JPH058753A - Electronic steering control device for bulldozer - Google Patents

Abstract

PURPOSE:To enhance the steering control ability, the comfortability, a durability and the like by controlling clutches for transmitting a power from an engine to right and left sprockets and brakes, independent from each other, with the use of electronic proportional control valves, respectively, and by controlling the electronic control valves in accordance with a steering degree of a steering lever. CONSTITUTION:A steering control device for a bulldozer transmits a power from engine to left and right sprockets 14R, 14L by way of a torque converter 2, a transmission 2, a steering unit 4, and by way of left and right clutches 8R, 8L and brakes 10R, 10L. With this arrangement, the clutches 8R, 8L and the brakes 10R, 10L are were controlled by exclusive right and left electronic proportional control valves 19R, 19L; 20R, 20L, respectively. Meanwhile, a steering signal generator 15a delivers a steering signal in accordance with a steering degree of a steering lever 15. Further, a controller 17 controls the electronic control valve 19R through 20L in accordance with a steering signal from the steering signal generator 15a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic steering control system for a bulldozer, and in particular, a smooth turning performance can be always obtained by a normal operation even if the operator does not perform fine control, and the ride comfort of the operator is improved. The present invention relates to an electronic steering control device for a bulldozer, which is characterized by improving durability of the device.

[0002]

2. Description of the Related Art A conventional clutch / brake steering control device for a bulldozer is constructed as shown in FIG. In FIG. 6, 1 is an engine, 2 is a torque converter unit composed of a torque converter 2a and a lockup clutch 2b, 3 is a forward / reverse clutch F, R, and 1st, 2nd and 3rd speed stage clutches 3a, 3b,
A transmission 4 composed of 3c includes an input shaft 5, a speed change gear mechanism 6, a lateral input shaft 7, and left and right clutches 8R, 8
L, intermediate shafts 9R, 9L, brakes 10R, 10L, output shafts 11R, 11L, a steering unit, 12
R and 12L are left and right final reduction gears, 13R and 13L are left and right output shafts, and 14R and 14L are left and right sprockets, which are driven by the components of the engine 1 to the left and right sprockets 14R and 14L. Further, FIG. 7 shows the left and right clutches 8R and 8L and the brakes 10R and 10 in FIG.
In the figure which showed the control device of L typically, 15R is a right steering lever, 15L is a left steering lever, 16 is a brake pedal, 46
R and 46L are steering levers, 47R and 47L are brake levers, 18 is a control pump, 49R and 49L are control hydraulic pressures for the left and right clutches 8R and 8L according to the operation amounts of the right steering lever 15R and the left steering lever 15L. 50R, 50L are brake operation valves for supplying control hydraulic pressure to the left and right brakes 10R, 10L, 51R, 51L are steering links, 52 is rods, 53 is brake links, and 54 is The return springs 55R and 55L of the rod 52 are adjusting bolts.

Next, the control method shown in FIGS. 6 and 7 will be described. Right steering lever 1 while bulldozer is running
When 5R is operated in the A direction, steering link 51R
First, the steering lever 46R starts pushing the rod 49r of the clutch operating valve 49R through the right lever 8R.
When the control pressure is started to be supplied to R, the right clutch 8R starts to open. When the steering lever 15R is further operated in the A direction, the right clutch 8R is completely released and the brake operating valve 5
When the 0R rod 50r is started to be pressed and the control pressure of the right brake 10R starts to decrease, the right brake 10R starts to be braked. Since the same applies to the case where the left steering lever 15L is operated in the A direction, the description thereof will be omitted. When the brake pedal 16 is operated during the right steering operation, the rod 52 causes the spring 54 to move.
The left and right brake levers 47R and 47L press down the rods 50r and 50l of the left and right brake valves 50R and 50L via the brake link 53, so that the right and left brake levers 47R and 47L can be pressed down in accordance with the operation amount of the brake pedal 16. The brakes 10R and 10L can be braked. At this time, the right brake operation valve 50R is the rod 50 of the right brake operation valve 50R by the right steering lever 15R.
It is controlled by the larger operation amount of the operation amount of r and the operation amount of the rod 50r of the right brake operation valve 50R by the brake pedal 16. 8 and 9 show the clutch OF
6 is a graph showing the modulation characteristics of the clutch and the brake when F is applied and the brake is turned on, in which the vertical axis represents the hydraulic pressure of hydraulic oil and the horizontal axis represents the elapsed time. FIG. 8 is a diagram showing a temporal change in the hydraulic pressure of the right clutch 8R and the hydraulic pressure of the right brake 10R when the right steering lever 15R is slowly operated, and FIG. 9 is a diagram when the right steering lever 15R is operated quickly. It is a figure similar to.

