car

Abstract

To provide a structure that can ensure scavenging of a crank case while ensuring an operation of a brake.SOLUTION: An engine includes a vacuum pump 25 assisting a brake booster 26, and an exhaust port of the vacuum pump 25 is connected to a crank case 39 via a scavenging passage 38. A vacuum passage 35 and a fresh air passage 36 are connected via a three-way valve 37. During non-operation of a brake in a high load region, while fresh air is taken in, the vacuum pump 25 is driven to scavenge the crank case 39. During operation of the brake, the vacuum pump 25 is driven to assist the brake booster 26. In a low load region, the brake booster 26 is driven with intake negative pressure, and when a gas concentration in the crank case 39 exceeds a reference value, while fresh air is taken in, the vacuum pump 25 is driven to forcedly scavenge the crank case 39.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle equipped with a brake booster assisted by a vacuum pump and a blow-by gas recirculation system, and in particular to a vehicle equipped with a hydrogen engine as a power source. Against It's made into an elephant. [Background technology]

[0002] Hydrogen has long been attracting attention as a clean fuel to replace petroleum, and research has been conducted into using hydrogen as a fuel for automobile engines, but it has not yet been put to practical use. One of the reasons for this is that hydrogen has only one-fifteenth the mass of air and is highly volatile and flammable. In other words, safety issues lie at the heart of the practical application of hydrogen engines.

[0003] The safety of hydrogen engines can be considered from several perspectives, one of which is blow-by gas. In both gasoline and diesel engines, a small amount of fuel blows from the combustion chamber into the crankcase as blow-by gas. This blow-by gas is then recirculated from the PCV passage to the intake passage with the oil removed. However, because hydrogen is highly flammable, even a small amount of flame could blow through to the crankcase, causing serious damage to the hydrogen that has been blown into the crankcase and burning.

[0004] Therefore, management of blow-by gas is extremely important in a hydrogen engine, and it is necessary to actively scavenge the crankcase 39 to maintain the hydrogen concentration of the blow-by gas below a safe value.

[0005] On the other hand, in the case of automobiles such as passenger cars (excluding buses and large trucks), the brake force is generally amplified by a vacuum-operated brake booster and transmitted to the master cylinder. However, due to the widespread use of turbochargers, there are cases where the necessary vacuum cannot be secured by the intake system alone, so a mechanical or electric vacuum pump is installed to generate the vacuum for the brake booster.

[0006] Patent Document 1 also discloses that the concentration of blow-by gas is reduced by sending exhaust from a vacuum pump for a brake booster to a crankcase (in this embodiment, a valve chamber) and scavenging the crankcase.

[0007] Specifically, Patent Document 1 discloses a flow path switching device that can be switched between a first position and a second position. When the engine is under low load and the intake passage has a negative pressure below a predetermined value, the switching device is in the second position, the PCV valve is open, and blow-by gas is naturally circulated, and the vacuum pump is activated to assist the brake booster. On the other hand, when the engine is under high load and the internal pressure of the intake passage is equal to or greater than a predetermined value, the switching device shifts to the first position, the vacuum pump is activated, and exhaust (fresh air) is forcibly sent to the crankcase to scavenge the crankcase. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-115683 Summary of the Invention [Problem to be solved by the invention]

[0009] In Patent Document 1, when the switching device is shifted to the first position, fresh air is drawn in by the vacuum pump and sent to the crankcase to scavenge the interior of the crankcase. However, in this state, the suction force of the vacuum pump does not act on the brake booster. Therefore, the vacuum pump cannot scavenge the crankcase while assisting the brake booster. However, the need to prioritize the brake booster may result in neglecting crankcase scavenging. Therefore, when applied to a hydrogen engine, concerns remain as to whether the crankcase can be scavenged to a safe state.

[0010] In addition, in either state, the brake booster is disconnected from the intake passage, and the brake booster is operated solely by the vacuum pump, so it is difficult to say that there are sufficient measures in place in case the vacuum pump fails.

[0011] The present invention was made against the background of the current situation. In hydrogen engine vehicles, The present invention discloses a technique for improving the reliability of brake booster operation and the reliability of blow-by gas scavenging. [Means for solving the problem]

[0012] The engine of the present invention comprises: " Hydrogen-fueled A PCV passage that returns blow-by gas that has passed through the engine crankcase to the intake passage, a vacuum passage connected to an exhaust port of the brake booster and a suction port of the vacuum pump; a scavenging passage communicating with an exhaust port of the vacuum pump and a crankcase; a PCV valve provided in the PCV passage so as to open when the intake passage is under negative pressure; and a fresh air passage communicating with the vacuum passage and the intake passage. This is the basic structure.

