Work vehicle

Abstract

To provide a work vehicle that enables suppression of uncomfortable feeling of a driver generated when connecting a centrifugal clutch.SOLUTION: A work vehicle includes: a transmission 12 for shifting speed of power from an engine E; a centrifugal clutch 11 provided between the engine E and the transmission 12; and a throttle mechanism 6 that electronically controls an opening of the throttle valve 60 of the engine E by using a throttle control section 50. The throttle control section 50 electronically controls the opening of the throttle valve 60 by using a filter value derivation section 52 that derives an opening filter value from engine speed of the engine E and the opening of the throttle valve. The filter value derivation section 52 derives the opening filter value that lowers accelerator responsiveness in a derivation condition where the engine speed is equal to or lower than centrifugal clutch connection rotating speed of the centrifugal clutch 11.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a work vehicle that is provided with a centrifugal clutch between an engine and a transmission, and is equipped with an electronically controlled throttle mechanism. [Background technology]

[0002] Patent Document 1 discloses a multipurpose vehicle equipped with a gear transmission that changes the speed of power from the engine by shifting, and a centrifugal clutch provided between the engine and the gear transmission. When an incomplete engagement state of the gear transmission is detected, this multipurpose vehicle suppresses gear noise by executing a fuel cut that reduces the amount of fuel supplied to the engine below a reference value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-155698 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the incomplete engagement state of the gear transmission is determined based on the detection signal of the engagement state detection sensor, and when the gear transmission is incompletely engaged, the increase in engine speed is suppressed even if the accelerator is operated at high speed, thereby suppressing gear noise. However, when the gear transmission is fully engaged, the control to suppress the increase in engine speed does not function, so the discomfort felt by the driver due to the engagement shock that occurs when the centrifugal clutch is engaged remains the same.

[0005] SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a work vehicle that reduces the sense of discomfort felt by the driver when the centrifugal clutch is engaged. [Means for solving the problem]

[0006] A work vehicle according to the present invention comprises an engine, a transmission that changes the speed of power from the engine, a centrifugal clutch provided between the engine and the transmission, and a throttle mechanism that electronically controls the opening of a throttle valve of the engine using a throttle control unit, wherein the throttle control unit electronically controls the opening of the throttle valve using a filter value derivation unit that derives an opening filter value from the engine speed of the engine and the opening of the throttle valve, and the filter value derivation unit derives the opening filter value that reduces accelerator responsiveness under the derivation condition that the engine speed is equal to or lower than the centrifugal clutch engagement speed of the centrifugal clutch.

[0007] According to this configuration, when the engine speed is below the centrifugal clutch engagement speed of the centrifugal clutch, i.e., when the centrifugal clutch is in a disengaged state, the accelerator responsiveness is set low, thereby suppressing the shock (discomfort felt by the driver) caused by the centrifugal clutch being engaged due to a sudden increase in engine speed when starting off.

[0008] If accelerator responsiveness is set low even near an engine idling speed, which is lower than the centrifugal clutch engagement speed, the vehicle's start response characteristics will be slow, making it difficult for the driver to start the vehicle as intended. For this reason, it is preferable to set accelerator responsiveness low at a predetermined low engine speed, for example, an engine speed range higher than idling speed and lower than the centrifugal clutch engagement speed. Therefore, in the present invention, the filter value derivation unit derives the opening filter value that lowers the accelerator responsiveness compared to the opening filter value derived under other conditions when the engine speed is higher than idling speed but lower than the centrifugal clutch engagement speed. With this configuration, when the engine speed increases close to the clutch engagement speed, the change in throttle opening in the throttle opening direction becomes gradual, thereby reducing the discomfort caused by clutch engagement. By appropriately setting the opening filter value, a good balance between engine responsiveness and shock-free starting behavior can be achieved. In addition, when the vehicle is stopped on an uphill road with the right foot on the foot brake and then the driver switches to the accelerator pedal, the clutch is properly engaged, preventing the vehicle from rolling backward when starting on an incline.

