Technical Field
[0001] The present invention relates to an engine with a throttle device including a sensor
that detects the opening of a throttle valve, and an engine-driven vehicle.
Background Art
[0002] A conventional throttle device is described in, for example, patent literature 1.
The throttle device disclosed in patent literature 1 includes a butterfly throttle
valve, a motor that drives the throttle valve, and a sensor configured to detect the
opening of the throttle valve.
[0003] The throttle valve includes a disc-shaped valve element and a throttle shaft that
rotates integrally with the valve element.
[0004] The throttle shaft is connected to the output shaft of the motor via a gear mechanism.
The gear mechanism decelerates the rotation of the motor and transfers it to the throttle
shaft. The gear mechanism includes a driving gear provided on the output shaft, a
driven gear provided on the throttle shaft, and a transmission gear that meshes with
the gears. The transmission gear is provided on an intermediate shaft located between
the output shaft and the throttle shaft.
[0005] The sensor detects the rotation angle of the intermediate shaft.
[0006] In a lightweight engine-driven vehicle such as a motorcycle, the throttle valve needs
to accurately follow an accelerator handler because the power weight ratio (weight
per unit horsepower) is low. To implement this, the opening of the throttle valve
(the rotation angle of the throttle shaft) needs to be detected at a high accuracy.
Related Art Literature
Patent Literature
[0007] Patent Literature 1: Japanese Patent Laid-Open No.
2010-19137
Disclosure of Invention
Problem to be Solved by the Invention
[0008] In the throttle device described in patent literature 1, it is difficult to accurately
obtain the rotation angle of the throttle shaft. This is because the intermediate
shaft whose rotation angle is detected by the sensor is connected to the throttle
shaft via the gears. That is, since a backlash exists in the meshing portion between
the gears, the rotation angle of the throttle shaft with respect to the rotation angle
of the intermediate shaft is unreliable.
[0009] This problem can be solved to some extent by directly detecting the rotation angle
of the throttle shaft using the sensor. However, when this arrangement is employed,
the sensor needs to be arranged near the end of the throttle shaft, and a projecting
portion made of the sensor is formed on a side of the throttle device. That is, the
throttle device becomes bulky, posing a new problem. In addition, since the rotation
angle of the throttle shaft is smaller than that of the intermediate shaft, the resolution
of the rotation angle detected by the sensor lowers.
[0010] The present invention has been made to solve the above-described problems, and has
as its first object to provide an engine with a throttle device capable of accurately
detecting the rotation angle of a throttle shaft while employing an arrangement that
causes a sensor to detect the rotation angle of a rotating shaft different from the
throttle shaft. It is the second object of the present invention to provide an engine-driven
vehicle easy to drive because a throttle valve accurately follows a throttle handler.
Means of Solution to the Problem
[0011] In order to achieve the object, according to the present invention, there is provided
an engine with a throttle device, comprising a throttle valve provided in an intake
passage of the engine, a throttle shaft that rotates integrally with a valve element
of the throttle valve, a spring member that biases the valve element in a direction
to close, a throttle valve driving motor connected to the throttle shaft via a gear
mechanism, a sensor that detects a rotation angle of a rotating shaft different from
the throttle shaft in the gear mechanism, and a throttle angle calculation unit that
obtains the rotation angle of the throttle shaft using a detection value of the sensor,
wherein the rotation angle of the rotating shaft detected by the sensor is defined
as a detection angle, the rotation angle of the rotating shaft corresponding to an
amount of backlash involved in a meshing portion of gears provided between the rotating
shaft and the throttle shaft is defined as a backlash angle, and the throttle angle
calculation unit calculates the rotation angle of the throttle shaft based on the
rotation angle obtained by subtracting the backlash angle from the detection angle.
[0012] According to the present invention, there is also provided an engine-driven vehicle
including an engine with a throttle device according to the above-described invention.
Effects of the Invention
[0013] According to the present invention, the backlash involved in the meshing portion
between the gears located between the rotating shaft and the throttle shaft is substantially
removed. For this reason, since the rotating shaft and the throttle shaft substantially
integrally rotate, the rotation angle of the throttle shaft can accurately be obtained.
