In addition, it is also possible to obtain an effect of stimulating the Meissner's corpuscle by further adding a component of a frequency band in a range from 10 Hz to 50 Hz to the vibration application waveform.

The first gain adjuster 120 performs first gain adjustment described below on the vibration application waveform.

The first gain adjustment is directed to increasing the gain of the vibration application waveform (increasing the amplitude of the vibration application waveform) when the clutch device is in a transition state between an engaged state and a disengaged state (a half clutch state where the clutch disc and the flywheel as well as the clutch cover are slipping from each other).

The first gain adjustment may be configured to increase the gain of the vibration application waveform in accordance with an increase in frictional vibration generated as a result of the half clutch state, for example.

FIG. 7 is a diagram schematically illustrating an example of the gain adjustment in the first gain adjuster.

In FIG. 7, the horizontal axis indicates acceleration of the frictional vibration, and the vertical axis indicates a gain multiplied by an added waveform.

The frictional vibration is caused by a slip-stick phenomenon in which, for example, a slip ratio between the clutch disc and the flywheel as well as the clutch cover varies cyclically.

It is possible to detect the frictional vibration based on, for example, an output of the clutch fluid pressure sensor 210 provided in the master cylinder 40.

The frictional vibration of the clutch device 1 is propagated to the master cylinder via the pipe L1 and the clutch fluid therein.

In addition, the frictional vibration may be detected using an acceleration sensor provided in a clutch housing or the pipe L1, for example.

In addition, the frictional vibration of the clutch disc may be estimated based on outputs of the engine rotation speed sensor 230 and the transmission input shaft rotation speed sensor 240. For example, when the output shaft rotational speed of the engine and the input shaft rotational speed of the transmission do not coincide with each other and the stroke of the clutch pedal 30 is not at a position corresponding to a disengaged state, a configuration may be adopted in which the frictional vibration is estimated to be increased on the assumption that the stroke of the clutch pedal 30 is in a half clutch state.

The second gain adjuster 130 performs second gain adjustment further described below on the vibration application waveform after the first gain adjustment.

The second gain adjustment is directed to performing gain adjustment in accordance with an operation speed of the clutch pedal 30.

The operation speed of the clutch pedal 30 (an angular speed at which the depressing surface member 31 rotates) is able to be determined by time differentiation of an operation amount (depression amount) of the clutch pedal 30 detected by the clutch fluid pressure sensor 210 or the clutch pedal stroke sensor 220.

FIG. 8 is a diagram schematically illustrating an example of gain adjustment in the second gain adjuster.

In FIG. 8, the horizontal axis indicates a pedal operation speed (e.g., an angular speed of the depressing surface member 31), and the vertical axis indicates a gain to be added to the gain after the first gain adjustment.

The gain may be configured to increase in accordance with an increase in the pedal operation speed (absolute value), for example.

Here, an increase rate of the gain with respect to the pedal operation speed is set to be larger, in a region where the operation speed of the pedal is low, than in a region where the operation speed is high. The increase rate of the gain with respect to the pedal operation speed is set to gradually decrease in accordance with an increase in the pedal operation speed.

In addition, when the absolute values of the pedal operation speed are equivalent, the gain on a returning side (engaging operation side) is set to be larger than the gain on a depressing side (releasing/disengaging operation side).

The second gain adjuster 130 may be configured to increase the gain in accordance with an increase in the operation amount (depression amount) of the clutch pedal 30, instead of or together with the pedal operation speed.

In this case, performing gain adjustment in accordance with the operation amount of the clutch pedal 30 makes it possible to achieve an effect as a spring/rigidity term.

The road surface vibration monitor 140 serves to monitor the output of the road surface input acceleration sensor 250 and to hold a history over a predetermined period of time.

FIG. 9 is a diagram schematically illustrating an example of an output history of the road surface input acceleration sensor.

In FIG. 9, the horizontal axis indicates time, and the vertical axis indicates a detection value (unsprung vertical acceleration) of the road surface input acceleration sensor 250.

Data on the output history of the road surface input acceleration sensor 250 is provided to the vibration amplitude calculator 150.

The vibration amplitude calculator 150 applies bandpass filter processing to the output of the road surface input acceleration sensor 250 provided by the road surface vibration monitor 140 to extract a component of a specific frequency region, and calculates a vibration amplitude of the frequency region.

FIG. 10 is a diagram schematically illustrating a calculation method of the vibration amplitude in the vibration amplitude calculator.

In FIG. 10, the horizontal axis indicates a frequency, and the vertical axis indicates a detection value of the road surface input acceleration sensor 250.

The bandpass filter may be configured, for example, to extract some of frequency bands (e.g., near 250 Hz) included in the band in a range from 100 Hz to 400 Hz.

A vibration amplitude A in the extracted frequency bands (e.g., an average value of the frequency bands) is provided to the third gain adjuster 160.

The third gain adjuster 160 performs third gain adjustment further described below on the vibration application waveform after the second gain adjustment.

The third gain adjuster 160 performs the third gain adjustment based on outputs of the road surface vibration monitor 140 and the vibration amplitude calculator 150.

FIG. 11 is a diagram schematically illustrating an example of gain adjustment in the third gain adjuster.

