JPH086613B2 - Engine control method for wheeled construction machine - Google Patents

Description

The present invention relates to an engine control method for a wheeled construction machine.

[Conventional technology]

Conventionally, the engine output characteristics of wheeled construction machines that perform work and travel have been designed to find a compromise between work performance that requires high torque and travel performance that requires high speed.
The type is fixed.

As described above, one type of engine output characteristic is fixed, so the power distribution when using a working machine and when traveling is not optimal.

Therefore, as shown in FIG. 5, one of the characteristics depending on the type of load (working state or running state), that is, the characteristic of the solid line A that is suitable for work during work, and the broken line that is suitable for running during running It is conceivable to control the engine so as to exhibit the characteristics of B.

[Problems to be solved by the invention]

However, the maximum value of the absorption torque of the torque converter for the engine output characteristic of the broken line B is larger than that for the engine output characteristic of the solid line A, and therefore the torque converter is designed for the engine output characteristic of the solid line A. In this case, if the engine output characteristic is switched to the characteristic indicated by the broken line B, there is a problem that the torque converter is overloaded.

The absorption torque of the torque converter has a small speed ratio,
And it becomes large when the engine rotation speed is high. For example, assuming that the absorption torque becomes maximum when the speed ratio e = 0, the intersections P ₁ and P _{2 of the} torque converter input shaft torque quadratic curve and the solid line A and the broken line B showing the engine output characteristic are shown.
Considering, the torque that the torque and the torque converter pump engine at these points will drive the torque converter absorbs indicates the maximum value of the matched each absorption torque, the absorption torque of the intersection P ₂ as mentioned above intersection It becomes larger than the absorption torque of P ₁ .

The torque converter is easier to design if the maximum absorption torque is smaller, and it is not preferable that the torque of the broken line B suitable for traveling is too small.

The present invention has been made in view of the above circumstances, and when the engine output characteristic is made variable, the generation of excessive torque applied to the torque converter is prevented, and the drive system etc. is protected. It aims at providing the engine control method of this.

[Means and Actions for Solving Problems]

According to the present invention, based on the accelerator operation amount and the engine rotation speed, the fuel injection amount increases as the accelerator operation amount increases when the engine rotation speed is the same, and the engine rotation speed decreases when the accelerator operation amount is the same. The engine is controlled by increasing the fuel injection amount and supplying at least an injection amount of fuel that is restricted so that the fuel injection amount does not exceed a maximum injection amount set in advance based on the engine speed. In an engine control method for a wheeled construction machine, a first maximum injection amount having an engine output characteristic suitable for work with respect to an engine rotation speed, and a second maximum injection amount having an engine output characteristic suitable for traveling. ,
The second maximum injection amount is within a predetermined engine speed range,
Further, when the speed ratio of the torque converter at that time is small, the absorption torque becomes larger than the maximum absorption torque of the torque converter at the time of the first maximum injection amount, and the torque converter in the predetermined engine rotation speed region. A third maximum injection amount for restricting the second maximum injection amount so that the absorption torque becomes smaller than the maximum absorption torque of the torque converter at least at the first maximum injection amount when the speed ratio is small. Are stored in the memory, and it is determined whether the wheeled construction machine is in a working state or a running state. When the wheeled construction machine is in a working state, the first maximum injection amount is set to the maximum value. When the fuel injection amount is selected and the vehicle is running, the engine speed is within the predetermined engine speed range and the torque The third maximum injection amount is selected as the maximum injection amount in a traveling state in which the speed ratio of the barter is small, and the second maximum injection amount is selected as the maximum injection amount in other traveling states. I am trying.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of an engine control device for a wheeled construction machine according to the present invention.

In the figure, the accelerator pedal position detection sensor 2 is
A signal corresponding to the depression position (operation amount) of the accelerator pedal 1 is output.

The target injection amount calculation circuit 3 calculates the target injection amount based on the above-mentioned signal applied from the accelerator pedal position detection sensor 2 and the rotation speed signal indicating the actual rotation speed of the engine applied from the engine rotation speed sensor 4, A signal indicating the target injection amount is output. Now, the calculation method of the target injection amount will be described by taking the full range rotation speed control method (all speed governor) as an example. As shown in the graph of FIG. A desired regulation line is selected by a signal corresponding to the input accelerator operation amount, and the position of the regulation line, that is, the injection amount is specified by the input rotation speed signal.

The signal indicating the target injection amount calculated in this way is PI
It is added to the small signal priority circuit 6 via the D compensation circuit 5.

A signal indicating the maximum injection amount that can be taken at the present engine speed is added from the maximum injection amount calculation circuit 7 to the other input of the small signal priority circuit 7.

