JP2018145705A - Work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a work vehicle capable of preventing an axle from overheating.SOLUTION: A wheel loader 1 comprises a front axle 43 in which a front brake device 45 is embedded, a first oil temperature sensor 46 detecting a first oil temperature T1 of cooling oil, and a controller 60. The controller 60 restricts a maximum speed of the wheel loader 1 to a second maximum speed MS2 when the first oil temperature T1 of cooling oil within the front axle 43 that is detected by the first oil temperature sensor 46 is equal to or more than a first threshold TH1.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a work vehicle.

  In a work vehicle (for example, a wheel loader or a forklift) equipped with a work machine, engine power is transmitted to wheels via a transmission and an axle. The axle has a built-in brake device that is cooled by cooling oil. The cooling oil serves to dissipate the frictional heat of the brake device, but if the frictional heat of the brake device is excessive, the oil temperature becomes excessively high and the axle (brake) is overheated.

  Here, for the purpose of warning the operator of the overheating of the axle, there has been proposed a method of detecting the overheating of the axle based on the vehicle speed, the brake operation pressure, and the brake operation time (see Patent Document 1).

JP 2004-75057 A

  However, in patent document 1, the proposal about the control for suppressing the overheating of an axle is not made | formed.

  Therefore, in order to suppress overheating of the axle, it is conceivable to limit the output of the engine, but there is a problem that the operating speed of the work machine is reduced or the low-speed torque is reduced.

  The present invention has been made in view of the above-described situation, and an object thereof is to provide a work vehicle that can suppress overheating of an axle.

  The work vehicle according to the first aspect of the present invention includes an axle that includes a brake device that is cooled by cooling oil, an oil temperature sensor that detects an oil temperature of the cooling oil, and the oil that is detected by the oil temperature sensor. A controller that limits the maximum speed of the work vehicle to a predetermined speed when the temperature is equal to or higher than a first threshold value;

  According to the work vehicle according to the first aspect of the present invention, the frictional heat generated in the brake device is reduced and the oil temperature of the cooling oil is lowered, so that overheating of the axle can be suppressed. At this time, since the output of the engine is not limited, it is possible to suppress a decrease in operating speed of the work implement or a decrease in low-speed torque. Thus, according to the work vehicle which concerns on the 1st side surface of this invention, the overheating of an axle can be suppressed, suppressing the fall of workability | operativity of a work vehicle.

  ADVANTAGE OF THE INVENTION According to this invention, the work vehicle which can suppress the overheating of an axle can be provided.

Wheel loader side view Block diagram showing the configuration of the wheel loader Block diagram showing the configuration of the controller Flow chart for explaining maximum speed limit control

(Wheel loader 1)
FIG. 1 is a side view showing a wheel loader 1 according to the present embodiment.

  The wheel loader 1 is used for transporting excavated earth and sand and loading it on a truck or the like. The wheel loader 1 is an example of a “work vehicle” provided with a work machine. The wheel loader 1 includes a front frame 2, a rear frame 3, and a steering cylinder 4.

  The front frame 2 is connected to the rear frame 3 via a steering cylinder 4. The front frame 2 can swing with respect to the rear frame 3 within a predetermined articulate angle range.

  A lift cylinder 21 and a tilt cylinder 22 are connected to the front frame 2. As the lift cylinder 21 expands and contracts, the bucket 24 moves up and down together with the boom 23. The bucket 24 is an example of a work machine attached to a work vehicle. As the tilt cylinder 22 expands and contracts, the bucket 25 tilts via the bell crank 25 and the link 26.

  The rear frame 3 is disposed behind the front frame 2. A cab 31 is disposed on the rear frame 3. The rear frame 3 supports the engine 32, the transmission 33, the hydraulic pump 34, and the like. The driving force of the engine 32 is transmitted to the front wheels 20 and the rear wheels 30 via a driving force transmission path 10 (see FIG. 2) described later. The hydraulic pump 34 supplies hydraulic oil to the lift cylinder 21 and the tilt cylinder 22.

(Configuration of wheel loader 1)
FIG. 2 is a block diagram showing the configuration of the wheel loader 1. The wheel loader 1 includes a driving force transmission path 10, a controller 60, and an alarm device 70.

1. Driving force transmission path 10
The driving force transmission path 10 includes a transmission 33, a PTO shaft 40, a front propeller shaft 41, a front drive shaft 42, a front axle 43, a rear propeller shaft 51, a rear drive shaft 52, and a rear axle 53. Each of the front axle 43 and the rear axle 53 is an example of an “axle”.