[0013] In the above basic configuration, "When the internal pressure of the intake passage becomes higher on the positive pressure side than a predetermined value, the vacuum pump is driven to increase the negative pressure acting on the brake booster, and when the concentration of blow-by gas in the crankcase becomes higher than a predetermined value, the fresh air passage and the vacuum passage are communicated, and the vacuum pump is controlled to be driven, even if the internal pressure of the intake passage is below the predetermined value." It has the following characteristics.

[0014] In the present invention, control is achieved by a combination of switching the passages and turning the vacuum pump on and off. The passages are switched using a valve, which can be a three-way valve or a two-way valve that simply opens and closes the flow path. Valve switching and vacuum pump operation can be controlled using factors such as hydrogen concentration, intake vacuum, brake vacuum, brake pedal force (acceleration), engine speed, and load. [Effects of the Invention]

[0015] In the present invention, the vacuum pump's negative pressure acts on the brake booster, while the exhaust gas from the vacuum pump is sent to the crankcase to scavenge the inside of the crankcase. This ensures reliable brake operation and ensures safe driving, while preventing the concentration of blow-by gas in the crankcase from exceeding the standard, allowing for safe engine operation. Furthermore, the brake booster can also be activated by intake negative pressure, further enhancing safety.

[0016] Therefore, B It is necessary to strictly control the concentration of roby gas. hydrogen This is suitable for automobiles equipped with an engine. In addition, since the crankcase is scavenged using the vacuum pump that operates the brake booster, the structure does not become complicated. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of an embodiment. [Figure 2] (A) and (B) are schematic diagrams of modified examples. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, an embodiment of the present invention will be described. This embodiment is embodied in an automobile equipped with a four-stroke multi-cylinder hydrogen engine. In the following, the terms "front-rear" and "left-right" are used to specify directions, but the front-rear direction is the direction of the engine crankshaft axis, and the left-right direction is the direction perpendicular to the crankshaft axis and the cylinder bore axis.

[0019] (1) Structure of the embodiment The engine is located in an engine room at the front of the vehicle. The basic structure of the engine is the same as that of a conventional engine, and the engine body comprises a cylinder block 1, a cylinder head 2 fixed to the upper surface of the cylinder block 1, a head cover 3 fixed to the upper surface of the cylinder head 2, and an oil pan 4 fixed to the lower surface of the cylinder block 1. The front surfaces of the cylinder block 1 and head cover 3 are covered by a front cover (not shown), and a timing chain (not shown) is located in the space enclosed by the front cover, cylinder block 1, and head cover 3.

[0020] A crankshaft 5 is rotatably held in the cylinder block 1 via a crank cap, and a piston 7 slidably inserted into the cylinder bore 3 and a crank pin 8 of the crankshaft 5 are connected by a connecting rod 9 so that they can move relative to each other.

[0021] The cylinder head 2 is formed with intake ports 10, each of which has a start end opening into the intake side surface 2a and a finish end opening into the cylinder bore 6, and exhaust ports 11, each of which has a start end opening into the cylinder bore 6 and a finish end opening into the exhaust side surface 2b. The intake ports 10 are opened and closed by intake valves 12, and the exhaust ports 11 are opened and closed by exhaust valves 13. Needless to say, the valves 12 and 13 are driven by cams attached to camshafts 14 and 15.

[0022] An intake manifold 16 is fixed to the intake side surface 2a of the cylinder head 2, and an exhaust manifold or an exhaust turbocharger (neither shown) is fixed to the exhaust side surface 2b of the cylinder head 2. The intake manifold 16 is equipped with a surge tank 16a and multiple branch passages 16b branching off from it. A throttle valve 17 is fixed to the surge tank 16a, and the branch passages 16b are connected to the intake port 10.

[0023] A fuel injection valve (injector) 18 is disposed above each intake port 10 in the cylinder head 2, while a spark plug (not shown) is disposed on the surface of the cylinder head 2 facing the cylinder bore 6. Therefore, although the engine of this embodiment is a port injection type, a direct injection type in which the fuel injection valve 18 is exposed toward the cylinder bore 6 can also be used.

[0024] The engine of this embodiment is a hydrogen engine that uses liquid hydrogen as fuel, and therefore the liquid hydrogen is atomized and ejected from the fuel injection valves 18. The hydrogen fuel may be supplied to each individual fuel injection valve 18 through piping, or may be supplied from a single delivery pipe extending longitudinally from front to rear.

[0025] The internal combustion engine is equipped with an air cleaner 19 as a component of its intake system, and an intake duct 20 is connected to a clean chamber 19a of the air cleaner 19, and the intake duct 20 is connected to a throttle valve 17. The intake duct 20 and the intake manifold 16 together form an intake passage.

