JP2013221425A - Injector control device of exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injector control device of an exhaust emission control device for avoiding addition of urea water in the timing except for predetermined time, while promoting thawing of the urea water.SOLUTION: An electric current control part 52 supplies an electric current more than a lower limit electric current value Ib and less than an upper limit electric current value Ia to a coil 33 of an electromagnetic driving part 23, when the temperature of the urea water in a urea water tank 14 detected by a urea water temperature sensor 42 is lower than the preset lower limit temperature Ti. A needle of an injector is driven when the electric current supplied to the coil 33 becomes the upper limit electric current value Ia or more, and is not driven when the electric current is less than the upper limit electric current value Ia. Thus, the injector does not inject the urea water when the electric current is less than the upper limit electric current value Ia. The coil 33 is heated by supplying the electric current of the lower limit electric current value Ib or more even when being less than the upper limit electric current value Ia. The urea water frozen by the injector is thawed by heating of the coil 33.

Description

  The present invention relates to an injector control device for an exhaust purification device that controls an injector used in an exhaust purification device for an internal combustion engine.

  Conventionally, a urea SCR system in which urea water is added to exhaust gas for the purpose of removing nitrogen oxide (NOx) contained in exhaust gas of an internal combustion engine is known. In this urea SCR system, urea water stored in a urea water tank is supplied to an injector provided in an exhaust passage by a urea water pump accommodated in the urea water tank. The injector is intermittently injected by driving a valve member for intermittently injecting urea water with an electromagnetic drive unit (see Patent Document 1).

  By the way, the urea water added to the exhaust gas from the injector is likely to be frozen due to a decrease in temperature unlike the fuel. When urea water is frozen by the injector, there is a problem that the valve member is fixed and the addition of urea water to the exhaust is hindered. On the other hand, if the urea water is thawed by the heat generated by the electromagnetic drive unit by energization, the urea water that has become liquid may be added to the exhaust gas at a time other than the predetermined time.

JP 2010-24981 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an injector control device for an exhaust purification device that avoids the addition of urea water at a time other than a predetermined time while promoting the thawing of urea water.

  In order to solve the above-mentioned problem, in the invention according to claim 1, the current control means generates a current less than the upper limit current value when the temperature of the urea water detected by the temperature detection means is lower than a preset lower limit temperature. Supply to the electromagnetic drive. The injector valve member that intermittently injects urea water is driven when the current supplied to the electromagnetic drive unit exceeds the upper limit current value. That is, when the valve member is less than the upper limit current value, the valve member is not driven even if a current is supplied to the electromagnetic drive unit. Therefore, the injector does not inject urea water when it is less than the upper limit current value. On the other hand, even if the electromagnetic drive unit is less than the upper limit current value, the electromagnetic drive unit generates heat when supplied with current. The entire injector is heated by the heat generated by the electromagnetic drive unit. Therefore, the urea water of the injector is thawed by the heat generated by the electromagnetic drive unit. Therefore, it is possible to avoid the addition of urea water at a time other than the predetermined time while promoting thawing of the urea water.

The block diagram which shows schematic structure of the injector control apparatus by one Embodiment. The schematic diagram which shows the exhaust gas purification apparatus to which the injector control apparatus by one Embodiment is applied Typical sectional drawing which shows the injector used for the injector control apparatus by one Embodiment The schematic diagram which shows the change of the electric current supplied to an injector from the injector control apparatus by one Embodiment. Schematic showing the flow of operation of the injector control device according to one embodiment

Hereinafter, an injector control device according to an embodiment will be described with reference to the drawings.
First, an embodiment of an exhaust gas purification apparatus to which an injector is applied will be described. As shown in FIG. 2, the exhaust emission control device 10 of this embodiment adds urea water to, for example, exhaust gas discharged from an internal combustion engine 11 mounted on a vehicle, and converts nitrogen oxide (NOx) contained in the exhaust gas. SCR (Selective Catalytic Reduction) system to reduce is configured. Exhaust gas discharged from the internal combustion engine 11 is discharged into the atmosphere via an exhaust passage 13 formed by the exhaust pipe member 12. The internal combustion engine 11 is a diesel engine, for example. The exhaust emission control device 10 may be applied not only to a diesel engine but also to a gasoline engine, a gas turbine engine, or the like.

