JP3384579B2 - Engine with turbocharger - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercharged engine in which one cylinder is provided with two or more intake valves and a supercharger is provided in an intake passage. It is. 2. Description of the Related Art Conventionally, there is widely known an engine in which a supercharger is provided in an intake passage to increase charging efficiency and increase torque. When the charging efficiency is increased by supercharging as described above, knocking is likely to occur in a low-rotation high-load region, and the exhaust temperature is likely to rise in a high-rotation high-load region. Therefore, the improvement of the filling efficiency is easily hindered. In order to prevent knocking in a supercharged engine with respect to such a problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 2-119620, the intake valve closing timing is delayed, or intake / exhaust air is exhausted. A technique for increasing the amount of overlap between valve opening periods is known. That is,
If the intake valve closing timing is greatly delayed from the bottom dead center, the effective compression ratio decreases and the temperature rise due to the compression work is suppressed, so that knock resistance is improved. In addition, when the overlap amount of the intake and exhaust valves during the valve opening period is set to be large, the scavenging property is enhanced, and the knock resistance is enhanced by the reduction of the residual exhaust gas. In order to suppress an increase in exhaust gas temperature in a supercharged engine, see, for example, Japanese Patent Application Laid-Open No. 3-23.
As disclosed in Japanese Patent Publication No. 327, there is an example in which the air-fuel ratio is made lean in a supercharging region. [0005] In order to suppress knocking, in addition to the above, it is conceivable to reduce the diameter of the cylinder bore to shorten the flame propagation distance.
In this case, the relationship between engine reliability and performance requirements has not been sufficiently elucidated. Further, as a method of suppressing the exhaust gas temperature,
In addition to the air-fuel ratio lean as described above, there are those which make the air-fuel ratio richer than necessary in terms of output, and those which increase the compression ratio. However, when the air-fuel ratio is made lean, the output becomes disadvantageous, when the air-fuel ratio is made richer than necessary, the fuel consumption becomes disadvantageous, and when the compression ratio is increased, the knock resistance becomes disadvantageous. Japanese Unexamined Patent Publication No. 60-237153 discloses a device in which EGR can be performed in a supercharged region in a supercharged engine. Therefore, only EGR is performed, and no consideration is given to knock resistance and exhaust temperature. The present invention has been made in view of the above circumstances, and it is possible to effectively suppress the rise in the exhaust temperature in a high-speed and high-load region while improving the knock resistance and increasing the torque by improving the charging efficiency of the engine. It is an object to provide a charged engine. SUMMARY OF THE INVENTION In order to achieve the above object, the intake of a spark-ignition reciprocating piston engine having two or more intake valves in one cylinder and a spark plug is provided. In a supercharged engine having a supercharger in a passage, a cylinder bore diameter is set to 50 mm to 70 mm, a single chamber volume of a cylinder is set to 150 cc to 400 cc, and a ratio (S) between a piston stroke (S) and a cylinder bore diameter (B) is set. / B)
Is 1.07 or more, and the maximum horsepower generating rotation speed of the engine
And the rotation speed (Nb) when the average intake Mach number is 0.5
The piston speed is the limit value 2.0 × 10 ⁴ mm /
s and the rotation speed (Na), and N
a ≧ Nb, Na−Nb ≦ 2000 rpm, Nb ≧ 500
0 rpm, set so that Na ≦ 8000 rpm,
EGR gas supply means for setting the geometric compression ratio (ε) of the engine to 9 or less and supplying EGR gas to the engine at least at high speed and high load via a cooler for cooling EGR gas. Is the geometric compression ratio (ε) of the engine and the EGR rate (R
%), The EGR gas is supplied such that the relationship with the following equation is satisfied. R ≧ (9−ε) · 3 According to the above structure, the knock bore is improved while the small bore having a small cylinder bore diameter is used.
The charging efficiency is increased by the supercharging, and the increase in the exhaust gas temperature at the time of high speed and high load is suppressed by EGR. In particular,
By setting the EGR rate in accordance with the geometric compression ratio ε related to the exhaust gas temperature, the effect of suppressing the exhaust gas temperature is properly obtained. An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows the overall structure of a supercharged engine according to one embodiment of the present invention. The engine illustrated in this figure is a V-type engine, in which an engine main body 1 includes a pair of banks 1A and 1B forming a V-shape with each other, and a plurality of cylinders 2 are arranged in each of the banks 1A and 1B. Three cylinders 2 each are provided. In each of the cylinders 2, first and second two intake ports 3a and 3b and first and second two exhaust ports 4a and 4b are formed so as to open to the combustion chamber. And an intake valve (not shown) in each of the intake ports 3a and 3b.
