JP6056201B2 - Engine warm-up device - Google Patents

Description

  The present invention relates to an engine warm-up device, and more particularly to an engine warm-up device that recovers waste heat and heats cooling water.

  Generally, at the time of engine warm-up operation, the cooling water temperature is raised early by diverting the cooling water heated by the engine from the radiator. Such an engine warm-up device is described in Patent Document 1, for example.

  In addition, as a pump that pumps cooling water, it has a water pump with an electromagnetic clutch that enables connection and disconnection of power transmitted from the engine, and during warm-up operation, the electromagnetic clutch is disconnected and the water pump is stopped, There is also known one that raises the cooling water temperature early. Such an engine warm-up device is described in Patent Document 2, for example.

  In these engine warm-up devices, generally, during warm-up operation, the engine speed is set high, and the cooling water is efficiently heated by the heat generated by the engine to promote warm-up.

JP 2004-301061 A Japanese Patent Laid-Open No. 11-13471

  However, if the engine speed is set high in order to promote warm-up of the engine, there is a concern that fuel consumption may be deteriorated due to an increase in engine load during warm-up operation.

  This invention is made | formed in view of such a point, The objective is to provide the warming-up apparatus of the engine which can improve a fuel consumption effectively, promoting warming-up.

  In order to achieve the above object, a warming-up device for an engine of the present invention is provided in an exhaust passage of the engine, and a heat exchange passage for exchanging heat between exhaust flowing through the exhaust passage and circulating coolant. A first cooling water passage formed in the cylinder block of the engine and for flowing cooling water through the cylinder block, a cooling water outlet portion of the heat exchange passage, and a cooling water inlet portion of the first cooling water passage A second cooling water channel connecting the first cooling water channel, a third cooling water channel connecting the cooling water outlet of the first cooling water channel and the cooling water inlet of the heat exchange channel, and the second And a pump for pumping the cooling water provided in the cooling water passage or the third cooling water passage.

  Further, a flow for switching an exhaust flow path provided at a branch exhaust passage formed by branching from an exhaust passage upstream of the heat exchange flow path and the exhaust passage and the branched exhaust passage. A flow path switching valve, and the flow path switching valve opens the exhaust flow path when the temperature of the cooling water heated in the heat exchange flow path is equal to or lower than a predetermined upper limit threshold value that prevents boiling of the cooling water. The exhaust passage provided with the heat exchange flow path is switched to the branch exhaust passage when the temperature of the cooling water heated in the heat exchange flow path becomes higher than the upper limit threshold. It may be.

  Further, an exhaust purification catalyst for purifying exhaust gas may be provided in the exhaust passage, and the heat exchange flow path may be provided in an exhaust passage downstream of the exhaust purification catalyst.

  According to the engine warm-up device of the present invention, it is possible to effectively improve fuel efficiency while promoting warm-up.

It is a typical whole lineblock diagram showing the warming-up device of the engine concerning one embodiment of the present invention. In one embodiment of the present invention, (a) is a diagram illustrating an exhaust flow path when the exhaust flow path switching valve is turned on, and (b) is an exhaust flow when the exhaust flow path switching valve is turned off. It is a figure explaining a path. In one embodiment of the present invention, (a) is a diagram illustrating a cooling water circuit at the start of warming up, (b) is a diagram illustrating a cooling water circuit at the time of continuing warming up, and (c) is when warming up is completed. It is a figure explaining the cooling water circuit. It is a flowchart which shows the control content which concerns on one Embodiment of this invention. It is a typical whole block diagram which shows the warming-up apparatus of the engine which concerns on other embodiment of this invention.

  Hereinafter, an engine warm-up device according to an embodiment of the present invention will be described with reference to FIGS. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  First, an exhaust system of a vehicle on which the engine warm-up device 20 according to this embodiment is mounted will be described with reference to FIG.