  The exhaust emission control device 10 includes a urea water tank 14, a urea water pump 15, a urea water piping unit 16, and a reduction catalyst 17. The urea water tank 14 stores an aqueous solution of urea. The urea water pump 15 is accommodated in the urea water tank 14. The urea water pipe section 16 forms a urea water passage 18. The reduction catalyst 17 is provided in the exhaust passage 13 formed by the exhaust pipe member 12.

  The exhaust emission control device 10 includes an injector 20 in addition to the above. The urea water piping part 16 is connected to the injector 20 at the end opposite to the urea water pump 15. The urea water discharged from the urea water pump 15 is supplied to the injector 20 via the urea water passage 18 formed by the urea water piping section 16. The injector 20 is provided in the exhaust pipe member 12 that forms the exhaust passage 13. The injector 20 penetrates the exhaust pipe member 12 and the tip is exposed to the exhaust passage 13. The urea water supplied from the urea water pump 15 to the injector 20 via the urea water passage 18 is injected from the injector 20 into the exhaust gas flowing through the exhaust passage 13. Exhaust gas discharged from the internal combustion engine 11 and urea water are mixed in the exhaust passage 13 and flow into the reduction catalyst 17. NOx contained in the exhaust gas is reduced by reacting with urea water supplied from the injector 20 in the reduction catalyst 17.

  As shown in FIG. 3, the injector 20 includes a body 21, a needle 22 as a valve member, an electromagnetic drive unit 23, and a cap 24. The body 21 is formed in a cylindrical shape and accommodates a needle 22 therein. The needle 22 can reciprocate in the axial direction of the body 21 on the inner peripheral side of the body 21. The needle 22 is formed in a cylindrical shape and forms a needle passage 25 on the inner peripheral side. The end of the needle passage 25 on the cap 24 side is connected to the cap passage 26. The cap passage 26 penetrates the cylindrical cap 24. The end of the cap passage 26 opposite to the needle passage 25 is connected to the urea water passage 18. Further, on the distal end side of the body 21, a distal end passage 27 is formed between the outer peripheral wall of the needle 22 and the inner peripheral wall of the body 21. The tip passage 27 is connected to a needle passage 25 that penetrates the needle 22.

  The cylindrical body 21 has a nozzle hole 28. The body 21 forms an annular valve seat 31 on the upstream side of the injection hole 28, that is, on the electromagnetic drive unit 23 side. The needle 22 has a seal portion 32 at the tip. When the seal portion 32 is seated on the valve seat 31, the tip passage 27 and the injection hole 28 are blocked. On the other hand, when the seal portion 32 is separated from the valve seat 31, the space between the tip passage 27 and the injection hole 28 is opened.

  The electromagnetic drive unit 23 includes a coil 33 and an elastic member 34. The coil 33 is accommodated in the body 21 made of a magnetic material. The elastic member 34 is formed of a coil spring, for example, and presses the needle 22 in the direction in which the seal portion 32 is seated on the valve seat 31. When a current is supplied to the coil 33 of the electromagnetic drive unit 23, the needle 22 is attracted in a direction in which the seal unit 32 is separated from the valve seat 31. The needle 22 has a flange portion 35 on the end side opposite to the seal portion 32. Thus, when a current is supplied to the coil 33 of the electromagnetic drive unit 23, a magnetic attractive force is generated between the body 21 that houses the coil 33 and the flange portion 35 of the needle 22. This magnetic attractive force varies depending on the magnitude of the current supplied to the coil 33.

  When no current is supplied to the coil 33, a magnetic attractive force that attracts the flange portion 35 of the needle 22 toward the coil 33 is not generated. Therefore, the needle 22 moves to the opposite side of the injection hole 28, that is, upward in FIG. 3 by the pressing force of the elastic member 34, and the seal portion 32 is seated on the valve seat 31. As a result, the tip passage 27 and the injection hole 28 are blocked, and urea water is not injected from the injection hole 28.

