JP4662492B2 - Steering control device for tracked vehicle - Google Patents

Description

  The present invention relates to a steering control device for a tracked vehicle such as a bulldozer.

    Conventionally, as a steering control device for a tracked vehicle such as a bulldozer, a left and right drive wheel is provided with a clutch and a brake and the clutch and the brake are controlled to perform a left and right turning motion of the vehicle. It has been. In this steering control device, if the steering lever is operated in the right turning direction while the vehicle is running, the right clutch is released, the right brake is braked, and only the right crawler is stopped, and the vehicle turns right. To do. When the steering lever is operated in the left turn direction, the left clutch is released, the left brake is braked, only the left crawler is stopped, and the vehicle turns left.

  By the way, in the steering control device as described above, a predetermined time interval is usually provided from when the clutch is released to when the brake is braked, or from when the brake is released to when the clutch is engaged. Thus, a smooth turn is made possible by reducing the shock during steering control. However, if the time interval of this clutch release to brake braking or brake release to clutch coupling is made constant, both the clutch and the brake on the side where the steering lever is operated are released when the vehicle travels on the slope. And a so-called reverse steering phenomenon causes the vehicle to turn in the opposite direction to the operation of the steering lever.

  In order to solve such a problem, for example, in Patent Document 1, the time interval between the release of the clutch and braking of the brake, and the release of the brake and engagement of the clutch is set to the vehicle body front-rear tilt angle. There has been proposed a system in which control is performed in accordance with this, thereby preventing a shock when operating the steering lever and preventing a reverse steering phenomenon.

  Further, for example, Japanese Patent Application Laid-Open No. H10-228707 discloses a purpose of performing a smooth turn without shock under various driving operation conditions. The steering control device described in this publication automatically adjusts the time interval until the brake begins to brake or the time until the clutch starts to be engaged according to the operating speed of the steering lever. It is configured to improve the performance.

  However, the conventional example does not perform steering control in consideration of the working state of the tracked vehicle, for example, during dosing work of a bulldozer or high-speed traveling work. There is a problem that it is impossible to perform proper control. In addition, in these conventional examples, control mainly focusing only on the static characteristics of the clutch / brake is executed, so that there is a problem that smooth and reliable turning control cannot be achieved in conformity with all work conditions. is there.

JP-A-4-366232 Japanese Patent Laid-Open No. 5-8753

The present invention has been made to solve such a problem, and is optimal for changing from a turning state to a straight traveling state according to various work states of the tracked vehicle, particularly when the vehicle is traveling at a high speed. An object of the present invention is to provide a steering control device for a tracked vehicle capable of obtaining steering performance.

In order to achieve the above object, a steering control device for a tracked vehicle according to the present invention includes:
A clutch and a brake provided on each of the left and right drive wheels, an electronic proportional control valve that controls the clutch and the brake, a steering lever, and a steering that generates a steering command signal according to the operation amount of the steering lever In a steering control device for a tracked vehicle comprising a command signal generator and a controller that outputs a steering control signal to the electronic proportional control valve based on an output from the steering command signal generator,
A vehicle speed detecting means for detecting the traveling speed of the vehicle and a pitch angle sensor for detecting an inclination angle in the front-rear direction of the vehicle are provided, and the pitch angle sensor is used to detect whether the vehicle is in an uphill traveling state exceeding a predetermined angle and the vehicle speed detecting means. When it is detected that the vehicle is in a high-speed running state, the controller detects the clutch from the start of clutch engagement to the end of engagement only when the steering lever is operated from the full stroke position to the neutral position. A steering control signal for obtaining a hydraulic characteristic in which a temporal change rate of the hydraulic pressure is set to be smaller than that during normal traveling is output to the electronic proportional control valve.

According to the present invention, by focusing on the dynamic characteristics of the clutches / brakes, when the vehicle is in a high-speed running state, only when the operation to the neutral position from the full stroke position of the steering lever, from the time of binding the start of a clutch The rate of change over time in clutch oil pressure until the end of engagement is set to be smaller than that during normal driving, and the clutch is engaged slowly. Thus, the shock due to the inertia of the vehicle when shifting from the turning state to the straight traveling state is reduced, and a smooth turning characteristic without a turning flow can be obtained.

  Next, a specific embodiment of a steering control device for a tracked vehicle according to the present invention will be described with reference to the drawings.

  An embodiment applied to a bulldozer will be described below. FIG. 1 is an external view of a bulldozer according to an embodiment of the present invention.

