JPH1061449A - Intake controller for engine with mechanical supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce air leakage in a throttle valve arrangement part at the time of the idle operation of an engine, by controlling clutch means for a supercharger to an uncoupling condition at the time of idle operation of the engine, and also controlling an opening/closing valve bypassed the supercharger to a closing condition. SOLUTION: An electromagnetic clutch 11 is uncoupled by a clutch control means 55 in a control unit 17 when an engine 1 is in a low load/low rotational area, so as to stop the operation of a supercharger by an engine 1. Then, the electromagnetic clutch 11 is changed over to a clamping condition at a point of time when the engine 1 is transferred from the low load/low rotational area to a high load area or a high rotational area. Also, an actuator 15 is controlled by a valve control means 56, so that an opening/closing valve 16 is made in an opening condition when a vehicle is traveled in the low load/low rotational area, and a supercharger is bypassed, then intake is supplied to the engine 1. Then, in the case that the engine 1 is put from this area to a supercharge operating area, the opening of the opening/closing valve 16 is gradually reduced and controlled to be transferred to a closing condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake control device for an engine with a mechanical supercharger, which is configured to transmit the driving force of the engine to a mechanical supercharger using clutch means such as an electromagnetic clutch. It is about.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Utility Model Publication No. 3-15784, for example, an engine with a mechanical supercharger in which a mechanical supercharger driven via an electromagnetic clutch is disposed in an intake passage. In the intake control device, an air bypass passage that bypasses the mechanical supercharger is provided, and an on-off valve that opens when the engine is under a low load is provided in the air bypass passage. And when the engine speed is equal to or higher than a predetermined value, the electromagnetic clutch is connected, and if the engine speed is equal to or higher than the predetermined value and the engine is in a low load operation state,
The on-off valve is opened while the electromagnetic clutch is connected.

[0003]

In the intake control apparatus for an engine with a mechanical supercharger, the time from when the engine is started until the engine load becomes equal to or more than a predetermined value or until the engine speed becomes equal to or more than a predetermined value. That is, during low-load low-speed operation of the engine, the electromagnetic clutch is disengaged to stop the operation of the mechanical supercharger, and the on-off valve is opened to prevent supercharging. In this case, there is a problem that the engine speed increases during idling operation of the engine and fuel efficiency deteriorates.

That is, during the idling operation, the engine load and the number of revolutions are both lower than a predetermined value, and the on-off valve of the air bypass passage is opened, so that the negative pressure of the engine passes through the air bypass passage. Acting on the downstream portion of the throttle valve, the pressure difference between the upstream portion and the downstream portion of the throttle valve is increased, and the air leakage in this portion is increased. Therefore, during idling operation with the throttle valve closed, there has been a problem that fuel consumption deteriorates because the engine speed increases more than necessary due to the air leakage.

Incidentally, it is conceivable to suppress the air leakage in this portion by reducing the hole diameter of the installation portion of the throttle valve. However, in such a configuration, there is a problem that the intake resistance increases. There is.

The present invention has been made in view of the above circumstances, and it is possible to effectively reduce air leakage at a throttle valve installation portion without increasing intake resistance and at the time of engine idling. An object of the present invention is to provide an intake control device for a charged engine.

[0007]

The invention according to claim 1 is
A throttle valve arranged on the upstream side of the mechanical supercharger,
An air bypass passage that connects the downstream side of the mechanical supercharger between the throttle valve and the mechanical supercharger, an open / close valve that opens and closes the air bypass passage, and mechanically supercharges the driving force of the engine body. And a clutch means for transmitting to the engine, the clutch means being disengaged at the time of low-load low-speed rotation of the engine, and the on-off valve being opened. The control device is provided with clutch control means for controlling the clutch means to be in a disengaged state when the engine is idling, and valve control means for controlling the on / off valve to be in a closed state.

According to the above configuration, when the engine is idling, the on-off valve of the air bypass passage is controlled to be closed, so that the negative pressure of the engine acts on the downstream portion of the throttle valve via the air bypass passage. In addition, by controlling the mechanical supercharger to the operation stop state by disengaging the clutch means, unnecessary supercharging is prevented.

According to a second aspect of the present invention, in the supercharge control apparatus for an engine with a mechanical supercharger according to the first aspect, an idle control passage for bypassing the throttle valve is provided, and a downstream side of the idle control passage is provided. Is connected to the downstream side of the mechanical supercharger.

