Work vehicle

Abstract

A work vehicle according to the present invention is controlled so that the discharge flow rate of a pump increases as the temperature of cooling oil detected by a temperature sensor increases. When the operation mode of the work vehicle is switched from a normal mode in which work accompanying the operation of the brake device is performed to a brake test mode in which the soundness of the brake device is determined, the brake test device is configured to test the brake device within at least a portion of the temperature range. The control unit controls the rotation speed of the cooling pump relative to the temperature of the cooling oil detected by the temperature sensor in the brake test mode so as to be higher than the rotation speed in the normal mode, and determines whether or not an abnormality has occurred in the brake device on the basis of the detection result from the pressure sensor in the brake test mode. When it is determined that an abnormality has occurred, abnormality occurrence information is output. This makes it possible to reduce fuel consumption during normal time, and to determine the soundness of the brake cooling circuit during spot inspection of the circuit.

Description

Technical Field

[0001] The present invention relates to a work vehicle. Background Art

[0002] At work sites such as mines, a number of large dump trucks are operated as work machines for transporting ore and topsoil from a loading site to an unloading site. For example, a brake device is mounted thereon that generates braking force by pressing together a rotating part that rotates together with an output shaft and a fixed part fixed to the vehicle body side.

[0003] In this type of brake device, in a braking state where the rotating part and the fixed part are pressed together, the rotating part generates heat due to friction, which may cause a loss of driving force and increase fuel consumption. In addition, even in a non-braking state where the rotating part and the fixed part are not pressed together, if there is a large amount of cooling oil between the rotating part and the fixed part, part of the driving force of the output shaft is transmitted from the rotating part to the cooling oil, which may also cause a loss of driving force.

[0004] Therefore, a brake cooling circuit is provided to suppress the temperature rise of the brake device, and the hydraulic oil for cooling circulates between the rotating parts and the fixed parts, thereby cooling the rotating parts and suppressing the temperature rise of the rotating parts. As a conventional technology of the brake cooling circuit, for example, the technology described in Patent Document 1 is known.

[0005] Patent document 1 discloses a braking device, in which, when the braking device is in a braking state in which a rotating part and a fixed part are pressed together, the supply amount of lubricating oil is set to a prescribed first supply amount, and when the braking device is switched from the braking state to the non-braking state, the temperature of the rotating part is obtained by calculation, and the lubricating oil supply time required for lowering the temperature of the rotating part to a prescribed target temperature by supplying the first supply amount of lubricating oil is calculated, and when the lubricating oil supply time has passed since the braking device was switched from the braking state to the non-braking state, the supply amount of lubricating oil is reduced from the first supply amount to a second supply amount that is less than the first supply amount.

[0006] In addition, in a hydraulic circuit system such as a brake device, when determining whether the hydraulic oil in the circuit is circulating normally, it is considered to use a pressure sensor to confirm the circuit pressure, and determine the circuit soundness based on the circuit pressure. However, depending on the flow rate of the hydraulic oil circulating in the hydraulic circuit, the circuit pressure may become a value that is insufficient for the pressure sensor to detect, and there is a concern that the soundness cannot be determined.

[0007] Regarding this problem, as a prior art for detecting circuit abnormalities independent of the circuit state, for example, the technology described in Patent Document 2 is known. Patent Document 2 discloses a hydraulic control system, which includes: a pump output switching device, which selectively switches the hydraulic pump to high output or low output; an accumulator, which is connected to the oil circuit between the hydraulic pump and the hydraulic instrument, and accumulates a portion of the hydraulic oil discharged from the hydraulic pump when the hydraulic pump is at high output, and supplies hydraulic oil to the hydraulic instrument when the hydraulic pump is at low output; a pump check valve, which allows the hydraulic oil to flow from the hydraulic pump to the hydraulic instrument and the accumulator, and prevents the hydraulic oil from flowing from the accumulator to the hydraulic pump; a pressure sensor, which detects the pressure of the hydraulic oil supplied to the hydraulic instrument from one of the hydraulic pump and the accumulator; and a controller, which controls the flow of hydraulic oil to the hydraulic instrument in the hydraulic system. When the hydraulic pump is in high output and the pressure detection value of the pressure sensor is above a preset upper limit value, a low output instruction is output to the pump output switching device in order to switch the hydraulic pump to low output. When the hydraulic pump is in low output and the pressure detection value of the pressure sensor is below a preset lower limit value, a high output instruction is output to the pump output switching device in order to switch the hydraulic pump to high output. The controller calculates the instruction duration time in which the instruction output to the pump output switching device does not change. When the instruction duration time is above a preset specified value, the pump output switching device is determined to be abnormal and the determination result is output.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: International Publication No. 2009 / 034890

