JP2020101103A - Exhaust heat recovery device of internal combustion engine - Google Patents

Abstract

To lower an exhaust temperature at a position on the upstream side of an aftertreatment member by using an exhaust heat recovery device.SOLUTION: An exhaust heat recovery device for recovering exhaust heat of an internal combustion engine 1, comprises: an exhaust heat recovery unit 23 that recovers exhaust heat at a position upstream of an aftertreatment member 24 in an exhaust passage 4 of the internal combustion engine, and transfers the recovered exhaust heat to cooling water; and a control unit 100 configured to control the exhaust heat recovery unit. The control unit operates the exhaust heat recovery unit when the exhaust gas temperature at the position upstream of the aftertreatment member exceeds a predetermined threshold.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an exhaust heat recovery system for an internal combustion engine, and more particularly to an exhaust heat recovery system for recovering exhaust heat from an internal combustion engine.

In some cases, the exhaust heat recovery device recovers the exhaust heat of the internal combustion engine, transfers the recovered exhaust heat to the cooling water of the internal combustion engine, heats the cooling water, and promotes warm-up of the internal combustion engine after a cold start. is there.

JP, 2010-133349, A

By the way, a post-treatment member such as a catalyst for performing exhaust post-treatment is installed in the exhaust passage of the internal combustion engine. The exhaust gas temperature at the upstream side of the post-treatment member has a preferable temperature range in which the post-treatment member can remove harmful components in the exhaust gas at a relatively high purification rate.

However, if the exhaust gas temperature exceeds such a temperature range, the purification rate of the post-treatment member may decrease, and the amount of harmful components discharged may increase.

Therefore, the present disclosure has been devised in view of such circumstances, and an object thereof is to reduce the exhaust gas temperature at a position on the upstream side of the post-treatment member by using the exhaust heat recovery device.

According to one aspect of the present disclosure,
An exhaust heat recovery device for recovering exhaust heat of an internal combustion engine,
An exhaust heat recovery device that recovers exhaust heat at a position upstream of the aftertreatment member in the exhaust passage of the internal combustion engine, and transfers the recovered exhaust heat to cooling water.
A controller configured to control the exhaust heat recovery device,
Equipped with
An exhaust heat recovery apparatus for an internal combustion engine is provided, wherein the control unit operates the exhaust heat recovery device when the exhaust gas temperature at a position on the upstream side of the post-treatment member exceeds a predetermined threshold value. ..

Preferably, the control unit has an exhaust gas temperature at a position on the upstream side of the post-treatment member exceeding a predetermined threshold value, and the cooling water temperature does not exceed an allowable limit even when the exhaust heat recovery device is operated. When such a predetermined permission condition is satisfied, the exhaust heat recovery device is operated.

Preferably, the permission condition includes that the first preliminary condition that the cooling water temperature is lower than a predetermined threshold value is satisfied, as the satisfaction condition.

Preferably, the permission condition includes that the second preliminary condition that the speed of the moving body on which the internal combustion engine is mounted is equal to or higher than a predetermined threshold is satisfied.

Preferably, the permission condition includes that the third preliminary condition that the rotation speed of the fan that generates the passing air of the radiator is less than a predetermined threshold is satisfied.

Preferably, the threshold value of the exhaust gas temperature is set equal to the upper limit temperature of the temperature range in which the post-treatment member operates with an efficiency of a predetermined value or higher.

According to the present disclosure, it is possible to lower the exhaust gas temperature at a position on the upstream side of the post-treatment member by using the exhaust heat recovery device.

1 is a schematic diagram showing a configuration of an embodiment of the present disclosure. It is a graph which shows the purification rate characteristic of a NOx catalyst. It is a flowchart which shows the control routine of cooling water temperature control. It is a flow chart which shows a control routine of an exhaust heat recovery machine. It is a flow chart which shows another control routine of an exhaust heat recovery machine.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the embodiments below.

FIG. 1 schematically shows the configuration of this embodiment. In this embodiment, an internal combustion engine (engine) 1 as a power source is mounted on a vehicle (not shown) as a moving body. The vehicle is a large vehicle such as a truck, and the engine 1 is a diesel engine. However, the types and uses of the vehicle and the internal combustion engine are not particularly limited. For example, the vehicle may be a small vehicle such as a passenger car, and the engine 1 may be a gasoline engine.

The moving body is not limited to the vehicle and may be another moving body such as a ship. The engine does not have to be mounted on a moving body, and may be a stationary type engine.

