JP2020063690A - Injection system - Google Patents

Abstract

To provide an injection system capable of suppressing temperature rise of an injection valve.SOLUTION: In an injection system (90) including an injection valve (81) for injecting a liquid material to an exhaust passage of an internal combustion engine (5) of a vehicle, a cooling device (100) for cooling the injection valve (81), and a cooling control unit (63) for controlling the cooling device (100), the cooling control unit (63) drives the cooling device (100) when a temperature in the exhaust passage after the stop of the internal combustion engine (5) is over a predetermined start threshold value, and terminates the driving of the cooling device (100) in a case when a predetermined termination condition is established.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an injection system mounted on a vehicle for injecting a liquid material into an exhaust passage of an internal combustion engine.

  An injection system for injecting a liquid material into an exhaust passage of an internal combustion engine of a vehicle is known. For example, in Patent Document 1, in order to forcibly burn PM deposited on a particulate filter for collecting particulate matter (hereinafter, also referred to as “PM”) contained in exhaust gas of an internal combustion engine, Discloses a technique for injecting fuel into the exhaust passage on the upstream side of the oxidation catalyst arranged on the upstream side of the particulate filter to raise the exhaust temperature. In the fuel injection system described in Patent Document 1, the flow rate of the fuel supplied to the injection valve attached to the exhaust pipe is controlled, and the injection valve opens when the pressure of the fuel exceeds the valve opening pressure of the injection valve. Then, fuel is injected.

Further, in Patent Document 2, in order to purify nitrogen oxides (hereinafter also referred to as “NO _x ”) contained in exhaust gas of an internal combustion engine, a liquid reducing agent is provided in an exhaust passage upstream of a reduction catalyst. There is disclosed a technique of injecting a reducing agent to supply a reducing agent to the reducing catalyst. In the reducing agent injection system described in Patent Document 2, fuel is injected by controlling opening / closing of an electronically controlled injection valve attached to an exhaust pipe.

JP, 2008-135868, A JP, 2018-127960, A

  Here, in the above injection system, the exhaust heat is transferred to the injection valve directly or via the exhaust pipe during operation of the internal combustion engine, and the injection valve is heated. In the fuel injection system described in Patent Document 1, if the injection valve is heated while fuel injection is stopped, the fuel may deteriorate in the injection valve or in the fuel pipe in the vicinity thereof. When the fuel deteriorates, the valve element may be damaged and the operation of the injection valve may be hindered. Further, in the reducing agent injection system described in Patent Document 2, when the injection valve is heated while the injection of the reducing agent is stopped, the reducing agent is crystallized or the electronically controlled injection valve is damaged. May occur.

  On the other hand, there is an injection system including a cooling device that cools the injection valve. For example, the temperature rise of the injection valve is suppressed by holding the injection valve in a cooling holder having a cooling chamber through which the cooling water of the engine can flow and circulating the cooling water in the cooling chamber. However, immediately after the internal combustion engine is stopped, the circulation of the cooling water of the engine is stopped even though the exhaust heat remains, so that the injection valve is easily exposed to the high temperature.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an injection system capable of suppressing a temperature rise of an injection valve.

  According to one aspect of the present invention, an injection system including an injection valve that injects a liquid material into an exhaust passage of an internal combustion engine of a vehicle, a cooling device that cools the injection valve, and a cooling control unit that controls the cooling device. The cooling controller drives the cooling device when the temperature in the exhaust passage exceeds a preset start threshold after the internal combustion engine is stopped, and ends the driving of the cooling device when a predetermined termination condition is satisfied. An injecting system is provided.

  According to the present invention, the temperature rise of the injection valve can be suppressed.

It is a schematic diagram showing an example of composition of an exhaust gas purification system using a fuel injection system concerning an embodiment of the invention. It is a schematic diagram which shows the structural example of the fuel injection system which concerns on the same embodiment. It is a schematic diagram which shows the structural example of the cooling water introduction passage of the fuel injection system which concerns on the same embodiment. It is a schematic diagram which shows the structural example of the cooling water introduction passage of the fuel injection system which concerns on the same embodiment. It is a schematic diagram which shows the structural example of the control apparatus of the fuel injection system which concerns on the same embodiment. 3 is a flowchart showing an example of cooling control during operation of the internal combustion engine by the control device for the fuel injection system according to the same embodiment. 3 is a flowchart showing an example of cooling control after the internal combustion engine is stopped by the control device of the fuel injection system according to the same embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, constituent elements having substantially the same functional configuration are designated by the same reference numerals, and duplicate description will be omitted.