[0011] Patent Document 2: International Publication No. 2018 / 179070 Summary of the invention

[0012] However, in the prior art described in Patent Document 2, when the accumulation time of the accumulator is longer than a predetermined value, that is, when the accumulator pressure does not change, the switching valve that is a valve for delivering hydraulic oil to the accumulator is considered to be defective. Therefore, when the flow rate is controlled to be reduced according to the oil temperature in order to reduce fuel consumption, the flow rate is kept at a low state when the oil temperature does not rise in the driving mode. In other words, since the condition for determining a defect is not met, the soundness cannot be determined.

[0013] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a working vehicle capable of reducing fuel consumption in normal times and determining the soundness of a brake cooling circuit during circuit inspection.

[0014] The present application includes a plurality of solutions to the above-mentioned problems, but if one example is cited, it is a work vehicle comprising: a brake device, which generates a braking force by pressing a rotating part rotating together with an output shaft and a fixed part fixed to a vehicle body side together, and can cool the rotating part by cooling oil; a pump, which supplies the cooling oil in an amount corresponding to the rotation speed to the brake device; a temperature sensor, which detects the temperature of the cooling oil; a pressure sensor, which detects the pressure of the cooling oil; and a controller, which controls the rotation speed of the pump based on the detection results from the temperature sensor and the pressure sensor, wherein in the work vehicle, the controller is configured to control the rotation speed of the pump based on the detection results from the temperature sensor and the pressure sensor. The pump is controlled in such a manner that the higher the temperature of the cooling oil is, the higher the rotation speed of the pump is; when the operation mode of the working vehicle is switched from a normal mode for performing operations accompanied by the action of the braking device to a braking test mode for judging the soundness of the braking device, the pump is controlled in such a manner that the rotation speed of the pump relative to the temperature of the cooling oil detected by the temperature sensor is higher in the braking test mode than in the normal mode within at least a part of the temperature range; based on the detection result from the pressure sensor in the braking test mode, it is judged whether an abnormality has occurred in the braking device; and when it is judged that an abnormality has occurred, abnormality occurrence information is output.

[0015] Effects of the Invention

[0016] According to the present invention, it is possible to reduce fuel consumption by reducing the flow rate in normal times, and to determine the soundness of the brake cooling circuit by increasing the flow rate during circuit inspection. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a plan view schematically showing the appearance of a dump truck which is an example of an electric drive work vehicle.

[0018] Figure 2 yes Figure 1 Cross-sectional view along line A in FIG.

[0019] Figure 3 The figure schematically shows the interior of the cab.

[0020] Figure 4 This diagram shows the wet brake cooling system together with related structures extracted.

[0021] Figure 5 This is a diagram of the hardware configuration of the control device.

[0022] Figure 6 This is a diagram showing an example of a control table used by the control device in the first embodiment.

[0023] Figure 7 This is a flowchart showing the flow of processing in the operation of the brake cooling system.

[0024] Figure 8 This is a diagram showing an example of a control table used by the control device in the second embodiment. DETAILED DESCRIPTION

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, in this embodiment, a dump truck having a cargo box for loading an object is described as an example of a work vehicle, but it can also be applied to other work vehicles having wet brakes.

[0026] In the following description, when there are multiple identical components, a letter may be added to the end of the reference numeral (number), but the letter may be omitted and the multiple components may be collectively represented. That is, for example, when there are two wet brakes 3a and 3b, they may be collectively represented as a wet brake 3. In addition, signal lines and the like whose connection relationship is made clear by the description may be omitted for simplicity.

[0027] <First embodiment>

[0028] Reference Figure 1 to Figure 7 The first embodiment of the present invention will be described in detail.

