JP2864768B2 - Power unit for catalyst with heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for a catalyst with a heater, and more particularly to a power supply for a catalyst with a heater for purifying exhaust gas of an internal combustion engine.

[0002]

2. Description of the Related Art In general, a catalyst for purifying exhaust gas of an internal combustion engine cannot be activated unless a predetermined temperature is reached, and a purifying function cannot be obtained. In particular, the catalyst is heated by the exhaust gas temperature, but the exhaust gas temperature is low during a cold start, and the combustion rate of the fuel is poor because the internal combustion engine body has not been warmed up yet.
Exhaust gas purification is difficult.

Therefore, conventionally, a heater (electric heating element) is provided in front of the catalyst, and this heater is connected to a starting circuit of the internal combustion engine to fill the catalyst with unburned components contained in exhaust gas when the internal combustion engine is started. Previously, there has been known an apparatus in which a gas is vaporized by a heater (Japanese Utility Model Laid-Open No. 49-36424).

[0004]

However, in the above-mentioned conventional apparatus, since the power supply of the heater is a battery and the resistance value of the heater is constant with respect to the temperature, the electric power supplied to the heater at the time of starting the engine is constant. Yes, rapid temperature rise cannot be expected. For this reason, in the above-described conventional apparatus, it takes time for the heater temperature to rise at the beginning of energization, and it is difficult to quickly warm up the catalyst.

[0005] The present invention has been made in view of the above points,
It is an object of the present invention to provide a heater-equipped catalyst power supply device that solves the above-mentioned problems by using a capacitor as a power supply for the heater.

[0006]

FIG. 1 is a block diagram showing the principle of the present invention. The present invention relates to a power supply device for a heater-equipped catalyst 11, which is provided in an exhaust gas passage of an internal combustion engine and includes a catalyst for purifying exhaust gas and a heater for heating the catalyst, which is charged in advance before turning on an ignition switch. And a controller 1 for applying at least a terminal voltage of the capacitor 12 as a heater power supply for the catalyst with heater 11 when the ignition switch is turned on.
And 3.

[0007]

In the present invention, the controller 13 applies the terminal voltage of the capacitor 12 as a power supply voltage to the heater in the catalyst with heater 11 so that when the same amount of power is supplied to the heater as when using the battery, the ignition switch is turned on. Sometimes, the initial power supply voltage value applied to the heater is higher than when the battery is used. For this reason, in the present invention, the heater can be rapidly heated in a short time as compared with the related art.

[0008]

FIG. 2 is a block diagram showing a first embodiment of the present invention.
In the figure, the same components as those of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 2, reference numeral 21 denotes a battery, which supplies power to a starter when the internal combustion engine is started, and supplies a power supply voltage to the controller 13. 22 is an alternator, and generate electrical energy receiving the rotational energy of the engine hand supplies power to the electrical load, battery-2
1 is charged.

Based on detection signals from a water temperature sensor, a throttle valve, and other various sensors (not shown), the charge controller 24 operates under an operating condition in which the electric energy generated by the alternator 22 has a margin, such as at the time of deceleration at a predetermined speed or more. The electric energy from the alternator 22 is supplied to the capacitor 12 via the backflow prevention diode 25 while boosting the voltage, and charging is performed. The charge controller 24 also charges the capacitor 12 even when the operation is stopped (charging for discharging the capacitor).

As described above, the terminal voltage of the capacitor 12 is applied to the catalyst with heater 11 via the controller 13 as a power supply voltage. Reference numeral 26 denotes an AI (air injection) pump, which injects secondary air to the upstream side of the heater-equipped catalyst 11 under the control of the controller 13. 27 is an internal combustion engine (engine).

FIG. 3 shows the catalyst with heater 11 and the engine 2.
7 shows an enlarged view of a peripheral mechanism such as 7. As shown in the figure, an AI is provided at the exit of the exhaust manifold 28 of the engine 27.
An inlet 29 is provided, and a catalyst 11 with a heater for heating the catalyst using electricity is provided downstream of the AI inlet 29.

The heater-equipped catalyst 11 may be, for example, an energizable metal monolith catalyst in which a metal monolith carrier is coated with alumina, or a monolith catalyst in which a platinum catalyst is formed on the surface of a heating element monolith carrier.

A temperature detector 30, a heater terminal 31, a battery voltage terminal 32, and the like for detecting the temperature of the heater are provided near the heater-equipped catalyst 11. The main catalyst 3 is located downstream of the heater-equipped catalyst 11.
3 are provided.

