an EGR valve, 100a is its valve body, 100b is an exhaust passage, 100c is a diaphragm, 100d is a negative pressure chamber, 100e is an atmospheric chamber, 102,1
03 is a control valve, 101, 104 to 106 are piping, and piping 106 is connected to the atmosphere.

In the above configuration, exhaust gas after engine combustion is sent to the exhaust pipe 8 when the exhaust valve 2 is open, and a portion of this exhaust gas is introduced into the EGR valve 100 through the pipe 01. The amount of this exhaust gas introduced into the intake pipe 7 is determined by the valve body 100.
This is determined by the change in the gap between the exhaust passage 100b and the valve body 100a due to the vertical movement of the valve a. The valve body 100a is fixed to a diaphragm 100C, and the diaphragm 100C moves up and down according to the pressure difference between the atmospheric chamber 100e and the negative pressure chamber 100d, changing the position of the valve body 100a. Negative pressure chamber 100d is connected to control valve 102 via piping 104.
, 103, the control valve 102 is connected to the intake pipe 7 via a pipe 105, and the control valve 103 is connected to a pipe 106.
The negative pressure in the intake pipe 7 is introduced into the negative pressure chamber 100d by opening the control valve 102, and the negative pressure in the intake pipe 7 is introduced into the negative pressure chamber 100d by opening the control valve 103. Room 1
Introduced in 00d. Therefore, the pressure in the negative pressure chamber 100d is controlled by turning the control valves 102 and 103 on and off, and the diaphragm 100C moves up and down in accordance with the difference between the pressure in the negative pressure chamber 100d and the pressure in the atmospheric chamber 100e. The opening areas of the exhaust passage 100a and the exhaust passage 100b change, and the amount of exhaust gas introduced into the intake pipe 7 is adjusted.

However, in the conventional device described above, when used for a long period of time, deposits adhere to the EGR valve 100 and the EGR amount changes, and the response to sudden acceleration/deceleration is slow and the exhaust gas purification performance deteriorates transiently. This has drawbacks such as deterioration in driving performance and contamination of the air-fuel mixture generating means due to intake pulsation since exhaust gas is introduced into the intake pipe 7.

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional technology, and is capable of reducing nitrogen oxidation by adjusting the amount of residual gas in the cylinder by controlling the closing timing of the exhaust valve of the engine without using an EGR valve. It is an object of the present invention to provide an engine exhaust valve control device that reduces the amount of exhaust gas.

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

In FIG. 2, 12 is an actuator that opens and closes the exhaust valve 2, 13 is a negative pressure sensor that detects the load condition of the engine, 14 is a negative pressure sensor 13, and a crank angle sensor 21.
and a control device that controls the actuator 12 based on input information from the idle switch 22, 2o is a rotating body coupled to the crankshaft 6, 21 is a crank angle sensor that picks up the rotation of the rotating body 2o, and 22 is an aperture switch. Valve 1o
This is an idle switch that detects the fully closed position of the

Next, the operation of the above device will be explained. Conventionally, the exhaust valve 2 has an opening/closing timing that is uniquely determined with respect to the rotation of the crankshaft 6, and normally the exhaust valve 2 is closed near the top dead center of the exhaust process, so it remains in the cylinder 9. The amount of exhaust gas is minimal. However, in this embodiment, the exhaust valve 2
The rotation of the crankshaft 6, that is, the closing timing relative to the position of the piston 5 can be freely controlled by the actuator 12, and as shown in FIG. By accelerating cylinder 5
It is possible to increase the amount of residual gas in the combustion chamber, thereby lowering the combustion temperature in the next combustion step and reducing NOx.

FIG. 4 shows the configuration of the control device 14 that drives the actuator 12 that controls the opening/closing timing of the exhaust valve 2, and 5o indicates a crank angle sensor 21 that counts the number of pulses generated as the engine rotates. A rotation speed detection circuit that calculates the rotation speed; 51 is an AD that converts an analog voltage proportional to the pressure in the intake pipe 7 of the negative pressure sensor 13 into a digital value;
Converter, 52 is a rotation speed detection circuit 50. A control circuit consisting of, for example, a microcomputer reads out data from a ROM (memory) 53 by inputting the output signals of the AD converter 5 and the idle switch 22, and calculates the drive timing of the exhaust valve 2. Reference numeral 54 indicates the control circuit 52 and a crank angle sensor. Actuator 12 receives the signal from 21.
This is a drive circuit that drives the.

