JP2005264891A - Heater control device for oxygen sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To energize an oxygen sensor with a heater before starting an engine without excessively reducing a battery voltage.
Immediately after the main switch is turned on (time t0), energization of the heater is started at a duty ratio of 100%. The battery voltage is monitored, and when the value falls below a predetermined heater stop determination voltage (time t1), the energization to the heater is stopped. When the engine is started (at time t2), the heater is energized again at a duty ratio of 100%. After the engine is started, power from the generator is supplied to the heater.
[Selection] Figure 3

Description

  The present invention relates to heating control of an oxygen sensor with a heater, and more particularly to heating control of an oxygen sensor with a heater that is provided in an exhaust system of an internal combustion engine and is used for air-fuel ratio control.

In general, an internal combustion engine detects an oxygen concentration from exhaust gas, and performs feedback control of an air-fuel ratio based on the oxygen concentration. As an oxygen sensor for detecting the oxygen concentration, one having a heater is widely used in order to maintain the active state of the sensor unit. The heater is energized at a duty ratio of 100% at the same time as the main switch is turned on (energization to the ECU) so that the oxygen sensor is activated early, for example. It continues until it reaches a predetermined temperature (Patent Document 1). In addition, there is also known one that stops energization of the heater when the engine is not started for a certain period of time after the main switch is turned on (Patent Document 2).
JP-A-8-278279 JP 11-218044 A

  However, until the engine is started after the main switch is turned on, power is supplied to the heater only from the battery, so that the battery may go up or the battery voltage may be excessively lowered. The startability of the engine may be deteriorated.

  An object of the present invention is to prevent an excessive decrease in battery voltage in energization before starting an engine to a heater of an oxygen sensor.

  An oxygen sensor heater control apparatus according to the present invention is an oxygen sensor heater control apparatus for controlling a heater provided in an oxygen sensor that detects an oxygen concentration in engine exhaust, and detects a battery voltage. A battery voltage detection unit and an energization control unit for controlling energization to the heater are provided, and the energization control unit controls energization to the heater based on the battery voltage value detected by the battery voltage detection unit. It is said.

  The oxygen sensor heater control device starts energizing the heater immediately after the main switch is turned on, for example, and stops energizing the heater when the battery voltage is equal to or lower than the heater stop determination voltage.

  Further, for example, the energization control means is constituted by pulse width control means for pulse-controlling the heater. The pulse width control means is constituted by duty control means for duty-controlling the heater, and the duty control means is based on the duty ratio according to the battery voltage from when the main switch is turned on until the engine is started. To energize the heater.

  At this time, the duty control means energizes the heater with a duty ratio of 100%, for example, immediately after the main switch is turned on, and stops energizing the heater when the battery voltage is equal to or lower than the heater stop determination voltage. The duty control means energizes the heater at a duty ratio of 100% after starting the engine.

  Further, for example, the duty ratio is set to be larger as the battery voltage is higher from when the main switch is turned on to when the engine is started, and when the battery voltage value is equal to or lower than the heater stop determination voltage, the duty ratio is 0. The duty ratio is 100% when the value of the battery voltage is equal to or higher than a predetermined voltage sufficient for driving the heater.

  As described above, according to the present invention, it is possible to prevent an excessive decrease in the battery voltage in energization before starting the engine to the heater of the oxygen sensor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an outline of an engine control system according to the first embodiment of the present invention.

  The engine control system 10 is mainly composed of an electronic control unit (ECU) 11 and includes various sensors, fuel injection devices, ignition devices, throttle control devices and the like provided in each part of the engine and intake and exhaust systems.

  Outside air is guided to each intake port of the cylinder head 12 via an air cleaner 13, a throttle body 14, and an intake manifold 15. The intake air is supplied with fuel from the fuel injection valve 16 before the intake port to form an air-fuel mixture having a predetermined air-fuel ratio, and is drawn into the cylinder from each intake port. A flow rate sensor 17 connected to the ECU 11 is provided on the upstream side of the throttle body 14. Further, the throttle valve 14B is opened and closed mechanically (for example, wire type) or electrically in conjunction with the accelerator position. In the present embodiment, the throttle valve 14B is rotated by, for example, a motor 14M, and the opening thereof is detected by a throttle opening sensor 14S. The rotation of the motor 14M is controlled by the ECU 11, and the opening detected by the throttle opening sensor 14S is sent to the ECU 11.

