JP5227153B2 - Bulldozer control device - Google Patents

Description

The present invention relates to a control device for a bulldozer that is steered by a steering clutch and a steering brake that are provided corresponding to left and right drive wheels.

A vehicle such as a conventional bulldozer has a torque converter having a pump impeller connected to an engine and a turbine runner connected to a transmission, and the rotational power from the engine is transmitted to each of the left and right via the torque converter. There is one that performs a left and right turning motion by controlling a steering clutch and a steering brake provided corresponding to each driving wheel in accordance with the operation of a steering lever. (See Patent Document 1).
In addition, a torque converter provided with a lock-up clutch and coupling or releasing the pump impeller and the turbine runner by engaging or disengaging the lock-up clutch is widely used (for example, Patent Documents). 2).

JP 2002-193137 A Japanese Patent Laid-Open No. 5-93429

In the bulldozer according to Patent Document 1, when the steering lever is operated in either the left or right turning direction during traveling, the coupled state of the steering clutch on the operating side is released and the steering brake on the operating side is braked. Then, it is designed to turn in the direction of the operation side.
In the bulldozer according to Patent Document 2, the rotation power from the engine is mechanically directed toward each drive wheel by performing the lockup mode in a state where the pump impeller and the turbine runner are coupled by engagement of the lockup clutch. The power transmission efficiency can be improved by direct transmission.

  However, in a vehicle equipped with this type of turning mechanism and a torque converter with a lock-up clutch, the steering brake on the turning operation side brakes when the turning operation is performed while driving down the slope in the lock-up mode. Because high-speed downhill driving is continued in this state, depending on the inclination angle of the slope, the steering brake on the turning operation side may be overloaded due to the weight of the vehicle and excessive vehicle speed, which may damage the steering brake There is.

The present invention has been made to solve such problems, and an object of the present invention is to provide a control apparatus for a bulldozer capable of preventing damage to a steering brake due to a turning motion when traveling at a high speed downhill. It is what.

In order to achieve the above object, a control apparatus for a bulldozer according to the present invention comprises:
Rotational power from the engine is transmitted to the left and right drive wheels via a torque converter with a lock-up clutch, and the steering clutch and steering brake provided for each drive wheel respond to the operation of the steering lever. In the control apparatus of the bulldozer configured to perform the left and right turning movements by being controlled,
Lock-up clutch control means for controlling the lock-up clutch;
A lever operation amount detector for detecting an operation amount of the steering lever;
An inclination angle sensor for detecting an inclination angle of the bulldozer in the front-rear direction;
When the lockup clutch is engaged by the lockup clutch control means, it is detected by the tilt angle sensor that the bulldozer is traveling downhill at a first predetermined tilt angle or more, and the lever operation When it is detected by the amount detector that the steering lever is operated, a lockup clutch disengagement command signal for commanding the disengagement of the lockup clutch is output to the lockup clutch control means. it is characterized in further comprising a brake protect control unit for executing a brake protection processing to protect the steering brakes by subtracting the vehicle speed by (first invention).

  In the present invention, when the detected tilt angle of the tilt angle sensor becomes equal to or smaller than a second predetermined tilt angle that is smaller than the first predetermined tilt angle, the brake protect control unit preferably releases the brake protect process. (Second invention).

In the present invention, when a turning motion is performed while traveling downhill on a slope having a first predetermined inclination angle or more with the lockup clutch engaged (lockup mode), the brake protection processing by the brake protection control unit is performed. Executed.
By executing the brake protection process, a lockup clutch disengagement command signal is output from the brake protection control unit to the lockup clutch control means to command the lockup clutch to be disengaged. The state is released (torque control mode).
Thus, by being switched from the lock-up mode to the torque converter mode, the bull dozer vehicle speed is reduced, it is possible to reduce the load of the turning operation side of the steering brakes.
Therefore, there is an effect that it is possible to prevent the steering brake from being damaged due to the turning motion at the time of traveling at a high speed downhill.
When driving downhill on a slope with less than the first predetermined tilt angle that does not affect the durability of the steering brake, the brake protection process is not executed and the lockup mode state is maintained, improving the power transmission efficiency. Can be achieved.

