JP2013209940A - Work machine - Google Patents

Abstract

[PROBLEMS] To reduce fuel consumption and noise of a cooling fan.
An engine, a radiator, a refrigerant temperature detecting means, an outside air temperature detecting means, a thermostat that opens and closes a path between fully closed and fully open according to the temperature of the refrigerant, and a cooling fan that blows outside air to the radiator And a hydraulic motor driven by the hydraulic oil discharged from the hydraulic pump to rotate the cooling fan, and a control characteristic in which the temperature of the refrigerant and the target rotation speed of the cooling fan are associated with each other. The rotation speed setting means for setting the target rotation speed according to the temperature, the rotation speed adjustment means for adjusting the actual rotation speed of the fan so as to be the target rotation speed set by the rotation speed setting means, and the thermostat is fully opened from fully closed Control that determines the control characteristics so that the target rotation speed set by the refrigerant temperature varies depending on the temperature of the outside air within the temperature range of the refrigerant And a sex determination means.
[Selection] Figure 5

Description

  The present invention relates to a work machine that controls the rotational speed of a cooling fan.

  In order to cool the cooling water (refrigerant) of the engine of a work machine such as a wheel loader, the work machine is equipped with a radiator and a cooling fan that blows cooling air (outside air) to the radiator. The cooling fan is driven by a hydraulic motor or the like that is driven independently from the engine. As a device for controlling the rotation speed of the cooling fan, an apparatus that changes the rotation speed of the cooling fan according to the temperature of the refrigerant of the engine or the outside air temperature is known (see Patent Document 1).

  In the cooling fan control device described in Patent Document 1, the outside air temperature is detected, and the minimum rotation speed of the cooling fan is determined according to the outside air temperature. In the cooling fan control device described in Patent Document 1, the cooler can be quickly activated by relatively increasing the minimum rotation speed of the fan in summer (when the outside air temperature is high). In winter (when the outside air temperature is low), it is possible to shorten the warm-up time and turn on the heater quickly by making the minimum rotation speed of the cooling fan relatively low.

Japanese Patent No. 4745202

In the cooling fan control device described in Patent Document 1, when the refrigerant temperature is equal to or higher than a predetermined temperature, the rotation speed is controlled according to a predetermined control characteristic for increasing the rotation speed in accordance with the increase in the refrigerant temperature. However, when the refrigerant temperature is equal to or higher than a predetermined temperature, for example, in the temperature range of the refrigerant in which the engine thermostat is fully closed to fully opened, the control characteristics depending on the refrigerant temperature are not changed according to the outside air temperature.
An object of the present invention is to reduce the fuel consumption and the noise of the cooling fan by driving the cooling fan at an appropriate rotational speed according to the temperature of the outside air and the temperature of the refrigerant.

According to the first aspect of the present invention, an engine, a radiator for cooling the refrigerant of the engine, a refrigerant temperature detecting means for detecting the temperature of the refrigerant, an outside air temperature detecting means for detecting the temperature of the outside air, and the refrigerant are supplied to the radiator. On the path, a thermostat that opens and closes the path between fully closed and fully open according to the temperature of the refrigerant, a cooling fan that blows outside air to the radiator, a hydraulic pump driven by the engine, and a pressure discharged from the hydraulic pump The target rotation speed is determined by the refrigerant temperature detected by the refrigerant temperature detecting means based on the hydraulic motor driven by oil and rotating the cooling fan, and the control characteristics in which the refrigerant temperature and the target rotation speed of the cooling fan are associated with each other. Rotational speed setting means for adjusting the actual rotational speed of the fan so as to be the target rotational speed set by the rotational speed setting means And the target rotational speed set by the detected refrigerant temperature is different depending on the temperature of the outside air detected by the outside air temperature detecting means within the temperature range of the refrigerant where the thermostat is fully closed to fully opened. And a control characteristic determination means for determining the control characteristic.
According to a second aspect of the present invention, in the work machine according to the first aspect, when the temperature of the outside air is equal to or higher than a predetermined value, the rotation speed setting means sets the target rotation set in accordance with the temperature of the refrigerant fully closed by the thermostat. The speed is set higher than when the outside air temperature is lower than a predetermined value. When the outside air temperature is equal to or higher than the predetermined value, the target rotational speed set according to the refrigerant temperature at which the thermostat is fully opened is The temperature is set higher than when the temperature is lower than a predetermined value.
According to a third aspect of the present invention, in the work machine according to the first or second aspect, when the temperature of the outside air is within a predetermined range, the rotation speed setting means is set in accordance with the temperature of the refrigerant fully closed by the thermostat. The target rotation speed is set to be the same value as when the outside air temperature is lower than the predetermined range. When the outside air temperature is within the predetermined range, the target rotation speed is set according to the refrigerant temperature at which the thermostat is fully opened. Is set to have the same value as when the temperature of the outside air is higher than a predetermined range.
The invention according to claim 4 further includes an abnormality determination unit that determines that an abnormality occurs when the outside air temperature detection unit cannot detect the temperature of the outside air in the work machine according to any one of claims 1 to 3. The rotation speed setting means sets the target rotation speed of the cooling fan based on a control characteristic determined when the temperature of the outside air is equal to or higher than a predetermined value when an abnormality is determined by the abnormality determination means.
According to a fifth aspect of the present invention, in the work machine according to any one of the first to fourth aspects, the storage device stores a plurality of control characteristic data, and the control characteristic determining means includes the detected outside air. One of the plurality of control characteristic data is selected according to the temperature of the motor, and the rotation speed setting means sets the target rotation speed of the cooling fan based on the selected control characteristic data. To do.
A sixth aspect of the present invention is the work machine according to any one of the first to fourth aspects, further comprising a storage device that stores reference control characteristic data used when the temperature of the outside air is equal to or higher than a predetermined value. The control characteristic determining means sets the reference control characteristic data to the detected outside air temperature by shifting the control characteristic data to the high temperature side of the refrigerant temperature in accordance with the amount of temperature decrease from a predetermined value. It is characterized in that the corresponding control characteristic is determined.

