GB2291226A

GB2291226A - Method of transporting workpieces in assembly line

Info

Publication number: GB2291226A
Application number: GB9519052A
Authority: GB
Inventors: Shigehiro Nakajima; Noriyuki Unose
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1992-09-02
Filing date: 1992-10-23
Publication date: 1996-01-17
Anticipated expiration: 2012-10-23
Also published as: GB2291226B; GB9519052D0

Abstract

In an assembly line in which workpieces W are transported by self-propelling transporting members 2, there is an automated working station 101. At the automated working station 101, the transporting members are stopped while assembly work is conducted on the workpieces. The transporting members 2 are restarted after a waiting time has elapsed following completion of the assembly work. If delays occur, a backlog builds up, which is eliminated by reducing the waiting time for each transporting member until the backlog has gone. <IMAGE>

Description

METHOD OF TRANSPORTING WORKPIECES IN ASSEMBLY LINE The present invention relates to a method of transporting workpieces in an assembly line.

An assembly line may include an intermediate portion at which there is a working region such as an automated working station for performing assembling works while transporting members on which the workpieces are carried are stopped. Succeeding transporting members may accumulate or get stacked on the upstream side of the working region if the restarting of the transporting members in the working region is delayed due to a trouble therein. This results in a delay in the assembling works on the downstream side of the working region and, consequently, in a decrease in the number of production.

According to the present invention there is provided a method of transporting workpieces in an assembly line in which workpieces are respectively transported by self-propelling transporting members and in which, in a region which is provided in an intermediate portion of said assembly line and in which said transporting members are stopped for performing assembling works therein, said transporting members are re-started at a time interval of a waiting time after said assembling works in said region have been finished, said method comprising the steps of, when said re-starting of any of said transporting mergers out of said region is delayed with a result that succeeding transporting members are accumulated on an upstrea side of said region, making shorter salt waiting time relative to the time of re-starting said succeeding transporting members out 0 said eis than a ordinary value of waiting time.

or a better understanding t ine resent invention and to snow made clearly now it may ii carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Fig. 1 is a plan view ot an assembly line to which the present invention method is applied; and Fig. 2, consisting ot Fig. 2(a) and Fig. 2(b), is a diagram showing the condition cf the assembly line in which a trouble has occurred (2a) and a diagram showing the condition in which the assembly line has been recovered frorn the trouble back to the normal condition 2(b).

As shown In Fig. 1, automobile bodies W as workpieces are transported along an assembly line 100 by self-propelling transporting carts 2 at a fixed pitch.

In an intermediate portion of the assembly line 100, there is provided an automated working station 101 in which assembling works by unillustrated robots or the like are performed. In manual working regions 102, 103 on respectively the upstream side and the downstream side thereof, workers perform predetermined assembling works on the automobile bodies W which are placed on the transporting carts 2, while they move together with the transporting carts 2 at each assembling step. In the automated working station 101, each of the transporting carts 2 is stopped at a predetermined position to perform assembling works on the automobile body by the automated device.

On a side of the assembly line at the automated working station 101, there are provided a controller 104, a sensor 105 which identifies the kind of automobile body through a type-identifying means attached to the automobile body or the transporting cart 2, and a signal transmitting means 106 which transmits signals to the transporting carts 2. The automated device is operated according to the kind of automobile body that has been identified by the sensor 105. Upon completion of the assembling works, the transporting cart 2 is re-started by the signal from the signal transmitting means 106 as described hereinbelow.

The speed and the pitch of the transporting carts 2 are set in accordance with a line tact to which is determined by a production schedule. Normally, the transporting cart 2 is sequentially transported from the upstream manual working region 102 into the automated working station 101 at a time interval o to. ere, the time t1 required for the assembling works In the a-.om2~ev working station 10i is snorter than to. At the lapse c a waiting time t2 which is the difference between t0 and tl after the assembling works in the automated working station 101 have been completed, a signal to re-start the transporting cart 2 is transmitted from the line-side controller 104 to the transporting cart 2 via the signal transmitting means 106. The transporting carts 2 are thus sequentially transported into the downstream manual working region 103 at the time interval of t0.

However, if the re-starting of the transporting cart 2 is delayed due to a trouble or the like in the automated device in the automated working station 101, the succeeding transporting carts 2 will be accumulated or get stacked on the upstream side of the automated working station 101 as shown in Fig. 7(a). vven if the trouble has been remedied and the assembling works in the automated working station 101 are started again, the accumulation on the upstream side will remain as it is if the transporting carts 2 are transported into the downstream manual working region 103 at the time interval of to. This results in a consequent delay in the assembling works on the downstream side and, accordingly, the schduled number of production cannot be attained.

