JPS60212608A - Engine exhaust gas cleaning device - Google Patents

Abstract

PURPOSE:To effectively maintain the temp. of a catalyst at an active temp. area by providing a heat storing material mode of a material whose melting point and freezing point are near the set temp. of a catalyst in an active temp. area, in an exhaust passage on the upper course side of said catalyst which is interposedly provided in said exhaust passage. CONSTITUTION:A catalyst 5 for cleaning an exhaust gas is interposed midway in an exhaust passage 4 which discharges the exhaust gas of an engine 1. A heat storing part 7 in which a heat storing material 6 which absorbs and stores the quantity of exhaust heat, is installed, and a branched part 4a consisting of a bypass prt 8 which bypasses the heat storing part 7, are provided on the upper course side of the catalyst 5, in the exhaust passage 4. A control valve 9 which adjusts the quantity of branched flow to each part 7, 8, at the branching point on the upper course sides of the heat storing part 7 and the bypass part 8, is provided on the branched part 4a. The valve 9 is controlled by a control circuit 15 in accordance with the output, etc. of a temp. sensor 13 attached to the catalyst 13. The heat storing material 7 is made of a material whose melting point and freezing point are near the set point of the catalyst 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in an exhaust gas purification device for an engine, which includes a catalyst for purifying exhaust gas in an exhaust passage of the engine.

(Prior Art) Conventionally, as an exhaust gas purifying device for this type of engine, a catalyst for purifying exhaust gas interposed in an exhaust passage of an engine has been disclosed, for example, in Japanese Patent Application Laid-Open No. 55-29018M. In addition, a bypass passage is provided in the engine exhaust passage to bypass the catalyst,
If the humidity of the exhaust gas is lower than the deterioration temperature of the catalyst, the exhaust gas is purified by the catalyst and then discharged to the outside air, while if the exhaust gas lfj IQ becomes higher than the deterioration temperature of the catalyst, It is known that this high-temperature exhaust gas is discharged to the outside air through a bypass passage, bypassing the catalyst, thereby preventing thermal deterioration of the exhaust gas purifying catalyst.

By the way, in order for the above exhaust gas purification catalyst to effectively demonstrate its exhaust gas purification performance, the active temperature range must always be 11 degrees Celsius, regardless of fluctuations in exhaust gas temperature due to fluctuations in engine operating conditions. It is preferable that it be kept within.

However, although the above conventional method can effectively prevent thermal deterioration of the catalyst caused by high-temperature exhaust gas, m IIJ, I11! is lower than the deterioration temperature of the catalyst. Since the exhaust gas is always discharged through the catalyst, the temperature of the catalyst changes significantly in response to fluctuations in the exhaust gas temperature, and as a result, the catalyst may deviate from its active range. Therefore, the exhaust gas cannot be purified stably.

(Object of the Invention) The present invention has been made in view of the above points, and an object of the present invention is to provide an engine exhaust gas purification device having a catalyst in the exhaust passage of the engine as described above. Once the heat is stored in the heat storage material, the heat is radiated to the catalyst for exhaust gas purification. By doing so, it is possible to moderate and suppress changes in the catalyst temperature in response to fluctuations in the exhaust gas temperature, allowing for catalyst preparation. The objective is to maintain the temperature within the active temperature range. Furthermore, by increasing the heat storage and release capacity of the heat storage material, it is possible to more effectively suppress the relaxation of changes in the catalyst temperature and maintain the catalyst temperature within the active temperature range.
: The goal is to do it effectively.

(Structure of the Invention) In order to achieve the above object, the solution means of the present invention provides an engine exhaust gas purification device-3- which is provided with a catalyst for purifying exhaust gas in the exhaust passage of the engine as described above. A heat storage material made of a substance whose melting point and freezing point are close to the set temperature within the active temperature range of the catalyst is provided in the exhaust passage on the upstream side of the catalyst.

As a result, in the present invention, when the exhaust gas temperature is high and the heat storage material temperature is low, the heat amount of the exhaust gas is absorbed and stored by the heat storage material, and the heat is radiated from the high-temperature exhaust gas to the catalyst. On the other hand, when the exhaust gas temperature is low and the heat storage material temperature is high, the catalyst temperature is reduced by releasing the heat stored in the heat storage material. In addition, the heat storage and release capacity of the heat storage material is increased by the amounts of latent heat of fusion and latent heat of solidification. be.