  According to the present invention, the control characteristics are determined so that the target rotational speed set according to the temperature of the refrigerant becomes different depending on the temperature of the outside air within the temperature range of the refrigerant where the thermostat is fully opened from the fully closed state. Since it did in this way, a cooling fan can be driven with the suitable rotational speed according to the temperature of external air, and the temperature of a refrigerant | coolant. For this reason, it is possible to reduce the fuel consumption and the noise of the cooling fan.

The side view of the wheel loader which is an example of the working machine which concerns on 1st Embodiment. The figure which shows schematic structure of a wheel loader. The figure which shows the valve opening characteristic of a thermostat. (A) is a figure which shows the relationship between the target rotational speed of a cooling fan, and the setting pressure of a relief valve, (b) is a figure which shows the relationship between the discharge pressure of the hydraulic pump for fan drive, and the actual rotational speed of a cooling fan. . The figure which shows the control characteristic which matched the cooling water temperature and the target rotational speed of the cooling fan. The flowchart which shows the processing content about rotation speed control of a cooling fan. The figure explaining the determination method of the control characteristic used for the working machine which concerns on 2nd Embodiment. The flowchart which shows the processing content about the rotational speed control of the cooling fan in the working machine which concerns on 3rd Embodiment.

Hereinafter, an embodiment of a work machine according to the present invention will be described with reference to the drawings.
-First embodiment-
FIG. 1 is a side view of a wheel loader 100 that is an example of a work machine according to the first embodiment. The wheel loader 100 includes a front vehicle body 110 having an arm 111, a bucket 112, a tire 113, and the like, and a rear vehicle body 120 having an operator cab 121, an engine compartment 122, a tire 123, and the like. An engine (not shown) is mounted in the engine chamber 122, and the engine chamber 122 is covered with a building cover 131. A counterweight 124 is attached to the rear of the rear vehicle body 120.

  The arm 111 rotates up and down (up and down) by driving the arm cylinder 117, and the bucket 112 rotates up and down (cloud or dump) by driving the bucket cylinder 115. The front vehicle body 110 and the rear vehicle body 120 are pivotally connected to each other by a center pin 101, and the front vehicle body 110 is refracted to the left and right with respect to the rear vehicle body 120 by expansion and contraction of the steering cylinder 116.

  A radiator frame 135 and a cooling fan unit 150 are disposed behind the building cover 131. The radiator frame 135 includes a radiator 14 that cools cooling water (refrigerant) of the engine 1, an oil cooler 16 that cools working oil, and a working fluid cooler that cools the working fluid of the torque converter 2, as shown in FIG. 15 is attached. The radiator frame 135 is fixed to the rear vehicle body 120. The cooling fan unit 150 includes a cooling fan 13 driven by the fan motor 11 and a fan shroud 151 shown in FIG. 2 to be described later, and is disposed behind the radiator frame 135.

  The radiator frame 135 and the cooling fan unit 150 are covered with a cooler building cover 132 on the side and upper surfaces thereof. The cooler building cover 132 is opened at the rear, and is covered by a grill 140 that can be opened and closed. The grill 140 is a cover provided with a plurality of openings so that intake air or exhaust air from the cooling fan 13 is circulated to the outside.

  FIG. 2 is a diagram illustrating a schematic configuration of the wheel loader 100. An output shaft (not shown) of the torque converter 2 (hereinafter referred to as torque converter) is connected to the output shaft of the engine 1, and an output shaft (not shown) of the torque converter 2 is connected to the transmission 3. The torque converter 2 is a fluid clutch including a known impeller, turbine, and stator, and the rotation of the engine 1 is transmitted to the transmission 3 via the torque converter 2. The transmission 3 has a hydraulic clutch that shifts the speed stage from the first speed to the fourth speed, and the rotation of the output shaft of the torque converter 2 is shifted by the transmission 3. The rotation after the shift is transmitted to the tire 6 through the propeller shaft 4 and the axle 5, and the wheel loader travels.

  The controller 19 is a control device that controls each part of the wheel loader 100. The controller 19 includes a CPU, an arithmetic processing unit having a storage device such as a ROM and a RAM, and other peripheral circuits.

  An accelerator pedal 21 is disposed in the cab 121 of the wheel loader 100. The number of revolutions of the engine 1 increases as the operation amount (depression amount) of the accelerator pedal 21 increases. When the engine speed increases, the rotational speeds of hydraulic pumps 7 and 8 described later increase, and the pump discharge amount increases.

  The wheel loader 100 includes a working hydraulic pump 7 driven by the engine 1, a control valve 17 that controls pressure oil discharged from the hydraulic pump 7, and a working hydraulic cylinder 18 (for example, a bucket cylinder 115 or an arm cylinder 117). ). The control valve 17 is driven by operating an operation lever (not shown), and the working hydraulic cylinder 18 is driven in accordance with the operation amount of the operation lever.

  The wheel loader 100 includes a fan-driven hydraulic pump 8 driven by the engine 1, a fan motor 11 driven by pressure oil discharged from the hydraulic pump 8, a cooling fan 13 rotated by the fan motor 11, A variable relief valve 9 for adjusting the rotational speed of the fan motor 11 and a check valve for preventing cavitation when the hydraulic circuit 12 that drives the fan motor 11 becomes negative due to a change in the rotational speed of the engine 1. 10. The fan motor 11 rotates a cooling fan 13 that blows outside air (cooling air) to the radiator 14, the oil cooler 16, and the working fluid cooler 15.