[0009] Since the opening filter value for adjusting accelerator responsiveness, or the so-called smoothing degree, is preferably determined based on the engine speed and the throttle valve opening, the filter value derivation unit is configured with an experimentally and empirically determined calculation formula or a three-dimensional map (look-up table) defined by the engine speed, the throttle valve opening, and the opening filter value. Considering the calculation speed and calculation load, it is preferable to use a three-dimensional map. Furthermore, it is also preferable that the relationship between the engine speed, the throttle valve opening, and the opening filter value be at least partially changed depending on the vehicle's individual characteristics, aging of the vehicle, driver preferences, etc. Therefore, in the present invention, the filter value derivation unit has a three-dimensional map consisting of the engine speed of the engine, the throttle valve opening, and the opening filter value, and the three-dimensional map is changeable in part or in whole.

[0010] A centrifugal clutch controls power transmission by centrifugal force, and each centrifugal clutch has its own characteristics, resulting in some degree of variation in clutch characteristics. Furthermore, the characteristics of a centrifugal clutch change over time. For this reason, the present invention proposes that part or all of the three-dimensional map be changed in response to changes in the characteristics of the centrifugal clutch over time. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. [Figure 2] FIG. 2 is a plan view of the driver's seat, passenger seat, and dashboard area. [Figure 3] 2 is a schematic functional block diagram showing the functions of a control system and a drive system of the work vehicle. FIG. [Figure 4] FIG. 2 is a schematic diagram showing the relationship between an engine control unit, a throttle mechanism, and an accelerator pedal. [Figure 5] FIG. 4 is a schematic diagram for explaining the function of a filter value derivation unit. [Figure 6] 10 is a graph showing the relationship between engine rotation speed and a filter value. DETAILED DESCRIPTION OF THE INVENTION

[0012] A multipurpose vehicle, which is an example of a work vehicle according to the present invention, will be described below. In the following description, with respect to the multipurpose vehicle, the direction of arrow F shown in the drawings will be referred to as the "front of the vehicle body," the direction of arrow B as the "rear of the vehicle body," the direction of arrow U as the "upper of the vehicle body," the direction of arrow D as the "lower of the vehicle body," the direction of arrow L as the "left of the vehicle body," and the direction of arrow R as the "right of the vehicle body."

[0013] As shown in Figure 1, the multipurpose vehicle is equipped with a pair of left and right front wheels 1 that can be driven and steered, and a pair of left and right rear wheels 2 that can also be driven, and a body frame 3 is supported on the ground by the front wheels 1 and the rear wheels 2. A driver's section 9 is formed at the front of the body frame 3. A cargo bed 30 is provided at the rear of the body frame 3. An engine E and a transmission T are mounted below the cargo bed 30. The driver's section 9 is surrounded by a ROPs 9C.

[0014] As shown in Figures 1 and 2, the driver's section 9 is provided with a driver's seat 9A and a passenger seat 9B. A steering wheel 90 is disposed in front of the driver's seat 9A, and a dashboard 91 including an instrument panel 92 is disposed in front of the steering wheel 90. The instrument panel 92 is provided with a meter panel 93 as a display device, a touch panel 94, and various operation buttons. The meter panel 93 and the touch panel 94 may be integrated. The driver's section 9 is provided with manual operation devices such as an accelerator pedal 71 for adjusting the driving speed, a gear shift lever 72 for changing gears, and a brake pedal (not shown) for braking.

