JP4664246B2 - Engine control device for work vehicle - Google Patents

Description

The present invention relates to an engine control device for a work vehicle.

  In the bulldozer, the engine output (torque) is distributed to the traveling load, the work machine load, and the cooling fan load via the PTO shaft. That is, the output (torque) of the engine is transmitted to the sprocket via a traveling power train (power transmission device) such as a torque converter and a transmission (hydraulic clutch). As a result, the crawler belt is driven to run. Thus, a part of the horsepower of the engine is consumed as traveling horsepower (torque absorption horsepower). The traveling horsepower input to the traveling power train needs to be kept below a certain horsepower in consideration of durability.

  Further, the output of the engine is transmitted to the work machine hydraulic pump, and the work machine hydraulic pump is driven. Thus, pressure oil is supplied from the work machine hydraulic pump to the work machine actuator (hydraulic cylinder, hydraulic motor), and the work machine (blade or the like) is operated to perform work. A part of the horsepower of the engine is consumed as work horsepower (work machine pump absorption horsepower).

  The engine output is transmitted to the fan hydraulic pump to drive the fan hydraulic pump. Thus, pressure oil is supplied from the fan hydraulic pump to the fan hydraulic motor, the cooling fan is rotated, and the cooling water is maintained at a desired target temperature. A portion of the engine horsepower is consumed as fan horsepower (fan hydraulic pump absorption horsepower).

Therefore,
The relationship of engine horsepower = running horsepower + working horsepower + fan horsepower is established. When working with a bulldozer, the proportion of engine horsepower occupied by running horsepower is large, and the proportion of work horsepower occupied is low. In addition, the cooling fan is large, and the working horsepower is smaller than the fan horsepower.

For this reason, the working horsepower can be virtually ignored,
Engine horsepower = traveling horsepower + fan horsepower can be substituted.

  The engine mounted on the bulldozer is a diesel engine, and its output is controlled by adjusting the amount of fuel injected into the cylinder. This adjustment is performed by controlling a governor attached to the fuel injection pump of the engine. As the governor, an all-speed control type governor is generally used, and the engine speed and the fuel injection amount are set according to the load so that the target speed according to the operation amount of the throttle dial, the accelerator pedal, or the like is obtained. adjust. That is, the governor controls the fuel injection amount so that there is no difference between the target engine speed and the actual engine speed.

  FIG. 1 shows the relationship between the engine speed Ne and the engine torque Te, that is, the engine power curve (maximum torque line) R. The region defined by the engine power curve R indicates the performance that the engine can produce. The governor is designed so that the torque does not exceed the engine power curve (maximum torque line) R so that the black smoke does not fall outside the exhaust smoke limit, and the engine speed Ne exceeds the high idle speed NH. The engine is controlled so as not to rotate.

  The running horsepower is obtained by subtracting the fan horsepower from the engine output.

  On the other hand, the target temperature of the cooling water (coolant) is set to a temperature at which the engine efficiency is optimal. The temperature of the cooling water is changed by adjusting the rotational speed (fan rotational speed) Nf of the cooling fan. The target temperature is controlled by adjusting the fan rotation speed Nf according to the actual temperature Tw of the cooling water. When the cooling water temperature Tw is low, the fan rotational speed Nf is adjusted to be small so as to match the target temperature. When the cooling water temperature Tw is high, the fan rotational speed Nf is adjusted so as to increase to match the target temperature. The fan horsepower increases as the fan rotational speed Nf increases.

  Therefore, as shown in FIGS. 2 (a), 2 (b), and 2 (c), as the cooling water temperature Tw increases, the fan horsepower increases (the area shown by hatching increases) and travels accordingly. Horsepower is reduced and traction is reduced.

  Thus, in the bulldozer, the output of one engine is used for both running horsepower and fan horsepower. For this reason, the engine output that can be used as the traction force depends on the value of the coolant temperature Tw, that is, the load of the cooling fan.

(Prior art found in patent literature)
Therefore, conventionally, inventions for controlling the engine so that the running horsepower (traction force) does not decrease in accordance with the increase in fan horsepower are already known as disclosed in Patent Documents 1 and 2 below.

  Patent Document 1 describes an invention in which a fan horsepower is calculated based on the number of fan revolutions, and the engine is controlled so that the traction force is constant according to the magnitude of the calculated fan horsepower.

  Patent Document 2 describes an invention in which an engine is controlled to increase the power of a diesel engine in accordance with the magnitude of a load such as a cooling fan or an air conditioning system compressor.

Further, in Patent Document 3, regarding the hydraulic excavator, the maximum absorption torque and capacity of the variable displacement hydraulic pump are changed according to various work modes, and work is performed with emphasis on the work amount, and fuel efficiency is emphasized. An invention is described in which work is performed.
JP-A-62-178754 JP 2003-161191 A Japanese Patent No. 2711833

  According to the invention described in Patent Document 3, by selecting each work mode, the hydraulic excavator can be operated in a work mode in which work amount is emphasized or a work mode in which fuel consumption is emphasized.

  However, this Patent Document 3 does not assume a bulldozer having a configuration in which a cooling fan is driven by an engine. That is, when Patent Document 3 is applied to such a bulldozer, the traveling horsepower and the working horsepower change according to the cooling water temperature. For this reason, there is a possibility that the desired work amount and fuel consumption originally assumed in each work mode cannot be obtained. Conversely, when the cooling water temperature is low, the driving load increases, and a driving load that is higher than originally assumed in each work mode is input to the driving power train, and the driving power is increased by excessive driving horsepower. The durability of the train may be reduced.

  On the other hand, according to the inventions described in Patent Documents 1 and 2, the engine output that can be used as a traction force is kept constant regardless of the value of the coolant temperature, that is, the load of the cooling fan. However, the work vehicle cannot be driven with an emphasis on the amount of work or with an emphasis on fuel consumption, depending on the situation.

  The present invention has been made in view of such circumstances, and a work vehicle in which a cooling fan or an auxiliary machine is driven by an engine is driven with an emphasis on the amount of work or with an emphasis on fuel consumption depending on the situation. And ensuring the durability of the traveling power train (or work equipment drive device) by preventing excessive traveling horsepower (or working horsepower) from being input no matter what working mode is selected. It is a problem to be solved.

The first invention is
The engine torque of the engine is transmitted to the traveling body or / and the work machine, and is also transmitted to the cooling fan so that the running or / and work is performed and the cooling fan is driven. Because
Work mode selection means for selecting each work mode according to the magnitude of the driving or / and work load,
Fan load detection means for detecting the size of the cooling fan load;
A power curve setting means in which a plurality of power curves showing the relationship between the engine speed and torque are set;
For each work mode, a selectable power curve is determined, and an upper limit value of input torque transmitted to the traveling body or / and the work implement is determined,
When the work mode is selected by the work mode selection means, the input torque transmitted within the range of the selectable power curve corresponding to the selected work mode and transmitted to the traveling body and / or the work implement is the upper limit of the input torque. Power curve selection means for selecting a power curve according to the load of the cooling fan so as not to exceed the value,
And a control means for controlling the engine so as to obtain the selected power curve.