  On the other hand, an exhaust manifold 20 is attached to each exhaust port of the cylinder head 12, and gas exhausted from the cylinder through the exhaust manifold 20 is discharged to the outside through the catalytic converter 21 and the muffler 22. Further, the exhaust manifold 20 is provided with a first oxygen sensor 23, and a second oxygen sensor 24 is provided downstream of the catalytic converter 21, and the first and second oxygen sensors are connected to the ECU 11, respectively. In the motorcycle, only the first oxygen sensor 23 is used, and the second oxygen sensor 24 is not used.

  The ECU 11 is further connected to a spark plug control device 18, a battery 19, an accelerator, and the like. The ECU 11 adjusts the fuel injection amount from the fuel injection valve 16 based on the information from the throttle opening sensor 14S, the flow sensor 17, the first and second oxygen sensors, the battery voltage, and the operation information of the accelerator, Adjust the air / fuel ratio.

  FIG. 2 is a side view of an oxygen sensor with a heater used for the first and second oxygen sensors 23 and 24, and a part of the sensor portion is shown as a cross-sectional view. The sensor unit 30 is, for example, an oxygen sensor using oxygen ion conductivity of a zirconia solid electrolyte, and a heater 32 is provided inside a hollow zirconia solid electrolyte 31 provided with electrodes (not shown) inside and outside. Is placed. Electric power is supplied to the heater 32 via a cable 33 and heat is generated when energized, and the surrounding zirconia solid electrolyte 31 is heated to an activation temperature (for example, 350 ° C.).

  Next, the energization control in the first embodiment of the heater 32 provided in the oxygen sensors 23 and 24 will be described with reference to FIG. 3 is a timing chart of energization control to the heater 32. FIG. 3 (a) is an on / off state of the main switch, FIG. 3 (b) is an engine start / stop state, and FIG. The energized state of the heater 32, FIG. 3 (d) shows the change in battery voltage over time. The horizontal axis is time.

  In the first embodiment, energization of the heater 32 is started at a duty ratio of 100% at the same time as the main switch is turned on (time point t0). Electric power is supplied only from the battery 19 to the heater 32, ECU 11, fuel injection valve 16, spark plug control device 18, etc. until the engine is started and power generation by the generator is started. Therefore, the battery voltage gradually decreases immediately after the main switch is turned on.

  The ECU 11 monitors the voltage value of the battery 19 and stops energization of the heater 32 when the battery voltage falls to a preset heater stop determination voltage V0 (time point t1). Thereafter, the engine is started (time t2), and when the power supply from the generator is started, the heater 32 is energized again with a duty ratio of 100%. When the engine is started, the battery is charged by the generator, and the battery voltage gradually recovers. The heater stop determination voltage V0 is set with the minimum voltage value that does not hinder the engine start performance as the lower limit.

  As described above, according to the first embodiment, the battery voltage is prevented from extremely decreasing due to energization of the heater of the oxygen sensor after the main switch is turned on until the engine is started. This can prevent the engine starting performance from deteriorating. Even before the engine is started, the heater is energized until the battery voltage reaches the heater stop determination voltage, so that the oxygen sensor is heated to a constant temperature before the engine is started. Therefore, the oxygen sensor can be immediately activated immediately after the engine is started.

  Next, a second embodiment of the present invention will be described with reference to FIGS. The electrical and mechanical configuration of the engine control system of the second embodiment is the same as that of the first embodiment, and the description thereof is omitted. The difference of the second embodiment from the first embodiment is only the energization control method, and FIG. 4 is a timing chart of energization control to the heater 32 corresponding to FIG. 3 of the first embodiment. 4A shows the main switch on / off state, FIG. 4B shows the engine start / stop state, FIG. 4C shows the energization state of the heater 32, and FIG. 4D shows the battery. The change in voltage over time is shown. FIG. 5 is a graph showing the relationship between the battery duty and the drive duty ratio of the drive signal supplied to the heater 32 from when the main switch is turned on until the engine is started.

  In the second embodiment, energization of the heater 32 is started based on the duty ratio shown in FIG. 5 at the same time when the main switch is turned on (time t0). As in the first embodiment, the electric power is supplied only from the battery 19 to the heater 32, the ECU 11, the fuel injection valve 16, the spark plug control device 18 and the like until the engine is started. Gradually decreases immediately after the main switch is turned on.