Are provided, and an exhaust valve (not shown) is provided in each of the exhaust ports 4a and 4b. The valve mechanism that drives the intake valve is provided with a variable valve timing mechanism 5 that can change the opening / closing timing of the intake valve by, for example, changing the phase of the camshaft 6 with respect to the cam pulley. Further, each cylinder 2 is provided with an ignition plug 7 as shown in FIG. 2, and this ignition plug 7 is connected to an ignition circuit 8 including an ignition coil and a distributor. As shown in FIG. 1, an independent intake passage 11 downstream of the intake passage 10 is connected to each of the intake ports 3a and 3b. Is provided. The intake passage 10 includes an intake manifold 12 having the independent intake passages 11 and an upstream common intake passage 13. In the common intake passage 13, an air cleaner 14, an air flow meter 15, and a throttle valve 16 are provided, and a supercharger 17 is provided. The illustrated supercharger 17 is a mechanical supercharger driven by a transmission means such as a belt by an engine output shaft, and more preferably, a supercharger such as a Richolm type supercharger so as to obtain a large pressure ratio. Is used. And, in order to reduce driving loss at low load, etc.
A supercharger 17 is arranged downstream of the throttle valve 16. Further, an intercooler 18 is provided downstream of the supercharger 17.
And a bypass passage 19 that bypasses the turbocharger 17 and a bypass control valve 20 that opens and closes the passage 19. Further, exhaust gas recirculation (EGR) is provided to the intake system.
In the illustrated embodiment, the EGR gas supply means is provided to perform the low load EGR passage 21 and the high load EG.
An R passage 22 is provided. One end of the low-load EGR passage 21 is connected to the exhaust manifold 23,
The other end is branched and connected to each of the independent intake passages 11. A low-load EGR valve 24 is provided in the middle of the low-load EGR passage 21. The high-load EGR passage 22 has one end connected to the exhaust passage 26 downstream of the exhaust purification catalytic converter 25 and the other end connected to the common intake passage 13 upstream of the supercharger 17. I have. The high load EGR passage 22 includes a carbon trap 27, an EGR cooler 28, and a high load EGR.
A valve 29 is provided. When EGR is performed through the high-load EGR passage 22, EGR gas is guided from a relatively downstream side of the exhaust passage to the combustion chamber through a relatively long path, and an EGR cooler 28 is provided. Thereby, the EGR gas is sufficiently cooled. Reference numeral 30 denotes a control unit (ECU) for controlling the engine.
5, and receives signals from the engine speed sensor 31, the throttle opening sensor 32, and the like, controls the fuel injection amount from the injector 9 according to the intake air amount and the like, and controls the ignition timing according to the operating state. In addition, control of the variable valve timing mechanism 5, the bypass control valve 20, and the EGR valves 24 and 29, and the like are performed. [0018] The control of the fuel injection amount, the area has a wide including supercharging region, so that the air-fuel ratio becomes the stoichiometric air-fuel ratio,
Feedback control is performed according to the output of the O ₂ sensor (not shown). In the high load region near the full load, the air-fuel ratio required to increase the output is A / F = 12 to
13 may be controlled. Further, the variable valve timing mechanism includes:
As shown in FIG. 3, the opening / closing timing of the intake valve can be changed between a first timing IV1 on the relatively advanced side and a second timing IV2 that is later than the first timing, thereby opening the exhaust valve (EV). The valve overlap amount O / L and the intake valve closing timing IC can be changed. The intake valve opening / closing timing is controlled by the control unit 30 according to the operation state. For example, the first timing IV1 is on the low load side, and the second timing IV2 is on the high load side. The bypass control valve 20 is controlled so as to be opened on the low load side and closed on the high load side. Also,
In the EGR control, both the EGR valves 24 and 29 are closed in an idling region, the low-load EGR valve 24 is opened in a low-load region other than the idling region, and the high-load EGR valve 29 is opened in a high-load region. It has become. In such an engine, the cylinder bore diameter B is 50 mm to 70 mm, and the single chamber volume of the cylinder is 15 mm.