  The cooling water of the engine 1 flows into the radiator 14 via the thermostat 22, is cooled by the radiator 14, and then returns to the engine 1 again. The thermostat 22 is provided in the middle of the cooling water piping from the engine 1 to the radiator 14. The thermostat 22 opens and closes the path between the fully closed state and the fully opened state in accordance with the temperature of the cooling water on the path for supplying the cooling water to the radiator 14.

  FIG. 3 is a graph showing the valve opening characteristics of the thermostat. In the thermostat 22 of the present embodiment, the fully closed temperature T1 at which the opening degree is 0% is 85 ° C., and the fully open temperature T2 at which the opening degree is 100% is 95 ° C. That is, the thermostat 22 is fully closed until the cooling water temperature TW touching the thermostat 22 is 85 ° C., and when the cooling water temperature TW exceeds 85 ° C., the thermostat 22 starts to gradually open and the opening area increases, When the water temperature TW reaches 95 ° C., the thermostat 22 is fully opened. Although not shown, the cooling water circulation path is provided with a bypass path for bypassing the cooling water so that the cooling water is not supplied to the radiator 14 when the cooling water temperature TW is low and the thermostat 22 is fully closed.

  The hydraulic oil is sucked up and discharged from the hydraulic oil tank 31 by the working hydraulic pump 7, flows into the oil cooler 16 through the control valve 17, is cooled by the oil cooler 16, and then returns to the hydraulic oil tank 31 again. Return. The working fluid of the torque converter 2 flows from the torque converter 2 into the working fluid cooler 15, is cooled by the working fluid cooler 15, and then returns to the torque converter 2 again.

  When the pressure oil discharged from the hydraulic pump 8 is supplied to the fan motor 11, the fan motor 11 and the cooling fan 13 rotate. The oil supplied to the fan motor 11 returns to the tank 31. When the cooling fan 13 rotates, cooling air (outside air) is blown from the cooling fan 13 toward the radiator 14, the oil cooler 16 and the working fluid cooler 15. The working fluid is cooled.

  A relief valve 9 of a variable set pressure type that limits the discharge side pressure of the hydraulic pump 8 (hereinafter referred to as pump discharge pressure Pp), which is the inlet side pressure (motor drive pressure) of the fan motor 11, discharges the hydraulic pump 8. It is interposed between the side pipe line and the return side pipe line to the tank 31.

  The relief valve 9 is an electromagnetic variable relief valve that defines the maximum pressure of the pressure oil supplied from the hydraulic pump 8 to the fan motor 11 according to the output current value (indicated value) from the controller 19. The pump discharge pressure Pp is controlled. The controller 19 controls the set pressure Ps of the relief valve 9 (hereinafter also referred to as relief pressure).

  The controller 19 changes the relief pressure Ps of the relief valve 9 to control the pump discharge pressure Pp, so that the actual rotational speed Nfa of the cooling fan 13 becomes a target rotational speed Nft that is set according to control characteristics described later. As described above, the actual rotational speed Nfa of the cooling fan 13 is adjusted.

  FIG. 4A is a diagram showing the relationship between the target rotational speed Nft of the cooling fan 13 and the set pressure (relief pressure) Ps of the relief valve 9. FIG. 4B is a diagram showing the relationship between the discharge pressure Pp of the fan-driven hydraulic pump 8 and the actual rotational speed Nfa of the cooling fan 13.

  A table shown in FIG. 4A is stored in the storage device of the controller 19 in order to control the relief pressure Ps. In the table shown in FIG. 4A, the relief pressure Ps is set to the minimum value Pmin according to the increase in the target rotational speed Nft of the cooling fan 13 (for example, when the target rotational speed Nft is the minimum rotational speed Nmin, Pmin is about 5 MPa. ) To a maximum value Pmax (for example, Pmax is about 19 MPa when the target rotational speed Nft is the maximum rotational speed Nmax).

  The relationship between the discharge pressure Pp of the hydraulic pump shown in FIG. 4B and the actual rotational speed Nfa of the cooling fan 13 is the same as in FIG. 4A, and as the discharge pressure Pp of the hydraulic pump 8 increases. The actual rotational speed Nfa of the cooling fan 13 increases. The table shown in FIG. 4A is obtained based on the characteristics shown in FIG.

  The controller 19 determines the relief pressure Ps with reference to the table of FIG. 4A using the target rotational speed Nft as an argument. When the relief pressure Ps of the relief valve 9 is set, the discharge pressure Pp of the hydraulic pump 8 becomes the relief pressure Ps, and the actual rotational speed Nfa of the cooling fan 13 is controlled to the target rotational speed Nft.

As shown in FIG. 4B, the actual rotational speed Nfa of the cooling fan 13 and the pump discharge pressure Pp are in a proportional relationship. The pump input power Li [kW] (= output from the engine) of the hydraulic pump 8 is obtained by the following equation (1).
Pump input power Li [kW] = T · Np / 9559.3 (1)
Np [rpm] is the rotational speed of the hydraulic pump 8 for driving the fan. T [N · m] is a pump driving torque and is obtained by the following equation (2).
Pump drive torque T [N · m] = Pp · q / (2π · ηm) (2)
Pp [MPa] is the discharge pressure of the hydraulic pump 8 for driving the fan as described above. q [cm ³ / rev. ] Is the displacement volume of the hydraulic pump 8, and ηm is the mechanical efficiency of the hydraulic pump 8.

  The pump input power Li is proportional to the pump discharge pressure Pp and the rotational speed Np of the hydraulic pump 8. Therefore, the pump input power Li is proportional to the actual rotational speed Nfa of the cooling fan 13. Therefore, when the actual rotational speed Nfa of the cooling fan 13 is low, the pump input power Li (engine output) is low and the fuel consumption is small. On the other hand, when the actual rotational speed Nfa of the cooling fan 13 is high, the pump input power Li (engine output) is high and the fuel consumption is large.

