JP2015169100A - Engine start assist device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine start assist device which can obtain favorable startability even if a cylinder in a valve-overlap state exists at a stop of the engine.SOLUTION: In an intake/exhaust system of an engine, there are arranged: a negative pressure chamber 45 which accumulates negative pressure; a negative pressure introduction passage 46 which introduces the negative pressure to the negative pressure chamber 45 from an intake passage; a first check valve 47 which is interposed at the negative pressure introduction passage, and permits the circulation of a gas to the intake passage side from the negative pressure chamber 45 side; an exhaust gas introduction passage 48 which introduces an exhaust gas to the negative pressure chamber 45 from an exhaust passage; a second check valve 49 which is interposed at the exhaust gas introduction passage 48, and permits the circulation of the gas to the negative pressure chamber 45 side from the exhaust passage side; and an exhaust introduction valve 50 which is interposed at the exhaust gas introduction passage 48, and valve-opened only at a start of an engine 1.

Description

  The present invention relates to an engine start assist device that controls the flow of intake and exhaust during engine start.

  2. Description of the Related Art Conventionally, in an engine mounted on a vehicle such as an automobile, various techniques have been proposed for improving startability by controlling the flow of intake and exhaust at the time of start. For example, Patent Document 1 discloses that when a request for starting an internal combustion engine is detected, the throttle valve is closed, the internal combustion engine is cranked by cranking means, and fuel injection from the fuel injection valve is started. In addition, a technique for reducing engine start shock while maintaining startability by opening a throttle valve to a predetermined opening is disclosed.

JP 2010-203346 A

  However, even when the countermeasures as described in Patent Document 1 described above are performed, for example, when there is a valve overlapped cylinder in which both the intake valve and the exhaust valve are opened in the stopped engine, When starting the engine, the exhaust gas may flow backward to the intake side through the valve overlap cylinder. When the exhaust gas flows backward to the intake side in this way, the ignitability of the fuel temporarily decreases, and there is a risk that a so-called long cranking state that takes a long time to complete the start-up may occur.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an engine start assist device capable of realizing good startability even when a valve overlapped cylinder exists when the engine is stopped. To do.

  An engine start assist device according to an aspect of the present invention includes a negative pressure chamber for accumulating negative pressure, a negative pressure introduction path for introducing a negative pressure from an intake passage to the negative pressure chamber, and an interposition in the negative pressure introduction path. A first check valve that allows gas to flow from the negative pressure chamber side to the intake passage side, an exhaust gas introduction passage that introduces exhaust gas from the exhaust passage to the negative pressure chamber, and the exhaust gas introduction A second check valve that is interposed in the passage and allows gas to flow from the exhaust passage side to the negative pressure chamber side, and an exhaust that is interposed in the exhaust gas introduction passage and opens only when the engine is started And an introduction valve.

  According to the engine start assist device of the present invention, good startability can be realized even when there are cylinders in a valve overlap state when the engine is stopped.

Schematic configuration diagram of the engine according to the first embodiment Same as above, schematic configuration diagram of engine start control system Same as above, flowchart showing engine start control routine Schematic configuration diagram of an engine related to the second embodiment Same as above, schematic configuration diagram of engine start control system Same as above, flowchart showing engine start control routine

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 3 relate to a first embodiment of the present invention, FIG. 1 is a schematic configuration diagram of an engine, FIG. 2 is a schematic configuration diagram of an engine start control system, and FIG. 3 is a flowchart showing an engine start control routine. is there.

  The engine 1 shown in FIG. 1 is a horizontally opposed engine, for example. The left and right banks of the engine 1 are provided with left and right cylinder heads 2, and each cylinder head 2 has an intake port 3 and an exhaust port 5 corresponding to the cylinder formed in each bank. Yes.

  The intake port 3 of each cylinder head 2 is gathered in the air chamber 6 via the intake manifold 4 on the upstream side. Further, a throttle passage 7 communicates with the upstream side of the air chamber 6, and an air cleaner 10 is attached to the upstream side of the throttle passage 7 via an intake pipe 9. The throttle passage 7 is provided with, for example, an electronically controlled throttle valve 8 that is opened and closed by a throttle actuator 8a.