The second invention is
This is an engine control device for a work vehicle in which engine torque is transmitted to a traveling body or / and a work machine, and is also transmitted to an auxiliary machine to perform traveling or / and work, and the auxiliary machine is driven. And
Work mode selection means for selecting each work mode according to the magnitude of the driving or / and work load,
Auxiliary load detecting means for detecting the load of the auxiliary machine,
A power curve setting means in which a plurality of power curves showing the relationship between the engine speed and torque are set;
For each work mode, a selectable power curve is determined, and an upper limit value of input torque transmitted to the traveling body or / and the work implement is determined,
When the work mode is selected by the work mode selection means, the input torque transmitted within the range of the selectable power curve corresponding to the selected work mode and transmitted to the traveling body and / or the work implement is the upper limit of the input torque. Power curve selection means for selecting a power curve according to the load of the auxiliary machine so as not to exceed the value,
And a control means for controlling the engine so as to obtain the selected power curve.

The third invention is
The engine torque is transmitted to the traveling body or / and the work machine, and is also transmitted to the cooling fan so that the traveling or / and work is performed and the engine control device of the work vehicle in which the cooling fan is driven. There,
Fan load detection means for detecting the size of the cooling fan load;
In the low speed range where the engine speed is less than or equal to the specified speed, the fan horsepower consumed by the cooling fan is lower than that in the high speed range in order to secure the horsepower required for the vehicle or / and the work equipment. Cooling fan control means for driving and controlling the cooling fan so as to limit to
A power curve showing the relationship between the engine speed and torque. In the low engine speed region, the same or substantially the same curve is drawn, and in the high engine speed region, multiple power curves are drawn. Set power curve setting means,
Determine the upper limit of the input torque transmitted to the traveling body and / or work implement,
A power curve selection means for selecting a power curve according to the detected load of the cooling fan so that the input torque transmitted to the traveling body or / and the work implement does not exceed the input torque upper limit value;
And a control means for controlling the engine so as to obtain the selected power curve.

4th invention is the engine control apparatus of the working vehicle of 3rd invention,
Work mode selection means for selecting each work mode according to the travel or / and work load size is provided,
For each work mode, a plurality of selectable power curves that draw the same or substantially the same curve in the low engine rotation region and different curves in the high engine rotation region are defined.
Determine the upper limit of the input torque transmitted to the traveling body and / or work implement,
When the work mode is selected by the work mode selection means, the power curve selection means is transmitted to the traveling body and / or the work implement within the range of the selectable power curve corresponding to the selected work mode. The power curve is selected according to the detected load of the cooling fan so that the input torque does not exceed the input torque upper limit value.

A fifth invention is an engine control device for a work vehicle according to the third invention,
In the power curve setting means, a maximum horsepower power curve that can obtain the maximum horsepower that the engine can produce and a low horsepower power curve that can obtain a horsepower lower than this maximum horsepower power curve are set,
This low horsepower curve draws a curve that provides the same or nearly the same torque as the torque on the maximum horsepower power curve in the low engine speed range, and the torque on the maximum horsepower power curve in the high engine speed range. It is characterized by the fact that it is set to a high torque rise power curve by drawing a curve that can obtain a lower torque than that and connecting these two curves.

A sixth invention is an engine control device for a work vehicle according to the fourth invention,
The power curve setting means is set with a maximum horsepower power curve that obtains the maximum horsepower that the engine can produce and a low horsepower power curve that obtains a horsepower lower than this maximum horsepower power curve,
This low horsepower curve draws a curve that provides the same or nearly the same torque as the torque on the maximum horsepower power curve in the low engine speed range, and the torque on the maximum horsepower power curve in the high engine speed range. It is characterized by the fact that it is set to a high torque rise power curve by drawing a curve that can obtain a lower torque than that and connecting these two curves.

  According to the first and second inventions, when the work mode is selected by the work mode selection switch 31, the controller 20 is within the range of the selectable power curve corresponding to the selected work mode (work mode P). Then, if the power curve R1, R2, R3, work mode S, the power curve R2, R3, if the work mode E, the power curve R3), and the input torque transmitted to the traveling power train 10 is As shown in FIG. 5, the cooling water temperature ranges A, B, and C and the selected work modes P, S, and E are set so as not to exceed the input torque upper limit (maximum torque line R4; equivalent to the rated output of 70 PS). Based on this, a power curve is selected from each of the power curves R1, R2, and R3 (FIG. 6A) so that the selected power curve is obtained as shown in FIGS. Engine 1 is controlled.

  Therefore, depending on the selection of the work modes P, S, and E, it is possible to drive with an emphasis on the work amount or with an emphasis on fuel consumption (FIGS. 7, 8, and 9). In addition, no matter which work mode P, S, E is selected, excessive traveling horsepower is not input to the traveling power train 10 (for example, the rated output is suppressed to 70 PS or less), and the traveling power train 10 can be ensured (FIGS. 7, 8, and 9).

  The same applies not only when the cooling fan 16 is driven by the engine 1 but also when auxiliary equipment such as a generator or a compressor is driven by the engine 1 (second invention).

  According to the third invention, the fourth invention, the fifth invention, and the sixth invention, as shown in FIG. 10 (b), in the low speed region where the rotational speed Ne of the engine 1 is equal to or lower than the predetermined rotational speed Nec, the traveling body Alternatively, the cooling fan 16 is driven and controlled so as to limit the fan horsepower consumed by the cooling fan 16 to a value lower than that in the high rotation region in order to secure the horsepower required for the work machine.

Then, as shown in FIG. 11B, a plurality of power curves R1, R2 ′ that draw the same or substantially the same curve in the low rotation region of the engine 1 and different curves in the high rotation region of the engine 1 are drawn. , R3 ′ is set.

Similarly to the first invention described above, a power curve is selected according to the selected work mode and the detected coolant temperature of the engine 1 (detected load of the cooling fan 16), and the selected power curve is The engine 1 is controlled so as to be obtained. For this reason, even if any of the power curves R1, R2 ′, R3 ′ is selected, the horsepower consumed by the traveling power train 10 is set to the upper limit in the high speed region of the engine 1 as in the first invention. While being able to suppress below, the cooling water temperature of the engine 1 can be maintained at target temperature.

When the maximum horsepower power curve R1 is selected, the fan horsepower is suppressed by the amount indicated by a in FIG. 10B in the low rotation region of the engine 1, and the traveling horsepower (or working horsepower) is correspondingly increased. ) Becomes larger. For this reason, engine stall can be prevented when the engine 1 falls into low rotation.

When the low horsepower curve R2 ′ is selected, the fan horsepower is suppressed by the amount indicated by a in FIG. 10B in the low rotation region of the engine 1, and as shown in FIG. 11B. A high torque similar to the maximum horsepower curve R1 is obtained (a torque higher by b than the low power curve R2 in FIG. 11A is obtained), and the running horsepower (or work horsepower) is increased by an amount corresponding to them. Become. For this reason, engine stall can be similarly prevented.