  In the bulldozer 1 of the present embodiment, a bonnet 3 and a driver's seat 4 are provided on the vehicle body 2, and crawler belts 5 for moving the vehicle body 2 forward, backward, and turn are provided on the left and right sides in the forward direction of the vehicle body 2. ing. These crawler belts 5 are independently driven for each crawler belt 5 by the corresponding sprocket 6 by the driving force transmitted from the engine.

  On the left and right side portions of the vehicle body 2, the base end portions of the left and right straight frames 8 and 9 that support the blade 7 on the distal end side are raised by trunnions (the right trunnion is not shown) 10. -It is pivotally supported so that it can descend. The blade 7 includes a pair of left and right blade lift cylinders 11 and 11 for raising and lowering the blade 7 between the body 2 and a brace 12 and a blade tilt cylinder 13 for inclining the blade 7 left and right. 12 is provided between the left straight frame 8 and the blade tilt cylinder 13 is provided between the right straight frame 9.

  Further, on the left side of the driver's seat 4, there is provided a steering lever 15 and a fuel control lever 17 that also serve as a forward / reverse shift lever, and on the right side is a blade control that raises, lowers, tilts left, and tilts right. A lever 18 and the like are provided. A dexel pedal (not shown) is provided in front of the driver seat 4.

  Next, in FIG. 2 in which the system configuration of this embodiment is shown, the rotational driving force from the engine 20 is transmitted to the torque converter 23 via the damper 21 and the PTO 22. Then, the rotational driving force is transmitted from the output shaft of the torque converter 23 to a transmission 24 which is, for example, a planetary gear wet multi-plate clutch transmission whose input shaft is connected to the output shaft. The transmission 24 has forward, reverse clutches and 1st to 3rd speed clutches, and the rotational driving force from the output shaft thereof is transferred via the transfer 25 and left and right clutches 26L, 26R and brakes 27L, 27R. Thus, the sprockets 6 and 6 that are transmitted to the pair of left and right final reduction gears 28L and 28R to travel the crawler belt 5 are driven.

  The clutches 26L and 26R and the brakes 27L and 27R are configured to be operated by a biasing force of a spring and to be released by an oil pressure. By the control signal output from the controller 29, the electromagnetic proportional control valves for the left and right clutches. It is controlled via 30L, 30R and the electromagnetic proportional control valves 31L, 31R for each brake. In order to execute this control, the controller 29 receives a signal from a steering command signal generator 15 a that generates a steering command signal in accordance with the operation amount of the steering lever 15. Further, the controller 29 includes rotation speed data of the engine 20 from the engine rotation sensor 32, rotation speed data of the output shaft of the torque converter 23 from the torque converter output shaft rotation sensor 33, and front and rear of the vehicle from the pitch angle sensor 34. Direction inclination angle data, output speed data of the output shaft of the transmission 24 from the transmission output shaft rotation sensor 35, data relating to the speed stage state from the transmission speed stage sensor 36, throttle amount data of the engine 20 from the throttle sensor 37, etc. Each data is input.

  FIG. 3 (a) shows the relationship (modulation characteristic diagram) between the stroke of the steering lever 15 and the hydraulic pressure (maintenance pressure) of the clutch or brake during normal running of the bulldozer, and FIG. 3 (b) (c). Shows the relationship between the clutch force and the hydraulic pressure, and the relationship between the brake force and the hydraulic pressure. The control characteristics of the clutch pressure and the brake pressure by the operation of the steering lever 15 will be described with reference to these drawings.

  As shown in FIG. 3A, initially, no pressure oil is sent to the clutch, and the clutch is on by the biasing force of the spring, while pressure oil is sent to the brake and the brake is off. In this state, the vehicle is going straight. When the steering lever 15 is operated, pressure oil is sent to the clutch at point A to increase the hydraulic pressure to point a, and the coupling force gradually decreases from point a toward point b. The clutch force is turned off slightly before (see FIG. 3B). On the other hand, in the brake, the pressure oil is returned to lower the hydraulic pressure to the point c, the braking force (braking force) is gradually increased from the point c toward the point d, and the brake is coupled at the point d. (See FIG. 3C). In this case, there is a delay time t between b and c, and the brake is turned on after the clutch is turned off. On the other hand, when the brake is turned off and the clutch is turned on, the delay time is set so that the clutch is turned on after the brake is turned off, thereby preventing a shock during operation.

  In this embodiment, the steering control is performed so that the static characteristics and dynamic characteristics of the clutch / brake hydraulic characteristics (static characteristics) during normal running as described above are changed according to the working state of the bulldozer. Executed. Below, the specific content of the steering control in a present Example is demonstrated, referring the flowchart shown by FIG.