  On the other hand, the downstream side of the exhaust port 5 of each cylinder head 2 is gathered via the exhaust manifold 11 and communicated with the exhaust pipe 12. A catalyst 13 is interposed in the middle of the exhaust pipe 12, and a muffler 14 is communicated with the downstream end of the exhaust pipe 12.

  In addition, an injector 31 is faced immediately upstream of the intake port 3 of each cylinder of the intake manifold 4, and a spark plug 32 is attached to a portion corresponding to each cylinder of the cylinder head 2 so that its ignition part faces the cylinder. ing.

  Each intake port 3 formed in the cylinder head 2 is provided with an intake valve 37, and each exhaust port 5 is provided with an exhaust valve 38. Further, the cylinder head 2 is provided with an intake cam shaft 39 and an exhaust cam shaft 40 that open and close the intake valve 37 and the exhaust valve 38 at a predetermined timing, and the cam shafts 39 and 40 are not shown in timing. Synchronous rotation is performed at 1/2 rotation with respect to one rotation of the crankshaft 1b via the belt. The intake valve 37 and the exhaust valve 38 that are opened and closed by the intake camshaft 39 and the exhaust camshaft 40 have a valve overlap period in which both valves open from the latter half of the exhaust stroke to the first half of the intake stroke. ing.

  Further, a crank rotor 34 is mounted on the crankshaft 1b, and an engine speed sensor 35 is provided on the outer periphery of the crank rotor 34. Protrusions (or slits) are formed on the outer periphery of the crank rotor 34 at predetermined intervals, and the engine speed sensor 35 detects the interval time when the passage of each protrusion (or each slit) of the crank rotor 34 is detected. The engine speed Ne is detected based on a preset crank angle.

  Further, the engine 1 configured as described above is provided with a negative pressure chamber 45 for accumulating negative pressure. For example, a throttle passage 7 constituting an intake passage of the engine 1 is communicated with the negative pressure chamber 45 via a negative pressure introduction passage 46 on the downstream side of the throttle valve 8. A first check valve 47 that allows gas to flow from the negative pressure chamber 45 side to the throttle passage 7 side is interposed in the middle of the negative pressure introduction path 46. As a result, negative pressure is introduced into the negative pressure chamber 45 by the venturi effect of the intake air flowing through the intake passage when the engine 1 is driven.

  Further, for example, the upstream side of the exhaust pipe 12 constituting the exhaust passage of the engine 1 is connected to the negative pressure chamber 45 via an exhaust gas introduction passage 48. A second check valve 49 that allows gas to flow from the exhaust pipe 12 side to the negative pressure chamber 45 side is interposed in the middle of the exhaust gas introduction path 48. Further, an exhaust introduction valve 50 that opens and closes the middle of the exhaust gas introduction path 48 is interposed in the middle of the exhaust gas introduction path 48. The exhaust introduction valve 50 is constituted by, for example, a normally closed electromagnetic valve, and opens when energized under the control of an engine control unit (ECU) 60 described later. When the exhaust introduction valve 50 is opened, the exhaust gas in the exhaust passage is introduced into the negative pressure chamber 45 by the negative pressure accumulated in the negative pressure chamber 45.

  The ECU 60 is mainly composed of a microcomputer and has a known CPU, ROM, RAM, and the like. The ECU 60 performs calculations necessary for various controls in accordance with a program stored in the ROM in the CPU.

  As shown in FIG. 2, for example, an engine speed sensor 35 is connected to the input side of the ECU 60, and further, an ignition switch 61, a starter switch 62, and the like are connected. On the other hand, to the output side of the ECU 60, for example, an exhaust introduction valve 50 is connected, and further, a starter motor 63 of the engine 1 is connected. The ECU 60 performs opening / closing control of the exhaust introduction valve 50 together with start control of the engine 1 using the starter motor 63.