It is set to 0 cc to 400 cc, and the ratio between the piston stroke (S) and the cylinder bore diameter (B) is a long stroke where S / B> 1. In addition, at the time of high speed and high load,
EGR rate R (%) of EGR gas supplied from passage 22
Is set so as to satisfy the following expression (1) with respect to the geometric compression ratio ε of the engine. R ≧ (9−ε) · 3 (1) The geometric compression ratio ε is set to 9 ≧ ε ≧ 5.5. According to the apparatus of the present embodiment as described above, the cylinder bore diameter B is set so as to be advantageous in suppressing knocking within a range that satisfies the requirements for securing reliability and preventing a sudden increase in intake resistance.
In addition, while the knock resistance is ensured by adjusting the ignition timing, the charging efficiency is increased by the supercharging, and the engine torque is increased. At high speed and high load, sufficiently cooled EGR gas is supplied from the high load EGR passage 22 to the engine at an EGR rate R that satisfies the above equation (1), thereby suppressing a rise in exhaust gas temperature. You. Such an operation will be described below based on the data shown in FIGS. Circumstances for Setting Cylinder Bore Diameter and Action In order to improve knock resistance in an engine with a turbocharger, it is desirable to reduce the cylinder bore diameter as much as possible, and to reduce the bearing load of the crankshaft, the cylinder bore diameter is also reduced. It is desirable. On the other hand, when trying to secure a predetermined displacement by increasing the piston stroke while reducing the cylinder bore diameter, it is necessary to consider the limit on the reliability of the piston speed and the limit due to the sudden increase in the intake resistance due to the reduction of the intake valve. There is. That is, considering the limit on the reliability of the piston speed, the average piston speed Um
Is obtained from the engine rotation speed N and the piston stroke S as in the following equation (2). Um = (N / 30) · S (2) By the way, the limit value of the average piston speed Um is usually Um = 20 m / s (= 2.0 × 10 ⁴ mm / s). ), And when this is substituted into the above equation, the piston stroke at that time is obtained according to the engine speed. Then, the single chamber volume corresponding to the cylinder bore diameter B is obtained based on the piston stroke. This Um = 2.0 ×
A single chamber volume of 10 ⁴ mm / s, with an engine speed of 4
1000rpm from 000rpm to 8000rpm
When each of them is shown corresponding to the cylinder bore diameter, it is as shown by a dashed line in FIG. Also, it is generally known that when the average intake Mach number Mi becomes Mi = 0.5, the intake resistance sharply increases, and thereby the volume efficiency sharply decreases. The average intake Mach number Mi can be expressed as in the following equation (3). [Equation 3] Mi = {Vh · (η _V / 100)} / {a · Fim · (θic−θio) / 6 · N} (3) where, Vh: single chamber volume η _V : Volumetric efficiency a: Sound velocity θic: Intake valve opening timing θio: Intake valve closing timing N: Engine rotation speed Fim: Average intake opening area. Note that the average intake opening area Fim is represented by Fim = Fia /
(Θic−θio). However, Fia
Is the intake valve effective angle area. The starting conditions are defined as follows. (1) Two intake valves and two exhaust valves are provided for each cylinder, the intake valves and the exhaust valves are the same size, and the area ratio between the intake valves and the exhaust valves is 1.5 at the throat portion. . (2) The volumetric efficiency is 100%. (3) Combustion chamber shape: pent roof type (4) Spacing between both intake valve valve seats: 2.5 mm or more (5) Spacing between intake and exhaust valve valve seats: 3.5 mm or more (6) Both exhausts Spacing between valve valve seats: 4.0 mm or more (7) Spacing between intake valve valve seats and spark plugs: 2.5
mm or more (8) Distance between exhaust valve seat and spark plug: 3.5
(9) Valve clamping angle: 30 degrees (10) Plug diameter: diameter 14 mm (11) Stem diameter: diameter 6 mm (12) Throat diameter = valve seat diameter-5 mm (13) Valve lift: 8.5 mm (14) ) Valve opening period: 256 degCA If these conditions are specified, the intake valve effective angle area F
ia and the cylinder bore diameter have a correspondence relationship as shown in FIG. 4, and the average Mach number Mi depends on the single chamber volume, the cylinder bore diameter, and the engine speed. Then, when the engine speed is between 4000 rpm and 8000 rpm, 1
Mi = 0.5 for cylinder bore diameter every 000 rpm