[0029] Figure 1 FIG. 2 is a plan view schematically showing the appearance of a dump truck as an example of a work vehicle according to the present embodiment. Figure 2 yes Figure 1 In addition, Figure 3 The figure schematically shows the interior of the cab.

[0030] Figure 1 as well as Figure 2 In the figure, the dump truck 100 is generally composed of: a main frame 4 extending in the front-rear direction and forming a supporting structure; a cargo box (cargo box: not shown) arranged on the upper part of the main frame 4 in a manner extending in the front-rear direction, and the lower part of the rear end thereof is connected to the main frame 4 so as to be tiltable; front wheels 103a, 103b (driven wheels) provided on the left and right sides of the lower front side of the main frame 4; rear wheels 1a, 1b, 1c, 1d (driving wheels) provided on the left and right sides of the lower rear side of the vehicle body; a cab 101 ( Figure 1 , Figure 21a, 1b, 1c, 1d (driving wheels) driven by the hydraulic motors for driving the rear wheels 1a, 1b, 1c, 1d (driving wheels) by the hydraulic oil discharged from the main pump 8, and the reducers 2a, 2b for supporting the rear wheels; the wet brakes 3a, 2b (brake devices) mounted inside the reducers 2a, 2b; the cooling pump 9 for supplying cooling oil to the wet brake 3; the electric motor 10 for driving the cooling pump 9; the oil tank 5 provided on the left side of the main frame 4 and storing the hydraulic oil discharged from the main pump 8 and the cooling oil of the wet brake 3 discharged from the cooling pump 9; the beam 13 provided on the upper part of the main frame 4 in a manner extending in the left-right direction of the vehicle body; and the electric control device 14 provided on the upper part of the beam 13 and controlling the electric system including the electric motor 10. In addition, a radiator 11 for cooling cooling water of the engine 6 and a cooling oil cooler 12 for cooling cooling oil supplied to the wet brake 3 are arranged in front of the vehicle body. The inside of the oil tank 5 is partitioned so as not to mix the working oil and the cooling oil.

[0031] The wet brake 3 is configured to generate braking force by pressing a rotating member that rotates together with the output shaft and a fixed member that is fixed to the vehicle body side together, and is configured to be able to cool the rotating member with cooling oil.

[0032] Figure 3 In the cab 101, there are provided: a switch 15 for brake test mode (mode switching switch), which selectively switches the operation mode of the dump truck 100 to either a normal mode for performing operations accompanied by the action of the braking device, or a brake test mode for judging the soundness of the braking device; a monitor 16, which notifies the operator of information such as abnormal occurrence information and the selected operation mode through a screen display; and a buzzer (not shown) which notifies the operator of information such as abnormal occurrence information through sound and voice.

[0033] Figure 4 This is a diagram showing the wet brake cooling system and related components extracted. Figure 5 This is a diagram of the hardware configuration of the control device.

[0034] Figure 4 In the cooling system of the wet brake 3, the cooling oil stored in the oil tank 5 is supplied to the wet brakes 3a and 3b via the cooling oil cooler 12 by the cooling pump 9 driven by the electric motor 10, thereby cooling the wet brakes 3a and 3b. The cooling oil used by the wet brakes 3a and 3b for cooling flows back to the oil tank 5.

[0035] In the oil circuit on the suction side (oil tank 5 side) of the cooling pump 9, a temperature sensor 17 is provided to detect the temperature of the cooling oil drawn from the oil tank 5 to the cooling pump 9 and transmit the temperature to the control device 19. In addition, in the oil circuit on the discharge side (cooling oil cooler 12 side) of the cooling pump 9, a pressure sensor 18 is provided to detect the pressure of the cooling oil discharged from the cooling pump 9 to the cooling oil cooler 12 and transmit the temperature to the control device 19, and a relief valve 9a is provided to limit the pressure of the oil circuit on the discharge side of the cooling pump 9 to a predetermined fixed pressure or less.