In FIG. 8, since the right brake 10R starts to be engaged after the right clutch 8R is released, the clutch and brake hydraulic pressure changes smoothly. This indicates that the vehicle is shock-free. In contrast,
In FIG. 9, the right brake 10R starts to be engaged before the right clutch 8R is completely released, so that the brake hydraulic pressure fluctuates greatly. This indicates that the vehicle has a large shock. In order to prevent the shock, the steering levers 46R and 46L are provided with adjusting bolts 55R and 55L.
L is provided, and the operation intervals of the clutches 8R, 8L and the brakes 10R, 10L are adjusted by the adjusting bolts 55R, 55L.

[0005]

In order to prevent the steering shock in the above-mentioned prior art, it takes time from the release of the clutch to the braking of the brake, or from the release of the brake to the engagement of the clutch. It is common to provide an interval, but when steering operation is performed on a sloping ground, there is a time when both the clutch and brake on the side that operated the steering lever are in the open state, so-called reverse steering phenomenon, etc. There is a drawback that causes the problem of. Therefore, each time interval is adjusted to a value that matches the driving operation conditions at that time, such as the operating speed and oil temperature of the steering lever, the engine speed, etc., to provide steering modulation characteristics that can obtain smooth turning without shock. At the same time, the above-mentioned problems such as the reverse steering phenomenon are prevented, but since the driving operation conditions change moment by moment, it is impossible to make a smooth turn without shock under all driving operation conditions. there were. The present invention has been made in view of the above problems, and an object of the present invention is to provide a steering control device for a bulldozer with improved riding comfort.

[0006]

In order to achieve the above object, a first aspect of the electronic steering control device for a bulldozer according to the present invention is that the left and right drive shafts are transmission-coupled to the output shaft of the transmission. In a steering control device for a bulldozer that transmits engine power to left and right sprockets via clutches and brakes, an electronic proportional control valve that independently controls each clutch and brake, a steering lever, and the steering lever are provided. A steering signal generator that generates a steering signal according to the amount of lever operation, and a controller that inputs the steering signal from the steering signal generator and outputs the steering control signal to each of the electronic proportional control valves. According to a second aspect of the present invention, the change with time of the steering control signal output from the controller to each electronic proportional control valve according to the first aspect operates the steering lever from neutral to full stroke. Is a first range in which the clutch hydraulic pressure changes from the complete coupling pressure to the clutch maintaining pressure according to the stroke of the steering lever when the brake hydraulic pressure is the full opening pressure, and the clutch hydraulic pressure is the clutch maintaining pressure or the clutch maintaining pressure. The second range is when the steering pressure changes from full pressure to full opening pressure, and the brake hydraulic pressure changes from the brake preparatory pressure to the complete braking pressure, which is slightly higher than the coupling start pressure. The clutch hydraulic pressure changes when the steering lever is operated from full stroke to neutral. A second range in which the brake hydraulic pressure changes from the complete braking pressure to the brake maintaining pressure corresponding to the stroke of the steering lever in the state of the full opening pressure; and the brake maintaining pressure corresponding to the stroke of the steering lever. Or, if the clutch maintenance pressure changes from the brake maintenance pressure to the full release pressure and the clutch hydraulic pressure is slightly higher than the coupling start pressure, Forming a first range varying from full coupling pressure,