  The driving force of the engine 32 is transmitted to the front wheels 20 through the PTO shaft 40, the transmission 33, and the front axle 43. Similarly, the driving force of the engine 32 is transmitted to the rear wheel 30 via the PTO shaft 40, the transmission 33 and the rear axle 53.

  The driving force of the engine 32 is transmitted to the hydraulic pump 34 via the PTO shaft 40. As a result, the hydraulic pump 34 is driven, and the lift cylinder 21 and the tilt cylinder 22 are operated by the hydraulic oil discharged from the hydraulic pump 34.

  The transmission 33 is disposed between the engine 32 and the axles 43 and 53. The transmission 33 transmits the driving force of the engine 32 to the axles 43 and 53. The transmission 33 is an example of a “transmission” that can change the gear ratio.

  The transmission 33 includes a forward clutch corresponding to the forward travel stage, a reverse clutch corresponding to the reverse speed stage, and two or more speed stage clutches corresponding to the respective speed stages. The number of speed stage clutches of 2 or more is not particularly limited, but the maximum speed stage clutch corresponding to the maximum speed stage and the low / medium speed stage corresponding to the low / medium speed stage lower than the maximum speed stage. Including clutch. The low / medium speed gear clutch may further include a plurality of clutches.

  When the maximum speed stage clutch is engaged, the wheel loader 1 can reach the first maximum speed MS1, and when the low / medium speed stage clutch is engaged, the wheel loader 1 starts from the first maximum speed MS1. It is possible to reach the second highest speed MS2 that is slower.

  The first maximum speed MS1 is not particularly limited, and is determined according to the speed ratio of the maximum speed stage clutch. The second maximum speed MS2 is not particularly limited, and is determined according to the gear ratio of the low / medium speed stage clutch. The second maximum speed MS2 is an example of a “predetermined speed” when the maximum speed of the wheel loader 1 is limited.

  Each clutch can be a wet multi-plate hydraulic clutch. In the transmission 33, the clutch is selectively engaged / released in accordance with the traveling direction, the desired driving force, and the desired speed, thereby performing a shift. The transmission 33 is provided with a control valve 33a for controlling the hydraulic pressure of the pressure oil supplied to and discharged from each clutch.

  The front axle 43 includes a front differential gear 44, a front brake device 45, and a first oil temperature sensor 46. The front differential gear 44 connects the front propeller shaft 41 and the front drive shaft 42. The front brake device 45 is provided on the front drive shaft 42. The front brake device 45 is cooled by the cooling oil in the front axle 43. The cooling oil plays a role of radiating the frictional heat of the front brake device 45 and is heated by the operation of the front brake device 45. The friction heat of the front brake device 45 increases as the vehicle speed of the wheel loader 1 increases. Therefore, as the vehicle speed of the wheel loader 1 increases, the oil temperature of the cooling oil stored in the front axle 43 (hereinafter referred to as “first oil”). Temperature T1 ") tends to be high. The first oil temperature sensor 46 detects the first oil temperature T1 of the cooling oil. The first oil temperature sensor 46 outputs the detected first oil temperature T1 to the controller 60. The first oil temperature sensor 46 is an example of an “oil temperature sensor”.

  The rear axle 53 includes a rear differential gear 54, a rear brake device 55, and a second oil temperature sensor 56. The rear differential gear 54 connects the rear propeller shaft 51 and the rear drive shaft 52. The rear brake device 55 is provided on the rear drive shaft 52. The rear brake device 55 is cooled by the cooling oil in the rear axle 53. The cooling oil plays a role of radiating the frictional heat of the rear brake device 55 and is heated by the operation of the rear brake device 55. The frictional heat of the rear brake device 55 increases as the vehicle speed of the wheel loader 1 increases. Therefore, as the vehicle speed of the wheel loader 1 increases, the oil temperature of the cooling oil stored in the rear axle 53 (hereinafter referred to as “second oil”). Temperature T2 ") tends to be high. The second oil temperature sensor 56 detects the second oil temperature T2 of the cooling oil. The second oil temperature sensor 56 outputs the detected second oil temperature T2 to the controller 60. The second oil temperature sensor 56 is an example of an “oil temperature sensor”.

2. Controller 60
FIG. 3 is a block diagram showing the configuration of the controller 60. The controller 60 includes a control signal generation unit 61.

  The control signal generator 61 generates an engine control signal for controlling the engine 32 to a desired rotational speed in accordance with the accelerator operation amount by the operator. The control signal generator 61 generates a transmission control signal for controlling the control valve 33a of the transmission 33 so that the clutch is engaged according to the operation of the shift lever by the operator.