(Effects of the Invention) Therefore, according to the engine exhaust gas purification device of the present invention, the hot stone change of the catalyst for exhaust gas purification is provided in the exhaust passage upstream of the catalyst and has a melting point of -4. The temperature of the catalyst and the freezing point are effectively moderated and suppressed by the large amount of heat storage and release of the heat storage material, which is made of a substance that is close to the set temperature within the active temperature range of the catalyst, so the catalyst temperature is kept within the active temperature range as much as possible. It is possible to stably perform exhaust gas purification by holding the exhaust gas, and thus it is possible to effectively improve exhaust gas purification performance.

<Example> Hereinafter, an example as a specific example of the technical means of the present invention will be described based on the drawings.

In FIG. 1, 1 is an engine, 2 is an intake passage for supplying intake air to the engine 1, and the intake passage 2 is provided with a throttle valve 3 for controlling the amount of intake air.

Further, reference numeral 4 denotes an exhaust passage for discharging exhaust gas from the engine 1, and a probe 15 for purifying the exhaust gas is provided in the middle of the exhaust passage 4.

The exhaust passage 4 on the upstream side of the catalyst 5 is provided with a heat storage material 6 that absorbs and stores heat from the exhaust gas flowing through the exhaust passage 4. and a bypass section 8 that bypasses the heat storage section 7, and the branch section 4a includes a flow divider section 4a consisting of a bypass section 8 that bypasses the heat storage section 7. A control valve 9 is provided to adjust the amount of exhaust gas flowing to the bypass portion 8 side. The above exhaust gas purification touch a! 5 is its active region (Tc I ~ TC2)
(for example, 400 to 900℃), the set temperature value TCo
(for example, around 600° C.), exhaust gas purification is performed most efficiently. Also,
The heat storage material 6 is made of a substance whose melting point and solidification point are close to the set temperature value TCo of the catalyst 5, and specifically, for example, a eutectic composition of sodium chloride and calcium chloride (melting point and freezing point are both 500℃),
A eutectic composition of sodium chloride and magnesium chloride (460'C), or only sodium chloride (460'C)
00℃), etc.

Further, 10 is a throttle opening sensor that detects the opening θTHR of the throttle valve 3, 11 is a heat storage material sensor that detects the temperature mTRE of the heat storage material-6-6, and 12 is the upstream side of the heat storage section 7 and the bypass section 8. Check the temperature IQTExt+ of the exhaust gas flowing on the 10-odd side of the collecting part 4
N gas hinge, 13 detects C^T under warm eating of catalyst 5 1
Each of the sensors 10 to 13 controls the operation of the Luli control valve 9 via an actuator 14.
It is connected to a control circuit 15 for transmitting and receiving signals.

Furthermore, 16 is an ignition timing adjustment device that adjusts the ignition timing of the engine 1, and the adjustment device 16 has inside thereof,
A rotation speed voltage generation circuit 18 that receives a signal from a crank angle sensor 17 that detects the engine rotation speed based on the rotation of the crankshaft 1a of the engine 1 and generates a voltage according to the engine rotation speed, and an intake passage of the engine 1. The load voltage generation circuit 20 receives a signal from the load sensor 19 that detects the engine load based on the negative pressure downstream of the throttle valve 3 of No. 2 and generates a voltage according to the engine load. -7- A retard amount calculation circuit 21 that determines the amount of retardation of the ignition timing based on the signal from the calculation circuit 20; An adjustment circuit 25 that adjusts the ignition timing of the plug 24 and a correction control circuit 25 in response to a retard or advance signal (described later) for exhaust gas temperature control from the control circuit 15. Correction circuit 2
6.