[0014] Hence, according to the present invention, it is possible to provide an engine with
a throttle device capable of accurately detecting the rotation angle of a throttle
shaft while employing an arrangement that causes a sensor to detect the rotation angle
of a rotating shaft different from the throttle shaft.
[0015] The engine-driven vehicle according to the present invention is easy to drive because
it includes the above-described throttle device, and the throttle valve accurately
follows the throttle handler.
Brief Description of Drawings
[0016]
Fig. 1 is a side view of a motorcycle including an engine with a throttle device according
to the first embodiment of the present invention;
Fig. 2 is a perspective view showing the arrangement of a throttle valve driving unit
according to the first embodiment of the present invention;
Fig. 3 is a side view showing the main portion of a throttle device according to the
first embodiment of the present invention;
Fig. 4 is a side view of a valve gear according to the first embodiment of the present
invention;
Fig. 5 is an enlarged side view showing the meshing portion between the valve gear
and a pinion gear according to the first embodiment of the present invention;
Fig. 6 is a block diagram showing the arrangement of a throttle angle calculation
unit according to the first embodiment of the present invention;
Fig. 7 is a flowchart for explaining a throttle angle calculation program according
to the first embodiment of the present invention;
Fig. 8 is a graph showing the relationship between the output value of an angle sensor
and the rotation angle of the throttle shaft according to the first embodiment of
the present invention;
Fig. 9 is a flowchart for explaining the operation of a CPU according to the first
embodiment of the present invention;
Fig. 10 is a flowchart for explaining a throttle angle calculation program according
to the second embodiment of the present invention;
Fig. 11 is a flowchart for explaining the operation of a CPU according to the second
embodiment of the present invention; and
Fig. 12 is a sectional view for explaining a technique as a reference to the present
invention.
Best Mode for Carrying Out the Invention
(First Embodiment)
[0017] An engine with a throttle device and an engine-driven vehicle according to an embodiment
of the present invention will now be described in detail with reference to Figs. 1
to 9. Here, an embodiment when applying the present invention to a motorcycle will
be explained. The first embodiment is an embodiment of the present invention described
in claims 1 to 4 and 7.
[0018] In a motorcycle 1 shown in Fig. 1, a driver (not shown) sits astride a seat 2 and
drives while gripping a steering handlebar 3 with hands. Reference numeral 4 denotes
a front wheel; 5, a front fork; 6, an engine; and 7, a rear wheel. The steering handlebar
3 is provided with an accelerator handler (not shown) to be operated by the driver.
[0019] The engine 6 is a four-stroke engine, and includes a crank case 11, and a cylinder
body 12 and a cylinder head 13 attached on the crank case 11. The cylinder body 12
is attached on the crank case 11 such that the axis points the upper front side of
the motorcycle 1.
[0020] An inlet pipe 14 is attached to the rear surface of the cylinder head 13. A throttle
valve driving unit 22 of an electric throttle device 21 to be described later is attached
to the upstream end of the inlet pipe 14.
[0021] The throttle device 21 is formed from the throttle valve driving unit 22 shown in
Fig. 2 and a throttle angle calculation unit 23 shown in Fig. 6.
[0022] The throttle valve driving unit 22 includes a butterfly throttle valve 24, a throttle
valve driving motor 26 connected to the throttle valve 24 via a gear mechanism 25,
and the like. Fig. 2 illustrates only the main members of the throttle valve driving
unit 22 while omitting members such a throttle body. The throttle valve 24 includes
one throttle shaft 27, and a plurality of disc-shaped valve elements 28 attached to
the throttle shaft 27.
[0023] The throttle shaft 27 is rotatably supported by the throttle body (not shown) while
extending in the width direction of the motorcycle 1. The throttle shaft 27 rotates
integrally with the valve elements 28. The throttle shaft 27 extends through a torsion
coil spring 29 (see Fig. 3). The torsion coil spring 29 biases the valve elements
28 in the closing direction. One end of the torsion coil spring 29 is hooked on a
valve gear 30 attached to the throttle shaft 27, and the other end is hooked on the
throttle body. The throttle shaft 27 rotates integrally with the valve gear 30.
[0024] As shown in Fig. 2, the valve elements 28 are provided in an intake passage 31. The
intake passage 31 extends from an air cleaner (not shown) into the cylinder head 13
via the throttle body and the inlet pipe 14.