According to a third aspect of the present invention, the clutch and brake maintaining pressure according to the stroke of the steering lever according to the second aspect is such that, when the stroke is increased, the brake hydraulic pressure is at the maximum maintaining pressure, and the clutch hydraulic pressure is from the full engagement pressure to the maximum maintaining pressure. Up to a first range where the clutch hydraulic pressure is at the maximum maintenance pressure, and a second range where the brake hydraulic pressure changes from the coupling start pressure to the complete coupling pressure. When the stroke is reduced, the clutch hydraulic pressure is at the maximum maintenance pressure. , A second range in which the brake hydraulic pressure changes from the complete coupling pressure to the maximum maintaining pressure, and a first range in which the clutch hydraulic pressure changes from the coupling starting pressure to the complete coupling pressure in the state where the brake hydraulic pressure is the maximum maintaining pressure. It is configured to adjust the overlapping range of the first range when increasing and the second range when reducing stroke, and claim 4 The time-dependent change of the steering control signal output from the controller to each electronic proportional control valve in the quest 2 is the brake preparatory pressure in the second range when the steering lever operation amount increases or when the steering lever operation amount decreases. The clutch preparation pressure in the first range is configured to be increased for a predetermined time for a predetermined time and then gradually decreased.
In claim 2, when the operation amount of the steering lever is increased, the brake braking is started after a predetermined time from the complete release of the clutch in the second range, and the first operation is performed when the operation amount of the steering lever is decreased.
The clutch is configured to start engagement after a predetermined time from the full release of the brake in the range, and the brake according to claim 5 has a predetermined time until the brake starts to be started, or a predetermined time until the clutch starts to be engaged. It is configured to be adjusted according to operating conditions.

[0008]

According to the above structure, the following operations are performed. According to the first aspect, unless the steering lever is operated while the vehicle is traveling, the steering control signal is not output from the controller to either the electronic control valve that controls the left and right clutches or the electronic control valve that controls the left and right brakes. Therefore, the left and right clutches are engaged and the left and right brakes are released. Therefore, the power of the engine transmitted to the left and right drive shafts that are transmission-coupled to the output shaft of the transmission is transmitted to the left and right sprockets in the same direction and at the same rotation, so that the vehicle travels straight.

As described above, when the steering lever is operated in the right turning direction while the vehicle is traveling straight, a steering signal is generated according to the operation amount of the steering lever and having a predetermined temporal characteristic. A steering control signal that is output from the device to the controller and that generates a clutch hydraulic pressure or a brake hydraulic pressure that exhibits a predetermined change with time according to the steering signal is transmitted to the right clutch and brake electronic control valve. Therefore, the right clutch hydraulic pressure increases according to the operation amount of the steering lever, and after the clutch is released, the brake is applied after a predetermined time interval adjusted by operating conditions such as the vehicle inclination angle and hydraulic oil temperature. Starts braking and the braking force of the brake gradually increases thereafter, so the power transmitted from the engine to the right sprocket gradually decreases, the rotation speed of the right sprocket is reduced, and the vehicle is shock-free and smooth. Turns to the right due to steering modulation characteristics.
Next, while the vehicle is turning to the right, when the steering lever that has been operated to the right is returned to the neutral direction, a steering signal that has a predetermined aging characteristic according to the operation amount of the steering lever is steered. The steering signal is output from the steering signal generator to the controller, and the steering control signal for generating the clutch hydraulic pressure or the brake hydraulic pressure showing a predetermined change with time according to the steering signal is transmitted to the right clutch and brake electronic control valve. To be done.
Therefore, the right clutch hydraulic pressure becomes lower according to the operation amount of the steering lever, and after the brake is released, the clutch oil pressure is adjusted after a predetermined time interval which is adjusted by operating conditions such as the inclination angle of the vehicle and the hydraulic oil temperature. The power transmitted to the right sprocket is gradually increased, the rotational speed of the right sprocket is increased, and the vehicle has an increased turning radius to the right due to smooth steering modulation characteristics without shock. Then, the vehicle goes straight back. It should be noted that when the steering lever is operated to the left and when the steering lever operated to the left is returned to the neutral direction, the description thereof will be omitted because it is the same as the operation of the steering lever.