Here, the maximum injection amount calculation circuit 7 uses, for example, three types of engine output characteristic curves A, B, and C indicating the maximum injection amount with respect to the engine speed in advance, as shown in the graph of FIG.
I remember. Engine output characteristic curve A shown by solid line
Is designed to be suitable for work requiring high torque, and is an engine output characteristic curve B indicated by abcde
The engine output characteristic curves indicated by and a-b-c-f-g-e are designed to be suitable for high speed running where high speed is required.

In addition, when the curve B and the curve C are compared, the curve B is c-
While having the maximum injection amount characteristic shown by d-g, the curve C
Has a maximum injection amount characteristic indicated by c-f-g so that the maximum absorption amount during this period is suppressed and the maximum absorption torque of the torque converter does not exceed the point P ₁ .

The maximum injection amount calculation circuit 7 is based on a selection signal from a determination circuit 20 that determines whether the wheeled construction machine is currently in a working state or in a traveling state, and whether or not the traveling state is high speed traveling. One of the three types of engine output characteristic curves A, B and C is selected, and based on the rotation speed signal indicating the rotation speed of the engine added from the engine rotation speed sensor 4 and the selected engine output characteristic curve. A signal indicating the maximum injection amount that can be taken at the current engine speed is output. The details of the discrimination circuit 20 will be described later.

The small signal priority circuit 6 gives priority to the smaller one of these two input signals and guides it to the rack position conversion circuit 8.

The rack position conversion circuit 8 converts the input signal indicating the fuel injection amount into a signal indicating the rack position, and outputs this rack position signal as a target value to the addition point 9. The rack refers to the control rack 12 used to rotate the plunger for changing the injection amount via the pinion in the fuel injection pump.

A signal indicating the rack position is added as a feedback value from the rack position sensor 13 to the other input of the addition point 9, and the addition point 9 takes the deviation of these input signals and outputs this deviation signal via the drive circuit 10. Linear solenoid 11
Add to

As a result, the linear solenoid 11 drives the control rack 12 so that the rack position of the control rack 12 reaches the target value.

Next, the details of the discrimination circuit 20 will be described with reference to FIG. 2, and the operation of the present invention will also be described.

The discriminating circuit 20 discriminates whether the wheeled construction machine is in a working state or a traveling state, and whether or not the vehicle is traveling at a high speed even in the traveling state. The accelerator pedal position detecting sensor 2 and the hydraulic pressure detecting sensor are used. 30, forward and backward lever position detection sensor 3
1, detection signals from the gear position lever position detection sensor and the vehicle speed sensor 33 are added.

Here, the accelerator pedal position detection sensor 2 outputs a signal H indicating the depression position (pedal height) of the accelerator pedal 1. The signal H decreases as the depression amount of the accelerator pedal 1 increases. The hydraulic pressure detection sensor 30 is arranged in the working machine hydraulic circuit and outputs a signal P indicating the hydraulic pressure of the hydraulic circuit. The forward / reverse lever position detection sensor 31
The signal "1" is output when the forward / reverse lever for selecting forward / reverse is in the forward position.

The gear position lever position detection sensor 32 outputs a signal indicating the gear position of the transmission gear shift lever. Note that, for simplicity of explanation, it is assumed that a two-stage transmission of IST and 2ND is used, and a signal "1" is output when the lever position is 2ND. The vehicle speed sensor 33 detects the vehicle speed and outputs a signal V indicating the actual vehicle speed.

As shown in FIG. 2, the discrimination circuit 20 is composed of comparators 21, 22, 23 and AND circuits 24, 25.

The comparator 21 has two comparison reference levels H ₁ and H ₂ , and outputs a signal “1” when the signal H indicating the pedal height from the accelerator pedal position detection sensor becomes smaller than the level H ₁ . When it becomes higher than the level H _{1, the} signal “1” is set to “0”. The comparison reference level H ₁ corresponds to the signal H when the accelerator pedal is depressed by a predetermined amount for high speed traveling.

Similarly, the comparator 22 has two comparison reference levels P ₁ and P ₂ and outputs a signal when the signal P indicating the hydraulic pressure from the hydraulic pressure detection sensor 30 becomes equal to or lower than the predetermined level P ₁ when no work is performed. When "1" is output and the level becomes H ₂ or more, the signal "1" is set to "0". In addition, the comparator 23 has two comparison reference levels.
It has V ₁ and V ₂ , and outputs a signal “1” when the signal V indicating the vehicle speed from the vehicle speed sensor 33 becomes equal to or higher than a predetermined level V ₂ during high speed traveling, and outputs the signal when the signal V becomes equal to or lower than the level V _1. "1"
To “0”.

The AND circuit 24 takes an AND condition of signals from the comparators 21 and 22, the forward / reverse lever position detection sensor 31, and the gear position lever position detection sensor 32, and when the AND condition is satisfied, a signal "1" indicating that the vehicle is in a traveling state. Further, the AND circuit 25 becomes operable when the signal “1” is applied from the AND circuit 24, and when the signal “1” is applied from the comparator 23,
This is output as a signal indicating that the vehicle is traveling at high speed.