  The wheel loader 100 includes a controller 19, an outside air temperature sensor 20, and a cooling water temperature sensor 23. Information on the coolant temperature from the coolant temperature sensor 23 and information on the outside air temperature from the outside air temperature sensor 20 are input to the controller 19.

  The cooling water temperature sensor 23 is a sensor that detects the temperature of the cooling water, and is provided in a pipe line or the like on the upstream side of the radiator 14. The outside air temperature sensor 20 is a sensor that detects the temperature of the outside air, and is provided at a predetermined position on the outer surface of the vehicle body that the outside air touches.

  FIG. 5 is a diagram illustrating control characteristics in which the coolant temperature TW and the target rotational speed Nft of the cooling fan 13 are associated with each other. The storage device of the controller 19 stores a control characteristic table for controlling the target rotational speed Nft of the cooling fan 13 based on the cooling water temperature TW. As shown in FIG. 5, in this embodiment, three types of control characteristic tables are stored in the storage device. As will be described later, the controller 19 sets a target rotational speed Nft of the cooling fan 13 based on the temperature of the cooling water detected by the cooling water temperature sensor 23 based on this control characteristic table. The actual rotational speed Nfa of the cooling fan 13 is adjusted following the target rotational speed Nft set according to the coolant temperature TW.

  The controller 19 selects one of the first to third control characteristics C1 to C3 according to the outside air temperature TO detected by the outside air temperature sensor 20. The controller 19 refers to the selected control characteristic table and sets the target rotational speed Nft of the cooling fan 13 using the coolant temperature TW detected by the coolant temperature sensor 23 as an argument.

  The first control characteristic C1 is selected when the outside air temperature TO is equal to or higher than a predetermined value TOH (for example, 30 ° C.) (TOH ≦ TO). The second control characteristic C2 is selected when the outside air temperature TO is higher than a predetermined value TL (for example, 10 ° C.) and lower than a predetermined value TOH (TOL <TO <TOH). The third control characteristic C3 is selected when the outside air temperature is equal to or lower than TL (TO ≦ TOL).

  The first control characteristic C1 is that the target rotational speed Nft is set to the minimum rotational speed Nmin when the coolant temperature TW is TL1 or lower (TW ≦ TL1), and the target rotational speed Nft is maximized when the coolant temperature TW is equal to or higher than TH1 (TH1 ≦ TW). The rotation speed is set to Nmax. In the first control characteristic C1, when the coolant temperature TW is higher than TL1 and lower than TH1 (TL1 <TW <TH1), the target rotational speed Nft is reduced to the minimum rotational speed Nmin (for example, as the coolant temperature TW increases). 500 rpm) to a maximum rotation speed Nmax (for example, 1600 rpm).

  The second control characteristic C2 is that the target rotational speed Nft is set to the minimum rotational speed Nmin when the cooling water temperature TW is TL2 or lower (TW ≦ TL2), and the target rotational speed Nft is maximized when the cooling water temperature TW is higher than TH2 (TH2 ≦ TW). The rotation speed is set to Nmax. In the second control characteristic C2, when the coolant temperature TW is higher than TL2 and lower than TH2 (TL2 <TW <TH2), the target rotational speed Nft is increased from the minimum rotational speed Nmin to the maximum as the coolant temperature TW increases. It is determined to increase linearly up to the rotational speed Nmax.

  The third control characteristic C3 is that the target rotational speed Nft is set to the minimum rotational speed Nmin when the coolant temperature TW is TL3 or lower (TW ≦ TL3), and the target rotational speed Nft is maximized when the coolant temperature TW is TH3 or higher (TH3 ≦ TW). The rotation speed is set to Nmax. In the third control characteristic C3, when the coolant temperature TW is higher than TL3 and lower than TH3 (TL3 <TW <TH3), the target rotational speed Nft is increased from the minimum rotational speed Nmin to the maximum as the coolant temperature TW increases. It is determined to increase linearly up to the rotational speed Nmax.

  In the first to third control characteristics C1 to C3, the magnitude relationship of the temperature TW = TL1 to TL3 of the cooling water that starts increasing the target rotational speed Nft of the cooling fan 13 is TL1 <TL2 <TL3. In the first to third control characteristics C1 to C3, the magnitude relationship of the temperature TW = TH1 to TH3 of the cooling water that limits the target rotational speed Nft of the cooling fan 13 to the maximum rotational speed Nmax is TH1 <TH2 <TH3. In each control characteristic, the rate of change of the target rotational speed Nft to be increased from the minimum rotational speed Nmin to the maximum rotational speed Nmax according to the coolant temperature TW is the same.

  Each control characteristic is such that the fully closed temperature T1 shown in FIG. 3 is in a range higher than TL1 and lower than TL2 (TL1 <T1 <TL2), and the full open temperature T2 is higher than TH2 and lower than TH3. (TH2 <T2 <TH3). That is, the target rotational speed Nft of the cooling fan 13 is within the temperature range (T1 <TW <T2) of the cooling water in which the thermostat 22 is fully closed to fully open, and is determined according to the outside air temperature TO. It is set based on one of the following.

  When the target rotational speed Nft is set, as described above, the controller 19 changes the relief pressure Ps based on the target rotational speed Nft, decreases or increases the pump discharge pressure Pp, and the actual rotational speed of the cooling fan 13. Nfa is controlled to the target rotational speed Nft.

  The controller 19 controls the actual rotational speed Nfa of the cooling fan 13 based on the outside air temperature TO and the cooling water temperature TW by controlling each part as follows. FIG. 6 is a flowchart showing the processing contents regarding the rotational speed control of the cooling fan 13. When an ignition switch (not shown) of the wheel loader 100 is turned on, a program for performing the processing shown in FIG. 6 is started and repeatedly executed by the controller 19.

  In step S101, the controller 19 acquires information on the outside air temperature TO from the outside air temperature sensor 20 and information on the cooling water temperature TW from the cooling water temperature sensor 23, and proceeds to step S111.