  When a current is supplied to the coil 33, a magnetic circuit is formed between the body 21 that houses the coil 33 and the needle 22, and a magnetic attractive force that attracts the flange portion 35 of the needle 22 toward the coil 33 is generated. When the magnetic attractive force generated between the flange portion 35 and the body 21 accommodating the coil 33 is smaller than the pressing force of the elastic member 34, the needle 22 moves to the coil 33 side even if current is supplied to the coil 33. do not do. When the current supplied to the coil 33 increases and the magnetic attraction force that attracts the flange portion 35 of the needle 22 toward the coil 33 becomes larger than the pressing force of the elastic member 34, the needle 22 resists the force of the elastic member 34. And move to the coil 33 side. The current supplied to the coil 33 when the needle 22 moves toward the coil 33 corresponds to the upper limit current value in the claims. When the needle 22 moves to the coil 33 side, the seal portion 32 of the needle 22 moves away from the valve seat 31. As a result, the urea water in the distal end passage 27 passes between the seal portion 32 and the valve seat 31 and is injected from the injection hole 28 to the exhaust passage 13.

When the supply of current to the coil 33 is stopped, the magnetic attractive force between the body 21 housing the coil 33 and the flange portion 35 of the needle 22 disappears. Therefore, the needle 22 moves again to the side opposite to the injection hole 28 by the pressing force of the elastic member 34. When the seal portion 32 of the needle 22 is seated on the valve seat 31 of the body 21, the tip passage 27 and the injection hole 28 are blocked. As a result, the injection of urea water from the nozzle hole 28 stops.
The configuration of the injector 20 shown in FIG. 3 described above is an example. Therefore, the injector 20 applied to the exhaust emission control device 10 may have another configuration as long as it includes a coil 33 that drives a valve member such as the needle 22.

Next, the injector control device 40 according to one embodiment will be described.
As shown in FIG. 2, the injector control device 40 includes a control unit 41 and a urea water temperature sensor 42 in addition to the injector 20 constituting the exhaust purification device 10. The urea water temperature sensor 42 detects the temperature of the urea water stored in the urea water tank 14. The urea water temperature sensor 42 outputs the detected temperature of the urea water to the control unit 41 as an electric signal.

  The injector control device 40 may include a urea water amount sensor 43 and a heater 44. The urea water amount sensor 43 detects the amount of urea water stored in the urea water tank 14. The urea water amount sensor 43 outputs the detected amount of urea water to the control unit 41 as an electrical signal. The heater 44 generates heat by the power supplied from the control unit 41. The urea water stored in the urea water tank 14 is heated by the heat generated by the heater 44.

  The control unit 41 has a control unit 50 as shown in FIG. The control unit 50 is composed of a microcomputer having a CPU, ROM and RAM (not shown). The control unit 50 implements the temperature acquisition unit 51 and the current control unit 52 in hardware by an integrated electronic circuit. In addition, you may implement | achieve these temperature acquisition parts 51 and the electric current control part 52 by combining with software or a hardware by running the computer program memorize | stored in ROM of the control part 50. FIG.

  The temperature acquisition unit 51 is connected to the urea water temperature sensor 42 and acquires the temperature detected by the urea water temperature sensor 42. In the case of this embodiment, the urea water temperature sensor 42 detects the temperature of the urea water stored in the urea water tank 14. The temperature of the urea water stored in the urea water tank 14 correlates with the temperature of the urea water in the injector 20. Therefore, in the case of the present embodiment, the temperature acquisition unit 51 acquires the temperature of the urea water in the injector 20 based on the temperature of the urea water in the urea water tank 14 detected by the urea water temperature sensor 42. Therefore, in the case of the present embodiment, the urea water temperature sensor 42 and the temperature acquisition unit 51 correspond to temperature detection means in the scope of claims for detecting the temperature of the urea water. The urea water temperature sensor 42 may be provided not in the urea water tank 14 but in the injector 20 so as to directly detect the temperature of the urea water in the injector 20. Further, the temperature acquisition unit 51 replaces the urea water temperature sensor 42 with the temperature of the urea water in the injector 20 based on, for example, the outside air temperature, the temperature of the cooling water of the internal combustion engine 11, or the temperature around the control unit 41. It is good also as a structure acquired indirectly. That is, the outside air temperature, the cooling water temperature of the internal combustion engine 11, or the temperature around the control unit 41 correlates with the temperature of the urea water in the injector 20. Therefore, the temperature of the urea water in the injector 20 may be indirectly acquired using an index that correlates with the temperature of the urea water in the injector 20.

