JPH0478819B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a supercharger equipped with an exhaust type supercharger, a mechanical supercharger, and an intake valve independently provided in the intake system from each supercharger. The present invention relates to a fed engine, and in particular to its intake valve device.

[Prior art] Engines with exhaust type superchargers that are equipped with an independent normally closed valve that opens at low speeds and high loads and during deceleration to introduce high pressure air into the combustion chamber have been developed since the early 1990s.
It is publicly known from the publication No. 60-187331.

Although exhaust type superchargers have particularly excellent supercharging performance in high-speed operating ranges, attempts have also been made to provide additional mechanical superchargers with the aim of improving supercharging performance in low-speed operating ranges. In that case, in order to effectively utilize the characteristics of each turbocharger, in addition to installing an intake valve at the intake port connected to the intake passage from the exhaust type turbocharger, it is necessary to connect the intake passage from the mechanical turbocharger to the intake valve. Each cylinder must be provided with an intake valve provided at the connected intake port.

[Problem to be solved by the invention] However, the exhaust type supercharger does not have a very good response in the low speed operating range, so the low speed torque of the engine tends to be insufficient. Although this problem can be solved by using a mechanical supercharger in combination with a mechanical supercharger, this mechanical supercharger causes an increase in load due to friction in high-speed operating ranges.

Therefore, the purpose of the present invention is to reduce the low-speed torque produced by the mechanical turbocharger with excellent response in the low-speed operation range by variable control of the opening/closing timing of the intake valve on the exhaust type turbocharger side and the intake valve on the mechanical turbocharger side. In addition, in the high-speed operating range, the friction load of the mechanical supercharger is reduced, and the high-speed torque of the exhaust supercharger is improved, making it possible to improve the high-speed torque of the exhaust supercharger and mechanical supercharger. An object of the present invention is to provide a supercharged engine that can maximize its characteristics.

[Means for Solving the Problems] In order to achieve the above problems, the present invention includes an exhaust type supercharger 11 and a mechanical type supercharger 19, and connects an intake passage 17 from the exhaust type supercharger 11. In a supercharged engine in which each cylinder 1 is equipped with an intake valve 6 provided in the intake port 2 connected to the intake port 2 and an intake valve 7 provided in the intake port 3 connected to the intake passage 18 from the mechanical supercharger 19, the piston top dead center (TDC), the opening operation of the mechanical supercharger-side intake valve 7 is delayed than the opening operation of the exhaust-type supercharger-side intake valve 6, and the exhaust-type supercharger opens near the piston bottom dead center (BDC). The closing operation of the mechanical supercharger side intake valve 7 is delayed compared to the closing operation of the side intake valve 6, and the exhaust type supercharger side intake valve closes before the piston bottom dead center (BDC) is reached in the low speed operating range. After the valve 6 is closed, the mechanical supercharger side intake valve 7 is closed after reaching the piston bottom dead center (BDC), and in the high-speed operation range, the intake valve 7 is closed when the piston bottom dead center (BDC) is reached. The invention is characterized in that the intake valve 4 on the exhaust type supercharger side is provided with a variable opening/closing timing function 31 that closes the intake valve 6 on the exhaust type supercharger side and the intake valve 7 on the mechanical turbocharger side. .

[Operation] In the low-speed operating range, air first enters from the intake port 2 on the exhaust type supercharger side through the intake valve 6 which is opened in advance. At this time, the exhaust type supercharger 11 is not yet very effective, so supercharging is not performed.

When a certain amount of air enters through the exhaust-type supercharger-side intake port 2, the intake valve 7 further opens, and air enters from the mechanical-type supercharger-side intake port 3. The mechanical supercharger 19 can increase supercharging pressure even at low speed rotation, so it pressurizes intake air and supercharges it.

Next, the intake port 2 on the exhaust type supercharger side is closed, and then the intake port 3 on the mechanical supercharger side is closed after reaching the piston bottom dead center (BDC).

In this way, in the low-speed operating range, supercharging by the mechanical supercharger 19 is performed while air is also passed through the exhaust supercharger 11.