[0015] FIG. 3 is a schematic functional block diagram showing the functions of the drive system and control system of a work vehicle. The drive system consists of an engine E and a transmission T that changes the speed of power from the engine E and transmits it to the drive wheels (front wheels 1 and rear wheels 2). This work vehicle can be switched between 4WD and 2WD, so the drive wheels are the front wheels 1 and the rear wheels 2. The transmission T is equipped with a centrifugal clutch 11 that initially receives engine power, and a speed change device 12 that changes the speed of the power from the centrifugal clutch 11. The centrifugal clutch 11 enters a power transmission state when it receives rotational power (engine power) equal to or greater than a preset centrifugal clutch engagement speed, and enters a power cut-off state when the rotational power falls below the centrifugal clutch engagement speed. The centrifugal clutch engagement speed is set to be equal to or less than the idling speed. In this embodiment, the speed change device 12 consists of a belt-type continuously variable transmission that receives power from the centrifugal clutch 11, and a gear transmission that receives speed-changing power from the belt-type continuously variable transmission, but other device configurations may be used.

[0016] The control system includes, as components related to the present invention, an engine control unit 4 and a meter control unit 8, which are interconnected via an on-board LAN. The engine control unit 4 outputs various control commands to the engine E and engine peripheral devices, and receives detection signals indicating the engine state of the engine E, such as engine speed, detected by various sensors, etc. The engine control unit 4 includes a throttle control unit 50 as a functional unit particularly related to the present invention.

[0017] The meter control unit 8 acquires detection signals indicating the vehicle driving state, vehicle operation state, driver state, etc. from various sensors provided in the vehicle equipment group 7. Furthermore, the meter control unit 8 notifies the vehicle driving state, vehicle operation state, and driver state through various meters, lamps, and a touch panel 94 arranged on a meter panel 93. The meter control unit 8 also acquires operation signals from various operation switches arranged on the meter panel 93 and provides these to the engine control unit 4 as necessary. Furthermore, some detection signals from the vehicle equipment group 7, for example, an operation signal indicating operation of the accelerator pedal 71, are provided directly to the engine control unit 4.

[0018] 4 is a schematic diagram showing the relationship between the engine control unit 4, the throttle mechanism 6, and the accelerator pedal 71. The engine control unit 4 includes a throttle control section 50. The throttle control section 50 provides a throttle control signal to the throttle valve 60 of the engine E to control the opening of the throttle valve 60. An operation signal indicating the operation of the accelerator pedal 71 is provided to the throttle control section 50.

[0019] The throttle control unit 50 electronically controls the opening of the throttle valve 60 using an opening filter value calculated from the engine speed and the current opening of the throttle valve 60. To this end, the throttle control unit 50 includes an opening calculation unit 51 and a filter value derivation unit 52. The throttle valve 60 and the throttle control unit 50 form a throttle mechanism 6.

[0020] The throttle control unit 50 generates a throttle control signal using an opening filter value (degree of smoothing) that smooths the opening (reduces accelerator responsiveness) under specific conditions. Specifically, under a derivation condition where the engine speed is equal to or lower than the centrifugal clutch engagement speed of the centrifugal clutch 11, preferably under a derivation condition where the engine speed is equal to or higher than the idling speed but equal to or lower than the centrifugal clutch engagement speed, the filter value derivation unit 52 derives an opening filter value that reduces accelerator responsiveness, and the throttle control unit 50 generates a throttle control signal using the opening filter value. In other words, under a condition where the engine speed is equal to or higher than the idling speed but equal to or lower than the centrifugal clutch engagement speed, the filter value derivation unit 52 derives an opening filter value that reduces accelerator responsiveness compared to the opening filter value derived under conditions other than the other conditions.

[0021] In this embodiment, as shown in Fig. 5, the filter value derivation unit 52 is configured as a lookup table having a three-dimensional map consisting of the engine speed of the engine E, the opening of the throttle valve 60, and the opening filter value. This lookup table is configured to derive the opening filter value from a derivation condition consisting of the engine speed and the current accelerator opening. Here, the idling speed is assumed to be 1500 rpm, and the centrifugal clutch engagement speed is assumed to be 2300 rpm.

[0022] In the lookup table, the engine speed and the accelerator opening are both represented by discrete numerical values ​​(values ​​for each of a plurality of divided stages), and the derived opening filter value is also assigned to each division. Note that the divisions in FIG. 5 are mainly for the purpose of explanation, and any division can be configured. Furthermore, if a derivation formula is used instead of a lookup table, it is also possible to calculate the opening filter value as a substantially continuous value.