The control signal generation unit 61 includes an oil temperature acquisition unit 62, an oil temperature determination unit 63, and a storage unit 64.
The oil temperature acquisition unit 62 acquires the first oil temperature T1 of the cooling oil stored in the front axle 43 from the first oil temperature sensor 46. The oil temperature acquisition unit 62 acquires the second oil temperature T2 of the cooling oil stored in the rear axle 53 from the second oil temperature sensor 56.

  The oil temperature determination unit 63 compares the first threshold value TH1 stored in the storage unit 64 with each of the first oil temperature T1 and the second oil temperature T2, and at least the first oil temperature T1 and the second oil temperature T2 are compared. It is determined whether one is equal to or greater than a first threshold value TH1. The first threshold TH1 is not particularly limited, and can be set to a temperature at which the front axle 43 and the rear axle 53 are likely to be adversely affected.

  When at least one of the first oil temperature T1 and the second oil temperature T2 is equal to or higher than the first threshold value TH1, the control signal generation unit 61 executes maximum speed limit control that limits the maximum speed of the wheel loader 1. In the present embodiment, the maximum speed of the wheel loader 1 is suppressed from the first maximum speed MS1 to the second maximum speed MS2 (<first maximum speed MS1) by executing the maximum speed limit control. Details of the maximum speed limit control will be described later.

  Thereby, the frictional heat generated in the front brake device 45 and / or the rear brake device 55 is reduced, and the first oil temperature T1 and / or the second oil temperature T2 is lowered. As a result, overheating of the front axle 43 and / or the rear axle 53 can be suppressed. Note that the control signal generation unit 61 does not limit the output of the engine 32 in the maximum speed limit control.

  The oil temperature determination unit 63 compares the second threshold value TH2 stored in the storage unit 64 with the first oil temperature T1 and the second oil temperature T2, respectively, and compares the first oil temperature T1 and the second oil temperature T2. It is determined whether or not at least one of them is equal to or greater than the second threshold value TH2. The second threshold TH2 is not particularly limited as long as it is higher than the first threshold TH1, but can be set to a temperature at which the overheat state of the front axle 43 and the rear axle 53 must be quickly eliminated. .

  When at least one of the first oil temperature T1 and the second oil temperature T2 is equal to or higher than the second threshold value TH2 higher than the first threshold value TH1, the control signal generator 61 issues a warning for causing the alarm device 70 to issue a warning. Generate an alarm signal.

3. Alarm 70
When the warning signal is output from the control signal generator 61, the alarm device 70 issues a warning. Examples of warnings include, but are not limited to, issuing warning sounds, warning lights, and displaying warning texts on operator monitors.

(Maximum speed limit control)
The maximum speed limit control executed by the controller 60 will be described with reference to the drawings. FIG. 3 is a flowchart for explaining the maximum speed limit control.

  In step S1, the controller 60 acquires the first oil temperature T1 of the cooling oil stored in the front axle 43 from the first oil temperature sensor 46, and the second oil temperature of the cooling oil stored in the rear axle 53. T2 is acquired from the second oil temperature sensor 56.

  In step S2, the controller 60 determines whether or not each of the first oil temperature T1 and the second oil temperature T2 is equal to or higher than the first threshold value TH1. If it is determined that at least one of the first oil temperature T1 and the second oil temperature T2 is equal to or higher than the first threshold value TH1, the process proceeds to step S3. When it is determined that both the first oil temperature T1 and the second oil temperature T2 are lower than the first threshold value TH1, the process ends.

  In step S <b> 3, the controller 60 determines whether or not the maximum speed stage clutch is engaged in the transmission 33. If the maximum speed clutch is engaged, the process proceeds to step S4. If the maximum speed clutch is not engaged, the process proceeds to step S5.

  In step S4, the controller 60 controls the control valve 33a to release the engaged maximum speed stage clutch and to engage the speed stage clutch that is one speed lower than the maximum speed stage. Thereby, the maximum speed of the wheel loader 1 is suppressed from the first maximum speed MS1 to the second maximum speed MS2.

  In step S5, the controller 60 does not accept the operation even if the operator operates the shift lever to engage the maximum speed clutch.

  In step S6, the controller 60 determines whether or not each of the first oil temperature T1 and the second oil temperature T2 acquired in step S1 is equal to or higher than a second threshold value TH2. If it is determined that at least one of the first oil temperature T1 and the second oil temperature T2 is equal to or higher than the second threshold value TH2, the process proceeds to step S7. When it is determined that both the first oil temperature T1 and the second oil temperature T2 are less than the second threshold value TH2, the process ends.