  In the exhaust system of the present embodiment, an oxidation catalyst (Diesel Oxidation Catalyst: hereinafter referred to as DOC) 12, diesel particulates, and the like are sequentially provided in an exhaust passage 11 of a diesel engine (hereinafter simply referred to as engine) 10 from the exhaust upstream side. A filter (Diesel Particulate Filter, hereinafter referred to as DPF) 13 and a selective catalytic reduction (hereinafter referred to as SCR) 14 are provided.

DOC12 generates the NO ₂ to oxidize NO in the exhaust, to NO in the exhaust to increase the proportion of NO _2, functions to raise the denitration efficiency by SCR 14.

  The DPF 13 collects particulate matter (hereinafter referred to as PM) in the exhaust gas, and when the collected amount of PM exceeds a predetermined amount, regeneration that accumulates and removes the accumulated PM is performed. The regeneration of the DPF 13 is performed by supplying unburned fuel to the DOC 12 on the upstream side of the exhaust by post-injection and increasing the exhaust temperature by heat due to oxidation.

  The SCR 14 adsorbs ammonia generated from urea water sprayed in the exhaust passage 11 by a urea water injector (not shown) and reduces and purifies NOx from the exhaust gas passing through the adsorbed ammonia.

  Next, a detailed configuration of the engine warm-up device 20 according to the present embodiment will be described. The warm-up device 20 includes a heat exchange exhaust passage 11a, a branch exhaust passage 11b, an exhaust passage switching valve 21, a waste heat recovery heat exchange passage 22, an upstream cooling water passage 23, and a cylinder block. A flow path 24, a water pump 32, a downstream cooling water flow path 25, a radiator flow path 26, a bypass flow path 27, a cooling water temperature sensor 35, and an electronic control unit (hereinafter referred to as ECU) 40 are provided. ing.

  In this embodiment, the cylinder block flow path 24 is the first cooling water flow path of the present invention, the upstream cooling water flow path 23 is the second cooling water flow path of the present invention, and the downstream cooling water flow path 25 is the present invention. This corresponds to the third cooling water flow path.

  The heat exchange exhaust passage 11a is formed in the exhaust passage 11 on the exhaust downstream side of the SCR 14 and a silencer (not shown). In the heat exchange exhaust passage 11a, a waste heat recovery heat exchange passage 22 described later in detail is interposed.

  The branch exhaust passage 11 b is formed by branching from the exhaust passage 11 located between the SCR 14 and the waste heat recovery heat exchange passage 22. In the present embodiment, the branch exhaust passage 11b and the heat exchange exhaust passage 11a also function as a tail pipe that discharges the exhaust to the outside.

  The exhaust flow path switching valve 21 is, for example, a known butterfly valve, and is provided at a branch portion between the heat exchange exhaust passage 11a and the branch exhaust passage 11b. When the exhaust flow path switching valve 21 is turned on in response to an instruction signal input from the ECU 40, the upstream end of the branch exhaust passage 11b is closed. That is, the exhaust gas from the SCR 14 flows into the heat exchange exhaust passage 11a and is released to the outside air (see FIG. 2A). On the other hand, when the exhaust flow path switching valve 21 is turned OFF in response to an instruction signal input from the ECU 40, the upstream end of the heat exchange exhaust passage 11a is closed. That is, the exhaust gas from the SCR 14 flows into the branch exhaust passage 11b and is released to the outside air (see FIG. 2B).

  The waste heat recovery heat exchange flow path 22 performs heat exchange between the cooling water flowing through the flow path and the exhaust gas flowing through the heat exchange exhaust passage 11a, and is disposed in the heat exchange exhaust passage 11a. It is formed to meander. In the present embodiment, the waste heat recovery heat exchange flow path 22 is provided on the exhaust downstream side of the SCR 14, so that the SCR 14 becomes lower than the catalyst activation temperature due to a decrease in exhaust temperature due to waste heat recovery. Can be prevented.

  The upstream cooling water flow path 23 supplies the cooling water whose temperature has been raised by heat exchange with the exhaust gas in the waste heat recovery heat exchange flow path 22 to the in-cylinder block flow path 24. Therefore, the upstream side cooling water flow path 23 is connected at its upstream end to the cooling water outlet of the heat exchange flow path 22 for waste heat recovery, and the downstream end is connected to the cooling water inlet of the flow path 24 in the cylinder block. Connected to the department.