In the figure, the intake path is indicated by a thin broken line arrow, the exhaust path is indicated by a thin one-dot chain line arrow, and the engine cooling water path is indicated by a thick solid line arrow.

The engine 1 includes an engine body 2 and an intake passage 3 and an exhaust passage 4 connected to the engine body 2. The engine body 2 includes structural parts such as a cylinder head, a cylinder block, and a crankcase, and movable parts such as a piston, a crankshaft, and a valve that are housed inside. The engine body 2 is provided with a plurality (four in this embodiment) of cylinders 5 and a fuel injection valve (not shown) for each cylinder. Further, the engine body 2 is provided with an in-engine water passage 6 for circulating cooling water therein. The in-engine water passage 6 includes a water jacket formed inside the cylinder head and the cylinder block.

The intake passage 3 is mainly defined by an intake manifold 10 connected to the engine body 2 and an intake pipe 11 connected upstream of the intake manifold 10. The intake pipe 11 is provided with a compressor 14C of the turbocharger 14 and an intercooler 15 in order from the upstream side.

The exhaust passage 4 is mainly defined by an exhaust manifold 20 connected to the engine body 2 and an exhaust pipe 21 connected downstream of the exhaust manifold 20. The exhaust pipe 21 is provided with a turbine 14T of the turbocharger 14. The exhaust pipe 21 on the downstream side of the turbine 14T is provided with a pre-stage post-treatment device 22, an exhaust heat recovery device 23, and a post-stage post-treatment device 24 in order from the upstream side.

The pre-stage post-treatment device 22 includes an oxidation catalyst (DOC: Diesel Oxidation Catalyst) and a filter (DPF: Diesel Particulate Filter) connected in series in order from the upstream side. The oxidation catalyst oxidizes and removes unburned components (hydrocarbons HC and carbon monoxide CO) in the exhaust, heats the exhaust gas by the reaction heat at this time, and oxidizes NO in the exhaust to NO ₂ . To do. The filter is a so-called continuous regeneration type filter with a catalyst, which collects particulate matter (PM: Particulate Matter) contained in the exhaust gas and continuously burns and removes the collected PM.

The exhaust heat recovery unit 23 is a heat exchanger that exchanges heat between the exhaust gas and the cooling water, recovers the heat of the exhaust gas, that is, the exhaust heat, and transfers the recovered exhaust heat to the cooling water. The exhaust heat recovery device 23 includes a recovery device main body 25 that is attached to the exhaust pipe 21 to perform substantial heat recovery and heat exchange, and a switching valve 26 that switches the operation and stop (on and off) of the exhaust heat recovery device 23. Equipped with.

The collector body 25 includes a heat exchanger that exchanges heat between the exhaust gas introduced therein and the cooling water. When the switching valve 26 is opened, it introduces cooling water into the collector body 25 to bring the exhaust heat collector 23 into an operating state (ON), and when closed, it inhibits the introduction of cooling water into the collector body 25 to remove exhaust heat. The collector 23 is stopped (off). As described above, in the present embodiment, the introduction of the cooling water is controlled to switch the operating state of the exhaust heat recovery device 23. Alternatively or additionally, the introduction of the exhaust gas is controlled to control the exhaust heat recovery device 23. The operating state of may be switched.

The post-stage post-treatment device 24 includes a selective reduction type NOx catalyst (SCR: Selective Catalytic Reduction) and a urea addition valve installed on the upstream side thereof. The urea water added from the urea addition valve into the exhaust pipe 21 is hydrolyzed to generate ammonia. The NOx catalyst continuously reduces and removes NOx in the exhaust gas using this ammonia as a reducing agent. An ammonia oxidation catalyst for oxidizing and removing the excess ammonia discharged from the NOx catalyst may be additionally provided on the downstream side of the NOx catalyst in the post-stage aftertreatment device 24.

The above-described oxidation catalyst, filter, NOx catalyst, and ammonia oxidation catalyst each form a post-treatment member for performing exhaust post-treatment. Particularly, in this embodiment, the NOx catalyst serves as a target post-treatment member for suppressing excessive temperature rise, which will be described later.

The engine 1 also includes an exhaust gas recirculation (hereinafter, EGR) device 30. The EGR device 30 includes an EGR passage 31 for returning a part of exhaust gas (referred to as EGR gas) in the exhaust passage 4 (in particular, the exhaust manifold 20) to the intake passage 3 (in particular, the intake manifold 10), and an EGR passage 31. An EGR cooler 32 that cools the EGR gas flowing through the passage 31 and an EGR valve 33 that adjusts the flow rate of the EGR gas are provided.

