Clutch control unit for working vehicle

The present invention relates to a clutch control device for a work vehicle that disengages a transmission clutch in response to a depression operation of a brake pedal and a clutch cut pedal.

Conventionally, in work vehicles such as wheel loaders, the brake device is operated by depressing the brake pedal, and the clutch of the traveling transmission is cut to cut off the transmission of power to the wheels to reduce the load on the engine. (See, for example, Patent Document 1). According to this, the cutoff pressure is set by the cutoff setter, and the clutch is disengaged when the brake pressure due to the brake operation becomes equal to or higher than this cutoff pressure.

<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2001-263384</text></patcit>

<p> In the device described in Patent Document 1 described above, if the cutoff pressure is set to a small value, the clutch is disengaged by simply depressing the brake pedal lightly during high-speed driving, and the engine brake (hydraulic brake) functions effectively. I can't. On the other hand, if the cutoff pressure is set to a large value, the clutch will not be disengaged unless the brake pedal is depressed significantly during low-speed driving, resulting in poor operability.</p>

<p> The clutch control device for a work vehicle according to the present invention is a clutch means that transmits the traveling driving force generated by the engine to the wheels or blocks the transmission of the traveling driving force to the wheels, and braking that detects a braking command by operating the pedal. The command detecting means, the braking device that applies the braking force according to the braking command, the vehicle speed detecting means for detecting the vehicle speed, the vehicle speed detected by the vehicle speed detecting means, and the magnitude of the braking command detected by the braking command detecting means. It is characterized by including a clutch control means for controlling the clutch means so as to block the transmission of the traveling driving force to the wheels. When the vehicle speed is less than the predetermined vehicle speed, the transmission of the traveling driving force to the wheels is blocked when the braking command exceeds the first predetermined value, and when the vehicle speed is equal to or higher than the predetermined vehicle speed, the braking command is larger than the first predetermined value. It is preferable to control the clutch means so as to block the transmission of the traveling driving force to the wheels when the value exceeds a predetermined value. When the invalid command is input by the invalid command member, the clutch means can be controlled so as to transmit the traveling driving force to the wheels regardless of the vehicle speed and the braking command. It is preferable to further provide an adjusting means for adjusting the first predetermined value and / or the second predetermined value.</p>

<p> According to the present invention, the clutch means is controlled according to the vehicle speed and the magnitude of the braking command by the operation of the pedal to block the transmission of the traveling driving force to the wheels, so that the timing of the clutch cut by the operation of the pedal is blocked. Can be changed according to the vehicle speed, and the engine brake can function effectively.</p>

Hereinafter, embodiments of the clutch control device according to the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is a diagram showing a schematic configuration of a clutch control device according to an embodiment of the present invention, and FIG. 2 is a traveling hydraulic circuit diagram of a wheel loader to which this clutch control device is applied.

As shown in FIG. 2, the variable displacement hydraulic pump 21 and the hydraulic motor 22 driven by the engine E are connected by a pair of main pipelines 23A and 23B in a closed circuit. A wheel 25 is connected to the hydraulic motor 21 via a transmission 24, and the wheel 25 is driven at a speed corresponding to the discharge amount of the hydraulic pump 21. The tilt angle of the hydraulic pump 21 is controlled by the regulator 26. The charge pump 27 is driven by the engine E, and the pressure oil from the charge pump 27 is controlled by the throttle 28 and supplied to the regulator 26. The discharge amount of the charge pump 27 increases or decreases according to the amount of depression of the accelerator pedal 11 (FIG. 3), and the regulator 26 is driven by this change in the discharge amount.

That is, when the accelerator pedal 11 is depressed, the discharge amount of the charge pump 27 increases due to the increase in the engine speed, and the tilt amount of the hydraulic pump 21 increases. As a result, the discharge amount to the hydraulic motor 22 increases, and the vehicle speed increases. On the other hand, when the accelerator pedal 11 is returned, the discharge amount of the charge pump 27 decreases due to the decrease in the engine speed, and the tilt amount of the hydraulic pump 21 decreases. As a result, the amount of discharge to the hydraulic motor 22 decreases, the hydraulic brake acts on the hydraulic motor 22, and the vehicle speed decreases. The direction of rotation of the hydraulic motor 22, that is, the flow of pressure oil to the regulator 26 is controlled by the electromagnetic switching valve 29.

