JPH10103082A - Intake throttle system for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regulate the flow rate of air through an intake throttle system while a diesel engine idles so as to fall within an idle flow rate range, while regulating the flow rate of air while the throttle system is fully closed so as to fall within a fully-closed flow rate range at lower costs. SOLUTION: An intake throttle system for a diesel engine, which regulates with a motor the opening angle of a throttle valve 4 adapted to turn for opening of closing an intake passage 2 of a diesel engine, is provided with a bypass passage 50 for which a flow regulating means 52 is provided. The inlet 50a or the outlet 50b of the bypass passage 50 is located so as not to be effective when the throttle valve 4 is fully closed. When the throttle valve 4 is operated for idling, the bypass passage 50 becomes effective to allow a bypass flow therethrough. The rate of the bypass flow is regulated by the flow regulating means 52. when the throttle valve 4 is fully closed on the other hand, the bypass passage 50 is shut off to allow no bypass flow therethrough.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an intake throttle device for a diesel engine.

[0002]

2. Description of the Related Art There is an intake throttle device for a diesel engine in which an opening degree of a throttle valve (also referred to as a throttle opening degree) that opens and closes by rotating an intake passage is controlled by a step motor (for example, Japanese Patent Laid-Open No. 6-307295). Reference).

FIG. 9 is an explanatory diagram related to the position of a throttle valve in an intake throttle device of a diesel engine.
In normal traveling, the throttle valve 4 opens and closes between a fully open position shown by a solid line in the figure and a half open position (idle position) shown by a dashed line in the figure, and the engine (E / G both). At the time of stop, it is further closed from the half-open position and is at a fully closed position (also referred to as a position at the time of E / G stop) indicated by a two-dot chain line in the figure. In FIG. 9, the throttle valve 4 is attached to the throttle shaft 3, and the throttle shaft 3 is rotatably supported by the body 1 forming the intake passage 2.

In the intake throttle device, a step motor
The drive causes the throttle valve 4 to operate in a step-like manner.
Therefore, the flow characteristics of the intake air are as shown in FIG. Figure
At 10, the horizontal axis represents the throttle opening (deg).
The vertical axis represents the flow rate of the intake air (m ^Three/ H), and the circles indicate
Suction empty due to the operation of each step of the step motor
The flow rate of air (also referred to as a flow point) is shown.

[0005] In a diesel engine,
Since there is no special need for an ignition device, it is desirable to shut off both fuel and air in order to reliably stop the engine,
When the engine is stopped, the throttle valve 4 is fully closed, and the flow rate of the intake air is equal to or less than a predetermined flow rate (this range is referred to as a fully-closed flow rate range), for example, 3 m ³ / h or less (see the lower hatched portion in FIG. 10). There is a need.

In order to precisely control the exhaust gas and improve drivability, the flow rate of the intake air at the idle position of the throttle valve 4 is set to a predetermined range (this range is referred to as an idling flow range), for example, 33. ３５35 m ³ / h (see the upper shaded portion in FIG. 10). However, in the above-described intake device, the throttle valve 4 operates in a step-like manner as described above, so that the flow rate point (see a circle in FIG. 10) changes stepwise. Further, since the throttle valve 4 is held at the idle position by the stepping motor, the variation due to individual differences of products is greater than in the case of the fully closed position where the position is held by the stopper means. This causes a problem that the flow point does not fall within the idle flow range (see the upper hatched portion in FIG. 10) while the throttle valve 4 is at the idle position.