Here, the amount of work is expressed as flow rate x pressure, so in this system where the amount of intake air passing through the mechanical supercharger 19 is reduced, compared to the normal system where all the air passes through the mechanical supercharger 19. Compared to this, the load due to friction of the mechanical supercharger 19 can be reduced.

In the high-speed operation range, the intake port 2 on the exhaust type supercharger side is open until after the piston bottom dead center (BDC) is reached, so the high speed rotation of the exhaust type supercharger 11 ensures sufficient pressurization. Air enters from port 2.

At this time, air also enters from the intake port 3 on the mechanical turbocharger side, but with this system in which the amount of intake air passing through the exhaust type turbocharger 11 is sufficiently increased, the air that passes through the mechanical turbocharger 19 is Since the flow rate is smaller than in a normal system (the rate of decrease in flow rate is larger than in the low-speed operating range), the load caused by friction on the mechanical supercharger 19 can be significantly reduced.

In this manner, in the high-speed operating range, the flow rate passing through the mechanical supercharger 19 is reduced, while supercharging is performed by the exhaust type supercharger 11, which sufficiently increases the flow rate passing through the mechanical supercharger 19.

[Example] Examples will be described below based on the accompanying drawings.

In FIG. 1 showing an example of an intake and exhaust system of an engine to which the present invention is applied, each cylinder 1 (not shown) is provided with a pair of intake ports 2, 3 and an exhaust port 4, 5, respectively. Each intake port 2,
3 are provided with respective intake valves 6, 7, and each exhaust port 4, 5 is also provided with a respective exhaust valve 8, 9.

An exhaust passage 10 is connected to and merges with the exhaust ports 4 and 5, which are opened and closed by the exhaust valves 8 and 9, respectively.
A turbine 11t of an exhaust type supercharger (referred to as a turbocharger in the following examples) 11 is disposed at the 11th, an O ₂ sensor 12 is installed downstream of the turbine 11t, and the exhaust gas passes through a downstream catalyzer 13 and a muffler (not shown) to the atmosphere. will be opened to Note that 15 is a waste gate valve provided in the bypass passage 14 of the turbine 11t.

On the other hand, intake passages 17 and 18 branched from the downstream side of the air cleaner 16 that sucks and purifies outside air are provided independently, and the compressor 11c of the turbocharger 11 is disposed in the intake passage 17, and the turbocharger 11 is connected to the exhaust passage 10. The rotation of the installed turbine 11t by the exhaust flow drives the compressor 11c installed in the intake passage 17, and the supercharging performance is particularly excellent in the engine high-speed operation range.

Furthermore, a mechanical supercharger (referred to as a supercharger in the following embodiments) 19 is arranged in another intake passage 18. This supercharger 19 is mechanically driven via a transmission device 23 by the rotation of a crankshaft 22 connected to a piston 20 in the cylinder 1 by a connecting rod 21, and has excellent supercharging performance, especially in low engine speed operating ranges. be.

Further, both intake passages 1 are arranged downstream of the respective turbochargers 11 and superchargers 19.
A common intercooler 24 is provided for the valves 7 and 18, and throttle valves 25 and 26 are provided on the downstream side.
Chamber-shaped surge tanks 27 and 28 are provided, and both intake passages 17 and 18 are connected to each intake port 2 and 3, respectively. Note that 30 is a bypass valve provided in the bypass passage 29 of the supercharger 19.

In the above, the turbocharger side intake valve 6 is provided with the variable opening/closing timing mechanism 31, and the following supercharging function is obtained by controlling the turbocharger side intake valve 6 equipped with the variable opening/closing timing mechanism 31. Note that 32 is a camshaft.

In the engine in which the turbocharger 11 and supercharger 19 are arranged in independent intake passages 17 and 18, the opening/closing timing of the turbocharger-side intake valve 6 and the supercharger-side intake valve 7 is controlled as shown in FIG. Perform as shown in Figure 3.