<1. Exhaust purification system overall configuration>
In the present embodiment, a fuel injection system that injects fuel into the exhaust passage will be described as an example of the injection system.

  First, with reference to FIG. 1, an example of an exhaust purification system 1 including a fuel injection system 90 according to the present embodiment will be described. FIG. 1 shows an example of the overall configuration of the exhaust purification system 1. The exhaust gas purification system 1 includes an oxidation catalyst 21, a particulate filter 22, a fuel injection system 90, and a control device 60. The exhaust gas purification system 1 is a system for purifying exhaust gas of a diesel engine, which is one mode of the internal combustion engine 5, and collects particulate matter (PM) contained in the exhaust gas of the internal combustion engine 5 with a particulate filter 22. To gather.

  Both the oxidation catalyst 21 and the particulate filter 22 are arranged in the exhaust pipe 11. The oxidation catalyst 21 is provided on the upstream side of the particulate filter 22. The exhaust gas discharged from the internal combustion engine 5 flows through the exhaust pipe 11, passes through the oxidation catalyst 21 and the particulate filter 22, and flows downstream. A device for removing other components such as nitrogen oxides in the exhaust gas may be arranged downstream of the particulate filter 22.

  The particulate filter 22 collects PM in the exhaust gas passing through the particulate filter 22. The particulate filter 22 may be a known particulate filter, and for example, a honeycomb structured filter made of a ceramic material is used. Most of the PM trapped in the particulate filter 22 is accumulated on the particulate filter 22 until the particulate filter 22 is regenerated.

  The oxidation catalyst 21 oxidizes the unburned fuel injected from the fuel injection system 90. The oxidation catalyst 21 raises the temperature of the exhaust gas passing through the oxidation catalyst 21 by the generated heat of oxidation. The oxidation catalyst 21 may be a known oxidation catalyst, and for example, a catalyst obtained by adding a predetermined amount of rare earth element such as cerium to a catalyst in which platinum is supported on alumina is used.

  Temperature sensors 50 and 52 are provided on the upstream side and the downstream side of the oxidation catalyst 21, respectively. Further, a differential pressure sensor 54 for detecting the differential pressure between the pressure on the upstream side and the pressure on the downstream side of the particulate filter 22 is provided. The sensor signals of these sensors are output to the control device 60, and the temperature and the differential pressure at each position are detected. If these temperatures and differential pressures can be estimated by calculation, these sensors may be omitted.

  The fuel injection system 90 measures the amount of fuel supplied from the fuel tank 30 and injects the fuel into the exhaust pipe 11. In the present embodiment, the fuel injection system 90 is provided branching from the fuel supply passage of the fuel supply system of the internal combustion engine 5. Specifically, the fuel supply system of the internal combustion engine 5 includes a fuel tank 30 for storing fuel, a fuel pump 32 for sucking up and pumping the fuel in the fuel tank 30, and a fuel for removing foreign matters mixed in the fuel. And a filter 34.

  The fuel in the fuel tank 30 is discharged by the fuel pump 32 and sent to the fuel filter 34 through the fuel supply passage 36. A part of the fuel that has passed through the fuel filter 34 is sent to the fuel injection system 90 through the fuel passage 38a. Further, another part of the fuel sent to the fuel filter 34 is sent to the internal combustion engine 5 through the fuel passage 37. Excess fuel of the fuel sent to the internal combustion engine 5 is returned to the fuel tank 30 through the fuel recirculation passage 35.

  In the present embodiment, the fuel is supplied to the fuel injection system 90 through the fuel passage 38a provided by branching from the fuel path for supplying the fuel to the internal combustion engine 5, but the fuel is supplied to the internal combustion engine 5. Fuel may be supplied to the fuel injection system 90 via an independent fuel path different from the fuel path that operates. Further, an independent fuel supply path different from the fuel supply system of the internal combustion engine 5 may be provided, such as a fuel tank provided separately from the fuel tank 30 that stores the fuel supplied to the internal combustion engine 5.

  The fuel injection system 90 comprises a metering unit 70 and an injection module 80. The metering unit 70 adjusts the flow rate of the fuel supplied to the injection module 80 via the fuel passage 38b. The injection module 80 includes an injection valve that opens and closes according to the pressure of the supplied fuel. The metering unit 70 is drive-controlled by the control device 60. The fuel passages 38a and 38b are one mode of the liquid passage.