[0023] In the lookup table of Figure 5, the opening filter values ​​(denoted by the symbol α in Figure 5) are shown as 6x9 matrix values. Among these matrix values ​​(opening filter values), the matrix values ​​(smoothing submatrices) enclosed in black squares indicate opening filter values ​​that reduce accelerator responsiveness compared to the other opening filter values. In other words, when the engine speed is greater than or equal to 1800 rpm and less than 2250 rpm, and the current accelerator opening is greater than or equal to 0% and less than 40%, opening filter values ​​α13, α14, α23, and α24 that reduce accelerator responsiveness are derived.

[0024] FIG. 6 shows a graph illustrating the relationship between engine speed and filter value. The drop area indicated by the elliptical region marked with the symbol Z in FIG. 6 corresponds to the matrix value (averaged submatrix) enclosed in a square frame in FIG. 5.

[0025] The opening filter value is related to accelerator responsiveness and is therefore an important factor in drivability. For this reason, it is preferable that the relationship between the engine speed, the opening of the throttle valve 60, and the opening filter value be at least partially changed depending on the characteristics of the vehicle, aging of the vehicle, driver preferences, etc. In this embodiment, the range of the opening filter value and the smoothing submatrix in the lookup table is changeable.

[0026] The centrifugal clutch 11 controls power transmission by centrifugal force, and the clutch characteristics of each centrifugal clutch 11 vary and change over time. For this reason, in this embodiment, some or all of the three-dimensional maps constituting the look-up table can be changed in accordance with changes in the characteristics of the centrifugal clutch 11 over time.

[0027] [Another embodiment] (1) In the above-described embodiment, a multipurpose vehicle is used as the work vehicle. However, instead of this, a brush cutter, a snow vehicle, an off-road vehicle, or the like may be used. (2) In the above-described embodiment, only the engine speed and the opening of the throttle valve 60 were used as derivation conditions for deriving the opening filter value, but other factors, such as weather, driving surface conditions, and regional characteristics, may also be added.

[0028] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0029] The present invention is applicable to a work vehicle in which a centrifugal clutch is provided in a power transmission path from an engine. [Explanation of symbols]

[0030] 4: Engine control unit 6: Throttle mechanism 8: Meter control unit 11: Centrifugal clutch 12: Transmission 30: Cargo bed 50: Throttle control unit 51: Opening degree calculation unit 52: Filter value derivation part 60: Throttle valve 71: Accelerator pedal 72: Gear shift lever E: Engine T: Transmission

Claims

1. Engine and a transmission that changes the speed of power from the engine; a centrifugal clutch provided between the engine and the transmission; a throttle mechanism that electronically controls the opening of a throttle valve of the engine by a throttle control unit; the throttle control unit electronically controls the opening of the throttle valve using a filter value derivation unit that derives an opening filter value from the engine speed of the engine and the opening of the throttle valve; The filter value derivation unit derives the opening filter value that reduces accelerator responsiveness under a derivation condition that the engine rotational speed is equal to or lower than a centrifugal clutch engagement rotational speed of the centrifugal clutch.

2. 2. The work vehicle according to claim 1, wherein the filter value derivation unit derives the opening filter value that reduces the accelerator responsiveness compared to the opening filter value derived under conditions other than those described above, when the engine rotational speed is equal to or higher than an idling rotational speed and equal to or lower than the centrifugal clutch engagement rotational speed.

3. 3. The work vehicle according to claim 1, wherein the filter value derivation unit has a three-dimensional map consisting of the engine speed of the engine, the opening of the throttle valve, and the opening filter value, and a part or all of the three-dimensional map is changeable.

4. 4. The work vehicle according to claim 3, wherein a part or all of the three-dimensional map is changed in accordance with changes in the characteristics of the centrifugal clutch over time.

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