JPH0330020B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a slip prevention device for a wheeled vehicle that steers by bending the vehicle body at the center. Work vehicles such as wheel loaders and motor scrapers use very expensive tires.
Prevention of tire wear and tear has become a top concern for users. When tire slip occurs in such a vehicle, not only does the tire wear out quickly, but there is a risk that the tire may be damaged if there are sharp falling rocks on the working ground. In particular, in vehicles equipped with a variable capacity torque converter, there are two routes: one route transmits the engine output to the wheels via the variable capacity torque converter, and the other route transmits it to the work equipment without going through the variable capacity torque converter. When there is a route and the engine output is increased to increase the power of the work equipment during work, the traction force transmitted to the wheels increases accordingly, making slips more likely to occur. Therefore, this type of vehicle has conventionally been provided with a slip prevention device. Conventional slip prevention devices detect the rotation speed of four wheels, calculate the rotation speed ratio between each wheel, and if even one of the calculated rotation speed ratios exceeds a preset slip judgment reference value. The output torque to the wheels was controlled (output torque reduced) to prevent slippage (stopping). However, in conventional slip prevention devices, the slip judgment reference value must be set to a value that is larger than the maximum value of the rotation speed ratio between the inner ring and the outer ring that inevitably occurs during turning, and the dead zone for slip detection is There was a huge drawback. The present invention has been made to solve the above-mentioned drawbacks, and an object of the present invention is to provide a slip prevention device that has high slip detection accuracy and is capable of effectively preventing slips. According to the present invention, the articulation angle of a wheeled vehicle that steers by bending the vehicle body at the center is detected, a slip judgment reference value is set corresponding to this articulation angle, and the rotation between each wheel is determined. When even one of the numerical ratios exceeds the slip judgment reference value,
The output torque to the wheels is reduced. The present invention will now be described in detail with reference to the accompanying drawings. FIGS. 1a and 1b are plan views of a wheel loader to which the slip device according to the present invention is applied, with FIG. 1a showing the loader when it is traveling straight, and FIG. 1B when it is turning. This wheel loader is equipped with a center pin 1 in the center of the vehicle body in order to improve maneuverability.
and the rear wheel truck 4 are rotatably connected to each other. When steering, a steering cylinder (not shown) disposed between the front wheel truck 3 and the rear wheel truck 4 is extended and contracted to bend the center of the vehicle body (the first (see figure b). Next, the rotation ratio between the inner ring and the outer ring during steering will be explained. FIG. 2 geometrically shows the relationship between the turning center O and various parts of the vehicle when the vehicle is articulated by an angle θ relative to when the vehicle is traveling straight. Now, as shown in Fig. 2, if the articulation angle is θ, the tread of the vehicle is t, and the wheelbase is l, then the turning radius of the vehicle (the distance between the turning center O and the tread center _t0 ) is: r=l/2cotθ/2 (1). On the other hand, if the rotation ratio between the inner ring and the outer ring is K, then K=r+t/2/rt/2 (2). Substituting the above equation (1) into equation (2), the rotation ratio K
The result is K=l cotθ/2+t/l cotθ/2−t (3). As is clear from this equation (3), the rotation ratio K between the inner ring and the outer ring is the articulation angle θ
can only be expressed as a variable. Currently, the tread length t is 2.26m and the wheelbase length is 3.05m.
Then, the relationship between the articulation angle θ and the rotation ratio K is as shown in the graph of FIG. Based on the relationship between the articulation angle θ and the rotation ratio K, the slip prevention device according to the present invention shown in FIG. 4 will be described in detail. In FIG. 4, the output of the engine 11 is applied to a hydraulic pump 13 for driving a working machine or the like and a hydraulic clutch 141 of a variable displacement torque converter 14 through appropriate power transmission means. The hydraulic clutch 141 is connected to a servo valve 43 which will be described later.
The slip control is performed by the engine 1
The driving force from the hydraulic clutch 141 is applied to the transmission 15 via the torque converter 142, which is another component of the variable capacity torque converter 14. The output from the transmission 15 is transmitted to the four wheels 19, 20, 21, 22 via appropriate gears 16 and differentials 17, 18.
is transmitted to. The input shaft and output shaft of the torque converter 142 are provided with a speed sensor 23 that detects the rotational speed of these and outputs a signal with a frequency corresponding to the speed.
and 24 are arranged respectively, and the speed sensor 2
The detection signal Si of 3 is applied to the frequency-voltage converter 25, and the detection signal So of the speed sensor 24 is applied to the input/output circuit 27 of the CPU (central processing unit) 26, which will be described later.
added to. Similarly, each wheel 19, 20, 21
Speed sensors 28, 29, 30, and 31 are arranged on the drive shafts 22 and 22, respectively, to detect the rotational speeds of these and output signals with frequencies corresponding to the speeds, and the detection signals of the speed sensors 28 to 31
W ₁ to _{W 4} are applied to the input/output circuit 27. The traveling driving force setting device 32 sets the magnitude of the driving force (torque) to be transmitted to the wheels, and the set output is converted into a corresponding digital signal Dt by the analog-to-digital converter 33 and sent to the input/output circuit 27.
Add to. The articulate angle detector 34 is
The articulation angle θ (see FIG. 2) formed between the front wheel bogie and the rear wheel bogie is detected, and a signal corresponding to this detected angle is converted into a digital signal Dθ by the analog-to-digital converter 35 and sent to the input circuit 27. Add. The ROM (read only memory) 36 is
A program showing the control procedure executed by the CPU 26 and a curve showing the relationship between the input shaft rotation speed and the output shaft rotation speed of the torque converter 142 for each torque size when the output torque is constant.
L ₁ , L ₂ , L ₃ , . . . , Ln (see FIG. 5) are stored, and the stored contents are read out by the CPU 26. Further, a RAM (random access memory) 37 constitutes a data storage section of the CPU 26, and its storage contents are written and read by the CPU 26. The interrupt timer 38 operates for a predetermined period of time (for example,
Generates an interrupt signal St every 100msec) and sends it to the CPU.
26, and thereby CPU2
6, an interrupt is generated at the timing when the interrupt signal St is applied, the program being executed at that point is interrupted, and the routine LU shown in FIG. 6 is executed. That is, first, the CPU 26 inputs the setting data Dt of the traveling driving force setting device 32 (input 110), and
A curve corresponding to the data Dt is selected from among the curves L ₁ to Ln stored in the ROM 36 (processing 12
0). Next, the output shaft rotational speed of the torque converter 142 is input (input 130). This input 1
At 30, for example, the output signal of the speed sensor 24 is
The generation interval or period of So is measured, the reciprocal of the counted value is calculated, and the result is input as the output shaft rotation speed. The CPU 26 then calculates the input shaft rotation speed corresponding to the output shaft rotation speed obtained at the input 130 based on the curve selected in the above process 120 (process 140). Next, the detected angle data Dt of the articulation angle detector 34 is input (input 150), and this data
Calculate the above-mentioned equation (3) based on Dt, the preset tread length t, and the wheelbase length l, calculate the rotation ratio K between the inner ring and the outer ring, and add an appropriate dead zone to this rotation ratio K. Then, a slip judgment reference value K' is calculated (process 160). Next, the rotation speeds W ₁ to _{W 4} of each wheel are input (input 170), and from these rotation speeds, the rotation ratios K ₁ to K ₁₂ between each wheel are calculated in a round robin game as shown in Table 1. (process 180).