  The fuel injection system 90 includes a cooling device 100. The cooling device 100 mainly cools the injection module 80 which is easily heated due to the influence of exhaust heat. In the present embodiment, the cooling device 100 cools the injection module 80 and the like by circulating the cooling water of the internal combustion engine 5 through the cooling water circulation passage 95 and radiating heat from the injection module 80 and the like.

  The injection module 80 is arranged in the middle of the cooling water circulation passage 95. Cooling water for the internal combustion engine 5 can flow through the injection module 80. The internal combustion engine 5 includes a cooling water circuit 4 that is formed in the engine block and circulates cooling water while passing the radiator 3. The cooling water circuit 4 includes a pump 2 that circulates the cooling water. The pump 2 is driven by the output of the internal combustion engine 5, for example, and discharges cooling water. The internal combustion engine 5 includes a temperature sensor 6 that measures the temperature of the cooling water circulating in the cooling water circuit 4. The cooling water circulation passage 95 branches from the cooling water circuit 4 at a branch portion 7 provided in the cooling water circuit 4 on the downstream side of the pump 2, and at a confluence portion 9 provided in the cooling water circuit 4 on the upstream side of the pump 2. Join the cooling water circuit 4.

  The cooling water circulation passage 95 includes a cooling water introduction passage 95 a for introducing cooling water into the injection module 80 and a cooling water discharge passage 95 b for discharging cooling water from the injection module 80. A part of the cooling water introduction passage 95a is arranged adjacent to the fuel passage 38b that connects the metering unit 70 and the injection module 80. While the internal combustion engine 5 is operating, the pump 2 is driven to circulate the cooling water in the cooling water circulation passage 95. The circulating cooling water radiates heat from the fuel in the injection module 80, the fuel in the fuel passage 38b and the injection module 80.

  Further, the cooling water circulation passage 95 includes a bypass passage 95c that connects the cooling water introduction passage 95a and the cooling water discharge passage 95b. A three-way valve 99 is provided at a connecting portion between the cooling water outlet passage 95b and the bypass passage 95c. A cooling water circulation pump 97 is provided in the middle of the bypass passage 95c. The three-way valve 99 and the cooling water circulation pump 97 are drive-controlled by the controller 60.

  In the present embodiment, the three-way valve 99 enables cooling water to flow from the injection module 80 side to the radiator 3 side in the non-energized state, while cooling the injection module 80 side to the bypass passage 95c side in the energized state. Allows water distribution. Therefore, the three-way valve 99 is energized and the cooling water circulation pump 97 is driven, so that the cooling water can be circulated through the injection module 80 even while the internal combustion engine 5 is stopped.

<2. Fuel injection system configuration>
Next, a configuration example of the fuel injection system 90 will be described with reference to FIG. FIG. 2 is a schematic diagram showing a configuration example of the fuel injection system 90. The fuel injection system 90 includes a metering unit 70 and an injection module 80. The injection module 80 is fixed to the exhaust pipe 11 on the upstream side of the oxidation catalyst 21, and injects fuel into the exhaust pipe 11. The metering unit 70 adjusts the injection amount of fuel injected from the injection module 80. The fuel passage 38a is connected to the metering unit 70, and a part of the fuel pumped by the fuel pump 32 is supplied to the metering unit 70 (see FIG. 1). The metering unit 70 and the injection module 80 are connected by the fuel passage 38b, and the fuel is supplied to the injection module 80 while being metered by the metering unit 70.

  The metering unit 70 includes a shutoff valve 72, an upstream pressure / temperature sensor 74, a control valve 76, and a downstream pressure sensor 78 in order from the upstream side along the fuel flow direction.

  The shutoff valve 72 opens the fuel passage 38a when fuel injection into the exhaust pipe 11 is performed, and shuts off the fuel passage 38a when fuel injection into the exhaust pipe 11 is not performed. The shutoff valve 72 is constituted by, for example, an on / off valve provided with an electromagnetic solenoid, opens the fuel passage 38a when energized, and shuts off the fuel passage 38a when deenergized. The drive of the shutoff valve 72 is controlled by the control device 60. For example, the control device 60 energizes the cutoff valve 72 when the forced regeneration control of the particulate filter 22 is performed, and stops energization of the shutoff valve 72 when the forced regeneration control is not performed. As a result, the supply and stop of fuel to the control valve 76 are switched.