According to the above configuration, a large pressure difference is generated between the atmospheric pressure acting on the upstream side of the idle control passage and the negative pressure of the engine acting on the downstream side of the idle control passage. By performing feedback control of the idle control valve provided in the control passage, the engine speed is quickly controlled.

According to a third aspect of the present invention, in the intake control apparatus for an engine with a mechanical supercharger according to the first or second aspect, a pressure balance hole located on an intake side of the mechanical supercharger; A pressure balance passage for communicating with a pressure balance hole located on the discharge side is provided, and the pressure balance passage is configured to communicate with the upstream side of the throttle valve through the communication passage.

According to the above configuration, when the rotor chamber of the mechanical supercharger enters a negative pressure state in accordance with the negative pressure of the engine, the pressure inside the respective pressure balance holes via the communication passage and the pressure balance passage. The introduction of the air suppresses the occurrence of a large pressure difference corresponding to the action of the negative pressure between the inside and outside of the mechanical seal member provided on the rotor shaft of the mechanical supercharger.

According to a fourth aspect of the present invention, when the engine shifts from the low-load low-rotation state to the supercharging operation state, the clutch means of the mechanical supercharger is operated with the on-off valve of the air bypass passage opened. 2. The method according to claim 1, wherein the fastening state is set.
3. The intake control device for an engine with a mechanical supercharger according to any one of 3 to 3, wherein when the engine shifts from an idling operation state to a supercharging operation state, control is performed to shift the on-off valve from a closed state to an open state. After a lapse of a predetermined time from the output of the signal, the clutch means is shifted to the engaged state.

According to the above configuration, when the engine load or the engine speed rises to the predetermined value from the idling operation state of the engine in which the on-off valve of the air bypass passage is closed and shifts to the supercharging operation state, When a predetermined time has elapsed after the on-off valve has been opened, the clutch means is engaged and the mechanical supercharger operates.

According to a fifth aspect of the present invention, in the intake control device for an engine with a mechanical supercharger according to the fourth aspect, the clutch means for transmitting the driving force of the engine body to the mechanical supercharger is provided by an electromagnetic clutch. In addition to the configuration, a pressure-pressing type actuator for driving an open / close valve of the air bypass passage is provided.

According to the above construction, when the engine is shifted from the idling operation state to the supercharging operation state in which the on-off valve of the air bypass passage is closed, the engine is driven by the pressure-push type actuator having poor responsiveness. After the control for opening the on-off valve is performed, when a predetermined time has elapsed, the clutch means including the electromagnetic clutch is engaged and the mechanical supercharger operates.

According to a sixth aspect of the present invention, in the intake control device for a mechanical supercharged engine according to the fourth or fifth aspect, the engine is connected to an engine connected to a manual transmission.

According to the above configuration, when the engine connected to the manual transmission, which is more susceptible to torque shock than the automatic transmission equipped with the torque converter, shifts from the idle operation state to the supercharging operation state, the air is discharged. Since the mechanical supercharger is operated after the opening and closing valve of the bypass passage is opened, the occurrence of a torque shock in which the engine torque rises temporarily temporarily is effectively prevented.

[0019]

FIG. 1 shows an embodiment of an intake control device for a mechanical supercharged engine according to the present invention.
The intake control device includes an air cleaner 3, an air flow meter 4, a throttle valve 5, a mechanical supercharger 6 provided sequentially from an upstream side of an intake passage 2 connected to an engine body 1.
It has an intercooler 7, a surge tank 8, and a fuel injection valve 9. The mechanical supercharger 6 is composed of a speed increasing gear-equipped resholm pump or the like, and is connected to an output shaft (crankshaft) of the engine body 1 via a clutch means including an electromagnetic clutch 11 and a power transmission belt 12.

The intake passage 2 is provided with a throttle valve 5 disposed upstream of the mechanical supercharger 6 and an air bypass passage 13 connected to a downstream portion of the mechanical supercharger 6. In addition, an idle control passage 14 that connects the upstream side of the throttle valve 5 and the downstream side of the mechanical supercharger 6 and bypasses the throttle valve 5 is provided. The air bypass passage 13 is provided with an opening / closing valve 16 which is opened and closed by a pressure-pressing actuator 15, and the pressure-pressing actuator 15 is provided in a control unit 17 comprising a microcomputer. The opening degree of the on-off valve 16 is adjusted by being driven in accordance with the control signal output from 56.