On the other hand, in the cooling system for the engine 1, the water pump 40 is provided at the inlet of the cooling water in the engine body 2. The cooling water discharged from the water pump 40 is branched into three directions as shown by the bold arrows, one is sent to the internal water passage 6 of the engine, one is sent to the oil cooler 7, and one is sent to the EGR cooler 32.

Further, the cooling water discharged from the EGR cooler 32 passes through the heater core 41 for heating the interior of the vehicle, and then is branched into two directions, one of which is sent to the switching valve 26 described above. The other is sent to the adjusting valve 42 provided at the outlet of the cooling water in the engine body 2. The downstream end of the water passage 6 in the engine is also connected to the adjusting valve 42.

The cooling water sent to the switching valve 26 is sent to the collector body 25 and heated by exhaust heat when the switching valve 26 is open. Then, after being discharged from the collector body 25, it is sent to the adjusting valve 42.

The adjusting valve 42 sends the cooling water sent from the in-engine water passage 6, the heater core 41, and the collector body 25 to one or both of the radiator 43 and the bypass passage 44 that bypasses the radiator 43. That is, the adjusting valve 42 adjusts the flow rate ratio of the cooling water flowing through the radiator 43 and the bypass passage 44. In the case of the present embodiment, it is assumed that the flow rate ratio of the radiator 43 increases as the opening degree of the adjusting valve 42 increases. For example, when the opening degree of the adjusting valve 42 is 100%, the flow rate ratio of the radiator 43 is 100% (that is, the flow rate ratio of the bypass passage 44 is 0%). On the contrary, when the opening degree of the adjusting valve 42 is 0%, the flow rate ratio of the radiator 43 is 0% (that is, the flow rate ratio of the bypass passage 44 is 100%). The opening degree of the adjusting valve 42 is continuously variable.

In the case of this embodiment, the regulating valve 42 is formed by an electric valve or a solenoid valve, and the opening degree thereof is electrically controlled. A water temperature sensor 45 is provided at the cooling water outlet of the engine body 2, and the opening of the adjusting valve 42 is controlled based on the water temperature detected by the water temperature sensor 45. However, the adjusting valve 42 may be a mechanical type such as a temperature-sensitive thermostat.

Both the cooling water discharged from the radiator 43 and the cooling water flowing through the bypass passage 44 are sent to the water pump 40.

On the other hand, the engine 1 is provided with a fan 46 for generating the airflow passing through the radiator 43. The fan 46 is installed on the rear side of the radiator 43 in the vehicle and on the front side of the engine body 2. The left side of FIG. 1 is the front side of the vehicle. The fan 46 sucks air from the rear side of the radiator 43 at the time of rotation and generates passing air passing through the radiator 43. However, a fan may be arranged and configured so as to discharge air and generate passing air.

In the case of the present embodiment, the rotation speed of the fan 46 (specifically, the number of rotations per unit time (rpm)), and thus the air volume of the fan 46 (the air volume passing through the fan 46) is arbitrary regardless of the engine rotation speed or the like. The fan 46 is configured by an electric fan so that the fan 46 can be controlled. However, the fan 46 may be configured by a more general mechanical fan driven by a crankshaft via a clutch.

On the other hand, the vehicle is equipped with a control device for controlling the vehicle and the engine. The control device includes an electronic control unit (ECU) 100 as a control unit, a circuit element, or a controller. The ECU 100 includes a CPU (Central Processing Unit) having an arithmetic function, a ROM (Read Only Memory) and a RAM (Random Access Memory) that are storage media, an input/output port, and a storage device other than the ROM and the RAM. The ECU 100 is configured and programmed to control the urea addition valve, the switching valve 26, the EGR valve 33, the adjusting valve 42, and the fan 46 described above.

The control device also includes, as sensors, the water temperature sensor 45, the exhaust gas temperature sensor 27, and the speed sensor 28 described above. The exhaust gas temperature sensor 27 is installed at a position upstream of the post-stage aftertreatment device 24 (specifically, the NOx catalyst) in the exhaust passage 4, and detects the exhaust gas temperature at the position. The speed sensor 28 detects the speed of a vehicle that is a moving body, that is, the vehicle speed.