[0036] The electric motor 10 generates electricity by the generator 7 driven by the engine 6, and is driven by the electricity supplied via the power control device 14. The power control device 14 controls the power supplied to the electric motor 10 according to the command from the control device 19, thereby controlling the rotation speed of the electric motor 10 and the cooling pump 9 driven by the electric motor 10. That is, the rotation speed of the cooling pump 9 is controlled according to the command from the control device 19. The cooling pump 9 supplies the cooling oil in an amount corresponding to the rotation speed to the wet brakes 3a and 3b via the cooling oil cooler 12.

[0037] The control device 19 controls the overall operation of the cooling system, uses the switching signal from the brake test mode switch 15, and the detection results from the temperature sensor 17 and the pressure sensor 18, based on a predetermined control table (described later), controls the speed of the cooling pump 9, and determines the health of the cooling system. If it is determined that an abnormality has occurred, the control device 19 outputs abnormality information to the monitor 16 and the buzzer (not shown), thereby notifying the operator of the occurrence of the abnormality.

[0038] Specifically, when the switch 15 (mode switching switch) for the brake test mode is switched to the normal mode, the rotation speed of the cooling pump 9 is controlled to be higher as the temperature of the cooling oil detected by the temperature sensor 17 is higher, according to the control table of the normal mode. In other words, the flow rate of the cooling oil supplied to the wet brakes 3a and 3b is controlled to be increased as the temperature of the wet brakes 3 and 3b (i.e., the temperature of the cooling oil returned to the oil tank 5 via the wet brakes 3a and 3b) is higher. Thus, when the frequency of use of the wet brakes 3a and 3b is high, a sufficient cooling effect can be obtained, and when the frequency of use is low, the flow rate of the cooling oil is reduced, thereby achieving low fuel consumption.

[0039] In addition, when the brake test mode switch 15 (mode switching switch) is switched to the brake test mode for judging the soundness of the cooling system, the control table of the brake test mode is used to control the rotation speed of the cooling pump 9 to be higher as the temperature of the cooling oil detected by the temperature sensor 17 is higher, that is, the flow rate of the cooling oil supplied to the wet brakes 3a and 3b is increased as the temperature of the wet brakes 3 and 3b (i.e., the temperature of the cooling oil returned to the oil tank 5 via the wet brakes 3a and 3b) is higher, and it is judged whether an abnormality has occurred in the cooling system based on whether the detection result of the pressure sensor 18 is within a predetermined range. In the control table of the brake test mode, the rotation speed of the cooling pump 9 relative to the temperature of the cooling oil detected by the temperature sensor 17 is controlled to be higher in the brake test mode than in the normal mode in at least a part of the temperature range. Thus, when the circuit is inspected, the soundness of the brake cooling system can be judged even if the frequency of use of the wet brakes 3a and 3b is low.

[0040] Furthermore, the control device 19 may perform control so as to stop the cooling pump 9 (that is, stop the electric motor 10 ) when determining that an abnormality has occurred.

[0041] Figure 5 In the embodiment, the control device 19 is composed of a central processing unit (CPU) 192, memories such as ROM (Read Only Memory) 193 and RAM (Random Access Memory) 194, and interfaces such as an input interface 191 and an output interface 195. The central processing unit (CPU) 192 executes a program pre-stored in the ROM 193 and RAM 194, and the central processing unit (CPU) 192 processes based on the set values ​​stored in the ROM 193 and RAM 194 and the signal input from the input interface 191, and outputs a signal from the output interface 195. In the present embodiment, the internal system of the control device 19 is executed as a combination of a plurality of programs, and is configured such that a signal from the brake test mode switch 15, the temperature sensor 17, and the pressure sensor 18 is input through the input interface 191, and the central processing unit (CPU) 192 performs processing, and then outputs a signal to the power control device 14 and the monitor 16 through the output interface 195.

[0042] Figure 6 : is a diagram showing an example of a control table used by the control device, wherein the horizontal axis represents the temperature of the cooling oil and the vertical axis represents the flow rate discharged from the cooling pump. Figure 6 In FIG. 1 , the vertical axis represents the flow rate of the cooling oil discharged from the cooling pump 9 . The discharge flow rate of the cooling pump 9 increases or decreases according to the rotation speed, so the control of the rotation speed and the control of the flow rate have the same meaning.