  The in-cylinder block flow path 24 circulates cooling water flowing from the upstream cooling water flow path 23 through a water jacket (not shown), and is formed in the cylinder block of the engine 10.

  The water pump 32 pumps and supplies cooling water, and is provided adjacent to the cooling water inlet of the in-cylinder block flow path 24. The water pump 32 is driven by power transmitted from a crankshaft (not shown) of the engine 10.

  The downstream-side cooling water flow path 25 allows the cooling water flowing through the cylinder block internal flow path 24 to flow into the heat exchange flow path 22 for waste heat recovery. Therefore, the downstream side cooling water passage 25 is connected at its upstream end to the cooling water outlet portion of the in-cylinder block passage 24 and at the downstream end thereof to the cooling water inlet of the heat exchange passage 22 for waste heat recovery. Connected to the department.

  The radiator flow path 26 allows cooling water to flow into the radiator 31 that performs heat exchange between the cooling water and the outside air, and connects the upstream side of the downstream cooling water path 25 and the downstream side of the upstream cooling water path 23. To do. A known thermostat 33 is provided at a branch portion between the radiator flow path 26 and the downstream-side cooling water flow path 25. The thermostat 33 opens when the cooling water temperature reaches 65 ° C. or higher, and switches the cooling water flow path from the downstream cooling water flow path 25 to the radiator flow path 26.

  The bypass flow path 27 bypasses the cooling water flow path from the radiator 31, and communicates the upstream side and the downstream side of the radiator flow path 26 with respect to the radiator 31. A known thermostat 34 is provided at a branch portion between the bypass flow path 27 and the radiator flow path 26. The thermostat 34 opens when the cooling water temperature reaches 87 ° C. or higher, and switches the cooling water flow path from the bypass flow path 27 to the radiator flow path 26.

  That is, in this embodiment, when the cooling water temperature is less than 65 ° C., the cooling water is the waste heat recovery heat exchange flow path 22 to the upstream cooling water flow path 23 to the cylinder block internal flow path 24 to the downstream cooling water flow path 25. It circulates through the cooling water circuit at the time of the warming-up start comprised by (refer Fig.3 (a)).

  On the other hand, when the cooling water temperature is 65 ° C. or higher and lower than 87 ° C., the cooling water flows in the cylinder block flow path 24 to the downstream side cooling water flow path 25 to the upstream side of the thermostat 33 and to the radiator flow upstream of the thermostat 34. It is comprised by the upstream cooling water flow path 23 downstream from the confluence | merging part with the radiator flow path 26-radiator flow path 26 downstream from the confluence | merging part with the path 26-bypass flow path 27-bypass flow path 27. Circulates through the cooling water circuit when the warm-up continues (see FIG. 3B).

  Further, when the cooling water temperature is 87 ° C. or higher, the cooling water merges with the in-cylinder block flow path 24 to the downstream cooling water flow path 25 to the upstream side of the thermostat 33 to the radiator flow path 26 to the radiator flow path 26. It circulates in the cooling water circuit at the time of completion of warm-up constituted by the upstream side cooling water flow path 23 on the downstream side of the section (see FIG. 3C).

The cooling water temperature sensor 35 detects the temperature of the cooling water heated by the heat exchange with the exhaust gas, and is provided in the upstream cooling water passage 23 adjacent to the cooling water outlet portion of the heat exchange passage 22 for waste heat recovery. Is provided. Coolant temperature T _CO detected by the coolant temperature sensor 35 is inputted to the electrically connected ECU 40.

  The ECU 40 performs various controls such as fuel injection of the engine 10, and includes a known CPU, ROM, RAM, input port, output port, and the like. In order to perform these various controls, output signals of various sensors are input to the ECU 40.