Next, the operation of the first embodiment shown in FIG. 2 will be described with reference to FIGS. FIG. 4 is a flowchart for explaining the operation of FIG. First, when the ignition switch is turned on (step 101), the battery 21
A check is made to determine whether the voltage of the heater-equipped catalyst 11 has fallen below the predetermined value (step 102). If the voltage is above the predetermined value, it is normal, and the controller 13 energizes the catalyst with heater 11 (step 103).

As described above, the charging of the capacitor 12 is normally completed before the ignition switch is turned on, and the energization of the catalyst 11 with the heater in step 103 is performed when the terminal voltage of the capacitor 12 is controlled by the controller. This is performed by applying a power supply voltage to the catalyst with heater 11 through the heater 13. This allows
As will be described later, the catalyst with heater 11 is supplied with a larger initial power than in the prior art.

Next, the controller 13 includes a temperature detector 30
The detected temperature of the heater-equipped catalyst 11 is compared with a preset temperature corresponding to a preset catalyst activation temperature (step 104).
3, the energization of the heater-equipped catalyst 11 is continued. When the detected temperature becomes higher than the set temperature, the energization of the heater-equipped catalyst 11 is turned off (step 105), and the engine is subsequently started (step 106). ). Note that step 102
If it is determined that the battery voltage is equal to or lower than the predetermined value, after the battery abnormality is displayed (step 107), the engine is started without energizing the catalyst 11 with heater (step 106).

After starting the engine, under predetermined operating conditions (for example, when the air-fuel ratio feedback loop does not work yet)
Then, the AI pump 26 is operated to introduce secondary air to the upstream side of the catalyst with heater 11 (step 108). As a result, the fresh air is mixed into the exhaust gas discharged from the combustion chamber of the engine 27 and passing through the exhaust manifold 28, so that hydrocarbons (HC) of unburned components in the exhaust gas are mixed.
And reburn carbon monoxide (CO). Thereafter, in each of the catalyst with heater 11 and the main catalyst 33, the oxidation and reduction reactions are simultaneously promoted by the catalytic action of the noble metal on the catalyst surface, and the exhaust gas is purified and discharged at a high purification rate.

On the other hand, since the heater-equipped catalyst 11 is cooled by the introduction of the secondary air, the controller 13 again applies the terminal voltage of the condenser 12 to the heater-equipped catalyst 11 (step 109), and the heater temperature becomes the catalyst activation temperature. Until the temperature becomes equal to or higher than the set temperature, the application (energization) of the terminal voltage of the capacitor 12 is continued (step 110). When the heater temperature of the catalyst with heater 11 becomes equal to or higher than the predetermined temperature, the above-described energization is terminated (step 111).

The above processing operation is performed when the engine 27 is started, and is performed every time the engine is started.

After the start of the engine 27, the charge controller 24 shown in FIG. 2 supplies the energy generated by the alternator 22 to the capacitor 12 through the charge controller 24 and the diode 25 so as to prevent a large load from being applied to the engine 27. I do.

Next, the change over time of the terminal voltage of the condenser 12 and the power consumption of the heater of the catalyst with heater 11 according to the present embodiment will be described. Now, it is assumed that the resistance value of the heater-equipped catalyst 11 is 0.01Ω, the resistance value of the wiring from the capacitor 12 to the heater-equipped catalyst 11 is 0.003Ω, and the voltage drop of the controller 13 is 1.4V (constant).

Here, when approximately the same amount of power is applied to the heater-equipped catalyst 11 using the capacitor 12 as when the heater-equipped catalyst 11 is energized at 4000 W for 20 seconds with a battery, the terminal voltage of the capacitor 12 becomes As indicated by V in FIG. 5, when the ignition switch is turned on (time t =
0), and then gradually and linearly decreases with time.

At this time, the actual voltage applied to the heater-equipped catalyst 11 changes linearly in inverse proportion to time, similarly to the terminal voltage V, as indicated by V 'in FIG. Therefore, the power consumption W of the catalyst with heater 11 is represented by V ' ² / (resistance value of the catalyst with heater 11). Therefore, as shown in FIG. 6, the power consumption is maximum at the time when the ignition switch is turned on (t = 0). Decrease over time.

