JPH06220892A - Slip preventing device for wheel type construction machine - Google Patents

Abstract

PURPOSE:To efficiently drive a wheel type construction machine by reducing a number of sensors so as to simplify the computation in order to reduce the cost while preventing a slip. CONSTITUTION:A pressure detector 61 detects a discharge pressure Ph of a working machine hydraulic pump 53, and a torque detector 63 detects a torque Tt of the output shaft of a toque converter Tt in a running device 40. Alternatively, the torque is calculated. A limit value Ts-limit of the torque of the output shaft is obtained, with which no slip occurs in accordance with the pump discharge pressure Ph, and then the detected or calculated output shaft torque is compared with the above-mentioned limit value Ts-limit. Accordingly, the engaging pressure of a running clutch is controlled so as to prevent a slip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slip prevention device for a wheel type construction machine such as a wheel loader.

[0002]

2. Description of the Related Art In a wheel-type construction machine such as a wheel loader, when excavation work is performed by operating a bucket, a boom or the like of a work device while traveling a vehicle by a traveling device,
When slip occurs between the wheels (tires) and the road surface, work efficiency is reduced and wear and damage of the wheels are increased.

In order to prevent the slip, the operator generally relies on his experience and intuition to determine the boom lever and bucket lever based on how the bucket bites into the object to be excavated, the operating speed of the bucket, and changes in the sound of the prime mover. The operation amount or the accelerator pedal depression amount is being adjusted. However, it is very troublesome to prevent the wheel slippage by such a manual operation, the physical and mental fatigue of the operator is great, and the control is inaccurate.

Therefore, as a means for automatically controlling so as not to cause a slip, a slip prevention device disclosed in Japanese Patent Laid-Open No. 189535/1988 is known. In this conventional device, the rotation speeds of the left front wheel and the right front wheel are detected, the slip of the wheels is detected by the difference in the rotation speeds, and on the other hand, the rotation angle of the boom and the rotation angle of the bucket are detected.
The supply pressure to the boom cylinder and the supply pressure to the bucket cylinder are detected, and the joint pressure of the power transmission clutch in the traveling device is controlled based on these detected values.

[0005]

According to the above-mentioned conventional device, a large number of sensors are required and there is a problem that the cost is high.

The present invention solves the above-mentioned problems of the prior art, reduces the number of detection means installed, simplifies the equipment configuration and arithmetic processing to reduce costs, and enables even an unskilled operator to operate efficiently without slipping the wheels. The purpose is to be able to.

[0007]

In order to achieve the above object, the present invention provides a wheel type construction machine with a pressure detecting means for detecting the discharge pressure of a hydraulic pump for a working device and a torque of a transmission shaft in a traveling device. A torque detecting means for detecting, a limit value calculating means for obtaining a limit value of a transmission shaft torque for preventing wheels from slipping based on the pump discharge pressure detected by the pressure detecting means, and a transmission detected by the torque detecting means. And a control means for controlling the engagement pressure of the traveling clutch so that the axial torque does not exceed the limit value calculated by the limit value calculating means (claim 1).

Instead of detecting the torque of the transmission shaft, the number of rotations of the prime mover and the number of rotations of the transmission shaft are detected, the torque of the transmission shaft is calculated based on the detected values, and the calculated transmission shaft torque is calculated. You may make it control based on (claim 2).

Further, instead of obtaining the limit value of the transmission shaft torque by the limit value calculating means, the engagement pressure of the traveling clutch for preventing the wheels from slipping based on the pump discharge pressure detected by the pressure detecting means. Of the clutch is detected by the second pressure detecting means so that the detected clutch engagement pressure does not exceed the limit value calculated by the limit value calculating means. The clutch engagement pressure may be controlled (claim 3).

A reference value setting means may be provided for variably setting the reference value when the limit value of the engagement pressure of the traveling clutch is obtained by the limit value calculating means.

[0011]

According to the above construction, when the wheel-type construction machine is in operation, the discharge pressure of the hydraulic pump for the working device, which changes according to the load of the working device, is detected, and the traveling device corresponding to the traction force of this machine is detected. The transmission shaft torque is detected (Claim 1) or the transmission shaft torque is calculated (Claim 2). Then, based on the pump discharge pressure, the limit value of the transmission shaft torque for preventing the wheels from slipping is calculated, so that the detected or calculated transmission shaft torque does not exceed the limit value. The engagement pressure is controlled, which drives the wheels so that they do not slip.