When the low horsepower curve R3 ′ is selected, the fan horsepower is suppressed by the amount indicated by a in FIG. 10B in the low rotation region of the engine 1, and as shown in FIG. 11B. A high torque similar to the maximum horsepower curve R1 is obtained (a torque higher by c than the low power curve R3 in FIG. 11A is obtained), and the running horsepower (or working horsepower) is increased by an amount corresponding thereto. Become. For this reason, engine stall can be similarly prevented.

The third invention can also be applied to a work vehicle that does not include the work mode selection switch 31. In the third invention, for example, as shown in FIG. 13C, when the detected cooling water temperature is in the high temperature range A, the power curve R1 is selected, and the detected cooling water temperature is in the intermediate temperature range B. When the power curve R2 is selected and the detected coolant temperature is in the low temperature range C, the power curve R3 ′ is selected, and the engine 1 is controlled so that the selected power curve is obtained.

The fourth invention is an invention applied to a work vehicle provided with a work mode selection switch 31.

In the fourth invention, for example, as shown in FIG. 13 (a), the currently selected work mode, that is, the power mode P, the standard mode S, the economy mode E, and the range of the currently detected coolant temperature Tw, That is, according to the high temperature range A, the intermediate temperature range B, and the low temperature range C, the engine 1 is controlled so that one of the power curves R1, R2 ′, and R3 ′ is selected and the selected power mode is obtained. Is done.

In the fifth and sixth inventions, for example, as shown in FIG. 12, in the low rotation region of the engine 1, a curve for obtaining a high torque that is the same or substantially the same as the torque on the maximum horsepower power curve R 1 is drawn. In the high rotation region, a curve (low horsepower power curve R3) that can obtain a low torque lower than the torque on the maximum horsepower power curve R1 is drawn, and by connecting these two curves, a low horsepower power curve R3 ′ of high torque rise is obtained. Is set. The same applies to the other low horsepower power curves R2 ′ and R4 ′. As described above, the power curves R2 ′, R3 ′, and R4 ′ are set to have characteristics with a large torque rise, so that the engine stall can be further suppressed.

(First embodiment)
Embodiments of an engine control device for a work vehicle according to the present invention will be described below with reference to the drawings.

  FIG. 3 shows the configuration of a bulldozer that is one embodiment of the present invention, with respect to the portion according to the present invention.

  As shown in FIG. 3, the output shaft of the bulldozer engine 1 is connected to the PTO shaft 6. The PTO shaft 6 is connected to the torque converter 2 and is also connected to a working machine hydraulic pump 7 and a fan hydraulic pump 9.

  The working machine hydraulic pump 7 and the fan hydraulic pump 9 are variable displacement hydraulic pumps, and the pump displacement q is changed by changing the tilt angles of the swash plates 7a and 9a by the swash plate driving units 7b and 9b, respectively. (Cc / rev) is changed.

The output of the engine 1 is transmitted to the sprocket 5 via the torque converter 2, the transmission 3, and the final reduction gear 4, and the sprocket 5 is rotationally driven. The torque converter 2, the transmission 3, and the final reduction gear 4 constitute a traveling power train (power transmission device) 10. When the sprocket 5 is driven to rotate, the crawler belt 8 meshed with the sprocket 5 is driven to run. Thus, a part of the horsepower of the engine 1 is consumed as traveling horsepower (torque absorption horsepower). The traveling horsepower input to the traveling powertrain 10 needs to be kept below a certain horsepower in consideration of durability.

The transmission 3 includes a forward hydraulic clutch, a reverse hydraulic clutch, and a speed clutch (for example, a first speed hydraulic clutch, a second speed hydraulic clutch, and a third speed hydraulic clutch). One of the hydraulic clutches is selected to perform forward travel or reverse travel, and one of the speed stage clutches is selected to perform a shift.

  The output of the engine 1 is transmitted to the work machine hydraulic pump 7.

  When the work machine hydraulic pump 7 is driven, the discharge pressure oil is supplied to the work machine hydraulic cylinder 13 via the work machine control valve 11.

  The working machine hydraulic cylinder 13 is connected to a blade provided at the front of the vehicle body. When pressure oil is supplied to the working machine hydraulic cylinder 13, the blade is actuated. The spool of the work implement control valve 11 is moved in response to an operation of a work implement control lever (not shown), and the opening area of the control valve 11 is changed accordingly, and the flow rate supplied to the work implement hydraulic cylinder 13. Is changed. The bulldozer is equipped with work machines other than blades, but in the figure, the work machine drive devices (7, 11, 13) for blades are shown as representatives. In this way, part of the horsepower of the engine is consumed as working horsepower (work machine pump absorption horsepower).

  The output of the engine 1 is transmitted to the fan hydraulic pump 9.

  When the fan hydraulic pump 9 is driven, the discharge pressure oil is supplied to the fan hydraulic motor 15. A rotating shaft of a cooling fan 16 is connected to the drive shaft of the fan hydraulic motor 15. When pressure oil is supplied to the fan hydraulic motor 15, the fan hydraulic motor 15 is driven, and the cooling fan 16 is rotated accordingly. Thus, part of the horsepower of the engine 1 is consumed as fan horsepower (fan hydraulic pump absorption horsepower).

As above
The relationship of engine horsepower = running horsepower + working horsepower + fan horsepower is established. When working with a bulldozer, the proportion of engine horsepower occupied by running horsepower is large, and the proportion of work horsepower occupied is low. Further, the cooling fan 16 is large and has a smaller working horsepower than the fan horsepower.

For this reason, the working horsepower can be virtually ignored,
Engine horsepower = traveling horsepower + fan horsepower can be substituted.

  A radiator 14 is disposed at a position facing the cooling fan 16. The water channel 12 communicates a passage (water jacket) 17 inside the engine 1 and a radiator 14. Cooling water (coolant) is circulated between a passage (water jet) 17 inside the engine 1 and the radiator 14 via the water channel 12.

  The water channel 12 is provided with a cooling water temperature sensor 18 for detecting the temperature Tw (° C.) of the cooling water. In the present embodiment, the cooling water temperature is detected by the cooling water temperature sensor 18 to detect the load of the cooling fan 16.

  A detection signal from the coolant temperature sensor 18 is input to the controller 20.

  The target temperature of the cooling water is set to a temperature at which the efficiency of the engine 1 is optimal. The temperature Tw of the cooling water is changed by adjusting the rotational speed (fan rotational speed) Nf of the cooling fan 16. The target temperature is controlled by adjusting the fan rotation speed Nf according to the actual temperature Tw of the cooling water. The fan rotational speed Nf is adjusted by driving the swash plate 9a of the fan hydraulic pump 9 by the swash plate driving section 9b, adjusting the tilt angle (capacity) thereof, and supplying the hydraulic oil 15 to the fan hydraulic motor 15. It is controlled by adjusting the flow rate (l / min).

In the controller 20, when the cooling water temperature Tw is low, the fan rotation speed Nf is adjusted so as to be reduced to coincide with the target temperature, and when the cooling water temperature Tw is high, the fan rotation speed Nf is increased. The fan speed is controlled to be adjusted to match the target temperature.

  FIG. 6B shows a fan speed control map showing the relationship between the cooling water temperature Tw and the fan speed Nf.