[0007] For example, the following countermeasures can be considered as countermeasures against the above-mentioned conventional problems. [Countermeasure Example 1] A gear transmission mechanism is provided in the power transmission path from the motor to the throttle shaft, and by setting the gear ratio of the gear transmission mechanism, the operating angle per one step of the throttle valve 4 is reduced to reduce the operation angle per step. A method in which the interval between flow points is set to be equal to or less than the idle flow range. [Countermeasure Example 2] A method in which the operating angle per step of the motor is reduced by changing the configuration of the motor or the driving method, and the interval between flow points for each step is set to be equal to or less than the idle flow range. [Countermeasure example 3] By adjusting the mounting position of the motor around the output shaft, as shown in the characteristic diagram of FIG. 11, the flow point in the above-mentioned conventional example (see the thin line ○ in the figure) is indicated by the thick line ○. overall is transitive, the method to fit the flow point P ₁ in the conventional example in the idling flow rate range. [Countermeasure Example 4] By providing a bypass passage for bypassing the throttle valve and adjusting the flow rate of the bypass flow flowing through the bypass passage with an adjusting screw, as shown in the characteristic diagram of FIG. in a method to fit a reference fine line ○ mark) thick line ○ is generally increased as indicated by the symbol, the flow point P ₁ in the conventional example in the idle flow range. A configuration in which a bypass passage having a flow rate adjusting means is provided is disclosed in, for example, Japanese Patent Application Laid-Open No. 56-115829.

[0008]

However, the above countermeasure example 1 is not practical because the gear ratio of the gear transmission mechanism is limited by the relationship between the motor torque and the rotation speed. Further, the countermeasure example 2 is not practical because the motor configuration is complicated. Further, in Countermeasure Example 3, it is not practical because a complicated operation of finely adjusting the mounting position while energizing the motor and adjusting the flow rate of the intake air is required. Also the countermeasure example 4, the flow rate of intake air varies across the throttle opening degree, the flow rate point P ₂ of the fully closed is fully closed flow range (Fig. 1
2 (see lower shaded area) is not practical. As described above, in the countermeasure examples 1 to 4, it is difficult to adjust the idle flow within the predetermined idle flow range while keeping the fully closed flow within the predetermined fully closed flow range at low cost. Remains.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a low-cost, fully-closed flow rate within a predetermined fully-closed flow rate range. It is an object of the present invention to provide an intake throttle device for a diesel engine capable of adjusting an idle flow rate within a predetermined idle flow rate range while keeping the idle flow rate low.

[0010]

According to a first aspect of the present invention, there is provided an intake throttle device for a diesel engine in which a motor controls the opening of a throttle valve that opens and closes by rotating an intake passage of the diesel engine. A bypass passage for bypassing the throttle valve is provided, and the bypass passage is provided with a flow rate adjusting means for adjusting a flow rate of a bypass flow, and an inlet or an outlet of the bypass passage is in a non-bypass state when the throttle valve is fully closed. This is an intake throttle device for a diesel engine, which is provided at a position.

According to the first aspect of the present invention, when the throttle valve is idling, the bypass flow flows through the bypass passage. Therefore, the flow rate of the bypass flow is adjusted by the flow rate adjusting means, so that the idling flow rate is adjusted. Can be kept within a predetermined idle flow rate range. In addition, when the throttle valve is fully closed, the bypass passage is in the non-bypass state and the bypass flow does not flow, so that the fully closed flow rate falls within a predetermined fully closed flow rate range. Further, since it can be dealt with by a simple design change such as a change in the position of the entrance or the exit of the bypass passage, it can be implemented at low cost.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 and 2 of the present invention will be described in order. Embodiment 1 Embodiment 1 will be described with reference to FIGS. For convenience, after describing the outline of the intake throttle device of the diesel engine, the main configuration according to the present invention will be described in detail. In FIG. 1 showing a front sectional view of an intake throttle device of a diesel engine, a substantially cylindrical body main body 1 has an intake passage 2 formed therein. A throttle shaft 3 is rotatably supported on the body 1 via bearings (omitted by reference numerals) while penetrating both side walls.
A throttle valve 4 that opens and closes the intake passage 2 is attached to the throttle shaft 3. Further, left and right boss portions 1a and 1b are formed in the body body 1. A housing 1c is continuously provided on the opening side of the right boss 1b.