According to the third aspect of the present invention, the discharge pressure of the working device hydraulic pump and the engagement pressure of the traveling clutch are respectively detected, and the wheels are slipped based on the detected pump discharge pressure. The limit value of the engagement pressure of the traveling clutch is determined so as not to prevent the engagement, and the engagement pressure of the traveling clutch is controlled so as not to exceed the limit value, and the wheels are operated so as not to slip.

When determining the limit value of the transmission shaft torque or the limit value of the engagement pressure of the traveling clutch, the reference value is changed according to the road surface condition, etc., so that optimum control is always performed. Wheel slip is more reliably prevented.

[0014]

EXAMPLE An example of a wheel-type construction machine to which the present invention is applied will be described with reference to FIG. This wheel-type construction machine includes a front frame 11, a rear frame 12, a driver's cab 20, a prime mover 30, a traveling device 40, and a working device 50.

The prime mover 30 is provided with a fuel injection pump 32 having a fuel injection amount adjusting actuator 31. An accelerator pedal 21 is provided in the cab 20,
By this pedal operation, the actuator 31 is operated via the link 22, the fuel injection amount of the fuel injection pump 32 is adjusted, and the rotation speed of the prime mover 30 is controlled.

The traveling device 40 is composed of a torque converter 41 connected to the prime mover 30, a transmission 42, drive shafts 43 and 44, axles 45 and 46, and wheels 47 and 48. When driving, the prime mover 30
Output of the wheels 4 through the torque converter 41 in the above order.
It is transmitted to 7, 48 and driven to travel.

The working device 50 comprises a front frame 11, a boom 54, a boom cylinder 55, a bucket 56, a bucket cylinder 57, a dump link 58, a cross link 59 and the like. Then, the control valve 52 is switched by operating the operating lever 51 provided in the operator's cab 20, and the working device hydraulic pump 53 is switched.
The pressure oil discharged from the cylinder is supplied to the boom cylinder 55 and the bucket cylinder 57 via the control valve 52, and the cylinders 55 and 57 are expanded and contracted to move the boom 54.
And the bucket 56 is rotated, and work such as excavation is performed. The working device hydraulic pump 53 is driven by the prime mover 30.

During the above operation, the output of the prime mover 30 is preferentially distributed to the hydraulic system such as the hydraulic pump 53 of the working device 50 via the torque converter 41, and the rest is consumed as power for the traveling device 40 via the torque converter 41. To be done. When the working device 50 is not operating, almost all of the output of the prime mover 30 is consumed by the traveling device 40 side except for some loss horsepower.

By the way, a general relationship between the traveling speed of the vehicle body and the traction force during operation of the wheel-type construction machine is shown in FIG. 5 (a). In FIG. 5A, a solid line A indicates a case where the work device hydraulic pump 53 is unloaded, a solid line B indicates a case where the working device hydraulic pump 53 is medium load, and a solid line C indicates a case where the work device hydraulic pump 53 is high load.

From FIG. 5A, the following can be said as the characteristics of the relationship among the load, the traction force, and the traveling speed of the working apparatus hydraulic pump 53.

1) When the load on the working device hydraulic pump 53 is increased, the traction force is reduced and slippage is less likely to occur.

2) The large load of the hydraulic pump 53 indicates that a large excavation resistance is acting on the working device 50, and the vertical component of the excavation resistance at that time increases the pressing force of the vehicle body against the ground. I will let you.
Along with this, the frictional resistance between the wheels and the road surface increases,
The slip limit value of the wheel increases accordingly.

From the above, in order to prevent the wheels from slipping, the slip limit value (minimum value) in FIG. 5 (a) when the working device hydraulic pump 53 is unloaded, that is, when only the vehicle body weight and the dynamic friction coefficient are present. ) Is a circle, and the maximum slip limit value that changes according to the discharge pressure of the hydraulic pump 53 is a circle, and a change between them is indicated by a solid line D according to the discharge pressure of the hydraulic pump 53. It can be said that the slip limit value is set and the operation may be performed so as not to exceed the slip limit value indicated by the solid line D.