  That is, when the cooling water temperature Tw is in the low temperature range C, the controller 20 adjusts the fan rotation speed Nf to be in the low rotation range Nfc. Further, when the cooling water temperature Tw is in the high temperature range A, the fan rotation speed Nf is adjusted to be in the high rotation range NfA. When the cooling water temperature Tw is in the intermediate temperature range B between the low temperature range C and the high temperature range A, the fan rotation speed Nf is an intermediate rotation between the low rotation speed range Nfc and the high rotation range NfA. It adjusts so that it may become the area | region NfB.

  The fan horsepower increases as the fan rotation speed Nf increases. Therefore, the fan horsepower, that is, the fan load, increases as the coolant temperature Tw shifts to the low temperature range C, the intermediate temperature range B, and the high temperature range A.

An engine speed setting device (throttle dial) 19 is provided in the cab of the bulldozer. The engine speed setter 19 is a setter for setting the target speed of the engine 1. When the engine speed setter 19 is operated, an engine target speed signal having a magnitude corresponding to the operation position is output. , Input to the controller 20.

  The controller 20 controls the engine 1 so as to achieve a target rotational speed corresponding to the operation amount of the engine rotational speed setting unit 19.

As shown in FIG. 4, an operation panel 30 is provided in the cab of the bulldozer.

  The operation panel 30 is provided with a work mode selection switch 31.

  The work mode selection switch 31 is a switch for selecting each work mode according to the magnitude of the traveling load. Each work mode includes a “power mode” P, a “standard mode” S, and an “economy mode” E.

The “power mode” P is a work mode that is selected in a work situation where the traveling load is large and a large engine output is required. “Power mode” P is a work mode that is selected when the amount of work is important. If this “power mode” P is selected, a large amount of work can be obtained while the engine is running, Will get worse.

  The “economy mode” E is a work mode that is selected in a work situation in which the travel load is small and the engine output is small. “Economy Mode” E is a work mode that is selected when fuel economy is important. If this “Economy Mode” E is selected, the fuel economy will be good while the engine is running. Only a small amount of work can be obtained.

  The “standard mode” S is a work mode selected when the work load is medium and the engine output is medium. “Standard mode” S is not as important as when “Power mode” P is selected, but requires more work than when “Economy mode” E is selected, and fuel consumption is more important than when “Economy mode” E is selected However, it is a work mode that is selected when it is desired to improve the fuel consumption more than when the “power mode” P is selected. If this “standard mode” S is selected, the fuel consumption during the operation of the engine is reduced to the “economy mode” E A good state between the selection and the “power mode” P is selected, and the amount of work while the engine is operating is an intermediate amount of work between the “economy mode” E and the “power mode” P.

  A signal indicating the work mode selected by the work mode selection switch 31 of the operation panel 30 is input to the controller 20.

  The engine 1 is a diesel engine, and its output is controlled by adjusting the amount of fuel injected into the cylinder. This adjustment is performed by controlling a governor attached to the fuel injection pump of the engine 1. As the governor, an all-speed control type governor is generally used, and the engine speed and the fuel injection amount are set according to the load so that the target speed according to the operation amount of the engine speed setting unit 19 is obtained. adjust. That is, the governor increases or decreases the fuel injection amount so that there is no difference between the target engine speed and the actual engine speed.

FIG. 1 shows the relationship between the engine speed Ne and the engine torque Te, that is, the engine power curve (maximum torque line) R. The region defined by the engine power curve R indicates the performance that the engine can produce. The governor is designed so that the torque does not exceed the engine power curve (maximum torque line) R so that the black smoke does not fall outside the exhaust smoke limit, and the engine speed Ne exceeds the high idle speed NH. The engine 1 is controlled so as not to rotate.

  From the equation “engine horsepower = traveling horsepower + fan horsepower”, the traveling horsepower is obtained by subtracting the fan horsepower from the engine output.

  On the other hand, as described above, the fan horsepower increases as the cooling water temperature Tw shifts to the low temperature range C, the intermediate temperature range B, and the high temperature range A.

Therefore, as shown in FIGS. 2 (a), 2 (b), and 2 (c), as the cooling water temperature Tw increases, the fan horsepower increases (the area shown by hatching increases) and travels accordingly. Horsepower is reduced and traction is reduced.

  Thus, in the bulldozer, the output of one engine 1 is used for both running horsepower and fan horsepower. For this reason, the engine output that can be used as the traction force depends on the value of the coolant temperature Tw, that is, the load of the cooling fan 16.

  Further, the running horsepower changes depending on the cooling water temperature Tw. For this reason, there is a possibility that the desired work amount and fuel consumption originally assumed in each work mode P, S, E may not be obtained. On the other hand, when the coolant temperature Tw is low, the traveling load becomes large, and a traveling load more than originally assumed in each work mode is input to the traveling power train 10 and an excessive traveling horsepower There is a risk that the durability of the traveling powertrain will be reduced.

  Therefore, in this embodiment, according to the selection of the work modes P, S, and E, it is possible to drive with emphasis on the work amount or with emphasis on fuel consumption, and any work mode P, S, E can be selected. Even if selected, based on the temperature ranges A, B, C of the coolant temperature Tw and the selected positions P, S, E of the work mode selection switch 31 so that excessive traveling horsepower is not input to the traveling power train 10. Thus, the optimum power curve R is selected to control the engine 1.

  As shown in FIG. 6A, the memory of the controller 20 stores a plurality of power curves R1, R2, and R3. For example, the power curves R1, R2, and R3 are set as power curves that increase the torque value and the rated output in the order of R3, R2, and R1. For example, the power curve R1 is a power curve with a rated output of 140 PS, the power curve R2 is a power curve with a rated output of 120 PS, and the power curve R3 is a power curve with a rated output of 100 PS.

  In addition, selectable power curves are defined for each of the work modes P, S, and E.

  R1, R2, and R3 are associated with the work mode P as selectable power curves.

  The work mode S is associated with R2 and R3 as selectable power curves.

  R3 is associated with the work mode E as a selectable power curve.

  Further, an upper limit value of input torque transmitted to the traveling power train 10 is determined. Specifically, the maximum torque line R4 shown in FIG. 6A indicates the upper limit value of the input torque transmitted to the traveling power train 10. The maximum torque line R4 corresponds to 70 PS in rated output. The maximum torque line R4 is set so that a sufficient traction force can be obtained when the power mode P is selected and the work can be performed with a sufficient work amount.

  R5 shown in FIG. 6A is a maximum torque line (corresponding to a rated output of 50 PS) having a smaller torque value and rated output than the maximum torque line R4, and R6 shown in FIG. 6A is a maximum torque line R4, A maximum torque line (corresponding to a rated output of 30 PS) having a torque value and a rated output smaller than those of R5.

  When the work mode is selected by the work mode selection switch 31, the controller 20 inputs the input torque transmitted to the traveling power train 10 within the range of the selectable power curve corresponding to the selected work mode. A power curve is stored based on the cooling water temperature ranges A, B, C and the selected work modes P, S, E so as not to exceed the torque upper limit (maximum torque line R4; equivalent to a rated output of 70 PS). The selected power curves R1, R2, and R3 are selected.