[0026] To be precise, the throttle valve 17 comprises a cylindrical throttle body, a butterfly valve element, and a motor (actuator) that drives the valve element, and the opening of the valve element is controlled by an ECU (engine control unit) 21. If the engine is equipped with a supercharger such as an exhaust turbocharger, a compressor of the supercharger will be located midway through the intake duct 20.

[0027] A PCV separator chamber 22 into which blow-by gas flows is provided on one side of the cylinder block 1, and the PCV separator chamber 22 and surge tank 16a are connected by a PCV passage 23. A PCV valve 24 that opens when negative pressure is applied is provided in the PCV separator chamber 22, but the PCV valve 24 can be provided at any location in the PCV passage 23.

[0028] The PCV separator chamber 22 may be provided in the head cover 3. That is, a baffle plate may be disposed inside the head cover 3, and the PCV separator chamber 22 may be formed between the baffle plate and the head cover 3. In this case, the head cover 3 and the surge tank 16a are connected by a PCV passage. In this case, blow-by gas flows into the PCV separator chamber 22 from passages provided in the cylinder block 1 and the cylinder head 2.

[0029] The engine is equipped with a vacuum pump 25 as an auxiliary device. The vacuum pump 25 is either mechanical or electric, and if mechanical, is driven by one of the camshafts 14, 15 or by power extracted from the crankshaft 5.

[0030] The vacuum pump 25 basically drives a brake booster 26, and when the driver steps on a brake pedal 27, the movement is amplified by the brake booster 26 and transmitted to a master cylinder (not shown). Reference numeral 28 denotes a cylinder, 29 a piston, 30 a valve chamber for switching negative pressure, and 31 a plunger that serves as a valve body, and the brake pedal 27, plunger 31, and piston 29 move together. The cylinder 28 and valve chamber 30 are connected by first and second pipes 32 and 33. Reference numeral 34 denotes an atmosphere release port.

[0031] The suction port of the vacuum pump 25 and the exhaust port of the brake booster 26 are connected by a vacuum passage 35, while a fresh air passage 36 branches off from the surge tank 16a (or the intake duct 20), and the fresh air passage 36 and the vacuum passage 35 are connected by a three-way valve 37.

[0032] The three-way valve 37 has three ports, 1st to 3rd, 37a, 37b, and 37c, with the first port 37a connected to the side of the vacuum passage 35 that faces the brake booster 26, the second port 37b connected to the fresh air passage 36, and the third port 37c connected to the side of the vacuum passage 35 that faces the vacuum pump 25.

[0033] The three-way valve 37 can be switched between a first state in which the three intake ports 37a, 37b, and 37c are connected to one another, and a second state in which the first port 37a is connected to the third port 37c and the second port 37b is blocked. The exhaust port of the vacuum pump 25 is connected to a crankcase 39 via a scavenging passage 38.

[0034] A number of sensors are electrically connected to the ECU 21 for control purposes, including a depression force sensor (acceleration sensor) 40 for the brake pedal 27, a negative pressure detection sensor 41 for the brake booster 26, an intake pressure sensor 42 provided in the surge tank 16a, a hydrogen concentration sensor 43 provided in the crankcase 39, and a rotation sensor 44 that detects the rotation speed (angular velocity) of the crankshaft 5. The drive motor and opening sensor for the throttle valve 17, the control unit for the fuel injection valve 18, and the like are also connected to the ECU 21.

[0035] (2) Summary In the above configuration, the vacuum pump 25 and three-way valve 37 are controlled based on factors such as the intake negative pressure in the surge tank 16a and the hydrogen concentration in the crankcase 39. That is, first, when the intake negative pressure in the surge tank 16a is lower than a predetermined reference value (higher on the negative pressure side) because the engine is in a low load range, and the hydrogen concentration inside the crankcase 39 is lower than the predetermined reference value, the three-way valve 37 is in a first state in which all ports 37a, 37b, and 37c are connected, and the vacuum pump 25 is not driven.

[0036] Therefore, in this state, the brake booster 26 is driven only by the intake vacuum. Also, because the PCV valve 24 opens due to vacuum, scavenging of the crankcase 39 is performed by the PCV valve 24. Note that, as shown by the dashed-dotted line, it is also possible to connect the clean chamber 18a of the air cleaner 19 to the head cover 3 via a ventilation passage 45. In this case, gas flows smoothly through the valve chamber and crankcase 39, thereby facilitating scavenging and ventilation by the PCV valve 24.