The pressure oil from the hydraulic pump 30 driven by the engine E is supplied to the forward hydraulic clutch 33 and the reverse hydraulic clutch 34 via the electromagnetic switching valves 31 and 32, respectively. The electromagnetic switching valves 31 and 32 are switched according to the operation of the forward / backward switching lever 13 (Fig. 3). That is, when the forward / backward switching lever 13 is operated to the forward side, the solenoid 31a of the electromagnetic switching valve 31 is energized, and the electromagnetic switching valve 31 switches to position b. As a result, pressure oil is supplied to the hydraulic clutch 33, and the clutch 33 is connected. When the forward / backward switching lever 13 is operated to the reverse side, the solenoid 32a of the electromagnetic switching valve 32 is energized, and the electromagnetic switching valve 32 switches to position b. As a result, pressure oil is supplied to the hydraulic clutch 34, and the clutch 34 is connected. When the forward / backward switching lever 13 is operated to the neutral position, the solenoids 31a and 32a of the electromagnetic switching valves 31 and 32 are de-energized, and the electromagnetic switching valves 31 and 32 are switched to the positions a, respectively. As a result, the supply of pressure oil from the hydraulic pump 30 to the hydraulic clutches 33 and 34 is stopped, the clutches 33 and 34 are cut (disengaged), and the state is in the neutral state. The clutches 33 and 34 are not only switched according to the operation of the forward / backward switching lever 13, but are also switched according to the vehicle speed as described later.

As shown in FIG. 1, such a hydraulically traveling vehicle is provided with a service brake 7 that is operated by operating the brake pedal 10. When the brake pedal 10 is operated in FIG. 1, the brake valve 1 is driven according to the amount of operation, the hydraulic oil from the hydraulic oil tank 4 is supplied to the brake cylinder 6 via the brake valve 1, and the service brake 7 is operated. .. Even if the clutch cut pedal 12, which will be described later, is operated, the brake valve 1 is driven according to the amount of operation, and the service brake 7 is activated.

Here, if the clutches 33 and 34 are disengaged during running deceleration, the transmission of power between the hydraulic motor 22 and the wheel 25 is cut off, and the hydraulic brake does not work. As a result, the load on the service brake 7 increases, and the life of the service brake 7 is shortened. On the other hand, when performing high-load work, the accelerator pedal 11 may be depressed to rotate the engine E at a high speed even during low-speed running. In this case, it is preferable to disengage the clutch in order to suppress an increase in the driving force of the hydraulic motor 22 and reduce the load on the engine and the service brake 7. Therefore, in the present embodiment, when decelerating by operating the brake pedal 10 or the clutch cut pedal 12, the clutch cut timing is controlled according to the vehicle speed.

As shown in FIG. 3, in addition to the brake pedal 10, an accelerator pedal 11 and a clutch cut pedal 12 that cuts the clutch by depressing operation are arranged in the driver's cab. Like the brake pedal 10, the clutch cut pedal 12 has a function of driving the brake valve 1 according to the amount of operation and operating the service brake 7. Therefore, during the running independent operation, the brake pedal 10 provided adjacent to the accelerator pedal 11 is operated by the right foot away from the accelerator pedal 11, and the running speed is controlled. During work by the combined operation of the front attachment and running, the accelerator pedal 11 is operated by the right foot and the clutch cut pedal 12 is operated by the left foot to control the operating speed and running speed of the front attachment. Further, a changeover switch 3 for instructing invalidation of the clutch cut control described later is arranged in the driver's cab. Reference numeral 13 denotes a forward / backward switching lever, and when the lever 13 is operated to the forward side or the reverse side, the electromagnetic switching valve 29 switches to the forward side or the reverse side.

As shown in FIG. 1, the controller 9 is connected to a pressure sensor 2 that detects the brake operating pressure p according to the operation amount of the brake pedal 10, a vehicle speed detector 5 that detects the vehicle speed v, and a changeover switch 3. There is. Although not shown, the pressure sensor 2 also detects the brake operating pressure p according to the operation amount of the clutch cut pedal 12. The controller 9 executes the following processing in response to the input signals from these, and outputs control signals to the solenoids 31a and 32a of the electromagnetic switching valves 31 and 32, respectively.