  In the following, the fan horsepower when the cooling water temperature Tw is in the low temperature range C, the intermediate temperature range B, and the high temperature range A (in the regions indicated by diagonal lines in FIGS. 2A, 2B, and 2C). The description will be made assuming that the corresponding horsepower is 30 PS, 50 PS, and 70 PS, respectively.

  FIG. 5 shows the currently selected work mode, that is, power mode P, standard mode S, economy mode E, and the range of currently detected coolant temperature Tw, that is, high temperature range A, intermediate temperature range B, and low. The data table which showed the relationship between the temperature range C and the selected power curves R1, R2, R3 is shown. This data table is stored in a memory in the controller 20.

The controller 20 selects the power curves R1, R2, and R3 shown in FIG. 6A from the memory according to the data table of FIG. 5, and controls the engine 1 so that the selected power curve is obtained. That is, the engine speed curve does not exceed the selected engine power curve (maximum torque line) R1, R2, R3 and does not exceed the exhaust smoke limit, and the engine speed Ne exceeds the high idle speed NH and does not overspeed. Thus, the engine 1 is controlled.

  FIGS. 7A, 7B, and 7C show the case where the power mode P is selected by the work mode selection switch 31, and the currently detected coolant temperature Tw is in the high temperature range A and intermediate. The power curves R1, R2, and R3 selected in the case of the temperature range B and the low temperature range C are shown.

  As shown in FIG. 7A, when the power mode P is in the high temperature range A, the engine 1 is controlled so as to obtain a power curve R1 (rated output 140 PS). At this time, the fan horsepower (indicated by the oblique lines) is 70 horsepower, and the torque input to the traveling power train 10 is limited to the maximum torque line R4 (corresponding to the rated output of 70 PS) or less.

  As shown in FIG. 7B, in the power mode P and the intermediate temperature range B, the engine 1 is controlled so as to obtain a power curve R2 (rated output 120PS). At this time, the fan horsepower (indicated by the oblique lines) is 50 horsepower, and the torque input to the traveling power train 10 is limited to the maximum torque line R4 (corresponding to the rated output of 70 PS) or less.

  As shown in FIG. 7C, when the power mode P is in the low temperature range C, the engine 1 is controlled so as to obtain a power curve R3 (rated output 100PS). At this time, the fan horsepower (indicated by the oblique lines) is 30 horsepower, and the torque input to the traveling power train 10 is limited to the maximum torque line R4 (corresponding to the rated output of 70 PS) or less.

  8A, 8B, and 8C show the case where the standard mode S is selected by the work mode selection switch 31, and the currently detected coolant temperature Tw is in the high temperature range A, intermediate. The power curves R2, R2, and R3 selected in the case of the temperature range B and the low temperature range C are shown.

  As shown in FIG. 8A, in the standard mode S and the high temperature range A, the engine 1 is controlled such that a power curve R2 (rated output 120PS) is obtained. At this time, the fan horsepower (indicated by diagonal lines) is 70 horsepower, and the torque input to the traveling power train 10 is limited to a maximum torque line R5 (corresponding to a rated output of 50 PS) or less.

  As shown in FIG. 8B, in the standard mode S and the intermediate temperature range B, the engine 1 is controlled so as to obtain a power curve R2 (rated output 120PS). At this time, the fan horsepower (indicated by the oblique lines) is 50 horsepower, and the torque input to the traveling power train 10 is limited to the maximum torque line R4 (corresponding to the rated output of 70 PS) or less.

  As shown in FIG. 8C, in the standard mode S and the low temperature range C, the engine 1 is controlled so as to obtain a power curve R3 (rated output 100 PS). At this time, the fan horsepower (indicated by the oblique lines) is 30 horsepower, and the torque input to the traveling power train 10 is limited to the maximum torque line R4 (corresponding to the rated output of 70 PS) or less.

  FIGS. 9A, 9B and 9C show a case where the economy mode E is selected by the work mode selection switch 31, and the currently detected cooling water temperature Tw is in the high temperature range A, intermediate The power curves R3, R3, and R3 selected in the case of the temperature range B and the low temperature range C are shown.

  As shown in FIG. 9A, in the economy mode E and the high temperature range A, the engine 1 is controlled so as to obtain a power curve R3 (rated output 100PS). At this time, the fan horsepower (indicated by oblique lines) is 70 horsepower, and the torque input to the traveling power train 10 is limited to a maximum torque line R6 (corresponding to a rated output of 30 PS) or less.

  As shown in FIG. 9B, in the economy mode E and the intermediate temperature range B, the engine 1 is controlled so as to obtain a power curve R3 (rated output 100PS). At this time, the fan horsepower (indicated by diagonal lines) is 50 horsepower, and the torque input to the traveling power train 10 is limited to the maximum torque line R5 (corresponding to a rated output of 50 PS) or less.

As shown in FIG. 9C, in the economy mode S and the low temperature range C, the engine 1 is controlled so as to obtain a power curve R3 (rated output 100PS). At this time, the fan horsepower (indicated by the oblique lines) is 30 horsepower, and the torque input to the traveling power train 10 is limited to the maximum torque line R4 (corresponding to the rated output of 70 PS) or less.

As can be seen from FIGS. 7 (a), 8 (a), and 9 (a), when the cooling water temperature is high, switching to each of the work modes P, S, and E sequentially causes the input to the traveling power train 10. The torque changes in sequence to a maximum torque line R4 (corresponding to a rated output of 70 PS), a maximum torque line R5 (corresponding to a rated output of 50 PS), and a maximum torque line R6 (corresponding to a rated output of 30 PS). For this reason, when the coolant temperature is high, it is possible to drive with an emphasis on the amount of work or with an emphasis on fuel consumption according to the selection of the work modes P, S, and E.

  The same applies when the torque input to the traveling power train 10 is averaged. The cooling water temperature fluctuates during the operating time of the day. For this reason, it is considered that the average value of the torque input at each of the cooling water temperatures A, B, and C is roughly input to the traveling power train 10.

As shown in FIGS. 7A, 7B, and 7C, the torque input to the traveling power train 10 when the power mode P is selected is large even on average (maximum torque line R4 at each cooling water temperature, The average horsepower of R4 and R4 is 70 PS), and as shown in FIGS. 8A, 8B and 8C, the torque input to the traveling power train 10 when the standard mode P is selected averages an intermediate value. (Average horsepower of the maximum torque lines R5, R4, R4 at each cooling water temperature is 63.3 PS), and the torque input to the traveling power train 10 when the economy mode S is selected is small even on average (each cooling water temperature The average horsepower of the maximum torque line R6, R5, R4 at the time is 50 PS).

  For this reason, even if it considers in the working time of one day, according to selection of work mode P, S, and E, it can drive | operate with an emphasis on work amount, or can drive | operate with an emphasis on fuel consumption.

  When the power mode P is selected, the maximum power curve R1 can be selected. However, when the cooling water temperature is in the intermediate range B and the low range C, the maximum power curve R1 is not the maximum power curve R1, but the torque value and the rated output are higher than that. Is selected, the input torque transmitted to the traveling power train 10 can be suppressed to an upper limit (equivalent to a rated output of 70 PS) or less (FIGS. 7B and 7C). ).

