JPS6250659B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an intake system for an engine.

[Prior art]

In general, an engine intake system is for supplying intake air to the combustion chamber of the engine. Conventionally, one type of this intake system is to divide a plurality of cylinders into at least two cylinder groups, and to divide each cylinder group into There is one in which a throttle valve is provided in each of the connected intake passages to reduce intake passage resistance in high load and high rotation ranges, thereby improving charging efficiency and obtaining high engine output.

However, in such an intake system in which a throttle valve is provided in the intake passage of each cylinder group,
If each throttle valve does not open to the same degree due to manufacturing errors, the charging efficiency among the cylinder groups will vary and the output will be unbalanced, causing the problem that the engine will not operate smoothly. This is particularly a problem in low load areas such as during idling when the amount of intake air is small.

In order to solve this problem, conventionally,
As shown in Japanese Patent Application Laid-Open No. 54-150512, a balance passage is connected between the intake passages of each cylinder group on the downstream side of the throttle valve, and the intake balance is maintained between the intake passages of each cylinder group via this balance passage. There is a method that performs correction to reduce variations in filling efficiency.

However, in systems that use balance passages to reduce the dispersion in filling efficiency between cylinder groups, when the operating conditions change and the dispersion in filling efficiency between cylinder groups fluctuates, the balance passage is removed. Because the flowing air flows backwards, the problem remains that the response of variation correction to changes in operating conditions is poor.

[Purpose of the invention]

In such a situation, it is an object of the present invention to provide an engine intake system that can more reliably prevent variations in filling efficiency between cylinder groups in a low load region than the system described in the above-mentioned prior art publication.

[Structure of the invention]

Accordingly, the present invention provides an engine intake system in which a throttle valve is disposed in the intake passage of each cylinder group, and a single intake system that bypasses each throttle valve and supplies intake air to the intake passage of each cylinder group. A sub-intake passage is provided, and a sub-throttle valve for adjusting the amount of intake air in a low load region is interposed in the sub-intake passage.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an engine intake system according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a V-type six-cylinder engine, and a plurality of cylinders of the engine 1 are divided into two cylinder groups 2a and 2b.In the cylinder head 3 of the engine 1, an intake passage 4 is provided for intake air of each cylinder. The upstream end of each intake passage 4 is connected to a surge tank 5a, 5b for each cylinder group 2a, 2b. Main throttle valves 6a, 6b are interposed near the upstream ends of the surge tanks 5a, 5b, and the upstream ends of the surge tanks 5a, 5b are rubber pipes 8a, 8a, 6b fitted at both ends of the main intake passage 7, respectively. 8b, and both the surge tanks 5a and 5b are provided substantially perpendicular to the direction in which intake air flows in the main intake passage 7. Further, an upstream rubber pipe 8a of the main intake passage 7 is connected to an air flow meter 9. In addition, in the figure, 10 is a fuel injection valve.

The upstream end of a single auxiliary intake passage 11 is connected to the center of the main intake passage 7.
A sub-throttle valve 12 is interposed near the upstream end of the throttle valve 1, and the sub-throttle valve 12 is connected to the main throttle valves 6a and 6b via a lost motion link mechanism 13. The downstream side of the auxiliary intake passage 11 is branched into two, and both ends thereof are connected to surge tanks 5a and 5b downstream of the main throttle valves 6a and 6b, respectively. Further, an EGR passage 14 of an exhaust gas recirculation (EGR) device is connected to the branch part of this sub-intake passage 11, and the EGR
An EGR valve 15 is interposed in the middle of the passage 14.

Next, the operation will be explained.

When the load is low and the amount of depression of the accelerator pedal is small, the auxiliary throttle valve 12 opens according to the amount of depression of the accelerator pedal, while the main throttle valves 6a and 6b are opened by the lost motion link mechanism 1.
It is maintained in the fully closed state by the action of 3. When air is drawn into the main intake passage 7 in this state, this intake air flows into the auxiliary intake passage 11 according to the opening degree of the auxiliary throttle valve 12, and splits into two parts in the middle of the auxiliary intake passage 11. The air is divided and flows into the surge tanks 5a and 5b, and further passes through the intake passage 4 and is sucked into the combustion chamber of each cylinder.