  The control valve 76 adjusts the injection amount of the fuel injected into the exhaust pipe 11 via the injection module 80. The control valve 76 is composed of, for example, an on / off valve provided with an electromagnetic solenoid, and is driven based on a PWM (Palse Width Modulation) signal transmitted from the control device 60. For example, the control device 60 uses the differential pressure obtained from the sensor signal of the upstream pressure / temperature sensor 74 and the sensor signal of the downstream pressure sensor 78 or the upstream pressure to inject a target injection amount of fuel obtained by a predetermined calculation. The duty ratio of the control valve 76 is controlled based on the sensor signal of the side pressure / temperature sensor 74. For example, when the control valve 76 is an on / off valve that opens when energized, the control device 60 controls the ratio of the energization time to the injection cycle time of each injection cycle. Thereby, the amount of fuel supplied to the injection module 80 is adjusted.

  The upstream pressure / temperature sensor 74 is provided in the fuel passage 39a that connects the shutoff valve 72 and the control valve 76, and the pressure of fuel upstream of the control valve 76 (hereinafter, also referred to as “upstream fuel pressure”). ) And the fuel temperature. Further, the downstream pressure sensor 78 is provided in the fuel passage 39b on the downstream side of the control valve 76 and detects the pressure of fuel on the downstream side of the control valve 76 (hereinafter, also referred to as “downstream fuel pressure”). . For example, the control device 60 sets the duty ratio of the control valve 76 based on the differential pressure between the upstream fuel pressure and the downstream fuel pressure or the upstream fuel pressure. When supplying the same amount of fuel to the injection module 80, the control device 60 sets the duty ratio of the control valve 76 to be smaller as the differential pressure or the upstream fuel pressure is relatively higher, while the differential pressure or The duty ratio of the control valve 76 is set to be larger as the upstream fuel pressure is relatively lower.

  A fuel recirculation pipe having an orifice passage or a one-way valve and communicating with the fuel tank 30 may be connected between the shutoff valve 72 and the control valve 76. By providing the fuel recirculation pipe, the pressure of the fuel supplied to the control valve 76 can be prevented from significantly increasing, and damage to parts such as the upstream pressure / temperature sensor 74 can be prevented.

  The injection module 80 includes an injection valve 81 and a cooling holder 87. The injection valve 81 is configured as a mechanical opening / closing valve that opens according to the pressure of the fuel supplied from the metering unit 70, for example. The injection module 80 includes a valve body 82, a valve spring 84, and a valve seat 86. The valve spring 84 biases the valve body 82 toward the valve seat 86. When the pressure of the fuel supplied from the metering unit 70 exceeds the valve opening pressure set according to the urging force of the valve spring 84, the valve body 82 separates from the valve seat 86 and opens the valve.

  The cooling holder 87 has a cooling chamber 88 through which cooling water for the internal combustion engine 5 can flow. The cooling chamber 88 is formed so as to surround the periphery of the injection valve 81, the cooling water is introduced into the cooling chamber 88 through the cooling water introduction passage 95a, and the cooling water is discharged from the cooling chamber 88 through the cooling water outlet passage 95b. Derived. While the cooling water circulates in the cooling water circulation passage 95, the heat of the injection valve 81 is transferred to the cooling water, and the heating of the injection valve 81 is suppressed. Further, a part of the cooling water introduction passage 95a is arranged adjacent to the fuel passage 38b. Thereby, the heat of the fuel in the fuel passage 38b is transferred to the cooling water, and the heating of the fuel is also suppressed.

  The injection module 80 includes a module temperature sensor 89 for measuring the temperature inside the module. The module temperature sensor 89 is preferably provided so as to measure the temperature near the valve body 82 of the injection valve 81.

  3 to 4 are explanatory views showing configuration examples of the fuel passage 38b and the cooling water introduction passage 95a. As shown in FIG. 3, a part of the fuel passage 38 b and a part of the cooling water introduction passage 95 a are both arranged in the heat insulating pipe 92. Thereby, the cooling efficiency at the time of cooling the fuel in the fuel passage 38b by the cooling water passing through the cooling water introduction passage 95a is improved. Instead of using the heat insulating pipe 92, the fuel passage 38b and the cooling water introducing passage 95a may be covered with a heat insulating material such as a heat insulating tape.