An idle control valve 18 for opening and closing the idle control passage 14 is provided in the idle control passage 14.
The idle control valve 18 is driven according to a control signal output from an idle control means 45 provided in the control unit 17 so that the opening of the idle control valve 18 is adjusted. Is configured. Further, an exhaust passage 62 having a catalytic converter 61 is connected to the engine body 1.

The structure of the mechanical supercharger 6 is shown in FIGS. The mechanical supercharger 6 includes a casing 20, and the inside of the casing 20 is partitioned into a rotor chamber 21 and a gear chamber 22. The rotor chamber 21 is provided with a female rotor 24 having a plurality of spiral grooves 23 and a male rotor 26 having a plurality of spiral protrusions 25. Each rotor 24, 26 has a rotor shaft 2
7 and 28, respectively. When the rotor shafts 27 and 28 are parallel to each other, the casing 20
And the groove 23 of the female rotor 24 and the ridge 25 of the male rotor 26 are engaged with each other.

The ends of the rotor shafts 27 and 28 project into the gear chamber 22. Gear 3 at each of these ends
1 and 32 are fixed, and both gears 31 and 32 are meshed with each other. Further, a small-diameter gear 33 for speed increase is connected to the tip of the rotor shaft 28. On the other hand, an input shaft 34 is rotatably supported by the casing 20 via a bearing 36, and a large-diameter gear 35 for speed increase is coupled to one end of the input shaft 34. And the small diameter gear 33 are meshed with each other. Thereby, with the rotation of the input shaft 34, the rotational force is transmitted in the order of the large-diameter gear 35, the small-diameter gear 33, the gear 32, and the gear 31,
The supercharging is performed by the synchronous rotation of the two rotors 24, 26.

The rotor shafts 31 and 32 are provided with mechanical seals 46 and 47 for sealing between the rotor chamber 21 and the bearing 33, and a pressure balance hole is provided in the rotor chamber 21 side. 48 and 49 are formed respectively. The pressure balance hole 48 located on the intake side of the mechanical supercharger 6 and the pressure balance hole 49 located on the intake discharge side are connected to each other by a pressure balance passage 50. Is connected to the upstream side of the throttle valve 5 through a communication passage 19 (see FIG. 1).

Next, the structure of the electromagnetic clutch 11 is shown in FIG.
It will be described based on. A rotary plate 41 is fixed to the other end of the input shaft 34, and an annular armature (rotated member to be sucked) 42 is fixed to the inner surface of the rotary plate 41 via a torsion damper (rubber) 43. .

On the other hand, a pulley 38 is rotatably supported at an end of the casing 20 via a bearing 37. A power transmission belt 1 shown in FIG.
2 is wound. An annular groove is formed in the pulley 38, and a coil (constituting an electromagnet) 39 is housed in the annular groove. When the coil 39 is energized, the armature 42 is magnetically attracted to the pulley 38 side, and the rotational force of the pulley 38 is transmitted to the output shaft 34. On the other hand, when the coil 39 is not energized, A minute gap 44 in the axial direction is secured between the armature 42 and the pulley 38.

The electromagnetic clutch 11 is brought into the engaged state by turning on the coil 39 in accordance with the output signal of the clutch control means 55 provided in the control unit 17 and the coil 39 is turned on. It is configured to be in a detached state by being stopped. That is, the control unit 17 includes a throttle sensor 51 for detecting the opening of the throttle valve 5, an engine speed sensor 52 for detecting the engine speed, an intake temperature sensor 53 for detecting the intake air temperature, and an engine coolant temperature. Detection signals output from various sensors such as a water temperature sensor 54 are input, and a control signal for driving the electromagnetic clutch 11 is output from the clutch control unit 55 based on the detection signals.

More specifically, as shown in FIG. 5, when the engine load is less than a fixed value P1 and the engine speed is a fixed value N
In a low-load low-speed region of less than 1, the electromagnetic clutch 11 is disengaged, and when the region shifts to the high-load region or the high-speed region, that is, when the engine load becomes equal to or more than the above value P1, or Is the above value N1
At this point, the electromagnetic clutch 11 is switched from the disengaged state to the engaged state. Further, the electromagnetic clutch 11 is maintained in the disengaged state during the idle operation of the engine shown by the oblique lines in FIG.