In FIG. 1 and FIG. 2 showing the left side view of FIG. 1, a first lever 7 is fixed to the left end of the throttle shaft 3 by fastening a nut 8. The first lever 7 has an engagement piece 7a and a mounting piece 7b on its outer peripheral portion. The tip of the engagement piece 7a is located on the body 1 (FIG. 1).
While the tip of the mounting piece 7b is bent in a direction opposite to the engaging piece 7a (to the left in FIG. 1).

In FIG. 1, a first spring 9 is fitted on a left boss 1a of the body 1.
One spring hook 9a of the first spring 9 is engaged with a spring stopper pin 10 of the body 1, and the other spring hook 9b is engaged with an engagement piece 7a of the first lever 7. The first spring 9 urges the first lever 7 with respect to the body 1 in the valve opening direction (the counterclockwise direction in FIG. 2). A spring guide 11 located between the first lever 7 and the first spring 9 is rotatably fitted to the throttle shaft 3.

In FIG. 2, the body 1 is provided with two mounting projections 12 and 13 which are located between the engaging piece 7a of the first lever 7 and the front and rear. A fully-open stopper screw 14 is screwed to the front mounting protrusion 12. The fully open stopper screw 14 comes into contact with the engagement piece 7a of the first lever 7 as shown in FIG. 2, thereby further increasing the valve opening direction of the first lever 7 (in the counterclockwise direction in FIG. 2). The rotation is prevented, and the throttle valve 4 is stopped at the valve opening restricted position (see the dotted line in FIG. 2). A fully-closed stopper screw 15 is screwed to the rear mounting projection 13. The fully-closed stopper screw 15 abuts the engagement piece 7a of the first lever 7 to prevent the first lever 7 from rotating further in the valve closing direction (clockwise direction in FIG. 2). Then, the throttle valve 4 is stopped at the fully closed position (see a two-dot chain line in FIG. 2).

A switch pressing screw 16 is screwed to the tip of the mounting piece 7b of the first lever 7. On the other hand, a full-open position detection switch (also referred to as a full-open switch) 17 is attached to the body 1 with a set screw 18. The fully open switch 17 detects the fully open position of the throttle valve 4 when the detection end 17a is pressed by the switch pressing screw 16 when the throttle valve 4 is at the fully open position as shown in FIG. 1
Engine control computer (also referred to as ECU)
Enter 20. The ECU 20 is provided with the full open switch 17.
In addition, it receives information from various sensors and switches (not shown) and performs arithmetic processing, and outputs drive signals corresponding to accelerator operation and engine operation conditions to the motors 23 and E described later.
Output to the negative pressure control valve 40 of the GR valve 33.

In FIG. 1, a lid plate 22 is fixed to the opening end surface of the housing portion 1c of the body main body 1.
A step motor 23 is provided on the cover plate 22. An output shaft 23a of the step motor 23 projects through the through-hole (not shown) of the cover plate 22 into the housing portion 1c, and has a pinion 24 at a projecting end thereof.

In FIG. 1 and FIG. 3 which is a cross-sectional view taken along the line AA of FIG. 1, a power transmission for transmitting power between the motor 23 and the throttle shaft 3 is provided at the right end of the throttle shaft 3. Means 25 are assembled. Power transmission means 2
5 comprises a sector gear 26 and a second lever 27.

The sector gear 26 has a gear 26a at the outer periphery and a boss 26b at the axis. On the other hand, the second
Lever 27 is substantially U-shaped, and the sector gear 2
6 which have both ends 27a facing both end surfaces and which have mounting holes (symbols omitted), and connecting portions 27 for connecting the both ends 27a to each other.
b. In a state where the sector gear 26 is arranged between both ends 27 a of the second lever 27, both ends 27 a of the second lever 27 and a boss 26 b of the sector gear 26 are fitted to the throttle shaft 3. The second lever 27 is fixed to the throttle shaft 3 by tightening the nut 21, and the sector gear 26 is rotatable with respect to the throttle shaft 3 and the second lever 27 in a state where it cannot be removed.