In the conventional apparatus in which the battery is energized to the heater-equipped catalyst 11, the power consumption of the heater-equipped catalyst 11 is constant at 4000 W regardless of the passage of time. On the other hand, according to the present embodiment, as can be seen from FIG. 6, immediately after the ignition switch is turned on, the power consumption is twice or more than the conventional power, and thereafter the power consumption W decreases. A larger electric power can be supplied than before.

Therefore, according to the present embodiment, the heater-equipped catalyst 11 can be rapidly heated immediately after the ignition switch is turned on, as compared with the prior art, so that the pre-heating until the heater-equipped catalyst 11 reaches the catalyst activation temperature. The time can be shortened (the temperature rise can be accelerated).

The catalyst with heater 11 is hardly broken at a low temperature even when a large current flows, and the heat radiation can be reduced by shortening the preheating time.

After a short operation, the condenser 12
May not be sufficiently charged and the heater-equipped catalyst 11 may not be heated, but the same can be considered for a battery. However, since the charging time of the capacitor 12 of this embodiment is shorter than that of the conventional battery, the heating of the catalyst with heater 11 can be more reliably performed than in the conventional battery. Next, a second embodiment of the present invention will be described. FIG. 7 shows a configuration diagram of the second embodiment of the present invention. 2, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. 7, the switch SW ₁ and SW ₂ are switched for connection respectively conjunction with the one of the terminals a and b. Switch SW ₁
And between each common terminal of the SW ₂ is connected to a capacitor 40. The capacitor 40 is a large-capacity capacitor corresponding to the capacitor 12 and having a withstand voltage of about 1 to 3 V.

The switch SW ₁ has a terminal a connected to the cathode of the backflow preventing diode 25 and a terminal b connected to the heater terminal of the catalyst 11 with a heater. The switch SW ₂ has a terminal a grounded and a terminal b connected to the alternator 22.

Next, the operation of this embodiment will be described. The switches SW ₁ and SW ₂ are normally connected to the terminal “a” by the controller 41 so that the capacitor 4
0 is charged by the power generation energy from the charging controller 24, diodes 25 and the alternator 22 is applied via the switch SW _1.

After turning on the ignition switch,
Switch SW before starting₁And SW _TwoAre connected to terminal b respectively.
Connection. As a result, the charge of the capacitor 40 is reduced.
Load SW₁Applied to the heater-equipped catalyst 11 through
And heat it.

When the heater temperature of the heater-equipped catalyst 11 is higher than a predetermined temperature corresponding to the catalyst activation temperature, the switch SW
_The switch ₁ and the switch SW ₂ are connected to the terminal a to switch off the power supply to the heater-equipped catalyst 11 and at the same time
Can be charged.

According to the present embodiment, almost all the charge of the capacitor 40 can be used for heating the catalyst 11 with a heater, the initial voltage is high, and the heater is heated quickly.

[0033]

As described above, according to the present invention, the heater can be rapidly heated by using the terminal voltage of the capacitor as the power source of the catalyst with a heater, so that the catalyst with the heater reaches the catalyst activation temperature. Preheating time can be shortened, and since the heat generation at the low temperature initial stage is large, when the catalyst with heater is started at a low temperature at a low temperature, the heat radiation loss ratio is reduced if the heat radiation loss is constant, and the temperature rise can be further accelerated. Further, it has features such as that the charging time can be shortened as compared with the battery.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram of a first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a heater-equipped catalyst and its peripheral mechanism.

FIG. 4 is a flowchart for explaining the operation of FIG. 2;

5 is a diagram showing a time change between a voltage applied to a catalyst with a heater and a capacitor terminal voltage in FIG. 2;

FIG. 6 is a diagram showing a change over time in heater power consumption of the catalyst with heater in FIG. 2;

FIG. 7 is a configuration diagram of a second embodiment of the present invention.

[Explanation of symbols]

 11 Catalyst with heater 12, 40 Condenser 13, 41 Controller 21 Battery 22 Alternator 24 Charge controller

Claims (1)

(57) [Claims] 1. A power supply device for a catalyst (11) provided with a heater, which is provided in an exhaust gas passage of an internal combustion engine and includes a catalyst for purifying exhaust gas and a heater for heating the catalyst.
A capacitor (12) charged before turning on the ignition switch, and at least the capacitor (1);
A controller (13) for applying the terminal voltage of (2) as a heater power supply of the catalyst (11) with the heater when the ignition switch is turned on.