[0043] like Figure 6 As shown, the control table when the brake test mode is turned on (brake test mode) is set to control the discharge flow rate (rotation speed) of the cooling pump 9 to be fixed regardless of the temperature within a temperature range where the temperature of the cooling oil detected by the temperature sensor 17 is lower than a predetermined first temperature, and within a temperature range higher than a second temperature set higher than the first temperature, and to control the discharge flow rate (rotation speed) of the cooling pump 9 to be increased (rotation speed increased) as the temperature of the cooling oil increases within a temperature range above the first temperature and below the second temperature.

[0044] In addition, the control table when the brake test mode is turned off (normal mode) is set to control the discharge flow rate (rotation speed) of the cooling pump 9 to be fixed regardless of the temperature within a temperature range where the temperature of the cooling oil detected by the temperature sensor 17 is lower than a predetermined third temperature and within a temperature range higher than a fourth temperature set higher than the third temperature, and to control the discharge flow rate (rotation speed) of the cooling pump 9 to be increased (rotation speed increased) as the temperature of the cooling oil increases within a temperature range higher than the third temperature and lower than the fourth temperature.

[0045] At this time, the first temperature is set lower than the third temperature, and the second temperature is set lower than the fourth temperature. That is, in the normal mode, when the wet brakes 3a and 3b are used frequently, a sufficient cooling effect can be obtained, and when the use frequency is low, the flow rate of the cooling oil is reduced, thereby achieving low fuel consumption. In addition, in the brake test mode, in at least a part of the temperature range ( Figure 6 In the example, in the range of the first temperature to the fourth temperature), the discharge flow rate (rotational speed) of the cooling pump 9 is controlled to be higher than the discharge flow rate (rotational speed) in the normal mode. Therefore, when the circuit is inspected, even when the frequency of use of the wet brakes 3a and 3b is low, that is, even when the discharge flow rate of the cooling pump 9 is small and the pressure is difficult to reach the specified value for judging the soundness of the circuit, the discharge pressure of the cooling pump 9 can be sufficiently increased, and the soundness of the brake cooling system can be judged.

[0046] In addition, a floating seal is built into the wet brake 3a, 3b to prevent leakage of cooling oil. The floating seal has a low withstand pressure, so it is necessary to suppress the pressure of the cooling oil applied to the wet brake 3a, 3b to be less than the withstand pressure of the floating seal. On the other hand, the viscosity of the cooling oil increases when the temperature is low, and the pressure of the oil when it flows tends to increase. Therefore, for example, the flow rate of the cooling oil is determined in such a way that it is less than the withstand pressure of the floating seal even at the assumed lowest oil temperature. However, since the oil flow resistance of the cooling oil cooler 12 is large, if the relief pressure of the relief valve 9a is accidentally caused to be lower than the withstand pressure of the floating seal, a large amount of cooling oil will flow back from the relief valve 9a, and the flow rate of the cooling oil flowing to the cooling oil cooler 12 and the wet brake 3a, 3b will decrease. Therefore, when the oil temperature is low, the discharge flow rate is changed in a way that suppresses the flow rate, thereby seeking to protect the floating seal, and the relief pressure is set within a range that can fully ensure the flow rate of the cooling oil to the wet brake 3a, 3b. Specifically, the relief pressure of the relief valve 9a is set so as to satisfy the relationship of (pressure received by the cooling oil cooler 12)>(relief pressure of the relief valve 9a)>(pressure received by the floating seal).

[0047] Figure 7 2 is a flowchart showing the flow of processing in the operation of the brake cooling system. The control device 19 repeatedly executes the processing of steps S100 to S150.

[0048] Figure 7 In the process, the control device 19 determines whether the brake test mode is on based on the switching signal from the brake test mode switch 15, that is, whether it is switched to the brake test mode (step S100). When the judgment result is no, the control table of the normal mode is maintained and the brake cooling system is controlled.

[0049] In addition, when the judgment result in step S100 is yes, that is, when switching to the brake test mode, switch to the control table of the brake test mode (step S110), and wait for a predetermined time (for example, 3 [seconds]) until the discharge flow of the cooling pump 9 stabilizes (step S120).