Next, a specific embodiment of the bulldozer of the control device according to the present invention will be described with reference to FIG surface.

FIG. 1 shows a side view of a bulldozer according to an embodiment of the present invention.
FIG. 2 is a schematic system configuration diagram of a bulldozer power line.

  A bulldozer 1 shown in FIG. 1 includes a tractor 2 having a crawler-type traveling device 2a, a blade device 3 as a front working machine, and a ripper device 4 as a rear working machine. The construction is such that the earthing / soiling work by the device 3 and the crushing / excavation work by the ripper device 4 are performed.

  In the power line 5 shown in FIG. 2, the rotational power from the engine 6 includes a damper 7, a PTO 8, a torque converter 9, a transmission 10, a horizontal shaft device 11, left and right final reduction gears 12L and 12R, and left and right sprockets (the present invention). This is transmitted to the left and right crawler belts 14L, 14R via 13L, 13R.

The engine 6 is provided with an electronic control fuel injection device 15. The electronically controlled fuel injection device 15 controls the fuel injection amount according to the fuel injection amount control signal Qf.
The rotational speed of the engine 6 is controlled based on a fuel injection amount control signal Qf given to the electronically controlled fuel injection device 15.

The torque converter 9 includes a pump impeller 9a, a turbine runner 9b, and a stator 9c. The pump impeller 9a is connected to the engine 6 as an input element, the turbine runner 9b is connected to the transmission 10 as an output element, and the stator 9c is provided as a reaction element between the pump impeller 9a and the turbine runner 9b. Yes.
The torque converter 9 is provided with a lockup clutch 16. The lockup clutch 16 couples or releases the pump impeller 9a and the turbine runner 9b.
In a speed range that does not require the characteristics of the torque converter 9, the lockup clutch 16 couples the pump impeller 9a and the turbine runner 9b to mechanically transmit the rotational power from the engine 6 directly to the transmission 10. The power transmission efficiency can be improved.

  A lockup clutch control valve 18 is connected to the lockup clutch 16 via a hydraulic line 17. The lockup clutch control valve 18 controls the hydraulic pressure applied to the lockup clutch 18 in accordance with the hydraulic control signal Pa.

  The transmission 10 is a three-speed transmission for each of forward and backward movements, and includes a forward travel stage 19, a reverse travel stage 20, and a first speed formed by a gear train (such as a planetary gear train and a parallel shaft gear train) (not shown). A stage 21, a second speed stage 22 and a third speed stage 23 are provided. In this transmission 10, hydraulically operated transmission clutches 24 and 25 corresponding to traveling stages 19 and 20 are provided, and hydraulically operated transmission clutches 26, 27 and 28 corresponding to speed stages 21, 22 and 23 are provided. Is provided. By switching the combination of engagement or disengagement states of these shift clutches 24 to 28, shift operations such as forward / reverse switching, shift up, and shift down are performed.

  Shift clutch control valves 34, 35, 36, 37, and 38 are connected to the shift clutches 24, 25, 26, 27, and 28 via hydraulic lines 29, 30, 31, 32, and 33. Each shift clutch control valve 34, 35, 36, 37, 38 controls the hydraulic pressure applied to each shift clutch 24, 25, 26, 27, 28 in response to the hydraulic control signals Pb, Pc, Pd, Pe, Pf. .

  The horizontal shaft device 11 includes a horizontal shaft 40, a bevel gear 41, and steering clutches 42L and 42R and steering brakes 43L and 43R provided corresponding to the left and right sprockets 13L and 13R.

The horizontal axis 40 is arranged in a direction perpendicular to the axial direction of the output shaft 10 a of the transmission 10.
The bevel gear 41 is fixed to the horizontal shaft 40 so as to mesh with a bevel pinion 44 fixed to the output shaft 10 a of the transmission 10.
Thus, the rotational power transmitted to the output shaft 10 a of the transmission 10 is distributed to the left and right of the horizontal shaft 40 by the bevel pinion 44 and the bevel gear 41.