  Similarly, when the standard mode P is selected, the maximum power curve R2 can be selected. However, when the cooling water temperature is in the range C, the maximum power curve R2 is not the maximum power curve R2, but the power with a smaller torque value and rated output than that. Since the curve R3 is selected, the input torque transmitted to the traveling power train 10 can be suppressed to an upper limit (equivalent to a rated output of 70 PS) or less (FIG. 8 (c)).

  For this reason, no matter which work mode P, S, E is selected, excessive traveling horsepower is not input to the traveling power train 10, and the durability of the traveling power train 10 can be ensured. In addition, it is not necessary to ensure the strength of the traveling power train 10 more than necessary, and the cost of the traveling power train 10 can be reduced.

  Various modifications can be made to the above-described embodiment.

  In the embodiment, as shown in FIG. 5, the power curves R1, R2, and R3 are switched according to the range of the cooling water temperature switched to A, B, and C, but hysteresis is provided to prevent hunting. Is also possible.

  In FIG. 5, the power curve is selected by dividing the temperature range of the cooling water temperature into three ranges A, B, and C. However, the temperature range of the cooling water temperature is two ranges (high temperature and low temperature). It may be four or more ranges.

  Further, although the power curve is selected according to the size of the cooling water temperature Tw, the cooling water temperature Tw is an example, and any parameter indicating the load size (fan horsepower) of the cooling fan 16 may be used. Instead of the cooling water temperature Tw, the fan rotational speed Nf, the swash plate tilt angle of the fan hydraulic pump 9 or the like may be used. Further, the horsepower and the load (torque) consumed by the cooling fan 16 may be directly measured, and the power curve may be selected according to the measured value.

  In the embodiment, the cooling fan 16 that cools the cooling water is assumed. However, this is an example, and the present invention can be applied to, for example, a cooling fan for cooling the hydraulic oil temperature. The medium cooled by the fan is arbitrary.

  In the embodiment, a hydraulically driven cooling fan 16 driven by the hydraulic pump 9 and the hydraulic motor 15 is assumed, but the cooling fan is optional as long as it is driven by the output of the engine 1. For example, the present invention can also be applied to an electric cooling fan driven by an engine 1 and driven by electric power generated by the generator.

  In the embodiment, it is assumed that three work modes P, S, and E can be selected as work modes. However, this is an example, and two or less work modes and four or more work modes are selected. In this case, the present invention can be similarly applied. Further, although it is assumed that the work mode is selected by switching in stages, the present invention can be applied to a case where the work mode is changed steplessly.

  In the embodiment, the case where the cooling fan 16 is large and the fan horsepower is not large enough to be ignored compared to the engine horsepower has been described. However, the present invention is similarly compared to the engine horsepower. The present invention can be applied to a case where an auxiliary machine having a size with which power consumption cannot be ignored is driven by the engine 1. For example, when an auxiliary machine such as a compressor or a generator is driven by the engine 1, it is possible to detect the load of the auxiliary machine and select a power curve according to the load of the auxiliary machine. Is possible. In this case, in the table shown in FIG. 5, “high temperature range A”, “intermediate temperature range B”, and “low temperature range C” are respectively “when the load of the auxiliary machine is large” and “the load of the auxiliary machine is It can be similarly implemented by substituting “in the case of an intermediate size” and “when the load on the auxiliary machine is small”.

  In addition, when a plurality of auxiliary machines are used at the same time, the present invention can be applied to a case where the auxiliary machine and a cooling fan are used at the same time.

In the embodiment, the working horsepower can be substantially ignored,
Description has been made assuming that the relationship of engine horsepower = running horsepower + fan horsepower is established.

However, depending on the work vehicle, the running horsepower can be virtually ignored,
The relationship of engine horsepower = working horsepower + fan horsepower may be established. In this case, the “traveling horsepower” in the embodiment can be replaced with “working horsepower”, and the operation can be similarly performed. In this case, instead of the upper limit value of torque input to the traveling power train 10 (70 PS at the rated output), the upper limit value of torque input to the work implement drive device (7, 11, 13) is determined. Whatever the work mode is selected, the engine power curve is selected so that the cooling water temperature is whatever the temperature and the torque input to the work implement drive device (7, 11, 13) does not exceed the upper limit value. It will be.

Of course, if you can't ignore the running horsepower and working horsepower,
The present invention can also be applied when the relationship of engine horsepower = running horsepower + working horsepower + fan horsepower is established. In this case, instead of the upper limit value of the torque input to the traveling power train 10 (70 PS at the rated output), the upper limit of the torque input to the traveling power train 10 and the work implement driving equipment (7, 11, 13). No matter what work mode is selected, the torque input to the traveling power train 10 and the work equipment drive equipment (7, 11, 13) exceeds the upper limit regardless of the cooling water temperature. The engine power curve is selected so that there is no.

(Second embodiment)
In the first embodiment described above, as shown in FIG. 6B, the cooling fan 16 is driven and controlled so as to increase the fan rotation speed Nf in accordance with the increase in the cooling water temperature Tw. In controlling the fan 16, the magnitude of the engine speed was not considered at all.

  In the following, an embodiment in which the cooling fan 16 is driven and controlled in consideration of the magnitude of the engine speed will be described.

  FIG. 10A is a diagram schematically showing a comparative example for the present embodiment, and shows the relationship between the rotational speed Ne of the engine 1 and the fan rotational speed Nf of the cooling fan 16. As shown in FIG. 10A, the rotational speed Nf of the cooling fan 16 increases in proportion to the increase in the rotational speed Ne of the engine 1. In other words, in the low speed region where the engine speed Ne is lower than the predetermined speed Nec, the fan speed Nf only decreases in proportion to the decrease in the engine speed Ne, and the fan horsepower is low. There was no significant decrease in the rotation region.

  However, in the low rotation region of the engine 1, the heat generation amount of the engine 1 is small. For this reason, there is little need to maintain large fan rotation speed Nf and fan horsepower and large cooling capacity in the engine low rotation region as shown in FIG. 10A, and as shown in FIG. Even if the fan rotation speed Nf is greatly reduced in the rotation region and the fan horsepower is greatly limited, the cooling capacity of the engine 1 is sufficient.

Rather, if the fan rotation speed Nf is greatly reduced in the low engine rotation range and the fan horsepower is not greatly limited, the engine horsepower can be reduced to running horsepower or working horsepower, and engine stall is likely to occur. In general, the power curve of the engine 1 is low in torque and horsepower in a region where the engine speed is low. It is said that. FIGS. 10 (a) and 10 (b) are schematic explanatory diagrams, and it is sufficient that the fan rotational speed has a generally increasing tendency as the engine rotational speed increases, and it is not always necessary to have a proportional relationship. Absent.
FIG. 11A shows the power curves R1, R2, and R3 set in the first embodiment in comparison with each other. As shown in FIG. 11 (a), when the low horsepower power curves R2 and R3 having a lower torque value and rated output than the power curve R1 with which the maximum horsepower that can be output by the engine 1 is obtained, the engine is low. There is a large drop in torque and horsepower in the rotation region. For this reason, when the cooling fan 16 is controlled so that the fan horsepower remains large in the low engine speed region (FIG. 10A), the absolute amount of the running horsepower or the working horsepower obtained by subtracting the fan horsepower from the engine horsepower is insufficient. As a result, engine stalls are more likely to occur.