A gear portion 26a of the sector gear 26 meshes with a pinion 24 of an output shaft 23a of the motor 23. An engaging groove 28 is formed in a peripheral surface portion of the sector gear 26 which is located on a side substantially opposite to the gear portion 26a.
In the engagement groove 28, a connecting portion 27b of the second lever 27 is relatively rotatably engaged within a range of a predetermined angle.

The boss 26b of the sector gear 26 has a second
Of springs 29 are fitted via a pair of spring guides 30. One spring hook 29a of the second spring 29 is engaged with the spring stopper pin 31 of the sector gear 26, and the other spring hook 2a.
9b is locked to the connecting portion 27b of the second lever 27.

The second spring 29 urges the sector gear 26 in the valve opening direction (clockwise direction in FIG. 3) and simultaneously urges the second lever 27 in the valve closing direction (clockwise direction in FIG. 3). I do. The urging force of the second spring 29 is set to be larger than that of the first spring 9 and smaller than the turning torque of the sector gear 26 driven by the motor 23. For this reason, normally, the urging force of the second spring 29 causes the connecting groove 27 of the second lever 27 and the engagement groove 2 of the sector gear 26 as shown in FIG.
8 is kept in contact with the valve closing groove wall (denoted by reference numeral 28a) (this state is referred to as the P state of the power transmission means 25).

The body body 1 has an EGR valve 33 of the exhaust gas recirculation device downstream of the throttle valve 4.
Has been assembled. In FIG. 1, the EGR valve 33
Is provided with a valve body 36 that opens and closes a valve seat 35 disposed at an end of an EGR gas passage 34 connected to the intake passage 2, and includes a negative pressure chamber 3 partitioned by a diaphragm 37.
The valve body 36 is closed when the negative pressure introduced into 8 is weaker than the urging force of the diaphragm spring 39, and the valve body 36 is opened when the negative pressure is stronger than the urging force. Negative pressure chamber 3
Numeral 8 communicates with the atmosphere or a negative pressure source by the switching operation of negative pressure control valve 40.

The negative pressure control valve 40 performs a switching operation based on an output signal from the ECU 20. That is, EC
When U20 determines that the introduction of EGR gas is unnecessary,
The switching of the negative pressure control valve 40 is controlled to communicate the negative pressure chamber 38 with the atmosphere. As a result, no negative pressure is introduced into the negative pressure chamber 38, so that the urging force of the diaphragm spring 39 closes the valve element 36, and shuts off the EGR gas passage 34 and the intake passage 2. When the ECU 20 determines that the introduction of the EGR gas is necessary, the negative pressure control valve 40 is switched to control the negative pressure chamber 38 to communicate with the negative pressure source so that the negative pressure from the negative pressure source is reduced. It is introduced into the chamber 38. Then, the valve body 36 is opened by the negative pressure acting on the diaphragm 37, and the EGR gas passage 34 and the intake passage 2 are communicated. And EGR
If the pressure of the gas is higher than the pressure of the intake air (also referred to as fresh air) flowing through the intake passage 2, the EGR gas flows into the intake passage 2 and becomes an air-fuel mixture and flows to the engine. Furthermore, when a large amount of EGR gas is required to flow to the engine quickly and in large quantities,
The pressure of fresh air flowing through the intake passage 2 may be reduced by closing the throttle valve 4.

In the intake throttle device for a diesel engine, the sector gear 26 of the power transmission means 25 and the second lever 27 are actuated by the second lever 29 by the urging force of the second spring 29 at normal times other than when the engine is stopped. 27 and the valve closing side groove wall 28a of the engagement groove 28 of the sector gear 26 are held in a P state where they are in contact with each other (see FIGS. 3 and 4).

When the motor 23 operates in this state, the driving force is transmitted from the pinion 24 of the output shaft 23a to the throttle shaft 3 via the sector gear 26 in the P state and the second lever 27. By throttle valve 4
Are opened and closed at a predetermined opening degree. The throttle valve 4
As in the known device, the motor 23 is set to a fully open position (see the solid line in FIG. 9) when the engine is loaded with the accelerator ON, and a half-open position (FIG. 9) when the engine is not loaded with the accelerator OFF. When the engine is stopped, it is in the fully closed position (see the two-dot chain line in FIG. 9).