When the single-chamber volume is obtained, the solid line in FIG. 5 is obtained. By the way, assuming that the engine speed at which Um = 2.0 × 10 ⁴ mm / s is Na and the engine speed at which Mi = 0.5 is Nb, if Nb> Na, the reliability is reduced. The cylinder bore diameter is set to be large enough to allow air to enter the high-speed side beyond the limit, which is contrary to the demand for a smaller cylinder bore diameter. On the other hand, Na-Nb> 20
If it is 00 rpm, the maximum horsepower generation rotation speed (the rotation speed near Nb) becomes too low as compared with the limit in reliability, which is not preferable in performance. In terms of performance, the maximum horsepower generating rotation speed is desirably 5000 rpm or more, and the reliability limit may be 8000 rpm or less. From these points, Na ≧ Nb, Na-Nb
≦ 2000 rpm, Nb ≧ 5000 rpm, Na ≦ 80
The range of 00 rpm, that is, the range indicated by hatching in FIG. 5 , satisfies the requirement for the reduction in the diameter of the cylinder bore and the requirement for the engine performance. Speaking of the cylinder bore diameter B, the range is approximately 50 ≦ B ≦ 70. The single chamber volume is in the range of 150 cc to 400 cc. What
In addition, Um in the above formula (2) is the limit of the average piston speed.
Value of 2.0 × 10 ⁴ mm / s, and N
When a ≦ 8000 rpm is applied, S ≧ 30 × 2.0
× 10 ^4/8000 = 75mm, and the piston straws
It is preferable that the diameter be 75 mm or more. And Shirin
The upper limit of the above range (50 ≦ B ≦ 70) of the dowel diameter B (7
0mm) and the lower limit of the preferred piston stroke range
(75 mm), the lower limit of the preferred range of S / B is 75
/ 70 and 1.07, so S / B is 1.0
7 or more is a preferable range. That is, by setting the cylinder bore diameter B and the volume of the single chamber within the above ranges, the cylinder bore diameter B is reduced while satisfying the requirements of the reliability and performance of the engine. Character will be enhanced. S / B> 1 (more preferably, S / B
Is 1.07 or more) , the cylinder bore diameter B is reduced in securing the same single chamber volume, so that the bearing load on the crankshaft can be reduced, and The burden can be reduced. Knock resistance improving function As described above, knock resistance is enhanced by reducing the diameter of the cylinder bore. In addition, the scavenging is promoted by increasing the overlap between the opening and closing periods of the intake and exhaust valves, and the cooled E
Knock resistance can also be improved by supplying the GR gas and reducing the geometric compression ratio ε. FIG. 6 shows experimental data obtained by examining a filling efficiency improvement margin (corresponding to an improvement in knocking resistance) that can be achieved with the same knocking resistance for these elements.
As is apparent from this figure, when the cylinder bore diameter is reduced, the knocking resistance is improved, and the filling efficiency can be increased. The exhaust temperature rise suppressing effect Figure 7 is a representation of the experimentally examined data on exhaust gas temperature reduced, the supply of cooled EGR gases, the compression ratio ε
The effects of the increase in the exhaust gas temperature on the exhaust gas temperature, the ignition timing, the air-fuel ratio, the intake air temperature, and the exhaust pressure The effect on temperature is also shown for comparison. As shown in this figure, when the cooled EGR gas is supplied, when the EGR rate R is increased by 10%, the exhaust gas temperature is reduced by 60 ° C., which is larger than when the air-fuel ratio is made rich. There is an exhaust temperature reduction effect. When the compression ratio ε increases by Δε = 1, the exhaust gas temperature is reduced by about 20 ° C. Conversely, the compression ratio ε
Lowering causes a rise in exhaust gas temperature of 20 ° C. per Δε = 1. The increase in the EGR rate R required to lower the exhaust gas temperature by 20 ° C. is 20/6 ≒ 3 (%). When the compression ratio ε increases to about 9, the EGR
Even if the rate R is set to 0, an increase in the exhaust gas temperature can be avoided. Accordingly, the relationship of the above equation (1) is obtained. By setting the EGR rate R in accordance with the compression ratio ε so as to satisfy this relationship, the exhaust gas temperature can be effectively reduced even when the compression ratio ε is low. Can be suppressed. Since there is no need to enrich the air-fuel ratio, fuel efficiency and the like can be kept good. In the engine with a supercharger according to the present invention, the supercharger is not limited to the rechargeable supercharger shown in the embodiment, but may be another mechanical supercharger or a turbocharger. . The present invention provides a spark-ignition supercharged engine provided with two or more intake valves in one cylinder and having a spark plug and having a cylinder bore diameter of 50 mm to 70 mm.