  Therefore, in this embodiment, as shown in FIG. 10B, the engine speed Ne decreases in the low speed region where the rotational speed Ne of the engine 1 is equal to or lower than the predetermined rotational speed Nec compared to the high speed region. Accordingly, the cooling fan 16 is driven and controlled in a proportional relationship that greatly reduces the fan rotational speed Nf. The fan rotation speed Nf in the low rotation region is set to a value that can ensure the required running horsepower or working horsepower without causing an engine stall in the engine low rotation region and obtain the minimum required fan horsepower. Compared with the comparative example shown in FIG. 10A, the fan speed Nf is limited to a lower value by the amount indicated by the hatched line a in FIG. Horsepower will be limited.

On the other hand, in the high speed region of the engine 1, the cooling fan 16 is driven and controlled so that the fan speed Nf increases as the engine speed Ne increases in the same proportional relationship as in the comparative example (FIG. 10A). . For this reason, the fan horsepower for maintaining the cooling water temperature of the engine 1 at the target temperature is ensured. The relationship between the cooling water temperature Tw and the fan rotation speed Nf is the same as that in FIG. 6B described above, and the cooling fan 16 is driven so that the fan rotation speed Nf is increased as the cooling water temperature Tw increases. Shall be controlled. In other words, the cooling fan 16 is driven and controlled in such a manner as to “lift” the curve shown in FIG. 10B in accordance with the increase in the cooling water temperature Tw.

FIG. 11B shows the power curves R1, R2 ′, R3 ′ set in the second embodiment in comparison.

As shown in FIG. 11B, a plurality of power curves R1, R2 ′, which draw the same or substantially the same curve in the low rotation region of the engine 1 and different curves in the high rotation region of the engine 1, R3 'is set.

As can be seen by comparing FIG. 11 (a) and FIG. 11 (b), in this embodiment, a low horsepower power curve that provides a lower horsepower than the maximum horsepower power curve R1 that provides the maximum horsepower that the engine 1 can produce. Although R2 ′ and R3 ′ are set in the same manner as in the first embodiment, the low horsepower power curves R2 ′ and R3 ′ are different from the power curves R2 and R3 in the first embodiment. In the low rotation region of the engine 1, a curve is obtained in which a high torque that is the same or substantially the same as the torque on the maximum horsepower power curve R1 is obtained, and in the high rotation region of the engine 1, it is lower than the torque on the maximum horsepower power curve R1. The curve is set to draw a low torque.

As in the first embodiment, a power curve is selected according to the selected work mode and the detected cooling water temperature of the engine 1 (detected load of the cooling fan 16), and the selected power curve is obtained. The engine 1 is controlled as shown. Therefore, regardless of which power curve R1, R2 ′, R3 ′ is selected, the upper limit of the horsepower consumed by the traveling power train 10 is the same as in the first embodiment in the high speed region of the engine 1. The cooling water temperature of the engine 1 can be maintained at the target temperature while being able to be suppressed below the value.

When the maximum horsepower power curve R1 is selected, the fan horsepower is suppressed by the amount indicated by a in FIG. 10B in the low rotation region of the engine 1, and the traveling horsepower (or working horsepower) is correspondingly increased. ) Becomes larger. For this reason, engine stall can be prevented when the engine 1 falls into low rotation.

When the low horsepower curve R2 ′ is selected, the fan horsepower is suppressed by the amount indicated by a in FIG. 10B in the low rotation region of the engine 1, and as shown in FIG. 11B. A high torque similar to the maximum horsepower curve R1 is obtained (a torque higher by b than the low power curve R2 in FIG. 11A is obtained), and the running horsepower (or work horsepower) is increased by an amount corresponding to them. Become. For this reason, engine stall can be similarly prevented.

When the low horsepower curve R3 ′ is selected, the fan horsepower is suppressed by the amount indicated by a in FIG. 10B in the low rotation region of the engine 1, and as shown in FIG. 11B. A high torque similar to the maximum horsepower curve R1 is obtained (a torque higher by c than the low power curve R3 in FIG. 11A is obtained), and the running horsepower (or working horsepower) is increased by an amount corresponding thereto. Become. For this reason, engine stall can be similarly prevented.

Next, how to set the low horsepower curve will be described with reference to FIG.

  FIG. 12 shows the maximum horsepower corresponding to the maximum torque lines (power curves) R1, R2 ′, R3 ′, R4 ′ and the maximum torque lines (power curves) R1, R2 ′, R3 ′, R4 ′ of this embodiment. Lines P1, P2 ', P3', P4 'are shown. The horizontal axis in FIG. 12 is the engine speed Ne, and the vertical axis in FIG. 12 is the torque (N · m) or the output (kW). For comparison, FIG. 12 shows power curves R2 and R3 of the first embodiment with broken lines. The power curve R4 is a maximum torque line having a smaller maximum torque than the power curve R3.

  In general, it is said that the engine is less likely to stall as the torque rise increases. Here, the torque rise is a scale representing the tenacity of the engine. When the torque value at the rated point G on the maximum torque line R1 is Tr and the torque value at the maximum torque point F is Tm, H = Tm -It is said that the larger the Tr, the harder it is to stall. Torque rise (%) is expressed by the following equation.

Torque rise (%) = (Tm−Tr) / Tr × 100
In the bulldozer, the vehicle travels at the operating point J on the maximum torque line R1 and reaches the operating point G when working, and when the load is further applied, the rotation of the engine decreases and reaches the operating point (maximum torque point) F. When a further load is applied, the operating point F is exceeded and the engine rotation is further reduced, leading to an engine stall. Here, if the torque rise is large, it is difficult to exceed the operating point F, and the engine stall can be suppressed.

The low horsepower power curve R3 ′ of the second embodiment is set as follows. First, an engine speed NeF ′ lower than the engine speed NeF corresponding to the maximum torque point F of the low horsepower power curve R3 of the first embodiment is set. The low engine speed NeF ′ is preferably lower than the threshold speed Nec shown in FIGS. 10 (a) and 10 (b). Next, the same curve as the low horsepower power curve R3 is drawn at a higher speed than the engine speed NeF, and the same curve as the maximum horsepower power curve R1 is drawn at a lower speed than the engine speed NeF '. To do. In the engine speed range from NeF 'to NeF, a curve connecting point F' corresponding to engine speed point NeF 'on maximum horsepower power curve R1 and point F on low horsepower curve R3 is drawn. To do.

In this way, the maximum torque point is F ′, and the high torque rise low horsepower power curve R3 ′ having a larger torque rise than the low horsepower power curve R3 is set.

That is, in the low rotation region of the engine 1, a curve is obtained in which a high torque that is the same or substantially the same as the torque on the maximum horsepower power curve R1 is drawn. By drawing a curve (low horsepower power curve R3) from which low torque can be obtained and connecting these two curves, a low horsepower power curve R3 ′ for high torque rise is set. The same applies to the other low horsepower power curves R2 ′ and R4 ′.