[Table] Rotation ratio K ₁ to K ₁₂ calculated in process 180 and process 1
60, and if all the rotation ratios K ₁ to _{K 12} are less than the reference value K', the output goes to 200, and one of the rotation ratios K ₁ to _{K 11} is
If any value is greater than the reference value K', output 21
0 (decision 190). The output 200 outputs the input shaft rotation speed calculated in the process 140 to the register 39, and the output 210 outputs the input shaft rotation speed calculated in the process 140.
The input shaft rotation speed calculated in process 140 is subtracted by a predetermined value and output to the register 39. That is, for example, among the curves L ₁ to Ln, the curve Ln indicating the set torque is selected, and the input 13
The output shaft rotational speed obtained at n ₀ is shown in Figure 5.
(RPM), and if it is determined that no slip has occurred, the input shaft rotational speed n _i (RPM) shown in the figure is set in the register 39, and it is determined that a slip has occurred. In this case, a value smaller than the input shaft rotational speed n _i (RPM) by a predetermined value is set in the register 39. After this, the CPU 26 returns to the original program from the routine LU. The set value of the register 39 is converted into a corresponding analog signal Sr by a digital-to-analog converter 40, and the signal Sr is applied to a subtracter 41. The output signal of the frequency-voltage converter 25, that is, the voltage signal corresponding to the frequency of the detection signal Si is applied to the subtracter 41. Therefore, the subtracter 41 has a voltage signal corresponding to the frequency of the detection signal Si. A signal Se representing the deviation is output.
The signal Se is then applied to the servo valve 43 via the amplifier 42 as a control signal. As a result, the flow rate of the hydraulic oil passing through the servo valve 43 is changed, and accordingly, the pressing force of the hydraulic cylinder 141a of the hydraulic clutch 141, that is, the engagement pressure of the hydraulic clutch 141 is changed, so that the amount of slippage of the hydraulic clutch is changed. The rotational speed of the output shaft increases or decreases. Thus, the hydraulic clutch 141 is controlled so that the rotational speed of the input shaft of the torque converter 142 is equal to the set value of the register 39. Therefore, when it is determined that no slip has occurred, the driving force (torque) transmitted to the wheels is controlled so as to always be equal to the traveling driving force set by the traveling driving force setting device 32, If it is determined that a slip has occurred, the running driving force is controlled to be smaller than the running driving force set by the running driving force setting device 32. That is, in the latter case,
The output torque is reduced and subsequent slips are prevented. In this embodiment, the slip judgment reference value is calculated sequentially each time the articulation angle is input. However, the slip judgment reference value corresponding to the articulation angle may be stored in advance. Then, the slip determination reference value corresponding to the articulation angle may be read out. As explained above, according to the present invention, the slip determination reference value is sequentially set based on the articulation angle, that is, the rotation ratio between the inner ring and the outer ring that inevitably occurs during steering.
The slip detection accuracy is improved, which makes it possible to prevent slips early and prevent tire wear.