  In step S111, the controller 19 determines whether or not the outside air temperature TO detected by the outside air temperature sensor 20 is equal to or higher than a predetermined value TOH. If a positive determination is made in step S111, the process proceeds to step S141, and if a negative determination is made, the process proceeds to step S121.

  In step S121, the controller 19 determines whether or not the outside air temperature TO detected by the outside air temperature sensor 20 is equal to or less than a predetermined value TOL. If a negative determination is made in step S121, the process proceeds to step S151, and if a positive determination is made in step S121, the process proceeds to step S161.

  When the outside air temperature TO is equal to or higher than the predetermined value TOH (TOH ≦ TO), in step S141, the controller 19 selects the first control characteristic C1, and refers to the table of the first control characteristic C1 to determine the coolant temperature TW. Is used as an argument to determine the target rotational speed Nft, and the process proceeds to step S171.

  When the outside air temperature TO is higher than the predetermined value TOL and lower than the predetermined value TOH (TOL <TO <TOH), in step S151, the controller 19 selects the second control characteristic C2, and the second control characteristic C2 The target rotational speed Nft is determined using the cooling water temperature TW as an argument with reference to the table, and the process proceeds to step S171.

  When the outside air temperature TO is equal to or lower than the predetermined value TOL (TO ≦ TOL), in step S161, the controller 19 selects the third control characteristic C3, refers to the table of the third control characteristic C3, and the coolant temperature TW. Is used as an argument to determine the target rotational speed Nft, and the process proceeds to step S171.

  In step S171, the controller 19 refers to the table of FIG. 4A and determines the relief pressure Ps using the target rotational speed Nft as an argument. The controller 19 outputs a control signal to the relief valve 9 based on the determined relief pressure Ps. When the relief pressure Ps is set by the controller 19, the pump discharge pressure Pp is controlled to the relief pressure Ps, and the actual rotational speed Nfa of the cooling fan 13 is adjusted to become the target rotational speed Nft.

  The operation of the present embodiment is summarized as follows when the outside air temperature TO is low, medium, and high. When the outside air temperature TO is a low temperature (for example, the outside air temperature TO = 5 ° C.), if the wheel loader 100 is operating, the coolant temperature TW of the engine 1 rises to the fully closed temperature T1 of the thermostat 22. .

  As shown in FIG. 3, the thermostat 22 is opened when the coolant temperature TW is T1 or higher and is fully opened at T2. The cooling water is supplied to the radiator 14 by opening the thermostat 22. The cooling water temperature TW settles at a constant temperature when the heat generation amount Qe of the engine 1 and the heat dissipation amount Qr of the radiator 14 are in an equilibrium state (hereinafter referred to as a thermal equilibrium state). The heat generation amount Qe of the engine 1 increases as the load on the engine 1 increases. The heat dissipation amount Qr of the radiator 14 increases as the outside air temperature TO decreases, increases as the actual rotational speed Nfa of the cooling fan 13 increases, and increases as the amount of cooling water supplied to the radiator 14 increases.

  (1) A case where the outside air temperature TO is a low temperature (for example, 0 ° C.) will be mainly described with reference to FIG. For convenience of explanation, a technique for setting the target rotational speed Nft with the first control characteristic C1 regardless of the outside air temperature TO will be referred to as a first comparative example, and the first embodiment will be described in comparison with the first comparative example. . In the first comparative example, when the wheel loader 100 is operated when the outside air temperature TO is 0 ° C., the cooling water temperature TW is higher than TL1 and lower than TH1, and the actual rotational speed Nfa of the cooling fan 13 is Nmin. Assume that a thermal equilibrium state is reached at a state of Na that is faster and slower than Nmax. At this time, the opening A of the thermostat 22 is a small opening A1 (for example, A1 = 10%) close to full closing (see FIG. 3).

  On the other hand, in the present embodiment, when the outside air temperature TO is 0 ° C., the controller 19 selects the third control characteristic C3. The third control characteristic C3 sets the target rotation speed Nft to the minimum rotation speed Nmin when the coolant temperature TW is equal to or lower than TL3.

  In the control based on the third control characteristic C3, the actual rotational speed Nfa of the cooling fan 13 does not increase even if the coolant temperature TW exceeds T1. For this reason, the coolant temperature TW rises above Ta. When the cooling water temperature TW rises, the opening degree A of the thermostat 22 increases, and the amount of cooling water supplied to the radiator 14 increases as compared with the first comparative example.

  In the present embodiment, TL3 in which the coolant temperature TW is higher than Ta, the actual rotational speed Nfa of the cooling fan 13 is Nmin slower than Na, and the opening A of the thermostat 22 is A4 larger than A1 (for example, , A4 = 70%) (see FIG. 3), a thermal equilibrium state is reached.

  In the present embodiment, the amount of cooling water increases as the cooling water temperature TW increases, so that the heat dissipation amount Qr is set to the first comparative example without increasing the actual rotational speed Nfa of the cooling fan 13 from the minimum rotational speed Nmin. Can be the same.

  In the first comparative example, the controller 19 sets the relief pressure Ps to Pa higher than the minimum value Pmin in order to set the actual rotational speed Nfa of the cooling fan 13 to Na higher than the minimum rotational speed Nmin (FIG. 4 (a )reference). Thereby, the discharge pressure Pp of the hydraulic pump 8 is controlled to Pa higher than the minimum value Pmin. In the first comparative example, since the load on the engine 1 is higher than when the discharge pressure Pp of the hydraulic pump 8 is controlled to the minimum value Pmin, the fuel consumption increases.