FIG. 4 is a flowchart showing an example of processing in the controller 9 according to the present embodiment. First, in step S1, it is determined whether or not the changeover switch 3 is turned on, that is, whether or not an invalid command for clutch cut control is input. If the changeover switch 3 is determined to be on, the process proceeds to step S6, and if it is determined to be off, the process proceeds to step S2. In step S2, it is determined whether or not the vehicle speed v detected by the vehicle speed detector 5 is equal to or higher than the preset set value v1. The predetermined value v1 is set to a vehicle speed (for example, about 15 km / h) at which the hydraulic braking force is above a certain level.

If step S2 is affirmed, the process proceeds to step S3, and it is determined whether or not the brake operating pressure p detected by the pressure sensor 2 is equal to or higher than a predetermined value p1. As shown in FIG. 5, the predetermined value p1 is set to a value smaller than the brake operating pressure pmax when the brake pedal 10 is fully operated. If step S3 is affirmed, the process proceeds to step S5, the outputs to the solenoids 31a and 32a are turned off, the electromagnetic switching valves 31 and 32 are switched to the positions a (neutral position), respectively, and the clutches 33 and 34 are disengaged. If step S3 is denied, the process proceeds to step S6, a control signal is output to the solenoid 31a or 32a according to the operation of the forward / backward switching lever 13, the electromagnetic switching valve 31 or 32 is switched to position b, and the clutches 33 and 34 Connect either one.

On the other hand, if step S2 is denied, the process proceeds to step S4, and it is determined whether or not the brake operating pressure p is equal to or greater than a predetermined value p2. Here, the predetermined value p2 is set to a value smaller than the predetermined value p1 as shown in FIG. If step S4 is affirmed, the process proceeds to step S5 to switch the electromagnetic switching valves 31 and 32 to position a, and if the step S4 is denied, the process proceeds to step S6 to switch the electromagnetic switching valve 31 or 32 to position b.

Next, the main operation of the clutch control device according to the present embodiment will be described. When working with the front attachment while driving the vehicle at low speed (v &lt;v1), such as scooping up earth and sand with a bucket, unloading earth and sand, loading, excavating, or removing snow with a snow blade, depress the accelerator pedal 11 to operate. While increasing the engine speed, the clutch cut pedal 12 is depressed to operate the service brake 7. When the brake operating pressure p becomes a predetermined value p2 or more by depressing the clutch cut pedal 12 (region A in FIG. 5), the electromagnetic switching valves 31 and 32 are switched to positions a (step S5). As a result, the clutches 33 and 34 are disengaged, and the load applied to the engine E and the service brake 7 is reduced. In this case, since the predetermined value p2 is set to a lower value, the brake operating pressure p becomes the predetermined value p2 or more even if the clutch cut pedal 12 is not depressed so much, and the workability is improved.

When the vehicle is running at high speed (v v1), the service brake 7 is activated by returning the accelerator pedal 11 and depressing the brake pedal 10. At this time, if the brake operating pressure p is less than the predetermined value p1 (region B in FIG. 5), the electromagnetic switching valve 31 or 32 switches to position b (step S6). As a result, the clutch engaged state is maintained, and the hydraulic brake acts on the hydraulic motor 22. In this case, since the predetermined value p1 is set to a value larger than the predetermined value p2, the clutch is not disengaged during high-speed traveling even if the depression amount is such that the clutch is disengaged during low-speed traveling. Therefore, the vehicle can be effectively decelerated without imposing a heavy burden on the service brake 7.

When the changeover switch 3 is turned on, the electromagnetic changeover valve 31 or 32 switches to position b according to the operation of the forward / backward changeover lever 13 regardless of the magnitude of the vehicle speed v and the brake operating pressure p (step S6). As a result, for example, when the vehicle is climbing at a low speed while operating the brake pedal 10, the clutch connected state is maintained, and it becomes easy to start on a slope.