  S1 to S2: In addition to the operation lever stroke signal from the steering command signal generator 15a, the rotation speed signal of the engine 20 from the engine rotation sensor 32, and the rotation of the output shaft of the torque converter 23 from the torque converter output shaft rotation sensor 33 Number signal, vehicle front-rear tilt angle signal from pitch angle sensor 34, rotation speed data of output shaft of transmission 24 from transmission output shaft rotation sensor 35, speed stage signal from transmission speed stage sensor 36, throttle sensor 37 Each sensor signal such as a throttle amount signal of the engine 20 is input. Then, the traction force of the vehicle is calculated from the rotation speed signal of the engine 20 and the rotation speed signal of the output shaft of the torque converter 23, the pitch angle of the vehicle is calculated from the tilt angle signal, and the vehicle speed is calculated from the rotation speed signal of the output shaft of the transmission 24. Is calculated.

S3: From the calculated pitch angle, it is determined whether or not the vehicle is traveling downhill at a predetermined angle (for example, 6 °) or more.
S4: Considering that the required turning torque of the inner crawler track becomes a large negative value when the vehicle is in a downhill traveling state with a predetermined angle or more, the steering static characteristic for the slope is selected as the modulation characteristic of the clutch / brake. As shown in FIG. 5 (a), the steering static characteristics for the sloping terrain are obtained by accelerating the brake control (see the arrow P) with respect to the characteristics during normal driving (see the arrow P), and the clutch and the brake are released simultaneously. The hydraulic pressure characteristic is changed so that there is no area (playing area). In this way, it is possible to prevent the reverse turning (reverse steering phenomenon) during downhill due to the release of the clutch. As shown in FIG. 5 (b), the static steering characteristic for the slope is compared with the characteristic shown in FIG. 5 (a) (indicated by a chain line), as shown in FIG. It is also possible to set a hydraulic pressure characteristic in which the brake starting hydraulic pressure (point c in FIG. 3 (a)) is lowered. According to such hydraulic characteristics, since the clutch coupling force and the braking force of the brake are corrected in the increasing direction, the vehicle can be steered with the same steering sensation as on a flat surface. It is.

S5: It is determined from the calculated traction force whether or not the vehicle is in a forward traveling state (dosing work state) with a large traction force.
S6: The clutch / brake modulation characteristics in consideration of the fact that the required turning torque of the inner crawler track becomes a positive value when the vehicle is in a high-load forward traveling state exceeding a predetermined tractive force (for example, 0.4 W; W is the vehicle weight). Select steering static characteristics for dosing. As shown in FIG. 6, the static steering characteristic for dosing is a characteristic in which the range Q of the clutch maintenance range is widened and the range R of the brake maintenance range is narrowed relative to the characteristic (chain line) during normal driving. In other words, the characteristic is obtained by shifting the points b and c in FIG. 3A to the right. In this way, the turning torque of the inner crawler belt becomes a positive value, and the half-clutch state will last for a long time, and even during dosing work, the earth and sand on the front of the blade can be smoothly pushed and optimized without shock The swivel characteristics can be obtained.

S7: It is determined from the throttle opening whether the engine speed is low.
S8: When the engine speed is low, the turning torque may be small. Therefore, the engine low speed steering static characteristic as shown in FIG. 7, that is, the brake coupling start hydraulic pressure is higher than that during normal driving (dashed line). A hydraulic characteristic with a reduced braking force is selected. In this way, it becomes possible to perform fine steering control adapted to fine operation by agile brake characteristics.

S9: On the other hand, the basic steering static characteristics shown in FIG. 3 (a) are selected when the vehicle is not in a downhill traveling state of a predetermined angle or more, is not in a high load traveling state of a predetermined tractive force or more, and is not at a low engine speed. Is done.
S10: It is determined from the calculated pitch angle whether or not the vehicle is in an uphill traveling state of a predetermined angle (for example, 6 °) or more.
S11: If the vehicle is not in an uphill traveling state with a predetermined angle or more, it is next determined whether or not the vehicle is in a high-load forward traveling state with a predetermined tractive force (for example, 0.4 W; W is the vehicle weight) or more.

  S12: When the vehicle is in an uphill traveling state of a predetermined angle or more, or is in a high-load forward traveling state (dosing work state) of a predetermined traction force (for example, 0.4 W; W is the vehicle weight) or more, Select characteristic parameters. That is, as shown in FIG. 8, when the steering lever is operated from the full stroke position to the neutral position, the temporal rate of change of the clutch hydraulic pressure from the start of clutch engagement to the end of engagement is determined during normal travel (indicated by a chain line). The characteristic that the clutch is engaged in a short time is selected. Thus, there is no torque interruption in the high-load operation state, no reverse steering phenomenon occurs in the uphill driving state, the shock at the time of transition from the turning state to the straight traveling state is reduced, and there is no smooth turning flow. It is possible to obtain a good turning characteristic.