In the normal state, when the engine is stopped, the throttle valve 4 is closed by closing the motor 23 so that the engagement piece 7a of the first lever 7 is fully closed. 15 (see the two-dot chain line in FIG. 2), whereby the throttle valve 4 is stopped at the fully closed position (see the explanatory diagram in FIG. 4). Further, if the motor 23 continues the closing operation by a predetermined amount, for example, about 5 steps even after the throttle valve 4 is stopped, the second lever 27 is engaged with the engagement piece 7a of the first lever 7 and the fully closed stopper screw 15. , The fan gear 26 rotates in the valve closing direction against the urging force of the second spring 29 (see the explanatory diagram of FIG. 5). As a result, the power transmission unit 25 enters a state in which the P state has been released (this state is referred to as a relief state). When the motor 23 is turned off after completing the closing operation, the second spring 2
The power transmission means 25 returns to the P state from the relief state by the urging force of 9 (see FIG. 4).

Next, the structure of the main part will be described in detail with reference to the sectional view of FIG. FIG. 6A shows the state when the throttle valve 4 is fully closed, and FIG. 6B shows the state when the throttle valve 4 is idle. FIGS. 6A and 6B correspond to a cross-sectional view taken along line BB of FIG. In FIG. 6, a bypass passage 50 that bypasses the throttle valve 4 is provided in the body 1. The body body 1 has a bypass passage 50
An adjusting screw 52 for adjusting the flow rate of the intake air flowing through the air, that is, the bypass flow, is screwed. The flow rate of the bypass flow is adjusted by rotating the adjusting screw 52 using a tool such as a screwdriver. After adjusting the flow rate of the bypass flow, a plug 53 for closing the opening is attached to the opening end of the cylindrical portion (reference numeral 1A) of the body 1 to which the adjusting screw 52 is screwed by press fitting or the like.

When the throttle valve 4 is idling (idle position), the inlet 50a of the bypass passage 50 is located upstream of the opening / closing end (reference numeral 4a) of the throttle valve 4, as shown in FIG. 6B. In addition, when the throttle valve 4 is fully closed (fully closed position), as shown in FIG. 6A, the throttle valve 4 is provided downstream of the open / close end 4a. The bypass passage 50
Is located downstream of the opening / closing end 4a of the throttle valve 4 regardless of the position of the throttle valve 4.

According to the intake throttle device of the diesel engine, when the throttle valve 4 is idling, FIG.
Since the bypass flow (see the arrow in the figure) flows through the bypass passage 50 as shown in FIG. 5, the flow rate at the time of idling can be kept within a predetermined idle flow rate range by adjusting the flow rate of the bypass flow by the adjusting screw 52. .
This point will be described in detail with reference to the characteristic diagram of FIG. FIG.
Indicates the flow rate characteristics of the intake air of the intake throttle device, the horizontal axis indicates the throttle opening (deg), the vertical axis indicates the flow rate of the intake air (m ³ / h), and the thick line ○ indicates a step motor. 2 shows the flow points of the intake air accompanying the operation of each step. Note that thin circles indicate the flow points in the conventional example (see FIG. 10).

That is, as shown in the characteristic diagram of FIG. 7, the flow point (see the thin line ○ in the figure) in the conventional example is raised as shown by the thick line に よ っ て by adjusting the adjusting screw 52. (in the figure, the upper shaded area reference.) at idle flow point P ₁ flow range e.g. 33~35m ³ / h in the example can be kept within. Therefore, the variation of the flow point at the idle position due to the individual difference of the product that opens and closes the throttle valve 4 by the step motor can be eliminated by adjusting the flow rate of the bypass flow.