mm, the volume of a single chamber is 150 cc to 400 cc, and the ratio of piston stroke to cylinder bore diameter is 1.07 or more.
The maximum intake power Mach number of the gin's maximum horsepower generation rotation speed is 0.
The rotation speed (Nb) and piston speed at 5 are the limit
The rotation speed (N at the boundary value of 2.0 × 10 ⁴ mm / s)
a), and Na ≧ Nb, Na−Nb ≦
2000 rpm, Nb ≧ 5000 rpm, Na ≦ 800
0 rpm, and the geometric compression ratio of the engine is set to 9 or less. As understood from the data shown in FIG. 5 and the like, while satisfying the requirements on the reliability and performance of the engine, Knock resistance can be greatly improved by reducing the diameter of the cylinder bore. Further, at least at high speed and high load, the EGR gas cooled by the cooler is supplied to the engine, and the EGR rate (R%) becomes R ≧ (9−ε) · 3 with respect to the geometric compression ratio (ε). EGR as
Since the gas supply means is configured, as can be understood from the data shown in FIG. 7, the increase in the exhaust gas temperature at the time of high speed and high load in the high supercharging state can be effectively suppressed by the EGR gas. Things.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall schematic diagram of a supercharged engine according to an embodiment of the present invention. FIG. 2 is a schematic view of an engine main body and a portion around the engine main body. FIG. 3 is a diagram showing valve timing. FIG. 4 is a diagram showing a relationship between a cylinder bore diameter and an intake valve effective angle area. FIG. 5 is a diagram showing a relationship between a cylinder bore diameter and a single chamber volume. FIG. 6 is a diagram showing an effect of improving knock resistance by various elements. FIG. 7 is a diagram showing the exhaust temperature reduction effect of various elements. [Description of Signs] 1 Engine main body 3a, 3b Intake port 10 Intake passage 17 Supercharger 22 EGR passage

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-22613 (JP, A) JP-A-54-91618 (JP, A) JP-A-4-262035 (JP, A) JP-A-54-21635 33915 (JP, A) JP-A-58-25559 (JP, A) JP-A-5-59948 (JP, A) JP-A-5-59947 (JP, A) Japanese Utility Model Publication No. 57-152453 (JP, U) Takeshi Katagiri, Toru Mukai, "F6A type 3 cylinder DOHC & SOHC 657cc Suzuki (Alto Works / A (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 25/07 550 F02M 25/07 570 F02B 23 / 00 F02B 23/08

Claims (1)

(57) [Claims 1] One cylinder is provided with two or more intake valves,
In a supercharged engine having a supercharger in an intake passage of a spark ignition type reciprocating piston type engine having a spark plug, a cylinder bore diameter is set to 50 mm to 70 mm,
The single chamber capacity of the cylinder is 150cc to 400cc, the ratio (S / B) of the piston stroke (S) to the cylinder bore diameter (B) is 1.07 or more, and the maximum horsepower of the engine
The raw rotation speed is the rotation speed when the average intake Mach number is 0.5
(Nb) and the piston speed are the limit values 2.0
Set between rotation speed (Na) at × 10 ⁴ mm / s
And Na ≧ Nb, Na−Nb ≦ 2000 rpm,
Nb ≧ 5000 rpm, Na ≦ 8000 rpm
EGR gas supply means for supplying the EGR gas to the engine via a cooler for cooling the EGR gas at least at a high speed and a high load while setting the geometric compression ratio (ε) of the engine to 9 or less. The EGR gas supply means controls the EGR so that the relationship between the geometric compression ratio (ε) of the engine and the EGR rate (R%) at high speed and high load satisfies the following equation.
An engine with a supercharger, which is configured to supply GR gas. R ≧ (9−ε) · 3