The coefficient of friction between the wheel and the road surface changes depending on the road surface condition. In such a case, a slip limit value with a lower reference value can be set as shown by the chain line C'in FIG. 5 (b). You can say that you should do so.

Therefore, the present invention intends to limit the engaging pressure of the traveling clutch by utilizing the above-mentioned characteristics so as to prevent the wheels 47 and 48 from slipping by a simple device configuration and calculation. . The running clutch is
It is provided in the transmission 42 of the traveling device 40 shown in FIG. 4, and is operated by the hydraulic circuit shown in FIG.

That is, in FIG. 6, 23 is a hydraulic pump, 24 is a speed stage switching control valve equipped in the transmission 42 (FIG. 4), 25 is a traveling clutch, and 26 is a pressure control means. The hydraulic pump 23 is driven by a prime mover 30. During normal traveling, the speed lever switching control valve 24 of the transmission 42 is operated by operating the clutch lever provided in the cab 20, and the hydraulic oil supplied from the hydraulic pump 23 to the traveling clutch 25 is controlled. Then, the traveling speed of the vehicle body and the clutch engagement pressure are controlled, and the traction force is controlled. At this time, the pressure control means 26 is operated by a signal from the controller 70 (FIG. 1), and the clutch 25 is operated.
The pressure input to the clutch, that is, the clutch engagement pressure is controlled, and the upper limit value of the traction force is limited. Hereinafter, a specific example of the control will be described.

Embodiment-1 FIG. 1 shows the discharge pressure Ph of the hydraulic pump 53 for working equipment,
The control block diagram in the case of detecting the transmission shaft torque of the traveling device 40 and controlling the engagement pressure of the traveling clutch 25 is shown. In FIG. 1, 61 is pressure detecting means, 62 is reference value setting means, 63 is torque detecting means, 70 is controller, 71 is limit value calculating means, 72 is comparing means, 73 is command value calculating means, and 74 is amplifying means. Indicates.

In the first embodiment, first, the pressure detection means 61 detects the discharge pressure Ph of the working machine hydraulic pump 53 driven by the prime mover 30, and sends the detected value to the controller 70. On the other hand, the torque detecting means 6
3, the transmission shaft torque of the traveling device 40 is detected, and the detected value is sent to the controller 70. The transmission shaft torque corresponds to the traction force, and in this embodiment-1, the output shaft torque of the torque converter 41 (FIG. 4) is detected by the torque detecting means 63.

Then, the working value hydraulic pump 5 detected by the pressure detecting means 61 by the limit value calculating means 71.
Based on the discharge pressure Ph of 3, the limit value Ts-limit of the output shaft torque for preventing the wheels from slipping is calculated (Equation 1).

[0030]

## EQU00001 ## Ts-limit = Tso + a.multidot.Ph where Tso is a reference value and a is a constant.
The deviation ΔTt between the output shaft torque Tt detected in step 1 and the limit value Ts-limit of the output shaft torque calculated in step 1 is calculated (step 2).

[0031]

## EQU2 ## .DELTA.Tt = Tt-Ts-limit After that, based on the deviation .DELTA.Tt, the command value calculation means 73
The control command value A for the engagement pressure of the traveling clutch 25 is
Calculate CC by the following formula.

[0032]

## EQU3 ## ACC = ACC '-. DELTA.ACC .DELTA.ACC = kt.DELTA.Tt where ACC is a new clutch engagement pressure command value ACC' is the current clutch engagement pressure value .DELTA.ACC is the clutch engagement pressure increase / decrease value kt is a constant A signal corresponding to the command value ACC of the clutch engagement pressure calculated by the command value calculation means 73 is amplified by the amplification means 74 and sent to the pressure control means 26, whereby the upper limit value of the clutch engagement pressure is calculated. The control is performed as shown by the solid line D of 5 (b) so that the wheels do not slip. Control of clutch engagement pressure in the case of this embodiment-1,
The effect of limiting the traction force due to this is shown in FIG. The shaded area in FIG. 5 (b) has been restricted.

Example-2 FIG. 2 shows the discharge pressure Ph of the hydraulic pump 53 for working equipment,
The control block diagram in the case of detecting the rotation speed Ne of the prime mover 30 and the rotation speed of the transmission shaft of the traveling device 40 to control the clutch engagement pressure is shown. Although the transmission shaft torque itself is detected in the first embodiment, the transmission shaft torque is calculated in the second embodiment.