As described above, in this embodiment, the power curves R2 ′, R3 ′, and R4 ′ are set to characteristics having a large torque rise, so that the engine stall can be further suppressed.

FIGS. 13A and 13B are diagrams corresponding to FIG. 5 of the first embodiment, and the contents of the data table in the second embodiment, that is, the selected work mode and the detected coolant temperature. The power curve to be selected corresponding to is shown.

FIG. 13A shows a data table when selectable power curves are R1, R2 ′, and R3 ′. The currently selected work mode, that is, power mode P, standard mode S, economy mode E, and currently detected coolant temperature Tw range, that is, high temperature range A, intermediate temperature range B, and low temperature range C. Accordingly, one of the power curves R1, R2 ′, R3 ′ is selected, and the engine 1 is controlled so that the selected power mode is obtained.

FIG. 13B shows a data table when selectable power curves are R1, R2 ′, R3 ′, and R4 ′. In this case, the power mode P, the first standard mode S1, the second standard mode S2, and the economy mode E can be selected by the work mode selection switch 31 of the operation panel 30, and the range of the cooling water temperature Tw can be selected. Classified into four more subdivided temperature ranges, namely, a high temperature range A, a first intermediate temperature range B1, a second intermediate temperature range B2, which is a temperature range lower than the first intermediate temperature range B1, and a low temperature range C. To do. Therefore, the currently selected work mode, that is, the power mode P, the first standard mode S1, the second standard mode S2, the economy mode E, the range of the currently detected coolant temperature Tw, that is, the high temperature range A, Depending on the first intermediate temperature range B1, the second intermediate temperature range B2, and the low temperature range C, any one of the power curves R1, R2 ′, R3 ′, and R4 ′ is selected, and the selected power curve is obtained. Thus, the engine 1 is controlled.

(Third embodiment)
In the second embodiment described above, the work vehicle provided with the work mode selection switch 31 has been described. However, the second embodiment described above can be applied to a work vehicle not provided with the work mode selection switch 31. Thus, the present invention may be modified as appropriate.

For example, as shown in FIG. 13C, when the detected cooling water temperature is in the high temperature range A as in the case of selecting the power mode P in FIG. 13A, the power curve R1 is selected and the detected cooling is performed. When the water temperature is in the intermediate temperature range B, the power curve R2 is selected, and when the detected cooling water temperature is in the low temperature range C, the power curve R3 ′ is selected so that the selected power curve is obtained. Alternatively, the engine 1 may be controlled.

The present invention is not limited to a bulldozer, and can be applied to any work vehicle as long as the engine output (engine torque) is distributed to a cooling fan or an auxiliary machine.

FIG. 1 is a graph showing the relationship between engine speed and engine torque. FIG. 2 is a diagram used to explain the difference in the magnitude of the fan horsepower consumed according to the magnitude of the cooling water temperature. Drawing 3 is a figure showing the composition of the bulldozer which is a work vehicle of an embodiment. FIG. 4 is a diagram showing a work mode selection switch provided on the operation panel. FIG. 5 shows the contents of the data table stored in the controller. FIG. 6A is a diagram showing each engine power curve, and FIG. 6B is a diagram showing that the number of fan rotations changes according to the cooling water temperature, and shows each cooling water temperature range. FIGS. 7A, 7B, and 7C show the case where the power mode is selected by the work mode selection switch, and the currently detected coolant temperature is high, intermediate, and low. It is a figure which shows the power curve selected in the case of each temperature range. FIGS. 8A, 8B, and 8C show the case where the standard mode is selected with the work mode selection switch, and the currently detected coolant temperature is high, intermediate, and low. It is a figure which shows the power curve selected in the case of each temperature range. FIGS. 9A, 9B, and 9C show a case where the economy mode is selected by the work mode selection switch, and the currently detected coolant temperature is high, intermediate, and low. It is a figure which shows the power curve selected in the case of each temperature range. FIG. 10A is a view showing a comparative example with respect to the present embodiment, and FIG. 10B is a view showing the present embodiment, and shows a relationship between the engine speed and the fan speed of the cooling fan. It is. FIG. 11A is a view showing a comparative example with respect to the present embodiment, and FIG. 10B is a view showing the present embodiment, showing a plurality of different power curves. FIG. 12 is a diagram showing a plurality of different power curves, and is a diagram showing a power curve for high torque rise. FIGS. 13A, 13B, and 13C are diagrams illustrating the contents of a data table used for selecting each power curve shown in FIG. 11B or FIG.

Explanation of symbols

  1 Engine 10 Traveling Powertrain 16 Cooling Fan 18 Cooling Water Temperature Sensor 20 Controller 31 Work Mode Selection Switch

Claims (2)

The engine torque of the engine is transmitted to the traveling body or / and the work machine, and is also transmitted to the cooling fan so that the running or / and work is performed and the cooling fan is driven. Because
Work mode selection means for selecting each work mode according to the magnitude of the driving or / and work load,
Fan load detection means for detecting the size of the cooling fan load;
A power curve setting means in which a plurality of power curves showing the relationship between the engine speed and torque are set;
A selectable power curve is defined for each work mode, and is selected from the selectable power curves determined for the selected work mode according to the detected load of the cooling fan. A power curve is determined, and a maximum torque line indicating the upper limit of the input torque transmitted to the traveling body and / or work implement is determined according to the selected work mode, the selected power curve and the detected load of the cooling fan. And
When the work mode is selected by the work mode selection means, the power curve is selected according to the load of the cooling fan within the range of the selectable power curve corresponding to the selected work mode. A power curve selecting means for selecting a maximum torque line according to the selected work mode, the selected power curve and the detected load of the cooling fan;
Control means for controlling the engine so that the selected power curve is obtained, and for controlling the engine torque transmitted to the traveling body and / or work implement so as not to exceed the upper limit indicated by the maximum torque line; Prepared
An engine control device for a work vehicle. This is an engine control device for a work vehicle in which engine torque is transmitted to a traveling body or / and a work machine, and is also transmitted to an auxiliary machine to perform traveling or / and work, and the auxiliary machine is driven. And
Work mode selection means for selecting each work mode according to the magnitude of the driving or / and work load,
Auxiliary load detecting means for detecting the load of the auxiliary machine,
A power curve setting means in which a plurality of power curves showing the relationship between the engine speed and torque are set;
A power curve that can be selected corresponding to each work mode is determined, and the power curve that can be selected corresponding to the selected work mode is selected according to the magnitude of the detected load of the auxiliary machine. A power curve is defined, and a maximum torque line indicating an upper limit value of the input torque transmitted to the traveling body and / or the work implement is determined according to the selected work mode, the selected power curve and the detected load of the auxiliary machine. ,
When the work mode is selected by the work mode selection means, the power curve is selected according to the load of the auxiliary machine within the range of the selectable power curve corresponding to the selected work mode. A power curve selection means for selecting a maximum torque line according to the work mode, the selected power curve and the detected load of the auxiliary machine;
Control means for controlling the engine so that the selected power curve is obtained, and for controlling the engine torque transmitted to the traveling body and / or work implement so as not to exceed the upper limit indicated by the maximum torque line; An engine control device for a work vehicle, comprising:

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