The amount of residual gas required in the cylinder 9 according to the engine speed and engine load (output of the negative pressure sensor 13) is normally shown in Figure 5 for NOx reduction.'': Sea urchin engine speed and engine load It is required to have properties that allow it to be used as a liquid for U7. Corresponding to such a request value, the ROM 53 stores in advance the closing timing of the exhaust valve 2 as a map for the engine speed and the negative pressure of the intake pipe 7, as shown in FIG. Rotation speed detection circuit 50 and AD
After receiving the signal from the converter 51, the exhaust valve 2 is transferred from the ROM 53.
Read the closing timing data. This data corresponds to the closing timing (rotation angle) based on the bottom dead center position of the piston 5 (reference value) obtained from the crank angle sensor 21, and this data and the minute rotation angle obtained from the crank angle sensor 2J. The number of signals is compared, and when the two match, the drive circuit 5
4 to control the actuator 12. In this way, the closing timing of the exhaust valve 2 after the bottom dead center is controlled according to the data stored in the ROM 53 in advance in accordance with the engine speed and engine load, so the amount of residual gas in the cylinder 9 can be adjusted as desired. . Incidentally, the engine load does not necessarily have to be detected by the negative pressure sensor 13, but may be detected by the opening degree of the throttle valve 10 or the amount of intake air.

On the other hand, during deceleration, the opening of the throttle valve 10 is almost fully closed and the idle switch 22 is activated, resulting in an engine braking state, but the strength of the engine braking largely depends on the pumping loss, and the magnitude of the pumping loss is It depends greatly on the timing of opening and closing of 2.

As shown in FIG. 7, when the closing timing of the exhaust valve 2 is advanced, the pumping loss is reduced. The actuator 12 is operated so that the closing timing after the bottom dead center is near the top dead center. In addition, when the engine is in an idling state, the amount of air-fuel mixture sucked into the cylinder 9 is small, so if a large amount of gas from the combustion tube remains in the cylinder 9, the safety of combustion deteriorates, causing misfires and engine speed. This causes a problem that the output becomes out of order. Therefore, when the throttle valve 10 is in an idling state where the opening degree is close to fully closed, the actuator 12 is operated so that the exhaust valve 2 closes at a time close to the top dead center of the piston 5 in the exhaust stroke, as in the case of deceleration. The residual gas in the cylinder 9 after combustion is kept as small as possible.

As described above, in the present invention, an actuator is provided to open and close the exhaust valve of the engine, and data on the closing timing of the exhaust valve that reduces the amount of nitrogen oxide in the exhaust gas is provided in response to the engine speed and engine load. A control means having a storage means for storing the closing timing data is provided, and the control means controls the actuator based on the closing timing data. Therefore, the amount of combustion cylinder gas remaining in the cylinder can be optimally adjusted, and nitrogen oxides [11] in the exhaust gas can be reduced. Moreover, since there is no need to provide the EGR valve, its control valve, and the piping attached to these as in the past, the configuration is greatly simplified, and the exhaust gas purification performance is reduced due to the accumulation of deposits in the EGR valve and piping. It also prevents the intake system's carburetor and intake pipe from being contaminated by various components (tar and acidic liquid) in the exhaust gas. In addition, since the amount of residual gas in the cylinder is controlled for each engine process, response is significantly improved compared to conventional EGR systems, and even transient conditions during acceleration and deceleration can interfere with nitrogen oxide reduction performance. It has an excellent effect in that it does not cause any problems and does not impair driving performance. Furthermore, during deceleration and idling, the amount of residual exhaust gas in the cylinder is approximately minimum, that is, the closing timing of the exhaust valve is controlled to be near the top dead center of the exhaust stroke, which improves engine braking performance and idling. The stability of combustion is not impaired at any time.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional device, Fig. 2 is a block diagram of a device of the present invention, Figs. 3, 5, and 7 are process characteristic diagrams of the present invention. FIG. 6, which is a block diagram of the control device, is a diagram of the contents of the storage means according to the present invention. 1-...Intake valve, 2...Exhaust valve, 5...Piston,
6...Crankshaft, 7--Intake pipe, 8...Exhaust pipe,
9... Cylinder, 10... Throttle valve, 11... Air-fuel mixture generation means, 12... Actuator, 13... Negative pressure sensor, 14... Control device, 21... Crank Angle sensor, 22...Idle switch, 53...R
OM. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa Fig. 1 Fig. 2 Fig. 4 Fig. 3 Fig. 5 Engine rotation function

Claims (2)

[Claims] (1) An engine rotation speed detection means for detecting the engine rotation speed, an engine load detection means for detecting the engine load, and an actuator for opening and closing the exhaust valve of the engine;
It has a memory means for storing exhaust valve closing timing data corresponding to the engine rotation speed and engine load so as to reduce the amount of nitrogen oxides emitted from the engine, and the exhaust valve closes according to the input from each of the detection means. An exhaust valve control device for an engine, comprising control means for controlling an actuator based on timing data and controlling the closing timing of an exhaust valve. (2) The control means controls the actuator so that when the engine is in a deceleration state or an idle state, the amount of exhaust gas remaining in the cylinder of the engine becomes substantially minimum. Range 1
Exhaust valve control device for the engine described in Section 3.