That is, in the torque converter 41 (FIG. 4), the output shaft torque Tt can be calculated from the ratio (speed ratio) between the input shaft rotation speed Ne and the output shaft rotation speed Nt.
In this case, if the size of the torque converter 41 is determined,
The torque ratio t and the input shaft torque coefficient τp are the speed ratio e
A certain relationship is established with respect to. Therefore, in FIG. 2, the rotation speed detection means 64 detects the rotation speed Ne of the input shaft of the torque converter 41, the rotation speed detection means 65 detects the rotation speed Nt of the output shaft of the torque converter 41, and the detected values thereof are detected. And the characteristic data of the torque converter 41 stored in the storage means 75, the torque calculation means 76 calculates the output shaft torque Tt by the following equation.

[0035]

[Equation 4] e = Ne / Nt

[0036]

## EQU00005 ## t = t [e]

[0037]

[Equation 6] τp = τp [e]

[0038]

Equation 7] Tp = τp · (Ne / 1000 ) 2 Tt = t · Tp However, Tp is an input shaft torque, Tt is in place on the measurement of the shaft torque when the output shaft torque thus in Example 1, calculated If the value is used for the control, it is possible to obtain the operational effect that the wheels can be efficiently driven so as not to slip, as in the case of the above-described first embodiment.

Embodiment-3 FIG. 3 shows the discharge pressure Ph of the hydraulic pump 53 for working equipment,
The control block diagram in the case of detecting the clutch engagement pressure and controlling the clutch engagement pressure is shown. In this case, since the clutch engagement pressure and the clutch transmission torque have a constant relationship as shown in FIG. 7, if the slip limit value is determined as shown by the solid line C in FIG. The command value of the clutch engagement pressure can be easily obtained. Also in the case of the third embodiment, as in the case of the first and second embodiments, it is possible to obtain the effect that the wheels can be efficiently driven so as not to slip.

By the way, in each of the above embodiments, in order to know the traction force, the output shaft torque of the torque converter 61 is detected as the transmission shaft torque of the traveling device, but instead of this, the output shaft torque of the transmission 42 or The drive shaft torque may be detected or calculated.

Further, in each of the above embodiments, when the limit value calculating means 71 calculates the slip torque limit value Ts-limit, the reference value Tso is calculated by the reference value setting means 62 such as a voltage adjusting device. It is desirable to set it variably according to the situation. By doing so, optimum control is always performed, and slipping of the wheels is more reliably prevented.

[0042]

As described above, according to the present invention, the discharge pressure of the hydraulic pump for the working device which changes according to the load of the working device,
The transmission shaft torque of the traveling device corresponding to the traction force of this machine is detected, and based on the pump discharge pressure, the limit value of the clutch engagement pressure for not slipping the wheels is determined,
Wheel slip is suppressed by controlling the clutch engagement pressure so that the detected value of the transmission shaft torque does not exceed the above limit value, so even unskilled operators can operate safely and efficiently. The energy saving effect can be enhanced. Moreover, since only the discharge pressure of the hydraulic pump and the transmission shaft torque are detected, the number of detectors to be installed can be reduced compared to the above-mentioned conventional device, and the device configuration and arithmetic processing can be simplified to reduce costs. You can Further, instead of detecting the transmission shaft torque, the rotation speed of the prime mover and the rotation speed of the transmission shaft are detected, and the transmission shaft torque is calculated and controlled to obtain the same effect.

Further, as described in claim 3, the clutch engagement pressure is detected, and the limit value of the clutch engagement pressure for preventing the wheels from slipping is obtained based on the pump discharge pressure detected in the same manner as above. By controlling the clutch engagement pressure so as not to exceed the limit value, it is possible to operate efficiently so that the wheels do not slip as in the above.

Further, when the limit value of the transmission shaft torque or the limit value of the clutch engagement pressure is determined, the reference value is changed according to the road surface condition, etc., so that optimum control can always be performed and wheel slippage can be performed. Can be prevented more reliably.

[Brief description of drawings]

FIG. 1 is a control block diagram showing an embodiment in which a discharge pressure of a hydraulic pump for a working device and a transmission shaft torque of a traveling device are detected to control an engagement pressure of a traveling clutch.