Next, the operation of the control circuit 15 will be explained based on the flowchart of FIG. 2 and the schematic diagram of FIG. 3. First, after starting, in step S1, the actual throttle jf1 degree value θ is determined based on the signal from the throttle opening sensor 1o.
Tl-IR is set to a predetermined opening value θc corresponding to a high load operating state.
If the throttle opening (0θTl-IR is greater than or equal to heavy duty θCo for a predetermined period of time), in other words, during high-load operation, in step S2, the actual catalyst temperature value Tc A T based on the signal from the catalyst sensor 13 is determined. Compare the deterioration temperature value TC2 (for example, 900°C or higher) of 5,
If the temperature value Tc AT is less than the deterioration temperature value TC2 (YES), it is determined that there is no risk of deterioration of the catalyst 5, and the control valve 9 is closed on the heat storage -8 part 7 side in step S3. Then, the exhaust gas passes through the bypass section 8 and flows smoothly with less resistance.
Touch (IJI comes out after purifying with l!115. On the other hand,
- If the answer in step S1 is YES during normal operation and not in a high load operation state. Then, the starvation trace control of the catalyst 5 is started.

Then, in step S4, the actual catalyst temperature value Tc
AT5 is compared in size with the set temperature value Tco of the contact at5, and if the set temperature value Tco is YES (no swirl), that is, if the catalyst 5 needs to be heated, first select which of the exhaust gas and the heat storage material 6 as the heating heat source. In order to determine whether the heating capacity is too large, in step S5, the current exhaust gas temperature value TEX+-1 based on the signal from the exhaust gas sensor 12 and the current heat storage material temperature value TR based on the signal from the heat storage material sensor 11 are determined.
Compare the size with E c. Then, the exhaust gas temperature value Tε
If ×H is higher than YES, that is, if the exhaust gas has a larger heating capacity, III DI is set in step S6 in order to heat the catalyst 5 with the exhaust gas.
The +valve 9 is controlled to close the heat storage section 7 side to allow high temperature gas to flow through the bypass section 8. After that, touch 1lI
In order to determine whether or not the heating state of lt5 is good, in step S7, the current exhaust gas temperature value TEXH and the current catalyst! The a degree value Tc A T is compared in size, and if the exhaust gas temperature value Tε×T1 is higher (YES), it is determined that the catalyst 5 is being heated properly due to the release of heat from the exhaust gas. On the other hand, if the exhaust gas temperature value TEXH is lower, the process returns to step S1.
．． It is determined that the heating condition is not good, and the exhaust gas temperature Tε×H is set to an upper limit. The signal is sent to the correction circuit 26 of the adjustment device 16 and the process returns to step S1.

On the other hand, in step S5, the current exhaust gas temperature value TE
X)-1 is lower than the current heat storage material temperature value TREC
In the case of , that is, when the heat storage material 6 has a larger heating capacity, in step S9, the current heat storage material temperature value TRE c is set to be lower than the set temperature surface property Tco of the catalyst 5 by a predetermined amount of leakage. High temperature value Tc.

′ compared in size. If the heat storage material temperature value TREG is No lower than the temperature value Tco', the heat storage material 6
It is determined that the amount of heat dissipated from
Touch if YES is higher than o'! l! It is judged that there is a large amount of heat dissipation time from it5, and the catalyst 5 is
In order to perform heating, the control valve 9 is controlled to close the bypass section 8 side in step Szn to allow the exhaust gas to flow through the heat storage section 7, and the process returns to step S1.

Also, in step S4 above, the current touch! T! + to hot water temperature value Tc If NO is higher than the set temperature value Tco of the catalyst 5, that is, if the catalyst 5 needs to be cooled, determine which of the exhaust gas and the heat storage material 6 has a larger cooling capacity. To make this determination, the current exhaust gas temperature value TEX+-1 and the current heat storage material temperature value TREG are compared in magnitude in step S++. Then, the heat storage material temperature value TRE c is lower Y
In the case of ES, if the cooling capacity of the heat storage material 6 is larger than that of the heat storage material 6, then in step S12, the heat storage material temperature value TREG is set to be lower than the set temperature value Tco of the catalyst 5 by a predetermined opening degree. lower temperature value T
co''. If YES is less than the temperature value Tco'', it is determined that the heat storage material 6 has a large heat storage capacity, and the heat amount of the high temperature exhaust gas is transferred to the heat storage material 6. After proceeding to step Sh+, the control valve 9 is controlled to close the bypass portion 8 side to allow the high temperature exhaust gas to flow to the heat storage portion 7 side, and then the process returns to step s1.

On the other hand, in step S I+, the exhaust gas temperature value T
EX+-1 is N lower than the heat storage material temperature value TRE c.