In FIG. 11, the horizontal axis indicates torque amplitude calculated by the vibration amplitude calculator 150, and the vertical axis indicates a gain to be added to the gain after the adjustments of the first and second gain adjustments.

As illustrated in FIG. 11, the third gain adjuster 160 increases a gain (increases the amplitude of the vibration application waveform) in accordance with an increase in vibration amplitude from a road surface.

In the third gain adjuster 160, when the vibration application amplitude added from the vibrator 101 is defined as ΔA and the vibration amplitude from the road surface obtained from the vibration amplitude calculator 150 is defined as A, ΔA/A is considered to be a Weber fraction W.

Thus, it is considered that performing gain adjustment to allow the Weber fraction W to be a predetermined value set in advance enables achievement of stable effects from a Weber-Fechner law.

The gain selector 170 generates vibration application waveforms corresponding to a plurality of gain values having different magnitudes in stages, based on gains having been subjected to the gain adjustments by the first gain adjuster 120, the second gain adjuster 130, and the third gain adjuster 160. The gain selector 170 also selects one vibration application waveform from the vibration application waveforms having been subjected to the amplitude adjustment performed by the plurality of gain values in accordance with a traveling mode selected by the traveling mode selector 270.

When the sports mode is selected as a traveling mode, for example, the gain selector 170 may be configured to select a larger gain than that of the normal mode (to increase the amplitude of the vibration application waveform) in order to further improve the operability of the clutch pedal 30.

According to the first embodiment described above, it is possible to obtain the following effects.

- (1) When the clutch device 1 is in a transition state (a half clutch state) between an engaged state and a disengaged state, applying vibration to the clutch pedal 30 stimulates receptors responsible for the skin sensation of the sole by which the driver performs a clutch operation and makes it easier for the driver to recognize a state of the clutch operation, thus making it possible to improve the operability of the clutch operation.

This makes it possible to improve drivability of the vehicle and smoothness of traveling.

- (2) The vibrator 101 applies vibration to the clutch pedal 30 with a vibration application waveform including a frequency component in a range from 100 Hz to 400 Hz to thereby apply vibration to the clutch pedal 30 in a frequency band with favorable sensitivity of a Pacinian corpuscle, which is a receptor responsible for skin sensation and is considered to have the fastest response in the skin sensation, thus making it easier for the driver to feel a change in pressure received from the sole, for example.

This enables the driver to have improved spatial resolving power that allows for perception of an amount of operation of the clutch device, thus making it possible to perform a more accurate clutch operation.

- (3) The clutch pedal 30 switches between a crimped state and a separated state of the flywheel as well as the clutch cover and the clutch disc, which are provided between the engine and the wheels, thereby switching between an engaged state and a disengaged state. The vibrator control unit 100 detects a transition state based on a slip state (a state of frictional vibration) of these elements, thereby making it possible to appropriately obtain the above-described effects.
- (4) Increasing the amplitude of the vibration application waveform in accordance with an increase in the operation speed (absolute value) of the clutch pedal 30 makes it possible to effectively improve sensitiveness of the driver for reaction force upon performing operations of disengaging and engaging the clutch. In particular, when the operation speed is fast, increasing the vibration application amplitude to emphasize a sense of reaction force (sense of pressure) allows the driver to feel a change corresponding to the operation speed, thus enabling an action as a damping term.
- (5) Increasing the amplitude of the vibration application waveform of the vibrator 101 in accordance with the increase in the amplitude of a vibration input from the road surface makes it possible to secure the above-described effects, even when vibration transmitted from the road surface increases due to, for example, a rough road surface or a rough tire pattern shape, by increasing the amplitude of the vibration application waveform.

Second Embodiment

Next, description is given of a second embodiment of the clutch operation device to which the invention is applied.

In the second embodiment, components similar to those of the foregoing first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted; description is given mainly of differences.

In the second embodiment, the vehicle is, for example, an electric vehicle including an electric motor as a traveling power source.

No physical clutch device as in the first embodiment is provided between the electric motor and a power transmission mechanism.

In the second embodiment, output torque of the electric motor is lowered in accordance with a depressing operation performed on the clutch pedal 30 to thereby generate, in a pseudo manner, effects similar to those of the case where the clutch is disengaged in the engine vehicle as in the first embodiment.

FIG. 12 is a diagram schematically illustrating a stroke of the clutch pedal in the clutch operation device of the second embodiment and a degree of power reduction in the electric motor.

In FIG. 12, the horizontal axis indicates the stroke of the clutch pedal, and the vertical axis indicates output torque (%) of the electric motor with respect to a clutch engaged state (a state in which the stroke of the clutch pedal is zero).

In the second embodiment, a configuration may be adopted in which a region R1, where a rate of a change in the output torque with respect to the stroke of the clutch pedal is a predetermined rate or more, is recognized as a transition region (a region corresponding to the half clutch of the physical clutch), thus improving an output gain of the vibration application waveform.

According to the second embodiment as described above, it is possible, even in the electric vehicle including no physical clutch device, to improve the operability of the clutch operation in the transition region in the same manner as the foregoing first embodiment.

MODIFICATION EXAMPLES

The invention is not limited to the embodiments described above, and various modifications or changes may be made, which are also within the technical scope of the invention.