[0050] Then, it is determined whether the detection result of the pressure sensor 18 is above a predetermined value (for example, 0.1 [MPa]) as a threshold (lower limit threshold) for determining an abnormality in the cooling system (step S130). If the determination result is negative, the abnormality occurrence information is output to the monitor 16 and the buzzer, thereby sounding an alarm and notifying the operator of the occurrence of the abnormality (step S131).

[0051] In addition, when the judgment result in step S130 is yes, or when the processing in step S131 is completed, it is then judged whether the brake test mode is on, that is, whether to switch to the brake test mode (step S140).

[0052] If the determination result in step S140 is YES, that is, if the switching to the brake test mode continues, the processing of steps S110 to S131 is repeated.

[0053] If the result of determination in step S140 is negative, that is, if the mode is switched to the normal mode, the control table of the normal mode is switched (step S150) to control the brake cooling system.

[0054] also, Figure 7 In the example, the case where the detection result of the pressure sensor 18 is less than a predetermined lower limit threshold is cited, and for example, it is judged that an abnormality such as leakage of cooling oil due to damage of a pipe constituting the hydraulic circuit and immobility of the cooling pump 9 due to an abnormality of the electric motor 10 has occurred. However, it is not limited to this. For example, an upper limit threshold different from the lower limit threshold may be set, and when the detection result of the pressure sensor 18 is greater than the upper limit threshold, it is judged that an abnormality such as blockage of the hydraulic circuit has occurred.

[0055] The effects of the present embodiment configured as above will be described.

[0056] In the prior art for determining whether hydraulic oil in a hydraulic circuit system such as a brake device is circulating normally, a switching valve that supplies hydraulic oil to an accumulator is determined to be defective when the accumulation time of the accumulator is greater than a specified value and when the accumulator pressure does not change.

[0057] However, for example, when the flow rate is reduced according to the oil temperature for the purpose of achieving low fuel consumption, the flow rate is kept low when the oil temperature does not rise in the driving mode. In other words, the condition for determining failure is not met, and thus the soundness cannot be determined.

[0058] In contrast, the present embodiment is configured to control the rotation speed of the cooling pump 9 to be higher (greater discharge flow rate) as the temperature of the cooling oil detected by the temperature sensor 17 is higher, and when the operation mode of the dump truck 100 is switched from a normal mode for performing operations accompanied by the action of the braking device to a brake test mode for judging the integrity of the braking device, the rotation speed of the cooling pump 9 relative to the temperature of the cooling oil detected by the temperature sensor 17 is controlled in the brake test mode than in the normal mode within at least a part of the temperature range, and based on the detection result from the pressure sensor 18 in the brake test mode, it is judged whether an abnormality has occurred in the braking device, and when it is judged that an abnormality has occurred, information on the occurrence of the abnormality is output, thereby enabling low fuel consumption under normal circumstances and judging the integrity of the brake cooling circuit during the inspection of the circuit.

[0059] <Second embodiment>

[0060] Reference Figure 8 The second embodiment of the present invention will be described in detail.

[0061] This embodiment shows a case where a control table of nonlinear characteristics is used instead of the control table of linear characteristics exemplified in the first embodiment. Figure 8 In the description, the same reference numerals are given to the same configurations as those in the first embodiment, and the description thereof will be omitted.

[0062] Figure 8 : is a diagram showing an example of a control table used by the control device in this embodiment, wherein the horizontal axis represents the temperature of the cooling oil and the vertical axis represents the flow rate discharged from the cooling pump. Figure 8 In FIG. 1 , the vertical axis represents the flow rate of the cooling oil discharged from the cooling pump 9 . The discharge flow rate of the cooling pump 9 increases or decreases according to the rotation speed, so the control of the rotation speed and the control of the flow rate have the same meaning.

[0063] It is generally known that the relationship between oil viscosity and temperature is expressed logarithmically, and the oil pressure loss is proportional to the square of the flow rate. Therefore, in this embodiment, the relationship between the flow rate, temperature and pressure loss of the cooling oil is experimentally obtained, and the control table of nonlinear characteristics is defined using this relationship.

[0064] The relationship between the kinematic viscosity and temperature of the cooling oil is obtained by the following (Formula 1).