In the case of the present embodiment, the exhaust temperature sensor 27 is installed at a position on the downstream side of the collector body 25. This makes it possible to detect the temperature of the exhaust gas after the temperature has dropped due to the exhaust heat recovery in the collector body 25, which is advantageous for control. However, the exhaust gas temperature sensor 27 can be installed at a position on the upstream side of the collector body 25.

Next, the control of this embodiment will be described.

In the above configuration, the exhaust temperature at a position upstream of the NOx catalyst, in other words, the temperature of the exhaust gas flowing into the NOx catalyst, is in a preferable temperature range where the NOx catalyst can remove NOx in the exhaust with a relatively high purification rate. There is.

FIG. 2 shows the purification rate characteristics of the NOx catalyst. The horizontal axis represents the exhaust gas temperature at the position of the exhaust gas temperature sensor 27, and is called the catalyst inlet temperature Te for convenience. The vertical axis represents the efficiency of the NOx catalyst, that is, the NOx purification rate η. As can be seen, the NOx purification rate η has a peak characteristic that it becomes maximum at a certain temperature, and the NOx catalyst has a temperature range of the catalyst inlet temperature Te at which the NOx purification rate η becomes a predetermined value η1 or higher, that is, There is an active temperature range ΔTe. The lower limit temperature of the active temperature range ΔTe is Te1 and the upper limit temperature thereof is Te2. For example, Te1=150° C. and Te2=350° C., but the numerical values are not limited to them. This activation temperature range ΔTe corresponds to the above-mentioned preferable temperature range.

However, the actual catalyst inlet temperature Te may fluctuate greatly depending on the engine operating state and the like, and the catalyst inlet temperature Te may exceed the activation temperature range ΔTe. Then, as shown by the point a, the NOx purification rate η of the NOx catalyst may be lower than the lower limit value η1 of the preferable NOx purification rate, and the NOx emission amount may increase.

Therefore, in the present embodiment, the exhaust gas heat recovery device is used to lower the catalyst inlet temperature Te. Specifically, when the catalyst inlet temperature Te exceeds a predetermined threshold, the ECU 100 opens the switching valve 26 and operates the exhaust heat recovery device 23. Here, the threshold value is set to be equal to the upper limit temperature Te2 of the activation temperature range ΔTe.

When the exhaust heat recovery device 23 is operated, cooling water is introduced into the recovery device main body 25, and exhaust heat is transferred to the cooling water in the recovery device main body 25. As a result, heat can be taken from the exhaust gas to lower the temperature of the exhaust gas. Then, as shown by the point b, the catalyst inlet temperature Te can be lowered to the upper limit temperature Te2 or lower and can be brought into the activation temperature region ΔTe, the NOx catalyst can be operated with high efficiency, and NOx emission can be suppressed.

By the way, since the cooling water is heated by the exhaust heat in this case, the temperature rise of the cooling water becomes a problem. That is, the adjusting valve 42 and the fan 46 are controlled so that the cooling water temperature matches the predetermined target temperature. However, when the cooling water temperature becomes too high with respect to the target temperature, the rotation speed of the fan 46 becomes unacceptable. Becomes higher, and fan drive loss increases. This causes deterioration of fuel efficiency.

Therefore, in the present embodiment, when the catalyst inlet temperature Te exceeds the threshold value, that is, the upper limit temperature Te2, a predetermined permission condition is satisfied such that the cooling water temperature does not rise above the allowable limit even when the exhaust heat recovery device 23 is operated. Exhaust heat recovery unit 23 is operated only in the case. In other words, the exhaust heat recovery device 23 is operated only when there is a relatively large margin between the current cooling water temperature and the allowable limit. As a result, when the cooling water temperature rises above the permissible limit, the operation of the exhaust heat recovery device 23 can be prohibited when the permission condition is not satisfied, and the fan rotation speed increases due to the cooling water temperature rise. The increase can be suppressed.

As can be understood from this explanation, the allowable limit of the cooling water temperature means the cooling water temperature at which the fan speed and the fan drive loss have the maximum values within the allowable range, and should be experimentally determined. Is possible. Hereinafter, for the sake of convenience that the cooling water temperature exceeds the allowable limit, it is also referred to as the cooling water temperature rising excessively.

In the present embodiment, the condition for satisfying the permit condition (satisfaction condition) is that at least one of the following preliminary conditions 1 to 3 is satisfied.