S13: Whether the vehicle is in a high-speed traveling state is determined from the calculated vehicle speed when the vehicle is not in an uphill traveling state with a predetermined angle or more and is not in a high-load forward traveling state with a predetermined tractive force or more.
S14: When the vehicle is in a high speed running state, a steering dynamic characteristic parameter for high speed running is selected. That is, as shown in FIG. 9, when the steering lever is operated from the full stroke position to the neutral position, the temporal rate of change of the clutch hydraulic pressure from the start of clutch engagement to the end of engagement is determined during normal travel (indicated by a chain line). The characteristic that the clutch is engaged slowly is selected. Thus, the shock due to the inertia of the vehicle when shifting from the turning state to the straight traveling state is reduced, and a smooth turning characteristic without a turning flow can be obtained.

S15: When the vehicle is not in a high-speed traveling state, a basic steering dynamic characteristic parameter (indicated by a chain line in FIGS. 8 and 9) during normal traveling is selected.
S16 to S17: The clutch / brake hydraulic pressure corresponding to the steering lever stroke command is calculated, and the left and right clutches 26L via the left and right clutch electromagnetic proportional control valves 30L and 30R and the brake electromagnetic proportional control valves 31L and 31R. , 26R and the brakes 27L, 27R are output with hydraulic pressure command signals, and the process returns to step S1.

  As described above, according to the present embodiment, it is possible to cope with various working states of the bulldozer in the case of running on slopes, dosing work, low engine speed running, high speed running, etc. Since the characteristics are selected, it is possible to obtain a bulldozer having no steering shock and having a steering performance suitable for the operator's feeling.

  In the present embodiment, the characteristic shown in FIG. 5 is selected as the steering static characteristic when traveling downhill, but it is also possible to select the same characteristic when traveling uphill. In this way, it is possible to avoid the occurrence of a phenomenon in which the turning radius of the vehicle becomes too large during climbing.

  Although the present embodiment has been described as being applied to a bulldozer, it goes without saying that the present invention can also be applied to other tracked vehicles.

1 is an external view of a bulldozer according to an embodiment of the present invention. System configuration diagram of this embodiment Modulation characteristic diagram of clutch / brake (a), diagram showing relationship between clutch force and hydraulic pressure (b), and diagram showing relationship between brake force and hydraulic pressure (c) Flow chart showing steering control procedure Graph showing steering static characteristics for slopes Graph showing the steering static characteristics for dosing Graph showing the steering static characteristics for engine low speed Graph showing steering dynamic characteristics for heavy loads Graph showing steering dynamic characteristics for high-speed driving

Explanation of symbols

1 Bulldozer 5 Track 6 Sprocket 15 Steering lever 15a Steering command signal generator 20 Engine 23 Torque converters 26L, 26R Clutch 27L, 27R Brake 29 Controller 30L, 30R Clutch electromagnetic proportional control valve 31L, 31R Brake electromagnetic proportional control valve 32 Engine rotation sensor 33 Torque converter output shaft rotation sensor 34 Pitch angle sensor 35 Transmission output shaft rotation sensor 36 Transmission speed stage sensor 37 Throttle sensor

Claims (1)

Clutch (26L, 26R) and brake (27L, 27R) provided on the left and right drive wheels, and electronic proportional control valves (30L, 30R; 31L) for controlling these clutch (26L, 26R) and brake (27L, 27R) , 31R), a steering lever (15), a steering command signal generator (15a) for generating a steering command signal in accordance with the operation amount of the steering lever (15), and the steering command signal generation In a steering control device for a tracked vehicle, comprising a controller (29) for outputting a steering control signal to the electronic proportional control valves (30L, 30R; 31L, 31R) based on an output from the vessel (15a),
A vehicle speed detecting means (35) for detecting the traveling speed of the vehicle and a pitch angle sensor (34) for detecting a tilt angle in the front-rear direction of the vehicle are provided, and the pitch angle sensor (34) causes the vehicle to travel in an uphill direction at a predetermined angle or more. And when the vehicle speed detecting means (35) detects that the vehicle is in a high speed running state, the controller (29) moves the steering lever (15) from the full stroke position to the neutral position. A steering control signal for obtaining a hydraulic characteristic in which the temporal change rate of the clutch hydraulic pressure from the start of coupling to the end of coupling is set to be smaller than that during normal driving only at the time of operation. A steering control device for a tracked vehicle, wherein the steering control device outputs to the electronic proportional control valves (30L, 30R).

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