In the case of , that is, when the exhaust gas has a larger cooling capacity, and in the case of NO in which the heat storage capacity of the heat storage material 6 is in a relatively small state in step 812, in step S13, in order to cool the catalyst 5 with the exhaust gas. The control valve 9 is controlled to close the heat storage section 7 side, and low-temperature exhaust gas is caused to flow to the bypass section 8. After that, step S1
In step 4, in order to determine whether or not the cooling state of the contact ts5 is good, the current tjl gas temperature value TEX+-1 and the current catalyst temperature value TcAT are compared in magnitude, and the exhaust gas Smallpox value TEX
In the case of YES, where H is lower than the temperature change value TcΔT of the touch tR, it is determined that the cooling of the touch ts5 is good due to the absorption of heat by the exhaust gas, and the process returns to step s1; If No is higher, it is determined that the catalyst cannot release heat and the cooling of the catalyst 5 is not good, and in step S+s, the ignition timing of the engine 1 is adjusted in order to reduce the exhaust gas humidity TEX+-1. An advance signal is issued to the correction circuit 26 of the ignition timing adjustment device 16 to advance the ignition timing, and the process returns to step $1.

Therefore, in the embodiment described above, the catalyst temperature value Tc
When AT is high and exceeds the set temperature Tco of the catalyst 5, that is, when it is necessary to suppress the temperature rise of the contact ts5, and when the heat storage material F TREc is lower than the exhaust gas temperature TEXH, the control is applied. The DI valve 9 closes the bypass part 8 side, the air gas flows through the heat storage part 7, and the amount of heat it has is transferred to the heat storage material 6.
Since the heat is absorbed and stored by the exhaust gas, the heating end that heats the contact ts5 by the exhaust gas is reduced accordingly, and the temperature rise of the contact W, 5 is suppressed as much as possible. At this time, the heat storage capacity of the heat storage material 6 has a melting point close to the set temperature Tco of the catalyst 5 and is large by the heat of the molten layer, so that the temperature rise of the catalyst 5 can be effectively suppressed. I can do it.

On the other hand, when the catalyst temperature Tc A T is low and less than the set temperature value Tco of the catalyst 5, that is, when it is necessary to suppress the temperature drop of the catalyst 5, the temperature T of the heat storage material 6 as a heating heat source is
When REG is higher than the exhaust gas temperature TEX+-1, the control valve 9 closes the bypass section 8 side, the exhaust gas flows through the heat storage material 6, and the amount of heat stored in the heat storage material 6 is transferred to the catalyst 5.
Therefore, the temperature drop of the catalyst 5 is suppressed as much as possible. At this time, the heat dissipation capacity of the heat storage material 6 has a solidification point close to the set temperature value Tco of the catalyst 5 and is large by the amount of latent heat of solidification, so that it is possible to effectively suppress the temperature drop of the temperature Wc5. Therefore, it is possible to effectively moderate and suppress the temperature change in the catalyst 15 and maintain the catalyst temperature Tc AT within the active temperature range as much as possible, thereby effectively improving the exhaust gas purification performance. can be achieved.

In the above embodiment, a bypass section 8 that bypasses the heat storage section 7 is provided in the middle of the exhaust passage 4, and the bypass section 8 side and the heat storage section 7 side are connected to each other by exhaust gas exhaust gas (TGTExH) and heat storage material (T).
Although the bypass section 8 is selectively switched by the control valve 9 based on the size comparison with the REG, the bypass section 8 does not have to be provided separately.
A heat storage material 6 may be provided in the exhaust gas, and the heat storage material 6 may store and release heat according to the exhaust gas level.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, with FIG. 1 being a general schematic diagram, FIG. 2 being a flow chart showing the operation of the control circuit, and FIG. 3 being an explanatory diagram showing the active hot water level region of the catalyst. 1... Engine, 4... Exhaust passage, 5... Catalyst,
6... Heat storage material.

Claims (1)

[Claims] (1) In an engine exhaust gas purification device equipped with a catalyst for purifying exhaust gas in an antagonism passage of the engine, in the exhaust passage upstream of the catalyst described in -, the melting point and freezing point of the catalyst are An exhaust gas purification device for an engine, characterized in that a heat storage material made of a substance near a set hot water level within a temperature range is provided.