FIG. 2 is a control block diagram showing an embodiment in which the clutch engagement pressure is controlled by detecting the discharge pressure of the working device hydraulic pump, the rotation speed of the prime mover, and the transmission shaft rotation speed of the traveling device. .

FIG. 3 is a control block diagram showing an embodiment in which the clutch engagement pressure is controlled by detecting the discharge pressure of the working device hydraulic pump and the engagement pressure of the traveling clutch.

FIG. 4 is a conceptual diagram showing an example of a wheel-type construction machine to which the present invention is applied.

5A is a graph showing general characteristics of the wheel-type construction machine, and FIG. 5B is a graph for explaining a function and effect of the present invention.

FIG. 6 is a hydraulic circuit diagram of a traveling clutch according to the present invention.

FIG. 7 is an explanatory diagram showing a relationship between an engagement pressure of a traveling clutch and a transmission torque.

[Explanation of symbols]

 Reference Signs List 11 front frame 12 rear frame 20 driver's cab 23 hydraulic pump 24 control valve for speed stage switching of transmission 25 traveling clutch 26 pressure control means 30 prime mover 40 traveling device 41 torque converter 42 transmission 43,44 drive shaft 45,46 Axles 47, 48 Wheels 50 Working device 51 Operating lever 52 Control valve 53 Hydraulic pump for working device 54 Boom 55 Boom cylinder 56 Bucket 57 Bucket cylinder 58 Cross link 59 Dump link 61 Pressure detecting means 62 Reference value setting means 63 Torque detecting means 64 prime mover rotation speed detection means 65 torque converter output shaft rotation speed detection means 66 reference value setting means 70 controller 71 slip torque limit value calculation means 72 comparison means 73 target value calculation means 74 amplification means 75 Torque converter characteristic storage means 76 Torque calculation means 77 Clutch engagement pressure limit value calculation means

Continued Front Page (72) Inventor Hiroshi Taji, 3-12-4 Gion, Asanan-ku, Hiroshima City Yutani Heavy Industries Co., Ltd.

Claims (4)

[Claims] 1. A pressure detecting means for detecting a discharge pressure of a hydraulic pump for a working device, a torque detecting means for detecting a torque of a transmission shaft in a traveling device, and a pump discharge pressure detected by the pressure detecting means. Limit value calculating means for obtaining a limit value of transmission shaft torque for preventing wheels from slipping, and a traveling clutch so that the transmission shaft torque detected by the torque detecting means does not exceed the limit value obtained by the limit value calculating means. And a control means for controlling the engagement pressure of the slip prevention device for a wheel-type construction machine. 2. A pressure detecting means for detecting a discharge pressure of a hydraulic pump for a working device, a prime mover rotation speed detecting means for detecting a rotation speed of a prime mover, and a transmission shaft rotation speed for detecting a rotation speed of a transmission shaft in a traveling device. Detection means, torque calculation means for calculating the torque of the transmission shaft based on the prime mover rotation speed and the transmission shaft rotation speed detected by the both rotation speed detection means, and the pump discharge pressure detected by the pressure detection means. Limit value calculating means for obtaining a limit value of the transmission shaft torque for preventing the wheels from slipping based on the above, and traveling so that the transmission shaft torque calculated by the torque calculating means does not exceed the limit value calculated by the limit value calculating means. And a control means for controlling the engagement pressure of the vehicle clutch, the slip prevention device for a wheel-type construction machine. 3. A first pressure detecting means for detecting a discharge pressure of a hydraulic pump for a working device, a second pressure detecting means for detecting an engaging pressure of a traveling clutch, and the first pressure detecting means. Limit value calculating means for obtaining a limit value of the engaging pressure of the traveling clutch for preventing the wheels from slipping based on the detected pump discharge pressure, and clutch engaging pressure detected by the second pressure detecting means. A slip prevention device for a wheeled construction machine, comprising: a control unit that controls a clutch engagement pressure so as not to exceed a limit value calculated by the limit value calculation unit. 4. A reference value setting means for variably setting a reference value when the limit value of the clutch engagement pressure is calculated by the limit value calculating means is provided. An anti-slip device for a wheel type construction machine as described in.