  In addition, in the present embodiment, as shown in FIG. 4, the cooling water introduction passage 95a has a first portion 95aa that is disposed in the heat insulating pipe 92 together with the fuel passage 38b, and a first portion that bypasses the first portion 95aa. 2 portions 95ab. The first portion 95aa and the second portion 95ab branch from the passage switching valve 96 as a base point, and the flow path of the cooling water is switched to the first portion 95aa or the second portion 95ab. The operation of the passage switching valve 96 is controlled by the control device 60. The passage switching valve 96 may be provided at a position where the first portion 95aa and the second portion 95ab join.

<3. Controller>
(3-1. Configuration example)
Next, the configuration of the control device 60 will be specifically described. The control device 60 controls the metering unit 70 to inject fuel into the exhaust pipe 11 via the injection module 80. Further, the control device 60 executes cooling control of the fuel injection system 90 after the internal combustion engine 5 is stopped. The control device 60 includes a processor such as a CPU (Central Processing Unit) and a storage element such as a RAM (Random Access Memory) or a ROM (Read Only Memory).

  FIG. 5 shows a functional configuration of the control device 60. The control device 60 includes an injection control unit 61 and a cooling control unit 63. The injection control unit 61 performs a forced regeneration control for forcibly burning the PM accumulated on the particulate filter 22. The control device 60 performs forced regeneration control, for example, when the differential pressure detected by the differential pressure sensor 54 exceeds a reference value. As the amount of accumulated PM trapped in the particulate filter 22 increases, the differential pressure between the pressure on the upstream side and the pressure on the downstream side of the particulate filter 22 increases. Further, the control device 60 may execute the forced regeneration control before the internal combustion engine 5 is stopped when the ignition switch of the internal combustion engine 5 is turned off. In the forced regeneration control, the control device 60 controls the fuel injection system 90 to inject fuel into the exhaust pipe 11 upstream of the oxidation catalyst 21.

  For example, the control device 60 performs intake throttle or post injection on the internal combustion engine 5 to raise the temperature of the exhaust gas to raise the temperature of the oxidation catalyst 21, and then performs the fuel injection from the fuel injection system 90. May be. As a result, the fuel is efficiently oxidized in the oxidation catalyst 21, and the temperature of the exhaust gas rapidly rises. At this time, the control device 60 adjusts the injection amount of fuel from the fuel injection system 90 so that the temperature of the exhaust gas flowing into the particulate filter 22 becomes about 300 to 600 ° C. In this way, the high-temperature exhaust gas flows into the particulate filter 22, and the PM in the particulate filter 22 burns. The forced regeneration control by fuel injection from the fuel injection system 90 is performed for about 15 to 30 minutes, for example, according to the estimated amount of trapped PM in the particulate filter 22.

  The cooling control unit 63 controls the operations of the passage switching valve 96, the cooling water circulation pump 97, and the three-way valve 99 to control the cooling of the fuel injection system 90. Specifically, the cooling control unit 63, based on the sensor signal of the temperature sensor 6, the temperature of the cooling water introduced into the injection module 80 via the cooling water circulation passage 95 (hereinafter, also referred to as “inlet cooling water temperature”). Get information about. In addition, the cooling control unit 63 acquires information on the temperature of the fuel introduced into the injection module 80 based on the sensor signal of the upstream pressure / temperature sensor 74.

  The cooling control unit 63 controls the operation of the passage switching valve 96 based on the information on the inlet cooling water temperature and the fuel temperature. When the inlet cooling water temperature is lower than the fuel temperature, the cooling control unit 63 operates the passage switching valve 96 so that the cooling water passes through the first portion 95aa of the cooling water introduction passage 95a. On the other hand, when the inlet cooling water temperature is equal to or higher than the fuel temperature, the cooling control unit 63 operates the passage switching valve 96 so that the cooling water passes through the second portion 95ab of the cooling water introducing passage 95a. Thereby, the passage of the cooling water is controlled so that the fuel is not heated by the cooling water.

  Further, the cooling control unit 63 drives the cooling device 100 when the temperature in the exhaust passage exceeds a preset start threshold after the internal combustion engine 5 is stopped, and drives the cooling device 100 when a predetermined termination condition is satisfied. To end. Specifically, after the internal combustion engine 5 is stopped, the drive of the pump 2 provided in the internal combustion engine 5 is stopped and the circulation of the cooling water to the cooling water circulation passage 95 is stopped. Then, the cooling water staying in the injection module 80 is heated to a boiling state, and the temperature of the injection valve 81 rises. Therefore, when the injection module 80 is in a state where it can be heated after the internal combustion engine 5 is stopped, the cooling control unit 63 drives the cooling water circulation pump 97 to circulate the cooling water to the injection module 80.