  However, in the duty control of the second embodiment, as shown in FIG. 5, the duty ratio of the energization control to the heater 32 is changed corresponding to the battery voltage. That is, between the time when the main switch is turned on and the time when the engine is started, the duty ratio is set to be larger as the battery voltage is higher. For example, when the battery voltage is lower than the heater stop determination voltage V0 (for example, 10V), the duty ratio is set to 0% (that is, not energized), and the battery voltage value is a predetermined voltage (for example, 14V) sufficient for driving the heater. At the above time, the duty ratio is set to 100% (that is, energized continuously). Note that the duty ratio is set to monotonically increase with respect to the battery voltage between the heater stop determination voltage and a predetermined voltage sufficient for driving the heater. In this embodiment, for example, the duty ratio is increased linearly. The This relationship may be a non-continuous step-like correspondence or a non-linear correspondence.

  Thereby, in 2nd Embodiment, the rapid fall of a battery voltage is suppressed and it becomes possible to supply with electricity to the heater 32 until an engine is started (time t2). That is, immediately after the main switch is turned on, energization is performed at a relatively high duty ratio, and the duty ratio is gradually reduced to a relatively low duty ratio as the battery voltage gradually decreases. . As a result, a sudden drop in battery voltage is suppressed, and duty control with a duty ratio> 0% can be continued until the engine is started. After the engine is started, energization is performed with a duty ratio of 100% as in the first embodiment.

  As described above, also in the second embodiment, the same effect as in the first embodiment can be obtained. In the second embodiment, since the effective duty control (duty ratio> 0%) can be continuously performed on the heater until the engine is started, the oxygen sensor is heated more effectively. be able to.

  In the present embodiment, the duty control is described as an example. However, the drive voltage control or the drive current control corresponding to the battery voltage may be performed instead of the duty control. Further, in the present embodiment, the on / off of the power supply to the heater is controlled in conjunction with the on / off of the main switch, but may be used in combination with the on / off of other switches. For example, it may be configured to start energization when the main switch is turned on and the hand switch is turned on.

1 is a block diagram illustrating an outline of an engine control system according to a first embodiment of the present invention. It is a side view of the 1st and 2nd oxygen sensor, The part is shown as a cross section. It is a timing chart of energization control to the heater in a 1st embodiment. It is a timing chart of the electricity supply control to the heater in 2nd Embodiment. It is a graph which shows the relationship between the drive duty ratio to the heater in 2nd Embodiment, and battery voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine control system 11 Electronic control unit 19 Battery 23 1st oxygen sensor 24 2nd oxygen sensor 32 Heater

Claims (7)

An oxygen sensor heater control device for controlling a heater provided in an oxygen sensor for detecting an oxygen concentration in engine exhaust,
Battery voltage detecting means for detecting the battery voltage;
An energization control means for controlling energization to the heater,
The oxygen sensor heater control apparatus, wherein the energization control unit controls energization to the heater based on a battery voltage value detected by the battery voltage detection unit.   The energization to the heater is started immediately after the main switch is turned on, and the energization to the heater is stopped when the battery voltage is equal to or lower than a heater stop determination voltage. The heater control apparatus for oxygen sensors described in 1.   2. The heater control device for an oxygen sensor according to claim 1, wherein the energization control means comprises pulse width control means for pulse-controlling the heater.   The pulse width control means is constituted by duty control means for duty-controlling the heater, and the duty control means has a duty ratio according to the battery voltage from when the main switch is turned on until the engine is started. The heater control device for an oxygen sensor according to claim 3, wherein the heater is energized based on the temperature.   The duty control means energizes the heater at a duty ratio of 100% immediately after the main switch is turned on, and stops energizing the heater when the battery voltage is equal to or lower than the heater stop determination voltage. The oxygen sensor heater control device according to claim 4.   The oxygen sensor heater control device according to claim 4, wherein the duty control means energizes the heater at a duty ratio of 100% after starting the engine. The duty ratio is set to be larger as the battery voltage is higher from when the main switch is turned on to when the engine is started, and when the value of the battery voltage is equal to or lower than the heater stop determination voltage. 5. The oxygen sensor according to claim 4, wherein the duty ratio is set to 0% when the duty ratio is set to 0% and the value of the battery voltage is equal to or higher than a predetermined voltage sufficient for driving the heater. Heater control device.

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