Preliminary condition 1: The cooling water temperature is lower than a predetermined threshold value. Specifically, when the water temperature Tw of the cooling water outlet of the engine body 2 detected by the water temperature sensor 45 is less than the predetermined threshold value Tw2, the preliminary condition 1 is satisfied. If the water temperature Tw is equal to or higher than the threshold value Tw2, the cooling water temperature may rise above the allowable limit when the exhaust heat recovery device 23 is operated. Therefore, the operation of the exhaust heat recovery device 23 is permitted only when the water temperature Tw is less than the threshold value Tw2. The threshold value Tw2 can be set to a value equal to or near the allowable limit of the cooling water temperature, and can be experimentally obtained.

Preliminary condition 2: The vehicle speed is equal to or higher than a predetermined threshold. Specifically, when the vehicle speed V detected by the speed sensor 28 is equal to or higher than the predetermined threshold value V1, the preliminary condition 2 is satisfied. If the vehicle speed V is less than the threshold value V1, the amount of traveling air supplied to the radiator 43 from the front of the vehicle is small, so that when the exhaust heat recovery device 23 is operated, the cooling water temperature exceeds the allowable limit due to insufficient radiation of the radiator 43. May rise. Therefore, the operation of the exhaust heat recovery device 23 is permitted only when the vehicle speed V is equal to or higher than the threshold value V1. The threshold value V1 can be experimentally obtained.

Preliminary condition 3: the rotation speed of the fan 46 is less than a predetermined threshold value. Specifically, when the rotation speed Nf of the fan 46 detected by the ECU 100 is less than the predetermined threshold value Nf1, the preliminary condition 3 is satisfied. Since the ECU 100 controls the rotation speed Nf of the fan 46, the ECU 100 itself and the rotation speed Nf of the fan 46 can be detected. The fan rotation speed Nf being equal to or higher than the threshold value Nf1 means that the cooling water temperature has already risen to some extent in the cooling water temperature control described later. Therefore, if the exhaust heat recovery device 23 is operated from this state, the temperature of the cooling water may further rise and exceed the allowable limit. Therefore, the operation of the exhaust heat recovery device 23 is permitted only when the fan rotation speed Nf is less than the threshold value Nf1. The threshold value Nf1 can be set to a value equal to or close to the maximum value of the fan rotation speed within the allowable range, and can be experimentally obtained. The threshold value Nf1 is a relatively low value.

These preliminary conditions 1 to 3 may be used alone or in combination.

Next, the control routine in this embodiment will be described. It should be noted that any of the routines described below is repeatedly executed by the ECU 100 at every predetermined calculation cycle τ (for example, 10 msec).

FIG. 3 shows a control routine for basic cooling water temperature control. First, in step S101, the ECU 100 acquires the value of the water temperature Tw detected by the water temperature sensor 45.

Next, in step S102, the ECU 100 controls the adjustment valve 42 and the fan 46 so that the detected water temperature Tw approaches the predetermined target temperature Twt. This control can be performed in various ways, but an example is given below.

The basic water temperature control is executed in such a manner that the fan 46 is not operated as much as possible. Therefore, basically, with the fan 46 turned off, the water temperature is adjusted only by adjusting the opening degree of the adjustment valve 42. When the detected water temperature Tw is lower than the target temperature Twt, the ECU 100 reduces the opening degree of the adjustment valve 42 to reduce the flow rate of the cooling water flowing through the radiator 43 (radiator flow rate) and the flow rate of the cooling water flowing through the bypass passage 44 ( Increase bypass flow rate). Thereby, the detected water temperature Tw can be increased. When the detected water temperature Tw is higher than the target temperature Twt, the reverse operation is performed.

If the detected water temperature Tw is still higher than the target temperature Twt even when the control valve 42 has an opening of 100% and the entire amount of cooling water has flowed to the radiator 43, the fan 46 is operated to increase the amount of air passing through the radiator. As the detected water temperature Tw becomes higher than the target temperature Twt, the fan rotation speed Nf is increased to increase the radiator passing air volume. As a result, it is possible to lower the detected water temperature Tw and bring it close to the target temperature Twt.

In controlling the adjusting valve 42 and the fan 46, it is possible to perform feedback control according to the difference between the detected water temperature Tw and the target temperature Twt.

Next, the control routine of the exhaust heat recovery device 23 will be described with reference to FIG.