[Brief explanation of the drawing]

Figures 1a and b are plan views of a wheel loader to which the slip prevention device according to the present invention is applied, and Figure 2 is used to calculate the rotation ratio between the inner ring and the outer ring in accordance with the articulation angle. The figure that was,
Fig. 3 is a graph showing an example of the relationship between articulation angle and rotation ratio, Fig. 4 is a block diagram showing an embodiment of the slip prevention device according to the present invention, and Fig. 5 is a torque converter when the output torque is constant. Figure 6 is a graph showing the relationship between the input shaft rotation speed and output shaft rotation speed for each torque size.
2 is a flowchart illustrating a control procedure. 14...Variable capacity torque converter, 23,2
4, 28, 29, 30, 31...speed sensor, 2
6...CPU, 32...Travel driving force setting device, 34
... articulation angle detector, 43 ... servo valve, 141 ... hydraulic clutch, 142 ... torque converter, θ ... articulation angle.

Claims (1)

[Claims] 1. In a wheeled vehicle that steers by bending the vehicle body at the center, there is provided an angle detector that detects an articulation angle at the center of the vehicle body, and an articulation angle detected by the angle detector. a setting means for setting a slip judgment reference value corresponding to the rate angle; a rotation speed detector for detecting the rotation speed of each wheel; and a rotation speed detector for detecting the rotation speed of each wheel; a calculation means for calculating a rotation speed ratio; and an output torque to the wheels when at least one of the rotation speed ratios calculated by the calculation means exceeds a slip determination reference value set by the setting means. and control means for reducing slippage. 2. The setting means calculates a rotational speed ratio between the inner ring and the outer ring based on the articulation angle detected by the angle detector and the tread length and wheelbase length of the vehicle, and 2. The slip prevention device according to claim 1, wherein the slip determination reference value is set by determining the slip determination reference value. 3. The slip prevention device according to claim 1, wherein the control means reduces the output torque to the wheels by reducing the engagement pressure of the clutch of a variable capacity torque converter comprising a clutch and a torque converter. .