According to a second aspect of the present invention, since each electronic proportional control valve according to the first aspect generates a hydraulic pressure proportional to an input steering control signal, the brake and clutch hydraulic pressures are output from the controller to each electronic proportional control valve. The hydraulic pressure is generated with the same temporal change as that of the steering control signal. Therefore, the first range and the second range when the operation amount of the steering lever increases and the second range and the first range when the operation amount of the steering lever decrease are formed. According to a third aspect of the present invention, in the clutch and brake maintaining pressure according to the stroke of the steering lever of the second aspect, the clutch is adjusted by adjusting the overlapping range of the first range when the stroke increases and the second range when the stroke decreases. Adjust the timing at which the and brakes are connected to prevent shocks during steering, and fine control improves steering performance. According to a fourth aspect, in the second aspect, the change with time of the steering control signal output from the controller to each electronic proportional control valve is
Brake preparation pressure in the second range when the operation amount of the steering lever increases, or the first when the operation amount of the steering lever decreases.
The clutch preparation pressure in the range was increased for a predetermined time for a predetermined time, and then gradually decreased to clarify the starting point of coupling between the clutch and the brake, and prevent the clutch and the brake from being coupled together. Claim 5 is Claim 4
A predetermined time until the start of braking in
Alternatively, the predetermined time until the clutch starts to be engaged is automatically adjusted according to the operating conditions, and when the operation speed of the operation lever is slow, the predetermined time is reduced to improve the fine controllability and the operation speed of the operation lever. If it is early, the predetermined time is increased to prevent shock due to simultaneous coupling and improve the ride comfort of the operator.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of an electronic steering control device for a bulldozer according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram of an electronic steering control device of a bulldozer, and the same parts as those of the prior art will be described with the same reference numerals. 1 is an engine, 2 is a torque converter unit including a torque converter 2a and a lockup clutch 2b, 3 is a forward clutch F, a reverse clutch R and a first speed,
A transmission 4 composed of second-speed and third-speed clutches 3a, 3b, 3c includes an input shaft 5, a speed change gear mechanism 6, a lateral input shaft 7, left and right clutches 8R and 8L, and an intermediate shaft 9.
R, 9L, brakes 10R, 10L, output shafts 11R, 1
1L steering unit, 12R, 12L are left and right final reduction gears, 13R, 13L are left and right output shafts, 14
R and 14L are left and right sprockets. Further, 15 is a steering lever, 15a is a steering signal generator, 16 is a brake pedal, 16a is a brake signal generator, and 17 is an operation signal from the steering signal generator 15a and the brake signal generator 16a. A controller, 18 is a control pump, 19R and 19L are electronic control valves for inputting a control signal from the controller 17 to hydraulically control the left and right clutches 8R and 8L, and 20R and 20L are input control signals from the controller 17. Then left and right brake 10
It is an electronic control valve that controls R and 10L by hydraulic pressure.

Next, the operation of the above configuration will be described. The power of the engine 1 includes the torque converter 2a or the lockup clutch 2b of the torque converter unit 2 and the forward clutch F or the reverse clutch R of the transmission 3
It is transmitted to the input shaft 5 of the steering unit 4 through the selected speed stage of any one of the speed, second and third speed stage clutches 3a, 3b, 3c, and is transmitted to the input shaft 5. The power of the engine 1 is transmitted to the lateral input shaft 7 via the speed change gear mechanism 6. If the steering lever 15 and the brake pedal 16 are not operated during traveling, the controller 17 controls the electronic control valves 19R, 19L for controlling the left and right clutches 8R, 8L and the electronic control for controlling the left and right brakes 10R, 10L. Since the control signal is not output, the left and right clutches 8R and 8L are engaged, and the left and right brakes 10R and 1L are connected.
0L is open. Therefore, the power of the engine 1 transmitted to the lateral input shaft 7 of the steering unit 4 is the left and right intermediate shafts 9R and 9L, the output shafts 11R and 11L, and the final reduction gear 1.
The vehicle travels straight because it is transmitted to the left and right sprockets 14R and 14L through the 2R and 12L and the output shafts 13R and 13L in the same direction and at the same rotation.