The valve control means 56 opens the on-off valve 16 when the vehicle is running in the low-load low-rotation region where the engine load is less than the constant value P1 and the engine speed is less than the constant value N1. It is configured to maintain. Then, when it is confirmed that the engine load has become equal to or more than the fixed value P1 or the engine speed has become equal to or more than the fixed value N1 and the vehicle has entered the supercharging operation region from the low load low rotation region, for example, as shown in FIG. From the point in time when the throttle opening becomes greater than or equal to A and the control signal for engaging the electromagnetic clutch 11 is output, the on-off valve 16
Is configured to output a control signal for performing feedback control of the pressure-pressing type actuator 15 so as to gradually reduce the opening degree of the actuator and shift from the open state to the closed state. In this feedback control, the opening degree of the target on-off valve 16 is changed over time,
By gradually changing the opening in accordance with the opening degree, the pressure-pressing type actuator 15 is operated so as to attain the changing target opening degree.

The idling control means 45 drives the idling control valve 18 of the idling control passage 14 to open and close to adjust the opening thereof while the throttle valve 5 of the intake passage 2 is closed during idling of the engine. Thus, idle control for setting the engine speed to a predetermined idle speed is executed.

When shifting from the idle operation state to the supercharging operation state, as shown in FIG. 7, the valve control means 56 shifts the on-off valve 16 in the closed state to the open state. T when the control signal to be output is output
A control signal for shifting the electromagnetic clutch 11 from the disengaged state to the engaged state is output from the clutch control means 55 to the electromagnetic clutch 11 at a time T2 when a predetermined time has elapsed from 1. This allows the on-off valve 16
A predetermined time lag t is provided between a time point T1 at which is shifted from the open state to the closed state and a time point T2 at which the electromagnetic clutch 11 is shifted from the disengaged state to the engaged state. Note that the broken line in FIG. 7 indicates a state in which the opening of the on-off valve 16 changes in an operation state other than the idle operation state of the engine.

As described above, the throttle valve 5 disposed on the upstream side of the mechanical supercharger 6 and the downstream side of the mechanical supercharger 6 are connected to the downstream side of the throttle valve 5 by mechanical supercharging. An air bypass passage 13 connected to the upstream side of the engine 6, an on-off valve 16 for opening and closing the air bypass passage 13, and an electromagnetic clutch 11 for transmitting the driving force of the engine body 1 to the mechanical supercharger 6. The electromagnetic clutch 11 is disengaged when the engine is running at a low load and low speed, and the on-off valve 1
In an intake control device for an engine with a mechanical supercharger configured to open the engine 6, the electromagnetic clutch 11 is disengaged and the on-off valve 16 is closed when the engine is idling. With this configuration, it is possible to effectively suppress the occurrence of air leakage at the installation portion of the throttle valve 5 during the idle operation of the engine.

That is, by closing the on-off valve 16 provided in the air bypass passage 13 during the idling operation, the influence of the negative pressure generated in the engine main body 1 is reduced by the throttle through the air bypass passage 13. The throttle valve 5 is prevented from reaching the downstream portion of the valve 5.
It is possible to suppress a large pressure difference from occurring between the upstream portion and the downstream portion, and thus it is possible to effectively reduce air leakage generated in this portion. Therefore,
This prevents the engine speed from increasing due to the air leakage during idling operation of the engine with the throttle valve 5 closed without employing a means such as reducing the diameter of the installation portion of the throttle valve 5. As a result, the fuel efficiency of the engine can be improved.

In the above embodiment, the throttle valve 5
Is connected to the downstream side of the mechanical supercharger 6. In this configuration, during the idling operation, since the on-off valve 16 of the air bypass passage 13 is closed, the negative pressure acting immediately below the throttle valve 5 is small. This is because, even if the downstream side portion is connected, a sufficient pressure difference does not occur between the upstream side portion and the downstream side portion of the idle control valve 18, and it becomes difficult to control the intake air amount.

On the other hand, as described above, the throttle valve 5
When the downstream side of the idle control passage 14 that bypasses the engine is connected to the downstream side of the mechanical supercharger 6, the atmospheric pressure acting on the upstream part of the idle control passage 14 and the downstream of the idle control passage 14 A large pressure difference can be generated between the engine and the negative pressure of the engine acting on the engine, thereby controlling the idle control valve 18 of the idle control passage 14 by feedback control to adjust the opening thereof. Control can be executed properly.