When the throttle valve 4 is fully closed, the inlet 50a and the outlet 50b of the bypass passage 50 are located downstream of the throttle valve 4 as shown in FIG. In this state, since the bypass flow does not flow, the fully closed flow rate falls within a predetermined fully closed flow rate range. That is, the flow point P when fully closed in FIG.
₂ falls within the fully closed flow range, for example, 3 m ³ / h or less (see the lower shaded portion in the figure), and does not deviate from the fully closed flow range as seen in the above-mentioned Countermeasure Example 4. Therefore, the engine of the diesel engine can be stopped quickly.

Further, since it can be dealt with by a simple design change such as a change in the position of the inlet 50a or the outlet 50b of the bypass passage 50, the cost can be reduced at a lower cost as compared with the first and second countermeasures.

[Second Embodiment] The second embodiment will be described with reference to FIG.
Since the second embodiment is a modification of the first embodiment, the changed portions will be described in detail, and the portions having the same or substantially the same configuration as those of the first embodiment will be denoted by the same reference numerals. Therefore, duplicate description will be omitted. FIG. 8A shows a state when the throttle valve 4 is fully closed, and FIG. 8B shows a state when the throttle valve 4 is idle. FIGS. 8A and 8B
Corresponds to a sectional view taken along line BB of FIG.

In FIG. 8, in the present embodiment, the bypass passage 50 in the first embodiment (see FIG. 6) is connected to the other opening / closing end (reference numeral 4) of the throttle valve 4 in the body main body 1.
b). The bypass passage 5
When the throttle valve 4 is idling (idle position), the outlet 50b is located downstream of the open / close end 4b of the throttle valve 4 as shown in FIG. In the (fully closed position), as shown in FIG. 8A, the throttle valve 4 is provided so as to be located upstream of the open / close end 4b. The inlet 50a of the bypass passage 50 is located upstream of the open / close end 4b of the throttle valve 4 regardless of the position of the throttle valve 4. According to the second embodiment, the same operation and effect as those of the first embodiment can be obtained.

The present invention is not limited to the above embodiment, but can be modified without departing from the scope of the present invention. For example, it is conceivable to use a valve capable of adjusting the flow rate instead of the adjusting screw 52 as the flow rate adjusting means.

[0037]

According to the intake throttle device for a diesel engine of the present invention, the idling flow rate can be adjusted within the predetermined idle flow rate range while keeping the fully closed flow rate within the predetermined full flow rate range at low cost. can do.

[Brief description of the drawings]

FIG. 1 is a front sectional view of an intake throttle device according to a first embodiment.

FIG. 2 is a left side view of FIG.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is an explanatory diagram showing a normal state of the power transmission means.

FIG. 5 is an explanatory diagram showing a relief state of the power transmission means.

FIG. 6 is a sectional view showing a configuration of a main part.

FIG. 7 is a characteristic diagram showing flow characteristics of intake air.

FIG. 8 is a cross-sectional view showing a main part configuration of the second embodiment.

FIG. 9 is an explanatory diagram relating to a position of a throttle valve.

FIG. 10 is a characteristic diagram showing a flow rate characteristic of intake air of a conventional example.

FIG. 11 is a characteristic diagram illustrating a flow characteristic of intake air of a countermeasure example 3;

FIG. 12 is a characteristic diagram showing a flow characteristic of intake air of Countermeasure Example 4.

[Explanation of symbols]

 2 Intake passage 4 Throttle valve 23 Motor 50 Bypass passage 50a Inlet 50b Outlet 52 Adjusting screw (flow rate adjusting means)

Claims (1)

[Claims] 1. An intake throttle device for a diesel engine, wherein a throttle valve that opens and closes an intake passage of the diesel engine by opening and closing is controlled by a motor, wherein a bypass passage that bypasses the throttle valve is provided. Wherein a flow rate adjusting means for adjusting a flow rate of a bypass flow is provided, and an inlet or an outlet of the bypass passage is provided at a position where a non-bypass state is provided when the throttle valve is fully closed.