  Such start control is executed, for example, according to the flowchart of the engine start control routine shown in FIG. In the present embodiment, the description will be made on the assumption that the negative pressure generated by the previous engine drive is accumulated in the negative pressure chamber 45 when the engine 1 is stopped.

  This routine is repeatedly executed at predetermined time intervals in the ECU 60 while the ignition switch 61 is ON. When the routine starts, the ECU 60 first checks in step S101 whether, for example, a determination to start cranking for the engine 1 has been made based on, for example, the pressed state of the starter switch 62 or the like.

  If it is determined in step S101 that it is currently determined to start cranking, the ECU 60 proceeds to step S102 to turn on the starter motor 63, and in step S103, the exhaust introduction valve 50 is turned on. After opening, exit the routine.

  By these controls, cranking of the engine 1 is started. Further, substantially simultaneously with the start of cranking, the exhaust gas in the exhaust passage is brought into the negative pressure chamber 45 by the negative pressure accumulated in the negative pressure chamber 45. be introduced. The introduction of the exhaust gas into the negative pressure chamber 45 creates a flow of exhaust gas from the exhaust port 5 toward the downstream side of the exhaust passage almost simultaneously with the start of cranking of the engine 1. Even if there is a cylinder in the valve overlap state at the time of stoppage of 1, the exhaust gas is prevented from flowing backward to the intake side.

  On the other hand, if it is determined in step S101 that it is not currently determined to start cranking, the ECU 60 proceeds to step S104 and checks whether the starter motor 63 is currently in the ON state.

  If it is determined in step S104 that the starter motor 63 is currently in the OFF state, the ECU 60 directly exits the routine.

  On the other hand, if it is determined in step S104 that the starter motor 63 is currently in the ON state, the ECU 60 proceeds to step S105, for example, based on the engine speed Ne detected by the engine speed sensor 35 and the like. Then, it is checked whether or not a determination to end the cranking (complete explosion determination or the like) has been made.

  If it is determined in step S105 that it is not currently determined to end the cranking, the ECU 60 directly exits the routine.

  On the other hand, if it is determined in step S105 that it is currently determined to end the cranking, the ECU 60 proceeds to step S106, turns off the starter motor 63, and in the subsequent step S107, the exhaust introduction valve 50 is turned off. After closing, exit the routine.

  By these controls, after the cranking of the engine 1 is completed and the starter motor 63 is turned off, the introduction of the exhaust gas into the negative pressure chamber 45 through the exhaust gas introduction path 48 is prohibited. Further, when the engine 1 is started and a flow velocity higher than a predetermined level is generated in the intake air flowing through the intake passage, the negative pressure is introduced into the negative pressure introduction passage 46 due to the venturi effect at the junction with the throttle passage 7 (intake passage). Will occur. Due to the generated negative pressure, the exhaust gas introduced into the negative pressure chamber 45 at the time of cranking is discharged to the exhaust passage side, and the negative pressure is accumulated in the negative pressure chamber 45 again.

  According to such an embodiment, the negative pressure chamber 45 that accumulates negative pressure, the negative pressure introduction path 46 that introduces negative pressure from the intake passage to the negative pressure chamber 45, and the negative pressure introduction path that is interposed in the negative pressure introduction path. A first check valve 47 that allows gas to flow from the pressure chamber 45 side to the intake passage side, an exhaust gas introduction passage 48 that introduces exhaust gas from the exhaust passage into the negative pressure chamber 45, and an exhaust gas introduction passage 48. A second check valve 49 that is interposed and allows gas flow from the exhaust passage side to the negative pressure chamber 45 side, and an exhaust introduction that is interposed in the exhaust gas introduction path 48 and opens only when the engine 1 is started. By providing the valve 50 in the intake / exhaust system of the engine 1, good startability can be realized even when there is a valve-overlapping cylinder when the engine 1 is stopped.