As described above, when the steering lever 15 is operated in the right turning direction to the full stroke while the vehicle is traveling straight,
Since the steering signal according to the operation amount of the steering lever 15 is output from the steering signal generator 15a to the controller 17,
From the controller 17, a control signal for generating a clutch hydraulic pressure or a brake hydraulic pressure with respect to time as shown in FIG. 4 is transmitted to each of the right electronic control valves 19R and 20R.
Therefore, the right clutch hydraulic pressure increases according to the operation amount of the steering lever 15, and after the clutch is released, after a predetermined time interval adjusted by operating conditions such as the inclination angle of the vehicle and the hydraulic oil temperature. Since the brake starts braking and the braking force of the brake gradually increases thereafter, the power transmitted from the engine 1 to the right sprocket 14R gradually decreases, the rotational speed of the right sprocket 14R is decelerated, and the vehicle is in shock. With a smooth steering modulation characteristic that does not exist, it is possible to turn to the right and at the same time prevent a problem such as the conventional reverse steering phenomenon. In addition, after the clutch is released, the brake starts braking after a predetermined time interval adjusted by operating conditions such as the inclination angle of the vehicle and the hydraulic oil temperature, and the braking force of the brake gradually increases thereafter. The power transmitted from 1 to the right sprocket 14R gradually decreases, and the right sprocket 14R
The rotation speed is reduced, and the vehicle turns right due to the smooth steering modulation characteristic without shock, and at the same time, it is possible to prevent the conventional problems such as the reverse steering phenomenon. Further, when the steering lever 15 is not operated to the full stroke but is operated to the middle of the full stroke, the clutch hydraulic pressure and the brake hydraulic pressure on the right in FIG. 4 are the clutch pressures corresponding to the operation amounts of the steering lever 15 shown in FIG. In order to maintain the maintenance pressure or the brake maintenance pressure, one of the clutches or brakes turns to the right with one open and the other half semi-engaged, or both are open.

Next, when the steering lever 15 that has been operated to the right is returned from the full stroke to the neutral while the vehicle is turning to the right, the clutch hydraulic pressure or the brake hydraulic pressure for the time shown in FIG. 5 is generated. A control signal is transmitted to each electronic control valve 19R and 20R on the right. Therefore, the right brake oil pressure increases according to the operation amount of the steering lever 15, and after the brake is released, after a predetermined time interval adjusted by the operating conditions such as the inclination angle of the vehicle and the hydraulic oil temperature. The clutch starts the engagement, and the engagement force of the clutch gradually increases thereafter, so that the power of the engine 1 is gradually transmitted to the right sprocket 14R, the rotational speed of the right sprocket 14R is increased, and the vehicle speed is increased. With the smooth steering modulation characteristic without shock, it is possible to return to the straight traveling direction and at the same time prevent the conventional problems such as the reverse steering phenomenon. In addition, steering lever 1
5 is operated to the middle of the neutral position without being operated to the neutral position, the clutch hydraulic pressure and the brake hydraulic pressure on the right in FIG. 5 are the clutch maintenance pressure or the brake depending on the operation amount of the steering lever 15 shown in FIG. To maintain the holding pressure, one of the clutches or brakes turns to the right with one open and the other semi-engaged, or both open. When the steering lever 15 is operated to the full stroke to the left or in the stroke increasing direction, and when the steering lever 15 that has been operated to the left is returned to the neutral position or to the neutral direction, the steering lever 15 is also used. Since the operation is the same as that of 15, the description is omitted.