  On the other hand, in the first embodiment, the actual rotational speed Nfa of the cooling fan 13 does not increase from the minimum rotational speed Nmin. The relief pressure Ps is set to the minimum value Pmin (see FIG. 4A), and the discharge pressure Pp of the hydraulic pump 8 is controlled to the minimum value Pmin. Therefore, in the first embodiment, when the outside air temperature TO is a low temperature (for example, 0 ° C.), the fuel consumption can be suppressed as compared with the first comparative example. Furthermore, according to the first embodiment, noise associated with the rotation of the cooling fan 13 can also be reduced as compared with the first comparative example.

  (2) A case where the outside air temperature TO is an intermediate temperature (for example, 20 ° C.) will be mainly described with reference to FIG. For convenience of explanation, the first embodiment will be described in comparison with the first comparative example. In the first comparative example, when the wheel loader 100 is operated when the outside air temperature TO is 20 ° C., the cooling water temperature TW is TH1, and the actual rotational speed Nfa of the cooling fan 13 is Nmax. Assume that equilibrium is reached. At this time, the opening degree A of the thermostat 22 is A2 (for example, A2 = 40%) (see FIG. 3).

  In contrast, in the present embodiment, when the outside air temperature TO is 20 ° C., the controller 19 selects the second control characteristic C2. In the second control characteristic C2, the target rotation speed Nft is linearly increased from the minimum rotation speed Nmin to the maximum rotation speed Nmax as the cooling water temperature TW rises in the range where the cooling water temperature TW is higher than TL2 and lower than TH2. Let

  In the control based on the second control characteristic C2, the target rotational speed Nft of the cooling fan 13 does not increase even when the cooling water temperature TW exceeds T1, and the target rotational speed Nft increases from Nmin when the cooling water temperature TW exceeds TL2. To do. In the control based on the second control characteristic C2, when the coolant temperature TW is TH1 higher than TL2, the target rotational speed Nft (= N1) is set lower than in the first comparative example, so that the thermal equilibrium state However, the cooling water temperature TW rises above TH1. When the cooling water temperature TW rises, the opening A of the thermostat 22 increases, and the amount of cooling water supplied to the radiator 14 increases as compared with the first comparative example.

  In the present embodiment, the cooling water temperature TW is Tb higher than TH1, the actual rotation speed Nfa of the cooling fan 13 is Nb slower than Nmax, and the opening A of the thermostat 22 is A3 (for example, , A3 = 60%) (see FIG. 3), a thermal equilibrium state is reached.

  In the present embodiment, the amount of cooling water increases as the cooling water temperature TW increases, so that the heat dissipation amount Qr is made the same as that of the first comparative example without increasing the actual rotational speed Nfa of the cooling fan 13 from Nb. can do.

  In the first comparative example, the controller 19 sets the relief pressure Ps to the maximum value Pmax in order to set the actual rotation speed Nfa of the cooling fan 13 to the maximum rotation speed Nmax (see FIG. 4A). As a result, the discharge pressure Pp of the hydraulic pump 8 is controlled to the maximum value Pmax, and the load on the engine 1 increases, so that the fuel consumption increases.

  On the other hand, in the first embodiment, the actual rotational speed Nfa of the cooling fan 13 is controlled to Nb lower than the maximum rotational speed Nmax. The relief pressure Ps is set to Pb smaller than the maximum value Pmax, and the discharge pressure Pp of the hydraulic pump 8 is controlled to Pb. Therefore, in the first embodiment, when the outside air temperature TO is an intermediate temperature (for example, 20 ° C.), the fuel consumption can be suppressed as compared with the first comparative example. Furthermore, according to the first embodiment, noise associated with the rotation of the cooling fan 13 can also be reduced as compared with the first comparative example.

  (3) A case where the outside air temperature TO is high (for example, 40 ° C.) will be described mainly with reference to FIG. For convenience of explanation, a technique for making the rotation speed Nf of the cooling fan 13 constant (for example, Nf = Nmin) regardless of the outside air temperature TO and the cooling water temperature TW is a second comparative example, and is compared with the second comparative example. However, the first embodiment will be described.

  In the second comparative example, when the wheel loader 100 is operated when the outside air temperature TO is 40 ° C., it cools in a shorter time than when the outside air temperature TO is a medium low temperature (for example, 20 ° C. or 0 ° C.). The water temperature TW exceeds the fully closed temperature T1, and substantially reaches the fully open temperature T2 (around). As the load on the engine 1 is higher, the calorific value Qe of the engine 1 is increased and the cooling water temperature TW is increased. Therefore, in a high load operation, the cooling water temperature TW is likely to increase. For this reason, in the second comparative example, the cooling water temperature TW becomes higher than the full opening temperature T2 during a high load operation, and overheating (generally the cooling water temperature TW ≧ 100 ° C.) may occur.

  On the other hand, in the present embodiment, when the outside air temperature TO is 40 ° C., the controller 19 selects the first control characteristic C1. In the control based on the first control characteristic C1, the target rotational speed Nft is set higher than the minimum rotational speed Nmin even when the cooling water temperature TW is the fully closed temperature T1, and the target rotational speed Nft is set to the maximum rotational speed when the cooling water temperature TW is equal to or higher than TH1. By setting it to Nmax, it becomes possible to suppress an increase in the cooling water temperature TW and to prevent overheating.

According to this Embodiment described above, there can exist the following effects.
(1) The target rotational speed Nft set by the cooling water temperature TW becomes a different value depending on the outside air temperature TO within the temperature range (T1 <TW <T2) of the cooling water in which the thermostat 22 is fully opened from the fully closed state. Control characteristics were determined as follows. Since the target rotation speed Nft is set based on the cooling water temperature TW based on the control characteristics determined according to the outside air temperature TO, the cooling fan has an appropriate rotation speed according to the outside air temperature TO and the cooling water temperature TW. 13 can be driven. For this reason, it is possible to reduce the fuel consumption and the noise of the cooling fan 13.