The steering clutches 42L and 42R and the steering brakes 43L and 43R are all configured to be operated by a biasing force of a spring and released by hydraulic pressure.
The steering clutches 42L and 42R have a function of cutting or connecting a power transmission path between the corresponding sprockets 13L and 13R and the horizontal shaft 40.
The steering brakes 43L and 43R have a function of braking the rotational movement of the corresponding sprockets 13L and 13R.

  Steering clutch control valves 47 and 48 are connected to the steering clutches 42L and 42R via hydraulic lines 45 and 46, respectively. The steering clutch control valves 47 and 48 control the hydraulic pressure applied to the steering clutches 42L and 42R according to the hydraulic control signals Pg and Ph.

  Steering brake control valves 51 and 52 are connected to the steering brakes 43L and 43R via hydraulic lines 49 and 50, respectively. The steering brake control valves 51 and 52 control the hydraulic pressure applied to the steering brakes 43L and 43R according to the hydraulic control signals Pi and Pj.

  The bulldozer 1 includes a steering lever 55, a shift up switch 56, a shift down switch 57, a shift mode changeover switch 58, a fuel dial 59 and a decel pedal 60 as operating devices related to the power line 5.

  The steering lever 55 performs forward operation, reverse operation, left turn operation, and right turn operation of the bulldozer 1.

The steering lever 55 includes a lever operation detector 61 that detects whether or not the steering lever 55 is operated in the forward operation direction (F) or the reverse operation direction (R) from the neutral position during the forward operation or reverse operation of the steering lever 55. It is attached.
Lever operation detector 61, when the steering lever 55 is operated to the forward operating direction (F) from the neutral position and outputs a forward operation detection signal C _F.
Lever operation detector 61, when the steering lever 55 is operated to the reverse operating direction (R) from the neutral position and outputs a reverse operation detection signal C _R.

The steering lever 55 is a lever that detects an operation amount from the neutral position to the left turning operation direction (LH) or the right turning operation direction (RH) when the steering lever 55 is turned left or right. An operation amount detector 62 is attached.
The lever operation amount detector 62 detects the amount of displacement from the neutral position of the steering lever 55 to the left turning operation direction (LH) when the steering lever 55 is operated from the neutral position to the left turning operation direction (LH). A corresponding left turn operation amount detection signal _CLH is output.
The lever operation amount detector 62 displaces the steering lever 55 from the neutral position to the right turning operation direction (RH) when the steering lever 55 is operated from the neutral position to the right turning operation direction (RH). A right turn operation amount detection signal _{CRH corresponding} to the amount is output.

The shift up switch 56 is used to perform a shift up operation to increase the speed stage from the first speed stage 21 to the second speed stage 22 or from the second speed stage 22 to the third speed stage 23. and outputs a shift-up operation signal S _uP shown.
The downshift switch 57 performs a downshift operation to lower the speed stage from the third speed stage 23 to the second speed stage 22 or from the second speed stage 22 to the first speed stage 21. A downshift operation signal S _DOWN is output.

The shift mode changeover switch 58 performs a switching operation between an automatic shift mode for automatically shifting the transmission 10 and a manual shift mode for manually shifting the transmission 10.
When the automatic transmission mode is selected by the switch switching operation, the transmission mode switching switch 58 outputs an automatic transmission mode selection signal TM _AUTO indicating that the automatic transmission mode is selected.
When the manual transmission mode is selected by the switch switching operation, the transmission mode switching switch 58 outputs a manual transmission mode selection signal TM _MANU indicating that the manual transmission mode is selected.

The fuel dial 59 is used to set the rotational speed of the engine 6. The fuel dial 59 is provided with a dial operation amount detector 63 that detects the operation amount of the fuel dial 59. The dial operation amount detector 63 outputs a fuel dial operation amount detection signal F _Q corresponding to the rotation angle displacement from the reference position of the fuel dial 59.

  The deceleration pedal 60 performs a speed reduction operation of the rotational speed of the engine 6. The decel pedal 60 is provided with a pedal operation amount detector 64 for detecting the depressing operation amount of the decel pedal 60. The pedal operation amount detector 64 outputs a decel pedal operation amount detection signal Ds corresponding to the depression operation amount of the decel pedal 60.

  The bulldozer 1 has a vehicle body controller 70 and an engine controller 71 as a control device related to the power line 5.