  The current control unit 52 controls the current I supplied to the coil 33 of the electromagnetic drive unit 23 to be less than the upper limit current value Ia or more than the upper limit current value Ia. Specifically, when the temperature of the urea water detected by the urea water temperature sensor 42 is lower than the preset lower limit temperature Ti, the current control unit 52 applies an upper limit current value to the coil 33 of the electromagnetic drive unit 23 under a predetermined condition. Supply current less than Ia. This lower limit temperature Ti corresponds to the melting point of urea water supplied from the urea water tank 14 to the injector 20. The melting point of the urea water varies depending on the concentration of the urea water. Therefore, the lower limit temperature Ti is set in advance based on the temperature of the urea water used in the exhaust purification device 10 and is stored in the control unit 41. On the other hand, the current control unit 52 supplies a current larger than the upper limit current value Ia to the coil 33 of the electromagnetic drive unit 23 when the temperature of the urea water detected by the urea water temperature sensor 42 is equal to or higher than the lower limit temperature Ti. As described above, when the temperature of the urea water is lower than the lower limit temperature Ti, the current control unit 52 sets the “urea water thawing mode” and controls the current supplied to the coil 33 to be less than the upper limit current value Ia. On the other hand, the current control unit 52 sets the “normal operation mode” when the temperature of the urea water is equal to or higher than the lower limit temperature Ti, and controls the current supplied to the coil 33 to be larger than the upper limit current value Ia.

  The current control unit 52 supplies a pulsed current to the coil 33 of the electromagnetic drive unit 23 as shown in FIG. When the temperature of the urea water is equal to or higher than the lower limit temperature Ti and the urea water is injected from the injector 20, the current control unit 52 supplies the current supplied to the coil 33 as the normal operation mode as indicated by the broken line in FIG. Set to Ia or higher. Thereby, the current control unit 52 supplies the coil 33 with a current equal to or higher than the upper limit current value Ia. As a result, the seal portion 32 of the needle 22 is separated from the valve seat 31, and urea water is injected from the injection hole 28 of the injector 20 into the exhaust gas flowing through the exhaust passage 13.

  On the other hand, when the temperature of the urea water detected by the urea water temperature sensor 42 is lower than the lower limit temperature Ti, the current control unit 52 sets the current supplied to the coil 33 as the urea water thawing mode to the upper limit as shown by the solid line in FIG. Set to less than current value Ia. Thereby, the current control unit 52 supplies the coil 33 with a current less than the upper limit current value Ia. As described above, when the current I supplied to the coil 33 in the normal operation mode exceeds the upper limit current value Ia, the electromagnetic drive unit 23 drives the needle 22. On the other hand, if the current I supplied to the coil 33 in the urea water thawing mode is less than the upper limit current value Ia, the current less than the upper limit current value Ia is supplied to the coil 33, but the body 21 that houses the coil 33 The magnetic attraction force generated between the needle 22 and the flange portion 35 is smaller than the pressing force of the elastic member 34. Therefore, the needle 22 is not driven and urea water is not injected from the injection hole 28. Thus, by controlling the current I supplied to the electromagnetic drive unit 23 to be less than the upper limit current value Ia, the current is supplied to the coil 33, but the needle 22 is not driven.

  Here, when the current I supplied to the electromagnetic drive unit 23 is appropriately controlled, the needle 22 is not driven, but the coil 33 of the electromagnetic drive unit 23 generates heat. Thus, the lower limit current value Ib is the lower limit current value at which the coil 33 of the electromagnetic drive unit 23 generates heat. That is, the coil 33 of the electromagnetic drive unit 23 generates heat by supplying a current having a lower limit current value Ib. Therefore, by controlling the current I supplied to the coil 33 to be less than the upper limit current value Ia and greater than or equal to the lower limit current value Ib, the coil 33 generates heat without generating a magnetic attractive force that can drive the needle 22. As a result, the coil 33 and the body 21 and the needle 22 around the coil 33 are heated by the heat generated by the coil 33. Thereby, even if the urea water supplied to the injector 20 is frozen, it is thawed by the heat generated by the coil 33. These upper limit current value Ia and lower limit current value Ib are arbitrarily set according to the characteristics of the injector 20 applied to the exhaust purification device 10.