[0025] As shown in Fig. 3, the gear mechanism 25 forms a two-stage gear reducer, and is
formed from four gears including the valve gear 30. The four gears include the valve
gear 30, a pinion gear 32 that meshes with the valve gear 30, a wheel gear 33 that
rotates integrally with the pinion gear 32, and a motor gear 34 that meshes with the
wheel gear 33. These gears are made of plastic. The pinion gear 32 and the wheel gear
33 are integrally formed so as to form one intermediate gear 35.
[0026] The valve gear 30 is formed from a so-called sector gear, and includes a fan-shaped
gear forming portion 30a. As shown in Fig. 4, the valve gear 30 includes a full close
stopper 36 and a full open stopper 37. The full close stopper 36 is used to set the
full close position of the throttle valve 24. As shown in Fig. 2, the full close stopper
36 is formed to have an L-shaped section and provided at one end of the gear forming
portion 30a in the rotational direction. When the full close stopper 36 abuts against
an adjusting bolt 38 (see Fig. 4) on the throttle body side, rotation of the valve
gear 30 in a direction to close the throttle valve 24 is regulated.
[0027] The full open stopper 37 is formed into a plate shape standing on the valve gear
30 and provided at the other end of the gear forming portion 30a in the rotational
direction. When the full open stopper 37 abuts against a pressure wall 39 of the valve
body, as indicated by the alternate long and two short dashed line in Fig. 4, rotation
of the valve gear 30 in a direction to open the throttle valve 24 is regulated.
[0028] That is, the valve gear 30 can rotate only by a designed rotation angle θ1 (see Fig.
4) from the full close position (full close abutting position) where the full close
stopper 36 abuts against the adjusting bolt 38 to the full open position (full open
abutting position) where the full open stopper 37 abuts against the pressure wall
39.
[0029] The intermediate gear 35 formed from the pinion gear 32 and the wheel gear 33 is
fixed to one end of an intermediate shaft 40 (see Figs. 2 and 3) and rotatably supported
by the throttle body via the intermediate shaft 40. The pinion gear 32 is provided
at one end of the wheel gear 33 adjacent to the intake passage 31. Because of a backlash
in the meshing portion to the valve gear 30, as shown in Fig. 5, the pinion gear 32
can rotate only by a backlash angle α with respect to the valve gear 30. Referring
to Fig. 5, a line C1 indicates the pitch circle of the pinion gear 32, and a line
C2 indicates the pitch circle of the wheel gear 33.
[0030] As shown in Figs. 2 and 3, a ring magnet 41 is attached to the other end of the wheel
gear 33 in the axial direction. The ring magnet 41 is formed into a ring shape and
fixed on the axis of the wheel gear 33 so as to be located on the same axis as the
wheel gear 33. The ring magnet 41 is magnetized so as to divide magnetic poles 41a
and 41b (see Fig. 2) by a virtual line perpendicular to the axis when viewed from
the axial direction of the wheel gear 33.
[0031] An angle sensor 42 is arranged at a position facing the ring magnet 41. The angle
sensor 42 detects the rotation angle of a rotating shaft 43 formed from the intermediate
gear 35 and the intermediate shaft 40, and is formed from a vector detection hole
IC. In this embodiment, the angle sensor 42 forms a "sensor" in the present invention.
The angle sensor 42 is supported by the throttle body while forming a predetermined
gap with respect to the ring magnet 41. That is, the angle sensor 42 detects the rotation
angle of the rotating shaft 43 different from the throttle shaft 27 in the gear mechanism
25. A detection angle that is a rotation angle of the rotating shaft 43 detected by
the angle sensor 42 is sent to the throttle angle calculation unit 23 (to be described
later) as a signal.
[0032] The motor gear 34 is provided on an output shaft 44 of the throttle valve driving
motor 26. That is, rotation of the motor 26 is transferred from the motor gear 34
to the valve gear 30 (throttle shaft 27) via the wheel gear 33 and the pinion gear
32. The motor 26 is supported by the throttle body. The operation of the motor 26
is controlled by the throttle angle calculation unit 23 to be described later.