In step S201, the ECU 100 acquires values of the water temperature Tw detected by the water temperature sensor 45, the catalyst inlet temperature Te detected by the exhaust temperature sensor 27, and the vehicle speed V detected by the speed sensor 28.

Next, in step S202, the ECU 100 compares the water temperature Tw with a predetermined threshold value (first threshold value) Tw1. The first threshold value Tw1 is different from the above-mentioned threshold value (second threshold value) Tw2, is a value lower than the second threshold value Tw2, and is a temperature for determining completion of warm-up of the engine. For example, Tw1=80° C., but the numerical value can be set arbitrarily.

When the water temperature Tw is lower than the first threshold value Tw1, the ECU 100 regards it as before warming up and proceeds to step S203 to open the switching valve 26 and operate the exhaust heat recovery unit 23. As a result, the cooling water can be heated by the exhaust heat recovered after the cold start, and the warming up of the engine can be promoted.

On the other hand, if the water temperature Tw is equal to or higher than the first threshold value Tw1, the ECU 100 considers that the warm-up is completed and proceeds to step S204.

In step S204, the ECU 100 determines whether the catalyst inlet temperature Te exceeds the threshold value Te2. If the threshold value Te2 is not exceeded, the ECU 100 proceeds to step S207 to close the switching valve 26 and stop the exhaust heat recovery device 23.

On the other hand, when it exceeds the threshold value Te2, the ECU 100 determines whether or not the permission condition is satisfied in steps S205 and S206. Here, it is determined in step S205 whether the preliminary condition 1 (water temperature condition) is satisfied, and in step S206, the preliminary condition 2 (vehicle speed condition) is determined. That is, the combination of the preliminary condition 1 and the preliminary condition 2 is used. However, the combination is not limited to this, and the preliminary conditions 1 to 3 may be used alone.

In step S205, the ECU 100 determines whether the water temperature Tw is less than the second threshold value Tw2. When the water temperature Tw is not lower than the second threshold value Tw2 (when it is equal to or higher than the second threshold value Tw2), the ECU 100 determines that the permission condition is not satisfied and proceeds to step S207 to stop the exhaust heat recovery device 23. As a result, it is possible to prevent an excessive increase in the temperature of the cooling water due to the exhaust heat recovery, and thus an increase in the fan rotation speed and the fan drive loss due to this.

On the other hand, when the water temperature Tw is lower than the second threshold value Tw2, the ECU 100 proceeds to step S206 and determines whether the vehicle speed V is equal to or higher than the threshold value V1. If the vehicle speed V is not equal to or higher than the threshold value V1 (less than the threshold value V1), the ECU 100 considers that the permission condition is not satisfied and proceeds to step S207 to stop the exhaust heat recovery device 23. As a result, it is possible to prevent the temperature of the cooling water from excessively increasing due to insufficient running air during exhaust heat recovery, which in turn can prevent the fan rotation speed and fan drive loss from increasing.

On the other hand, when the vehicle speed V is equal to or higher than the threshold value V1, the ECU 100 regards the permission condition as being satisfied, proceeds to step S203, opens the switching valve 26, and operates the exhaust heat recovery device 23. As a result, it is possible to operate the exhaust heat recovery device 23 after confirming that the cooling water temperature does not excessively rise, and it is possible to prevent an increase in fan drive loss and deterioration of fuel efficiency during exhaust heat recovery. ..

In this control, the exhaust heat recovery device 23 is operated when both steps S205 and S206 are YES, that is, both the preliminary condition 1 and the preliminary condition 2 are satisfied. As a result, it is possible to reliably prevent an excessive rise in the temperature of the cooling water during exhaust heat recovery by tightening the permission conditions. On the other hand, alternatively, the exhaust heat recovery device 23 may be operated when either the preliminary condition 1 or the preliminary condition 2 is satisfied. In this case, the permission conditions can be relaxed to increase the chances of exhaust heat recovery.

The former is an example in which the preliminary condition 1 and the preliminary condition 2 are connected by an AND condition (AND), and the latter is an example in which the preliminary condition 1 and the preliminary condition 2 are connected by an OR condition (OR). Preliminary conditions 1 to 3 can be combined arbitrarily and connected under an AND or OR condition.

Next, another control routine of the exhaust heat recovery device 23 will be described with reference to FIG. This routine is different from the control routine in that the preliminary condition 3 is used instead of the preliminary condition 2.

Steps S302 to S305 and S307 of this routine are the same as steps S202 to S205 and S207 of the control routine. Steps S301 and S306 of this routine are different from steps S201 and S206 of the control routine.