  The vehicle body controller 70 is mainly composed of a microcomputer having a microprocessor (MPU), a memory, an I / O circuit, and the like. In this vehicle body controller 70, the MPU receives necessary signals via the I / O circuit according to instructions of a predetermined program stored in the memory, receives necessary data from the memory, and programs from the received signals and data. The calculation is executed as described above, and the calculation result is sent to the memory, or the control signal based on the calculation result is output via the I / O circuit. In the vehicle body controller 70, the predetermined program is executed by the MPU, thereby realizing the functions of the steering clutch / brake control unit 70a, the shift control unit 70b, the brake protect control unit 70c, and the minimum value selection unit 70d. .

The steering clutch and brake control unit 70a, is given a left rotation operation amount detection signal C _LH or right rotation operation amount detection signal C _RH from lever operation amount detector 62. The steering clutch / brake control unit 70a is configured to output the hydraulic pressure to be output to the steering clutch control valves 47 and 48 based on the respective turning operation amount detection signals C _LH and _CRH and the characteristic diagram shown in FIG. The control signals Pg and Ph and the hydraulic control signals Pi and Pj to be output to the steering brake control valves 51 and 52 are respectively calculated, and the hydraulic control signals Pg and Ph and the hydraulic control signals Pi and Pj based on the calculation results are respectively calculated in the steering clutch. Output to the control valves 47 and 48 and the steering brake control valves 51 and 52.

Here, FIG. 3A shows the relationship (modulation characteristic diagram) between the stroke of the steering lever 55 and the hydraulic pressures of the steering clutches 42L and 42R and the steering brakes 43L and 43R, and FIG. The relationship between the hydraulic pressure supplied to the steering clutch and the steering clutch force is shown, and FIG. 3C shows the relationship between the hydraulic pressure supplied to the steering brake and the steering brake force.
Next, the control characteristics of the hydraulic pressure of the steering clutches 42L and 42R or the steering brakes 43L and 43R by the operation of the steering lever 55 will be described with reference to these drawings.

As shown in FIG. 3A, initially, no pressure oil is sent to the steering clutches 42L and 42R, and the steering clutches 42L and 42R are in a coupled state by the urging force of the spring.
On the other hand, the bulldozer is traveling straight in a state where pressure oil of a predetermined hydraulic pressure is sent to the steering brakes 43L and 43R and the braking force is released.
When the steering lever 55 is turned left or right, when the lever stroke reaches A, pressure oil is sent to the steering clutch 42L or the steering clutch 42R to increase the hydraulic pressure to point a. As the lever stroke is further increased, the hydraulic pressure is gradually increased from the point a toward the point b to decrease the coupling force (see FIG. 3B). When the lever stroke exceeds B, the maximum hydraulic pressure is supplied, and the steering clutch 42L or the steering clutch 42R is completely released (see FIG. 3B).
On the other hand, in the steering brake 43R or the steering brake 43L, when the lever stroke reaches C, the hydraulic pressure is reduced to point c and braking is started. When the lever stroke is further increased, the hydraulic pressure is gradually decreased from the point c toward the point d to increase the braking force (see FIG. 3C). When the lever stroke reaches D, the hydraulic pressure becomes 0, and the braking force due to the urging force of the spring is fully exhibited, and the maximum braking force is obtained (see FIG. 3C).
As shown in FIG. 3, B <C is established, and when the operation stroke of the steering lever 55 is gradually increased, the steering clutch is first released and then the steering brake is activated. ing.

As shown in FIG. 2, the shift control unit 70b includes (a) an automatic shift mode selection signal TM _AUTO or a manual shift mode selection signal TM _MANU from the shift mode changeover switch 58, and (b) a lever operation detector 61. Forward operation detection signal C _F or reverse operation detection signal C _R , (c) shift up operation signal S _UP from shift up switch 56 or shift down operation signal S _DOWN from shift down switch 57, and (d) transmission 10 A transmission output shaft rotational speed detection signal TM _REV is _supplied from a transmission output shaft rotational speed detection sensor 72 for detecting the rotational speed of the output shaft 10a.
The configuration including the shift control unit 70b and the lockup clutch control valve 18 corresponds to the “lockup clutch control means” of the present invention.