[0033] The throttle angle calculation unit 23 obtains the rotation angle of the throttle
shaft 27 using the detection angle detected by the angle sensor 42, and operates the
throttle shaft 27 so as to interlock with the accelerator handler. As shown in Fig
6, the throttle angle calculation unit 23 according to this embodiment is formed from
an ECU 54 (Electronic Control Unit) including a CPU 51, a nonvolatile memory 52, a
motor driver 53, and the like.
[0034] The throttle angle calculation unit 23 is provided in a control device 55 (see Fig.
1) arranged under the seat 2 of the motorcycle 1. The control device 55 controls the
operation of the engine 6 of the motorcycle 1.
[0035] The CPU 51 includes an AD (analog/digital converter) 56 that receives a signal. The
angle sensor 42, an accelerator manipulation amount sensor 57, and the like are connected
to the AD 56. The accelerator manipulation amount sensor 57 detects the manipulation
amount of the accelerator handler and sends it to the AD 56 as a signal.
[0036] The nonvolatile memory 52 is used to store programs to be used by the CPU 51, numerical
data calculated by the CPU 51, and the like. In this embodiment, the nonvolatile memory
52 corresponds to a "storage device" in the present invention. The motor driver 53
is used to drive the throttle valve driving motor 26.
[0037] The CPU 51 according to this embodiment calculates the rotation angle of the throttle
shaft 27 using a throttle angle calculation program to be described later.
[0038] When the throttle angle calculation program is executed, a rotation angle θ2 of the
throttle shaft 27 is calculated by calculation using the detection angle of the angle
sensor 42, the backlash angle α, the designed rotation angle θ1, and the like.
[0039] The CPU 51 sends a control signal to the motor driver 53 to operate the throttle
valve driving motor 26 such that the difference between the rotation angle θ2 of the
throttle shaft 27 calculated by executing the throttle angle calculation program and
a target rotation angle θ3 corresponding to the manipulation amount of the accelerator
handler becomes 0.
[0040] The throttle angle calculation program is configured as shown in the flowchart of
Fig. 7, and recorded in the nonvolatile memory 52. The CPU 51 reads out the throttle
angle calculation program from the nonvolatile memory 52 as needed and uses it.
[0041] The throttle angle calculation program according to this embodiment employs a configuration
for calculating the actual backlash angle α and then calculating the rotation angle
θ2 of the throttle shaft 27. The backlash angle α is assumed to be calculated upon
shipment from the factory or upon power-on.
[0042] Calculation of the backlash angle α is performed in steps S1 to S3 of the flowchart
shown in Fig. 7. Calculation of the rotation angle θ2 of the throttle shaft 27 is
performed in step S4. In step S1, first, the CPU 51 causes the throttle valve driving
motor 26 to close the throttle valve 24. The CPU 51 acquires an output value A of
the angle sensor 42 in a state in which the throttle valve 24 is at the full close
abutting position. The full close abutting position is the position of the throttle
valve 24 when the full close stopper 36 abuts against the adjusting bolt 38.
[0043] In step S2, first, the CPU 51 causes the throttle valve driving motor 26 to open
the throttle valve 24. The CPU 51 acquires an output value B of the angle sensor 42
in a state in which the throttle valve 24 is at the full open abutting position. The
full open abutting position is the position of the throttle valve 24 when the full
open stopper 37 abuts against the pressure wall 39 of the throttle body. When the
motor operates the throttle valve 24 from the full close abutting position to the
full open abutting position in this way, the rotation angle θ2 of the throttle shaft
27 increases, as shown in Fig. 8.
[0044] The abscissa of Fig. 8 represents the output value of the angle sensor 42, and the
ordinate represents the rotation angle θ2 of the throttle shaft 27. When the motor
26 is operated as described above, the output value of the angle sensor 42 increases
from the output value A to an output value C only by the amount of backlash, and after
that, the throttle shaft 27 starts rotating. That is, the output value of the angle
sensor 42 acquired at the full open abutting position includes the backlash.
[0045] After the throttle valve 24 opens up to the full open abutting position, the CPU
51 subtracts a second operation angle from a first operation angle to be described
later to obtain the backlash angle α in step S3. The first operation angle is a rotation
angle of the throttle valve 24 including the backlash. The "rotation angle of the
throttle valve 24 including a backlash" can be obtained by subtracting the output
value A of the angle sensor 42 when the throttle valve 24 is fully closed by driving
of the motor 26 from the output value B of the angle sensor 42 when the throttle valve
24 is fully opened by driving of the motor 26.