Next, details of the controller 17 shown in FIG. 1 will be described with reference to FIG. In the figure, 21 is a steering mode selector, 22 is a maintenance pressure / build-up rate setting device, 2
3 is a steering control signal generator, 24 is a braking mode selector, 25 is a maintenance pressure / build-up rate setting device, 26 is a brake control signal generator, and 27 is a brake control signal comparator. When a steering signal is input from the steering signal generator 15a of the steering lever 15 to the steering mode selector 21 in the controller 17, the steering mode selector 21 operates according to the operating direction and operating speed of the steering lever 15. The steering mode is selected and the stroke of the steering lever 15 and the operation speed signal are output to the maintenance pressure / build-up rate setting device 22 and the steering mode is output to the steering control signal generator 23. The clutch control signal ic generated by the steering control signal generator 23 is a clutch electronic proportional control valve 20R, 2
When output to 0L, the electronic proportional control valves 20R and 20L
Is supplied to the clutches 8R and 8L from the control hydraulic pressure proportional to the clutch control signal ic. The change with time of the steering control signal shown in the steering control signal generator 23 is the same as in FIG. 4 showing the cases of the mode 1 and the mode 2 in the steering mode selector 21, and is the same as the mode 3 and the mode 4.
In the case of, the change with time is the same as that shown in FIG. Further, the build-up rate .theta.1 of the steering control signal shown in the steering control signal generator 23 does not necessarily require the same brake and clutch. When the brake pedal 16 is operated during the steering control, a brake signal corresponding to the operation of the brake pedal 16 is output from the brake signal generator 16a to the braking mode selector 24 of the controller 17. When the stroke and operation speed of the brake pedal 16 are input from the braking mode selector 24 to the maintenance pressure / built-up rate setting device 25, the setting device 25
From the brake control signal generator 26, the brake maintaining pressure pb
The build-up rate θ1 is output, and the brake control signal generator 26 outputs the brake pedal current ib2 to the brake control signal comparator 27. The build-up rate θ1 output from the setting unit 25 does not necessarily have to be the same as the build-up rate θ1 of each of the brakes and clutches shown in the steering control signal generator 23. On the other hand, the brake control signal ib1 generated by the steering control signal generator 23 is also output to the brake control signal comparator 27,
Of these, the larger control signal is the brake control signal ib
Left and right brake electronic proportional control valves 20R, 20L
Then, the control hydraulic pressure proportional to the brake control signal ib is supplied from the electronic proportional control valves 20R and 20L to the brakes 10R and 10L.

FIG. 3 is an explanatory diagram showing the relationship between the stroke of the steering lever 15 and the clutch or brake maintaining pressure in FIG. When the operation amount of the steering lever 15 is increased, the strokes 0 to c are in the neutral range, and the stroke c is
From stroke b to stroke b is set as the first range, and from stroke b to full is set as the second range. When the operation amount of the steering lever 15 decreases, the stroke full to stroke a is set to the second range.
Range, the first range from stroke a to stroke c,
Stroke c to stroke 0 is set as the neutral range. As described above, while the stroke of the steering lever 15 is short, the steering operation side clutches 8R and 8L start to be released, and subsequently, the clutches 8R and 8L are completely released.
Since the brakes 10R and 10L start to be coupled and the sprocket wheels 14R and 14L on the steering side are decelerated to a speed corresponding to the stroke of the steering lever 15, the vehicle is steered with a turning radius corresponding to the stroke of the steering lever 15. be able to.

[0017]

As described in detail above, according to the present invention, the following effects can be obtained. (1) Since it is not necessary to finely control the steering lever and a smooth steering characteristic can be obtained under all operating conditions by a normal steering operation, the steering operability of the operator can be improved. (2) Even if the steering lever is operated normally, there is no shock at the time of connecting the clutch and the brake under all operating conditions, so that the riding comfort of the operator can be improved and the durability of the clutch and the brake can be improved. It is possible to improve the property. (3) Since the electronic steering control device independently controls each clutch and brake, by inputting each operating condition to the controller, the ride comfort of the operator without shock is improved under all operating conditions. The steering control device can be obtained, and it can be manufactured at a lower cost than the link type.

[0018]

[Brief description of drawings]

FIG. 1 is a diagram showing an electronic steering control device for a bulldozer according to the present invention.

FIG. 2 is a diagram showing details of a controller in FIG.

FIG. 3 is a diagram showing a relationship between a stroke of an operation lever and a clutch or brake maintaining pressure in FIG.

FIG. 4 is a diagram showing a time-dependent characteristic of a clutch or brake hydraulic pressure when an operation amount of an operation lever is increased.

FIG. 5 is a diagram showing a time-dependent characteristic of a clutch or brake hydraulic pressure when the operation amount of the operation lever is reduced.

FIG. 6 is a view similar to FIG. 1 in the prior art.

FIG. 7 is a diagram showing a steering operation device according to a conventional technique.

FIG. 8 is a diagram showing clutch and brake hydraulic pressure characteristics in the conventional technique.

FIG. 9 is a diagram showing clutch and brake hydraulic pressure characteristics in a conventional technique.