Therefore, when the assembling works in the automated working station 101 have been re-startec, the waiting time from te completion of assembln works in the automatec working station 1G1 to the re-starting of the transporting carts 2 is made shorter than the above-described t2 by a value obtained by multiplying the normal value t2 (= to t1) by a predetermined ratio d of shortening. By thus making shorter the stopping time of the transporting cart 2 in the automated working station 101 than t0, the accumulation on the upstream side is eliminated.

In this case, in the manual working region 103 on the downstream side of the automated working station 101, the pitch of the transporting carts 2 becomes narrower as shown in Fig. 7(b), with the result that a heavy load will be imposed on the workers therein. This heavy load may be alleviated by temporarily allocating, to the downstream manual working region 103, the workers who have already finished their own assembling works, during the accumulation, in the upstream manual working region 102.

Let the time by which the transporting carts 2 which is inside the automated working station 101 during the occurrence of the trouble exceeds the normal stopping time to (= t1 + t2), be a value of t. Then, the number m of the transporting carts 2 accumulated on the upstream side cf the automated working station 101 during that time wIll be tit0.

The stopping time of the transporting cart 2 at the automated working station 101 after the recovery rom tne trouble will be t1 + (1 ) t2 and is mate shorter the normal stopping time of t1 + 22 by a value of αt2. Let the number of transporting carts 2 whose stopping time shaffli be shortened be n. Then, the time will be saved by α t2n. If this value becomes t (= t0m), the accumulation on the upstream side will have been eliminated.

Accordingly, if the excess stopping time t of the transporting cart 2 at the automated working station 101 is measured, the number n of transporting carts whose waiting time shall be shortened, among all of the succeeding transporting carts 2, is made to be n = t/αt2 (below decimal point cut down), and the waiting time of the (n + 1 )th transporting cart and downwards is returned to t2, there will be no excessive load imposed on the workers on the downstream side.

A sensor for detecting the degree of accumulation of the transporting carts 2 may be provided on a side of the assembly line on the upstream side or t automated working station 101 in order to determine the timing for returning the waiting time to t2 depending on the degree of accumulation. However, if the number of the transporting carts whose waiting time shall be shortened is determined by the above-described method, there will be require no special sensor and is therefore advantageous from t viewpoint of costs.

As disclosed in our co-pending parent application No. @@@2352.8, plural kinds oi automobile bodies W may be transported @@@@@@ along the assembly line 100. When, if the waiting @@@@ the transporing parts 2 to transport the kind of automobile bodies re@@@@@ Larger number of assembling man-hours within one assembling or processing step is shortened equally as that for the transporting carts 2 to transport the kind of automobile bodies requiring smaller number of assembling man-hours, there will be imposed an excessive load on the works for the automobile bodies requiring larger number of assembling man-hours.In such a case, the rate Or of shortening the waiting time is set for each kind of automobile body and is stored in the controller 104 such that the smaller becomes the number of man-hours, the larger becomes the rate of shortening. When the kind of the automobile body W on the transporting cart 2 which is in the automated working station 101 is identified by the above-described sensor 105, a rate > of shortenIng corresponding to that kind is searched to compute the waiting time.

However, the rate. > of shortening needs not be variec for each kind of automobile body if a different normal value t2 of waiting time is set for each kind of automobile body such that the larger becomes the number of assembling manhours, the longer becomes the transporting pitch of the workpiece W and the smaller becomes the number Ci assembling man-hours, the shorter it becomes even at t norma time.

Claims

1. A method of transporting workpieces in an assembly line in which workpieces are respectively transported by self-propelling transporting members and in which, in a region which is provided in an intermediate portion of said assembly line and in which said transporting members are stopped for performing assembling works therein, said transporting members are re-started at a time interval of a waiting time after said assembling works in said region have been finished, said method comprising the steps of, when said re-starting of any of said transporting members out of said region is delayed with a result that succeeding transporting members are accumulated on an upstream side of said region, making shorter said waiting time relative to the time of re-starting said succeeding transporting members out of said region than an ordinary value of waiting time.

2. A method of transporting workpieces in an assembly line according to claim 1, further comprising the steps of detecting a degree of accumulation of said transporting members on said upstream side of said region and, according to said degree of accumulation, determining a timing for returning said waiting time back to said ordinary value of waiting time.

3. A method of transporting workpieces in an assembly line according to claim 1, further comprising the steps of measuring a time of stopping of any of said transporting members in said region which is delayed in re-starting out of said region, and determining, according to said time ot stopping, the number of transporting members whose waiting times are shortened.

4. A method if c > < Ss workpieces In an assembly line according to any one Ci the preceding claims, wherein said ass lit Ine is a In in which workpieces of different kinds are transported by mixture, said method further comprising the step of varying a rate of shortening said waiting time of said succeeding transporting members relative to said ordinary value, according to the kind of workpieces to be transported by said succeeding transporting members.

5. A method of transporting workpieces as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.