In the above embodiment, the mechanical supercharger 6
A pressure balance passage 50 is provided for communicating a pressure balance hole 48 located on the suction side with a pressure balance hole 49 located on the discharge side, and the pressure balance passage 50 is connected upstream of the throttle valve 5 by the communication passage 19. The communication passage 19 and the pressure balance passage 5 when the inside of the rotor chamber 21 is in a negative pressure state in accordance with the negative pressure in the engine body 1 because of the communication with the side portion.
By introducing air into each of the pressure balance holes 48, 49 through the holes 0, it is possible to prevent a large pressure difference between the inside and outside of the mechanical seal members 46, 47 provided on the rotor shafts 31, 32. Can be. Therefore,
It is possible to effectively reduce a decrease in the sealing performance and durability of the mechanical seal members 46 and 47 due to the generation of a large pressure difference corresponding to the negative pressure action inside and outside the mechanical seal members 46 and 47. Can be prevented.

When the pressure balance holes 48, 49, the pressure balance passage 50, and the communication passage 19 are provided as described above, the air introduced into the pressure balance holes 48, 49 is supplied to the engine body 1. Therefore, if air leakage occurs more than this, the engine speed will increase significantly during idling. Therefore,
When the engine is idling, the air bypass passage 13
By setting the on-off valve 16 in the closed state, it is possible to obtain an effect of improving fuel efficiency by preventing the engine speed from increasing remarkably.

In the above embodiment, when the engine shifts from the low-load low-rotation region to the supercharging operation region, the electromagnetic valve of the mechanical supercharger 6 is opened with the on-off valve 16 of the air bypass passage 13 opened. A control signal for shifting the on-off valve 16 from the closed state to the open state when the engine shifts from the idling operation state to the supercharging operation state in the intake control device for the engine configured to put the clutch 11 into the engaged state. The control signal for shifting the electromagnetic clutch 11 to the engaged state is output after a lapse of a predetermined time from the output time of the electromagnetic clutch 11, so that the electromagnetic clutch 11 is engaged before the on-off valve 16 is opened. It is possible to prevent an increase in engine torque due to the supply.

Therefore, as shown in FIG.
In a state in which the air is bypassed by the air bypass passage 13 with the air conditioner 6 open, the electromagnetic clutch 11 is shifted to the engaged state and the mechanical supercharger 6 is operated to gradually increase the supercharging amount. So you can
It is possible to reliably prevent the occurrence of a torque shock in which the engine torque temporarily increases.

The above-described pressure-pressing type actuator 1
Instead of 5, the opening / closing valve 16 may be driven by an actuator composed of a stepping motor, and a clutch means other than the electromagnetic clutch 11 may be used. However, as shown in the above embodiment, the driving of the engine body 1 is performed. In the case where the clutch means for transmitting the force to the mechanical supercharger 6 is constituted by the electromagnetic clutch 11 and the opening / closing valve of the air bypass passage 13 is driven by the actuator comprising the pressure-pressing type actuator 15, Is because the response of the electromagnetic clutch 11 is good and the response of the pressure-pressing type actuator is poor.
When a control signal for simultaneously operating the electromagnetic clutch 11 and the pressure-pressing type actuator is output, the supercharging is performed by the electromagnetic clutch 11 being engaged before the on-off valve 16 is opened. Tends to be easy.

Accordingly, when the engine shifts from the idling operation state to the supercharging operation state as described above, after a lapse of a predetermined time t from the output point of the control signal for shifting the open / close valve 16 from the closed state to the open state. Preferably, a control signal for shifting the electromagnetic clutch 11 to the engaged state is output from the clutch control means 55 to prevent the occurrence of the torque shock.

In the intake control device for an engine connected to a manual transmission, a torque shock is more likely to occur than in an automatic transmission having a torque converter. When a predetermined time t elapses from the output of the control signal for shifting the open / close valve 16 of the air bypass passage 13 from the closed state to the open state, the clutch means including the electromagnetic clutch 11 is brought into the engaged state. By providing a control signal to be shifted, there is an advantage that the occurrence of the torque shock can be effectively prevented.