That is, first, in a low-speed operating range, as shown in Fig. 2, the turbocharger side intake valve 6 is opened slightly ahead of the piston top dead center (TDC) during the intake stroke, and the engine is gradually lifted (see the solid line lift curve T).
In the vicinity of this turbocharger side intake valve 6 reaching the maximum lift amount, the supercharger side intake valve 7
Open and gradually lift (dotted line lift curve S). After the turbocharger side intake valve 6 is closed in the vicinity of the supercharger side intake valve 7 reaching the maximum lift amount and before reaching the piston bottom dead center (BDC), after the turbocharger side intake valve 6 is closed after the piston bottom dead center (BDC) is reached. Close the supercharger side intake valve 7.

In the high-speed operating range, the closing timing of the turbocharger side intake valve 6 is particularly delayed as shown in FIG. In other words, the turbocharger side intake valve 6 is kept open until the piston bottom dead center (BDC) is reached (solid line lift curve T), and after the piston bottom dead center (BDC) is reached, the turbocharger side intake valve 6 is closed and the supercharger is continued. Close the side intake valve 7.

By providing an intake valve device with such a variable opening/closing timing function, the rotational speed (Ne)-intake flow rate (ηv) characteristic shown in FIG. 4 can be obtained.

In other words, in the low speed and low load operating range as shown in Figure 4,
The amount of air flowing into the supercharger side intake port 3 can be set larger than the amount of air flowing into the turbocharger side intake port 2, so supercharging by the supercharger 19 can be performed. Furthermore, as the rotation increases, the amount of air flowing into the Tarhoe charger side intake port 2 is gradually increased, and the amount of air flowing into the supercharger side intake port 3 is gradually decreased. Since the amount of air flowing into the turbocharger side intake port 2 can be set to be larger than the amount of air flowing into the supercharger side intake port 3, supercharging by the turbocharger 11 can be performed.

As described above, low-speed torque can be improved in the low-speed operation range by the supercharging function of the supercharger 19 with excellent response, and in the high-speed operation range, the load due to the friction of the supercharger 19 is reduced while the supercharger 11 is overloaded. High-speed torque can be improved by the supply function.

[Effects of the Invention] As described above, according to the present invention, the mechanical supercharger performs supercharging while passing air through the exhaust type supercharger in the low-speed operating range, and the mechanical supercharger performs supercharging in the high-speed operating range. This engine is equipped with a variable opening/closing timing function on the intake valve on the exhaust type supercharger side, which reduces the amount of flow passing through the charger while increasing the flow rate through the exhaust type supercharger. In the low-speed operating range, the mechanical supercharger with excellent response can improve low-speed torque, and in the high-speed operating range, the load due to friction of the mechanical supercharger is reduced and the high-speed torque produced by the exhaust supercharger is improved. be able to.

Therefore, the characteristics of both the exhaust type supercharger and the mechanical type supercharger can be exhibited to the maximum.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an intake and exhaust system of a supercharged engine showing an embodiment of the present invention, Fig. 2 is a diagram of intake operation characteristics of both intake valves in a low-speed operating range, and Fig. 3 is a diagram in a high-speed operating range. FIG. 4 is a rotational speed-intake flow rate characteristic diagram showing the ratio of the intake flow rate flowing through each intake port of each supercharger. In addition, in the drawing, 1 is a cylinder, 2 and 3 are intake ports,
6 and 7 are intake valves, 17 and 18 are intake passages, 11 is an exhaust type supercharger, 19 is a mechanical supercharger, and 31 is a variable opening/closing timing mechanism.

Claims (1)

[Scope of Claims] 1. Includes an exhaust type supercharger and a mechanical supercharger, an intake valve provided at an intake port connected to an intake passage from the exhaust type supercharger, and an intake passage from the mechanical supercharger. In a supercharged engine in which each cylinder has an intake valve installed in an intake port connected to a The valve opening operation of the mechanical supercharger side intake valve is delayed compared to the valve closing operation of the exhaust type supercharger side intake valve near the bottom dead center of the piston, and the piston bottom dead center is delayed in the low speed operating range. The intake valve on the exhaust type turbocharger side is closed before reaching the piston bottom dead center, and then the intake valve on the mechanical turbocharger side is closed after the piston bottom dead center is reached. The intake valve on the exhaust type turbocharger side is equipped with a variable opening/closing timing function that closes the intake valve on the exhaust type turbocharger side and the mechanical turbocharger side after reaching the dead center. A supercharged engine.