According to the above embodiment, the following actions and effects are obtained. (1) Brake operation that clutch-cuts by operating the brake pedal 10 and clutch cut pedal 12 during high-speed driving (v v1) The set value p2 of the brake operating pressure is clutch-cut during low-speed driving (v &lt;v1). It was made larger than the pressure set value p1. As a result, the hydraulic brake can be operated together with the service brake 7 during high-speed driving, and the life of the service brake 7 can be suppressed from being shortened. (2) Clutch can be cut by operating the brake pedal 10 and the clutch cut pedal 12 which are few when traveling at low speed, and high load work can be performed well while traveling at low speed. (3) Since the changeover switch 3 for instructing the invalidation of the clutch cut is provided, it is easy to start on a slope.

In the above embodiment, the predetermined values p1 and p2 are fixed values, but the predetermined values p2 (first predetermined value) and / or the predetermined value p1 (second predetermined value) may be variable values. it can. In this case, a setting dial is provided as an adjustment means in the driver's seat, and predetermined values p1 and p2 are set by operating the setting dial, or a setting switch is provided in the driver's seat and the brake operating pressure p when the setting switch is operated is specified. It can be set as the values p1 and p2. As a result, the brake operating pressure p for disengaging the clutch can be adjusted according to the preference of the occupant, and good operability can be obtained.

In the above embodiment, as the set value of the brake operating pressure p when the clutch is disengaged, the set value p1 when the predetermined vehicle speed is v1 or higher is made smaller than the set value p2 when the predetermined vehicle speed is less than v1, but the vehicle speed v If the clutch cut timing is controlled in response to the braking command by the brake operation, the configuration of the clutch control means is not limited to that described above. For example, in FIG. 5, the predetermined value p2 may be gradually changed to p1 according to the vehicle speed. Further, although the controller 9 outputs a control signal to the solenoids 31a and 32a of the electromagnetic switching valves 31 and 32 to engage and disengage the clutches 33 and 34, the clutch control means may have another configuration. Although the electromagnetic switching valves 31 and 32 are switched on and off, they may be gradually switched according to the vehicle speed v or the brake operating pressure p.

In the above embodiment, the hydraulic pump 21 is driven by the engine E, the hydraulic motor 22 is rotated by the pump discharge oil to generate a traveling driving force, and the traveling driving force generated by this engine is generated by the hydraulic clutches 33 and 34. It is transmitted or not transmitted to the wheel 25, but the clutch means is not limited to this. A changeover switch 3 is provided in the driver's cab, but the invalid command member is not limited to this. Although the vehicle speed sensor 5 is used as the vehicle speed detection means, the vehicle speed can be detected by a vehicle other than the vehicle speed sensor. The clutches 33 and 34 were controlled according to the amount of operation of the brake pedal 10 and the clutch cut pedal 12 (brake operating pressure p), but the clutches 33 and 34 were controlled according to the amount of operation of either one (for example, the brake pedal 10). You may. Although the pressure sensor 2 is used as the braking command detecting means, the operation amount of the brake pedal 10 and the clutch cut pedal 12 may be detected by a potentiometer or the like. However, if the pressure sensor 2 is used, not only the pedal operation amount but also the influence of temperature (oil viscosity) is taken into consideration, which is preferable for the control of the hydraulic clutches 33 and 34.

Although the above embodiment is applied to a wheel loader, it can also be applied to other work vehicles such as a wheel excavator. Therefore, the traveling hydraulic circuit is not limited to that shown in FIG. That is, the present invention is not limited to the clutch control device of the embodiment as long as the features and functions of the present invention can be realized.

<figref num="1">The figure which shows the schematic structure of the clutch control device which concerns on embodiment of this invention.</figref><figref num="2">The running hydraulic circuit diagram of the wheel loader to which this invention is applied.</figref><figref num="3">The figure which shows the arrangement of the operation member in the cab of the wheel loader to which this invention is applied.</figref><figref num="4">The flowchart which shows an example of the processing in the controller of FIG.</figref><figref num="5">The characteristic diagram which shows the operation of this embodiment.</figref>

Code description

E Engine 2 Pressure sensor 3 Changeover switch 5 Vehicle speed sensor 7 Service brake 9 Controller 10 Brake pedal 25 Wheel 31,32 Electromagnetic changeover valve