[0046] The second operation angle is the true rotation angle of the throttle valve 24 and
corresponds to the rotation angle θ2 of the throttle valve 24 throttle shaft 27 when
the valve elements 28 of the throttle valve 24 are moved from the full close position
to the full open position. As the second operation angle, a designed value such as
the designed rotation angle θ1 shown in Fig. 4 or a measured value obtained by performing
measurement while actually operating the throttle valve 24 can be used.
[0047] When step S3 is executed, the backlash angle α corresponding to the difference between
the output value C and the output value A shown in Fig. 8 is calculated. In step S3,
the CPU 51 stores, in the nonvolatile memory 52, the backlash angle α calculated in
the above-described way.
[0048] In step S4, the CPU 51 calculates the rotation angle θ2 of the throttle shaft 27
based on the rotation angle obtained by subtracting the backlash angle α from the
detection angle of the angle sensor 42. The detection angle is a rotation angle of
the rotating shaft 43 detected by the angle sensor 42.
[0049] The CPU 51 according to this embodiment executes steps S1 to S3 at the time of shipment
from the factory and executes step S4 after power-on. The backlash angle α to be used
when executing step S4 is read out from the nonvolatile memory 52 and used. After
power-on, the CPU 51 operates based on an operation program shown in the flowchart
of Fig. 9.
[0050] More specifically, after power-on in step P1 of the flowchart shown in Fig. 9, the
CPU 51 reads out the backlash angle α from the nonvolatile memory 52 in step P2. In
step P3, the CPU 51 acquires the current rotation angle, that is, the detection angle
of the rotating shaft 43 using the angle sensor 42.
[0051] In step P4, the CPU 51 determines whether the detection angle is smaller than the
backlash angle α. In other words, the CPU 51 determines whether the rotation angle
of the rotating shaft 43 detected by the angle sensor 42 is a rotation angle between
the backlash angle α and the rotation angle at the time of fully closing the throttle.
If this determination results in YES, that is, when the detection angle is smaller
than the backlash angle α, the process advances to step P5, and the CPU 51 sets the
rotation angle θ2 of the throttle shaft 27 as the rotation angle at the time of fully
closing the throttle.
[0052] When the detection angle is equal to or larger than the backlash angle α, the process
advances to step P6 to execute step S4 described above. That is, in step P6, the CPU
51 calculates the rotation angle θ2 of the throttle shaft 27 based on the value obtained
by subtracting the backlash angle α from the detection angle.
[0053] After that, in step P7, the CPU 51 operates the motor 26 such that the rotation angle
θ2 of the throttle shaft 27 matches the target rotation angle.
[0054] Steps P3 to P7 are repetitively executed until power-off in step P8.
[0055] According to the engine with a throttle device having the above-described arrangement,
the backlash involved in the meshing portion of the gears located between the rotating
shaft 43 and the throttle shaft 27 is substantially removed. For this reason, since
the rotating shaft 43 and the throttle shaft 27 substantially integrally pivot, the
rotation angle θ2 of the throttle shaft 27 can accurately be obtained.
[0056] Hence, according to this embodiment, it is possible to provide an engine with a throttle
device capable of accurately detecting the rotation angle θ2 of the throttle shaft
27 while employing an arrangement that causes the angle sensor 42 to detect the rotation
angle of the rotating shaft 43 different from the throttle shaft 27.
[0057] The throttle angle calculation unit 23 according to this embodiment sets the rotation
angle θ2 of the throttle shaft 27 as the rotation angle at the time of fully closing
the throttle when the rotation angle of the rotating shaft 43 detected by the angle
sensor 42 is a rotation angle between the backlash angle α and the rotation angle
at the time of fully closing the throttle.
[0058] Hence, according to this embodiment, it is possible to accurately detect the fully
closed state of the throttle valve 24.
[0059] The throttle angle calculation unit 23 according to this embodiment calculates the
backlash angle α by subtracting the true second operation angle of the throttle valve
24 from the first operation angle of the throttle valve 24 including the backlash
obtained based on the detection value of the angle sensor 42.