Further, in the above-described embodiment, an example has been described in which the on-off valve 15 of the air bypass passage 13 is fully opened at the time of low-load low-speed rotation of the engine shown in FIG. The on-off valve 15 may be configured to be in a half-open state.

[0044]

As described above, according to the present invention, the throttle valve disposed on the upstream side of the mechanical supercharger and the downstream side of the mechanical supercharger An air bypass passage connected between the upstream side of the turbocharger, an on-off valve for opening and closing the air bypass passage, and clutch means for transmitting the driving force of the engine body to the mechanical supercharger, In the intake control device for an engine with a mechanical supercharger, which is configured to disengage the clutch means at the time of low load and low rotation of the engine and to open the open / close valve, at the time of idling operation of the engine, Since the clutch means is disengaged and the on-off valve is closed, the engine negative pressure acts on the downstream portion of the throttle valve via the air bypass passage during idling operation. Preventing, the throttle valve can be great pressure on the upstream portion and the downstream portion is prevented from occurring, it is possible to prevent the leakage of air occurs in this portion.

Therefore, during idle operation of the engine with the throttle valve closed, the engine speed due to the air leakage is reduced without employing means such as reducing the diameter of the installation portion of the throttle valve. The effect of suppressing the intake flow resistance by preventing the rise and setting the diameter of the installation portion of the throttle valve to a predetermined value, and the effect of improving the fuel efficiency by suppressing the increase in the engine speed during idling operation. There is an advantage that it can be obtained at the same time.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram illustrating an example of a mechanical supercharged engine including an intake control device according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional side view of the mechanical supercharger.

FIG. 3 is a sectional front view of the mechanical supercharger.

FIG. 4 is a sectional side view of an electromagnetic clutch provided in the mechanical supercharger.

FIG. 5 is an explanatory diagram showing an operating region of the engine.

FIG. 6 is a graph showing a relationship between a throttle opening degree and an open / closed state of an on-off valve.

FIG. 7 is a time chart showing the opening / closing operation of the on-off valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 6 Mechanical supercharger 11 Electromagnetic clutch (clutch means) 14 Idle control passage 18 Idle control valve 16 On-off valve 17 Control unit 19 Communication passage 48, 49 Pressure balance hole 50 Pressure balance passage 55 Clutch control means 56 Valve control means

Claims (6)

[Claims] 1. A throttle valve disposed on an upstream side of a mechanical supercharger, and an air bypass passage connecting a downstream side of the mechanical supercharger between the throttle valve and the mechanical supercharger. When,
An opening / closing valve for opening and closing the air bypass passage, and clutch means for transmitting the driving force of the engine body to the mechanical supercharger. An intake control device for an engine with a mechanical supercharger configured to open an on-off valve; a clutch control means for controlling the clutch means to be in a disengaged state when the engine is idling; Valve control means for controlling a valve to be in a closed state. 2. The mechanical system according to claim 1, wherein an idle control passage for bypassing the throttle valve is provided, and a downstream side of the idle control passage is connected to a downstream side of the mechanical supercharger. Supercharging control device for supercharged engine. 3. A pressure balance passage which communicates a pressure balance hole located on a suction side of a mechanical supercharger with a pressure balance hole located on a discharge side, and the pressure balance passage is formed by a communication passage. 3. The intake control device for an engine with a mechanical supercharger according to claim 1, wherein the intake control device is configured to communicate with an upstream side of the throttle valve. 4. When the engine shifts from a low-load low-rotation state to a supercharging operation state, the clutch means of the mechanical supercharger is brought into the engaged state with the on-off valve of the air bypass passage opened. The intake control device for a mechanically-charged engine according to any one of claims 1 to 3, wherein the on-off valve is closed from a closed state when the engine shifts from an idle operation state to a supercharged operation state. An intake control device for an engine with a mechanical supercharger, wherein the clutch means is shifted to an engaged state after a lapse of a predetermined time from the output of a control signal for shifting to an open state. 5. A clutch means for transmitting a driving force of an engine body to a mechanical supercharger is constituted by an electromagnetic clutch, and a pressure-pressing actuator for driving an on-off valve of an air bypass passage is provided. The intake control device for an engine with a mechanical supercharger according to claim 4, wherein 6. The intake control device for an engine with a mechanical supercharger according to claim 4, wherein the intake control device is provided in an engine connected to a manual transmission.