[0019]

[Explanation of symbols]

1 engine 2 torque converter unit 3 transmission 4 Steering unit 5 input axes 6 speed change gear mechanism 7 Horizontal input shaft 8R, 8L left and right clutch 9R, 9L Left and right intermediate shaft 10R, 10L Left and right brake 11R, 11L Left and right output shafts 12R, 12L Left and right final reducer 13R, 13L Left and right output shafts 14R 14L Left and right sprockets 15 Steering lever 15a Steering signal generator

[0020] 16 brake pedal 16a Brake signal generator 17 Controller 18 Control pump 19R, 19L Electronic proportional control valve for left and right clutch 20R, 20L Electronic proportional control valve for left and right brakes 21 Steering mode selector 22 Maintaining pressure / build-up rate setting device 23 Steering control signal generator 24 Braking mode selector 25 Maintaining pressure / build-up rate setting device 26 Brake control signal generator 27 Brake control signal comparator

Claims (6)

[Claims] 1. A steering control device for a bulldozer, wherein left and right drive shafts transmission-coupled to an output shaft of a transmission transmit engine power to left and right sprockets via a clutch and a brake. An electronic proportional control valve that controls the brake independently, a steering lever,
A steering signal generator that generates a steering signal according to the operation amount of the steering lever, and a steering signal from the steering signal generator are input to output steering control signals to the electronic proportional control valves. An electronic steering control device for a bulldozer, which is provided with a controller for outputting. 2. The change with time of the steering control signal output from the controller to each electronic proportional control valve according to claim 1, is that when the steering lever is operated from neutral to full stroke, the brake hydraulic pressure is in a completely open pressure state. The first range in which the clutch hydraulic pressure changes from the complete coupling pressure to the clutch maintaining pressure according to the stroke of the steering lever, and the clutch hydraulic pressure changes from the clutch maintaining pressure or from the clutch maintaining pressure to the complete opening pressure, and the brake hydraulic pressure changes. It consists of a second range that changes from the brake preparation pressure to the complete braking pressure, which is slightly higher than the coupling start pressure. When operating the steering lever from full stroke to neutral, the clutch hydraulic pressure is at the full opening pressure and the brake hydraulic pressure is at the complete braking pressure. The second range that changes from the pressure to the brake maintaining pressure according to the stroke of the steering lever, and the brake hydraulic pressure is the steering range. Forming a first range in which the brake maintaining pressure is changed according to the stroke of the bar, or changes from the brake maintaining pressure to the full opening pressure, and the clutch hydraulic pressure changes from the clutch preparation pressure slightly higher than the engagement start pressure to the full engagement pressure. An electronic steering control device for bulldozers. 3. The clutch and brake maintaining pressure according to the stroke of the steering lever according to claim 2, the clutch hydraulic pressure changes from the complete coupling pressure to the maximum maintaining pressure while the brake hydraulic pressure is at the maximum maintaining pressure when the stroke is increased. It consists of a first range and a second range in which the clutch hydraulic pressure is at the maximum maintenance pressure and the brake hydraulic pressure changes from the coupling start pressure to the complete coupling pressure. Is a second range in which the clutch pressure changes from the full engagement pressure to the maximum maintenance pressure, and a first range in which the clutch hydraulic pressure changes from the engagement start pressure to the full engagement pressure when the brake oil pressure is at the maximum maintenance pressure. First range and second when stroke is reduced
An electronic steering control device for a bulldozer, which is characterized by adjusting a range overlapping with the range. 4. The time-dependent change of the steering control signal output from the controller to each electronic proportional control valve according to claim 2 is the brake preparation pressure in the second range when the operation amount of the steering lever is increased, or the steering lever An electronic steering control device for a bulldozer, wherein a clutch preparation pressure in a first range when a manipulated variable is decreased is increased for a predetermined time and then gradually decreased. 5. The brake according to claim 2, wherein braking is started a predetermined time after the clutch in the second range is completely released when the operation amount of the steering lever is increased, and the brake is completely in the first range when the operation amount of the steering lever is decreased. An electronic steering control device for a bulldozer, characterized in that the clutch starts to be engaged after a predetermined time from the release. 6. The electronic steering control of a bulldozer according to claim 5, wherein the predetermined time until the start of the brake braking or the predetermined time before the engagement of the clutch is adjusted according to the operating condition. apparatus.