Further, ECU 40, depending on the coolant temperature T _CO detected by the coolant temperature sensor 35, and controls the exhaust flow switching valve 21. More specifically, the ECU 40 stores a temperature (for example, 80 ° C.) that prevents boiling of the cooling water as the cooling water temperature upper limit threshold T _LIM1 . ECU40, the cooling water temperature T _CO input from coolant temperature sensor 35 when the cooling water temperature upper threshold T _LIM1 following inputs an instruction signal to the ON exhaust flow switching valve 21. That is, the upstream end of the branch exhaust passage 11b is closed, and the exhaust flows into the heat exchange exhaust passage 11a (see FIG. 2A).

On the other hand, the cooling water temperature T _CO input from coolant temperature sensor 35 is more than the cooling water temperature upper threshold T _LIM1, ECU 40 inputs an instruction signal to the OFF exhaust flow switching valve 21. That is, the upstream end of the heat exchange exhaust passage 11a is closed, and the exhaust flows into the branch exhaust passage 11b (see FIG. 2B).

  Next, based on FIG. 4, the control flow by the warming-up apparatus 20 of this embodiment is demonstrated. This control starts simultaneously with the start of the engine 10 (key switch ON of the ignition switch).

  In step (hereinafter, step is simply referred to as S) 100, the water pump 32 is driven by the start of the engine 10, and an instruction signal for turning on the exhaust flow path switching valve 21 is input from the ECU 40. That is, the temperature of the cooling water is raised by heat exchange with the exhaust gas in the waste heat recovery heat exchange flow path 22, and the raised cooling water is transferred to the cylinder block flow path 24 via the upstream side cooling water flow path 23. Then, the engine 10 is warmed up by waste heat recovery. At this time, the cooling water circulates through a cooling water circuit (see FIG. 3A) at the start of warm-up that bypasses the radiator flow path 26 and the bypass flow path 27.

  Thereafter, when the cooling water temperature rises to 65 ° C. or higher, the thermostat 33 is opened in S110. That is, the cooling water circulates through the cooling water circuit (see FIG. 3B) during the warming-up that bypasses the radiator 30 and the waste heat recovery heat exchange passage 22.

In S120, whether or not the cooling water temperature T _CO input from coolant temperature sensor 35 reaches the coolant temperature upper threshold T _LIM1 (e.g. 80 ° C.) is determined. When the cooling water temperature T _CO exceeds the cooling water temperature upper threshold T _LIM1, in order to avoid boiling of the coolant, an instruction signal to OFF exhaust path switching valve 21 from the ECU40 in S130 is input.

  Further, when the cooling water temperature rises to 87 ° C. or higher, the thermostat 34 is opened in S140. That is, the cooling water circulates through the cooling water circuit (see FIG. 3C) at the time of completion of warming that bypasses the bypass flow path 31 and flows through the radiator 30, and this control is returned.

  Next, functions and effects of the engine warm-up device 20 according to the present embodiment will be described.

  In a general engine warm-up device, during the warm-up operation, the coolant is bypassed from the radiator and the engine speed is set high to promote warm-up. On the other hand, in the warm-up device 20 of the present embodiment, the cooling water is effectively heated by heat exchange with the exhaust gas in the waste heat recovery heat exchange passage 22 without increasing the engine speed during the warm-up operation. To promote warm-up.

  Therefore, according to the warming-up device 20 of the present embodiment, it is possible to efficiently heat the cooling water by waste heat recovery and complete warming up early without increasing the engine speed, and during warming-up operation. The fuel consumption can be effectively improved.

  Further, in the warm-up device 20 of the present embodiment, the waste heat recovery heat exchange passage 22 for performing heat exchange between the cooling water and the exhaust is provided on the exhaust downstream side of the SCR 14.

  Therefore, according to the warming-up device 20 of the present embodiment, the exhaust gas (NOx emission) is effectively prevented from deteriorating by avoiding the SCR 14 from lowering than the catalyst activation temperature due to a decrease in exhaust temperature due to waste heat recovery. can do.

  Further, in the warm-up device 20 of the present embodiment, before the cooling water temperature reaches the boiling temperature, the exhaust passage is switched from the heat exchange exhaust passage 11a to the branch exhaust passage 11b, and the heat of the exhaust and the cooling water is changed. The exchange is stopped.