  The cooling control unit 63 stops the cooling water circulation pump 97 and terminates the circulation of the cooling water to the injection module 80 when the risk of heating the injection module 80 disappears. As a result, the injection module 80 is heated after the internal combustion engine 5 is stopped, and damage or sticking of the injection valve 81 due to deterioration of the fuel is suppressed.

(3-2. Operation example)
Next, an operation example when the cooling control unit 63 of the control device 60 controls the cooling of the fuel injection system 90 will be described.

  FIG. 6 is a flowchart showing an example of processing of the control device 60 until the operation of the internal combustion engine 5 is stopped. The cooling control unit 63 controls the upstream pressure / temperature sensor 74 during operation of the internal combustion engine 5, that is, while the pump 2 provided in the internal combustion engine 5 is driven to circulate the cooling water in the cooling water circulation passage 95. It is determined whether the measured fuel temperature T_f is higher than the inlet cooling water temperature T_c measured by the temperature sensor 6 (step S11).

  When the fuel temperature T_f is higher than the inlet cooling water temperature T_c (S11 / Yes), the cooling control unit 63 operates the passage switching valve 96 so that the cooling water passes through the first portion 95aa of the cooling water introduction passage 95a. (Step S13). As a result, the fuel in the fuel passage 38b is cooled by the cooling water. On the other hand, when the fuel temperature T_f is equal to or lower than the inlet cooling water temperature T_c (S11 / No), the cooling control unit 63 operates the passage switching valve 96 so that the cooling water passes through the second portion 95ab of the cooling water introduction passage 95a. (Step S15). This can prevent the temperature of the fuel in the fuel passage 38b from rising under the influence of the heat of the cooling water.

  Then, the cooling control unit 63 determines whether the internal combustion engine 5 has stopped (step S17). While the internal combustion engine 5 is operating (S17 / No), the cooling control unit 63 repeats the operation control of the passage switching valve 96 based on the fuel temperature T_f and the inlet cooling water temperature T_c, while the internal combustion engine 5 is stopped ( (S17 / Yes), the operation control of the passage switching valve 96 is ended. In this way, the cooling control unit 63 suppresses the temperature rise of the fuel supplied to the injection module 80 during the operation of the internal combustion engine 5.

  FIG. 7 is a flowchart showing an example of processing of the control device 60 after the ignition switch of the internal combustion engine 5 is turned off. After the ignition switch of the internal combustion engine 5 is turned off, the injection control unit 61 injects fuel into the exhaust pipe 11 on the upstream side of the oxidation catalyst 21 via the injection module 80 for a predetermined period (step S21). During this period, the operation of the internal combustion engine 5 is continued, the PM accumulated on the particulate filter 22 is burned by the exhaust gas having a high temperature, and the particulate filter 22 is regenerated. When the regeneration control of the particulate filter 22 ends, the internal combustion engine 5 stops. As a result, the circulation of the cooling water by the pump 2 provided in the internal combustion engine 5 is stopped.

  Next, when the internal combustion engine 5 is stopped, the cooling control unit 63 determines whether or not the exhaust gas temperature T_g measured by the temperature sensor 50 exceeds a preset start threshold value T_0 (step S23). The start threshold T_0 may be set to an appropriate temperature in consideration of the temperature at which the fuel may be thermally deteriorated, the heat transfer coefficient from the exhaust pipe 11 to the injection valve 81, and the like. When the exhaust gas temperature T_g is equal to or lower than the start threshold value T_0 (S23 / No), it is considered that there is no possibility of damaging the injection module 80 due to thermal deterioration of the fuel, and therefore the cooling control unit 63 ends this routine.

  On the other hand, when the exhaust temperature T_g is higher than the start threshold value T_0 (S23 / Yes), the cooling control unit 63 causes the cooling water in the cooling water outlet passage 95b to flow into the cooling water introduction passage 95a via the bypass passage 95c. The three-way valve 99 is operated to start driving the cooling water circulation pump 97 (step S24). As a result, the cooling water circulates to the injection module 80 even though the internal combustion engine 5 is stopped. Therefore, even when the exhaust heat remaining after the internal combustion engine 5 is stopped is transferred to the injection module 80, the temperature rise of the injection module 80 can be suppressed.