  That is, when the engine 1 is started (cranking), the exhaust introduction valve 50 is opened, and the exhaust gas is introduced into the negative pressure chamber 45 using the negative pressure accumulated in the negative pressure chamber 45. The exhaust gas flow from the upstream side to the downstream side can be generated in the exhaust passage (particularly, in the exhaust manifold 11). By generating the flow of exhaust gas in this way, even if a cylinder in a valve overlap state exists when the engine 1 is stopped, the exhaust gas is brought to the intake side through the valve overlap cylinder. Backflow can be accurately prevented, and long cranking caused by a temporary decrease in the ignitability of the fuel can be prevented.

  Next, FIGS. 4 to 6 relate to a second embodiment of the present invention, FIG. 4 is a schematic configuration diagram of an engine, FIG. 5 is a schematic configuration diagram of an engine start control system, and FIG. 6 is an engine start control routine. It is a flowchart to show. In the present embodiment, the negative pressure chamber provided in the brake booster of the brake device is also used as a negative pressure chamber for assisting when the engine 1 is started. It differs primarily from one embodiment. In addition, about the structure similar to the above-mentioned 1st Embodiment, a same sign is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 4, the brake booster 70 includes a booster cylinder 71. The booster cylinder 71 accommodates a power piston 74 that is linked to the brake pedal 73 via the operating rod 72, and the power piston 74 is slidable in the booster cylinder 71. The booster cylinder 71 is partitioned into a booster negative pressure chamber 75 and a booster atmospheric chamber 76 by the power piston 74.

  The booster negative pressure chamber 75 communicates with the downstream side of the throttle passage 7 via the negative pressure introduction path 46, and further communicates with the upstream side of the exhaust pipe 12 via the exhaust gas introduction path 48.

  On the other hand, a branch passage 46 a that branches from the negative pressure introduction passage 46 and an air passage 77 that opens the booster atmosphere chamber 76 to the atmosphere are connected to the booster atmosphere chamber 76. Further, a switching valve 80 is interposed in the middle of the branch passage 46 a and the air passage 77. The switching valve 80 variably switches the communication amount of the branch passage 46 a and the air passage 77 with respect to the booster atmospheric chamber 76 in conjunction with the operation amount of the brake pedal 73.

  That is, the switching valve 80 includes a valve body 81 interposed in the middle of the branch path 46 a and the air passage 77, and a valve plunger 82 accommodated in the valve body 81. A brake pedal 73 is connected to the valve plunger 82 via an operating rod 72. The valve plunger 82 decreases the amount of communication of the branch path 46a with the booster atmospheric chamber 76 as the amount of depression of the brake pedal 73 increases. The communication amount of the air passage 77 can be increased. As a result, a differential pressure is generated between the booster negative pressure chamber 75 and the booster atmospheric chamber 76, and the brake booster 70 increases the brake pedal force of the driver by this differential pressure.

  In the present embodiment having such a configuration, the booster negative pressure chamber 75 is also used as a negative pressure chamber for introducing the exhaust gas in the exhaust passage when the engine 1 is started.

  Here, in order to prevent the exhaust gas introduced into the booster negative pressure chamber 75 from being discharged to the outside through the branch passage 46a, the booster atmospheric chamber 76, and the air passage 77, for example, FIG. As shown in FIG. 5, an air chamber opening valve 83 that is closed when the engine 1 is started is interposed in the middle of the branch path 46a under the control of the ECU 60.

  Further, in the present embodiment in which the booster negative pressure chamber 75 is also used as the negative pressure chamber, the carbon component in the exhaust gas is prevented from being introduced into the brake booster 70 in the middle of the exhaust gas introduction path 48. For this purpose, a filter 84 is interposed.

  In such a configuration, for example, as shown in FIG. 6, in step S <b> 103, the ECU 60 closes the atmosphere chamber opening valve 83 in addition to the opening operation of the exhaust introduction valve 50.

  In step S107, the ECU 60 opens the atmosphere chamber opening valve 83 in addition to closing the exhaust introduction valve 50. The opening operation of the atmospheric chamber opening valve 83 is preferably performed after a predetermined delay time from the closing operation of the exhaust introduction valve 50.