  Therefore, according to the warming-up device 20 of this embodiment, it is possible to reliably avoid the cooling water from being heated more than necessary due to waste heat recovery and boiling.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

  For example, although the heat exchange exhaust passage 11a and the branch exhaust passage 11b have been described as being formed in the exhaust passage 11 on the exhaust downstream side of the silencer, they may be formed immediately downstream of the SCR 14, and the catalyst heater If provided, it may be formed on the exhaust upstream side of the SCR 14.

  Further, as shown in FIG. 5, an electric pump 38 may be provided in the downstream side cooling water flow path 25 and an electromagnetic clutch 39 capable of connecting / disconnecting power transmitted from the engine 10 to the water pump 32 may be provided. In this case, the electromagnetic clutch 39 is disengaged during the warm-up operation to stop the driving of the water pump 32, and if the cooling water is pumped only by the electric pump 38, the engine load is reduced and the fuel efficiency during the warm-up operation is reduced. This can be further improved.

  The engine 10 is not limited to a diesel engine, and may be a gasoline engine or the like.

DESCRIPTION OF SYMBOLS 10 Engine 11 Exhaust passage 11a Heat exchange exhaust passage 11b Branch exhaust passage 21 Exhaust flow path switching valve 22 Waste heat recovery heat exchange flow path (heat exchange flow path)
23 Upstream cooling water flow path (second cooling water flow path)
24 Cylinder block flow path (first cooling water flow path)
25 Downstream cooling water flow path (third cooling water flow path)
32 Water pump 40 ECU

Claims (3)

An engine warm-up device for heating engine coolant when starting the engine,
A heat exchange flow path that is provided in the exhaust passage of the engine and exchanges heat between the exhaust flowing through the exhaust passage and the circulating cooling water.
A first cooling water flow path formed in a cylinder block of the engine for circulating cooling water in the cylinder block;
A second cooling water channel connecting the cooling water outlet of the heat exchange channel and the cooling water inlet of the first cooling channel;
A third cooling water channel connecting the cooling water outlet of the first cooling channel and the cooling water inlet of the heat exchange channel;
A pump provided in the second cooling water flow path or the third cooling water flow path to pump the cooling water;
A radiator channel connecting the upstream side of the third cooling water channel and the downstream side of the second cooling water channel;
A radiator provided in the radiator flow path for performing heat exchange between cooling water and outside air;
A bypass passage communicating the upstream side and the downstream side of the radiator in the radiator flow channel,
The third cooling water flow is provided at a branch portion between the radiator flow channel and the third cooling water flow channel, and the cooling water from the first cooling water flow channel is not circulated through the radiator flow channel. A first thermostat that is circulated only through the passage and opens when the temperature of the cooling water is equal to or higher than the first temperature, and switches the cooling water flow path from the third cooling water flow path to the radiator flow path;
Provided at a branch portion between the bypass flow path and the radiator flow path, and opens when the temperature of the cooling water reaches a second temperature higher than the first temperature, which is a temperature at the completion of warming-up, A second thermostat for switching the water flow path from the bypass flow path to the radiator flow path;
An engine warm-up device comprising: A branched exhaust passage formed by branching from an exhaust passage upstream of the heat exchange passage;
A flow path switching valve provided at a branch portion between the exhaust passage and the branch exhaust passage to switch an exhaust flow path,
The flow path switching valve is provided with an exhaust flow path when the temperature of the cooling water heated in the heat exchange flow path is equal to or lower than a predetermined upper limit threshold value that prevents boiling of the cooling water. When the temperature of the cooling water heated in the heat exchange flow path becomes higher than the upper limit threshold, the exhaust flow path is switched to the branch exhaust passage.
The engine warm-up device according to claim 1, wherein an exhaust purification catalyst for purifying exhaust gas is provided in the exhaust passage, and the heat exchange flow path is provided in an exhaust passage downstream of the exhaust purification catalyst.   The engine warm-up device according to claim 1 or 2, wherein the first temperature is 65 ° C and the second temperature is 87 ° C.