Shift control section 70b hydraulic advance operation detection signal C _F or reverse operation detection signal C _R hydraulic control signal to be output to the transmission clutch control valve 34, 35 based on Pb, the Pc is calculated, obtained by the calculation result The control signals Pb and Pc are output toward the shift clutch control valves 34 and 35.

The shift control unit 70b selects a shift mode to be executed based on the automatic shift mode selection signal TM _AUTO or the manual shift mode selection signal TM _MANU .

In the automatic shift mode, the shift control unit 70b reads the automatic shift map shown in FIG. 4 from the memory, takes in the transmission output shaft rotational speed detection signal TM _REV , calculates the vehicle speed V, and obtains the vehicle speed obtained by the calculation. Based on V and the automatic shift map of FIG. 4, the hydraulic control signal Pa to be output to the lockup clutch control valve 18 and the hydraulic control signals Pd, Pe, Pf to be output to the shift clutch control valves 36, 37, 38 are obtained. The hydraulic pressure control signal Pa and the hydraulic pressure control signals Pd, Pe, and Pf obtained from the calculation results are output to the lockup clutch control valve 18 and the shift clutch control valves 36, 37, and 38, respectively.
The shift control unit 70b can determine which speed stage the transmission 10 is currently in, based on the vehicle speed V and the automatic shift map of FIG.
Furthermore, the shift control unit 70b is currently in a lockup mode in which the pump impeller 9a and the turbine runner 9b are coupled by the engagement of the lockup clutch 16 based on the vehicle speed V and the automatic shift map of FIG. It can be determined whether the torque converter mode is in a state in which the pump impeller 9a and the turbine runner 9b are released by disengaging the lockup clutch 16.

Here, in the automatic shift map shown in FIG. 4, the vertical axis indicates the traction force, and the horizontal axis indicates the vehicle speed.
A one-dot chain line is a running performance curve in the torque converter mode, which is a torque converter mode first speed running performance curve TC ₁ , a torque converter mode second speed running performance curve TC _2, and a torque converter mode third speed running performance curve TC ₃ .
A solid line is a running performance curve in the lockup mode, which is a lockup mode first speed running performance curve LU ₁ , a lockup mode second speed running performance curve LU ₂ , and a lockup mode third speed running performance curve LU ₃ .
The torque converter travel performance curve and the lockup travel performance curve intersect at points a, b, c, d, and e in the figure.
In the automatic shift map, the low speed range than a point (0 to V ₁₎ In the torque converter mode first speed is selected, the speed range between a point ~b point _(V 1 ~V ₂₎ In the lockup mode 1 speed is In the speed range between points b and c (V _{2 to} V ₃ ), the torque converter mode 2 speed is selected, and in the speed range between points c and d (V _{3 to} V ₄ ), the lockup mode 2nd speed is selected. It is selected, and the speed range between point d ~e point _(V 4 _{~V 5)} in the torque converter mode third speed is selected, the high speed region from the point e (V 5 _~) in the lock-up mode the third speed is selected.

In manual mode, the shift control unit 70b determines the current up-shifting operation signal S _UP or next speed stage to be selected from the shift down operation signal S _DOWN Decreases the selected speed stage as a reference, based on the determination The hydraulic control signals Pd, Pe, and Pf to be output to the transmission clutch control valves 36, 37, and 38 are calculated, and the hydraulic control signals Pd, Pe, and Pf obtained from the calculation results are calculated as the transmission clutch control valves 36, 37, and 38. Output to.
When the shift control unit 70b shifts to the speed stage to be selected next, the speed stage after the shift is updated as the currently selected speed stage. It can be determined whether the vehicle is in the speed stage.