[0060] Hence, according to this embodiment, since the backlash is obtained by subtracting
the second operation angle including no backlash from the first operation angle including
the backlash in the meshing portion between the gears, the backlash angle α can easily
and accurately be calculated by calculation.
[0061] In this embodiment, the device includes the nonvolatile memory 52 that stores the
backlash angle α calculated by the throttle angle calculation unit 23. The throttle
angle calculation unit 23 according to this embodiment calculates the backlash angle
α upon shipment from the factory and stores it in the nonvolatile memory 52. After
that, when operating the engine, the throttle angle calculation unit 23 calculates
the rotation angle θ2 of the throttle shaft 27 using the backlash angle α read out
from the nonvolatile memory 52.
[0062] Hence, according to this embodiment, the backlash angle α need not be calculated
every time the device is powered on. That is, according to this embodiment, it is
possible to provide an engine with a throttle device capable of quickly starting.
[0063] The motorcycle 1 according to this embodiment includes the above-described throttle
device 21 and is easy to drive because the throttle valve 24 accurately follows the
throttle handler.
(Second Embodiment)
[0064] A throttle angle calculation program and an operation program can be configured as
shown in Figs. 10 and 11. The same reference numerals as described in Figs. 1 to 9
denote the same or similar members in Figs. 10 and 11, and a detailed description
thereof will be omitted.
[0065] The throttle angle calculation program according to this embodiment employs a configuration
that rotates a rotating shaft 43 until the teeth of a pinion gear 32 hit those of
a valve gear 30, and detects a backlash angle α based on the rotation angle at this
time, although details will be described later.
[0066] In step S1 of the flowchart shown in Fig. 10, a CPU 51 of a throttle angle calculation
unit 23 according to this embodiment causes a throttle valve driving motor 26 to close
a throttle valve 24. The CPU 51 acquires an output value A of an angle sensor 42 in
a state in which the throttle valve 24 is at the full close abutting position. In
this embodiment, the output value A corresponds to a "first output value" in the invention
described in claim 5.
[0067] In step S20, the CPU 51 acquires an output value D of the angle sensor 42 in a state
in which the rotating shaft 43 is at a control full close position to be described
later. The control full close position is the position of the rotating shaft 43 when
the pinion gear 32 rotates only by the amount of backlash with respect to the valve
gear 30. To locate the rotating shaft 43 at the control full close position, the throttle
valve driving motor 26 applies a predetermined small torque to a throttle shaft 27.
[0068] The predetermined small torque here is a torque smaller than the initial torque of
a torsion coil spring 29. That is, the torque rotates only the rotating shaft 43 without
rotating the throttle shaft 27 against the spring force of the torsion coil spring
29. When the small torque is applied to the rotating shaft 43, the rotating shaft
43 rotates only by the amount of backlash. The output value D is the detection angle
of the angle sensor 42 when the rotating shaft 43 rotates in this way. In this embodiment,
the output value D corresponds to a "second output value" in the invention described
in claim 5.
[0069] In step S30, the CPU 51 subtracts the output value A (first output value) from the
output value D (second output value), thereby calculating a backlash angle α. After
that, the CPU 51 calculates a rotation angle θ2 of the throttle shaft 27 in step S4,
as in the first embodiment.
[0070] The throttle angle calculation program shown in Fig. 10 is incorporated in the operation
program shown in Fig. 11 and executed after power-on. That is, after power-on in step
P1 of the flowchart shown in Fig. 11, the CPU 51 executes steps S1, S20 and S30 of
the throttle angle calculation program to obtain the backlash angle α. The backlash
angle α is stored in a nonvolatile memory 52 by the CPU 51.
[0071] In step P2, the CPU 51 reads out the backlash angle α from the nonvolatile memory
52. In step P3, the CPU 51 acquires the current rotation angle, that is, the detection
angle of the rotating shaft 43 using the angle sensor 42.
[0072] In step P4, the CPU 51 determines whether the detection angle is smaller than the
backlash angle α.
In other words, the CPU 51 determines whether the rotation angle of the rotating shaft
43 detected by the angle sensor 42 is a rotation angle between the backlash angle
α and the rotation angle at the time of fully closing the throttle.