  In step S7, the controller 60 issues a warning to the alarm device 70 to notify the operator that the front axle 43 and / or the rear axle 53 is in an overheated state.

(Feature)
(1) In the present embodiment, when the first oil temperature T1 of the cooling oil in the front axle 43 detected by the first oil temperature sensor 46 is equal to or higher than the first threshold value TH1, the controller 60 The speed is limited to a predetermined speed (second maximum speed MS2).

  As a result, the frictional heat generated in the front brake device 45 is reduced and the first oil temperature T1 is lowered, so that overheating of the front axle 43 can be suppressed. At this time, since the output of the engine 32 is not limited, it is possible to suppress a decrease in the operation speed of the bucket 24 or a decrease in the low-speed torque. Thus, according to the maximum speed limit control according to the present embodiment, overheating of the front axle 43 can be suppressed while suppressing a decrease in workability of the wheel loader 1.

  The above-described effects can also be obtained in the maximum speed limit control for the rear axle 53.

  (2) In the present embodiment, the controller 60 has the first oil temperature T1 of the cooling oil in the front axle 43 detected by the first oil temperature sensor 46 equal to or higher than the second threshold value TH2 (> first threshold value TH1). In this case, a warning is issued from the alarm device 70.

  Thereby, it is possible to promptly notify the operator that the front axle 43 is in an overheated state.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and various changes or modifications can be made without departing from the scope of the present invention.

  Although the wheel loader 1 has been described as an example of the work vehicle in the above embodiment, the present invention is not limited to this. Examples of work vehicles include wheel loaders, forklifts, motor graders, and dump trucks.

  In the above-described embodiment, the bucket 24 has been described as an example of a work machine, but is not limited thereto. Examples of work machines include buckets, forks, cutters, and breakers.

  In the above-described embodiment, the transmission 33 has been described as an example of the transmission, but is not limited thereto. As the transmission, a continuously variable transmission capable of continuously changing the gear ratio using a mechanism other than the gear can be used in addition to the transmission 33 using a gear. When a continuously variable transmission is used as the transmission, “restricting the transmission to the maximum speed stage of the transmission” means that the speed is changed so as not to use the region where the original maximum speed comes out (maximum speed stage). To do.

  In the above embodiment, the controller 60 limits the maximum speed of the wheel loader 1 by stopping the use of the maximum speed clutch of the transmission 33 in the maximum speed limit control. However, the present invention is not limited to this. . For example, the controller 60 may limit the maximum speed by decreasing the maximum rotation speed of the engine 32, or may limit the maximum speed by increasing the consumption amount of hydraulic oil in the hydraulic pump 34. .

  In the above embodiment, the controller 60 executes the maximum speed limit control for both the front axle 43 and the rear axle 53, but the maximum speed for only one of the front axle 43 and the rear axle 53. Restriction control may be executed. In this case, it is not necessary to provide an oil temperature sensor for the axle that does not execute the maximum speed limit control.

  In the above embodiment, the controller 60 sets the same first threshold value TH1 for each of the first oil temperature T1 and the second oil temperature T2, but different first values for the first oil temperature T1 and the second oil temperature T2. A threshold value TH1 may be set.

  In the above embodiment, the controller 60 sets the same second threshold value TH2 for each of the first oil temperature T1 and the second oil temperature T2, but different second values are used for the first oil temperature T1 and the second oil temperature T2. A threshold value TH2 may be set.

1 Wheel loader (work vehicle)
24 bucket 32 engine 33 transmission 43 front axle 45 front brake device 46 first oil temperature sensor 53 rear axle 55 rear brake device 56 second oil temperature sensor 60 controller TH1 first threshold value TH2 second threshold value MS1 first maximum speed MS2 second Maximum speed (predetermined speed)

Claims (3)

An axle with a built-in brake device that is cooled by cooling oil;
An oil temperature sensor for detecting the oil temperature of the cooling oil;
A controller that limits the maximum speed of the work vehicle to a predetermined speed when the oil temperature detected by the oil temperature sensor is equal to or higher than a first threshold;
Work vehicle equipped with. The transmission ratio can be changed, and a transmission for transmitting the driving force of the engine to the axle is provided.
The controller limits the maximum speed to the predetermined speed by limiting a shift to a maximum speed stage of the transmission;
The work vehicle according to claim 1. The controller issues a warning from an alarm device when the oil temperature is equal to or higher than a second threshold higher than the first threshold.
The work vehicle according to claim 1 or 2.

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