  Next, the cooling control unit 63 determines whether or not the ending condition for ending the circulation of the cooling water is satisfied (step S27). The termination condition may be, for example, that the rising speed of the predetermined temperature correlated with the temperature of the injection valve 81 is lower than a preset termination reference value. Specifically, the termination condition may be that the rising rate of the module temperature measured by the module temperature sensor 89 is below a predetermined termination reference value. That is, when the influence of exhaust heat on the injection valve 81 is reduced and it can be determined that the subsequent temperature increase width is small, the circulation of the cooling water can be terminated.

  Further, the termination condition may be that the driving time of the cooling device 100, that is, the elapsed time from the start of the circulation of the cooling water by the cooling water circulation pump 97 exceeds the preset end reference value. That is, it is possible to terminate the circulation of the cooling water after performing the circulation of the cooling water for the time period after which the temperature rise width of the injection valve 81 is expected to be small.

  In addition, the termination condition is that after a predetermined correlation temperature that correlates with the temperature of the injection valve 81 rises, the correlation temperature is an initial value when the cooling device 100 is driven, or the termination of adding a predetermined value to the initial value. It may be a decrease to the reference value. For example, after the module temperature measured by the module temperature sensor 89 has risen, the module temperature is a value when the cooling water circulation pump 97 starts circulating the cooling water, or an end reference value obtained by adding a predetermined value to the initial value. When the temperature drops to 0, the circulation of the cooling water can be terminated.

  Further, the termination condition may be that the exhaust gas temperature T_g measured by the temperature sensor 50 falls to a preset termination reference value. Since the internal combustion engine 5 has already stopped, the temperature rise width of the injection valve 81 is expected to be small after the exhaust gas temperature T_g has decreased to the termination reference value. Therefore, the circulation of the cooling water is terminated when such a condition is satisfied. be able to.

  In the present embodiment, the cooling control unit 63 determines that the ending condition is satisfied when any one of the above four conditions is satisfied. Accordingly, it is possible to prevent an excessive temperature rise of the injection valve 81 while avoiding an excessively long cooling control time.

  When the end condition is not satisfied (S27 / No), the cooling control unit 63 repeats the determination of step S27 until the end condition is satisfied. Then, when the end condition is satisfied (S27 / Yes), the cooling control unit 63 stops the driving of the cooling water circulation pump 97 and ends the operation of the three-way valve 99 (step S29). This ends the cooling control.

  Even after the internal combustion engine 5 is stopped, when the fuel temperature T_f is higher than the inlet cooling water temperature T_c, the cooling water is passed through the first portion 95aa of the cooling water introducing passage 95a, so that the cooling water is introduced into the fuel passage 38b. It is also possible to suppress the temperature rise of the retained fuel. Thereby, thermal deterioration of the fuel can be further suppressed.

  As described above, according to the fuel injection system 90 of the present embodiment, the cooling device 100 is driven when the injection module 80 can be heated by the influence of exhaust heat after the internal combustion engine 5 is stopped. . As a result, damage or sticking of the injection valve 81 due to thermal deterioration of the fuel can be suppressed.

  Further, according to the fuel injection system 90 of the present embodiment, a part of the cooling water introduction passage 95a for introducing the cooling water of the internal combustion engine 5 into the injection module 80 is a fuel passage for supplying the fuel to the injection module 80. It is arranged adjacent to 38b. As a result, the fuel in the fuel passage 38b can also be cooled, and damage or sticking of the injection valve 81 due to thermal deterioration of the fuel can be further suppressed.

  The preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, but the present invention is not limited to these examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above-described embodiment, the cooling water introduction passage 95a for introducing the cooling water into the injection module 80 branches into the first portion 95aa and the second portion 95ab, and the first portion 95aa of the first portion 95aa is provided in the fuel passage 38b. Although they are arranged adjacent to each other, in the present invention, it is not essential that a part of the cooling water introduction passage 95a is arranged adjacent to the fuel passage 38b.

  Further, the configuration in which a part of the cooling water introduction passage 95a is arranged adjacent to the fuel passage 38b is not limited to the example of the above embodiment. The cooling water introduction passage 95a is a single passage having no branch portion, while the fuel passage 38b is provided with a first portion adjacent to the cooling water introduction passage 95a and a second portion for bypassing the first portion. It may be configured separately. In this case, when the fuel temperature T_f is higher than the inlet cooling water temperature T_c, by controlling the fuel to pass through the first portion, it is possible to suppress the temperature rise of the fuel introduced into the injection module 80. it can.