[0037] Next, when the engine is in a high load state, etc., and the intake negative pressure in the surge tank 16a is higher on the positive pressure side than a predetermined value, the negative pressure acting on the brake booster 26 is insufficient, so when the brake pedal 27 is depressed, the three-way valve 37 is switched to the second state in which the fresh air passage 36 is blocked and the first port 37a and the third port 37c are connected, and the vacuum pump 25 is driven.

[0038] In this case, the vacuum pump 25 is nearly idling, but when the brake pedal 27 is depressed, the engine slows down and the surge tank 16a becomes negative pressure, which opens the PCV valve 24 and allows hydrogen in the crankcase 39 to be discharged.

[0039] Under high-load operating conditions, the amount of blow-by gas also increases, but if the accelerator pedal continues to be depressed without the brake pedal 27 being depressed (or if there is no significant change in the opening of the throttle valve 17), and if the hydrogen concentration in the crankcase 39 exceeds a reference value, the three-way valve 37 is switched to the second state and the vacuum pump 25 is driven, so that fresh air is sent from the exhaust port of the vacuum pump 25 to the crankcase 39, thereby scavenging the crankcase 39. In this case, a pressure difference occurs between the crankcase 39 and the surge tank 16a, and the surge tank side of the PCV passage 23 becomes relatively negative pressure, so the PCV valve 24 opens and the hydrogen (blow-by gas) in the crankcase 39 is discharged.

[0040] Next, when the load is low and the negative pressure in the surge tank 16a is lower than a predetermined value, but the hydrogen concentration in the crankcase 39 is higher than the reference value, the three-way valve 37 remains in the first position and drives the vacuum pump 25. As a result, fresh air is exhausted from the vacuum pump 25 and flows into the crankcase 39, creating a pressure difference between the crankcase 39 and the surge tank 16a, opening the PCV valve 24 and scavenging the hydrogen gas.

[0041] In this case, both the negative pressure of the surge tank 16a and the negative pressure of the vacuum pump 25 act on the brake booster 26, but the brakes can be applied appropriately in either case. As described above, this embodiment ensures the operation of the brake booster 26 while scavenging the inside of the crankcase 39 as needed, thereby keeping the hydrogen concentration below the reference value regardless of the operating state and ensuring safety.

[0042] The above explanation is the basics of control, but it can be corrected based on auxiliary factors. For example, if the negative pressure in the brake booster 26 differs from the negative pressure in the surge tank 16a, the switching of the three-way valve 37 and the ON / OFF of the vacuum pump 25 can be controlled by giving priority to the negative pressure in the brake booster 26.

[0043] 1 uses a three-way valve 37 as the valve device, but as an example of the valve device, as shown in Figure 2(A), a simple switching valve 46 may be provided only in the fresh air passage 36, or as shown in Figure 2(B), a switching valve 46 may be provided in the fresh air passage 36 and also in the vacuum passage 35 on the brake booster 26 side. In the example of Figure 2(B), by closing the switching valve 46 in the vacuum passage 35 and opening the switching valve 46 in the fresh air passage 36, fresh air can be sucked in by the vacuum pump 25 and sent to the crankcase 39. [Industrial Applicability]

[0044] The present invention is a vacuum pump equipped hydrogen The present invention can be applied to engine-driven automobiles, and therefore can be used industrially. [Explanation of symbols]

[0045] 1 Cylinder block 2. Cylinder head 3 Headcover 6 cylinder bore 7 Pistons 16. Intake manifold that forms the intake passage 16a Surge Tank 17 Throttle valve 20 Intake duct that constitutes the intake passage 21 ECU 22 PCV separator room 23 PCV passage 24 PCV valve 25 Vacuum Pump 26 Brake booster 27 Brake pedal 35 Vacuum Passage 36 New Air Passage 37 Three-way valve 38 Scavenging passage 39 Crankcase

Claims

[Claim 1] A PCV passage that returns blow-by gas that has passed through the crankcase of a hydrogen-fueled engine to an intake passage; a vacuum passage connected to an exhaust port of the brake booster and a suction port of the vacuum pump; a scavenging passage communicating with an exhaust port of the vacuum pump and a crankcase; a PCV valve provided in the PCV passage so as to open when the intake passage is under negative pressure; a fresh air passage communicating with the vacuum passage and the intake passage, When the internal pressure of the intake passage becomes higher on the positive pressure side than a predetermined value, the vacuum pump is driven to increase the negative pressure acting on the brake booster, and when the concentration of blow-by gas in the crankcase becomes higher than a predetermined value, the fresh air passage and the vacuum passage are communicated with each other and the vacuum pump is driven, even if the internal pressure of the intake passage is equal to or lower than the predetermined value. car.

Images