The brake protection control unit 70c includes (a) a left turn operation amount detection signal C _LH or a right turn operation amount detection signal C _RH from the lever operation amount detector 62, and (b) an inclination angle of the bulldozer 1 in the front-rear direction. A tilt angle detection signal θp is supplied from the tilt angle sensor 73 for detecting (pitch angle).
Further, the current speed stage information [TM _DATA ] from the shift control unit 70b is given to the brake protect control unit 70c.
As the current speed stage information [TM _DATA ], information indicating whether the current mode is the lock-up mode or the torque converter mode, and the speed stage currently selected in the transmission 10 is any one of the first to third speed stages. Information on whether or not.
The brake protect control unit 70c takes in the turning operation amount detection signals C _LH and C _RH , the tilt angle detection signal θp and the current speed stage information [TM _DATA ], and executes predetermined processing according to the algorithm shown in the flowchart of FIG. .
The flowchart of FIG. 5 will be described in detail later.

The minimum value selection unit 70d, decelerator pedal operation amount detection signal Ds from the fuel dial operation amount detection signal F _Q and the pedal operation amount detector 64 from the dial operation amount detector 63 is provided, respectively.
The minimum value selecting section 70d is configured to calculates the engine rotational speed command signal N ₁ based on the fuel dial operation amount detection signal F _Q, calculates the engine rotational speed command signal N ₂ based on the decelerator pedal operation amount detection signal Ds.
The minimum value selecting section 70d compares the engine rotational speed command signal N ₁ and the engine rotational speed command signal N _2, as a target value of the rotational speed of these engine speed command signal N _1, N ₂ is the smallest Is output to the engine controller 71.

The engine controller 71 is composed mainly of a microcomputer, like the vehicle body controller 70.
The engine controller 71, the engine speed command signal N ₁ or engine rotational speed command signal N ₂ from the minimum value selecting unit 70d, an engine rotational speed detection signal from the engine rotational speed sensor 74 for detecting the rotational speed of the engine 6 N _REV is given respectively.
Engine controller 71, an engine rotating speed of the speed detection signal N _REV from determined current engine 6, for example, the engine rotational speed command signal N ₁ fuel injection amount control to match the target value of the engine speed 6 given by The signal Qf is calculated, and the fuel injection amount control signal Qf obtained from the calculation result is output to the electronic control fuel injection device 15.

In the bulldozer 1 configured as described above, the shift clutch control valves 34 and 35 are controlled by the shift control unit 70b by the forward operation or reverse operation of the steering lever 55, and the bulldozer 1 travels forward. Or reverse drive is performed.
When the automatic transmission mode is selected by the transmission mode changeover switch 58, the lockup clutch control valve 18 and the transmission clutch control valve 36 by the transmission control unit 70b based on the automatic transmission map and the vehicle speed V of FIG. , 37 and 38 are respectively controlled, and switching between the torque converter mode and the lockup mode, and switching of the speed stage in the transmission 10 are automatically performed according to the automatic shift map of FIG.
When the manual shift mode is selected by the shift mode switch 58, the shift clutch control valves 36, 37, 38 are controlled by the shift control unit 70b based on the operation of the shift up switch 56 or the shift down switch 57. The speed stage in the transmission 10 is manually switched.
When the steering lever 55 is turned left or right, the coupling state of the steering clutch 42L or the steering clutch 42R is released based on the modulation characteristic diagram of FIG. 3A, and the steering brake 43L or the steering brake 43R. Is braked based on the modulation characteristic diagram, and a left turning motion or a right turning motion is performed.

  Next, the processing contents of the brake protection control unit 70c will be described below mainly using the flowchart of FIG.

(Step S1)
It is determined whether the brake protection process is in the execution state (flag = 1) or in the release state (flag = 0).

(Step S2)
If it is determined in step S1 that the brake protection process is in the release state (flag = 0), the current lock speed mode information [TM _DATA ] from the shift control unit 70b is currently used in the lock-up mode. Judge whether there is.

(Step S3)
If it is determined in step S2 that the lock-up mode is currently in effect, a value of the detected inclination angle is obtained based on the inclination angle detection signal θp from the inclination angle sensor 73, and the obtained value of the detected inclination angle is obtained. Is greater than or equal to a first predetermined tilt angle θ ₁ (for example, 3 °).
In order to avoid the influence of vibration or the like, the detection angle is obtained by a moving average of the tilt angle detection signal θp.