Next, when the amount of depression of the accelerator pedal increases to reach a high load region, the sub-throttle valve 12 becomes almost fully open, and the main throttle valve 6
a, 6b begin to open, and most of the intake air in the main intake passage 7 is then directly transferred to the surge tank 5 according to the opening degree of the main throttle valves 6a, 6b.
a, 5b, this surge tank 5a, 5
The air is drawn into the combustion chamber of each cylinder through each intake passage 4 from b.

On the other hand, in the EGR device, the EGR valve 15 opens according to the operating state of the engine, and the EGR passage 14 is opened by the EGR valve 15 due to the action of the engine's intake negative pressure.
5 flows, and this exhaust gas is also distributed and sucked into the surge tanks 5a and 5b via the auxiliary intake passage 11.

In the device of this embodiment as described above, when the load is low, intake air is distributed and supplied to each cylinder of the two cylinder groups through only a single auxiliary intake passage, so that the air is distributed between the two cylinder groups. Therefore, the charging efficiency does not vary due to variations in the opening degree of the main throttle valve, and as a result, the engine operates smoothly. Moreover, by distributing and supplying intake air through a single sub-intake passage,
Since the intake air always flows in one direction, variations in filling efficiency can be more reliably prevented than when the intake balance is corrected using a balance passage as in the device described in the above-mentioned conventional publication.

In addition, when distributing intake air to two groups of cylinders, conventionally the main intake passage is split into two in the middle to form a roughly T-shape, and both ends of the passage are connected to the surge tank of each cylinder group. Connections are being made. In contrast, in this device, the upstream ends of the two surge tanks are connected to the almost straight main intake passage, and the intake passage has less curvature than the conventional structure described above, so there is less intake passage resistance. As a result, charging efficiency can be further improved and engine output can be increased.

Furthermore, as an EGR recirculation method, as shown in the above-mentioned conventional publication, the tip of the EGR passage is connected in the middle of a balance passage provided between cylinder groups, and exhaust gas is sent to each cylinder group via this balance passage. There is a recirculation method, but in this method, if the intake balance between the cylinder groups is lost, the intake air flows in one direction through the balance passage, and the exhaust gas is recirculated to only one cylinder group, while the other There is a risk that it will not be refluxed. On the other hand, in this device, the intake air is evenly distributed to the downstream side of both branch portions of the auxiliary intake passage, so that the exhaust gas is always evenly distributed and supplied to the cylinder group.

In the above embodiment, the cylinders of the engine are divided into two cylinder groups, but the present invention may be divided into any number of cylinder groups as long as there are two or more cylinder groups. Further, the EGR device does not necessarily need to be provided. Furthermore, the main throttle valve may be opened and closed using, for example, intake negative pressure instead of the lost motion link mechanism.

[Effects of the Invention] As described above, according to the present invention, in an engine intake system in which cylinders are divided into two or more cylinder groups and throttle valves are arranged in the intake passages of each cylinder group, each A single auxiliary intake passage is provided that bypasses the throttle valve and supplies intake air to the intake passages of each cylinder group.During low-load operation, intake air is distributed to the intake passages of each cylinder group via this auxiliary intake passage. Since the fuel is supplied, it is possible to reliably prevent the occurrence of variations in filling efficiency between cylinder groups in a low load region, and there is an effect that the engine can operate smoothly.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional plan view of an engine intake system according to an embodiment of the present invention, and FIG. 2 is a partially sectional plan view of the main parts of the device. 1...Engine, 2a, 2b...Cylinder group, 5
a, 5b...Surge tank (intake passage), 6a,
6b...Main throttle valve, 11...Sub-intake passage, 12...Sub-throttle valve.

Claims (1)

[Claims] 1. In an engine intake system in which a plurality of cylinders are divided into at least two cylinder groups, and a throttle valve is interposed in the intake passage of each cylinder group,
A single auxiliary intake passage is provided that bypasses each of the above throttle valves and supplies intake air to the intake passage of each cylinder group, and the auxiliary intake passage is provided with an auxiliary throttle valve that adjusts the amount of intake air in a low load region. An engine intake device characterized by having a.