[0073] If this determination results in YES, that is, when the detection angle is smaller
than the backlash angle α, the process advances to step P5, and the CPU 51 sets the
rotation angle θ2 of the throttle shaft 27 as the rotation angle at the time of fully
closing the throttle.
[0074] When the detection angle is equal to or larger than the backlash angle α, the process
advances to step P6 to execute step S4 described above. That is, in step P6, the CPU
51 calculates the rotation angle θ2 of the throttle shaft 27 based on the value obtained
by subtracting the backlash angle α from the detection angle.
[0075] After that, in step P7, the CPU 51 operates the motor 26 such that the rotation angle
θ2 of the throttle shaft 27 matches the target rotation angle.
[0076] The operation program according to this embodiment is repetitively executed until
power-off in step P8. That is, the CPU 51 calculates the rotation angle θ2 of the
throttle shaft 27 using the backlash angle α read out from the nonvolatile memory
52 until power-off.
[0077] The CPU 51 of the throttle angle calculation unit 23 according to this embodiment
detects the first output value (output value A) of the angle sensor 42 when the throttle
valve 24 is fully closed by driving of the throttle valve driving motor 26. In addition,
the CPU 51 detects the second output value (output value D) of the angle sensor 42
when the throttle valve driving motor 26 applies a torque smaller than the initial
torque of the torsion coil spring 29 to the throttle shaft 27 in a direction to open
the throttle valve 24. The CPU 51 subtracts the first output value from the second
output value, thereby calculating the backlash angle α.
[0078] Hence, according to this embodiment, the backlash angle α can be calculated every
time the device is powered on. It is therefore possible to remove an increase in the
backlash angle α caused by aging as well and more accurately obtain the rotation angle
θ2 of the throttle shaft 27.
[0079] In this embodiment, the device includes the nonvolatile memory 52 that stores the
backlash angle α calculated by the throttle angle calculation unit 23. The throttle
angle calculation unit 23 calculates the backlash angle α upon power-on and stores
it in the nonvolatile memory 52. In addition, the throttle angle calculation unit
23 calculates the rotation angle θ2 of the throttle shaft 27 using the backlash angle
α read out from the nonvolatile memory 52 until power-off.
[0080] Hence, according to this embodiment, when operating an engine 6, calculation of the
backlash angle α can be done only once upon power-on. Hence, according to this embodiment,
it is possible to provide an engine with a throttle device capable of avoiding waste
in unnecessarily calculating the backlash angle α during an operation.
(Reference Technique)
[0081] The rotating shaft 43 whose rotation angle is detected by the angle sensor 42 can
be formed as shown in Fig. 12. The same reference numerals as described in Figs. 1
to 11 denote the same or similar members in Fig. 12, and a detailed description thereof
will be omitted.
[0082] The pinion gear 32 of the rotating shaft 43 shown in Fig. 12 is formed from a fixed
portion 61 formed integrally with the wheel gear 33, a movable portion 62 that is
rotatable with respect to the fixed portion 61, and a torsion coil spring 63 that
biases the movable portion 62 in one direction toward the fixed portion 61. The movable
portion 62 is rotatably supported by the intermediate shaft 40 while being arranged
on a side of the fixed portion 61 in the axial direction.
[0083] According to this embodiment, since the pinion gear 32 forms a so-called scissors
gear, an error caused by the backlash can be solved. The throttle device 21 described
in the first or second embodiment can obtain the same effects using a simple gear,
unlike the case where the scissors gear is used. Hence, when the first or second embodiment
is employed, the manufacturing cost can be suppressed low as compared to the case
where the scissors gear is used.
[0084] In the above-described embodiments, an example in which the present invention is
applied to a motorcycle has been explained. However, the present invention is applicable
to any vehicle as long as it includes an engine with a throttle device. The present
invention is applicable to, for example, a scooter, a motor tricycle, a four wheel
vehicle, an off-road vehicle, a snowmobile, a small planning boat, and the like.
Explanation of the Reference Numerals and Signs
[0085] 1...motorcycle, 6...engine, 21...throttle device, 23...throttle angle calculation
unit, 24...throttle valve, 25...gear mechanism, 26...throttle valve driving motor,
28...valve element, 27...throttle shaft, 29...torsion coil spring (spring member),
31...intake passage, 42...angle sensor, 43...rotating shaft, α...backlash angle