(Step S4)
In the determination at step S3, if the value of the detected inclination angle is equal to or a first predetermined inclination angle theta ₁ above, left rotation operation amount detection signal C _LH or right turning operation from the lever operation amount detector 62 Based on the amount detection signal _CRH , it is determined whether or not the steering lever 55 is turned left or right. Specifically, the presence or absence of the turning operation is determined based on whether or not the lever stroke exceeds B (see FIG. 3A).

(Step S5)
If it is determined in step S4 that the steering lever 55 has been turned left or right, a lockup clutch disengagement command signal CL _OFF that commands disengagement of the lockup clutch 16 is issued. Is transmitted to the shift control unit 70b, the flag is set to “1”, and the process returns to the start.

(Step S6)
If it is determined in step S1 that the brake protection process is in the execution state (flag = 1), the value of the detected inclination angle is obtained based on the inclination angle detection signal θp from the inclination angle sensor 73. It is determined whether or not the value of the detected tilt angle is equal to or smaller than a second predetermined tilt angle θ ₂ (for example, 2 °).
As described above, the detection angle is obtained by the moving average of the tilt angle detection signal θp.

(Step S7)
In the determination at step S6, if the value of the detected inclination angle is determined to be the second predetermined inclination angle theta ₂ below, the process proceeds to step S7, the flag as "0", the start without performing the braking protect processing Return.
The second predetermined inclination angle θ ₂ <the first predetermined inclination angle θ ₁ is satisfied.

In the determination at step S6, the bulldozer 1 is when it is determined that the downhill traveling state of a large tilt angle than the second predetermined cant angle theta _2, the process proceeds to step S2.

In each of the following cases (1) to (3), the process proceeds to step S7. As described above, in step S7, the flag is set to “0” and the process returns to the start without performing the brake protection process.
(1) in the determination at step S2, if it is judged that it is not a lock-up mode (2) in the determination at step S3, if the bulldozer 1 is determined to be in the downhill running state of the first smaller than the predetermined inclination angle theta ₁ ( 3) When it is determined in step S4 that the steering lever 55 is not operated to turn left or right

As described above, the brake protect control unit 70c determines that the turning movement of the first predetermined cant angle theta ₁ or more slope during downhill travel is performed by the lockup mode (step S2~ step S4), and the brake protection Processing is executed (step S5).
By executing the brake protect process in step S5, the lockup clutch disengagement command signal CL _OFF for instructing the disengagement of the lockup clutch 16 is output from the brake protect control unit 70c to the shift control unit 70b.
When receiving the lockup clutch engagement release command signal CL _OFF from the brake protect control unit 70c, the transmission control unit 70b calculates a hydraulic control signal Pa for releasing the engagement of the lockup clutch 16, and obtains the result of the calculation. The hydraulic control signal Pa is output toward the lockup clutch control valve 18. In response to the hydraulic pressure control signal Pa, the lockup clutch control valve 18 controls the hydraulic pressure applied to the lockup clutch 18 in accordance with the hydraulic pressure control signal Pa to release the engagement of the lockup clutch 16.
Thus, the engagement of the lock-up clutch 16 is released, so that the torque converter mode is established in which the pump impeller and the turbine runner are released.

For example, when the bulldozer 1 is traveling downhill at a vehicle speed V ₇ on a slope having a first predetermined inclination angle θ ₁ or more in the third speed in the lockup mode, the power line 5 has the lockup mode third speed travel performance curve of FIG. The tractive force W ₀ corresponding to the point f on LU ₃ is exhibited.
When the brake protection process associated with the turning motion during the downhill driving is performed to switch from the third speed in the lockup mode to the third speed in the torque converter mode, the vehicle speed of the bulldozer 1 is g point on the torque converter mode third speed traveling performance curve TC ₃ in is decelerated to a vehicle speed V ₆ matching the tractive force W _0.
Thus, by being switched to the lock-up mode 3 gear torque converter mode third speed, when the vehicle speed of the bulldozer 1 is subtracted from V ₇ to the V _6, as shown in FIG. 6, a steering brake heat rate from Q ₂ since decreased to Q _1, it is possible to reduce the load of the turning operation side of the steering brakes of the steering brakes 43L and steering brake 43R.
Therefore, it is possible to prevent damage to the steering brakes 43L and 43R due to the turning motion during high-speed downhill traveling.
Incidentally, the steering brakes 43L, at the time of downhill travel of the first predetermined cant angle theta ₁ less than the slope does not affect the durability of the 43R ( "NO" in step S3), and the brake protection process is not performed, the lock Since the state of the up mode is maintained (step S7), the power transmission efficiency can be improved.