In step S301 of this routine, the ECU 100 obtains the value of the fan rotation speed Nf which is grasped by itself, in addition to the water temperature Tw and the catalyst inlet temperature Te.

In step S306 of this routine, the ECU 100 determines whether the preliminary condition 3 (fan rotation speed condition) is satisfied. Specifically, it is determined whether the fan rotation speed Nf is less than the threshold value Nf1. When the fan rotation speed Nf is not less than the threshold value Nf1 (when it is equal to or more than the threshold value Nf1), the ECU 100 considers that the permission condition is not satisfied, proceeds to step S307, closes the switching valve 26, and stops the exhaust heat recovery device 23. As a result, it is possible to prevent an increase in the fan rotation speed during exhaust heat recovery, and thus an increase in fan drive loss.

On the other hand, if the fan rotation speed Nf is less than the threshold value Nf1, the ECU 100 regards the permission condition as being satisfied and proceeds to step S303 to open the switching valve 26 and operate the exhaust heat recovery device 23.

In this routine, the preliminary condition 1 and the preliminary condition 3 are connected by an AND condition, and when both of them are satisfied, the exhaust heat recovery device 23 is operated as the permission condition is satisfied.

As can be seen from the above description, the ECU 100 of the present embodiment corresponds to the control unit in the claims. Further, the preliminary conditions 1 to 3 of the present embodiment correspond to the first to third preliminary conditions in the claims.

Although the embodiments of the present disclosure have been described above in detail, various other embodiments of the present disclosure are possible.

(1) For example, in the above-described embodiment, the switching valve 26 is installed on the upstream side in the cooling water flow direction of the collector main body 25, but alternatively or additionally, it may be installed on the downstream side in the cooling water flow direction.

(2) In the above-described embodiment, the post-treatment member whose temperature is to be suppressed is the NOx catalyst, but it may be another post-treatment member such as an oxidation catalyst.

The embodiments of the present disclosure are not limited to the above-described embodiments, and all modifications, applications, and equivalents included in the concept of the present disclosure defined by the claims are included in the present disclosure. Therefore, the present disclosure should not be limitedly interpreted, and can be applied to any other technique belonging to the scope of the idea of the present disclosure.

1 Internal combustion engine (engine)
4 Exhaust passage 23 Exhaust heat recovery device 24 Post-treatment device 25 Recovery device body 26 Switching valve 27 Exhaust temperature sensor 28 Speed sensor 43 Radiator 45 Water temperature sensor 46 Fan 100 Electronic control unit (ECU)

Claims (6)

An exhaust heat recovery device for recovering exhaust heat of an internal combustion engine,
An exhaust heat recovery device that recovers exhaust heat at a position upstream of the aftertreatment member in the exhaust passage of the internal combustion engine, and transfers the recovered exhaust heat to cooling water.
A controller configured to control the exhaust heat recovery device,
Equipped with
The exhaust heat recovery apparatus for an internal combustion engine, wherein the control unit operates the exhaust heat recovery device when the exhaust gas temperature at a position on the upstream side of the post-treatment member exceeds a predetermined threshold value. The control unit controls the exhaust temperature at a position on the upstream side of the post-treatment member to exceed a predetermined threshold value, and the cooling water temperature does not rise above an allowable limit even when the exhaust heat recovery device is operated. The exhaust heat recovery device for an internal combustion engine according to claim 1, wherein the exhaust heat recovery device is operated when the permission condition of is satisfied. The exhaust heat recovery device for an internal combustion engine according to claim 2, wherein the permission condition includes that a first preliminary condition that the cooling water temperature is lower than a predetermined threshold value is satisfied. 4. The internal combustion engine according to claim 2, wherein the permission condition includes that a second preliminary condition that a speed of a moving body on which the internal combustion engine is mounted is equal to or higher than a predetermined threshold is satisfied. Exhaust heat recovery device. The permission condition includes, in the satisfaction condition, that a third preliminary condition that a rotation speed of a fan that generates the air passing through the radiator is lower than a predetermined threshold value is satisfied. An exhaust heat recovery device for an internal combustion engine as described above. The exhaust heat recovery device for an internal combustion engine according to any one of claims 1 to 5, wherein the threshold value of the exhaust gas temperature is set to be equal to an upper limit temperature of a temperature range in which the post-treatment member operates at an efficiency of a predetermined value or more. ..

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