Next, the operation of the injector control device 40 configured as described above will be described with reference to FIG.
In the exhaust emission control device 10, the temperature acquisition unit 51 always acquires the temperature of the urea water from the urea water temperature sensor 42 (S101). Specifically, the temperature acquisition unit 51 acquires the temperature of the urea water stored in the urea water tank 14 from the urea water temperature sensor 42 provided in the urea water tank 14. The urea water in the urea water tank 14 correlates with the temperature of the urea water in the injector 20 as described above.

  The control unit 50 determines whether or not the temperature of the urea water acquired in S101 is equal to or higher than the lower limit temperature Ti (S102). When determining that the temperature of the urea water is equal to or higher than the lower limit temperature Ti in S102 (S102: Yes), the current control unit 52 sets the drive mode of the injector 20 to the normal operation mode (S103). Accordingly, the current control unit 52 sets the current I supplied to the coil 33 of the electromagnetic drive unit 23 to be equal to or higher than the upper limit current value Ia. The current control unit 52 supplies a current I equal to or higher than the upper limit current value Ia to the coil 33, and drives the injector 20 (S104). As a result, when current is supplied from the current control unit 52, the injector 20 injects urea water.

  On the other hand, when determining that the temperature of the urea water is lower than the lower limit temperature Ti in S102 (S102: No), the control unit 50 sets the drive mode of the injector 20 to the urea water thawing mode (S105). As a result, the current control unit 52 sets the current I supplied to the coil 33 of the electromagnetic drive unit 23 to be less than the upper limit current value Ia. Therefore, the current control unit 52 supplies the current I less than the upper limit current value Ia to the coil 33 (S106). By controlling the current I supplied to the coil 33 of the electromagnetic drive unit 23 to be not less than the lower limit current value Ib and less than the upper limit current value Ia, the coil 33 generates heat by the supplied current, but the needle 22 is not driven. Therefore, although the needle 22 is not driven, the injector 20 is heated by the heat generated by the coil 33 (S107). As a result, the urea water of the injector 20 considered to be frozen at a temperature lower than the lower limit temperature Ti is thawed by the heat generated by the coil 33.

  The control unit 50 determines whether or not the temperature of the urea water in the urea water tank 14 is equal to or higher than the lower limit temperature Ti even after supplying the current to the coil 33 in S106 (S108). That is, the current control unit 52 determines whether or not the thawing of the urea water in the injector 20 is completed based on the temperature of the urea water in the urea water tank 14. When the controller 50 determines in S108 that the temperature of the urea water is equal to or higher than the lower limit temperature Ti (S108: Yes), the control mode of the injector 20 is set to the normal operation mode (S109). Accordingly, the current control unit 52 sets the current I supplied to the coil 33 of the electromagnetic drive unit 23 to be equal to or higher than the upper limit current value Ia. The current control unit 52 supplies a current I equal to or higher than the upper limit current value Ia to the coil 33, and drives the injector 20 (S110). As a result, the injector 20 injects urea water by supplying current from the current control unit 52. On the other hand, when the control unit 50 determines in S108 that the temperature of the urea water is lower than the lower limit temperature Ti (S108: No), the control unit 50 returns to S107 and continues heating by the heat generation of the coil 33.

  In one embodiment, when the temperature of the urea water in the urea water tank 14 detected by the urea water temperature sensor 42 is lower than a preset lower limit temperature Ti, the current control unit 52 is equal to or higher than the lower limit current value Ib. A current less than the current value Ia is supplied to the coil 33 of the electromagnetic drive unit 23. The needle 22 of the injector 20 that intermittently injects urea water is driven when the current supplied to the coil 33 of the electromagnetic drive unit 23 exceeds the upper limit current value Ia. That is, the needle 22 is not driven even when a current is supplied to the coil 33 when the needle 22 is less than the upper limit current value Ia. Therefore, the injector 20 does not inject urea water when it is less than the upper limit current value Ia. On the other hand, even if the coil 33 of the electromagnetic drive unit 23 is less than the upper limit current value Ia, the coil 33 generates heat by supplying a current equal to or higher than the lower limit current value Ib. Due to the heat generated by the coil 33, the entire injector 20 is heated. Therefore, when the urea water in the injector 20 is frozen, the frozen urea water is thawed by the heat generated by the coil 33 of the electromagnetic drive unit 23. Therefore, it is possible to avoid the addition of urea water at a time other than the predetermined time while promoting thawing of the urea water.