  (2) When the outside air temperature TO is equal to or higher than TOH, the target rotational speed Nft set according to the fully closed temperature T1 is set higher than when the outside air temperature TO is lower than TOH (Nft = N1). > Nmin). When the outside air temperature TO is equal to or higher than TOH, the target rotational speed Nft set according to the full opening temperature T2 is set higher than when the outside air temperature TO is lower than TOH (Nft = Nmax> N2). Thus, the engine 1 is effectively cooled when the outside air temperature TO is high, and the fuel consumption can be suppressed when the outside air temperature TO is low.

  (3) When the outside air temperature TO is TOL <TO <TOH (medium temperature), the target rotational speed Nft set according to the fully closed temperature T1 is set to a value when the outside air temperature TO is lower than TOL (low temperature). It set so that it might become the same value (Nft = Nmin). When the outside air temperature TO is TOL <TO <TOH (medium temperature), the target rotational speed Nft set according to the full opening temperature T2 becomes the same value as when the outside air temperature TO is higher than TOH (high temperature). (Nft = Nmax). Thereby, when the cooling water temperature TW is low (TW <TL2), when the outside air temperature TO is medium temperature (TOL <TO <TOH), similarly to the low temperature (TO ≦ TOL), the high temperature (TOH) Compared with ≦ TO), fuel consumption can be reduced. When the coolant temperature TW is high (TH2 <TW), when the outside air temperature TO is medium (TOL <TO <TOH), the low temperature (TO ≦ TOL) is the same as when the high temperature (TOH ≦ TO). The cooling effect can be enhanced compared to the case of.

-Second Embodiment-
A second embodiment will be described with reference to FIG. FIG. 7 is a diagram illustrating a method for determining control characteristics used in a work machine such as a wheel loader according to the second embodiment. Hereinafter, differences from the first embodiment will be described.

  In the second embodiment, the control characteristic determination method used for setting the target rotational speed Nft of the cooling fan 13 in accordance with the coolant temperature TW is different from that in the first embodiment. In the first embodiment, a table of three types of control characteristics C1 to C3 is stored in a storage device, and control is performed by selecting any one of the three types according to the outside air temperature TO. The characteristics were determined.

  On the other hand, in the second embodiment, as shown in FIG. 7, a table of reference control characteristics used when the outside air temperature TO is equal to or higher than TOH is stored in the storage device. As the reference control characteristic table, the control characteristic C1 table described in the first embodiment is used. The reference table of the control characteristics C1 is used when the outside air temperature TO is equal to or higher than TOH.

  In the second embodiment, when the detected outside air temperature TO is lower than TOH, the table of the control characteristic C1 serving as a reference is used as a reference for the high temperature side of the cooling water temperature TW according to the amount of temperature drop from the TOH. The control characteristic according to the outside air temperature TO is determined by shifting the control characteristic data.

  The storage device stores a table of shift amounts with respect to the temperature decrease amount, and the controller 19 compares the detected outside air temperature TO and TOH and calculates the difference (temperature decrease amount). The controller 19 refers to the shift amount table and determines the shift amount using the temperature decrease amount as an argument. The controller 19 adds the shift amount to the target rotational speed data constituting the table of the control characteristics C1, and determines the control characteristics according to the outside air temperature.

  Thus, even when the control characteristic according to the outside air temperature TO is determined by shifting the table of the single control characteristic C1 to the high temperature side of the cooling water temperature TW according to the temperature decrease amount from the TOH, The same effects as those of the first embodiment are obtained. Furthermore, according to the second embodiment, when the outside air temperature TO gradually changes, the shift amount also gradually changes according to the outside air temperature TO. Therefore, it is more appropriate than the first embodiment. The actual rotational speed Nfa of the cooling fan 13 can be adjusted.

-Third embodiment-
A third embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing the processing content of the rotational speed control of the cooling fan 13 in a work machine such as a wheel loader according to the third embodiment. FIG. 8 is obtained by adding step S306 to the flowchart of FIG. Hereinafter, differences from the first embodiment will be described.

  As shown in FIG. 8, in the third embodiment, in step S <b> 306, the controller 19 has acquired information on the outside air temperature TO in step S <b> 101, that is, a signal of the outside air temperature TO from the outside air temperature sensor 20. It is determined whether or not it has been detected.

  If a negative determination is made in step S306, that is, if it is determined that the outside temperature TO signal cannot be detected, the process proceeds to step S141. If an affirmative determination is made, that is, the outside temperature TO signal is detected. If it is determined as normal, the process proceeds to step S111. When the controller 19 is in an abnormal state in which the outside air temperature TO cannot be detected, in step S141, the controller 19 refers to the control characteristic C1 table and sets the target rotational speed Nft of the cooling fan 13 using the cooling water temperature TW as an argument.

  In the third embodiment, when the outside temperature TO cannot be detected, the target rotational speed Nft of the cooling fan 13 is set based on the control characteristic C1 determined when the temperature is equal to or higher than TOH. Thereby, in addition to the same effect as 1st Embodiment, even if it is when outside temperature cannot be detected, overheating can be prevented. In the third embodiment, the control characteristic C1 is selected at the time of abnormality, but the control characteristic C2 may be selected. Even in this case, since the cooling performance can be improved compared to the case where the control characteristic C3 is selected, overheating can be prevented.

The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.
[Modification]
(1) Although the outside air temperature sensor 20 is provided at a predetermined position on the outer surface of the vehicle body that is touched by outside air, the present invention is not limited to this. For example, an intake air temperature sensor provided in the work machine for measuring the intake air temperature of the engine 1 may be used as the outside air temperature sensor. The controller 19 reads the temperature detected by the intake air temperature sensor as the outside air temperature, and determines the control characteristics according to the outside air temperature (intake air temperature).

  (2) In the above embodiment, the table is stored in the storage device as the control characteristic data, but the present invention is not limited to this. The approximate expression may be stored in the storage device as control characteristic data, and the target rotational speed Nft may be calculated based on the coolant temperature TW.