The maximum injection amount calculation circuit 7 selectively outputs the optimum engine output characteristic curve as shown in the following table based on the output from the determination circuit 20.

That is, when the wheeled construction machine is in a working state, a signal indicating the maximum injection amount according to the curve A is output based on the engine rotation speed, and is in a traveling state and at a high speed (when the engine rotation speed is high and the transmission is high). (When the speed ratio e is large), a signal indicating the maximum injection amount according to the curve B is output based on the engine speed, and when the vehicle is running and running at low speed (when the engine speed and the speed ratio e are other than those described above). In the case of), a signal indicating the maximum injection amount according to the curve C is output based on the engine rotation speed.

As described above, when the wheeled construction machine is in a running state, the engine output characteristic is changed to be suitable for high speed, and when the absorption torque of the transmission becomes larger than the maximum absorption torque during work, the curve As shown in C, the maximum injection amount is limited to prevent an increase in the absorption torque of the transmission.

It should be noted that in the present embodiment, the speed ratio e of the transmission is large (e
= 1), the curve B is selected because the absorption torque is small, and the curve C is selected at other times. However, parameters other than the vehicle speed, that is, the engine rotation speed and the speed ratio e are directly obtained to determine the transmission. The injection amount may be limited so that the absorption torque of does not exceed the maximum absorption torque during work.

Further, the types and combinations of the detection sensors for determining whether the wheeled construction machine is in the working state or the traveling state are not limited to the present embodiment.

Furthermore, in the present embodiment, there is one type of engine output characteristic curve suitable for running, but a plurality of engine output characteristic curves are prepared for each speed stage, and each engine speed characteristic curve is prepared for each speed stage according to the lever position of the transmission speed stage lever. A suitable engine output characteristic curve may be selected.

〔The invention's effect〕

As described above, according to the present invention, since the engine output characteristic is changed according to the type of load (work, running) of the wheeled construction machine, engine power distribution can be economically and optimally performed. In particular, since the engine output characteristics are further changed so that the absorption torque of the transmission does not rise above a predetermined value during traveling, it is possible to prevent the generation of excessive torque applied to the torque converter and to protect the drive system.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the details of the discrimination circuit of FIG. 1, and FIGS. 3 and 4 are the target injection amount calculation circuit of FIG. FIG. 5 is a graph used to explain the maximum injection amount calculation circuit, and FIG. 5 is a diagram used to explain problems when the engine output characteristic is made variable. 1 ... Accelerator pedal, 2 ... Accelerator pedal position detection sensor, 3 ... Target injection amount detection circuit, 4 ... Engine speed sensor, 6 ... Small signal priority circuit, 7 ... Maximum injection amount calculation circuit, 8 ...... Rack position conversion circuit, 11 …… Linear solenoid, 12 …… Control rack, 13 …… Rack position sensor, 20 …… Discrimination circuit, 12,22,23 …… Comparator, 2
4,25 ... AND circuit, 30 ... Oil pressure detection sensor, 31 ... Forward / reverse lever position detection sensor, 32 ... Gear shift lever position detection sensor, 33 ... Vehicle speed sensor.

Claims (2)

[Claims] 1. When the engine operating speed is the same based on the accelerator operating amount and the engine rotating speed, the fuel injection amount is larger as the accelerator operating amount is larger, and when the engine operating speed is the same, the fuel is smaller. A device for controlling the engine by increasing the injection amount and supplying at least an injection amount of fuel that is limited so that the fuel injection amount does not exceed a preset maximum injection amount based on the engine rotation speed. In an engine control method for a wheeled construction machine, a first maximum injection amount having an engine output characteristic suitable for work with respect to an engine rotation speed, and a second maximum injection amount having an engine output characteristic suitable for traveling, The second maximum injection amount is within the predetermined engine speed range, and when the speed ratio of the torque converter at that time is small, the absorption torque is the above-mentioned first When the speed ratio of the torque converter is small in the predetermined engine speed range, the absorption torque is at least the first maximum injection amount. Whether the wheeled construction machine is in a working state by storing the respective third maximum injection amounts for controlling the second maximum injection amount so as to be smaller than the maximum absorption torque of the torque converter at the time. When the wheeled construction machine is in a working state, the first maximum injection amount is selected as the maximum injection amount, and when the vehicle is in a running state, the engine rotation speed is determined. Is in the predetermined engine speed range, and when the speed ratio of the torque converter at that time is small, the third maximum injection amount is set to the maximum value. Selected as the injection quantity, a wheeled construction machine engine control method characterized by selecting a maximum injection amount of the second as the maximum injection amount in the other running state of the. 2. A running state in which the speed ratio of the torque converter is small in the predetermined engine speed range and at that time is detected by the speed stage and vehicle speed of the wheeled construction machine. A method for controlling an engine of a wheeled construction machine as described.