  In one embodiment, the lower limit temperature Ti is set to the melting point of urea water. Therefore, the current control unit 52 controls the current supplied to the coil 33 to be less than the upper limit current value Ia only when the urea water stored in the urea water tank 14 is frozen. Therefore, energization for useless thawing is reduced, and energy consumption can be reduced.

  Furthermore, in one embodiment, the temperature of the urea water in the injector 20 is determined based on the temperature of the urea water detected by the urea water temperature sensor 42 of the urea water tank 14. The urea water temperature sensor 42 of the urea water tank 14 is always provided when configuring the exhaust purification device 10. Therefore, a new configuration is not required to acquire the temperature of the urea water, and an increase in the number of parts and a complicated structure can be suppressed.

(Other embodiments)
In the above-described embodiment, the control unit 50 determines whether or not the thawing of the urea water is completed based on the temperature of the urea water in the urea water tank 14 in S108. However, determination of thawing of urea water may be performed based on other criteria instead of the above example. Specifically, the control unit 50 acquires an elapsed time after starting the supply of current to the coil 33 of the injector 20 in S106, and determines whether or not this elapsed time has reached a preset thawing time. May be. That is, when sufficient time has elapsed since the supply of current to the coil 33 of the injector 20 is started in S106, it is highly likely that the urea water of the injector 20 has been thawed. Therefore, even if the current control unit 52 determines that the thawing of urea water in the injector 20 has been completed based on whether or not the elapsed time since the supply of current to the coil 33 has started reaches the thawing time. Good. Further, the control unit 50 determines that the thawing of the urea water in the injector 20 is completed in S108 when a preset duration has elapsed after the temperature of the urea water in the urea water tank 14 is equal to or higher than the lower limit temperature Ti. May be.

  In this way, by determining whether the urea water is thawed based on the thawing time or the duration time, the timing for stopping the energization of the coil 33 is controlled with a simple configuration. Further, unnecessary energization to the coil 33 is also reduced. Therefore, it is possible to avoid a complicated structure and reduce power consumption.

  The present invention described above is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

  In the drawings, 10 is an exhaust purification device, 13 is an exhaust passage, 14 is a urea water tank, 20 is an injector, 22 is a needle (valve member), 23 is an electromagnetic drive unit, 40 is an injector control device, and 42 is a urea water temperature sensor. (Temperature detection means), 51 is a temperature acquisition part (temperature detection means), 52 is a current control part (current control means).

Claims (4)

A valve member (22) for intermittently injecting urea water, and when the supplied current exceeds a preset upper limit current value, the valve member (22) is driven to supply liquid to the exhaust flowing through the exhaust passage (13). An injector (20) having an electromagnetic drive (23) for injecting urea water;
Temperature detecting means (42, 51) for directly or indirectly detecting the temperature of the urea water supplied to the injector (20);
When the temperature of the urea water detected by the temperature detection means (42, 51) is lower than a preset lower limit temperature, a current control means (supplies current less than the upper limit current value) to the electromagnetic drive unit (23). 52),
An injector control device for an exhaust emission control device.   The injector control device for an exhaust emission control device according to claim 1, wherein the lower limit temperature is a melting point of the urea water.   The current control means (52), when starting a supply of a current less than the upper limit current value to the electromagnetic drive unit (23) and a preset thawing time has elapsed, to the electromagnetic drive unit (23) The injector control device according to claim 1 or 2, which stops energization.   The injector control device according to any one of claims 1 to 3, wherein the temperature detecting means is a urea water temperature sensor (42) for detecting a temperature of the urea water stored in the urea water tank.

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