Brake protect processing, the value of the detected inclination angle is performed at a first predetermined cant angle theta ₁ or more (step S3~ step S5), and the second predetermined value of the detected inclination angle is smaller than the first predetermined inclination angle theta ₁ Part It is released by the inclination angle theta ₂ below (step S6~ step S7), and has a hysteresis between the running operation and the release operation of the brake protect processing.
Further, the value of the detected tilt angle used in each of the steps S3 and S6 is obtained by moving and averaging the tilt angle detection signal θp from the tilt angle sensor 73.
Thus, by providing hysteresis between the execution and release operations of the brake protection process, and using the value of the detected tilt angle determined by the moving average, the execution and release hunting of the brake protection process is reliably prevented. can do.

Although the bulldozer control device of the present invention has been described based on one embodiment, the present invention is not limited to the configuration described in the above embodiment, and the configuration is appropriately set within the scope of the invention. It can be changed. For example, in the above embodiment, as a condition for outputting a lock-up clutch disengagement command, in addition to the conditions described in the above embodiment, as shown in the flowchart of FIG. 7, the speed stage is the highest speed gear The lockup clutch disengagement command signal CL _OFF may be output only when (Yes in step S8).
Further, as a condition for outputting the lock-up clutch engagement release command, in addition to the condition shown in the above embodiment, as shown in the flowchart of FIG. The lockup clutch disengagement command signal CL _OFF may be output only when it exceeds (“Yes” in step S8 ′).

The side view of the bulldozer which concerns on one Embodiment of this invention Outline system configuration diagram of bulldozer power line Modulation characteristic diagram of steering brake / clutch (a), relationship diagram between hydraulic pressure supplied to steering clutch and steering clutch force (b), relationship diagram between hydraulic pressure supplied to steering brake and steering brake force (c) Automatic shift map with traction and vehicle speed as parameters Flowchart explaining processing contents of brake protection control unit Relationship diagram between steering brake heat generation rate and vehicle speed during turning motion in forward three-speed downhill traveling The flowchart explaining the other example (1) of the processing content of a brake protection control part Flowchart for explaining another example (2) of the processing content of the brake protection control unit

Explanation of symbols

1 Bulldozer 6 Engine 9 Torque converter 9a Pump impeller 9b Turbine runner 13L, 13R Sprocket (drive wheel)
16 Lock-up clutch 18 Lock-up clutch control valve (lock-up clutch control means)
42L, 42R Steering clutch 43L, 43R Steering brake 55 Steering lever 62 Lever operation amount detector 70 Car body controller (control device)
70b Shift control unit (lock-up clutch control means)
70c Brake protection control unit 73 Inclination angle sensor

Claims (2)

Rotational power from the engine is transmitted to the left and right drive wheels via a torque converter with a lock-up clutch, and the steering clutch and steering brake provided for each drive wheel respond to the operation of the steering lever. In the control apparatus of the bulldozer configured to perform the left and right turning movements by being controlled,
Lock-up clutch control means for controlling the lock-up clutch;
A lever operation amount detector for detecting an operation amount of the steering lever;
An inclination angle sensor for detecting an inclination angle of the bulldozer in the front-rear direction;
When the lockup clutch is engaged by the lockup clutch control means, it is detected by the tilt angle sensor that the bulldozer is traveling downhill at a first predetermined tilt angle or more, and the lever operation When it is detected by the amount detector that the steering lever is operated, a lockup clutch disengagement command signal for commanding the disengagement of the lockup clutch is output to the lockup clutch control means. bulldozer control device, characterized in that it comprises a brake protect control unit for executing a brake protection processing to protect the steering brakes by subtracting the vehicle speed by. 2. The bulldozer according to claim 1, wherein when the detected tilt angle of the tilt angle sensor is equal to or smaller than a second predetermined tilt angle smaller than the first predetermined tilt angle, the brake protect control unit releases the brake protect process. Control device.

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