  Further, in the above embodiment, as the cooling device 100 that cools the injection module 80 after the internal combustion engine 5 is stopped, a device in which the bypass passage 95c, the cooling water circulation pump 97, and the three-way valve 99 are added to the cooling water circulation passage 95 is used. However, the present invention is not limited to such an example. As the cooling device 100 that cools the injection module 80 after the internal combustion engine 5 is stopped, an independent cooling device that does not use the cooling water circulation passage 95 may be used.

  Further, the injection system according to the above-described embodiment is not limited to the fuel injection system, but can be applied to a reducing agent injection system that supplies a liquid reducing agent into the exhaust passage. In this case, cooling control is performed by the cooling control unit so that the temperature of the injection module or the electromagnetically controlled injection valve does not exceed the heat resistant temperature of the injection valve or the temperature at which the composition of the liquid reducing agent can change.

1: Exhaust gas purification system, 4: Cooling water circuit, 5: Internal combustion engine, 6: Temperature sensor, 11: Exhaust pipe, 21: Oxidation catalyst, 22: Particulate filter, 38a / 38b: Fuel passage, 50: Temperature sensor, 60: control device, 61: injection control unit, 63: cooling control unit, 70: metering unit, 74: upstream pressure / temperature sensor, 80: injection module, 81: injection valve, 87: cooling holder, 88: cooling Chamber, 89: Module temperature sensor, 90: Fuel injection system, 92: Adiabatic pipe, 95: Cooling water circulation passage, 95a: Cooling water introducing passage, 95aa: First portion, 95ab: Second portion, 95b: Cooling water Outlet passage, 95c: bypass passage, 96: passage switching valve, 97: cooling water circulation pump, 99: three-way valve, 100: cooling device

Claims (8)

An injection valve (81) for injecting a liquid material into an exhaust passage of an internal combustion engine (5) of a vehicle, a cooling device (100) for cooling the injection valve (81), and a cooling control for controlling the cooling device (100). An injection system (90) comprising a part (63),
The cooling control unit (63),
The cooling device (100) is driven when the temperature in the exhaust passage exceeds a preset start threshold after the internal combustion engine (5) is stopped, and the cooling device (100) is driven when a predetermined ending condition is satisfied. Drive of the
An injection system characterized by the above. The termination condition is that the rising speed of a predetermined temperature correlated with the temperature of the injection valve (81) is lower than a preset termination reference value.
The injection system according to claim 1, wherein: The end condition is that the driving time of the cooling device (100) exceeds a preset end reference value.
The injection system according to claim 1, wherein: The end condition is an initial value when the cooling device (100) is driven by the correlation temperature after a predetermined correlation temperature that correlates with the temperature of the injection valve (81) rises, or a predetermined value is set to the initial value. It is to decrease to the end reference value that added value,
The injection system according to claim 1, wherein: The termination condition is that the temperature in the exhaust passage falls to a preset termination reference value.
The injection system according to claim 1, wherein: The cooling device (100) is
A cooling holder (87) having a cooling chamber (88) through which a cooling medium passes, and holding the injection valve (81);
An introduction passage (95a) for introducing the cooling medium into the cooling chamber (88);
A discharge passage (95b) for discharging the cooling medium from the cooling chamber (88),
A part of the introduction passage (95a) is arranged in contact with a liquid passage (38b) for supplying the liquid material to the injection valve (81).
The injection system according to any one of claims 1 to 5, characterized in that The introduction passage (95a) is
A first portion (95aa) arranged in contact with the liquid passage (38b), a second portion (95ab) bypassing the first portion (95aa), and a passage through which the cooling medium passes A passage switching valve (96) for switching to the first portion (95aa) or the second portion (95ab),
The cooling control unit (63),
Passing the cooling medium through the first portion (95aa) when the temperature of the liquid material is higher than the temperature of the cooling medium,
Passing the cooling medium through the second portion (95ab) when the temperature of the liquid material is lower than the temperature of the cooling medium,
The injection system according to claim 6, wherein: The liquid passage (38b) is
A first portion disposed in contact with the introduction passage (95a), a second portion that bypasses the first portion, and a passage path of the liquid material through the first portion or the second portion. And a passage switching valve for switching to
The cooling control unit (63),
Passing the liquid material through the first portion when the temperature of the liquid material is higher than the temperature of the cooling medium,
Passing the liquid material through the second portion when the temperature of the liquid material is lower than the temperature of the cooling medium,
The injection system according to claim 6, wherein:

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