  (3) Although the three types of control characteristics C1 to C3 are determined in the first embodiment, the present invention is not limited to this. The target rotation speed may be determined based on two types or four or more types of control characteristics.

  (4) In the above-described embodiment, the control characteristics that are set so as to linearly increase the target rotation speed Nft from the minimum rotation speed Nmin to the maximum rotation speed Nmax as the cooling water temperature TW increases are described. However, the present invention is not limited to this. For example, the control characteristics may be determined so that the target rotation speed Nft is increased stepwise as the cooling water temperature TW rises or gradually.

  (5) In the above embodiment, the rate of change (slope) of the target rotational speed Nft that is increased from the minimum rotational speed Nmin to the maximum rotational speed Nmax according to the coolant temperature TW is the same regardless of the outside air temperature. However, the present invention is not limited to this. The control characteristics may be determined so that the rate of change (slope) varies depending on the outside air temperature.

  (6) Although the cooling water temperature sensor 23 is provided in the pipe line between the thermostat 22 and the radiator 14 in the above embodiment, the present invention is not limited to this. A cooling water temperature sensor 23 may be provided on the upstream side of the thermostat 22.

  (7) The controller 19 controls the relief pressure of the relief valve 9 to adjust the actual rotational speed Nfa of the cooling fan 13 so that the set target rotational speed is reached. It is not limited to.

  (8) In the above embodiment, the wheel loader 100 has been described as an example of a work machine. However, the present invention is not limited to this, and may be other work machines such as a forklift, a telehandler, a lift truck, and the like. May be.

  The present invention is not limited to the above-described embodiment, and can be freely changed and improved without departing from the gist of the invention.

1 engine, 2 torque converter (torque converter), 3 transmission, 4 propeller shaft, 5 axle, 6 tires, 7 hydraulic pump, 8 hydraulic pump, 9 relief valve, 10 check valve, 11 fan motor, 12 hydraulic circuit, 13 cooling fan , 14 Radiator, 15 Working fluid cooler, 16 Oil cooler, 17 Control valve, 18 Working hydraulic cylinder, 19 Controller, 20 Outside air temperature sensor, 21 Accelerator pedal, 22 Thermostat, 23 Cooling water temperature sensor, 31 Tank, 100 Wheel loader , 101 Center pin, 110 Front car body, 111 Arm, 112 Bucket, 113 Tire, 115 Bucket cylinder, 116 Steering cylinder, 117 Arm cylinder, 120 Rear car body, 121 Cab Down chamber, 123 tires, 124 counterweight 131 housing cover, 132 cooler housing cover, 135 radiator frame 140 grills, 150 cooling fan unit, 151 fan shroud

Claims (6)

Engine,
A radiator for cooling the refrigerant of the engine;
Refrigerant temperature detecting means for detecting the temperature of the refrigerant;
An outside air temperature detecting means for detecting the outside air temperature;
A thermostat that opens and closes the path between fully closed and fully open according to the temperature of the refrigerant on a path for supplying the refrigerant to the radiator;
A cooling fan for blowing outside air to the radiator;
A hydraulic pump driven by the engine;
A hydraulic motor driven by pressure oil discharged from the hydraulic pump to rotate the cooling fan;
A rotation speed setting means for setting the target rotation speed based on the refrigerant temperature detected by the refrigerant temperature detection means, based on a control characteristic in which the temperature of the refrigerant and the target rotation speed of the cooling fan are associated with each other;
A rotational speed adjusting means for adjusting the actual rotational speed of the fan so as to be the target rotational speed set by the rotational speed setting means;
Within the temperature range of the refrigerant in which the thermostat is fully closed to fully opened, the target rotational speed set by the detected refrigerant temperature becomes a different value depending on the outside air temperature detected by the outside air temperature detecting means. As described above, a work machine comprising control characteristic determining means for determining the control characteristic. The work machine according to claim 1,
The rotational speed setting means sets a target rotational speed that is set according to the temperature of the refrigerant at which the thermostat is fully closed when the temperature of the outside air is equal to or higher than a predetermined value, compared to when the temperature of the outside air is less than the predetermined value. Set high,
When the temperature of the outside air is equal to or higher than the predetermined value, the target rotational speed set according to the temperature of the refrigerant at which the thermostat is fully opened is set higher than that when the temperature of the outside air is lower than the predetermined value. Work machine. The work machine according to claim 1 or 2,
When the outside air temperature is within a predetermined range, the rotation speed setting means sets the target rotation speed set according to the temperature of the refrigerant fully closed by the thermostat to the same value as when the outside air temperature is lower than the predetermined range. Set to be
When the outside air temperature is within a predetermined range, the target rotational speed set according to the refrigerant temperature at which the thermostat is fully opened is set to the same value as when the outside air temperature is higher than the predetermined range. Features a working machine. The work machine according to any one of claims 1 to 3,
When the outside air temperature detecting means cannot detect the temperature of the outside air, it further comprises an abnormality determining means for determining an abnormality.
The rotation speed setting means sets a target rotation speed of the cooling fan based on a control characteristic determined when an outside air temperature is equal to or higher than a predetermined value when an abnormality is determined by the abnormality determination means. Work machine. The work machine according to any one of claims 1 to 4,
A storage device storing a plurality of control characteristic data;
The control characteristic determining means selects any one of a plurality of control characteristic data according to the detected temperature of the outside air,
The rotation speed setting means sets a target rotation speed of the cooling fan based on the selected control characteristic data. The work machine according to any one of claims 1 to 4,
A storage device storing reference control characteristic data used when the outside air temperature is equal to or higher than a predetermined value;
The control characteristic determining means is configured to shift the control characteristic data from the reference control characteristic data so that the control characteristic data is shifted to a higher temperature side of the refrigerant temperature in accordance with a temperature drop amount from the predetermined value. A work machine characterized by determining control characteristics according to the temperature of the machine.

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