[0065] log(log(v+K))=n-m*log(T)...(Formula 1)

[0066] In the above (Formula 1), v [cSt] is the dynamic viscosity, T [K] is the absolute temperature, and k, m, and n are constants determined by the oil.

[0067] In addition, the relationship between the flow rate of cooling oil and the pressure loss is obtained by the following (Formula 2).

[0068] ΔP=ρ / 2*λ*L / D*V^2*10^6…(Formula 2)

[0069] In the above (Formula 2), ΔP [MPa] is the pressure loss, ρ [kg / m^3] is the density, λ is the tube friction coefficient, L [m] is the tube length, D [m] is the tube diameter, and V [m / s] is the flow velocity in the tube.

[0070] like Figure 8 As shown, the control table when the brake test mode is turned on (brake test mode) is set to control the discharge flow rate (rotation speed) of the cooling pump 9 to be constant regardless of the temperature within the temperature range where the temperature of the cooling oil detected by the temperature sensor 17 is lower than the first temperature set in advance, and within the temperature range where the temperature of the cooling oil detected by the temperature sensor 17 is higher than the second temperature set higher than the first temperature, and to control the discharge flow rate of the cooling pump 9 to be nonlinearly increased (rotation speed increased) as the temperature of the cooling oil increases within the temperature range from the first temperature to the second temperature. At this time, the flow rate of the cooling oil is set to be increased within the range where the pressure of the cooling oil does not reach the bearing pressure of the floating seal, so that the pressure of the cooling oil can be reliably detected by the pressure sensor 18 in the brake test mode.

[0071] In addition, the control table when the brake test mode is turned off (normal mode) is set to control the discharge flow rate (rotation speed) of the cooling pump 9 to be fixed regardless of the temperature within the temperature range where the temperature of the cooling oil detected by the temperature sensor 17 is lower than the predetermined third temperature and within the temperature range where the temperature is higher than the fourth temperature set higher than the third temperature, and to control the discharge flow rate (rotation speed) of the cooling pump 9 to be nonlinearly increased (rotation speed increased) as the temperature of the cooling oil increases within the temperature range from the third temperature to the fourth temperature. At this time, the flow rate of the cooling oil is set so that the pressure of the cooling oil does not reach the pressure at which the relief valve 9a operates, thereby further suppressing the occurrence of losses.

[0072] The first temperature is set lower than the third temperature, and the second temperature is set lower than the fourth temperature. That is, in the normal mode, when the wet brakes 3a and 3b are used frequently, a sufficient cooling effect can be obtained, and when the use frequency is low, the flow rate of the cooling oil is reduced to achieve low fuel consumption. In addition, in the brake test mode, in at least a part of the temperature range ( Figure 6In the example, in the range of the 1st temperature to the 4th temperature), the discharge flow rate (rotation speed) of the cooling pump 9 is controlled to be higher than the discharge flow rate (rotation speed) in the normal mode. Therefore, when the circuit is inspected, even when the frequency of use of the wet brakes 3a and 3b is low, that is, even when the discharge flow rate of the cooling pump 9 is small and the pressure is difficult to reach the specified value of the brake test, the discharge pressure of the cooling pump 9 can be sufficiently increased, and the soundness of the brake cooling system can be judged.

[0073] In addition, as described above, the effects of the first temperature and the second temperature in the brake test mode are different from the effects of the third temperature and the fourth temperature in the normal mode, and thus it can also be set that the shape of the curve of the flow change between the first temperature and the second temperature in the brake test mode is different from the shape of the curve of the flow between the third temperature and the fourth temperature in the normal mode.

[0074] <Note>

[0075] In addition, the present invention is not limited to the above-described embodiment, and includes various modifications and combinations within the scope not departing from the gist thereof.

[0076] For example, in the above embodiment, the cooling pump 9 is driven by the electric motor 10 , but the cooling pump 9 may be driven by another power (for example, a hydraulic motor and a hydraulic pump) whose rotation speed can be arbitrarily changed.

[0077] In the above embodiment, the case where the electric motor 10 is driven by the electric power generated by the generator 7 driven by the engine 6 is exemplified, but the electric power stored in a battery or the like may be used.