  According to such an embodiment, in addition to the effects obtained by the first embodiment described above, the booster negative pressure chamber 75 of the brake booster 70 is used to improve the startability of the engine 1 with a simple configuration. There is an effect that can be done.

  In this case, the exhaust gas introduced into the booster negative pressure chamber 75 is accurately released into the atmosphere by providing the branch passage 46a with the atmospheric chamber opening valve 83 that is closed when the engine 1 is started. Can be prevented.

  In addition, this invention is not limited to each embodiment described above, A various deformation | transformation and change are possible, and they are also in the technical scope of this invention. For example, it goes without saying that the configurations of the above-described embodiments may be appropriately combined.

  Here, in each of the above-described embodiments, an example in which the exhaust introduction valve 50 is opened to assist the start of the engine 1 when cranking is started according to the operation of the starter switch 62 has been described. Since the start assistance of the engine 1 is based on the premise that a sufficient negative pressure is accumulated in the negative pressure chamber, the engine 1 can be stopped and restarted for a short time, for example, in addition to the start time described above. Particularly suitable application is possible in idle stop control or the like repeatedly performed during the period.

DESCRIPTION OF SYMBOLS 1 ... Engine 1b ... Crankshaft 2 ... Cylinder head 3 ... Intake port 4 ... Intake manifold 5 ... Exhaust port 6 ... Air chamber 7 ... Throttle passage 8 ... Throttle valve 8a ... Throttle actuator 9 ... Intake pipe 10 ... Air cleaner 11 ... Exhaust manifold DESCRIPTION OF SYMBOLS 12 ... Exhaust pipe 13 ... Catalyst 14 ... Muffler 31 ... Injector 32 ... Spark plug 34 ... Crank rotor 35 ... Engine speed sensor 37 ... Intake valve 38 ... Exhaust valve 39 ... Intake cam shaft 40 ... Exhaust cam shaft 45 ... Negative pressure chamber 46 ... Negative pressure introduction path 46a ... Branch path 47 ... First check valve 48 ... Exhaust gas introduction path 49 ... Second check valve 50 ... Exhaust introduction valve 61 ... Ignition switch 62 ... Starter switch 63 ... Starter motor 70 ... Blur Booster 71 ... Booster cylinder 72 ... Operating rod 73 ... Brake pedal 74 ... Power piston 75 ... Booster negative pressure chamber 76 ... Booster air chamber 77 ... Air passage 80 ... Switching valve 81 ... Valve body 82 ... Valve plunger 83 ... Air chamber release valve 84… Filter

Claims (3)

A negative pressure chamber for accumulating negative pressure;
A negative pressure introduction path for introducing a negative pressure from the intake passage to the negative pressure chamber;
A first check valve that is interposed in the negative pressure introduction path and allows gas to flow from the negative pressure chamber side to the intake passage side;
An exhaust gas introduction path for introducing exhaust gas from the exhaust passage into the negative pressure chamber;
A second check valve that is interposed in the exhaust gas introduction passage and allows gas to flow from the exhaust passage side to the negative pressure chamber side;
An engine start assist device comprising: an exhaust introduction valve that is interposed in the exhaust gas introduction path and opens only when the engine is started.   The said negative pressure chamber is combined with the said booster negative pressure chamber of the brake booster which increases the brake depression force of a driver by the differential pressure of a booster negative pressure chamber and a booster atmospheric | air chamber. Engine start assist device. The brake booster is connected to the booster negative pressure chamber, the negative pressure introduction path and the exhaust gas introduction path, and a branch path branched from the negative pressure introduction path to the booster atmospheric chamber; An air passage that opens the booster atmosphere chamber to the atmosphere, and a brake booster that is variably communicated via a switching valve;
The engine start assist device according to claim 2, further comprising an atmosphere chamber opening valve that is interposed in the branch path and closes when the engine is started.

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