[0078] In addition, the present invention is not limited to all the structures described in the above embodiments, and also includes a solution in which part of the structures is deleted. In addition, the above structures, functions, etc. can also be implemented in part or in whole, for example, by integrated circuit design. In addition, the above structures, functions, etc. can also be implemented by software by a processor parsing and executing a program that implements each function.

[0079] Description of Reference Numerals

[0080] 1a, 1b, 1c, 1d…rear wheel, 2a, 2b…reducer, 3a, 3b…wet brake, 4…main frame, 5…oil tank, 6…engine, 7…generator, 8…main pump, 9…cooling pump, 9a…relief valve, 10…electric motor, 11…radiator, 12…cooling oil cooler, 13…beam, 14…electric control device, 15…switch for brake test mode, 16…monitor, 17…temperature sensor, 18…pressure sensor, 19…control device, 100…dump truck, 101…cab, 103a, 103b…front wheel, 191…input interface, 192…central processing unit (CPU), 193…ROM (Read Only Memory), 194…RAM (Random Access Memory), 195…output interface.

Claims

1. A working vehicle having: A brake device that generates braking force by pressing a rotating member that rotates together with the output shaft and a fixed member that is fixed to the vehicle body side together, and that can cool the rotating member with cooling oil; a pump that supplies the cooling oil to the brake device in an amount corresponding to the rotation speed; a temperature sensor for detecting the temperature of the cooling oil; a pressure sensor for detecting the pressure of the cooling oil; as well as a controller that controls the rotation speed of the pump based on detection results from the temperature sensor and the pressure sensor, The working vehicle is characterized in that: The controller is configured as follows: The pump is controlled so that the rotation speed thereof increases as the temperature of the cooling oil detected by the temperature sensor increases. When the operation mode of the work vehicle is switched from a normal mode for performing work accompanied by the operation of the brake device to a brake test mode for determining the soundness of the brake device, The pump is controlled in at least a part of the temperature range so that the rotation speed of the pump relative to the temperature of the cooling oil detected by the temperature sensor is higher in the brake test mode than in the normal mode. Based on the detection result from the pressure sensor in the brake test mode, it is determined whether an abnormality has occurred in the brake device, and when it is determined that an abnormality has occurred, abnormality occurrence information is output.

2. The working vehicle according to claim 1, characterized in that: When the controller determines that an abnormality has occurred in the brake device, the controller outputs the abnormality occurrence information to at least one of an external system, a monitor, and a buzzer, wherein: The external system is arranged outside the working vehicle. The monitor is provided in a cab in which an operator who operates the work vehicle rides, and notifies the operator of information through a screen display. The buzzer is provided in a cab in which an operator who operates the work vehicle rides, and notifies the operator of information through sound and voice.

3. The working vehicle according to claim 1, characterized in that: have: A mode switching switch, which selectively switches the operation mode of the working vehicle to one of the normal mode and the brake test mode; as well as A monitor is provided in a cab in which an operator who operates the work vehicle rides, and notifies the operator of information through a screen display. The controller causes the monitor to display the operation mode selected by the mode switching switch.

4. The working vehicle according to claim 1, characterized in that: The controller is configured as follows: In the brake test mode, within a temperature range where the temperature of the cooling oil detected by the temperature sensor is lower than a predetermined first temperature and within a temperature range where the temperature is higher than a second temperature set higher than the first temperature, the rotation speed of the pump is controlled so as to be constant regardless of the temperature, and within a temperature range where the temperature is higher than the first temperature and lower than the second temperature, the rotation speed of the pump is controlled so as to increase as the temperature of the cooling oil increases. In the normal mode, the pump is controlled such that the rotation speed of the pump becomes constant regardless of the temperature within a temperature range where the temperature of the cooling oil detected by the temperature sensor is lower than a predetermined third temperature and higher than a fourth temperature set higher than the third temperature, and the pump is controlled such that the rotation speed of the pump becomes higher as the temperature of the cooling oil becomes higher within a temperature range from the third temperature to the fourth temperature. The first temperature is lower than the third temperature, and the second temperature is lower than the fourth temperature.

5. The working vehicle according to claim 1, characterized in that: The controller stops the operation of the pump when determining that an abnormality has occurred in the brake device.

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